Method for reducing pressure peaks in a hydraulic braking system and braking system therefor

Abstract

The present invention relates to a method for reducing pressure peaks in a hydraulic braking system having an electric pressure application device (5), according to which a drive resistance variable of the pressure application device (5), in particular the torque, is measured, a speed variable of the pressure application device (5) is measured, a quotient (201) of the drive resistance variable and the speed variable is calculated, the quotient (201) thus determined is monitored for the occurrence of an abrupt change, and if an abrupt change is identified, the speed requirement of the pressure application device (5) is reduced and / or a hydraulic valve (6, 122) is controlled for pressure reduction.

Description

[Technical field]

[0001] The present invention relates to a method for reducing pressure peaks in a hydraulic brake system including an electromechanical pressurizing device. [Background technology]

[0002] In modern braking systems, in the case of braking interventions independent of the driver, the pressure actuation of the hydraulic system of the braking system is provided by an electric pressurizing device. In the case of what are known as brake-by-wire braking systems, the pressure actuation is provided by an electric pressurizing device, even in the case of braking interventions triggered by the driver. In many operating conditions, the pressurizing device operates at least briefly against closed valves and thus against a very stiff system. This is the case, for example, when the inlet valves of the wheel brakes suddenly close while the pressurizing device is actively volumetrically delivering. As a result, the mass moment of inertia of the pressurizing device can cause pressure peaks at the level of several hundred bars within a few milliseconds, which have a negative effect on the service life of the hydraulic components.

[0003] In order to avoid such pressure peaks, it is known to evaluate the data of the system pressure sensors and to intervene in wheel pressure regulation in the event of excessively high pressures. Brake systems must usually have a high degree of redundancy, so that multiple control units are often used that communicate with each other via interfaces in order to ensure reliable braking of the vehicle even in the event of failure of some systems. However, such communication involves a large time delay, so that any regulating action taken may be too late to reliably prevent the occurrence of pressure peaks. Summary of the Invention [Problem to be solved by the invention]

[0004] It is therefore an object of the present invention to specify a method by which the occurrence of pressure peaks can be prevented even in highly redundant brake systems. [Means for solving the problem]

[0005] This object is achieved by a method for reducing pressure peaks in a hydraulic brake system including an electric pressure application device according to claim 1. A drive resistance variable of the pressure application device, in particular the torque, is measured and a speed variable of the pressure application device is measured. A quotient is calculated from these two measured values, the drive resistance variable and the speed variable. It has been shown that the two measured values ​​lose their validity in the opposite direction in the event of an abrupt change, the effect of which is amplified by the formation of the quotient according to the invention. If the quotient thus determined is monitored for the occurrence of an abrupt change, the abrupt change is particularly clearly indicated, in particular in the initial phase. If an abrupt change is identified, the speed requirement of the pressure application device is reduced and / or a hydraulic valve for dissipation of pressure is activated. As a result, the pressure peak is already efficiently suppressed at the outset.

[0006] In one preferred embodiment of the invention, the pressure application device is configured as a linear actuator. It is a pressure application device that can be hydraulically connected to the wheel brakes and has a pressure piston that can be moved in a pressure chamber with the aid of a motor to provide a system pressure for actively increasing the pressure of the wheel brakes. Here, the motor is typically connected to the piston via a rotary / translatory gear mechanism. As a speed variable, the rotational speed of the motor can be measured. For this purpose, for example, a rotor position sensor of the pressure application device can be utilized. The acting torque can be determined, for example, from the power consumption of the motor or can be measured by a sensor provided for this purpose.

[0007] In a further preferred embodiment of the invention, an abrupt change is detected if the absolute value of the calculated quotient exceeds a first threshold value. This type of evaluation can be performed in a particularly simple manner and is particularly advantageous when the measurements are relatively inaccurate or very noisy.

[0008] In one particularly preferred embodiment of the invention, the first threshold value is between 1 mNm / rpm and 2 mNm / rpm, preferably 1.5 mNm / rpm, where the speed variable is selected as the rotational speed, measured in revolutions per minute (rpm), and the torque is given in millinewton meters (mNm).

