JP2012101749A - Electric parking brake device - Google Patents

Abstract

An object of the present invention is to improve durability of an actuator and a brake assembly by preventing further tension applied to a cable due to inertial driving of a motor.
When brake operation is performed, an initial duty ratio is output by a PWM circuit to drive an electric motor (time t1), and a duty ratio is increased from the initial duty ratio to output a target duty ratio (time t2). . When the cable tension reaches the pre-end target cable tension value TS lower than ΔL1 than the predetermined brake force set in advance (time t3), the duty ratio is changed from the target duty ratio to the pre-end duty ratio so as to reduce the rotation speed of the electric motor. And lower. When the cable tension reaches a predetermined braking force, the duty ratio is set to 0% and the electric motor is stopped (time t4).
[Selection] Figure 4

Description

  The present invention relates to an electric parking brake device in which a parking brake is actuated and released electrically by an electric motor and a cable.

  In this type of electric parking brake, which operates and releases the parking brake with an electric motor and cable, a load sensor is interposed in the cable, and the tension of the cable is detected from this load sensor, and the parking brake is operated. In this case, the cable is pulled by driving the electric motor in the normal direction, for example. Then, when the cable tension from the load sensor increases with the pulling operation of the cable and reaches a preset tension, the electric motor is stopped and the pulling operation of the cable is stopped assuming that a certain braking force is secured. . As a result, the brake is applied.

  Also, when releasing the parking brake, the electric motor is driven in reverse to perform the cable return operation (release), and the brake is released (released) when the cable tension from the load sensor drops to a predetermined value. As a result, the electric motor is stopped and the cable return operation is stopped. As a result, the brake is released and the vehicle is ready to run.

  As described above, for example, Japanese Patent Application Laid-Open Publication No. 2004-259542 is one in which the cable tension from the load sensor interposed in the cable is detected to operate and release the parking brake.

JP 2009-202618 A

  Patent Document 1 discloses an actuator that operates and releases a parking brake via a control cable that is pulled and returned by a forward and reverse drive of a motor, and an operation direction and a release direction of a control cable that operates on the parking brake. An electric parking brake system including a sensor that outputs a corresponding output voltage, and a control device that controls rotational driving of the motor in accordance with an output voltage from the sensor.

  In Patent Document 1, when the parking brake is operated, the motor is driven to rotate in the forward direction until the cable reaches a predetermined load, and when the parking brake is released, the load is applied to the cable. The cable is released by reversely driving the motor to the released position where it is not applied.

  However, in Patent Document 1, when the parking brake is operated, the motor is stopped when a predetermined cable tension is reached. Therefore, even if the brake operation state is shifted to the brake holding state, there is a problem in that the inertia of the actuator and the brake assembly is excessively applied due to the inertial rotation of the motor, and the life of the actuator and the brake assembly is shortened.

  Even when the parking brake is released, the motor is stopped when the cable tension is released. Therefore, even if the motor is stopped, the cable bends unnecessarily due to inertial rotation of the motor. End up. Therefore, a time lag occurs at the next brake operation, and the driver may feel uncomfortable.

  The present invention has been provided in view of the above-described problems, and it is an object of the present invention to improve durability of an actuator and a brake assembly by preventing further tension applied to a cable by inertial driving of a motor. An electric parking brake device is provided.

Therefore, in the electric parking brake device of the present invention, the brake assembly 4, the cable 3 for operating the brake assembly 4, and the brake assembly 4 are brought into an activated state or a released state via the cable 3 by forward / reverse rotation driving. An electric parking brake device comprising an electric motor 11 and a load sensor 15 for detecting a tension applied to the cable 3,
A motor control unit for controlling the rotational drive of the electric motor 11;
The motor control unit is
A cable tension determination unit 31 that determines that a cable tension of the cable 3 for generating a braking force in a brake operating state is equal to or greater than a pre-end target cable tension value TS based on a load signal from the load sensor 15;
An operation for reducing the rotational speed of the electric motor 11 stepwise when the cable tension is equal to or greater than the pre-termination target cable tension value TS before the brake operation is finished when the brake operation state is shifted to the brake holding state. And a drive control unit for performing pre-end control.

