DE19604058B4 - Anti-lock braking system (ABS) for road vehicles - Google Patents

Abstract

Anti-lock braking system for a road vehicle of the type that works in such a way that in response to an impending Radblockier- / Gleitzustand at a given wheel of the actuating pressure, to a brake actuator is applied to the brake associated with this wheel, is reduced and the pressure later is reapplied when the tendency of this wheel to block is reduced, the system being controlled by an electronic control device (108) is controlled and includes a plurality of solenoid valves (131), in the hydraulic supply of the brake actuation elements (105) to the individual wheels or axes are arranged, wherein hydraulic fluid from one through a Electric motor (111) driven hydraulic pump (135) to the solenoid valves (131), characterized in that the system comprises means (10a, 17), which causes the rotation of the electric motor (111) is stopped quickly after pumping is finished.

Description

The The invention relates to an anti-lock braking system (ABS) for road vehicles and particularly concerns the problem of reducing the noise, that from the ABS pump motors is generated after the ABS has been switched off.

ABS systems work in such a way that they open an impending state of blocking / sliding of a special one Rades respond by applying the actuation pressure to this Rad assigned brake applied will, reduce (lower) and later apply this pressure again, if the tendency of this wheel to block is reduced.

such ABS systems are powered by a dedicated electronic control unit (ECU) controlled by the battery / alternator of the vehicle is powered. The system closes the control of solenoid valves a in the hydraulic supply of the brake actuators to the individual Axles or wheels are arranged, wherein hydraulic fluid from one through a Electric motor driven hydraulic pump to the solenoid valves is delivered.

Anti-lock braking systems, the previously described "lowering and pumps "principle use, make it necessary that the electric pump motor after the trigger of the last solenoid for is operated for a short period of time. The length of time in which the engine keeps running, must be long enough be to the low pressure / expansion chambers of the Absenksolenoids to empty. After the pump motor has finished this process, it turns off and can go into a sleep state.

The The result is that the amount of time that the engine takes to to go to sleep after being shut down, longer is the time the engine is actually performing work the time and thus the sound that the driver or occupants hear at the end of an ABS cycle, considerably extended (possibly more than doubled). The pump noise and the following Comfort busses for The driver or passengers mainly come at the end of a stop on when the vehicle has come to a standstill and the other "road or road noise" have stopped.

It can not, to shorten the time before switching off the engine, as it must be guaranteed that the low-pressure expansion chambers are emptied.

From the DE 38 13 172 A1 A method for operating two auxiliary pumps of an anti-lock control device is known. The movements of the working pistons, the pressures in the pressure chambers of the tandem master cylinder of the ABS device and the speed of the pump drive motor are detected and processed with volume signals due to control algorithms in an electric motor controller to output signals for the control of the engine. In this way, the delivery volumes of the pumps are varied. Due to the variation of the delivery volumes, a positioning of the brake pedal is achieved before its starting position.

From the not previously published (PatG §3 Abs.2) DE 44 26 348 A1 is a hydraulic brake system with brake slip control known. To reduce noise, automatic draining of the low-pressure accumulator to the master cylinder is enabled when pedal-operated braking is stopped. For this purpose, a non-return valve device is set to the brake line from the low-pressure accumulator. As soon as the brake line is depressurized, the low-pressure accumulator can automatically empty into the after-reservoir without operating the pump. The master cylinder is no longer exposed to the high delivery pressure of the return pump when opening the connection to the reservoir. In addition, the loud noises caused by high pressure differences and by the running of the pump.

According to the present The invention thereby overcomes the aforementioned problem of continuing noise mitigated that the engine is stopped as soon as possible after the pump was stopped.

In a preferred embodiment this is achieved by the pump motor during the Continuation or follow-up phase of an electrical load suspended which generates an additional braking torque on the rotor of the engine, to help bring this to a halt quickly.

In an embodiment one side of the motor is permanently grounded or grounded and the other side is arranged in series with a switch, which is controlled by an electrical control unit of the ABS system is, with a closure of the switch the other side of the engine connects to a power supply and being the other side of the Motors are arranged so that they are also connected to ground is when the switch is open is to disconnect the motor from the power supply.

This can be achieved, for example, by switching the switch to double or bipolar, wherein a movable switch contact in a switching position one side of the motor connects to the power supply and in one other switching position with ground.

