The present invention relates to a flow control valve according
to the preamble of claim 1 having a spool valve movably held in a valve sliding
space of a valve casing for adjusting an opening area of a fluid passage of a fluid
port in order to control flow amount of fluid, such as fuel, oil, or air and so
on. More particularly, the present invention relates to a suction fuel amount adjusting
valve, which is assembled in a fuel supply pump for a common rail fuel injection
system, and which adjusts fuel amount flowing from a feed pump into a pressurizing
chamber of the fuel supply pump.
In a common rail fuel injection system conventionally known
as a fuel injection system for a diesel engine, a high pressure fuel is accumulated
in a common rail, and the high pressure fuel accumulated in the common rail is injected
into combustion chambers of respective cylinders of the engine, through multiple
injectors provided at the respective cylinders of the engine, at a predetermined
timing. The high pressure fuel is supplied into the common rail from a fuel supply
pump through a high pressure fuel pipe, wherein the fuel supply pump pressurizes
fuel fed into a pressurizing chamber through an electromagnetic valve, because it
is necessary to always accumulate in the common rail the high pressure fuel corresponding
to a fuel injection pressure.
A fuel discharge amount discharged from the fuel supply
pump is controlled by adjusting an opening area of a fuel suction passage communicating
the feed pump with the pressurizing chamber through a suction valve, wherein fuel
suction amount of the fuel flowing from the feed pump into the pressurizing chamber
is adjusted by a pump driving current to a solenoid coil of the electromagnetic
valve. An electromagnetic valve for the above purpose is proposed (for example,
Japanese Patent Publication No.2002-106740
), in which an electromagnetic type suction fuel amount ad justing valve
comprises; a spool valve having a function of a valve body for adjusting an opening
area of fluid passage by moving in a valve sliding space and having a function of
an armature for forming a magnetic circuit; and a valve casing having a function
of a cylinder for movably accommodating the spool valve and having a function of
a stator for forming the magnetic circuit.
In the electromagnetic type suction fuel amount adjusting
valve disclosed in the above Japanese Patent publication, however, a centering of
the spool valve in the valve sliding space of the valve casing can not be easily
achieved due to a difference in a magnetic force, which is caused by a deviation
of a clearance formed between an outer peripheral surface of a sliding portion of
the spool valve and an inner surface of the valve sliding space of the valve casing.
Then, the outer peripheral surface of the sliding portion of the spool valve is
pressed against the inner surface of the valve sliding space of the valve casing,
and thereby a lubricating performance is deteriorated between the outer peripheral
surface of the sliding portion of the spool valve and the inner surface of the valve
sliding space of the valve casing. As a result, the sliding portion of the spool
valve may be stuck to the inner surface of the valve sliding space, and it may cause
a problem of a decrease of durability. In the above method, in which the spool valve
is moved relative to the fluid port of the valve casing to adjust the fuel flow
amount, since the spool valve is slowly moved to control the opening area of the
fluid passage of the fluid port, a sliding speed of the spool valve with respect
to the fluid port of the valve casing is extremely low, it would become difficult
to form an oil film between the outer peripheral surface of the sliding portion
of the spool valve and the inner surface of the valve sliding space of the valve
casing. The lubricating performance is thereby further deteriorated.
Accordingly, the sliding portion of the spool valve can
not be smoothly moved with respect to the fluid port of the valve casing, when the
pump driving current is applied to the solenoid coil of the electromagnetic type
fuel suction amount adjusting valve and the armature of the spool valve is attracted
toward an attracting portion of the stator of the valve casing. For example, an
adjusting performance for fuel flow amount is deteriorated, as a result that response
of the electromagnetic valve is deteriorated with respect to a pedal stroke of an
acceleration pedal operated by a vehicle driver. Accordingly, a fuel suction amount
of the fuel flowing from the feed pump into the pressurizing chamber may not quickly
reach at a target amount, a time period during which the fuel amount discharged
from the fuel supply pump reaches at a target amount would become longer, and a
fuel pressure in the common rail can not quickly reach at a target fuel pressure
as the vehicle driver desired. As a consequence, a delay of increasing an engine
rotational speed may occur due to a delay of increase in the fuel injection amount,
with respect to a change of the pedal stroke of the acceleration pedal operated
by the vehicle driver. As above, a problem has occurred, in which an engine performance,
such as an acceleration response and so on, is decreased.
In another prior art flow control valve for a common rail
fuel injection system, for example, as discloses in
Japanese (PCT) Patent Publication No. 2005-530568
, the flow control valve adjusts an opening area of a fuel suction passage
communicating a low pressure pump (a feed pump) with a high pressure pump (a supply
pump), by controlling a magnetomotive force at a solenoid coil and thereby a relative
position of a spool valve to a valve casing.
In the flow control valve disclosed in the above Japanese
(PCT) Patent Publication, however, a lower side of an outer surface of the spool
valve is always kept in contact with the valve casing due to gravity, and a partial
wear may be caused because the spool valve is moved to slide in the valve casing
with such a condition. Furthermore, a gap between the spool valve and the valve
casing becomes smaller at a surrounding area of the contact portion between the
spool valve and the valve casing, and thereby a larger magnetomotive force of the
solenoid coil is applied to increase the contacting force, so that the partial wear
is facilitated.
According to microscopic observation, streaked vestiges
of wear are formed in the spool valve and the valve casing in a sliding direction
of the spool valve, due to the wear. A contacting area is further increased between
the spool valve and the valve casing, and frictional force is increased. This frictional
force breaks a balance between the spring force and the magnetomotive force of the
solenoid coil, to thereby cause a bad operation (a bad sliding movement) of the
spool valve, to deteriorate controllability of fuel pressure in the common rail,
and to cause a variation of fuel injection amount. Furthermore, it may increase
harmful exhaust gas, deteriorate drivability, increase engine noise, and so on.
The electromagnetic valve disclosed in
Japanese Patent Publication No. 2002-106740
, as described above, comprises the valve casing having the valve sliding
space straightly extending in the axial direction, and the cylindrical spool valve
movable in the valve sliding space of the valve casing in the axial direction to
control a communication condition between an outlet port and a communication port.
A through-hole penetrates through an inside of the spool valve. A spring space is
formed, to accommodate a spring, in the valve casing at one side of the spool valve
in the axial direction for biasing the spool valve in its valve closing direction.
The spring space is communicated with an inlet port of the valve casing through
the through-hole.
In the above electromagnetic fuel suction amount control
valve, however, fuel is supplied into the through-hole of the spool valve from the
inlet port of the valve casing, and the fuel supplied into the outlet port of the
valve casing through a flow amount adjusting groove. And the fuel in the spring
space mostly stays in the spring space. When a foreign material flowing into the
electromagnetic fuel suction amount control valve together with the fuel, or wear-out
powder generated by sliding movement between a sliding surface of the spool valve
and a sliding surface of the valve casing flows into the spring space, they stay
in the spring space. Therefore, it may cause a problem that the foreign material
or the wear-out powder may not easily flow out from the spring space.
A flow amount control portion is formed to control fuel
flow amount by changing the opening area of the flow passage of the outlet port,
when the spool valve is moved in its axial direction within the valve sliding space
of the valve casing. For that purpose, a minimum gap, which is necessary in order
that the spool valve is moved in its axial direction within the valve sliding space
of the valve casing, is formed between the sliding surface of the spool valve and
the sliding surface of the valve casing. Then, the foreign materials or the wear-out
powder staying in the spring space may flow into the gap along with the axial movement
of the spool valve, to break into the gap between the sliding surface of the spool
valve and the sliding surface of the valve casing. A sliding resistance of the spool
valve with respect to the sliding surface of the valve casing may be increased.
As a result, a sliding performance of the spool valve is deteriorated and may cause
a problem of a bad sliding movement of the spool valve. In the case that such bad
sliding movement has occurred, a control characteristic of a pump discharge amount
is deteriorated with respect to a value of a pump driving current to the solenoid
coil of the flow control valve, and finally it may cause a problem of a decrease
of an engine output.
According to the prior art disclosed in
WO 97/00400 A
, the recess and the grooves are provided. The recess is provided for communicating
with the communication port. The grooves are formed around the outer diameter of
the spool for equalizing the pressure acting around the spool. However, the grooves
are merely formed in the surface of the spool and no connection to each other or
to a high pressure source is provided or suggested. That is, the grooves according
to this prior art are supplied by fluid which is present between the outer surface
of the spool and the inner surface of the housing.
