DE4028552A1 - Hydraulic brakes installation for motor vehicle - has servo pump fed via openbrakes circuit for non-driven wheels providing wheel-spincontrol - Google Patents

Abstract

During wheelspin control the pump (17) is connected to the fluid reservoir (4) via the brake circuit of the non-driven wheels (9), by opening the return valve (15) for the latter. This provides a simple feed to the pump without any additional valves. The driven wheel circuit is operated separately, with its return flow controlled to the pump. The two brake circuits are separated from the master cylinder by two isolating valves (11,12). During normal travel both valves are open to provide a compensating path to the reservoir (4). During wheelspin control one valve is closed to isolate the driven wheel brakes. ADVANTAGE - Simple control circuit; rapid response wheelspin control.

Description

The invention relates to a hydraulic brake system with a device for regulating the braking and / or on drive slip for a motor vehicle with driven and non-driven wheels consisting of a pedal operated master brake cylinder, a pressure medium reservoir, a pressure with when the master brake cylinder is not actuated tel connection between the working chambers of the master cylinder and the pressure medium reservoir, a brake circuit which the wheel brakes both powered and not comprises driven wheels, the wheel brakes via a Brake line with the master brake cylinder and via a pressure line are connected to the outlet of a pump, wherein the input of the pump via a return line to the wheel brake on driven and non-driven wheels is bound, modulation valves for regulating the wheel brake pressure depending on the turning behavior of the wheels.

Such a brake system is in DE OS 36 35 054 be wrote. The pressure modulation device consists of egg nem pair of valves, the inlet valve the Druckmittelver Binding the wheel brake to the master cylinder and the outlet valve the pressure medium connection of the wheel brake to the suction side (Input) of the pump checked. The pump delivers over egg ne pressure line in the brake line branch to the wheel brake of the driven wheel, being in the brake line branch Isolation valve between the master brake cylinder and the Einmün point of the pressure line is inserted. The suction side of the Pump is directly connected to a check valve Pressure medium reservoir connected to the atmosphere is open and contains at least as much pressure medium that  the brake circuits can be filled. This facility is one of them set up, both the brake slip and the drive control slip. During a regulation the Pump drive switched on so that the pump over the Pressure lines promotes pressure medium in the brake circuits. By Actuation of the intake and exhaust valves can increase the brake pressure a slip-dependent value can be set. In the event of a traction control system, the isolating valve is blocked, so that the pump pressure medium exclusively to the wheel brake promotes the driven wheels.

The system has two disadvantages

• 1. The pumps and the modulation valves are usually combined into a control unit connected to the main brake cylinder is attached so that the brake lines and pressure lines at least in this area as pressure middle channels are shown in a housing. Additional Lich, however, now the connection of the suction side of the pump with the pressure medium reservoir as a freely laid lei tion are carried out. In addition to the additional construction work there is a risk that this line will become brittle, what has the consequence that no more slip control can be led.
• 2. In the pressure medium connection between the master brake cylinder and the wheel brake is on in addition to the intake valve Isolation valve used. Each valve has a certain flow resistance. One tries therefore in the Brake lines to provide as few valves as possible, so that when the pedal is pressed, pressure builds up quickly is possible.

The invention is based on the object of a brake system to develop the preamble of the main claim so that there is no need for an additional suction line, where with the number of valves in the brake lines if possible should be low.

The invention is achieved with the means which characterize ning part of claim 1 are mentioned. In the case of an The pump therefore does not directly promote traction control from the storage container but via the brake line and the return line of the non-driven wheel. The ge named pressure medium connection can for the duration of an traction control are provided, or at least so long until there is sufficient pressure in the brake circuit is there.

A brake system is known from DE OS 38 31 426, where there is no additional suction line. In this system, the master cylinder is in the case of a Traction control from the brake circuit hydraulically ge separates and is connected to the suction side of the pump. The Pump therefore pumps over from the pressure medium reservoir the master brake cylinder in the brake circuit. This plant too does not require an additional suction line. But she has that Disadvantage that an additional valve in the brake line is provided, the rapid brake pressure build-up, as he refines, hinders the way. Furthermore, this is System not readily usable for a brake system with diagonal division.

