Method for operating brake system of motor vehicle, control device, hydraulic brake system and motor vehicle

Abstract

The invention relates to a method for actuating a brake system of a motor vehicle, in which a hydraulic pressure in the brake system is monitored and, if a pressure loss is determined, an electric pressure generator is actuated in principle in order to increase the hydraulic pressure. The invention also relates to an associated control device, an associated hydraulic brake system and an associated motor vehicle.

Description

Technical Field

[0001] The present invention relates to a method, control device, hydraulic braking system for a motor vehicle, and a motor vehicle having the braking system. Background Technology

[0002] Braking systems are typically used to selectively decelerate motor vehicles. Many braking systems operate by establishing hydraulic pressure via a manually operated master brake cylinder and / or an electrically operated pressure generator, which is then used to generate braking pressure in the wheel brakes. Modern braking systems usually have devices for measuring the pressure within the hydraulic system. However, how to respond to any detectable pressure drops can be problematic. Summary of the Invention

[0003] Therefore, an object of the present invention is to provide a method for operating a braking system of a motor vehicle, which is implemented alternatively or more preferably than known embodiments, for example, exhibiting an improved response to detected pressure drops. Another object of the present invention is to provide a control device and a hydraulic braking system for performing the method. Furthermore, an object of the present invention is to provide a motor vehicle having this braking system.

[0004] According to the present invention, the above-mentioned objectives are achieved by the method, control device, hydraulic braking system, and motor vehicle according to the respective independent claims. Advantageous designs may be derived, for example, from the respective dependent claims. The content of the claims is expressly incorporated herein by reference.

[0005] This invention relates to a method for using a braking system for operating a motor vehicle. The motor vehicle typically has at least two axles, each axle having at least one wheel. The braking system has one or more brakes, each brake being correspondingly assigned to at least one wheel for applying braking torque. The braking system is hydraulic and has at least one electric pressure generator for establishing hydraulic pressure. Preferably, the motor vehicle, in addition to the aforementioned braking system, has another braking system that is preferably operable independently of the aforementioned braking system.

[0006] The method includes the following steps: - Monitor the hydraulic pressure in the braking system; and - In cases where pressure loss is confirmed, always operate the pressure generator to generate or increase hydraulic pressure.

[0007] This method allows for an advantageous response to determined pressure losses. It is recognized that, in the presence of an alternative braking system capable of operation independently of the main braking system, hydraulic pressure can, in principle, be generated or increased by a pressure generator. This is because even in situations where pressure losses are due to leakage, and the hydraulic braking system is expected to be depleted, the alternative braking system remains available and capable of braking the vehicle. Therefore, generating or increasing hydraulic pressure, in principle, does not result in a loss of safety. In particular, measures that ensure braking system functionality even in the event of leakage within the braking system can be eliminated.

[0008] This method is particularly applicable to braking systems, and more precisely, their control devices, where no response is made to pressure loss other than the one described above. In other words, the response to determining the presence of pressure loss is in response to the determination of the pressure loss. The two axles are typically a front axle and a rear axle. In principle, the front and / or rear of a motor vehicle may also have more than one axle, for example, two rear axles may be provided in vehicles such as trucks or buses. For multi-track motor vehicles, an axle typically has at least two wheels. It may be specified that only one wheel exists on each side of the motor vehicle. However, multiple wheels can also be provided on each side, such as in a dual-tire configuration. For single-track motor vehicles, each axle typically has only one wheel. This corresponds, for example, to a typical implementation of a motorcycle. However, hybrid forms are also possible, such as a three-wheeled motorcycle with only one wheel at the front and two wheels at the rear.

[0009] The brake can be implemented as a friction brake, such as a drum brake or a disc brake. If it is assigned to only one wheel, it brakes that wheel. If it is assigned to multiple wheels, such as the two wheels in a dual-tire configuration, it brakes all of them.

[0010] Hydraulic braking systems typically contain a certain volume of hydraulic fluid, such as brake fluid. This hydraulic fluid can be pressurized by a pressure generator. This pressure is typically used in the brake to generate braking force or braking torque. For this purpose, valves are usually provided that control the pressure buildup at the corresponding brake. The pressure generator is particularly electric, meaning that it can generate pressure without human intervention.

[0011] The other braking system can be operated independently of the braking system. This particularly ensures the vehicle's independent braking capability, so that preferably even if the braking system completely fails, the vehicle can still be braked by the other braking system.

