Method for checking hydraulic backup layer availability, control device and power brake apparatus

Abstract

The invention relates to a method for detecting the availability of a hydraulic backup layer in an electronically slip-controllable assisted brake system, an electronic control device and an electronically slip-controllable assisted brake system. The assisted brake system (10) performs the braking process in normal operation without the driver participating in brake pressure formation. The braking request is detected by the electronic control device (24) and assigned to a brake pressure which is then set by electrical actuation of the drive (22) of a primary pressure generator (20). The assisted brake system (10) is equipped with electrically actuable secondary pressure generators (30) multiple times, for example in order to brake pressure to be matched to the slip conditions present on the wheels individually for each wheel. The secondary pressure generators are in contact with the wheel brakes (16) in parallel to the primary pressure generator (20) and can be used to assume brake pressure formation in the hydraulic backup layer. It is proposed for safety reasons to check the availability of the hydraulic backup layer at defined time intervals during normal operation of the assisted brake system (10).

Description

Technical Field

[0001] This invention relates to a method for detecting the availability of a hydraulic reserve layer in an electronically adjustable power-assisted braking device, as described in claim 1. Furthermore, the invention relates to an electronic control device for an electronically adjustable power-assisted braking device, as described in claim 8, and an electronically adjustable power-assisted braking device having an electronic control device, as described in claim 9. Background Technology

[0002] This invention is based on electronically adjustable power-assisted braking devices known in the prior art. For example, reference is made to the disclosure of document DE 10 2018 222 488 A1.

[0003] Known power-assisted braking devices include service brakes, which are operated with assistance, and auxiliary brakes, which are operated by muscle force. The service brake allows braking under normal conditions without driver intervention in brake pressure formation. Braking requirements are predetermined or identified by the driver or vehicle sensors and communicated to the electronic control unit. This control unit calculates the necessary braking pressure and accordingly drives the actuator of the pressure generator. The auxiliary brake exists so that, in the event of service brake failure, the driver can brake the vehicle by muscle force.

[0004] Known power-assisted braking devices consist of multiple components. These components are, for example, constructed separately from each other and in hydraulic contact. This is due to the confined space within a vehicle and the possibility of arranging the components in different locations with this dispersed structure. The first component is configured to detect the driver's predetermined braking desire. For this purpose, the first component is equipped with the aforementioned brake operating element and a primary or first pressure generator for generating the required braking pressure. The primary pressure generator has an electrically controllable actuator, whose control is achieved through an electronic control device.

[0005] The second component is used to individually match the adjusted braking pressure to a wheel-specific slip condition under normal conditions, which currently exists on the wheel's brakes. For this purpose, the second component is equipped with an electrically controlled, actuated secondary or second pressure generator and additionally with an electrically controlled valve mechanism. This valve mechanism includes multiple switchable check valves.

[0006] The two components are hydraulically and in parallel contact with the wheel brakes of the motor vehicle.

[0007] Known power-assisted braking devices can operate in different operating modes. In the first operating mode (normal operation), the braking pressure is provided by the primary or first pressure generator as described above and is individually adjusted by the secondary or second pressure generator as needed.

[0008] In the second operating mode (hydraulic backup layer) of the power-assisted braking device, the pressure generation of the first component is disrupted, and a secondary pressure generator with additional functionality is used to apply braking pressure to the wheel brakes. Therefore, the second component is additionally configured to regulate the braking pressure for the individual wheels to protect the power-assisted braking device from possible interference with the first component. Based on the redundancy provided in pressure generation, the power-assisted braking device is suitable for application in autonomous or drivable motor vehicles.

[0009] Because the second component is rarely activated under normal conditions, there is a risk that potential functional interference with the second component may not be identified in a timely manner, and the hydraulic backup layer may be unavailable when needed. Summary of the Invention

[0010] To promptly identify interference with the second component and, if necessary, warn the driver, claim 1 proposes: using its secondary or second pressure generator to periodically check the availability of the hydraulic backup layer and thus the functional capability of the second component during normal operation of the power-assisted braking device for safety reasons. The time interval between each detection cycle can be arbitrarily determined and, for example, can be varied according to the stress implemented by the power-assisted braking device.

