GB1574650A - Control circuits for screen wipers - Google Patents

Description

(54) IMPROVEMENTS IN AND RELATING TO CONTROL CIRCUITS FOR SCREEN WIPERS (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 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 circuits for controlling drive motors of motor vehicle wiper arrangements.

A known circuit has two motors, an electrically determined parked position for each drive motor and a single actuating switch for setting the two drive motors in operation.

Said circuit switches off each drive motor after a predetermined operating programme when the wiper associated with this driving motor is in its parked position.

In known wiper systems of motor vehicles having more than one drive motor, in particular in headlamp wiper systems in which each wiper is driven by its own electric motor, it is necessary for the wipers to operate in synchronism. In many cases it is also required for the windscreen wiper system and headlamp wiper system to operate simultaneously and for them to be switched on by means of a single operating switch.

However, since for reasons of manufacture it is impossible to design all driving motors of the wiper system at reasonable cost in such a manner that they have exactly the same speed, difficulties may arise during disconnection of the motors -- when the relevant wiper moves into a parked position since the motors are electrically interconnected because of the common operating switch. Thus, even if the faster motor is switched off, it will continue to operate through the current path of the slower motor and may, through its - own current path, move the slower motor out of its parked position. In order to avoid such an "eternal" operation relatively expensive decoupling circuits have been disposed in known wiper systems of the type mentioned above. Another suggestion is to provide instead of decoupling circuits blocking diodes which make the motors independent of one another. Another solution to the problem is to use an operating switch in the form of a double maker so that two completely independent circuits for the driving motors may be switched on simultaneously and with a single press-button action. All these solutions are however too expensive.

An aim of the invention is to decouple the motors of the entire wiper system of a motor vehicle using simple means and avoiding the above-mentioned disadvantages.

A switch having a switching member which is rotatably connected to a drive.

motor and cooperates with a switching contact of a wiper control circuit starting from the parked position of the wiper in dependence upon the revolutions completed by the motor, are regularly used as so-called parking or limit switches, the switching member in these switches usually being a contact disc with which several sliding contacts cooperate. The construction of such switches is also expensive and complex.

The present invention provides a circuit arrangement for operating first and second electrical screen-wiper drive motors of a motor vehicle screen wiper arrangement, said circuit arrangement comprising an operating switch in an operating circuit for the first motor for setting the latter in motion, a rotary switch adapted to be rotated by the first motor and having first and second contact springs operated by respective cam lobes and co-operating with a counter-contact, the first contact spring lying in a holding circuit for the first motor and the second contact spring lying in an operating circuit for the second 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 rotary switch, by virtue of its first contact spring, and the further switch being adapted to switch the first and second motors off respectively after said operating circuits have been interrupted respectively by open ins of the operating switch and lifting of said second contact spring, from the counter- con 'tact and when the wipers have respectively reached their parking positions.

Preferably 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 a'nd co-operating with a counter-contact, such contact -s'pring lying in the holding cir cuit for the second motor. The two rotary switches are advantageously of identical construction, in which case the second con tact spring of the second rotary switch can be used in an operating circuit for a third electric drive motor, e.g. for a fluid pump for screen-wash liquid. The third drive motor may, of course alternatively be used to drive a further wiper.

The invention is further described, by way of example, with reference to the accom panying drawings which is a diagram of a circuit arrangement according to the inven tion, with rotary switches thereof shown dia grammatically in perspective.

The circuit shown in the drawing has two driving motors 10 and 11, each of which 'drives a respective windscreen wiper (not shown). A rotary cam 50,70 of a respective rotary switch 12.13 is connected to each of the motors 10,11 by means 42,43 so that the cams 50 and 70, which are respectively journalled in frames 51 and 71 are rotated in the direction of the arrows 14 and 15 when the motors are running. A normally open operating switch 17 in the form of a key is disposed in an operating current branch 16 of the driving motor 10.

The rotary switch 12 has two contact springs 53 and 54 held in a support block 52 on the frame 51.

In the illustrated position, the contact spring 53 eneazes a fixed counter-contact 57 but the contact spring 54 is held away from the counter-contact 57, which is connected to the negative side of the motor 10. A negative supply 31 which, like the operating switch 17, is connected to the negative side of a voltage source leads to a terminal lug 55 of the contact spring '53. A terminal lug 56 of the contact spring 54 is connected to the operating line 33 of the electric motor 11 so as to assume the function of an opera ting switch for the latters operating circuit 33,34.