It is the object of the present invention to provide a
flow control valve having an increased durability, reliability and response.
The object is solved by a flow control valve having the
combination of the features of claim 1. Further advantageous developments of the
present invention are defined in the dependent claims.
It is another aim of the present invention to decrease
wear of a spool valve and a valve casing of a flow control valve. It is a further
object of the invention to provide a common rail fuel injection system, in which
the increase of the harmful exhaust gas, the deterioration of the drivability, and
the increase of the engine noise, etc. can be suppressed.
Furthermore, an aim of the present invention is to provide
a flow control valve, in which foreign materials having flown from an outside into
an inside of the flow control valve or wear-out powder generated in the inside of
the flow control valve may be actively exhausted to the outside along with the fluid,
and thereby a problem to be caused by the foreign materials or the wear-out powder
can be prevented.
According to the present invention, the present invention
can be applied to a flow control valve which comprises;
a valve casing (21) having a cylindrical body portion (33) and a closed end portion
(32), a valve sliding space (39) being formed in the cylindrical body portion (33),
one end of the valve sliding space (39) forming a first fluid port (41) and the
other end of the valve sliding space (39) being closed by the closed end portion
(32), a second fluid port (22) being formed in the cylindrical body portion (33)
and extending in a radial direction perpendicular to an axial line of the valve
casing (21);
a spool valve (23) movably supported in the valve sliding space (39) of the valve
casing (21) and movable in an axial direction of the valve casing (21), a through-hole
(42) being formed in the spool valve (23) for communicating both of first and second
axial ends of the spool valve (23) with each other, a first communication port (48)
being formed in the spool valve (23) for communicating the through-hole (42) with
an outside of the spool valve (23), the first communication port (48) being operatively
communicated with the second fluid port (22) of the valve casing (21) when the spool
valve (23) is moved in the axial direction, and an outer surface of the spool valve
(23) being substantially fluid-tightly in a sliding contact with an inner surface
of the valve sliding space (39) of the valve casing (21);
a fluid space (43) formed in the valve sliding space (39) and defined by the closed
end portion (32) and the spool valve (23), the fluid space (43) being communicated
with the through-hole (42) of the spool valve (23); and
a spring (25) disposed in the fluid space (43) for biasing the spool valve (23)
in one direction.
In the above flow control valve; a first circular groove
(45) is formed at the outer surface of the spool valve (23) communicated with the
first communication port (48), so that the first communication port (48) is operatively
communicated with the second fluid port (22) through the first circular groove (45),
wherein an opening area of the second fluid port (22) is changed depending on a
relative position of the spool valve (23) with respect to the valve casing (21)
in order that flow amount of the fluid flowing through the second fluid port (22)
is controlled; a first and second sliding surface portions (23a, 23b) are formed
by the outer surface at both axial sides of the first circular groove (45); and
multiple circular oil grooves (47) are formed at the first and second sliding surface
portions (23a, 23b), wherein the fluid flows into the multiple circular oil grooves
(47) so that the spool valve (23) is smoothly moved in the axial direction within
the valve sliding space (39).
According to the present invention; a second circular groove
(46) is formed at the outer surface of the spool valve (23) between the first circular
groove (45) and the second sliding surface portion (23b) of the spool valve (23);
and a second communication port (49, 64) is formed in the spool valve (23) for communicating
the through-hole (42) with the second circular groove (46), so that high pressure
fluid is supplied from the through-hole to the second circular groove (46) through
the second communication port (49, 64) to carry out a centering of the spool valve
(23) within the valve sliding space (39).
According to the present invention, a circular seal portion
is formed on the outer surface of the spool valve (23) between the first and second
circular grooves (45, 46), so that the first and second circular grooves (45, 46)
are fluid tightly sealed from each other.
According to an example, a first longitudinal groove (63)
is formed on the first sliding surface portion (23a), extending in the axial direction
of the spool valve (23) from the first axial end to the first circular oil groove
(47), so that high pressure fluid flows into the first circular oil groove (47).
According to an example, a second longitudinal groove (63)
is formed on the second sliding surface portion (23b), extending in the axial direction
of the spool valve (23) from the second axial end to the second circular oil groove
(47), so that high pressure fluid flows into the second circular oil groove (47).
According to the present invention; a second circular groove
(46) is formed at the outer surface of the spool valve (23) between the first circular
groove (45) and the second sliding surface portion (23b) of the spool valve (23);
and a second longitudinal groove (63) is formed on the second sliding surface portion
(23b), extending in the axial direction of the spool valve (23) from the second
axial end to the second circular groove (46), so that high pressure fluid flows
from the fluid space (43) into the second circular oil groove (47) through the second
longitudinal groove (63) to carry out a centering of the spool valve (23) within
the valve sliding space (39).
According to the present invention, a center line of the
second communication port (64) is displaced from a radial line extending in a radial
direction of the spool valve (23), when viewed on a plane perpendicular to the axial
line of the spool valve (23), so that the spool valve (23) is rotated within the
valve sliding space (39) when the high pressure fluid flows out of the through-hole
(42) into the second circular groove (46) through the second communication port
(64).
According to the present invention, a center line of the
first communication port (48) is displaced from a radial line extending in a radial
direction of the spool valve (23), when viewed on a plane perpendicular to the axial
line of the spool valve (23), so that the spool valve (23) is rotated within the
valve sliding space (39) when the high pressure fluid flows out of the through-hole
(42) into the first circular groove (45) through the first communication port (48).
According to the present invention, the flow control valve
is used in a common rail fuel injection system for a diesel engine, which comprises;
a common rail (1) for accumulating high pressure fuel; a high pressure fuel pump
(5) for pressurizing the fuel and supplying the high pressure fuel into the common
rail (1); and a low pressure pump for feeding the low pressure fuel to the high
pressure pump (5), wherein the flow control valve (6) is arranged in a fuel supply
line for feeding the low pressure fuel from the low pressure pump to the high pressure
pump (5), in order that the flow control valve (6) controls flow amount of the fuel
from the low pressure pump to the high pressure pump (5).
According to the present invention, the fuel pressure in
the common rail (1) is controlled in such a manner that the fuel pressure is controlled
at a predetermined value in the case in which an operational condition of the engine
meets a predetermined condition, wherein the predetermined value is higher than
the fuel pressure in the other cases in which the operational condition of the engine
does not meet the predetermined condition.
According to the present invention, the operational condition
of the engine meets the predetermined condition, when an engine rotational speed
is within a predetermined range, and a fuel injection amount is within a predetermined
amount.
According to an example, a foreign material exhausting
passage (62, 63) is formed in at least one of the spool valve (23) and the valve
casing (21), the foreign material exhausting passage (62, 63) extend from the fluid
space (43) to the second fluid port (22) or to the first communication port (48),
and the foreign material exhausting passage (62, 63) bypasses the through-hole (42).
The above and other objects, features and advantages of
the present invention will become more apparent from the following detailed description
made with reference to the accompanying drawings. In the drawings:
- Fig. 1 is a schematic view showing a common rail fuel injection system, to which
a flow control valve of the present invention is applied;
- Fig. 2 is a cross sectional view of the flow control valve according to a first
embodiment of the present invention;
- Fig. 3 is a schematic top plan view showing a spool valve of the flow control
valve of Fig. 2;
- Fig. 4 is a schematic top plan view showing a spool valve of the flow control
valve according to a second embodiment of the present invention;
- Fig. 5A is a schematic top plan view showing a spool valve of the flow control
valve according to a third embodiment of the present invention;
- Fig. 5B is a cross sectional view taken along a line VB-VB of Fig. 5A;
- Fig. 6 is a cross sectional view of the flow control valve according to a fourth
embodiment of the present invention;
- Fig. 7 is a schematic top plan view showing a spool valve of the flow control
valve of Fig. 6;
- Fig. 8 is an enlarged cross sectional view taken along a line VIII-VIII of Fig.
7;
- Fig. 9 is a graph showing a relation among a spool valve rotating force, a pressure
loss at a communication port, and an offset amount of the communication port;
- Fig. 10 is a graph showing a relation between a pump driving current and a fuel
discharge amount;
- Fig. 11 is a graph showing a relation an engine rotational speed and a fuel
injection amount;
- Fig. 12 is a flow chart for explaining the fourth embodiment;
- Fig. 13A is a cross sectional view of the flow control valve according to a
comparative example;
- Fig. 13B is a cross sectional view taken along a line XIIIB - XIIIB of Fig.
