GB2038432A

GB2038432A - Hydraulic Supply Priority Valves

Info

Publication number: GB2038432A
Application number: GB7939226A
Authority: GB
Original assignee: Alfred Teves GmbH
Current assignee: Continental Teves AG and Co OHG
Priority date: 1978-11-17
Filing date: 1979-11-13
Publication date: 1980-07-23
Also published as: FR2441749A1; FR2441749B1; IT1125814B; GB2038432B; IT7927336A0

Abstract

An accumulator charging valve (1) connected to a pump (3) gives to a port (9), which is connected to a brake booster (11), priority of supply over port (5), which is connected to power steering gear. When accumulator pressure is low, ball valve (13) allows flow from pump (3) through passage (14) and throttle (6) to the non-return valve (8) in the accumulator inlet, and to the inlet chamber (21) of control valve (19), so that when the booster (11) operates, pressure in line (3) moves the control valve spool (27) and pressure from chamber (21) closes the valve (4). When accumulator pressure is high, ball valve (13) closes throttle (6) and vents passages (18,21) so that there is no control pressure available to close valve (4). The fluid source (3) thus only has to deliver fluid under high pressure if the booster is in operation, thereby reducing noise and prolonging the life of the pump as well as reducing the pump's energy consumption. <IMAGE>

Description

SPECIFICATION Accumulator Charging Valve This invention relates to an accumulator charging valve including a pressure port connectible in use to a source of pressuretransmitting fluid, a first user port connectible with a first user component, a second user port connectible with a pressure accumulator and a second closed-centre user component, a valve device, operative in response to the accumulator pressure, via which the pressure port is connectible with the second user port through a throttle below a predetermined accumulator pressure and is connectible with the first user port above the predetermined accumulator pressure, wherein the valve device includes a non-return valve controllable by a control pressure and adapted to shut off the connection of the pressure port to the first user port below the predetermined accumulator pressure.

The expression "closed-centre" used herein means that the passage of the user component, which may be a valve, is closed in the normal position. There is no flow through this valve to a piston adapted to be exposed to pressure. If this user component is to be put into operation, the passage of the valve will be opened so that pressure can act on the piston.

The expression "open-centre" used herein means that the passage of the user component, which may be a valve or a power steering gear, is in the normal position open. Fluid flows more or less without pressure through the passage of the user component to a reservoir. If this user component is to be put into operation the passage will be more or less closed so that pressure will build up to act upon the user component.

Such an accumulator charging valve is known from German printed and published patent application DE-OS 2,364,413. With the accumulator loaded, in this accumulator charging valve the fluid delivered by the source of pressuretransmitting fluid is completely fed through the open non-return valve to the first user component, which may be a power steering gear operating according to the open-centre principle.

If the accumulator pressure drops below the predetermined level, the valve device will switch such that the passageway of the non-return valve is at least largely closed and the fluid delivered is supplied to the pressure accumulator until it is again pressurized to its predetermined level. The accumulator pressure will, however, drop not only when the second user component, which may be a brake booster in an automotive vehicle, is added to the circuit, but also as a result of leakage on the individual valves. If the second user component is rarely activated, which is the case, for example, when travelling long distances on a motorway where the brake is rareiy applied, the pressure accumulator will become depleted after some time by leakage.In that case, whenever the accumulator pressure drops below a predetermined magnitude, the pump forming the source of pressure-transmitting fluid, which, with the accumulator loaded, delivers fluid to the reservoir at only low pressure through the non return valve and the power steering gear which is usually operated in the open-centre mode, is required to recharge the accumulator at a high pressure although there is presently no fluid demand at the second user component, i.e., the brake booster.

However, when fluid is delivered at a high pressure, the pump noise will increase substantially as compared to the delivery of fluid at low pressure. Such noise is very annoying, in particular when the accumulator charging valve is fitted to an automotive vehicle.

According to the present invention there is provided an accumulator charging valve including a pressure port connectible in use to a source of pressure-transmitting fluid, a first user port connectible with a first user component, a second user port connectible with a pressure accumulator and a second closed-centre user component, a valve device, operative in response to the accumulator pressure, via which the pressure port is connectible with the second user port through a throttle below a predetermined accumulator pressure and is connectible with the first user port above the predetermined accumulator pressure, wherein the valve device includes a non-return valve controllable by a control pressure and adapted to shut off the connection of the pressure port to the first user port below the predetermined accumulator pressure, and wherein the valve passageway of the non-return valve is adapted to be shut off with the second user component operating in the open-centre mode.

