Device and method for operating an electric parking brake of a vehicle

Abstract

Device for operating an electric parking brake (102) of a vehicle (100) which can be supplied with energy by a battery (124), wherein the battery (124) can be charged by an energy generator (128) via a charging line (130), wherein the device also comprises a generator (134) configured to provide energy for supplying the electric parking brake (102) of the vehicle (100), and a control device (118) configured to control the generator (134) for supplying the electric parking brake (102) with energy depending on a result of monitoring an energy supply to the electric parking brake (102), wherein the device comprises a drive device (136) for the generator (134) which is kinematically connectable or connected to an axle of the vehicle (100).

Description

State of the art

[0001] The invention relates to a device and a method for operating an electric parking brake of a vehicle.

[0002] DE 10 2011 084 534 A1 relates to a fail-safe parking brake for motor vehicles. It includes an electronic control unit for the vehicle's braking system, with an interface to a parking brake operating switch and two control circuits for electric parking brake actuators. Two independent microcontrollers are directly connected to each other via a data bus. To protect against power supply failures, the two core-redundant microcontrollers have at least partially independent power supplies. These can be independent DC-DC converters, each with its own fuse, connected to a battery and / or a generator.

[0003] German patent DE 10 2013 208 671 A1 discloses a vehicle braking system comprising a hydraulic service brake system and an electric parking brake, and a method for controlling the same. In the event of a malfunction or functional impairment of a brake booster in the hydraulic service brake system, the driver is relieved of the burden of controlling the electric parking brake.

[0004] It would be desirable to further improve such a braking system. Disclosure of the invention

[0005] This is achieved by the device and the method according to the independent claims.

[0006] A device for operating an electric parking brake of a vehicle, which can be powered by a battery, wherein the battery can be charged by a power source via a charging line, wherein the device further comprises a generator configured to provide energy for supplying the electric parking brake of the vehicle, and a control device configured to control the generator to supply energy to the electric parking brake depending on the result of monitoring the energy supply to the electric parking brake, wherein the device includes a drive unit for the generator, which is kinematically connectable to or connected to an axle of the vehicle. As long as the vehicle is moving, the generator is driven by it to ensure a sufficient energy supply to the electric parking brake.This means that deceleration can still occur even if the hydraulic braking system and the main power supply for the electric parking brake fail.

[0007] Preferably, in a first operating state of the vehicle, the electric parking brake can be supplied with energy by a power supply unit independently of the generator, wherein the control unit is configured to supply the electric parking brake with energy from the generator in a second operating state of the vehicle, either in addition to or instead of the energy from the power supply unit. This allows the best possible energy supply to be adjusted depending on the situation.

[0008] Preferably, the control unit is designed to detect a fault in the power supply to the electric parking brake by means of monitoring and to supply the electric parking brake with energy from the generator when the fault occurs. Faults can thus be handled independently of other control units.

[0009] Preferably, the control unit is configured to actuate the electric parking brake in the closing direction while the generator supplies energy to the electric parking brake. This configuration of generator and parking brake enables the vehicle to decelerate independently of the availability of the hydraulic braking system or the main power supply to the electric parking brake.

[0010] Preferably, the control unit can be supplied with energy from the generator in addition to or instead of energy from the power supply unit. This improves the availability of the control unit.

[0011] A method for operating an electric parking brake of a vehicle, which is powered by a battery, wherein the battery is charged by a power source via a charging line, the device further comprising a generator configured to provide energy for supplying the electric parking brake of the vehicle, the generator being controlled to supply energy to the electric parking brake depending on the result of monitoring the energy supply to the electric parking brake, the generator being driven by a drive unit that is kinematically connectable to or connected to an axle of the vehicle. This enables a sufficient energy supply from the kinematic energy of the moving vehicle. This further improves the braking system of a vehicle.

[0012] Preferably, in a first operating state of the vehicle, the electric parking brake is supplied with energy by a power supply device independently of the generator, wherein in a second operating state of the vehicle, the electric parking brake is supplied with energy from the generator in addition to or instead of the energy from the power supply device.

[0013] The additional use allows for a smaller main power supply, which can be completely replaced if necessary.

[0014] Preferably, the monitoring system detects a fault in the power supply to the electric parking brake and supplies the electric parking brake with energy from the generator when the fault occurs. This can significantly improve availability, especially in the event of a fault.

[0015] Preferably, the electric parking brake is activated in the closing direction while the generator supplies energy to the electric parking brake. This reliably improves the vehicle's deceleration.

[0016] Preferably, the control unit is powered by the generator in addition to or instead of power from the power supply unit. This improves the availability of the control unit and its functions in the event of a main power supply failure.