13A;
- Fig. 14A is a schematic top plan view showing a spool valve of the flow control
valve of Fig. 13A;
- Fig. 14B is a cross sectional view taken along a line XIVB - XIVB of Fig. 14A;
and
- Fig. 15 is a cross sectional view of a spool valve according to a further comparative
example.
The present invention will be explained below with reference
to the embodiments and examples.
(First Embodiment)
Figs. 1 to 3 show a first embodiment of the present invention,
wherein Fig. 1 is a view showing an entire structure of a common rail fuel injection
system, Fig. 2 is a view showing an electromagnetic valve, and Fig. 3 is a view
showing a spool valve of the electromagnetic valve for a supply pump.
A fuel injection apparatus for an internal combustion engine
according to the embodiment is installed in a vehicle, such as an automotive vehicle.
The fuel injection apparatus is, for example, a common rail fuel injection system
(a fuel accumulated type injection apparatus) known as a fuel injection system for
an internal combustion engine, such as a diesel engine (a multi cylinder diesel
engine, hereinafter referred to as an engine). In the fuel injection apparatus,
high pressure fuel accumulated in a common rail 1 is injected into combustion chambers
of respective cylinders of the engine via multiple (four in this embodiment) electromagnetic
fuel injection valves (injectors) 3 provided at respective engine cylinders.
The common rail fuel injection system comprises a common
rail 1 for accumulating high pressure fuel, the pressure of which corresponds to
a fuel injection pressure, multiple injectors 3 for injecting fuel into combustion
chambers of the respective engine cylinders at a predetermined timing, a fuel supply
pump (a high pressure pump) 5 of a fuel suction amount adjusting type for pressurizing
fuel fed into a pressurizing chamber through an electromagnetic flow control valve
6 (SCV: hereinafter referred to as an electromagnetic valve), and an engine control
unit (hereinafter referred to as ECU) 10 for electronically controlling multiple
electromagnetic valves 4 of the injectors 3 as well as the electromagnetic valve
6 of the supply pump 5. In Fig. 1, only one injector 3 for one of cylinders of a
four cylinder engine is shown, whereas the injectors for the other cylinders are
omitted. An output shaft (for example, a crank shaft) of the engine drives a drive
shaft or a cam shaft of the supply pump 5 via a belt.
The common rail 1 is connected with a discharge port of
the supply pump 5 for discharging the high pressure fuel, through a fuel supply
pipe 12. A depressurizing valve 2 of a normally-closed type is provided at a pressure
relief pipe 14 from the common rail 1 to a fuel tank 7, wherein the valve 2 adjusts
an opening degree of a fuel return passage communicated to the fuel tank 7. The
depressurizing valve 2 is an electromagnetic valve, which has a superior pressure
decreasing performance for quickly decreasing the fuel pressure (the common rail
pressure) in the common rail 1 from its high pressure to a low pressure, by electronically
controlling with a pressure decreasing driving current supplied from the ECU 10
through a pressure decreasing driving circuit, when a vehicle speed is reduced or
an engine operation is stopped.
The depressurizing valve 2 comprises a valve body (not
shown) for adjusting the opening degree of the fuel return passage for returning
the fuel from the common rail 1 to the fuel tank 7, a solenoid coil (not shown)
for driving the valve body in a valve opening direction, and a valve biasing means
(not.shown), such as a spring, for biasing the valve body in a valve closing direction.
The depressurizing valve 2 adjusts fuel return amount of the fuel returning from
the common rail 1 to the fuel tank 7 through the pressure relief pipe 14, in proportion
to a value of the pressure decreasing driving current to be applied to the solenoid
through the pressure decreasing driving circuit, to change the fuel pressure (the
common rail pressure) in the common rail 1. A pressure limiter can be provided,
instead of the depressurizing valve 2, to the pressure relief pipe 14, wherein the
pressure limiter controls the fuel pressure in the common rail 1 below a predetermined
pressure limit, by opening its valve when the fuel pressure in the common rail 1
exceeds the predetermined pressure limit.
The multiple injectors 3 provided at the respective engine
cylinders are connected to downstream ends of multiple branched pipes 13 branched
off from the common rail 1. The injector 3 comprises a fuel injection nozzle for
carrying out a fuel injection into the combustion chambers of the respective engine
cylinders, the electromagnetic valve 4 for driving a nozzle needle (not shown) accommodated
in the fuel injection nozzle in a valve opening direction, a needle biasing means,
such as a spring, for biasing the nozzle needle in a valve closing direction, and
so on. The fuel injection for the combustion chambers of the respective cylinders
carried out by the injectors 3 of the respective cylinders is electronically controlled
by supply and non-supply of electric current (ON/OFF) to the solenoid coil (not
shown) of the electromagnetic valve 4, which controls an increase and a decrease
of fuel pressure in a back pressure chamber for controlling an operation of a command
piston moved together with the nozzle needle. Namely, the high pressure fuel accumulated
in the common rail 1 is injected into the combustion chambers of the respective
engine cylinders, during a time period in which the electric current is supplied
to the solenoid coil of the electromagnetic valve 4 of the injector 3 and thereby
multiple injection ports formed at a forward end of the nozzle body are opened by
the nozzle needle. The engine is thereby operated. A leak port is provided at the
injector 3 for leaking a surplus fuel or the fuel discharged from the back pressure
chamber to a low pressure side of the fuel system. Therefore, the leaked fuel from
the injectors 3 returns to the fuel tank 7 via a fuel return pipe 15.
The supply pump 5 is a high pressure fuel supply pump,
which comprises two (or more than two) pressurizing systems for pressurizing the
low pressure fuel fed into the pump, namely two cylinders (or more than two cylinders)
for pump elements, wherein one electromagnetic valve 6 controls the fuel discharge
amount from the two (or more than two) pressurizing systems by adjusting the fuel
suction amount of the fuel fed into respective pressurizing chambers. The supply
pump 5 comprises a well known feed pump (a low pressure fuel supply pump: not shown)
for drawing low pressure fuel from the fuel tank 7 when a pump driving shaft (a
drive shaft or a cam shaft) is rotated by a rotation of the crankshaft of the engine,
a cam (not shown) driven to rotate by the pump driving shaft, two (or more than
two) plungers (not shown) reciprocating between a top dead center and a bottom dead
center when it is driven by the cam, two (or more than two) pressurizing chambers
(plunger chambers: not shown) for pressurizing the fuel flowing thereinto to a high
pressure when the plungers are reciprocated in a cylinder head (not shown) provided
in a pump housing, two (or more than two) suction valves (not shown) which are closed
when the fuel pressure in the respective pressurizing chambers exceeds a predetermined
value, and two (or more than two) discharge valves (not shown) which are opened
when the fuel pressure in the respective pressurizing chambers exceeds a predetermined
value.
Accordingly, the supply pump 5 pressurizes the low pressure
fuel drawn from the fuel tank 7 into the two pressurizing chambers through a fuel
supply pipe 11, by reciprocating the respective plungers in the cylinder head (the
pump cylinder). A fuel filter 8 is provided in the fuel supply pipe 11. Each of
the two suction valves comprises a check valve provided at an upstream side of the
respective pressurizing chambers, namely in fuel suction passage lines from the
feed pump to the two pressurizing chambers through the single electromagnetic valve
6. Each of the two discharge valves comprises a check valve provided at a downstream
side of the respective pressurizing chambers, namely in fuel discharge passage lines
from the pressurizing chambers to the discharge port. A leak port is provided at
the supply pump 5 in order that the fuel temperature inside of the pump may not
become to high temperature, and the leaked fuel from the supply pump 5 returns to
the fuel tank 7 through a fuel return pipe 16.
The electromagnetic valve 6 is provided in the fuel suction
passage lines (not shown) formed in the supply pump 5 communicating the feed pump
with two pressurizing chambers through the two check valves, for adjusting the fuel
suction amount of the fuel fed into the pressurizing chambers. The electromagnetic
valve 6 comprises, as shown in Fig. 2, a valve casing 21 of a sleeve shape fixed
to the pump housing, a valve body (hereinafter referred to as a spool valve) 23
for controlling an opening area of a fuel passage of an outlet port (a fluid port)
22 formed in the valve casing 21 and opening in a radial direction, a linear solenoid
actuator 24 for driving the spool valve 23 in a valve opening direction, and a return
spring 25 for biasing the spool valve 23 in a valve closing direction.
