JP2007120728A - Disk brake - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To release a parking brake without using a large-sized electric motor nor performing any extra hydraulic operation in a disk brake with a parking brake mechanism. <P>SOLUTION: The parking brake mechanism 20 operated by an electric motor serving as a drive source fitted to the outside of a housing 18 integral with the cylinder 13 is added to a caliper 4 with a piston 15 disposed in the cylinder 13. The parking brake mechanism 20 has a nonreversible gear mechanism 26 comprising a worm gear 41 fixed to a rotating shaft 40 of the electric motor, and a worm wheel 43 meshed with the worm 41; and a screw mechanism which converts the rotation of the gear mechanism 26 into linear motion to press the piston 15 in a driving direction. The screw mechanism is formed into a reversible structure of engaging a square screw 22 of a shaft 23 rotated by the gear mechanism 26 with a square screw 24 of a nut 25 locked to the piston 15, and a thread part can be easily loosened by the electric motor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

  A disc brake generally propels a pair of pads arranged on both sides of a disc and a piston slidably arranged in a bottomed cylinder by introducing hydraulic pressure into the cylinder, and The caliper that generates a braking force by pressing the pad against the disc has recently been put into practical use with a parking brake function added thereto.

  Conventionally, as a disc brake to which a parking brake function is added, for example, there is one described in Patent Document 1. This is an electric motor provided outside the cylinder of the caliper, a worm gear mechanism (deceleration mechanism) that increases the rotational torque of the electric motor, and the rotation increased by the worm gear mechanism is converted into a linear motion. A screw mechanism (rotation-linear motion conversion mechanism) that presses the piston in the propulsion direction, and the worm gear after releasing the hydraulic pressure in the cylinder of the piston propelled by supplying the hydraulic pressure into the cylinder It functions to mechanically hold the piston in the braking position (parking brake position) by the irreversible action (automatic sticking action) between the mechanism and the screw mechanism.

JP-A-8-244596 ([0024], [0025], [0028], [0029])

  However, according to the disc brake having the parking brake function described in Patent Document 1, since a large axial force is applied from the piston to the irreversible screw mechanism, in order to release the parking brake by reverse rotation of the electric motor, A large motor torque is required to overcome the rotational torque generated by the axial force, and a large electric motor is required, so that the caliper cannot be enlarged.

  In order to cope with the above problem, it is only necessary to apply hydraulic pressure to the cylinder once and remove the axial force transmitted from the piston to the screw mechanism, and then reversely rotate the electric motor. Since an operation to apply hydraulic pressure is required, a new problem arises that the parking brake cannot be released quickly.

  The present invention has been made in view of the above-described conventional problems, and the problem is that the parking brake can be released without using a large electric motor and without performing an extra hydraulic operation. Thus, an object of the present invention is to provide a disc brake that greatly contributes to downsizing the caliper and improving the operability of the parking brake.

  In order to solve the above problem, the invention according to claim 1 is characterized in that a pair of pads disposed on both sides of a disk and a piston slidably disposed in a bottomed cylinder are provided in the cylinder. It is driven by a caliper that generates a braking force by pressing the pair of pads against the disc and an electric motor provided outside the cylinder, and the hydraulic pressure into the cylinder In the disc brake having a parking brake mechanism that mechanically holds the piston driven by the supply in the braking position even after the hydraulic pressure in the cylinder is released, the parking brake mechanism increases the rotational torque of the electric motor. A speed reduction mechanism, and a rotation-linear motion conversion mechanism that converts the rotation increased by the speed reduction mechanism into a linear motion and presses the piston in the propulsion direction. Consisting of the gear mechanism, the rotary - linear motion converting mechanism is characterized by comprising a reversible screw mechanism.

  In the disc brake configured as described above, the rotation-linear motion conversion mechanism is composed of a reversible screw mechanism that hardly generates a rotational torque even when receiving an axial force from the piston. Does not require motor torque and does not require extra hydraulic operation. In addition, since the irreversible gear mechanism is interposed between the screw mechanism and the electric motor, the piston is mechanically held at the parking brake position, so that the parking brake function is not impaired.

  According to a second aspect of the present invention, in the first aspect of the present invention, the gear mechanism includes a worm fixed to the rotating shaft of the electric motor and a worm wheel meshed with the worm, and the screw The mechanism includes a shaft having one end connected to the worm wheel and a square screw formed on the other end, and a nut that has a square screw that meshes with the square screw of the shaft on the inner surface and is prevented from rotating around the piston. It is characterized by that.

  Further, the invention described in claim 3 is characterized in that, in the invention described in claim 2, the tip end portion of the rotating shaft of the electric motor extends through the caliper.

  According to the first aspect of the present invention, since a small electric motor can be used, the caliper can be reduced in size, and an extra hydraulic operation is not required. Improvement can be achieved.

  Further, according to the invention described in claim 2, in addition to the effect of the invention described in claim 1, since a gear mechanism and a screw mechanism that are simple in structure and low in cost are used, it is possible to ensure good assemblability, An increase in manufacturing cost can be suppressed.

