JP4502749B2 - Electric parking brake device and method for estimating actual position of brake pad in electric parking brake device - Google Patents

Description

The present invention relates to an electric parking brake device that brakes wheels by converting a rotational motion of an electric motor into a linear motion by a driving force conversion mechanism and moving a brake pad, and a method for estimating the actual position of the brake pad in the electric parking brake device. .

When the vehicle is stopped and the electric brake device is in a non-braking state, a current of a predetermined magnitude is supplied to the motor of the electric brake device to shift to the braking state, and the actual position of the brake pad detected in the braking state A technique for calculating a contact start position (0-point position) at which the brake pad starts to contact the brake disc based on (reference position) is known from Patent Document 1 below.
JP 2000-55094 A

  However, in the above-mentioned patent document 1, when detecting the reference position of the brake pad, it is necessary to energize the motor to shift the electric brake device from the non-braking state to the braking state. There is a problem that the amount of time and power consumption for detecting the reference position increase as the amount increases.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to make it possible to estimate the position of a brake pad in a short time while minimizing the power consumption of an electric motor of an electric parking brake device.

In order to achieve the above object, according to the first aspect of the present invention, an electric motor, a driving force conversion mechanism that converts the rotational motion of the electric motor into a linear motion, and a wheel that is moved by the driving force conversion mechanism. An electric parking brake comprising a brake pad for braking the vehicle, a braking force holding mechanism for restricting the movement of the brake pad in the braking release direction by restricting the driving force conversion mechanism, and a current sensor for detecting a current flowing through the electric motor A device that temporarily energizes the electric motor during operation of the braking force holding mechanism and drives the electric motor in a rotational direction that moves the brake pad in the braking direction, and the current value detected by the current sensor at that time An electric parking brake device characterized in that the actual position of the brake pad is estimated based on the above.

  According to the invention described in claim 2, in addition to the configuration of claim 1, the initial position of the brake pad at the time of non-braking is determined based on the estimated actual position of the brake pad. An electric parking brake device is proposed.

According to the invention described in claim 3, an electric motor, a driving force conversion mechanism that converts the rotational motion of the electric motor into a linear motion, a brake pad that moves by the driving force conversion mechanism and brakes the wheel, The actual position of the brake pad in the electric parking brake device provided with a braking force holding mechanism that restricts the movement of the brake pad in the braking release direction by restraining the driving force conversion mechanism and a current sensor that detects a current flowing through the electric motor In the estimation method, the electric motor is temporarily energized during the operation of the braking force holding mechanism, and the electric motor is driven in a rotational direction that moves the brake pad in the braking direction. The restraint of the driving force conversion mechanism is released, and the actual position of the brake pad is estimated based on the current value detected by the current sensor at that time. Actual position estimation method of the brake pads in the electric parking brake system, which comprises an effective restraint of the driving force converting mechanism by the power holding mechanism again is proposed.

  The ratchet mechanism R of the embodiment corresponds to the braking force holding mechanism of the present invention, and the ball screw mechanism S of the embodiment corresponds to the driving force conversion mechanism of the present invention.

According to the configuration of the first aspect, the electric motor is temporarily energized during the operation of the electric parking brake device, and the electric motor is driven in the rotational direction to move the brake pad in the braking direction, and then detected by the current sensor. Since the actual position of the brake pad is estimated based on the current value, compared with the case where the actual position of the brake pad is estimated by energizing the electric motor until the electric parking brake device is activated from the inactive state, It is possible to minimize the power consumption of the electric motor and reduce the time required for estimation.

  According to the configuration of the second aspect, since the initial position of the brake pad during non-braking is determined based on the estimated actual position of the brake pad, the brake pad is always stopped at an appropriate initial position having a constant pad clearance. Thus, dragging of the brake pad can be prevented while ensuring high operation responsiveness.