Another advantage of the inventive system is there rin that hy during a control of the master cylinder is drastically locked and the wheel brakes hydraulically by  are separated from each other. The pump delivers via the pressure line device in the wheel brakes, whereby by controlling the outlet valve the pressure medium flow flowing from the wheel brake is regulated. If the current flowing is greater than that to The pressure in the wheel brake is reduced when it flows outflowing current is smaller than the inflowing, so the Wheel brake pressure increased.

The valve device for locking the master brake cylinder and to disconnect the wheel brakes can be done in different ways will be realized. On the one hand, the Brake line one electromagnetically operated isolation valve each be provided. If both valves are closed, then both the master cylinder hydraulically locked as well Wheel brake cylinder hydraulically separated.

But there can also be a valve in the common brake line be provided and a valve in the branch brake line to the driven wheel. This in turn can be advantageous hydraulically operated.

There are non-return valves in the pressure lines of the pumps til and a throttle provided.

A low-pressure accumulator takes pressure fluid from the wheel brake on who is not immediately promoted by the pump that can. There is a high pressure on the pressure side of the pump memory provided, which also absorb pressure medium can and specifies a pressure on the pressure side of the pump.

The brake is applied during regulation of the traction slip line and the return line of the non-driven wheel opened so that the pump pressure over this pressure medium path  can suck medium from the reservoir. The pump for changes in both pressure lines, so that only a part of the För the amount reaches the wheel brake of the driven wheel. The other parts get into the depressurized brake branch and will constantly pumped around. To the associated loss of performance to prevent, it is proposed in the pressure line to a non-driven wheel to insert a check valve, which in the Locks a traction control system, so that the ge total delivery volume of the pump to the wheel brake of the drive NEN wheel. The check valve can be a pressure relief valve can be connected in parallel, the pressure at the outlet of the Pump limited.

The following is intended to illustrate three examples put in a figure, the inventive idea closer to be refined.

Fig. 1

The brake system consists of a master brake cylinder 1 , which is actuated by means of a pedal. To support the pedal forces, a vacuum brake booster 3 is easily seen. At the master cylinder 1 is a Druckmit telvorratspeicher 4th As long as the pedal is not operated, there is a pressure medium connection between the pressure medium reservoir 4 and the working chambers of the Hauptbremszy cylinder 1 . When the pedal is pressed, the working pistons of the master brake cylinder are moved and at the same time the connection between the pressure medium reservoir 4 and the working chambers is interrupted. The pressure medium of the working chamber is pushed into the brake circuits so that a brake pressure is built up.

A master brake cylinder usually has two working chambers to which a brake circuit is connected. in the Exemplary embodiment is shown for only one brake circuit two wheels of a vehicle. The other brake circuit for that other wheels are constructed accordingly.

At one chamber of the master cylinder, a brake line 5 is connected, the main part 6 branches into two lines 7 and 8 , each leading to a wheel brake 9 and 10 . The wheel brake 9 belongs to a rear wheel and the wheel brake 10 to a front wheel. Both wheels are diagonally opposite the vehicle. The front wheels of the vehicle are driven. The exchange of the wheel connections leads to a brake system for a vehicle with a driven rear axle.

A separating valve 11 , 12 is inserted in each of the branch lines 7 and 8 . The isolating valves are actuated electromagnetically, keeping the branch lines open in their basic positions. If the actuating solenoids of the valves are controlled, they switch the valves into their blocking position. The wheel brake is connected to the suction side of a pump 17 via a return line 13 , 14 . An outlet valve 15 , 16 is inserted into each return line 13 , 14 . These valves are also controlled electromagnetically, whereby they block the return lines in their basic position. When the actuating magnet is actuated, the valves switch into a position that releases the return line. A low-pressure accumulator 18 is attached to the suction side of the pump; the accumulator can hold a limited amount of pressure medium at a low pressure level. The output of the pump 17 is connected to the wheel brakes via a pressure line 19 , 20 each. In each pressure line branch a check valve 24 , 25 and a throttle 22 , 23 is inserted. In addition, a check valve 26 can be provided in the pressure line 19 to the non-driven wheel, which is actuated electromagnetically and is open in its basic position. When the actuating magnet is activated, the valve switches to the blocking position. In parallel to this blocking valve, a pressure relief valve 27 is connected, which blocks the pump. It limits the pressure on the pressure side of the pump to a certain value.