The electromagnetic valve 6 is an electromagnetic flow
control valve of a normally closed type for adjusting the fuel suction amount of
the fuel fed into the pressurizing chambers of the supply pump 5, when the electromagnetic
valve is electronically controlled by a pump driving current applied from the ECU
10 through a pump driving circuit (not shown). Namely, the electromagnetic valve
6 controls the opening area of the fuel passage of the outlet port 22 formed in
the valve casing 21 by moving the spool valve 23 in its stroke direction (an axial
direction), in proportion to a value of the pump driving current to be applied to
the linear solenoid actuator 24 through the pump driving circuit. Accordingly, the
fuel suction amount of the fuel fed from the feed pump into the pressurizing chambers
through the fuel passage lines and the suction valves is controlled. As a result,
the fuel discharge amount of the fuel discharged from the pressurizing chambers
of the supply pump 5 to the common rail 1 is controlled at a most appropriate value
corresponding to an operational condition of the engine (for example, the engine
rotational speed, the pedal stroke of the acceleration pedal, the command fuel injection
amount, etc.), and the fuel pressure in the common rail 1, namely the common rail
pressure, corresponding to the injection pressure of the fuel to be injected from
the injectors 3 into the combustion chambers of the respective engine cylinders
is changed.
The linear solenoid actuator 24 comprises a stator portion
(a stator core) 26 of a cylindrical sack shape integrally formed with and at a right
hand side (in the drawing) of the valve casing 21, an armature portion (an armature
or a moving core) 27 integrally formed with and at a right hand side (in the drawing)
of the spool valve 23, a coil bobbin 28 made of resin and arranged at an outer periphery
of a cylindrical portion of the stator portion 26, a solenoid coil 29 wound on an
outer periphery of the coil bobbin 28, a terminal 30 electrically connected to lead
wires (not shown) of the solenoid coil 29, a cylindrical housing 31 covering an
outer peripheral portion of the solenoid coil 29, and so on. The stator portion
26 of the valve casing 21 operates as an electromagnet when electric current is
supplied to the solenoid coil 29, and forms as an attracting portion (a closed end
portion) 32 for attracting the armature portion 27 of the spool valve 23. The attracting
portion 32 is connected to an accommodating portion (a cylindrical body portion)
33, which movably accommodates the spool valve 23, via a thin-walled portion 34
and a cylindrical wall portion 35.
The solenoid coil 29 is a coil, in which electrically conductive
wires covered with insulating film are wound by multiple turns, and which generates
a magnetomotive force when the electric current is supplied thereto, to attract
the armature portion 27 in its stroke direction (in the axial direction) by magnetizing
the stator portion 26 of the valve casing 21 and the armature portion 27 of the
spool valve 23. The solenoid coil 29 comprises a coil portion wound between a pair
of flanged portions of the coil bobbin 28, and a pair of lead wires (terminal wires)
drawn out of the coil portion. The housing 31 is integrally formed from resin material
having a high insulation performance, and comprises a cylindrical portion covering
the outer peripheral portion of the solenoid coil 29 and a cylindrical connector
portion 36 for holding the terminal 30. A cylindrical bracket 37 is provided at
an outer periphery of the housing 31, wherein the bracket 37 is fixed to a circular
flange portion formed at the outer periphery of the valve casing 21 by means of
caulking. A circular flange portion formed at an outer periphery of the bracket
37 is fixed to an outer surface of the pump housing of the supply pump 5 with a
fixing means (not shown), such as screws. An insertion hole 38 is formed in the
flange portion for inserting the fixing means therethrough.
The valve casing 21 of the electromagnetic valve 6 has
a function of a cylinder (the accommodating portion 33) for movably accommodating
the spool valve 23, and a function of a stator (the stator portion 26) for forming
the magnetic circuit. The valve casing 21 is made of soft magnetic material, such
as ferritic stainless steel (SUS13), in order that the valve casing 21 performs
the function of the stator. The soft magnetic material can not be heat-treated,
such as a heat treatment of hardening, because a magnetic property may be deteriorated.
It is required, however, to improve wear resistance and surface hardness, in order
that the valve casing performs its function of the cylinder as its original function.
Therefore, a hardening coating of nickel-phosphor plating is formed on an inner
surface of a spool space (a valve sliding space) 39 of the valve casing 21. A cylindrical
guiding portion is formed at the inner surface of the spool space 39 of the valve
casing 21, to guide (attract) the spool valve 23 in the axial direction (the stroke
direction).
A left hand portion (in the drawing) of the valve casing
21 is press fitted into a recess (not shown) formed at an outer surface of the pump
housing of the supply pump 5, and a sealing element 40, such as an O ring, is provided
between an inner surface of the recess of the pump housing and the outer periphery
of the valve casing 21, to prevent the fuel from leaking. An inlet port (a first
fluid port) 41 is formed at the left hand portion (in the drawing) of the valve
casing 21, wherein the inlet port 41 is communicated with a fuel pooling portion
(not shown) into which the fuel is fed from the feed pump. Four outlet ports (second
fluid ports) 22 are formed, which are connected to latter halves of the fuel suction
passage lines communicated with the two pressurizing chambers through the two suction
valves. A fuel passage diameter at an inlet side of the outlet ports 22 is made
smaller than that at an outlet side. The valve casing 21 has the spool space (the
valve sliding space) 39, in which the spool valve 23 is to slide. An inner flow
passage (a first inner flow passage: a fluid space) 43 is formed in the right hand
portion (in the drawing) of the spool space 39, wherein the first inner flow passage
43 is communicated with the inlet port 41 through an inner flow passage (a second
inner flow passage: a through-hole) 42 formed in the inside of the spool valve 23.
The inner flow passage 43 also functions as a spring space for accommodating the
return spring 25.
The spool valve 23 of the electromagnetic valve 6 is a
spool type valve of a sleeve shape having the inner flow passage (the through-hole)
42 in the longitudinal (axial) direction in the inside thereof. The spool valve
23 has sliding portions 44 at its outer periphery, which are in contact with the
inner surface of the spool space 39 in a sliding manner. The spool valve 23 controls
the opening area of the fuel passage at the outlet ports 22 of the valve casing
21, so that the fuel flow amount (fuel suction amount) of the fuel fed into the
two pressurizing chambers through the two suction valves is controlled. The spool
valve 23 has a function of a valve, as an original function of the valve body, for
changing the opening area of the fuel passage at the outlet ports 22 with the sliding
movement in the spool space 39 of the valve casing 21, and also has a function of
an armature (the armature portion 27) for forming the magnetic circuit. The spool
valve 23 is made of soft magnetic material, such as pure iron or low carbon steel,
in order that the spool valve 23 performs the function of the armature. The soft
magnetic material can not be heat-treated, such as a heat treatment of hardening,
because a magnetic property may be deteriorated. It is required, however, to improve
wear resistance and surface hardness, in order that the spool valve 23 performs
its function of the valve. Therefore, a hardening coating of nickel-phosphor plating
is formed at the outer surface of the sliding portion 44 of the spool valve 23.
An initial position of the spool valve 23 is defined by
a ring shaped stopper 50 press inserted into an inner surface of a left hand portion
(in the drawing) of the valve casing 21. And the spool valve 23 is always biased
by the return spring 25 provided in the inner flow passage 43. Accordingly, the
spool valve 23 is limited in its sliding movement of the valve closing direction
of the spool valve 23, at a position of the stopper 50 at which a forward (left-hand)
end is brought into contact. The cylindrical armature portion 27 is integrally formed
at the right hand end (in the drawing) of the spool valve 23, wherein the armature
portion 27 opposes to the stator portion 26 of the valve casing 21 with a predetermined
gap. The inner flow passage (the through-hole) 42 is formed in the inside of the
spool valve 23, so that the inlet port 41 of the valve casing 21 is communicated
with the inner flow passage (the fluid space) 43. An inner diameter of the right
hand portion of the inner flow passage 42 is made smaller than that of the left
hand portion. The spool valve 23 is easily moved by allowing the fuel to flow into
or to flow out of the inner flow passage 43, when the spool valve 23 is moved in
the longitudinal direction.
