GB1592286A

GB1592286A - Control circuit for the electric motor of a pump

Info

Publication number: GB1592286A
Application number: GB5070377A
Authority: GB
Original assignee: SWF Spezialfabrik fuer Autozubehoer Gustav Rau GmbH
Current assignee: SWF Auto Electric GmbH
Priority date: 1976-12-08
Filing date: 1977-12-06
Publication date: 1981-07-01
Also published as: FR2373912A1; FR2373912B3; DE2655585C2; IT1088315B; DE2655585B1

Description

(54) CONTROL CIRCUIT FOR THE ELECTRIC MOTOR OF A PUMP (71) We, SWF-SPEZIALFABRIK FüR AUTOZUBEHaR GUSTAV RAU GMBH a joint stock company organised under the Laws of Germany, of Stuttgarter Strasse119 712 Bietigheim, Bissingen, Germany, 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: The invention relates to a control circuit for an electric motor of a pump.

In modern motor vehicles auxiliary units as brake servo unit, power-steering, servo-clutch or door and window closing devices are increasi- ingly being driven with the assistance of a hydraulic or pneumatic energy storage. In new developments the pump serving for creating the necessary vacuum or excess pressure is driven by an electric motor which is controlled by a hysteresis switch in a way that e.g. the vacuum is kept between two boundary values of 0,5 and 0,7 atu (1 atu = 14,223 lbs/sq. in. under pressure). In contrast to the known systems in which a pump is permanently driven by the vehicle engine, the electric motor and the pump are only switched on when the vacuum (stored energy) decreases to the lower boundary value. On the other hand this entails the disadvantage that upon putting into operation the auxiliary unit, as a rule the maximum vacuum is not available and a certain time passes until the electric motor of the pump is switched on.

According to the present invention there is provided a control circuit for the electric motor of a pump for filling up an energy store for actuating auxiliary units in automotive vehicles, for example a brake servo unit, said circuit comprising, for controlling the electric motor, a hysteresis switch which responds to different predetermined boundary values of the energy stored, and means whereby the electric motor will also be started independent of the value of the stored energy upon putting into operation the auxiliary unit.

By putting into operation the auxiliary unit the energy storage is thus filled up without delay. Thereby according to a first embodi- ment of the invention the electric motor remains switched on during the operating time of the auxiliary unit, in that in a very simple manner with respect to the circuit wiring it is controlled in parallel to the hysteresis switch through a switch, e.g. the stop-light switch. It is, however, not ensured that the energy storage is filled up completely, on the other hand this solution has the advantage of a short running time of the electric motor and of the pump.

In another embodiment it is provided that the electric motor remains switched on beyond the operating time of the auxiliary unit until the hysteresis switch responds te the upper boundary value of the stored energy. Thus the storage is completely filled up after each starting up of the auxiliary unit.

This can be realized in that by putting into operation the auxiliary unit the hysteresis switch is switched over into the conductive switching condition and is arrested in this switching condition during the operating period of the auxiliary unit. In a preferred embodiment an electromagnet serves for switching over which is controlled through the stop-light switch, but also an embodiment is imaginable which is merely mechanically controlled by the brake pedal.

As a third alternative it is possible to switch over the hysteresis switch to the electromagnet by putting into operation the auxiliary unit through a brief control pulse, but then not to provide blocking, so that, when the storage is completely filled up, the electric motor can also be switched off during the operating period of the auxiliary unit.

The invention is described below in detail by way of the embodiments shown in the accompanying drawings, in which Fig. 1 is a first embodiment of a control circuit, Fig. 2 is a second embodiment with reversal of the hysteresis switch and Figure 3 is a longitudinal section through a vacuum switch.

In Fig. 1 an electric motor which serves for driving a vacuum pump 11 shown only schematically is designated by 10. The vacuum created by the pump 11 is measured by a vacuum switch 12 the movable contact member 13 of which serves for closing the motor circuit. The vacuum switch 12 has a hysteresis so that the electric motor 10 is switched on at a vacuum of 0,5 atu and switched off again at a vacuum of 0,7 atu. The vacuum in the energy storage (not shown) thus varies between these two values.

In practice the maximum vacuum will not be available when an auxiliary unit is switched on such as the brakes being applied and the operational safety can be endangered if the energy stored is used up too abruptly. In addition to the automatic control through the vacuum switch 12 the electric motor is directly controllable through the switch 14 which is actuated upon putting into operation the auxiliary unit. In brake servo units the stoplight switch will preferably be used which is switched in parallel to the hysteresis switch and which is closed during the operation time of the brake, so that the pump is operating during this time. In this manner an extreme energy loss is balanced without delay.

