GB1582550A

GB1582550A - Rotary switch and electric motor drive device for at least one load

Info

Publication number: GB1582550A
Application number: GB20118/77A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1976-05-14
Filing date: 1977-05-13
Publication date: 1981-01-07
Also published as: FR2351532A1; FR2351532B1; DE2621370A1; IT1084640B; SE7705564L; DE2621370B2; DE2621370C3

Description

(54) ROTARY SWITCH AND ELECTRIC MOTOR DRIVE DEVICE FOR AT LEAST ONE LOAD (71) We, ROBERT BOSCH GMBH.

a German Company, of Postfach 50, 7 Stuttgart 1, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent 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: The invention relates to a device for driving at least one electrical load, for example, a screen cleaning device in a motor vehicle, the device having a rotary switch which is driven rotatably by a drive motor and co-operates with a switching contact located in the operating circuit of the load.

In a known screen-wiper device for motor vehicle screens, a driven contact disc is disposed as a switching member and controls the wiper movement of the wiper blades in cooperation with sliding contacts disposed in its contact deck. The known rotary switch is bulky in construction, relatively expensive and is exposed during operation to specific wear and tear.

In accordance with the invention, there is provided a device for driving a load, the device comprising an electric motor, a stepdown transmission whose input is the motor output and whose output is connectible to the load and includes a member provided with a toothed ring, and a rotary switch which comprises a switching cam connected to a drive pinion with which the toothed ring cooperates, and first and second contact springs which co-operate with a fixed countercontact and which are respectively raised therefrom by corresponding axially spaced cam lobes of said switching cam, the first contact spring lying in a holding circuit for said motor to ensure that the load stops at a predetermined position when an operating circuit for setting the motor in motion is interrupted, the second contact spring serving to control an operating circuit for a second electric motor for driving a second load.

Preferably the first and second contact springs cooperate with a common fixed counter-contact.

Advantageously, the rotary switch is in a circuit arrangement for operating first and second electrical screen-wiper drive motors of a motor vehicle screen-wiper arrangement, said circuit arrangement further comprising an operating switch in the operating circuit for the first motor for setting the latter in motion, and a further switch lying in a holding circuit for the second motor and operated by the latter, the further switch being adapted to switch the second motor off after the respective operating circuit has been interrupted by the lifting of the second contact spring of the rotary switch from the counter-contact and when the respective wiper has reached a predetermined parked position.

Thus, in its preferred aspect, the present invention represents an improvement in the circuit arrangement described and claimed in Patent Application No. 12361/77 (Serial No. 1 574 650).

As a switching member, therefore, a cam is sufficient which only has a small cam lobe for raising the contact spring from its countercontact. Such a cam may be manufactured particularly easily, for example injection moulded from synthetic material. Also, in the device according to the invention, the sliding contacts pressed on contact decks are omitted so that the wear inevitable with this no longer occurs.

To obtain an intermitent drive of the rotary switch giving clearly defined switching positions, in a further development of the invention the toothed ring has preferably two singly disposed teeth.

Advantageously, the teeth of the toothed ring lie, relative to the toothed ring centre, at an acute angle to one another. By suitably turning the rotary switch it is then possible for the pinion, in a position of rest, to lie within this acute angle, the tooth just having passed the pinion having stopped the driving motor. The other tooth is already positioned, however, shortly in front of the pinion so that immediately after reconnection of the drive there is a switching movement and therefore a switching pulse by means of which the holding circuit for the drive motor is closed or another load is switched on.

If a pendulum gear is disposed after the transmission gear, for example, for driving a wiper shaft, the crank wheel is advantageously used as a carrier for the gear edge.

In order to avoid automatic adjustment of the turning pin, whose pinion meshes with the gear ring having the separate teeth for only a short time, in a further development of the invention a frame-fixed, springily deflectable safety element engages between the teeth of the pinion of the turning pin, said element being preferably a stop cam moulded on a housing which surrounds the transmission gear.

The invention is described further, by way of example, with reference to the accompany ing drawings, wherein: Fig. 1 is a circuit diagram of the device according to the invention and various loads driven by the device, Fig. 2 is a perspective diagram, to a larger scale, of a rotary switch of the device according to the invention, Fig. 3 is a partial view of a drive unit for a wiper shaft incorporated in the device according to the invention, Fig. 4 is a crank wheel belonging to the drive unit of Fig. 3 and a pinion of the rotary switch cooperating with a toothed ring of the crank wheel, and Fig. 5 is a plan view of the completely asembled drive unit of Fig. 3.

