JP4061584B2 - Electric disc brake - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To cancel the braking operation of an electric disc brake when failing. <P>SOLUTION: The electric disc brake reduces the speed of the rotation of a rotor 17 of an electric motor 9 using a differential reducing mechanism 10 and drives a rotary disc 27 of a ball ramp mechanism 12 to move a direct acting disc 30 forward against the spring force of a disc spring 38, thrust brake pads 5, 6 against a disc rotor 2 and generate braking force. When the driving force of the electric motor 9 is lost by failure such as breakage during braking operation, the spring force of the disc spring 38 moves the direct acting disc 30 backward against resistance force on the direct action of the direct acting disc 30, generated by the rotating resistance force relative to the rotary disc 27 of the ball ramp mechanism 12, the differential reducing mechanism 10 and the electric motor 9, thus accurately canceling the braking operation. <P>COPYRIGHT: (C)2004,JPO&amp;NCIPI

Description

[0001]
[Industrial application fields]
The present invention relates to an electric disc brake that generates a braking force by converting a rotary motion of a rotary actuator such as an electric motor into a linear motion and pressing a brake pad against a disc rotor.
[0002]
[Prior art]
The rotational motion of the rotor of the electric motor is converted into the linear motion of the piston using a rotation-linear motion conversion mechanism such as a ball screw mechanism or a ball ramp mechanism, and the braking force is increased by pressing the brake pad against the disc rotor by the piston. An electric disc brake adapted to be generated is known. The electric disc brake can detect a driver's brake pedal depression force (or displacement amount) with a sensor and a controller can control the rotation of the electric motor based on the detected value to obtain a desired braking force. .
[0003]
[Problems to be solved by the invention]
By the way, in such an electric disc brake, when the electric motor stops due to the occurrence of a failure such as disconnection during braking, the brake pad remains pressed against the disc rotor by an internal resistance or the like of the rotation-linear motion conversion mechanism, etc. The braking may be locked and cannot be released. In this case, problems such as difficulty in moving the vehicle occur.
[0004]
For this reason, in order to release the braking lock at the time of failure, for example, Patent Document 1 is provided with spring means for applying a return force (rotational force) to the rotor of the electric motor, and Patent Document 2 is a deceleration of the electric motor. The mechanism is provided with an auxiliary motor for returning the brake pad at the time of failure, and Patent Document 3 discloses that at the time of failure, the lock mechanism is released and the entire rotation-linear motion conversion mechanism is retracted to return the brake pad. What is made is described.
[0005]
[Patent Document 1]
International Publication No. 00-60255 Pamphlet [Patent Document 2]
JP 2000-507333 A [Patent Document 3]
JP 2000-506348 A [0006]
However, all of those described in Patent Documents 1 to 3 have a complicated structure and have problems in terms of space constraints and manufacturing costs.
[0007]
The present invention has been made in view of the above points, and an object of the present invention is to provide an electric disc brake that can release a braking lock with reliability with a simple structure.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the invention according to claim 1 includes a conversion mechanism capable of mutually converting the rotational motion of the rotating member and the linear motion of the linear motion member, and a rotary actuator that drives the rotating member. An electric disc brake that generates a braking force by pressing a brake pad against the disc rotor by the linear motion member,
An urging means for urging the linear motion member in a direction away from the disk rotor is provided, and the urging force of the urging means is the linear motion member of the conversion mechanism when the rotary actuator is not driven. larger than the rotation resistance force for the rotating member acting against the movement of the rather,
The conversion mechanism is a ball ramp mechanism, and the inclined groove of the ball ramp mechanism is pressed against the vertical plane in the moving direction of the linear motion member rather than the tilt in a range where the pressing force to the brake pad is large. It is characterized in that the inclination in a small pressure range is large .
With this configuration, when the driving force of the rotary actuator disappears in the braking state, the direct acting member moves against the rotational resistance force of the rotating member by the urging force of the urging means, The braking is released. In addition, since the inclination of the inclined groove is small in the range where the pressing force to the brake pad is large, the boost ratio by the ball ramp mechanism is large, and in the range where the pressing force is small, the inclination of the inclined groove is large. The return torque of the rotating member due to the reaction force acting on the linear motion member increases.
