Wheel end braking device, braking system and electric vehicle

Abstract

The invention discloses a wheel end braking device, a braking system and an electric vehicle, and relates to the technical field of new energy automobiles. The wheel end braking device comprises a braking unit and a parking unit, the braking unit comprises a braking motor driving circuit and a braking motor, the parking unit comprises a parking unit driving circuit, a power supply switch and a parking actuator, and the parking unit driving circuit is used for receiving power supplied by a low-voltage battery through the power supply switch and driving the parking actuator to execute parking. In the parking process of the electric vehicle, the power supply switch is used for conducting connection between the parking unit driving circuit and the low-voltage battery, and the parking unit driving circuit receives power supplied by the low-voltage battery and outputs driving current to the parking actuator so that the parking actuator can execute parking. When the electric vehicle is in a non-parking state, the power supply switch is used for disconnecting the parking unit driving circuit from the low-voltage battery. According to the scheme, the reliability of the wheel end braking device and the safety of the electric vehicle are improved with low cost.

Description

Technical Field

[0001] This application relates to the field of electric vehicles, and more specifically, to a wheel-end braking device, a braking system, and an electric vehicle. Background Technology

[0002] Electric vehicle brake-by-wire products include electronic mechanical brakes (EMB) and electronic parking brakes (EPB). The EMB's brake motor and movement mechanism generate braking force. The EPB replaces the manual operation of the original parking brake lever and cable with electronic control, thus completing the entire parking braking process. The EMB's movement mechanism is not self-locking; if the motor loses power, the mechanism will spring back and release the brake. Prolonged power supply to the EMB's motor can lead to severe overheating. The EPB locks the EMB's movement mechanism when prolonged braking or parking is required, preventing it from springing back and maintaining braking or parking. The functional safety objective of the EPB includes avoiding unexpected parking braking forces. If unexpected braking forces are generated during vehicle operation, it may cause the rear wheels to lock up, resulting in unexpected yaw and vehicle instability.

[0003] Therefore, how to avoid the unexpected activation of the electronic parking brake is a problem that needs to be solved. Summary of the Invention

[0004] This application provides a wheel-end braking device, braking system, and electric vehicle. By adding a power supply switch to the power bus of the electronic parking brake for control, the switch remains disconnected when there is no parking command, so that no current flows through the drive circuit of the electronic parking brake, ensuring that it will not start unexpectedly. Even if any electronic component of the electronic parking brake fails, the safety objectives will not be violated. This improves the reliability of the wheel-end braking device and the safety of the electric vehicle at low cost.

[0005] In a first aspect, this application provides a wheel-end braking device, comprising a braking unit and a parking unit. The braking unit includes a brake motor drive circuit and a brake motor. The parking unit includes a parking unit drive circuit, a power supply switch, and a parking actuator. The brake motor drive circuit receives power from a low-voltage battery and drives the brake motor to output braking torque. The parking unit drive circuit receives power from the low-voltage battery via the power supply switch and drives the parking actuator to perform parking. During parking of the electric vehicle, the power supply switch connects the parking unit drive circuit to the low-voltage battery, and the parking unit drive circuit receives power from the low-voltage battery and outputs a drive current to the parking actuator to perform parking. In the non-parked state of the electric vehicle, the power supply switch disconnects the parking unit drive circuit from the low-voltage battery.

[0006] Wheel-end braking devices are used to output braking force to brake the wheels of electric vehicles and also to perform parking maneuvers. The brake motor of the braking unit outputs braking torque, but because the moving mechanism of the braking unit that outputs braking force is not self-locking, maintaining braking force for extended periods requires continuous power, which can cause the brake motor to overheat, affecting its efficiency and safety. Therefore, parking is performed through the parking actuator of the parking unit. When prolonged braking or parking is required, the parking actuator locks the moving mechanism of the braking unit to maintain braking force. For the parking actuator to perform parking maneuvers, the parking unit drive circuit receives power from the low-voltage battery and outputs drive current to the parking actuator to drive it.

[0007] The braking unit in this application is also called the electromechanical braking (EMB) unit, and the parking unit is also called the electronic parking brake (EPB) unit, which will not be described further hereafter.

[0008] In existing solutions, a malfunction in the electronic components of the parking unit's drive circuit could cause the parking actuator to unexpectedly receive current, leading to unintended parking and causing the wheel-end braking devices to output unexpected braking force, thus affecting the safety of the electric vehicle. Therefore, the parking unit also includes a power supply switch, which is used to connect or disconnect the low-voltage battery from the parking unit's drive circuit. When the electric vehicle is parking, or in a parked state, the power supply switch connects the low-voltage battery and the parking unit's drive circuit. The parking unit's drive circuit receives power from the low-voltage battery through the power supply switch and outputs drive current to the parking actuator, thereby enabling the parking actuator to perform parking. However, when the electric vehicle is not parked, such as while driving, the power supply switch disconnects the parking unit's drive circuit from the low-voltage battery. Therefore, the parking unit's drive circuit cannot receive power from the low-voltage battery and cannot drive the parking actuator. The parking unit will not perform parking, and the wheel-end braking devices will not output unexpected braking force.

[0009] It should be understood that when the electric vehicle is in a non-parking state, the power supply switch only disconnects the connection between the parking unit drive circuit and the low-voltage battery, without affecting the connection between the brake motor drive circuit and the low-voltage battery. Therefore, the brake motor drive circuit can normally receive power from the low-voltage battery and drive the brake motor, and the brake unit can normally output braking torque at this time.

[0010] According to the solution of this application, a power supply switch is added to the power supply bus of the electronic parking brake for control. The switch remains disconnected when there is no parking command, so that no current flows through the drive circuit of the electronic parking brake, ensuring that it will not start unexpectedly. Even if any electronic component of the electronic parking brake fails, the safety objective will not be violated. This improves the reliability of the wheel-end braking device and the safety of electric vehicles at low cost.

