JP2006142935A - Electric parking brake device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To judge whether a parking brake is applied or disengaged accurately without using a rotation angle sensor. <P>SOLUTION: After the parking brake is applied by an electric motor M, the rotation of the motor M in the direction of disengaging the parking brake using a ratchet mechanism R is restricted mechanically, and the current flowing in the motor M is sensed by a current sensor 52 while a voltage is impressed in this condition on the motor M in the direction of disengaging the parking brake. As long as the parking brake is in normal operation, the operating condition of the parking brake can be judged on the basis of the sensed amperage because the amperage sensed by the current sensor 52 heightens owing to restriction of the motor rotation made by the ratchet mechanism R. As the operating condition of the parking brake can be judged without letting the rotation angle sensor sense the rotation angle of a gear etc. existing in the transmitting path for the driving force generated by the motor M, it is possible to construct the electric parking brake device in a smaller size. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In the present invention, after the electric motor is rotated in one direction and the parking brake is operated, the reverse rotation of the electric motor is mechanically restricted by the rotation restricting means so that the parking brake is kept in the operating state. The present invention relates to a parking brake device.

In the electric parking brake device that transmits the rotation of the hoisting gear driven by the electric motor to the parking brake unit via the cable, the rotation angle of the hoisting gear is detected by the rotation angle sensor, and the parking brake is operated based on the rotation angle. It is known from Patent Document 1 below to determine whether it is operating or released.
JP 2001-310713 A

  However, the one described in Patent Document 1 requires a rotation angle sensor for detecting the rotation angle of the hoisting gear driven by the electric motor, so that the parking brake drive system is enlarged by the rotation angle sensor. There was a problem. Further, when the cable is disconnected, the parking brake does not operate even when the hoisting gear rotates, so that there is a problem that the operating state of the parking brake cannot be determined from the output of the rotation angle sensor.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to make it possible to accurately determine whether the parking brake is operating or not, without using a rotation angle sensor.

  To achieve the above object, according to the first aspect of the present invention, an electric motor that operates the parking brake and a rotation restricting means that mechanically restricts the rotation of the electric motor in the direction of releasing the parking brake. And a current sensor that detects a current flowing through the electric motor, and an operating state determination that applies a voltage in a direction to release the parking brake to the electric motor and determines an operating state of the parking brake based on a current value detected by the current sensor. An electric parking brake device is provided.

  The ratchet mechanism R of the embodiment corresponds to the rotation restricting means of the present invention, and the electronic control unit U of the embodiment corresponds to the operating state determining means of the present invention.

  According to the configuration of the first aspect, after the parking brake is operated by the electric motor, the rotation restricting means mechanically restricts the rotation of the electric motor in the direction of releasing the parking brake, and the electric motor is parked in this state. A current flowing through the electric motor is detected by a current sensor while applying a voltage in a direction to release the brake. At this time, if the parking brake is operating normally, the current value detected by the current sensor is increased by the rotation regulating means regulating the rotation of the electric motor, and conversely, if the parking brake is not operating normally. Since the rotation restricting means does not restrict the rotation of the electric motor, the current value detected by the current sensor becomes low, so the operating state determining means can determine the operating state of the parking brake based on the current value.

  In this way, the operation state of the parking brake is determined from the current flowing through the electric motor without detecting the rotation angle of the gear or the like existing in the transmission path of the driving force generated by the electric motor, by the rotation angle sensor. It is possible not only to reduce the size of the apparatus by eliminating the rotation angle sensor from the driving force transmission path, but also to determine the operating state of the parking brake even when the driving force transmission path is damaged. .

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on examples of the present invention shown in the accompanying drawings.

  1 to 9 show an embodiment of the present invention, FIG. 1 is a cross-sectional view of an electric brake device having the function of an electric parking brake device, and FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. 1, FIG. 4 is an explanatory diagram of an operation when the electric parking brake is operated, FIG. 5 is an explanatory diagram of an operation when the electric parking brake is forcibly released, and FIG. FIG. 7 is a diagram illustrating a waveform of a voltage applied to the electric motor at the time of operating state determination, and FIG. 8 is a diagram illustrating a current waveform of the electric motor at the time of operating state determination.

  As shown in FIGS. 1 to 3, the electric brake device that can also be used as an electric parking brake device includes a brake caliper 11 that is supported by a knuckle or the like so as to be movable in the left-right direction in FIG. 1. Brake pads 14a and 14b that can be brought into contact with opposite sides of a pair of back plates 12a and 12b supported by guide means (not shown) so as to be able to approach and separate from each other. Is provided. A brake piston 15 is supported on the main body 11a of the brake caliper 11 so as to be able to advance and retreat. The brake caliper 11 is pressed against the back surface of one back plate 12a by the brake piston 15 so that the brake caliper 11 is moved to the right in FIG. The arm portion 11c connected to the main body portion 11a of the brake caliper 11 via the bridging portion 11b presses the back surface of the other back plate 12b, so that both brake pads 14a and 14b A braking force is generated in contact with both side surfaces. A dustproof boot 16 is mounted between the brake piston 15 and the brake caliper 11.

