GB2224089A

GB2224089A - A device for moving-off anti-slip regulation (ASR)

Info

Publication number: GB2224089A
Application number: GB8920866A
Authority: GB
Inventors: Wolf-Dieter Jonner; Gunter Kas
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1988-09-21
Filing date: 1989-09-14
Publication date: 1990-04-25
Anticipated expiration: 2009-09-14
Also published as: FR2636575A1; DE3832023A1; GB8920866D0; DE3832023C3; GB2224089B; FR2636575B1; JP2911498B2; JPH02169357A; DE3832023C2

Description

24 0 85 1 I '.I-

-1DESCRIPTION A DEVICE FOR MOVING-OFF ANTI-SLIP REGULATION (ASR)

The invention relates to a device for moving-off anti-slip regulation (ASR) or for assisting moving-off on hills.

In a braking system for motor vehicles, it is known to utilise existing ABS (anti-lock system) components for drive slip regulation or to assist moving-off on hills or on a slippery suface (British Patent Specification No. 2 119 883), wherein a special form of anti-lock system is used, namely the so-called ABS 2 type. In this anti-lock system, pressure medium accumulators are provided in connection with a return pump, wherein, in the "pressure reduction" mode of the anti-lock system, the pressure medium accumulators draw in pressure medium frorn the wheel brake cylinders through correspondingly switched ABS regulation valves, usually three-way, three-position valves. This pressure medium then passes by way of the return pump, which is connected to accumulator tanks or chambers. into the connecting line between the master brake cylinder and the wheel brake cylinders, wherein the connection is upstream of the ABS regulation valves.

If this known separate ABS 2 system is used as the basis for moving-off anti-slip regulation, an -2additional pressure accumulator is provided, in accordance with British Patent Specification No. 2 119 883, which, in the event of a moving-off anti-slip regulation operation, is connected by way of a three-port, two- position valve to the presssure line leading to the wheel brake cylinder. Depending on how the ABS regulation valves are triggered for the moving off anti-slip regulation function to be carried out, the pressure medium pressure present in the pressure accumulator passes to the respective wheel brake cylinder of the driven axle, which wheel brake cylinder is to be actuated selectively in the sense of a locking differential effect, wherein the ABS regulating valves for this case are triggered in an inverse manner, which can be effected by way of a correspondingly designed control logic circuit for the event of combined anti-lock/moving- off anti-slip regulation.

In order to utilise the components of the anti-lock regulator to achieve an inexpensive but fully effective drive slip control, a further pressurecontrolled change-over valve, an excess-pressure valve and a pressure switch are provided in addition to the pressure accumulator and the solenoid valve which connects it to the wheel brake cylinders.

1 The pump is a suction pump which, when there is insufficient pressure in the pressure accumulator on switching over the solenoid valve to effect the moving-off anti-slip regulation functions, is controlled either by way of the pressure switch or directly by the electronic control device in order to feed pressure medium into the pressure accumulator or the closed brake cicuit. The pressure-controlled change-over valve, which is additionally provided, opens when a predetermined minimum pressure is reached at the outlet of a feed pump accumulator chamber, thus allowing pressure medium to flow from the master brake cylinder to the accumulator chamber as well as providing replenishment. Finally, the non-return valve which is also provided is used to prevent the pressure between the solenoid valve, which changes over in the event of realisation of movingoff anti-slip regulation functions, and the ABS valves in the region of the wheel brakes becoming too high.

It is known from USA Patent Specification No. 4 416 347 to use ABS components for moving-off anti-slip regulation or to assist in moving-off on hills, with corresponding "inverse" control of the ABS regulation valves and modification of other components, wherein, however, in the event of both driven wheels spinning excessively, additional means -4are provided which reduce the output power of the drive machine by acting on the mechanical connection between the accelerator pedal and the throttle valve in the intake manifold of the internal combustion engine. This can be done using an electromagnetically controlled three-port, two- position valve.

In another combined device for carrying out ABS and ASR functions using the same components, the anti-lock system has an additional pressure accumulator which serves to supply brake pressure when ASR functions occur. This pressure accumulator can be charged under valve control with the aid of the return pump of the anti-lock system, wherein, during the pressure reduction phases of the drive slip control, the return pump operates into the pressure accumulator. Outside these control phases, that is during normal operation, the pressure accumulator can be recharged either by actuating the motor vehicle brake or by automatic activation of a charging circuit, with the co-operation of the return pump, when the motor vehicle is stationary or is in a non-braked driving state (German Offenlegungsschrift No. 31 37 287).

