The present invention relates to a gearbox configuration of an industrial
In i. e. industrial robots with six axes, which have a vertically
articulated arm mounted on a stand (fig. 2), the driving means of the arm are placed
near the centre of rotation of the arm. The remaining three driving means are arranged
closer to the working tool of the robot. The aim is inter alia to give the industrial
robot a compact construction and to contribute to keeping the weight of the arm
low. Accordingly, the three driving means are arranged in the lower part of the
robot towards the stand and generally comprise electrical motors. Each motor drives
one shaft each for driving of the different degrees of freedom of the robot through
gear and transmission. The gear generally comprises a toothed transmission gear
enclosed in a gear housing filled with cooling and lubricant medium, which usually
consist of oil.
The patent document US 4 671 732 discloses an industrial robot with
six axes having three driving means 21, 22 and 23 arranged in the lower part of
the robot near the stand. The three driving means are identical, which simplifies
the design and possible repair of the robot. The three driving units are completely
separated from each other regarding accommodation for lubricant. The robot is designed
to tolerate high requirements for accuracy despite wear of the parts included.
In operation the industrial robot is generally part of a production
line, which can include e. g. a press. The robot supplies the press with moulding
blanks that come to the robot over some type of conveyor.
The technical development aims at faster presses and also faster conveyors.
This has entailed that the speed of the robot has had to increase concurrently
with the development. The speed of driving and translation has increased approximately
fivefold in the last fifteen years. This has led to that the enclosed toothed transmission
gears under high bearing pressure must be driven with ever higher velocity, which
requires increasing effect supply and gives increasing generation of heat in the
gears, which increases the friction heat on the teeth.
For the purpose of absorbing and disposing heat from the teeth a cooling
and lubricant medium encloses the gear. Problems arise when the driving and translation
speed of the robot and the heat generation are so high that the cooling medium
cannot cool the gear. Then, the flanks of the gear run the risk of being damaged
from the high temperature. Thus, too high temperatures drastically decrease the
lifetime of the gear. The risk of frequent shut downs and expensive repairs of
the robot increases.
The three lower driving units in the robot are not driven equally
and the corresponding gears are heated unequally. This results in an uneven distribution
of the generated heat, which leads to different local thermal expansions in the
material / metal of the robot, which in turn leads to deformities in the construction
of the robot. The accuracy of the robot is decreased and the robot cannot fulfil
the requirements called for by the user of the robot.
Another problem that arises at high temperatures is that the accuracy
of the work of the robot is increased. In a robot with six axes the driving unit,
which drives the rotational movement of the robot around the vertical axis A (fig.
2) and its gear, is charged the most and must be driven at very high speed. There,
the temperature becomes very high and causes temperature differences to occur in
different parts of the cooling and lubricant medium in the gearbox of the motor.
This entails in turn means that the turn plate around which the robot is constructed
and which secures the rotation around axis A is heated unevenly, which has a negative
influence on the accuracy.
Traditionally the above problems are solved through arranging cooling
flanges on the outside of the gearboxes. Even an external cooler e. g. a cooling
fan can help to decrease the temperature. All such solutions are bulky and insufficient
and they are not suitable for an industrial robot, which is part of a production
Another problem is that three completely separated gearboxes require
filling and discharge of cooling and lubricant medium and also aeration in three
different places. This takes time, is dirty to handle and leads to unwanted or
unnecessarily long shutdowns.
In production of industrial robots the need arises for a robot which
can make fast speed with maintained accuracy. Furthermore, it should be easy to
give the robot the necessary operation service.
The robot in the cited American patent document cannot fulfil this
Further industrial robots, having a common gear housing, are known
from EP 0 322 670 A and US 4 586 868 A.
SUMMARY OF THE INVENTION
In producing industrial robots a manipulator is equipped with i.e.
control system and also motor driven gears and optional appurtenant transmissions.
The development of robots has the aim of creating a faster robot, which corresponds
to the possibilities of the surrounding equipment and the requirements of the customer.
The aim is also to simplify and shorten the time for operative service of the robot.
Accordingly, the object of the present invention is to achieve an
industrial robot including at least two motor driven gears, where the gears are
arranged so that the requirement of sufficient cooling is fulfilled at the same
time as the robot reaches provided requirements of accuracy and the time for service
This object is solved by the features of claims 1(apparatus) and 4
A gear box requires an opening for filling and a separate opening
for discharging cooling and lubricant medium and also magnetic stoppers to keep
the medium, e. g. the oil, free from wear particles. During operation an overpressure
occurs in the gear unit e. g. because of heat expansion of the cooling and lubricant
medium and therefore the gearbox often is provided with a type of breathing stopper.
It is also included in the scope of invention to design the gear housing
with only one opening for common filling of lubricant oil and moreover only one
discharge place for the oil. Aeration also can occur jointly through one or several
DESCRIPTION OF THE DRAWING
The invention will be explained in greater detail by describing an
example of an embodiment with reference to the enclosed drawing, where:
DESCRIPTION OF EMBODIMENTS
- Fig. 1 shows a gearbox configuration arranged in an industrial robot in accordance
with the present invention,
- Fig. 2 shows an industrial robot with six axes arranged with three driving units
in the lower part of the robot.
In an industrial robot comprising a manipulator with a control system
(fig. 2) electrically driven gears are arranged in the lower part of the robot
at the stand to give the movements of the robot arm. Each electrical motor transmits
rotational movements to a toothed transmission gear, which usually drives a transmission
that transmits movements to the robot arm. In fig. 2, a six axes industrial robot
1 with a stand 2 is shown, and also the thereon rotationally mounted robot foot
3. A first driving unit 4 (fig. 1) is arranged to rotate the robot around the vertical
axis A through a first toothed transmission gear 5. A second driving unit 6 is
arranged to rotate the robot arm around a horizontal axis B through a second toothed
gear transmission 7. A third driving unit 8 is arranged to rotate the robot arm
around the horizontal axis C through a third toothed transmission gear 9. The first
5, second 7 and third gear 9 are arranged in a common gear housing 10. The gear
housing 10 is cast in one piece, and because of technical reasons of design and
strength the housing is subdivided into several inner compartments 10a, 10b and
10c, which are connected with passage channels. The gear housing 10 is filled with
cooling and lubricant medium 12, which surrounds the gears 5, 7 and 9.
During operation of the robot the first, second and third motor and
their gears are working in different degrees to make the robot perform the desired
Through driving of the different gears, the surrounding cooling and
lubricant medium 12 is caused to circulate. The cooling and lubricant medium absorbs
heat from the teeth and through the circulation in the common gear housing and
any temperature differences in the medium 12 are levelled out, and a uniform temperature
is obtained in the whole housing.
To facilitate / speed up the circulation of the agent 12, an external
device 13 can be connected to the gear housing viz. a pump (not shown).