In the circuit diagram shown in Fig. 1, a first screen-wiper drive motor 10 is opera tionally connected to a first rotary switch 12 by step-down transmission means 11 which may be formed, for example, by a gear. The rotary switch 12 has a cam with two switching cam lobes 13 and 14 which cooperate with associated contact springs 15 and 16 disposed in specific portions of the circuit. The direc tion of rotation of the switching cam 13, 14 is indicated by the arrows 17. A second screen wiper drive motor 20, like the drive motor 10, is operationally connected by step-down transmission means 21 to a rotary switch 22 which similarly has a cam with two switching cam lobes 23 and 24. The cam lobes 23 and 24 of the switch 22 cooperate with contact springs 25 and 26 similarly disposed in specific portions of the circuit. The direction of rota tion of the switching cam 23, 24 is indicated by the arrows 27.

Fig. 2 shows the rotary switch 12 of Fig.

1. The following description of the rotary switch is limited to the switch 12 and its associated contact springs 15 and 16. It is, however, also completely applicable to the rotary switch 22 and its contact springs 25 and 26.

The rotary cam of the rotary switch 12 is journalled in a fixed frame and has thereon the switching cam lobes 13 and 14. The rotary switch also has a frame-fixed support block 30 in which the contact springs 15 and 16 are held. The contact springs 15 and 16 have terminal lugs 31 and 32 for connection of the electrical lines. In the illustrated position, the contact spring 15 rests against a fixed countercontact 33. The switching cam lobes 13 and 14 cooperate with the free ends of the contact spring 15 when the cam is rotated in the direction of the arrow 34. In so doing, the cam lobe 14 raises the contact spring 16 off the counter-contact 33 so that the circuit closed by the contact spring 16 is interrupted.

When the cam lobe 13 runs against the contact spring 15, the latter is also raised off the common counter-contact 33. Seen in the direction of rotation, 34, both switching cam lobes 13 and 14 end at an edge 35 so that in a range of rotation 36 both contact springs 15 and 16 rest against the counter-contact 33.

The switch shown in Figs. 3 to 5, which basically corresponds to the switching device of Fig. 2, is also part of a screen wiper drive whose electrical drive motor 10 (see Fig. 1) has a motor drive shaft provided with a worm 40. The worm 40 meshes with a worm wheel 41 which is journalled in a gear housing 42 to form a step-down transmission. The front face of the worm wheel 41 is provided with a gear wheel 43 which is firmly connected thereto and which meshes with a crank wheel 44 shown in Fig. 4. The crank wheel 44 is journalled by a pin 45 in a bearing bush 46 of the gear housing 42. The crank wheel 44 is also provided with a toothed ring 47 which cooperates with a pinion 48, the front face of said pinion being connected to a rotary cam 49 of a rotary switch corresponding to the switch 12 or 13 of Fig. 1. The toothed ring 47 has only two widely spaced, i.e. separately disposed teeth 50 and 51 which, relative to the toothed ring centre, lie at an acute angle to to one another. Owing to the necessity for clarity in the drawings, Fig. 3 shows only the pinion 48 with its rotary cam 49 but to this belongs the crank wheel 44 shown in Fig.

4 in the position there shown with its pin 45 inserted into the bearing bush 46. In this position there is on each side of the pinion 48 a tooth 50 and 51 of the toothed ring 47.

The pinion 48 therefore lies within the acute angle o: at which the two circumferentially spaced teeth 50 and 51 lie relative to one another. As Fig. 3 shows, in this switching position two contact springs 52 and 53 are raised off their common counter-contact 54 because their free ends rest on switching cam lobes 55 and 56 on the periphery of the cam 49. The cam lobes 55 and 56 correspond to the cam lobes 13 and 14 of the embodiment of rotary switch of Fig. 2. Similarly, the fixed counter-contact 54 of Fig. 3 corresponds to the counter-contact 33 of Fig. 2. However, in the embodiment of Fig. 3, each switching spring 52 and 53 is held in a separate support block 57 and 58. The crank wheel 44 is driven in the direction of the arrow 59 so that the pinion 48 rotates in the direction of the arrow 60. As may also be seen from Figs.

3 and 4, a detent cam 61 which is fixed to the gear housing 42 engages between the teeth of the pinion 48. The detent cam 61 may be springily deflected and serves as a safety element for the pinion 48 to prevent its automatic rotation when its teeth are not meshed with one of the teeth 50 or 51 of the toothed ring 47.

The two drive motors 10 and 20 shown in Fig. 1 are used to separately drive two screen wipers which are to be operated in dependence upon one another. A third drive motor 70 operates a supply pump for washing fluid and is to be controlled in dependence upon the drive motor 20.