[0009] In a further preferred embodiment of the present invention, a temporal profile of the quotient is stored, and an abrupt change is detected if the gradient of the calculated quotient of the stored profile exceeds a second threshold. The gradient monitoring can be used as an alternative to or in addition to the absolute value monitoring. To improve the accuracy of the method, the calculated quotient can be smoothed. For this purpose, for example, a temporal averaging can be performed.

[0010] In one particularly preferred embodiment of the invention, the second threshold value is between 0.1 Nm / rpm*sec and 0.3 Nm / rpm*sec, in particular 0.15 Nm / rpm*sec.

[0011] In a further preferred embodiment of the invention, a time profile of the quotient is stored and an abrupt change is detected if the curvature of the calculated quotient of the stored profile exceeds a third threshold. Thus, a second derivative of the quotient with respect to time is formed and monitored. This type of monitoring allows reliable detection of abrupt changes and thus pressure peaks, which are expected especially in the early stages, especially if the measured values ​​are precisely well smoothed.

[0012] In a further preferred embodiment of the invention, the hydraulic valve is actuated to be at least partially open, in this way allowing hydraulic volume or brake fluid to flow through the hydraulic valve, so that pressure peaks are minimized.

[0013] In a further preferred embodiment of the invention, the actuation of the hydraulic valve is carried out by the same control unit which also regulates the pressurizing device. In particular, the system pressure sensor of the brake system is located in a different control unit, and not in the same control unit as the controller of the hydraulic valve and the pressurizing device. In this way, latencies due to communication between different control units are avoided and the monitoring can react particularly quickly.

[0014] In a further preferred embodiment of the invention, the hydraulic valve is arranged between the pressurizing device and the non-pressurized brake fluid reservoir or pressure medium storage container, in particular directly between these components, in this way allowing a particularly rapid dissipation of pressure as soon as an occurring pressure peak is detected.

[0015] In a further preferred embodiment of the invention, the hydraulic valve comprises at least one inlet valve of a wheel brake of the braking system. Here, the inlet valve is not simply opened, but the control current of the inlet valve is reduced. The inlet valve is a normally open valve for redundancy reasons, i.e. the inlet valve is supplied with a current to close and keep it in a closed position. The pressure difference between the high pressure on the side facing the pressurizing device and the low pressure on the side facing the wheel brake tries to push the valve open. The closing current counteracts this force and keeps the valve in a closed position. However, depending on the closing current set, there is a hydraulic pressure at which the inlet valve can no longer be kept sealed and the hydraulic volume can pass through. The closing current of the inlet valve is therefore reduced to a value which still keeps the hydraulic valve closed during normal operation, but allows the hydraulic volume to pass at pressure values ​​corresponding to pressure peaks (100-300 bar).

[0016] Furthermore, the object is achieved by a braking system for a motor vehicle arranged to carry out one of the above methods.

[0017] Further features, advantages and possible applications of the invention emerge from the following description of exemplary embodiments and from the drawings, in which: All the features described and / or shown, individually and in any combination, belong to the subject matter of the invention, independently of their abstraction in the claims or their references. [Brief description of the drawings]

[0018] [Figure 1] 1 illustrates diagrammatically a braking system according to a first embodiment of the invention; [Diagram 2] 2 shows a schematic of the electronic structure of the brake system of FIG. 1; [Diagram 3] 2 shows diagrammatically a braking system according to a second embodiment of the invention; [Figure 4] 4 illustrates an exemplary measurement of a quotient in accordance with the present invention. [Diagram 5] 5 shows the average of the derivatives of the exemplary measurements of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The braking system for a motor vehicle shown in Fig. 1 comprises four hydraulically actuable wheel brakes 8a-8d. The braking system comprises a brake master cylinder 2, which can be actuated by an actuation or brake pedal 1, a movement simulator or simulation device 3 interacting with the brake master cylinder 2, a pressure medium storage vessel 4 under atmospheric pressure, an electrically controllable pressurizing device 5, and wheel-specific brake pressure regulating valves configured according to the example as inlet valves 6a-6d and outlet valves 7a-7d. Furthermore, the braking system comprises an electronic control and regulating system 12 comprising a plurality of control units for actuating the electrically actuable components of the braking system.

[0020] By way of example, wheel brake 8a is assigned to the front left wheel (FL), wheel brake 8b is assigned to the front right wheel (FR), wheel brake 8c is assigned to the rear left wheel (RL) and wheel brake 8d is assigned to the rear right wheel (RR).