[0012] Specifically, it can be specified that the aforementioned braking system and the other braking system can independently fulfill the braking requests of the driver and / or vehicle control system. The aforementioned braking system and the other braking system can be operated simultaneously and / or in combination to fulfill the driver's braking requests. Advantageously, if the other braking system is a hydraulic braking system, it has a hydraulic circuit completely decoupled from the aforementioned braking system. It can also be specified that the aforementioned braking system and the other braking system are powered by different on-board power supplies or can be powered by different on-board power supplies, thereby ensuring independent power supply. Other measures can also be designed to ensure independent operation capability. Specifically, it can be specified that the other braking system can thus be operated independently of the aforementioned braking system, i.e., the other braking system has no common components with the aforementioned braking system, and / or is connected to another on-board power supply, and / or is powered by an on-board power supply different from the aforementioned braking system. As an alternative to power supply from other on-board power supplies, it can also be specified that the aforementioned braking system and the other braking system are powered by the same two on-board power supplies, so that in the event of failure of one on-board power supply, both braking systems can still maintain normal operation.

[0013] Hydraulic pressure in the braking system can be monitored, for example, by one or more pressure sensors. This can be done continuously, for example, at certain time intervals. For example, this can determine if there is a pressure loss, i.e., the measured hydraulic pressure drops below a threshold and / or remains below a predetermined threshold for a predetermined shortest period of time. In this case, a response to the detected pressure loss is required. According to the invention, this response is always, in principle, by manipulating a pressure generator to generate or increase hydraulic pressure. "Generate" here is specifically understood to mean that the pressure generator does not generate hydraulic pressure before the hydraulic pressure is generated by manipulating the pressure generator. "Increase hydraulic pressure" here is specifically understood to mean that the pressure generator already generates hydraulic pressure before the manipulation described in this application, but increases it by this manipulation. The generated hydraulic pressure can then be further increased.

[0014] Specifically, the hydraulic braking system may be specified to have, in addition to an electric pressure generator, a manually and / or muscle-operated brake cylinder that also generates hydraulic pressure. This may include, for example, a master brake cylinder, such as a tandem master brake cylinder. The braking system may also include a simulator. Typically, the manually and / or muscle-operated brake cylinder and the simulator are isolated from the rest of the braking system via a release valve. During normal braking operation, the force generated in the master brake cylinder is usually applied to the simulator, where the release valve is closed. Braking requests are then made via the electric pressure generator and / or another braking system.

[0015] By generating or increasing hydraulic pressure using an electric pressure generator as described in this application, one can advantageously respond to situations where a pressure drop is caused by the formation of bubbles or other air bubbles in the hydraulic system, which must be compressed before pressure can be built up, thus hindering pressure establishment. This condition is often not immediately distinguishable from a pressure loss caused by leakage. In the embodiments described in this application, the principle response is to increase the pressure, thereby responding to the first mentioned cause, especially without requiring a sealing test. However, if the second mentioned cause, namely leakage, actually exists, this is not a safety risk in the embodiments described in this application because another braking system can be used for braking tasks.

[0016] Specifically, it can be specified that the pressure generator is operated to produce or increase hydraulic pressure immediately after a pressure loss is determined, or at a predetermined time after a pressure loss is determined. This ensures that the same response is always made to a determined pressure loss. Therefore, whether and when the pressure generator is operated is particularly independent of other parameters, such as test output. The predetermined time can be set in such a way that it is fixedly stored in the braking system, more precisely, the controller of the braking system. The operation of the pressure generator is performed specifically after the first identification of a pressure loss. Therefore, it is preferable not to wait until multiple pressure losses are identified.

[0017] Specifically, it can be specified that the pressure generator is operated independently of the sealing test to generate or increase hydraulic pressure. Therefore, once a pressure loss is determined, the same response is always made. In particular, a sealing test or similar test is not performed before operating the pressure generator. Practice has shown that this is unnecessary in the embodiments described in this application.

[0018] Specifically, it can be stipulated that the valve connecting the pressure generator and the brake shall not be closed when a pressure loss is determined, between the determination of a pressure loss and the operation of the pressure generator to generate or increase hydraulic pressure, and / or during the operation of the pressure generator to generate or increase hydraulic pressure. This prevents the brake from being disengaged, which would otherwise render the brake incapable of providing braking effect.

[0019] Specifically, when a pressure loss is determined, the pressure generator can always remain connected to at least one brake, or to some or all of the brakes, or establish a connection with the aforementioned brakes. This ensures direct braking action. Advantageously, it eliminates the need to disconnect the brakes and / or the pressure generator to prevent the braking system from being emptied due to leakage. If the pressure generator is already connected to the corresponding brake before a pressure loss is determined, it can remain connected. Otherwise, a connection can be established. This can be achieved, in particular, through appropriate switching of existing valves.

[0020] According to the implementation scheme, after a pressure loss is determined, the pressure generator is maintained connected to all brakes for at least the time the pressure generator is operated to generate or increase hydraulic pressure, or the connection is maintained until the braking system stops operating. According to the implementation scheme, after a pressure loss is determined, the pressure generator is maintained connected to at least one brake, or to some but not all brakes, for at least the time the pressure generator is operated to generate or increase hydraulic pressure, or the connection is maintained until the braking system stops operating. The valve can be switched in particular so that the pressure generator remains connected to the brake as described. Thus, the action of the pressure generator is applied to the brake. Advantageously, measures requiring fluid separation between the pressure generator and the brake, such as a sealing test, can be omitted. The braking system can be stopped, for example, when the vehicle is parked or turned off.

