Method for operating a brake system of a motor vehicle and corresponding brake system
By limiting the speed gradient and combining it with anti-lock braking system diagnostics, the problem of vehicle lock-up caused by the parking brake at high speeds was solved, and reliable parking brake control at low speeds was achieved to ensure safe braking.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- AUDI AG
- Filing Date
- 2023-04-17
- Publication Date
- 2026-06-02
AI Technical Summary
In the existing technology, the parking brake device of a motor vehicle is prone to causing the vehicle to lock up when the speed is too high, and cannot reliably prevent mishandling.
By briefly following the speed measurement value and limiting the speed gradient, the speed value is determined, and the parking brake is only allowed to be operated when the speed is below the threshold. Combined with the diagnosis of the anti-lock braking system and the reliability check of wheel speed, it is ensured that the operation of the parking brake is prohibited when the speed is too high.
It effectively prevents vehicle lock-up caused by incorrect operation of the parking brake, ensuring reliable vehicle fixation at appropriate speeds, especially providing safe braking control when wheel speeds are unreliable or the anti-lock braking system malfunctions.
Smart Images
Figure CN116946083B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for using a braking device for a motor vehicle, wherein the braking device includes a parking brake that allows operation of the parking brake to generate a parking braking force acting on the wheels of the motor vehicle only when the speed value is below a speed threshold. This invention also relates to a braking device for a motor vehicle. Background Technology
[0002] For example, prior art document DE 10 2014 018 365 A1 is known. This document describes a method for activating an electric parking brake in a motor vehicle equipped with a manually operated emergency disconnection control element and a disconnection device for disconnecting a voltage supply from the vehicle's electrical grid when the emergency disconnection control element is actuated. The method includes steps (a) if the speed of the motor vehicle is not greater than a predetermined first threshold when the emergency disconnection control element is actuated, then: (a1) activate the electric parking brake and (a2) set a delay time of the disconnection device to a first value; and (b) if the speed of the motor vehicle is greater than the predetermined first threshold when the emergency disconnection control element is actuated, then: (b1) set a delay time of the disconnection device to a second value greater than the first value; (b2) determine the braking requirement for the electric service brake; and (b3) once the speed of the motor vehicle is less than the predetermined second threshold, then activate the electric parking brake. Summary of the Invention
[0003] The object of the present invention is to provide a method for operating a braking device for a motor vehicle, which has the advantage over known methods that it reliably allows operation of the parking brake device, especially when the speed of the motor vehicle is sufficiently low.
[0004] According to the invention, a speed value is determined by a speed measurement that is associated with the speed of the motor vehicle for at least a short time, wherein when the speed measurement is lower than the speed value, the speed value follows / tracks the speed measurement with a speed gradient that is limited to a speed gradient limit.
[0005] This method is used to operate a braking device. This braking device is preferably an integral part of the motor vehicle, however, it can also exist separately from the motor vehicle. The braking device is used to brake the motor vehicle, i.e., to reduce the speed of the motor vehicle, especially until it comes to a stop, and / or to fix the motor vehicle when it is stationary. Firstly, the braking device, for example, has a service brake, which preferably generates braking force on all wheels of the motor vehicle.
[0006] To secure a stationary motor vehicle, the braking system includes a parking brake. This parking brake preferably acts only on a subset of the vehicle's wheels, at least only on the wheels already mentioned. These wheels are preferably a component of a plurality of wheels, and the parking brake briefly generates a parking braking force on each wheel. For example, the parking brake generates a parking braking force only on the wheels of the vehicle's single axle, particularly the rear or front axle. Within the scope of this specification, parking braking force is understood as the braking force generated by the parking brake or the braking force of the parking brake itself.
[0007] The braking force generated by the service brake can generally be set arbitrarily. This braking force is preferably selected such that lock-up of the corresponding wheel is avoided at least briefly. If such lock-up or at least one impending lock-up is detected, the braking force is reduced, especially until lock-up no longer occurs or impending lock-up is no longer detected. For this purpose, the braking device or service brake preferably has an anti-lock braking system. The parking brake device, on the other hand, allows for the setting of a braking force preferably only sufficient to lock up the wheel or the corresponding wheel. By operating the parking brake, the wheels are locked to secure the stationary motor vehicle.