As a result of this arrangement, loading of the accumulator and thus a pump delivery at high pressure is possible only if both the accumulator pressure has dropped below a predetermined magnitude and the second user component is activated. This means that fluid is supplied to the second user port only if there is indeed a fluid demand at the second user component. In addition to reducing the noise, the accumulator charging valve thus constructed also prolongs the life of the pump because the load applied to it is substantially less. The reduced pump load results further in a reduced consumption of driving energy.

Embodiments of the invention will now be described with reference to the accompanying drawings, in which: Fig. 1 shows a sectional view of an accumulator charging valve constructed in accordance with one embodiment; and Fig. 2 shows a sectional view of accumulator charging valve constructed in accordance with another embodiment.

The accumulator charging valve 1 shown in the Figures includes a pressure port 2 to which a pump 3 is connected with its delivery line. Via a non-return valve 4, pressure port 2 is connectible with a first user port 5 to which a power steering gear, operating in the open-centre mode, of an automotive vehicle may be connected.

Via a throttle 6 and a pilot valve 7 as well as a check valve 8, pressure port 2 is also connectible with a second user port 9. Connected to the second user port 9 is both a hydro-pneumatic pressure accumulator 10 and a hydraulic brake booster 11.

The pilot valve 7 includes a chamber 12 accommodating a ball 13 serving as a valveclosure member. Opening into chamber 12 on opposite sides are the connection 14 of the pressure port to the pilot valve 7 and a line leading to an unpressurized return line 15, with the orifices of the connection 14 and of the line leading to the return line 1 5 forming valve seats at chamber 12 for seating engagement with the valve-closure member (ball 13). Which of these two fluid-pressure channels is shut off by ball 13 is dependent upon the pressure in the accumulator 10.

Above a predetermined accumulator pressure, ball 13 will be displaced into the position shutting off the connection 14 by an operating piston 1 6 subjected to accumulator pressure against the force of a spring 17, whereas below a predetermined accumulator pressure spring 1 7 will displace the operating piston 1 6 into the opposite direction so that ball 13 shuts off the connection of chamber 12 to return line 1 5.

Further, opening into chamber 12 equally on opposite sides are a line 1 8 leading from chamber 12 via check valve 8 to the second user port 9, and a supply line 21 leading from chamber 12 via a control valve 1 9 to a pressure chamber 20 of non-return valve 4. Thus supply line 21 and line 18 are connected with pressure port 2 or with the unpressurized return line 15, depending on the position of pilot valve 7 and consequently depending upon the pressure level in accumulator 10.

The non-return-valve 4 comprises a piston 23 which is axially slidable in a cylindrical bore 22 and divides the cylindrical bore 22 into pressure chamber 20 and a chamber 24 connected to pressure port 2, so that the end surface of piston 23 pointing towards pressure chamber 20 may be subjected to a control pressure while its end surface pointing towards chamber 24 is subjected to the discharge pressure of the pump 3. Piston 23 at least largely shuts off the first user port 5 opening radially into the cylindrical bore 22, with piston 23 being adapted to be subjected to the discharge pressure of pump 3 in the opening direction and, in addition to the control pressure, to the force of a spring 25 in the closing direction.

The control pressure is a pressure which is reduced compared to the pump discharge pressure by throttle 6 and is ailowed to be supplied from chamber 12 of pilot valve 7 to pressure chamber 20 through supply line 21 only with the pilot valve 7 open and the control valve 1 9 in the appropriate position.

Control valve 1 9 whose closure member 26 is a valve spool, connects in one valve position the pressure chamber 20 of the non-return valve 4 with the unpressurized return line 1 5 and, in the other valve position, with the chamber 12 of pilot valve 7 via supply line 21. Closure member 26 includes an effective surface 27 which may be subjected to pressure against the force of a spring 28.