[0011] The proposed method is implemented without driver involvement, i.e., without driver intervention, and ensures that the vehicle can still be safely braked to a stop even if the first component, particularly the primary pressure generator, is disrupted according to its intended function. It is not important here whether the disruption is attributable to, for example, a mechanical cause in the pressure generator, an electrical cause in the actuator of the pressure generator, and / or an electronic cause in the drive control of the actuator.

[0012] Advantageous improvements to the proposed detection method are protected by dependent claims.

[0013] Claim 2, for example, proposes that, in the presence of a braking desire, during normal operation, the driver of the primary pressure generator is suppressed by an electronic control device, and the driver of the secondary pressure generator is electrically driven instead of the driver of the primary pressure generator. In other words, during a selected braking process, braking pressure is generated not through the primary pressure generator as per standard, but through the secondary pressure generator, in order to test its functional capability.

[0014] If the braking pressure is generated as desired by the secondary pressure generator, that is, the braking pressure is generated as desired, and the desired braking pressure is reached within a desired time interval from the start of the electrical drive of the secondary pressure generator, then the braking process can be performed according to the prescribed state based on the hydraulic backup layer. The braking process according to claim 2 can then be subsequently implemented by the primary pressure generator according to standard.

[0015] In contrast, the method according to claim 3 proposes that if there is no braking desire and the hydraulic connection between the secondary pressure generator and the contacting wheel brake is subsequently interrupted simultaneously with the electrical drive of the secondary pressure generator being interrupted, then the secondary pressure generator is electrically driven. For this purpose, a valve mechanism of the second component can preferably be used.

[0016] In this method, no braking pressure is generated in the wheel brakes, and therefore no braking process occurs on the vehicle. Braking pressure is applied only to a region of the power-assisted braking device that, hydraulically, is located between the secondary pressure generator and the wheel brakes.

[0017] Pressure formation in this area can be detected and analyzed by sensors, regardless of their presence, to regulate the braking pressure of the power-assisted braking system. The method according to claim 3 can also be implemented during the vehicle's normal operating conditions, provided that braking events are not required.

[0018] A particular advantage of the method according to claim 3 is that the noise generation involved in the adjustment of the secondary pressure generator is based on the fact that the existing driving and environmental noise is not perceived as interference by the vehicle passengers, or ideally, is not recorded by the vehicle passengers by the final detection method.

[0019] Claim 4 proposes that the method be implemented if the vehicle stops. This differs from the method of claim 3, which also applies braking pressure to the wheel brakes. Furthermore, in this case, the process of brake pressure formation can be monitored and evaluated, but for this purpose, there is no need to interrupt the connection between the secondary pressure generator and the wheel brakes. The method is therefore characterized in that only a small number of electrically controllable actuators of the power-assisted braking device should be operated, or thus only a small amount of electrical power is necessary for the implementation of the method.

[0020] After a parking process during normal driving operation, or if the vehicle is parked or stopped, then the vehicle is in a stopped state. The method of claim 4 therefore does not necessarily presuppose that the vehicle's actuators are active or that the driver is present.

[0021] Claim 5 proposes, as a possible criterion for determining the availability of the hydraulic backup layer, that the braking pressure generated by the secondary pressure generator (actual braking pressure) is compared with a limit value (rated braking pressure) stored in the electronic control unit for that braking pressure. If the generated braking pressure is greater than or equal to or greater than this limit value, then the availability of the hydraulic backup layer exists. As mentioned above, pressure detection can be implemented using a sensing device for braking pressure regulation that is present in the power-assisted braking device in any way, thereby incurring no additional component costs.

