Method for protecting brake fluid

Abstract

The invention relates to a method for controlling a brake system in the event of a leak, the brake system having a main brake cylinder (2) which can be operated mechanically, which is connected to a first sub-reservoir (10) of a brake fluid reservoir (4), the brake system having an electrically operated linear actuator (5) which is connected to a second sub-reservoir (11) of the brake fluid reservoir (4), wherein the main brake cylinder (2) and the linear actuator (5) are connected to one another via an electrically closable circuit isolation valve (40). In order to protect the brake fluid, in the event of a leak, the linear actuator (5) is actuated in order to take up a brake fluid volume from the first sub-reservoir (10) via the open circuit isolation valve (40) and to move it into the second sub-reservoir (11) when switching to a stand-by state.

Description

[0001] The present invention relates to a method for controlling a braking system in the event of a leak, the braking system having a mechanically operable master brake cylinder connected to a first sub-storage of a brake fluid reservoir; the braking system having an electrically operated linear actuator connected to a second sub-storage of the brake fluid reservoir, wherein the master brake cylinder and the linear actuator are connected to each other via an electrically closable circuit isolation valve.

[0002] When initializing such a braking system, such as when unlocking the vehicle or when the driver approaches the vehicle, the brake fluid reservoir level is typically checked. If the level is below a threshold, a leak is considered to exist in the braking system.

[0003] In the event of an external leak, the braking system is degraded, and circuit isolation is implemented. To do this, the single-circuit line control system is isolated into a dual-circuit system by energizing the circuit isolation valve. This dual-circuit system consists of a driver circuit with a master brake cylinder and a plunger circuit with a linear actuator.

[0004] In the event of a power outage, particularly in standby / stop mode when the vehicle is off, the braking system remains a single-circuit system because the circuit isolation valve must be energized for circuit disconnection. Therefore, in the event of a leak in the direction of one of the four wheels, a loss of brake fluid volume occurs in the first sub-chamber connected to the master brake cylinder.

[0005] To minimize brake fluid loss, the completed circuit disconnection is typically maintained for an extended operating period, such as 48 hours, with the ignition device off and the circuit valve energized. Furthermore, after being awakened from standby mode and a plunger circuit leak is detected, the first sub-chamber is refilled with brake fluid from the second sub-chamber.

[0006] However, both functions are limited. The extended operating period is time-limited. It must switch to a single-loop braking system no later than the end of the extended operating period, thus resulting in a loss of volume in the first sub-chamber. The duration of the extended operating period depends on the battery charge level. The extended operating period also does not completely eliminate the possibility of volume loss in the first sub-chamber. Gravity pressure creates leakage flow via the closed loop isolation valve, which can cause the sub-chamber to empty. Refilling the first sub-chamber reduces the braking fluid volume in the second sub-chamber by a corresponding amount. Therefore, refilling is limited.

[0007] Therefore, the object of the present invention is to improve the readiness / preparedness of the braking system in the event of a leak.

[0008] This objective is achieved by the method according to the invention as described in claim 1, wherein, in the event of a leak, the linear actuator is operated to retrieve the brake fluid volume from the first sub-memory via an open circuit isolation valve and move the brake fluid volume to the second sub-memory when transitioning to a standby state. Thus, brake fluid leakage is prevented even in standby mode when the valve is not energized.

[0009] In a preferred embodiment of the invention, when a leak is detected, the braking system is separated into two sub-circuit via a closed circuit isolation valve. The first sub-circuit includes at least a master brake cylinder along with a first sub-reservoir and two first wheel brakes along with associated inlet and outlet valves. The second sub-circuit includes at least a linear actuator along with a second sub-reservoir and two second wheel brakes along with associated inlet and outlet valves. Thus, for example in standby mode, particularly before the circuit separation is cancelled, movement of brake fluid volume from the first sub-reservoir to the second sub-reservoir can be performed.

[0010] In a preferred embodiment of the invention, in the event of a leak in the second sub-circuit, only the movement of brake fluid volume from the first sub-chamber to the second sub-chamber is performed. Specifically, the method can also be implemented precisely when at least one wheel brake in the second sub-circuit has a leak while at least one wheel brake does not.

