JP2008128358A - Electric parking brake system for vehicles - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric operated parking brake system with a load sensor having a main spring and a sub spring for accurately controlling target pulling force by detecting a point of change between sub spring property and main spring + sub spring property during the operation of a parking brake, and by correcting a zero position of the main spring. <P>SOLUTION: Output voltage Vs of a hole IC 27 corresponding to the point of change between the sub spring property and main spring + sub spring property is corrected to be zero point voltage Vs0 of the main spring 24. A voltage value ΔV for the target pulling force of a cable 3 corresponding to spring deflection is added to the zero point voltage Vs0 to be a voltage value Vtc for the target pulling force. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electric parking brake system for a vehicle in which a parking brake is operated and released electrically by a motor and a cable.

  2. Description of the Related Art Conventionally, there is provided an electric parking brake system for a vehicle in which a parking brake is operated and released electrically by a motor and a cable, and the cable is a load sensor for detecting the tension (load) of the cable. Is intervening. The parking brake is operated and released by feeding back an output voltage signal from the load sensor and controlling the motor.

  As this type of electric parking brake system, for example, the following Patent Document 1 is cited.

JP 2006-17158 A

The load sensor (force sensor) used in this Patent Document 1 is a Hall IC element in which a magnet is fixed, and a Hall IC element that can reciprocate with respect to the shaft and changes an output voltage in accordance with a relative displacement with the magnet. And a main spring that is interposed between the shaft and the case and elastically deforms in accordance with a reciprocating force acting between the shaft and the case.
In this load sensor, in the state in which the amount of elastic deformation of the main spring is substantially zero, in the reciprocating direction of the case with respect to the shaft, between the flange portion of the shaft and one end of the main spring, and the other end of the case and the main spring. A secondary spring for applying a preload is provided so that no gap is generated between the portions.

With this configuration, when the amount of elastic deformation of the main spring becomes substantially zero, the backward movement of the shaft relative to the case is stopped by the preload of the auxiliary spring, and the magnet and the Hall IC element are arranged. , And the output voltage of the Hall IC element does not change.
Such an operation can be obtained in the same manner even when the main spring is set and the size of the main spring in the elastic deformation direction is changed, thereby detecting the time when the output voltage of the Hall IC element does not change. Thus, it is possible to accurately detect the time point when the release of the force is completed (when the force becomes substantially zero). And if it sets so that reverse rotation drive of a motor may be stopped at that time, it is possible to prevent overrelease of a parking brake.

  Moreover, in this patent document 1, when it is detected that the force acting on the parking brake has become substantially zero, the output voltage from the load sensor is updated as a reference value, so that the main spring in the load sensor is reduced. Even if it occurs, the parking brake can be brought into the initial braking state.

However, in this Patent Document 1, since the motor is stopped immediately when the output voltage of the Hall IC element with respect to only the main spring changes, a time delay occurs and the cable is released. There is a problem that the force (cable unwinding force) cannot be controlled accurately.
Moreover, in this patent document 1, since the time when the elastic deformation amount of the main spring becomes substantially zero with respect to the release direction of the parking brake is detected, the case of pulling the cable to operate the parking brake is detected. There is also a problem that the spring zero position of the main spring relative to the setback of all the main springs cannot be corrected, and the operating force of the cable cannot be accurately controlled.

  The present invention has been provided in view of the above-described problems, and includes a load sensor having a main spring and a sub spring, and a sub spring characteristic and a main spring characteristic + sub spring characteristic during operation of a parking brake. It is an object of the present invention to provide an electric parking brake system for a vehicle that can accurately control a target pulling force by detecting a change point of the main spring and correcting a zero position of a main spring.