[0022] Claim 6 alternatively proposes that, instead of the generated pressure, the power consumption of the actuator be analyzed and processed by a secondary pressure generator during the generation of braking pressure, since the power consumption is proportional to the pressure formation. The power consumption of the actuator by the secondary pressure generator can be detected by measuring the current intensity flowing to the actuator by the electronic control unit of the power-assisted braking device (claim 7).

[0023] Further advantages or beneficial improvements of the invention may arise, if necessary, from the following description of the invention. Attached Figure Description

[0024] The invention is explained in detail below with reference to the accompanying drawings.

[0025] This accompanying figure includes several figures, among which: Figure 1A And 1B shows the hydraulic layout of the power-assisted braking device on which the present invention is based; Figure 2 A flowchart illustrating a first embodiment of the present invention is shown; Figure 3 A flowchart illustrating a second embodiment of the invention is shown; and Figure 4 A flowchart illustrating a fourth embodiment of the present invention is shown. Detailed Implementation

[0026] Figure 1 illustrates the principle structure and division of the power-assisted braking device upon which this invention is based, according to the hydraulic circuit symbols and their interconnections. For details regarding this power-assisted braking device, please refer to the disclosure in document DE 10 2018 222 488 A1; the following description further details the essential elements necessary for understanding this invention.

[0027] The power-assisted braking device (10) is divided into two components (12; 14) as described above, which are structurally separate but hydraulically in contact with each other. These two components (12; 14) are hydraulically connected in parallel and supply pressure medium at braking pressure to, for example, the four wheel brakes (16) of the power-assisted braking device (10). Each of the four wheel brakes is combined in pairs to form one of the two total braking circuits of the power-assisted braking device (10).

[0028] The first component (12) further includes an operating element (18) by which the driver of the motor vehicle can predetermine the braking desire. The operating element (18) is shown as a pedal, but could also be a lever. Furthermore, the first component (12) includes a primary pressure generator (20), which is operated by an electrically driven actuator (22). The electrical drive is determined by an electronic control unit (24), which retrieves a drive signal corresponding to the braking desire and forwards it to the actuator (22) of the primary pressure generator (20). The driven pressure generator (20) further supplies a pressure medium at a uniform braking pressure to the wheel brakes (16) of the power-assisted braking device (10).

[0029] Hydraulically connected in parallel with the first component (12) and in contact with the wheel brake (16) is the second component (14), which is equipped with a second or secondary pressure generator (30). In addition to the secondary pressure generator (30) and its actuator (32), the second component (14) includes a valve mechanism (34) consisting of multiple check valves for controlling the power-assisted braking device (10). These check valves are also electrically actuated, as are the actuators (32) of the secondary pressure generator (30). The task of the second component (14) is to individually adjust the braking pressure of the wheel and, in doing so, match the slip condition currently present on the wheel assigned to the wheel brake (16). The actuator (32) of the secondary pressure generator (30) and, if necessary, the corresponding electrical actuation of the check valves of the valve mechanism (34) are also determined and performed by an electronic control unit (24) as needed.

[0030] The power-assisted braking device (10) configured in this way is operable under normal operation, as described above, or in the hydraulic backup layer. In the hydraulic backup layer, there is interference in the pressure generation of the first component (12), and the braking pressure is generated by the electrical drive of the secondary pressure generator (30) of the second component (14). At the same time, a warning is output to the driver to prompt repair of the power-assisted braking device (10).

[0031] The second component (14) therefore protects the functionality of the power-assisted braking device (10) in the hydraulic backup layer and therefore its functionality should be checked from time to time for safety reasons. The following method is illustrated in the following figures.

[0032] Figure 2 This invention illustrates a first method for detecting the availability of a hydraulic reserve layer in an electronically adjustable power-assisted braking device (10). The method is predicated on the power-assisted braking device (10) being in normal operating mode, and the first method step S1 of this detection method is therefore inquired as follows.