[0011] In a preferred embodiment of the invention, when transitioning to a standby state, the circuit is disconnected for a predetermined period of time, wherein at the end of the predetermined period of time, the brake fluid volume in the first sub-chamber is moved to the second sub-chamber. This allows for the protection of the brake fluid even when the battery's state of charge is low.

[0012] In a preferred embodiment of the invention, the braking system is designed such that, in the power-off state, the first sub-chamber is connected to the wheel brake. An advantage of this braking system is that it can also operate purely hydraulically in the absence of electricity.

[0013] In a preferred embodiment of the invention, the brake fluid volume is continuously moved from the first sub-reservoir to the second sub-reservoir until the first sub-reservoir is emptied. This can be monitored and controlled by a level sensor in the first sub-chamber, or the brake fluid volume can be continuously moved until it can be assumed to be emptied given the existing size conditions of each container.

[0014] In a preferred embodiment of the invention, to move the brake fluid volume from the linear actuator to the second sub-reservoir, the circuit isolation valve is closed, the inlet valve of the leaking wheel brake is closed, the inlet and outlet valves of the leak-free wheel brake are opened, and the linear actuator is operated in the direction of pressure build-up. Therefore, the brake fluid volume is delivered to the brake fluid reservoir via the wheels without leakage. To determine which wheel brake is leaking, for example, the linear actuator can be individually and sequentially connected to these wheel brakes in a flow-open manner, and hydraulic pressure can be built up through the linear actuator. In doing so, the distance required to build up pressure in each case is checked, thereby identifying whether the corresponding wheel brake is leaking. Thus, the wheel brake where the leak is located is identified.

[0015] In a preferred embodiment of the invention, in order to remove the brake fluid volume from the first sub-chamber and deliver it into the linear actuator, a flow-open connection is established between the linear actuator and the first sub-chamber, and the linear actuator is operated in the direction of decreasing pressure. Therefore, the brake fluid is extracted from the first sub-chamber.

[0016] In a preferred embodiment of the invention, the flow-open connection is established via the master brake cylinder and / or via the inlet and outlet valves of at least one wheel brake. Here, suction is preferably performed via the master brake cylinder, as this prevents the brake fluid from being circumvented through the inlet and outlet valves. Such circumventing poses a risk of contamination.

[0017] In a preferred embodiment of the invention, when the brake fluid volume is removed from the first sub-chamber, the linear actuator is operated such that the resulting vacuum level remains numerically below a threshold.

[0018] In a preferred embodiment of the invention, the linear actuator is connected to the second sub-chamber via a check valve (45) that opens under a check differential pressure, the threshold of which is less than twice the check differential pressure. This prevents the linear actuator from being primarily drawn out of the second sub-chamber. This threshold is preferably less than 150% of the check differential pressure, and particularly preferably less than 100% of the check differential pressure.

[0019] This objective is also achieved by a braking system for a motor vehicle, comprising a mechanically operable master brake cylinder and an electrically operated linear actuator. The master brake cylinder is connected to a first sub-storage of a brake fluid reservoir, and the linear actuator is connected to a second sub-storage of the brake fluid reservoir. The master brake cylinder and the linear actuator are connected to each other via an electrically closable circuit isolation valve, wherein the control unit of the braking system is designed to perform one of the aforementioned methods.

[0020] Other features, advantages, and possible applications of the invention can also be found in the following description of exemplary embodiments and the accompanying drawings. All features described and / or illustrated are individually and in any combination, and independently of their summary in the claims or their reverse reference, and are part of the subject matter of the invention.

[0021] Figure 1 The braking system according to the present invention is illustrated schematically.

[0022] Figure 2 A graph showing the braking fluid volume in the first sub-chamber is provided.

[0023] Figure 3 A graph showing the braking fluid volume in the second sub-chamber is provided.

[0024] Figure 4 A graph showing the braking fluid volume in the first sub-chamber is provided.

[0025] Figure 5 A graph showing the braking fluid volume in the second sub-chamber is provided.

[0026] Figure 6 A flowchart illustrating method steps according to the present invention is shown.