[0011] In conjunction with the first aspect, in some implementations of the first aspect, the wheel-end braking device includes a DC bus for receiving power from a low-voltage battery, the DC bus for supplying power to the brake motor drive circuit and for supplying power to the parking unit drive circuit via a power supply switch.

[0012] The wheel-end braking device receives power from the DC bus powered by the low-voltage battery, the brake motor drive circuit receives current from the DC bus, and the parking unit drive circuit receives current from the DC bus through the power supply switch. Therefore, the power supply switch only controls the conduction and cutoff between the parking unit drive circuit and the DC bus, and does not affect the connection between the brake motor drive circuit and the DC bus.

[0013] According to the solution in this application, the power supply switch is located between the parking unit drive circuit and the DC bus, which avoids affecting the normal power supply of the braking unit and improves the reliability and safety of the wheel-end braking device.

[0014] In conjunction with the first aspect, in some implementations of the first aspect, the wheel-end braking device further includes a DC bus switch, the DC bus being used to receive power from a low-voltage battery via the DC bus switch.

[0015] The wheel-end braking system also includes a DC bus switch, which controls the connection and disconnection between the wheel-end braking system and the low-voltage battery. When the DC bus switch is off, the entire wheel-end braking system, including the brake motor drive circuit and the parking unit drive circuit, cannot receive power from the low-voltage battery. The DC bus switch and the power supply switch have different positions and functions.

[0016] According to the solution of this application, the DC bus switch controls the connection between the entire wheel-end braking device and the low-voltage battery, which can disconnect the power supply to the wheel-end braking device, prevent the failure of the wheel-end braking device from spreading to the low-voltage battery, and improve the reliability and safety of the wheel-end braking device.

[0017] In conjunction with the first aspect, in some implementations of the first aspect, one end of the power supply switch is used to receive power from the DC bus, and the other end of the power supply switch is used to supply power to the parking unit drive circuit.

[0018] There are various ways to implement a power supply switch, such as a relay, a single-pole single-throw switch, or a switching device composed of an insulated-gate bipolar transistor and anti-parallel diodes. One end of the power supply switch is connected to the DC bus, and the other end is connected to the parking unit drive circuit.

[0019] In conjunction with the first aspect, in some implementations of the first aspect, the wheel-end braking device is specifically used to control the brake motor to output braking torque during the parking process of the electric vehicle, then control the power supply switch to be turned on, and control the parking unit drive circuit to drive the parking actuator to perform parking.

[0020] The wheel-end braking system performs parking maneuvers in two stages: EMB motor clamping and EPB locking. During parking maneuvers, the braking unit first outputs braking force. Once the braking force reaches the required parking force, the power supply switch connects the parking unit drive circuit and the low-voltage battery. The parking unit drive unit receives power from the low-voltage battery and then controls the parking brake unit drive circuit to output drive current, thereby driving the parking actuator to perform parking maneuvers.

[0021] According to the solution of this application, the power supply switch remains open before the braking unit outputs braking torque, so that no current flows through the drive circuit of the electronic parking brake, ensuring that it will not start unexpectedly. When the braking unit outputs braking torque, the power supply switch is turned on, so that the parking unit can perform parking, avoiding the wheel-end braking device from outputting unexpected braking force, improving the reliability of the wheel-end braking device and the safety of electric vehicles.

[0022] In conjunction with the first aspect, in some implementations of the first aspect, the wheel-end braking device is specifically used to control the parking unit drive circuit to stop outputting drive current to the parking actuator so that the parking actuator can release the parking during the process of releasing the electric vehicle from parking, and then control the power supply switch to disconnect.

[0023] When the electric vehicle is released from parking, that is, when the electric vehicle changes from a parked state to a non-parked state, the control circuit of the parking unit stops outputting drive current to the parking actuator, thereby releasing the parking actuator and no longer locking the brake motor. The power supply switch is disconnected after the parking is released, returning to the non-parked state, disconnecting the connection between the parking unit drive circuit and the low-voltage battery, and no current flows through the electronic parking brake drive circuit, ensuring that the parking actuator will not start unexpectedly.

[0024] According to the solution in this application, after the parking brake is released, the control power supply switch is disconnected, so that no current flows through the drive circuit of the electronic parking brake, ensuring that it will not start unexpectedly, thereby improving the reliability of the wheel-end braking device and the safety of electric vehicles at low cost.

[0025] In conjunction with the first aspect, in some implementations of the first aspect, the wheel-end braking device is also used to first control the power supply switch to be turned on and then control the power supply switch to be turned off during the power-on self-test process of the electric vehicle.

[0026] Electric vehicles perform self-tests upon startup. For example, when the unlock button is pressed, the door is opened, or the start button is pressed, the various electronic control units of the electric vehicle send test signals to the corresponding sensors and actuators to test whether they are functioning properly. During the power-on self-test, the wheel-end braking system controls the power supply switch to turn on and off, actively testing whether the power supply switch can turn on and off according to instructions, thus eliminating latent faults.

[0027] According to the solution in this application, during the power-on self-test process, the wheel-end braking device actively tests whether the power supply switch can be turned on and off according to the command, thereby eliminating latent faults in the power supply switch and improving the reliability of the wheel-end braking device and the safety of electric vehicles at low cost.

[0028] In conjunction with the first aspect, in some implementations of the first aspect, the wheel-end braking device is used to report a fault signal when the power supply switch fails to conduct within a preset time period or fails to disconnect after being conducted during the power-on self-test of the electric vehicle.

[0029] During the power-on self-test of the wheel-end braking device, if the power supply switch fails to conduct and disconnect normally as instructed, such as failing to conduct within the preset time or failing to disconnect after conduction, it indicates that the power supply switch has malfunctioned. This may cause the parking unit to malfunction, affecting the safety of the electric vehicle. A fault signal needs to be reported to remind the driver.

