DE2624088A1 - HYDRAULIC MASTER CYLINDER FOR VEHICLE BRAKING SYSTEMS - Google Patents

Description

GIRLING LIMITED,
Birmingham, England

concerning
Hydraulic master cylinder for vehicle braking systems

The invention relates to a hydraulic master cylinder for vehicle brake systems with an externally stepped piston assembly which works in a stepped bore in a housing and is advanced in the stepped bore when the master cylinder is actuated to initially remove a pressure chamber located in front of the piston assembly from a fluid container and then to put the fluid in the pressure chamber under pressure, and has relatively adjustable piston sections and a spring device which is able to hold the piston sections in a first relative position in which the pressure chamber is exposed to the entire surface of the piston until the pressure in the pressure chamber is one predetermined value equal to the spring load of the spring device, after which a red piston section of larger area is prevented by the pressure in the pressure chamber from advancing further in the bore, and the pressure in the pressure chamber is prevented by a piston section of k, which is adjusted relative to the first piston section Smaller area can be increased further.

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When a hydraulic master cylinder of the type described is incorporated into a brake system that the pressure chamber is connected to at least one brake, the fluid volume required to compensate for the brake clearances becomes supplied by the entire surface of the piston, which allows a large volume of fluid to be supplied to the brake and is rapidly pressurized to said predetermined value, the pressure thereafter by a smaller one Area that is exposed to a larger operating force is increased or reinforced.

In a tandem master cylinder, the pressure in the pressure chamber acts, except that it is transmitted directly to a brake , on a secondary piston assembly or floating piston assembly, which in a secondary pressure chamber, which in turn is connected to the same or a different brake can be connected , capable of pressurizing fluid.

In a known hydraulic master cylinder of the type described, the piston assembly does not have one interrupted by openings rod, which extends through the bore, in a smaller diameter Bore section works and carries a lip seal, of which the inboard end of the rod is in a rest position usually spaced, and a piston in the form of a sleeve, which in the larger in diameter Bore section works and serves as a slide guide for the rod, and the spring device has a first compression spring, between a support at the end facing away from the bore section with a smaller diameter is arranged on the rod, and a second support acts, which always rests on the adjacent end of the piston and usually rests against a shoulder on the rod, as well as a second compression spring weaker than that first and between the opposite inboard end of the piston and a shoulder in the bore on Diameter transition works. The first feather must be considerable

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be stronger than the second spring, since it must counteract not only this, but also a force which the over the area of the piston has effective pressure in the pressure chamber.

In such a known embodiment between the piston and the bore and between the piston and the Rod separate inner and outer hydraulic seals may be provided, with one from the other outer seal inwardly located point between the piston and the bore an additional outer sealing member is arranged, which at Operating the master cylinder is able to close a filling opening connected to the container. When the operating force is canceled, the lip seal also tends to move from the pressure in the pressure chamber to the contact at the inner end being pushed back by the rod and can then be bent back and damaged if the called the inner end of the rod is withdrawn from it.

In the case of a master cylinder of the type described at the outset, the piston assembly according to the invention has an externally stepped one first piston with a first piston portion of larger diameter, which in the bore portion of larger Diameter works, and a second piston section of smaller diameter, which is in the bore section of smaller diameter works, and a second piston, which in one between the bore sections of larger and Smaller diameter located third bore section and works on one between the first and the second KoI-benaschnitt arranged intermediate piston section is displaceably guided; the spring device has a first spring, which acts between the first piston portion of the first piston and an adjacent end of the second piston to the second To pretension the piston in an advanced operating position, and a second spring, which acts on the smaller free,

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inboard end of the first piston acts to the piston assembly To urge into a retracted position, the housing has a fluid container communicating with the pressure chamber Filling opening and on the side of it a relief opening which always connects the container with a chamber, which is formed in the bore between the first piston portion and the second piston, and a check valve is arranged between the relief port and the container, which prevents the second piston from moving prematurely with rapid actuation of the master cylinder.

Since the first and second springs do not act on a common movable member, their loads are apart independent. The second spring only acts as a return spring, while the first spring acts as a pressure limiter, in order to prevent the second piston from moving relative to the first piston until the pressure in the pressure chamber exceeds the above reached a predetermined value. Thus, the strength of the first spring is chosen so that it is predetermined with the aforementioned Pressure is compatible, which can therefore be specified within very narrow limits.

