DE2430448A1 - Electro-mechanical control for car brakes - with brake pedal operation controlling braking via retardation sensor for reproducible effect - Google Patents

Abstract

The brake pedal is fitted with a monitor to measure the pedal deflection and provide an output signal. An inertial mass in the braking control produces a retardation signal and the two signals are compared by a simple electronic control. The system is designed to produce a set retardation for a set brake pedal travel, irrespective of brake pad wear etc. It provides the driver with a maximum of control. The system can be fitted with a brake modulation control to act as an anti-skid braking facility.

Description

Vehicle brake system The invention relates to a vehicle brake system for wG'fl: at least one vehicle wheel with a brake actuation device which is a first electrical signal that is dependent on the degree of brake actuation generated, in which a brake pressure source is provided in the connection A valve arrangement is switched on between the brake pressure source and the wheel brake, which temporarily establishes the connection between the brake pressure source and the wheel brake cylinder and for the purpose of reducing the pressure on the wheel brake cylinder, this temporarily has an outlet connects.

State of the art The vehicle brakes commonly used today - this applies to brake systems with pedal operated master brake cylinder or brake booster and for so-called h1 l-power systems "control brake pressure on the wheel brakes one that depends solely on the degree of brake actuation, with changes in the brake system, such as brake pad wear or changes the elongation properties of the brake lines, loading of the vehicle, coefficient of friction in the brake, etc., cause a change in the ratio of brake actuation to brake pressure.

There are. also known as electric brake systems, which are used in Depending on the brake actuation on the wheel brake, a certain brake pressure adjust (OS 2 128 169). This requires a device that measures the brake pressure, its signal compared with the signal generated by the Breritsbetäteinrichtiing is, the signal generated by the comparison effects the pressure regulation.

Task and solution The invention is based on the task to design this vehicle brake system so that a certain amount of brake actuation corresponds to a certain vehicle deceleration.

This object is achieved by the features specified in claim 1. The brake system according to the invention can be designed hyeraulically or pneumatically.

The brake system according to the invention accordingly has the advantage of aass it controls a brake pressure that is required by the degree of brake actuation Vehicle deceleration. Depending on the coefficient of friction in the brake, the Achieving this vehicle deceleration controlled different pressures. The those Vehicle deceleration determining device can be in any known manner be designed, e.g. be a device in which, depending on the Delay moves a mass that changes a resistance or by approaching it a magnet influences a magnetic field-sensitive member or via one of the Mass operated pulse wheel direct digital signals generated. That The generated signal can be an analog signal or a digital signal and also the comparison can be done analog or digital. Because such decelerators also depend on the inclination of the vehicle are dependent, the vehicle deceleration sensor is designed so that his position or

its initial value v'FO is determined at the start of braking.

The change in the vehicle deceleration value from this value v FO is then compared with the signal dependent on the pedal actuation and thus used for pressure control. A signal is used for regulation that corresponds to the difference between the instantaneous value and the output value FO.

Advantageous further developments In order to prevent the failure of the Brake pressure source, which has a pump - possibly with a connected storage chamber - may be, a breakdown of the brake system occurs, is according to a further development the invention with the brake actuating device connected to a piston in a Cylinder is movable, which is in communication with the wheel brake cylinder. This When the brake actuation device is actuated, the piston becomes over a certain amount moved out and then provides an emergency brake pressure generator together with the cylinder The connection between the brake pressure source and the wheel brake cylinder is preferably used here interrupted.

When the cylinder chamber is switched on accordingly in the line between the brake pressure source and the wheel brake cylinder is determined solely by the displacement of the piston achieves that a closed system between the emergency pressure generator and the wheel brake is effective, so that a fixed volume between 'these elements is included. However, according to a development of the invention, in particular if the emergency pressure generator is connected in the shunt, also a separate one provide further valve device between the first valve device and the wheel brake cylinder is switched on, due to a piston displacement, in particular is operated via a mechanical connection. The actuation of the valve can according to another possibility; ç when the brake pressure drops under a predetermined value can be made, including the valve is preferably designed as a pressure-controlled valve.

The valve device causing the pressure control can also be used the further valve device can be combined.