Therefore, in the electric parking brake system for a vehicle according to claim 1 of the present invention, the parking brake is activated via the cable 3 by the forward drive of the motor 11, and the parking brake is turned on by the reverse drive of the motor 11. An actuator 2 that controls the release state via the cable 3;
A load sensor 15 for detecting a load of the cable 3 acting on the parking brake;
A control device 1 that controls the rotational drive of the motor 11 according to the output voltage Vs from the load sensor 15;
The load sensor 15 is elastically compressed and deformed when the cable 3 is in an operating state, and has an elastic compression deformation amount substantially zero when the cable 3 is released, and a no-load region when the cable 3 is released. The secondary spring 25 having a spring constant different from that of the main spring 24, the magnet 26 that reciprocates with the reciprocation of the cable 3, and the relative displacement caused by the reciprocation of the magnet 26. A Hall IC 27 whose output voltage Vs changes according to the
During the operation of the cable 3, the secondary spring characteristic of the secondary spring 25 and the change point of the main spring + sub-spring characteristic between the main spring 24 and the auxiliary spring 25 are detected, and the detection time point of the main spring 24 is detected. A control means for correcting the zero position is provided.

  In the electric parking brake system for a vehicle according to claim 2, the output voltage Vs of the Hall IC 27 corresponding to the change point of the auxiliary spring characteristic and the main spring + sub spring characteristic is corrected to the zero point voltage Vs 0 of the main spring 24. The voltage value ΔV corresponding to the spring deflection of the target attractive force of the cable 3 is added to the zero point voltage Vs0 to obtain a target attractive force voltage value Vtc.

  According to the electric parking brake system for a vehicle according to the first aspect of the present invention, the secondary spring characteristic of the secondary spring 25 and the main spring + secondary spring of the main spring 24 and the secondary spring 25 during the operation of the cable 3. Since the control means for detecting the change point of the spring characteristic and correcting the detected time as the zero position of the main spring 24 is provided, the target attractive force can be accurately controlled.

According to the electric parking brake system for a vehicle according to claim 2, even if the main spring 24 is set and the zero position of the main spring 24 is changed, it corresponds to the amount of bending of the spring during the operation of the cable 3. The change point from the secondary spring characteristic to the main spring + sub spring characteristic in the output voltage Vs of the Hall IC 27 is detected, and the detection point of this change point is taken as the zero position of the main spring 24, and the Hall IC 27 corresponding to this zero position is detected. The output voltage Vs is corrected to a zero point voltage Vs0 corresponding to the zero position of the main spring 24.
A voltage value ΔV corresponding to the amount of spring deflection between the secondary spring 25 and the main spring 24 having a target pulling force set in advance is added to the zero point voltage Vs0, and the added voltage value is a voltage value of the target pulling force. Vtc. During the operation, the cable 3 is pulled until the output voltage Vs from the Hall IC 27 reaches the target pulling force voltage value Vtc. This makes it possible to accurately control the target attractive force.

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 comprising a microcomputer, an actuator 2 controlled by the control device 1, and a pulling operation of a control cable 3 by the actuator 2 are released. Thus, the brake assembly 4 and the like for operating and releasing the parking brake are constituted.
The electric parking brake system includes an operation switch 5 that sends a command to the control device 1 to operate and release the parking brake, and a warning lamp 6 that notifies the abnormality when an abnormality (failure) in each part is detected. In addition, a CAN (Controller Area Network) bus or the like is provided for transmitting such failure part information to a host computer.

The actuator 2 is driven to rotate by a motor 11 that can be rotated forward and backward by the control device 1, a speed reduction mechanism 12 that decelerates the rotational speed of the motor 11, and an output of the speed reduction mechanism 12. The screw 13 is reciprocated in the axial direction of the screw 13 by the rotation of the screw 13 and includes an nut 14 constituting an equalizer mechanism, a load sensor 15 described later, and the like.
Further, the control cable 3 on the left side in the figure is connected to one end of the nut 14, and the control 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 ends of both control cables 3 are connected to the brake assembly 4 side. The control cable 3 is composed of an outer outer cable and an inner cable that is slidable inside the outer cable.

