GB2309799A - Controller for reversible electric motor - Google Patents

Abstract

A controller for a reversible electric motor M having brushes 1, 2 comprises a start switch S1 and a sequence control device 12 comprising control tracks 13-16 rotatable in synchronism with the motor M and arranged to sequence the motor M from its forward direction of rotation to its reverse direction of rotation and back to its forward direction of rotation at desired intervals in the rotation of the motor M. The sequence control device 12 causes changeover of set/reset relay R2 which reverses the motor. The start switch supplies power to both the control device 12 and to the motor M via relay R1.

Description

CONTROLLER FOR A REVERSIBLE ELECTRIC MOTOR The present invention relates to a controller for a reversible electric motor and is particularly, though not exclusively, concerned with a controller for a windscreen wiper motor for a vehicle.

It is well known in the art to provide for the alternation of windscreen wiper arms between forward and reverse sweeps across a vehicle windscreen, such alternation normally being provided by means of a mechanical crank arm mechanism connected at the output of the windscreen wiper motor and in the drive chain to the windscreen wiper arms.

It is also known in the art to forward and reverse a windscreen wiper motor through electronic control thereof involving micro-processors and/or logical circuits.

It is an object of the present invention to provide a controller for a reversible electric motor in which automatic sequencing between its forward and reverse motions may be achieved by an effective, yet more economic arrangement than has hitherto been available.

Accordingly, the present invention provides a controller for a reversible electric motor having a first brush and a second brush, the controller comprising a switching device for selectively directing connection from a supply voltage to a desired one of the first and second brushes in order to selectively energise the motor either in a forward direction of rotation or a reverse direction of rotation, and a sequence control device comprising control tracks rotatable in synchronism with the motor and arranged to sequence the motor from its forward direction of rotation to its reverse direction of rotation and back to its forward direction of rotation at desired intervals in the rotation of the motor, the sequence control device being operative to cause changeover of the switching device at the desired intervals to provide alternation of the direction of rotation of the motor.

Preferably the switching device includes an electro-mechanical set/reset relay having a first output signal line connected to the first brush of the motor, and a second output signal line connected to the second brush of the motor. This set/reset relay has a first input signal line connected to a pair of relay terminals, one of which is a normally closed terminal and the other being a normally open terminal, and a second input signal line also connected to a pair of relay terminals, one of which is a normally open terminal and the other of which is a normally closed terminal.The arrangement is such that in any operational configuration of this relay, one of its output signal lines is connected to either a normally closed contact of one of the input signal lines or to a normally open contact of the other one of the input signal lines, with the other output signal line oppositely connected. And, upon switching of this relay to its alternative state, the connections of the output signal lines to the input signal lines become reversed by switching of the output signal line connections between the pairs of input signal line terminals.

The control tracks of the sequence control device may be connected electrically in series with the energisation lines of the switching device in order to set and reset automatically the relay of this switching device to provide the specified sequencing of the motor directions of rotation.

Preferably the sequence control device comprises an electrically non-conductive disc rotatable with or by the motor and on which the control tracks are provided, the control tracks each comprising an electrically conductive and an electrically nonconductive sector arranged end-to-end along the length of the track. Preferably each control track is provided by a part of an annulus on the non-conductive disc.

Preferably the controller of the present invention is adapted to control a reversible electric motor for vehicle windscreen wipers, the control tracks being arranged such that they provide for a forward sweep of a windscreen wiper arm across a vehicle windscreen, followed by a reverse sweep of the arm across the windscreen, with automatic electrical reversal at the sweep extremities.

Preferably the controller also comprises a second switching device which includes an electro-mechanical relay having a normally open contact connected to ground.

Preferably the controller also comprises a third switching device comprising a double-pole switch having a first signal line connected to the firstmentioned switching device and a second signal line connected to the second switching device. Preferably third and fourth signal lines of the double-pole switch are connected to respective contact fingers, each associated with a respective control track on the control disc, the control tracks being a motor forward direction control track and a motor park control track. Preferably a motor reverse direction control track on the disc is connected by another line, not passing through the double-pole switch, connected directly to the first-mentioned switching device.

Preferably the first signal line of the double-pole switch is connected to a set terminal of the firstmentioned switching device, and the directly connected line from the control disc is connected to a reset terminal of the first-mentioned switching device. The arrangement is such that, with the double-pole switch in a first configuration, the motor will automatically be sequenced, under control of the forward direction control and reverse direction control tracks of the sequence control device, to automatically execute forward and reverse sweeps of the windscreen wiper arms across the vehicle windscreen.With the doublepole switch in its other configuration, and under control of the park control track of the sequence control device, the motor will be dynamically braked and parked such that the windscreen wiper arms are electrically "locked" in a depress parked condition on the windscreen.