[0008] For this reason, as long as the vehicle is in motion, i.e., its speed is not zero or is greater than or equal to a speed threshold, the parking brake should not be operated. Therefore, the parking brake should only be operated when the speed is below the speed threshold. This reliably prevents vehicle lock-up caused by operating the parking brake while the vehicle is in motion. When comparing the speed value with the speed threshold, the absolute values are compared, i.e., the absolute value of the speed value is compared with the absolute value of the speed threshold, thus achieving a sign-independent comparison.
[0009] In order to reliably permit or desist the operation of the parking brake based on a speed value, the speed value must reflect the actual speed of the vehicle as accurately as possible. For this reason, the speed value is determined by a speed measurement value, which corresponds to the vehicle's speed at least briefly. A speed measurement value is a measured value, that is, a value measured using a sensor. This value is measured such that it corresponds to the vehicle's actual speed at least briefly. For example, the wheel speed of the vehicle's wheels is measured first, particularly using a wheel speed sensor, and the speed measurement value is determined from the wheel speed.
[0010] However, if a wheel locks up at the point when its rotational speed is measured, the speed measurement determined from that speed will differ from, sometimes significantly, the actual speed of the vehicle. Therefore, in a fully locked wheel, the rotational speed is zero. Thus, although the vehicle remains in motion, the parking brake can still be operated to generate parking braking force in this state.
[0011] To avoid this, the velocity value is not directly set to equal the measured velocity value. Instead, it is stipulated that the velocity value follows only the measured velocity value, at least briefly. This is achieved by adapting the velocity value to a constrained velocity gradient when the measured velocity value is lower than the velocity value. In other words, if the measured velocity value is less than the velocity value, the velocity value is adapted only in the direction of the constrained velocity gradient toward the measured velocity value.
[0012] It should be understood that a velocity gradient with respect to time is calculated, which exists when the velocity value is directly set as the velocity measurement value. If this velocity gradient is greater than a velocity gradient limit, then the velocity gradient is limited to the velocity gradient limit, and the velocity value is adapted only in the direction of this limited velocity gradient toward the velocity measurement value.
[0013] The velocity gradient is constrained in the direction of larger velocity gradients, thus limiting the velocity gradient upwards to the velocity gradient limit. Therefore, the constrained velocity gradient is always less than or equal to the velocity gradient limit. It is also preferable to use absolute values for the constraint, so that the absolute value of the velocity gradient is limited to the absolute value of the velocity gradient limit, in order to avoid the influence of the corresponding sign.
[0014] If the measured speed exceeds the measured speed value, then it can be stipulated that the measured speed value be directly set to be equal to the measured speed value, that is, directly following the measured speed value without speed gradient limitations. However, other variations are also possible.
[0015] The described technical means has the following advantages: even when the measured speed differs from the actual speed of the vehicle, it can reliably prevent the operation of the parking brake when the vehicle's speed is too high. This is based on the assumption that the vehicle's deceleration, i.e., the reduction of its speed, cannot occur arbitrarily rapidly, but always occurs at a speed gradient corresponding to a speed gradient limit. This is particularly advantageous if the vehicle is designed as an electric vehicle. In this case, there is no mechanical braking system, such as one based on lubricant pressure, that can prevent the operation of the parking brake, especially a parking brake designed as a parking lock or parking lock.
[0016] Preferably, the aforementioned technical means are used only when the wheel speed cannot be reliably determined. Such situations include, for example, a malfunction of the wheel speed sensor used to measure the wheel speed, and / or an unreliable wheel speed value, or a malfunctioning or at least unreliably malfunctioning anti-lock braking system associated with the wheel. In the first case, the wheel speed cannot be directly determined; in the latter case, it is unclear whether the wheel speed measured by the wheel speed sensor corresponds to the actual wheel speed. In particular, it is possible that the wheel may lock up, for example, due to the braking force applied by the service brake, and therefore the measured wheel speed is less than the value corresponding to the current speed of the vehicle, for example, equal to zero. Especially in the aforementioned situations, the aforementioned technical means can reliably prevent the erroneous operation of the parking brake to generate parking braking force.
