WO1997038884A1

WO1997038884A1 - Hydraulic brake booster

Info

Publication number: WO1997038884A1
Application number: PCT/EP1997/001634
Authority: WO
Inventors: Rainer Seeger; Werner Volkmar; Bernd SCHÜTT
Original assignee: Itt Manufacturing Enterprises, Inc.
Priority date: 1996-04-16
Filing date: 1997-04-01
Publication date: 1997-10-23
Also published as: DE19614909A1

Abstract

The invention relates to a hydraulic brake booster, especially for motor vehicle braking systems, with at least one transmission piston (4d) in an brake booster housing (1) to which fluid from a power supply (1d) can be applied via a valve body (13) in the brake booster housing (1). Depending on the position of an actuating piston (4a), the fluid from the power supply (1d) is applied via the valve body (13) to a pressure chamber (112) accepting the transmission piston (4d), or the pressure chamber (112) is connected pressurelessly to a container connection (1c). The valve body (13) is fitted on a stepped regulating piston (4b) which is guided to be axially movable in the actuating piston (4a), and the valve seat (4c) is secured at the end of the actuating piston (4a), through the drilling of which penetrates an extension of the valve body (13) extending as far as a valve drilling (7) in the piston of the pressure rod (5).

Description

Hydraulic amplifier

The invention relates to a hydraulic amplifier, in particular for motor vehicle brake systems according to the preamble of patent claim 1.

From DE 40 21 700 AI a hydraulic power booster has already become known, which in its design as a so-called tube booster has a booster piston in the booster housing, which, via a valve body acting as a seat valve, introduces the pressure of an energy supply into a pressure chamber receiving the booster piston, provided that the actuating piston is under force. In the pedal release position, the pressure chamber is connected to an atmospheric container connection without pressure. In this amplifier, which is provided with a ball valve, there is noise as a result of the axial play of the ball or even reactions on the pedal as a result of a pressure pulsation in the energy supply.

Furthermore, from DE 40 15 883 AI a hydraulic power booster has already become known, which is also designed as a tube booster and carries out the pressure medium control in the direction of the surface to be acted upon on the booster piston by means of a slide valve. With this power amplifier, the pressure of the energy supply is not sent directly to the slide valve, but is preset by means of a pressure reducing and pressure limiting valve. The use of a slide valve requires tight fit play to be observed, which increases the cost of manufacturing the power amplifier. It is therefore the object of the invention to improve a hydraulic amplifier of the type mentioned at the outset such that an inexpensive, universally usable and comfortably operable power amplifier can be produced using simple, functionally reliable means.

This object is achieved for the power amplifier of the generic type according to the features of claim 1.

Further features, advantages and possible uses of the invention will become apparent from the description of two exemplary embodiments.

Show it:

1 is an overall view of the power amplifier according to the invention in longitudinal section,

2 shows an enlarged partial section of essential features of the power amplifier according to FIG. 1.

Fig. 1 shows the structure of the hydraulic amplifier, consisting of an amplifier housing 1, with the adaptation of a master cylinder la, a mounting flange lb, a container connection lc, with a connection for a power supply ld and the adaptation of a step valve le. Furthermore, the illustration shows a pressure reducing valve 2, which is inserted obliquely to the longitudinal axis into the valve housing 1 and to which the energy supply ld (pump-storage unit) is connected. An actuating unit 4 inserted as a cartridge insert into the amplifier housing 1 in the longitudinal direction consists of a hollow actuating piston 4a, which has a regulating piston 4b and a valve seat 4c attached to the actuating piston 4a. There is also a booster piston 4d between the rear Housing receptacle 4e of the actuating unit 4 and the push rod 5 slipped over the actuating piston 4a. All of the above-mentioned parts of the actuation unit 4 are aligned coaxially with one another and, as it were, nested with one another.

The push rod 5 has a return spring 5a and a spring bearing 5b, which is held in the region of the master cylinder flange. These parts are also in a coaxial arrangement with respect to the actuation unit 4, which structurally fulfills the features of a so-called tube amplifier.

1 also shows a step valve 6 with a valve housing 6a, a step piston 6b located therein, a cover 6c, a screw 6d and a sealing plate 6e for flanging the step valve 6 onto the booster housing 1. Two stage valves 6 are flanged to the booster housing 1 in a twin arrangement for a two-circuit brake system. These step valves 6 are a significantly simplified and less expensive version of the changeover valve described in DE 40 32 206 AI, which has been expanded to include an essential function. This expansion of functions includes the division of the brake fluid volume per circuit into a so-called application volume and a so-called pressure increase volume, which is necessary for the legally required minimum braking in the event of an amplifier failure.

