GB2459383A

GB2459383A - Circuit arrangement and method for controlling an electric motor unit, in particular a wiper motor unit

Info

Publication number: GB2459383A
Application number: GB0907007A
Authority: GB
Inventors: Gunter Eisermann; Heinz Tetzel; Manfred Scheuch; Christoph Steinberg
Original assignee: MAN Nutzfahrzeuge AG
Current assignee: MAN Truck and Bus SE
Priority date: 2008-04-23
Filing date: 2009-04-23
Publication date: 2009-10-28
Anticipated expiration: 2029-04-23
Also published as: AT506848A1; DE102008020316B4; AT506848B1; DE102008020316A1; GB0907007D0; GB2459383B

Abstract

A circuit arrangement and a method controls an electric wiper. A motor unit (EA) comprises an electric motor (M) and a limit switch (ES), wherein at least the limit switch (ES) is connected to a voltage source (SQ). Switching means (SM), which are activated during wiper operation, are provided for isolating the limit switch (ES) from the voltage source (SQ) and for connecting the limit switch (ES) to the earth potential (-).

Description

Circuit arrangement and method for controlling an electric motor unit, in particular a wiper motor unit The invention relates to a circuit arrangement for controlling an electric motor unit, in particular a wiper motor unit, according to the preamble of claim 1 and an associated method according to the preamble of claim 10.

For automatically cleaning the windscreens of a vehicle or commercial vehicle, various windscreen wiper systems are known which are each adapted to the cleaning requirements existing in different vehicles or commercial vehicles.

A windscreen wiper system of this type usually comprises an electric motor unit or wiper motor unit consisting of an electric motor with a transmission for pivoting at least one wiper arm, and a limit switch unit associated with the electric motor.

The limit switch unit is arranged in the electric circuit of the wiper motor unit, and the electric motor or wiper motor is connectable via the limit switch unit to a voltage source internal to the vehicle. The limit switch unit is mechanically controlled, for example by linkage driven via the electric motor, in such a way that it is open in an end position of the at least one wiper arm and is closed in any other position of the wiper arm.

Various other methods of determining the position of the at least one wiper arm, for example Hall sensors, etc., are also known from the state of the art. Depending upon the respective position of the at least one wiper arm, the electric motor or wiper motor is still supplied with voltage via the limit switch unit or a comparable electronic limit controller after the windscreen wiper system has been switched off until the at least one wiper arm has reached its predetermined end position.

Furthermore, a windscreen wiper system comprises a control circuit for the various operating modes of the windscreen wiper, for example wiper operation and intermittent operation, and preferably a multi-function switch for the generation of control signals for the various aforementioned control units, which switch is usually mounted on the steering column or on the dashboard in the immediate vicinity of the steering wheel.

In the case of the conventional electrical installation of a windscreen wiper system, the electric motor unit is combined with the limit switch unit to form a structural unit which is connected via numerous electrical lines to the multi-function switch, a central control unit optionally with an intermittent switching relay, in order to be able to carry out the various wiper functions for wiper operation and for intermittent wiper operation.

During activation of the windscreen wiper system, namely during wiper operation, spurious electromagnetic radiation is disadvantageously generated in the vehicle by the alternate opening and closing of the limit switch unit and exceeds permissible EMC ("electromagnetic compatibility") limit values, particularly in special-purpose vehicles.

Starting from the described state of the art, the object of the present invention is to provide an improved circuit arrangement and an associated method of controlling an electric motor unit, in particular a wiper motor unit, in which in particular the spurious electromagnetic radiation generated by the limit switch unit is reduced. Starting from the preambles of claims 1 and 10, the object is achieved by the respective characterising features thereof.

The significant aspect of the circuit arrangement according to the invention is to be seen in that switching means, which are activated during wiper operation, are provided for isolating the limit switch unit from the voltage source and for connecting the limit switch unit to the earth potential. During wiper operation, the limit switch unit is advantageously switched in a completely currentless or voltage-free manner and the build-up of spurious radiation is thereby effectively prevented.

Furthermore, the switching means advantageously comprise at least one logic unit and at least one switching relay, preferably a first and a second switching relay, wherein at least one switching input or switching output of the limit switch unit is connected to the positive terminal (+) of the voltage source via the at least one switching relay.

In addition, the at least one switching relay has a first and a second switching position, wherein at least one switching input or switching output of the limit switch unit is connected to the positive terminal in the first switching position and to the earth potential in the second switching position.

