GB2301652A - Servo valve arrangement - Google Patents

Servo valve arrangement Download PDF

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Publication number
GB2301652A
GB2301652A GB9614403A GB9614403A GB2301652A GB 2301652 A GB2301652 A GB 2301652A GB 9614403 A GB9614403 A GB 9614403A GB 9614403 A GB9614403 A GB 9614403A GB 2301652 A GB2301652 A GB 2301652A
Authority
GB
United Kingdom
Prior art keywords
pressure
control valve
displacer
connection
valve
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB9614403A
Other versions
GB9614403D0 (en
GB2301652B (en
Inventor
Wolfgang Jorg
Jaromir Bordovsky
Aydogan Cakmaz
Hubert Heck
Arno Rohringer
Claus Gall
Reinhold Abt
Rainer Strauss
Karl-Hans Kohler
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Daimler Benz AG
Original Assignee
Daimler Benz AG
Mercedes Benz AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from DE19944422553 external-priority patent/DE4422553C2/en
Application filed by Daimler Benz AG, Mercedes Benz AG filed Critical Daimler Benz AG
Priority claimed from GB9513035A external-priority patent/GB2290850B/en
Publication of GB9614403D0 publication Critical patent/GB9614403D0/en
Publication of GB2301652A publication Critical patent/GB2301652A/en
Application granted granted Critical
Publication of GB2301652B publication Critical patent/GB2301652B/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
    • B60T8/32—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration
    • B60T8/34—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration having a fluid pressure regulator responsive to a speed condition
    • B60T8/341—Systems characterised by their valves
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T13/00—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems
    • B60T13/10—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with fluid assistance, drive, or release
    • B60T13/12—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with fluid assistance, drive, or release the fluid being liquid
    • B60T13/14—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with fluid assistance, drive, or release the fluid being liquid using accumulators or reservoirs fed by pumps
    • B60T13/141—Systems with distributor valve
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
    • B60T8/32—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration
    • B60T8/34—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration having a fluid pressure regulator responsive to a speed condition
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
    • B60T8/32—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration
    • B60T8/34—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration having a fluid pressure regulator responsive to a speed condition
    • B60T8/36—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration having a fluid pressure regulator responsive to a speed condition including a pilot valve responding to an electromagnetic force
    • B60T8/3615—Electromagnetic valves specially adapted for anti-lock brake and traction control systems
    • B60T8/363—Electromagnetic valves specially adapted for anti-lock brake and traction control systems in hydraulic systems
    • B60T8/364—Electromagnetic valves specially adapted for anti-lock brake and traction control systems in hydraulic systems switching between a number of discrete positions as a function of the applied signal, e.g. 3/3-valves
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D5/00—Power-assisted or power-driven steering
    • B62D5/06—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle
    • B62D5/08—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle characterised by type of steering valve used

Abstract

A servo valve arrangement has a high-pressure P, low-pressure T and motor connection P1/2 and with a pressure control valve 4, 10; arranged between the high-pressure connection and motor connection and a return control valve 74, 75 arranged between the motor connection and low-pressure connection, the pressure control valve normally being closed and the return control valve normally being open. The return control valve comprises a closure member 75 which is moved into contact with a seat on a movable body 68 to dose an axial passage 71 in the movable body. Cutting off the motor connection from the low-pressure connection. Further movement of the actuator 74 moves the movable body 68 and opens the pressure control valve. The valve arrangement is suitable, in particular, for hydraulic power steering systems of motor vehicles with a so-called closed centre.

