GB1562425A - Screen wiper drive units for motor vehicles - Google Patents

Description

(54) IMPROVEMENTS IN SCREEN WIPER DRIVE UNITS FOR MOTOR VEHICLES (71) We, ROBERT BOSCH GmbH, a Germany Company of 50 Postfach, 7000 Stuttgart 1, Germany, do hereby declare the invention, for which we pray that a ;)atent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a motor vehicle screen wiper drive unit comprising a drive motor and reduction gearing, preferably worm gearing, the driven wheel of which has on one side face thereof a crank driving pin, eccentric to the axis of rotation of the wheel, which pin is engaged by a crank belonging to an oscillatory gearing.

In a known drive unit of this type, the eccentric pin rotates in an annular path centred on the axis of the driven wheel and the centre of this side face of the driven wheel has to remain completely unobstructed, so that the crank can move freely. For this reason, the crank has to be mounted on the side face of the driven wheel remote from the wheel bearing, which involves a complex design and comparatively expensive construction because, for example, the means of control for the sweep or end stop of the wipers cannot be arranged directly on the driven wheel. Furthermore, the eccentric pin and the driven wheel must be made from strong materials, owing to the high alternating loads on the pin during operation, which may involve relatively high manufacturing costs.

It is an aim of the invention to develop a wiper drive unit in which the disadvantages mentioned are avoided.

In accordance with the invention there is provided a motor vehicle screen wiper drive unit comprising a drive motor and reduction gearing having a driven wheel provided on one side face thereof with a bearing pin by which the driven wheel is journalled and provided on the same side face with a crank driving pin which is eccentric to the rotary axis of said wheel and which engages a crank of an oscillatory gear arrangement, the diameter of the crank pin being greater than twice the distance between the crank pin axis and the axis of said driven wheel and the bearing pin projecting from the free end of the crank pin.

It is possible to arrange the crank driving pin on the same side face of the driven wheel as the bearing pin of the driven wheel, because the bearing pin of the driven wheel may be situated within the outer contour of the crank driving pin. Consequently the other side face of the driven wheel is left completely free and may thus be used to carry means of control for the sweep or end stop of the wipers. i;Toreover, the crank driving pin in the wiper drive unit in accordance with the invention may have a large cross-sectional area which is a substantial fraction of that of the driven wheel itself, permitting material of lesser strength than has been customary to be used in the manufacture of the pin. Hence it is possible, if desired, to manufacture the driven wheel integrally with the crank driving pin, for example, of an inexpensive plastics material.

A simple limitation of the axial play of the driven wheel can be achieved in a wiper drive unit in accordance with the invention, by providing an adjustment means at the side of the driven wheel remote from the crank driving pin. This is possible because no crank is arranged on the side of the wheel remote from the bearing thereof.

Preferably the crank driving pin is made from a self-lubricating plastics material.

Conveniently, the outer contour of the crank driving pin is provided with resilient means which deflect inwards during fitting of the crank onto said pin, and then engwe with the crank. Thanks to this, the length of the crank driving pin may be limited to the thickness of the crank and additional components such as locking washers arc not required.

The invention is described further, by way of example, with reference to the accompanying drawings, wherein: Fig. 1 is a partial section through a wiper drive unit in accordance wish the invention; Fig. 2 is a similar sectiun, taken in a transverse plane through the drive v nit shown in Fig. 1 Fig. 3 is an enlarged representation of a portion of Fig. 1; showing the driven wheel of the reduction gearing and the crank which is operatively connected to the driven wheel; and fig. 4 is a section along the line IV-IV in Fig. 3.