The brake actuation device is preferably designed so that as the pedal travel increases, the force counteracting the brake actuation is disproportionately high, e.g. increases in a square or parabolic manner. Furthermore, the system can be designed in such a way that that the rate of pressure increase depends on the pedal speed and that such that as the pedal speed increases, so does the rate of pressure increase increases. This can be achieved in a simple manner by using pulsed Generates signals for the actuation of the valve arrangement and the duty cycle of these pulsed signals changes.

In the same way, the rate of pressure change can be changed as a function of the vehicle speed, the rate of pressure change the lower the higher the vehicle speed. According to a further training According to the invention, there is first a pressure increase with a predetermined time for a predetermined time Speed, which may also be dependent on other variables (pressure), and only then does a fine control of the pressure change set in accordance with the vehicle deceleration a (rate of change = f (v'F) It should also be mentioned that if necessary the vehicle deceleration sensor or its signals to eliminate fast Changes, e.g. due to bumps, must be dampened. If the size changes the brake actuation, this damping is preferably made ineffective.

The combination of the braking system according to the invention is particularly advantageous with an anti-lock controllerf being an arrangement known per se for varying the brake pressure into the connection between the valve assembly and brake cylinder or the emergency thickness generator and the brake cylinder is switched on. This arrangement for brake pressure variation, which is controlled by an electrical control circuit when there is a tendency to lock of a wheel is operated accordingly, a modulator (i.e. an arrangement, which interrupt the connection to the wheel brake cylinder and the volume for the trapped Pressure medium can vary) or a valve arrangement, depending on the switching position a pressure increase and pressure decrease and, if necessary, a pressure constant maintenance evokes. It is of particular advantage if the delay generator is also within of the anti-jock controller, e.g. according to an older suggestion for monitoring the functionality of the anti-lock regulator.

So far, the application of the braking system according to the invention has been carried out treated on a vehicle wheel. It can also be used with multiple bikes, it is possible to have one brake pressure source for all brake circuits of the vehicle to use. However, one of the number of brake circuits is preferably one Number of emergency pressure generators provided, one of which is assigned to a brake circuit is. Here it is beneficial to use the means to interrupt the connection between Brake pressure source and wheel brake cylinder when the piston shifts or when the brake pressure drops to be provided separately for each brake circuit, since then in the event of a fault in the brake system two completely separate brake circuits are effective, so that in the event of a fault in one Circle the other circle remains intact.

As usual, if several wheels are involved, arrangements can be made for Assign brake pressure variation in the event of a tendency to lock to the individual wheels or wheel groups.

The existing measured value of the vehicle deceleration is cheaper brought to the driver's attention by means of a corresponding display device and possibly to the accident; Lllr = nzl.yse possibly in connection with the 3remssusganXsgescheiindigkeit saved.

The invention also relates to an arrangement for the simultaneous Wear, the application of which in particular with the brake system according to the invention from Interest, which can, however, also be used in other braking systems.

DESCRIPTION OF THE FIGURES In FIG. 1 of the drawing is an exemplary embodiment of the invention shown. The electrical lines are thinner in this drawing executed as the hydraulic lines.

Fig. 2 shows a preferred embodiment of the delay generator and Fig. 3 shows an arrangement in the brake system according to the invention a uniform Wear of the brake pads causes.

The pressure generator exists in the exemplary embodiment according to the invention from a motor 1 which drives a pump 2, the pressure medium from the reservoir 3 sucks. The pressure generator also includes a small pressure accumulator 4, which at the same time can also be designed as a pressure gauge. Those in the lines between pressure generators and the wheel brake is switched on and serves to apply pressure to the brakes 5 is designed as a three-stage solenoid valve. It connects in the drawn unexcited Position the wheel brake cylinder 6 a and 7 a of the front wheels 6 and 7 and the wheel brake cylinder 8 a and 9 a of the rear wheels 8 and 9 with the return line leading to the reservoir 3 10 and thus keeps the brakes depressurized. In another switch position, due to a first control signal is caused, a disconnection of the line effected and in a third position caused by a second switching signal the pressure source is connected to the wheel brake cylinder. Behind the valve 5 takes place a separation into two brake circuits, namely one brake circuit for the front wheels 6 and 7 and one for the rear wheels 8 and 9. This division is only effective, when the valves 11 and 12 in the not shown Position switched be what happens in the embodiment when the pressure of the pressure source 1 to 4 drops below a predetermined value, for which purpose the valves 11 and 12 are pressure-sensitive Valves of known design are formed. In the of the valves 11 and 12 to the wheel brake cylinders 6a and 7a or 8a and 9a leading lines are here for the front wheels separate (13, 14) and a common solenoid valve for the rear wheels 15 switched on for pressure variation when there is a tendency to block. These valves are also designed as three-stage valves, the pressure increase in the position shown allow, but can be switched to positions in which the pressure on the wheel brake cylinders either kept constant or by allowing brake fluid to flow out into the Return line 10 is lowered. Instead of the three-stage valves there would also be one Combination of inlet and outlet valve or (without constant pressure maintenance) a three-way valve usable.

