Driving unit with an electric driving motor and a worm gear conn

Details Driving unit with an electric driving motor and a worm gear conn Driving unit with an electric driving motor and a worm gear conn

1996-08-23

1999-03-23

LaBalle, Clayton

Electrical generator or motor structure

Dynamoelectric

Rotary

310 83, 74425, H02K 7116, H02K 516, F16H 116

Patent

active

058864377

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

Drive units of the generic type in question are used to operate accessory devices in motor vehicles. When used for instance in motor vehicle windshield wiper systems, the drive shaft, formed by the armature shaft and the worm shaft, are subjected to an alternating axial load during operation, which varies from 0--when the wiper blades are at the turning points--to a maximum--when the wiper blades are being accelerated on leaving the turning points or being slowed down on approaching them. This axial load induced into the drive shaft by the worm gear leads to undesired knocking noises in the drive unit, if the drive shaft has longitudinal play between an axial stop toward the motor and an axial stop toward the gear.
For long-term elimination of this drive shaft longitudinal play, in a commercially available drive unit a threaded bore has been disposed on the side toward the worm shaft, penetrating the unit housing in the extension of the drive shaft axis of rotation, and a threaded pin is rotated in this bore. The threaded pin has a central blind bore, open toward the drive shaft, in such a helical compression spring is disposed that presses with prestressing against a mushroom-shaped stop placed on the face end of the shaft toward it. The prestressing of the helical compression spring, which belongs to the spring means, must be greater than the maximum axial load acting on the drive shaft, which load, because of the existing worm pitch direction, is always oriented toward the free end of the worm shaft portion of the drive shaft. This known type of eliminating drive shaft longitudinal play is cost-intensive, because of the disposition of the threaded bore in the unit housing. The known version also requires at least one manual and hence expensive assembly step.


SUMMARY OF THE INVENTION

In the drive unit according to the invention, which according has the characteristics of the body of the main claim, the threaded bore can be omitted. Neither a mushroom-shaped stop nor the threaded pin are required either, because their functions are taken over by the leaf-spring-like spring element. Furthermore, the fixation of the spring element in the housing can be designed to be performed by robot, thus further reducing production costs for the drive unit.
If in a further feature of the invention the end edges of the spring element are fixed on opposed housing shoulders, and furthermore the spacing between the housing shoulders is less than the spacing between the two edges of the spring element, the spring element necessarily tenses upon assembly, if it is inserted between the shoulders of the housing, toward the face end of the drive shaft on the gear side.
An especially simple assembly suitable for robots is obtained if the housing shoulders are disposed on inner walls of the housing, and on the side remote from the worm shaft, in terms of the spring element, at least one of the housing walls is provided with a setback, so that in this region the spacing between the inner housing walls is greater than the spacing between the two end edges of the spring element.
Suitably, the spring element in plan view has the shape essentially of a rectangle, whose end edges are formed on the shorter sides of the rectangle, and the two end portions, with the end edges of the rectangle, are bent outward from the plane of the middle portion to the same side by an angle of at least 30.degree.. Such an embodiment of the spring element makes it easier to install in the unit housing.
To stabilize the spring element, its peripheral regions forming the two long sides of the rectangle are bent by approximately 90.degree. to the same side as are the end portions along with the end edges.
Advantageously, the two peripheral regions are narrower than the two end portions. If furthermore, the cutting edge, located on the side of the worm shaft, of the end edge is provided with a ridge, then this cutting edge digs into the housing shoulders in such a way that separate fastening means for the spring element can be o

REFERENCES:
patent: 3170739 (1965-02-01), Lange
patent: 4050130 (1977-09-01), Pitner
patent: 4742726 (1988-05-01), Adam et al.
patent: 4993277 (1991-02-01), Adam et al.
patent: 5169245 (1992-12-01), Harada et al.
patent: 5212999 (1993-05-01), Kitada

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