GB1560886A

GB1560886A - Electrical drives for piston pumps

Info

Publication number: GB1560886A
Application number: GB2856376A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1975-07-11
Filing date: 1976-07-09
Publication date: 1980-02-13
Also published as: FR2317525B1; SE426679B; DE2531016A1; JPS5211376A; JPS5932342B2; SE7607820L; IT1067064B; FR2317525A1

Description

(54) IMPROVEMENTS IN OR RELATING TO ELECTRICAL DRIVES FOR PISTON PUPS (71) We, ROBERT BOSCH GMBH, a German Company, of Postfach 50, 7 Stuttgart 1, Federal Republic of 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 an electrical drive for a piston pump in which the piston is displaced by means of an electromagnetically driven armature or by means of a motor-driven cam plate.

By way of example, brake systems having anti-locking regulating systems require, on the one hand, pumps for, for example, produring the brake pressure or for returning the brake fluid discharge during regulation, and, on the other hand, valves for, for example, regulating the brake pressure. Both the pumps and the valve each normally have a separate electrical drive. It is important to minimize the cost of the system, particularly in the case of anti-locking regulators.

Consequently, an object of the invention is to save one of the electrical drives required when a valve arrangement and a pump are provided.

According to the present invention there is provided an electrical drive for a piston pump in which the piston is displaced by means of an electromagnetically driven armature or by means of a motor-driven cam plate, and in which the armature or the cam plate also acts as a drive for the movable member of a multi-position valve unit which controls at plurality of valve passages, and in which means are provided for rendering the pump ineffective at least when the armature or the cam plate is required to drive the movable member of the multi-position valve unit into a selected position.

One embodiment of the invention which will be described hereinafter in some detail includes an electromagnetic drive for the pump. In other embodiments, however, an electric motor having an eccentric can act as an equivalent of this drive. The pump and the valve arrangement can be driven simultaneously by the drive, and when required the pumping action can be rendered ineffective or one of the parts, particularly the movable valve member, can be decouplable from the drive.

In one embodiment of the invention, during a pure pumping operation, the distance between the movable member of the valve arrangement and the armature or the pump member driven by the armature is greater than the travel of the armature at least during a pure pumping operation. The movable member of the valve arrangement is acted upon by a spring force such that the movable valve member is urged towards the armature. Mechanical means are provided to be introduced between. the armature or the driven pump member and the movable valve member for transmitting the movement to the movable valve member.

Couplings are also conceivable which connect the movable valve member to the armature or to a member connected to the armature. Likewise, the pump piston can also be selectively connectible to the armature.

The same principle can also be used in the case of a motor drive having an eccentric, wherein the motor for the pump drive rotates continuously in one direction and, upon coupling to the valve, only rotates through predetermined angles. Preferably, however, for the purpose of simplification, the motor is rotated in only one direction even when the driving the valve.

By correlating displacement of the movable valve member with displacement of the armature, it is possible to operate the armature with strokes of differing amplitude during pure pumping dperations on the one hand and during driving the movable valve member on the other hand, so that the valve arrangement is actuated only by large amplitude strokes of the armature.

When the invention is used in brake system having anti-locking regulators, the armature or the eccentric can be coupled to the movable member of the valve (or of the pump) upon the occurrence of a predetermined measured value, for example when a predetermined pressure is reached in a brake circuit. By way of example, the valve arrangement can have a resilient or spring-biassed member which is subjected to such pressure and which, upon displacement, actuates a lever which effects the coupling operation. In another embodiment, a pressure sensor might switch on a circuit for the switching-on of an electromagnetic coupling.

When the pumping action is not required during actuation of the valve, since, for example, the volume of brake fluid stored in a small spring-loaded accumulator is an adequate source of brake pressure for the regulating operation in an anti-locking regulator, the pump can be rendered ineffective by, for example, disconnecting the armature or eccentric from the pump piston or, alternatively, by opening a valve, particularly an inlet valve, of the pump. When using the above-mentioned lever for actuating the coupling means, such valve may also be opened by way of this lever.

The valve arrangement whose movable member is to be driven by the armature or eccentric is preferably a multi-position valve unit, wherein differing spring forces act upon the armature upon transition of the movable valve member from one position to the next. The electrical drive can be operated with differing degrees of electrical power according to the desired position, although, at least when the valve has several positions, it is more advantageous to provide control means for sensing the displacement of the armature or the rotation of the motdr. Such control means, which may include, for example, switching contacts or contactless switches (for example Hall generators, switches which are sensitive to magnetic fields, optical scanning), can either interrupt the electrical energy acting upon the drive upon attaining the corresponding position and render the full power effective again after a certain return movement of the armature (two-state regulation), or, alternatively, corerspondingly reduce the electrical power to that required to hold the armature or motor in the corresponding portion after the desired position has been attained; this can be achieved by high-frequency pulses having a different duty ratio according to each individual position or by reducing the power level.

