DE10236360A1 - Electrohydraulic brake system for road vehicle has hydraulic auxiliary pressure source and brake function regulating and monitoring system - Google Patents

Abstract

The brake circuit has a sensor (25) for measuring pressure in the outer chamber of a high-pressure reservoir. There is a valve in the bottom of the reservoir and inlet valves (17,18,37,38), with pressure sensors (30,40). There are also pressure equalizing valves (13,19). There are pressure release valves (27,28,47,48) controlling wheel blocking during braking by releasing individual wheel brakes (7-10).

Description

The invention relates to a electro-hydraulic brake system for a motor vehicle with a hydraulic auxiliary pressure source, via an electronic one Control unit controllable valve system connected to wheel brakes is, the auxiliary pressure source with a pump and with a Bottom valve and a high-pressure storage chamber is provided, the bottom valve closes when the high pressure accumulator is almost empty, leaving a residual pressure remains in the receiving chamber, and a device for checking the Functionality of the Has bottom valve, and wherein also the auxiliary pressure source via a or more normally closed inlet valves of the valve system is connected to wheel brakes or groups of wheel brakes and means are provided which are in contact with the inlet valves Record form.

Such braking systems are already in Variety has been described.

A high pressure accumulator that is used comes in such a braking system, z. B. in WO 00/31420 shown and explained. It is a metal bellows accumulator with a Metal bellows as a media separating element between the receiving chamber and a gas-filled pressure chamber. With such a store, it is absolutely necessary that the receiving chamber does not become depressurized, otherwise the gas pressure will depress the metal bellows radially loaded and this because of the lack of back pressure in the Receiving chamber damaged.

Such a situation is caused by the bottom valve prevents; it is namely from a partition plate of the metal bellows are closed when they are emptied of the memory to the closing member of the Bottom valve creates and brings it into its closed position, with a Residual pressure remains in the receiving chamber. The bottom valve will first belched again, when new pressure medium is pumped into the receiving chamber.

So that the remaining pressure is actually in The bottom valve must be maintained in the receiving chamber be absolutely tight. If this is not the case, the Auxiliary pressure source can be switched off.

To check the functionality the high-pressure accumulator sees a displacement sensor of the bottom valve according to WO 00/31420 to determine the displacement path of the media separating element, with which the degree of filling is immediate of the high pressure accumulator is measured. This drops, although the bottom valve is closed, this is considered a defect in the bottom valve. Such a sensor with parts movable against one another is relative susceptible to interference.

It also has the braking system a pressure sensor that measures the pressure upstream of the intake valves. This information is necessary because the height of the form in comparison to the pressure currently prevailing in the wheel brakes the speed of pressure build-up in the wheel brakes determined when the intake valve open becomes. This must be done when calculating the opening times for the intake valves considered become.

Generally one tries hard to Number of components in the brake system and thus also the number of them Sensors if possible keep small to avoid potential sources of error.

The invention is therefore based on the Problem, a braking system with as much as possible to create few sensors that both function properly the high pressure accumulator can be tested as well as information to the form available at the inlet valves.

To solve the problem she sees Invention for a brake system according to the preamble of claim 1 that a storage pressure sensor directly with the receiving chamber is connected, the electronic Control unit via comparison means features, around the value determined by the accumulator pressure sensor with a limit value to compare, which is below the residual pressure at which the Bottom valve closes, falling below the limit value as an indication of a defect in the Bottom valve is evaluated, and that of the accumulator pressure sensor pressure value supplied by the electronic control unit at least is then considered as a pre-pressure when the bottom valve is open.

This arrangement comes as before said, typically for use in a brake system with a High-pressure accumulator in which the media separating element is a bellows with one opposite the bottom valve Partition plate is, this to rest on the closing element of the bottom valve reaches when the high pressure accumulator is almost empty is.

Because the accumulator pressure sensor immediately the pressure in the receiving chamber can be detected with the help of the storage pressure sensor also the level be determined. This is done with the help of the specific for the high pressure accumulator Relationship between the volume of the receiving chamber and that there prevailing pressure on the degree of filling of the high pressure accumulator closed.

For The supervision the functionality of the Bottom valve can be the condition that the bottom valve is closed is brought about in a targeted manner become. This condition occurs during normal operation of the brake system but inevitably on. If such a condition exists, it is only necessary to ensure that the high-pressure accumulator for some Time is not refilled. The course of the residual pressure can be determined during this time. If it drops, this indicates a defect in the bottom valve.