[0021] Specifically, when pressure loss is detected, the braking system can always remain in a mode where the hydraulic pressure is established entirely or partially by an electric pressure generator. Advantageously, this eliminates the need for measures to disconnect the pressure generator to prevent the braking system from emptying due to potential leaks. Existing valves can be switched accordingly.

[0022] Another braking system can be an electromechanical braking system. This advantageously combines the strengths of both hydraulic and electromechanical braking systems. In an electromechanical braking system, the electromechanical brake actuator typically acts directly on the corresponding brake, meaning that hydraulic intervention is generally unnecessary. Braking force can thus be generated directly through the electromechanical brake actuator.

[0023] According to one embodiment, the braking system may have brakes located only on one or more front axles of the vehicle. According to another embodiment, the braking system may have brakes located only on one or more rear axles of the vehicle. This concentrates the action of the braking system on a single axle. Therefore, instability in the vehicle due to different failure events in the braking system can be avoided.

[0024] The braking system may be designed to eliminate the need for brakes, particularly at at least one axle of the vehicle. This reduces costs. In this implementation, the braking system may be selectively used to brake one or more axles, but not all axles.

[0025] Another braking system may have one or more brakes at the axle of the motor vehicle, while the aforementioned braking system does not have brakes at the axle.

[0026] Another braking system may have brakes only at one or more axles of the vehicle, while the aforementioned braking system has no brakes at those axles. This allows for the allocation of the two braking systems such that each axle is either braked by the aforementioned braking system or by the other braking system.

[0027] According to one embodiment, each axle of the motor vehicle may have at least two or exactly two wheels. This corresponds to a typical embodiment of a multi-track motor vehicle. However, in principle, the embodiment described in this application can also be used for single-track motor vehicles. An embodiment with multiple wheels on each side of each axle is also feasible, which can be understood as a dual-tire configuration.

[0028] In particular, pressure loss can be determined based on the hydraulic pressure dropping below a predetermined threshold or a dynamic threshold. The predetermined threshold can be fixedly programmed, for example. For instance, the predetermined threshold can be designed to be changed only with considerable effort, such as using specialized programming equipment in a repair shop. The dynamic threshold can be changed, for example, based on driving conditions, environmental influences, or other parameters.

[0029] Specifically, it can be specified that a pressure loss is determined based on the hydraulic pressure remaining below a predetermined threshold or dynamic threshold for at least a predetermined period of time. This avoids triggering measures due to occasional short-term threshold drops, even if the event is unlikely to be caused by a malfunction.

[0030] The following describes feasible implementation schemes that can be carried out within the framework of the above-described method, but can also be carried out independently, and thus constitute separate aspects of the invention. Therefore, these implementation schemes and the specific implementation schemes mentioned can also be claimed independently of the above-described method features and other features.

[0031] It may be stipulated that when the braking system and / or the motor vehicle is deactivated, the following steps shall be performed: - Determine at least one value for the operating parameters of the braking system; - Determine whether the values ​​of the operating parameters are within the critical range; and – When the operating parameters are within a critical range, manipulate the pressure generator to increase the hydraulic pressure.

[0032] In this way, the formation of air bubbles within the hydraulic system can be particularly avoided. This method is especially useful when the braking system is not in use, such as when the vehicle is off. This can be demonstrated, for example, by an activated parking brake or a deactivated ignition. Operating parameters can be selected such that specific value ranges indicate an increased risk of air bubble formation. Such air bubbles can cause difficulty in pressure build-up, thus indicating a pressure loss. Especially when the vehicle is stationary, air bubble formation can be prevented by specifically increasing the hydraulic pressure using a pressure generator, and the braking system continues to operate normally.

[0033] Operating parameters can be, in particular, the temperature of components in the braking system. This temperature can be measured, for example, by a temperature sensor. Temperature can also be determined by a temperature model, which typically estimates the temperature based on one or more other parameters. For example, energy flow can be considered for this purpose. The temperatures of multiple components can also be considered, and / or other operating parameters can be used. These parameters can be evaluated collectively, for example, or each operating parameter can be evaluated individually. In the latter case, it can be specified, in particular, that each operating parameter can individually trigger the operation of the pressure generator.

[0034] This method may also include the following steps before, during, or after manipulating the pressure generator to increase hydraulic pressure: - Control one or more valves in the braking system so that the hydraulic pressure is locked in a part of the braking system.

[0035] This section can be a portion of the braking system, rather than the entire hydraulic system. For example, this section can be isolated from the rest of the hydraulic system by switching valves. This maintains pressure in that section and prevents pressure drops that might occur outside that section. Therefore, it also prevents bubble formation.

