Electric parking brake system

Abstract

To provide an electric parking brake system capable of surely performing re-operation (operation return) of an electric parking brake.SOLUTION: In a situation where operation of an electric parking brake is interrupted due to a decrease in a battery voltage (YES determination in a step ST2), re-operation of the electric parking brake is permitted (step ST9) on condition that the battery voltage becomes equal to or higher than a value of when normal operation had been possible before the interruption (YES determination in a step ST7).SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an electric parking brake system mounted on a vehicle.

Background Art

[0002] Conventionally, an electric type (electric parking brake) has been known as a parking brake for a vehicle. In a system equipped with this electric parking brake (electric parking brake system), in consideration of the possibility that the operation may stop due to a decrease in battery voltage or the like (for example, a decrease in battery voltage due to an increase in electrical load caused by the use of an air conditioner, audio, etc.) during the operation of the electric parking brake, a reference value (for example, a voltage reference value) for determining the return of the operation is set as a fixed value. And when the battery voltage becomes equal to or higher than the reference value, the restart (operation return) of the electric parking brake is permitted.

[0003] Also, in Patent Document 1, the lower limit value of the battery charge rate required to restart the electric parking brake immediately after releasing (brake release) the electric parking brake is held, and in the process of determining whether the restart of the electric parking brake is possible, if the battery charge rate is equal to or higher than the lower limit value, the operation of the electric motor is permitted, while if the battery charge rate is less than the lower limit value, the operation of the electric motor is prohibited.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, depending on the individual variations of the electric parking brake (individual variations due to factors such as aging deterioration and gear efficiency), even if the battery voltage meets the reference value (fixed value), there may be a possibility that the electric parking brake cannot be restarted properly. If the operation of the electric parking brake is repeated in an incomplete state, there is a concern about the adverse effects caused by the interference of parts inside the electric parking brake.

[0006] The present invention has been made in view of such points, and an object thereof is to provide an electric parking brake system capable of surely restarting (restoring operation) the electric parking brake.

Means for Solving the Problems

[0007] The solution means of the present invention for achieving the above object is premised on an electric parking brake system including an electric parking brake in which an electric motor operates to switch the application and release of braking force to a wheel. And this electric parking brake system permits the restart of the electric parking brake on the condition that the battery voltage becomes equal to or higher than the value when it was normally operable before the interruption in a situation where the operation of the electric parking brake is interrupted due to a decrease in the battery voltage.

[0008] According to this specific matter, the value of the battery voltage when it was normally operable before the operation of the electric parking brake was interrupted is a value reflecting the individual variations of the electric parking brake (individual variations due to factors such as aging deterioration and gear efficiency) (a value at which the electric parking brake can operate even if aging deterioration or the like has occurred). Therefore, if the battery voltage is equal to or higher than this value, it can be said that the electric parking brake can be surely restarted. In this solution means, since the restart of the electric parking brake is permitted on the condition that the battery voltage becomes equal to or higher than this value, the restart (restoring operation) of the electric parking brake can be surely performed.

Effect of the Invention

[0009] In the present invention, the reactivation of the electric parking brake is permitted on the condition that the battery voltage becomes equal to or higher than the value when it was normally operable before the operation of the electric parking brake was interrupted. Thereby, the operation of the electric parking brake can be surely restored.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. This embodiment will describe the case where the present invention is applied to a drum brake device provided on the rear wheels of a vehicle and adopting an electric parking brake.

[0012] - Schematic Configuration of Electric Parking Brake System - FIG. 1 is a diagram showing a schematic configuration of an electric parking brake system 1 according to this embodiment. As shown in this FIG. 1, the electric parking brake system 1 includes an electric parking brake 2. The electric parking brake 2 is for generating a braking force (braking force during parking) in the drum brake devices 5, 5 provided on the left and right rear wheels 4L, 4R of the vehicle, and generates a braking force in the drum brake devices 5, 5 by the operation of an electric motor 22 for braking.

[0013] The electric parking brake 2 includes a motor gear unit 21 having an electric motor 22 for braking and a motion conversion mechanism 23. The motion conversion mechanism 23 is connected to the drum brake devices 5, 5 via cables 24a, 24b, converts the rotation of the electric motor 22 into linear motion, and transmits the driving force of the electric motor 22 to the cables 24a, 24b. Thereby, when the cables 24a, 24b are pulled by the operation of the electric motor 22, the inner cables built in the drum brake devices 5, 5 are also pulled, and the drum brake devices 5, 5 operate as parking brakes.