  The electric motor M housed in the main body 11a of the brake caliper 11 includes a plurality of stator coils 17 fixed to the inner surface of the main body 11a, and a ball bearing 18 that is rotatable around the axis L inside the stator coils 17. And a plurality of permanent magnets 20 fixed to the outer peripheral surface of the motor output shaft 19 so as to face the inner peripheral surface of the stator coils 17. A cylindrical female screw member 21 is supported inside the motor output shaft 19 by a pair of ball bearings 22 and 23 so as to be relatively rotatable. Between the male screw member 24 extending integrally on the axis L from the back surface of the brake piston 15. Are arranged with a plurality of balls 25. These female screw member 21, male screw member 24 and balls 25 ... constitute a ball screw mechanism S.

  A planetary gear mechanism P is arranged inside the main body 11 a of the brake caliper 11 so as to connect the electric motor M and the ball screw mechanism S. The planetary gear mechanism P disposed on the axis L includes a sun gear 31 fixed to the motor output shaft 19, a ratchet wheel 32 serving also as a planetary carrier fixed to the female screw member 21 of the ball screw mechanism S, and an outer periphery of the ratchet wheel 32. And a plurality of pinions 35 that are supported by the ratchet wheel 32 via pinion shafts 34 and mesh with the sun gear 31 and the ring gear 33 at the same time. Between the ratchet wheel 32 and the inner surface of the main body 11a, a thrust bearing 36 for supporting a braking reaction force that the brake piston 15 receives from the brake disc 13 is disposed.

  The electric brake device includes a ratchet mechanism R for causing it to function as an electric parking brake device. The ratchet mechanism R includes the ratchet wheel 32, a ratchet pole 42 having a central portion pivotably supported by a fulcrum pin 41 and having a ratchet pawl 42a engageable with a ratchet tooth 32a of the ratchet wheel 32 at one end. The torsion coil spring 43 that urges the ratchet pole 42 in the direction in which the ratchet pawl 42a is detached from the ratchet teeth 32a, and the one end side of the ratchet pole 42 are pressed to engage the ratchet pawl 42a with the ratchet teeth 32a. And a bolt 45 that can press the other end of the ratchet pole 42.

  The electronic control unit U that controls the operation of the electric motor M and the solenoid 44 receives a signal from a current sensor 52 that detects a current flowing through the electric motor M and a signal from a parking switch 53 that is operated by a driver. The

  Next, the operation of the embodiment of the present invention having the above configuration will be described.

  When the electric brake device is used as a service brake, since the rotation of the motor output shaft 19 is input to the sun gear 31 of the planetary gear mechanism P when the electric motor M is driven forward, the ring gear 33 is fixed so as not to rotate. The rotation of 31 is transmitted to the female screw member 21 of the ball screw mechanism S via the pinions 35 and the ratchet wheel 32. When the female screw member 21 rotates, the male screw member 21 engaged therewith via the balls 25... Moves forward together with the brake piston 15, and the brake piston 15 abuts the brake pads 14 a and 14 b against the brake disk 13 to generate a braking force. To do. When the electric motor M is driven in reverse, the brake piston 15 moves backward, the brake pads 14a and 14b are separated from the brake disc 13, and the braking force is released.

  Next, the operation when the electric brake device is used as an electric parking brake device will be described based on the flowchart of FIG.

  First, when the driver turns on the parking switch 53 in step S1 and the parking brake operating condition is established, the electric motor M is rotated forward in accordance with a command from the electronic control unit U in step S2, and the brake piston 15 moves forward. The braking force is generated in the same manner as in the case of the service brake. When a predetermined braking force is generated, the solenoid 44 is energized, and the ratchet pole 42 pressed by the solenoid 44 is counteracted around the fulcrum pin 41 against the elastic force of the torsion coil spring 43 as shown in FIG. By swinging clockwise, the ratchet pawl 42a of the ratchet pole 42 engages with the ratchet teeth 32a of the ratchet wheel 32.

  When energization of the electric motor M is stopped in this state, the brake pads 14a and 14b are retracted by the reaction force received from the brake disc 13, and the ratchet wheel 32 is about to rotate in the brake release direction, so that the ratchet pole 42 ratchet The pawl 42a meshes strongly with the ratchet teeth 32a of the ratchet wheel 32, and the parking brake is maintained in the operating state even when the energization of the solenoid 44 is released.

  In the subsequent step S3, in order to determine whether or not the parking brake is correctly operated, a step-like voltage shown in FIG. The polarity of this voltage is the polarity that rotates the electric motor M in the direction of releasing the parking brake (see FIG. 4).