[0021] The brake master cylinder 2 comprises a brake master cylinder piston 15 within a housing 16 which defines a fluid pressure chamber 17, forming a single circuit brake master cylinder. The pressure chamber 17 contains a restoring spring 9 which places the piston 15 in a starting position when the brake master cylinder 2 is not actuated.

[0022] The pressure chamber 17 is firstly connected to the pressure medium reservoir 4 via a radial bore configured in the piston 15 and a corresponding pressure equalization line 41, which can be interrupted by a relative movement of the piston 17 in the housing 16. Secondly, the pressure chamber 17 is connected by a hydraulic line section (also called the first feed line) 22 to the brake supply line 13, to which the inlet ports of the inlet valves 6a-6d are connected. Thus, the pressure chamber 17 of the brake master cylinder 2 is connected to all the inlet valves 6a-6d.

[0023] In this embodiment, no valves, in particular electrically or hydraulically operable valves and no check valves, are arranged in the pressure equalization line 41 or in the connection between the pressure chamber 17 and the pressure medium storage container 4.

[0024] Alternatively, a diagnostic valve (in particular normally open) can be included in the pressure equalization line 41 or between the brake master cylinder 2 and the pressure medium reservoir 4, preferably in a parallel connection of the normally open diagnostic valve with a check valve closing against the pressure medium reservoir 4.

[0025] An isolation valve 23 is arranged between the feed line 22 connected to the pressure chamber 17 and the brake supply line 13, or the pressure chamber 17 is connected to the brake supply line 13 via a first feed line 22 having the isolation valve 23. The isolation valve 23 is configured as an electrically actuatable, preferably normally open, 2 / 2-way valve. The isolation valve 23 makes it possible to cut off the hydraulic connection between the pressure chamber 17 and the brake supply line 13.

[0026] A piston rod 24 couples the pivotal movement of the brake pedal 1 as a result of pedal actuation to a translational movement of the brake master cylinder piston 15, the actuation movement of which is detected by a preferably redundant displacement sensor 25. The corresponding piston movement signal is then indicative of the brake pedal actuation angle, which represents the vehicle driver's braking demand.

[0027] A pressure sensor 20 connected to the first feed line 22 detects the pressure built up in the pressure chamber 17 as a result of the displacement of the piston 15. This pressure value can likewise be evaluated to characterize or determine the braking request of the vehicle driver. As an alternative to the pressure sensor 20, a force sensor 20 can also be used to determine the braking request of the vehicle driver.

[0028] According to an example, the simulation device 3 is of hydraulic construction and is hydraulically coupled to the brake master cylinder 2. The simulation device 3, for example, substantially comprises a simulator chamber 29, a simulator rear chamber 30 and a simulator piston 31 separating the two chambers 29, 30 from one another. The simulator piston 31 is supported on the housing via an elastic element 33 (for example a simulator spring) arranged in the simulator rear chamber 30 (dry according to an example). According to an example, the hydraulic simulator chamber 29 is connected to the pressure chamber 17 of the brake master cylinder 2 by a preferably electrically actuable, preferably normally closed, simulator enable valve 32.

[0029] For each hydraulically actuable wheel brake 8a-8d the braking system or brake system comprises an inlet valve 6a-6d and an outlet valve 7a-7d which are hydraulically connected in pairs to each other via a central port and to the wheel brake 8a-8d. A non-return valve (not shown in detail) opening into the brake supply line 13 is connected in parallel to the inlet valve 6a-6d in each case. The outlet ports of the outlet valves 7a-7d are connected to the pressure medium reservoir 4 via a common return line 14.

[0030] The electrically controllable pressure-providing device 5 is configured as a hydraulic cylinder / piston arrangement (or single-circuit electrohydraulic actuator (linear actuator)) whose piston 36 can be actuated by a diagrammatically illustrated electric motor 35, with a also diagrammatically illustrated rotary / translatory gear mechanism 39 connected between the piston 36 and the electric motor 35. The piston 36 defines a single pressure space 37 of the pressure-providing device 5. A rotor position sensor, only diagrammatically illustrated, serving to detect the rotor position of the electric motor 35 is indicated by the reference number 44. This can be used to evaluate the current rotation speed.