During motor drive, the displacement can be sensed on the movable pump member, or the angle of adjustment can be sensed on a coroating member, in order to determine the drive power. Reversal of the motor can be prevented by switching on the motor again or by a holding power. A stepping motor can be used.

At least some of the individual valves of the multi-position valve unit can be in the form of seat valve (poppet valves), wherein one member of each such valve, particularly the valve closure member, must be displaceable relative to the carrying member.

Differing pump strokes, i.e. differing pump outputs, can be realised with the means described above (sensing displacement and controlling the electrical power fed), and also the above-mentioned differing armature movements for pump operation only or for additional valve actuation.

The invention will be further described by way of example with reference to the accompanying drawings in which: Fig. I is a diagrammatic illustration partly in section of an integrated brake force booster including an anti-locking regulator for regulating the pressure on the brakes of a vehicle and embodying an electro; magnetic device according to a first embodiment of the invention, Fig. 2 is a diagrammatic illustration partly in section of a booster similar to that of Fig. 1 but embodying slide-valves and an electromagnetic drive according to a second embodiment of the invention, Fig. 3 is a diagrammatic illustration partly in section of a booster similar to that of Fig. 2 but embodying an elecromagnetic drive according to a third embodiment of the invention, and Fig. 4 is a diagrammatic illustration partly in section of a booster similar to that of Fig. 2 but embodying an electromagnetic drive according to a fourth embodiment of the invention.

Referring to Fig. 1, an electromagnetic drive comprises a coil 2, an armature 3 and a spring 6. When an auxiliary piston 14 is in one position, brake fluid flows from a reservoir 4 by way of a line 5 to a pump cylinder and is delivered by way of a nonreturn valve 8 to a spring-loaded accumulator 9 by means of a pump piston 7 moved by the drive. In this instance, the pump and the accumulator 9 constitute a source of brake pressure. The auxiliary piston 14 is slidable in a first clylinder bore 14a of a tandem master cylinder and its working face is exposed to a pressure chamber 14b at the inner end of the cylinder bore 14n with which the accumulator 9 communicates through a non-return valve 9a.Displacement of a push rod 10 carried by part 13a of a two-part control piston 13 of which part 13b is connected to a brake pedal 1, opens a brake valve 11 in the auxiliary piston 14 for introducing pressure from the accumulator 9 and the pressure chamber 14b into a line 12. Since this pressure also reacts upon the brake pedal by way of part 13-h of the piston 13 and a reaction force transmitted in the form of a spring 13c, the driver receives information concerning the level of the pressure introduced.

In this instance, it is immaterial that the piston 14 is also movable and can act as an emergency piston.

The pressure introduced into a line 12 is applied by way of an open valve 15 and a valve 17 of a five-position valve unit 16 to the rear axle brake circuit connected to brake line 18 (the latter being connected to valve 17), and is applied to a further piston 19 by way of the open valve 15, a line 15g and control chamber 36. The pressure in a second brake circuit connected to a line 20 is built up by displacement of the piston 19. This second brake circuit is divided in the five-position valve unit 16 into two circuit branches 23 and 24 which lead to the individual front wheels and which are incorporated valves 21 and 22 for the independent reduction of pressure in these circuit branches. Furthermore, the pressure introduced influences the position of a spring biassed piston 25 arranged in the valve unit.When a predetermined, but relatively low, pressure is reached, a lever 26 is deflected to an extent where coupling means, in the form of a roller 27 in the present instance, move into a position between a tappet member 28 moved by the drive 2, 3 and 6, and a movable actuating member 29 of the valve unit 16. The member 29 is used to the right by a spring 30, and the distance between the members 28 and 29 is such that the members 28 and 29 are engaged during a pure pumping operation and the members 28 and 29 are only coupled to one another after the roller 27 has been swung in between them as shown by a broken line.

A push rod 31 is also connected to the lever 26 and opens the valve 32 upon dis- placement of the piston 25 and thus renders the pump inoperative. The resilient construction of the wall 33 allows displacement of the rod 31.

The electromagnetic drive unit comprising the coil 2, the armature 3, the spring 6 and the piston 7 fulfils two functions. When the roller 27 is in the position shown in Fig.

1, members 28 and 29 are disconnected from one another and the pump fulfills a pure pumping operation to draw brake fluid from the reservoir 4 and charge it into the accumulator 9; this occurs when the pedal 1 is not operated to apply the brakes. When the pedal 1 is operated, brake fluid is admitted through brake valve 11 to line 12 and when a predetermined pressure is reached in line 12, piston 25 is displaced to the right to move the push rod 31 to the right to open the inlet valve 32 and render the pumping action of the piston 7 ineffective, and to insert roller 27 between the members 28 and 29. The coil 2, armature 3, spring 6 and piston 7 can now function to displace the member 28 to the left and thereby move the actuating member 29 of the 5-position valve unit 16.Anti-skid regulation of the brakes at the wheels is effected by sensing the wheel rotational behaviour and appropriately energising the coil 2 in response thereto to displace the actuating member into an appropriate position sensed by the respective contacts K to K,.