The Invention will be described below with reference to preferred embodiments exemplified with reference to the accompanying drawings, in of the

1 Figure 3 is a schematic representation of the basic hydraulic and electrical arrangement of a typical ABS brake system to which the invention may be applied;

2 is a schematic, partially sectioned view of a typical conventional pressure modulator and a single control channel;

3 Fig. 10 is a simplified circuit diagram of a conventional pump motor control system;

4 a simplified circuit diagram of an embodiment of a pump motor control system according to the invention is;

5 a circuit diagram of a pump motor control system according to the invention is provided with a monitoring means for providing a warning in the event that there is an error in the engine control;

6 a detailed illustration that is an alternative to a part of the system 5 is; and 7 and 8th Curves of engine speed over time for the known engine control system after 3 or the new system 4 are.

In 1 is very schematically the braking system of a four-wheeled vehicle 114 shown, two front wheels 114a . 114b and two rear wheels 114c and 114d , The system has a type of X-division with independent hydraulic circuits, wherein the first circle 107a (black) the brakes 105a . 105d the front-facing and the rear-facing wheel and the second circle 107b the brake 105b . 105c the front facing and the rear remote wheel actuated. A brake pedal (not shown) is mechanical with the actuating piston 120 a dual-circuit main cylinder 101 connected. The master cylinder 101 is one with a variety of control channels 113 with control valves 103 having modulator 102 connected by control lines 104 with an electronic control unit (ECU) 108 connected, the control valves 103 the connection between the master cylinder 101 and the brake actuators 105 Can control the wheels 114 control or control. The speed of each wheel 114 is customized by wheel speed sensors 106a - 106d recorded with the ECU 108 connected to the control valves 103 of the modulator 102 in response to signals from the wheel speed sensors 106 be received.

The ECU 108 is powered by a battery / alternator circuit 109 of the vehicle via an ignition switch 110 powered. The battery / alternator circuit 109 also supplies power to the modulator pump motor 111 via a servo valve 112 which is controlled by signals coming from the ECU 108 be generated. Should the ECU 108 determine that a certain error has occurred, an error warning display (warning lamp) 115 activated.

In 2 is a possible embodiment of a modulator 102 shown the structure of a single control channel 113 shows. For equivalent components, the same reference numerals as in FIG 1 used. 2 shows the ECU 108 receiving signals from a single wheel speed sensor 106 receives the rotational speed of one of a brake actuator 105 braked wheel 114 detected.

The master cylinder 101 leads liquid to the brake actuator 105 over the modulator 102 , the at least one control channel 113 comprising, for example, a flow valve 132 and a solenoid controlled drain valve 131 consists. Alternatively, the control channel could be formed by two solenoid-controlled valves of the known intake and lowering configuration.

An electrically operated pump motor 111 is designed to be a pump 135 To drive to liquid by opening the lowering valve 131 was released from the brake, from a low pressure accumulator or from an expansion chamber 133 attributed to that of the brake actuator 105 drained liquid back to the master cylinder 101 fed back to the controlled re-actuation of the brake through the control channel 113 ,

Referring now to 3 is in conventional arrangements of the control of the pump motor 111 (usually a permanent magnet motor) one side of this pump motor simply in series with a solenoid controlled servo switch 10 and a power supply 12 connected and the other side is connected to earth or ground (vehicle chassis). The on / off state of the solenoid switch 10 is through a solenoid 14 controlled by the electronic control unit (ECU) 108 of the ABS is selectively energized.

4 shows the circuit of 3 modified according to one embodiment of the control system of the invention. In the system after 4 in which the same components have the same reference numerals as in FIG 3 becomes a modified two-pole switch 10a used by when the switch 10a is in its engine OFF position, the switch contact and thus the normally not grounded side of the motor 111 with ground (chassis) over a wire 17 connected is. The fact that the engine is thus shorted to ground when it is off, it stops faster than when it is simply open, which results from the fact that when running (freewheeling) the engine acts like a generator when the ground circuit is closed, so that its "rotor" then undergoes an electrical load or a braking torque as a result of the opposite forces generated in its rotor and stator.

7 shows a typical curve of a pump motor speed over time for a conventional control circuit of the type 3 is shown, and 8th shows a typical curve of a pump motor speed over time for a control circuit according to the invention. In this example, the time required for the pump motor to stop in the conventional system is 100 ms, while using the invention, the time is reduced to 64 ms. This is just one example of the advantages that can be achieved, and in practice significantly higher time reductions are possible in percentage terms.

In 5 is an evolution of the circuit after 4 shown, which allows to generate a warning when certain errors occur.