  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 time chart when the electric parking brake is forcibly released, FIG. 8 is a flowchart illustrating a procedure for estimating the position of the brake pad, and FIG. 9 is a relationship between the motor current and the brake pad position. It is a graph.

  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, on both sides of the brake disc 13 fixed to the wheel. 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 includes a signal from the rotary encoder 51 that detects the rotational position of the motor output shaft 19 of the electric motor M, that is, the position of one brake pad 14a, and electric A signal from the current sensor 52 that detects the current flowing through the motor M and a signal from the parking switch 53 that is operated by the driver are input.

  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 causes the brake pads 14 a and 14 b to contact the brake disc 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 with reference to the time charts of FIGS. 6 and 7.

  In the time chart of FIG. 6, when the driver turns on the parking switch 53, the electric motor M rotates forward and the brake piston 15 moves forward, thereby generating a braking force with the same action as in the case of the service brake described above. 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 Even if the claw 42a meshes strongly with the ratchet teeth 32a of the ratchet wheel 32 and the energization of the solenoid 44 is released, the electric parking brake is maintained in the operating state.

  In the time chart of FIG. 7, when the driver turns off the parking switch 53, the electric motor M is driven in the forward rotation direction for a moment, and the ratchet wheel 32 rotates slightly 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 electric 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 electric parking brake, the ratchet mechanism R cannot be disengaged, the electric parking brake remains operated, 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 ratchet teeth 32a of the wheel 32 can be forcibly separated. Thus, it is possible to avoid a situation in which the operation of the electric parking brake cannot be released when the electric motor M including the failure of the power source cannot be operated.

  Next, the position estimation of the brake pad 14a executed by the electronic control unit U will be described based on the flowchart of FIG.

First, in step S1, it is confirmed that the brake pedal is not depressed by the driver. This is because when the brake pedal is depressed, the electric brake device operates as a service brake, and the position of the brake pad 14a cannot be estimated. When the brake pedal is not depressed in step S1 and the electric brake device is operating as a parking brake in step S2, the electric motor M is temporarily energized in step S3 to move the brake pad in the braking direction. Driving in the forward direction and slightly rotating the ratchet wheel 32 in the braking direction of FIG. The ratchet pole 42 is rotated to the position shown in FIG. 3 by the elastic force of 43 to release the restraint of the ratchet wheel 32, and the current value of the electric motor M at that time is detected by the current sensor 52 in step S4.

  FIG. 9 is a graph showing the relationship between the current value of the electric motor M and the position of the brake pad 14a. When the electric brake device is operated and the brake pads 14a and 14b are pressed against the brake disc 13, the electric motor is shown. The relationship of the position of the brake pad 14a with respect to the current value of M (that is, the output torque of the electric motor M) is known in advance. Therefore, if the current value of the electric motor M detected in step S4 is Ia, the actual position Pa of the brake pad 14a at that time can be read as the output of the rotary encoder 51.

  9, reference symbol Pb is a contact start position at which the brake pad 14a starts to contact the brake disc 13, and reference symbol Pc is a position where the brake pad 14a is returned from the position Pb by the pad clearance Lb (the initial position of the brake pad 14a). ). Therefore, when the actual position Pa of the brake pad 14a is estimated as described above, the distance La from the graph of FIG. 9 to the actual position Pa and the contact start position Pb can be known, and this distance La is set in advance. By adding the pad clearance Lb, the initial position Pc of the brake pad 14a can be known.

  Since there is a fixed relationship between the rotation angle of the motor output shaft 19 of the electric motor M and the position of the brake pad 14a, which is determined by the reduction ratio of the planetary gear mechanism P and the pitch of the ball screw mechanism S, it corresponds to the actual position Pa. From the output of the rotary encoder 51, the output of the rotary encoder 51 corresponding to the initial position Pc can be calculated.

