WO2024062168A1

WO2024062168A1 - Method for diagnosing a supply fault affecting an electrically actuated parking brake

Info

Publication number: WO2024062168A1
Application number: PCT/FR2023/051172
Authority: WO
Inventors: Olivier BALENGHIEN
Original assignee: Stellantis Auto Sas
Priority date: 2022-09-23
Filing date: 2023-07-26
Publication date: 2024-03-28
Also published as: FR3140047B1; FR3140047A1

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 FAULT IN AN ELECTRICALLY ACTUATED PARKING BRAKE

[001] The present invention claims the priority of French application No. 2209670 filed on 09.23.2022, the content of which (text, drawings and claims) is here incorporated by reference.

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

[003] 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 transmission shaft line of the vehicle and a locking finger linked to a fixed component of the vehicle, also called "park finger", of which actuation in the tightened or loosened position is controlled by an electric motor and a control unit.

[004] We know the patent document US10953862B2 describing a method of operating an electrically actuated parking brake based on the measurement of the supply current. This method proposes that a temporal sequence of current variations be sent to the terminals of an interface for an operator control element of the parking brake. When power is supplied, a current measurement is carried out at one terminal of the interface. The driver demand is determined based on the current measurement. The electric parking brake is actuated based on current measurements. This document does not describe a diagnostic solution for open-circuit faults. [005] An open circuit anomaly of the power supply of the actuation motor results from the fact that the power supply wires of the actuation motor are broken or unsoldered from their connector. To check open circuit faults of the parking brake, a diagnostic function is generally provided which is in charge of monitoring the presence of a supply current at the motor terminals when it is actuated for engagement in the locked 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.

[006] However, there are normal operating situations where the current of the actuating motor is at 0 amperes. This leads to cases of false open circuit detection of the locking finger actuation motor. In other situations, unwanted micro-cuts are not detected.

[007] 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.

[008] 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 electric actuation motor and a control unit. control of the motor, the method comprising the following successive steps in the event of detection of a request to actuate the motor for engagement/disengagement of the parking brake:

- measuring the supply current and the voltage at the motor supply terminals,

- monitoring the current measured in relation to a first current threshold.

[009] According to the invention, the method further comprises: - comparing 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 greater than the second voltage threshold, signaling a parking brake anomaly and activating a vehicle reconfiguration mode including inhibition of engine operation.

[010] 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 equal to 50 milliseconds.

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

[012] According to a variant, the method further comprises, when the reconfiguration mode is activated and in the event of detection of a motor actuation request:

- monitoring the current measured in relation to a third current threshold,

- the parking brake rehabilitation command if the current is greater than the third current threshold for at least a second duration.

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

[014] According to a variant, the method further comprises controlling the rehabilitation of a recharging operation of the vehicle's traction battery. [015] Preferably, reporting the anomaly includes the generation of a fault code and a command to turn on a parking brake fault indicator light.

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

[017] We further envisage a motor vehicle comprising an electrically actuated parking brake comprising an electric brake actuation motor and the preceding parking brake control unit.

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

[019] The invention makes it possible to detect open circuit situations of the actuating motor of a vehicle parking brake. The invention strengthens existing diagnostics thanks to immediate detection based on current monitoring and monitoring of the presence of a bias voltage immediately after the outage. Detection can act in tens of milliseconds instead of usually a second or more. This makes it possible to put the engine in a fault state and warn the driver immediately before releasing the brake pedal. This improves the safety of the vehicle.

[020] Other characteristics and advantages of the present invention will appear more clearly on reading the detailed description which follows including embodiments of the invention given by way of non-limiting examples and illustrated by the appended drawings, in which : [021] [Fig.1] schematically represents a motor vehicle powertrain intended to implement the diagnostic method according to the invention.

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

[023] Figure 1 represents a motor vehicle powertrain comprising a traction motor 1 designed to transmit a driving torque to the drive wheels 11. The traction motor 1 can be an internal combustion engine or an electric traction machine. The powertrain can be thermal, hybrid or fully electric.

[024] A motor shaft 2 of the traction motor 1 is capable of rotating a transmission shaft line comprising a transmission member 12 of the motor torque. The transmission member 12 can be an automated gearbox, a reduction gear or a differential depending on the architecture of the vehicle.

[025] The powertrain further comprises a parking brake 3 comprising a toothed wheel 7 linked in rotation to a shaft of the transmission line, for example a shaft of the transmission member 12. Thus, the toothed wheel 7 can be linked to a reduction gear, a gearbox or a differential depending on the architecture of the vehicle. The parking brake 3 further comprises a locking finger 4, an electric actuation motor 6 and a motor control unit 5. The locking finger 4 is linked 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 actuation motor is powered by 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 actuation 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 as soon as that the driver places his foot on the brake pedal, while the vehicle is operating, preferably at a speed less than 5 km/h, before starting the vehicle, or that a braking force is exerted on the wheels.

[026] When an actuation request is received by the control unit 5, the actuation motor 6 can engage the locking finger 4 to move it in the toothed wheel 7 in the blocked position or disengage the locking finger 4 to move it to the released position. When the locking finger 4 blocks the toothed wheel 7 the entire transmission shaft line is stopped from rotating and the vehicle is therefore immobilized.