In operation, an operating circuit for the motor 10 is closed by means of a key 71 and- the motor 10 starts. At the same time, the rotary switch 12 is rotated in the direction of the arrow 17 so that the camlobes 13 and 14 allow the contact springs 15 and 16, which are spring-biassed in the direction of the arrow 72, to move against their common counter-contact 73. In this switching position, the drive motor 10 is operated through a so-called holding circuit which remains closed until the switching cam lobe 13 raises the contact spring 15 off its counter-contact 73. Simultaneously with closure of the holding circuit by the contact spring 15 and the counter-contact 73, however, an operating circuit 74 for the drive motor 20 is closed, because the contact spring 16, which is likewise spring-biassed in the dircetion of the arrow 72, comes to rest on the fixed countercontact 73. When the drive motor 20 starts, the contact springs 25 and 26, which are also spring-biassed in the direction of the arrow 72, come to rest on their common countercontact 75 so that the contact spring 25 closes a holding circuit for the drive motor 20 and the spring contact 26 closes an operating circuit 76 for the pump motor 70. After aproximately half a revolution of the rotary switches 12 and 22, the switching cam lobes 14 and 24 raise the associated contact springs 16 and 26 off their counter-contacts 73 and 75. As- a result, the operating circuits 74 and 76 for the drive motors 20 and 70 are interrupted. This switching process has no effect upon the drive motor 20 since it is still operated by its own holding circuit while the pump is stopped.

When the switching cam lobes 13 and 23 have completed approximately one revolution, they raise their contact springs 15 and 25 off the counter-contacts 73 and 75 so that the holding circuits of the drive motors 10 and 11 are interrupted. The motors 10 and 20 are stopped and the wiper blades driven by them are located in their parked positions. It is clear therefore that, after the stoppage of the washing fluid supply pump driven by the motor 70, the wiper blades continue to move for a specific amount of time so that the screen being cleaned is wiped dry.

The rotary switches 12 and 22 therefore provide a simple mechanical wiper control to replace the known, relatively expensive and complex electronic controls. The motors therefore have a mechanical control which may have, for example, the following logic in the case of screen wipers for motor vehicle headlamp lenses: a) during the first two wiping operations water is simultaneously applied, b) the subsequent wiping operations then clean the wetted headlamps without water.

The design of the rotary switch is advantageously such that, in the wiper parking position shown in Figs. 3 and 4, the tooth 51 of the toothed ring 47 has effected interruption of the holding circuit during the just effected cooperation with the pinion 48. If the key 71 is then actuated and the motor 10 is therefore switched on, the tooth 50 lying in readiness moves the pinion 48 on one tooth pitch further so that the two contact springs 52 and 53 come to rest against the countercontact 54. Consequently, the key 71 only has to be actuated for a short time because afterwards the drive motors 10 and 20 are operated by means of the holding circuits. The size of the angle depends upon the moment of inertia of the entire motor because renewed switching on of the motor must not occur owing to the running on of the motor after the switching off process.

In the diagram of Fig. 5, a cover part 80 is inserted in the housing 42 of the gear and has a recess 81 through which a boss 82 of the crank wheel 44 projects. A bearing bore 83 in the cover part 80 serves to journal the worm wheel 41 or the gear wheel 43. A gear rack 85 is pivoted to a crankpin 84 on the boss 82 and is received in a guide 86 so as to be held in with a driving pinion 87 which is firmly connected to a wiper shaft 88. In operation, the gear rack 85 is moved by the crankpin 84, which rotates in the direction of the arrow 59 (Fig. 4), back and forth in the direction of the double arrow 89 and acts as a thrust rod so that the wiper shaft 88 is set in a pendulum motion by means of the driving pinion 87.

In the rotary switch 12 as shown in Fig. 2, the drive for the switching cam 13, 14 is com pletely omitted. The mode of operation of the rotary switch 12, however, corresponds exactly to the mode of operation of the rotary cam 49 of Figs. 3 and 4. The parked or deposit position of the screen wipers is therefore attained when the two contact springs 15 and 16 are raised off their counter-contact 33. This occurs when the switching cam lobe 13 raises the contact spring 15 and the switching cam lobe 14 raises the contact spring 16 off the counter-contact 33. When the motor starts and has released (the edge 35) the two contact springs 15 and 16 for cooperation with the counter-contact 33, a first switching position is attained in which, related to Fig. 1, the drive motor 10 is operated through the des cribed holding circuit. This function is taken over by the contact spring 15. The contact spring 16 closes the operating circuit 74 and therefore switches on the second drive motor 20.

The parts designated 52, 53, 54, 55 and 56 of the rotary switch of Figs. 3 to 5 correspond in function to the parts 13 (23), 14 (24), 15 (25), 16 (26), and 73 (75) of the rotary switch of Fig. 1.

Apart from the initially mentioned advan tages of the device according to the invention, its special construction results in a lower switch outlay and simple wiring. Also, the circuit arrangement is unusually economical to assemble.

Naturally, the described circuit arrangement for the device may be used with both the pol arities as shown and with the polarities reversed.