  Furthermore, according to the invention of claim 3, in addition to the effect of the invention of claim 2, even if the electric motor breaks down, the tip of the motor rotating shaft extending outside the housing is manually Since the parking brake can be released by rotating the vehicle, the reliability of the device is improved.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.

  1-4 show one embodiment of a disc brake according to the present invention. In these drawings, 1 is a disk rotor, 2 and 3 are a pair of pads arranged on both sides of the disk rotor 1, and 4 is a pair of pads 2 and 3 that are pressed against both sides of the disk rotor 1 to control them. This caliper generates power. The disc brake is configured as a caliper floating type, and the pair of pads 2 and 3 and the caliper 4 are connected to a carrier 5 bolted to a non-rotating portion (for example, a knuckle) of the vehicle and a shaft of the disc rotor 1. It is supported to be movable in the direction. More specifically, each of the pads 2 and 3 is configured such that the left and right ear portions 6 provided on both sides thereof are fitted into guide grooves 7 provided facing the inner sides of the left and right support columns 5a of the carrier 5, thereby 5 is slidably supported (FIG. 2). In addition, the caliper 4 is inserted into guide holes (not shown) provided in the bridge part 5b of the carrier 5 by inserting guide pins (not shown) attached to the left and right arm parts 4a using bolts 8; The carrier 5 is slidably supported (FIGS. 2 and 4). 2 and 4, reference numeral 9 denotes screw holes for bolting the carrier 5 to the non-rotating portion of the vehicle, and is provided at two left and right sides of the carrier 5.

  The caliper body 10 constituting the caliper 4 has a cylinder portion 11 on the base end side facing the pad (inner pad) 2 on the vehicle inner side, and a claw portion 12 on the distal end side facing the pad (outer pad) 3 on the vehicle outer side. Have. The cylinder portion 11 is formed with a bottomed cylinder 13 having an opening on the inner pad 2 side and the other end closed by a bottom wall 13a. Inside the cylinder 13, a piston seal 14 is interposed. The piston 15 is slidably mounted. Here, the piston 15 has a cup shape and is accommodated in the cylinder 13 so that the bottom thereof faces the inner pad 2. A space between the piston 15 and the bottom wall 13a of the cylinder 13 is defined as a fluid pressure chamber 16, and a fluid (not shown) is provided in the fluid pressure chamber 16 through a port (not shown) provided in the cylinder portion 11. The hydraulic pressure is supplied from a pressure source (for example, a master cylinder). The piston 15 is propelled according to the supply of hydraulic pressure to the hydraulic chamber 16 and presses the inner pad 2 against the disc rotor 1. The piston 15 is prevented from rotating by engaging a convex portion 2a provided on the back surface of the inner pad 2 with a concave portion 15a provided on the bottom surface thereof. In addition, a dust boot 17 is interposed between the bottom of the piston 15 and the caliper body 10 to prevent foreign matter from entering the cylinder 13.

  In the present embodiment, a housing 18 is fixed to the rear end of the caliper body 10 by a plurality of bolts 19. The bottom wall 13 a of the cylinder 13 is placed in the housing 18 and the cylinder portion 11 of the caliper body 10. A parking brake mechanism 20 is disposed with the gap therebetween. The parking brake mechanism 20 is inserted into a through hole 21 provided in the bottom wall 13a, and one end side is extended into the housing 18, and a shaft 23 having a male screw 22 on the other end side located in the cup portion of the piston 15; A nut 25 which is disposed in the cup portion 15 and meshes the internal thread 24 of the inner surface with the male thread 22 of the shaft 23; a gear mechanism (deceleration mechanism) 26 which is disposed in the housing 18 and rotates the shaft 23; An electric motor 28 that is externally attached to the housing 18 using bolts 27 (FIGS. 2 and 4) and drives the gear mechanism 26 is schematically configured. A seal member 29 is provided on the inner surface of the through hole 21 of the bottom wall 13a so as to seal between the shaft 23 and the fluid pressure chamber 16 in the cylinder 13 is maintained fluid-tight.

  The shaft 23 is disposed on the axis of the cylinder 13, and an intermediate portion of the shaft 23 is rotatably supported by a bearing (thrust bearing) 30 disposed on the bottom wall 13a. The shaft 23 also has a flange portion 31 provided at an intermediate portion thereof in contact with the bearing 30, while a retaining ring 32 attached to one end extended into the housing 18 is abutted against the boss portion of the bottom wall 13 a. By contacting, it is restrained in the axial direction. On the other hand, the nut 25 meshed with the shaft 23 is made non-rotatable by engaging a plurality of projections 33 provided radially on the outer periphery of the tip end with a plurality of axial grooves 34 formed on the inner surface of the piston 15. And it is arranged to be movable in the axial direction. In accordance with the rotation of the shaft 23, the nut 25 moves linearly in the guide in the axial groove 34 of the piston 15, and a tip thereof is brought into contact with the inner bottom of the piston 15 to apply a pressing force in the propulsion direction to the piston 15. Therefore, the shaft 23 and the nut 25 constitute a screw mechanism (rotation-linear motion conversion mechanism) that converts the rotation of the gear mechanism 26 into a linear motion and presses the piston 15 in the propulsion direction. A convex surface 35 that forms a part of a spherical surface is formed at the tip of the nut 25, and a conical surface 36 is formed on the inner bottom of the piston 15. The nut 25 causes the convex surface 35 to abut on the conical surface 36. Thus, a pressing force is applied to the piston 15.