The bottom valve is actuated at a certain minimum level, with which a certain residual pressure is linked. Because the context between the pressure in the receiving chamber and the level temperature-dependent is the residual pressure at which the bottom valve closes. To ensure, that the review at a closed bottom valve, the pressure at which the review is done temperature-dependent set. This also applies to the limit value, which is below is regarded as an indication of a defect in the bottom valve.

The invention also relates to a method of monitoring the functionality of a electrohydraulic brake system with a high pressure accumulator, in which the functionality of the Bottom valve of the high pressure accumulator is monitored. The high pressure accumulator consists of a housing, that into a pressure chamber and one of these through a media separation element separate receiving chamber is divided, the pressure chamber with a pressurized gas is filled and the receiving chamber with a liquid pressure medium over a hydraulic connection can be filled is in which a bottom valve is used, the closing body through the media separating element can be actuated is so a complete Emptying the receiving chamber is prevented and that in the receiving chamber remaining pressure medium remains under a residual pressure.

So far, a displacement sensor was used which detects the displacement of the media separating element. Such sensors are complicated and prone to failure.

To make the process more secure, The invention provides that the residual pressure in the receiving chamber with a closed bottom valve by means of a storage pressure sensor is detected and falling below a limit that is below the Residual pressure is at which the Bo closes the valve as Defect of the bottom valve is assessed.

The invention also relates to a method for controlling an electro-hydraulic brake system for a Motor vehicle with a hydraulic auxiliary pressure source, which has a valve system controllable by an electronic control unit Wheel brakes is connected, the auxiliary pressure source being connected to a pump and with a bottom valve and a receiving chamber High-pressure accumulator is provided, the bottom valve in any case then closes when the high pressure accumulator is almost empty, leaving a residual pressure remains in the receiving chamber, the auxiliary pressure source also via a or more normally closed inlet valves of the valve system is connected to wheel brakes or groups of wheel brakes and means are provided which are in contact with the inlet valves Record the admission pressure, the respective inlet valve for pressurization of the wheel brakes according to one Control algorithm opened which takes into account the admission pressure applied to the inlet valve.

To the number of sensors in the brake system if possible To keep it low, the invention provides that the control algorithm the pressure value measured by the accumulator pressure sensor on the high-pressure accumulator uses and evaluates as a form.

Instead of a separate, immediate A storage pressure sensor is arranged in front of the inlet valves at the receiving chamber of the high-pressure accumulator uses the signals also for monitoring of the high pressure accumulator can be used.

In addition, the storage pressure sensor on High-pressure accumulator also for determining the degree of filling of the high-pressure accumulator be used. This is achieved in that the electronic Control unit via data describing the high-pressure accumulator and is therefore able to from the pressure value supplied by the storage pressure sensor the degree of filling of the Determine high pressure storage.

The following is based on an exemplary embodiment the invention closer explained become. To show:

l a hydraulic circuit diagram of an electro-hydraulic brake system and

2 a section through a typical high pressure accumulator, which in a brake system according l is used.

In the 1 The electro-hydraulic brake system shown has one by means of an actuation pedal 1 actuatable two-circuit master cylinder or tandem master cylinder 2 on that with a pedal travel simulator 3 cooperates and in which two separate pressure chambers are formed, which have a pressureless pressure medium reservoir 4 stay in contact. At the first pressure chamber (primary pressure chamber) are by means of a lockable first hydraulic line 5 for example, wheel brakes assigned to the rear axle 9 . 10 connected. Shutting off the line 5 takes place by means of a first isolating valve 11 while in between the wheel brakes 9 . 10 switched line section 12 an electromagnetically actuated, preferably normally open (SO) pressure compensation valve 13 is inserted, which enables wheel-specific brake pressure control if required.

The second pressure chamber of the master brake cylinder 2 to which a pressure sensor 15 can be connected via a second isolating valve 14 lockable second hydraulic line 6 with the other pair of wheel brakes assigned to the front axle 7 . 8th connectable. In one between the wheel brakes 7 . 8th switched line section 16 is again an electromagnetically actuated, preferably normally open (SO) pressure compensation valve 19 inserted.

As can be seen from the drawing, there is a motor-pump unit serving as an auxiliary pressure source 20 with a high pressure accumulator 21 provided, which in turn consists of an electric motor 22 driven pump 23 as well as one of the pump 23 pressure relief valve connected in parallel 24 consists. The high-pressure accumulator described in more detail below 21 is with a 5 store pressure sensor 25 provided, which is connected to the receiving chamber receiving the pressure medium and thus directly measures the storage pressure.