The controller for a reversible electric motor according to the present invention thus enables vehicle windscreen wipers to be operated automatically through forward and reverse motions across the vehicle windscreen and, upon cancellation of operation of the windscreen wipers, to be depress parked at a position a few degrees below the normal reversal point at the extremity of the reverse sweep, where the wiper arms and blades will be out of the way of wind, for improved vehicle aerodynamics. The aforesaid operation of the windscreen wipers is accomplished by effective, yet economic, means as provided in this invention.

The present invention will now be described in greater detail, and by way only of example, with reference to the accompanying drawing.

In the drawing there is shown a reversible electric motor M for operating windscreen wipers of a vehicle, the motor M having a first commutator brush 1, and a second commutator brush 2.

Mounted so as to be rotated by or with the armature of the motor M is a gear wheel in the windscreen wiper arm drive chain and affording a control disc 12 of electrically insulating material and one of whose circular faces is provided with electrically conductive tracks, or sectors of tracks, 13, 14, 15 and 16. These tracks or sectors 13 to 16 are electrically connected to each other. The track 13 is connected directly to ground and therefore acts as a ground track. It is electrically conductive throughout, being in the form of a closed geometric figure, preferably an annulus. Each of the other tracks 14 to 16 comprises an electrically nonconductive sector of major annular extent and an electrically conductive sector of minor annular extent.

Each track 13 to 16 is contacted by a stationary finger, such as the finger 13', which runs on the respective track as the disc 12 rotates. Each finger is connected to a respective electrical conductor by which the respective track or sector is further connected to the other components of the circuit.

As shown in the drawing, the innermost sector 16 is of relatively short extent and lies adjacent the sector 14 of relatively longer extent, both these sectors 14 and 16 lying on the inner margin of the ground track 13. By contrast, the sector 15 lies on the outer margin of the ground track 13 and is of substantially the same angular extent as the sector 14. The fingers associated with the tracks 14 to 16 are disposed relative to the sectors as shown, with the finger 17 associated with track 15 being normally in contact with the electrically non-conductive sector of the track and at some angular distance from the electrically conductive sector of the track.

Track 16 on the disc 12 is connected by a line 18, 19, including a double-pole switch S1, to an on/off relay R1 for starting and stopping the motor M.

The track 14 on the disc 12 is connected to a line 20, 21, also including the double-pole switch S1, for selective "motor forward" energisation of a motor direction control relay R2. Also, the track 15 on the disc 12 is connected directly by a line 22 for selective "motor reverse" energisation of the motor direction control relay R2. The lines 21, 22 are connected, respectively, to the set and reset terminals 28, 29 of the direction control relay R2.

Each of these terminals 28, 29 is further connected by a respective resistor 10, 11 to a supply voltage line normally connected to a motor vehicle 12 volt supply.

The direction control relay R2 is a set/reset relay which is continuously energised from the vehicle 12 volt supply line during energisation of the vehicle ignition circuit, and which changes state upon a change of voltage level at one or the other of its set 28, or reset 29, terminals. Its operation will become more apparent from the description which follows.

The mode of operation of the controller of the present invention will now be described commencing with the configuration as shown in the Figure.

In this configuration, with the lines 20, 21 continuous through the double-pole switch S1 as shown by the solid line, the set terminal 28 of the relay R2 is grounded through the tracks 14, 13. Voltage supply is, therefore, taken from the vehicle 12 volt line through the normally closed contact 8 of on/off relay R1 and signal input line 23 to relay R2 to its normally closed contact 6 and, thence, to the signal output line 26 connected to motor supply brush 1.

Concurrently, motor supply brush 2 is connected by signal output line 27 and normally closed contact 7 of relay R2 to ground. The motor M is thus caused to rotate, in this case in the forward direction as indicated by the arrow A.

Such rotation of the motor M is accompanied by a forward sweep of the vehicle windscreen wiper arms across the vehicle windscreen, and the control disc 12 is rotated by or with the motor M in synchronism therewith. As the control disc 12 rotates, also in the direction indicated by the arrow A, the sectors of the tracks 14, 15 and 16 of the disc move relative to their contact fingers until eventually a leading edge of the electrically conductive sector of track 15 makes contact with its associated contact finger 17 connected to the line 22. At this juncture the line 22 is thus connected to ground via the tracks 15, 13, the reset terminal 29 of relay R2 thus being grounded, causing this relay R2 to change state.The supply voltage is now connected from the normally open contact 4 of relay R2 and line 27 to the motor supply brush 2, whereas the motor supply brush 1 and line 26 are grounded via the normally open contact 5 of relay R2. The motor M is thus caused to reverse its direction of rotation.

