JP2021004646A - Disc brake - Google Patents

Abstract

To provide a disc brake improved in vehicle mountability by reducing a length dimension along an axial direction of a piston as a whole.SOLUTION: A disc brake 1 includes an electric motor 32, a piston 18 for pressing an inner brake pad 2 to a disc rotor D, a nut member 41 axially moved by a spindle 40 rotated by driving of the electric motor 32 to advance the piston 18, and a fail open mechanism 62 for moving the piston 18 in a direction to release braking force when rotary torque from the electric motor 32 is not generated. At least a part of the fail open mechanism 62 is disposed between the piston 18 and the nut member 41 in a radial direction. As a result, a length dimension along the axial direction of the piston 18 can be reduced as the whole disc brake 1, and vehicle mountability can be improved.SELECTED DRAWING: Figure 1

Description

The present invention relates to a disc brake used for braking a vehicle.

The conventional disc brake is provided with a fail-open mechanism in which the braking force is quickly released when the power source or the like is lost during braking. For example, in the electric disc brake described in Patent Document 1, when the motor is driven to generate a braking force as a fail-open mechanism, elastic energy is applied to the elastic member by the frictional force accompanying the action of the clamping force of the caliper housing. Is stored, and when the power source or the like is lost during braking, the braking force is released by the elastic energy stored in the elastic member.

Japanese Unexamined Patent Publication No. 2017-197164

In the fail-open mechanism adopted in the electric disc brake described in Patent Document 1 described above, since the elastic member and the friction member are arranged from the support portion of the spindle to the gear assembly side, the disc brake as a whole has a piston. The length dimension along the axial direction of the vehicle becomes large, which may deteriorate the vehicle mountability.

An object of the present invention is to provide a disc brake that improves vehicle mountability by reducing the length dimension along the axial direction of the piston in the entire disc brake.

As a means for solving the above problems, the disc brake according to the present invention is moved in the axial direction by an electric motor, a piston that presses the braking member against the braked member, and a screw member that is rotated by driving the electric motor. A disc brake including a nut member that advances the piston and a fail-open mechanism that moves the piston in a direction in which the braking force is released when the rotational torque from the electric motor is not generated. Therefore, at least a part of the fail-open mechanism is provided between the piston and the nut member in the radial direction.

According to the disc brake of the present invention, the length dimension of the disc brake as a whole along the axial direction of the piston can be reduced to improve the vehicle mountability.

Sectional drawing of the main part of the disc brake which concerns on this embodiment. An exploded perspective view of the fail-open mechanism adopted in the disc brake according to the present embodiment.

Hereinafter, the present embodiment will be described in detail with reference to FIGS. 1 and 2.
The disc brake 1 according to the present embodiment is an electric brake device that generates a braking force by driving an electric motor 32 during normal traveling. In the following description, the inside of the vehicle (inner side) will be referred to as one end side (cover member 30 side), and the outside of the vehicle (outer side) will be referred to as the other end side (disc rotor D side). That is, in FIG. 1, the right side is referred to as one end side and the left side is referred to as the other end side.

As shown in FIG. 1, the disc brake 1 according to the present embodiment is a pair of braking members arranged on both sides in the axial direction with the disc rotor D as a braking member attached to a rotating portion of the vehicle. The inner brake pad 2, the outer brake pad 3, and the caliper 4 are provided. The disc brake 1 is configured as a floating caliper type. The pair of inner brake pads 2, the outer brake pads 3, and the caliper 4 are supported by a bracket 5 fixed to a non-rotating portion such as a knuckle of a vehicle so as to be movable in the axial direction of the disc rotor D.

As shown in FIG. 1, the caliper 4 transmits the rotation from the caliper main body 8 which is the main body of the caliper 4 and the electric motor 32 to the piston 18 in the cylinder portion 13 of the caliper main body 8 and thrusts the piston 18. The transmission mechanism 9 and the like are provided. The caliper main body 8 is arranged on the base end side facing the inner brake pad 2, and has a cylindrical cylinder portion 13 that opens facing the inner brake pad 2 and an outer side straddling the disc rotor D from the cylinder portion 13. A pair of claws 14, 14 arranged on the tip side, which extend to the outer brake pad 3 and face the outer brake pad 3, are provided.