The electric disk brake according to the invention of claim 2 is provided with a pad wear compensation mechanism capable of adjusting a position of the brake pad and the linear motion member in accordance with wear of the brake pad in the configuration of claim 1. The urging means urges the linear motion member directly.
With this configuration, the position of the brake pad and the linear motion member is adjusted by the pad wear compensation mechanism in accordance with the wear of the brake pad, and the relative position between the linear motion member and the rotating member does not change. The urging force of the urging means on the moving member is kept constant .
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1, the electric disc brake 1 according to the present embodiment has a caliper body 3 disposed on one side (usually inside the vehicle body) of a disc rotor 2 that rotates with wheels (not shown). The caliper body 3 is integrally coupled with a claw portion 4 formed in a substantially C shape and extending to the opposite side across the disk rotor 2 by bolts (not shown). Brake pads 5 and 6 are provided on both sides of the disc rotor 2, that is, between the disc rotor 2 and the caliper body 3, and between the disc rotor 2 and the tip of the claw portion 4, respectively. The brake pads 5 and 6 are supported by a carrier 7 fixed to the vehicle body so as to be movable along the axial direction of the disc rotor 2, and receive the braking torque by the carrier 7. Further, a slide pin (not shown) is attached to the caliper body 3, and the slide pin is slidably inserted into the carrier 2 so that the caliper body 3 moves along the axial direction of the disc rotor 2. Guided as possible.
[0010]
The caliper body 3 includes an electric motor 9 (rotation actuator), a differential reduction mechanism 10 that reduces the rotation of the electric motor 9, and a rotary movement of the electric motor 9 that is decelerated by the differential reduction mechanism 10 is converted into a linear movement. A ball ramp mechanism 12 (conversion mechanism) that moves the piston 11 that contacts the brake pad 5 forward and backward, and a pad wear compensation mechanism 13 that adjusts the position of the piston 11 according to the wear of the brake pads 5 and 6. It has been.
[0011]
The electric motor 9 includes a stator 14 fixed to the caliper body 3, and a hollow rotor 17 rotatably supported by the caliper body 3 by bearings 15 and 16, and is connected to a controller (see FIG. The rotating position is detected by a resolver 19 mounted on the rotor 17 and rotated by a desired angle.
[0012]
In the differential reduction mechanism 10, a hollow eccentric shaft 20 is formed integrally with the rotor 17 of the electric motor 9, and a cylindrical external gear member 21 is rotatably attached to the outer periphery of the eccentric shaft 20 via a bearing 22. It has been. The external gear member 21 is formed with input side external teeth 23 and output side external teeth 24 on both sides in the axial direction. A fixed ring gear 25 having internal teeth that mesh with the input side external teeth 23 of the external gear member 21 is fixed to the caliper body 3 by bolts 26. The output side external teeth 24 are meshed with internal teeth of a ring gear 28 formed integrally with a rotary disk 27 (described later) of the ball ramp mechanism 12.
[0013]
Thereby, the rotation of the rotor 17 is transmitted as an eccentric rotation to the external gear member 21 by the eccentric shaft 20 and the bearing 22, and the external tooth member 21 in which the input side external teeth 23 are engaged with the fixed ring gear 25 rotates while rotating. The rotating disk 27 in which the ring gear 28 is engaged with the output side external teeth 24 of the external tooth member 21 rotates with a predetermined reduction ratio.
[0014]
The reduction ratio N of the differential reduction mechanism 10 is the number of teeth Z1 of the input side external teeth 23 of the external gear member 21, the number of teeth Z2 of the internal teeth of the fixed ring gear 25, the number of teeth Z3 of the output side external teeth 24, the ring gear 28 If the number of inner teeth is Z4, N = 1− (Z2 × Z3) / (Z1 × Z4).
