JP2001280385A - Method of detecting pad wear of electric disc brake - Google Patents

Abstract

(57) [Problem] To provide a method of detecting pad wear of an electric disc brake, which can detect the amount of pad wear satisfactorily. SOLUTION: When brake pads are worn,
The value M ₃ corresponding to the intermediate data M ₂ to the pad clearance, including wear amount of the pad clearance and brake pads
And the difference (corresponding to the amount of pad wear) M
_{4 (n) (M 4 (} n) = M 2 -M 3) the calculated (step S5), M
₄ = M _{4 (n-1)} + M _{4 (n)} is calculated, and M _{4 (n)} is added to the wear amount (M _{4 (n-1)} ) of the brake pad up to that time, and the total wear amount M ₄ is obtained (step S7). Pad wear can be quantitatively determined in real time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting wear of a pad of an electric disc brake which generates a braking force by the rotational force of an electric motor.

[0002]

2. Description of the Related Art Recently, an electric disk brake which generates a braking force by an output of an electric motor without using a brake fluid has been used. An example of the electric disc brake is disclosed in Japanese Patent Application No. 11-114232 proposed by the present applicant. This electric disc brake includes a pair of brake pads arranged on both sides of a disc rotor, a piston pressing the brake pad, an electric motor, and a rotary motion of the electric motor converted into a linear motion to move the piston forward and backward. A ball ramp mechanism, and a pad wear compensation mechanism for advancing the piston in accordance with the wear of the brake pad, the ball ramp mechanism is driven by an electric motor,
The brake pad is pressed against the disk rotor by the piston to generate a braking force. Further, the pad wear compensation mechanism adjusts the relative position between the piston and the movable disk of the ball ramp mechanism according to the wear of the brake pad to compensate for the wear of the pad.

[0003]

Incidentally, it is desired that the detection of pad wear can be performed with high accuracy in order to secure a good braking force. However, in the above-described prior art, since the rotor rotation angle of the ball ramp mechanism is limited, a large displacement in the linear motion direction cannot be obtained. For this reason, the pad wear is compensated by the pad wear compensation mechanism. However, in the above-described conventional technique, the rotation amount of the motor rotor and the pad wear amount do not match, and the monitoring of the pad wear amount using the motor rotor rotation angle is not properly performed. I couldn't do it.

In a hydraulic disc brake, a wear sensor is generally mounted on the back metal of the pad, and the wear of the wear sensor makes contact with the disk rotor to generate a contact sound, thereby detecting pad wear. In a hydraulic disc brake without a wear sensor, the pad wear is detected by advancing the piston and reducing fluid due to pad wear and turning on a liquid level warning lamp in the reservoir. However, the above-described hydraulic disc brake that detects pad wear by contact sound has a problem that the contact sound causes discomfort and the driver may not be able to understand the meaning of the contact sound. . Also, in the above-described hydraulic disc brake that detects pad wear by turning on the liquid level warning lamp, it may happen that the driver cannot understand the meaning of turning on the lamp, and the electric disc brake that does not use fluid may be used. There is a problem that it cannot be applied.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method of detecting pad wear of an electric disc brake, which can detect the amount of pad wear satisfactorily.

[0006]

