DE3205482A1 - BRAKE FORCE CONTROLLER FOR A HYDRAULIC VEHICLE BRAKE SYSTEM - Google Patents

Description

PATENT LAWYERS "* *". 3> · "* dY.-Ync. Fkanz vuesthoff

WUESTHOFF- v.-pECHMANN -BEHRENS-GOETZ «·». '«« «« .- "«> *' »» «thof

DIPL.-1NG. GERHARD PUlS

EUROPEAN PATENT TATTORNEYS r . _D1Fl .. _CMEM . _OR . _{E. PRIVER OF} Pechmann

DR.-1NC. DIETER BEHRENS DIPL.-ING>; DIPL.-VIRTSCH.-ING. RUPERT GOETZ

LA-54 470 - D-8000 MUNICH 90

Lucas Industries Ltd.

SCHWEIGERSTRASSE 2

phone: (089) 66 20 ji Telegram: protectpatent telex: 514070

Brake force regulator for a hydraulic vehicle brake system

The invention relates to a brake force regulator for a hydraulic one Vehicle brake system with a housing in which

a first and a second inlet chamber and a first and a second outlet chamber for a first and second respectively Brake circuit are formed,

- the two outlet chambers are separated from each other by a compensating piston,

- A stepped piston is arranged between the first inlet and outlet chambers, which with its larger end face the first outlet chamber bounds and loaded by a spring in the sense of a reduction in size of this outlet chamber is,

- Between the first inlet and outlet chambers also one of the position of the stepped piston with respect to the compensating piston pressure-dependent controlled valve is arranged

- And a further controlled valve is arranged between the second inlet and outlet chambers.

Brake force regulators of this type are mainly for diagonal divided vehicle brake systems are provided, in which the two brake circuits each have a front wheel and this one diagonally opposite rear wheel are connected. In such vehicle brake systems, the brake force regulator has the

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Task, the pressure increase at the rear brakes compared to the pressure increase occurring at the front brakes to be reduced as soon as the pressure on the rear brakes has reached a certain amount and, if applicable, that Vehicle has reached a certain deceleration.

In a known brake force regulator of the described Genus (DE-OS 28 20 768) the stepped piston is arranged axially next to the compensating piston. Both pistons are hollow and each contain a valve body and a spring that move the associated valve body towards one in the valve seat in question is loaded. Both valve bodies each have an axially outwardly projecting one Continuation on. In the rest position, the valve body arranged in the stepped piston is supported with its extension on the Compensating piston and the valve body arranged in the compensating piston is supported with its extension on the housing away. As a result, both valves are kept open in the rest position, so that the first inlet chamber through the Stepped piston through with the first outlet chamber, and the second inlet chamber through the equalizing piston is connected to the second outlet chamber. The second inlet chamber is in addition to the second outlet chamber connected via channels that bypass the valve located in the compensating piston and a delay-controlled one Valve included. The delay-dependent valve consists of a valve ball, which is in a counter the two pistons axially offset bore of the housing is movable, and a valve seat on one of these Bore closing plug is formed.

If, in this known brake force regulator, the pressure in the first outlet chamber has a certain value during braking Exceeds the amount, the stepped piston moves against the force of the spring loading it in Rieh-

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direction away from the balance piston with the tendency to take the first To enlarge outlet chamber. The compensating piston follows the stepped piston and thereby maintains the pressure equilibrium the two outlet chambers upright. As a result of the displacement of the compensating piston, this closes in this arranged valve, so that the pressure in the second outlet chamber only rise under the condition It is possible that the delay-dependent valve is still open. If the stepped piston is moved further, it closes then also the valve arranged in this and then the pressure in the two outlet chambers can only be in one compared to the pressure in the two inlet chambers increase the reduced ratio, that of the area ratio of the depends on both faces of the stepped piston.

If the first brake circuit of the known brake force regulator fails connected vehicle brake system, the compensating piston works without the aid of the stepped piston against the spring loading the stepped piston; as a result, a pressure limitation occurs in the second outlet chamber only at a pressure at which with a blocking of the one connected to the second brake circuit Rear wheel must be expected. If, on the other hand, the second brake circuit fails, it closes in the stepped piston contained valve prematurely, as the compensating piston no longer follows the stepped piston in this case. Consequently the pressure in the first outlet chamber becomes premature relative to the pressure in the first inlet chamber reduced, which is also undesirable, since this results in the braking of the connected to the still intact first brake circuit Rear wheel is weaker than in the normal state of both brake circuits.

