Method for diagnosing a supply fault affecting an electrically actuated parking brake

Abstract

The subject of the present invention is a method for diagnosing a supply fault affecting an electrically actuated parking brake of a vehicle, the method comprising the following successive steps in case of detection of an actuation request (E1): measuring (E2) the supply current (Ip) and voltage (Vp) across the supply terminals of the motor; monitoring (E3) the measured current (Ip) with respect to a current-related first threshold (S1); comparing (E4) the measured voltage (Vp) with a voltage-related second threshold (S2) should the current (Ip) be detected to be lower than the current-related first threshold (S1) for at least a first length of time (D1); and, if the voltage (Vp) is greater than the voltage-related second threshold (S2), reporting (E5) malfunction of the parking brake and activating (E5) a reconfiguration mode of the vehicle comprising inhibition of operation of the motor. The invention relates to motor vehicles comprising an electrically actuated parking brake.

Description

DESCRIPTION Title: METHOD FOR DIAGNOSING A POWER SUPPLY FAULT IN AN ELECTRICALLY ACTUATED PARKING BRAKE

[0001] The present invention claims priority from French application No. 2209670 filed on 09 / 23 / 2022, the content of which (text, drawings and claims) is incorporated herein by reference.

[0002] The field of the invention relates to a method for diagnosing an operating anomaly of an electrically actuated parking brake, in particular for detecting an open circuit in the power supply to the actuating motor.

[0003] The parking brake, also called "parking brake", is used to immobilize the vehicle when it is already stationary without action on the brake pedal. Conventionally, an electrically actuated parking brake system comprises a toothed wheel coupled in rotation to the vehicle's drive shaft and a locking finger linked to a fixed component of the vehicle, also called "parking finger", the actuation of which in the applied or released position is controlled by an electric motor and a control unit.

[0004] Patent document US10953862B2 describes a method for operating an electrically actuated parking brake based on the measurement of the supply current. This method proposes that a time sequence of current variations is sent to the terminals of an interface for a control element operating the parking brake. During power supply, a current measurement is taken at a terminal of the interface. The driver's request is determined based on the current measurement. The electric parking brake is actuated based on the current measurements. This document does not describe a diagnostic solution against open-circuit faults.

[0005] An open circuit fault in the actuating motor power supply results from the actuating motor power wires being broken or unsoldered from their connector. To check for open circuit faults in the parking brake, a diagnostic function is usually provided that is responsible for monitoring the presence of a supply current at the motor terminals when it is actuated for engagement in the applied position or disengagement in the released position of the parking brake. One strategy is to detect zero current for at least 1 second, in which case an alert is raised.

[0006] However, there are normal operating situations where the actuator motor current is at 0 amps. This leads to false detection of an open circuit in the locking finger actuator motor. In other situations, nuisance micro-outages are not detected.

[0007] There is therefore a need to overcome the aforementioned problems and to improve the diagnostic function against open circuit faults of an electrically actuated parking brake. Another objective of the invention is to secure the vehicle in the event of detection of an open circuit problem.

[0008] More specifically, the invention relates to a method for diagnosing a power supply fault in an electrically actuated parking brake of a vehicle, the parking brake comprising an electrically actuated motor and a motor control unit, the method comprising the following successive steps in the event of detection of a request to actuation of the motor for engagement / disengagement of the parking brake: - measurement of the supply current and voltage at the motor supply terminals, - monitoring of the measured current in relation to a first current threshold.

[0009] According to the invention, the method further comprises: - the comparison of the measured voltage with respect to a second voltage threshold in the event of detection that the current is lower than the first current threshold for at least a first duration, - if the voltage is higher than the second voltage threshold, the signaling of a parking brake anomaly and the activation of a vehicle reconfiguration mode including inhibition of engine operation.

[0010] According to a variant, the first current threshold is between 5 milliamps and 15 milliamps, or preferably is equal to 10 milliamps, and the first duration is between 20 milliseconds and 200 milliseconds, between 30 milliseconds and 100 milliseconds, between 40 milliseconds and 70 milliseconds, or preferably is equal to 50 milliseconds.

[0011] According to one variant, the second threshold has a value between 4 volts and 8 volts, or preferably is equal to 6 volts.

[0012] According to a variant, the method further comprises, when the reconfiguration mode is activated and in the event of detection of a request to actuation of the motor: - monitoring of the measured current in relation to a third current threshold, - the parking brake rehabilitation command if the current is higher than the third current threshold for at least a second period.