In the embodiment according to Fig. 2 the armature 15 of an electromagnet 16 acts upon the movable contact member 13 of the vacuum switch 12, the electromagnet being controlled through the stop-light switch 14. By taking into operation the auxiliary unit the contact member 13 is therefore switched over into the stable switching position in which the motor circuit is closed. The contact member is kept in this switching position by the electromagnet, also if the vacuum passes the one boundary value of for instance 0,7 atu. On the other hand this means that this switching position will also be maintained, if the vacuum has not reached this boundary value, when the auxiliary unit is switched off. In this case the electric motor and thereby the pump continues running also after the auxiliary unit was switched off and it is ensured that the energy storage is completely filled up upon each actuation of the auxiliary unit. In this manner in comparison to the known system a high operational safety is reached with a substantially reduced running time of the pump.

In Fig. 2 it is schematically shown that the electromagnet 16 and the vacuum switch 12 are combined in a constructional unit. This constructional unit has connecting contacts 20 and 21 for the connection to the positive and negative terminal of a voltage source and- on the input side a further contact 22 for the connection to the stop-light switch 14. On the output side the contacts 24 and 25 are provided for the connection of the electric motor 10. Within the constructional unit the winding of the electromagnet is connected to the negative terminal. The electric motor is connectable directly to said constructional unit and a separate ground lead from the voltage source to the electric motor 10 is-no longer necessary.

In Fig. 3 is shown a longitudinal section of said constructional unit. In a metallic housing 30 a movable diaphragm 31 is mounted. On this diaphragm a switching member 32 acts on which a snap spring 33 is secured which serves as the movable contact member 13. The housing is closed by a bottom plate 34, which simultaneously serves as a coil form for the winding 35 of the electromagnet 16. The armature 36 of the electromagnet is fixedly connected with the switching member 32 and on the other side is urged by an adjustable pressure spring 37. Said pressure spring presses the armature 36 and thereby the switching member 32 against the diaphragm 31, so that in the normal case the switching over the mov able contact member 13 is effected by the movement of the diaphragm.

In the drawing the switching position of the vacuum switch is shown in which the motor circuit is closed. The contact member 33 rests upon two stationary contacts, of which one is shown and designated by 38. This stationary contact is electrically connected to the connecting contact 20 (Fig. 2). As soon as the pump is running the diaphragm 31 is deflected in direction of the arrow A until the snap spring jumps over and switches off the electric motor, when the boundary value is reached.

When the electromagnet 16 is energised, the armature 36 moves in the direction of the arrow B against the force of the snap spring 33, so that the snap spring 33 again jumps over to its other stable position. Thereby the switching member 32 lifts up from the diaphragm and the vacuum (stored energy) does not influence the switching behaviour until, after the operating time, the armature 36 is again released. Thus the vacuum switch 12 is latched in the conductive switching condition during the operating time.

The basic idea of the invention is also applicable in systems comprising an hydraulic pressure reservoir. Then the vacuum switch has to be replaced by a suitable pressure switch with hysteresis behaviour.