The individual structural and functional features of the invention are discussed below with reference to FIG. 1. In the release position, the accumulator pressure is applied via a connection for the energy supply ld on the input side (area difference of the surfaces 166-165) of the pressure reducing valve 2, which works as a pressure limiter in this functional position and the accumulator pressure on the Output side 52 of the pressure reducing valve 2 limited to a fixed value. The accumulator pressure becomes the reduced accumulator pressure, which passes through the inclined housing bore 53 into the annular space 54 of the receptacle 4e and from there through the channel bores 55 into the annular space 56 of the actuating piston bore. This bore is smaller on the reinforcement side in the guide area of the actuating piston 4a than on the opposite side in the area of the pedal rod. The diameter of the actuating piston 4a is up to its annular groove 9 smaller than at the outwardly sealed end section of the actuating piston 4a. Along this annular gap, the reduced pressure passes from the annular space 56 into the annular groove 9 and from there into the bores 10, 11 of the actuating piston 4a into the control piston space 4f, through the piston bore 12 and past the valve body clamping into the pressure control space 112. The valve body 13 has this Task to seal the reduced storage pressure at valve seat 4c. All other wet rooms in the amplifier housing 1, in the stepped valve 6 and in the master cylinder la are depressurized during this sealing effect and connected to an expansion tank (tank connection lc). The end position of the actuating piston 4a in the release position is defined as follows: Due to the unevenly large diameter on the actuating piston 4a, there is an area difference (annular surface) which is acted upon by the reduced storage pressure and which results in a force component against the pedal input force direction. This force component is directly proportional to the hydraulic pressure applied. The hydraulic pressure is constant (static) in the release position of the amplifier due to the pressure limitation value defined in the pressure reducing valve 2, in the braking position the hydraulic pressure on the actuating piston 4a increases (dynamic) due to the regulated hydraulic pressure. Through the tapered section on the actuating piston 4a, the reduced accumulator pressure not only reaches the regulating piston 4b, but one is created Hydraulic restoring action on the actuating piston 4a opposite to the direction of the input force, which caused it to come to a stop via the collar 15 of the valve seat 4c axially secured in the actuating piston 4a via the end faces of the booster piston 4d on the end face of the receptacle 4e. The receptacle 4e is fixed in position by a locking ring in the amplifier housing 1.

In the following, essential functional features of the actuation unit 4 are explained with reference to FIG. 2, which shows an enlarged section of the amplifier according to FIG. 1. The actuation unit 4 has a valve seat 4c, a valve body 13 with a control piston 4b and a compression spring 33, which is supported on the actuation piston 4a. As already mentioned at the beginning, all parts are arranged coaxially in the actuating piston 4a. The valve body 13 and the valve seat 4c form a ball-sealing-seat control element combination. To open such a hydraulically pressurized combination, an actuating force corresponding to the pressurized area times the feed pressure is necessary, that is, a high path-independent force increase with design of these control elements in accordance with the volume throughput. In addition, such a seat valve arrangement either generates noise or transmits pressure pulsations to the pedal. Such behavior is rarely acceptable with an amplifier. In known series amplifiers, therefore, a much more expensive slide valve is often used. The actuating unit 4 now claimed compensates for all static and dynamic influences by functional combination of the valve body 13 with a stepped control piston 4b. This is done in that the reduced storage pressure is present through a central bore 12 on both sides of the control piston 4b. The surface difference of the piston surfaces 70 and 80 corresponds to a correction factor of the pressurized surface 90 of the Valve body 13 so that the forces are balanced in total. The force required to lift the valve body 13 at the start of the actuation is determined only by the friction of the sealing elements on the control piston 4b and the design of the compression spring 33. In the dynamic range and thus during the hydraulic pressure control, this balance is not disturbed by a force resulting from the regulated accumulator pressure on the surface 90 and not by flow-related influences, since the annular surface 100 of the control piston 4b through bores 110 with the regulated hydraulic pressure in the pressure chamber 112 is connected. Since the annular surface 100 corresponds to the surface 90 and since the regulated pressure on the surface 90 and on the annular surface 100 is the same, the pressure-related influences and the flow-related influences neutralize. They become a constant variable, which is inversely proportional to the opening gap of the actuators.

2 also shows the booster piston 4d, which coaxially surrounds the actuating piston 4a. The push rod 5 is a separate component which is guided centered on the amplifier side in the booster piston 4d without a fixed connection and seals the hydraulic pressure in the regulated pressure chamber 112 on the booster piston 4d with respect to the container connection 1c exposed to atmospheric pressure by means of sealing element 43. On the master cylinder side, the push rod 5 is mounted in the pressure piston by means of a spherical surface. This condition must be maintained if the amplifier is intact. This is particularly true in the start-up phase of the booster piston 4d, ie if the regulated hydraulic pressure has not yet reached the so-called start-up pressure and this also applies to a brake circuit failure of the upstream master cylinder la. To ensure this function, this module meets the following conditions: 1. The sealed diameter on the push rod 5 is smaller than the master cylinder nominal diameter.

