WINDSCREEN-WIPER DEVICE FOR MOTOR VEHICLES

Abstract: A windscreen-wiper device for motor vehicles comprising first and second geared motor units (2,4) operating respective wiper arms (6,8) which can wipe overlapping areas of the window, first and second position sensors (12,14) associated with respective wiper arms and arranged to signal predetermined positions of the respective wiper arms, and a control and operating circuit (16) which cooperates with the position sensors (12,14) to operate the first and second geared motor units (2,4) for a predetermined period and arranged to emit operating signals for the first and second geared motor units (2,4) alternately when the position sensor member (14,12) associated with the wiper arm of the other geared motor unit (4,2) signals the predetermined position of that arm.

Description: The present invention relates to an apparatus for controlling a vehicle windscreen-wiper system and to the windscreen-wiper system comprising such apparatus From FR-A-2 538 327, it is known to provide an apparatus for controlling a vehicle windscreen-wiper system having a pair of geared motor units effective to drive wiper arms through repeating, overlapping patterns across a vehicle windscreen. Such control apparatus comprises: a position sensor for each wiper arm effective to generate a signal representing a predetermined position of the wiper arm on the windscreen, and a control circuit responsive to the signals from the position sensors for operating each of the geared motor units for a predetermined period of time. The present invention provides an apparatus of the above mentioned type characterised in that the control circuit is effective to operate each of the geared motor units alternatively as soon as the wiper arm driven by the other of said geared motor unit has reached its predetermined position. Naturally, the predetermined positions and the period of operation of the geared motor units will be selected in such a way as to prevent the wiper arms from being superimposed during their operation. The advantages and further characteristics of the apparatus according to the invention will become clear from the detailed description which follows, purely by way of non-limiting example, with reference to the appended drawings, in which: Figures 1 and 2 are schematic views illustrating two variants of a windscreen-wiper -system comprising the apparatus according to the invention. The windscreen-wiper system itself constitutes a further subject of the invention. In the drawings, geared motor units with internal mechanisms of known type and carried by the structure of the motor vehicle, not illustrated, are indicated 2 and 4, and are each provided with a respective wiper arm 6 and 8 with respective wiper blades 10 which wipe the glass C of a motor vehicle windscreen. The wiper arms are positioned so that the areas wiped by each wiper arm and its respective blade have an overlapping zone I indicated by hatching. In Figure 1, the centres of rotation of the wiper arms are positioned on opposite sides of a transverse axis of symmetry a-a of the window and the arms, illustrated in their starting,positions, extend in diverging directions. The variant of Figure 2 differs in that the arms extend in converging directions. Although further variants are also possible with regard to the starting positions of the wiper arms, the arrangements illustrated in Figures 1 and 2 are preferred as they enable the zone of overlap I between the areas wiped by the wiper arms to be made wider. Each geared motor unit includes a position sensor 12 and 14, associated with a respective wiper arm and arranged to supply a signal to a control and operating circuit 16 when the wiper arm associated with it has reached a predetermined position in its stroke. The control and operating circuit 16 is arranged to operate each geared motor unit for a predetermined period of time and to emit operating signals for the geared motor units 2 and 4 alternately when the position sensor (14 and 12 respectively) associated with the wiper arm of the other geared motor unit signals that the arm associated with it has reached the predetermined position. The period of operation of each geared motor unit is preferably such as to permit a complete stroke of the wiper arm. In one embodiment, the sensors are arranged to signal the starting position of the wiper arms so that the control circuit causes the alternating operation of the two geared motor units. Each wiper arm starts its stroke when the other arm has reached a stop position corresponding to its starting position. In this case, the position sensor may consist of a known type of end-of-stroke switch and be used automatically to stop the arm in the end-of-stroke position, whatever momentary position the arm assumes at the instant when the supply is switched off. According to one variant, the position sensors may be arranged to signal to the control and operating circuit an intermediate position in the stroke of the respective wiper arm, and preferably a position near the zone I of intersection of the surfaces wiped by the wiper arms, such that the consequent operation of the other wiper arm does not give rise to the two arms being superimposed. In this case, therefore, the control and operating circuit operates one arm from its stop position, which corresponds to the starting position, when the other arm is still completing its stroke. The advantages arising from the characteristics of the windscreen-wiper device according to the invention lie principally in that it has good reliability in combination with a low manufacturing cost. In fact, the use of two separate independent geared motor units with wiper arms which wipe overlapping areas means that, in the event of failure of one geared motor unit, the windscreen-wiper can carry on operating to afford sufficient visibility for the driver. Furthermore, the device does not require the use of complicated mechanisms for transmitting the drive and is thus economical, compact and, moreover, very quiet. The control and operating circuit may also be arranged to cause independent and continuous operation of each of the geared motor units upon operation of a manually-controlled switch 18 connected to the circuit. Operation of the switch to cause operation of a single geared motor unit may be convenient, for example, in conditions of a low level of charging of the battery of the motor vehicle.

Claims: 1. Apparatus for controlling a vehicle windscreen-wiper system having a pair of geared motor units (2, 4) effective to drive wiper arms (6, 8) through repeating, overlapping patterns across a vehicle windscreen, the control apparatus comprising: a position sensor (12, 14) for each wiper arm (6, 8) effective to generate a signal representing a predetermined position of the wiper arm (6, 8) on the windscreen, and a control circuit (16) responsive to the signals from the position sensors (12, 14) for operating each of the geared motor units (2, 4) for a predetermined period of time, characterised in that the control circuit (16) is effective to operate each of the geared motor units (2, 4) alternatively as soon as the wiper arm (8, 6) driven by the other of said geared motor unit (4, 2) has reached its predetermined position. 2. An apparatus according to claim 1, characterised in that the position sensor members (12, 14) are arranged to signal the end-of-stroke position of the respective arm. 3. An apparatus according to claim 2, characterised in that the position sensors (12, 14) consist of end-of-stroke switches. 4. An apparatus according to claim 1, characterised in that the position sensors (12, 14) are arranged to signal an intermediate position in the stroke of the respective wiper arm. 5. An apparatus according to any one of claims 1 to 4, characterised in that the control and operating circuit (16) is further arranged to cause-independent operation of each of the geared motor units upon operation of a manually-controlled switch connected to this circuit. 6. A windscreen-wiper system comprising an apparatus according to any of claims 1 to 5. 7. A windscreen-wiper system according to claim 6, characterised in that the wiper arms (6, 8) are arranged with their respective centres of rotation on opposite sides of the transverse axis of symmetry of the window, and in that they extend in diverging directions in their starting positions. 8. A windscreen-wiper system according to claim 6, characterised in that the wiper arms (6, 8) are arranged with their centres of rotation on opposite sides of the transverse axis of symmetry of the window, and in that they extend in converging directions in their starting positions.

Inventors: MAY, PIERLUIGI, PEDANI, GIUSEPPE
Applicants: INDUSTRIE MAGNETI MARELLI S.P.A.
Application year: 1988
Main classification: B60S1
IPC codes: B60S1