Between the valves 11 and 12 and the solenoid valves 13 to 15 is An emergency pressure generator in the form of a cylinder 16 or 17 is provided for each brake circuit. In these cylinders pistons 16a and 17a are arranged, which by springs 18 in the position drawn.

A pedal 19 is provided for brake actuation, when it is actuated a displacement of the part 22 occurs against the force of the spring 20, whereby a signal is generated in the encoder 21, which of the amount of displacement and so that depends on the force applied. For example, the giver can be based on the principle the different influencing of a magnetic field sensitive member, e.g. Magnetic field sensitive semiconductor, work when a magnet approaches. That analog or digital output signal of the encoder is via the member 23, which is the Signal matching can be used, fed to the comparator 25. There is also a delay generator 26 is provided as a pendulum 26a and receiver 26b is indicated. The signal that is dependent on the deflection and thus on the vehicle deceleration is likewise fed via an adaptation element 24 to the comparator 25, which in the case of a larger generated by the signal derived from the encoder 21, a first control signal when they match of the signals generates a second signal and, if the signal from the encoder 21 is smaller, a 0 signal. By means of the AND gate 27 it is achieved that the valve 5 only when the Brake pedal can be excited. The link 28 is coupled to the pedal 19 Counter. illit 29 is the control circuit for valves 13 to 15, the e.g. via the lines 30 rotational speed signals from the wheels 6, 7 and 8/9 attached, not shown speed sensor and over the Lines 31 are fed to the rotation deceleration signals of the front wheels and the out these signals on the lines leading to the valves 13 to 15 32 control signals generated for these valves.

The vehicle speed is shown in the top line on the panel 33 represented digitally, in the middle line the corresponding converted (element 34) Vehicle deceleration and the bottom line indicates a brake system malfunction and / or anti-lock controller displayed.

The system shown works as follows: If the pedal 19 is pressed, gate 27 is prepared by member 28, so that with a larger signal from the encoder 21 output signal generated by the comparison element bring valve 5 into position in which the brake pressure on the wheel brake cylinders increases. Because of the braking a vehicle deceleration comes along, which a corresponding signal from the sender 26 triggers. Does the vehicle deceleration correspond to that caused by the actuation of the pedal 19 required delay, a signal is generated in the comparator 25 that the Brings valve 5 into an intermediate position, iñ the ger pressure is kept constant (Disconnected position). If the pedal pressure is reduced, the output signal becomes of the comparison element 25 is zero and the valve 5 is as long as it is shown in the drawing Switch position until the deceleration of the vehicle corresponds to the required deceleration.

If the pressure drops due to a system fault (leak, pump failure) a predetermined value, the pressure-sensitive double valve 11/12 switches over and thus creates a common two-circuit braking system. The pistons 16a and 17a become by the driver, if the abnormal braking effect does not occur, by further actuation of the pedal 14 moved over the rod 35. This shift occurs when the part 22 has approximately reached the encoder 21, so after covering a predetermined Way.

In both operating modes described, the blocking tendency of the individual wheels actuated by the control circuit 29, the solenoid valves 13 to 15 and thereby the brake pressure at the wheel brake and the coefficient of friction between the tires Adapted to the road. Of this, the pressure control is through the valve 6 or the piston 16a and 17a completely independent.

The valves 11 and 12 can, as by the mechanical connection 34 indicated, can then be switched via this mechanical connection when the rod 35 is moved, so the emergency pistons 16a and 17a are actuated.

In Fig. 2 is again the pendulum 26a, for example a magnet 26c and the receiver 26b is shown, e.g.

has one or two magnetic field sensitive semiconductors.