[0017] An improved embodiment of the present invention specifies that, when a control signal is present, the parking brake device is operated to increase the actual parking braking force generated by the parking brake device when the speed value is less than a speed threshold, and to decrease the actual parking braking force or keep the actual parking braking force constant when the speed value is greater than or equal to the speed threshold. The control signal is understood as a signal set for operating the parking brake device. For example, the control signal is generated based on the user's preset settings, particularly based on adjustments to the vehicle's operating elements. Preferably, no control signal is generated during the first adjustment of the operating elements, and a control signal is generated during the second adjustment.
[0018] The parking brake is operated according to a control signal. Preferably, when no control signal is present, the parking brake is operated to reduce the actual parking braking force, particularly to reduce it to zero. Conversely, if a control signal is present, the speed value is compared to a speed threshold. If the speed value is less than the speed threshold, the parking brake is operated to increase the actual parking braking force, i.e., to increase the actual parking braking force in the direction of (normal) parking braking force, preferably until (normal) parking braking force is reached.
[0019] If the speed value is at least equal to a speed threshold (i.e., the speed value is greater than or equal to the speed threshold), then the parking brake should be operated to reduce the actual parking braking force or keep it constant, with the former being preferred. Particularly preferably, the parking brake is operated in this case to reduce the actual parking braking force to zero. This achieves the advantageous characteristics of the braking device already described.
[0020] An improved embodiment of the invention specifies that the speed measurement value is determined at least briefly by the wheel speed measured by a wheel speed sensor and / or at least briefly by the speed of the power unit technically connected to the axle. The use of wheel speed for determining the speed measurement value has already been pointed out. Additionally or alternatively, the speed measurement value may be determined at least briefly by the speed of the power unit.
[0021] The power unit is technically connected to the axle and is thus technically coupled to it, preferably rigidly coupled, at least briefly. This means that the rotational speed of the power unit is at least briefly proportional to the rotational speed of the wheels. Accordingly, the rotational speed of the power unit corresponds at least briefly to the speed of the vehicle and can be used to determine the speed measurement value. However, in this technical means, the speed measurement value may also differ from the actual speed of the vehicle, especially when the wheels lock up. For this reason, in this case, following the speed value described in relation to the speed measurement value is beneficial to the safety of the vehicle.
[0022] An improved embodiment of the present invention specifies that if the wheel speed passes the reliability check, the speed measurement value is determined by the wheel speed measured using a wheel speed sensor; otherwise, the speed measurement value is determined by the speed of the power unit. Ideally, the measured wheel speed is used to determine the speed measurement value. This is achieved if the wheel speed meets the reliability check. "Reliability check" is understood as monitoring the measured wheel speed itself or other parameters of the braking device, i.e., whether the wheel speed corresponds to the actual speed of the vehicle.
[0023] For example, this involves checking whether the measured wheel speed is within a specific speed range, and especially whether it differs from zero. The parameters of the braking system, particularly the functional parameters of the anti-lock braking system (ABS), are also considered. If the functional parameters indicate that the ABS is functioning correctly, the speed measurement value is determined from the measured wheel speed. Conversely, if the functional parameters indicate an error, the rationality check fails, and the speed measurement value is preferably determined from the speed of the power unit. This technique is based on the fact that wheel speed sensors are typically part of the ABS, thus assuming a wheel speed sensor malfunction when the ABS is not operating. The described technique enables reliable operation of the parking brake based on the speed value.
[0024] An improved embodiment of the present invention specifies that when the measured speed value exceeds the measured speed value, the measured speed value is set to be equal to the measured speed value, or the measured speed value follows the measured speed value with a speed gradient that is restricted to another speed gradient limit. The first technical approach corresponds to direct following between the measured speed value and the measured speed value. Within the scope of the technical approach mentioned in the second case, following is achieved with a restricted speed gradient not only when the measured speed value is lower than the measured speed value, but also when the measured speed value exceeds the measured speed value. Here, one speed gradient limit is used for the case where the measured speed value is lower than the measured speed value, and another speed gradient limit is used for the case where the measured speed value exceeds the measured speed value. The speed gradient limit can also be referred to as the first speed gradient limit, and the other speed gradient limit can also be referred to as the second speed gradient limit.