According to the first aspect of the present invention,
A pair of brake pads disposed on both sides of the disk rotor and a piston for pressing the brake pads, an electric motor, and a ball ramp mechanism for converting the rotational motion of the electric motor into linear motion to advance and retract the piston, A pad wear compensation mechanism for advancing the piston in accordance with the wear of the brake pad, wherein after the brake is released when the brake pad is worn, a predetermined pad clearance is provided between the brake pad and the piston by operating the pad wear compensation mechanism. In a method for detecting pad wear of an electric disc brake in which the piston is positioned so as to ensure that the piston is on standby for the next braking operation, the piston position when generating a braking force with respect to the return position of the ball of the ball ramp mechanism is determined. Calculated as braking position data, and from the piston braking position data Give the pad wear amount by subtracting the pad clearance value determined because, each time the pad wear amount due to the braking operation is obtained, wherein the addition of pad wear amount.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. As shown in FIGS. 1 to 4, the electric disc brake 50 of the second embodiment has a caliper body 52 on one side (usually inside the vehicle body) of a disc rotor 51 that rotates with wheels (not shown). A claw 53 formed substantially in a C-shape and extending to the opposite side across the disk rotor 51 is integrally connected to the caliper body 52 by a bolt 53A. Brake pads 54 and 55 are provided on both sides of the disk rotor 51, that is, between the disk rotor 51 and the caliper body 52 and between the tip of the claw 53. Brake pad
54 and 55 are movably supported along the axial direction of the disk rotor 51 by a carrier 56 fixed to the vehicle body side.
The braking torque is received by the carrier 56, and the caliper main body 52 is slidably guided along the axial direction of the disk rotor 51 by a slide pin 57 attached to the carrier 56.

An electric motor 59 and a rotation detector 60 are provided in a substantially cylindrical case 58 of the caliper main body 52 to which the annular flange 53B of the claw 53 is connected. Is inserted into the rotor 62 of the electric motor 59 from the side of the annular flange 53B. A cover 63 is attached to the rear end of the case 58 with bolts 63A.

The electric motor 59 is rotatable by the bearings 65 and 66 on the stator 58 fixed to the inner peripheral portion of the case 58 and opposed to the inner peripheral portion of the stator 64 by the bearings 65 and 66, and moves in the axial direction. And a rotatably supported rotor 62.
The rotation detector 60 includes a resolver stator fixed to a resolver case 67 attached to the case 52 by bolts 67A.
68, and a resolver rotor 69 fixed to the rotor 62 so as to face the resolver stator 68, and detects the rotation speed (rotation speed) of the rotor 62 based on the relative rotation of these. The cover 63 includes an electric motor 59 and a rotation detector 60.
The electric motor 59 rotates the rotor 62 by a desired angle at a desired torque in response to a control signal (electric signal) from a controller (not shown). It has become.
The connector 70 and the cable 71 are inclined with respect to the axial direction of the disk rotor 51 and extend radially outward to avoid interference with members such as arms, links, knuckles, and struts of the suspension device of the vehicle. Have been.

The ball lamp unit 61 includes an electric motor 59
A ball ramp mechanism 72 that converts the rotational motion of the rotor 62 into a linear motion, and a piston 73 that presses the brake pad 54
And an adjustment nut 74 interposed therebetween, and a limiter mechanism 75 for transmitting the rotation of the ball ramp mechanism 72 to the adjustment nut 74.

The ball ramp mechanism 72 is in contact with the flange portion 53B of the claw portion 53, and is fixed to an annular fixed disk 77 so as not to rotate by a pin 76, and a movable disk 78 disposed opposite to the fixed disk 77. And a ball 79 (steel ball) interposed between them. The movable disk 78 is integrally formed with a cylindrical portion 80 that is inserted into the fixed disk 77 and extends to the inside of the case 58. The cylindrical portion 80 is spline-coupled to the inner peripheral portion of the rotor 62. Play is provided.

As shown in FIG. 7, three ball grooves 81 and 82 are formed on the opposing surfaces of the fixed disk 77 and the movable disk 78, respectively, extending in an arc along the circumferential direction. The three ball grooves 81 and 82 are equally extended and arranged at equal intervals in the range of the central angle of 90 °. As shown in FIG. 8, each of the ball grooves 81 and 82 is inclined in the same direction with a height difference Δh from the deepest portion a at one end to the shallowest portion at the other end b. Further, the respective ball grooves 81 of the fixed disk 77 and the respective ball grooves 82 of the movable disk 78 are arranged so that the deepest portions a face each other at the original position, and the ball is provided between the deepest portions a. 79 are charged. As a result, when the movable disk 78 rotates with respect to the fixed disk 77, the ball 79 rolls in the ball grooves 81 and 82 toward the shallowest portion b, and the fixed disk 77 moves in accordance with the rotation angle. It moves along the axial direction in a direction away from 78. In this case, when the movable disk 78 rotates clockwise from its original position,
The fixed disk 77 moves rightward in FIG. 1 and presses the debrake pad 54 to the disk rotor 51 via the claw 53.

