DE3217060A1 - CONTROL VALVE FOR A HYDRAULIC STEERING BRAKE SYSTEM OF A VEHICLE - Google Patents

Description

Control valve for a hydraulic steering brake system of a vehicle

The invention relates to a control valve for a hydraulic steering brake system of a vehicle, each one pair in front and has rear wheels, wheel sets or chains, hereinafter simply referred to as front and rear wheels, and relates in particular to a control valve for the hydraulic front wheel brakes of a vehicle with separately actuatable hydraulic rear wheel brakes.

Certain vehicles, especially agricultural tractors and construction vehicles, have independently operable ones Hydraulic rear wheel brakes so that steering is carried out by braking one or the other rear wheel or can be supported. Such vehicles usually have two separate brake pedals, each with a master cylinder operate, each of which acts on one of the rear brakes. With a mechanical link you can operate the two brake pedals together when, for example, when driving on a road, with both rear brakes should be braked together. With a view to their use on public roads, such vehicles additionally equipped with hydraulic front wheel brakes

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be. Then it is desirable that the front brakes put themselves out of operation with an automatic device when the rear brakes are used separately to steer the vehicle. Such a device is from the U.S. Patent 3,459,000 is known. However, this device is very intricate and therefore expensive to manufacture.

The invention is based on the object of using simple means to create an economically producible control valve, that when the rear brakes of a vehicle are operated separately, the front brakes are automatically out of operation puts.

According to a solution concept of the invention, a control valve for the supply of hydraulic fluid from two separately operable master cylinders to front wheel brakes in a hydraulic steering brake system of a vehicle has a first and a second inlet opening, which are in communication with a first and a second inlet chamber, a first and a second a second outlet opening communicating with a first and a second outlet chamber, respectively, a first valve which can be opened to establish communication between the first inlet chamber and the first outlet chamber and closed to interrupt this communication, a second valve which can be closed can open to establish the connection between the second inlet chamber and the second outlet chamber and close to interrupt this connection, and a control member which separates the first outlet chamber from the second outlet chamber and which is adjustable as a function of a pressure difference between the outlet chambers and the one valve closes, the st i associated with the outlet chamber with the higher pressure.

In the preferred embodiment of the invention, the control member is one in a bore in the housing of the control valve

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sliding piston. The piston is biased by a spring into a stable central position, in the opposite one Pins protruding from the sides of the piston hold both the first and second valves open. When the pressure difference exceeds a predetermined amount between the outlet chambers, the piston moves against the biasing force the spring and closes the valve that is assigned to the outlet chamber with the higher pressure.

In the preferred embodiment of the invention, the control valve is of particularly simple construction and is the only one movable control element a piston which actuates separate valves assigned to separate brake circuits. The preferred one Embodiment of the invention can be produced particularly easily using a valve housing, which has a circular cross-section bore that has a single step between a portion of relatively large Diameter and a section of relatively small diameter. All components of the control valve can be used in the stepped bore can be installed, so that the production of a particularly simple and inexpensive control valve is simplified.

An embodiment of the invention is explained in more detail below with reference to a single schematic drawing, which shows an axial section through a control valve according to the invention.

The control valve 1 shown has a housing 2 with a bore 3, which consists of a section 4 of relatively large diameter and a section -5 is composed of relatively small diameter. Sections 4 and 5 are separated by a step or shoulder 6. To simplify manufacturing, it extends from the outside of the housing 2 to the section 5 of smaller diameter

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Bore 3 is a passage 7 of small diameter, which, however, plays no role in the actuation of the control valve 1. The bore 3 could be designed as a blind bore with an end wall, one end of the section 5 of smaller Diameter locks.

In the housing 2 are a first inlet opening 8, a first outlet opening 9, a second inlet opening 10 and a second outlet opening 11 incorporated.

In the end of the bore 3 sits a first sealing plug 12, which carries O-rings 13, which against the wall of the section 5 seal the hole 3 with a smaller diameter. The closure plug 12 has a first inlet chamber 14 forming Bore that connects to the first inlet opening 8 via a radial passage 15 and a circumferential groove 16 in the closure plug 12 communicates. A valve seat 17 is attached to the plug, through which the first Inlet chamber 14, in the example shown, a valve body 18 designed as a ball is held captive, which is biased towards the valve seat 17 by a spring arranged in the first inlet chamber 14.