[0036] When operating one or more valves, at least one valve is particularly suitable for closing, isolating the master brake cylinder and / or simulator from the rest of the braking system. The master brake cylinder is typically a hydraulic pressure generator that can be manually and / or by muscle force. The simulator is typically a device that absorbs the pressure generated by the master brake cylinder during normal braking operation, thus providing the driver with a realistic braking feel, while the actual hydraulic pressure used in the brakes is applied by an electric pressure generator. Pressure drops within these components are prevented by isolating the master brake cylinder and / or the simulator, which can occur, for example, when the brake pedal is pushed outward or a spring within the simulator is compressed.

[0037] Especially when the operating parameters are within critical ranges, the controllable pressure generator can increase the hydraulic pressure by at least 5 bar and / or up to 15 bar. Such increased pressure values ​​have proven advantageous for typical applications because they effectively prevent unwanted bubble formation while avoiding component overload. However, other values ​​can also be used in principle. The pressure increase can be determined, in particular, relative to the pressure immediately before the pressure generator is operated to increase the pressure.

[0038] Especially when the operating parameters are within a critical range, the controllable pressure generator can increase the hydraulic pressure to a predetermined pressure range. Thus, regardless of the existing pressure, a specific pressure range can be set, or alternatively, only a single pressure value can be set, which advantageously prevents bubble formation.

[0039] Especially when the operating parameters are within a critical range, the controllable pressure generator can increase the hydraulic pressure above ambient pressure. Increasing the pressure above ambient pressure prevents bubble formation. Ambient pressure can be, in particular, the surrounding air pressure. This air pressure can be measured or implemented in the controller as a predetermined value. For example, an average pressure of one atmosphere or 1.013 mbar / mbar can be assumed here.

[0040] After determining that the operating parameters are within a critical range, and especially during the braking system and / or vehicle shutdown, the pressure generator can be operated again to increase the hydraulic pressure. This can be done in addition to the previously mentioned operations to increase the hydraulic pressure, and / or especially after the previous operation has ended and a certain period of time has elapsed. The pressure generator can be operated again at predetermined time intervals and / or when the hydraulic pressure drops below a predetermined activation threshold. Thus, the function described above, which prevents bubble formation by increasing pressure after the braking system or vehicle shutdown, can be performed not only once but multiple times.

[0041] According to one embodiment, it can be specified that the operating parameters are determined to be within a critical range only when the brake system's operating time counter reaches at least one predetermined value. According to another embodiment, it can be specified that the pressure generator is actuated to increase the hydraulic pressure only when the brake system's operating time counter reaches at least one predetermined value, based on the fact that the operating parameter value is within a critical range. This embodiment prevents the pressure from being increased to prevent bubble formation when the brake system's operating time is short and bubble formation is unlikely even with increased temperature. The operating time counter can be set to zero during vehicle production and / or reset to zero after brake fluid replacement. The operating time counter typically indicates the operating time of the brake system since the last reset. The operating time counter does not necessarily have to display the number of operating times itself; alternatively, it can display a value that can be converted into a number of operating times or otherwise indicates a number of operating times.

[0042] Preferably, the established pressure is reduced before the vehicle is restarted.

[0043] Specifically, it can be specified that when the value of an operating parameter is higher or lower than a predetermined critical threshold, the value of that operating parameter is determined to be within a critical range. The critical range can, for example, extend from the critical threshold to the corresponding endpoint of the numerical range. Alternatively, the numerical range can be defined more narrowly. For example, the critical threshold could be the boiling point of the hydraulic fluid. Thus, for example, when the temperature, which can be used as an operating parameter, exceeds the boiling point, evaporation of the hydraulic fluid can be prevented by increasing the pressure.

[0044] In particular, once the operating parameters fall outside the critical range again, the hydraulic pressure can be reduced and / or one or more valves in the braking system can be opened. Thus, when the risk of bubble formation is no longer present, the aforementioned measures to prevent bubble formation can be cancelled. This avoids overloading the components.

[0045] The present invention also relates to a control device for a braking system, particularly a hydraulic braking system, designed to implement the method described in this application. Reference can be made to all embodiments and variations described in this application regarding this method. In particular, the control device can be designed to always respond to pressure loss as mentioned above. In particular, it can be specified that no response other than that mentioned to pressure loss is made. In particular, it can be specified that no sealing test of the braking system is performed.

[0046] The present invention also relates to a non-volatile computer-readable storage medium having program code stored thereon, which, when executed, enables a processor to implement the methods described in this application. Reference can be made to all embodiments and variations described in this application regarding this method.

[0047] The present invention also relates to a hydraulic braking system for motor vehicles. This braking system includes one or more brakes, at least one electric pressure generator for generating hydraulic pressure to operate the brakes, and a control device designed to implement the method described in this application. Reference can be made to all embodiments and variations described in this application regarding this method. The advantages already mentioned are thus realized. In particular, all embodiments related to this method, including those involving device features, can be applied to braking systems.