[0027] Figure 1 The braking system shown for a motor vehicle includes four hydraulically operable wheel brakes 8a-8d. The braking system includes: a master brake cylinder 2, operable by means of an operating pedal or brake pedal 1; a stroke simulator or simulation device 3, which interacts with the master brake cylinder 2; a pressure medium reservoir 4, which is at atmospheric pressure; an electrically controllable pressure application device 5; and wheel-specific brake pressure modulation valves, which, according to the example, are configured as inlet valves 6a-6d and outlet valves 7a-7d. Furthermore, the braking system includes an electronic control adjustment unit 12 for controlling the electrically operable components of the braking system. The electronic control adjustment unit may also consist of multiple independent control devices.

[0028] According to this example, wheel brake 8a is assigned to the left front wheel (FL), wheel brake 8b is assigned to the right front wheel (FR), wheel brake 8c is assigned to the left rear wheel (RL), and wheel brake 8d is assigned to the right rear wheel (RR).

[0029] The master brake cylinder 2 has a master brake cylinder piston 15 within the housing 16 that defines a hydraulic pressure chamber 17, and constitutes a single-circuit master brake cylinder. The pressure chamber 17 receives a return spring 9, which positions the piston 15 in its initial position when the master brake cylinder 2 is not actuated. At one end, the pressure chamber 17 is connected to a pressure medium reservoir 4 via a radial hole formed in the piston 15 and a corresponding pressure balance line 41, wherein this connection can be closed by relative movement of the piston 17 within the housing 16. At the other end, the pressure chamber 17 is connected to the brake supply line 13 via a hydraulic line section (also referred to as the first supply line) 22, to which the input connections of the inlet valves 6a-6d are connected. The pressure chamber 17 of the master brake cylinder 2 is thus connected to all inlet valves 6a-6d.

[0030] According to the example, no valve is arranged in the pressure balance line 41 or in the connection between the pressure chamber 17 and the pressure medium tank 4, in particular no electrically or hydraulically actuated valve is arranged and no check valve is arranged.

[0031] Alternatively, a normally open diagnostic valve may be included in the pressure balance line 41 or between the master brake cylinder 2 and the pressure medium reservoir 4, preferably a parallel line of a normally open diagnostic valve and a check valve that closes toward the pressure medium reservoir 4.

[0032] An isolation valve 23 is arranged between the supply 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 supply line 22 having the isolation valve 23. The isolation valve 23 is designed to be an electrically operable, preferably normally open (SO-), two-position two-way valve. The hydraulic connection between the pressure chamber 17 and the brake supply line 13 can be closed by the isolation valve 23.

[0033] The piston rod 24 couples the pivoting motion of the brake pedal 1 caused by pedal actuation to the translational motion of the master brake cylinder piston 15, the actuation stroke of which is detected by a preferably redundant stroke sensor 25. In this way, the corresponding piston stroke signal is a measurement of the brake pedal actuation angle, representing the braking demand of the vehicle driver.

[0034] A pressure sensor 20 connected to the first supply line 22 detects the pressure built up in the pressure chamber 17 due to the displacement of the piston 15. This pressure value can also be evaluated to characterize or determine the braking demand of the vehicle driver. Alternatively, a force sensor 20 can be used to determine the braking demand of the vehicle driver.

[0035] According to this example, the simulation device 3 has a hydraulic configuration and is hydraulically connected to the master brake cylinder 2. The simulation device 3 mainly includes, for example, a simulator chamber 29, a simulator rear chamber 30, and a simulator piston 31 that separates the two chambers 29 and 30 from each other. The simulator piston 31 is supported on the housing by an elastic element 33 (e.g., a simulator spring), which is arranged in the simulator rear chamber 30 (which is dry according to this example). According to this example, the hydraulic simulator chamber 29 is connected to the pressure chamber 17 of the master brake cylinder 2 by means of a preferably electrically operable, preferably normally closed simulator activation valve 32.

[0036] The braking system or braking device includes inlet valves 6a-6d and outlet valves 7a-7d for each hydraulically actuated wheel brake 8a-8d. The inlet and outlet valves are hydraulically interconnected in pairs and connected to the wheel brakes 8a-8d via a central connection. Each of the inlet valves 6a-6d is connected in parallel with a check valve (not specifically designated in the drawings) that opens toward the brake supply line 13. The output connection of the outlet valves 7a-7d is connected to the pressure medium reservoir 4 via a common return line 14.