The load sensor 15 detects a load (tension) acting on the inner cable of the control cable 3 (hereinafter simply referred to as the control cable 3), and has a basic configuration as shown in FIGS. The members include a shaft 20, a rod 22, a main spring 24, a secondary spring 25, a magnet 26, a Hall IC 27, a case main body 30 that accommodates these members, and the like.
In addition, FIG.2 (c) is AA sectional drawing of FIG.2 (b). The case body 30 includes a box-shaped case 31 having an open upper surface and a lid body 32 that covers the opening surface of the case 31.

The shaft 20 can reciprocate in the axial direction of the shaft 20 with respect to the case main body 30, and the control cable 3 is connected to an end protruding outside the case main body 30. A disc-shaped flange portion 21 is integrally connected and fixed to the end portion of the shaft 20.
The rod 22 has an end protruding from the case body 30 and is rotatably connected to the nut 14. A disc-shaped flange 23 is integrally connected and fixed to the end of the rod 22. . The flange portion 23 of the rod 22 and the flange portion 23 of the shaft 20 face each other.

A magnet 26 is disposed on the upper surface of the flange portion 21 of the shaft 20, and can reciprocate along the axial direction of the shaft 20 along with the reciprocating motion of the shaft 20. The upper portion of the magnet 26 is located in a recess 33 formed in the lid body 32, and can reciprocate with the shaft 20 along the longitudinal direction of the recess 33.
A hole IC 27 is disposed on one side surface of a protrusion 34 having a substantially U-shaped cross section forming the recess 33, and the hole IC 27 and the magnet 26 are disposed at a predetermined interval. ing. By reciprocating the magnet 26 together with the shaft 20, the relative displacement between the magnet 26 and the Hall IC 27, that is, the amount of compression and expansion deformation of the main spring 24 and the auxiliary spring 25 corresponding to the load of the control cable 3 is satisfied. The output voltage Vs is output to the control device 1.

  The coil spring-shaped main spring 24 is a compression spring provided between the inner surface 31 a of the case 31 and the side surface 21 a of the flange portion 21 of the shaft 20. In the state shown in FIG. 2, the parking brake is released, the main spring 24 is released, and the amount of elastic deformation is zero. Note that the main spring 24 is elastically compressed and deformed when the parking brake is in operation.

The secondary spring 25 in the form of a compression coil spring is assembled on the outer peripheral surface side of the shaft 20 and is provided in an elastically biased state between the inner surface 31 a of the case 31 and the side surface 21 a of the flange portion 21 of the shaft 20. ing.
The spring constant of the auxiliary spring 25 is set to be smaller than the spring constant of the main spring 24, and the flange portion 21 of the shaft 20 is always attached to the flange portion 23 side of the rod 22 by the elastic force of the auxiliary spring 25. It is fast.

Here, when the main spring 24 of the load sensor 15 is opened, it is not necessary that the tip surface of the main spring 24 and the side surface 21a of the flange portion 21 of the shaft 20 are in contact with or elastically, which will be described later. As described above, the spring zero position of the main spring 24 can be corrected by the action of the auxiliary spring 25.
In addition, the secondary spring of the said patent document 1 is used in order to take the backlash of a main spring, and the secondary spring 25 of this invention reliably returns the inner cable of the control cable 3 to a no-load area ( This is used to reliably return the unloaded sliding resistance of the inner cable.

  FIG. 3 is a block diagram related to the electric parking brake device of the present invention. The control device 1 includes a signal from the current sensor 16 that detects the current flowing through the motor 11, and the output voltage Vs detected by the Hall IC 27. , A signal (operation, release) from the operation switch 5 is input. Further, the control device 1 outputs a signal for controlling the motor 11 and a signal for turning on / off the warning lamp 6.

  The control device 1 monitors a current value from the current sensor 16 to detect an abnormality of the motor 11, a voltage value input unit 42 to which the output voltage Vs from the Hall IC 27 is input, a predetermined value A calculation unit 43 that calculates the slope of the output voltage Vs for each time, a comparison unit 44 that compares the calculation result of the calculation unit 43 with the previous one, a motor drive control unit 45 that controls the drive of the motor 11, and a timer unit 46. A storage unit 47 including a RAM that temporarily stores the result (data) calculated by the arithmetic unit 43, a ROM that stores a control program of the control device 1, and a control that controls the entire control. It consists of part 48 etc.