The brake booster 11 which forms the second user component includes an inlet chamber 29 which is closed with the brake in the inactivated state. When the brake is applied, the inlet chamber 29 is connected to a piston chamber 32 via a valve spool 31 having a passage bore 30, and a piston 33 acting as a brake booster is pressurized. With the passage bore 30 shut off, piston chamber 32 is connected to an unpressurized reservoir via port 34.

From piston chamber 32 in Fig. 1, a channel 35 leads to effective surface 27 of closure member 26 of control valve 19, so that with the brake applied and piston chamber 32 pressurized, effective surface 27 is subjected to pressure whereby control valve 1 9 opens the connection of supply line 21 to the pressure chamber 20 of the non-return valve 1 9. With the brake not applied, piston chamber 32 is unpressurized as a result of which effective surface 27 is not subjected to pressure. In that case, spring 28 shifts closure member 26 into the position in which pressure chamber 20 is connected to the unpressurized return line 1 5. If the accumulator pressure drops below a predetermined magnitude without the brake being applied, pressure chamber 20 of the non-return valve 4 remains unpressurized.Piston 23, which has bearing on it in the closing direction only the spring 25, whilst in the opening direction it is subjected to the discharge pressure of pump 3, remains in the open position so that the fluid supplied flows from pressure port 2 to the first user port 5.

Piston 23 of non-return valve 4 will assume the same position if the accumulator pressure exceeds a predetermined magnitude.

However, if the accumulator pressure is below the predetermined magnitude so that chamber 12 of pilot valve 7 is connected to pressure port 2 through connection 14 and throttle 6, and if in addition the brake is applied, pressure will act on effective surface 27 of closure member 26 of control valve 1 9 from the pressurized piston chamber 32 of brake booster 11, causing the control valve to assume a position in which pressure chamber 20 of non-return valve 4 is connected to chamber 12 of pilot valve 7 through supply line 21. This enables the pressure prevailing in chamber 12, which pressure serves as control pressure, to act upon piston 23 in pressure chamber 20 and displace it in the closing direction together with spring 25. Thereby the first user port 5 is at least largely isolated from pressure port 2, and the fluid discharged is supplied to the second user port 9 as well as to pressure accumulator 10 through connection 14, throttle 6, pilot valve 7 and check valve 8, thus ) loading the accumulator.

Thus, when the accumulator pressure has dropped below a predetermined magnitude, for example as a result of leakage on the individual valves, it will be loaded only if there is in fact a fluid demand at the brake booster. Such depletion of the pressure accumulator may occur, for example, when driving a long distance on the motorway without applying the brake.

Fitted to brake booster 11 in Fig. 2 is a tandem master cylinder 36 which forms a pressureproducing unit and is actuatable by push rod 37 of brake booster 11.

Tandem master cylinder 36 includes a first pressure chamber 38 associated with a front-axie brake circuit 39, and a second pressure chamber 40 associated with a rear-axle brake circuit 41.

Through a first pressure line 42, the front-axle brake circuit 39 and thus the first pressure chamber 38 are connected to a 3-way, 2-position directional control valve, while the rear-axle brake circuit 41 1 and thus the second pressure chamber 40 are connected to that valve through a second pressure line 44. In the first and second valve positions, the first or second pressure line 42 and 44, respectively, is connected to a control line 45 leading to effective surface 27 of control valve 1 9.

In its first valve position, the 3-way, 2-position directional control valve 43 is sp.ing-loaded and urged into the second valve position by the pressure of the first pressure chamber 38 and into the first valve position by the pressure of the second pressure chamber 40. In addition, the 3 way, 2-position directional control valve 43 can be locked in its second valve position.

When the brake is applied, the push rod 37 of brake booster 11 acts upon push-rod piston 46 of tandem master cylinder 36 and, through the pressure fluid contained in the second pressure chamber 40, upon piston 47 so that pressure develops in both pressure chambers 38 and 40.

Through pressure line 42 and 3-way, 2-position directional control valve 43, the pressure in pressure chamber 38 acts on effective surface 27 of the closure member 26 of control valve 1 9 so that with the brake applied control valve 1 9 opens the connection of supply line 21 to pressure chamber 20 of non-return valve 4.