  (1) According to the electric parking brake device of the present invention, in the brake operating state, the rotational speed of the electric motor 11 is reduced before the brake operation is completed, and the brake operating state is changed to the brake holding state. The inertial rotation of the electric motor 11 can be reduced by reducing the number of revolutions before stopping the motor rotation at the time of shifting, and therefore, the brakes of the actuator 2 and the brake assembly 4 can be prevented from being overcut. Thereby, durability of the actuator 2 and the brake assembly 4 can be improved.

  (2) According to the electric parking brake device of the present invention, when the tension value of the cable 3 reaches the pre-termination target cable tension value TS, the duty ratio of the PWM control pulse is used as a method for controlling the rotation speed of the electric motor 11. By controlling this, it is possible to easily control the decrease in the rotational speed before stopping the motor rotation.

  (3) According to the electric parking brake device of the present invention, the pulse is changed from the initial duty ratio to the target duty ratio at a predetermined time at the start of the brake operation state. Therefore, an excessive load on the cable 3 can be prevented, and the durability of the cable 3 can be improved.

  (4) According to the electric parking brake device of the present invention, the pre-release end control is performed such that the rotational speed of the electric motor 11 is reduced before the brake release ends when the brake holding state is shifted to the brake release operating state. As a result, the cable 3 does not bend excessively due to inertial rotation of the electric motor 11, so that the time lag at the time of actual brake operation at the time of the next brake operation can be eliminated, and the driver can release the foot brake. There is no need to worry about the time lag of parking brake operation.

1 is a schematic block configuration diagram of an electric parking brake system in an embodiment of the present invention. It is a block diagram in an embodiment of the invention. It is a figure which shows the specific circuit of the motor drive circuit in embodiment of this invention. It is a timing chart which shows the control action at the time of the brake operation in the embodiment of the present invention, and brake release. It is a flowchart which shows the control action at the time of the brake action in embodiment of this invention. It is a flowchart which shows the control action at the time of the brake release in embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic block diagram of an electric parking brake system. A control device 1, an actuator 2 controlled by the control device 1, and a pulling operation and release of a cable 3 by the actuator 2 are performed. The brake assembly 4 is configured such that the brake is operated and released.
Further, this electric parking brake system is provided with an operation switch 5 for sending a signal to the control device 1 in order to operate and release the parking brake.

The actuator 2 includes an electric motor 11 that can be rotated in the forward and reverse directions by the control device 1, a reduction mechanism 12 that includes a plurality of gears that reduce the rotational speed of the electric motor 11, and the reduction mechanism 12. The screw 13 is rotationally driven by the output of the screw 13, is reciprocated in the axial direction of the screw 13 by the rotation of the screw 13, and includes a nut 14 constituting an equalizer mechanism, a load sensor 15 described later, and the like. Yes.
Also, the cable 14 on the left side in the figure is connected to one end of the nut 14, and the cable 3 (right side in the figure) via the load sensor 15 is connected to the other end side of the nut 14. The other end of 3 is connected to the brake assembly 4 side.

  The load sensor 15 detects a load (tension) acting on the cable 3, and sends the cable tension detected by the load sensor 15 to the control device 1. The load sensor 15 includes a shaft 20, a main spring 21, a secondary spring 22, a magnet 23, a Hall IC 24, and the like as main components.

  As the cable 3 is pulled and released, the shaft 20 reciprocates in the axial direction, and the magnet 23 reciprocates as the shaft 20 reciprocates. The Hall IC 24 arranged corresponding to the magnet 23 by the reciprocating motion of the magnet 23 applies a voltage corresponding to the compression and expansion deformation amount of the main spring 21 and the auxiliary spring 22 corresponding to the load of the cable 3 to the cable tension. Is output to the control device 1.