The left end of the bore 3 according to the drawing is closed with a second plug 20, which is of a spring or snap ring 21 is held in place and carries O-rings 13A which against the wall of section 4 of Seal the larger diameter of the hole 3. A second inlet chamber 14A is formed in the plug 20, in FIG which, similar to the plug 12, is designed as a ball Valve body 18A and a valve spring 19A are held captive by a valve seat 17A. The second Inlet chamber 14A and the second inlet port 10 are continuous through a radial passage IbA and a circumferential groove 16A connected with each other.

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In the vicinity of the shoulder 6 in the section 5 of smaller diameter of the bore 3 is a control member 22 in the form of a Piston arranged displaceably. The control member 22 is normally in the position shown, in which his left End face 23 lies in a plane with shoulder 6, held by a compression spring 24, which is between an intermediate disk 25 and a component 26 provided with a flange is clamped. The intermediate disk 25 rests on the shoulder on, the component 26 at the right end of the plug 20 and on a flange 27 which is formed on a pin 28 which is screwed into the control member 22. The distance between the flange 27 and the end face 23 of the Control member 22 is at least approximately open by means of the screw connection between the pin 28 and the control member 22 the same amount as the distance between the shoulder 6 and the right end face of the plug 20 can be adjusted. Thus, the control member 22 is at least approximately from the compression spring 24 under normal operating conditions held in the position shown.

In the bore 3, a first and a second outlet chamber 29 and 30 are formed on both sides of the control member 22. O-rings 31 are arranged in grooves in the control member 22, which enable the control member 2 to be displaced in the section 5 of smaller diameter of the bore 3 while maintaining the fluid separation between the outlet chambers 29 and 30.

The two inlet ports 8 and 10 are connected to separate hydraulic ones Rear wheel brake circuits of a vehicle can be connected to the two outlet openings 9 and 11 in a similar manner associated hydraulic front wheel brake circuits. The outlet openings 9 and 11 are on the same with the front brakes Vehicle side like the rear wheel brakes corresponding to the inlet openings 8 and 10 or, to the diagonal or X-shaped Distribution of the overall braking system, with the brakes of the diametrically opposed wheels connectable.

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In the illustrated position of the control member 22, the valve body 18A is at a sufficient distance from the pin 28 held by its valve seat 17A and the valve body 18 is held by its valve seat 17 by the with the control member rigidly connected pin 32 kept away. In the left end face of the component 26 and / or in the right end face of the plug 20 radial grooves are formed, and between the component 26 and the bore 3 there is radial Clearance so that when the valve body 18A is held a sufficient distance from the valve seat 17A, an unobstructed connection between the second inlet chamber 14A and the second outlet chamber 30 is established. When the valve body 18 is sufficient Distance from its valve seat 17, there is similarly an unobstructed connection between the first inlet chamber 14 and the first outlet chamber 29.

Thus, when the two brake pedals of the vehicle are operated together and consequently both hydraulic rear wheel brake circuits are pressurized at the same time, the two inlet ports 8 and 10 are at least approximately the same Pressures are applied and hydraulic fluid flows from the Inlet ports 8 and 10 via the associated inlet chambers 14 and 14A and outlet chambers 29 and 30 to the outlet ports 9 and 11. Accordingly, hydraulic fluid is delivered to the front brakes of the vehicle and the pressure in the brake circuits increases accordingly. Under these conditions, the pressures in the outlet chambers 29 and 30 remain in the essentially the same, and the control member 22 retains the position shown essentially at.

To ensure that the two inlet ports 8 and 10 when the brake pedals are operated together, at least approximately the same pressures are obtained, are those for the brake pedals belonging master cylinder preferably connected to one another by a fluid pressure equalization line and to

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for this purpose preferably designed in accordance with GH-PS 1 211 047.

If the brake pedals of the vehicle are not connected to each other and only one of the rear wheels is used to brake the associated brake pedal is actuated, hydraulic brake pressure is only supplied to one inlet port 8 or 10.