A circular flow amount adjusting groove 45 (a circular
flow passage: a first circular groove), a circular centering groove 46 (a second
circular groove), and multiple (two or three) circular oil grooves 47a, 47b are
formed at an outer peripheral surface of the sliding portion 44 of the spool valve
23. The sliding portion 44 comprises multiple sliding surface portions (first sliding
surface portions 23a and second sliding surface portions 23b). The flow amount adjusting
groove 45 is positioned between neighboring first and second sliding surface portions
23a, 23b, and is formed by making an outer diameter of the spool valve 23 smaller
than that of the sliding portion 44. The flow amount adjusting groove 45 is formed
in a circumferential direction at the sliding portion 44, and is communicated with
the inner flow passage (the through-hole) 42 through first communication ports 48,
a flow passage diameter of which is smaller than that of the flow amount adjusting
groove 45. Four communication ports 48 are opened to the flow amount adjusting groove
45. The centering groove 46 is positioned between the neighboring second sliding
surface portions 23b, and is formed by making the outer diameter of the spool valve
23 smaller that that of the sliding portion 44. The centering groove 46 is shallower
than the flow amount adjusting groove 45, and is formed in the circumferential direction
of the sliding portion 44 as being longer in the longitudinal direction than the
flow amount adjusting groove 45 (See Fig. 2). The centering groove 46 is communicated
with the inner flow passage (the through-hole) 42 through a second communication
port 49, a flow passage diameter of which is smaller than that of the centering
groove 46. Two communication ports 49 are opened to the centering groove 46.
The multiple oil grooves 47a and 47b are circumferential
grooves for forming oil films between the inner surface of the spool space 39 of
the valve casing 21 and the outer surface of the sliding portion 44 of the spool
valve 23, wherein fuel flows into the grooves 47a and 47b from a gap between the
spool space 39 of the valve casing 21 and the left hand portion in the drawing (forward
end) or the right hand portion in the drawing (backward end) of the spool valve
23. With respect to the sliding portions 44 of the spool valve 23 according to the
present embodiment, a sealing portion is formed between the outer surface of the
spool valve 23 (the sliding surface portion 23a of the right-hand side, and the
sliding surface portion 23b of the left-hand side) and the inner surface of the
spool space 39 of the valve casing 21, so that the flow amount adjusting groove
45 is liquid tightly sealed from the centering groove 46. Furthermore, with respect
to the sliding portions 44 of the spool valve 23, a predetermined clearance, which
is necessary for the spool valve 23 to slide in the spool space 39 of the valve
casing 21, is formed between the outer surface of the multiple first and second
sliding surface portions 23a and 23b and the inner surface of the spool space 39
of the valve casing 21.
The ECU 10 is formed as a micro computer of a well known
structure, which comprises CPU for performing a control process and calculation
process, a memory device (memories, such as ROM, RAM etc.) for storing various programs
and data, an input circuit, an output circuit, a battery circuit, an injector driving
circuit (EDU), a pump driving circuit, a depressurizing valve driving circuit, and
so on. Sensor signals from various sensors are inputted into the micro computer
after they are converted from analog to digital signals by A/D converters. The ECU
10 is further formed, as shown in Fig. 1, so that a voltage signal from a fuel pressure
sensor (a fuel pressure detecting means) 55 and sensor signals from the other various
sensors are inputted into the micro computer of the ECU 10, after they are converted
from analog to digital signals by A/D converters.
The ECU 10 is formed in such a manner that the ECU electronically
controls, for example, the electromagnetic valves 4 of the injectors 3 and the electromagnetic
valve 6 of the supply pump 5, based on the control program or a control logic stored
in the memory device, when an engine key is returned to an IG position and an ignition
switch (not shown) is turned on (IG·ON) after the engine is cranked up. Connected
to the micro computer are a crank angle sensor 51 for detecting a rotational angle
of an engine crank shaft, an acceleration sensor 52 for detecting an opening degree
of an acceleration pedal (ACCP), an engine cooling water sensor 53 for detecting
temperature of engine cooling water (THW), a fuel temperature sensor 54 for detecting
temperature of the fuel (THF) on a pump suction side flowing into the supply pump
5, and so on. The ECU 10 operates as a rotational speed detecting means for detecting
the engine rotational speed (NE) by measuring interval times of NE signal pulses
outputted from the crank angle sensor 51.
(Operation of the first Embodiment)
An operation of the supply pump 5 of the embodiment is
explained with reference to Fig. 1 to Fig. 3.
When the pump driving shaft (the drive shaft or cam shaft)
of the supply pump 5 is driven to rotate by the crankshaft of the engine via the
belt, two plungers reciprocate on the sliding surfaces of the cylinder head. When
one of the plungers, for example, positioned at the top dead center is moved down,
the pressure in the pressurizing chamber is decreased to open the suction valve,
so that the fuel is fed into the pressurizing chamber from the feed pump through
the fuel pooling portion, the inlet port 41 of the electromagnetic valve 6, the
inner flow passage 42, the first communication ports 48, the flow amount adjusting
groove 45, the outlet ports 22, the fuel passage line and the suction valve. When
the plunger is upwardly moved again after having reached at the bottom dead center,
the pressure in the pressurizing chamber is increased, the suction valve is closed,
and the pressure in the pressurizing chamber is further increased. When the pressure
in the pressurizing chamber exceeds the valve opening value of the discharge valve,
the discharge valve is opened, so that the high pressure fuel is supplied from the
pressurizing chamber to the common rail 1 through the fuel supply pipe 12.
The fuel in the other pressurizing chamber is likewise
supplied to the common rail 1 through the discharge valve and the fuel supply pipe
12, since the other plunger is reciprocated between the top dead center and the
bottom dead center as in the same manner to the above plunger. As above, the supply
pump 5 is so arranged that a cycle of the suction stroke and discharge stroke is
carried out twice for each rotation of the pump driving shaft. The high pressure
fuel accumulated in the common rail 1 can be injected into the combustion chambers
of the respective engine cylinders at a predetermined timing, by driving the electromagnetic
valve 4 of the injector 3 at desired fuel injection timing.
The discharge amount of the fuel discharge from the supply
pump 5 to the common rail 1 through the discharge valve and the fuel supply pipe
12 is controlled in such a manner that the pump driving current to be applied to
the solenoid coil 29 of the electromagnetic valve 6 is controlled by the ECU 10,
a stroke amount of the spool valve 23 of the electromagnetic valve 6, namely the
opening area of the fuel passage of the fuel suction passage line, in particular,
the opening area of the fuel passage of the outlet ports 22 is thereby controlled,
and finally the suction amount of the fuel fed from the feed pump into the pressurizing
chamber through the suction valve is controlled.
Namely, the suction amount of the fuel fed into the two
pressurizing chambers is controlled in proportion to the value of the pump driving
current to be applied to the solenoid coil 29 through the pump driving circuit,
as a result the ECU 10 electronically controls the electromagnetic valve 6 by a
pump driving signal in accordance with the engine rotational speed (NE), the acceleration
opening degree (ACCP), the command fuel injection amount (Q), and so on. Accordingly,
it becomes possible to control the common rail pressure as the vehicle driver demands
(for example, the pedal stroke: the acceleration opening degree), by changing the
discharge amount of the fuel discharged from the pressurizing chambers, wherein
the common rail pressure corresponds to the injection pressure of the fuel to be
injected into the combustion chambers of the respective engine cylinders through
the injection ports of the injectors mounted to the respective engine cylinders.
(Effects of the first Embodiment)
As explained above, according to the supply pump 5 of this
embodiment, the circular flow amount adjusting groove (the first circular groove)
45 for controlling the suction amount of the fuel, the circular centering groove
(the second circular groove) 46 for centering (the oil pressure centering) the sliding
portion 44 of the spool valve 23 within the spool space (the valve sliding space)
39 of the valve casing 21, and the multiple circular oil grooves 47a and 47b for
forming the oil film between the spool space 39 of the valve casing 21 and the sliding
portion 44 of the spool valve 23 are formed at the outer peripheral surface of the
sliding portion 44 of the spool valve 23. Furthermore, the inner flow passage (the
through-hole) 42 is communicated with flow amount adjusting groove 45 through the
first communication port 48, and the inner flow passage 42 is communicated with
the centering groove 46 through the second communication port 49. And the fuel flowing
from the feed pump into the inner flow passages 42 and 43 through the fuel pooling
portion and the inlet port (the first fluid port) 41 is supplied to the centering
groove 46 through the second communication port 49, and furthermore supplied to
the multiple circular oil grooves 47b through the gap formed between the spool space
39 of the valve casing 21 and the sliding portion 44 of the spool valve 23.
