GB1573900A

GB1573900A - Drive system for vehicle windscreen wipers

Info

Publication number: GB1573900A
Application number: GB2458078A
Authority: GB
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1978-05-30
Filing date: 1978-05-30
Publication date: 1980-08-28

Description

(54) A DRIVE SYSTEM FOR VEHICLE WINDSCREEN WIPERS (71) We, LUCAS INDUSTRIES LIMITED, a British Company of Great King Street, Birmingham B 19 2XF, 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:- This invention relates to a windscreen wiper drive system for a vehicle.

In vehicles having two or more windscreen wipers, it is normal to use a single electric motor operating by way of a series of linkages to drive both or all of the windscreen wipers. However, this known arrangement suffers from the problem that, owing to the complexity of the linkages involved, it is not always possible to obtain movement of the wipers over the full wiping area on the windscreen, especially when the windscreen is dry or packed with snow.

To minimise this problem, it is also known to provide a two windscreen wiper system in which a separate electric motor is used for each windscreen wiper. This has the advantage that the linkages required to couple the motors to the wipers are simplified and hence there is less difficulty in obtaining the full area of wipe under adverse conditions. However, with a system employing separate motors to drive two windscreen wipers, it is necessary to cater for the fact that the motors may drive their associated wipers at slightly different speeds since, of course, this could lead to the wipers impeding one another. It is therefore, an object of the present invention to provide a simple and convenient arrangement for allowing two or more windscreen wipers to be driven in synchronism by separate motors.

Accordinglv. the invention resides in a windscreen wiper drive system for a vehicle, including first and second electric motors, first and second drive spindles each adapted to receive a respective windscreen wiper of the vehicle. means coupling the first and second motors to the first and second drive spindles respectively so that each motor is operable to impart angular reciprocating movement to its associated spindle from and to a parked position, and first switch means connected in circuit with the motors and arranged so that, in use, if the motors drive their associated spindles out of synchronism such that one spindle reaches its parked position in advance of the other spindle, said switch means temporarily de-energise the motor driving said one spindle until the other spindle reaches its parked position, said first switch means including for each motor a plurality of switch contacts mounted external to the motor and an operating member movable to operate said contacts in response to the motor driving its associated spindle to its parked position.

The system described above has the advantage that conventional windscreen wiper motors can be employed since the switch contacts required to synchronise movement of the motors are mounted external to the motors. Moreover, the operating member required to operate the switch contacts associated with each motor is normally present in a conventional single motor, windscreen wiper system as part of a parking switch for ensuring that, when the driver of the vehicle operates his manual control to switch off the wipers, the wipers continue their stroke until they reach a parked position before the motor Is deenergised. Thus, in the system described above, a common operating member can be used to control operation of said plurality of switch contacts associated with each motor and a parking switch for the motor.

Preferably, therefore, the system also includes manually operable, second switch means for controlling the supply of power to each motor, and third switch means associated with each motor and connected in circuit with said second switch means and the associated motor so that, in use, when said second switch means is opened, said third switch means permits the supply of power to the motor until the associated spindle reaches its parked position, the first and third switch means associated with each motor sharing a common operating member.

Conveniently, each operating member operates its associated switch contacts directly.

Alternatively, each operating member operates at least some of its associated switch contacts by way of relay.

Conveniently, said system includes a third electric motor coupled to a third windscreen wiper-geceiving, drive spindle for imparting angular reciprocatory movement thereto from and to a parked position, and said first switch means is also associated with said third motor to permit temporary de-energisation thereof if said third spindle is driven into its parked position in advance of the first spindle and/or the second spindle.

In the accompanying drawings, Figures 1 to 6 are circuit diagrams of a windscreen wiper drive system, according to a first example of the invention, illustrating various stages respectively of operation of the system, Figure 7 is a circuit diagram similar to Figure 1 of a system according to a modification of said first example, and Figure 8 is a circuit diagram of a windscreen wiper drive system according to a second example.