As described above, the fixed disk 77 and the movable disk 78 face each other, and are formed with three ball grooves 81 and 82 extending in an arc shape along the circumferential direction, respectively. The three balls 79 roll in the ball grooves 81 and 82 by the relative rotation of the fixed disk 77 and the movable disk 78, and the fixed disk 77 and the movable disk 78 Move relative to each other in the axial direction.

The adjustment nut 74 comprises a cylindrical portion 83 and a flange portion 84 formed outside one end of the cylindrical portion 83.
Is inserted into the cylindrical portion 80 of the movable disk 78, and is rotatably supported by a slide bearing 85. The flange portion 84 is in contact with one end of the movable disk 78 and is rotatably supported by a thrust bearing 86. The cylindrical portion 83 of the adjusting nut 74 extends to the inside of the rotor 62 in the case 58, and a limiter mechanism 75 is mounted on the outer periphery of the distal end.

The limiter mechanism 75 includes a cylindrical portion of the adjustment nut 74.
A limiter 87 and a spring holder 88
Are rotatably fitted to each other, and are connected to each other by a coil spring 89. The limiter 87 and the spring holder 88 are engaged with each other so as to be able to rotate relative to each other within a predetermined range, and a predetermined set load is applied to the rotation direction by a coil spring 89. Accordingly, the coil spring 89 can be rotated clockwise (clockwise when viewed from the left in FIG. 1, the same applies hereinafter) against the set load of the coil spring 89. An engagement recess 87A formed in the limiter 87 is engaged with an engagement protrusion 80B formed at the end of the cylindrical portion 80 of the movable disk 78. Can rotate relatively. A clutch spring 90 (coil spring) is wound around the outer periphery of the tip of the cylindrical portion of the adjustment nut 74, and one end of the clutch spring 90 is attached to a spring holder.
The clutch spring 90 is actuated as a one-way clutch by expanding and contracting the diameter by torsion, and transmits only the clockwise rotation of the spring holder 89 to the cylindrical portion 83 of the adjusting nut 74. It has become.

The piston 73 is screwed into a screw portion 91 formed on the inner peripheral portion of the adjusting nut 74, and advances toward the brake pad 54 when the adjusting nut 74 rotates clockwise with respect to the piston 73. It has become. In the cylindrical portion 83 of the adjustment nut 74, a rotation preventing rod 92 whose one end is fixed to the resolver case 67 by a nut 92A is inserted, and the other end of the rotation preventing rod 92 is slidable on the piston 73 in the axial direction. And is engaged so as to restrict rotation. A plurality of disc springs 95 are interposed between a flange portion 93 formed in an intermediate portion of the rotation preventing rod 92 and a flange portion 94 formed in the cylindrical portion 83 of the adjustment nut 74, and the spring force is provided. The adjustment nut 74 is biased rightward in FIG. And the non-rotating rod 92 is
By moving the position in the axial direction, the urging force (set load of the disc spring 95) on the adjustment nut 74 can be adjusted.

The ball ramp mechanism 72, the adjusting nut 74, and the piston 73 are provided with a case 96 for covering them and integrally sub-assembling the ball lamp unit 61. The case 96 is adjusted with the front flange of the case 96. nut
A wave washer 97 for providing an appropriate resistance to the rotation of the adjustment nut 74 is interposed between the flange portion 84 and the flange portion 84. In the drawing, reference numeral 98 denotes a piston boot, and 99 denotes a pin boot. Further, the device is provided with a controller (not shown), which controls the drive of the electric motor 59 and detects pad wear as described later.

Next, the operation of the embodiment constructed as described above will be described.