[0033] If the query result is positive, step S2 queries whether a current braking demand or braking desire exists. If so, the electronic control unit (24) obtains and outputs the braking pressure corresponding to the braking desire and the corresponding drive control signal for driving the secondary pressure generator (30) or its driver (32) (step 3). At the same time, the electrical drive control of the driver (22) of the primary pressure generator (20) that generates braking pressure during normal operation is suppressed.

[0034] In step S4, the brake pressure formation that occurs is detected by the electronic control unit (24) in the power-assisted braking device (10). There, a logic device configured for this purpose analyzes, for example, the rate of pressure formation and / or the pressure level reached within a time interval. If a comparison with the rated values ​​stored in the control unit (24) (step S5) results in the brake pressure formation being achieved as desired, then the availability of the hydraulic reserve layer is inferred and the method ends. If the brake pressure formation does not correspond to the desired level, then an interference with the presence of the hydraulic reserve layer is inferred, and a warning signal, for example, audible and / or visual, is issued to the driver.

[0035] If the query in step S1 or S2 results in a negative result, the method is interrupted and restarted after a determinable time interval has elapsed.

[0036] Figure 3 Explain the alternative second method.

[0037] First, implement step S1b in the method and query for normal operation.

[0038] If normal operation exists, then in step S2b below, the braking demand is queried, and this method differs from that based on Figure 2The method continues only when there is no desire to brake. Using step S3b, the secondary pressure generator (30) of the power-assisted braking device (10) is now operated, and simultaneously, with the start of this operation, the pressure medium connection to the wheel brakes (16) is interrupted. Furthermore, the valve of the valve mechanism (34) of the second component (14) can be advantageously electrically driven accordingly. Thus, braking pressure is applied only to the area of ​​the power-assisted braking device (10) located between the secondary pressure generator (30) and the wheel brakes (16), but not to the wheel brakes (16) themselves. Therefore, no braking process occurs on the vehicle.

[0039] In step S4b, the brake pressure formation is detected and analyzed by the electronic control unit (24). If a comparison with the rated value stored in the control unit (24) results in the brake pressure formation corresponding to the desired value, then in S5b, the availability of the hydraulic reserve layer is inferred and the method ends. If the brake pressure formation does not correspond to the desired value, then an interference with the presence of the hydraulic reserve layer is inferred, and a warning signal, for example, audible and / or visual, is issued to the driver.

[0040] If the query in step S1b results in a negative result or the query in step S2b results in a positive result, then the method is interrupted and restarted after a determinable time interval has elapsed.

[0041] Figure 4 The second alternative detection method is explained, and its flowchart corresponds to that based on Figure 2 The method.

[0042] In this second alternative, step S1c queries whether the power-assisted braking device is in normal operation. If yes, it queries whether the vehicle is stopped. The method continues only if there is positive feedback and is otherwise interrupted or subsequently restarted.

[0043] Step S3c subsequently enables electrical drive control of the driver of the secondary pressure generator (30) via the electronic control unit (24), and consequently enables pressure formation in the power-assisted braking device (10), including the wheel brakes (16) connected thereto. Electronic detection and analysis of the pressure formation occurs in the electronic control unit (24) in step S4c. Steps S4c and S5c correspond to steps S4, S5 or S4b, S5b as described above.

[0044] Of course, modifications or additions to the method are conceivable without departing from the basic concept of the invention as claimed in the independent claims.

[0045] It should be noted that in all the aforementioned variations, pressure formation is directly detected and analyzed by a secondary pressure generator (30) by means of a pressure measurement in the hydraulic circuit of the power-assisted braking device (10) using an existing brake pressure regulating sensor.

[0046] Indirect pressure detection is, in principle, equally conceivable. This can be considered in terms of the power absorbed by the driver (32) of the secondary pressure generator (30) during pressure formation. This power can be derived from the electrical current intensity flowing to the driver (32) and is proportional to the generated braking pressure.