Referring to Figures 1 to 6, the system shown is intended for use in a private passenger vehicle having two windscreen wipers and includes first and second electric motors 21. 22 respectively having drive shafts which are coupled by linkages (not shown) to respective drive spindles (not shown). Each drive spindle is adapted to receive one of the windscreen wipers of the vehicle and the arrangement of the linkages is such that each motor is operable, in use, to impart angular reciprocatory movement to its associated spindle and windscreen wiper from and to a limit position. The limit position is normally known as the parked position of the associated windscreen wiper and in this position the wiper is located just above the lower edge of the vehicle windscreen. Since each windscreen wiper is driven by a separate motor, there is a possibility that the inevitable differences in the operating characteristics of the motors 21, 22 will result in the movement of the windscreen wipers becoming sufficiently out-of-phase to impede one another. The object of the system shown is therefore to avoid this potential problem.

Considering now the overall circuit of the system of the first example, the motor 21 has one terminal connected to the movable contact of a first two-position switch 23 and to one fixed contact of a second twoposition switch 24 having its other fixed contact connected to earth. Connected to the other terminal of the motor 21 is one fixed contact of a third two-position switch 25 having its movable contact connected to one fixed contact of the switch 23 and its other fixed contact connected to the negative terminal of the vehicle battery 26, the positive terminal of which is earthed.

Also connected to the other terminal of the motor 21 is the movable contact of a fourth two-position switch 27 having one fixed contact earthed and its other fixed contact connected to the movable contact of the switch 24.

With regard to the second motor 22, one terminal thereof is connected to the movable contact of a fifth two-position switch 28 and to one fixed contact of a sixth two-position switch 29 having its other fixed contact earthed. Connected to the other terminal of the motor 22 is the movable contact of a seventh two-position switch 31 having one fixed contact earthed and its other fixed contact connected to the movable contact of the switch 29. Further connected to the other terminal of the motor 22 is one fixed contact of an eighth two-position switch 32 having its other fixed contact connected through the other fixed contact of the switch 23 to the negative terminal of the battery 26 and having its movable contact connected to one fixed contact of the switch 28, the other fixed contact of which is connected to the negative battery terminal.

The movable contacts of the switches 23, 28 are coupled to a common operating member which is mounted on the vehicle dashboard and which defines the main onoff control for the vehicle windscreen wipers.

The movable contacts of the switches 24, 25, 31 are connected to a further common operating member which is engageable by a cam (not shown) carried by the drive shaft of the motor 21 when the associated drive spindle and windscreen wiper are moved into their parked position. The arrangement is such that the movable contacts of the switches 24, 25, 31 are normally urged into engagement with their fixed contacts indicated by the letters R in the drawings, which for the sake of convenience will be referred to as the run positions of the switches. The movable contacts of the switches 24, 25, 31 are, however, moved by their common operating member into engagement with their alternative fixed contacts indicated by the letters P (parked) when, during each rotation of the drive shaft of the motor 21, the drive spindle and its associated windscreen wiper are moved into their parked position and said cam engages the operating member. The movable contacts of the switches 27, 29, 32 are arranged in a similar manner to the movable contacts of the switches 24, 25, 31 but are connected to a separate common operating member which is engageable by a further cam (not shown) carried by the drive shaft of the motor 22. All the contacts of switches 24, 25, 27, 29, 31, 32 are mounted external to their associated motors 21, 22 so that conventional windscreen wiper motors can be employed and faulty switches can be replaced without replacing the motors.