[0015]
The ball ramp mechanism 12 is supported by a caliper body 3 rotatably supported by a bearing 29 (axial bearing) and fixed in the axial direction, and a rotating disk 27 (rotating member) supported in an axially movable and rotatable manner. Between the circumferential ball grooves 31 and 32 (inclined grooves) formed on the mutually facing surfaces of the rotating disk 27 and the linearly moving disk 30, the linearly moving disk 30 (linearly moving member) is disposed opposite to each other. A ball 33 (steel ball) which is a rolling element is inserted. When the rotating disk 27 rotates, the ball 33 rolls in the inclined ball grooves 31 and 32, so that the linearly moving disk 30 moves in the axial direction according to the rotation angle of the rotating disk 27. An adjustment screw member 34 fixed to the piston 11 is screwed to the linear motion disk 30. By rotating the linear motion disk 30 and the adjustment screw member 34 relative to each other, the piston 11 is moved relative to the brake pad 5. The pad clearance can be adjusted by moving forward and backward.
[0016]
The rotating disk 27 is integrally formed with a cylindrical portion 35 that is inserted into the eccentric shaft 20 of the electric motor 9, and the linear motion disk 30 passes through the cylindrical portion 35 of the rotating disk 27 and is electrically driven. A cylindrical portion 36 inserted into the nine rotors 17 is integrally formed. A support rod 37 that extends along the axis of the rotor 17, the rotary disk 27, and the linear motion disk 30 is attached to the caliper body 3 by nuts 37A. A plurality of stacked disc springs 38 (biasing means) are interposed between the flange portion formed on the support rod 37 and the tip portion of the cylindrical portion 36 of the linear motion disk 30. Due to this spring force (biasing force), the linearly moving disk 30 is constantly urged in the direction away from the rotating disk 27, that is, in the direction away from the disk rotor 2.
[0017]
The ball ramp mechanism 12 is capable of mutually converting the rotation of the rotating disk 27 and the linear motion of the linearly moving disk 30, and by rotating the rotating disk 27, the linearly moving disk 30 can be directly moved. On the other hand, the inclination angles of the ball grooves 31 and 32 are set so that the rotary disk 27 can be rotated by linearly moving the linear disk 30. The spring force of the disc spring 38 is the rotational resistance of the rotating disk 27 in the state where the driving force of the electric motor 9 is lost, that is, the rotation of the ball ramp mechanism 12, the differential reduction mechanism 10 and the electric motor 9. It is larger than the resistance force against the movement (linear motion) of the linear motion disk 30 caused by the resistance force, and the electric motor 9 rotates the rotary disk 27 to move the linear motion disk 30 against the spring force of the disc spring 38. After that, when the driving force of the electric motor 9 is lost, the rotating disk 27 is rotated in the reverse direction against the rotational resistance force of the ball ramp mechanism 12, the differential reduction mechanism 10 and the electric motor 9, thereby moving the linearly moving disk 30. Is set to a size that can return to the original position.
[0018]
The pad wear compensation mechanism 13 includes a spring holder 39 and a limiter 40 that are fitted to the outer periphery of the cylindrical portion 36 of the linear motion disk 30, and a coil spring 41 that elastically couples them with a predetermined set load in the rotational direction. (Torsion spring). The spring holder 39 is fixed to the cylindrical portion 36 by a pin 42, and the limiter 40 has a predetermined range so that relative rotation within a certain range corresponding to the pad clearance is possible between the limiter 40 and the cylindrical portion 35 of the rotating disk 27. The end portion of the cylindrical portion 35 is engaged with play. Then, the rotation of the rotating disk 27 is transmitted to the linear motion disk 30 via the coil spring 41, so that when the brake pads 5 and 6 are worn, the linear motion disk 30 rotates together with the rotational disk 27, The adjustment screw member 34 is advanced, and the pad clearance is adjusted to be constant.
[0019]
The operation of the present embodiment configured as described above will be described next.
