Electric motor, especially for a windshield wiping system of a m

Details Electric motor, especially for a windshield wiping system of a m Electric motor, especially for a windshield wiping system of a m

1993-03-18

1995-01-31

Skudy, R.

Electrical generator or motor structure

Dynamoelectric

Rotary

310 75A, 310 97, 310 98, 1525030, 267155, H02K 710

Patent

active

053861655

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND

The invention refers to an electric motor, especially to a small-size motor, adapted to drive at least one wiper arm of a windshield wiping system of a motor vehicle, with a rotatably mounted armature spindle, wherein one of the spindle ends is axially acted upon by means of a spring loaded prestressing member. The spring has the form of a spring winding with one spring leg retained by a housing, while the other spring leg is connected with the prestressing member which is rotatably mounted in this housing.
An electric motor of this type is known from the German specification DE-OS 20 52 541 which provides a prestressing member having an adjusting screw, the inner end of which abuts directly on the driving shaft of the motor and which is loaded by means of the spring in the tightening direction. Due to the advancement of the adjusting screw, there is no axial play. Because the screw may play in the internal screw thread, an impeded motion results which can be compensated only by a strong spring.


SUMMARY OF THE INVENTION

Consequently, the object of the invention is to improve upon an electric motor to provide relative ease of motion of the armature spindle while eliminating the axial play automatically.
In order to achieve this object, it is suggested according to the invention that the electric motor be designed with a prestressing member having an eccentric portion with an axis of rotating which runs transversely to the longitudinal axis of the armature spindle and a surface which abuts the end of the armature spindle. The design of the eccentric achieves a large axial movement by a means of a relatively small angle of rotation. Because the axial play of such an electric motor changes by relatively small amounts only, the prestressing member need not be turned considerably. The eccentricity of the eccentric is chosen in such a way that a complete self-locking device is achieved. Because the armature spindle is loaded in axial direction, the occurring friction losses have to be taken into consideration when dimensioning the spring. However, structural effort is not considerably augmented compared to the traditional construction.
A further embodiment of the invention provides that the axis of rotation of the eccentric runs vertically to the geometric axis of the armature spindle. In this way the eccentric essentially always makes contact at the area of the geometric axis of the armature spindle.
An especially preferred variation of the embodiment results from the preassembly of the spring with an integral unit including the eccentric and the pivot or axis of rotation of the eccentric, the spring being already pretensioned to the necessary extent before the assembly of the whole unit. However, as the spring tension is communicated towards the outside, this unit can be assembled especially easily and without problems. At an appropriate moment the spring or its one spring leg respectively, is released, whereby the spring power can be effective, and the eccentric is pressed against the end of the armature spindle. Of course, this moment and the local conditions have to be chosen in the way that the released spring leg does not make any uncontrolled movement.
A further embodiment of the invention provides a contact surface on the housing which allows the spring leg to be removed from its support axially to the direction of rotation of the eccentric facilitating the assembly and the release of the spring leg automatically during the assembly at the right moment. The spring leg, preferably protruding from the eccentric in the radial direction, is moved to abut on the contact surface disposed in its range of motion during the assembly operation of the unit. The relative movement of the unit towards the one captive spring leg which now is inevitable to occur, effects the release of the spring leg from its support edge or surface. If the assembly of this unit is performed while the cover is put on, the cover prevents the released spring leg, which is under corresponding tension, from making an uncontro

REFERENCES:
patent: 2311121 (1943-02-01), Nette et al.
patent: 2979352 (1961-04-01), Anderson
patent: 3128400 (1964-04-01), Hornschuch et al.
patent: 4227104 (1980-10-01), Hamman

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