[0014] The electric parking brake system 1 includes an electric parking brake ECU 25. The electric parking brake ECU 25 includes a processor such as a CPU (Central Processing Unit), a ROM (Read-Only Memory) that stores a control program, a RAM (Random-Access Memory) that temporarily stores data, and input / output ports, etc., and is adapted to transmit and receive information to and from other ECUs mounted on the vehicle via a CAN (Controller Area Network). Also, examples of sensors connected to the CAN include a G sensor 31, a shift position sensor 32, and a wheel speed sensor 33, etc. The G sensor 31 detects, for example, the longitudinal acceleration of the vehicle. The shift position sensor 32 detects the operation position of the shift lever. The wheel speed sensor 33 detects the rotational speed (vehicle speed) of the wheels. By the electric parking brake ECU 25 receiving the output signals from these sensors 31, 32, 33, it is possible to determine whether the vehicle is stopped or not.

[0015] The electric motor 22 is controlled based on a command from the electric parking brake ECU 25. The electric parking brake ECU 25 is connected to a parking brake switch 26, and outputs an operation command signal to the drive circuit 27 of the electric motor 22 according to a signal from this parking brake switch 26. The parking brake switch 26 is a switch that is operated by the driver when switching between the locked state and the released state of the drum brake devices 5, 5. Also, the electric parking brake ECU 25 is connected to a battery 6 and is capable of detecting the battery voltage. Specifically, the configuration is such that battery voltage information detected by a voltage sensor (not shown) connected to the positive line and the negative line of the battery 6 is transmitted to the electric parking brake ECU 25 as a voltage detection signal.

[0016] As a basic function of the electric parking brake ECU 25, considering that during the operation of the electric parking brake 2 (during the operation of the electric motor 22), the operation may stop due to a decrease in the voltage of the battery 6 (battery voltage) etc. (for example, a decrease in battery voltage due to an increase in electrical load caused by the use of an air conditioner, audio, etc.), a reference value (voltage reference value) for determining the resumption of operation is set. And when the battery voltage becomes equal to or higher than the voltage reference value, the restart (operation resumption) of the electric parking brake 2 is permitted. The feature of this embodiment lies in the method of setting this voltage reference value. This will be specifically described below.

[0017] In this embodiment, as the voltage reference value, it is set as the battery voltage when the operation of the electric parking brake 2 (the operation of the electric motor 22) was normally operable before the interruption of the operation (in the situation where the operation of the electric parking brake 2 was normal just before the interruption of the operation). That is, in this embodiment, as the voltage reference value for determining whether the restart (restart of the electric motor 22) of the electric parking brake 2 is possible, it is not a fixed value, but is set as the battery voltage when the operation of the electric parking brake 2 was normally operable before the interruption of the operation.

[0018] Then, the reactivation of the electric parking brake 2 is permitted on the condition that the battery voltage becomes equal to or higher than this voltage reference value (the value when normal operation was possible before the operation of the electric parking brake 2 was interrupted). That is, the value of the battery voltage when normal operation was possible before the operation of the electric parking brake 2 was interrupted is a value that reflects the individual variations of the electric parking brake 2 (individual variations due to effects such as aging deterioration and gear efficiency) (a value that allows the operation of the electric parking brake 2 even when aging deterioration or the like has occurred). Therefore, if the battery voltage becomes equal to or higher than this value, it can be said that the situation is such that the reactivation of the electric parking brake 2 can be reliably performed. In the present embodiment, since the reactivation of the electric parking brake 2 is permitted on the condition that the battery voltage becomes equal to or higher than this value, the reactivation (operation restoration) of the electric parking brake 2 can be reliably performed.

[0019] More specifically, in the present embodiment, the electric parking brake ECU 25 monitors the value of the battery voltage at predetermined time intervals during the operation of the electric parking brake 2 (during normal operation before interruption) and stores the value. For example, each time the electric parking brake ECU 25 receives information on the battery voltage at a predetermined time interval, it overwrites and stores the value of the battery voltage. Then, when the operation of the electric parking brake 2 is interrupted, the stored battery voltage (the battery voltage that is the latest information) is set as the voltage reference value, and the reactivation of the electric parking brake 2 is permitted on the condition that the battery voltage becomes equal to or higher than this voltage reference value (the battery voltage becomes equal to or higher than the voltage reference value due to charging of the battery 6 accompanying the driving of the engine or a decrease in the electrical load).

[0020] -Parking Brake Control- Next, the parking brake control in the electric parking brake system 1 configured as described above will be described with reference to the flowchart of FIG. 2.

[0021] First, in step ST1, it is determined whether there is a request to operate the electric parking brake 2. That is, it is determined whether the parking brake switch 26 is operated by the driver and whether the operation requests the locked state of the drum brake device 5.

[0022] If there is no request to operate the electric parking brake 2 and a NO determination is made in step ST1, the process simply returns.

[0023] On the other hand, if there is a request to operate the electric parking brake 2 and a YES determination is made in step ST1, the operation of the electric parking brake 2 is started and the process proceeds to step ST2, where it is determined whether the operation of the electric parking brake 2 has been interrupted due to a decrease in the battery voltage (the operation of the electric motor 22 has been interrupted).