[0048] The present invention also relates to motor vehicles having the braking system described in this application. Reference can be made to all embodiments and variations described in this application regarding this braking system. The advantages already described are thus realized.

[0049] Motor vehicles may have a separate braking system, which is preferably operable independently of the aforementioned braking system. This allows for the realization of the advantages already described, namely, a substantially identical response to identified pressure losses without adversely affecting the safety of the motor vehicle.

[0050] Another braking system can be an electromechanical braking system. However, in principle, a hydraulic braking system can also be used as another braking system.

[0051] In other words, when a vehicle's braking system, equipped with hydraulic or wheel brakes, is subjected to extreme temperature-related conditions, such as during prolonged downhill driving, the brake fluid can locally and rapidly heat up in the wheel brake area. If this exceeds the brake fluid's boiling point, vapor bubbles form. These vapor bubbles, as additional volume, must first be compressed by the brake pressure generator before pressure can be built up, allowing the brakes to generate clamping force and ultimately braking torque. This prolongs the pressure build-up time, and in extreme cases, the pressure generator may reach its volume limit, negatively impacting braking performance. This is known as the "pedal fall" due to brake overheating. Increased water content in the brake fluid lowers the boiling point and increases the likelihood of this malfunction. Therefore, for most motor vehicles, it is recommended to change the brake fluid every two years to prevent excessive water content.

[0052] In braking systems with hydraulic simulators (also known as brake-by-wire systems with hydraulic backup levels), a pressure generator draws new volume from the brake fluid reservoir during brake-by-wire operation, compressing vapor bubbles. However, this presents a conflicting system monitoring problem. When system pressure is insufficient, system pressure monitoring can disengage from brake-by-wire operation and switch to the hydraulic backup level, potentially leading to direct driver control. This is, for example, to prevent the pressure generator from failing to build up pressure in the event of a hydraulic leak, thus allowing for timely shutdown. On the other hand, volume monitoring is preferable to remain in brake-by-wire operation and compensate for insufficient volume, which is the correct strategy in the case of vapor bubbles. However, with significant additional volume / capacity, leaks and vapor bubbles are often indistinguishable, potentially leading to shutdown and, in the case of vapor bubbles, causing the pedal to slip. For example, in hybrid systems that operate electrohydraulically at the front axle and electromechanically at the rear axle, or vice versa, another strategy can be chosen: maintaining brake-by-wire operation in principle, regardless of whether it's due to additional volume / capacity during a leak or a potential vapor bubble formation failure. If the system malfunctions, only braking force is lost at one axle; the other axle can still brake because the vapor bubbles there will not jeopardize the system. This achieves effective vapor bubble compensation, and the system, at least in terms of safety, can eliminate the need for brake fluid replacement or extend the replacement interval, for example, from two years to six years.

[0053] However, boiling brake fluid not only produces water vapor bubbles but also bubbles through degassing, which cannot completely disappear after the liquid cools down. Therefore, after the extreme temperature condition of boiling fluid, although the immediate danger can be avoided, the braking system should be bled during subsequent maintenance to reduce residual air to below the monitoring threshold.

[0054] Since liquid overheating mostly occurs in the closed state after temperature limit conditions, especially in the so-called "heat soaking", the following method is proposed, which can be performed alone or in combination with other methods described in this application.

[0055] In the event of such extreme operation, where vapor bubbles may form in the closed state, the system can remain active in the closed state and supply low pressure (e.g., 10 bar) to the wheel brakes via a drive-by-wire pressure generator, then lock this state volumetrically by closing the master cut-off valve (MCV) or disconnect valve. Since pressure may vary due to cooling or reheating, the device remains active and maintains pressure within predetermined limits, particularly between upper and lower thresholds, such as 10 bar ± 5 bar. The threshold intervals are predetermined, particularly through the precision of the pressure setting. It is especially important to ensure that pressure above ambient pressure is always present. Compensation for minor valve leakage may also be necessary. This volumetric limitation prevents accidental expansion or formation of vapor bubbles. Once the temperature drops below the boiling point or other points, the device can reduce the braking pressure or restore connection to the atmosphere by opening the MCV. The MCV can be, in particular, a valve that isolates the master brake cylinder and / or simulator from the rest of the hydraulic system, also referred to as a disconnect valve. Temperature can be controlled, in particular, through a temperature model capable of determining cooling with sufficient precision. This can be supported by input data such as ambient temperature, input braking energy, and, if necessary, temperature measurements from force sensors and, in the case of, electromechanical brakes. As a result, for example, the vehicle may not require subsequent bleeding after the aforementioned operating conditions, because the measures described in this application prevent the formation of vapor bubbles in the closed state.