[0030] In one scenario, a short circuit occurs in the power supply switch. At this time, the parking unit can control the current through the parking unit drive circuit to enable the parking actuator to perform parking and release. However, since there is no power supply switch to disconnect the parking unit drive circuit from the low-voltage battery in the non-parking state, when the parking unit drive circuit fails, it may cause the wheel-end braking device to start unexpectedly, affecting the driving safety of electric vehicles and reducing the functional safety of the parking system.

[0031] In another scenario, if the power switch is open, the parking unit drive circuit cannot receive power from the low-voltage battery and therefore cannot drive the parking actuator to perform parking. In this case, the EPB will not work and needs to report a fault signal to remind the driver.

[0032] According to the solution in this application, during the power-on self-test process, the wheel-end braking device actively tests whether the power supply switch can be turned on and off according to the command, thereby eliminating latent faults in the power supply switch and improving the reliability of the wheel-end braking device and the safety of electric vehicles at low cost.

[0033] In conjunction with the first aspect, in some implementations of the first aspect, the wheel-end braking device includes a brake control chip, which is used to control the magnitude of the current output from the brake motor drive circuit to the brake motor, and is also used to control the on and off of the power supply switch. The brake control chip meets the requirements of the Automotive Safety Integrity ASIL D level.

[0034] The wheel-end braking device includes a parking control chip, which is used to control the parking unit drive circuit to adjust the drive current output to the parking actuator. During the parking process of the electric vehicle, the parking control chip controls the parking unit drive circuit to output drive current to the parking actuator; when the electric vehicle is not parked, it controls the parking unit drive circuit to stop outputting current to the parking actuator.

[0035] The brake control chip, or EMB control chip, is used to control the brake motor drive circuit. High-functional-safety-level chip models are available; therefore, reusing the brake control chip to control the power supply switch can improve the functional safety level of the parking unit. The power supply switch is directly controlled by the brake control chip, which meets the ASIL D level requirements for automotive safety integrity. Combined with power-on self-test to eliminate latent faults in the power supply switch, the system meets ASIL C requirements. In this case, the parking control chip (EPB driver chip) for the parking unit drive circuit can be used at QM level without considering functional safety requirements.

[0036] According to the solution of this application, a braking control chip is used to control the power supply switch. The braking control chip meets the requirements of the Automotive Safety Integrity ASIL D level, thereby improving the reliability of the wheel-end braking device and the safety of electric vehicles at low cost.

[0037] In conjunction with the first aspect, in some implementations of the first aspect, the wheel-end braking device includes a main control chip, which is used to control the on and off of the power supply switch, and the main control chip meets the requirements of the Automotive Safety Integrity ASIL D level.

[0038] The main control chip is an additional control chip that meets the ASIL D level requirements for automotive safety integrity. It controls the on / off state of the power supply switch. By meeting ASIL D requirements and combining it with power-on self-test to eliminate latent faults in the power supply switch, the system achieves ASIL C requirements. In this case, the control chip for the parking unit drive circuit, i.e., the EPB drive chip, can be used at QM level without considering functional safety requirements.

[0039] According to the solution in this application, a separate main control chip is used to control the power supply switch. The main control chip meets the requirements of the Automotive Safety Integrity ASIL D level, thereby improving the reliability of the wheel-end braking device and the safety of electric vehicles at a low cost.

[0040] In conjunction with the first aspect, in some implementations of the first aspect, the wheel-end braking device is also used to control the brake motor to rotate in the reverse direction after the parking unit drive circuit receives power from the low-voltage battery and outputs drive current to the parking actuator to enable the parking actuator to perform parking.

[0041] After the parking actuator completes the parking maneuver, the wheel-end braking device controls the brake motor to rotate in the opposite direction to confirm whether parking is complete. Once parking is complete, the vehicle is in the parking state, at which point the brake motor is locked and cannot reverse.

[0042] According to the solution in this application, after parking is performed, the EMB motor is reversed to confirm that it has been locked, which improves the reliability of the wheel-end braking device for parking and the safety of electric vehicles.

[0043] In conjunction with the first aspect, in some implementations of the first aspect, the wheel-end braking device is used to control the brake motor to output the braking torque indicated by the opening of the brake pedal of the electric vehicle when the electric vehicle is not parked; and to control the brake motor of the braking unit to output a preset braking torque when the electric vehicle is parked.

[0044] When the electric vehicle is in motion, the wheel-end braking system outputs braking force indicated by the brake pedal opening. When the electric vehicle is parked or in a parked state, the wheel-end braking system outputs a preset braking torque to achieve parking.

[0045] In this application, the brake pedal is also referred to as the brake or brake pedal. The opening degree of the brake pedal indicates the amount of braking force required by the driver. The larger the opening degree of the brake pedal, the greater the driver's braking demand, and the greater the braking force required from the wheel-end braking device. During normal vehicle operation, the brake motor drive circuit controls the current output to the brake motor according to the brake pedal opening degree, so that the brake motor outputs the braking torque indicated by the brake pedal opening degree. The larger the brake pedal opening degree, the greater the current output by the brake motor drive circuit, and thus the greater the braking torque output by the brake motor. Conversely, the smaller the brake pedal opening degree, the smaller the current output by the brake motor drive circuit, and thus the smaller the braking torque output by the brake motor.

[0046] In conjunction with the first aspect, in some implementations of the first aspect, the wheel-end braking device is also used to control the brake motor to increase the output braking torque after the parking unit drive circuit receives power from the low-voltage battery and outputs drive current to the parking actuator to enable the parking actuator to perform parking.

[0047] When electric vehicles experience high-speed driving, downhill driving, and continuous braking, the brake disc temperature can increase. If forced parking is applied under these conditions, the brake calipers, after clamping the brake disc, will cool down due to air convection, causing the disc to contract and reducing the actual clamping force. This affects braking efficiency and may result in insufficient parking braking force. Because the parking actuator locks the brake motor in one direction, the brake motor can increase its output braking torque to further tighten the brakes.

[0048] According to the solution in this application, the power supply switch will not affect the re-clamping function of the wheel-end braking device, thereby improving the parking reliability of the wheel-end braking device and the safety of the electric vehicle.