The arrangement of the leading edge of the electrically conductive sector of track 15 on the control disc 12 relative to the disposition of the associated control finger 17 connected to the line 22 is such that such reversal of the motor direction occurs as the windscreen wiper arm reaches the outer extremity of its sweep across the vehicle windscreen.

With the motor M now rotating in a direction opposite that shown by the arrow A, and the control disc 12 similarly rotating in such opposite direction, the windscreen wiper arms make a reverse sweep across the vehicle windscreen. Eventually a leading edge of the electrically conductive sector of the track 14 on the control disc 12 is contacted by the contact finger connected to the line 20, whereupon the set terminal 28 of relay R2 is grounded. This relay R2 again changes state with subsequent reversal of the motor M to its forward direction of rotation which is accompanied by a reversal of the vehicle windscreen wiper arms.As in the case of the electrically conductive sector of track 15 and its associated contact finger 17, leading edge of the electrically conductive sector of track the 14 and its associated contact finger are disposed relative to each other such that this latest change of direction of the motor M to its forward direction occurs just as the windscreen wiper arms reach the extremities of their inward sweep across the vehicle windscreen.

In this manner, so long as the switch S1 remains in the position shown in solid lines in the Figure whereby the lines 20,21 are connected thereby, the motor M will continue to execute alternating forward and reverse motions which are transmitted to the vehicle windscreen wiper arms.

The main function of the resistors 10, 11 is to maintain the set 28 and reset 29 terminals of the relay R2 high until one of the two set/reset lines is pulled to ground via the forward 14 or reverse 15 tracks of the control disc 12.

In order to cancel operation of the windscreen wipers, the double-pole switch S1 is operated to the alternative position in which both lines 19, 21 are connected (through the dotted line paths shown within the switch S1) to the line 18 and its contact finger associated with the track 16 on the control disc 12.

Since, during any normal forward or reverse stroke of the motor M, the contact finger connected to line 18 will not contact the electrically conductive sector of the track 16, this changeover of the doublepole switch S1 has no immediate effect upon the motor M regardless of its present direction of rotation or the rotational position of the control disc 12 relative to its associated contact fingers. Thus, if at the time of changeover of the double-pole switch S1, the motor M is executing a forward motion, it will continue to do so since no change of voltage has appeared at either the set 28 or reset 29 terminal of the relay R2.And, as described above, when the leading edge of the electrically conductive sector of track 15 contacts its associated contact finger connected to line 22, the change in voltage at reset terminal 29 of relay R2 will still cause reversal of the direction of the motor M and synchronous reversal of direction of the control disc 12.

However, in this new configuration of the circuit, with connections in the double-pole switch S1 made through the dotted line paths shown in the Figure, when the contact finger associated with line 20 crosses the leading edge of the electrically conductive sector of track 14, no change of voltage occurs at the set terminal 28 of relay R2 since the lines 20, 21 are now discontinuous with each other.

The motor M thus continues to rotate in its reverse direction until, a short while later, the contact finger associated with line 18 passes over a leading edge of the electrically conductive sector of track 16 on the control disc 12. At this juncture the line 18, continuous with line 21 through the double-pole switch S1, is grounded via tracks 16, 13 on the control disc 12, and the set terminal 28 of relay R2 is similarly grounded. Simultaneously line 19, continuous through double-pole switch S1 with line 18, is grounded, causing energisation of relay R1 which, thus, changes state. The signal input line 23 of relay R2 is now grounded via the normally open contact 9 of relay R1 so that both brushes 1, 2 of motor M are grounded whereby the motor and the windscreen wiper arms are dynamically braked to a halt.Moreover, because the motor M and control disc 12 have undergone reverse direction rotation slightly beyond their normal extent, (by virtue of the relatively short annular extent of the electrically conductive sector of track 16 compared with the rather longer extent of track 14) the windscreen wiper arms are effectively depress parked at a position a few degrees below their normal reversal point, so that the wipers will be out of the way of the wind; this gives improved vehicle aerodynamics.

Furthermore, because both brushes 1, 2 of the motor M are held grounded, in this latter state of the double-pole switch S1, throughout the entire period when the vehicle ignition circuits are energised, the windscreen wiper arms are effectively electrically "locked" in position on the windscreen, in the depressed park position. This means they cannot be deflected from this position.