[0037] The electrically controllable pressure supply device 5 is designed as a hydraulic cylinder-piston assembly (or a single-loop electro-hydraulic actuator (linear actuator)), the piston 36 of which can be operated by an electric motor 35, schematically indicated, with a similarly schematically shown rotary-translational mechanism 39 connected intermediately. The piston 36 defines a single pressure chamber 37 of the pressure supply device 5. A rotor position sensor, schematically indicated only, for detecting the rotor position of the electric motor 35, is indicated by reference numeral 44.

[0038] Line section 38 (also referred to as the second supply line) is connected to the pressure chamber 37 of the electrically controlled pressure supply device 5. Supply line 38 is connected to the brake supply line 13 via an electrically operable, normally closed sequence valve 26. Sequence valve 26 allows the hydraulic connection between the pressure chamber 37 of the electrically controlled pressure supply device 5 and the brake supply line 13 (and thus the input connections to inlet valves 6a-6d) to be opened and closed in a controlled manner. Actuator pressure generated by the force of piston 36 on the pressure medium enclosed in pressure chamber 37 is supplied to the second supply line 38. In brake-by-wire mode, particularly in a fault-free state of the braking system, supply line 38 is connected to the brake supply line 13 via sequence valve 26. In this way, during normal braking, the forward and backward movement of piston 36 establishes and reduces wheel braking pressure for all wheel brakes 8a-8d.

[0039] As the pressure is reduced by the rearward movement of the piston 36, the pressure medium that was previously moved from the pressure chamber 37 of the pressure supply device 5 to the wheel brakes 8a-8d flows back into the pressure chamber 37 in the same manner.

[0040] Alternatively, different wheel braking pressures specific to each wheel can be easily set using inlet valves 6a-6d and outlet valves 7a-7d. When the corresponding pressure decreases, a portion of the pressure medium discharged via outlet valves 7a-7d flows into the pressure medium reservoir 4 via return line 14. With sequence valve 26 closed and piston 36 moving backward, additional pressure medium can be drawn into pressure chamber 37 by allowing the pressure medium to flow from reservoir 4 into actuator pressure chamber 37 via line 42 having check valve 45 (which opens in the direction of actuator 5). Check valve 45 typically opens from a differential pressure of approximately 0.08 bar.

[0041] According to the example, when the piston 36 is not actuated, the pressure chamber 37 is also connected to the pressure medium reservoir 4 via one or more compensation holes. When the piston 36 is (fully) actuated in the actuation direction, this connection between the pressure chamber 37 and the pressure medium reservoir 4 is broken.

[0042] In the brake supply line 13, an electrically operable normally open circuit isolation valve 40 is arranged. The brake supply line 13 can be separated into a first line section 13a and a second line section 13b by means of this isolation valve. The first line section (via isolation valve 23) is connected to the master brake cylinder 2, and the second line section (via sequence valve 26) is connected to the pressure supply device 5. The first line section 13a is connected to the inlet valves 6a and 6b of the wheel brakes 8a and 8b, and the second line section 13b is connected to the inlet valves 6c and 6d of the wheel brakes 8c and 8d.

[0043] With the circuit isolation valve 40 open, the braking system is a single-circuit design. By closing the circuit isolation valve 40, the braking system can be separated or divided into two braking circuits (sub-circuits) I and II, depending on the situation. Here, in the first braking circuit I, the master brake cylinder 2 (via the isolation valve 23) is connected only to the inlet valves 6a and 6b of the wheel brakes 8a and 8b of the front axle VA, and in the second braking circuit II, the pressure supply device 5 (with the sequence valve 26 open) is connected only to the wheel brakes 8c and 8d of the rear axle HA.

[0044] With the circuit isolation valve 40 open, pressure can be supplied to the input connections of all inlet valves 6a-6d via the brake supply line 13. This pressure corresponds to the brake pressure provided by the pressure supply device 5 in the first operating mode (e.g., "brake-by-wire" operating mode). In the second operating mode (e.g., in the power-off backup operating mode), the pressure in the pressure chamber 17 of the master brake cylinder 2 can be applied to the brake supply line 13.

[0045] The braking system advantageously includes a level measuring device 50 for determining the pressure medium level / fill level in the pressure medium reservoir 4. The pressure medium reservoir 4 has a first sub-chamber 10 and a second sub-chamber 11, which are separated from each other by a partition. The first sub-chamber 10 supplies brake fluid to the main brake cylinder 2 via a pressure balancing line 41. On the other hand, the second chamber 11 supplies brake fluid to the linear actuator 5 via a pressure balancing line 42 and a check valve 120.