[0013] According to a variant, the reconfiguration mode further comprises an inhibition of a recharging operation of a traction battery of the vehicle carried out by an on-board charger of the vehicle.

[0014] According to a variant, the method further comprises the control of rehabilitation of a recharging operation of the traction battery of the vehicle.

[0015] Preferably, the fault signaling includes the generation of a fault code and a command to illuminate a parking brake fault indicator light.

[0016] The invention further provides a control unit for a vehicle parking brake comprising means for implementing the diagnostic method according to any one of the preceding embodiments.

[0017] Further contemplated is a motor vehicle comprising an electrically actuated parking brake comprising an electric brake actuating motor and the foregoing parking brake control unit.

[0018] The invention further provides a computer program comprising instructions which, when the program is executed by a control unit of a vehicle parking brake, cause the latter to implement the method according to any one of the preceding embodiments.

[0019] The invention makes it possible to detect open circuit situations of the actuating motor of a vehicle parking brake. The invention strengthens existing diagnostics by means of immediate detection based on current monitoring and checking for the presence of a polarization voltage immediately after the cut-off. The detection can take effect in a few tens of milliseconds instead of the usual one second or more. This makes it possible, in particular, to put the motor in a fault state and warn the driver immediately before he releases the brake pedal. This improves vehicle safety.

[0020] Other characteristics and advantages of the present invention will appear more clearly on reading the detailed description which follows, comprising embodiments of the invention given as non-limiting examples and illustrated by the appended drawings, in which:

[0021] [Fig.1] schematically represents a motor vehicle powertrain designed to implement the diagnostic method according to the invention.

[0022] [Fig.2] represents an embodiment of the algorithm of the diagnostic method according to the invention.

[0023] Figure 1 shows a motor vehicle powertrain comprising a traction motor 1 provided for transmitting engine torque to the drive wheels 11. The traction motor 1 may be an internal combustion engine or an electric traction machine. The powertrain may be of the thermal, hybrid or fully electric type.

[0024] A drive shaft 2 of the traction motor 1 is capable of rotating a transmission shaft line comprising a transmission member 12 for transmitting the engine torque. The transmission member 12 may be an automated gearbox, a reducer or a differential depending on the architecture of the vehicle.

[0025] The powertrain further comprises a parking brake 3 comprising a toothed wheel 7 rotatably connected to a shaft of the transmission line, for example a shaft of the transmission member 12. Thus, the toothed wheel 7 can be connected to a reducer, a gearbox or a differential depending on the architecture of the vehicle. The parking brake 3 further comprises a locking finger 4, an electric actuating motor 6 and a motor control unit 5. The locking finger 4 is connected for example to the casing of the transmission member 12. The motor 5 of the parking brake is electrically powered by a low-voltage on-board network. The actuating motor is powered at 12 volts in this example, or a lower voltage.The control unit 5 comprises means for acquiring data and requests, sensors for measuring the supply current Ip and the supply voltage Vp at the terminals of the actuating motor 6 and means of communication in cooperation with other computers 8, 10, 12 and 13 of the vehicle, in particular. The control unit 5 is electrically powered from. that the driver places his foot on the brake pedal, while the vehicle is running, preferably at a speed below 5 km / h, before starting the vehicle, or that a braking force is being exerted on the wheels.

[0026] When an actuation request is received by the control unit 5, the actuation motor 6 can engage the locking finger 4 to move it into the gear wheel 7 in the locked position or disengage the locking finger 4 to move it in the released position. When the locking finger 4 blocks the gear wheel 7, the entire drive shaft line is immobilized in rotation and the vehicle is therefore immobilized.

[0027] The engagement and disengagement of the parking brake can be controlled by a position of the gear lever (position "Park") or a button or even by an automated function of the vehicle. A signal and a specific command are provided to transmit the actuation request to the control unit 5 of the parking brake.

[0028] In this embodiment, the powertrain is hybrid or electric and comprises control means comprising a control unit 8 of the traction motor 1, a supervisor 10 of the vehicle, a control unit 12 of a traction battery system and a control unit 13 of an on-board charger of the traction battery, possibly. Data communication means 9, of the CAN bus type ("Control Area Network") for example, allow the communication of data and information between the computers 5, 9, 8, 10, 12, 13. The powertrain may comprise (not shown in FIG. 1) a high-power traction battery system (having a voltage greater than 300 volts) and an electric charger of the traction battery connectable to an external energy source.

[0029] As part of the diagnostic method, the supervisor 10 is provided to record a diagnostic and fault log, including open circuit faults of the brake actuating motor. parking, and to signal an anomaly to the driver via a human-machine interface (not shown in figure 1), for example a dashboard screen or a light and / or sound indicator.