The motor controller of the present invention thus provides an automatic reversing motor control circuit which electrically reverses the windscreen wiper motor at the wiper arm reversal points without the need for complex and costly electronics such as those involving microprocessors and/or logical circuits. The necessary switching action is achieved in the present invention by means of the reverse track sector on the control disc 12 and by inclusion of the set/reset relay R2. Further, the motor controller of the present invention provides for dynamic braking and depress parking of the windscreen wiper arms. The present invention thus provides an effective, yet economic solution to the problem of reversing, braking and depress parking the vehicle windscreen wiper arms.

Whilst the controller of the present invention has been described hereinabove with reference to the currently preferred embodiment thereof, the scope of the present invention is not to be restricted thereto but extends to all such variants as fall within the broadest scope of the invention as set out herein.

For example, the inventive concept of the controller could be employed with other motors than windscreen wiper motors.

Claims (13)

1. A controller for a reversible electric motor having a first brush and a second brush, the controller comprising a switching device for selectively directing connection from a supply voltage to a desired one of the first and second brushes in order to selectively energise the motor in either a forward direction of rotation or a reverse direction of rotation, and a sequence control device comprising control tracks rotatable in synchronism with the motor and arranged to sequence the motor from its forward direction of rotation to its reverse direction of rotation and back to its forward direction of rotation at desired intervals in the rotation of the motor, the sequence control device being operative to cause changeover of the switching device at the desired intervals to provide alternation of the direction of rotation of the motor.

2. A controller according to claim 1, wherein the switching device includes an electro-mechanical set/reset relay having a first output signal line connected to the first brush of the motor, a second output signal line connected to the second brush of the motor, a first input signal line connected to a pair of relay terminals, one of which is a normally closed terminal and the other of which is a normally open terminal, and a second input signal line also connected to a pair of relay terminals, one of which is a normally open terminal and the other of which is a normally closed terminal, the arrangement being such that in any operational configuration of the relay, one of its output signal lines is connected to either a normally closed contact of one of the input signal lines or to a normally open contact of the other one of the input signal lines, with the other output signal line oppositely connected, and, upon switching of the relay to its alternative state, the connections of the output signal lines to the input signal lines become reversed by switching of the output signal line connections between the pairs of input signal line terminals.

3. A controller according to claim 1 or 2, wherein the control tracks of the sequence control device are connected electrically in series with the energisation lines of the switching device, in order to set and reset automatically the relay of the switching device to provide the specified sequencing of the motor directions of rotation.

4. A controller according to claim 1, 2 or 3, wherein the sequence control device comprises an electrically non-conductive disc rotatable with or by the motor and on which the control tracks are provided, the control tracks each comprising an electrically conductive and an electrically nonconductive sector arranged end-to-end along the length of the track.

5. A controller according to claim 4, wherein each control track is provided by a part of an annulus on the non-conductive disc.

6. A controller according to any preceding claim adapted to control a reversible electric motor for vehicle windscreen wipers, the control tracks being arranged such that they provide for a forward sweep of a windscreen wiper arm across a vehicle windscreen, followed by a reverse sweep of the arm across the windscreen, with automatic electrical reversal at the sweep extremities.

7. A controller according to any preceding claim comprising also a second switching device which includes an electro-mechanical relay having a normally open contact connected to ground.

8. A controller according to claim 7 comprising also a third switching device including a double-pole switch having a first signal line connected to the first-mentioned switching device and a second signal line connected to the second switching device.

9. A controller according to claim 8, wherein the double-pole switch includes third and fourth signal lines connected to respective contact fingers each associated with a respective control track on the control disc, the control tracks being a motor forward direction control track and a motor park control track.

10. A controller according to claim 8 or 9, wherein a motor reverse direction control track on the disc is connected by another line not passing through the double-pole switch, but connected directly to the first-mentioned switching device.

11. A controller according to claim 8, 9 or 10, wherein the first signal line of the double-pole switch is connected to a set terminal of the firstmentioned switching device and the directly connected line from the control disc is connected to a reset terminal of the first-mentioned switching device, the arrangement being such that, with the double-pole switch in a first configuration, the motor is sequenced automatically, under control of the forward direction control and reverse direction control tracks of the sequence control device, to execute automatically forward and reverse sweeps of the windscreen wiper arms across the vehicle windscreen, and, with the double-pole switch in its other configuration and under control of the park control track of the sequence control device, the motor is braked and parked dynamically, such that the windscreen wiper arms are electrically locked" in a depress parked condition on the windscreen.

12. A controller for a reversible electric motor, substantially as hereinbefore described with reference to the accompanying drawings.

13. A reversible electric motor for vehicle windscreen wipers, incorporating a controller according to any preceding claim.