DE102017214130A1 - Method for testing and operating a proportional valve - Google Patents

Abstract

The present invention relates to a method for testing a proportional valve (USV) of a brake system (100), which is characterized in that in a step of operating an electric motor (M) driving a return pump (RP) of the brake system (100) is operated To promote brake fluid to the proportional valve (UPS), in a step of setting a valve position of the proportional valve (UPS) is set to set a flow resistance for the brake fluid, and in a step of determining an operating point of the proportional valve (UPS) using an am Electric motor (M) detected current flow and the valve position is determined.

Description

Field of the invention

The invention relates to a method for testing a proportional valve of a brake system and a method for operating a proportional valve of a brake system.

State of the art

A proportional valve has different flow cross-sections depending on a valve position. By changing the valve position so a fluid flow can be changed by the proportional valve. Due to manufacturing tolerances, different proportional valves have different flow cross sections at the same valve position. These differences can lead to an asymmetrical pressure distribution to brake devices of the brake system, in particular in the case of a symmetrical or parallel circuit structure, as in a brake system.

Disclosure of the invention

Against this background, a method for testing a proportional valve of a brake system and a method for operating a proportional valve of a brake system and corresponding computer program products according to the independent claims are 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 allow to check proportional valves of a brake system in the installed state, by detecting the pressure on a proportional valve using known sizes without the aid of external aids and is correlated with a set valve position. Conversely, the associated valve position can thus be selected for a desired pressure.

A method for testing a proportional valve of a brake system is presented, which is characterized in that in a step of operating an electric motor driving a return pump of the brake system is operated to promote brake fluid to the proportional valve, in a step of setting a valve position of the proportional valve is set to set a flow resistance for the brake fluid, and in a step of determining an operating point of the proportional valve using a current detected at the electric motor and the valve position is determined.

Furthermore, a method for operating a proportional valve of a brake system is presented, which is characterized in that in a step of reading using a target pressure value, an operating point of the proportional valve is read from a map of the proportional valve, and in a step of outputting using the operating point Valve position setpoint for the proportional valve is output.

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

In a multi-circuit brake system with multiple separate brake circuits, multiple return pumps may be driven by a common electric motor to increase brake pressure in the brake system. For example, a brake assist of the vehicle may recall the increased brake pressure to achieve a greater deceleration than a driver dictates by a pedal force. Since the return pumps are mechanically coupled to each other, a delivery rate of each return pump is determined by a speed of the electric motor. The brake pressure in the respective brake circuit is adjusted by discharging a volume flow on a pressure side of the return pump using a proportional valve. The proportional valve may be referred to as a changeover valve.

The volume flow through the proportional valve depends on a pressure difference between both sides of the proportional valve and a released flow cross section. The flow area defines a flow resistance of the proportional valve and is determined by a valve position of the proportional valve. The valve position is adjusted by a drive of the proportional valve.

Manufacturing tolerances of the proportional valves and the drives result in different volume flows through different proportional valves with otherwise identical settings. The different volume flows result in different brake pressures in the various brake circuits.

In order to achieve in the various brake circuits substantially the same brake pressures even with different proportional valves, it is necessary to know at which valve position which pressure is set on a proportional valve.

The pressure could be measured using a special pressure sensor between the return pump and the proportional valve. However, such pressure sensors are expensive and are therefore often not used today.

In the approach presented here, the pressure is detected via the electric motor, since the greater the pressure, the more torque the electric motor requires to turn the return pump. The greater the required torque, the more power the electric motor draws. A current flow through windings of the electric motor is thus directly related to the pressure. The pressure is therefore known about the context in approximation. The current flow is already detected by an engine control unit of the electric motor and can be retrieved as a current flow value. Also, the speed and rotor position of the electric motor are detected by the engine control unit and can be retrieved as a speed value or position value.

A valve position is set and the current flow value and the speed value recalled. The valve position can therefore be assigned a current flow. Through the flow of current, the valve position, a torque and consequently a pressure can be assigned. An operating point is characterized by the sensed speed, valve position and current flow.