When the drive is in the illustrated starting position, the contact Ki is closed and pressure can be built up at all the brakes.

if the movable member 29 of the 5-position valve unit 16 is to be moved into position 2 in which the valve 15 is closed, the armature 3 is moved until the contact K, is closed and this signals that this position has been reached. When in this position, any further build-up of pressure at all the wheels is prevented. When the movable member 29 of the valve unit is in position 3, determined by closing of the contact K the push rod 34 has raised a valve closure member of the valve 35 from its seat, so that the pressure in the control chamber 36 is reduced by convection through valve 35 to line 37, and pressure is also reduced in the rear axle circuit connected at 18 by convection through the non-return valve 17 and the valve 35 to the return line 37.However there is no reduction in pressure at the frdnt wheels because the non-return valves 21 and 22 of the valve unit 16 become effective. Normally a spring-biassed element 57 holds the non-return valves 21 and 22 in their illustrated open position.

Element 57 can be raised by a piston 56a which is subjected on one side to the pressure in the line 12 in front of the valve 15, the other side of the piston 56a being subjected to the pressure in the line 20 in front of the valves 21 and 22. When the movable member 29 is in position 4 contacts K3 becomes effective. When the movable member is in this position, valve 17 is also closed and the push rod 38 opens nonreturn valve 26 (assuming the element 57 has been lifted by the piston 56a), so that pressure is reduced in circuit branch 24, and only in that circuit branch 24.When the armature reaches its end position (without a separate contact in this instance), the valve closure member of valve 22 is pressed against a second seat, and the valve closure member of valve 21 is raised from its seat (again assuming the element 57 has been lifted), so that the pressure is reduced in the circuit branch 23, and only in that circuit branch 23.

It will be seen from the drawing that the valves in the five-position valve unit 16 are seat valves (poppet valves), the individual closure members being movable relative to the movable actuation members 29 of the five-position valve unit 22 against spring pressure. These spring forces, together with the spring 30, determine the total spring force acting upon the armature and increasing in stages.

The reaching of the individual contacts K1 to Ks signals to the control circuit for the coil 2 when the armature has reached a particular desired position. The power supplied to the coil 2 is then reduced to hold the armature in that position. If the five-position valve unit is to be brought into, for example, the position in which the pressure in the circuit branch 24 is reduced, the control circuit applies the full control power to the coil 2 as a result of the signal of an evaluating circuit until the contact K3 signals that this position has been reached and causes a reduction in power applied to the coil 2 to hold the armature 3 in the corresponding position.

Referring to Fig. 2, the five-position valve unit 16 of Fig. 1 is replaced by two coupled five-position slide valves 40 and 41 which are illustrated diagrammatically. Solely for the sake of convenience and similarity with the embodiment of Fig. 1, the conditions set up by the slide valves read from right to left: thus the conditions illustrated correspond to position 1, whilst the second from the right correspond to position 2, the third from the right to position 3, the fourth from the right to position 4, and the fifth from the right to the end position.

Since the actuating member 43 is shown in its normal or starting position 1 from which it will be displaced to the left as seen in Fig. 2 to its other position, the effect is equivalent to the line convections (rather than the slide) being displaced step-wise to the left. Whereas the valves of the fiveposition valve unit 16 of the embodiment of Fig. 1 operate at least partly as nonreturn valves, the slide valves 40 and 41 are illustrated as having their line apertures.

Here also, the electromagnetic armature 3 is couplable to the movable valve member 43 by the interposition coupling means 44. A contactless position sensor 45 is shown for sensing the displacement and determines the displacement during driving of the movable valve member or in the case of a variable pump stroke. All the other parts shown in Fig. 2 correspond to those shown in Fig. 1, Referring to Fig. 3, a motor 50 acts as the drive and an eccentric 51 driven thereby normally drives the pump piston 7 and, upon the introduction of coupling means 53, also drives a movable valve actuating member 54 of the multi-position slide-valves 55. In this instance, the pump 52 is put out of operation upon coupling the movable valve actuating member by the inlet valve 32 being opened at the same time. The position of the motor is sensed by way of a rotary angle sensor 56.Alternatively, the motor may be a stepping motor.

Referring to Fig. 4, a motor 60 continuously drives pump 61 and also drives movable valve actuating member 62 of the multi-position slide-valves 64 during a pumping operation. For actuating the slide valves the motor is stopped in specific position as determined by a rotary angle sensor 63.