The rotary switch 13 is of identical con fstruction to the rotary switch 12. 'Thus the switch 13 has two contact spring 73 and 174 Aheld in a support block 72 on the frame 71 so as to co-operate with a fixed counter contact 77 connected to the working line 33 'at the negative side of the motor 11 whose positive side is connected to a positive sup -ply line 34. A negative supply line 35 is con nected to a terminal lug 75 of the contact spring 73 and a terminal lug 76 of the contact spring 74 is connected to a working circuit 36,40 of a third driving motor 41. The latter-is used to drive a supply pump for washing fluid to be sprayed onto the windscreens to he cleaned.

The surface of each rotary cam 50,70 is provided with switching cam lobes 58,78 and 59,79 which co-o'-perate respectively with the free ends of the contract springs 53,73 and 54,74. When the rotary cam 50,70 is rotated by its respective driving motor 10,11 in the direction of the arrow 14,15, the cam lobe 59,79 raises the contact spring 54,74 off the counter-contact 57,77, as shown, so that the circuit 33 and 34 or 36 and 40 closed by that contact spring is in interrupted. When the cam lobe 58,78 comes against the contact spring 53,73, the later too is raised from the counter-contact 57 to interrupt a respective by-pass circuit 31,35 as described below.

Seen in the direction of rotation 14,15, both cam lobes 58,78 and 59,79 terminate at a common trailing edge 61,81 so that, over an angular range 62,82, both contact springs 53,73 and 54,74 engage the counter-contact 57,77.

The cam lobe 58,78 extends over a small arc, commensurate with the angle through which the cam 50,70 continues to turn after its motor 10,11 has been switched off. On the other hand the cam lobe 59,79 extends over a large arc supplementary to the angular range 62,82.

To switch on the driving motors 10,11 and 40, the operating switch 17 is simply closed so that current flows in the operating circuit 16 and the motor 10 rotates. By virtue of the connection means 42, which may for example incorporate a reduction gear, the cam 50 is driven in the direction of the arrow 14. The operating switch 17 must be kept closed until the cam lobe 58 has released the contact spring 53 whereupon the motor 10 is operated by means of a so-called holding circuit formed by the positive side of the working circuit 16, the counter-contact 57, the contact spring 53 and the negative supply 31. Simultaneously the cam lobe 59 releases the contact spring 54 so that the operating circuit for the motor 11 is closed through the counter-contact 57, the contact spring 54 and the lines 33 and 34. The motor 11 then rotates the cam 70 in the direction of the arrow 15. In so doing, the cam lobe 78 releases the contact spring 73 so that the latter completes the holding circuit 35,34 for the motor 11.

At the same time the cam lobe 79 releases the contact spring 74 so that the motor 41 is switched on through the negative side of the auxiliarv circuit 35, the contact spring 73, the counter-contact 77, the contact spring 74, the lead 36 and the positive supply 40.

When the cam 50 has rotated through a control angle determined by the angular range 62, the connection circuit is interrupted because the contact spring 54 is lifted from the counter-contact 57 by the larger cam lobe 51. From this instant on, the driving motor 11 is operated by its holding circuit formed by the positive side of the working circuit 34, the counter-contact 77, the contact spring 73 and the negative side of the auxiliary circuit 35. When the cam 70 has rotated through its control angle determined by the angular range 82, the contact spring 74 is lifted from the counter-contact 77 so that the motor 41 is switched off.

From the instant that the contact spring 54 is lifted from the counter-contact 57, the two electric motors 10 and 11 are elec- trically decoupled. They both continue to be operated but independently of one another by the above-mentioned holding circuits.

When the cams 50 and 70 have rotated so far that the switching blades 53 and 73 are lifted from their counter-contacts 57 and 77, the holding circuits are broken and the driving motors 10 and 11 are switched off.

The wipers are then in their parked or resting positions.

The early electrical decoupling of the driving motors 10 and 11 described above ensures that the working current branches of one motor can no longer influence the other motor. The size of the cam lobes 59 and 79 is determined by the required control times for the motors 11 and 41 which are to be put in motion. The lengths of the switching times may be influenced by suitably dimensioning the cam lobes over angular extent in their direction of rotation.