FIG. 2 is a block diagram related to the electric parking brake of the present invention. The control device 1 is composed of a CPU (Central Processing Unit) 30 composed of a microcomputer and a motor drive circuit 40. The CPU 30 includes a cable tension determination unit 31, a PWM circuit 32, a control unit 33, a storage unit 34, and the like.
The control unit 33 controls the whole according to a predetermined program procedure, and the storage unit 34 temporarily stores data from the ROM storing the program, the load sensor 15 and the like. It consists of RAM etc. to save.

The cable tension determination unit 31 constantly monitors the tension of the cable 3 based on the load signal from the load sensor 15, and in particular, when the parking brake is operated, the tension of the cable 3 is a predetermined value or more as will be described later. When releasing the parking brake, it is determined whether the tension of the cable 3 is equal to or less than a predetermined value.
The PWM circuit 32 outputs a signal having a predetermined duty ratio in response to a signal from the control unit 33, and the motor drive circuit 40 controls the electric motor 11 of the actuator 2 according to a predetermined output signal from the PWM circuit 32. The rotation is controlled in the forward / reverse direction with the duty ratio.

  FIG. 3 shows a specific circuit diagram of the motor drive circuit 40. The motor drive circuit 40 is configured by a full bridge circuit with switching elements Q1 to Q4 made of FETs. The electric motor 11 is connected to the equilibrium point of the full bridge circuit, the sources of the switching element Q1 and the switching element Q2 are connected to each other, and a DC voltage + Vb is applied to this connection point. Further, the sources of the switching element Q3 and the switching element Q4 are connected to each other, and this connection point is grounded.

  The PWM circuit 32 of the CPU 30 is controlled by the control unit 33 so that the switching elements Q1 and Q4 of the motor driving circuit 40 are turned on or off at a predetermined duty ratio, and the switching elements Q2 and Q3 are turned off or on, thereby The rotation of the motor 11 is controlled so as to have a predetermined rotation speed.

  The present invention controls the rotational speed of the electric motor 11 to be reduced as the pre-operation control before the brake operation ends in the brake operation state, and this control operation will be described below with reference to FIGS. . 4A shows a PWM drive duty ratio of pulses when the motor drive circuit 40 is driven by the PWM circuit 32, FIG. 4B shows the rotation speed of the electric motor 11, FIG. 4C shows the tension of the cable 3, and FIG. (D) shows each motor current. FIG. 5 shows a flowchart when the brake is operated.

As shown in step S1 of FIG. 5, the electric motor 11 is rotationally driven, for example, in the normal rotation direction to operate the operation switch 5 shown in FIG. Then, the process proceeds to step S2, and the control unit 33 controls the PWM circuit 32 to output an initial duty ratio, and the motor drive circuit 40 drives the electric motor 11 to rotate forward (see time t1 in FIG. 4).
Next, the process proceeds from step S2 to step S3, and the control unit 33 controls the PWM circuit 32 so as to increase the duty ratio little by little from the initial duty ratio, and when a predetermined time elapses, the process proceeds from step S4 to step S5. To do.

  In step S5, the control unit 33 controls the PWM circuit 32 to output a target duty ratio (see time t2 in FIG. 4), and continues to drive the electric motor 11 at this target duty ratio. In this state, as shown in FIG. 4C, the tension of the cable 3 continues to increase, and the rotation speed of the electric motor 11 increases rapidly until time t2, and then decreases gently.

  Here, as shown in FIG. 4 (c), assuming that the cable tension when the brake is completely applied is “predetermined brake force”, the electric motor 11 is conventionally used at the target duty ratio until the “predetermined brake force” is reached. However, in the present invention, a “pre-end target cable tension value TS” that is lower by ΔL1 before the “predetermined braking force” is set in advance, and this pre-end target cable tension value TS is set to the CPU 30. The information is stored in the storage unit 34.