[0030] Furthermore, the control units 12 and 13 of the traction battery system and the on-board charger can inhibit a charging operation, in particular if a parking brake fault is detected.

[0031] Figure 2 is a diagram showing an embodiment of the diagnostic method against an open-circuit fault implemented by the parking brake control unit. The control unit 5 is provided with an integrated circuit computer and electronic memories, the computer and the memories being configured to execute the diagnostic method. But this is not mandatory. Indeed, the computer could be external to the control unit 5, while being coupled to the latter 5. In the latter case, it can itself be arranged in the form of a dedicated computer comprising a possible dedicated program, for example. Consequently, the control unit, according to the invention, can be produced in the form of software modules (or computer software), or electronic circuits (or hardware), or a combination of electronic circuits and software modules.

[0032] In a first step E1 of the diagnostic process, the parking brake control unit detects a request to activate the parking brake. At this step, the parking brake control unit is electrically powered. The vehicle is stationary and the driver has his foot on the brake. The request comes, for example, from the vehicle supervisor. The request is a command to the motor to actuate the locking finger from a released position to a locking position, or vice versa from a locking position to a released position. The request can be generated by a command of the gear lever to the "Park" position or by a command of a button by the driver, or possibly from an automated function of the vehicle.

[0033] Following detection of the actuation request, the control unit measures in a second step E2 the electric current Ip and the voltage Vp at the motor terminals.

[0034] Then, in accordance with the diagnostic method, the method comprises a third step E3 of monitoring the current Ip with respect to a current threshold S1, having a value of 10 milliamperes for example. In the event of detection that the current Ip is lower than the current threshold S1 for a continuous period t greater than a duration D1, the method then monitors in a fourth step E4 the measured voltage Vp at the power supply terminals of the actuating motor. This verification step has the advantage of checking whether there is a polarization state of the motor at the time of the power cut. This situation is abnormal.

[0035] The duration D1 is between 20 milliseconds and 200 milliseconds maximum, or between 30 milliseconds and 100 milliseconds, or between 40 milliseconds and 70 milliseconds, preferably equal to 50 milliseconds.

[0036] The duration D1 is judiciously chosen at a short duration value, preferably 50 milliseconds, to still be able to observe the presence of a residual polarization voltage at the motor terminals as soon as the power cut is detected. Indeed, in the event of a circuit cut, the passive discharge causes a decrease in voltage and its observation confirms the presence of an unwanted micro-cut.

[0037] On the other hand, if Ip remains lower than S1 only for a period t having a duration less than D1, that is to say that the current Ip passes quickly after the instant of detection of the actuation request to a value greater than S1, expected for the operation of the motor, this is a situation which must not trigger an anomaly removal. In this situation, the method returns to step E1 of waiting for detection of an actuation request.

[0038] In the fourth step E4, if it is detected that the voltage Vp is greater than a voltage threshold S2, this is an open circuit anomaly situation because a polarization voltage is still observed and consequently the method triggers in a fifth step E5 the signaling of an anomaly of the parking brake and the activation of a vehicle reconfiguration mode including an inhibition of the operation of the engine. The threshold S2 is between 4 volts and 8 volts, preferably is equal to 6 volts. The value is chosen at a discharge polarization voltage expected after the elapse of the duration D1. The observation of a polarization voltage after the duration D1 confirms the presence of an open circuit.

[0039] In the fourth step E4, if it is detected that the voltage Vp is lower than the threshold S2, this is a situation for which the control unit does not generate an anomaly signal. The process then returns to step E1.

[0040] More specifically, reporting the E5 fault involves generating a fault code in a so-called permanent state for recording in a diagnostic log administered by the vehicle supervisor and consultable by an after-sales technical service. The parking brake control unit issues the fault code via the communication bus. In addition, the parking brake control unit generates a command to illuminate a warning light and / or audible message on the vehicle's dashboard to warn the driver of a fault.

[0041] Specifically, vehicle reconfiguration step E5 involves inhibiting the operation of the parking brake motor until a motor rehabilitation is performed. At this step, the brake control unit is in an error state.

[0042] Furthermore, preferably, step E5 comprises an inhibition of a recharging operation because it is judged that the vehicle is not in a safe situation to carry out a charge by connecting to a recharging terminal or an external energy source, because its parking cannot be ensured by the brake. The control unit of the The parking brake generates this inhibition request, which is then implemented by the vehicle supervisor. This charging inhibition is implemented in cooperation with the supervisor, the on-board charger, and the traction battery system. An alert associated with this charging inhibition is eventually generated and signaled to the driver.