Accordingly, the oil pressure centering (the fluid pressure
centering) of the spool valve 23 is carried out within the spool space 39 of the
valve casing 21, by supplying the fuel into the gap between the inner surface of
the spool space 39 of the valve casing 21 and the outer peripheral surface of the
sliding portion 44 of the spool valve 23. As a result, the spool valve 23 can be
smoothly moved in the stroke direction within the spool space 39 of the valve casing
21, when the electric current is supplied to the solenoid coil 29, and thereby the
reliability as well as the response can be enhanced. Namely, the engine performance
of the acceleration response and so on can be stabilized, because the control response
of the spool 23 of the electromagnetic valve 6 is improved.
Furthermore, the fuel is supplied into the gap between
the inner surface of the spool space 39 of the valve casing 21 and the outer peripheral
surface of the sliding portion 44 of the spool valve 23, so that the oil film is
formed between the inner surface of the spool space 39 of the valve casing 21 and
the outer peripheral surface of the sliding portion 44 of the spool valve 23. The
lubrication performance is thereby increased, and the durability of the electromagnetic
valve 6 is likewise increased, because the sliding portion 44 of the spool valve
23 can be prevented from sticking to the spool space. Furthermore, according to
the present embodiment, the centering groove 46 for centering the sliding portion
44 of the spool valve 23 is formed in the sliding portion 44 of the spool valve
23, namely between the neighboring sliding surface portions 23b. The workability
and productivity can be improved, when compared with a case in which the centering
groove is formed in the inner surface of the spool space 39 of the valve casing
21, because the centering groove 46 can be formed by an outside cutting process
or a groove cutting process at the sliding portion 44 of the spool valve 23.
(Second Embodiment)
Fig. 4 shows a second embodiment of the present invention,
and is a view showing a spool valve 23 of the electromagnetic valve 6 of the supply
pump.
According to the supply pump 5 of this embodiment, as in
the same manner to the first embodiment, the circular flow amount adjusting groove
45, the circular centering groove 46 and multiple circular oil grooves 47a and 47b
are formed at the sliding portion 44 of the spool valve 23 for controlling the suction
amount of the fuel with sliding movement of the spool valve in the spool space 39
of the valve casing 21 of the electromagnetic valve 6. According to the embodiment,
the first communication port 48 for communicating the inner flow passage (the through-hole)
42 with the flow amount adjusting groove 45 is formed, whereas the second communication
port 49 for communicating the inner flow passage (the through-hole) 42 with the
centering groove 46 is not formed. Instead of the second communication port 49,
multiple communicating grooves 63b are formed at outer peripheries of the second
sliding surface portions 23b, so that the fuel is supplied to the centering groove
46 as well as the multiple circular oil grooves 47b from the inlet port 41 of the
valve casing 21 or from the inner flow passage (the fluid space) 43 through the
gap between the inner surface of the spool space 39 and the outer peripheral surface
of the sliding portion 44 of the spool valve 23.
The communicating grooves 63b of more than 4 grooves are
formed at the outer peripheries of the second sliding surface portions 23b at equal
intervals, for example by the outside cutting process. In this case, as in the same
manner to the first embodiment, the durability of the electromagnetic valve 6 can
be likewise increased, because the lubrication performance is increased and the
sliding portion of the spool valve 23 is prevented from sticking to the spool space.
Furthermore, the reliability as well as the response of the electromagnetic valve
6 can be increased, since the centering of the spool valve 23 in the spool space
39 can be realized and thereby the spool valve 23 can be smoothly moved in its stroke
direction in the spool space 39 when the electric current is supplied to the solenoid
coil 29.
(Third Embodiment)
Figs. 5A and 5B show a third embodiment of the present
invention, and views showing a spool valve 23 of the electromagnetic valve of the
supply pump.
According to the embodiment, communication ports 64, which
communicate two centering grooves 46 respectively formed between the first and second
sliding surface portions 23a and 23b of the sliding portion 44 with the inner flow
passage (the through-hole) 42, are formed in the spool valve 23 to penetrate the
sleeve portion thereof from its inner surface to its outer surface and formed at
such positions eccentric to a perpendicular line of a center line for the spool
valve 23. Namely, a center line of the respective second communication ports 64
is displaced from a radial line extending in a radial direction of the spool valve
23, when viewed on a plane perpendicular to the axial line of the spool valve 23.
With such an arrangement, the spool valve 23 will be rotated
in the spool space 39 with respect to its center line, due to a differential pressure
of the fuel supplied to the centering grooves 46 from the inner flow passage (the
through-hole) 42 through the communication ports 64. Accordingly, it is suppressed
that the inner surface of the spool space (the valve sliding space) 39 and the sliding
portions 44 of the spool valve 23 are always exposed to the wear-out at the same
positions, and the wear resistance as well as durability of the electromagnetic
valve 6 can be enhanced.
(Fourth Embodiment)
A fourth embodiment will be explained with reference to
Figs. 6 to 8.
As shown in Fig. 8, the first communication port 48 extends
in a direction perpendicular to an axial line 23a of the spool valve 23, and an
axial line 48a of the first communication port 48 is displaced from the axial line
23a of the spool valve 23 when viewed in the direction of the axial line 23a of
the spool valve 23. In other words, when a line 48b, which passes over the axial
line 23a of the spool valve 23 and which is parallel to the axial line 48a of the
communication port 48, is regarded as a reference line, the first communication
port 48 is formed at a position offset from the reference line 48b by an offset
amount "Lt" (hereinafter, referred to as a communication port offset amount). Although
one communication port 48 is shown in the embodiment, multiple-ports can be formed.
According to the above structure of the spool valve 23,
a rotational force "Frot" (hereinafter, referred to as a spool valve rotational
force) is generated at the spool valve 23 by the fuel flowing out of the first communication
port 48, and the spool valve 23 is rotated in the spool space 39 around the axial
line 23a. Accordingly, the contacting surface between the spool valve 23 and the
valve casing 21 is changed, and it is suppressed that the inner surface of the spool
space 39 and the outer surface of the sliding portions 44 of the spool valve 23
may wear out always at the same portions. The partial wear of the spool valve 23
and the valve casing 21 can be prevented, the wear of the spool valve 23 and the
valve casing 21 can be decreased, and a bad operation of the spool valve 23 can
be prevented. As a result, the increase of harmful exhaust gas, the deterioration
of the drivability, the increase of engine noise and so on, which may be caused
by the deterioration of controllability of fuel pressure in the common rail and
a variation of fuel injection amount, can be suppressed.
Then, a design method in a hardware aspect is explained
to generate the rotation of the spool valve 23 at a desired condition.
In this specification, a frictional force generated between
the valve casing 21 and the spool valve 23 when the spool valve 23 is rotated is
referred to as a rotational friction force "Ffr", a pressure at an upstream side
of the first communication port 48 is referred to as an upstream pressure "Pfeed",
a pressure at a downstream side of the first communication port 48 is referred to
as a downstream pressure "Psuc", and a differential pressure is referred to as a
pressure loss "Pfeed - Psuc".
As shown in Fig. 9, the spool valve rotational force "Frot"
becomes larger, as the pressure loss "Pfeed - Psuc" becomes larger, and the spool
valve rotational force "Frot" becomes larger, as the communication port offset amount
"Lt" becomes larger. Therefore, when the pressure loss "Pfeed - Psuc" and the communication
port offset amount "Lt" are designed as such values, which are included in a rotation
enabling range indicated by hatched lines, the spool valve rotational force "Frot"
becomes larger than the rotational friction force "Ffr", so that the spool valve
23 can be rotated.
Furthermore, as shown in Fig. 10, an amount "Qscv" of the
fuel (hereinafter, referred to as fuel suction amount) fed into the pressurizing
chamber through the suction flow control valve 6 is increased, as the pump driving
current "i" is increased. A fuel suction amount, which is necessary for rotating
the spool valve 23, is referred to as a rotation starting fuel suction amount "Qt",
a fuel suction amount "Qscv", which is obtained when the pump driving current "i"
is at its predetermined value "it", is referred to as a predetermined fuel suction
amount "Qscv·it". In the case that "Qt = Qscv·it", the spool valve 23
can be rotated in a range of "Qt ≥ Qscv·it", namely in the range indicated
by a hatched area in Fig. 10.