The operating point may also be read using a speed setpoint for the electric motor. The electric motor can be operated speed controlled. The speed setpoint can be specified by the engine control unit and is known. The engine control unit regulates the speed to the speed setpoint. To achieve the speed setpoint, the pressure-dependent current flow through the turns is required.

The electric motor can be operated in the following regulated to at least a second speed. Alternatively or additionally, at least one second valve position of the proportional valve can be provided. At least one second operating point can be determined using the second rotational speed and / or the second valve position and a second current flow at the electric motor. At least one size may be changed to achieve a different operating point of the proportional valve. The other operating point may also be reproducible.

In the step of determining, a map of the operating points can also be created, which includes speed characteristics and / or valve position characteristics. The speed characteristics may represent operating points at constant valve position and varying speeds. The valve position characteristics may represent operating points at constant speed and varying valve position. A map can be stored in a multidimensional table. The map characterizes the proportional valve and the connected return pump. Depending on the requirement, different valve positions for different pressure setpoints can be read out through the characteristic map.

Intake valves of a brake circuit of the brake system may be closed and exhaust valves may be opened 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. Closing the intake valves does not pressurize the brake devices. The inlet valves are also proportional valves that can be tested with the approach presented here. In this case, the switching valve of the brake circuit can be closed. By closing the other valves on the pressure side of the return pump, the flow rate of the return pump flows only through the Asked proportional valve. The pressure can be determined more easily. By opening the switching valves, the brake fluid flowing through the proportional valve can flow back to the suction side of the return pump. In addition, by opening the exhaust valves, the recirculation pump may further draw in brake fluid from the brake devices. By opening the high-pressure switching valve, the return pump can 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 essentially constant and not materially relevant to the approach presented here.

A further return pump of a further brake circuit of the brake system can be subsequently operated by the electric motor to brake fluid to a further proportional valve of the to promote further brake circuit. Another valve position of the further proportional valve can be set to set a further flow resistance for the brake fluid. Another operating point of the further proportional valve can be determined by using a further current flow at the electric motor and the further valve position. The approach presented here can also be applied in other supplied by the electric motor brake circuits. This allows the proportional valves of the entire brake system to be tested.

The electric motor can be operated with one of the speed in the first brake circuit corresponding further speed. The further valve position can be changed until a value of the further current flow corresponds to a previously detected value of the current flow in the first brake circuit. A correction factor for the further proportional valve can be determined using the first valve position and the other valve position. Due to the correction factor for the valve position, the same pressure can be set in both brake circuits.

During operation, a further operating point for a further proportional valve of a further brake circuit of the brake system can be read out using a further pressure setpoint from a characteristic diagram of the further proportional valve. Using the further operating point, a further valve position setpoint for the further proportional valve can also be output. So different pressures can be set in different brake circuits.

Alternatively, the further valve position setpoint for the further proportional valve may be output using the operating point and a correction factor for the further proportional valve. A correction factor represents a relationship between the valve positions of the different valves to achieve the same pressure.

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.

It should be understood that some of the possible features and advantages of the invention are described herein with reference to different embodiments. A person skilled in the art will recognize that the features of the methods can be suitably combined, adapted or replaced in order to arrive at further embodiments of the invention.

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

For safety reasons, current ESP brake systems are typically divided into two separate hydraulic circuits. In a braking maneuver with active pressure build-up by the return pump, such as a comfort braking, a pressure difference in the two circles can arise, which is caused by manufacturing tolerances of regulated UPS pressure valves. That can e.g. cause the vehicle to "go wrong" during such maneuvers. The oblique pulling creates a force that must be compensated by countersteering the driver.

The pressure difference can be detected by one pressure sensor in each of the two circuits. The pressure difference can be compensated by a suitable valve control. For this purpose, a calibration of the valves in the manufacturing process can be carried out in order to keep the pressure difference small.