Thus, all the known combined systems require additional hardware components, at least one further pressure accumulator and hydraulic lines connecting it 1 1 -5to the other components, wherein the pressure required for realising the moving-off ASR functions results from this additional pressure accumulator.

It is an object of the present invention, using an anti-lock system of the ABS 2 type as a basis, to design such a system with the minimum additional means in such a way that, given additional software which can readily be inserted into the respective control device (computer), effective moving-off anti-slip regulation or assistance in moving-off on hills can be realised, the pressure level of which is independent of the function of the accumulator chamber which is always provided in the ABS 2 type, and in which there is always sufficient pressure medium volume and adequate pressure build-up for intensive moving-off ASR operation as well.

In accordance with the present invention, there is provided a device for moving-off anti-slip regulation (ASR) and/or for assisting moving-off (on hills), wherein a selective brake effect can be exerted in the manner of a locking differential effect on the driven wheels of a motor vehicle by integrating and utilising components belonging to an anti-lock system, including ABS multiple-way control valves connected between the wheel brake cylinders and the brake master cylinder, an accumulator for receiving pressure medium volume relieved as a result of an ABS effect, and a self- priming return pump for returning the pressure medium in the accumulator to the master brake cylinder, wherein an ABS solenoid valve, which is triggered for ASR operation, is connected in a main connection line between the brake master cylinder and the ABS control valves leading to the wheel brake cylinders, said ABS solenoid valve connecting the brake master cylinder, and hence its supply tank, by way of an inlet to the chamber of the accumulator and simultaneously braking said main connecting line leading to the ABS solenoid valves in such a way that said self-priming ABS return pump removes pressure medium from the storage tank of the master brake cylinder during ABS operation and feeds it to the ABS control valves to generate an ASR brake pressure modulation to selectively actuate the wheel brake cylinders.

Such a system has the advantage that an additional energy supply can be dispensed with and yet only a very small additional outlay is required to achieve effective brake pressure generation in the sense of a locking differential effect at the spinning wheel in order to realise ASR functions.

The only additional hardware required is a change-over valve, preferably a three-port, two-position version, and in an advantageous embodiment., some more non- return valves for the sake of completeness. The invention uses the existing basic components of an anti-lock system corresponding to the ABS 2 type, that is, the existing return pump, which in this case, however, is a self7priming pump, as well as the pressure accumulator, which is there as an ABS component, wherein, however, it is not that evaluation takes place of the pressure which may be generated and even limited by this accumulator, but that pressure medium is taken from the region of the master brake cylinder by the return pump to generate the desired selective brake pressure effect in the event of moving-off anti-slip regulation.

Normal braking and the realisation of ABS functions can be carried out regardless of the additional ASR functions possible.

The inve-ntion utilises the knowledge that, in the event of moving-off anti-slip regulation or as an aid to moving-off on a hill or a slippery surface, particularly high demands are not necessarily or do not necessarily have to be made on the pressure build-up time at the spinning wheel. For this reason, the invention dispenses completely with the use of stored energy, thus eliminating the problem of gas permeation from a pressure accumulator into the brake t -8fluid, as well as with the necessity of providing further hydraulic connections.

In other embodiments, one-way valves are connected parallel to the changeover solenoid valve provided in the direction of the wheel brake and the master brake cylinder, in order, even during the realisation of ASR functions during which the changeover solenoid valve is triggered, to allow the brake to be actuated as well as to prevent the pressure buildup during ASR operation becoming too large. When a predetermined pressure is exceeded, the one-way valve in the direction of the master brake cylinder relieves the rest of the circuit, which is fed by the selfpriming return pump and separated from the master brake cylinder by the change-over valve.

The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings, in which:- Fig. 1. illustrates schematically a portion only of a motor vehicle braking system having a master brake cylinder and several ABS components as well as several other modifications necessary to the present invention; and Fig. 2 is a flow diagram of the computer functions performed in the realisation of moving-off anti-slip regulation or to aid moving off on hills.

