DE3329498A1 - LOAD-RELATED BRAKE FORCE FOR VEHICLES - Google Patents

Description

PATENT LAWYERS dr.-ing. franz wuesthoff

WUESTHOFF- ν. PECHMANN-BEHRENS-GOETZ ™ - ™ .l.freda »ubsthoff

DIPL.-ING. GERHARD PULS (19J2-I971)

EUROPEAN PATENT ATTORNEYS d.pl.-chem. dr. ε. Baron von Pechman

2 DR.-ING. DIETER BEHRENS

"3 OOQ L QP DIPL.-ING .; DIPU-VIRTSCh ₁ -ING. RUPERT GOl

lA-57 151

D-8000 MUNICH 90 Lucas Industries Schweigerstrasse 2

08/16/1983 phone: (089) 66 20 ji

TELEGRAM: PROTECT PATENT

telex: j 24 070

Load-dependent brake force regulator for vehicles

The invention relates to a load-dependent brake force regulator for vehicles with

- An inlet chamber which can be connected to a controlled pressure medium source, in particular a master brake cylinder is,

- an outlet chamber which can be connected to at least one wheel brake cylinder,

- two pistons, one of which delimits the inlet chamber and the other delimits the outlet chamber,

- An actuator that is adjustable according to the load on the vehicle and at least one of the two Piston supported depending on load,

- And a pressure reducing valve, which is arranged between the inlet and outlet chamber, controlled by one of the two pistons and is open in an idle state.

For vehicles whose rear axle is only lightly loaded when the vehicle is unloaded, it is common to connect the wheel brake cylinders of the front wheels directly to a master brake cylinder, while the wheel brake cylinders the rear wheels via a common or via a load-dependent brake force regulator to the main brake cylinder are connected. Such brake force regulators are usually designed so that the pressure in the rear wheel

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brake cylinders up to a switching pressure in the same Way rises like the pressure in the master cylinder, that the pressure in the rear wheel brake cylinders however above of the switching pressure only rises by a certain fraction of the pressure increase in the master brake cylinder. The aim is to approximate the ideal pressure curve at which the pressure in the rear wheel brake cylinders generally increases approximately parabolic in relation to the pressure in the front brake cylinders.

In some vehicles, the slope of the ideal pressure curve in the loaded state of the vehicle is one other than when empty. For such vehicles, load-dependent brake force regulators are those described at the beginning Genus has been created that compares the pressure in the rear brake cylinders to the pressure in the master brake cylinder if the vehicle is loaded, reduce it relatively less than if the vehicle is empty.

For example, from DE-OS 30 41 B79 a brake force regulator is the described type known in which the two, the inlet and outlet chamber delimiting pistons via a Rocker are coupled to each other, the pivot axis of which depends on the load condition of the vehicle by means of a Linkage is adjustable in such a way that the lever arms of the two pistons with respect to the pivot axis are accordingly change in the opposite direction to the load condition. The pressure reducing valve is from the one that delimits the outlet chamber Piston controlled and is also suspended with a certain backlash on a stepped piston, the two different Has large effective end faces, of which the smaller is constantly the pressure in the inlet chamber and the larger is constantly exposed to the pressure in a front brake circuit via a separate connection. With intact Front brake circuit allows the stepped piston to reduce the pressure

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derventil to close the freedom if it is of the associated piston delimiting the outlet chamber accordingly is controlled. However, if the front brake circuit fails, the stepped piston will hold the pressure reducing valve in a position in which it cannot close, so that the pressure of the master cylinder is undiminished reaches the rear brake cylinders. However, it is in no way possible to reduce the pressure in the rear wheel brake cylinders to let rise more strongly than in the master brake cylinder. Such a greater increase can, however even with the front brake circuit intact, it may be desirable if the vehicle is designed to accommodate its payload mainly loads the rear axle. This is possible, for example, with passenger cars that are behind the rear axle have a large trunk.

The invention is therefore based on the object of designing a load-dependent brake force regulator in such a way that it can be adapted to different axle load distributions better than known brake force regulators.

Based on a load-dependent brake force regulator of the type described above with two pistons, one of which one controls a pressure reducing valve, the object described is achieved according to the invention in that

- At least the other of the two pistons is a stepped piston with two effective end faces of different sizes is, of which the larger of the inlet chamber and the smaller of the outlet chamber faces,

- And between the inlet and outlet chamber, a pressure booster valve is additionally arranged, which is from the latter Piston controlled and is also open in an idle state.

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Load-dependent brake force regulator with stepped piston and associated Pressure booster valves have been known per se for a long time, for example from DE-AS 1 163 695. Such Brake force regulators are arranged between a master cylinder and front brake cylinders; you are not able to reduce the pressure increase in the rear wheel brake cylinder compared to the pressure increase in the master cylinder To reduce the need.