The piston 18 is housed in the cylinder portion 13 of the caliper main body 8, that is, in the cylinder bore 16 of the cylinder portion 13 so as to be non-rotatable relative to the cylinder portion 13 and movable in the axial direction. The piston 18 presses the inner brake pad 2 and is formed in a bottomed cup shape. The piston 18 is housed in the cylinder bore 16 of the cylinder portion 13 so that the bottom portion thereof faces the inner brake pad 2. The piston 18 is non-rotatably supported with respect to the cylinder bore 16 and the caliper body 8 by the detent engagement between its bottom and the inner brake pad 2.

A seal member 20 is arranged on the inner peripheral surface on the other end side of the cylinder bore 16 of the cylinder portion 13. Then, the piston 18 is housed in the cylinder bore 16 so as to be movable in the axial direction in a state of being in contact with the seal member 20. A dust boot 21 is interposed between the outer peripheral surface on the bottom side of the piston 18 and the inner peripheral surface on the other end side of the cylinder bore 16. The seal member 20 and the dust boot 21 prevent foreign matter from entering the cylinder bore 16 of the cylinder portion 13.

An insertion hole 25 through which the spindle 40 described later is inserted is formed in the bottom wall 23 of the cylinder portion 13. The gear housing 28 is integrally connected to the bottom wall 23 side (one end side) of the cylinder portion 13 of the caliper main body 8. The opening on one end side of the gear housing 28 is airtightly closed by the cover member 30. Inside the gear housing 28, an electric motor 32, which will be described later, which is a part of the configuration of the transmission mechanism 9, and a gear reduction mechanism 33 to which rotation from the electric motor 32 is transmitted are arranged. The rotation from the electric motor 32 is transmitted to the piston 18 via the transmission mechanism 9. The transmission mechanism 9 includes a gear reduction mechanism 33 that increases the rotational torque from the electric motor 32, and a rotation linear motion conversion mechanism 34 that converts the rotation from the gear reduction mechanism 33 into linear motion and applies thrust to the piston 18. And have.

With reference to FIG. 2, the rotation linear motion conversion mechanism 34 includes a spindle 40 which is a screw member to which rotation from the gear reduction mechanism 33 is transmitted, and a nut member 41 screwed with the spindle 40. ing. A polygonal shaft portion 43 is formed on one end of the spindle 40. A male screw portion 44 is formed on the other end side of the spindle 40. The spindle 40 is provided with an annular support portion 45 that protrudes radially from the male screw portion 44 to one end side. The polygonal shaft portion 43 of the spindle 40 is connected to one component of the gear reduction mechanism 33 so as not to rotate relative to each other. As a result, rotational torque can be transmitted to each other between the gear reduction mechanism 33 and the spindle 40. A thrust bearing 47 is arranged between the annular support portion 45 of the spindle 40 and the bottom wall 23 of the cylinder portion 13. The thrust bearing 47 rotatably supports the spindle 40 on the bottom wall 23 of the cylinder portion 13.

The thrust bearing 47 includes an annular first thrust plate 51 arranged on the bottom wall 23 side of the cylinder portion 13, an annular second thrust plate 52 arranged on the annular support portion 45 side of the spindle 40, and a first thrust. It is composed of a plurality of thrust balls 53 that are rotatably arranged between the plate 51 and the second thrust plate 52. A rolling groove 51A on which each thrust ball 53 rolls is formed on the other end surface of the first thrust plate 51. A rolling groove 52A on which each thrust ball 53 rolls is formed on one end surface of the second thrust plate 52. A plurality of thrust balls 53 are rotatably arranged between the rolling groove 51A provided on the other end surface of the first thrust plate 51 and the rolling groove 52A provided on one end surface of the second thrust plate 52. Will be done. These plurality of thrust balls 53 are held by the retainer 55 at regular intervals in the circumferential direction.