1 1 1 Attention is drawn to the fact that the Fig. 1 shows only those hardware components required for. achieving the invention in this embodiment, wherein the existing electromagnetic change-over and control valves are triggered by an electronic control circuit (not shown), prefeiably in the form of a programcontrolled computer, which effects the necessary controls and change-overs using the output signals fed to it by the wheel sensors, together with other information where appropriate. Such control circuits are known for normal braking systems including associated ABS components as well as for combined ABS/ASR systems, and therefore do not need to be described in any further detail.

In the drawing, a master brake cylinder of a braking system is designated 10. It comprises a brake pedal actuator 11 and a supply tank for the pressure medium. In the present case, two separate brake circuits 1 and II are provided which either lead to the wheels of one of the axles or, in the event of a diagonally split brake cicuit, act on one front wheel and the opposite rear wheel.

Let it be assumed that, in the embodiment shown, the brake cicuit I, which is shown in detail, is connected, split in its different modes, to the wheel brake cylinders of the wheels of the driven axle, 1 -10wherein, in a known manner, the multiple-way solenoid valves 12a, 12b, which realise the ABS functions of pressure build-up, pressure maintenance and pressure reduction, are connected as three-port, three- position valves in the pressure line coming from the master brake cylinder 10 between said master brake cylinder and the wheel brake cylinders (not shown).

In order to accommodate excess pressure medium in the ABS "pressure reduction" function, the respective valve connection 13a, 13b is connected to an accumulator chamber 14, which contains in a cylindrical housing 15 a piston 17 which is prestressed by a spring 16. In order to return the pressure medium contained in the accumulator chamber to the brake circuit, a return pump 18, abbreviated as RFP, is connected by way of a pump inlet valve 19 to the storage chamber 14 and by way of a pump outlet valve 20 to the master connecting line 21 between the master brake cylinder 10 and the wheel brake cylinders or the ABS solenoid valves.

The return pump is a self -priming (ABS) return pump. Details of this type of pump can be found in the above-mentioned British Patent Specification No. 2 119 883.

In order to realise moving-off anti-slip regulation or to assist movingoff on hills using such t -11a braking system having an anti-lock system of the ABS 2 type in accordance with the present invention, the only additional hardware component is a solenoid change-over valve 22, abbreviated as ASR-W, which is installed in the master brake cylinder circuit I of the driven axle upstream of the ABS control valves 15a. 15b. The change-over solenoid valve 22 is preferably a three-port, two-position valve. The three-port, two-position solenoid valve 22 is switched in such a way that, in the event of normal braking or even in the event of ABS operation, the master connecting line 21 from the master brake cylinder to the ABS solneoid valves 12a, 12b is open, that is switched through, whereas when the ASR solenoid valve 22 is triggered, this master connecting line, which comes from the ABS solenoid valves 12a, 12b, is broken. wherein the flow from the master brake cylinder 10 is switched to an additional line 23, which is directly connected to the storage chamber 14 or by way of the non- return valve 19, which is disposed between the storage chamber and the return pump 18, to said return pump. In its non-energised first position, the ASR solenoid valve 22 connects the master brake cylinder to the wheels. In its energised position, the master brake cylinder is connected to the accumulator chamber of the ABS pressure-reduction -12circuit so that, in the event of ASR operation, the ABS return pump is in a position to suck in pressure medium volumes by way of the central valve of the master brake cylinder 10 from its storage tank (not shown) and to pump them into the corresponding wheel brake cylinders of the drive wheels (by way of the ABS solenoid valves 12a. 12b) since the connection between the pressure side of the pump and the master brake cylinder is, as mentioned above, simultaneously blocked off by this threeport, two-position ASR solenoid valve.

Pressure modulation in ASR operation is effected in a known way by the ABS solenoid valves 12a, 12b by utilising the pressure generated by the return pump 18.

In order to prevent pressure in the unit becoming too high during operation of the return pump 18 when the inlet of the ABS solenoid valves 12a, 12b is closed, it is recommended to connect a relief valve 24, which is prestressed by, for example 160 bar, parallel to the ASR solenoid valve 22 in the direction of the master brake cylinder.

It is also advantageous to connect a second non-return valve 25 parallel to the ASR solenoid valve 22 in the direction of the wheel brakes in order to allow a pressure in the direction of the wheel brake when the ASR solenoid valve 22 is energised, that is 1 -13during ASR operation, when the brake pedal 11 is actuated, in case a normal braking operation is started at the same time.