[0046] According to this example, the hydraulic components (i.e., the master brake cylinder 2, the simulation device 3, the pressure supply device 5, valves 6a-6d, 7a-7d, 23, 26, 40 and 32, and the hydraulic connection including the brake supply line 13) are arranged together in the hydraulic control unit 60 (HCU). An electronic control unit (ECU) 12 is assigned to the hydraulic control unit 60. The hydraulic control unit 60 and the electronic control unit 12 are preferably configured as a single unit (HECU).

[0047] The braking system includes a pressure sensor 19 or a system pressure sensor for detecting the pressure supplied by the pressure supply device 5. Here, viewed from the pressure chamber 37 of the pressure supply device 5, the pressure sensor 19 is located downstream of the sequence valve 26.

[0048] If a pressure drop occurs over a relatively long period of time, or if multiple successive pressure drops occur, at the outlet valves 7a to 7d of the wheel brakes 8a to 8d, the piston 36 of the linear actuator 5 moves forward successively until the piston reaches its foremost position, from which point it can no longer provide additional volumetric flow. At the latest at this point, the linear actuator must be refilled by means of a refilling device.

[0049] For this refilling of the linear actuator 5, the sequence valve 26 closes, and then the piston 36 moves backward. Therefore, brake fluid is drawn from the chamber 4 via the check valve 45.

[0050] When initializing the braking system, such as when unlocking the vehicle, the level measuring device 50 checks whether the brake fluid level is sufficient. If the brake fluid level is sufficient, the braking system starts in normal operating mode. If the brake fluid level is below a threshold, the single-circuit braking system is switched to a dual-circuit braking system by closing the circuit isolation valve 40. This effectively protects the sub-circuit from leakage.

[0051] In addition, a leak check is typically performed to locate leaks. For this purpose, the linear actuator 5 is sequentially connected to each wheel brake 8 via a sequence valve 26 and an open inlet valve 6, the outlet valves 7 of which are closed. The remaining inlet valves 6 are also closed. Here, pressure is built up by means of the linear actuator 5, and the required stroke is controlled. If the stroke is abnormally high or the pressure cannot be maintained, the braking system assumes a leak in the corresponding wheel.

[0052] When the braking system enters standby mode after the vehicle has come to a stop, all valves typically move to their de-energized positions. Since the circuit isolation valve 40 is configured as a normally open valve, circuit disconnection disappears in standby mode. To prevent this, circuit disconnection could be maintained for a specific period during the so-called operating period in standby mode. However, due to the limited energy reserves of the vehicle battery, the extended operating period is also limited.

[0053] Figures 2 to 5 The time curves of the volumes of the first sub-chamber 10 and the second sub-chamber 11 are shown when the vehicle repeatedly runs in loop separation for one hour and then stops in standby mode for 23 hours.

[0054] Figure 2 and Figure 3 A method known from the prior art is shown. A leak is detected at the rear axle wheel brake 8d, and active circuit separation is implemented by closing the circuit isolation valve 40. Additionally, the sequence valve 26 is closed, and the linear actuator 5 is deactivated. Accordingly, the braking system applies braking force through the driver's muscle strength and the master brake cylinders 2 on wheel brakes 8a and 8b. Figure 2 As shown, the filling liquid level of the first sub-chamber 10 is initially slightly below 20 cm. 3 This corresponds to the filling of the first sub-chamber 10. Due to leakage, some brake fluid volume is slowly lost during operation via the closed loop isolation valve 40, because the loop isolation valve is not fully closed. Protected by the closed sequence valve 26, the volume of the second sub-reservoir 11 remains constant, as it can be drawn from... Figure 3As seen in the graph. When the vehicle is turned off, the braking system enters a power-off standby mode, resulting in the cancellation of circuit disconnection. Therefore, there is a direct flow-open connection between the leakage part of the rear wheel brake 8d and the first sub-chamber 10 via the master brake cylinder 2. The first sub-chamber 10 becomes empty. This can be seen in the graph. Figure 2 The graph shows that the volume of the first sub-chamber 10 rapidly drops to zero. During subsequent vehicle operation, the braking system is reinitialized and the emptied first sub-chamber 10 is detected. To enable braking, brake fluid is pumped from the second sub-chamber 11 into the first sub-chamber 10. This can be achieved... Figure 2 and Figure 3 As seen in the figures, these diagrams illustrate how the volume of the second sub-chamber decreases precisely to the point where the volume of the first sub-chamber 10 rises again. These steps are repeated during each subsequent initialization of the braking system, resulting in a successive decrease in the volume of the second sub-chamber. During the fourth initialization, the remaining brake fluid volume in the second sub-chamber 11 is no longer sufficient to completely fill the first sub-chamber 10. Therefore, safe braking operation is no longer possible.