The loads operated by the device according to the invention may alternatively be, for ex ample, driving motors of auxiliary devices in motor vehicles, such as for example sun roofs, window-lifting devices etc.

WHAT WE CLAIM IS: 1. A device for driving a load, the device comprising an electric drive motor, a step down transmission whose input is the motor ouput and whose output is connectible to the load and includes a member provided with a toothed ring, and a rotary switch which comprises a switching cam con nected to a drive pinion with which the toothed ring co-operates, and first and second contact springs which co-operate with a fixed counter-contact and which are respec tively raised therefrom by corresponding axially spaced cam lobes of said switching cam, the first contact spring lying in a holding circuit for said motor to ensure that the load stops at a predetermined position when an operating circuit for setting the motor in motion is interrupted, the second contact spring serving to control an operating circuit for a second electric motor for driving a second load.

2. A device as claimed in claim 1, in which the first and second contact springs co-operate with a common fixed counter-contact.

3. A device as claimed in claim 2, in which the rotary switch is in a circuit arrangement for operating first and second electrical screenwiper drive motors of a motor vehicle screenwiper arrangement, said circuit arrangement further comprising an operating switch in the operating circuit for the first motor for setting the latter in motion, and a further switch lying in a holding circuit for the second motor and operated by the latter, the further switch being adapted to switch the second motor off after the respective operating circuit has been interrupted by the lifting of the second contact spring of the rotary switch from the countercontact and when the respective wiper has reached a predetermined parked position.

4. A device as claimed in claim 3, in which said further switch comprises a second rotary switch adapted to be rotated by the second motor and having a contact spring operated by a respective cam lobe and co-operating with a counter-contact, such contact spring lying in the holding circuit for the second motor.

5. A device as claimed in claim 3 or 4, which includes an operating circuit for a third electric drive motor, e.g. for a fluid pump, such operating circuit containing another switch adapted to be operated by the second motor.

6. A device as claimed in claim 5 when appendant to claim 4, in which said other switch comprises a second contact spring of said second rotary switch, such second contact spring being operated by a respective cam lobe and co-operating with said counter-contact of the second rotary switch.

7. A device as claimed in claim 4 or 6, in which the two rotary switches are of identical construction.

8. A device as claimed in any preceding claim, in which the toothed ring has two circumferentially spaced teeth.

9. A device as claimed in claim 8, in which the teeth are disposed at an acute angle relative to one another with respect to the centre of the toothed ring.

10. A device as claimed in any preceding claim, in which the output of the transmission comprises a crank wheel, to which the toothed ring is attached, and a crank rod pivoted to the crank wheel and adapted to produce a pendulum motion of the load.

11. A device as claimed in claim 10, in which the crank rod comprises a toothed rack meshing with a pinion forming the input to the load.

12. A device as claimed in any preceding claim, in which a deflectable detent engages between the teeth of said drive pinion of the rotary switch to prevent undesired rotation of the latter.

13. A device as claimed in claim 12, in which the detent is fixed to a housing which encloses the transmission.

14. A device for driving a load, constructed and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. occurs when the switching cam lobe 13 raises the contact spring 15 and the switching cam lobe 14 raises the contact spring 16 off the counter-contact 33. When the motor starts and has released (the edge 35) the two contact springs 15 and 16 for cooperation with the counter-contact 33, a first switching position is attained in which, related to Fig. 1, the drive motor 10 is operated through the des cribed holding circuit. This function is taken over by the contact spring 15. The contact spring 16 closes the operating circuit 74 and therefore switches on the second drive motor 20. The parts designated 52, 53, 54, 55 and 56 of the rotary switch of Figs. 3 to 5 correspond in function to the parts 13 (23), 14 (24), 15 (25), 16 (26), and 73 (75) of the rotary switch of Fig. 1. Apart from the initially mentioned advan tages of the device according to the invention, its special construction results in a lower switch outlay and simple wiring. Also, the circuit arrangement is unusually economical to assemble. Naturally, the described circuit arrangement for the device may be used with both the pol arities as shown and with the polarities reversed. The loads operated by the device according to the invention may alternatively be, for ex ample, driving motors of auxiliary devices in motor vehicles, such as for example sun roofs, window-lifting devices etc. WHAT WE CLAIM IS:

1. A device for driving a load, the device comprising an electric drive motor, a step down transmission whose input is the motor ouput and whose output is connectible to the load and includes a member provided with a toothed ring, and a rotary switch which comprises a switching cam con nected to a drive pinion with which the toothed ring co-operates, and first and second contact springs which co-operate with a fixed counter-contact and which are respec tively raised therefrom by corresponding axially spaced cam lobes of said switching cam, the first contact spring lying in a holding circuit for said motor to ensure that the load stops at a predetermined position when an operating circuit for setting the motor in motion is interrupted, the second contact spring serving to control an operating circuit for a second electric motor for driving a second load.