The invention is based on the object of a brake force regulator of the type described above, the effect

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the failure of a brake circuit to reduce the pressure curve in the outlet chamber of the other brake circuit and to make the brake force regulator simpler and more space-saving overall.

The object is achieved in that the Stepped piston arranged together with the spring loading it and the pressure-dependent valve in the compensating piston and the pressure-dependent valve from the stepped piston is independent of the position of the compensating piston with respect to the housing is controlled.

The brake force regulator according to the invention thus only contains a pressure-dependent valve and this, together with the stepped piston that controls it, is inside the Compensating piston arranged to save space. The action of this valve is independent of any movement of the Balance piston with respect to the housing; as a result, the pressure-dependent valve switches as long as the first Brake circuit is intact, always at the same pressure, regardless of whether the second brake circuit is also intact is or not. The second brake circuit, however, only contains the additional controlled valve; as a result is it is ruled out that the pressure in the second outlet chamber is still undiminished after this valve is closed increases.

The compensating piston is expediently between two The same springs supported on the housing are arranged with a flat characteristic curve.

A preferred embodiment of the invention is based on the feature of the known generic brake force controller on that the additional valve is controlled delay-dependent. According to the invention, between the two

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th inlet and outlet chambers, coaxial with the compensating piston and movable independently of it, a second Arranged stepped piston, which has a valve seat on its smaller end face delimiting the second inlet chamber of the delay-dependent valve and in the idle state assumes a stop position in which the second inlet chamber has its smallest volume.

This has the additional advantage that the delay-dependent valve arranged in the second brake circuit is achieved does not act as a pressure limiting valve, but rather as a pressure reducing valve and in this respect is comparable with the pressure-dependent valve belonging to the first brake circuit. After closing both valves, the compensating piston would indeed equalize the pressure between the two outlet chambers bring about the delay-dependent valve even if only the pressure-dependent valve is used as a pressure-reducing valve Valve, however, would be designed as a pressure relief valve; the formation of both valves as pressure reducing valves however, it has the advantage that after the two valves are closed, the pressure between the two outlet chambers is equalized is possible without or with very little movement of the compensating piston.

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

Fig.l shows an axial section of an inventive Brake force regulator and

FIG. 2 shows an axial section of a braking force regulator modified compared to FIG.

The brake force regulator shown in Fig.l has a housing 10 made of simple profile steel with a rectangular cross-section with a stepped bore whose axis is hereinafter referred to as

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Longitudinal axis 12 is designated. The brake force regulator is provided to be mounted in a motor vehicle so that the longitudinal axis 12 in a vertical The longitudinal plane of the vehicle is inclined by about 30 ° from the horizontal and is arranged in such a way that the left in Fig.l End of the housing is at the front and higher than the right, rear end. For this attachment is a no The bolt shown is provided which extends through a transverse bore 14 in the housing 10.

The stepped bore is along the longitudinal axis 12 from the front incorporated into the housing 10 and consists of a front threaded section closed with a threaded plug 16 18, an adjoining front cylinder section 20, the diameter of which is only slightly is smaller than the inner diameter of the threaded portion 20, a central cylinder portion 22 of the middle Diameter and a rear cylinder portion 24 of smaller diameter.

The middle region of the front cylinder section 20 forms a first inlet chamber 26 which has a master cylinder connection 28 can be connected to a first master cylinder HzI indicated only by an arrow. The front one The area of the front cylinder section 20 forms a first outlet chamber 30, which via a brake connection 32 can be connected to a first wheel brake cylinder RzI, also indicated only by an arrow, on a rear wheel. Near the rear end of the front cylinder section 20, a vent chamber 34 is provided, which has a Dust filter 36 is connected to the atmosphere.

At the rear end of the rear cylinder portion 24, a second inlet chamber 38 is formed, which has a second master cylinder connection 40 to a turn only with

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an arrow indicated second master cylinder HzII can be connected. Furthermore, the front end forms the middle Cylinder section 22 together with the rear end of the front cylinder section 20 a second outlet chamber 42, which via a second brake connection 44 to a second wheel brake cylinder, likewise only indicated by an arrow RzII can be connected to the second rear wheel of the vehicle.