Considering now operation of the system of the first example, Figure 1 illustrates the situation where the main on-off control defined by the combination of switches 23, 28 is in its on or run position and the windscreen wipers are in the middle of the wiping stroke. In this situation, all the switches 24, 25, 27, 29, 31, and 32 are in their run positions so that the motor 21 is energised by the battery 26 through the switches 23, 27, and 24, while the motor 22 is energised through the switches 28, 31 and 29. Assuming now that the motor 21 rotates faster than the motor 22, the windscreen wiper associated with the motor 21 will reach its parked position while the windscreen wiper associated with the motor 22 is still effecting its wiping cycle. Thus, if the main on-off control is still in its on position, the situation shown in Figure 2 will be reached, in which the switches 24, 25 and 31 are now moved to their parked positions, while the switches 27, 29 and 32 are still in their run positions. In this situation, it will be seen that the circuit between the battery 26 and the motor 21 is broken at the switch 24, while the motor 22 is still energised, although now by way of the switches 28 and 31 alone. Thus, in the situation of Figure 2,the motor 21 is held de-energised with its associated windscreen wiper in its parked position, while the windscreen wiper associated with the motor 22 is still being driven. When the windscreen wiper driven by the motor 22 subsequently completes its wiping cycle, the situation shown in Figure 3 is reached in which the switches 27, 29 and 32 as well as the switches 24, 25 and 31 are in their parked positions. Thus, assuming the main on-off control is still in its run position, it will be seen from Figure 3 that the motor 21 is now energised by way of the switch 23 and switch 27, while the motor 22 is still energised through the switches 28 and 31.

Thus, the motors 21, 22 now move off together to start a further wiping cycle.

Turning now to Figure 4, this illustrates the situation where the driver of the vehicle employing the system shown turns the main on-off control defined by the switches 23, 28 into its off or parked position at a time when both windscreen wipers are in the middle of a wiping cycle. In this situation, although the switches 23, 28 are in their parked positions. it will be seen that the motor 21 is energised by the battery 26 through the switches 25, 23, 27, and 24 while the motor 22 is energised through the switches 32, 28, 31 and 29. Assuming as before that the motor 21 rotates faster than the motor 22, the next stage will be where the motor 21 has driven its associated windscreen wiper into its parked position, while the windscreen wiper associated with the motor 22 is still only part of the way through its wiping cycle. This is the situation illustrated in Figure 5 from which it will be seen that the switches 24, 25 and 31 have now moved to their parked positions so that the circuit between the battery 26 and the motor 21 is broken at switch 25, while the motor 22 is still connected to the battery 26, although now by way of the switches, 32, 28 and 31 alone. Thus, the motor 22 continues rotating until the associated windscreen wiper completes its wiping cycle when, as shown in Figure 6, the switches 27, 29 and 32 move into their parked positions so as to disconnect the motor 22 from the battery 26.

Although the preceding discussion has only dealt with the situation where the motor 21 rotates faster than the motor 22, it can readily be shown that the system of the first example operates in a similar manner to that described above if the motor 22 rotates faster than the motor 21, although of course it is now the motor 22 which is temporarily de-energised at the end of each of its wiping cycles.

In the modification shown in Figure 7, the system includes the provision for driving each motor 21, 22 at two separate- speeds and each motor therefore includes an additional switch 33 operable to bypass part of the rotor winding of the motor. The switches 33 would normally be ganged and combined with the switches 23, 28 as a double pole, double throw switch mounted on the vehicle dashboard to provide a single manual control for the driver of the vehicle.

Moreover, in the system of Figure 7, when the switches 33 are in the positions shown so that each motor 21, 22 is being driven at its faster speed, it is necessary to ensure that the switches 27, 31 temporarily remain in their run positions after the switches 24, 29 are moved to their parked positions by their respective motor driven cams. This delay should be of sufficient duration to ensure that the switches 27, 31 remain in their run positions during dynamic braking of the motors.

Referring to Figure 8, the system of the second example is intended for use in a commercial vehicle having three windscreen wipers and includes three separate electric motors 41, 42, 43 for imparting angular reciprocatory movement to the windscreen wipers respectively.

