DE102017214138A1 - Method for testing a brake system - Google Patents

Abstract

The present invention relates to a method of testing a brake system (100), characterized in that in a first step of operation, an electric motor (M) driving a return pump (RP) of the brake system (100) is operated to apply brake fluid to a proportional valve (UPS) of the brake system (100), in a step of setting a valve position of the return valve (RP) connected to the proportional valve (UPS) is set to set a flow resistance for the brake fluid, in a first step of detecting a first electrical Current flow at the electric motor (M) is detected, in a step of waiting the electric motor (M) is switched off, in a second step of operating the electric motor (M) is operated again after a waiting time at the valve position to again brake fluid to the proportional valve ( UPS), in a second step of detecting a second electric current flow at the E Lektromotor (M) is detected, and in a step of comparing the first current flow with the second current flow is compared.

Description

Field of the invention

The invention relates to a method for testing a brake system.

State of the art

Leakage can occur in a brake system. The leakage can be detected by a visual inspection. More reliably, the leak can be detected by a static pressure test using a brake tester.

Disclosure of the invention

Against this background, a testing of a brake system, as well as a corresponding computer program product according to the independent claims is presented with the approach presented here. Advantageous developments and improvements of the approach presented here are described in the dependent claims.

Advantages of the invention

Embodiments of the present invention may advantageously enable a brake system without an external brake tester and without additional circuit pressure sensors to be tested for leakage or creeping pressure loss within the system.

A method for testing a brake system is presented, which is characterized in that in a first step of the operation, an electric motor driving a return pump of the brake system is operated to supply brake fluid to a proportional valve of the brake system, in a step of setting a valve position of the brake system provided with the return pump connected to the return valve to set a flow resistance for the brake fluid, in a first step of detecting a first electric current flow is detected on the electric motor is switched off in a step of waiting for the electric motor, in a second step of operating the electric motor after is operated again at the valve position to again to promote brake fluid to the proportional valve, in a second step of detecting a second electric current flow is detected at the electric motor, and in a step of comparing the first Str omfluss is compared with the second current flow.

Ideas for embodiments of the present invention may be considered, inter alia, as being based on the thoughts and findings described below.

In a static pressure test, a hydraulic system is pressurized and then closed. The pressure is monitored. If the pressure in the closed system decreases over time, a medium escapes from the system somewhere. The system has a leak.

In a brake system, a return pump can actively build pressure against a valve. The brake system can be pressurized once and then wait for a wait. If the brake system leaks or brake fluid escapes through closed valves, the pressure in the brake system drops slowly during the waiting period. Subsequently, the remaining pressure can be detected.

The pressure in the brake system can be determined using a current flow through windings of the electric motor used to build up the pressure, since the pressure correlates with a torque at the return pump and the torque correlates with the flow of current.

If the pressure drops over the waiting time, the second time pressure is applied, the torque is lower and increases again with increasing pressure. Therefore, the current flow on the second time to bring pressure is only lower and increases with the rising pressure again.

When the valve position on the proportional valve releases a flow area, the proportional valve can be closed during the waiting time. After the waiting time, the proportional valve can be returned to the same valve position.

For example, the electric motor can be operated until a certain current flow results. After the waiting period, the motor can be operated until the current flow again results. At the same current flow results in both times to pressure Bring the same pressure in the brake system when the electric motor is turned off. In this case, the brake system can be brought to a maximum pressure, for example, in order to simulate an extreme situation.

The electric motor can be operated speed controlled. The resulting torque or the resulting current flow is so well comparable. By a speed-controlled operation, a delivery rate of the return pump per unit time is constant. In this case, a time period can be evaluated in addition, which passes until after the waiting time again the flow of current that has flowed before the waiting period or the pressure set before the waiting time is reached. The time duration is proportional to a leaked fluid quantity.

The proportional valve can be placed in a closed valve position. Due to the closed valve position, the maximum pressure can be built up. The closed valve position correlates with an end position of a drive of the proportional valve. As a result, the closed valve position can be set securely.

The first current flow may be detected at least at the end of the first step of the operation. The second current flow can be detected at the beginning of the second step of the operation. The first current flow represents a maximum reached value. The second current flow represents a lower initial value compared to this. A difference between the two current flows represents the leakage.

A warning message may be provided if the second current flow deviates from the first current flow by more than one warning tolerance. If the second current flow is significantly lower than the first current flow, this represents a significant pressure loss over the waiting period. The pressure loss can be tolerated up to a predetermined limit. From the limit, the warning message can be provided.