[0056] The measures described in this application are particularly applicable to brake systems controlled by wire, especially brake systems controlled by wire with simulators. Specifically, a hydraulic implementation can be provided at the front axle, and an electromechanical implementation at the rear axle. However, the reverse is also feasible. Other allocation methods are also possible.

[0057] The temperatures of each brake component, as well as the brake fluid temperature, can be modeled, in particular, by balancing the input braking energy, vehicle-specific cooling conditions, and measured temperatures (e.g., via sensors, force sensors, or motor temperatures). This allows for the identification and warning of brake fluid boiling that could lead to additional volume / additional volume. Specifically, it can be specified that drive-by-wire operation will continue under any circumstances, even if significant amounts of vapor bubbles are likely to occur.

[0058] In the off state, volume limitation can be achieved, in particular, by shutting down the MCV and / or actively replenishing the lost volume, especially through system pressure monitoring, to prevent vapor bubbles from forming in the quiescent state. The existing system pressure can be adjusted between two thresholds, with the lower threshold preferably higher than the ambient pressure. The control and cessation of volume limitation in the quiescent state can be performed, in particular, via a temperature model. The resulting advantages include, in particular, the ability to extend the interval between brake fluid changes. Vapor bubbles generated by temperature rise in the braking system no longer pose a typical hazard. Attached Figure Description

[0059] Other features and advantages will become apparent to those skilled in the art from the embodiments described below in conjunction with the accompanying drawings. Wherein: Figure 1 The braking system is shown; and Figure 2 A motor vehicle is shown. Detailed Implementation

[0060] Figure 1 A braking system BS according to an embodiment of the present invention is shown in a purely illustrative manner. The braking system BS has a master brake cylinder HBZ, which can be manually operated via the brake pedal BP. The braking system BS has a simulator S, which is connected to the master brake cylinder HBZ via a simulator valve SIV. As shown, both the master brake cylinder HBZ and the simulator valve SIV are connected to a release valve MCV. Opposite to the above two components, namely the master brake cylinder HBZ and the simulator S, a connecting valve ZV is connected to the release valve MCV, and the connecting valve ZV is connected to a pressure generator DE opposite to the release valve MCV. In this embodiment, the pressure generator DE is implemented as a linear actuator and is driven by an electric motor M. This enables discontinuous pressure generation. Alternatively, a piston pump, for example, can also be used, which is particularly capable of continuous delivery.

[0061] The braking system BS has a brake fluid reservoir BFB. This brake fluid reservoir BFB allows brake fluid to be supplied to the braking system BS in a pressureless manner. As shown in the figure, the brake fluid reservoir BFB is connected to the pressure generator DE via a check valve and is also connected to the master brake cylinder HBZ for drawing in brake fluid.

[0062] The braking system BS has a first brake B1 and a second brake B2. These two brakes act on the first wheel R1 and the second wheel R2, respectively. Brakes B1 and B2 are connected to the pressure generating components via a first inlet valve E1 and a second inlet valve E2. Furthermore, brakes B1 and B2 are also connected to the brake fluid reservoir BFB via a first drain valve A1 and a second drain valve A2. Thus, pressure can be selectively applied to brakes B1 and B2, and the pressure can also be reduced again via drain valves A1 and A2.

[0063] To measure hydraulic pressure, two pressure sensors, labeled U / p, are shown here. One pressure sensor, U / p, is connected to the master brake cylinder HBZ, and the other pressure sensor is connected to the opposite side of the release valve MCV, thereby enabling the pressure sensors to measure the pressure existing between the release valve MCV, the turn-on valve ZV, and the inlet valves E1 and E2.

[0064] The braking system BS has a control device SV. This control device is specifically designed to detect when the braking system BS or the vehicle containing it is turned off and parked. In this case, the control device calculates the temperature of the components of the braking system BS using a temperature model. If the temperature exceeds a critical threshold, which is specifically the boiling point of the brake fluid used, the pressure generator DE or its electric motor M is actuated to increase the pressure within the braking system to above atmospheric pressure, specifically to a value approximately 10 bar higher than the previously existing pressure. This state is maintained until the temperature model indicates that the temperature has dropped below the critical threshold. After pressure is generated, the release valve MCV closes, thereby locking the generated pressure. This prevents pressure loss due to yielding of components in the master brake cylinder HBZ or the simulator S. This measure prevents brake fluid evaporation and the formation of bubbles due to excessively high temperatures, such as those that may occur during prolonged downhill driving and subsequent immediate vehicle shutdown, which could adversely affect the function of the braking system BS.