  FIG. 4 is a diagram showing the relationship between the output voltage (spring deflection amount) Vs (V) of the Hall IC 27 and the pulling force (N) of the control cable 3. This is a characteristic line with the spring 24. Vss0 on the horizontal axis is the output voltage value of the Hall IC 27 corresponding to the zero point position of the auxiliary spring 25, Vs0 is the output voltage value of the Hall IC 27 corresponding to the zero point position of the main spring 24, and Vtc is the control cable 3 The output voltage value of the Hall IC 27 corresponding to the target attractive force. ΔV is a voltage value (Vtc−Vs0) corresponding to the spring deflection of the main spring 24 having the target pulling force. The Vss0 and ΔV are numerical values set in advance.

When the parking brake is operated, the motor 11 is driven to rotate forward until the output voltage Vs from the Hall IC 27 reaches Vtc indicated by the spring characteristic line A, and the control cable 3 is operated. When Vtc is reached, the target pulling force is reached and the operation is completed.
When the parking brake is released, the motor is driven reversely until the output voltage Vs from the Hall IC 27 reaches Vss0 of the spring characteristic line A, and the control cable 3 is unwound, and the output voltage Vs becomes Vss0. At this point, the motor 11 is stopped.

As described above, in the electric parking brake system having the configuration shown in FIG. 1, the deflection of the springs (main spring 24, auxiliary spring 25) attached to the load sensor 15 is converted into a voltage value (the output voltage Vs of the Hall IC 27). The pulling force of the control cable 3 is controlled.
However, when the main spring 24 is set loose (spring contraction) with use, the zero position of the main spring 24 changes as shown by the spring characteristic line B. Will change.

  Therefore, in the present invention, if the zero position of the main spring 24 changes, the target pulling force cannot be accurately controlled. Therefore, the secondary spring characteristic and the change point of the main spring + sub spring characteristic during the operation of the parking brake (FIG. 4). The target pulling force can be accurately controlled by detecting the coupling point between the broken line and the solid line) and correcting the spring zero position of the main spring 24.

As shown in FIG. 4, the pulling force on the auxiliary spring 25 has a smaller spring constant than that of the main spring 24, so that the pulling force of the control cable 3 is small, and therefore the inclination is gentle. Since the pulling force with respect to the main spring 24 has a large spring constant, the pulling force becomes large from the time when the zero position of the main spring 24 has passed, and therefore the inclination is considerably tighter than that of the auxiliary spring 25.
In addition, the inclination of the auxiliary spring characteristic of only the auxiliary spring 25 and the main spring + sub-spring characteristic of the main spring 24 and the auxiliary spring 25 is constant, and the main spring + sub-spring characteristic or the main spring + The inclination changes when the auxiliary spring characteristic changes to the auxiliary spring characteristic, and this change is detected.

FIG. 5 shows the relationship between the time (sec) in the operating direction of the control cable 3 and the output voltage Vs of the Hall IC 27. The slope of the output voltage Vs of the Hall IC 27 with respect to time is opposite to that in FIG. . That is, since the spring constant is small in the case of the secondary spring 25, the amount of change in the output voltage Vs of the Hall IC 27 per time is large, and in the case of the secondary spring 25 + the main spring 24, the spring constant is large, so The amount of change of the main spring 24 of the Hall IC 27 is small.
The amount of change, that is, the point where the inclination changes greatly indicates the zero position of the main spring 24. From the inclination of the output voltage Vs corresponding to the auxiliary spring 25, the inclination of the output voltage Vs corresponding to the auxiliary spring 25 + the main spring 24. Is calculated every predetermined time, a point where the slope of the output voltage Vs changes greatly is detected, the change point is corrected as the zero position of the main spring 24, and the control cable 3 is controlled.