[0055] Then, Figure 4 and Figure 5 A corresponding graph is shown for the method according to the present invention, which is in... Figure 6 The steps are shown one by one.

[0056] In step 101, a leak is detected in wheel brake 8d, and it is simultaneously determined that wheel brake 8c has no leak. During the transition to standby mode, the volume of the first sub-chamber 10 is moved to the second sub-chamber 11. For this purpose, in step 102, sequence valve 26 is opened and circuit isolation valve 40 is closed. The inlet valve 6d and outlet valve 7d of the leaking wheel are closed, while the inlet valve 6c and outlet valve 7c of the non-leaking wheel are open. In step 103, the linear actuator 5 then moves to its front end position, resulting in the brake fluid volume contained therein being moved to the second sub-chamber 11 via the inlet valve 6c and outlet valve 7c of the non-leaking wheel.

[0057] In step 104, loop isolation valve 40 and isolation valve 23 are opened. All inlet valves 6 are closed. In step 105, the linear actuator is then operated back to its rear position at a significantly reduced speed of 30 to 40 rpm. The resulting slight vacuum of approximately 0.1 bar allows only a small amount of brake fluid to be drawn out via check valve 45 and exit the second sub-chamber 11. The linear actuator 5 draws brake fluid from the first sub-chamber 10 through the open sequence valve 26, loop isolation valve 40, isolation valve 23, and through the master brake cylinder 2.

[0058] Figure 4 picture Figure 2Correspondingly, it is shown that at the end of the activation hour, the volume of the first sub-chamber 10 drops sharply, but this volume is not lost due to leakage; instead, it is supplied to the second sub-chamber 11, which... Figure 5 As can be seen, the brake fluid volume is protected from leakage by the closed sequence valve 26. During subsequent initialization of the braking system, the first sub-chamber 10 is refilled from the second sub-chamber 11.

[0059] The steps of drawing brake fluid from the first sub-chamber 10 and moving it to the second sub-chamber 11 are repeated in step 106 for a predetermined number of cycles, such as three cycles. Alternatively, a sensor may be placed in the first sub-chamber 10, and the brake fluid may be continuously moved until the sensor indicates that the first sub-chamber 10 has been emptied.

[0060] This invention avoids the loss of brake fluid in standby mode, thereby ensuring that the braking system can operate for a long time.

[0061] List of reference numerals in the attached diagram:

[0062] 1. Brake pedal

[0063] 2. Main brake cylinder

[0064] 3. Simulation device

[0065] 4. Pressure Medium Storage Tank

[0066] 5. Pressure application device

[0067] 6a to d inlet valves

[0068] 7a to d outlet valves

[0069] Wheel brakes from 8a to d

[0070] 9. Return spring

[0071] 10 First subchamber

[0072] 11 Second sub-chamber

[0073] 12 Control System

[0074] 13 Brake supply lines

[0075] 14 Return line

[0076] 16. Shell

[0077] 17 Pressure Chamber

[0078] 19 System pressure sensor

[0079] 20 Master cylinder pressure sensor

[0080] 22 First Supply Pipeline

[0081] 23 Isolation Valve

[0082] 24 Piston Rod

[0083] 25 Stroke Sensors

[0084] 26 Sequence valve

[0085] 29 Simulator Chambers

[0086] 30 Simulator Rear Chamber

[0087] 31 Simulator Pistons

[0088] 32 Simulator Enable Valve

[0089] 33 Elastic elements

[0090] 35 Piston

[0091] 36 Electric motors

[0092] 37 Pressure Chamber

[0093] 38 Supply lines

[0094] 39 Rotation-translation mechanism

[0095] 40-loop isolation valve

[0096] 41 Pressure Balance Circuit

[0097] 42 pipelines

[0098] 44 Rotor position sensor

[0099] 45 Check valve

[0100] 50. Braking fluid volume in the first sub-chamber

[0101] 51. Braking fluid volume in the second sub-chamber

[0102] 52. Braking fluid volume in the first sub-chamber

[0103] 53. The volume of braking fluid in the second sub-chamber.