Description

Servo valve arrangement The invention relates to a servo valve arrangement with high-pressure, low-pressure and motor connections and with a pressure control valve arranged between the highpressure connection and motor connection and a return control valve arranged between the motor connection and lowpressure connection, the pressure control valve normally being closed and the return control valve normally being open, and both valves having axially displaceable control parts which are arranged equiaxially with one another and can be actuated by means of a common actuating member, whilst closing the return control valve and opening the pressure control valve.
In the case of hydraulic power steering systems which are currently customary in motor vehicles, hydraulic medium flows virtually constantly through the associated servo valve arrangement, specifically even when no servo force is required at all - such as, for example, in normal straight-ahead travel. The servo valve arrangement consists in principle of two parallel throttle routes which are arranged between a pressure connection and a low-pressure connection and each comprise two throttles which are controlled in opposite directions, are arranged in series, and between which a motor connection branches off in each case.Depending on the direction and magnitude of an actuating moment to be applied at the steering wheel, the input-side throttle of the one throttle route is increasingly opened and, at the same time, the output throttle of this throttle route is increasingly throttled, while the throttles of the other throttle route are controlled in the opposite direction in each case. In this way, a pressure difference which can be controlled according to direction and magnitude is generated between the motor connections of the two throttle routes, such that an appropriate servomotor generates a controllable servo force in the one direction or the other. In operating states in which no servo force is required, all the throttles assume a central position so that the medium flows evenly through both throttle routes and there is pressure equilibrium between the motor connections.
Since, in these known power steering systems, a constant hydraulic flow has to be maintained, power is required constantly.
In terms of a reduction in the power requirement of motor vehicles, it is basically known to provide power steering systems with a so-called closed centre, i.e. as long as no servo force is required, the servomotor has no connection at all to the pressure source; in contrast, in this state the servomotor is only connected to the lowpressure connection or hydraulic reservoir in order to allow passive mobility of the servomotor.
In this context, attempts have already been made to implement power steering systems using the servo valve arrangements specified at the beginning. Essentially, two servo valve arrangements of the type specified at the beginning then have to be arranged parallel to one another between a pressure source or a pressure accumulator and a hydraulic reservoir. Depending on the actuating moment to be applied at the steering wheel, the pressure control valve of the one servo valve arrangement or the other is then opened to a greater or lesser extent so that in each case the motor connection of the one servo valve arrangement or the other is connected with controllable throttle resistance to the pressure source or the pressure accumulator and, at the same time, is blocked off relative to the low-pressure connection.The servomotor connected between the motor connections of the two servo valve arrangements thus generates a servo force in the one direction or the other.
The present invention seeks to ensure particularly good control characteristics in a servo valve arrangement of the type specified at the beginning.
According to the present invention there is provided a servo valve arrangement with high-pressure, low pressure and motor connections and with a pressure control valve arranged between the high-pressure connection and motor connection and a return control valve arranged between the motor connection and low-pressure connection, the pressure control valve normally being closed and the return control valve normally being open, and both valves having axially displaceable control parts which are arranged equiaxially with one another and can be actuated by means of a common actuating member, whilst closing the return control valve and opening the pressure control valve, wherein the pressure control valve is a seat valve, and a displacer displaceable in an operating space is located in the control part of the pressure control valve, which displacer operating space is in continuous communication with the motor connection, the displacer being subject to the pressure in the displacer operating space in the direction of a stop located on the control part of the pressure control valve and is subject to a resilient force, which is effective between a stationary part and the displacer in a direction which reduces the volume of the displacer operating space.
In this way it is guaranteed that the control part of the pressure control valve is actuated against a resistive force, which is dependent on the pressure at the engine connection. This resistive force, however, remains limited because at higher hydraulic pressures the displacer hits the stop of the control part of the pressure control valve, so that a further increase of the hydraulic pressure cannot effect a further increase of the said resistive force.