If the piston assembly is quickly adjusted during emergency braking, the chamber between the first piston section will be and the second piston separated from the container by the check valve, which is caused by the sudden flow of fluid is adjusted so that it closes the container outlet. In this way the chamber acts like a massive rod and prevents premature compression of the second spring.

The check valve preferably has a valve disk on a flexible membrane, one in the valve disk Drain port is formed. The check valve is preferably in a space between an outlet opening for Container and the base of an opening formed in the housing, the fill opening and the relief opening are formed in said base.

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In the case of a master cylinder with a single pressure chamber, the second spring is supported on the closed end of the bore. In the case of a tandem master cylinder, however, the second spring acts between the first piston and a secondary piston or floating piston that can pressurize a second pressure chamber.

In that a first piston section which is larger in diameter seals against the larger diameter bore section, it is possible at the front end of the second Piston to arrange a single valve sealing member, the directly seals between the bore and the first piston and the connecting the fluid container with the pressure chamber ! Fill opening controls.

The second piston section of the piston preferably always penetrates a sealing member in the smaller one in diameter Bore section and is never withdrawn from the sealing member. This ensures that the sealing member even when releasing the brake does not tend to be pushed back by the Eestdruck in the pressure chamber or in any other way getting damaged.

Two exemplary embodiments of the invention are explained below with reference to schematic drawings. It shows:

1 shows a longitudinal section through a hydraulic master cylinder for a vehicle brake system with a single pressure chamber and

2 shows a longitudinal section through a hydraulic master cylinder in tandem design.

The master cylinder shown in Fig. 1 has a housing 1 with a longitudinal bore 2 open at the end, at its inner end a bore widening 3 for Receiving an annular plate provided with openings

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Has. The plate 4 is clamped against a shoulder 5 at the diameter transition by means of a plug 6, which is inserted into the inner End of the bore 2 is screwed and acts via an apertured spacer 7, which in turn a sealing member 8 presses against the plate 4. The openings in the plate 4 are with the inwardly facing end face of the sealing member 8 via passages 9 in connection. The wall of the housing 1 has an outlet opening 10 to which the pn brakes can be connected is and opens into the bore widening 3 between the plug 6 and the sealing member 8. The sealing member 8 has a flexible lip.

The inwardly facing circular surface of the plate 4 and the remaining part of the bore 2 on that of the bore widening 3 facing away from the side of the plate 4 form a stepped bore in which a piston assembly 11 works. This one has one externally stepped first piston 12 and a second piston 13 displaceably arranged thereon. The first piston has a first piston portion 14 of larger diameter, which is in a portion 15 of larger diameter Stepped bore works, and a second piston section 16 of smaller diameter, the plate 4 and the sealing member 8 penetrates and protrudes into the bore extension 3. The piston portion 14 carries a sealing member 17, which against the bore section 15 seals. An actuating member 18 acts on the piston section 14 in order to move the piston assembly 11 to advance in the stepped bore in the direction of the plug 6.

The second piston 13 has a sleeve 19 which is displaceable on an intermediate section 20 of the first piston 12 is guided, the diameter of which is the same as that of the second piston section 16. At the inner end of the sleeve 19, a radial flange 21 provided with openings and having a working fit is arranged in the bore section 15 and supports a valve sealing member 22 that? between the bore section 15 and the intermediate section 20

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seals. In a retracted position of the piston assembly 11 are the valve sealing member 22 and the Splash 21 between hill and relief openings 23 formed at a distance from one another in the wall of the housing 1 and 24. The valve sealing member 22 and the flange 21 are in this position of a one engaging the valve sealing member 22 fixed support 25 and held by a movable support 26 engaging at the free end of the sleeve 19. The movable support 26 has a split collar that is attached to a section of the reduced diameter Intermediate section 20 slidably arranged and usually by a first spring 27, in the example shown one Compression spring against a shoulder 28 at the transition from the Durohmesser is pretensioned, which forms a fixed stop for absorbing the force in the spring 27. The spring 27 acts between the support 26 and the piston portion 14 and must be compressed before the piston 13 in the direction of the piston section 14 can move.