Intake valves of a brake circuit of the brake system can be opened and exhaust valves closed to allow pressure buildup by the return pump and the proportional valve in the brake circuit. Alternatively or additionally, a high-pressure switching valve of the brake circuit can be opened. By opening the intake valves, the brake devices are pressurized and can thus be checked for leaks. By opening the high-pressure switching valve, brake fluid flowing through the proportional valve can flow back to the suction side of the return pump. By opening the high-pressure switching valve, the return pump can also suck in brake fluid from the reservoir on the master cylinder.

Further intake valves and further exhaust valves of a further brake circuit of the brake system can be opened. Alternatively or additionally, a further proportional valve and a further high-pressure switching valve of the further brake circuit can be opened in order to prevent pressure build-up in the further brake circuit. By opening the valves in the other brake circuit, the torque of the electric motor can be used essentially at the return pump in the brake circuit to be tested. Frictional losses are constant and not relevant for the approach presented here.

A further return pump of a further brake circuit of the brake system can be operated by the electric motor to promote brake fluid to a further proportional valve of the further brake circuit, a further valve position of another proportional valve can be set to set a further flow resistance for the brake fluid, Another first electrical Current flow through the electric motor can be detected. Another second electrical current flow through the electric motor can be detected and the further first current flow can be compared with the further second current flow. By carrying out the approach presented here in at least one further brake circuit of the brake system, the entire brake system can be tested in several steps.

Also of advantage is a computer program product or computer program with program code which can be stored on a machine-readable medium and used to carry out, implement and / or control the steps of one of the methods described above.

list of figures

• 1 zeigt eine Darstellung eines Schaltplans eines Bremssystems eines Fahrzeugs.

Embodiments of the invention will now be described with reference to the accompanying drawings, wherein neither the drawings nor the description are to be construed as limiting the invention.

• 1 shows a representation of a circuit diagram of a brake system of a vehicle.

The figure is merely schematic and not to scale.

Embodiments of the invention

1 shows a representation of a hydraulic circuit of a brake system 100 of a vehicle. The brake system 100 includes a transmitter unit 102 , a brake control unit 104 and braking devices 106 at the wheels of the vehicle. The transmitter unit 102 consists here of a coupled via a rod with a brake pedal brake booster and a dual-circuit master cylinder with two chambers. On the master cylinder MC is a reservoir 108 arranged for brake fluid or brake fluid. Two pistons, which are moved simultaneously by the brake pedal or the brake booster, are arranged in the master brake cylinder MC. Each piston acts on its own volume. A first master cylinder chamber MC1 is with a first brake circuit 110 the brake control unit 104 fluidly connected. The second master cylinder chamber MC2 is with a second brake circuit 112 the brake control unit 104 connected. Every brake circuit 110 . 112 supplies two of the brake devices 106 , Here X-brake circuits are shown. Each of the brake circuits 110 . 112 each supplies a front wheel and a diagonally opposite rear wheel. The first brake circuit 110 thus supplies the braking device 106 of the left front wheel LV and the brake device 106 the right rear wheel RH. The second brake circuit 112 provides the braking device 106 the right front wheel RV and the braking device 106 of the left rear wheel LH.

Both brake circuits 110 . 112 are the same. Therefore, here is just one of the brake circuits 110 . 112 described. Components of the first brake circuit 110 are marked with the number one. Components of the second brake circuit 112 are marked with the number two. Components that are clearly assigned to a wheel are marked with the abbreviation of the wheel.

The respective output of the master cylinder MC is connected to the inputs of a proportional valve UPS and a switching valve HSV. The proportional valve UPS can be called a changeover valve. The switching valve HSV can be referred to as a high-pressure switching valve. Both valves are electromagnetically actuated. The proportional valve UPS is normally open. The switching valve HSV is normally closed. The switching valve HSV has only two switching positions, open or closed. The proportional valve UPS can take a variety of valve positions. A flow cross-section of the proportional valve UPS depends on the valve position. In the first brake circuit 110 is between the output of the master cylinder MC1 and the inputs of the proportional valve UPS1 and the switching valve HSV1 a pressure sensor 114 arranged.