Fig. 1 shows the hydraulic circuitry with reference to a front axle/rear axle brake circuit split I and II, wherein it is understood that the invention can also be used in a diagonally split brake circuit in which a second changeover valve would accordingly be required for ASR operation (three-port, two-position solenoid valve).

Because of the self-priming characteristics of the pump, it may be recommendable to additionally dispose a non-return valve 26, which is, for example, prestressed by around only 0.5 - 1 bar, in the ABS pressurereducing circuit to the accumulator chamber 14 between the outlets 13a, 13b of the ABS solenoid valves and the accumulator chamber in order to prevent an underpressure in the wheel brake cylinders being generated during ABS operation by the self-priming pump when the ABS solenoid valves are triggered for a long time in the third pressure-relief position.

Triggering of the solenoid valves shown in the drawing and change-over between normal brakes, brakes having ABS functions, and ASR operation, are carried out in a conventional way by an electronic control device designed for these fuctions, which is supplied 1 -14with appropriate information, in particular about spinning or locking wheels, by peripheral sensors, in particular wheel sensors.

The flow diagram of Fig. 2 shows the functions, which have already been described above, which have to be carried out by the computer for programcontrolled realisation of moving-off anti-slip regulation or to aid moving-off (on hills). It will be understood that, in addition to the hardware described above, the invention is preferably part of a programcontrolled system in the region of the ABS/ASR control device. The ASR functions are called up, for example, by spinning wheels which are detected by the wheel sensors, preferably in a speed range below 40km/h.

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Claims

-15CLAIMS 1. A device for moving-off anti-slip regulation (ASR) and/or for assisting moving-off (on hills), wherein a selective brake effect can be exerted in the manner of a locking differential effect on the driven wheels of a motor vehicle by integrating and utilising components belonging to an anti-lock system, including ABS multiple-way control valves connected between the wheel brake cylinders and the brake master cylinder, an accumulator for receiving pressure medium volume relieved as a result of an ABS effect, and a self-priming return pump for returning the pressure medium in the accumulator to the master brake cylinder, wherein an ABS solenoid valve, which is triggered for ASR operation, is connected in a main connection line between the brake master cylinder and the ABS control valves leading to the wheel brake cylinders, said ABS solenoid valve connecting the brake master cylinder, and hence its supply tank, by way of an inlet to the chamber of the accumulator and simultaneously braking said main connecting line leading to the ABS solenoid valves in such a way that said self-priming ABS return pump removes pressure medium from the storage tank of the master brake cylinder during ABS operation and feeds it to the ABS control valves to generate an ASR brake pressure modulation to selectively actuate the wheel brake cylinders.

1

2. A device as claimed in claim 1, wherein said self-priming ABS return pump removes brake pressure medium by way of a central valve of the brake master cylinder and feeds it by way of a pump outlet valve to said main connecting line between the brake master cylinder and the wheel brake cylinders.

3. A device as claimed in claim 1 or 2, wherein a first non-return valve is connected parallel to the ASR solenoid valve in the direction of the master brake cylinder, in order to limit pressure during operation of the return pump when the ABS control valves are closed.

4. A device as claimed in any of claims 1 to 3, wherein a second nonreturn valve is connected parallel to the ASR solenoid valve in the direction of the wheel brake cylinder, in order to permit normal braking when the ASR change-over solenoid valve is energised for ASR operation.

5. A device as claimed in any of claims 1 to 4, wherein a third nonreturn valve is connected between the outlet connections of the ABS solenoid valves in the ABS pressure-reduction circuit and the inlet to the chamber of the accumulator.

6. A device as claimed in claim 5, when apendant to claims 3 and 4, wherein the first non-return valve parallel to the ASR solenoid valve is prestressed by 1 -17approx. 160 bar, the second parallel non-return valve is prestressed by approx. 4 bar and the third non-return valve in the ABS pressure reduction circuit is prestressed by approx. 1 bar.

7. A device for moving-off anti-slip regulation and/or for assisting moving-off (on hills),. substantially as hereinbefore described with reference to and as illustrated in Figure I of the accompanying drawings.

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as 1990 atThe Patent Office, State House, 66'71 High iioibor--i, LondoLWCIR4TP.FUrLher copies maybe obtained from ThefttentOffice Was Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent. Cori 1187