[0047] The described detection methods are repeated at time intervals. The time interval between two detection cycles can be arbitrarily determined and can be, for example, based on the stress changes achieved by the power-assisted braking device during this period.

Claims

1. A method for checking the availability of a hydraulic spare layer in an electronically adjustable power-assisted braking device (10), in, The power-assisted braking device (10) has multiple pressure generators (20; 30) for supplying pressure medium under braking pressure to the connected wheel brakes (16), and the corresponding drivers (22; 32) of the pressure generators can be driven independently by at least one electronic control device (24). The power-assisted braking device (10) is capable of operating under normal conditions, during which braking events are detected by an electronic control unit (24) and distributed to braking pressure, which can be adjusted by corresponding electrical control of the driver (22) of the primary pressure generator (20) on the wheel brake (16). The system includes at least one electrically controllable secondary pressure generator (30) to match the braking pressure to wheel slippage, which occurs precisely on each wheel assigned to the wheel brake (16). The power-assisted braking device (10) can operate in a hydraulic backup layer, where, due to a malfunction in the generation of braking pressure achieved by the primary pressure generator (20), the braking pressure can be adjusted by the corresponding electronic drive control of the driver (32) of the secondary pressure generator (30) in the wheel brake (16) of the power-assisted braking device (10). Its features are, The availability of the hydraulic backup layer is checked at determinable time intervals during normal operation of the power-assisted braking device (10). The availability of the hydraulic backup layer is checked by the electronic control device (24) suppressing the driver (22) of the primary pressure generator (20) and electrically driving the driver (32) of the secondary pressure generator (30) during normal operation of the power-assisted braking device (10) in the presence of braking desire, so as to generate braking pressure in the wheel brake (16).

2. The method according to claim 1, Its features are, The availability of the hydraulic backup layer is checked by electrically driving the driver (32) of the secondary pressure generator (30) in the absence of braking desire during normal operation of the power-assisted braking device (10), and at the latest interrupting the hydraulic connection between the secondary pressure generator (30) and the wheel brake (16) when electrically driving the driver (32) of the secondary pressure generator (30).

3. The method according to claim 1, Its features are, After a motor vehicle equipped with the power-assisted braking device (10) stops, the availability of the hydraulic backup layer is checked, wherein during the stop, the drive (32) of the secondary pressure generator (30) is electrically driven to generate braking pressure in at least one wheel brake of the wheel brake (16).

4. The method according to any one of claims 1 to 3, Its features are, If the braking pressure generated by the secondary pressure generator (30) is equal to or greater than the predetermined limit value for the braking pressure stored in the electronic control device (24) of the power-assisted braking device (10), then it is inferred that the availability of the hydraulic backup layer exists.

5. The method according to any one of claims 1 to 3, Its features are, The braking pressure generated by the electrically driven secondary pressure generator (30) in the power-assisted braking device (10) can be directly measured and analyzed, or the occurrence of braking pressure can be indirectly inferred based on the characteristic value of the power consumed by the driver (32) of the secondary pressure generator (30).

6. The method according to claim 5, Its features are, The power of the secondary pressure generator (30) is detected by measuring the current intensity flowing to the driver (32) of the secondary pressure generator.

7. The method according to claim 1, Its features are, The power-assisted braking device (10) is an electronically adjustable power-assisted braking device for motor vehicles.

8. The method according to claim 1, Its features are, The availability of the hydraulic backup layer is checked by electrically driving the driver (32) of the secondary pressure generator (30) in the absence of braking desire during normal operation of the power-assisted braking device (10), and at the latest, interrupting the hydraulic connection between the secondary pressure generator (30) and the wheel brake (16) by electrically driving the valve mechanism (34) of the second component (14) when electrically driving the driver (32) of the secondary pressure generator (30).

9. An electronic control device (24) for an electronically adjustable power-assisted braking device (10), configured to implement the method according to any one of claims 1 to 8.

10. An electronically adjustable power-assisted braking device (10) equipped with an electronic control device (24) according to claim 9.

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