A channel in a connector which forms a connection point 29 to a fluid container is via the fill opening 23 connected to a pressure chamber 30 in front of the valve sealing member 22, and an annular space between the valve sealing member 22 and the sealing member 8 is with the part of the pressure chamber forming bore widening 3 via radial openings 31 in connection on the inside of the sealing member 8 are formed in the second piston section 16, but with an axially directed recess 32 in the end of the second piston section 16 are in communication. The connection point 29 also always eats via the relief opening 24 ait an annular space 33 between the Diaphragm 17 and the valve sealing member 22 are connected.

Sine on the stopper 6 and on the bottom of the recess 32 are supported second spring 34, in the example shown a compression spring, acts as a return spring to the piston assembly 11 to push into the withdrawn position, in

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which it rests against a rear stop 35, the open The end of the bore 2 has a stop ring on which a head of the actuating member 18 engages.

The mode of operation of the master cylinder is as follows: When the actuating member 18 is actuated, the Piston assembly 11 advanced in bore 2, wherein the first piston 12 and the second piston 13 together against the force in the second acting as a return spring Move spring 34. The initial movement causes the valve sealing member 22 to close the fill port 23 to the To separate the connection point 29 from the pressure chamber 30, and essentially at the same time the openings 31 through the sealing member 8 locked. Thereafter, in the pressure chamber 30 is located Fluid pressurized to deliver it to the brakes via the outlet port 10. After closing the Openings 31 is fluid, which is located in the space between the sealing member 8 and the valve sealing member 22, at the The lip of the die member 8 is pressed over and into the bore extension 3. At the beginning of the pressurization, the total effective area of the piston assembly 11 on the Fluid, so that a large amount of fluid is moved to compensate for the brake clearances. However, as soon as the pressure in the pressure chamber 30 reaches a predetermined value at which the compressive force acting on the surface of the flange 21 is equal the force in the spring 27 »causes further adjustment of the actuating member 18 in the same direction that only the first piston 12 moves because the second piston 13 in a relieved, fixed position is held. In this way, the pressure space 30 is further pressurized only through the area of the piston section 16.

When the actuation force is released, the pulls as a return spring Acting spring 34 moves the piston 12 back relative to the piston 13 until the movable support 26 is attached again the shoulder 28 applies. Thereafter, the pressure relief rate remains the same until the fill port 23 and the ports

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are exposed so that the excess volume that is is still in front of the piston, can be discharged.

When the piston assembly 11 is advanced in the bore 2 The relief port 24 allows fluid to be returned to the container from the space between the valve sealing member and the sealing member 17 'to prevent the operation of the piston assembly 11 from being obstructed. When pressed quickly of the master cylinder, the piston 12 tends to to move relative to the piston 13, which can move itself backward relative to the piston 12, still before said predetermined pressure in pressure chamber 30 is reached. Between the relief opening 24 and the connection point 29 is therefore a check valve with a Valve head 37 and a drain port 38 formed therein to reduce the speed with the fluid in the space between the valve sealing member 22 and the sealing member 17 can be returned to the container, so that fluid in said space can counteract any movement of the piston 13 to the rear. The check valve is arranged on a flexible, conical membrane 39.

In a modified embodiment, the valve sealing member 22 can be replaced by a sealing member similar to the sealing member 8 and equipped with a lip.

In the case of the tandem master cylinder shown in FIG. 2, the length of the housing 1 is the same as that of the one in the open end of the bore 2 screwed Sbpfens 6 enlarged. The plug 6 has an axially directed fluid bore 40, in which a secondary piston or floating piston 41 works to fluid in a secondary pressure chamber 42 to be put under pressure which is in front of the piston 41 and via a second outlet opening 43 in the end of the plug 6 can be connected to the same or a different brake. The second spring 34 acts between the intermediate section

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and the piston 41, and between the piston 41 and the closed end of the fluid bore 40, a return spring 44 »acts around the secondary piston 41 in a retracted position To push position with abutment against a rear stop 46.

A connection point 47 formed in the wall of the housing 1 and connected to the same or to a different container can be connected, stands with the secondary pressure chamber 42 via a filling opening 48 and with an annular recess between spaced apart sealing members 49 and 50 on the piston 41 via a second opening 51 in connection. The opening 51 is arranged to the rear opposite the filling opening 48. The fill opening 48 and the opening 51 are arranged in the wall of the stopper 6, with sealing members 52 and 53 arranged between them at an intermediate distance there is a recess.