  In FIG. 5, the calculation interval includes three cases of the auxiliary spring characteristic, the auxiliary spring characteristic to the auxiliary spring + main spring characteristic, and the main spring + sub spring characteristic. The sub-spring 25 is drawn for the sake of clarity in order to change from the sub-spring 25 to the sub-spring 25 + the main spring 24. Actually, the slope of the output voltage Vs is calculated until the control cable 3 is pulled and stopped. Note that, after detecting the change point corresponding to the zero position of the main spring 24, the slope of the output voltage Vs may not be calculated.

  Next, the control operation of the present invention will be described based on a flowchart. FIG. 6 shows a case where the parking brake is operated. First, when the operating switch 5 is operated, the motor 11 is driven to rotate forward as shown in step S1. Next, in step S2, for example, the motor abnormality detection unit 41 monitors whether the motor 11 is abnormal by using a current value. If an abnormality (failure) is detected in step S3, the warning lamp 6 is turned on and the motor 11 is stopped. Then (see step S4), and then shifts to fail-safe control (see step S5).

If there is no failure in step S3, the process proceeds to step S6, and the slope Vs ′ of the output voltage Vs is calculated. This calculates a change amount of the output voltage Vs per fixed time during operation, for example, every 50 msec, and the change amount of the output voltage Vs becomes a slope Vs ′. The output voltage Vs from the Hall IC 27 is input to the voltage value input unit 42 of the control device 1, and the calculation unit 43 calculates the amount of change every 50 msec by a timer signal from the timer unit 46.
For example, if the fixed time is 50 msec as described above,
Slope Vs ′ = (previous output voltage Vs−current output voltage Vs) / 50 msec
The above-mentioned “previous output voltage Vs” is the output voltage Vs before 50 msec.

In this way, the amount of change (inclination Vs ′) of the output voltage Vs from the Hall IC 27 is calculated during operation by the calculation unit 43. In step S7, at the zero position of the main spring 24 shown in FIG. When the slope Vs ′ changes to the main spring + sub spring characteristic due to the characteristics of the spring 24 + sub spring 25, the process proceeds to step S8.
Here, in the main spring + sub-spring characteristic, the amount of change (inclination Vs ′) becomes small as shown in FIG. 5, and the inclination Vs ′ calculated at that time and the previous calculation and storage in the storage unit 47 are stored. The comparison unit 44 compares the slope Vs ', and if the comparison results in a change in the slope Vs', the zero position of the main spring 24 is detected and the signal is sent to the control unit 48. Output to.

  As shown in step S <b> 8, the output voltage Vs from the Hall IC 27 when the current main spring + sub spring characteristic is changed is corrected as the zero point voltage Vs <b> 0 of the main spring 24. Next, the process proceeds to step S9 to calculate a target attractive force voltage value Vtc. Here, as shown in FIG. 4, the voltage value Vtc of the target attractive force is calculated by adding the voltage value ΔV corresponding to the spring deflection of the target attractive force to the zero point voltage Vs0 of the main spring 24.

  In step S10, a failure is determined in the same manner as in step S2. In step S11, if there is a failure, the process proceeds to steps S4 and S5 as described above. If there is no failure, the process proceeds to step S12. In step S12, the comparison unit 44 compares the stored voltage value Vtc of the target attractive force from the storage unit 47 with the output voltage Vs from the voltage value input unit 42, and the input output voltage Vs is obtained. When the voltage value Vtc of the target attractive force is reached, the process proceeds to step S13. When the process proceeds to step S13, the motor 11 is controlled to be stopped by the motor drive control unit 45, whereby the operation is completed.