During braking, the controller detects the driver's brake pedal depression force (or displacement) with the brake pedal sensor, and based on this detection value, the driver circuit supplies a drive current to the electric motor 9 of the electric disc brake 1 of each wheel. The rotor 17 is rotated by a predetermined rotation angle with a predetermined torque. The rotation of the rotor 17 is decelerated at a predetermined reduction ratio by the differential reduction mechanism 10 and converted into a linear motion by the ball ramp mechanism 12 to advance the piston 11. One brake pad 5 is pressed against the disk rotor 2 by the piston 11, and the reaction force causes the caliper body 3 to move along the slide pin of the carrier 7, so that the claw portion 4 moves the other brake pad 6 to the disk rotor 2. Press on. Thereby, a braking force is generated. Further, at the time of releasing the brake, the electric motor 9 is reversely rotated to retract the piston 11, and the brake pads 5, 6 are separated from the disc rotor 2 to release the brake.
[0020]
Next, the operation of the pad wear compensation mechanism 13 will be described.
If the brake pads 5 and 6 are not worn, the rotating disk 27 rotates with respect to the linearly moving disk 30 by the amount of play with the limiter 40 corresponding to the pad clearance by the rotation of the rotor 17 of the electric motor 9 in the initial stage of braking. As a result, the linear motion disk 30 moves forward by the pad clearance, and the brake pads 5 and 6 come into contact with the disk rotor 2. When the rotating disk 27 further rotates, the frictional resistance of the threaded portion between the adjusting screw member 34 and the linearly moving disk 30 increases due to the reaction force when the brake pads 5 and 6 are pressed against the disk rotor 2, and the spring increases. The set load of the coil spring 41 between the holder 39 and the limiter 40 becomes larger, and the rotation of the linear motion disk 30 is prevented. As a result, the coil spring 41 is bent and the rotating disk 27 and the linearly moving disk 30 rotate relative to each other, whereby the linearly moving disk 30 moves forward and presses the brake pads 5 and 6 against the disk rotor 2.
[0021]
If the brake pads are worn, in the initial stage of braking, the rotation of the rotor 17 of the electric motor 9 causes the rotating disk 27 to rotate relative to the linearly moving disk 30 by the amount of play with the limiter 40 corresponding to the pad clearance. Even so, the brake pads 5 and 6 do not contact the disk rotor 2 due to wear. In this state, the frictional resistance of the thread portion between the adjustment screw member 34 and the linear motion disk 30 is smaller than the set load of the coil spring 41 between the spring holder 39 and the limiter 40, so the rotating disk 27 further rotates. Then, the rotational force rotates the linearly moving disk 30 via the coil spring 41, and the adjustment screw member 34 is advanced to fill the gap for pad wear until the brake pads 5, 6 contact the disk rotor 2. After the brake pads 5 and 6 come into contact with the disk rotor 2, as described above, the frictional resistance of the screw portion between the adjusting screw member 34 and the linear motion disk 30 increases, and the rotation of the linear motion disk 30 is prevented. As a result, relative rotation occurs between the rotating disk 27 and the linearly moving disk 30, and the linearly moving disk 30 moves forward and presses the brake pads 5 and 6 against the disk rotor 2.
[0022]
In this way, the adjusting screw member 34 can be advanced in accordance with the wear of the brake pads 5 and 6, and the pad clearance can be always adjusted to be constant.
[0023]
Next, a case where the driving force of the electric motor 9 is lost due to the occurrence of a failure such as disconnection during braking will be described.
When the driving force of the electric motor 9 disappears due to the occurrence of a failure such as disconnection during braking, the spring force of the disc spring 38 compressed by the movement of the linear motion disk 30 during braking causes the rotating disk 27 to move to the ball ramp mechanism 12, While rotating against the rotational resistance force of the differential reduction mechanism 10 and the electric motor 9, the linear motion disk 30 is retracted to the original position. As a result, the brake pads 5 and 6 can be separated from the disc rotor 2, and braking can be released.
[0024]
Thus, when a failure such as a disconnection occurs during braking, the braking can be reliably released, so that the vehicle can be easily moved and retracted. By using the spring force of the disc spring 38, braking can be reliably released with a simple mechanical structure, so there is no need for a separate power source, high reliability, low cost, and small size. Is possible. Further, by adjusting the positions of the brake pad 5 and the linear motion disk 30 according to the wear of the brake pads 5 and 6 by the pad wear compensation mechanism 13, the ball ramp mechanism 12 can be adjusted regardless of the wear of the brake pads 5 and 6. Since the stroke can be kept constant, the spring force of the disc spring 38 does not increase excessively due to wear of the brake pads 5 and 6, and stable operation can be obtained. As a result, even when the resistance at the time of brake release is increased by the differential reduction mechanism 10 provided to increase the boost ratio, the brake can be reliably released at the time of failure, and the differential reduction mechanism The problem of braking lock by 10 can be solved.