[0025] The first and second velocity gradient limits may correspond to each other or differ from one another, particularly in their absolute values. For example, the second velocity gradient limit is greater than the first velocity gradient limit. Preferably, the second velocity gradient limit corresponds to the product of the first velocity gradient limit and a factor greater than 1. Preferably, this factor is at least 2, at least 3, at least 4, at least 5, or at least 6. Additionally or alternatively, the factor is at most 10, at most 8, or at most 6. In other words, the factor is, for example, not less than 2 and not greater than 10, not less than 3 and not greater than 8, not less than 4 and not greater than 6, or not less than 4 and not greater than 6.
[0026] For example, the first velocity gradient limit is at least 0.25 m / s. 2 And the highest is 1.75 m / s 2 At least 0.5 m / s 2 And the highest is 1.5 m / s 2 or at least 0.75 m / s 2 And the highest is 1.25 m / s 2 Preferably, the first velocity gradient limit is exactly or approximately 1 m / s. 2 This assumption is based on the fact that the coefficient of friction between the vehicle's wheels and the ground is always at least 0.1, and therefore at least the aforementioned deceleration can be achieved even when the wheels lock up. Particularly preferably, a higher possible deceleration is assumed, thus the first speed gradient limit is at least 1 m / s². 2 And the highest is 3 m / s 2 or at least 1 m / s 2 And the highest is 2m / s 2 Overall, the parking brake can be controlled with particularly reliable technical means as described.
[0027] An improved embodiment of the invention specifies that the speed gradient limit and / or other speed gradient limits are determined to be constant; or the speed gradient limit and / or other speed gradient limits are determined based on the speed value. For example, one or more of the mentioned speed gradient limits are determined to be one of the mentioned values or ranges of values. However, it can also be specified that at least one of the speed gradient limits is determined variably based on the speed value. Preferably, the larger the speed value, the larger the corresponding speed gradient limit is selected. In summary, achieving speed values that are continuously greater than or equal to the actual speed of the vehicle allows for reliable operation of the parking brake device.
[0028] An improved embodiment of the present invention specifies that, in a first operating mode, the speed value is determined by a speed measurement under a speed gradient constraint; and in a second operating mode, the speed value is determined by a speed measurement without constraint. Therefore, the aforementioned technical means of limiting the speed gradient to a speed gradient limit is only implemented in the first operating mode.
[0029] However, in addition to the first operating mode, a second operating mode is also implemented, allowing switching between the two modes. In the second operating mode, the speed value is determined from the speed measurement value without restriction, specifically by setting the speed value to be equal to the speed measurement value. Importantly, the second operating mode is always attached to the first operating mode. The described technical means enables reliable control of the parking brake device in such a way that a meaningful assumption is made about the speed value when needed, but the speed measurement value is also used directly as the speed value for short periods.
[0030] An improved embodiment of the present invention specifies that the anti-lock braking system (ABS) of the braking device is diagnosed, wherein a first operating mode is executed when a fault in the ABS is identified, and a second operating mode is executed when the ABS is fault-free. The ABS is configured and designed to prevent wheel lock-up of a motor vehicle. For this purpose, the actual wheel speed is determined by wheel speed sensors, and when the actual speed differs from the theoretical speed determined within a model range, the actual braking force acting on the wheels is reduced. Therefore, the ABS is at least associated with a component of the service brake or the service brake itself.
[0031] If the anti-lock braking system (ABS) is functioning properly, it can be assumed that wheel lock-up is reliably prevented. Conversely, if the ABS malfunctions, this may not be the case. Therefore, in the event of an ABS malfunction, the first operating mode is used. However, if the ABS is functioning normally, the second operating mode is used, in which the speed value is determined from the speed measurement without restrictions. This improves the accuracy of the speed value.
[0032] An improved embodiment of the invention specifies the use of a parking brake and / or a parking lock as a parking braking device. The parking brake preferably acts directly on the wheels of the motor vehicle. The parking lock, for example, is a component of the vehicle's transmission mechanism, which is technically positioned between the power unit and the wheels. The parking lock is used to secure at least one axle of the vehicle transmission mechanism, thus also securing the wheels based on their technical connection to the transmission mechanism. This achieves reliable wheel securing.