In the front cylinder section 20 are two weak springs 46 and 48 arranged, of which the front on the plug 16 and the rear on one between the cylinder sections 20 and 22 arranged perforated plate 50 is supported. A compensating piston is located between the two springs 46 and 48 52 arranged with a low axial bias. The two springs 46 and 48 are, for example, as cruciform Leaf springs designed with a gently rising force-displacement curve; this means that the springs are at axial Deflections of the compensating piston 52, which is arranged floating between them, only have very low restoring forces on them exercise that is just enough to return it to its center position as shown after each brake actuation.

The compensating piston 52 has on its outer circumferential surface three ring seals 54, 56 and 58 which separate the first inlet chamber 26 from the first outlet chamber 30 and from the ventilation chamber 34 or this from the second Disconnect outlet chamber 42. The balance piston 52 is hollow and contains a sleeve attached to its front end 60 with an axial bore 62. The bore 62 guides a first stepped piston 64 at its front section, in which it has its largest diameter. In the rear part of the compensating piston that is closed to the rear 52, a bore 66 is formed which has a smaller one

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Has diameter than the bore 62 and a corresponding rear portion of the stepped piston 64 receives. The stepped piston 64 is sealed against both bores 62 and 66 with an annular seal 68 and 70, respectively; further the sleeve 60 is sealed against the compensating piston 52 by an annular seal 80. The one behind the ring seal 70 lying area of the bore 66 is connected to the atmosphere via the ventilation chamber 34 and the filter 36.

Inside the compensating piston 52, around the first stepped piston 64, there is a helical, conical front and rear cylindrical compression spring 82 is arranged, which is with its rear end on the balance piston 52 and with her front end is supported on the stepped piston 64 and strives to this on a perforated, front end wall 84 of the Keep sleeve 60 lying close. At the front end of the stepped piston 64, an annular valve seat 86 is made of a Fastened elastomer, which together with a valve body 88 guided axially displaceably in the stepped piston 64. pressure-dependent valve 86,88 forms. The valve body 88 is arranged within the stepped piston 64 of one helical compression spring 90 biased forward and has a front extension 92, which is shown in the In the rest position abuts against the front end wall 84 and holds the valve body 88 lifted from the valve seat 86.

In the middle cylinder section 22 and in the rear cylinder section 24, a second stepped piston 94 is arranged and sealed with an annular seal 96 and 98, respectively. the The front end face 100 of the second stepped piston 94, together with the compensating piston 52, delimits the second Outlet chamber 42. The rear end face 102, which has a smaller area than the front end face 100, delimits the second inlet chamber 38; at this rear

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• ■ 44.

End face 102 an annular valve seat 104 made of an elastomer is attached, which together with a valve body 106 forms a delay-dependent valve 104,106. The valve body 106 is in the example according to Fig.l a Ball which is axially movably guided in a cage 108 attached to the second stepped piston 94.

The second stepped piston 94 has an axial through it Channel 110 which opens inside the valve seat 104 and contains a pin 112. The pin 112 is based on the Perforated plate 50 and does not quite reach the valve seat 104 when the second stepped piston 94 is drawn Assumes the rest position in which it rests on an annular shoulder 114 between the cylinder sections 22 and 24 supports. A relief bore 116 leads from the shoulder 114 into the open.

For the following description of the mode of operation of the brake force regulator shown in Fig. 1, it is initially assumed that both. Brake circuits HzI-RzI and HzII-RzII are OK and the vehicle is only lightly loaded. at Actuation of the two main cylinders HzI and HzII (which are usually arranged in a common housing are), the pressure-dependent valve 86, 88 and the delay-dependent valve 104, 106 are both open. The in The pressure gradually increasing in the inlet chambers 26 and 38 is therefore undiminished into the outlet chambers 30 and 42 transfer.

At a certain pressure increase, the vehicle reaches a delay that causes the spherical valve body 106 to roll forward and upward within the cage 108 and can be placed against the valve seat 104 so that the delay-dependent valve 104,106 closes. The characteristic the spring 82 is chosen so that that reached by then

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An increase in pressure in the outlet chamber 30 moves the stepped piston 64 backward until the valve seat 86 is closed against the valve body 88 and consequently the pressure-dependent valve 86,88 when the vehicle is unladen at the same time as the delay-dependent valve 104,106 closes. Should one of the two valves be before the other close, movement of the compensating piston would prevent the two outlet chambers 30 and 42 from entering Pressure difference arises.