The nut member 41 is arranged on the radial outer side of the male threaded portion 44 of the spindle 40. A female threaded portion 57 is formed on the inner peripheral surface of the nut member 41 on one end side. Then, the male threaded portion 44 of the spindle 40 and the female threaded portion 57 of the nut member 41 are screwed together. The nut member 41 is supported so as not to rotate relative to the piston 18. A plurality of engaging groove portions 59 are formed on the outer peripheral surface of the nut member 41 near the other end at intervals in the circumferential direction. With reference to FIG. 2, a fail-open mechanism 62 capable of quickly releasing the braking force in the event of a failure of the power source or the like is provided on the outer side in the radial direction of the nut member 41. The fail-open mechanism 62 includes a guide member 64, a coil spring 65 which is an elastic member, and a friction member 66. The guide member 64 is formed in a cylindrical shape as a whole. The guide member 64 is configured by integrally connecting a large-diameter guide portion 69 arranged on one end side and a small-diameter guide portion 70 arranged on the other end side.

A slit 71 extending in the axial direction is formed in the peripheral wall portion of the large diameter guide portion 69. An annular groove 74 is formed on the outer peripheral surface of the large-diameter guide portion 69 on one end side. A plurality of engaging protrusions 76 projecting inward are provided on the inner peripheral surface of the small diameter guide portion 70 at intervals in the circumferential direction. Then, each engaging protrusion 76 provided on the small diameter guide portion 70 of the guide member 64 engages with each engaging groove portion 59 provided on the outer peripheral surface of the nut member 41, so that the guide member 64 becomes the nut member 41. It is connected so that it cannot rotate relative to the relative direction and cannot move relative to the axial direction. An annular gap 77 is provided between the inner peripheral surface of the large-diameter guide portion 69 and the outer peripheral surface of the nut member 41.

The coil spring 65 is arranged in the annular gap 77 between the inner peripheral surface of the large diameter guide portion 69 and the outer peripheral surface of the nut member 41. One end of the coil spring 65 protrudes outward in the radial direction, and the one end is inserted into a slit 81 provided in the friction member 66. The other end of the coil spring 65 also protrudes outward in the radial direction, and the other end is inserted into the slit 71 provided in the guide member 64. The friction member 66 includes a cylindrical portion 78 and an annular flange portion 79 extending inward in the radial direction from one end of the cylindrical portion 78. A plurality of protrusions 80 projecting inward are formed on the peripheral wall portion on the other end side of the cylindrical portion 78 at intervals in the circumferential direction. A slit 81 extending from the other end is formed in the peripheral wall portion of the cylindrical portion 78. One end of the coil spring 65 is inserted through the slit 81. Each protrusion 80 is engaged with an annular groove 74 provided in the large diameter guide portion 69 of the guide member 64. The spindle 40 is inserted inside the annular flange portion 79 of the friction member 66.

The annular flange portion 79 of the friction member 66 is arranged between the annular support portion 45 of the spindle 40 and the second thrust plate 52 of the thrust bearing 47. The friction member 66 is supported so as to be rotatable relative to the guide member 64. The guide member 64 and the friction member 66 can move relative to each other along the axial direction by the difference between the width length (length in the axial direction) of the annular groove portion 74 of the guide member 64 and the thickness of the protrusion 80. As described above, the fail-open mechanism 62 has a part thereof, that is, the other end of the cylindrical portion 78 of the guide member 64, the coil spring 65 and the friction member 66, and the annular gap 77 between the piston 18 and the nut member 41. Placed in.

The drive of the electric motor 32 is controlled by a command from a control device (not shown). During braking in normal driving, the control device is used to detect signals from detection sensors that meet the driver's demands, various detection sensors that detect various situations that require braking, and rotation angle detection means (not shown). The drive of the electric motor 32 is controlled based on the detection signal of the above and the detection signal from the thrust sensor (not shown).