[0049] In conjunction with the first aspect, in some implementations of the first aspect, the parking actuator includes a ratchet and a pawl. The ratchet is mechanically connected to the drive motor. When the parking actuator performs parking, the pawl engages with the ratchet and is used to lock the ratchet in one direction to prevent the drive motor from rotating in the opposite direction. When the parking actuator releases parking, the pawl disengages from the ratchet.

[0050] In a second aspect, this application provides a braking system including a central controller and four wheel-end brakes, wherein the four wheel-end brakes include at least one wheel-end braking device as described in the first aspect and its various implementations, the central controller being used to control the four wheel-end brakes to output braking force to brake an electric vehicle, and the central controller being used to control the wheel-end braking devices to perform parking.

[0051] Not all four wheel-end brakes in a braking system necessarily include a parking unit; in some cases, only some wheel-end brakes include a parking unit.

[0052] Thirdly, this application provides an electric vehicle including a wheel-end braking device, a brake pedal, and a parking button as described in the first aspect and its various implementations, wherein the brake pedal is used to instruct the wheel-end braking device to output braking force to the wheels of the electric vehicle, and the parking button is used to instruct the electric vehicle to engage or disengage parking.

[0053] Other beneficial effects can be found in the description of the first aspect, and will not be repeated here. Attached Figure Description

[0054] Figure 1 This is a schematic diagram of the electric vehicle architecture provided in an embodiment of this application;

[0055] Figure 2 This is a schematic diagram of a wheel-end braking device provided in an embodiment of this application;

[0056] Figure 3This is a schematic diagram of another wheel-end braking device provided in an embodiment of this application;

[0057] Figure 4 This is a schematic diagram of a parking actuator provided in an embodiment of this application;

[0058] Figure 5 This is a schematic diagram of the parking actuator performing the parking process according to an embodiment of this application;

[0059] Figure 6 This is a circuit diagram of a wheel-end braking device provided in an embodiment of this application. Detailed Implementation

[0060] The technical solutions in this application will now be described in conjunction with the accompanying drawings. The detailed descriptions and drawings of the following embodiments are used to exemplarily illustrate the principles of this application, but should not be used to limit the scope of this application; that is, this application is not limited to the described embodiments.

[0061] The electronic park brake (EPB) replaces the manual operation of the parking brake lever and cable with electronic control, thus completing the entire parking braking process. The moving mechanism of the electronic mechanical brake (EMB) system is not self-locking; if the motor is de-energized, the moving mechanism will spring back and release the brake. However, prolonged power supply to the motor of the electronic mechanical brake system can lead to severe overheating. The electronic parking brake locks the moving mechanism of the electronic mechanical brake system when prolonged braking or parking is required, preventing it from springing back and thus maintaining braking or parking.

[0062] Some safety objectives of the braking system include: the braking system should avoid failure leading to unintended parking force (ASIL D level) and the braking system should avoid failure leading to excessively low parking force (ASIL C level). These two safety objectives are related to the electronic parking brake, which is completed in two steps: first, the brake motor enables the caliper to clamp; second, the electronic parking brake enables locking. Failure scenarios are divided into parking failure and parking release failure. Examples include: loss of vehicle parking braking force (ASIL C level); unintended activation of the vehicle parking brake (ASIL D level); loss of vehicle parking brake release, considering the vehicle is stationary and poses no safety risk (QM level); and unintended activation of the vehicle parking brake release (ASIL C level). Considering these four processes, the highest level of hazard for unintended release of the vehicle parking function is ASIL C, and the highest level of hazard for unintended activation of the vehicle parking function is ASIL D.

[0063] To address the aforementioned issues, this application provides a wheel-end braking device, braking system, and electric vehicle. By adding a power supply switch to the power bus of the electronic parking brake for control, the switch remains disconnected when there is no parking command, thus ensuring that no current flows through the drive circuit of the electronic parking brake and preventing unexpected activation. Even if any electronic component of the electronic parking brake fails, the safety objectives will not be violated, thereby improving the reliability of the wheel-end braking device and the safety of the electric vehicle at a low cost.

[0064] Figure 1 This is a schematic diagram of the architecture of the electric vehicle 10 provided in the embodiments of this application.

[0065] like Figure 1 As shown, the electric vehicle 10 includes wheels and a braking system. The braking system includes four wheel-end brakes 110 and a central controller 120. The electric vehicle 10 also includes a brake pedal and a parking button. The driver controls the vehicle's driving state via the brake pedal and the parking button. During driving, when the electric vehicle 10 needs to brake, the driver presses the brake pedal. The central controller 120 receives the braking signal from the brake pedal and outputs braking torque signals to the four wheel-end brakes 110. The central controller 120 controls the four wheel-end brakes 110 to output braking force to brake the electric vehicle 10. When the driver presses the parking torque button, the central controller 120 also controls the wheel-end brake devices 100 among the four wheel-end brakes 110 to perform parking.

[0066] The parking signal comes from the Electronic Parking Brake (EPB) system. When the driver presses the parking button, the EPB system generates a parking signal and transmits it to the central controller 120. Alternatively, the parking signal may come from other parking systems, such as when the driver shifts the vehicle into Park (P) gear, or from the Auto Hold system.

[0067] The four wheel-end brakes 110 include at least one wheel-end brake device 100 provided in this application.

[0068] Figure 2 and Figure 3 This is a schematic diagram of the wheel-end braking device 100 according to an embodiment of this application.

[0069] like Figure 2As shown, the wheel-end braking device 100 includes a braking unit and a parking unit. The braking unit includes a brake motor drive circuit 104 and a brake motor 105. The parking unit includes a parking unit drive circuit 102, a power supply switch 101, and a parking actuator 103. The brake motor drive circuit 104 is used to receive power from the low-voltage battery 20 and drive the brake motor 105 to output braking torque. The parking unit drive circuit 102 is used to receive power from the low-voltage battery 20 through the power supply switch 101 and drive the parking actuator 103 to perform parking.