If the pressure in the two inlet chambers 26 and 38 continues to rise, the pressure-dependent valve 86, 88 acts in connection with the first stepped piston 64 as a pressure reducing valve, which increases the pressure in the outlet chamber 30 only to a certain extent lets the opposite to the pressure increase in the inlet chamber 28 in the ratio of the effective end faces of the first stepped piston 64 is reduced. The delay-dependent acts in a corresponding manner. Valve 104.106 in Connection to the second stepped piston 94 as a pressure reducing valve, which reduces the pressure in the second outlet chamber 42 can only increase to an extent that compared to the pressure in the second inlet chamber 38 in the ratio of effective end faces 100 and 102 of the second stepped piston 94 is reduced.

When the vehicle is heavily loaded, the pressure increase in the outlet chambers 30 and 42 at which the first stepped piston 64 is moved backwards and the pressure-dependent valve 86, 88 closes, do not decelerate the vehicle so much, that the delay-dependent valve 104,106 would also close. As a result, the will continue to rise Pressure of the second master cylinder HzII transmitted undiminished in the outlet chamber 4 2 and caused thereby Movement of the compensating piston 52 forwards causes the pressure in the outlet chamber 30 to rise to the same extent as

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in the outlet chamber 42. Both wheel brake cylinders RzI and RzII are thus with a pressure that continues to rise supplied until the vehicle finally decelerates> in which the delay-dependent valve 104,106 closes and a further increase in pressure in the Outlet chamber 42, and because of the mobility of the compensating piston 52 also in the outlet chamber 30, only with a relative to the further increase in pressure in the inlet chambers 26 and 38 reduced rate of increase.

If the first brake circuit HzI-RzI has failed, the compensating piston 5 2 moves into its front, fixed by the plug 16 end position, so that the outlet chamber 4 2 correspondingly more brake fluid picks up and the driver to the failure of the first brake circuit by a longer travel of the brake pedal gets to feel. The delay-dependent valve 104,106 closes at the delay caused by the setting the angle of inclination of the longitudinal axis 12 with respect to the horizontal has been selected. The second stepped piston 94 However, if the pressure continues to build up in the inlet chamber 38, it shifts more rapidly than if the first brake circuit is intact HzI-RzI and consequently the pin 112 lifts the valve body 106 from the valve seat 104, so that the pressure in of outlet chamber 42 to that in inlet chamber 38 adjusted again and the rear wheel, to which the wheel brake cylinder RzII is assigned, braked correspondingly more strongly is than if the first brake circuit was intact.

If, on the other hand, the second brake circuit HzII-RzII fails, the compensating piston 52 moves in with each braking its rear, right end position in the drawing, which is determined by the perforated plate 50; the pressure-dependent However, valve 86,88 operates normally.

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The modified brake force regulator shown in FIG differs from that according to FIG. 1 only in the details of its rear, right of the perforated plate 50 lying area. The cylinder section 22 extends here further to the rear and from the rear is in the housing 10 a sleeve 118 tightly attached, the inner diameter of which is smaller than that of the cylinder portion 22. In the cylinder section 22 and in the sleeve, a stepped piston 120 is guided, the design and Dimensions with the stepped piston 64 coincides. While the stepped piston 64 according to FIG. 2, in accordance with FIG a controlled by the pressure-dependent valve 86,88 connection between the first inlet chamber 26 and the first Is outlet chamber 30, the stepped piston 120 forms one controlled by a pressure-dependent valve 122, 124 Connection between the second inlet chamber 38 and the second outlet chamber 42. The valve 122, 124 includes a An annular valve seat 122 fastened to the front end of the stepped piston 120 and an axial valve seat 122 in the stepped piston 120 displaceably guided valve body 124, which is supported by a spring 126 in Direction to the valve seat 122 is loaded and has a front extension 128. In the illustrated rest position the extension 128 is supported on the perforated plate 50 so that it holds the valve body 124 raised from the valve seat 122.