An engine operational range, in which "Qt ≥ Qscv·it"
is realized, corresponds to areas hatched in Fig. 11, namely an area of an engine
starting period and an area of a high load operation. A vertical axis of Fig. 11
is an amount of the fuel to be injected into the combustion chambers of the respective
engine cylinders, namely a fuel injection amount "Qinj", while a horizontal axis
of Fig. 11 is the engine rotational speed "Ne".
When designing a hardware, the rotation starting fuel suction
amount "Qt" is decided at first. The engine operational range, in which the spool
valve 23 can be rotated, namely the hatched areas shown in Fig. 11 can be decided,
by deciding the rotation starting fuel suction amount "Qt".
Then, a total passage area "St" of the first communication
port 48 (hereinafter, referred to as a communication port total passage area), and
the communication port offset amount "Lt" will be provisionally decided. In the
case that the first communication port 48 comprises multiple ports, a sum of the
passage areas of all communication ports 48 corresponds to the communication port
total passage area "St".
Then, the spool valve rotational force "Frot" is calculated
based on the provisionally decided communication port total passage area "St" and
the communication port offset amount "Lt", etc. In the case that the calculated
spool valve rotational force "Frot" is larger than the rotational friction force
"Ffr", the fuel suction amount "Qscv" is calculated based on the provisionally decided
communication port total passage area "St" and the pressure loss "Pfeed - Psuc",
etc.
When the calculated fuel suction amount "Qscv" is larger
than the initially decided rotation starting fuel suction amount "Qt", the spool
valve 23 can be rotated. Therefore, the provisionally decided communication port
total passage area "St" and the communication port offset amount "Lt" are defined
as the final values.
On the other hand, when the calculated fuel suction amount
"Qscv" is smaller than the initially decided rotation starting fuel suction amount
"Qt", the spool valve 23 can not be rotated. Therefore, the calculation will be
repeated until the calculated fuel suction amount "Qscv" becomes larger than the
initially decided rotation starting fuel suction amount "Qt". More specifically,
the fuel suction amount "Qscv" is made larger by increasing the communication port
total passage area "St".
As a result of designing the hardware as above, the spool
valve 23 can be surely rotated at the engine starting period and at the high load
operation of the engine.
Now, an operational control for rotating the spool valve
23 at a desired range is explained. As described above, the spool valve 23 can be
surely rotated at the engine starting period and at the high load operation of the
engine. The operational control described below is to rotate the spool valve 23
when a certain condition is met at a range, other than the engine starting period
and the high load operation of the engine.
Fig. 12 is a flow chart of a program performed by the CPU
of the ECU 10. An operational control for rotating the spool valve 23 is carried
out at steps A30 to S50, when a vehicle has run by a predetermined distance (YES
at a step S10) after the operation of rotating the spool valve 23 had been carried
out in the previous operation at which the certain condition had been met, and when
a rotation starting condition is satisfied (YES at a step S20). The rotation starting
condition is regarded as "satisfied", when both of the engine rotational speed "Ne"
and the fuel injection amount "Qinj" are within predetermined ranges.
Then, the fuel suction amount "Qscv" is calculated (at
the step S30). When the calculated fuel suction amount "Qscv" is smaller than the
rotation starting fuel suction amount "Qt" (NO at the step S40), the spool valve
23 can not be rotated. Therefore, the fuel suction amount "Qscv" is increased by
increasing the fuel injection pressure "Pc" (at the step S50). When the fuel injection
pressure "Pc" is increased, an amount of leaked fuel from the injectors 3 as well
as an amount of leaked fuel from the supply pump 5 is increased. The fuel suction
amount "Qscv" is increased by the amount of increased leaked fuel, even when the
fuel injection amount "Qinj" is the same.
After the fuel injection pressure "Pc" is increased at
the step S50, the fuel suction amount "Qscv" is calculated again at the step S50,
and the calculated fuel suction amount "Qscv" is compared with the rotation starting
fuel suction amount "Qt" at the step S40. The steps S 30 to S50 are repeated until
the calculated fuel suction amount "Qscv" becomes larger than the rotation starting
fuel suction amount "Qt".
According to the above operational control, the spool valve
23 can be surely rotated when the certain condition is met at the range, other than
the engine starting period and the high load operation of the engine.
In the case that the certain condition is met, the fuel
injection pressure "Pc" becomes higher and thereby a fuel injection ratio is increased.
As a result, the engine noise may be increased. Accordingly, it is desirable to
set, as the condition for starting the rotation at the step S20, the range of the
engine rotational speed "Ne" and the fuel injection amount "Qinj" at such a range,
in which the increase of the engine noise may not cause a problem.
(Comparative example)
A comparative example which does not fall within the invention
will be explained with reference to Figs. 13A, 13B, 14A and 14B.
The electromagnetic valve 6 comprises, as shown in Fig.
13A, the valve casing 21 of the sleeve shape fixed to the pump housing, the spool
valve 23 for controlling the opening area of the fuel passage of the outlet port
(the fluid port) 22 formed in the valve casing 21 and opening in the radial direction
perpendicular to the axial direction of the valve casing, the linear solenoid actuator
24 for driving the spool valve 23 in the valve closing direction, and the return
spring 25 for biasing the spool valve 23 in the valve opening direction.
As understood when comparing Fig. 13A with Fig. 2 (the
first embodiment), the present example differs from the first embodiment in that
the electromagnetic valve 6 of Fig. 13A is the normally opened type valve, whereas
the electromagnetic valve 6 of Fig. 2 is the normally closed type valve. Although
the second circular groove (the centering groove) 46 and the second communication
port 49 of the first embodiment are not provided in the present example, they can
be also formed in the electromagnetic valve of this example.
According to the electromagnetic valve 6 of the example,
multiple (four in the example) longitudinal grooves (recesses) 61 are formed at
the second sliding surface portions 23b of the spool valve 23, as shown in Figs.
13A to 14B, wherein the longitudinal grooves 61 straightly extend in the axial direction
of the spool valve 23. Accordingly, multiple (four in the example) foreign material
exhausting passages 62 are formed between the inner surface of the valve sliding
space 39 of the valve casing 21 and the sliding portion of the spool valve 23, in
order to exhaust the foreign materials or the wear-out powder from the fluid space
(the inner space) 43 to the outside of the electromagnetic valve 6 through the communication
ports 48 (or the flow amount adjusting groove 45) and the outlet ports 22.
The foreign material exhausting passages 62 are fluid passages,
which straightly extend from the fluid space 43 toward the communication ports 48
(and the flow amount adjusting groove 45) in parallel to the axial line of the spool
valve 23, which bypass the through-hole 42 formed in the inside of the spool valve
23, and which communicate the fluid space 43 with the communication ports 48 (or
the flow amount adjusting groove 45). The multiple longitudinal grooves 61 are formed
at the outer surface of the spool valve 23, at a predetermined interval (equal intervals;
90 degrees) of the circumferential direction of the spool valve 23. A depth of the
longitudinal grooves 61 may be deeper than or shallower than, or equal to, that
of the multiple circular oil grooves 47b. The multiple circular oil grooves 47a,
47b may be eliminated.
According to the above structure, the spool valve 23 of
the present embodiment is moved within the valve sliding space 39 of the valve casing
21 in its axial direction, and the opening area of the outlet ports 22 of the valve
casing 21, namely the overlapped area (the communication area) between the outlet
ports 22 of the valve casing 21 and the communication ports 48 (or the flow amount
adjusting groove 45) is changed, so that fuel flow amount (the fuel suction amount)
to be fed into the two pressurizing chambers through the two suction valves can
be controlled. A centering groove (46) can be formed at the sliding portion of the
spool valve 23, as in the first embodiment.
(Effects of the example)
The fuel flows from the outside of the electromagnetic
valve 6 into the through-hole 42 of the inside of the spool valve 23 through the
inlet port 41 of the valve casing 21, then the fuel flows from the through-hole
into the communication ports 48, and flows out of the electromagnetic valve 6 from
the outlet ports 22. Accordingly, most of the fuel in the fluid space 43 communicated
with the through-hole 42 may stay in the fluid space 43. Therefore, once the foreign
materials having flown into the electromagnetic valve 6 along with the fuel, or
the wear-out powder generated by the sliding movement between the sliding portion
of the spool valve 23 and the sliding surface of the valve casing 21 flows into
the fluid space 43, they may easily stay in the fluid space 43.