  Thus, when the initial position Pc of the brake pad 14a is estimated in step S5 and stored in the non-volatile memory in the electronic control unit U, the ratchet mechanism R is operated in step S6 to bring the electric brake device into the operating state. In step S7, the power supply to the electric motor M is turned off.

  When the parking brake is released in step S8, the electric motor M is reversed in step S9, and the brake pad 14a is returned to the initial position Pc stored in the electronic control unit U while monitoring the output of the rotary encoder 51. The brake pad 14a can always be stopped at an appropriate initial position Pc having a constant pad clearance Lb. Therefore, when the electric brake device is operated as a service brake in step S10, dragging of the brake pads 14a and 14b can be prevented while ensuring high operation responsiveness of the electric brake device.

  As described above, when the actual position Pa of the brake pad 14a is estimated, and thus when the initial position Pc of the brake pad 14a is estimated, a current is temporarily supplied to the electric motor M to detect the current value Ia. Therefore, the power consumption of the electric motor M can be minimized and the estimation time can be shortened.

  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.

  The braking force holding mechanism is not limited to the ratchet mechanism R of the embodiment, and other appropriate mechanisms can be adopted.

  The driving force conversion mechanism is not limited to the ball screw mechanism S of the embodiment, and other appropriate mechanisms can be adopted.

  In the embodiment, the position of the brake pad 14a is indirectly detected by the rotary encoder 51 provided on the motor output shaft 19 of the electric motor M. However, the position of the brake pad 14a is directly detected by a non-contact sensor or the like. May be.

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 Time chart when the electric parking brake is activated Time chart when the electric parking brake is forcibly released Flowchart explaining the procedure for estimating the position of the brake pad Graph showing the relationship between motor current and brake pad position

14a Brake pad 52 Current sensor Ia Current value M Electric motor Pa Actual position Pc Initial position R Ratchet mechanism (braking force holding mechanism)
S Ball screw mechanism (driving force conversion mechanism)

Claims (3)

An electric motor (M);
A driving force conversion mechanism (S) that converts the rotational motion of the electric motor (M) into linear motion;
A brake pad (14a) that is moved by the driving force conversion mechanism (S) to brake the wheel;
A braking force holding mechanism (R) that restrains the driving force conversion mechanism (S) and restricts the movement of the brake pad (14a) in the braking release direction;
A current sensor (52) for detecting a current flowing through the electric motor (M);
An electric parking brake device comprising:
During the operation of the braking force holding mechanism (R), the electric motor (M) is temporarily energized to drive the electric motor (M) in the rotational direction that moves the brake pad (14a) in the braking direction. An electric parking brake device characterized by estimating an actual position (Pa) of a brake pad (14a) based on a current value (Ia) detected by a sensor (52).   The electric parking brake according to claim 1, wherein the initial position (Pc) of the brake pad (14a) during non-braking is determined based on the estimated actual position (Pa) of the brake pad (14a). apparatus. An electric motor (M);
A driving force conversion mechanism (S) that converts the rotational motion of the electric motor (M) into linear motion;
A brake pad (14a) that is moved by the driving force conversion mechanism (S) to brake the wheel;
A braking force holding mechanism (R) that restrains the driving force conversion mechanism (S) and restricts the movement of the brake pad (14a) in the braking release direction;
A current sensor (52) for detecting a current flowing through the electric motor (M);
A method for estimating the actual position of a brake pad in an electric parking brake device comprising:
The electric motor (M) is temporarily energized during the operation of the braking force holding mechanism (R), and the electric motor (M) is driven in a rotational direction that moves the brake pad (14a) in the braking direction. The restraint of the driving force conversion mechanism (S) by the braking force holding mechanism (R) is released, and the actual position of the brake pad (14a) based on the current value (Ia) detected by the current sensor (52) at that time (Pa) is estimated, and then the restraint of the driving force converting mechanism (S) by the braking force holding mechanism (R) is re-enabled, and the brake pad actual position estimating method in the electric parking brake device is characterized in that .

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