In step S5, the target duty ratio is output from the PWM circuit 32 to drive the electric motor 11. The cable tension determination unit 31 constantly monitors the cable tension from the load sensor 15 and the “pre-termination target cable tension value TS” stored in the storage unit 34, and from the load sensor 15 as shown in step S6. Step S5 and Step S6 are repeated until the cable tension value reaches (predetermined braking force−ΔL1).
When the cable tension value from the load sensor 15 reaches (predetermined braking force−ΔL1) (see time t3 in FIG. 4), the control unit 33 controls the PWM circuit 32 to set the duty ratio from the target duty ratio. Control is performed so as to reduce the rotational speed of the electric motor 11 step by step by outputting the lowered duty ratio before completion.

Next, when the process proceeds from step S7 to step S8 and the cable tension from the load sensor 15 reaches a predetermined braking force, the process proceeds to step S9, and the control unit 33 causes the PWM circuit 32 so that the duty ratio becomes 0%. Is controlled to stop the electric motor 11 (see step S10, time t4 in FIG. 4). Thereby, the inertial rotation of the electric motor 11 can be prevented, and an excessive tension is prevented from being applied to the cable 3.
Here, as shown in FIG. 4, the time t1 to the time t4 are in the brake operating state, and the time t4 to the time t5 are in the brake holding state.

  Here, the drive control unit of the motor control unit described in the claims is composed of the control unit 33, the PWM circuit 32, and the motor drive circuit 40 of the control device 1, and the drive control unit and the cable tension determination. The motor control unit is configured with the unit 31.

  As described above, in the brake operating state, the rotational speed of the electric motor 11 is reduced before the brake operation ends, and before the motor rotation is stopped when the brake operating state is shifted to the brake holding state. By reducing the rotational speed, the inertial rotation of the electric motor 11 can be reduced, and therefore, the brake of the actuator 2 and the brake assembly 4 can be prevented from being overcut. Thereby, durability of the actuator 2 and the brake assembly 4 can be improved.

Further, when the tension value of the cable 3 reaches the target cable tension value TS before completion, as a method of controlling the rotation speed of the electric motor 11, the duty ratio of the pulse of PWM control is controlled, so that the motor rotation It is possible to easily control the decrease in the rotational speed before stopping.
Furthermore, since the pulse is changed from the initial duty ratio to the target duty ratio at a predetermined time at the start of the brake operation state, an unreasonable load on the cable 3 can be avoided. An unreasonable load can be prevented and the durability of the cable 3 can be improved.

  Next, the brake release control operation in which the rotational speed of the electric motor 11 is reduced stepwise as the pre-release end control before the brake release operation ends in the brake release operation state will be described with reference to FIGS.

As shown in step S21 of FIG. 6, the electric motor 11 is rotated in the reverse direction, for example, in order to release the brake by operating the operation switch 5 shown in FIG. In step S22, the control unit 33 controls the PWM circuit 32 to output an initial duty ratio, and the motor drive circuit 40 drives the electric motor 11 in reverse (see time t5 in FIG. 4).
Next, the process proceeds from step S22 to step S23, and the control unit 33 controls the PWM circuit 32 so as to increase the duty ratio little by little from the initial duty ratio. If a predetermined time elapses, the process proceeds from step S24 to step S25. To do.

  In step S25, the control unit 33 controls the PWM circuit 32 to output a target duty ratio (see time t6 in FIG. 4), and continues to drive the electric motor 11 at this target duty ratio. In this state, as shown in FIG. 4C, the tension of the cable 3 continues to decrease, and the rotational speed of the electric motor 11 increases rapidly until time t6 and is substantially constant thereafter.

  Here, as shown in FIG. 4 (c), when the cable tension when the brake is completely released is “release brake force”, the electric motor is conventionally driven at the target duty ratio until this “release brake force” is reached. However, in the present invention, a “cable tension value TK before release” that is higher by ΔL2 before the “release brake force” is set in advance, and the cable tension value TK before release is stored in the CPU 30. Stored in the unit 34.