The drive unit 10 in accordance with the invention comprises an electric motor 11 and a gear train 12 (Fig. 2). The gear train 12 is housed in a gear box 13 flanged to the electric motor 11 (Fig. 1). The gear train 12 forms reduction gearing, pieferably in the form of a worm gear arrangement, the driven gear of which is the wormwheel 14. The driven wheel 14 of the reduction gearing however forms at the same time a crank wheel for an oscillatory gearing. The oscillatory gearing comprises a crank 15, which is operatively connected to the driven wheel 14, said crank 15 having a tooth segment 16 which engages with a pinion 17. To ensure that the tooth segment 16 and the pinion 17 are permanently in engagement, these two elements of the gearing are secured in relation to one another by a strap 18. The driven wheel 14 of the reduction gearing has on its side face 14a a crank driving pin 20, which is eccentric to the axis of rotation 19 (Fig. 3) of the wheel 14 and which is encircled by a hub 21 of the crank 15. The crank driving pin 20, which is circumscribed and defined by an annular recess formed n the side face 14a of the wheel 14, is provided on its Outer contour with resilient, hookshaped detents 22 which are joined integrally to the crank pin 20 and which, on fitting of the crank 15 onto the eccentric pin 20, deflect inwards, and then engage with and secure the crank 15. The diameter v f the crank pin 20, joined integrally to the driven wheel 14, is more than twice as large as the amount of eccentricity 23 of the crank pin 20 on the driven wheel 14 of the reduction gearing. Thanks to this, it is possible to arrange a bearing for the driven wheel 14 on the same side face of the driven wheel 14 as the crank pin 20, which itself is preferably made of a selflubricating plastics material. As can be seen in particular from Fig. 3, a bearing pin 24 of the driven wheel 14 is arranged on the side face of the crank pin 20 and projects from the pin 20 within the circumference of said pin. Thus the crank 15 can be driven without the bearing pin 24 representing an obstacle to the crank move ment. Consequently the side face 25 of the driven wheel 14 remote from the bearing pin 24 is kept completely free of bearing elements, so that an element in the form of an adjusting screw 26 can be arranged there to compensate for or to limit the axial play of the driven wheel 14 (Fig. 2). Furthermore, this side face 25 of the driven wheel 14 can be provided with a control pIate 27 which co-operates with switching contacts 29 arranged on a lid 28 of the gear box 13. The switching contacts 29 may serve, for example, for the control of the sweep of the wiper blades.

WHAT WE CLAIM IS:- 1. A motor vehicle screen wiper drive unit comprising a drive motor and reduc- tion gearing having a driven wheel provided on one side face thereof with a bearing pin by which the driven wheel is journalled and provided on the same side face with a crank driving pin which is eccentric to the rotary axis of said wheel and which engages a crank of an oscillatory gear arrangement, the diameter of the crank pin being greater thn twice the distance between the crank pin axis and the axis of said driven wheel and the bearing pin projecting from the free end of the crank pin.

2. A wiper drive unit as claimed in claim 1, in which the bearing pin for the driven wheel of the reduction gearing projects from said side face of said wheel within the circumference of said driving pin.

3. A wiper drive unit as claimed in Claim 1 or 2, in which means are provided at the side of the driven wheel remote from the crank driving pin for limiting axial play of the driven wheel.

4. A wiper drive unit as claimed in any of Claims 1 to 3, in which the crank driving pin is integral with the driven wheel of the reduction gear.

5. A wiper drive unit as claimed in Claim 4, in which said one side face of said drive wheel has an annular recess formed therein and the portion of said side face isolated by said recess constitutes said crank driving pin.