Operation of the motors 41, 42, 43 is governed by twelve two-position switches 44 to 55 respectively which are arranged and controlled in a similar manner to the switches of the first example, although there are now four extra switches to cater for the addition of the extra motor. Thus the movable contacts of the switches 44 to 46 are coupled to a single operating member defining the main on-off control for the windscreen wipers, while the movable contacts of the switches 47, to 49, 50 to 52, and 52 to 55 are coupled to respective common operating members associated with the drive shafts of the motors 41 to 43 respectively so as to be movable in use from a normal run position to a parked position at the end of each wiping cycle of the associated windscreen wiper.

Turning now to the specific circuit arrangement of the system of the second example, each of the motors 41 to 43 has one terminal connected to the movable contact of one of the switches 44 to 46 respectively, each of the latter having one fixed contact connected to the negative terminal of the vehicle battery 56 which has its positive terminal earthed. The other fixed contact of each of the switches 44 to 46 is connected to the movable contact of one of the switches 49, 52, 55 respectively, the latter each having one fixed contact connected to the negative terminal of the battery 56 and their other fixed contacts connected to the other terminal of the motors 41 to 43 respectively. Said other terminals of the motors 41 to 43 are further connected to the movable contacts of the switches 47, 50, 53 respectively which each have one fixed contact earthed and have their other fixed contacts commonly connected to the movable contact of the switch 48. One fixed contact of the switch 48 is connected to said one terminal of the motor 41, while the other fixed contact is conected to the movable contact of the switch 51. The switch 51 has one fixed contact connected to said one terminal of the motor 42, while its other fixed contact is connected to the movable contact of the switch 54, one fixed contact of the latter being connected to said one terminal of the motor 43 and the other fixed contact being earthed.

In Figure 8, the system of the second example is shown with the main on-off control defined by the combination of switches 44 to 46 in its off position and each of the switches 47 to 55 in its parked position so that the motors 41 to 43 are all de-energised. However, by following a similar sequence of operations to those illustrated in Figures 1 to 6, it can readily be demonstrated that the system of the second example allows each of the motors 41 to 43 to be temporarily de-energised if it reaches the end of its wiping cycle before one or both of the other motors.

Although in the above examples an operating member coupled to the drive shaft of each windscreen wiper motor directly operates a plurality of separate switches at the end of each wiping cycle, it is to be appreciated that as an alternative the operating member could operate at least some of the switches by way of a multicontact relay. Thus, for example, in the system of Figure 1 closure of the switch 31 by the operating member associated with the motor 21 could energise a relay coil to close sets of associated contacts defining the switches 24, 25.

WHAT WE CLAIM IS: 1. A windscreen wiper drive system for a vehicle, including first and second electric motors, first and second drive spindles each adapted to receive a respective windscreen wiper of the vehicle, means coupling the first and second motors to the first and second drive spindles respectively so that each motor is operable to impart angular reciprocating movement to its associated spindle from and to a parked position, and first switch means connected in circuit with the motors and arranged so that, in use, if the motors drive their associated spindles out of synchronism such that one spindle reaches its parked position in advance of the other spindle, said switch means temporarily de-energise the motor driving said one spindle until the other spindle reaches its parked position, said first switch means including for each motor a plurality of switch contacts mounted external to the motor and an operating member movable to operate said contacts in response to the motor driving its associated spindle to its parked position.

2. A system as claimed in Claim 1 and further including manually operable. second switch means for controlling the supply of power to each motor, and third switch means associated with each motor and connected in circuit with said second switch means and the associated motor so that. in use, when said second switch means is opened, said third switch means permits the supply of power to the motor until the associated spindle reaches its parked position, the first and third switch means associated with each motor sharing a common operating member.

3. A system as claimed in Claim 1 or Claim 2 wherein each operating member operates its associated switch contacts directly.