A third hydraulic line 26 connects the high pressure accumulator 21 with the input connections of two electromagnetically controlled, normally closed proportional valves 17 . 18 that act as intake valves to the wheel brakes 7 and 8th are connected upstream, as well as with the input connections of two further electromagnetically controlled, normally closed proportional valves 37 . 38 that act as intake valves to the wheel brakes 10 and 9 are upstream. In addition, the wheel brakes 7 . 8th Via an electromagnetically controlled, normally closed proportional valve or exhaust valve 27 . 28 and the wheel brakes 9 . 10 Via an electromagnetically controlled, normally closed proportional valve or exhaust valve 47 . 48 to a fourth hydraulic line 29 connected, on the other hand with the unpressurized pressure medium reservoir 4 communicates. The one in the wheel brakes 7 . 8th prevailing hydraulic pressure is with the help of a pressure sensor 30 . 31 determined while in the wheel brakes 10 . 9 prevailing hydraulic pressure with the help of one pressure sensor each 40 . 41 is recorded.

The common control of the motor-pump unit 20 and the solenoid valves 11 . 13 . 14 . 17 . 18 . 19 . 27 . 28 serves an electronic control unit 32 , which as input signals the output signals of one with the operating pedal 1 interacting actuation travel sensor 33 and the aforementioned pressure sensor 15 are supplied, both of which enable driver deceleration request recognition. However, other means, for example the actuating force on the actuating pedal, can also be used to identify the driver's deceleration request 1 sensing force sensor can be used. The electronic control unit 32 the output signals of the pressure sensors 30 . 31 . 40 . 41 and the output signals corresponding to the speed of the vehicle are supplied by wheel sensors, which are only indicated schematically, the wheel brakes 10 . 9 assigned wheel sensors with the reference numerals 34 . 35 are provided.

In normal operation or in the "Brake-by-wire" operating mode, the in 1 Brake system shown as follows: When the driver steps on the brake pedal, he feels a path-dependent counterforce, which is predetermined by the defined characteristics of the pedal simulator. When sensing a braking request using the actuation travel sensor 33 and / or the pressure sensor 15 become the isolation valves 11 . 14 closed and the wheel brakes 7 to 10 from the master brake cylinder 2 Cut. This builds up in the master brake cylinder 2 a pressure on that from the operating force on the operating pedal 1 results. From the signals of the actuation travel sensor 33 and / or the pressure sensor 15 the driver's braking request is calculated, for example, as a target deceleration or as a target braking force. The individual target wheel brake pressures are formed from this braking request. Depending on the driving condition and slip condition, these pressures are modified and via the pressure control valves 17 . 18 . 37 . 38 , such as 27 . 28 . 47 . 48 adjusted by their control. In a closed control loop with each wheel brake 7 - 10 the current pressures at the wheel pressure sensors are used for the target-actual comparison. If there are different target pressures in the left and right wheels of a vehicle axle, the pressure compensation valves 13 . 19 closed and in each wheel brake the predetermined target pressure is adjusted to the target brake pressure by controlling the intake and exhaust valves in the sense of regulating the actual brake pressure. For pressure build-up on a wheel brake using the auxiliary pressure source mentioned above 20 the inlet valve is energized until the desired pressure in the wheel brake develops with the desired dynamics. Pressurized fluid flows from the auxiliary pressure source 20 and primarily from the high-pressure accumulator 21 to the wheel brakes. A pressure reduction is achieved accordingly by energizing the outlet valve, the pressure medium via the return line 29 in the pressure medium reservoir 4 flowing back. A control of the pump 23 takes place when the storage pressure in the high-pressure accumulator drops 21 below a predetermined value.

The in 2 high-pressure accumulator shown in detail 21 has a housing 51 on whose interior by means of a media separating element 52 in two pressure rooms or chambers 53 . 54 is divided. The media separator 52 is preferably formed by a thin-walled metallic bellows, which is pressure-tight with the housing 51 closing lid 65 is connected and on the other hand by means of a plate 66 is closed. The interior of the bellows 52 forms the pressure chamber 53 that have one in the lid 65 provided filling connection, not shown, can be filled with a gas which is generally under high pressure. In the lower part of the housing 51 is a hydraulic connection 55 trained in which a bottom valve 56 is arranged, the closing body 57 into the reception chamber 54 protrudes. The bottom valve 56 is preferably designed such that on the one hand the receptacle was filled mer 54 with a pressurized liquid pressure medium, for example a brake fluid, and on the other hand a complete emptying of the receiving chamber 54 prevented. It is also located in the pressure chamber 53 a compression spring 67 between the lid 65 and the plate mentioned earlier 66 is clamped and thus the bellows 52 towards the bottom valve 56 biases. This ensures that the in the receiving chamber 54 prevailing hydraulic pressure is always higher than that in the pressure chamber 53 prevailing gas pressure. To finally center the bellows 52 in the housing 51 to reach is a slotted ring 68 provided the bellows 52 encompasses and in the assembled state on the wall of the housing 51 is applied.