6. A wiper drive unit as claimed in any of claims 1 to 5, in which the crank driving pin is made of a plastics material.

7. A wiper drive unit as claimed in claim 6 wherein the plastics material is self lubricating.

8. A wiper drive unit as claimed in any of claims 1 to 7, in which the periphery of the crank driving pin is provided with resilient means arranged to deflect inwards during fitting of the crank onto said crank pin, and- then to secure the crank.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. Fig. 1 is a partial section through a wiper drive unit in accordance wish the invention; Fig. 2 is a similar sectiun, taken in a transverse plane through the drive v nit shown in Fig. 1 Fig. 3 is an enlarged representation of a portion of Fig. 1; showing the driven wheel of the reduction gearing and the crank which is operatively connected to the driven wheel; and fig. 4 is a section along the line IV-IV in Fig. 3. The drive unit 10 in accordance with the invention comprises an electric motor 11 and a gear train 12 (Fig. 2). The gear train 12 is housed in a gear box 13 flanged to the electric motor 11 (Fig. 1). The gear train 12 forms reduction gearing, pieferably in the form of a worm gear arrangement, the driven gear of which is the wormwheel 14. The driven wheel 14 of the reduction gearing however forms at the same time a crank wheel for an oscillatory gearing. The oscillatory gearing comprises a crank 15, which is operatively connected to the driven wheel 14, said crank 15 having a tooth segment 16 which engages with a pinion 17. To ensure that the tooth segment 16 and the pinion 17 are permanently in engagement, these two elements of the gearing are secured in relation to one another by a strap 18. The driven wheel 14 of the reduction gearing has on its side face 14a a crank driving pin 20, which is eccentric to the axis of rotation 19 (Fig. 3) of the wheel 14 and which is encircled by a hub 21 of the crank 15. The crank driving pin 20, which is circumscribed and defined by an annular recess formed n the side face 14a of the wheel 14, is provided on its Outer contour with resilient, hookshaped detents 22 which are joined integrally to the crank pin 20 and which, on fitting of the crank 15 onto the eccentric pin 20, deflect inwards, and then engage with and secure the crank 15. The diameter v f the crank pin 20, joined integrally to the driven wheel 14, is more than twice as large as the amount of eccentricity 23 of the crank pin 20 on the driven wheel 14 of the reduction gearing. Thanks to this, it is possible to arrange a bearing for the driven wheel 14 on the same side face of the driven wheel 14 as the crank pin 20, which itself is preferably made of a selflubricating plastics material. As can be seen in particular from Fig. 3, a bearing pin 24 of the driven wheel 14 is arranged on the side face of the crank pin 20 and projects from the pin 20 within the circumference of said pin. Thus the crank 15 can be driven without the bearing pin 24 representing an obstacle to the crank move ment. Consequently the side face 25 of the driven wheel 14 remote from the bearing pin 24 is kept completely free of bearing elements, so that an element in the form of an adjusting screw 26 can be arranged there to compensate for or to limit the axial play of the driven wheel 14 (Fig. 2). Furthermore, this side face 25 of the driven wheel 14 can be provided with a control pIate 27 which co-operates with switching contacts 29 arranged on a lid 28 of the gear box 13. The switching contacts 29 may serve, for example, for the control of the sweep of the wiper blades. WHAT WE CLAIM IS:-

1. A motor vehicle screen wiper drive unit comprising a drive motor and reduc- tion gearing having a driven wheel provided on one side face thereof with a bearing pin by which the driven wheel is journalled and provided on the same side face with a crank driving pin which is eccentric to the rotary axis of said wheel and which engages a crank of an oscillatory gear arrangement, the diameter of the crank pin being greater thn twice the distance between the crank pin axis and the axis of said driven wheel and the bearing pin projecting from the free end of the crank pin.

2. A wiper drive unit as claimed in claim 1, in which the bearing pin for the driven wheel of the reduction gearing projects from said side face of said wheel within the circumference of said driving pin.

3. A wiper drive unit as claimed in Claim 1 or 2, in which means are provided at the side of the driven wheel remote from the crank driving pin for limiting axial play of the driven wheel.

4. A wiper drive unit as claimed in any of Claims 1 to 3, in which the crank driving pin is integral with the driven wheel of the reduction gear.

5. A wiper drive unit as claimed in Claim 4, in which said one side face of said drive wheel has an annular recess formed therein and the portion of said side face isolated by said recess constitutes said crank driving pin.

6. A wiper drive unit as claimed in any of claims 1 to 5, in which the crank driving pin is made of a plastics material.

7. A wiper drive unit as claimed in claim 6 wherein the plastics material is self lubricating.

8. A wiper drive unit as claimed in any of claims 1 to 7, in which the periphery of the crank driving pin is provided with resilient means arranged to deflect inwards during fitting of the crank onto said crank pin, and- then to secure the crank.

9. A motor vehicle screen wiper drive

unit constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.