At the time of braking, when the rotor 62 of the electric motor 59 rotates clockwise with a predetermined torque in response to a signal from a controller (not shown), the spline coupling portion is connected to the movable disk of the ball ramp mechanism 72 via 80A. 78 rotates,
The ball 79 rolls along the ball grooves 81 and 82 to advance the movable disk 78 toward the brake pad 54 along the axial direction. This thrust is transmitted to the adjustment nut 74 via the thrust bearing 86, and further transmitted to the piston 73 via the screw portion 91, so that one of the brake pads 54 is pressed against the disk rotor 51, and the reaction force thereof causes the caliper main body. 52 is the carrier
The claw portion 53 moves along the slide pin 57 of 56 and presses the other brake pad 55 against the disk rotor 51, and a braking force is generated according to the torque of the electric motor 59.

When the braking is released, the electric motor 59 is rotated in the reverse direction, and the movable disk 78 is rotated counterclockwise to the original position.
The adjustment nut 74 and the piston 73 are retracted, the brake pads 54 and 55 are separated from the disk rotor 51, and the braking is released.

Next, compensation of wear of the brake pads 54 and 55 will be described with reference to FIGS. Since the relative positional relationship between the piston 73 and the brake pad 54 and the relative position between the claw portion 53 and the brake pad 55 are the same, FIGS. 5 and 6 show only the relationship between the piston 73 and the brake pad 54.

When there is no wear on the brake pad 54, or after the wear adjustment described later has been performed, as shown in FIG.
When the brake pad 54 moves forward from the non-braking position (A) by the pad clearance C to the braking start position (B) where the brake pad 54 contacts the disk rotor 51, the engaging projection 80B of the cylindrical portion 80 of the movable disk 78 is moved to the limiter. It rotates along the engaging concave portion 87A of 87 and moves from one end to the other end of the engaging concave portion 80B. Further, when the piston 73 presses the brake pad 54 against the disk rotor 51 and moves to the braking position (D), the engaging projection 80B rotates the limiter 87 clockwise, and the rotational force is applied to the coil spring 89 and the clutch spring. It is transmitted to the adjustment nut 74 via 90. At this time, the piston
Since 73 presses the brake pad 5 and a large frictional force is generated in the screw portion 91 between the piston 73 and the adjustment nut 74, the coil spring 89 bends and the adjustment nut 74 does not rotate. When the piston 73 retreats to the non-braking position (A) due to the reverse rotation of the movable disk 78 when the braking is released, the engaging projection 80B abuts against one end of the engaging recess 80B, and the limiter 62 and the spring holder 88 are engaged. Is rotated counterclockwise, but the piston 73 does not rotate because the clutch spring 90 expands in diameter and idles. In this way, pad wear is not adjusted and constant pad clearance is maintained.

When the brake pad 54 is worn, as shown in FIG. 6, during braking, the brake pad 54 is moved from the non-braking position (A) to the position (B) by the pad clearance C due to the clockwise rotation of the rotor 62 during braking. Move up to the engaging protrusion
Even if 80B moves from one end of the engagement recess 87A to the other end,
The piston 73 does not press the brake pad 54 due to the wear W. When the rotor 62 further rotates, the movable disk 78
And the adjustment nut 74 is positioned toward the disk rotor 51 (D)
The piston 73 moves forward to bring the brake pad 54 into contact with the disk rotor 51. During this time, the engagement projection 80B rotates the limiter 87 clockwise, and the rotational force is applied to the adjustment nut via the coil spring 89 and the clutch spring 90.
However, since the piston 73 does not press the brake pad 54 and a large frictional force is not generated in the screw portion 91 between the piston 73 and the adjustment nut 74, the adjustment nut 74 is transmitted.
Rotates clockwise to further advance the piston 73 toward the brake pad 54 to adjust the wear of the pad.

When the piston 73 moves to the position (E) where the brake pad 54 is pressed against the disk rotor 51, a large frictional force is generated in the screw portion 91 between the piston 73 and the adjusting nut 74, and The flexure of the spring 89 causes the rotation of the adjustment nut 74 to stop. When the piston 73 is retracted to the non-braking position (A) by the counterclockwise rotation of the rotor 62 at the time of braking release, the engaging projection 80B comes into contact with one end of the engaging recess 87A, and the limiter 87 is rotated counterclockwise. However, since the clutch spring 90 expands in diameter and idles, the adjustment nut 74 does not rotate. In this way, the brake pad 54 in the non-braking position caused by wear
The gap W between the brake pad 54 and the piston 73 is reduced to W ', and the gap W is reduced by a certain percentage of the wear amount of the brake pad 54.
With each operation, the piston 73 can be advanced from the adjustment nut 74 to the brake pad 54 side. By repeating this, the wear of the pad can be adjusted.