The slide valves 55 of the embodiment of Fig. 3 and the slide valves 64 of the embodiment of Fig. 4 correspond to, and are illustrated in the same manner as the slide valves 40 and 41 of the embodiment of Fig.

2, though in Fig. 4, as will be apparent from the illustrated position of the piston 7, the valve actuating member 62 is illustrated in its end position and not its starting position.

In the complete specificaion of our copending Patent Application No. 28562/76 (Serial No. 1551944) we have disclosed and claimed a master brake cylinder assembly for a dual circuit brake system comprising an auxiliary piston displaceable in a first cylinder bore and having a working face exposed to a pressure chamber connectible to 2 brake pressure source, a brake control valve disposed in the auxilary piston for connecting the pressure chamber to a first brake circuit, a control piston displaceably mounted in the auxiliary piston for opening the brake control valve, the control piston being actuable externally from the side of the auxiliary piston remote from its working face for applying the brakes, the pressure in the first brake circuit being applied to the control piston against the actuating force, and a further piston displaceable in a second cylinder bore and dividing the latter into a brake chamber for a second brake circuit and a control chamber to which is applied at least indirectly the pressure in the first brake circuit or a pressure derived therefrom, the control piston after a predetermined travel relatively to the auxiliary piston, upon actuation, engaging the auxiliary piston to take it along axially with it, and an extension piece extending into the control chamber and transmitting movement of the auxiliary piston to a further piston, upon actuation of the control piston and after a predetermined relative travel of the auxiliary piston towards the further piston.

Claims

WHAT WE CLAIM IS:

1. An electrical drive for a piston pump in which the piston is displaced by means of an electromagnetically driven armature or by means of a motor-driven cam plate, and in which the armature or the cam plate also acts as a drive for the movable member of a multi-position valve unit which controls a plurality of valve passages, and in which means are provided for rendering the pump ineffective at least when the armature or the cam plate is required to drive the movable member of the multiposition valve unit into a selected position.

2. A drive as claimed in claim 1, in which at least one of two members is selectively couplable to the drive.

3. A drive as claimed in claim 2, in which said one member is the movable member of the multi-position valve unit.

4. A drive as claimed in claim 1, 2 or 3, in which during a pure pumping operation the distance between the movable member of the multi-position valve unit and the armature or the cam plate is greater than the travel of the armature or the throw of the cam plate, mechanical means are provided to be introduced between the armature or the cam plate and the movable member of the multi-position valve unit, and means are provided for producing a spring force which acts upon the movable member of the multi-position valve unit such that the movable member is urged towards the armature or the cam plate.

5. A drive as claimed in any of claims 1 to 4, in which said means for rendering the pump ineffective comprises a pressure sensitive device which becomes operative in response to a pressure derived from operation of the pump reaching a predetermined value.

6. A drive as claimed in claim 5, in which said means for rendering the pump ineffective comprises a valve which is opened by said pressure sensitive device when it becomes operative.

7. A drive as claimed in claim 6, in which the pump has a resilient wall through which passes in sealed relationship a member linking said valve with said pressure sensitive device.

8. A drive as claimed in claim 7, in which said valve is a pump inlet valve and said member is a push rod.

9. A drive as claimed in claim 5, 6, 7 or 8 when dependent on claim 4, in which there is associated with said pressure sensitive device a lever connected to the mechanical means to be introduced between the armature or the cam plate and the movable member of the multi-position valve unit.

10. A drive as claimed in any preceding claim, in which differing spring forces opposing the drive to the movable member of the multi-position valve unit are effective upon the transition of the movable member from one position to the next.

11. A drive as claimed in any preceding claim, in which control means are provided for sensing the extent of displacement of the armature or of rotation of the cam plate, and through which upon the movable member of the multi-position valve unit or the cam plate reaching a predetermined position, the power fed to the electromagnet is reduced to a value sufficient to hold the armature in a corresponding position or the power fed to the motor is discontinued.

12. A drive as claimed in any preceding claim, in which at least some of the valves of the multi-position valve unit are seat or poppet valves, the valve closure member or a valve seat of a valve being displaceable at least partially and to a specific extent relative to a movable member which carries it.

13. A drive as claimed in any of claims 1 to 11, in which the multi-position valve unit comprises a slide valve.

14. A drive as claimed in claim 11, 12 or 13, in which the control means are jointly used for sensing the displacement of the armature and for producing different pump strokes.

15. A drive as claimed in any preceding claim, when used in an anti-locking brake control system in a vehicle, in which the pump, together with a pressure accumulator, acts as a brake pressure source, and the multi-position valve unit acts as a regulating valve for anti-locking brake regulation.

16. An electrical drive constructed and arranged and adapted to operate substantially as hereinbefore particularly described with reference to and as illustrated in Fig.

1, or Fig. 2, or Fig. 3, or Fig. 4 of the accompanying drawings.