Again 2 can also be seen, the hydraulic connection provided with an inlet or outlet opening 55 a bore, which is designed as a stepped bore and a first section 61 larger diameter and a second section 62 has a smaller diameter. The transition area between the two sections 61 . 62 is preferably formed by a conical ring surface. In the hole sections 61 . 62 becomes the aforementioned closing body 57 guided, with the guide in the first bore section 61 a collar with at least one opening 69 is provided while guiding in the second bore section 62 a second fret 71 serves the multiple radial flow channels 72 having. The flow channels 72 together with the aforementioned passage form a flow connection between the receiving chamber 54 and the filling or

Outlet opening of the hydraulic connection 55 , An end face of the second collar facing away from the filling or outlet opening 71 forms a flank of a radial groove that forms a sealing element 58 takes up, which is formed in the example shown by a sealing sleeve. With the bottom valve open 56 is the first fret 69 under tension of a compression spring 64 at a stop 74 on.

Closing the bottom valve 56 takes place in two phases. Just before the receiving chamber is emptied 54 starts the bellows 52 sealing plate 66 the preferably hemispherical end of the closing body 57 to touch. If the pressure medium continues to escape, the closing body 57 contrary to that of the compression spring 64 applied force adjusted or pressed down in the drawing until the outer sealing lip of the sealing sleeve 58 comes into contact with the conical ring surface and thus the flow around the closing body 57 prevented. At this moment the closing body catches 57 to perform the function of a hydraulic piston and is by the in the receiving chamber 54 prevailing residual pressure adjusted further down. This will make the sealing element 58 in the bore section 62 larger diameter until the closing body 57 has reached its lower stop and above it with any greater force on the housing 51 supports, the sealing element 58 the function of a to the admission chamber 54 check valve opening.

The bottom valve is opened 56 characterized in that liquid pressure medium from the outside in the high pressure according to the invention 21 is pumped. when the boost pressure is in the receiving chamber 54 prevailing residual pressure or internal pressure, the outer sealing lip of the sealing sleeve folds 58 around and leaves over from the wall of the bore section 62 Limited sealing gap flow pressure medium, the compression spring 64 at the same time the closing body 57 pushes back. This will loosen the sealing collar 58 or their outer sealing lip from the bore wall and clears the way for the inflowing pressure medium. As with closing, the contour of the sealing collar changes 58 receiving annulus only when on the sealing collar 58 applied pressure difference is small. The closing body 57 through the compression spring 64 pressed further up until it is again on the bellows 52 sealing plate 66 is applied. When filling the receiving chamber further 54 gives way to the plate 66 back and the path of the closing body 57 again from the top stop 74 limited.

In the side wall of the case 51 there is a connection for the 1 mentioned storage pressure sensor 25 , with which the pressure in the receiving chamber immediately 54 can be measured. The accumulator pressure sensor 25 is connected to the electronic control unit via a signal line, not shown here 32 in connection.

The accumulator pressure sensor 25 can now be used in various procedures for regulating and monitoring the brake system:

Determination of the form

As long as the bottom valve 56 is open, the pressure in the receiving chamber is correct 54 of the high pressure accumulator 21 with the pressure immediately before the intake valves 17 . 18 . 37 . 38 match. The electronic control unit 32 can therefore be from the storage pressure sensor 25 equal the measured pressure directly to the admission pressure and when regulating the wheel brake pressure in the connected wheel brakes 7 . 8th . 9 . 10 consider. This is possible at least as long as the admission pressure is above the possibly temperature-compensated residual pressure at which the bottom valve closes.

Level measurement:

As long as the bottom valve 56 is open, which means that the pressure of the pressure medium in the on receiving chamber 54 If there is a temperature-corrected residual pressure, that of the accumulator pressure sensor 25 measured value with the fill level of the high pressure accumulator 21 be correlated because of the bellows 52 the more compressed the higher the pressure in the receiving chamber 54 is. Since this relationship is temperature-dependent, a temperature-dependent correction may also have to be carried out here.

Functional check of the Bottom valve:

With a closed bottom valve, which means that of the accumulator pressure sensor 25 measured pressure is below the possibly corrected residual pressure, the pressure curve in the receiving chamber 54 tracked.