The logic unit is advantageously formed for the generation of a relay switching signal for switching the at least one switching relay from the first into the second switching position and vice versa. The logic unit is also provided for the generation of a modified intermittent switching signal.

Advantageous further developments of the circuit arrangement according to the invention, in particular a method of controlling an electric motor unit at least during wiper operation or intermittent wiper operation, are set out in the remaining claims.

According to another aspect of the present invention there is provided a circuit arrangement (SA) for controlling an electric motor unit (EA), in particular a wiper motor unit, for vehicles or commercial vehicles at least during wiper operation or intermittent wiper operation, at least comprising an electric motor (M) and a limit switch unit (ES), wherein the circuit arrangement (SA) comprises a voltage input and an earth potential input and wherein at least the limit switch unit (ES) is connectable to the to a voltage input, characterised in that switching means (SM), which are activated during wiper operation, are provided for isolating the limit switch unit (ES) from the voltage input and for connecting the limit switch unit (ES) to an earth potential (-).

The invention will be further described hereinbelow with the aid of an embodiment and with reference to figures, wherein: Fig. 1 shows, by way of example, a schematic block diagram of the circuit arrangement according to the invention; and Fig. 2 shows, by way of example, a schematic block diagram of the logic unit according to Figure 1.

Fig. 1 shows, by way of example, a schematic block diagram of a circuit arrangement SA for controlling an electric motor unit EA for vehicles or commercial vehicles. In particular, the circuit arrangement SA forms a series module for controlling the wiper motor unit EA of a windscreen wiper system.

In this case, the electric motor unit or wiper motor unit EA has an electric motor M which drives at least one wiper arm of a windscreen wiper system and co-operates with a limit switch unit ES connected to the electric motor unit EA. The limit switch unit ES is preferably mechanically connected to the electric motor M. The electric motor unit or wiper motor unit EA is controlled by a further control unit (not shown in the figures) at least during wiper operation and intermittent wiper operation. In a preferred embodiment, the electric motor M and the limit switch unit ES form a structural unit together with a transmission unit (not shown in the figures) provided for driving the wiper arms.

The limit switch unit ES is connectable via the circuit arrangement SA to a voltage source SQ provided in the vehicle, preferably a d.c. voltage source, namely to an electric positive terminal + conducting a positive voltage and an electric negative terminal -not conducting a voltage. The electric negative terminal will be referred to hereinbelow as the earth potential -. In addition, the circuit arrangement SA is connected to the voltage source SQ.

The circuit arrangement SA according to the invention comprises switching means SM, which are activated during wiper operation, for isolating the limit switch unit ES from the voltage source SQ and for connecting the limit switch unit ES exclusively to the earth potential or the negative terminal -of the voltage source SQ, wherein in the present embodiment one terminal of the limit switch unit ES is already permanently connected to the earth potential -. Therefore, during wiper operation of the wiper motor unit EA, the limit switch unit ES is intentionally completely isolated from the voltage source SQ by means of the circuit arrangement SA instead of by conventionally switching over the limit switch unit ES, and all terminals or inputs and outputs of the limit switch unit ES are connected to the earth potential -.

In a preferred embodiment, the switching means SM are assembled from at least one logic unit LE and at least one switching relay, preferably a first and a second switching relay Ri, R2, wherein the first and the second switching relay Ri, R2 have, for example, a first and a second switching position I, II.

When a first or second switching signal Si, S2 is applied to the motor unit M, the electric motor unit or wiper motor unit EA is operated in wiper mode. The first or second switching signal Si, S2 is usually generated by a multi-function switch unit which is provided in the vehicle and which is mounted, for example, on the steering column or on the dashboard in the immediate vicinity of the steering wheel of a vehicle. Alternatively, the first or second switching signal Si, S2 can also be generated by a central control unit, in particular an onboard computer unit which generates the first or second switching signal Si, S2 as a function of the sensor signal supplied by a sensor unit.

When the first switching signal Si is applied, the motor unit M is operated e.g. at a first speed and when the second switching signal S2 is applied it is operated e.g. at a second speed. The first and the second switching signal Si, S2 are tapped before being supplied to the motor unit M and are transmitted to the circuit arrangement SA.

The first and second switching signals Si, S2 are rectified within the circuit arrangement SA, for example via a first and second diode Dl, D2, and are then combined to form a switching signal SS which indicates the wiper operation of the motor unit M. The switching signal SS is applied to a first input Ii of the logic unit LE and the switching information contained in the switching signal SS is evaluated in the logic unit LE.