Advantageous embodiments of the invention will now be described by way of example with reference to the drawing, which shows: an embodiment in which the maximum actuating force is limited in a predeterminable manner.
The embodiment of the invention illustrated in Figure 1 has a valve sleeve 68 which is guided so as to be displaceable inside the axial bore 3 of the valve cartridge 1 and is seated in the normal position, in a similar manner to the valve sleeve of Figure 2, with a cone section 10 on the annular edge 4 of the axial bore 3, the helical compression spring 9 attempting to keep the valve sleeve 68 in this position. In this way, the radial bores 6 of the valve cartridge 1 leading to the motor connection P1 or P2 are normally hydraulically separated from the radial bores 7 connected to the pressure connection P. Arranged on the valve cartridge 1 axially above and below the valve sleeve 68 are radial bores 69 and 70 which are connected to the low-pressure connection T.
The valve sleeve 68 has radial bores 16 which communicate with the radial bores 6 of the motor connection P1 or P2 in all positions of the valve sleeve 68.
A piston 72 is arranged so as to be axially displaceable to a limited extent above the radial bores 16 in the stepped axial bore 71 of the valve sleeve 68, the upward stroke of the piston 72 being bounded relative to the valve sleeve 68 by a stop ring arranged in the axial bore 71, and the downward stroke being bounded by an annular step in the axial bore 71. This piston 72 is forced in the downward direction by a helical compression spring 73 supported on the base part 2 of the valve cartridge 1, such that it constantly attempts to assume its lower end position in the valve sleeve 68.
Arranged displaceable in the axial bore 3 of the valve cartridge 1 below the valve sleeve 68 is a ram 74 which bears a, for example, spherical closure part 75 which interacts with the facing end opening of the axial bore 71 of the valve sleeve 68.
The ram 74 normally assumes the lower end position illustrated, in which the closure part 75 is remote from the facing end opening of the axial bore 71 of the valve sleeve 68, and the section of the axial bore 71 below the piston 72 communicates with the radial bores 70 and thus with the lowpressure connection T. At the same time, the valve sleeve 68 assumes the lower end position illustrated. Correspondingly, the motor connection P1 or P2 is, on the one hand, shut off relative to the pressure connection P and, on the other hand, connected - via the axial bore 71 of the valve sleeve 68 - to the low-pressure connection T. Since there is no pressure or only little pressure inside the axial bore 71 below the piston 72, the piston 72 also assumes its lower end position inside the valve sleeve 68.
As soon as the ram 74 is now moved to a sufficient extent in the upward direction, the closure part 75 closes the axial bore 71 of the valve sleeve 68 at the bottom, as a result of which the motor connection P1 or P2 is separated from the low-pressure connection T. In the case of further upward displacement of the ram 74, the cone section 10 of the valve sleeve 68 is lifted off the annular edge 4 of the valve cartridge 1, and the motor connection P1 or P2 is connected to the pressure connection P. The hydraulic pressure prevailing at the motor connection P1 or P2 also acts on the piston 72, such that the latter is forced hydraulically in the direction of its upper end position inside the valve sleeve 68 counter to the force of the helical compression spring 73.As long as this end position has not yet been reached, a further upward movement of the ram 74 is opposed by a hydraulically generated resistance whose magnitude depends on the pressure at the motor connection P1 or P2 and on the effective cross-section of the piston 72. This is because the pressure acting upon the piston 72 also acts in the downward direction on the valve sleeve 68 and the closure part 75. This hydraulically generated resistance varies analogously to the pressure at the motor connection P1 or P2.
As soon as the pressure at the motor connection P1 or P2 is sufficient to bring the piston 62 into the upper end position inside the valve sleeve 68, the hydraulically generated resistance counteracting a further upward displacement of the ram 74 can virtually no longer rise, i.e. during a further upward displacement of the ram 74, only the increasing spring tensions of the helical compression springs 9 and 73 have to be taken into account.
In practice, this means that the maximum force for actuating the ram 74 is limited.
The servo valves described are not only suitable for power steering systems of motor vehicles.
It is also possible, for example, to control the pressure in a (single-action) displacer or piston/cylinder assembly using one of the servo valves described, such that a (comparatively high) setting force is generated analogously to the actuating force of the displacer or piston/cylinder assembly acting on the servo valve.
In this case, the servo valve and the displacer or piston/cylinder assembly can be combined to form a so-called linear booster.
The braking force of a vehicle brake can otherwise also be controlled using the servo valves according to the invention if said brake is designed as a pressure accumulator brake, in which the pressure of a pressure accumulator is fed under control to an actuating assembly of the brake designed as a displacer assembly.