Should the front-axle brake circuit 39 be defective so that pressure does not build up in pressure chamber 38 during braking, the second pressure chamber 40 will nevertheless be pressurized. Because the 3-way, 2-position directional control valve 43 is only loaded into the direction of the second valve position, it will switch to that second valve position against the spring load and become locked there. Then the pressure prevailing in second pressure chamber 40 is allowed to act upon effective surface 27 of control valve 1 9 through pressure line 44 and 3 way, 2-position directional control valve 43 and control line 45 and thus switch that valve.

With the brake not applied, effective surface 27 is not pressurized. In that case, spring 28 shifts closure member 26 into the position in which pressure chamber 20 is connected to the unpressurized return line 1 5. If the accumulator pressure drops below a predetermined magnitude without the brake being applied, pressure chamber 20 of non-return valve 4 remains unpressurized. Piston 23, which has bearing on it in the closing direction only the spring 25, whilst in the opening direction it is subjected to the discharge pressure of pump 3, remains in the open position so that the fluid supplied flows from pressure port 2 to the first user port 5.

However, if the accumulator pressure is below a predetermined magnitude so that chamber 12 of pilot valve 7 is connected to pressure port 2 through connection 14 and throttle 6, and if in addition the brake is applied, pressure from one of the pressure chamber 38 or 40 will act on effective surface 27 of closure member 26 of control valve 19, causing it to assume the position in which pressure chamber 20 of nonreturn valve 4 is connected to chamber 12 of pilot valve 7 through supply line 21. This enables the pressure prevailing in chamber 12, which pressure serves as control pressure, to act upon piston 23 is pressure chamber 20 and displace it in the closing direction together with spring 25.

Thereby the first user port 5 is at least largely isolated from pressure port 2, and the fluid discharged is supplied to the second user port 9 as well as to pressure accumulator 10 through connection 14, throttle 6, pilot valve 7 and check valve 8, thus loading the accumulator.

The present invention avoids the pump 3 being required to operate at high pressure and load accumulator 10 although there is no fluid demand at brake booster 11. The magnitude of the pressure delivered through non-return valve 4 to the power steering gear mostly operating in the open-centre mode is substantially lower than the pressure required for loading accumulator 10.

Because the discharge of fluid under high pressure causes substantially higher noise than the discharge of fluid under low pressure, and because the accumulator charging valve constructed according to this invention substantially reduces the discharge of fluid under high pressure, the noise which is particularly annoying in automotive vehicles is materially reduced, too.

Claims

1. An accumulator charging valve including a pressure port connectible in use to a source of pressure-transmitting fluid, a first user port connectible with a first user component, a second user port connectible with a pressure accumulator and a second closed-centre user component, a valve device, operative in response to the accumulator pressure, via which the pressure port is connectible with the second user port through a throttle below a predetermined accumulator pressure and is connectible with the first user port above the predetermined accumulator pressure, wherein the valve device includes a non-return valve controllable by a control pressure and adapted to shut off the connection of the pressure port to the first user port below the predetermined accumulator pressure, and wherein the valve passageway of the non-return valve is adapted to be shut off with the second user component operating in the open-centre mode.

2. An accumulator charging valve as claimed in claim 1, wherein the non-return valve is capable of being actuated by the control pressure in the closing direction, and wherein a supply line for the control pressure to the non-return valve is controllable by a control valve which is closed with the second user component operating in the closed-centre mode.

3. An accumulator charging valve as claimed in claim 2, wherein the control valve is a 3-way, 2position directional control valve in one position of which the supply line of the control pressure and in the other position of which an unpressurized return line is connnected to the non-return valve.

4. An accumulator charging valve as claimed in claim 3, wherein the control valve includes a closure member having an effective surface which is adapted to be subjected to pressure whereby to provide a connection of the supply line of the control pressure to the non-return valve, and which is connected to a chamber of the second user component subjected to pressure in the opencentre mode and relieved of pressure in the closed-centre mode.

5. An accumulator charging valve as claimed in claim 4, wherein the closure member of the control valve has bearing on it a spring urging it into the valve position in which the connection of the supply line of the control pressure to the nonreturn valve is shut off, the spring force being lower than the force of the pressure acting on the effective surface when the second user component is operating in the open-centre mode.