A resistance 20 low value is in series with the permanently grounded side of the motor 111 connected and the voltage across this resistor 20 is through an amplifier 22 monitored to provide a signal representative of the present motor current. The output of the amplifier 22 is in a comparator 24 compared with a low / zero voltage to a high output from the comparator 24 in the event that the motor voltage and thus the current is greater than the low / zero voltage. The output of the comparator 24 controls a first switch 26 , which comes with a "count stop" input of a timer 28 connected is. The timer 28 is also via a second switch 30 and an inverter or converter 32 with the solenoid 14 connected such that the inverter or converter sends a high signal to the switch 30 which is used to count the timer 28 to start when the solenoid is turned off, according to disconnecting the motor from the power supply 12 through the switch 10a , The counting output of the timer 28 is in a second comparator 34 is compared with a signal X representing a predetermined or prescribed time, whereby the comparator 34 an input signal to the ECU 108 over a line 36 provides when the above system determines that the time it takes the motor to stall (zero output of the amplifier 22 ) exceeds the predetermined / prescribed time represented by the signal X.

The above system after 5 emits a warning signal when the motor lag time is passed to the comparator 34 applied predetermined value X exceeds. This would provide an indication that, for example, the switch contacts 10a or the switching mechanism that applies the electrical load to the motor does not turn on properly and the motor trailing time is too long. However, it may also or alternatively be useful to determine that the engine overrun time is below a predetermined value to provide an indication, for example, that the engine itself is starting to seize or that the motor driven pump is being exposed to a hydraulic load. The system may thus include means for generating a warning signal when the time required for stopping the engine is outside a predetermined range or less than a predetermined value. One possible way in which such a device could be configured is in FIG 6 shown at the comparator 34 from 5 through two comparators 34a . 34b is replaced, so that the comparator 34a on input B <input A responds and the comparator 34b to input B> input A, where input A of the comparator 34a with a lower predetermined limit Y and input A from comparator 34b is connected to an upper predetermined limit value X.

Claims (8)

Anti-lock braking system for a road vehicle of the type functioning to reduce, in response to an impending wheel lock / slip condition at a particular wheel, the actuating pressure applied to a brake actuator on the brake associated with that wheel and the pressure again later is applied when the tendency of this wheel to lock is reduced, the system being controlled by an electronic control device ( 108 ) and several solenoid valves ( 131 ), which in the hydraulic supply of the brake actuation elements ( 105 ) at the individual wheels or axles are arranged, wherein hydraulic fluid from a by an electric motor ( 111 ) driven hydraulic pump ( 135 ) to the solenoid valves ( 131 ), characterized in that the system comprises a device ( 10a . 17 ), which causes the rotation of the electric motor ( 111 ) is stopped quickly after pumping is finished. Anti-lock braking system according to claim 1, wherein the Engine stop means is designed such that it causes the pump while its trailing phase is exposed to an electrical load, causing an additional Braking torque is generated on the rotor of the engine to help this quickly bring to a halt. Anti-lock braking system according to claim 2, wherein one side of the engine ( 111 ) permanently connected to ground and the other side connected in series with a switch ( 10a ) arranged by the electrical control device ( 108 ), wherein closing the latter switch causes the other side of the motor ( 111 ) with a power supply ( 12 ) and where the other side of the engine ( 111 ) is designed so that it is also connected to ground when the switch ( 10a ) is opened to disconnect the motor from the power supply. Anti-lock braking system according to claim 3, wherein the switch ( 10a ) is bipolar, wherein a movable switching contact connects one side of the motor in a switching position with the power supply and in the other switching position to ground. Anti-lock braking system according to one of claims 1 to 4, comprising means for generating a warning signal when the time it takes is, so that the engine comes to a standstill, outside a predetermined Area lies. Anti-lock braking system according to one of claims 1 to 4, comprise means for generating a warning signal when the time that the engine needs to come to a halt is less than a predetermined one Value. Anti-lock braking system according to one of claims 1 to 4, comprising means for generating a warning signal when the time that the engine needs to come to a halt, exceeds a predetermined value. An anti-lock braking system according to claim 7 when dependent on claim 3 or 4, wherein said means for generating a warning signal comprises means ( 22 ), which generates a signal representing the motor current, a timer ( 28 ) which is designed to be started when the switch ( 10a ) is opened to the engine ( 111 ) from the power supply, a device ( 24 . 26 ) responsive to the motor current signal for generating a signal to stop the timer when the motor current signal is zero and means ( 34 ) for generating the warning signal when the count of the timer exceeds a predetermined value.