[0017] Further advantageous features will become apparent from the following description and the drawing. The drawing shows... Fig. 1. Schematic diagram of parts of a vehicle with an electric parking brake, Fig. 2 schematic parts of the electric parking brake, Fig. 3 schematically a procedure for operating the electric parking brake.

[0018] Fig. Figure 1 schematically depicts parts of a vehicle 100 with an electric parking brake 102. The vehicle 100 comprises a front axle 104 and a rear axle 106. Two wheels 108 are arranged at opposite ends of each axle. In this example, the front axle 104 is driven by a motor 110, which is kinematically connected to the front axle 104 via an output shaft 112, a transmission 114, and a drive shaft 116. In this example, the rear axle 106 is free-running. The vehicle 100 can also be equipped with rear-wheel drive or all-wheel drive.

[0019] The electric parking brake 102 comprises a control unit 118 and actuators 120 arranged on each of the two wheels 108 of the rear axle 106. The actuators 120 are connected to the control unit 118 via respective electrical lines 122. In this example, the actuators 120 are drives, more precisely motors, with which brake shoes can be moved.

[0020] The electric parking brake 102 is powered by an energy supply unit 124, for example, a battery. In this example, the energy supply unit 124 supplies the control unit 118 with energy via an energy supply line 126. The actuators 120 are powered by the control unit 118.

[0021] The control unit 118 is configured to actuate the actuators 120 to brake the wheels 108 into a braking position. In the braking position, the actuators 120 clamp the brake discs of the wheels 108 between the brake shoes, thus holding the vehicle 100 in place. The control unit 118 is also configured to actuate the actuators 108 to release the wheels 108 into a rest position, in which the wheels 108 rotate freely. In doing so, the actuators 120 release the clamped brake shoes from the brake discs.

[0022] Energy is required to move the actuators 120 from the rest position to the braking position or back. No energy is required to hold the actuators 120 in the rest position or in the braking position.

[0023] A hydraulic braking system, also located in vehicle 100, which is in Fig. 1, which is not shown, is designed to move the brake shoes towards the brake discs as needed, in order to brake the vehicle 100 more or less strongly.

[0024] In this example, the energy supply device 124 is a battery that is charged by an energy generator 128 via a charging line 130. The energy generator 128 is, in this example, an alternator that can be driven via a kinematic connection 132 to the output shaft 112.

[0025] The vehicle 100 also includes a generator 134, which is configured to provide energy for the electric parking brake 102 of the vehicle 100. The generator 134 is kinematically or permanently connected to an axle of the vehicle 100 via a drive unit 136. In this example, the generator 134 is kinematically connected to the front axle 104. The drive unit 136 is, for example, a shaft that is driven by the front axle 104, for example, via a friction wheel or a belt drive, and rotates a rotor of the generator 134 as long as the front axle 104 is rotating. The generator 134 can also be arranged directly on the axle of the vehicle 100, so that the rotor is connected to the axle.

[0026] The generator 134 is connected to the control unit 118 via an electrical line 138 to supply the electric parking brake 102.

[0027] In a first operating state of the vehicle 100, the electric parking brake 102 can be supplied with energy by the energy supply unit 124 independently of the generator.

[0028] In a second operating state of the vehicle 100, the electric parking brake 102 can be supplied with energy by the generator 134 additionally or instead of the supply by the energy supply unit 124.

[0029] The control device 118 is designed to control the generator 134 to supply the electric parking brake 102 with energy depending on the result of monitoring the energy supply of the electric parking brake 102.

[0030] In the first operating state, the generator 134 is not used to supply the electric parking brake 102. For example, the generator 134 is kinematically disconnected from the drive unit 136, or the electrical line 138 is temporarily interrupted.

[0031] The control unit is designed to detect, by means of monitoring, a fault in the power supply to the electric parking brake 102 by the power supply unit 124 and to supply the electric parking brake 102 with energy via the generator 134 when the fault occurs. The fault may be, for example, insufficient power from the power supply unit 124 or a defect in the power supply unit 124 or the power supply line 126. Such a fault can be detected, for example, in the control unit 118 by monitoring the voltage or current at the power supply line 126.

[0032] The control unit 118 is configured to actuate the electric parking brake 102 in the closing direction while the generator 134 supplies the electric parking brake 102 with energy. The closing direction refers to the direction from the rest position of the actuators 120 to their braking position. The energy from the generator 134 is sufficient to close the electric parking brake 102 while the vehicle 100 is still moving. During operation, the generator 134 also brakes the vehicle 100. With the electric parking brake 102 closed, the vehicle 100 continues to decelerate even without further energy from the generator 134, since the closed electric parking brake 102 requires no energy once the actuators 120 have reached the braking position. The vehicle 100 will therefore continue to decelerate even in the event of a failure of the hydraulic brake system and the power supply unit 124.