[0070] like Figure 3 As shown, the braking unit specifically includes a brake motor 105 and a brake caliper. The brake motor 105 outputs braking torque to drive the brake caliper to clamp the brake disc of the electric vehicle 10. The clamping force generates friction between the brake caliper and the brake disc. The braking unit includes a thrust bearing, a ball screw assembly, and a piston, etc. The braking unit converts the rotational torque of the brake motor 105 into a linear clamping force, which applies pressure to the brake disc through friction pads, thereby achieving the braking effect. During vehicle braking, the brake motor drive circuit 104 drives the brake motor 105 to generate braking torque, and the brake motor 105 then drives the brake caliper to clamp the brake disc.

[0071] Figure 4 This is a schematic diagram of a parking actuator 103 provided in an embodiment of this application.

[0072] The wheel-end braking device 100 includes a parking unit. The parking unit includes a parking motor and a parking actuator 103. During the operation of the electric vehicle 10, when the central controller receives a parking signal, the central controller transmits the parking signal to the wheel-end braking device 100. The wheel-end braking device 100 first controls the brake motor 105 to drive the brake caliper to clamp the brake disc. After the brake disc is clamped, the wheel-end braking device 100 controls the parking actuator 103 to lock the brake motor 105 using a locking mechanism such as a locking lever, so that the actuator remains in the state of clamping the brake disc and does not release, thereby keeping the vehicle in a parked state.

[0073] In one embodiment, the parking actuator 103 includes a ratchet and a pawl. The ratchet is mechanically connected to a drive motor. When the parking actuator 103 performs parking, the pawl engages with the ratchet and is used to lock the ratchet in one direction to prevent the drive motor from rotating in the opposite direction. When the parking actuator 103 releases parking, the pawl disengages from the ratchet.

[0074] like Figure 4As shown, the parking unit includes a pawl and a ratchet that cooperate with each other. The ratchet is mounted on the rotor of the brake motor 105. When the brake motor 105 rotates, it drives the ratchet to rotate along with the rotor of the brake motor 105. When the vehicle is parked, the parking actuator 103 drives the pawl to move so that the pawl engages in the gear groove of the ratchet, thereby locking the brake motor 105.

[0075] Figure 5 This is a schematic diagram of the parking actuator 103 performing the parking process according to an embodiment of this application. Figure 5 (a) is a schematic diagram when the vehicle is not parked. In the non-parked state, the pawl is outside the tooth groove of the ratchet, and the rotor of the brake motor 105 can rotate freely, that is, the brake motor 105 is not locked. Figure 5 In (b), when the vehicle is parked, the ratchet gets stuck in the tooth groove of the ratchet, and the rotor of the brake motor is locked and cannot rotate freely. Since the brake motor 105 cannot rotate, the actuator can always keep clamped to the brake disc, so the electric vehicle 10 is in the parking state.

[0076] In one embodiment, the wheel-end braking device 100 is used to control the brake motor 105 to output the braking torque indicated by the opening of the brake pedal of the electric vehicle 10 when the electric vehicle 10 is not parked; and to control the brake motor 105 of the braking unit to output a preset braking torque when the electric vehicle 10 is parked.

[0077] While the electric vehicle 10 is in motion, the wheel-end braking device 100 outputs braking force indicating the brake pedal opening degree. During or while the electric vehicle 10 is parked, the wheel-end braking device 100 outputs a preset braking torque to achieve parking.

[0078] Based on the working principle of the parking brake unit, unintended release of the EPB will directly cause harm. However, the EPB has no clamping force after being unexpectedly enabled; braking force will only appear after the brake motor 105 intervenes, leading to harm. Therefore, unintended release of the EPB relies entirely on the parking brake unit itself. However, in the current solution, the EPB driver chip lacks a functional safety rating and cannot meet the system's ASILC requirements.

[0079] See also Figure 2 The parking unit includes a power supply switch 101. During the parking process of the electric vehicle 10, the power supply switch 101 connects the parking unit drive circuit 102 to the low-voltage battery 20. The parking unit drive circuit 102 receives power from the low-voltage battery 20 and outputs drive current to the parking actuator 103 to perform parking. When the electric vehicle 10 is not parked, the power supply switch 101 disconnects the parking unit drive circuit 102 from the low-voltage battery 20.

[0080] The brake motor 105 of the braking unit is used to output braking torque. However, since the motion mechanism of the braking unit that outputs braking force is not self-locking, maintaining the braking force for a long time requires continuous power supply, which would cause the brake motor 105 to overheat, affecting its efficiency and safety. Therefore, parking is performed by the parking actuator 103 of the parking unit. When long-term braking or parking is required, the parking actuator 103 locks the motion mechanism of the braking unit to maintain the braking force. In order to perform parking, the parking unit drive circuit 102 needs to receive power from the low-voltage battery 20 and output drive current to the parking actuator 103 to drive the parking actuator 103.

[0081] The functional safety objective of the parking unit is to avoid generating unexpected parking braking forces (ASIL-D level). If unexpected braking forces are generated during the operation of the electric vehicle 10, it may cause the rear wheels to lock up, resulting in unexpected yaw and vehicle instability. The EPB's safety control functions have high safety requirements. To meet these requirements, the EPB's parking unit drive circuit 102 needs to meet functional safety requirements in terms of diagnostic coverage and hardware failure rate. However, currently, there are no high ASIL-level EPB drive chips available. Therefore, in the existing solution, when electronic components in the parking unit drive circuit 102 malfunction, the parking actuator 103 may unexpectedly receive current, causing unexpected parking activation. This results in the wheel-end braking device 100 outputting unexpected braking forces, affecting the safety of the electric vehicle 10.