2. The spring force of the auxiliary spring 5a is greater than the force product of the push rod area and the starting pressure.

3. The frictional resistance of the seal 47 on the booster piston 4d is smaller than the product of the push rod ring surface 80 and the starting pressure. Freewheel pressure is the pressure that must be built up to overcome all friction and spring forces in the booster piston / push rod functional unit.

If the hydraulic boost fails, the regulated storage pressure of the energy supply ld is missing or the reduced storage pressure or the regulated pressure become ineffective due to leakage. After overcoming the valve closing path (axial air gaps between collar 15 of valve seat 4c and bottom of push rod 5), actuating piston 4a pushes push rod 5 out of its bearing in booster piston 4d against auxiliary spring 5a. The booster piston 4d remains in its current position, the seal between the regulated pressure chamber 112 and the container connection 1c for the atmospheric hydraulic supply is broken. The push rod 5 slides on its centering ribs 110 in the housing bore. In this emergency operation, the frictional resistance of the seal 47, the spring force of the hydraulic spring action and the loss of splashing, which occurs when actuated by pumping the brake fluid through the expansion tank at the tank connection 1c in the pressure chamber 112, are eliminated. In the event of an amplifier failure, the collar 15 of the valve seat 4c comes to the bottom of the push rod 5. A mechanical connection between the master cylinder la and the brake pedal is thus established. By breaking the seal between the piston of the pressure rod 5 and the booster piston 4d, the pressure chamber 112 is connected to the pressure rod chamber leading to the expansion tank. Possibly pumped from the expansion tank into the pressure chamber 112 by foot force Brake fluid volume can compensate directly via the gaps in the guide ribs 110 and thus past the collar 15 in the direction of the push rod space. The restoring force of the compression spring 5a is designed to a minimum for this emergency. When using a stepped valve 6, this also lacks the regulated accumulator pressure in the valve housing 6a, whereupon the brake pressure applied from the master cylinder la shifts the stepped piston 6b from a certain pressure level, and the hydraulic translation of the master cylinder pressure takes place in accordance with the specified parameter.

In the brake actuation position, the input force acts on the actuation piston 4a via the pedal rod. After overcoming the hydraulic restoring force and the friction of the sealing elements on the actuating piston 4a, the entire actuating piston 4a is displaced by an empty travel, so that the ball of the valve body 13 tightly closes the valve bore 7 arranged in the push rod 5. The collar 15 of the valve seat 4c lifts the same way from the end face of the booster piston 4a, the end face of the valve seat 4c is still a long way away from the opposite stop face in the push rod 5. If the input force is increased by the spring force of the compression spring 33 and by the friction of the sealing elements on the regulating piston 4b, the actuating piston 4a moves further in the direction of the push rod 5, while the valve body 13 with the stepped piston is supported on the valve bore 7 via the ball and the Cannot follow the path of the actuating piston 4a. The valve body sealing surface is thus lifted from the valve seat 4c free of free travel and reduced accumulator pressure can flow into the connected pressure chamber 112 along the annular gap between the actuating piston and the booster piston 4d. A pressure builds up behind the booster piston 4d, which causes it to follow in the direction of movement of the actuating piston 4a. The push rod 5 seated against the stop is also displaced with the valve bore 7 against the auxiliary spring 5a. The valve body 13 supported on the valve bore 7 also follows and thus closes the gap between the valve body sealing surface and the valve seat again, thus ending the pressure build-up behind the booster piston 4d.

If the input force is now increased further, the actuating piston 4a moves again in the direction of the push rod 5 without the valve body 13 being able to follow. The control cycle described above can start again. With each increase in the input force, the pressure in the closed pressure chamber 112 (regulated pressure) consequently increases and the booster piston 4d reinforces this effect. This regulated pressure is applied via the bore 155 to the piston surface 165 of the pressure reducing valve 2 and via the bore 17 to the inside diameter of the stepped piston 6b in the stepped valve.

In the pressure reducing valve 2, each increase in the regulated pressure via the piston surface 165 causes a brief displacement (opening) of the control elements 119, 120 of the pressure reducing valve 2 and thus an increase in the reduced storage pressure according to defined parameters.

In the stepped valve 6, the stepped piston 6b is pressed by the regulated pressure against a soft stop in the cover 6c and held there. The pressure from the master cylinder la through the bore 123, 124 is passed unchanged through the bore 125 to the wheel cylinder.

In summary, it can now be seen that the invention relates to a hydraulic amplifier (booster housing 1) arranged in series between the brake pedal and master brake cylinder la, which is actuated by the brake pedal by means of an actuating device 4 Foot strength proportionally increased according to the principle of hydraulic translation of surfaces.