[0024] If the operation of the electric parking brake 2 has not been interrupted and a NO determination is made in step ST2, the process proceeds to step ST3, where the operation of the electric parking brake 2 continues. Then, in step ST4, it is determined whether the operation of the electric parking brake 2 has been completed normally (the locked state has been completed).

[0025] If the operation of the electric parking brake 2 has not yet ended, the process returns to step ST2 and the above-described operations are repeated. On the other hand, if the operation of the electric parking brake 2 has been completed normally and a YES determination is made in step ST4, it means that the operation of the electric parking brake 2 has ended normally without being interrupted, so the process simply returns.

[0026] If the operation of the electric parking brake 2 has been interrupted and a YES determination is made in step ST2, it is determined whether there was an operation instruction for the electric parking brake 2 in that interrupted state. Examples of this operation instruction for the electric parking brake 2 include the operation of the parking brake switch 26 by the driver, the operation of the shift lever between the P (parking) position and a non-P position, and the issuance of a continuous drive instruction.

[0027] When there is an operation instruction for the electric parking brake 2 and a YES determination is made in step ST5, the process proceeds to step ST6, where information on the battery voltage when the electric parking brake 2 was normally operable before the operation was interrupted is acquired, and then the process proceeds to step ST7.

[0028] In step ST7, the current battery voltage (current battery voltage) is compared with a voltage reference value (the value when the electric parking brake 2 was normally operable before the operation was interrupted: battery voltage during normal operation).

[0029] And while the state where the current battery voltage is less than the voltage reference value (current battery voltage < battery voltage during normal operation) continues, a NO determination is made in step ST7, and the process proceeds to step ST8 to prohibit the restart operation of the electric parking brake 2 (restart operation of the electric motor 22). This avoids the occurrence of interference between components inside the drum brake device 5 due to the operation of the electric parking brake 2 being repeated in an incomplete state.

[0030] On the other hand, when the current battery voltage becomes equal to or higher than the voltage reference value (current battery voltage ≥ battery voltage during normal operation) and a YES determination is made in step ST7, the process proceeds to step ST9 to permit the restart operation of the electric parking brake 2 (restart operation of the electric motor 22). As a result, the drum brake device 5 will operate toward the locked state by the operation of the electric parking brake 2. And when the operation of the electric parking brake 2 is normally completed (the locked state is completed), a YES determination is made in step ST4 and the electric parking brake control ends.

[0031] - Effects of the Embodiment - As described above, in this embodiment, the re-operation of the electric parking brake 2 is permitted on the condition that the battery voltage becomes equal to or higher than a voltage reference value (the value when normal operation was possible before the operation of the electric parking brake 2 was interrupted). As a result, regardless of the individual variations of the electric parking brake 2 (individual variations due to factors such as aging deterioration and gear efficiency), the deterioration of the battery 6, and the operating conditions of other in-vehicle devices, the operation of the electric parking brake 2 can be reliably restored. In addition, it is possible to avoid the adverse effects caused by interference of components inside the drum brake device 5 due to repeated operation of the electric parking brake 2 in an incomplete state.

[0032] -Other Embodiments- Note that the present invention is not limited to the above-described embodiment, and all modifications and applications included in the scope of the claims and the scope equivalent thereto are possible.

[0033] For example, in the above-described embodiment, the voltage reference value was set to the battery voltage in a situation where the operation of the electric parking brake 2 was interrupted immediately before and the operation was proceeding normally. The present invention is not limited to this, and the battery voltage in a situation where the operation was proceeding normally a predetermined time before retroactively from the timing when the operation of the electric parking brake 2 was interrupted may be set as the voltage reference value. Also, not limited to the battery voltage in the same trip, the battery voltage in a situation where the operation of the electric parking brake 2 was proceeding normally in the previous trip may be set as the voltage reference value. That is, "before interruption" in the "value (battery voltage value) when normal operation was possible before interruption" as referred to in the present invention is not limited to immediately before the operation is interrupted, but is a concept including the time point when the operation of the electric parking brake 2 was proceeding normally in a previous state.

[0034] Also, the type of the drum brake device 5 to which the present invention is applicable is not particularly limited, and it can be applied to various types such as leading-trailing type and two-leading type.

[0035] In addition, in the above-described embodiment, the electric parking brake 2 is of the cable pull type, but it may be of the type with an in-built drum.

Industrial Applicability

[0036] The present invention is applicable to an electric parking brake system equipped with an electric parking brake.

Explanation of Reference Numerals

[0037] 1 Electric parking brake system 2 Electric parking brake 22 Electric motor 25 Electric parking brake ECU 4R, 4L Rear wheels (wheels) 6 Battery

Claims

【Claim 1】 In an electric parking brake system equipped with an electric parking brake in which an electric motor operates to switch the application and release of braking force to wheels, In a situation where the operation of the electric parking brake is interrupted due to a decrease in battery voltage, the electric parking brake system is characterized in that the re-operation of the electric parking brake is permitted on the condition that the battery voltage becomes equal to or higher than the value when it was normally operable before the interruption.

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