On the pressure side of the pump, a high-pressure accumulator 21 is provided, the piston of which is held against a stop by a strong spring. As soon as the pump delivers pressure medium into the memory, the piston lifts off the stop, so that the pressure medium is under the action of the force of the spring, and a pressure proportional to the spring force is generated on the pressure side of the pump.

The rotational behavior of the wheels can be detected by means of sensors S. , the sensor signals are not shown by one th electronic evaluation unit detected. The evaluation unit unit evaluates these signals according to a specific algorithm and provides signals for the exhaust valves, the separating veins tile and possibly for the check valve. Furthermore, the Evaluation unit a switching signal for the pump drive.

The braking system works according to the following scheme There are three operating modes.

• 1. uncontrolled braking.
• 2. Brake slip control or ABS mode (ABS stands for anti Blocking system).
• 3. Traction control or ASR mode.

In an uncontrolled braking, the pedal is actuated and a brake pressure is built up in the brake circuits which corresponds to the pedal force. The isolating valves 11 , 12 are open, the outlet valves 15 , 16 are blocked. The check valves 24 , 25 prevent pressure medium from reaching the high-pressure accumulator 21 . With such braking, the Radrehverhal th is continuously monitored. It can be used to determine immediately whether one of the wheels is about to lock up. In this case, the system switches to ABS mode. This means that the pump drive is switched on and the isolating valves 11 , 12 are switched over. The master cylinder is now hydraulically locked and the wheel brakes are separated. The exhaust valves 15 , 16 are now driven according to a certain algorithm. In order to lower the pressure in the wheel brakes, the outlet valve is opened so that pressure medium flows out of the wheel brake and is pumped into the high-pressure accumulator. From there it flows back to the wheel brake with a delay via the throttle 22 , 23 . The flow rate through the outlet valve can now be determined by the ratio of opening and closing times. If the flow rate is greater than the amount of pressure medium flowing in per unit of time, pressure is removed from the wheel brake, so that the pressure in the wheel brake drops. If the flow rate through the valve is smaller than the amount of pressure medium flowing in per unit time via the throttle 22 , 23 , pressure medium is supplied to the wheel brake so that the pressure rises. The pressure in the wheel brake can now be set independently of the pedal pressure and in such a way that a slip value is set on the wheel, which probably allows high braking forces and sufficient cornering forces to be transmitted. The vehicle is braked and can be steered at the same time.

The ASR mode occurs when the drive torques generated by the vehicle engine are greater than the torques that can be transmitted between the tire and the road. As a result, the driven wheel spins. This can e.g. B. are prevented by the fact that braking torques are exerted on the driven wheel which compensate the drive torque so far that the remaining torque with the forces which can be transmitted between the tire and the road surface is har. The pump drive is switched on in ASR mode. The isolating valve in the brake line branch to the driven wheel is switched to the blocking position and the outlet valve in the return line to the non-driven wheel is brought into its open position. So that there is a Druckmittelverbin connection between the suction side of the pump and the storage container ter 4th This runs over the main part of the brake line 6, the brake line branch 7 to the non-driven wheel and the return line 13 from the non-driven wheel to the suction side of the pump. This connection is maintained during the entire control phase, or until the wheel brake is filled with pressure medium. The pressure medium drawn from the reservoir is conveyed by the pump 17 via the pressure line 20 to the wheel brake of the driven wheel. A brake pressure is generated there, which partially compensates for the drive torque. To regulate the brake pressure, the outlet valve 16 in the return line 14 is activated. As a result, the pressure in the wheel brake can be increased and decreased so that the wheel runs in a certain slip range, which allows both driving forces and cornering forces to be transmitted.