At the rear end of the housing 10 is on a bearing pin 130, which extends transversely to this at a distance from the longitudinal axis 12, a lever 132 is mounted at its end a spring indicated by an arrow 134 is attached. The spring 134 is connected in a known manner to an axle of the associated vehicle in such a way that the lever 132 is adjusted in the direction of arrow 134 with increasing load. The lever 132 is essentially coaxial with the longitudinal axis 12 an adjusting screw 136

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screwed and fixed with a lock nut 138. The adjusting screw 136 is with a sleeve 140 against the Housing 10 and the sleeve 118 sealed and lies with its end on the rear end face of the stepped piston 120 at. The lever 132, and thus also the adjusting screw 136, are shown in a position which easy loading of the vehicle.

If, during braking, the pressure in the second inlet chamber 38 (as well as in the first inlet chamber 26) only rises moderately, it is transferred through the opened valve 122, 124 into the second outlet chamber 42, exceeds If the pressure in the outlet chamber 4 2 is an amount predetermined by the setting of the spring 134, the stepped piston 120 is set by the differential force occurring on it against the resistance of the spring 134 to the rear, in Fig.2 thus shifted to the right, so that the valve seat 122 lies against the valve body 124 and the connection interrupts between the second inlet chamber 38 and the second outlet chamber 42. If the pressure continues to rise in the In the inlet chamber 38, the stepped piston 120 is shifted somewhat forwards again, so that the valve 122, 124 temporarily is opened and the pressure in the outlet chamber 42 with increasing pressure in the inlet chamber 38 in a ratio which corresponds to the ratio of the effective end faces of the stepped piston 120.

But when the vehicle is heavily loaded and thus the spring 134 is loaded more, it holds the lever 132 in a Position that is pivoted a few degrees clockwise from the position shown. The stepped piston As a result, 120 takes an initial position when the brakes are not applied a, which is offset slightly to the front in relation to the position shown, i.e. to the left in FIG. If it is now braked and the pressure in the inlet chamber

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38 and the outlet duct 42 rises, a more significant one is required Pressure increase in order to move the stepped piston 120 backwards until the valve seat 122 the Valve body 124 reached. The valve 122, 124 therefore only closes when the vehicle is heavily loaded a higher pressure in the outlet chamber 42 is reached. That Valve 122, 124 is therefore a valve dependent on the load on the vehicle, which is the one shown in FIG. the deceleration of the vehicle dependent valve 104,106 replaced.

Claims (3)

Claims (1. ^ Brake force regulator for a hydraulic vehicle brake system <each with a housing (10) in which - a first and a second inlet chamber (26,38) and a first and a second outlet chamber (30,42) for one first or second brake circuit (HzT-RzI or HzII-RzII) are formed, - the two outlet chambers (30,42) by a compensating piston (52) are separated from each other, - A stepped piston (64) is arranged between the first inlet and outlet chambers (26, 30), which with its larger End face the first outlet chamber (30) bounded and by a spring (82) in the sense of a reduction in size of this outlet chamber (30) is charged, - Between the first inlet and outlet chambers (26, 30) also one of the position of the stepped piston (64) in With respect to the compensating piston (52) a pressure-dependent controlled valve (86,88) is arranged, - and a further controlled valve (104,106) is arranged between the second inlet and outlet chambers (38, 42), characterized in that the stepped piston (64) together with the one loading it The spring (82) and the pressure-dependent valve (86, 88) are arranged in the compensating piston (52) and the pressure-dependent Valve (86,88) from the stepped piston (64) regardless of the - 2 - 54 470 Position of the compensating piston (52) with respect to the housing (10) is controlled. 2. Brake force regulator according to claim 1, characterized in that the compensating piston (52) between, two on the housing (10) supported, the same springs (46,48) is arranged with a flat characteristic. 3. Brake force regulator according to claim 1 or 2, wherein the arranged between the second inlet and outlet chambers (38,42) Valve is a delay-controlled valve (104,106), characterized in that between the second inlet and outlet chambers (38, 42), A second stepped piston (94) is arranged coaxially with the compensating piston (52) and movable independently of it is, which on its smaller, the second inlet chamber (38) delimiting the end face (102) has a valve seat (104) of the Has delay-dependent valve (104,106) and in the rest state assumes a stop position in which the second inlet chamber (38) has its smallest volume.