[0031] A line section (also called second feed line) 38 is connected to a pressure space 37 of the electrically controllable pressure providing device 5. The feed line 38 is connected to the brake supply line 13 via an electrically actuatable, preferably normally closed, sequence valve 26. The sequence valve 26 allows for opening and closing in a controlled manner the fluid pressure connection between the pressure space 37 of the electrically controllable pressure providing device 5 and the brake supply line 13 (and thus the inlet ports of the inlet valves 6a-6d).

[0032] The actuator pressure generated by the action of the force of the piston 36 on the pressure medium contained in the pressure space 37 is fed to a second feed line 38. In the "brake-by-wire" actuation type, in particular in an undisturbed condition of the brake system, the feed line 38 is connected to the brake supply line 13 via the sequence valve 26. In this way, during normal braking, the forward and rearward movements of the piston 36 result in a build-up of wheel brake pressure and a dissipation of pressure in all wheel brakes 8a-8d.

[0033] In the event of dissipation of pressure by rearward movement of the piston 36, the pressure medium displaced forward from the pressure space 37 of the pressure-applying device 5 into the wheel brakes 8a-8d likewise flows back into the pressure space 37.

[0034] Alternatively, different wheel brake pressures can be set in a simple wheel-specific manner by means of the inlet valves 6a-6d and the outlet valves 7a-7d. In the event of corresponding pressure dissipation, the portion of the pressure medium discharged via the outlet valves 7a-7d flows via the return line 14 into the pressure medium reservoir 4.

[0035] Refilling of the pressure space 37 with pressure medium is possible by retraction of the piston 36 when the sequence valve 26 is closed, whereby pressure medium can flow out of the container 4 via the line 42 into the actuator pressure space or into the pressure space 37, with the non-return valve 53 open in the direction of flow to the actuator 5. According to an example, the pressure space 37 is further connected to the pressure medium reservoir 4 via one or more leak holes in the non-actuated state of the piston 36. This connection between the pressure space 37 and the pressure medium reservoir 4 is disconnected when the piston 36 is (fully) actuated in the actuation direction 27.

[0036] An electrically actuable, normally open circuit isolation valve 40 is arranged in the brake supply line 13, by means of which the brake supply line 13 can be separated into a first line section 13a connected to the brake master cylinder 2 (via the isolation valve 23) and a second line section 13b connected to the pressure providing device 5 (via the sequence valve 26). The first line section 13a is connected to the inlet valves 6a, 6b of the wheel brakes 8a, 8b and the second line section 13b is connected to the inlet valves 6c, 6d of the wheel brakes 8c, 8d.

[0037] With the circuit isolation valve 40 open, the brake system is of single-circuit design. By closing the circuit isolation valve 40, the brake system, which is controlled in a manner suitable for the particular situation, can be separated or divided into two brake circuits I and II, where in the first brake circuit I the brake master cylinder 2 is connected (via the isolation valve 23) only to the inlet valves 6a, 6b of the wheel brakes 8a, 8b of the front axle VA, and in the second brake circuit II the pressure application device 5 is connected (with the sequence valve 26 open) only to the wheel brakes 8c and 8d of the rear axle HA.

[0038] When the isolation valve 40 is open, in a first type of operation (e.g., a "brake-by-wire" type of operation), the inlet ports of all inlet valves 6a-6d may be supplied by the brake supply line 13 with a pressure corresponding to the brake pressure provided by the pressure providing device 5. In a second type of operation (e.g., a no-current fallback type of operation), the brake supply line 13 may be subjected to the pressure of the pressure chamber 17 of the brake master cylinder 2.

[0039] The braking system advantageously comprises a level measuring device 50 for determining the pressure medium level in the pressure medium storage vessel 4. Awareness of the circuit isolation by the circuit isolation valve 40 is advantageously achieved via the level measuring device 50.

[0040] According to an example, the hydraulic components, i.e. the brake master cylinder 2, the simulation device 3, the pressure providing device 5, the valves 6a-6d, 7a-7d, 23, 26, 40 and 32 and the hydraulic connections including the brake supply line 13 are arranged together in a (single) hydraulic control and regulating unit 60 (HCU). The hydraulic control and regulating unit 60 is assigned to an electronic control and regulating system (ECU) 12 with a number of control units. The hydraulic and electronic control and regulating units 60, 12 are preferably configured as one unit (HECU).