Claims (5)

Claims
1. A servo valve arrangement with high-pressure, low-pressure and motor connections and with a pressure control valve arranged between the high-pressure connection and motor connection and a return control valve arranged between the motor connection and low-pressure connection, the pressure control valve normally being closed and the return control valve normally being open, and both valves having axially displaceable control parts which are arranged equiaxially with one another and can be actuated by means of a common actuating member, whilst closing the return control valve and opening the pressure control valve, wherein the pressure control valve is a seat valve, and a displacer displaceable in an operating space is located in the control part of the pressure control valve, which displacer operating space is in continuous communication with the motor connection, the displacer being subject to the pressure in the displacer operating space in the direction of a stop located on the control part of the pressure control valve and is subject to a resilient force, which is effective between a stationary part and the displacer in a direction which reduces the volume of the displacer operating space.
2. Servo valve arrangement according to Claim 1, wherein a spring supported on a stationary counter bearing urges a piston, which forms the displacer, against the hydraulic pressure in the displacer working room.
3. Servo valve arrangement according to Claim 1 or Claim 2, wherein the control part of the return control valve and the control part of the pressure control valve are axially juxtaposed in a housing bore.
4. Servo valve arrangement according to any one of Claims 1 to 3, wherein the return control valve is normally throttled.
5. A servo valve arrangement substantially as described herein with reference to and as illustrated in the accompanying drawing.
GB9614403A 1994-06-28 1995-06-27 Servo valve arrangement Expired - Fee Related GB2301652B (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19944422553 DE4422553C2 (en) 1994-06-28 1994-06-28 Servo valve arrangement
GB9513035A GB2290850B (en) 1994-06-28 1995-06-27 Servo valve arrangement

Publications (3)

Publication Number Publication Date
GB9614403D0 GB9614403D0 (en) 1996-09-04
GB2301652A true GB2301652A (en) 1996-12-11
GB2301652B GB2301652B (en) 1997-05-28

Family

ID=25937785

Family Applications (2)

Application Number Title Priority Date Filing Date
GB9614403A Expired - Fee Related GB2301652B (en) 1994-06-28 1995-06-27 Servo valve arrangement
GB9614404A Expired - Fee Related GB2301653B (en) 1994-06-28 1995-06-27 Servo valve arrangement

Family Applications After (1)

Application Number Title Priority Date Filing Date
GB9614404A Expired - Fee Related GB2301653B (en) 1994-06-28 1995-06-27 Servo valve arrangement

Country Status (1)

Country Link
GB (2) GB2301652B (en)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1994019226A1 (en) * 1993-02-26 1994-09-01 Zf Friedrichshafen Ag Power-assisted steering for motor vehicles
WO1995011153A1 (en) * 1993-10-20 1995-04-27 Zf Friedrichshafen Ag Power-assisted steering system for motor vehicles

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1155146A (en) * 1967-01-05 1969-06-18 Ford Motor Co Valves For Fluids
DE1916334A1 (en) * 1969-03-29 1970-10-08 Teves Gmbh Alfred Control valve in the form of a seat valve
CH499739A (en) * 1969-04-22 1970-11-30 Lucifer Sa Reed valve
GB1413111A (en) * 1971-10-28 1975-11-05 Dowty Mining Equipment Ltd Fluid valve
EP0192641B1 (en) * 1983-11-05 1988-01-07 ZF FRIEDRICHSHAFEN Aktiengesellschaft Rack servo-steering, particularly for motor vehicles
DE4126020A1 (en) * 1991-08-06 1993-02-11 Zahnradfabrik Friedrichshafen AUXILIARY STEERING

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1994019226A1 (en) * 1993-02-26 1994-09-01 Zf Friedrichshafen Ag Power-assisted steering for motor vehicles
WO1995011153A1 (en) * 1993-10-20 1995-04-27 Zf Friedrichshafen Ag Power-assisted steering system for motor vehicles

Also Published As

Publication number Publication date
GB9614403D0 (en) 1996-09-04
GB9614404D0 (en) 1996-09-04
GB2301653B (en) 1997-05-28
GB2301652B (en) 1997-05-28
GB2301653A (en) 1996-12-11

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Legal Events

Date Code Title Description
732E Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977)
732E Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977)
PCNP Patent ceased through non-payment of renewal fee

Effective date: 20010627