[0082] The power supply switch 101 is used to connect or disconnect the low-voltage battery 20 from the parking unit drive circuit 102. When the electric vehicle 10 is parking, or when the electric vehicle 10 is in a parking state, the power supply switch 101 connects the low-voltage battery 20 and the parking unit drive circuit 102. The parking unit drive circuit 102 receives power from the low-voltage battery 20 through the power supply switch 101 and outputs drive current to the parking actuator 103, thereby enabling the parking actuator 103 to perform parking. When the electric vehicle 10 is in a non-parking state, such as during driving, the power supply switch 101 disconnects the parking unit drive circuit 102 from the low-voltage battery 20. Therefore, the parking unit drive circuit 102 cannot receive power from the low-voltage battery 20, and thus cannot drive the parking actuator 103. The parking unit will not perform parking, and the wheel-end braking device 100 will not output unexpected braking force.

[0083] It should be understood that when the electric vehicle 10 is in a non-parking state, the power supply switch 101 only disconnects the connection between the parking unit drive circuit 102 and the low-voltage battery 20, without affecting the connection between the brake motor drive circuit 104 and the low-voltage battery 20. Therefore, the brake motor drive circuit 104 can normally receive power from the low-voltage battery 20 and drive the brake motor 105. At this time, the braking unit can normally output braking torque.

[0084] According to the solution of this application, a power supply switch 101 is added to the power supply bus of the electronic parking brake for control. It remains disconnected when there is no parking command, so that no current flows through the drive circuit of the electronic parking brake, ensuring that it will not start unexpectedly. Even if any electronic component of the electronic parking brake fails, the safety objective will not be violated. This improves the reliability of the wheel-end braking device 100 and the safety of the electric vehicle 10 at low cost.

[0085] Figure 6 This is a circuit diagram of a wheel-end braking device 100 provided in an embodiment of this application.

[0086] like Figure 6 As shown, the wheel-end braking device 100 includes a DC bus for receiving power from the low-voltage battery 20. The DC bus is used to supply power to the brake motor drive circuit 104 and to supply power to the parking unit drive circuit 102 via the power supply switch 101.

[0087] The wheel-end braking device 100 receives power from the DC bus powered by the low-voltage battery 20, the brake motor drive circuit 104 receives current from the DC bus, and the parking unit drive circuit 102 receives current from the DC bus through the power supply switch 101. Therefore, the power supply switch 101 only controls the conduction and cutoff between the parking unit drive circuit 102 and the DC bus, and does not affect the connection between the brake motor drive circuit 104 and the DC bus.

[0088] In one embodiment, the wheel-end braking device 100 further includes a DC bus switch, the DC bus being used to receive power from the low-voltage battery 20 via the DC bus switch.

[0089] The wheel-end braking device 100 also includes a DC bus switch, which controls the connection and disconnection between the wheel-end braking device 100 and the low-voltage battery 20. When the DC bus switch is off, the entire wheel-end braking device 100, including the brake motor drive circuit 104 and the parking unit drive circuit 102, cannot receive power from the low-voltage battery 20. The DC bus switch and the power supply switch 101 are located and function differently.

[0090] In one embodiment, one end of the power supply switch 101 is used to receive power from the DC bus, and the other end of the power supply switch 101 is used to supply power to the parking unit drive circuit 102.

[0091] The power supply switch 101 can be implemented in various ways, such as a relay, a single-pole single-throw switch, or a switching device composed of an insulated-gate bipolar transistor and an anti-parallel diode. One end of the power supply switch 101 is connected to the DC bus, and the other end is connected to the parking unit drive circuit 102.

[0092] In one embodiment, the wheel-end braking device 100 is specifically used to control the brake motor 105 to output braking torque during the parking process of the electric vehicle 10, then control the power supply switch 101 to be turned on, and control the parking unit drive circuit 102 to drive the parking actuator 103 to perform parking.

[0093] The wheel-end braking device 100 performs parking in two processes: EMB motor clamping and EPB locking. During the parking process, the braking unit first outputs braking force. When the braking force output by the braking unit reaches the parking braking force, the power supply switch 101 is controlled to connect the parking unit drive circuit 102 and the low-voltage battery 20. The parking unit drive unit receives power from the low-voltage battery 20 and then controls the parking brake unit drive circuit to output drive current to drive the parking actuator 103 to perform parking.

[0094] In one embodiment, the wheel-end braking device 100 is specifically used to control the parking unit drive circuit 102 to stop outputting drive current to the parking actuator 103 so that the parking actuator 103 can be released during the process of releasing the parking of the electric vehicle 10, and then control the power supply switch 101 to be disconnected.

[0095] When the electric vehicle 10 is released from parking, that is, when the electric vehicle 10 changes from the parking state to the non-parking state, the control parking unit drive circuit 102 stops outputting drive current to the parking actuator 103, thereby releasing the parking actuator 103 and no longer locking the brake motor 105. The power supply switch 101 is turned off after the parking is released, returning to the non-parking state, disconnecting the connection between the parking unit drive circuit 102 and the low-voltage battery 20, and no current flows through the drive circuit of the electronic parking brake, ensuring that the parking actuator 103 will not start unexpectedly.

[0096] In one embodiment, the wheel-end braking device 100 is also used to control the power supply switch 101 to be turned on and then control the power supply switch 101 to be turned off during the power-on self-test process of the electric vehicle 10.

[0097] When the electric vehicle 10 starts, it performs a self-test. For example, when the unlock button is pressed, the door is opened, or the start button is pressed, each electronic control unit of the electric vehicle 10 sends test signals to the corresponding sensors and actuators to test whether they are working properly. During the power-on self-test, the wheel-end braking device 100 controls the power supply switch 101 to turn on and off, actively testing that the power supply switch 101 can turn on and off according to the instructions, thus eliminating latent faults.

[0098] According to the solution of this application, during the power-on self-test process, the wheel-end braking device 100 actively tests whether the power supply switch 101 can be turned on and off according to the command, eliminates the latent fault of the power supply switch 101, and improves the reliability of the wheel-end braking device 100 and the safety of the electric vehicle 10 at low cost.

[0099] In one embodiment, the wheel-end braking device 100 is used to report a fault signal when the power supply switch 101 fails to turn on within a preset time period or fails to turn off after turning on during the power-on self-test process of the electric vehicle 10.