[0041] The braking system includes a pressure sensor 19 or a system pressure sensor for detecting the pressure provided by the pressure providing device 5. Here, the pressure sensor 19 is disposed downstream of the sequence valve 26 when viewed from the pressure chamber 37 of the pressure providing device 5.

[0042] FIG. 2 shows the control system 12 of the brake system of FIG. 1. The control system 12 comprises two separate control units 45, 46, each designed to control and regulate a part area of ​​the brake system. The motor control unit, as the controller from which it takes its name, comprises a motor controller 47, which regulates a motor 49 of a pressurizing device. The valve control device 46, in addition to the valve controller from which it takes its name 48, comprises electronics for reading a system pressure sensor 50. The two control units can communicate with each other via an interface. If regulating operations are to be carried out that depend on the data of the pressure sensor 50 in order to avoid pressure peaks, a communication must take place between the two control units 46 and 47 in order to carry out the intervention of the motor controller 47. This type of communication introduces delays, so that the pressure peaks cannot be prevented sufficiently quickly. According to the invention, the method can therefore be carried out only in the motor control unit 45.

[0043] 3 shows a brake system in a further preferred embodiment. The brake system comprises three modules 70, 72, 74, each with a separate control and regulation unit 80, 82, 84. The module 70 comprises a brake master cylinder 2 configured as a tandem brake master cylinder with a primary chamber 90 and a secondary chamber 92, and a simulator or simulation device 3. By means of a simulator enable valve 32, the primary chamber 90 can be connected in by-wire mode to the simulator chamber 29. The two chambers 90, 92 of the brake master cylinder can be hydraulically connected to a pressure medium storage container 4a. A partition 100 in this container ensures that even if in any case one of the two brake circuits I, II connected to the chambers 90, 92 leaks, the other brake circuit still has pressure medium available. The control and regulation unit 80 of the module 80 is responsible for substantially controlling the valve 32.

[0044] The braking system comprises driver brake demand detection means, including a pedal movement sensor 25 and a pressure sensor 20 for measuring the pressure in the brake master cylinder. A second module 72 with a control and regulating unit 82 comprises a pressure providing device 5 and two sequence valves 26a, 26b, via which the pressure space 37 of the pressure providing device 5 can be hydraulically connected to the wheel brakes. Furthermore, the second module 72 comprises one rotor position sensor 44 and a pressure sensor 20 for measuring the pressure in the primary chamber 90. The two chambers 90, 92 can be hydraulically isolated from the wheel brakes by means of isolation valves 23a, 23b in brake-by-wire mode, so that the driver can move brake fluid from the primary chamber 90 to the simulator chamber 29 when the simulator enable valve 22 is open.

[0045] The pressure chamber 37 is hydraulically connected to a pressure medium reservoir 4b from which it can be replenished with braking medium, the return flow of pressure medium from the pressure chamber 37 to the reservoir 4b being prevented by a check valve 120.

[0046] When the isolation valves 23a, 23b are closed during by-wire operation, hydraulically isolating the brake master cylinder 2 from the wheel brakes 8a-8d, excess brake capacity can be conveyed via line 124 and an opening in the drain valve 122 to the reservoir 4b.

[0047] An intermediate wall 130 is provided in the pressure medium storage vessel 4b, which defines two separate chambers when the filling level falls below the height of the intermediate wall 130. The control and regulating unit 82 is responsible for actuating the pressure providing device 5 and the valves 26a, 26b, 23a, 23b, 122.

[0048] A third module 74 with a control and regulating unit 84 comprises the inlet valves 6a-6d and the outlet valves 7a-7d assigned to the wheel brakes. In each case a pump 140, 142 is provided in each brake circuit, which can be hydraulically connected to a pressure providing device via a pump sequence valve 160, 162 in the intake path in each case.

[0049] The pressure that can be raised by each pump 140, 142 can in each case be set by means of an overflow valve 150, 153. If a pump 140, 142 delivers too much and the pressure rises, this valve 150, 152 is pushed open and the pressure in the pump space can still be regulated by this valve 150, 152 and its flow.