  At this time, as shown in FIG. 4, if the ratchet pawl 42 is in a state of restricting the rotation of the ratchet wheel 32 in the braking release direction, the electric motor M is also locked to be non-rotatable. The current of the motor M becomes a constant lock current as shown in FIG. Therefore, when the lock current is detected in step S4, the electronic control unit U determines that the parking brake is normally operated, and sets the vehicle stop flag to “1” in step S5.

  For example, when the solenoid 44 fails and it becomes impossible to drive the ratchet pole 42 in the engaging direction, it is restrained by the ratchet pole 42 at the moment when the current that drives the electric motor M in the braking direction is cut off. The ratchet wheel 32 that has not been rotated rotates in the braking release direction due to the reaction force from the brake disc 13, and the parking brake is released. When the step-like voltage shown in FIG. 7 is applied to the electric motor M in such a state, the electric motor M can freely rotate because the ratchet wheel 32 is not restrained. As shown in FIG. 8B, the current of the electric motor M gradually decreases after a relatively large inrush current first flows, and does not reach the lock current. Accordingly, the electronic control unit U can determine that the parking brake is not operating normally and can issue an alarm to the driver.

  In such a situation, when the solenoid 44 operates normally and drives the ratchet pole 42 in the engaging direction, the tip of the ratchet pawl 42a of the ratchet pole 42 hits the tip of the ratchet teeth 32a of the ratchet wheel 32, It occurs in the same way when the meshing is not successful.

  Subsequently, when the driver turns off the parking switch 53 in step S6 and the parking brake release condition is satisfied, the vehicle stop flag is reset to “0” in step S7, and the electric motor M is rotated in the forward direction for a moment in step S8. To slightly rotate the ratchet wheel 32 in the braking direction. As a result, the ratchet pawl 42a of the ratchet pole 42 is disengaged from the ratchet teeth 32a of the ratchet wheel 32, and the ratchet pole 42 rotates clockwise to the position of FIG. Thus, the restraint of the ratchet wheel 32 is released. Then, the brake pads 14a and 14b are automatically retracted by the reaction force received from the brake disc 13, and the operation of the parking brake is released. At this time, the electric motor M may be reversed to assist the reaction force received by the brake pads 14a, 14b from the brake disc 13.

  If the electric motor M fails during the operation of the parking brake, the ratchet mechanism R cannot be disengaged, the parking brake remains activated, and the vehicle cannot run. In such a case, as shown in FIG. 5, by manually rotating the bolt 45, the ratchet pole 42 is pressed to swing clockwise around the fulcrum pin 41, and the ratchet pawl 42a of the ratchet pole 42 is ratchet. The wheel 32 can be forcibly separated from the ratchet teeth 32a. As a result, it is possible to avoid a situation in which the operation of the parking brake cannot be released when the electric motor M including the failure of the power supply cannot be operated.

  As described above, since the operating state of the parking brake can be determined from the current value of the electric motor M detected by the current sensor 52, the rotation angle sensor can be eliminated from the transmission path of the driving force of the electric motor M. It is possible to reduce the size and cost of the apparatus.

  Further, since the operation state of the parking brake is not determined based on the rotation angle of the ratchet wheel 32, for example, even when the ball screw mechanism S is damaged and slips, an erroneous determination can be avoided.

  Although the embodiments of the present invention have been described above, various design changes can be made without departing from the scope of the present invention.

  For example, although the electric brake device (service brake) is also used as the electric parking brake device in the embodiments, the present invention can also be applied to a dedicated electric parking brake device that is not used as a service brake.

  Further, the rotation restricting means of the present invention is not limited to the ratchet mechanism R of the embodiment, and other appropriate mechanisms can be adopted.

Cross-sectional view of an electric brake device having the function of an electric parking brake device 2-2 sectional view of FIG. 3-3 sectional view of FIG. Action explanatory diagram at the time of operation of electric parking brake Action explanatory diagram at the time of forced release of electric parking brake Flowchart explaining operation and release of electric parking brake The figure which shows the waveform of the voltage applied to the electric motor at the time of operation state judgment The figure which shows the electric current waveform of the electric motor at the time of operation state judgment

Explanation of symbols

52 Current sensor M Electric motor R Ratchet mechanism (rotation restricting means)
U Electronic control unit (operating state judging means)

Claims (1)

An electric motor (M) for operating the parking brake;
A rotation restricting means (R) for mechanically restricting the rotation of the electric motor (M) in the direction to release the parking brake;
A current sensor (52) for detecting a current flowing through the electric motor (M);
An operating state determining means (U) for applying a voltage in a direction for releasing the parking brake to the electric motor (M) and determining an operating state of the parking brake based on a current value detected by the current sensor (52);
An electric parking brake device comprising:

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