[0033] The present invention also relates to a braking device for a motor vehicle, particularly for performing a method according to an embodiment within the scope of this specification, wherein the braking device has a parking brake, and the parking brake is only permitted to be operated to generate a parking braking force acting on the wheels of the motor vehicle when the speed value is below a speed threshold. Here, the braking device is configured and designed to determine a speed value from a speed measurement value corresponding at least briefly to the speed of the motor vehicle, wherein when the speed measurement value is below the speed threshold, the speed value follows the speed measurement value with a speed gradient limited to a speed gradient limit.
[0034] The advantages of this design or technical approach for the braking device have been pointed out. Based on the implementation scheme, the braking device and the operating method for it can be improved within the scope of this specification, and reference is made to this specification.
[0035] The features and combinations thereof described in the specification, especially those described in the following description of the drawings and / or shown in the drawings, can be applied not only in the corresponding described combinations, but also in other combinations or individually, without departing from the scope of the invention. Therefore, embodiments not explicitly shown or illustrated in the specification and / or drawings, but which can be obtained from or derived from the illustrated embodiments, are also considered to be included in the invention. Attached Figure Description
[0036] The invention is described in detail below with reference to embodiments shown in the accompanying drawings, without limiting the scope of the invention. Herein:
[0037] Figure 1 The first graph is shown, which, purely exemplarily, illustrates the actual speed of the motor vehicle, the measured speed value, and the time curve of the speed value.
[0038] Figure 2 The second graph is shown, which displays the actual speed, the measured speed, and the time curve of the speed value.
[0039] Figure 3 The third graph is shown, in which the actual speed, speed measurement, and speed value over time are displayed again. Detailed Implementation
[0040] Figure 1 A graph is shown, in which speed curves 1, 2, and 3 are illustrated purely as an example. Speed curve 1 describes the actual speed of the vehicle, speed curve 2 describes the measured speed, and speed curve 3 describes the speed value determined from the measured speed. A speed threshold 4 is also shown. The two speed curves 1 and 2 coincide. This means that the measured speed always corresponds to the actual speed of the vehicle.
[0041] The velocity value is determined from the measured velocity value based on velocity curve 3. This is done in such a way that if the measured velocity value exceeds the measured velocity value, the velocity value is set to be equal to the measured velocity value. Conversely, if the measured velocity value is lower than the measured velocity value, then the velocity value follows the measured velocity value, i.e., it follows the measured velocity value with a constrained velocity gradient. Here, the velocity gradient is constrained to a velocity gradient limit.
[0042] This technique can be clearly seen from the comparison between speed curves 1, 2, and 3. As the vehicle decelerates to a stop according to speed curve 1, the speed value decreases more slowly than the measured speed value due to the constrained speed gradient. Therefore, speed curve 3 decreases below the speed threshold 4 later than speed curve 2, i.e., by a time difference Δt.
[0043] The described method for determining a speed value is used to operate the parking brake of a motor vehicle as needed. Therefore, if the speed value is less than a speed threshold, operation of the parking brake should be permitted to generate a parking braking force acting on the wheels of the motor vehicle. Thus, compared to using a speed measurement value as the speed value, operation of the parking brake to generate a parking braking force is permitted with a time difference Δt delay.
[0044] Figure 2 Another graph is shown, illustrating speed curves 1, 2, and 3 over time, and a speed threshold 4. It is clear that speed curves 1 and 2 are now different from each other. This is due to wheel lock-up. If the speed measurement is used only to operate the parking brake as needed, a parking braking force can be generated on the axle before the vehicle actually reaches a speed below the speed threshold. However, because the speed value is determined from the speed measurement with a limited speed gradient, reliable operation of the parking brake is possible despite wheel lock-up. As seen in the graph, the speed value only drops below the speed threshold after the vehicle's actual speed, i.e., after a time difference Δt.
[0045] Figure 3A graph is shown. This graph further shows velocity curves 1, 2, and 3 over time, as well as a velocity threshold. However, an extended method is used to determine the velocity value. In this extended method, the velocity gradient is limited not only when the measured velocity value is below the velocity value, but also when the measured velocity value exceeds the velocity value.