Furthermore, an intermittent switching signal IS generated e.g. by the multi-function switch unit is supplied directly to the circuit arrangement SA, namely to a second input 12 of the logic unit LE.

Upon evaluation of the switching signal SS and the intermittent switching signal IS, the logic unit LE generates a relay switching signal RS which is transmitted via a first output El to a first switching input SI1R1, Sll of the first and second switching relay Ri, R2. The logic unit LE generates a modified intermittent switching signal 1S which, instead of the intermittent switching signal IS, is further transmitted via the second output E2 or an output of the switching arrangement SA to a central control unit (not shown in the figures), for example an onboard computer unit in the vehicle. The logic unit LE is also connected, for energy supply, to the voltage source SQ provided in the vehicle.

When an intermittent switching signal IS or the modified intermittent switching signal IS* is applied, the windscreen wiper system or the electric motor unit M is controlled in intermittent mode via the control unit (not shown in the figures) which comprises an intermittent switching relay, for example.

A second switching input SI2gi, SI2 of the first and second switching relay Ri, R2 is also connected to the earth potential -of the voltage source SQ. The relay switching signal RS generated by the logic unit LE is applied via the first output El to the first switching input SI1R1, SIli of the first and second switching relay Ri, R2 and, upon application of the relay switching signal RS, the first and second switching relays Ri, R2 are each switched from the first switching position I into the second switching position II.

In the following, it is assumed for illustrative purposes that the limit switch unit is formed by a limit switch ES. A third switching input SI3R1 of the first switching relay R 1 is permanently connected to a switching input SIES of the limit switch ES and a third switching input SI31 of the second switching relay R2 is connected to a switching output SEES of the limit switch ES. The first switching output SE1R1 ("first switching position F) of the first switching relay Ri is connected to a component of the control unit in the vehicle, in particular the intermittent switching relay, and the second switching output SE2R1 ("second switching position II") of the first switching relay Ri establishes a connection to the earth potential -.

Furthermore, the first switching output SE1g ("first switching position I") of the second switching relay R2 leads to the positive terminal + and the second switching output SE2 ("second switching position II") of the second switching relay R2 also establishes a connection to the earth potential -. Consequently, when the first and second switching relays Ri, R2 are switched from the first into the second switching position I, II, both the switching input SIES and the switching output SEES of the limit switch ES are connected to the earth potential -. According to whether the relay switching signal RS is applied to the first or second switching relay Ri, R2, the first or second switching relay Ri, R2 is switched and the connection of the limit switch ES to the voltage source SQ, in particular its positive terminal +, is thereby interrupted and the limit switch ES is completely earthed.

In a preferred embodiment, the logic unit LE is formed in accordance with the schematic block diagram shown in Fig. 2.

The logic unit LE has a first and second AND logic element &, & and at least one delay element V, wherein the first and second AND logic elements &, & each comprise a first and second signal input ii, il*, i2, i2* and a signal output e. An inverter is connected upstream of each second signal input i2, i2*.

According to the embodiment shown in the figure, the first input Ii of the logic unit LE is connected to the first signal input ii of the first AND logic element & and the second input 12 of the logic unit LE is connected to the second signal input i2 of the first AND logic element & and to the first signal input ii of the second AND logic element &*.

The signal output e of the first AND logic element & is connected via the delay element V to the first output El of the logic unit LE and to the second signal input i2 of the second AND logic element &*. Lastly, the signal output e* of the second AND logic element &* leads to the second output E2 of the logic element LE.

The control signal SS applied to the first input Ii and the inverted intermittent switching signal IS applied to the second input 12 are supplied to the first AND logic element & and, by means of a logical AND connection of said signals, a signal is generated which undergoes a temporal delay by means of the delay element V and then forms the relay switching signal RS. For example, a temporal increase of approximately 2.5 milliseconds or more is produced by means of the delay element V, triggered by a rising edge.

The intermittent switching signal IS applied to the second input 12 is supplied to the second AND logic element & together with the inverted relay switching signal RS and, by means of a logical AND connection of said signals, a modified, preferably time-delayed intermittent switching signal IS is generated which is applied to the output e* of the second AND logic element &.

Consequently, when the first or second switching signal Si, S2 is applied during wiper operation, i.e. the intermittent switching signal IS is absent, a relay switching signal RS is generated, and during intermittent wiper operation, i.e. the intermittent switching signal IS is present and the first and second switching signal Si, S2 are absent, a time-delayed, modified intermittent switching signal IS* is generated.

In a preferred embodiment, two further delay elements V*, can be provided, wherein the one further delay element V* is provided between the first AND logic element & and the delay element V and the other further delay element V is connected downstream of the second AND logic element &*.