[0033] The control unit 118 can be configured to supply the electric parking brake 102 with energy from the generator 134 in addition to the energy from the power supply unit 124. In this case, the power output of the power supply unit 124 can be lower. The power supply unit 124 can therefore be smaller without impairing the function of the electric parking brake 102.

[0034] The control unit 118 includes a separate output stage 140 for each of the actuators 120. The output stages 140 are supplied, for example, directly by the generator 134 with the energy required to operate the actuators 120. The control unit 118 can also be powered by the energy supplied by the generator 134. This ensures reliable operation of the electric parking brake even in the event of a power supply failure from the power supply unit 124.

[0035] Fig. Figure 2 schematically depicts parts of the electric parking brake 102. More precisely, the actuator 120 is shown in Fig. Figure 2 shows the actuator 120 comprising a drive 202, in particular a motor, configured to move a brake shoe 204 back and forth across an air gap to a brake disc 206. In this example, the brake shoe 204 is moved by a drive device 208, which acts on a brake piston 210. A cylinder 212 guides the brake piston 210.

[0036] A method for operating the electric parking brake 102 is described below using the following: Fig. 3 described. Fig. Figure 3 schematically represents a curve over time t of a vehicle speed V FZG of vehicle 100, a voltage U occurring at generator 134 gen , a rotational speed ω occurring in the electric parking brake 102 APB_Motor the drive of one of the actuators 120, a current I APB_Motorthis drive and a force F occurring in the process APB on the brake shoe(s). The force F APB is a clamping force. Voltage U gen , drives the drive. When the drive is idling, the rotational speed ω APB_Motor proportional to the voltage U gen .

[0037] The process is divided into five sequential phases, each beginning in Fig. 3 is labelled with numbers 1 to 5 as time t increases.

[0038] The power supply is monitored before section 1. In this example, vehicle 100 moves at a constant, non-zero vehicle speed V. FZG Generator 134 is already driven and generates a non-zero voltage U. gen , which is proportional to the speed. Before section 1, the electric parking brake 102 is not supplied with energy by the generator 134. The current I APB_Motoris zero. The electric parking brake 102 is in its rest position; the force F that occurs is zero. APB is zero.

[0039] The monitoring system detects a fault in the power supply to the electric parking brake 102 by the power supply unit 124. When the fault occurs, the electric parking brake 102 is supplied with energy by the generator 134 from the time marked 1 in the illustrated example. The energy supply depends on the result of this monitoring. That is, from the time marked 1, the electric parking brake 102 is actuated in the closing direction while the generator 134 supplies the electric parking brake 102 with energy.

[0040] In this example, an emergency stop is initiated at time 1 using the electric parking brake 102.

[0041] Between times 1 and 2, the vehicle speed V remains constant. FZG and the voltage U genInitially constant. The rotational speed ω APB_Motor The drive voltage rises steeply to a maximum value. During this steep rise, a current impulse I occurs. APB_Motor on, which subsides when the rotational speed ω APB_Motor reached its maximum value. The force F APB Initially, it remains zero.

[0042] That is, the vehicle speed V FZG and thus the voltage U gen are constant. The actuators 120 are driven. The drive quickly reaches its idle speed, close to its maximum value. After a brief motor start-up peak, the current I drops. APB_Motor The motor returns to an idle current. The brake shoes with the brake linings now overcome the air gap and move towards the brake disc. The clamping force F APB The status is still zero. Vehicle 100 is not yet being delayed.

[0043] From time 2 onwards, the rotational speed ω decreases. APB_Motorthe drive initially slowly, then faster until the rotational speed ω APB_Motor Zero is reached at time 3. From time 2 onwards, the force F increases. APB The current I increases steadily up to a maximum value at time 3. The current I increases proportionally to this. APB_Motor on and the voltage U drops gen The vehicle 100 is decelerated by the action of the electric parking brake 102. The vehicle speed V FZG decreases. During the build-up of force F APB is the force F APB approximately proportional to the motor current I APB_Motor .

[0044] The drive has advanced far enough that the brake pads are now touching the brake disc. The brake pads are now pressing against the brake disc. The clamping force begins to build up, i.e., the force F APB increases. The motor current, i.e., the current I, increases. APB_MotorThe clamping force on the rear wheels now leads to a deceleration of the vehicle by 100. The deceleration increases further as the clamping force increases.

[0045] From time 3 onwards, the force F remains constant. APB constant. The vehicle speed V FZG and the voltage U gen They decrease as a result and reach zero at time 5. The current I APB_Motor The current drops to zero between time 3 and time 4. Between time 4 and time 5, the current I APB_Motor Zero. The electric parking brake has already reached the braking position. The vehicle will continue to decelerate.