[0025]
Next, the inclination of the ball grooves 31 and 32 of the ball ramp mechanism 12 will be described with reference to FIGS.
In the ball ramp mechanism 12, when the driving force of the electric motor 9 acting on the rotating disk 27 in the braking state is released, the rotating disk 27 is moved to the original position by the reaction force acting on the linearly acting disk 30 from the brake pads 5 and 6. A return torque is generated to return to the side. On the other hand, the rotational resistance force of the rotating disk 27 itself, the differential speed reduction mechanism 10, the electric motor 9, etc. acts on the rotating disk 27. Then, when the return torque is greater than the rotational resistance force, the rotating disk 27 rotates to the original position side and stops when it balances the rotational resistance force.
[0026]
Here, the return torque T0 of the rotating disk 27 includes the pressing force F (reaction force from the disk rotor 2) of the brake pads 5 and 6 to the disk rotor 2, the lead L of the ball grooves 31 and 32 (one of the rotating disks 27). (The linear motion distance of the linear motion disk 30 per rotation), the ball ramp mechanism 12, the differential reduction mechanism 10 and the reverse efficiency η ′ of the electric motor 9 (mechanical efficiency at the time of conversion from linear motion to rotational motion)
T0 ＝ F × L / 2π ・ η´
The rotation resistance torque T1 for the rotating disk 27 is a function K (F) with the pressing force F as a variable, the rotation of the ball ramp mechanism 12, the differential reduction mechanism 10 and the electric motor 9 at no load. If the resistance torque is K0,
T1 = K (F) + K0
Can be expressed as
[0027]
As shown in FIG. 2, the relationship between the return torque T0 and the pressing force F when the lead L of the ball grooves 31, 32 is reduced (L = L1) and increased (L = L2), and the rotational resistance torque T1 FIG. 4 shows the relationship between the pressure and the pressing force F. In FIG. 4, the line segment (1) is the return torque T0 of the ball ramp mechanism 12 when the lead L = L1 (constant), and the line segment (2) is the ball ramp mechanism 12 when the lead L = L2 (constant). The return torque T0, curve (3) is the rotational resistance torque T1 for the rotary disk 27, and curve (4) is the return torque T0 of the ball ramp mechanism 12 when L1 and L2 are combined as the lead L as will be described later. Show.
[0028]
As can be seen from FIG. 4, when the driving force of the electric motor 9 disappears when the pressing force F = F1, when the lead L is small (L = L1), the return torque T0 is greater than the rotational resistance torque T1. In the large region, when the rotary disk 27 is returned to the original position side and the pressing force F becomes F = F2, the return torque T0 and the rotational resistance torque T1 balance and the rotary disk 27 stops. Further, when the lead L is large (L = l2), in the region where the return torque T0 is larger than the rotational resistance torque T1, the rotary disk 27 is returned to the original position side, and the pressing force F becomes F = F3. At this time, the return torque T0 and the rotation resistance torque T1 are balanced, and the rotating disk 27 stops. Thus, by increasing the lead L, the ratio of the return torque T0 to the pressing force F increases, and the region where the return torque T0 is larger than the rotational resistance torque T1 can be widened. The return amount of the disk 27 can be increased.
[0029]
On the other hand, the pressing force F of the brake pads 5 and 6 to the disc rotor 2 is determined by the driving torque T of the electric motor 9, the positive efficiency η of the differential reduction mechanism 10 and the ball ramp mechanism 12 (during conversion from rotational motion to linear motion Mechanical efficiency), and the reduction ratio n of the differential reduction mechanism,
F = T × 2πηn / L
Can be expressed as When the lead L is increased, the boost ratio is decreased, and the drive torque T necessary for the electric motor 9 is increased.