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 two master cylinders MC. On the master cylinder MC is a reservoir 108 arranged for brake fluid or brake fluid. The transmitter unit 102 is executed in two circles. In the master cylinder MC two simultaneously moving by the brake pedal or the brake booster pistons are arranged. Each piston acts on its own volume. A first master cylinder piston MC1 is with a first brake circuit 110 the brake control unit 104 fluidly connected. The second master brake cylinder piston MC2 is with a second brake circuit 112 the brake control unit 104 connected. Every brake circuit 110 . 112 supplies two of the braking 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 braking 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 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 with the inputs of a proportional valve UPS and a switching valve HSV connected. The proportional valve UPS can be referred to as 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 switch 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 other proportional valves EV are also electromagnetically operated and normally open. The other proportional valves EV can be throttled. In de-energized state of the proportional valve UPS and the other proportional valves EV there is a direct fluidic connection between the master cylinder MC and the braking 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 be present at the proportional valve UPS flow past. The brake fluid can therefore at any time of the master cylinder MC in the direction of the braking devices 106 stream.

Between the inputs and the outputs of the other proportional valves EV also check valves are arranged. At a higher pressure at the outlet than at the inlet, brake fluid may be present at the respective further proportional valve UPS flow past. 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 connected. Via the switching valve HSV is the return pump RP So with the reservoir 108 on the master cylinder MC connected. 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 connected.

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.

If the pressure on the pressure side of the return pump RP increases, also increases 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 with the braking devices 106 connected. Between the return pump RP and the braking devices 106 is ever another switching valve AV arranged. The other switching valves AV may 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 is a spring-loaded check valve RVR arranged to reduce a suction pressure of the return pump RP.

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 switch position without intermediate positions. The proportional valves UPS and the other 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.

It becomes a cost effective method of pressure balancing between both brake circuits 110 . 112 presented.

This is a measured motor current for the pressure comparison in the two brake circuits 110 . 112 used. The ESP UHD uses an electrically commutated electric motor M with current measurement in ground path. By the approach presented here, the pressure in the two brake circuits can be without pressure sensors 110 . 112 be aligned.

The process is in two parts. A first part is a calibration or acquisition of maps at standstill or during service. A second part is the use of the determined maps as a manipulated variable in active maneuvers.

Calibration is only performed when the vehicle is at a standstill. It can take place at the end of production, during servicing and repairs to the brake system, or when the ignition is switched on. The aim of the calibration is to create a calibration table with which in the maneuver with active pressure build-up the proportional valves UPS, by means of which the pressure in the brake circuit is adjusted, can be energized so that the hydraulic pressure in both brake circuits 110 . 112 as equal as possible. The calibration method is based on the brake pressure in the brake circuit correlating with the motor current. The motor current is proportional to the torque generated by the load of the return pump RP is determined. As a result, the motor current is also connected to the hydraulic pressure. Thus, the pressure in the brake circuit can be estimated indirectly via the motor current.

For calibration, first the exhaust valves AV disabled, so switched off, and the intake valves EV opened, so also switched off. In the first brake circuit 110 the switching valve HSV is opened, so energized, and the proportional valve UPS subjected to different currents. At the same time, the electric motor M is controlled and the motor current is measured. The control can be done eg with constant speed. The measured motor current is stored. After that, the same procedure in the second brake circuit 112 be carried out, with the difference that the current for the proportional valve UPS is varied so that the motor current reaches the same value as in the measurement in the first brake circuit 110 , This can be done for example by a linear current change or a current ramp. The ratio of the valve currents in both brake circuits 110 . 112 at the same pressure, the correction factor that can be used is around both brake circuits 110 . 112 to be adjusted during maneuvers with active pressure build-up.

For the pressure setting accuracy based on the motor current measurement during operation of the vehicle, only the stored table with correction factors is used.

In other words, both return pumps RP are simultaneously driven by the electric motor M since they are mechanically coupled together. Only on one of the return pumps RP a pressure is built up by the flow area of the proportional valve UPS in one of the brake circuits 110 . 112 is narrowed. So that the brake fluid back to the suction side of the return pump RP can flow back, the switching valve HSV is opened. Due to the incompressibility of the brake fluid, a pressure arises within a short time between the return pump RP and the proportional valve UPS. The return pump RP now promotes against the pressure and applied by the electric motor M torque increases. The increasing torque requires an increasing output of the electric motor M and more current flows through the windings of the electric motor M. The current flow is directly related to the torque and thus the pressure. The detected current flow and the signal strength at the proportional valve UPS represent an operating point of the proportional valve UPS ,

Alternatively, a pressure build-up between the return pump RP and one of the other proportional valves EV respectively. Then the proportional valve UPS closed and the associated additional switching valve AV opened for the return flow of the brake fluid to the return pump RP. Thus, a further operating point of the further proportional valve can be determined.