[0043] Then, in a sixth step E6, if the parking brake control unit detects a new request to actuation the motor, in engagement or disengagement of the locking finger, the method comprises a seventh step E7 of checking the current Ip at the terminals of the motor with respect to a current threshold S3, in this example set at 10 milliamps.

[0044] If the control unit detects that the current Ip is greater than S3 for at least one continuous period t greater than a duration D2 of 100 milliseconds, then it rehabilitates the operation of the parking brake in an eighth step E8. The duration D2 can be chosen to be a value in a range between 80 milliseconds and 200 milliseconds. The fault code generated in step E5 is indicated as being in a transient state in the fault log. This makes it possible to inform a vehicle technical service of the occurrence of the fault and that it has been resolved by itself.

[0045] In addition, the E8 rehabilitation includes a step of rehabilitation of a traction battery recharging operation by the on-board charger. This rehabilitation is implemented in cooperation with the vehicle supervisor, the on-board charger and the traction battery.

[0046] Optionally, the E8 rehabilitation can be manually controlled by an operator during a technical service inspection or repair. It is planned that he will be able to control the rehabilitation through a vehicle interface.

[0047] Once rehabilitation is activated, the process returns to the initial step E1.

[0048] The invention applies to vehicles comprising an electrically actuated parking brake, preferably to electric or hybrid motor vehicles, preferably rechargeable, as well as to any type of vehicle comprising an electric battery, such as an airplane, tractor, electric bicycle, etc.).

[0049] The invention is described in the above by way of example. It is understood that the person skilled in the art is able to produce different variant embodiments of the invention by associating, for example, the different characteristics above taken alone or in combination, without departing from the scope of the invention.

Claims

CLAIMS 1. Method for diagnosing a power supply fault in an electrically actuated parking brake (3) of a vehicle, the parking brake (3) comprising an electrically actuated motor (6) and a control unit (5) for the motor (6), the method comprising the following successive steps in the event of detection of an actuation request (E1) for the motor (6): - measurement (E2) of the supply current (Ip) and the voltage (Vp) at the motor supply terminals (6), - monitoring (E3) of the current (Ip) measured relative to a first current threshold (S1), the method being characterized in that it further comprises: - the comparison (E4) of the measured voltage (Vp) with respect to a second voltage threshold (S2) in the event of detection that the current (Ip) is lower than the first current threshold (S1) for at least a first duration (D1), - if the voltage (Vp) is higher than the second voltage threshold (S2), the signaling (E5) of an anomaly of the parking brake (3) and the activation (E5) of a vehicle reconfiguration mode including an inhibition of the operation of the engine (6).

2. Diagnostic method according to claim 1, characterized in that the first current threshold (S1) is between 5 milliamps and 15 milliamps, or preferably is equal to 10 milliamps, and the first duration (D1) is between 20 milliseconds and 200 milliseconds, or preferably is equal to 50 milliseconds.

3. Diagnostic method according to claim 1 or 2, characterized in that the second threshold (S2) has a value between 4 volts and 8 volts, or preferably is equal to 6 volts.

4. Diagnostic method according to any one of claims 1 to 3, characterized in that it further comprises, when the reconfiguration mode (E5) is activated and in case of detection of an actuation request (E6) of the motor (6): - monitoring (E7) of the measured current (Ip) in relation to a third current threshold (S3), - the rehabilitation command (E8) of the parking brake if the current (Ip) is greater than the third current threshold (S3) for at least a second duration (D2).

5. Diagnostic method according to any one of claims 1 to 4, characterized in that the reconfiguration mode (E5) further comprises an inhibition of a recharging operation of a traction battery of the vehicle carried out by an on-board charger of the vehicle.

6. Diagnostic method according to claims 4 and 5, characterized in that it further comprises the rehabilitation control (E8) of a recharging operation of the traction battery of the vehicle.

7. Diagnostic method according to any one of claims 1 to 6, characterized in that the signaling (E5) of the anomaly comprises the generation of a fault code and a command to illuminate a parking brake anomaly indicator light.

8. Control unit (5) of a vehicle parking brake (3) comprising means for implementing the diagnostic method according to any one of claims 1 to 7.

9. Motor vehicle comprising an electrically actuated parking brake (3) comprising an electric brake actuating motor (6) and a control unit according to claim 8.

10. Computer program comprising instructions which, when the program is executed by a control unit (5) of a vehicle parking brake (3), cause the latter to implement the method according to any one of claims 1 to 7.

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