When pressure is supplied to the inlet port 8, fluid is passed from the inlet port 8 via the inlet chamber 14, the outlet chamber 29 and the outlet port 9 to each other. However, before the relevant front brake is applied, a small counterpressure arises due to brake shoe return springs, friction, etc., which is not compensated for by a corresponding pressure in the outlet chamber 30. Thus, a differential pressure is generated at the control member 22, which moves the control member 22 to the left as shown in the drawing, the latter lifting the intermediate disk 25 from the shoulder 6 and compressing the compression spring 24. This movement moves the pin 32 to the left and enables the spring 19 to apply the valve body 18 to the valve seat 17, whereby the inlet chamber 14 is separated from the outlet chamber. As a result of a further increase in the brake pressure supplied to the inlet opening 8, the valve body is only held more firmly in contact with the valve seat 17, and a brake actuation pressure is not supplied to any of the front wheel brakes.

When the other brake pedal is depressed and hydraulic pressure only the inlet port 10 .wird is supplied, it occurs in the Outlet chamber 30 initially to a similar pressure rise and it is a differential pressure generated, which the tendency has to move the control member 22 to the right. As soon as the differential pressure is big enough, it moves

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Control member 22 to the right and the flange 27 attaches itself to the component 26, which he moves to the right and thereby compresses the compression spring 24. This movement of the tenon 28 enables the valve body 18A to be applied by the spring 19A to its valve seat 17A. Accordingly, will the fluid communication between the pressurized inlet port IO and the associated outlet opening 11 interrupted.

The embodiment described is relative simple structure because they are used to open and close separate, two completely independent brake circuits associated valves relies on a single control member 22, which is held in position by a single compression spring 24 is. Fluid transfer between the brake circuits is prevented by the O-rings 31. Although furthermore the housing 2 of the control valve 1 is particularly simple and has only a single step or shoulder 6 between a bore section 4 of a relatively large diameter and a bore section 5 of a relatively small diameter a symmetrical operation of the control valve 1 is achieved because the valve bodies 18 and 18A by means of a fluid pressure difference are opened and closed on two faces of the same effective area of the control member 22 acts, and despite the asymmetrical bore 3 on opposite sides of the control member 22 in which the components are arranged.

Claims (6)

Patent claims: 1J control valve for the supply of hydraulic fluid with two separately actuatable master cylinders for front wheel brakes in a hydraulic steering brake system of a vehicle a first and a second inlet port communicating with a first and a second inlet chamber, respectively, a first and a second outlet opening, which with a first and second outlet chamber are in communication, a first valve, which is used to establish the connection between the first inlet chamber and the first outlet chamber can be opened and closed to break this connection, and a second valve adapted to establish communication between the second inlet chamber and the second The outlet chamber can be opened and closed to interrupt this connection, characterized in that a control member (22) separating the first outlet chamber (29) from the second outlet chamber (30) as a function of one Pressure difference between the outlet chambers (29,30) adjustable and that valve (17,18 or 17A.18A) closes, which is assigned to the outlet chamber (29 or 30) with the higher pressure. 2. Control valve according to claim 1, characterized in that the control member (22) is one in one Bore (3) in the housing (2) of the control valve (l) is displaceable Piston is. OZ. I / U U U ■ · ·· - 2 - 55 919 3. Control valve according to claim 3, characterized in that g e k e η η shows that the bore (3) is stepped and has a section (4) of larger diameter and a section (5) of smaller diameter, the piston (22) being displaceable in the section (5) of smaller diameter and one of the cross-sectional area of the section (5) has the same effective area, which towards both outlet chambers (29,30) exposed. 4. Control valve according to claim 2 or 3, characterized in that the bore (3) at each of its Ends with a sealing plug (12,20) is closed and the inlet chambers (14,14A) of bores in the associated Sealing plugs (12, 20) are formed. 5. Control valve according to one of claims 1 to 4, characterized in that the piston (22) through Spring force is biased into a central position between the outlet chambers (29,30), in the pin firmly connected to it (28,32) the valve bodies (18,18A) of each valve (17,18 or 17A, 18A) at a sufficient distance from the associated valve seat (17 or 17A). 6. Control valve according to claim 5, characterized in that g'e k e η η draws that the piston (22) of a single Compression spring (24) is biased into its central position and movement of the piston (22) in each axial direction compression of the compression spring (24) leads.