[0065] Figure 2 A vehicle KF is shown in a purely illustrative manner, equipped with a braking system BS, wherein all components of the braking system BS are not shown. Here, the braking system BS acts on the front axle, with the first wheel R1 being the left front wheel and the second wheel R2 being the right front wheel. Furthermore, the vehicle KF also has another braking system WBS. This other braking system is controlled by another control device WSV, and in this embodiment, it is constructed as a purely electromechanical braking system. Therefore, the other braking system has no hydraulic components. The vehicle KF has a rear axle with a left rear wheel (the third wheel R3) and a right rear wheel (the fourth wheel R4). The third wheel R3 is braked by the third brake B3 of the other braking system WBS. The fourth wheel R4 is braked by the fourth brake B4 of the other braking system WBS. The braking systems BS and WBS can be operated completely independently and are implemented completely independently of each other. This ensures that if one of the two braking systems BS or WBS fails, the other braking system can still function normally.

[0066] The control device SV is configured to identify pressure loss within the braking system BS by means of at least one of two pressure sensors U / p. This is particularly effective when the measured pressure drops below a threshold. In this case, the control device SV, in principle, manipulates the pressure generator DE to increase the pressure. Here, Figure 2 Inlet valves E1 and E2 (not shown) are opened. This ensures that, in the event of pressure loss due to bubble formation, the bubbles are compressed, and pressure is built up for braking. While pressure loss could also be due to leakage, where increasing pressure and opening the valves could cause brake fluid to leak out, this has no critical impact on safety in this embodiment because the other braking system, WBS, is implemented completely independently and redundantly from the braking system BS, so the vehicle KF can always still brake through this other braking system, WBS.

[0067] The steps described above in the method according to the invention can be performed in the given order. However, these steps can also be performed in other orders, provided it is technically reasonable. The method according to the invention can be implemented in its embodiments, for example, in a specific combination of steps without performing other steps. However, other steps, including those not mentioned, can also be performed in principle.

[0068] It should be noted that some features may be described in combination in the claims and description (e.g., for ease of understanding), although these features may also be used individually. Those skilled in the art will recognize that these features may also be combined independently with other features or combinations thereof.

[0069] References in dependent claims may indicate preferred combinations of the corresponding features, but do not exclude other combinations of features.

[0070] List of reference numerals

[0071] BS braking system

[0072] DE pressure generator

[0073] M electric motor

[0074] BP brake pedal

[0075] HBZ master brake cylinder

[0076] BFB brake fluid container

[0077] SV control device

[0078] R wheel

[0079] B Brake

[0080] A discharge valve

[0081] E Inlet Valve

[0082] U / p pressure sensor

[0083] ZV Connecting Valve

[0084] MCV Separation Valve

[0085] SIV simulator valve

[0086] S simulator

[0087] WBS other braking system

[0088] Another control device for WSV

[0089] KF Motor Vehicle.

Claims

1. A method for operating a brake system (BS) of a motor vehicle (KF), wherein The motor vehicle (KF) has at least two axles, each axle having at least one wheel (R), wherein the braking system (BS) has one or more brakes (B) respectively assigned to at least one wheel (R) for applying braking torque, wherein the braking system (BS) is hydraulic, and has at least one electric pressure generator (DE) for establishing hydraulic pressure, wherein, in addition to having the braking system (BS), the motor vehicle (KF) also has another braking system (WBS) capable of being operated independently of the braking system, wherein the method includes the steps of: monitoring the hydraulic pressure in the braking system (BS); and, in the event of a determined pressure loss, always manipulating the pressure generator (DE) to generate or increase the hydraulic pressure.

2. The method of claim 1, wherein, The pressure generator (DE) is operated immediately after a pressure loss is detected, or after a predetermined time following the detection of a pressure loss, to generate or increase hydraulic pressure.

3. The method according to any of the preceding claims, characterized in that, The pressure generator (DE) is operated independently of the sealing test to generate or increase hydraulic pressure.

4. The method according to any of the preceding claims, characterized in that, When a pressure loss is determined, between the determination of a pressure loss and the operation of the pressure generator to generate or increase hydraulic pressure, and / or during the operation of the pressure generator to generate or increase hydraulic pressure, the valve fluidly connected between the pressure generator (DE) and the brake (B) shall not be closed.

5. The method according to any of the preceding claims, characterized in that, In cases where pressure loss is determined, the pressure generator (DE) is always kept connected to at least one brake (B), or to some or all of the brakes (B), or is connected to the brake.

6. The method according to any of the preceding claims, characterized in that, After a pressure loss is determined, the pressure generator (DE) is kept connected to all brakes (B) for at least as long as the pressure generator (DE) is operated to generate or increase hydraulic pressure, or the connection is kept until the braking system (BS) stops operating.

7. The method according to any one of claims 1 to 5, characterized in that, After a pressure loss is determined, the pressure generator (DE) is kept connected to at least one brake (B), or to some but not all of the brakes (B), for at least as long as the pressure generator (DE) is operated to generate or increase hydraulic pressure, or the connection is kept until the braking system (BS) stops operating.

8. The method according to any of the preceding claims, characterized in that, When pressure loss is detected, the braking system (BS) always remains in a mode in which hydraulic pressure is established, either entirely or partially, by the electric pressure generator (DE).

