DE10244375B4 - Hydraulic vehicle brake system - Google Patents

Abstract

Hydraulic vehicle brake system, having a brake pressure generator which can be actuated by a brake actuation device and which can be connected to wheel brakes (30, 31) of the vehicle via a hydraulic line (14), the brake pressure generator consisting of a master brake cylinder (11) and an upstream hydraulic booster (7), which is connected to a pressure medium reservoir (13) via a line (12) in which a first analog or analog valve (6) is arranged and which has a coaxially to the master cylinder (11) arranged reinforcing chamber (47) and a booster piston arranged therein (41 ) which in the power output direction via an actuating element (42) is operatively connected to a master brake cylinder piston (51) and which for the purpose of brake booster with a hydraulic pressure of an external pressure source (4, 19, 20) can be acted upon, the motor-pump unit (19, 20) and a high pressure hydraulic accumulator (4) and with the hydrau Electrical amplifier (7) is connected via a line (50) in which a second analog or analog valve (5) is arranged, characterized in that the wheel brakes (30, 31) of the vehicle with the master cylinder (11) are connected via a return line (17), in which exhaust valves (16.1, 16.2), a low pressure accumulator (18) and a changeover valve (8) are arranged, and that the motor-pump unit (19, 20) also serves as a return pump.

Description

The invention relates to a hydraulic vehicle brake system according to the preamble of claim 1.

In the wake of new engine technology, such. As diesel, or gasoline direct injection, a sufficient vacuum supply for braking assistance is increasingly rare. This requires brake systems with an active hydraulic brake assist or with an additional vacuum pump for operating a vacuum brake booster.

When vacuum brake booster principle, its relatively large volume of construction is disadvantageous. Problems also occur in the packaging, since its installation is difficult to vary. Furthermore, there is a demand to simplify systems of construction costs without significantly restricting their functionality.

Systems with active hydraulic brake assist, the driver by means of a controllable hydraulic pump, z. As the ABS return pump, assist in the brake pedal operation, can lead to disadvantages in the comfort area. In some situations, a pedal feel sets in, which deviates negatively from a "usual" vacuum brake booster support. These systems increase the output point of a vacuum brake booster without replacing it. An insufficient vacuum supply or dimensioning of the vacuum brake booster can - be compensated - with the disadvantages described.

Known hydraulic brake booster are expensive due to the high construction cost of the amplifier, complicated and require additional components to actively build up pressure. This is especially true for brake-by-wire systems, such as electrohydraulic brake systems (EHB).

From the generic DE 197 10 862 A1 a hydraulic, operable with external force brake system for motor vehicles, with a master cylinder, which is preceded by a hydraulic brake booster having a booster piston and a working chamber to which an auxiliary pressure source is connectable, wherein an actuatable by means of an electromagnetic actuator valve means is provided which in a first switching position, a hydraulic connection between the working chamber and a non-pressurized pressure medium reservoir and in a second switching position establishes a connection between the working chamber and the auxiliary pressure source. The valve device is formed by an analog controllable slide valve.

The invention has for its object to provide a simple and inexpensive brake system whose components allow safe and comfortable hydraulic brake power assistance.

According to the invention, this object is solved by the features of the independent claim. Preferred embodiments are specified in the subclaims.

According to the invention, it is provided in a hydraulic vehicle brake system, with one of a brake actuator, in particular a brake pedal operable brake pressure transducer, which is connectable via a hydraulic line to a wheel brake of the vehicle, provided that the brake pressure transducer essentially of a master cylinder and an upstream hydraulic booster, which is connected to a pressure medium reservoir via a line in which a first analog or analogized valve is arranged and which has a substantially coaxial with the master cylinder arranged boosting chamber and a booster piston arranged therein, in the power output direction via an actuating element with a Master brake cylinder piston is operatively connected and the purpose of brake booster with a hydraulic pressure of an external pressure source is acted upon, which is connected to the hydraulic booster via a Leit ung, in which a second analogous or analogized valve is arranged.

An analog or analog valve can take all positions between OPEN and CLOSE by means of an electric or electronic external control, so that the brake pressure for control or comfort braking can be increased or decreased continuously. Preferably, the analog or analogized valve is set with a current value.

The master cylinder is preferably two-circuit and in particular designed as a tandem master cylinder (THZ) and the pressure medium reservoir is depressurized.

According to the invention, the external pressure source to a motor-pump unit and a hydraulic high-pressure accumulator, wherein an already existing in a brake system hydraulic return pump or a return-motor-pump unit is used.

According to the invention, an electronic control and regulating unit is provided by means of which the analog or analogized valves are regulated or be controlled, for the purpose of acting on the booster piston of the hydraulic booster with a certain hydraulic pressure.