WHAT WE CLAIM IS:- 1. Control circuit for the electric motor of a pump for filling up an energy store for actuating auxiliary units in automotive vehicles, for example a brake servo unit, said circuit comprising, for controlling the electric motor, a hysteresis switch which responds to different predetermined boundary values of the energy stored, and means whereby the electric motor will also be started independent of the value of the stored energy upon putting into operation the auxiliary unit.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Figure 3 is a longitudinal section through a vacuum switch. In Fig. 1 an electric motor which serves for driving a vacuum pump 11 shown only schematically is designated by 10. The vacuum created by the pump 11 is measured by a vacuum switch 12 the movable contact member 13 of which serves for closing the motor circuit. The vacuum switch 12 has a hysteresis so that the electric motor 10 is switched on at a vacuum of 0,5 atu and switched off again at a vacuum of 0,7 atu. The vacuum in the energy storage (not shown) thus varies between these two values. In practice the maximum vacuum will not be available when an auxiliary unit is switched on such as the brakes being applied and the operational safety can be endangered if the energy stored is used up too abruptly. In addition to the automatic control through the vacuum switch 12 the electric motor is directly controllable through the switch 14 which is actuated upon putting into operation the auxiliary unit. In brake servo units the stoplight switch will preferably be used which is switched in parallel to the hysteresis switch and which is closed during the operation time of the brake, so that the pump is operating during this time. In this manner an extreme energy loss is balanced without delay. In the embodiment according to Fig. 2 the armature 15 of an electromagnet 16 acts upon the movable contact member 13 of the vacuum switch 12, the electromagnet being controlled through the stop-light switch 14. By taking into operation the auxiliary unit the contact member 13 is therefore switched over into the stable switching position in which the motor circuit is closed. The contact member is kept in this switching position by the electromagnet, also if the vacuum passes the one boundary value of for instance 0,7 atu. On the other hand this means that this switching position will also be maintained, if the vacuum has not reached this boundary value, when the auxiliary unit is switched off. In this case the electric motor and thereby the pump continues running also after the auxiliary unit was switched off and it is ensured that the energy storage is completely filled up upon each actuation of the auxiliary unit. In this manner in comparison to the known system a high operational safety is reached with a substantially reduced running time of the pump. In Fig. 2 it is schematically shown that the electromagnet 16 and the vacuum switch 12 are combined in a constructional unit. This constructional unit has connecting contacts 20 and 21 for the connection to the positive and negative terminal of a voltage source and- on the input side a further contact 22 for the connection to the stop-light switch 14. On the output side the contacts 24 and 25 are provided for the connection of the electric motor 10. Within the constructional unit the winding of the electromagnet is connected to the negative terminal. The electric motor is connectable directly to said constructional unit and a separate ground lead from the voltage source to the electric motor 10 is-no longer necessary. In Fig. 3 is shown a longitudinal section of said constructional unit. In a metallic housing 30 a movable diaphragm 31 is mounted. On this diaphragm a switching member 32 acts on which a snap spring 33 is secured which serves as the movable contact member 13. The housing is closed by a bottom plate 34, which simultaneously serves as a coil form for the winding 35 of the electromagnet 16. The armature 36 of the electromagnet is fixedly connected with the switching member 32 and on the other side is urged by an adjustable pressure spring 37. Said pressure spring presses the armature 36 and thereby the switching member 32 against the diaphragm 31, so that in the normal case the switching over the mov able contact member 13 is effected by the movement of the diaphragm. In the drawing the switching position of the vacuum switch is shown in which the motor circuit is closed. The contact member 33 rests upon two stationary contacts, of which one is shown and designated by 38. This stationary contact is electrically connected to the connecting contact 20 (Fig. 2). As soon as the pump is running the diaphragm 31 is deflected in direction of the arrow A until the snap spring jumps over and switches off the electric motor, when the boundary value is reached. When the electromagnet 16 is energised, the armature 36 moves in the direction of the arrow B against the force of the snap spring 33, so that the snap spring 33 again jumps over to its other stable position. Thereby the switching member 32 lifts up from the diaphragm and the vacuum (stored energy) does not influence the switching behaviour until, after the operating time, the armature 36 is again released. Thus the vacuum switch 12 is latched in the conductive switching condition during the operating time. The basic idea of the invention is also applicable in systems comprising an hydraulic pressure reservoir. Then the vacuum switch has to be replaced by a suitable pressure switch with hysteresis behaviour. WHAT WE CLAIM IS:-

1. Control circuit for the electric motor of a pump for filling up an energy store for actuating auxiliary units in automotive vehicles, for example a brake servo unit, said circuit comprising, for controlling the electric motor, a hysteresis switch which responds to different predetermined boundary values of the energy stored, and means whereby the electric motor will also be started independent of the value of the stored energy upon putting into operation the auxiliary unit.

2. Control circuit according to claim 1,

wherein the electric motor remains switched on during the operating period of the auxiliary unit.

3. Control circuit according to claim 1 or 2, wherein the electric motor remains switched on beyond the operating period of the auxiliary unit until the hysteresis switch responds to the upper boundary value of the stored energy.

4. Control circuit according to claim 2, wherein the electric motor is controllable through a switch in parallel to the hysteresis switch which is closed during the operating period of the auxiliary unit.

5. Control circuit according to claim 1 or 3, wherein the hysteresis switch is switched over into the conductive condition by putting into operation the auxiliary unit.

6. Control circuit according to claim 5, wherein the hysteresis switch is blocked in the conductive condition during the operating period of the auxiliary unit.

7. Control circuit according to claims 5 and 6, wherein the hysteresis switch is switched over by an electromagnet.

8. Control circuit according to claim 7, wherein the electromagnet is controlled through a switch being closed during the operating period of the auxiliary unit.

9. Control circuit according to claim 7, wherein the hysteresis switch and the electromagnet are combined in a unit, this unit on the one hand being provided with connecting contacts for the connection to the positive and to the negative terminal of a voltage source and for connecting the switch and on the other hand two connecting contacts for connecting the motor.

10. Control circuit according to claim 9, wherein the hysteresis switch is provided with a diphragm on which is supported a movable contact with a snap-action spring, and wherein said contact is connected with a concentrically arranged armature of the electromagnet, said armature being movable in axial direction and against the force of a pressure spring removing the contact from the diaphragm and thereby switching over the snap spring into its stable switching position in which the motor circuit is closed.

11. A control circuit substantially as hereinbefore described with reference to and as illustrated in Fig. 1 or Fig. 2 of the accompanying drawings.

12. A control circuit as claimed in claim 1 including a hysteresis switch substantially as hereinbefore described with reference to and as illustrated in Fig. 2 or Fig. 3 of the accompanying drawings.

13. A motor vehicle having a control circuit according to any of claims 1 to 12 arranged to control a servo control unit of the vehicle.

14. A vehicle according to claim 13, wherein the control unit is a brake servo unit and a switch controlling the vehicle stop lights is arranged as part of the control circuit to start the electric motor independently.