In step S25, the target duty ratio is output from the PWM circuit 32 to drive the electric motor 11. The cable tension determination unit 31 constantly monitors the cable tension from the load sensor 15 and the “pre-release cable tension value TK” stored in the storage unit 34, and as shown in step S26, Steps S25 and S26 are repeated until the decreasing cable tension value reaches (release brake force + ΔL2).
When the cable tension value from the load sensor 15 reaches (release brake force + ΔL2) (see time t7 in FIG. 4), the control unit 33 controls the PWM circuit 32 to make the duty ratio lower than the target duty ratio. The duty ratio before termination is output and the rotational speed of the electric motor 11 is controlled to decrease stepwise.

  Next, the process proceeds from step S27 to step S28, and when the cable tension from the load sensor 15 decreases and the release brake force is reached, the process proceeds to step S29, and the control unit 33 sets the duty ratio to 0%. The PWM circuit 32 is controlled to stop the electric motor 11 (see step S20, time t8 in FIG. 4). Thereby, the inertial rotation of the electric motor 11 can be prevented, and the electric motor 11 is stopped without the cable 3 being bent, and the brake is released by the stop of the electric motor 11. Here, as shown in FIG. 4, the time t5 to the time t8 is the brake release operation state.

  In this way, by performing the pre-release end control of reducing the rotation speed of the electric motor 11 before the end of the brake release when shifting from the brake holding state to the brake release operation state, the inertial rotation of the electric motor 11 is performed. Since the cable 3 does not bend excessively unnecessarily, it is possible to eliminate the time lag at the time of actual brake operation at the time of the next brake operation, and the driver needs to worry about the time lag of the parking brake operation when releasing the foot brake There is no.

Here, the duty ratio of the PWM control shown in FIG. 4 is 50% when the initial duty ratio is, for example, 100%, and the duty ratio before termination is, for example, 80%. It is not limited to a numerical value, and an arbitrary numerical value may be set.
In addition, the duty ratio is rapidly reduced from the target duty ratio at the time of brake activation to the pre-end duty ratio at the time of brake release, but gradually decreased from the target duty ratio to the pre-end duty ratio in multiple stages. Also good.

DESCRIPTION OF SYMBOLS 1 Control apparatus 2 Actuator 3 Cable 4 Brake assembly 11 Electric motor 15 Load sensor 30 CPU
31 Cable tension judgment part 32 PWM circuit 33 Control part 40 Motor drive circuit TS Target cable tension value before termination TK Cable tension value before release

Claims (4)

A brake assembly (4), a cable (3) for operating the brake assembly (4), and an electric motor that brings the brake assembly (4) into an activated state or a released state via the cable (3) by forward and reverse rotation driving. An electric parking brake device comprising a motor (11) and a load sensor (15) for detecting a tension applied to the cable (3),
A motor control unit for controlling the rotational drive of the electric motor (11);
The motor control unit is
Cable tension determination for determining that the cable tension of the cable (3) for generating the braking force in the brake operating state is equal to or greater than the pre-termination target cable tension value (TS) based on the load signal from the load sensor (15). Part (31);
If the cable tension is equal to or greater than the pre-termination target cable tension value (TS) before the brake operation is completed when the brake operation state is shifted to the brake holding state, the rotational speed of the electric motor (11) is stepped. An electric parking brake device, comprising: a drive control unit that performs control before the end of operation to be lowered. The motor control unit is
The electric motor (11) is controlled by pulses;
After the cable tension reaches the pre-end target cable tension value (TS) in the brake operating state, the pre-end control is performed by setting the duty ratio of the pulse to a pre-end duty ratio that is changed by a predetermined amount. The electric parking brake device according to claim 1. The motor control unit is
At the start of the brake operation state, the pulse is changed from the initial duty ratio to the target duty ratio for a predetermined time,
3. The drive control of the electric motor (11) using the pulse as the target duty ratio is performed after elapse of the predetermined time and before the control before the end of operation. The electric parking brake device described in 1. The motor controller is
Before the brake release operation ends in the brake release operation state,
When the cable tension determination unit (31) is not more than a predetermined cable tension value (TK) before release based on a load signal from the load sensor (15), the drive control unit is configured to transmit the electric motor (11). The electric parking brake device according to any one of claims 1 to 3, wherein the pre-release control is performed to stepwise decrease the rotational speed of (1).

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