During operation, acts in the pressure chamber 30 between the piston assembly 11 and the secondary piston 41 pressurized fluid in such a way that it the secondary piston 41 advances in the fluid bore 40 to first close the filling opening 48 and then fluid in the secondary pressure chamber 42 pressurized.

Structure and mode of operation of the embodiment shown in FIG are otherwise the same as in the embodiment according to FIG. 1.

/ Claims 609850/0785

Claims (12)

Claims ¹ · / Hydraulic master cylinder for vehicle brake systems ¹ MaIt an externally stepped piston assembly that works in a stepped bore in a housing and is advanced in the stepped bore when the master cylinder is actuated in order to initially separate a pressure chamber located in front of the piston assembly from a fluid container and then to put the fluid in the pressure chamber under pressure, and has relatively adjustable piston sections and a spring device which is able to hold the piston sections in a first relative position in which the pressure chamber is exposed to the entire surface of the piston until the pressure in the pressure chamber is one predetermined, the spring load of the spring device reaches the same value, after which a first piston section veA larger area is prevented by the pressure in the pressure chamber from advancing further in the stepped bore, and the pressure in the pressure chamber by a piston section that adjusts relative to the first piston section of smaller area che can be increased further, wherein the piston assembly comprises an externally stepped first piston with a first piston portion of larger diameter, which works in the bore portion of larger diameter, and a second piston portion of smaller diameter, which works in the bore portion of smaller diameter, and a having a second piston which works in a third bore section located between the bore sections of larger and smaller diameter and is displaceably guided on an intermediate piston section arranged between the first and the second piston section, the spring device further comprising a first spring which is positioned between the first Piston portion of the first piston and an adjacent end of the second piston acts around the 609850/0785 / 12 - 12 - 47 991 preloading the second piston into an advanced operating position, and a second spring on the smaller diameter free, inboard end of the first The piston acts to urge the piston assembly into a retracted position, and further wherein the housing is a one Fluid container with the pressure chamber connecting filling opening and laterally has a relief opening which the container always connects to a chamber formed in the bore between the first piston portion and the second piston is, characterized in that a check valve between the relief opening (24) and the container (Valve plate 37, drain opening 38, membrane 39) is arranged, which prevents the second piston (13) from getting to move prematurely when the main cylinder is actuated quickly. 2. Master cylinder according to claim 1, characterized in that g e k e η η, that the check valve has a valve disk (37) arranged on a flexible membrane (39). 3. Master cylinder according to claim. 1 or 2, characterized in that the check valve is a Has drain opening (38). 4. Master cylinder according to one of claims 1 to 3 »characterized in that the check valve (37 »38.39) is arranged in a space between the Connection point (29) to the container and the base of an opening in the housing (1) is created in which the connection point (29) is arranged, the filling opening (23) and the relief opening (24) being formed in said base. 5. Master cylinder according to one of claims 1 to 4, characterized in that the second Spring (34) is supported on the closed end of the bore (2). 609850/0785 - 13 - 47 991 6. Master cylinder according to one of claims 1 to 5 designed as a tandem master cylinder, characterized g e k e η η ζ e i without t, that it also has a floating piston (41) which is in a front of the second piston section (16) of the first piston (12) formed secondary pressure chamber (42) operates, the second spring (34) acting between the first piston (12) and the floating piston (41). 7. Master cylinder according to one of claims 1 to 6, characterized in that a single valve sealing member (22) is arranged at the front end of the second piston (13), seals directly between the bore (2) and the first piston (12) and when the master cylinder is ^{actuated, the I 1} UlI opening (23) closes. 8. Master cylinder according to claim 7, characterized in that an apertured radial Splash (21) is arranged at the front end of the second piston (13) and a support for the valve sealing member (22) forms. 9. Master cylinder according to claim 8, characterized in that g e k e η η, that a fixed support (25) on the first piston (12) engages the valve sealing member (22) and one movable support (26) which is arranged displaceably on the first piston (12) at the free end of the second Piston (13) attacks. 10. Master cylinder according to claim 7, 8 or 9 »characterized in that the valve sealing member (22) has a flexible lip. 11. Master cylinder according to one of claims 1 to 10, characterized in that the second piston section (16) of the first piston (12) a second sealing member (8) in the smaller diameter bore section always penetrates. 609850/0785 / 14 - 14 - 47 991 12. Master cylinder after. Claim 11, characterized in that g e k e η η shows that the second sealing member (8) has a flexible lip. 609850/0785