[0030]
Therefore, as shown in FIG. 3, the lead L of the ball grooves 31 and 32 has two stages, and in the non-braking side region that does not require a large pressing force F, that is, in the range where the pressing force to the brake pad 5 is small, By increasing the inclination of the ball grooves 31 and 32 and increasing the lead L (L = L2), in the braking side area that requires a large pressing force F, that is, in the range where the pressing force to the brake pad 5 is large, the ball By reducing the inclination of the grooves 31 and 32 and reducing the lead L (L = L1), at the time of braking, it is possible to obtain a sufficient braking force by increasing the boost ratio with the small lead L1. When the driving force of the motor 9 is lost, the return torque T0 can be increased to increase the return amount. In this case, as indicated by curve (4) in FIG. 4, in the region where the pressing force F is large, the return torque T0 is generated by the lead L1, and in the region where the pressing force F is small, the return torque T0 is generated by the lead L2. Thus, the rotating disk 27 can be returned until the pressing force F becomes F = F3.
[0031]
Thereby, since the load of the disc spring 38 can be reduced and the spring force can be reduced, the driving torque of the electric motor 9 necessary for braking can be reduced, and power saving can be achieved.
[0032]
【The invention's effect】
As described above in detail, according to the electric disc brake of the invention of claim 1, when the driving force of the rotary actuator disappears in the braking state, the linearly acting member is rotated by the urging force of the urging means. It is possible to move against the rotational resistance force and to release the brake reliably. Furthermore, in the range where the pressing force to the brake pad is large, the inclination of the inclined groove is small, so the boost ratio by the ball ramp mechanism is large. In the range where the pressing force is small, the inclination of the inclined groove is large. The return torque of the rotating member due to the reaction force acting on the linear motion member increases. As a result, sufficient braking force can be obtained, and braking can be reliably released during a failure.
According to the electric disc brake of the invention of claim 2, the position of the brake pad and the linear motion member is further adjusted by the pad wear compensation mechanism according to the wear of the brake pad, and the linear motion member and the rotary member Since the relative position does not change, the urging force of the urging means with respect to the linear motion member is maintained constant, and a stable operation can be obtained .
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an electric disc brake according to an embodiment of the present invention.
2 is an enlarged view showing a ball groove of a ball ramp mechanism having a certain lead in the apparatus of FIG. 1;
FIG. 3 is an enlarged view showing a ball groove of a ball ramp mechanism having a two-stage lead in the apparatus of FIG. 1;
4 is a graph showing the relationship between the return torque and rotational resistance torque of the rotating disk and the pressing force of the brake pad in the apparatus of FIG. 1. FIG.
[Explanation of symbols]
1 Electric disc brake
2 Disc rotor
5,6 Brake pads
9 Electric motor (rotary actuator)
12 Ball ramp mechanism (conversion mechanism)
13 Pad wear compensation mechanism
27 Rotating disc (Rotating member)
30 Linear motion disk (linear motion member)
31,32 Ball groove (inclined groove)
38 Disc spring (biasing means)

Claims (2)

A conversion mechanism capable of mutually converting the rotational motion of the rotary member and the linear motion of the linear motion member; and a rotary actuator that drives the rotary member, and the brake pad is pressed against the disk rotor by the linear motion member to control the rotation. An electric disc brake for generating power,
An urging means for urging the linear motion member in a direction away from the disk rotor is provided, and the urging force of the urging means is the linear motion member of the conversion mechanism when the rotary actuator is not driven. larger than the rotation resistance force for the rotating member acting against the movement of the rather,
The conversion mechanism is a ball ramp mechanism, and the inclined groove of the ball ramp mechanism is pressed against the vertical plane in the moving direction of the linear motion member rather than the tilt in a range where the pressing force to the brake pad is large. An electric disc brake characterized by a large inclination in a small pressure range .   A pad wear compensation mechanism capable of adjusting the position of the brake pad and the linear motion member according to wear of the brake pad is provided, and the biasing means directly biases the linear motion member; The electric disc brake according to claim 1, wherein

Images