[0050] Furthermore, low-pressure accumulators 164, 166 are provided in each case for each of the two brake circuits. The outflow of pressure medium from the delivery circuits of the pumps 140, 142 in the direction of the outlet valves 7a-7d is prevented in each case by means of non-return valves 168, 170. The control and regulating unit 84 is responsible for actuating the pumps 140, 142 and the valves 67a-67d, 7a-7d, 160, 162, 150, 152. Furthermore, the module 74 includes a system pressure sensor 19.

[0051] The two pressure medium reservoirs 4 a, 4 b are hydraulically connected to a common pressure medium reservoir 4 .

[0052] In this braking system, the pressure providing device 5 serves to provide the system pressure, and the pumps 140 , 142 are used, among other things, to regulate the operation and assist the pressure build-up by the pressure providing device 5 .

[0053] The three control and regulating units 80, 82, 84 are connected to one another on the signal side, in particular via a CAN bus.

[0054] The method according to the invention can therefore advantageously be implemented in a second control unit 82, which regulates the linear actuator 5 and therefore contains in particular the data of the rotor position sensor 44. If the ECU2 82 identifies an abrupt change in the torque-rotational speed quotient, it can in particular open the exhaust valve 122, which is controlled on the same printed circuit board, and thus react very quickly to the occurrence of a pressure peak.

[0055] Figure 4 shows as an example the quotient of the measured torque and rotational speed of a linear actuator. During normal operation (forward range of measurement) the value of the quotient fluctuates by approximately 0.5 mNm / rpm. As soon as the inlet valve is suddenly closed, the value of the quotient also rises sharply and exceeds the first threshold value of 1.5 mNm / rpm. The system then assumes a pressure peak and initiates corresponding measures.

[0056] Figure 5 shows the evaluation of the slope 203 of the quotient. The data was calculated by differentiation of the quotient of Figure 4 and time averaged. In normal operation, the value fluctuates below the second threshold 204. As soon as the inlet valve is closed, the slope increases sharply and exceeds the second threshold 204, and corresponding measures are initiated.

[0057] The method according to the invention therefore makes it possible to ensure reliable avoidance of pressure peaks even in the case of redundant braking systems in which the controller is divided into several control units, and thus to extend the service life of hydraulic components. The present invention may also include the following aspects: 1. A method for reducing pressure peaks in a hydraulic brake system including an electric pressurizing device (5), comprising measuring a drive resistance variable of said pressurizing device (5), in particular the torque, measuring a speed variable of said pressurizing device (5), calculating a quotient (201) of said drive resistance variable and said speed variable, said quotient (201) thus determined being monitored for the occurrence of an abrupt change, and in case of an abrupt change being identified, the speed requirement of said pressurizing device (5) is reduced and / or a hydraulic valve (6, 122) for dissipating pressure is activated. A method comprising: 2. The method according to claim 1, wherein the pressure device (5) is configured as a linear actuator. 3. The method according to claim 1 or 2, characterized in that an abrupt change is detected if the absolute value of the calculated quotient (201) exceeds a first threshold value (202). 4. The method according to claim 3, wherein the first threshold (202) is between 1 mNm / rpm and 2 mNm / rpm. 5. A method according to any one of 1. to 4. above, characterized in that a temporal profile of the quotient (201) is stored and an abrupt change is detected when the gradient (203) of the calculated quotient (201) of the stored profile exceeds a second threshold (204). 6. The method described in 5. above, wherein the second threshold (204) is 0.1 Nm / rpm*sec to 0.3 Nm / rpm*sec. 7. A method according to any one of 1. to 6. above, characterized in that a temporal profile of the quotient (201) is stored and an abrupt change is detected when the curvature of the calculated quotient (201) of the stored profile exceeds a third threshold. 8. The method according to any one of 1. to 7. above, wherein the hydraulic valve (122) is actuated to at least partially open. 9. The method according to any one of claims 1 to 7, characterized in that the actuation of the hydraulic valve (122) is carried out by the same control unit that also regulates the pressurizing device. 10. The method according to any one of claims 1 to 9, characterized in that the hydraulic valve (122) is disposed between the pressurizing device (5) and a non-pressurized brake fluid reservoir (4). 11. A method according to any one of claims 1 to 10, characterized in that the hydraulic valve includes at least one inlet valve (6) of a wheel brake (8) of the braking system, and the control current of the inlet valve (6) is reduced. 12. A braking system for an automobile, configured to carry out any one of the methods described in 1. to 11. above. [Explanation of symbols]