As described above, in this embodiment, even if the main spring 24 is set and the zero position of the main spring 24 changes, the output voltage Vs of the Hall IC 27 corresponding to the amount of spring deflection during the operation of the control cable 3. The change point from the secondary spring characteristic to the main spring + secondary spring characteristic is detected, and the detection time of this change point is set as the zero position of the main spring 24, and the output voltage Vs of the Hall IC 27 corresponding to this zero position is used as the main spring 24. The zero point voltage Vs0 corresponding to the zero position is corrected.
A voltage value ΔV corresponding to the amount of spring deflection between the secondary spring 25 and the main spring 24 having a target pulling force set in advance is added to the zero point voltage Vs0, and the added voltage value is a voltage value of the target pulling force. Vtc. During operation, the control cable 3 is pulled until the output voltage Vs from the Hall IC 27 reaches the target pulling force voltage value Vtc. This makes it possible to accurately control the target attractive force.

  Next, the operation of releasing the parking brake will be described with reference to FIG. First, by performing a release operation with the operation switch 5, the motor 11 is driven in reverse to be controlled to return the control cable 3 as shown in step S21. In step S22, whether or not the motor 11 has failed is determined in the same manner as in FIG. 6, and in the case of a failure, the process proceeds from step S23 to step S24 to stop the motor 11 and fail-safe control is performed (step S25). reference).

  If there is no failure in step S23, the process proceeds to step S26, and whether or not the output voltage Vs of the Hall IC 27 decreases to the zero point voltage value Vss0 (see FIG. 4) corresponding to the zero point position of the auxiliary spring 25. To be judged. When the output voltage Vs from the Hall IC 27 reaches the zero point voltage value Vss0, the process proceeds to Step S27 and the motor 11 is stopped to complete the parking brake releasing operation.

1 is a schematic block configuration diagram of an electric parking brake system in an embodiment of the present invention. (A) (b) is sectional drawing and the side view of a load sensor in an embodiment of the invention, and (c) is an AA sectional view of Drawing 2 (b). It is a block diagram in an embodiment of the invention. It is a figure which shows the relationship between the output voltage (spring deflection amount) of Hall IC and the pulling force of a control cable in embodiment of this invention. It is a figure which shows the relationship with the output voltage of Hall IC in the action | operation of the control cable in embodiment of this invention. It is a flowchart which shows the operation | movement operation | movement of the control cable in embodiment of this invention. It is a flowchart which shows the operation | movement of cancellation | release of the control cable in embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Control apparatus 2 Actuator 3 Control cable 11 Motor 15 Load sensor 24 Main spring 25 Secondary spring 26 Magnet 27 Hall IC

Claims (2)

An actuator that activates the parking brake via the cable (3) by the forward rotation of the motor (11) and controls the parking brake to the released state via the cable (3) by the reverse rotation of the motor (11). (2) and
A load sensor (15) for detecting a load of the cable (3) acting on the parking brake;
A control device (1) for controlling the rotational drive of the motor (11) according to the output voltage (Vs) from the load sensor (15),
The load sensor (15) is elastically compressed and deformed when the cable (3) is in an operating state, and has an elastic compression deformation amount of substantially zero when the cable (3) is released, and the main spring (24), In order to return the cable (3) to the no-load range when the cable (3) is released, the secondary spring (25) having a spring constant different from that of the main spring (24) and the reciprocating motion of the cable (3) A magnet (26) that reciprocates along with the Hall IC (27) in which the output voltage (Vs) changes according to relative displacement by the reciprocation of the magnet (26),
During the operation of the cable (3), the secondary spring characteristic of the secondary spring (25) and the change point of the main spring + secondary spring characteristic of the main spring (24) and the secondary spring (25) are detected, An electric parking brake system for a vehicle, comprising control means for correcting the detection time as the zero position of the main spring (24).   The output voltage (Vs) of the Hall IC (27) corresponding to the change point of the auxiliary spring characteristic and the main spring + auxiliary spring characteristic is corrected to the zero point voltage (Vs0) of the main spring (24), and this zero point voltage is corrected. 2. The vehicle according to claim 1, wherein a voltage value (ΔV) corresponding to a spring deflection of the target pulling force of the cable (3) is added to (Vs0) to obtain a voltage value (Vtc) of the target pulling force. Electric parking brake system.

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