[0100] During the power-on self-test of the wheel-end braking device 100, if the power supply switch 101 fails to perform normal conduction and disconnection as instructed, such as failing to conduct within the preset time or failing to disconnect after conduction, it indicates that the power supply switch 101 has malfunctioned. This may cause the parking unit to malfunction, affecting the safety of the electric vehicle 10. A fault signal needs to be reported to remind the driver.

[0101] In one scenario, if the power supply switch 101 short-circuits, the parking unit can control the current through the parking unit drive circuit 102 to enable the parking actuator 103 to perform parking and release. However, since the power supply switch 101 is not disconnected from the low-voltage battery 20 in the non-parking state, when the parking unit drive circuit 102 fails, the wheel-end brake device 100 may experience unexpected parking start, affecting the driving safety of the electric vehicle 10 and reducing the functional safety of the parking system.

[0102] In another scenario, if the power switch 101 is open, the parking unit drive circuit 102 cannot receive power from the low-voltage battery 20, and therefore cannot drive the parking actuator 103 to perform parking. In this case, the EPB cannot work and needs to report a fault signal to remind the driver.

[0103] In one embodiment, the wheel-end braking device 100 includes a braking control chip, which is used to control the current output from the brake motor drive circuit 104 to the brake motor 105. The braking control chip is also used to control the on and off of the power supply switch 101. The braking control chip meets the requirements of the Automotive Safety Integrity ASIL D level.

[0104] The wheel-end braking device 100 includes a parking control chip. The parking control chip is used to control the parking unit drive circuit 102 to adjust the drive current output to the parking actuator 103. During the parking process of the electric vehicle 10, the parking control chip controls the parking unit drive circuit 102 to output drive current to the parking actuator 103; when the electric vehicle 10 is not parked, the parking unit drive circuit 102 stops outputting current to the parking actuator 103.

[0105] In one implementation, the parking unit drive circuit 102 is an H-bridge circuit used to control the electromagnet. When the current flowing through the parking unit drive circuit 102 exceeds a threshold, the electromagnet instantly engages, thereby enabling the parking actuator 103 to perform parking. The parking control chip is of QM grade.

[0106] The brake control chip, i.e., the EMB control chip, is used to control the brake motor drive circuit 104. High-functional-safety-level chip models are available; therefore, reusing the brake control chip to control the power supply switch 101 can improve the functional safety level of the parking unit. The power supply switch 101 is directly controlled by the brake control chip, which meets the automotive safety integrity ASIL D level requirements. Combined with power-on self-test to eliminate latent faults in the power supply switch 101, the system meets the ASIL C requirements. At this point, the parking control chip (EPB driver chip) of the parking unit drive circuit 102 can be used at the QM level without considering functional safety requirements, thus reducing selection costs.

[0107] According to the solution of this application, the power supply switch 101 is controlled by a brake control chip. The brake control chip meets the requirements of the Automotive Safety Integrity ASIL D level, thereby improving the reliability of the wheel-end braking device 100 and the safety of the electric vehicle 10 at low cost.

[0108] In one embodiment, the wheel-end braking device 100 includes a main control chip, which is used to control the on and off of the power supply switch 101. The main control chip meets the requirements of the Automotive Safety Integrity ASIL D level.

[0109] The main control chip is an additional control chip that meets the ASIL D level requirements for automotive safety integrity. It controls the on / off state of the power supply switch 101. By meeting the ASIL D level requirements and combining it with power-on self-test to eliminate latent faults in the power supply switch 101, the system achieves the ASIL C requirement. In this case, the control chip for the parking unit drive circuit 102, i.e., the EPB driver chip, can be used at the QM level without considering functional safety requirements, thus reducing selection costs.

[0110] According to the solution of this application, a separate main control chip is used to control the power supply switch 101. The main control chip meets the requirements of the Automotive Safety Integrity ASIL D level, thereby improving the reliability of the wheel-end braking device 100 and the safety of the electric vehicle 10 at low cost.

[0111] In one embodiment, the parking unit drive circuit 102 includes a master switch controlled by a parking control chip. The master switch is used to turn on or off the current input to other control switches in the parking unit drive circuit 102. When the master switch is on, the parking unit drive circuit 102 can receive power from the low-voltage battery 20; when the master switch is off, the parking unit drive circuit 102 does not receive power from the low-voltage battery 20. This master switch is part of the parking unit drive circuit 102 and is controlled to be turned on by the parking control chip when driving the parking actuator 103. However, currently, there are no high ASIL-rated models of parking control chips (EPB drive chips). When using a low ASIL-rated parking control chip to control the master switch, it is impossible to improve the system's functional safety level by controlling the turn-on and turn-off of the master switch. This main switch differs from the power supply switch 101, which is controlled by a high ASIL-level control chip. It remains open when there is no parking command, ensuring that the parking unit will not start unexpectedly. Even if any electronic component of the electronic parking brake fails, the safety objectives will not be violated. This improves the reliability of the wheel-end braking device 100 and the safety of the electric vehicle 10 at low cost.

[0112] In one embodiment, the wheel-end braking device 100 is also used to control the brake motor 105 to rotate in the reverse direction after the parking unit drive circuit 102 receives power from the low-voltage battery 20 and outputs drive current to the parking actuator 103 to enable the parking actuator 103 to perform parking.

[0113] After the parking actuator 103 completes the parking maneuver, the wheel-end braking device 100 controls the brake motor 105 to rotate in the reverse direction to confirm whether parking is complete. Once parking is complete, the vehicle is in the parking state, at which point the brake motor 105 is locked and cannot be reversed.

[0114] In one embodiment, the wheel-end braking device 100 is further configured to control the brake motor 105 to increase the output braking torque after the parking unit drive circuit 102 receives power from the low-voltage battery 20 and outputs drive current to the parking actuator 103 to enable the parking actuator 103 to perform parking.