The receiver 26b generates a message from the relative position of the magnet 26c to the receiver 26b dependent signal. To one by the inclination of the vehicle dependent deflection of the Eliminating pendulum is when braking begins by means of a corresponding signal on terminal 26d of the initial position the value corresponding to the pendulum is stored in the memory 26e. In member 26f then the difference between the signal corresponding to the momentary swing of the pendulum and the stored signal and this difference is then the comparator 25 supplied for pressure control.

With the braking system according to the invention is a simple way Arrangement can be combined to ensure that the brake pads wear evenly. An exemplary embodiment for this is shown in FIG. 3. For this purpose, there is at least one brake lining 40 of a front wheel and in at least one brake pad of a rear wheel (not shown) a lining wear indicator 41 in the form of a contact 43 is embedded. At a Wear of the brake lining in the direction of arrow 42, the web 44 is abraded. This creates a signal at the output of the negation gate 46, which together with the At the terminal 47 occurring signal during braking, the AND gate 43 is permeable makes and thus the valves 13 and 14 of FIG. 1 via the OR gates 49 and 50 can respond, so prevents an increase in pressure on the front brakes, if the lining on the front axle is already heavily rubbed off. Accordingly would a Pressure build-up at the rear wheel brakes via the AND gate 52 and the OR gate 53 and prevented by valve 15 when there is a corresponding wear signal generated and would be present at terminal 51. So that the loading of a part the braking takes place only in the partial braking area, the valve 5 of FIG. 1 is activated The output signal of the comparator 25 of FIG. 1 is fed to a timing element which, at actuation of the valve 5 via the OR gate 55 for more than 100 msec and 56 blocks AND gates 48 and 52, i.e. valves 13 to 15 (those via the Terminals 57 the control signals are fed in when there is a tendency to block) for reasons of the lining compensation does not respond. Wear occurs on both coverings indicating signal, the warning lamp 59 is controlled via the UD gate 58 and at the same time via the OR gate 60 the Anchen of valves 13-bis 15 prevented. The response of these valves is also prevented if the Terminal 61 has a signal -) that indicates that the anti-lock brake controller is in operation is. Finally, the valves 13 to 15 are also prevented from responding or suppressed if the brake is actuated several times within a specified time will. Then a downhill section is assumed. For this purpose the counter 64 is used with e.g. 4 counting positions, which advances by one position when each braking process occurs is, the monostable element 62, which is caused by a pulse occurring during braking is triggered and then emits a pulse for a certain time, e.g. 60 seconds and AND gates 63 and 65. Occur within the time in which the monostable Link is in its unstable position, four braking impulses, so that comes after four pulses occurring tusgangssignql of the counter 64 via the AND gate 63 to Timing element 66, which extends the signal to 300 seconds, for example. This signal causes through the OR gate 55 that the valves 13 to 15 by a brake pad wear signal can be excited.

This signal also blocks the input of the counter via AND gate 65. Both an output of the counter 64 and the tilting back of the monostable Element 62 reset the counter to its initial position.

Claims -

Claims (25)