In a preferred embodiment of the invention the pressure increasing valve arranged in series with the pressure reducing valve. This is the order of the two valves not decisive. Preferably, however, the pressure booster valve together with the associated piston is between the outlet chamber and the pressure reducing valve together with the associated piston.

The latter embodiment of the invention is preferred further developed in that both pistons are designed as stepped pistons and are effective with their larger ones End faces facing each other.

The two pistons can, as in the known generic brake force regulator (DE-OS 30 41 879), side by side be arranged. A particularly space-saving and low manufacturing cost design of the invention Braking force controller is possible when the two pistons are coaxially arranged. Here can an intermediate piston which is connected to the actuator can be arranged between the two pistons. The actuator can then be an eccentric which engages in a recess in the intermediate piston.

Embodiments of the invention are described below with reference to schematic drawings with further details explained. It shows:

copy

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Fig.l a first brake force regulator in an axial

Cut,

2 shows a pressure diagram of the first braking force regulator, 3 shows a second brake force regulator in an axial one

Cut.
4 shows a third brake force regulator in an axial one

Cut,
5 shows the side view in the direction of arrow V in

Fig. 4 /
6 shows a pressure diagram of the third brake force regulator

and
7 shows a fourth brake force regulator in an axial section.

The brake force regulator shown in Fig.l has a housing 10 with a connection hole 12 for a line which
comes from a master cylinder, not shown.
The connection bore 12 is connected to an inlet chamber 14 which is part of a first stepped bore 16 and extends around a first stepped piston 18.

The first stepped piston 18 has a continuously connected to the inlet chamber 14 transverse bore 20, which in a
Longitudinal bore 22 opens. "The longitudinal bore 22 extends
through that part of the first stepped piston 18,
which has the largest diameter; this delimits the inlet chamber 14 with an annular smaller end face 24 and has on its other, in Fig.l the upper one
Side, a larger end face 26. Arranged within the longitudinal bore 22 is an annular valve seat 28 which, together with a valve body 30 and a valve spring 32, forms a pressure reducing valve 34. The valve spring 32 tries to press the valve body 30 against the valve seat 28 and thereby to close the pressure reducing valve 34
conclude; however, this works in the depicted rest position

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ment of the first stepped piston 18 against a formed on the valve body 30 extension 3 6, which is through the Valve seat 28 extends therethrough and abuts against the wall of a transverse connecting channel 38.

The housing 10 has a further connection bore 42 which is connected to an outlet chamber 44. This is part of it a second stepped bore 46 which surrounds a second stepped piston 48 in a ring shape and continuously is connected via a transverse bore 50 with a longitudinal bore 52 of this stepped piston. The longitudinal bore 52 extends through that part of the second stepped piston 48 which has the largest diameter, the outlet chamber 44 bounded by an annular smaller end face 54 and a larger end face facing away from this 56 has.

An annular valve seat 58 is formed within the longitudinal bore 52, which together with a valve body 60 and a valve spring 62 forms a pressure booster valve 64. The valve spring 62 strives to the valve body 60 to press against the valve seat 58, however, in the illustrated rest position of the second stepped piston 48 prevented by an extension 66 formed on the valve body 60, which against a threaded plug 68 bumps.

The space of the second stepped bore 46, which is delimited by the larger end face 56 of the second stepped piston 48, is sealed off from the outside by the threaded plug 68 and only with the space through the connecting channel 38 connected to the first stepped bore 16, which is delimited by the larger end face 26 of the first stepped piston 18 is. The connecting channel 38 can be opened to vent the brake force regulator, but is in operation, as shown, closed to the outside.

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A pivot bearing 70 is formed on the housing 10, the geometric axis of which is approximately in the middle between the geometric axes of the two stepped bores 16 and 4f and extends at right angles to the common plane of the last two axes. In the swivel bearing 70 is a two-armed lever

Actuator 72 mounted; this is connected to the rear axle of a vehicle in a manner not shown, in j that the brake force regulator is installed. The connection j is such that the actuator 72 is in the unloaded state of the vehicle assumes the position shown with full lines, with a full load, on the other hand, the position shown in dash-dotted lines Position indicated by lines.

On the actuator 72 is supported on one side of the pivot bearing 70 from a spring 74, which in turn the first Stepped piston 18 is supported. On the other side of the pivot bearing 70, a plunger 76 is supported, which is in the second stepped bore 46 is slidably guided; between this tappet 76 and the second stepped piston 48 a spring 78 is clamped.