It is provided according to the invention that the master cylinder is connected to the wheel brakes of the vehicle via a brake line, in which a separating valve is inserted, and via subsequent brake pipe parts, in each of which an inlet valve is arranged.

According to the invention, the wheel brakes of the vehicle are connected to the master cylinder via a return line, in which outlet valves, a low pressure accumulator and a changeover valve are arranged.

It is provided according to the invention that the pump is connected on the input side to the return line and the output side via a branch point with the wheel brakes of the vehicle or with the high-pressure accumulator is connected and that between the pressure side of the pump and the branch point, a check valve and a damper chamber are arranged.

It is provided according to the invention that from the branch point, the pump is connected to the high-pressure accumulator via a line in which a first controllable valve is arranged, and that of the branch point, the pump is connected to the brake pipe parts via a line in the one another controllable valve is arranged.

It is provided according to the invention that the controllable valves are controlled or controlled by means of the electronic control and regulation unit, for the purpose of controlling a hydraulic brake pressure or pressure build-up in the high-pressure accumulator.

In the following an embodiment with reference to drawings ( 1 and 2 ) described in more detail by way of example.

Show it:

1 a brake pressure generator for the brake system according to the invention

2 a braking system according to the invention

To 1 the brake pressure transducer has a hydraulic booster ( 7 ) acting as an extension of the actuator unit (THZ) 11 with container 13 is trained. The amplifier piston 41 is guided in an amplifier housing, with a push rod 42 of the booster piston 41 in the piston 51 the push rod circle of the THZ 11 supports or by a corresponding disc-like magnification 52 of the diameter in the THZ hole 53 to be led. The amplifier housing 40 Can as a component with the THZ housing 40 be executed, but also as a separate component to the THZ 11 be flanged. After mounting the booster piston 41 with push rod 42 , or after mounting the THZ pistons 51 . 54 and the intensifier piston 41 becomes the amplifier housing 40 suitably closed. Behind the booster piston at rest 41 is a hydraulic connection 43 provided, which is a control line 50 picks up and into a room behind the amplifier piston 41 lying room 47 empties. On the side of the push rod 42 is a vent hole 44 (or for ventilation) provided. The travel of the intensifier piston 41 corresponds to the added stroke of both circles (swim circle SF and push rod circle DK) of the THZ 11 , On the back of the amplifier 7 (Closure side) is an opening 45 provided by the push rod 46 the brake pedal 26 in the amplifier 7 penetrates. By this construction is an emergency operation of the THZ 11 possible if the amplifier 7 should fail. This emergency operation corresponds to the emergency operation of a vacuum brake booster.

A_Verstärker:

Fläche des Verstärkerkolbens

A_THZ:

Fläche des THZ-Kolbens

P_HDS:

Druck des Hochdruckspeichers

P_{THZ,verstärkt}:

THZ-Druck der mit der Verstärkung erreicht werden kann

The area ratio of booster piston 41 and THZ area, in conjunction with the pressure provided by a high pressure source, gives the THZ pressure to be achieved with gain. (A _amplifier / A _THZ ) · p HDS = P _{THZ, amplified} With:

A _amplifier :

Surface of the intensifier piston

A _THZ :

Area of the THZ piston

P _HDS :

Pressure of the high-pressure accumulator

P _{THZ, reinforced} :

THZ pressure which can be achieved with the reinforcement

It is therefore intended to vary the pressure requested by a control or regulation by the area ratios or the pressure of the high-pressure accumulator.

As a high pressure source, a hydraulic high-pressure accumulator is used, which is supplied by a hydraulic pump with pressurized brake fluid, that is "charged". For example, a high-pressure gas storage with a volume of 200 to 300 cm ³ and a gas filling pressure of about 10 to 15 bar at 20 ° C is used. The memory is loaded after braking to Example when reaching a hydraulic pressure in the memory of less than 40 to 50 bar, which corresponds to a brake pressure (control pressure) of 80 to 90 bar. Until reaching an upper limit for the hydraulic pressure in the reservoir of 50 to 70 bar, corresponding to a control pressure of 100 to 110 bar, a charging time by the pump of about 2 to 3.5 sec. Is required. Is repeated by repeated braking, z. B. a number of about 15 braking, the hydraulic accumulator completely emptied, then the pump takes about 30 to 40 sec. To refill the hydraulic accumulator up to a hydraulic pressure of 50 to 70 bar. By this design, a sufficient supply of the hydraulic brake booster and thus support the driver's foot force can be ensured by auxiliary power.

On to the operating unit 11 connected brake circuit (from a total of two brake circuits), on two wheel brakes 30 . 31 is acting in 1 shown. The second brake circuit for the other two wheel brakes is identical in construction and function with the brake circuit shown and therefore need not be described in detail.