Patent claims 1 * vehicle brake system for at least one vehicle wheel, in which a brake operating device is provided which is one of the extent of the Brake actuation-dependent first electrical signal generated, in which a brake pressure source is provided in the connection between the brake pressure shafts and the wheel brake a valve arrangement is switched on, which the connection between the brake pressure source and wheel brake cylinder temporarily manufactures and for the purpose of pressure reduction on the wheel brake cylinder this temporarily connects to an outlet, characterized in that one the Vehicle deceleration-determining device is provided on the vehicle, which a generated by the vehicle deceleration dependent electrical signal and that switching means to compare the signal that is dependent on the brake actuation and to generate it a control signal are provided for the valve arrangement, such that one a certain amount of brake actuation associated with a certain vehicle deceleration is. 2. Vehicle brake system according to claim 1, characterized in that with the brake actuation device a piston in one with the wheel brake cylinder connected cylinder is connected in such a way -that when the brake actuation device is actuated the piston and the cylinder act as emergency brake pressure generators beyond a specified level are effective. 3. Vehicle brake system according to claim 2, characterized in that Means are provided which establish the connection between the brake pressure source and the wheel brake cylinder interrupt when moving the piston. 4. Vehicle brake system according to claim 2 or 3, characterized in that that means are provided that the connection between the brake pressure source and the wheel brake cylinder. interrupt if the pressure of the brake pressure source falls below a predetermined value. 5. Vehicle brake system according to claim 3 or 4, characterized in that that one on the pressure of the pressure source or the mechanical deflection of the brake actuator responsive valve in the connection between the valve assembly and the wheel brake cylinder is switched on. 6. Vehicle brake system according to one of claims 1 to 5, characterized in that that in the from the valve assembly and / or the cylinder-piston assembly to the wheel brake cylinder leading line an arrangement for modulating the brake pressure is switched on and that a control circuit for influencing this arrangement in dependence is provided by a tendency of the wheel to lock. 7. Vehicle brake system according to claim 6, characterized in that the arrangement for modulation consists of a valve device which, depending on the switching position an increase or decrease in pressure and, if necessary, a constant pressure maintenance -allows. 8. Vehicle brake system according to one of claims 1 to 7, characterized by applying them to multiple vehicle wheels. 9. Vehicle brake system according to claim 8, characterized in that when divided into several brake circuits, one pressure source is used for all circuits is. 10. Vehicle brake system according to claim 2, 8 or 9, characterized in that that a number of piston / cylinder arrangements corresponding to the number of brake circuits is provided that are assigned to the brake circuits. 11. Vehicle brake system according to one of claims 3 or 5 and one of claims 8 to 10, characterized in that the means for interrupting the connection between the brake pressure source and the wheel brake cylinder when the piston is displaced or lowering of the brake pressure are provided separately for each brake circuit. 12. Vehicle brake system according to one of claims 6 to 11, characterized characterized in that arrangements for modulating the brake pressure as a function of blocking tendencies of the wheels provided for individual wheels and / or wheel grips are. 13. Vehicle brake system according to one of claims 1 to 12, characterized characterized in that a display arrangement is provided for displaying the vehicle deceleration is. 14. Vehicle brake system according to one of claims 1 to 13, characterized characterized in that means are provided for obtaining a signal from the speed of the pedal operation depends and that further means are provided to whom this signal is fed and those with increasing pedal speed increase the rate of pressure rise. 15. Vehicle brake system according to one of claims 1 to 14, characterized characterized in that means are provided to control the rate of pressure rise to influence depending on the vehicle speed in such a way that the The rate of pressure increase decreases with increasing vehicle speed. 16. Vehicle brake system according to one of claims 1 to 15, characterized characterized in that means are provided which a first pressure at the start of braking steer in and that only then on the pressure control according to the vehicle deceleration is switched. 17. Vehicle brake system according to one of claims 1 to 16, characterized by such an interpretation of the vehicle deceleration sensor that its position is measured at the start of braking and the change in vehicle deceleration compared to this measured value is used for brake pressure control. 18th to. Fahr- eugbremsanlage, in particular according to one of the claims 1 to 17, characterized in that at least one brake lining on each vehicle axle a signal generator is arranged, which when reaching a certain wear of the Lining generates a signal in the connecting lines to the wheel brake cylinders additional solenoid valves are switched on to block the pressure build-up, and that switching means are provided to which the signal is fed and then one Blocking the supply of pressure medium to the brakes of the axis cause the major Has lining wear. 19. Vehicle brake system according to claim 18, characterized in that that the valves are also used to modulate the brake pressure when there is a risk of blocking. 20. Vehicle brake system according to claim 18 or 19, characterized in that that switching means are provided which prevent the control of the shut-off valves, when a pad wear signal is generated on all axles. 21. Vehicle brake system according to one of claims 18 to 20, characterized characterized in that switching means are provided, the one addressing of the valves if the driver applies emergency braking. 22. Vehicle brake system according to one of claims 18 to 21, characterized characterized in that switching means are provided which, when the brake is actuated several times Generate a signal within a specified time indicating that the valves are activated prevented. 23. Vehicle brake system according to one of claims 19 to 22, characterized characterized in that when the valves are used, switching means are also used for brake pressure modulation are provided that control the valves by the lining wear signal Prevent the occurrence of a signal indicating the tendency to block. 24. Vehicle brake system according to one of claims 1 to 23, characterized characterized in that the vehicle decelerator also acts as a transmitter for the Vehicle deceleration is exploited in an anti-lock control system. 25. Vehicle brake system according to one of claims 1 to 23, characterized characterized in that the vehicle decelerator also acts as a trigger for triggering the filling of an air bag is used. Blank page