Hereinafter, a method for detecting pad wear of an electric disc brake according to an embodiment of the present invention will be described with reference to the drawings.

The controller detects pad wear by using the output of the rotation detector 60 and the like as follows. The method will be described below with reference to FIGS.

As shown in the flowchart of FIG. 11, first, in step S1, it is detected that the ball 79 is at the return position A (FIG. 8) corresponding to the bottom of the ramp of the ramp mechanism 72 (see step S2 described later). It is determined whether or not it has been performed.
If NO is determined in step S1 (the ball 79 is not detected to be at the return position A), the process proceeds to step S2, where it is determined that the ball 79 is at the return position A, and the ball 79 is returned to the return position A. In this case, the detection is performed using the fact that the current value of the motor increases as shown in FIG. Then, the detection result is stored as return position data M ₀ along with its value M ₀ (distance from a preset reference position) (not shown).
To memorize. The detection that the ball 79 is at the return position A is performed by turning off the motor current and moving the ball 79 rightward in FIG.
This may be performed by providing a spring that pulls the spring.

YES at step S1 (ball 79 returns to position A
Is detected, the process proceeds to step S3, where the contact position B between the pad and the disk rotor 51 is detected, and the detection result (distance from the reference position) is used as the contact position (M ₁ ) [piston stored with the value M ₁ in the storage means as a braking position data]. The detection of the contact position B
As shown in FIG. 10, the motor is controlled to the right of the lamp in FIG. 8 to detect a point where the current value becomes large. In addition,
When the brake pad is worn due to braking, the pad wear mechanism is activated, and the piston 73 advances as much as the wear of the brake pads 54 and 55, as described above, and the piston 73 moves from the non-braking position to the braking start position. The pad clearance C up to (the position where the brake pads 54 and 55 abut on the disk rotor 51) is secured. For this reason, the value M ₁ of the contact position (M ₁ ), together with the return position data M ₀ (distance from the reference position to the return position) and the pad clearance C, when the brake pads 54 and 55 are worn, , Brake pads 54 and 55 are included.

Subsequent to step S3, an operation of M ₂ = M ₁ -M ₀ is performed to obtain intermediate data M ₂ . The intermediate data M ₂ is
When the brake pads 54 and 55 are worn together with the pad clearance C, the wear includes the wear of the brake pads 54 and 55 (step S4).

[0030] Following step S4, the subtracted value M ₃ corresponding to the intermediate data M ₂ to the pad clearance C which is predetermined as described above, (which corresponds to the pad wear amount) the difference M 4 _{(n) (M 4 (n) = M} 2 -M 3) seek (step S5). Next, it is determined whether M4 _(n) is greater than 0 (step S6). YES at step S5 (greater than M 4 _(n) is 0. Pad wear compensation mechanism indicating that is activated.) And it is determined, the process proceeds to step S6, M ₄ = M
_{4 (n-1) + M} 4 performs a computation of _(n), which until the amount of wear M _{4 (n-1)} to be added M _{4 (n)} of cumulative wear amount M ₄ of the brake pads 54 and 55 Ask (step S7). Following step S7,
Enter the total amount of wear M ₄ obtained in step S6 to multi-display controller (not shown) is displayed as a pad wear amount (step S8). In this case, a warning lamp may be turned on when the amount of pad wear exceeds a predetermined reference value, so that the driver can reliably recognize the wear of the pad.

When YES is determined in step S6 (M4 _(n) is 0 or less, indicating that the pad wear compensation mechanism does not operate), the flow advances to step S8 to display the amount of pad wear.
Following step S8, stores the M ₄ in the storage means as M _{4 (n-1),} waits to step S7 in the next braking, returns to the main routine (not shown). Note that M4 _(n-1) is set to 0 in the initial stage in step S8.