In the following, the operation of the brake force controller shown in Fig.l is described, initially assuming that the associated vehicle is not or only lightly loaded, so that the actuator 72 assumes its position shown with full lines. When braking begins, brake fluid passes from the master cylinder through the connection bore 12 into the inlet chamber 14, further through the open pressure reducing valve 34 into the connecting channel 38 and from there through the likewise open pressure increasing valve 64 into the outlet chamber 44 and further via the connection bore k2 into the Rear brake cylinder. Thus, at the beginning of braking, the pressure generated in the master brake cylinder continues to be effective in the rear wheel brake cylinders.

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This pressure generates a resulting, force directed away from the connecting channel 38, but which is not strong enough to produce the resistance the spring 74 to overcome. The first stepped piston 18 therefore retains its position in a first braking phase shown position in which the pressure reducing valve 34 remains open. The same pressure is even more incapable of to overcome the resistance of the spring 78, since this is more biased by the actuator 72 than the spring 74. Therefore, the second stepped piston 48 remains in its illustrated position and the pressure booster valve 64 also remains open.

As a result, when the vehicle is unladen, the In the first phase of braking, the pressure increase from zero point 0 to a switchover point A shown in FIG in a ratio of 1: 1; There is an outlet pressure in the outlet chamber 44 and thus also in the rear wheel brake cylinders P 44, which corresponds to the inlet pressure P 14 prevailing in the inlet chamber 14. However, if a The pressure increase up to the switchover point A overcomes the pressure acting on the first stepped piston 18 The resulting compressive force increases the resistance of the spring 74, so that the first stepped piston away from the connecting channel 38 is moved with the result that the pressure reducing valve 34 closes. The pressure booster valve 64, however, remains open, since the pressure reached at switchover point A is not yet capable, a resulting pressure at the second stepped piston 48 To generate force that could overcome the resistance of the spring 78. With a further increase in the inlet pressure P 14 the outlet pressure P 44 rises only disproportionately. The pressure curve is thus that in Fig. 2 with a full line drawn, parabola-like curve approximating the ideal pressure curve with unloaded Vehicle represents.

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When the vehicle is loaded, the actuator 72 takes the in Fig.l a position indicated by dash-dotted lines, in which the spring 74 is stronger, the spring 78 is weaker is preloaded than when it is unloaded. As a result, according to FIG Pressure increase in the ratio 1: 1 only from zero point 0 to a switchover point B. As soon as this is achieved is, the resulting compressive force acting on the second stepped piston 48 overcomes the resistance the spring 78 so that the pressure increasing valve 64 closes while the pressure reducing valve 34 remains open. at further increase in the inlet pressure P 14, which acts on the larger end face 56 of the second stepped piston 48, This moves further away from the connecting channel 38 and generates with its smaller end face 54 an outlet pressure P 44 which is greater than the inlet pressure P 14. The outlet pressure P 44 thus rises from the switchover point B to a further switching point C, at which the inlet pressure P 14 has risen so far that the resulting Pressure force on the first stepped piston 18 the resistance overcomes the spring, which is more strongly pretensioned when the vehicle is loaded, so that the pressure reducing valve 34 closes. As a result, if the inlet pressure P 14 is increased further, there is only a flatter increase of the outlet pressure P 44. Overall, the pressure curve is that in Fig. 2 with a dash-dotted line, too parabola-like curve approximated ideal pressure curve with a loaded vehicle.

The steepness of the further pressure increase above the switchover point C depends on the size ratio of the effective End faces 24 and 26 as well as 54 and 56 of both stepped pistons 18 and 48. Depending on the design of these area ratios can be achieved that the outlet pressure P 44 above the switchover point C either as well as

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in the first phase of the pressure increase from O to B in proportion 1: 1 with the inlet pressure P 14 increases or even a little steeper than from 0 to B, but flatter than from B to C or, as shown in Fig. 2, flatter than from 0 to B, but a little steeper than the pressure increase, which takes place above switching point A when the vehicle is unladen.

The brake force regulator according to FIG. 3 agrees with that in FIG largely coincide, which is why comparable components are provided with the same reference numerals as in Fig.l. The only difference is essentially that the actuator 72 according to FIG. 3 only acts on the first stepped piston 18 acts, while the second stepped piston 48 is supported directly on the housing 10 via its spring 78 is. As a result, only the switching pressure of the pressure reducing valve 34 is from the load condition of the vehicle addicted; the pressure booster valve 64, however, invariably switches at a certain pressure in the connecting channel 38.