The brake circuits are according to 2 from a master cylinder (THZ) 11 acted upon by a hydraulic reservoir of a container 13 supplied with hydraulic fluid. The master cylinder 11 is via the hydraulic brake booster described above 7 actuated. That of the respective control or regulation of an electronic unit 28 requested pressure is via the hydraulic booster 7 and the master cylinder 11 generated.

By an actuating element (push rod, 46 ), the driver can but in the event of a failure or a failure of the hydraulic pressure on the piston 41 , this also directly, ie by mechanical means, operate. Thus, the system ensures a fail-safe function by means of direct hydraulic-mechanical penetration.

The wheel brakes 30 . 31 are powered by normally open (SO) valves 15.1 and 15.2 directly from the THZ 11 over a line 14 , an SO separating valve 9 and subsequent wires 14.1 and 14.2 pressurized, the THZ 11 over the hydraulic amplifier 7 is actuated by a pressure source 4 . 19 . 20 can be acted upon by hydraulic pressure.

Degradation of brake pressure is via a return line 17 and normally closed (SG) valves 16.1 and 16.2 , a low pressure accumulator 18 and a SG switching valve 8th performed.

In general, the charge of a high-pressure accumulator 4 by opening a valve 2 completed. In this case, when the pressure in the high pressure accumulator falls below a predetermined setpoint, in particular below 50 bar to 70 bar, brake fluid from the THZ 11 over the open change-over valve 8th and by means of the engine 20 operated pump 19 sucked. About one on the pressure side 21 the pump 19 subsequent check valve 23 , a damping chamber 57 , via a branch line 22 and a line 24 into which the valve 2 and a pressure sensor 3 are inserted, the brake fluid is in the high-pressure accumulator 4 pumped. The motor 20 is thereby controlled until a predetermined target pressure is reached. The pressure is controlled by a pressure sensor (pressure sensor 3 ). When filling the high-pressure accumulator 4 (Memory Store) is the one in a line 50 between high-pressure accumulator 4 and amplifiers 7 arranged valve 5 closed. The pressure side of the pump is also over the branch 22 and a subsequent line 25 into which a valve 1 is inserted, with the wheel brakes 30 . 31 connected. Preferably, the valve 1 normally closed (SG valve) and the valve 2 normally open (SO valve). Then these valves are not energized during storage charging, which then advantageously only the switching valve 8th must be energized for filling. It is also possible to use the valve 1 as SO valve and the valve 2 form as SG valve, in which case the switching states are to be reversed accordingly.

At high control frequencies with low volume requirement in the wheel brake, the whole or parts of the volume removed for loading the high-pressure accumulator 4 be used.

When a braking by the driver is detected, the charging process of the high-pressure accumulator 4 immediately canceled. Charging operations in acceleration phases are preferably carried out without regulation). The Einbremserkennung via a pedal travel sensor 60 or another, the driver's braking request detecting sensor.

Is a braking request by the sensors 60 detected, which is preferably analog valve to be operated 5 depending on travel of the push rod 46 the brake pedal 24 and / or the actuation speed correspondingly open, so that brake fluid from the charged high-pressure accumulator 4 in the room behind the amplifier piston 47 can flow. The construction of the pressure in the amplifier 7 This is about the pressure in the THZ with a pressure sensor 10 supervised. That is, a particular path is assigned and adjusted to a particular pressure in the THZ. The booster piston moves 41 in front of the pressure rod, which is increasingly penetrating into the booster chamber 46 the brake pedal 26 without a contact arises or must arise. Preferably, it is provided between the push rod 46 and the intensifier piston 41 to provide an elastic means, in particular a spring, in order to achieve a resilient coupling.

If the driver takes the brake pedal back, d. h is the way smaller again, the valve becomes 5 closed and a likewise preferably analog operated valve 6 in a pipe 12 between the high-pressure accumulator 4 and the container 13 , according to the withdrawal of the driver's request opened analogously and the brake fluid can be returned to the reservoir 13 flow back. By preferably design of the valve 6 As SO valve, it is possible to operate the amplifier in case of system failure, without negative pressure in the amplifier 4 (or in the booster room 47 ), because there is a volume compensation via the valve 6 , The driver must overcome in this Einbremserkennung only the additional force, by the already in the amplifier 7 set pressure is generated. This additional force is only dependent on the surface of the push rod 46 in the amplifier 7 penetrates.