According to the electromagnetic valve 6 of the present
example, however, multiple longitudinal grooves 61 are formed at the outer peripheral
surface of the spool valve 23, and multiple foreign material exhausting passages
62 are formed between the inner surface of the valve casing 21 and the outer surface
of the spool valve 23. A differential pressure is generated between the fluid pressure
at the side of the outlet ports and the communication ports and the fluid pressure
in the spring space, when the electromagnetic valve 6 is opened, and the fluid flows
through the through-hole 42 and the communication ports 48 of the spool valve 23,
and the outlet ports 22 of the valve casing 21. Namely, since the fluid flow speed
at the communication ports 48 and the outlet ports 22 is high, while the fluid flow
speed of the fuel staying in the fluid space 43 is low, the fuel pressure in the
fluid space 43 becomes higher than the fuel pressure at the outlet ports 22 or the
communication ports 48. By use of such differential pressure, the foreign materials
having flown into the fluid space 43 or the wear-out powder staying in the fluid
space 43 are moved with the fuel to the communication ports 48 through the foreign
material exhausting passages 62 and exhausted to the outside of the electromagnetic
valve 6 through the outlet ports 22.
As the foreign materials and the wear-out powder can be
actively exhausted from the inside to the outside of the electromagnetic valve 6,
the problem to be caused by the foreign materials or the wear-out powder can be
prevented. For example, the foreign materials or the wear-out powder can be prevented
from breaking into the gap between the sliding surface of the spool valve 23 and
the sliding surface of the valve sliding space 39. Furthermore, the foreign materials
or the wear-out powder can be prevented from sticking to the sliding surface of
the spool valve 23, to the sliding surface of the valve sliding space 39, or to
both of them as bridging the gap between the sliding surfaces of the spool valve
23 and the valve sliding space 39. Accordingly, the bad sliding movement of the
spool valve 23 can be prevented, because the sliding resistance of the spool valve
23 with respect to the valve casing 21 is decreased, and the sliding performance
of the spool valve 23 is thereby improved. As a result, an increase of the engine
output and improvement of the emission control can be achieved, because the control
characteristic of the pump discharge amount can be optimized with respect to the
pump driving current to be applied to the solenoid coil 29 of the electromagnetic
valve 6.
(Comparative example)
Fig. 15 shows a comparative example which does not fall
within the invention, and is a view showing a spool valve of the electromagnetic
valve to be assembled into the supply pump.
Multiple (four in the example) communication passages 63
are formed in the inside of the spool valve 23, wherein the communication passages
63 straightly extend from the spring space 43 toward the communication ports 48
(or the flow amount adjusting groove 45) and the communication passages 63 are inclined
against the axial line of the spool valve 23. The communication passages 63 function
as the foreign material exhausting passages for exhausting the foreign materials
or the wear-out powder from the spring space (fluid space) 43 to the outside of
the electromagnetic valve 6 by use of the differential pressure. Accordingly, the
present example has the same effect to the previous example.
The outlet port 22 can be used as the inlet port, whereas
the inlet port 41 is used as the outlet port. And the fuel pooling portion, into
which the fuel is supplied from the feed pump, can be formed at an upstream side
of the inlet port, and the latter half of the suction passage line communicating
with the pressurizing chambers through the suction valves can be provided at a downstream
side of the outlet port. The pump driving signal of pulse shape to be outputted
to the pump driving circuit as well as the pump driving current to be applied to
the solenoid coil 29 of the electromagnetic valve 6 can be feedback controlled based
on a PID control (or a PI control), in order that the common rail pressure (PC)
detected by the fuel pressure sensor 55 may reach at the target common rail pressure
(the target fuel pressure: PFIN), which is determined in accordance with the operational
condition of the engine (for example, the engine rotational speed (NE), the command
fuel injection amount (Q), and so on). A control accuracy of the fuel injection
amount can be thereby increased.
The pump driving signal of the pulse shape is preferably
controlled by a duty control (DUTY). Namely, a ratio of ON and OFF of the pump driving
signal (a current supply ratio: a duty ratio) for a unit time is adjusted based
on a differential pressure (&Dgr;P) between the common rail pressure (PC) and
the target common rail pressure (PFIN), so that an average current value of the
pump driving current to be applied to the solenoid coil 29 of the electromagnetic
valve 6 is controlled. The change of the opening area of the flow passage at the
outlet port 22 is thereby controlled by the duty control. With such control, a digital
control of a high accuracy can be possible, and a control response (a pressure control
response), a follow-up control performance as well as pressure stability can be
improved with respect to the common rail pressure (PC) against the target common
rail pressure (PFIN). The command fuel injection amount (Q) can be obtained based
on a base amount of the fuel injection decided by the engine rotational speed (NE)
and the acceleration opening degree (ACCP), wherein the base amount is corrected
by a correction amount which is calculated from the engine cooling water temperature
(THW), the fuel temperature and so on. The command fuel injection amount (Q) can
be obtained based on a driver demand torque calculated from a pedal stroke of the
vehicle driver.
According to the above embodiments and examples, the supply
pump 5 is used, wherein the pump has two plungers and pressurizing chambers, which
are arranged at a diametrical direction to a rotational center axis (an axial direction)
of the pump driving shaft (the cam shaft or the drive shaft), or the supply pump
5 is used, wherein the pump has more than three plungers and pressurizing chambers,
which are arranged at equal intervals in the circumferential direction of the pump
driving shaft (the cam shaft or the drive shaft). However, such a supply pump (a
high pressure supply pump) can be used, wherein the pump has multiple plungers arranged
at predetermined intervals (for example, equal intervals) in a direction of a rotational
center axis (an axial direction) of the pump driving shaft (the cam shaft or the
drive shaft). Furthermore, the valve casing 21 commonly has the cylinder function
and the stator function. However, a stator core having only the stator function
can be assembled to the valve casing 21 having only the cylinder function. Furthermore,
the electromagnetic valve may be used as the electromagnetic valve 4 of the injector
3, or as an electromagnetic flow amount control valve for controlling the flow amount
of liquid, such as oils of other lubricating oil, working oil, water, and so on,
or the flow amount of gas, such as air, exhaust gas, re-circulated exhaust gas,
and so on.
Furthermore, an electric type flow control valve, which
is driven by an electric motor to open or close its valve, can be used instead of
the electromagnetic valve. The present invention can be applied to a fluid passage
switching valve, or a fluid passage opening-closing valve.
According to the above previous example, the multiple longitudinal
grooves (the recesses) 61 are formed at the outer peripheral surface of the spool
valve 23, and thereby the multiple foreign material exhausting passages 62 are formed
between the inner surface of the valve sliding space 39 and the outer surface of
the spool valve 23. However, multiple longitudinal grooves (recesses) can be formed
at the inner surface of the valve sliding space 39 of the valve casing 21, and thereby
multiple foreign material exhausting passages may be formed between the inner surface
of the valve sliding space 39 and the outer surface of the spool valve 23.
Furthermore, multiple longitudinal grooves (recesses) can
be formed at both of the inner surface of the valve sliding space 39 and the outer
surface of spool valve 23, to form the multiple foreign material exhausting passages
between the inner surface of the valve sliding space 39 and the outer surface of
spool valve 23. The number of the longitudinal grooves (recesses) 61 and the number
of the foreign material exhausting passages 62 can be respectively one, two or three,
or more than five. Furthermore, the foreign material exhausting passages 62 can
be formed as being slightly curved as an arc from the spring space 43 to the communication
ports 48 (and the flow amount adjusting groove 45).
According to the present example, the multiple communication
passages 63 are formed in the inside of the spool valve 23, and the communication
passages 63 are used as the foreign material exhausting passages. However, multiple
communication passages can be formed in the inside of the valve casing 21, and such
communication passages can be used as the foreign material exhausting passages.
The number of the communication passages (the foreign material exhausting passages)
can be one, two or three, or more than five. Furthermore, the communication passages
63 can be formed as being slightly curved as an arc from the spring space 43 to
the communication ports 48 (and the flow amount adjusting groove 45).
A spool valve (23) is movably provided in a valve sliding
space (39) of a valve casing (21). The spool valve (23) has a through-hole (42)
formed in the inside thereof, and a communication port (48) formed in the spool
valve (23) is operatively communicated with a fluid port (22) for controlling an
opening area of the fluid port (22) by moving within the valve sliding space (39).
Multiple circular oil grooves (47a, 47b) are formed at an outer peripheral surface
of the spool valve (23), into which high pressure fluid is supplied so that the
spool valve (23) can be smoothly moved in the valve sliding space (39).