[0046] As can be seen, speed curve 2 differs from speed curve 1 for a short period. During the corresponding time period, the vehicle's wheels rotate. However, because the change in speed value only occurs with a constrained speed gradient when the measured speed value exceeds the speed value, the speed value also follows the measured speed value with a delay within that time range. This improves the modeling of the speed value and, unlike techniques that only constrain the speed gradient when the measured speed value is below the speed value, improves the time difference Δt.
[0047] In general, the described method for operating braking devices in motor vehicles allows for reliable operation of the parking brake. To this end, speed values are modeled, and the parking brake is controlled based on these speed values. A practical estimate of the speed values is made using physically meaningful assumptions about the maximum possible acceleration and / or maximum possible deceleration of the motor vehicle, and this speed value always follows the actual speed of the motor vehicle.
[0048] List of reference numerals in the attached diagram:
[0049] 1. Velocity curve
[0050] 2. Velocity measurement curve
[0051] 3. Velocity value curve
[0052] 4. Speed threshold curve
Claims
1. A method for operating a braking device for a motor vehicle, wherein, The braking device has a parking brake device that allows the parking brake device to be operated to generate a parking braking force acting on the wheels of the motor vehicle only when the speed value (3) is lower than the speed threshold (4). The device is characterized in that the speed value (3) is determined by a speed measurement value (2) that is associated with the speed (1) of the motor vehicle for at least a short time, wherein when the speed measurement value (2) is lower than the speed value (3), the speed value (3) is made to follow the speed measurement value (2) with a speed gradient that is limited to a speed gradient limit. When a control signal is present, the parking brake device is operated to increase the actual parking braking force generated by the parking brake device when the speed value (3) is less than the speed threshold (4), and to decrease the actual parking braking force or keep the actual parking braking force constant when the speed value (3) is greater than or equal to the speed threshold (4).
2. The method according to claim 1, characterized in that, The speed measurement (2) is determined at least briefly by the wheel speed measured by means of a wheel speed sensor, and / or at least briefly by the speed of the power unit connected to the axle in the drive technology.
3. The method according to claim 1 or 2, characterized in that, If the wheel speed passes the reliability check, the speed measurement value is determined by the wheel speed measured by the wheel speed sensor (2). If the wheel speed fails the reliability check, the speed measurement value is determined by the speed of the power equipment.
4. The method according to claim 1 or 2, characterized in that, When the speed measurement value (2) exceeds the speed value (3), the speed value (3) is set to be equal to the speed measurement value (2), or the speed value is made to follow the speed measurement value (2) with a speed gradient that is restricted to another speed gradient limit.
5. The method according to claim 4, characterized in that, The velocity gradient limit and / or other velocity gradient limits are determined to be constants; or the velocity gradient limit and / or other velocity gradient limits are determined based on the velocity value (3).
6. The method according to claim 1 or 2, characterized in that, In the first operating mode, the speed value (3) is determined by the speed measurement value (2) under the condition of limiting the speed gradient; in the second operating mode, the speed value (3) is determined by the speed measurement value (2) under the condition of no restriction.
7. The method according to claim 6, characterized in that, The anti-lock braking system (ABS) of the braking equipment is diagnosed. When a fault is detected in the ABS, a first operating mode is executed, and when the ABS is fault-free, a second operating mode is executed.
8. The method according to claim 1 or 2, characterized in that, The parking brake device is a parking brake and / or a parking lock.
9. A braking device for a motor vehicle, the braking device being used to perform the method according to any one of claims 1-8, wherein, The braking device has a parking brake device that allows the parking brake device to be operated to generate a parking braking force acting on the wheels of the motor vehicle only when the speed value (3) is lower than the speed threshold (4). The braking device is characterized in that it is configured and designed to determine the speed value (3) from a speed measurement value (2) that corresponds to the speed (1) of the motor vehicle for at least a short time, wherein when the speed measurement value (2) is lower than the speed value (3), the speed value (3) follows the speed measurement value (2) with a speed gradient that is limited to a speed gradient limit.