The inventive combination of the hydraulic amplifier and the auxiliary pressure source with high-pressure accumulator 4 can be designed so that the entire required brake pressure is generated by the amplifier. However, this increases the required storage pressure in the high-pressure accumulator 4 ,

Another embodiment provides only a reduced maximum brake pressure of the booster (control pressure) to provide (similar to a vacuum brake booster). This then already covers a large range of all braking, z. B. all "normal brakes" in a range of up to 60 to 80 bar resulting brake pressure from. The brakes, which are a region above this control point brake pressure (about 60-80 bar) required area are then by additional pressure build-up by means of the hydraulic pump 19 built up. This can cause a "pulling away" of the THZ piston. Then it will be over the line 50 and valve 5 Pressure medium in the booster room 47 headed and so the piston 41 tracked. By this embodiment is preferred, since so the space is further reduced. Another advantage is the fact that then only relatively small volume flows are to be moved to brake fluid, whereby the system dynamics is increased. This also reduces the loading times of the high-pressure accumulator 4 , Due to the additional hydraulic support by pump 19 can the volume of high-pressure accumulator 4 be designed for a lower repetition frequency of braking. This means that the number of possible stunts without intermediate charging of the high-pressure accumulator can be reduced to z. B. 2 times 60 bar to 90 bar, preferably about 80 bar, THZ pressure. In the rare cases of a pressure request beyond this can then by means of a pump 19 a corresponding brake pressure can be generated.

The system described is advantageously suitable for electronic brake control systems, such as ABS (Antilock Braking System), EDS (Electronic Differential Lock, Traction Control), ESP (Electronic Stability Program), or HDC (Hill Descent Control, Downhill Control). In addition, an application for systems with a distance and sequence control (ACC, Adaptive Cruise Control) is possible because of an automatic pressure equalization of the circles through the THZ.

Claims (7)

Hydraulic vehicle brake system, with a brake pressure generator which can be actuated by a brake actuation device and which is connected via a hydraulic line ( 14 ) with wheel brakes ( 30 . 31 ) of the vehicle is connectable, wherein the brake pressure generator from a master cylinder ( 11 ) and an upstream hydraulic amplifier ( 7 ) provided with a pressure medium reservoir ( 13 ) is connected via a line ( 12 ), in which a first analog or analog valve ( 6 ) is arranged and one coaxial with the master cylinder ( 11 ) arranged reinforcing chamber ( 47 ) and a booster piston ( 41 ), in the power delivery direction via an actuating element ( 42 ) with a master brake cylinder piston ( 51 ) is operatively connected and for the purpose of brake booster with a hydraulic pressure of an external pressure source ( 4 . 19 . 20 ), which is a motor-pump unit ( 19 . 20 ) and a high-pressure hydraulic accumulator ( 4 ) and with the hydraulic booster ( 7 ) is connected via a line ( 50 ), in which a second analog or analog valve ( 5 ), characterized in that the wheel brakes ( 30 . 31 ) of the vehicle with the master cylinder ( 11 ) are connected via a return line ( 17 ) into which exhaust valves ( 16.1 . 16.2 ), a low pressure accumulator ( 18 ) and a switching valve ( 8th ) are arranged, and that the motor-pump unit ( 19 . 20 ) also serves as a return pump. Hydraulic vehicle brake system according to claim 1, characterized in that the master cylinder ( 11 ) zweikreisig and the pressure fluid reservoir ( 13 ) is formed without pressure. Hydraulic vehicle brake system according to one of claims 1 to 2, characterized in that an electronic control and Control unit ( 28 ) by means of which the analog or analogue valves ( 5 . 6 ) are controlled or controlled, for the purpose of loading the booster piston ( 41 ) of the hydraulic amplifier ( 7 ) with a certain hydraulic pressure. Hydraulic vehicle brake system according to one of claims 1 to 3, characterized in that the master cylinder ( 11 ) with the wheel brakes ( 30 . 31 ) of the vehicle is connected via a brake line ( 14 ) into which a separating valve ( 9 ) and via subsequent brake pipe parts ( 14.1 . 14.2 ), in each of which an inlet valve ( 15.1 . 15.2 ) is arranged. Hydraulic vehicle brake system according to one of claims 1 to 4, characterized in that the pump ( 19 ) on the input side with the return line ( 17 ) and on the output side via a branching point ( 22 ) with the wheel brakes ( 30 . 31 ) of the vehicle or with the high-pressure accumulator ( 4 ) is connectable and that between the pressure side ( 21 ) of the pump ( 19 ) and the branching point ( 22 ) a check valve ( 23 ) and a damper chamber ( 57 ) are arranged. Hydraulic vehicle brake system according to claim 5, characterized in that from the branching point ( 22 ) the pump ( 19 ) with the high-pressure accumulator ( 4 ) via a line ( 24 ), into which a controllable valve ( 2 ) and that from the branching point ( 22 ) the pump ( 19 ) with the brake pipe parts ( 14.1 . 14.2 ) is connected via a line ( 25 ) into which a controllable valve ( 1 ) is arranged. Hydraulic vehicle brake system according to claim 6, characterized in that by means of an electronic control unit ( 28 ) the controllable valves ( 1 . 2 ) are controlled or controlled for the purpose of brake pressure regulation or establishment of a hydraulic pressure in the high-pressure accumulator ( 4 ).

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