The invention describes an injection valve according to the preamble
of claim 1.
Modern injection valves have a very dynamic closing and opening function. This
is necessary for attaining a precise starting point of the injection and a precise
ending point of the injection. However, the fast opening and closing function results
in a high speed of the closing member that pushes against a valve seat for closing
the valve. To reduce the speed of the needle high forces are necessary which are
induced in the valve seat and in the sealing faces of the needle. The high forces
cause a relatively high abrasion on the sealing face and on the valve seat.
To reduce the bouncing effect, the state of art proposes an anti-bounce
disc, which reduces the needle speed when approaching the valve seat. The anti-bounce
disc, however, has the disadvantage that it is within the hydraulic flow path of
the injected fuel and causes a hydraulic resistance to the fuel.
On the other hand it is also known to use a valve seat made of an
elastomere to attain a soft impact of the needle on the valve seat.
It is a task of the present invention to provide an injection valve
with a needle and a valve seat, whereby the bouncing of the needle on the valve
seat is dampened.
The task of the invention is attained by an injection valve according
to claim 1. One advantage of the inventive injection valve is that the needle can
be slided in a holding element and between the holding element and the needle a
damping spring is arranged. The needle slides against the tension of the damping
spring when the needle is pushed onto the valve seat. Therefore the force with which
the needle is pushed onto the valve seat is reduced because only the mass of the
needle is pushed onto the valve seat and not the mass of the holding element. Furthermore
the tension of the damping spring afterwards holds the needle on the valve seat
in a closed position. The needle does not lift off the valve seat in the closed
In a preferred embodiment of the invention, the holding element is
shaped as a sleeve and the needle is guided within the sleeve. The spring is arranged
between a wall of the sleeve and the needle, biasing the needle in direction of
the valve seat. The shape of the sleeve has the advantage that the needle can be
guided precisely along a longitudinal axis of the injection valve and it is enough
space for providing a relatively strong spring.
In a further preferred embodiment of the invention, the sleeve is
realized as a stepped sleeve with two different diameters. The needle is guided
in the region with the smaller diameter. In the region with the greater diameter
a rim of the needle is arranged. The rim of the needle has a greater diameter than
the smaller diameter of the sleeve and the spring is arranged between the rim of
the needle and an opposite side wall of the sleeve.
Brief description of the drawings.
- Fig. 1 depicts a longitudinal sectional view of an injector according to an
embodiment of the present invention, and
- Fig. 2 depicts a detailed view of the needle assembly.
Before one embodiment of the inventions is explained in detail, it
is to be understood that the invention is not limited in this application to the
details of construction and the arrangements of the components set forth in the
following description or illustrated in the drawings. The invention is capable of
other embodiments and of being practiced or being carried out in various ways.
A preferred embodiment of a fuel injector according to the present
invention will now be described with reference to the drawings. Fig. 1 shows a longitudinal
view of a fuel injector 1 used in a motor vehicle engine. The fuel injector is basically
symmetrical to a central symmetry axis.
The injection valve 1 includes a valve body 2. Inside the valve body
2, an orifice plate 3 is arranged adjacent to a lower end of the valve body 2. The
orifice plate 3 includes an orifice 4 in a central position. The orifice in the
orifice plate 3 provides fluid communication between the fuel injector 1 and a combustion
chamber of a motor vehicle engine. In the orifice plate 3 a metallic valve seat
5 is provided. At an inner side of the orifice plate 3, the valve seat 5 surrounds
the orifice 4, the purpose of which will be described below.
The valve body 2 also houses a needle assembly. The needle assembly
comprises an armature 7 that is connected by a needle 6 with a closing member 8.
The closing member 8 is a tip of the needle 6 that is dedicated to the valve seat
5. The armature 7 can be moved within the valve body 2 along a longitudinal axis
of the fuel injector 1. Depending on the position of the armature 7, the closing
member 8 is in a closed position biased against the valve seat 5, closing the orifice
4 preventing a fuel injection. In an opening position, the needle 6 is lift off
the valve seat 5.
The armature 7 is shaped as a sleeve with an upper end ring face 9
and a central bore 10. The closing member 8 is appropriately sized to be received
in the valve seat 5. In conjunction, the needle 6 and the valve seat 5 operate as
a fuel valve that selectively opens and closes the injected valve 1.