The described construction of the circuit results in a particularly low outlay for switches and particularly simple wiring. The circuit is also unusually economical to assemble.

Naturally, the described circuit may be wired as a positive or as a negative circuit.

WHAT WE CLAIM IS:- 1. A circuit arrangement for operating first and second electrical screen-wiper drive motors of a motor vehicle screen-wiper arrangement comprising an operating switch in an operating circuit for the first motor for setting the latter in motion, a rotary switch adapted to be rotated by the first motor and having first and second contact springs operated by respective cam lobes and co-operating with a counter-contact, the first contact spring lying in a holding circuit for the first motor and the second contact spring lying in an operating circuit for the second 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 rotary switch, by virtue of its first contact spring, and the further switch being adapted to switch the first and second motors off respectively after said operating circuits have been interrupted respectively by opening of the operating switch and lifting of said second contact spring from the counter-contact and when the wipers have respectively reached their parking positions.

2. A circuit arrangement as claimed in claim 1, 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 countercontact, such contact spring lying in the holding circuit for the second motor.

3. A circuit arrangement as claimed in claim 1 or 2, 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.

4. A circuit arrangement as claimed in claim 3 when appendant to claim 2, 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.

5. A circuit arrangement as claimed in claim 2 or 4, in which the two rotary switches are of identical construction.

6. A circuit arrangement for operating screen-wiper drive motors, constructed and adapted to operate substantially as herein described with references to and as illustrated in the accompanying drawing.

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

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. When the cam 50 has rotated through a control angle determined by the angular range 62, the connection circuit is interrupted because the contact spring 54 is lifted from the counter-contact 57 by the larger cam lobe 51. From this instant on, the driving motor 11 is operated by its holding circuit formed by the positive side of the working circuit 34, the counter-contact 77, the contact spring 73 and the negative side of the auxiliary circuit 35. When the cam 70 has rotated through its control angle determined by the angular range 82, the contact spring 74 is lifted from the counter-contact 77 so that the motor 41 is switched off. From the instant that the contact spring 54 is lifted from the counter-contact 57, the two electric motors 10 and 11 are elec- trically decoupled. They both continue to be operated but independently of one another by the above-mentioned holding circuits. When the cams 50 and 70 have rotated so far that the switching blades 53 and 73 are lifted from their counter-contacts 57 and 77, the holding circuits are broken and the driving motors 10 and 11 are switched off. The wipers are then in their parked or resting positions. The early electrical decoupling of the driving motors 10 and 11 described above ensures that the working current branches of one motor can no longer influence the other motor. The size of the cam lobes 59 and 79 is determined by the required control times for the motors 11 and 41 which are to be put in motion. The lengths of the switching times may be influenced by suitably dimensioning the cam lobes over angular extent in their direction of rotation. The described construction of the circuit results in a particularly low outlay for switches and particularly simple wiring. The circuit is also unusually economical to assemble. Naturally, the described circuit may be wired as a positive or as a negative circuit. WHAT WE CLAIM IS:-

1. A circuit arrangement for operating first and second electrical screen-wiper drive motors of a motor vehicle screen-wiper arrangement comprising an operating switch in an operating circuit for the first motor for setting the latter in motion, a rotary switch adapted to be rotated by the first motor and having first and second contact springs operated by respective cam lobes and co-operating with a counter-contact, the first contact spring lying in a holding circuit for the first motor and the second contact spring lying in an operating circuit for the second 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 rotary switch, by virtue of its first contact spring, and the further switch being adapted to switch the first and second motors off respectively after said operating circuits have been interrupted respectively by opening of the operating switch and lifting of said second contact spring from the counter-contact and when the wipers have respectively reached their parking positions.

2. A circuit arrangement as claimed in claim 1, 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 countercontact, such contact spring lying in the holding circuit for the second motor.

3. A circuit arrangement as claimed in claim 1 or 2, 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.

4. A circuit arrangement as claimed in claim 3 when appendant to claim 2, 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.

5. A circuit arrangement as claimed in claim 2 or 4, in which the two rotary switches are of identical construction.

6. A circuit arrangement for operating screen-wiper drive motors, constructed and adapted to operate substantially as herein described with references to and as illustrated in the accompanying drawing.