[0115] When the electric vehicle 10 experiences high-speed driving, downhill driving, and continuous braking, the brake disc temperature will increase. If forced parking is performed under these conditions, after the brake calipers clamp the brake discs, the discs will cool down due to air convection, causing them to contract and reducing the actual clamping force. This affects braking efficiency and may result in insufficient parking braking force. Since the parking actuator 103 locks the brake motor 105 in one direction, the brake motor 105 can increase its output braking torque to further tighten the brakes.

[0116] According to this application, by adding a power supply switch 101 to the power supply bus of the electronic parking brake for control, the switch remains disconnected when there is no parking command, so that no current flows through the drive circuit of the electronic parking brake, ensuring that it will not start unexpectedly. Combined with power-on self-test, latent faults are eliminated. Even if any electronic component of the electronic parking brake fails, the safety objective will not be violated. This improves the reliability of the wheel-end braking device 100 and the safety of the electric vehicle 10 at low cost.

[0117] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A wheel-end braking device, characterized in that, The wheel-end braking device includes a braking unit and a parking unit. The braking unit includes a brake motor drive circuit and a brake motor. The parking unit includes a parking unit drive circuit, a power supply switch, and a parking actuator. The brake motor drive circuit receives power from a low-voltage battery and drives the brake motor to output braking torque. The parking unit drive circuit receives power from the low-voltage battery via the power supply switch and drives the parking actuator to perform parking. During the parking process of the electric vehicle, the power supply switch is used to connect the parking unit drive circuit to the low-voltage battery. The parking unit drive circuit receives power from the low-voltage battery and outputs drive current to the parking actuator to enable the parking actuator to perform parking. When the electric vehicle is not parked, the power supply switch is used to disconnect the parking unit drive circuit from the low-voltage battery.

2. The wheel-end braking device according to claim 1, characterized in that, The wheel-end braking device includes a DC bus for receiving power from the low-voltage battery. The DC bus is used to supply power to the brake motor drive circuit and to supply power to the parking unit drive circuit through the power supply switch.

3. The wheel-end braking device according to claim 2, characterized in that, The wheel-end braking device also includes a DC bus switch, the DC bus being used to receive power from the low-voltage battery through the DC bus switch.

4. The wheel-end braking device according to claim 2 or 3, characterized in that, One end of the power supply switch is used to receive power from the DC bus, and the other end of the power supply switch is used to supply power to the parking unit drive circuit.

5. The wheel-end braking device according to any one of claims 1-4, characterized in that, The wheel-end braking device is specifically used for: During the parking process of the electric vehicle, the brake motor is first controlled to output braking torque, then the power supply switch is controlled to be turned on, and the parking unit drive circuit is controlled to drive the parking actuator to perform parking.

6. The wheel-end braking device according to any one of claims 1-5, characterized in that, The wheel-end braking device is specifically used for: During the process of releasing the electric vehicle from parking, the driving circuit of the parking unit is controlled to stop outputting driving current to the parking actuator so that the parking actuator can release the parking, and then the power supply switch is controlled to disconnect.

7. The wheel-end braking device according to any one of claims 1-6, characterized in that, The wheel-end braking device is also used for: During the power-on self-test of the electric vehicle, the power supply switch is first turned on, and then turned off.

8. The wheel-end braking device according to claim 7, characterized in that, The wheel-end braking device is used for: During the power-on self-test of the electric vehicle, if the power supply switch fails to conduct within a preset time or fails to disconnect after being conducted, a fault signal is reported.

9. The wheel-end braking device according to any one of claims 1-8, characterized in that, The wheel-end braking device includes a braking control chip, which is used to control the current output by the brake motor drive circuit to the brake motor. The braking control chip is also used to control the on and off of the power supply switch. The braking control chip meets the requirements of the Automotive Safety Integrity ASIL D level.

10. The wheel-end braking device according to any one of claims 1-8, characterized in that, The wheel-end braking device includes a main control chip, which is used to control the on and off of the power supply switch. The main control chip meets the requirements of the Automotive Safety Integrity ASIL D level.

11. The wheel-end braking device according to any one of claims 1-10, characterized in that, The wheel-end braking device is also used for: After the parking unit drive circuit receives power from the low-voltage battery and outputs drive current to the parking actuator to enable the parking actuator to perform parking, it controls the brake motor to rotate in the opposite direction.

12. The wheel-end braking device according to any one of claims 1-11, characterized in that, The wheel-end braking device is used for: When the electric vehicle is not parked, the brake motor is controlled to output the braking torque indicated by the opening of the brake pedal of the electric vehicle. During the parking process of the electric vehicle, the brake motor of the braking unit is controlled to output a preset braking torque.

13. The wheel-end braking device according to any one of claims 1-12, characterized in that, The wheel-end braking device is also used for: After the parking unit drive circuit receives power from the low-voltage battery and outputs drive current to the parking actuator to enable the parking actuator to perform parking, it controls the brake motor to increase the output braking torque.

14. The wheel-end braking device according to any one of claims 1-13, characterized in that, The parking actuator includes a ratchet and a pawl, the ratchet being mechanically connected to the drive motor. When the parking actuator performs parking, the pawl engages with the ratchet, and the pawl is used to lock the ratchet in one direction to prevent the drive motor from rotating in the opposite direction; When the parking actuator releases the parking brake, the pawl separates from the ratchet.

15. A braking system, characterized in that, The braking system includes a central controller and four wheel-end brakes, wherein at least one wheel-end brake device is included as claimed in any one of claims 1-14. The central controller is used to control the four wheel-end brakes to output braking force to brake the electric vehicle. The central controller is also used to control the wheel-end brake device to perform parking.

16. An electric vehicle, characterized in that, The electric vehicle includes a wheel-end braking device, a brake pedal, and a parking button as described in any one of claims 1-14, wherein the brake pedal is used to instruct the wheel-end braking device to output braking force to the wheels of the electric vehicle, and the parking button is used to instruct the electric vehicle to park or release parking.

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