[0058] 1 Brake pedal 2 Brake master cylinder 3. Simulation Device 4 Pressure medium storage vessel 5. Pressure Device 6a~d Inlet valve 7a~d Outlet valve 8a~d Wheel brakes 9. Return spring 12 Control System 13 Brake supply line 14 Return line 16 Housing 17 Pressure Chamber 19 System Pressure Sensor 20 Master cylinder pressure sensor 22 First Feed Line 23 Isolation valve 24 Piston rod 25 Displacement Sensor 26 Sequence valve 29 Simulator Chamber 30 Simulator rear chamber 31 Simulator piston 32 Simulator enable valve 33 Elastic Elements 35 Piston 36 Electric motor 37 Pressure Space 38 Feed Line 39 Rotational / translational gear mechanism 40 Circuit isolation valve 41 Pressure Equalization Line 42 Line 44 Rotor Position Sensor 45 Motor Control Unit 46 Valve Control Unit 47 Motor Controller 48 Valve Controller 49 Motor 50 System Pressure Sensor Module 70 First Module 72 Second Module 74 Third Module 80 First control unit 82 Second control unit 84 Third Control Unit 90 Primary Chamber 92 Secondary Chamber 120 Check valve 122 Exhaust valve 124 lines 130 Intermediate Wall 140 First Pump 142 Second Pump 150 First overflow valve 152 Second overflow valve 160 First pump sequence valve 162 Second pump sequence valve 164 First low pressure accumulator 166 Second low pressure accumulator 168 First check valve 170 Second check valve 201 Torque / speed quotient 202 First Threshold 203 Differentiation of a Quotient 204 Second Threshold

Claims

1. In a method for reducing pressure peaks in a hydraulic brake system including an electric pressurizing device (5), a drive resistance variable, in particular the torque, of said electric pressurizing device (5) is measured, a speed variable of said electric pressurizing device (5) is measured, a quotient (201) of said drive resistance variable and said speed variable is calculated, said quotient (201) thus determined is monitored for the occurrence of an abrupt change, and if an abrupt change is identified, the speed requirement of said electric pressurizing device (5) is reduced and / or a hydraulic valve (6, 122) for pressure dissipation is activated. A method comprising:

2. 2. The method according to claim 1, characterized in that the electric pressure device (5) is configured as a linear actuator.

3. 3. The method according to claim 1 or 2, characterized in that an abrupt change is detected if the absolute value of the calculated quotient (201) exceeds a first threshold (202).

4. The method of claim 3, characterized in that the first threshold (202) is between 1 mNm / rpm and 2 mNm / rpm.

5. The method according to any one of claims 1 to 4, characterized in that a temporal profile of the quotient (201) is stored and an abrupt change is detected when a gradient (203) of the calculated quotient (201) of the stored profile exceeds a second threshold (204).

6. The method of claim 5, wherein the second threshold (204) is between 0.1 Nm / rpm*sec and 0.3 Nm / rpm*sec.

7. The method according to any one of claims 1 to 6, characterized in that a temporal profile of the quotient (201) is stored and an abrupt change is detected if a curvature of the calculated quotient (201) of the stored profile exceeds a third threshold.

8. The method according to any one of the preceding claims, characterized in that the hydraulic valve (122) is actuated to at least partially open.

9. Method according to any one of the preceding claims, characterized in that the actuation of the hydraulic valve (122) is performed by the same control unit which also regulates the electric pressurizing device (5).

10. The method according to any one of the preceding claims, characterized in that the hydraulic valve (122) is arranged between the electric pressurizing device (5) and a non-pressurized brake fluid reservoir (4).

11. The method according to any one of the preceding claims, characterized in that the hydraulic valve comprises at least one inlet valve (6) of a wheel brake (8) of the hydraulic braking system, and the control current of the inlet valve (6) is reduced.

12. A braking system for a motor vehicle, characterized in that it is adapted to carry out the method according to any one of the preceding claims.

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