Should the pressure despite the closed bottom valve 56 Falling below a limit can result in a leak in the bottom valve 56 are closed and the braking system is at least partially switched off. This eliminates the need to regulate the pressure in the wheel brakes 7 . 8th . 9 . 10 , which are now directly from the pedal-operated tandem master cylinder 2 be operated.

Claims (7)

Electrohydraulic brake system for a motor vehicle with a hydraulic auxiliary pressure source, which is connected to wheel brakes via a valve system that can be controlled by an electronic control unit, the auxiliary pressure source being provided with a pump and with a high-pressure accumulator having a bottom valve and a receiving chamber, the bottom valve then in any case closing, when the high-pressure accumulator is almost empty so that a residual pressure remains in the receiving chamber and has a device for checking the functionality of the bottom valve, and the auxiliary pressure source is also connected to wheel brakes or groups of wheel brakes via one or more normally closed inlet valves of the valve system and Means are provided that detect the admission pressure applied to the inlet valves, characterized in that a storage pressure sensor ( 25 ) directly with the receiving chamber ( 54 ) is connected, the electronic control unit ( 32 ) has comparison means to compare the pressure from the accumulator pressure sensor ( 25 ) Compare the determined value with a limit value that is below the residual pressure at which the bottom valve ( 56 ) closes, falling below the limit value as an indication of a defect in the bottom valve ( 56 ) is evaluated, and that that of the accumulator pressure sensor ( 25 ) delivered pressure value from the electronic control unit ( 32 ) is considered at least as a pre-pressure if the bottom valve ( 56 ) is open. Brake system according to claim 1, characterized in that the electronic control unit ( 32 ) via the high pressure accumulator ( 21 ) has descriptive data and is therefore able to use the storage pressure sensor ( 25 ) delivered pressure value the filling level of the high pressure accumulator ( 21 ) to determine. Brake system according to claim 1 or 2, characterized in that the media separating element is a bellows ( 52 ) with a bottom valve ( 56 ) opposite partition plate ( 66 ), so that it is in contact with the closing element ( 57 ) of the bottom valve ( 56 ) arrives when the high pressure accumulator ( 21 ) is almost empty. Brake system according to claim 1, characterized in that the limit is temperature dependent is. Method for monitoring the functionality of an electrohydraulic brake system with a high-pressure accumulator, in which the operability of the bottom valve of the high-pressure accumulator is monitored, the high-pressure accumulator consisting of a housing which is divided into a pressure chamber and a receiving chamber separated from it by a media separating element, the pressure chamber is filled with a pressurized gas and the receiving chamber can be filled with a liquid pressure medium via a hydraulic connection, in which a bottom valve is inserted, the closing body of which can be actuated by the media separating element, so that complete emptying of the receiving chamber is prevented and that in the Receiving chamber remaining pressure medium remains under a residual pressure, characterized in that the residual pressure in the receiving chamber ( 54 ) with a closed bottom valve ( 56 ) by means of a storage pressure sensor ( 25 ) is detected and if the limit value falls below the residual pressure at which the bottom valve ( 56 ) closes as a defect in the bottom valve ( 56 ) is evaluated. Method for regulating an electro-hydraulic brake system for a motor vehicle with a hydraulic auxiliary pressure source which is connected to wheel brakes via a valve system which can be controlled by an electronic control unit, the auxiliary pressure source being provided with a pump and a high-pressure accumulator having a bottom valve and a receiving chamber, the bottom valve in any case then closes when the high-pressure accumulator is almost empty, so that a residual pressure remains in the receiving chamber, the auxiliary pressure source also being connected to wheel brakes or groups of wheel brakes via one or more normally closed inlet valves of the valve system, and means being provided that Detect the admission pressure applied to the intake valves, the respective intake valve for pressurizing the wheel brakes being opened according to a control algorithm in which the admission pressure applied to the intake valve is taken into account, characterized in that the control algorithm detects the pressure from the accumulator pressure sensor ( 25 ) on the high pressure accumulator ( 21 ) uses the measured pressure value and evaluates it as a pre-pressure. A method according to claim 5 or 6, characterized in that the storage pressure sensor ( 25 ) the pressure in the receiving chamber ( 54 ) even when the bottom valve is open ( 56 ) recorded and from the measured value with the help of the for the high pressure accumulator ( 21 ) specific relationship between the volume of the receiving chamber ( 54 ) and the pressure there on the degree of filling of the high-pressure accumulator ( 21 ) is closed.