9. The method according to any of the preceding claims, characterized in that, The other braking system (WBS) is an electromechanical braking system.

10. The method according to any of the preceding claims, characterized in that, The braking system (BS) has only brakes (B) on one or more front axles of the motor vehicle (KF).

11. The method according to any one of claims 1 to 9, characterized in that, The braking system (BS) has only brakes (B) on one or more rear axles of the motor vehicle (KF).

12. The method according to any of the preceding claims, characterized in that, The braking system (BS) has no brakes (B) at at least one axle of the motor vehicle (KF).

13. The method according to any one of the preceding claims, characterized in that, The other braking system (WBS) has one or more brakes (B) at one axle of the vehicle (KF), while the braking system (BS) does not have brakes (B) at that axle.

14. The method according to any one of the preceding claims, characterized in that, The other braking system (WBS) has brakes (B) only at one or more axles of the vehicle (KF), while the braking system (BS) does not have brakes (B) at those one or more axles.

15. The method according to any one of the preceding claims, characterized in that, Each axle of the motor vehicle (KF) has at least two wheels (R).

16. The method according to any one of the preceding claims, characterized in that, Pressure loss is determined when the hydraulic pressure drops below a predetermined or dynamic threshold.

17. The method according to any one of the preceding claims, characterized in that, Pressure loss is determined when the hydraulic pressure remains below a predetermined or dynamic threshold for at least a predetermined period of time.

18. The method according to any one of the preceding claims, characterized in that, With the braking system (BS) and / or the vehicle (KF) off, the method further includes the following steps: - Determine at least one value of the operating parameter of the braking system (BS); - Determine whether the values ​​of the operating parameters are within a critical range; and - In response to the fact that the value of the operating parameter is within a critical range, the pressure generator (DE) is manipulated to increase the hydraulic pressure.

19. The method according to claim 18, characterized in that, The operating parameter is the temperature of the components of the braking system (BS).

20. The method according to claim 18 or 19, characterized in that, Before, during, or after manipulating the pressure generator (DE) to increase the hydraulic pressure, the method further includes the step of manipulating one or more valves of the braking system (BS) such that the hydraulic pressure is confined within a portion of the braking system (BS).

21. The method according to claim 20, characterized in that, When operating one or more valves, at least one valve (MCV) is closed, which isolates the master brake cylinder (HBZ) and / or simulator (S) from the rest of the braking system (BS).

22. The method according to any one of claims 18 to 21, characterized in that, When the values ​​of the operating parameters are within the critical range, the pressure generator (DE) is manipulated to increase the hydraulic pressure by at least 5 bar and / or up to 15 bar.

23. The method according to any one of claims 18 to 22, characterized in that, When the values ​​of the operating parameters are within the critical range, the pressure generator (DE) is manipulated to increase the hydraulic pressure to a predetermined pressure range.

24. The method according to any one of claims 18 to 23, characterized in that, When the values ​​of the operating parameters are within the critical range, the pressure generator (DE) is manipulated to increase the hydraulic pressure to above the ambient pressure.

25. The method according to any one of claims 18 to 24, characterized in that, When the braking system (BS) and / or the vehicle (KF) are off, after determining that the values ​​of the operating parameters are within a critical range, the pressure generator (DE) is operated again to increase the hydraulic pressure.

26. The method according to claim 25, characterized in that, The pressure generator (DE) is operated again at predetermined time intervals and / or when the hydraulic pressure drops below a predetermined activation threshold.

27. The method according to any one of claims 18 to 26, characterized in that, When the value of the operating parameter is higher or lower than a predetermined critical threshold, the value of the operating parameter is determined to be within the critical range.

28. The method according to any one of claims 18 to 27, characterized in that, After the operating parameters are once again outside the critical range, the hydraulic pressure is reduced again and / or one or more valves of the braking system (BS) are opened.

29. The method according to any one of claims 18 to 28, characterized in that, The operating parameter is determined to be within a critical range only when the operating time counter of the braking system (BS) reaches at least one predetermined value; and / or the pressure generator (DE) is manipulated to increase the hydraulic pressure only when the operating time counter of the braking system (BS) reaches at least one predetermined value, in response to the value of the operating parameter being within a critical range.

30. A control device (SV) for a braking system (BS), the control device being designed to implement the method according to any one of the preceding claims.

31. A hydraulic braking system (BS) for a motor vehicle (KF), the braking system having one or more brakes (B), at least one electrically operated pressure generator (DE) for generating hydraulic pressure to operate the brakes (B), and a control device (SV) designed to implement the method according to any one of claims 1 to 29.

32. A motor vehicle (KF) having a braking system (BS) according to claim 31.

33. The motor vehicle (KF) according to claim 32, wherein, The vehicle also has another braking system (WBS) that can be operated independently of the braking system (BS).

34. The motor vehicle (KF) according to claim 33, characterized in that, The other braking system (WBS) is an electromechanical braking system.

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