[0046] The vehicle speed V FZG At time 3, the voltage has dropped so low that the generated voltage U gen It is no longer sufficient to keep the drive running. The drive is now stopped. The current I APB_Motor This is now calculated using an electrical resistance value R for the motor from IAPB_Motor = U gen / R. The current I APB_Motor The clamping force decreases linearly with the voltage. The clamping force is now constant and no longer increases. The vehicle deceleration is also now constant and no longer increases. The vehicle speed V FZG decreases linearly until it comes to a standstill.

[0047] At time 4, the voltage U gen The voltage has now dropped so low that control unit 118 shuts down. Power stage 140 now shuts down. The current I APB_Motor falls to zero.

[0048] At time 5, the vehicle is now stationary and is held by a constant clamping force.

[0049] In this example, the vehicle is decelerated to a standstill regardless of the effect of the hydraulic braking system. As can be seen from the following estimate, generator 134 supplies sufficient energy for this:

[0050] Kinetic energy of the moving vehicle with mass m = 1000 kg and a speed of V FZG = 2m / s: E1=1 / 2*m*vFZG2=2000 Joules.

[0051] Energy for an actuator 120 at a voltage of U = 9 volts, a current of I = 8A and a time period to move the actuator into the braking position of t = 2 seconds: E2=U*I*t=9V*8A*2sec=144 joules.

[0052] Energy for two actuators 120: E3=2*E2=288 Joules.

[0053] Even taking into account converter losses in the generator and in the control unit 118, the kinetic energy of the moving vehicle is significantly higher than the energy required to tension the two actuators 120.

Claims

[1] Device for operating an electric parking brake (102) of a vehicle (100) which can be supplied with energy by a battery (124), wherein the battery (124) can be charged by an energy generator (128) via a charging line (130), wherein the device also comprises a generator (134) configured to provide energy for supplying the electric parking brake (102) of the vehicle (100) with energy, and a control device (118) configured to control the generator (134) for supplying the electric parking brake (102) with energy depending on a result of monitoring an energy supply to the electric parking brake (102), wherein the device comprises a drive device (136) for the generator (134) which is kinematically connectable or connected to an axle of the vehicle (100). [2] Device according to claim 1, characterized by, that the electric parking brake (102) in a first operating state of the vehicle (100) can be supplied with energy by a power supply device (124) independently of the generator (134), wherein the control device (118) is configured to supply the electric parking brake (102) in a second operating state of the vehicle (100) with energy from the generator (134) in addition to or instead of the energy from the power supply device (124). [3] Device according to any one of the preceding claims, characterized by , that the control device (118) is designed to detect, by means of monitoring, a fault in the supply of the electric parking brake (102) by the power supply device (124) and to supply the electric parking brake (102) with energy by the generator (134) when the fault occurs. [4] Device according to any one of the preceding claims, characterized by, that the control device (118) is designed to control the electric parking brake (102) in the closing direction, while the generator (134) supplies energy to the electric parking brake (102). [5] Device according to any one of the preceding claims, characterized by , that the control device (118) can be supplied with energy from the generator (134) in addition to or instead of the energy from the power supply device (124). [6] Method for operating an electric parking brake (102) of a vehicle (100) which is supplied with energy by a battery (124), wherein the battery (124) is charged by an energy generator (128) via a charging line (130), wherein the device also comprises a generator (134) which is configured to provide energy for supplying the electric parking brake (102) of the vehicle (100), wherein the generator (134) is controlled to supply the electric parking brake (102) with energy depending on a result of monitoring an energy supply to the electric parking brake (102), wherein the generator (134) is driven by a drive device (136) which is kinematically connectable or connected to an axle of the vehicle (100). [7] Method according to claim 6, characterized by, that in a first operating state of the vehicle (100) the electric parking brake (102) is supplied with energy by a power supply device (124) independently of the generator (134), wherein in a second operating state of the vehicle (100) the electric parking brake (102) is supplied with energy from the generator (134) in addition to or instead of the energy from the power supply device (124). [8] Method according to claim 6 or 7, characterized by , that by means of the monitoring a fault in a supply of the electric parking brake (102) by the power supply unit (124) is detected and the electric parking brake (102) is supplied with energy by the generator (134) when the fault occurs. [9] Method according to any one of claims 6 to 8, characterized by , that the electric parking brake (102) is controlled in the closing direction, while the generator (134) supplies the electric parking brake (102) with energy. [10] Method according to any one of claims 6 to 9, characterized by , that the control unit (118) is supplied with energy from the generator (134) in addition to or instead of the energy from the power supply unit (124).

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