The valve body 2 houses an inlet tube 18. The inlet tube 18 is typically
made from metal and includes a lower end ring face 13. The end ring face 13 is adjacent
to the upper end ring face 9 of the armature 7. The inlet tube 18 also includes
a bore that houses an adjustment sleeve 14 and a portion of a spring 15. The spring
15 is constrained between the lower end of the adjustment sleeve 14 and a seat inside
the bore 10 of the armature 7. The adjustment sleeve 14 is adjustably fixed relative
to the inlet tube 18 and biases the spring 15 against the seat in the armature bore
10, thereby biasing the needle 6 into a first position, wherein the closing member
8 rests in the valve seat 5 and blocks fluid communication between the fuel injector
1 and the combustion chamber. While in the closed position, the upper end ring face
9 of the armature 7 is arranged at a distance from the lower end ring face 13 of
the inlet tube 18 creating a gap of approximately 20 microns between the armature
7 and the inlet tube 18.
The injection valve 1 further includes an electromagnetic coil assembly
16 that encircles a portion of the inlet tube 18 and is housed within a metallic
housing 17. The electromagnetic coil assembly 16 can be selectively charged to create
a magnetic field that attracts the armature 7 towards the lower end ring face 13
of the inlet tube 18 into a second position. The biasing force of the spring 15
is overcome in such a way that the closing member 8 is raised from the valve seat
5, allowing fuel to flow through the orifice of the orifice plate 3 into the combustion
chamber. While in the open position, the upper end ring face 9 of the armature 7
contacts the lower end ring face 13 of the inlet tube 18. The needle 6 remains in
the open position until the charge is removed from the electromagnetic coil assembly
16 at which point the spring 15 biases the valve member 6 back into the first position.
At an upper end of the inlet tube 18 a fuel filter 19 is arranged.
A fuel passage way 20 leads through the fuel filter 19, the bore of the adjustment
sleeve 14, the inlet tube 18, the bore of the armature 7 and holes 11 of the holding
element to an injection chamber 28 that is arranged between the valve body 2 and
the needle 6.
The electromagnetic coil assembly 16 is selectively charged via an
external power lead that applies electricity to the electromagnetic coil assembly
16. The power lead is connected to the coil assembly 16 via a connector terminal
21 that is mounted on an outer surface of the inlet tube 18 via a clip portion.
The connector terminal 21 is electrically connected, via soldering or any other
suitable method, to terminals of the coil assembly 16.
The fuel injector 1 also includes a second housing 22 that surrounds
portions with the inlet tube 18, clip connector 21, metallic housing 17 and valve
body 2. The second housing 22 is preferably plastic and is preferably molded over
the injection valve 1.
Figure 2 depicts in greater detail a sectional view of the lower part
of the fuel injection valve of Figure 1. The spring 15 is biased against a rim 35
that is arranged at the lower end of the sleeve part of the armature 7. A second
sleeve 32 is fixed to the sleeve part of the armature 7. The second sleeve 32 extends
into a third sleeve 33. The diameter of the second sleeve 32 is larger than the
diameter of the third sleeve 33. The needle 6 is guided by the third sleeve 33 and
extends in the second sleeve 32 with a plate 34. The plate 34 has the shape of a
circular plate, the diameter of which is larger than the diameter of the third sleeve
33 and smaller than the diameter of the second sleeve 32. Between the plate 34 and
the rim 35 of the armature 7 a second spring 36 is arranged. The second spring 36
biases the needle 6 towards the valve seat 5. Between the needle 6 and the valve
body 2 a fuel chamber 28 is arranged that is connected with the fuel passage way.
The second sleeve 32 comprises the holes 11 and provides a fluid connection between
the fuel chamber 28 and the inlet tube 18. The bore 10 of the armature 7 is connected
with the inner region second sleeve 32, in which the second spring 36 is arranged.
During the injector standard operation, the armature 7 is pulled towards
the lower end ring face 13 of the support tube 12. If the injection is completed,
the coil assembly 16 is deenergized and the armature 7 is biased down in direction
of the valve seat 5 by the spring 15 to close the orifice 4. The needle 6 is also
moved to the valve seat 5. At the end of the closing travel, the needle 6 contacts
the valve seat 5 with its sealing face. The contact between the needle 6 and the
valve seat 6 generates a bouncing effect that the invention intends to eliminate.
The invention provides a non-rigid link between the armature 7 and the needle 6.
The link is established by a slideable guiding connection between the armature 7
and the needle 6 and the second spring 36 that is arranged between the armature
7 and the needle 6. When the needle is pushed onto the valve seat 5 by closing the
injection valve, the needle 6 is moved upwards relative to the armature 1 against
the tension of the second spring 36. In this way the impulse of the armature 7 and
the second and third sleeve 32, 33 is not transferred to the valve seat 5. Therefore
the impulse by means of which the needle 6 is pushed onto the valve seat 5 is reduced.
The tension of the second spring 36 holds the needle 6 in the closed position after
pushing the needle 6 onto the valve seat by the armature 7.