Next, in the disc brake 1 according to the present embodiment, the actions of braking and releasing braking in normal driving will be described.
At the time of braking in normal traveling, the electric motor 32 is driven by a command from the control device, and the rotation in the positive direction, that is, the braking direction is transmitted to the spindle 40 via the gear reduction mechanism 33. Subsequently, when the spindle 40 rotates with the rotation of the gear reduction mechanism 33, the nut member 41 screwed with the spindle 40 advances to advance the piston 18. As the piston 18 moves forward, the inner brake pad 2 is pressed against the disc rotor D. Then, the caliper body 8 moves toward the inner side with respect to the bracket 5 due to the reaction force against the pressing force on the inner brake pad 2 by the piston 18, and the outer brake pads 3 are moved to the disc rotor D by the claws 14 and 14, respectively. Press. As a result, the disc rotor D is sandwiched between the pair of inners and the outer brake pads 2 and 3, and a frictional force is generated, which in turn generates a braking force of the vehicle.

During this braking, the disc rotor D is sandwiched between the pair of inner and outer brake pads 2 and 3, and when the disc rotor D begins to be pressed, the reaction force is applied to the piston 18, the nut member 41, the spindle 40, and the friction member 66. The friction force of a certain level or more is generated between the annular support portion 45 of the spindle 40 and the annular flange portion 79 of the friction member 66. From this point, the friction member 66 rotates in the same direction as the spindle 40 rotates in the braking direction. Then, due to the rotation of the friction member 66 in the braking direction, the coil spring 65 arranged between the friction member 66 and the guide member 64 is elastically deformed in the torsional direction, and elastic energy is stored.

On the other hand, at the time of braking release, the electric motor 32 rotates in the opposite direction, that is, in the braking release direction, and the rotation in the opposite direction is transmitted to the spindle 40 via the gear reduction mechanism 33 by a command from the control device. As a result, as the spindle 40 rotates in the opposite direction, the nut member 41 screwed with the spindle 40 retracts and returns to the initial state, and the pair of inners to the disc rotor D and the outer brake pads 2, 3 Braking force is released.

At the initial stage when the spindle 40 rotates in the braking release direction at the time of this braking release, the frictional force is maintained between the annular support portion 45 of the spindle 40 and the annular flange portion 79 of the friction member 66, and the spindle The friction member 66 also rotates in the same direction as the 40 rotates in the braking release direction. As a result, the coil spring 65 elastically deformed at the time of braking is restored, and the restoring force is supplied to the spindle 40 as a rotational torque in the braking release direction, and the braking force is quickly released.

Further, even when the power supply or the like is lost during braking and the rotational torque from the electric motor 2 is not generated, the frictional force is still generated between the annular support portion 45 of the spindle 40 and the annular flange portion 79 of the friction member 66. The coil spring 65, which is in a maintained state and elastically deformed during braking, is restored, that is, the elastic energy stored during braking is released, so that the spindle 40 rotates together with the friction member 66 in the braking release direction, and the spindle 40 is rotated. As a result, the nut member 41 retracts, and the braking force of the pair of inners and outer brake pads 2 and 3 on the disc rotor D is released.

As described above, in the disc brake 1 according to the present embodiment, particularly in the fail-open mechanism 62, a part thereof, that is, the other end of the cylindrical portion 78 of the guide member 64, the coil spring 65 and the friction member 66 is , Is provided in the annular gap 77 between the piston 18 and the nut member 41. As a result, the length of the disc brake 1 as a whole along the axial direction of the piston 18 can be reduced, and as a result, the vehicle mountability can be improved.

1 Disc brake, 2 Inner brake pad (braking member), 3 Outer brake pad (braking member), 18 Piston, 32 Electric motor, 40 Spindle (Screw member), 41 Nut member, 44 Male thread part, 57 Female thread part, 62 Fail Open mechanism, 77 annular gap, D disc rotor (braked member)

Claims (1)

With an electric motor
A piston that presses the braking member against the braking member,
A nut member that moves in the axial direction and advances the piston by a screw member that is rotated by the drive of the electric motor.
A fail-open mechanism that moves the piston in the direction in which the braking force is released when the rotational torque from the electric motor is not generated.
It is a disc brake equipped with
A disc brake characterized in that at least a part of the fail-open mechanism is provided between the piston and the nut member in the radial direction.

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