The brake force regulator according to Figure 4 and 5 is opposite to the in Fig.l and 3 further modified in that the two stepped bores 16 and 46 are coaxially arranged and merge directly into one another, with only one perforated between them Partition 80 as a stop for the extensions 36 and 66 of the two valve bodies 30 and 60 in the housing 10 is attached. Accordingly, the two stepped pistons 18 and 48 are also arranged coaxially, namely such that they face one another with their larger end faces 26 and 56. The housing 10 contains in addition to Stepped bores 16 and 46 visible in FIG. 4 and stepped pistons 18 and 48 arranged therein, of these completely separately a second pair of such stepped bores and stepped pistons, so that two brake force regulators are formed, each of which is assigned to a rear wheel brake (not shown)

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get sorted. These two brake force regulators, which are hydraulically separated from one another, have a common actuator 72 assigned, which, as in the embodiment according to 3, of a one-armed lever mounted on the housing 10 is formed. Between the actuator 72 and the first stepped piston 18 of the two brake force regulators is a Balance beam 82 is arranged, which ensures that the dependent on the load of the vehicle, on the actuator 72 effective forces are evenly distributed between the two stepped pistons 18. These forces are from the rear axle of the vehicle transmitted in a manner not shown to a push rod 84 and from there on via a Sleeve 86 and a compression spring 88 on actuator 72.

In the braking force regulator shown in FIGS the frontal area ratios of the two stepped pistons 18 and 48 are selected in such a way and in such a way as to depend on the load condition dependent influence of the actuator 72 on the stepped piston 18 matched that each of the two in common Housing 10 arranged brake force regulator has the pressure diagram shown in Figure 6. According to this Diagram closes the pressure increasing valve 64 independently of the load status of the vehicle in front of the pressure reducing valve til 34, so that the switchover point B is reached in any case, from which the outlet pressure P 44 is stronger increases as the inlet pressure P 14. When the vehicle is unladen, however, the pressure reducing valve 34 closes after one brief further pressure increase at switchover point A, so that the outlet pressure P 44 with a further increase in the inlet pressure P 14 only increases gently. When the vehicle is loaded, the steep rise in pressure is above the switchover point B, however, continued up to the switchover point C; above that, P 44 only rises to the same extent, how it rises above the Umschaltpunk tes A when the vehicle is unladen.

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The brake force regulator according to Fig. 7 differs from that shown in FIGS. 4 and 5 mainly in that the housing 10 is divided in the middle, both stepped pistons 18 and 48 completely encloses and immobile between them instead of the one shown in FIG Intermediate wall 80 contains an intermediate piston 92. The two stepped pistons 18 and 48 are through each of their associated springs 74 and 78 are biased towards the intermediate piston '92. The intermediate piston 92 is from the connecting channel 38 bypassed and has only a mechanical function as an adjustable stop for the extensions 36 and 66 of the two valve bodies 30 and 60.

The actuator 72 is in turn a lever pivotably mounted on the housing 10; 7, however, is on the actuator 72 an eccentric 94 is attached, which within the housing 10 is essentially free of play in a recess 96 of the intermediate piston 92 is received. Actuator 72 and eccentric 94 are in Figure 7 with full lines in the Drawn position that they take when the vehicle is unloaded; with dashed lines is the position at laden vehicle indicated.

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Claims (7)

Claims 1.) Load-dependent brake force regulator for vehicles with - An inlet chamber (14) which is connected to a controlled pressure medium source, in particular a master brake cylinder can be connected, - An outlet chamber (44) connected to at least one wheel brake cylinder is connectable, - two pistons (18,48), one of which delimits the inlet chamber (14) and the other delimits the outlet chamber (44), "~ - an actuator (72) which is adjustable according to the load on the vehicle and at least one of the supports both pistons (18,48) depending on the load, - And a pressure reducing valve (34), which is arranged between the inlet and outlet chamber (14, 44), of one of the two Piston (18,48) is controlled and open in an idle state, characterized , - That at least the other of the two pistons (18,48) is a stepped piston (48) with two different sizes effective End faces (54,56), of which the larger (56) of the inlet chamber (14) and the smaller (54) of the outlet chamber (44) is facing, - And between the inlet and outlet chamber (14,44), a pressure booster valve (64) is additionally arranged, which from last-mentioned piston (48) is controlled and is also open in a rest state. - 2 - 57 2. Brake force regulator according to claim 1, characterized in that the pressure increasing valve (64) with the pressure reducing valve (34) is arranged in series. 3. Brake force regulator according to claim 2, characterized in that the pressure booster valve (64) together with the associated piston (48) between the outlet chamber (44) and the pressure reducing valve (34) together with the associated piston (18) is arranged. 4. Brake power regulator according to claim 3, characterized in that both pistons (18, 48) are designed as stepped pistons and with their larger effective end faces (26,56) face one another. 5. Brake force regulator according to one of claims 1 to 4, characterized in that the two pistons (18, 48) are coaxially arranged are. 6. brake force regulator according to claim 5, characterized in that there is an intermediate piston between the two pistons (18, 48) (92) is arranged, which is connected to the actuator (72). 7. brake force regulator according to claim 6, characterized in that the actuator (72) has an eccentric (94) which engages in a recess (96) of the intermediate piston (92).