As described above, when the brake pads 54 and 55 are worn, a value M ₃ corresponding to the pad clearance C is obtained from the pad clearance C and the intermediate data M ₂ including the wear of the brake pads 54 and 55. subtracting, the difference (corresponding to the pad wear _{amount) M 4 (n) (M} 4 (n) = M 2 -
M ₃ ) (step S5), and M ₄ = M _{4 (n-1)} + M _{4 (n )}
Performs the operation of it wear of the brake pads 54 and 55 up to _{(M 4 (n-1)} ) to be added M ₄ a _(n) obtains the total amount of wear M ₄ (step S7), and displays it (Step S8), the pad wear amount can be read in real time. In this embodiment, since the display as input to the multi-display controller (not shown) the total amount of wear M ₄ pad wear amount (step S8), and it is possible that the driver accurately grasp the pad remaining amount, thereby braking The pads can be exchanged at good timing.

[0033] In the above embodiment, although an example case of displaying the total amount of wear M ₄ at step S8, leave set the thickness of the advance brake pads in the storage means, the pad for each wear detection due to braking The remaining amount may be obtained by calculation, and the remaining amount of the pad may be displayed on a display. Further, when the remaining amount of the pad reaches a predetermined pad thickness reference value, the driver may be quickly notified of the fact by a notification means such as an alarm device.

[0034]

According to the first aspect of the present invention, since the amount of wear of the pad can be quantitatively determined, the driver can accurately grasp the remaining amount of the pad, so that the brake pad can be replaced at a good timing. It can be carried out. Also,
Since the abrasion amount of the pad can be detected without generating the contact sound performed in the related art, the occupant such as the driver is not discomforted.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an electric disc brake according to one embodiment of the present invention.

FIG. 2 is a side view showing the device of FIG. 1 with a part cut away.

FIG. 3 is a plan view showing the device of FIG. 1 with a part cut away.

FIG. 4 is a front view showing the device of FIG. 1 with a part cut away.

FIG. 5 is an explanatory view showing an operation of the pad wear compensating mechanism of FIG. 1 when a pad has no wear.

FIG. 6 is an explanatory diagram showing an operation when the pad of the pad wear compensation mechanism of FIG. 1 is worn.

FIG. 7 is a front view showing an arrangement of ball grooves of a ball ramp mechanism of the apparatus of FIG. 1;

8 is a cross-sectional view of the ball groove of FIG. 7 taken along line CC.

FIG. 9 is a diagram schematically showing a state in which the ball of FIG. 1 is at a return position.

10 is a diagram showing a relationship between a motor position (motor rotation angle) of the electric motor of FIG. 1 and a current.

FIG. 11 is a flowchart illustrating a pad wear detection method according to an embodiment of the present invention.

[Explanation of symbols]

 50 Electric disc brake 51 Disc rotor 52 Caliper body 53 Claw 54,55 Brake pad 59 Electric motor 62 Rotor 72 Ball ramp mechanism 73 Piston 77 Fixed disc 78 Movable disc 79 Ball

Claims (1)

[Claims] 1. A pair of brake pads disposed on both sides of a disk rotor, a piston pressing the brake pad, an electric motor, and a rotary motion of the electric motor converted into a linear motion to move the piston forward and backward. A ball ramp mechanism; and a pad wear compensation mechanism for advancing the piston in accordance with wear of the brake pad. After the brake is released when the brake pad is worn, the pad wear compensation mechanism activates the space between the brake pad and the piston. In a method of detecting pad wear of an electric disc brake which positions a piston so that a predetermined pad clearance is secured and waits for a next braking operation, when a braking force is applied to a ball return position of the ball ramp mechanism Is obtained as piston braking position data. A pad wear amount is obtained by subtracting a predetermined pad clearance value from the position data, and adding a pad wear amount every time the pad wear amount is obtained with a braking operation. Detection method.