If no shut-off valve 26 is provided in the pressure line 19 to the non-driven wheel, the pump delivery flow is divided, a part reaching the non-driven wheel and only being pumped around by the pump. To meet these sätzlichen energy required to prevent, a valve may be provided in the pressure line 19, which blocks the pressure line 19 in the ASR mode. The medium sucked in by the pump is therefore completely conveyed into the pressure line 20 to the driven wheel.

Fig. 2

The brake system according to FIG. 2 largely corresponds to the brake system of FIG. 1. The only difference is in the illustration of the isolating valves. While two electromagnetically operated valves are seen in the brake system in FIG. 1, one valve being inserted into each branch line of the brake line, the brake system according to FIG. 2 sees an electromagnetically operated main isolating valve in the main part 6 of the brake line 5 and a hydraulic one is controlled auxiliary isolating valve in the branch line 8 to the driven wheel. The hydraulically driven valve is actuated by the pressure at the pump outlet. In the basic position of both valves, the brake line is open.

In ABS mode, the main isolating valve 28 is actuated electromagnetically in the main line of the brake and hydraulically locks the master brake cylinder. The pressure that builds up at the outlet of the pump acts in a control line 30 on the secondary isolating valve 29 , so that it switches into the blocking position and hydraulically separates the wheel brakes from one another.

In the ASR mode, the main isolating valve 28 remains open, while the second isolating valve 29 is switched over by the pressure in the control line 30 . This prevents the pressure medium, which is pumped from the pump to the driven wheel, can flow into the pressure medium reservoir 4 . A check valve 31 is connected in parallel with the main isolating valve 28 and opens towards the master brake cylinder. This is achieved during an ABS control that the pressure increases at least in the non-driven wheel over the Hauptbremszy cylinder pressure.

In contrast to the two previous Ausführungsfor men, the brake system according to FIG. 3 each has an inlet valve 40 , 41 in the branch lines 7 and 8 of the brake line. The inlet valves 40 , 41 are actuated electromagnetically and are open in their basic position. In the branch line 8 to the front wheel brake (driven), a isolating valve 28 is inserted, which corresponds to the isolating valve in the embodiments presented above.

The pressure line of the pump opens into the branch line 8 to the driven wheel, namely between the isolating valve and the inlet valve 40 . The other branch line 7 branches off from the main brake line 6 . The branch point lies between the master brake cylinder and the isolation valve 28 .

In ABS mode, the isolation valve 28 is open, the brake system works according to the so-called return principle. This means that the inlet valves are closed to maintain pressure or to lower the pressure and the pump promotes pressure medium back into the master brake cylinder 1 , from where it gets back into the wheel brakes as soon as pressure build-up is necessary.

In the ASR mode, the isolating valve 28 is closed, the inlet valve 41 and the outlet valve 15 , which are assigned to the non-driven wheel, being opened. The pump can then suck pressure medium via the branch line 7 and convey it via the pressure line into the branch line 8 to the driven front wheel. By switching valves 40 and 16 , the pressure in the front wheel brake can be adjusted.

Reference symbol list

1 master brake cylinder
2 pedal
3 vacuum brake booster
4 pressure medium storage tanks
5 brake line
6 main line
7 branch line
8 branch line
9 wheel brake
10 wheel brake
11 isolation valve
12 isolating valve
13 return line
14 return line
15 exhaust valve
16 exhaust valve
17 pump
18 low pressure accumulators
19 pressure line
20 pressure line
21 high pressure accumulators
22 throttle
23 throttle
24 check valve
25 check valve
26 shut-off valve
27 pressure relief valve
28 main isolating valve
29 secondary isolating valve
30 control line
31 check valve
40 inlet valve
41 inlet valve

Claims (13)