6. An accumulator charging valve as claimed in any one of claims 1-3, in combination with a pressure producing unit comprising the second user component, the pressure-producing unit including a pressure chamber adapted to be pressurized with the second user component operating in the open-centre mode, and wherein the supply line of the control pressure to the nonreturn valve is controllable by the control valve operating in response to the pressure in the pressure chamber.

7. An accumulator charging valve as claimed in claim 6, wherein the control valve includes a closure member having an effective surface which is adapted to be subjected to pressure in the sense of providing a connection of the supply line of the control pressure to the non-return valve and which is connected to the pressure chamber of the pressure-producing unit.

8. An accumulator charging valve as claimed in claim 7, wherein the closure member of the control valve has bearing on it a spring urging it into the valve position in which the connection of the supply line of the control pressure to the nonreturn valve is shut off, the spring force being lower than the force of the pressure developed in the pressure chamber arid acting on the effective surface.

9. An accumulator charging valve as claimed in claim 2 or any one of the claims 3 to 8 as appendant to claim 2, wherein the supply line for the control pressure leads from the connection of the pressure port to the second user port downstream of the throttle to the non-return valve, and wherein a pilot valve and the control valve are arranged in series in the supply line.

10. An accumulator charging valve as claimed in claim 9 as appendant to claim 3, wherein the pilot valve is an accumulator-pressure-responsive 3-way, 2-position directional control valve by which, above the predetermined accumulator pressure, that part of the supply line that leads from the pilot valve to the non-return valve is connected to the unpressurized return line whereas, below the predetermined accumulator pressure, it is connected to that part of the supply line that leads from the connection to the pilot valve.

11. An accumulator charging valve as claimed in claim 9 as appendant to claim 3, wherein the pilot valve is an accumulator-pressure-responsive 4-way, 2-position directional control valve by which, above the predetermined accumulator pressure, the supply line leading from the pilot valve to the non-return valve is connected to the unpressurized return line and to a line leading to the second user port, in which line a check valve inhibiting a return flow from the second user component to the pilot valve is arranged, and by which, below the predetermined accumulator pressure, the supply line leading from the pilot valve to the non-return valve is connected to a connection leading from the pressure port via the throttle to the pilot valve and the line.

12. An accumulator charging valve as claimed in claim 7 or claim 8, wherein the pressure producing unit forms part of a brake booster, which pressure-producing unit is a master cylinder whose pressure chamber is connected to the effective surface of the control valve.

13. An accumulator charging valve as claimed in claim 12, wherein the master cylinder is a tandem master cylinder having a first and second pressure chamber each associated with a respective brake circuit, the pressure chambers being connectible with the effective surface of the control valve through a further valve device.

14. An accumulator charging valve as claimed in claim 13, wherein the first and second pressure chambers are connectible to a control line through respective pressure lines and, through the control line, to the effective surface of the control valve, with the pressure chamber pressure lines each having a check valve arranged therein inhibiting return flow to the respective pressure chamber.

1 5. An accumulator charging valve as claimed in claim 13, wherein the first and second pressure chambers are each connectible through a respective first and second pressure line to a 3 way, 2-position directional control valve in whose first valve position the first pressure line, and in whose second valve position the second pressure iine, is connected to a control line leading to the.

effective surface of the control valve, wherein the 3-way, 2-positon directional control valve, in the unactuated position and with both the first and second pressure chambers pressurized, is in its first valve position, while it is in its second valve position when the first pressure chamber is unpressurized and the second pressure chamber is pressurized.

16. An accumulator charging valve as claimed in claim 15, wherein the 3-way, 2-position directional control valve is urged into its first valve position by a spring, and wherein the pressures in the first and second pressure chamber urges it into the second and first valve position, respectively.

17. An accumulator charging valve as claimed in claim 16, wherein 3-way, 2-position directional control valve can be locked in its second valve position with the first pressure chamber unpressurized and the second pressure chamber pressurized.

18. An accumulator charging valve as claimed in claim 15, wherein the tandem master cylinder is a stepped tandem master cylinder and wherein the first pressure chamber forms the smaller step, and the second pressure chamber forms the larger step.

1 9. An accumulator charging valve substantially as herein described with reference to Fig. 1 or Fig. 2 of the accompanying drawings.

20. An accumulator charging valve in combination with a brake booster and substantially as herein described with reference to Fig. 1 or Fig. 2 of the accompanying drawings.