An output of the proportional valve UPS is with the braking devices 106 connected. Between the proportional valve UPS and the braking devices 106 is ever another proportional valve EV arranged. The further proportional valves EV can be referred to as intake valves. The further proportional valves EV are also actuated electromagnetically and normally open. The further proportional valves EV can be throttled. In the de-energized state of the proportional valve UPS and the further proportional valves EV there is a direct fluidic connection between the master cylinder MC and the brake devices 106 ,

Between the input and the output of the proportional valve UPS, a check valve is arranged. At a higher inlet pressure than at the outlet, brake fluid may bypass the proportional valve UPS. The brake fluid can thus at any time of the master cylinder MC in the direction of the braking devices 106 stream.

Check valves are also arranged between the inputs and the outputs of the further proportional valves EV. At a higher pressure at the outlet than at the inlet, brake fluid can flow past the respective further proportional valve UPS. Brake fluid can therefore at any time from the brake devices 106 stream away.

An output of the switching valve HSV is connected to a suction side of a return pump RP. About the switching valve HSV is the return pump RP so with the reservoir 108 connected to the master cylinder MC. A pressure side of the return pump RP is connected to the output of the proportional valve UPS and the inputs of the further proportional valves EV.

The return pumps RP1 . RP2 both brake circuits 110 . 112 are coupled to a common electronically commutated electric motor M. The electric motor M is here a brushless DC motor and is powered by an engine control unit 116 provided. The engine control unit 116 has among other things an inverter 118 for providing a polyphase, in particular rectangular AC voltage for windings of the electric motor M, a current detection device 120 for detecting the resulting current flows through the windings and a position detecting device 122 for detecting a rotor position and rotational speed of a rotor of the electric motor M via a rotor position sensor.

When a voltage signal is applied to the windings of the electric motor M, the rotor and coupled pump rotors of the return pumps rotate RP1 . RP2 , The current flows through the windings are adjusted according to a torque required for rotating the pump rotors. A volume delivered by a return pump RP depends on a pump speed of the pump rotor. The pump speed is in a fixed ratio to the speed of the rotor of the electric motor M. Here, the pump rotors are coupled with no intervening transmission to the rotor, therefore, the pump speed corresponds to the speed.

As the pressure on the pressure side of the return pump RP increases, so does the required torque. With the torque, the current flows increase. Since the torque can be calculated via the current flows and the pressure can be calculated via the torque, the pressure can be calculated using the current flows. The current flows can also be combined to a resulting current flow at the electric motor M.

The suction side of the return pump RP is also connected to the brake devices 106 connected. Between the return pump RP and the brake devices 106 is ever another switching valve AV arranged. The further switching valves AV can be referred to as exhaust valves. The other switching valves AV are electromagnetically operated and normally closed. The other switching valves AV can be throttled. Between the outputs of the other switching valves AV and the suction side of the return pump RP, a low-pressure accumulator A is arranged. The low-pressure accumulator A is formed as a cylinder with a spring-loaded piston therein. Between the low-pressure accumulator A and the suction side of the return pump RP, a spring-loaded check valve RVR for reducing a suction pressure of the return pump RP is arranged.

All valves of the brake control unit 104 are controlled by electrical signals. The switching valves HSR and further switching valves AV each have an open or a closed switching position without intermediate positions. The proportional valves UPS and the further proportional valves EV also have intermediate positions as a function of a signal value of the triggering electrical signal. A flow cross-section of the proportional valves UPS and further proportional valves EV depends on the valve position.

A detection of a leak in the pressure supply of a brake system is presented.

The proposed method allows a check or evaluation of the leakage in the ESP brake system including the exhaust valves, high-pressure shut-off valve HSV, proportional valve UPS, pump elements and brake lines.

The proposed method uses the measured motor current as information about a motor torque. By a special control of the engine and the valves, the pressure loss is estimated.

The method is based on the fact that it is possible with an electrically commutated motor to approach an exact rotor position and to run a defined number of revolutions or a defined rotation angle.

In the proposed method, the valves are switched so that a pressure build-up by the engine is possible. Exhaust valves are closed. By controlling the motor, a certain pressure is generated, which is adjustable by the current in the proportional valve UPS. The motor current at the pressure reached is measured and stored. Thereafter, the engine is stopped for a defined period of time. During this time, the pressure in the brake system may drop due to leakage. Then the engine is turned further. The motor current at the beginning of the movement or a current increase during the movement give information about the pressure loss or the leakage in the brake system. The measurement can be carried out in each case in a brake circuit. A larger current difference indicates a greater pressure drop. If a certain limit is exceeded, the system is detected as defective.