The valves in the other brake circuit 110 . 112 can be opened to prevent pressure build-up.

Through the process presented here several operating points can be determined at different valve positions. Likewise, a rotational speed of the electric motor can be varied in order to set different volume flows.

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 (14)

Method for testing a proportional valve (USV) of a brake system (100), characterized in that in a step of operating, an electric motor (M) driving a return pump (RP) of the brake system (100) is operated to supply brake fluid to the proportional valve (UPS) in a step of setting a valve position of the proportional valve (UPS) is set to set a flow resistance for the brake fluid, and in a step of determining an operating point of the proportional valve (UPS) using a detected at the electric motor (M) current flow and the valve position is determined. Method according to Claim 1 in which, in the step of operating, the electric motor (M) is operated speed controlled, and wherein in the step of determining the operating point is further determined using a rotational speed of the electric motor (M). Method according to Claim 2 in which in the step of operating the electric motor (M) is operated regulated to at least a second speed and / or in the setting step, at least one second valve position of the proportional valve (UPS) is set, and in the step of determining at least a second operating point using the second speed and / or the second valve position and a second current flow to the electric motor (M) is determined. Method according to Claim 3 in which the step of determining further establishes a map of the operating points, the map including speed characteristics and / or valve position characteristics, the speed characteristics representing operating points at constant valve position and varying speeds, and the valve position characteristics representing operating points at constant speed and valve position variation. Method according to one of the preceding claims, wherein in the setting step further intake valves (EV) of a brake circuit (110) of the brake system (100) are closed and exhaust valves (AV) are opened 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 5 in which in the step of placing further inlet valves (EV) and Further exhaust valves (AV) of a further brake circuit (112) of the brake system (100) are opened, and / or another proportional valve (USV2) and another high-pressure switching valve (HSV2) of the further brake circuit (112) is opened to a pressure build-up in the other Brake circuit (112) to prevent. Method according to one of the preceding claims, wherein in the step of operating a further return pump (RP2) of another brake circuit (112) of the brake system (100) by the electric motor (M) is operated to brake fluid to another proportional valve (USV2) further To promote brake circuit (112), in the step of setting another valve position of the further proportional valve (USV2) is set to set a further flow resistance for the brake fluid, and in the step of determining another operating point of the further proportional valve (USV2) using another Current flow at the electric motor (M) and the other valve position is determined. Method according to Claim 7 in which, in the step of operating, the electric motor (M) is operated at a speed corresponding to the speed in the first brake circuit (110), in the step of setting the further valve position is changed until a value of the further current flow reaches a previously detected value the current flow in the first brake circuit (110) corresponds, and in a step of determining a correction factor for the further proportional valve (USV2) is determined using the first valve position and the further valve position. Method for operating a proportional valve (USV) of a brake system (100), characterized in that in a readout step using a setpoint pressure value, an operating point of the proportional valve (UPS) is read from a characteristic map of the proportional valve (UPS), and in a step of Outputting a valve position setpoint for the proportional valve (UPS) using the operating point. Method according to Claim 9 wherein, in the readout step, the operating point is further read using a speed command value for an electric motor (M) driving a return pump (RP) of the brake system (100), further outputting the speed command value for the electric motor (M) in the step of outputting , Method according to one of Claims 9 and 10 in which, in the read-out step, a further operating point for another proportional valve (USV2) of the brake system (100) is read from a map of the further proportional valve (USV2) using a further pressure setpoint, wherein in the step of outputting using the further operating point further another valve position setpoint is output for the further proportional valve (USV2). Method according to one of Claims 9 and 10 in which, in the step of outputting using the operating point and a correction factor for another proportional valve (USV2) of the brake system, a further valve position setpoint for the further proportional valve (USV2) is further output. Computer program product adapted to perform the method according to any one of Claims 1 to 8th and / or 9 to 12 execute, implement and / or to control. Machine readable storage medium carrying the computer program product according to Claim 13 is stored.

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