In a preferred embodiment, the one further delay element V* is triggered by a falling edge and the other further delay element V** is triggered by a rising edge, wherein in each case a delay of the respective generated signal of approximately 0.1 millisecond is provided, for example.

Owing to the temporal delay of the relay switching signal RS at least by means of the delay unit V, it is ensured that, after the first or second switching signal Si, S2 or the control signal SS formed therefrom has been switched off, sufficient voltage continues to be supplied to the motor unit M, namely via the limit switch unit ES which is still conducting voltage or is still connected to the voltage source SQ. In this way, it is ensured that the at least one wiper arm is returned to its end position even after the windscreen wiper system has been switched off.

The invention has been described hereinabove with the aid of an embodiment. It goes without saying that numerous variations and modifications are possible without departing from the inventive concept on which the invention is based.

List of reference numerals -negative terminal or earth potential & first AND logic element & second AND logic element + positive terminal Dl first diode D2 second diode e, e* signal output El first output E2 second output EA electric motor unit or wiper motor unit ES limit switch unit I first switching position Ii first input ii, ii * first signal input 12 second input 12, 12* second signal input II second switching position IS intermittent switching signal IS' modified intermittent switching signal LE logic unit M electric motor Ri first switching relay R2 second switching relay Si first switching signal S2 second switching signal SA circuit arrangement SE1R1, SEi first switching output SE2R1, SE2R2 second switching output SEES switching output SI1R1, SIli first switching input SI2R1, SI2i second switching input SI3R1, SI31 third switching input SIES switching input SM switching means SQ voltage source SS switching signal V delay element V, further delay elements

Claims

CLAIMS: A circuit arrangement (SA) for controlling an electric motor unit (EA), in particular a wiper motor unit, for vehicles or commercial vehicles at least during wiper operation or intermittent wiper operation, at least comprising an electric motor (M) and a limit switch unit (ES), wherein at least the limit switch unit (ES) is connected to a voltage source (SQ), characterised in that switching means (SM), which are activated during wiper operation, are provided for isolating the limit switch unit (ES) from the voltage source (SQ) and for connecting the limit switch unit (ES) to the earth potential (-).
2. A circuit arrangement according to claim 1, characterised in that the switching means (SM) comprise at least one logic unit (LE) and at least one switching relay, preferably a first and a second switching relay (Ri, R2).
3. A circuit arrangement according to claim 1 or 2, characterised in that at least one switching input or switching output (SIEs, SEES) of the limit switch unit (ES) is connected to the positive terminal (+) of the voltage source (SQ) via the at least one switching relay (Ri, R2).
4. A circuit arrangement according to any one of claims 1 to 3, characterised in that the at least one switching relay (Ri, R2) has a first and a second switching position (I, II), wherein at least one switching input or switching output (SIES, SEES) of the limit switch unit (ES) is connected to the positive terminal (+) in the first switching position (I) and to the earth potential (-) in the second switching position (II).
5. A circuit arrangement according to any one of claims 1 to 4, characterised in that at least one switching signal (Si, S2, SS) is provided for controlling the electric motor unit (M) during wiper operation and at least one intermittent switching signal (IS, IS*) is provided for control during intermittent wiper operation.
6. A circuit arrangement according to any one of claims 2 to 4, characterised in that the logic unit (LE) is formed for the generation of a relay switching signal (RS) for switching the at least one switching relay (Ri, R2) from the first into the second switching position (I, II) and vice versa.
7. A circuit arrangement according to claim 5 or 6, characterised in that the logic unit (LE) is provided for the generation of a modified intermittent switching signal (IS*).
8. A circuit arrangement according to any one of claims 5 to 7, characterised in that the logic unit (LE) has at least one AND logic element (&) for the logical AND connection of the at least one switching signal (SS) and the inverted intermittent switching signal (IS).
9. A circuit arrangement according to claim 8, characterised in that at least one delay element (V) for the generation of a relay switching signal (RS) is connected downstream of the AND logic element (&).
10. A method of controlling an electric motor unit (EA), in particular a wiper motor unit, for vehicles or commercial vehicles at least during wiper operation or intermittent wiper operation, wherein the electric motor unit (EA) at least comprises an electric motor (M) and a limit switch unit (ES) which is connected to a voltage source (SQ), characterised in that, in activated wiper mode, the limit switch unit (ES) is isolated from the voltage source (SQ), in particular the positive terminal (+), and is entirely connected to the earth potential (-).