1. Hydraulic brake system with a device for regulating the brake and / or drive slip for a motor vehicle with driven and non-driven wheels consisting of a pedal-operated master brake cylinder, a pressure medium reservoir, with a non-actuated master brake cylinder a pressure medium connection between the working chambers of the master brake cylinder and the pressure medium reservoir, a brake circuit which comprises the wheel brakes of both driven and non-driven wheels, the wheel brakes being connected via a brake line to the master brake cylinder and via a pressure line to the outlet of a pump, the input of the pump being connected via a return line is connected to the wheel brakes of driven and non-driven wheels, modulation valves for regulating the wheel brake pressure in dependence on the rotational behavior of the wheels, characterized in that for generating a pressure in the wheel brake e ( 10 ) of the driven wheel regardless of the actuation of the main brake cylinder ( 1 ), as is necessary, for example, in the case of a traction control system, the pressure fluid connections ( 6 , 7 , 13 ) between the wheel brake of the non-driven wheel ( 9 ) on the one hand and the master brake cylinder ( 1 ) and the pump ( 17 ) on the other hand are at least temporarily open during the control phase. 2. Brake system according to claim 1, characterized in that in each return line ( 13 , 14 ) an outlet valve ( 15 , 16 ) is inserted and that the brake circuit has a valve device ( 11 , 12 , 28 , 29 ) which is capable the master brake cylinder ( 1 ) must be hydraulically locked and the wheel brakes ( 9 , 10 ) hydraulically separated. 3. Brake system according to claim 2, characterized in that the master brake cylinder ( 1 ) via a branching brake line ( 5 ) with the wheel brake ( 10 ) of a driven and with the wheel brake ( 9 ) of a non-driven wheel is connected, in each branch line ( 7 , 8 ) an electromagnetically operable isolating valve ( 11 , 12 ) is inserted. 4. Brake system according to claim 2, characterized in that the master brake cylinder ( 1 ) via a branching brake line ( 5 ) with both the wheel brake ( 10 ) of a driven and with the wheel brake ( 9 ) of a non-driven wheel is the verbun, in which not yet branched part of the brake line, an electromagnetically operated main isolation valve ( 28 ) is inserted and in the branch line piece ( 8 ) to the wheel brake ( 10 ) of the driven wheel, an auxiliary isolation valve ( 29 ) is inserted, which is actuated by the pump pressure. 5. Brake system according to claim 1, characterized in that in the pressure lines ( 19 , 20 ) between the pump ( 17 ) and the wheel brakes ( 9 , 10 ) each a check valve ( 24 , 25 ) is inserted, the pump ( 7 ) out locks. 6. Brake system according to claim 5, characterized in that each check valve ( 24 , 25 ) a constant throttle ( 22 , 23 ) is switched before or after. 7. Brake system according to claim 2, characterized in that the exhaust valves ( 15 , 16 ) can be actuated electromagnetically. 8. Brake system according to one of the preceding claims, characterized in that a low-pressure accumulator ( 18 ) connects to the suction side of the pump ( 17 ). 9. Brake system according to claim 2, characterized in that on the pressure side of the pump ( 17 ) is connected to a high-pressure accumulator ( 21 ), the storage piston of which is held by a prestressed spring at an impact. 10. Brake system according to claim 5, characterized in that in the pressure line ( 19 ) to the non-driven wheel ( 9 ) a check valve ( 26 ) (ASR valve) is provided, which is connected to a pressure relief valve ( 27 ) in parallel. 11. Brake system according to one of the preceding claims characterized in that the wheel brakes egg Nes brake circuit are assigned to the wheels that are driving Stuff diagonally opposite. 12. A method for controlling a brake system according to any one of the preceding claims, characterized in that when the drive wheel ( 10 ) is turned, the pump ( 17 ) is switched on, the outlet valve ( 15 ) of the non-driven wheel receives a pulse, whereby the Corresponding return line ( 13 ) is open and the Ventileinrich device ( 11 , 12 , 28 , 29 ) is switched such that the wheel brakes are hydraulically separated and a pressure medium connection between the master cylinder ( 1 ) and the wheel brake ( 9 ) of the non-driven wheel at least at least temporarily, namely for the duration of the pulse for the exhaust valve. 13. The method according to claim 12, in particular for a Bremsan location with the features of claim 10, characterized in that in the case of a traction control system, the ASR valve ( 26 ) receives a continuous pulse, so that the pressure line ( 19 ) to the wheel brake of the non-driven Wheel is broken.