4. A system as claimed in Claim 1 or Claim 2 wherein each operating member operates at least some of its associated

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Operation of the motors 41, 42, 43 is governed by twelve two-position switches 44 to 55 respectively which are arranged and controlled in a similar manner to the switches of the first example, although there are now four extra switches to cater for the addition of the extra motor. Thus the movable contacts of the switches 44 to 46 are coupled to a single operating member defining the main on-off control for the windscreen wipers, while the movable contacts of the switches 47, to 49, 50 to 52, and 52 to 55 are coupled to respective common operating members associated with the drive shafts of the motors 41 to 43 respectively so as to be movable in use from a normal run position to a parked position at the end of each wiping cycle of the associated windscreen wiper. Turning now to the specific circuit arrangement of the system of the second example, each of the motors 41 to 43 has one terminal connected to the movable contact of one of the switches 44 to 46 respectively, each of the latter having one fixed contact connected to the negative terminal of the vehicle battery 56 which has its positive terminal earthed. The other fixed contact of each of the switches 44 to 46 is connected to the movable contact of one of the switches 49, 52, 55 respectively, the latter each having one fixed contact connected to the negative terminal of the battery 56 and their other fixed contacts connected to the other terminal of the motors 41 to 43 respectively. Said other terminals of the motors 41 to 43 are further connected to the movable contacts of the switches 47, 50, 53 respectively which each have one fixed contact earthed and have their other fixed contacts commonly connected to the movable contact of the switch 48. One fixed contact of the switch 48 is connected to said one terminal of the motor 41, while the other fixed contact is conected to the movable contact of the switch 51. The switch 51 has one fixed contact connected to said one terminal of the motor 42, while its other fixed contact is connected to the movable contact of the switch 54, one fixed contact of the latter being connected to said one terminal of the motor 43 and the other fixed contact being earthed. In Figure 8, the system of the second example is shown with the main on-off control defined by the combination of switches 44 to 46 in its off position and each of the switches 47 to 55 in its parked position so that the motors 41 to 43 are all de-energised. However, by following a similar sequence of operations to those illustrated in Figures 1 to 6, it can readily be demonstrated that the system of the second example allows each of the motors 41 to 43 to be temporarily de-energised if it reaches the end of its wiping cycle before one or both of the other motors. Although in the above examples an operating member coupled to the drive shaft of each windscreen wiper motor directly operates a plurality of separate switches at the end of each wiping cycle, it is to be appreciated that as an alternative the operating member could operate at least some of the switches by way of a multicontact relay. Thus, for example, in the system of Figure 1 closure of the switch 31 by the operating member associated with the motor 21 could energise a relay coil to close sets of associated contacts defining the switches 24, 25. WHAT WE CLAIM IS:

1. A windscreen wiper drive system for a vehicle, including first and second electric motors, first and second drive spindles each adapted to receive a respective windscreen wiper of the vehicle, means coupling the first and second motors to the first and second drive spindles respectively so that each motor is operable to impart angular reciprocating movement to its associated spindle from and to a parked position, and first switch means connected in circuit with the motors and arranged so that, in use, if the motors drive their associated spindles out of synchronism such that one spindle reaches its parked position in advance of the other spindle, said switch means temporarily de-energise the motor driving said one spindle until the other spindle reaches its parked position, said first switch means including for each motor a plurality of switch contacts mounted external to the motor and an operating member movable to operate said contacts in response to the motor driving its associated spindle to its parked position.

switch contacts by way of relay.

5. A system as claimed in any preceding claim and further including a third electric motor coupled to a third windscreen wiperreceiving, drive spindle for imparting angular reciprocatory movement thereto from and to a parked position, and said first switch means is also associated with said third motor to permit temporary deenergisation thereof if said third spindle is driven into its parked position in advance of the first spindle and/or the second spindle.

6. A windscreen wiper drive system as claimed in Claim 1 comprising the combination and arrangement of parts substantially as hereinbefore described with reference to, and as shown in Figures 1 to 6, or Figure 7 or Figure 8 of the accompanying drawings.