[027] The engagement and disengagement of the parking brake can be controlled by a position of the gear lever (“Park” position) 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.

[028] 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 system of traction battery and a control unit 13 of an on-board charger for the traction battery, possibly. Data communication means 9, of the type of a CAN bus (“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 Figure 1) a high-power traction battery system (having a voltage greater than 300 volts) and an electric charger for the traction battery connectable to an external energy source.

[029] As part of the diagnostic process, the supervisor 10 is designed to record a diagnostic and anomaly log, in particular open circuit anomalies of the brake actuation 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 audible indicator.

[030] In addition, the control units 12 and 13 of the traction battery system and the on-board charger can inhibit a recharging operation, in particular in the event of detection of an anomaly of the parking brake.

[031] Figure 2 is a diagram representing 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 calculator and electronic memories, the calculator and the memories being configured to execute the diagnostic process. But this is not obligatory. 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 including 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 (or even “software”)), or of electronic circuits (or “hardware”), or even of 'a combination of electronic circuits and software modules.

[032] At a first step E1 of the diagnostic method, the parking brake control unit detects a request for actuation of the parking brake. At this stage, 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 of 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 in the “Park” position or by a button command by the driver, or possibly by an automated function of the vehicle. [033] Following detection of the actuation request, the control unit measures in a second step E2 the electric current Ip and the voltage Vp across the motor terminals.

[034] Then, in accordance with the diagnostic method, the method comprises a third step E3 of monitoring the current Ip in relation to a current threshold S1, having a value of 10 milliamps for example. If it is detected 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 actuation motor. This verification step has the advantage of checking whether we are in the presence of a motor polarization state at the moment of the power cut. This situation is abnormal.

[035] 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.

[036] 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 bias voltage at the motor terminals as soon as the power cut is detected. Indeed, in the event of a circuit break, the passive discharge causes a reduction in voltage and its observation confirms the presence of an undesirable micro-cut.

[037] On the other hand, if Ip remains less than S1 only during 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 motor operation, this is a situation which should not trigger an anomaly raising. In this situation, the method returns to step E1 of waiting for detection of an actuation request. [038] In the fourth step E4, if it is detected that the voltage Vp is greater than a voltage threshold S2, this is a situation of open circuit anomaly because a bias voltage is still observed and consequently in a fifth step E5, the method triggers the signaling of a parking brake anomaly and the activation of a vehicle reconfiguration mode comprising inhibition of engine operation. The threshold S2 is between 4 volts and 8 volts, preferably equal to 6 volts. The value is chosen at an expected discharge bias voltage after the expiration of the duration D1. The observation of a polarization voltage after the duration D1 confirms the presence of an open circuit.

[039] 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.

[040] More precisely, reporting the anomaly E5 consists of generating an anomaly code in a so-called permanent state for its recording in a diagnostic log administered by the vehicle supervisor and consultable by an after-sales technical service. . The parking brake control unit outputs the fault code through the communication bus. In addition, the parking brake control unit generates a command to turn on a warning light and/or audible message on the vehicle dashboard in order to warn the driver of a fault.

[041] More precisely, step E5 of reconfiguring the vehicle includes inhibiting the operation of the parking brake motor until a rehabilitation of the motor is carried out. At this stage, the brake control unit is in an error state.

[042] Furthermore, preferably, step E5 includes an inhibition of a charging operation due to the fact that it is judged that the vehicle is not in a safe situation to carry out charging when connected to a charging station or an external energy source, because its parking cannot be ensured by the brake. The control unit of 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 possibly generated and reported to the driver.

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

[044] 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 at a value in the 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 appearance of the anomaly and that it has been resolved by itself.

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

[046] Optionally, the E8 rehabilitation can be controlled manually by an operator during a check or repair in technical service. It is expected that it can control the rehabilitation through a vehicle interface.

[047] Once the rehabilitation is activated, the process returns to the initial step E1. [048] 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 bike, etc...).

[049] The invention is described in the above by way of example. It is understood that the person skilled in the art is able to carry out different alternative embodiments of the invention by combining for example the different characteristics above taken alone or in combination, without departing from the scope of the invention.

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 electric actuation motor (6) and a control unit control (5) of the motor (6), the method comprising the following successive steps in the event of detection of an actuation request (E1) of the motor (6):

- measuring (E2) the supply current (Ip) and the voltage (Vp) at the motor supply terminals (6),

- monitoring (E3) of the current (Ip) measured in relation 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 greater 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 comprising an inhibition of the operation of the motor (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 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 the event 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 inhibition of a recharging operation of a vehicle traction battery operated by a charger boarded 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 vehicle's traction battery.

7. Diagnostic method according to any one of claims 1 to 6, characterized in that the reporting (E5) of the anomaly includes the generation of a fault code and a command to turn on a warning light. parking brake fault.

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 actuation motor (6) of the brake 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), lead it to implement the method according to one any of claims 1 to 7.