Claims

1. A method for controlling a braking system in the event of a leak, the braking system having a mechanically operable master brake cylinder (2) connected to a first sub-chamber (10) of a brake fluid reservoir (4); the braking system having an electrically operated linear actuator (5) connected to a second sub-chamber (11) of the brake fluid reservoir (4), wherein, The main brake cylinder (2) and the linear actuator (5) are connected to each other via a circuit isolation valve (40) that can be closed electrically. The linear actuator (5) is operated to remove the brake fluid volume from the first sub-chamber (10) and move the brake fluid volume to the second sub-chamber (11) via the open circuit isolation valve (40) when switching to a standby state in the event of a leak.

2. The method as described in claim 1, characterized in that, When a leak is detected, the braking system is separated into two sub-circuits (I, II) by closing the circuit isolation valve (40). The first sub-circuit (I) includes at least the master brake cylinder (2) together with the first sub-chamber (10) and two first wheel brakes (8a, 8b) together with the associated inlet valves (6a, 6b) and outlet valves (7a, 7b). The second sub-circuit (II) includes at least the linear actuator (5) together with the second sub-chamber (11) and two second wheel brakes (8c, 8d) together with the associated inlet valves (6c, 6d) and outlet valves (7c, 7d).

3. The method as described in claim 2, characterized in that, If a leak is present only in the second sub-circuit (II), a braking fluid volume movement is performed from the first sub-chamber (10) to the second sub-chamber (11).

4. The method as described in any one of the preceding claims, characterized in that, When switching to standby mode, the circuit is disconnected for a predetermined period of time, wherein at the end of the predetermined period of time, the braking fluid volume of the first sub-chamber (10) is moved into the second sub-chamber (11).

5. The method as described in any one of the preceding claims, characterized in that, The braking system is designed such that, in the power-off state, the first sub-chamber (10) is connected to the wheel brake.

6. The method as described in any one of the preceding claims, characterized in that, The brake fluid volume is continuously moved from the first sub-chamber (10) to the second sub-chamber (11) until the first sub-chamber (10) is emptied.

7. The method as described in any one of the preceding claims, characterized in that, In order to move the brake fluid volume from the linear actuator (5) into the second sub-chamber (11), the circuit isolation valve (40) is closed, the inlet valve (6d) of the wheel brake (8d) with leakage is closed, the inlet valve (6c) and outlet valve (7c) of the wheel brake (8c) without leakage are opened, and the linear actuator (5) is run in the direction of pressure building.

8. The method as described in any one of the preceding claims, characterized in that, In order to extract the braking fluid volume from the first sub-chamber (10) and send it into the linear actuator (5), a flow-open connection is established between the linear actuator (5) and the first sub-chamber (10), and the linear actuator (5) is operated in the direction of decreasing pressure.

9. The method as described in claim 8, characterized in that, The flow-open connection is established via the master brake cylinder and / or via the inlet and outlet valves of at least one wheel brake.

10. The method as described in any one of the preceding claims, characterized in that, When the braking fluid volume is removed from the first sub-chamber (10), the linear actuator (5) is operated so that the resulting vacuum level remains numerically below the threshold.

11. The method as described in claim 10, characterized in that, The linear actuator (5) is connected to the second sub-chamber (11) via a check valve (45) that opens under a check differential pressure, the threshold of which is less than twice the check differential pressure.

12. A braking system for a motor vehicle, comprising a mechanically operable master brake cylinder (2) and an electrically operated linear actuator (5), the master brake cylinder being connected to a first sub-chamber (10) of a brake fluid reservoir (4); the linear actuator being connected to a second sub-chamber (11) of the brake fluid reservoir (4), the master brake cylinder (2) and the linear actuator (5) being connected to each other via an electrically closable circuit isolation valve (40), characterized in that, The control unit (12) of the braking system is designed to perform the method as described in any one of claims 1 to 11.

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