To optimize the function, the booster is preferably operated with brake fluid (monofluid), the container connection lc is provided in the connection area of the booster housing 1 to the master cylinder la and the booster piston 4d and the push rod 5 are separate components.

Instead of a compression spring on the outside

Actuating rod or on the inside of the booster piston, a hydraulic return action on the actuating piston 4a is additionally used to return the actuating unit to the release position 4, which results from the area difference at the actuating piston 4a, acted upon by the reduced accumulator pressure, and which is approximately 60% of the total restoring force . A further advantage with regard to the functional quality results from the arrangement of a hydraulically controlled pressure reducing valve 2, which reduces the storage pressure as required. A functional expansion of the amplifier is ensured by a stepped valve 6 adapted to the amplifier housing 1 and controlled by the regulated accumulator pressure, as a result of which the main cylinder surface which is pressurized in effect is reduced in the event of an amplifier failure. Due to its design, the amplifier is therefore able to achieve a gain factor between 4.8 - 10.

Furthermore, the valve housing 1 is suitable by a corresponding housing adaptation for the adaptation of master cylinders, which have previously been combined with vacuum boosters. The design of the moving internal parts of the amplifier are geared towards the smallest possible diameter, friction, spring forces and number of moving parts To achieve the lowest possible input power losses in the event of amplifier failure. Likewise, the chosen design of the amplifier allows a fully automatic assembly. A relatively simple change in the amplification factor is achieved by replacing the booster piston 4d and adapting the receiving bore for the booster piston 4d. Because of the continuous bore of the housing and the short precision surfaces, the design is particularly easy to manufacture. Expensive precision control elements can be dispensed with using the selected 4-4e actuation unit. The selected arrangement of the internal amplifier parts not only ensures a reduction in size, but also the permissible operating pressure can be increased.

The arrangement of the container connection 1c away from the booster piston 4d means that seals can be saved in the displacement path of the booster piston 4d, which reduces the friction.

The push rod 5 is a separate component, which is advantageously guided centered in the booster piston 4d without a fixed connection on the amplifier side and seals the hydraulic pressure in the regulated pressure chamber 112 against the booster piston 4d by means of a sealing element 43.

Reference list

1 amplifier housing la master cylinder lb mounting flange lc tank connection ld power supply le step valve adapter

2 pressure reducing valve

3 lids

4 actuating unit 4a actuating piston 4b control piston

4c valve seat

4d booster piston

4e recording

5 push rod

5a return spring

5b spring bearing

6 step valve 6a valve housing 6b step piston 6c cover

6d screw

6e sealing plate

7 valve bore 9 annular groove 10,11 bores

12 piston bore

13 valve body 15 collar

47 seal

52 Output side

53 Housing bore

54 annulus

55 channel bore Annulus 0 piston surface area annular surface bore guide ribs pressure chamber bore, 124 bore, 120 control element

Claims

claims

1.Hydraulic booster, in particular for motor vehicle brake systems, with at least one booster piston arranged in an booster housing which can be acted upon by the fluid of an energy supply via a valve body arranged in the booster housing, the fluid of the energy supply in one of the two depending on the position of an actuating piston via the valve body Compressor piston receiving pressure chamber is present, or the pressure chamber is connected to a container connection without pressure, characterized in that the valve body (13) is attached to a stepped control piston (4b) which is axially movable in the actuating piston (4a) and that a valve seat (4c) is attached to the end of the actuating piston (4a), the bore of which is penetrated by an extension of the valve body (13) which extends up to a valve bore (7) in the piston of the push rod (5).

2. Hydraulic amplifier according to claim 1, characterized in that the control piston (4a) is penetrated by a central bore (12), so that the fluid of the energy supply (ID) is present on both end faces of the control piston (4b).

3. Hydraulic amplifier according to claim 1 or 2, characterized in that the annular surface (100) on the step of the control piston (4b) approximately corresponds to the pressurized closing surface of the valve body (13) on the valve seat (4c).

4. Hydraulic amplifier according to one of the preceding claims 1 to 3, characterized in that on the A pressure spring (33), which is supported in the actuating piston (4a), is attached to the smaller end face of the control piston (4b) facing away from the valve seat (4c).

5. Hydraulic amplifier according to claim 3, characterized in that the actuating piston (4a) at the stage of the control piston (4b), in the region of the annular surface (100), is penetrated transversely by a bore (110) which in a pressure chamber (112 ) flows into, which can be connected to the energy supply (ld).

6. Hydraulic amplifier according to claim 5, characterized in that the energy supply (ld) via a pressure reducing valve (2) and via the actuating unit (4) is connected to the pressure chamber (112).

7. Hydraulic amplifier according to claim 1, characterized in that the piston on the push rod (5) in the booster piston (4) is centered and by means of a sealing element (43) the hydraulic pressure in the pressure chamber (112) opposite that at the container connection (lc) Push rod space seals.