In other words, in the method presented here for checking the brake system 100 a brake circuit 110 . 112 of the brake system 100 with closed proportional valve UPS and closed outlet valves AV brought to the same pressure twice in succession. In between, a wait is waiting. In doing so, at the end of the first time on pressure, a first value of the current flow is noted and compared with a second value of the current flow at the beginning of the second time on pressure. If the pressure between the two times drops to pressure, the second value is lower. The difference in the values is greater, the greater the pressure loss. If the difference is too large, you can be warned about the pressure loss. The same procedure can subsequently in the other brake circuit 110 . 112 of the brake system are executed.

The components of the braking system 100 are controlled via electrical control signals of one or more control units. The control unit has electronic components for providing the control signals. The components are driven in accordance with a stored in a memory of the controller computer program product. The computer program product is designed to implement and execute the steps of the method presented here or of the methods presented here.

The control device may comprise an electrical device having at least one computing unit for processing signals or data, at least one memory unit for storing signals or data, and at least one interface and / or a communication interface for reading in or outputting data embedded in a communication protocol, be. The arithmetic unit can be, for example, a signal processor, a so-called system ASIC or a microcontroller for processing sensor signals and outputting data signals as a function of the sensor signals. The storage unit may be, for example, a flash memory, an EPROM or a magnetic storage unit. The interface can be used as a sensor interface for reading the sensor signals from, for example, the current detection device 120 and / or the position detection device 122 and as an actuator interface for outputting control signals for, for example, the inverter 118 be educated. The communication interface can be designed to read in or output the data wirelessly and / or by cable. The interfaces may also be software modules that are present, for example, on a microcontroller in addition to other software modules.

Finally, it should be noted that terms such as "comprising," "comprising," etc., do not exclude other elements or steps, and terms such as "a" or "an" do not exclude a multitude. Reference signs in the claims are not to be considered as limiting.

Claims (10)

Method for testing a brake system (100), characterized in that, in a first step of the operation, an electric motor (M) driving a return pump (RP) of the brake system (100) is operated to apply brake fluid to a proportional valve (UPS) of the brake system (100 ), in a step of setting a valve position of the return valve (RP) connected to the proportional valve (UPS) is set to set a flow resistance for the brake fluid, detected in a first step of detecting a first electric current flow to the electric motor (M) is switched off in a step of waiting the electric motor (M) is operated again in a second step of operating the electric motor (M) after a waiting period at the valve position to again brake fluid to the proportional valve (UPS) to promote in one second step of detecting a second electric current flow at the electric motor (M) is detected, and in one step comparing the first current flow with the second current flow is compared. Method according to Claim 1 in which in the steps of operating the electric motor (M) is operated speed-controlled. Method according to one of the preceding claims, in which, in the setting step, the proportional valve (UPS) is placed in a closed valve position. Method according to one of the preceding claims, wherein in the first step of detecting the first current flow is detected at least at the end of the first step of the operation, and in the second step of detecting the second current flow is detected at the beginning of the second step of the operation. A method according to any one of the preceding claims, wherein in the step of comparing, a warning message is provided when the second current flow deviates from the first current flow by more than a warning tolerance. Method according to one of the preceding claims, in which, in the setting step, further inlet valves (EV) of a brake circuit (110) of the brake system (100) are opened and exhaust valves (AV) are closed in order to establish a pressure build-up by the return pump (RP1) and the proportional valve ( USV1) in the brake circuit (110) and / or a high-pressure switching valve (HSV1) of the brake circuit (110) is opened. Method according to Claim 6 in which further exhaust valves (AV) and intake valves (EV) of a further brake circuit (112) of the brake system (100) are also opened in the step of setting, and / or a further proportional valve (USV2) and another high-pressure switching valve (HSV2) of the further Brake circuit (112) is opened to prevent pressure build-up in the further brake circuit (112). Method according to one of the preceding claims, wherein in the operating steps a further return pump (RP2) of a further brake circuit (112) of the brake system (100) is operated by the electric motor (M) to deliver brake fluid to a further proportional valve (USV2) of the another brake circuit (112) to promote, in the step of setting a further valve position of another proportional valve (USV2) is set to set a further flow resistance for the brake fluid, in the first step of detecting a further first electrical current flow detected by the electric motor (M) is detected in the second step of detecting a second electrical current flow through the electric motor (M) is compared and in the step of comparing the further first current flow with the further second current flow. Computer program product adapted to perform the method according to any one of Claims 1 to 8th execute, implement and / or control. Machine readable storage medium carrying the computer program product according to Claim 9 is stored.

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