  Therefore, the male screw 22 of the shaft 23 and the female screw 24 of the nut 25 are square screws having a square section, as well shown in FIG. The reason why the male screw 22 and the female screw 24 are square screws in this manner is to prevent a rotational torque from being almost generated even if an axial force is received from the piston 15. Therefore, the shaft 23 and the nut 25 constitute a reversible screw mechanism.

  On the other hand, the gear mechanism 26 for rotating the shaft 23 is attached to a worm 41 fixed to the rotating shaft 40 of the electric motor 28 and non-rotatably attached to one end of the shaft 23 via a key 42, and is engaged with the worm 41. The worm wheel 43 is combined. The worm wheel 43 is supported at its front and rear ends by bearings (thrust bearings) 44 and 45 disposed in the housing 18, and the worm wheel 43 is guaranteed to rotate smoothly by these bearings 41 and 42. Yes. The gear mechanism 26 formed by meshing the worm 41 and the worm wheel 43 is irreversible. Therefore, even when the electric motor 28 is stopped in a state where the braking force is generated and the axial force is received, The reverse rotation of the shaft 23 is prevented by the gear mechanism 26, and the piston 15 is mechanically held at the parking brake position.

  The electric motor 28 is disposed on the lower side of the housing 18, and the rotation shaft 40 extends from the lower side to the upper side across the housing 18. The distal end portion of the rotary shaft 40 extends through the housing 28 to the outside (upper portion), and the extended end portion 40a is processed into a two-sided width so as to be suitable for gripping the rotary jig. Yes. The extended end portion 40 a of the rotating shaft 40 that has been processed by the two-sided width is always covered with a cap 46. In FIG. 1, the upper side and the lower side of the center line are indicated by different cut ends (cross sections).

The operation of the disc brake configured as described above will be described below.
When operating as a normal brake, when the hydraulic pressure is supplied from the hydraulic pressure source to the hydraulic pressure chamber 16 in the caliper 4 in response to depression of a brake pedal (not shown), the piston 15 propels and the inner pad 2 is moved to the disc. Press against the rotor 1. On the other hand, the caliper body 10 is moved to the inside of the vehicle by the reaction force at this time, and the claw portion 12 presses the outer pad 3 against the other surface of the disk disk rotor 1, whereby the disk rotor 1 is moved by the pair of pads 2 and 3. A braking force corresponding to the fluid pressure is generated. Also, when the hydraulic pressure in the hydraulic chamber 16 is released by releasing the brake pedal from this state, the piston 15 is retracted by the elastic restoring force of the piston seal 14, and the pair of pads 2 and 3 are moved to the disc rotor accordingly. The brake is released away from 1.

  In the case of operating as a parking brake, the electric motor 28 is rotated in a state where the normal brake is operated by supplying the hydraulic pressure to the hydraulic chamber 16 (a state in which a braking force is generated). Then, the worm 40 rotates integrally with the rotating shaft 40 of the electric motor 28, and the rotation is transmitted to the shaft 23 via the worm wheel 43. The rotation of the shaft 23 is converted into a linear motion of the nut 25 by the meshing (screw portion) of the male screw 22 and the female screw 24, and the nut 25 moves linearly (advances). Thereby, the convex surface 35 at the tip of the nut 25 abuts on the conical surface 36 on the inner bottom of the piston 15 to press the piston 15 in the propulsion direction. The caliper body 10 is warped with the generation of the braking force, and the nut 25 screwed with the shaft 23 is slightly inclined with respect to the piston 15, but the piston 35 is brought into contact with the convex surface 35 and the conical surface 36. The inclination of the nut 25 with respect to 15 is absorbed, whereby the pressing force of the nut 25 is efficiently transmitted to the piston 15.

  Thereafter, the hydraulic pressure in the hydraulic chamber 16 is released, and at the same time, the electric motor 28 is stopped. Then, although the shaft 23 tries to rotate by the axial force received from the piston 15, the rotation of the shaft 23 is restricted by the irreversible gear mechanism 26 composed of the worm 41 and the worm wheel 43. As a result, the piston 15 is mechanically held at the braking position (parking brake position) as it is.

  On the other hand, to release the parking brake, the electric motor 28 is rotated in the reverse direction. In this case, since the shaft 23 and the nut 25 are composed of a reversible screw mechanism in which a male screw 22 and a female screw 24 that are square screws mesh with each other, even if a large axial force is received from the piston 15, the screw portion is almost rotated. Torque is not generated, and therefore the reverse rotation of the electric motor 28 causes the shaft 23 to rotate smoothly, and the nut 25 moves backward in the direction away from the piston 15. That is, a large motor torque is not required for releasing the parking brake, and the small electric motor 28 can be used correspondingly. In addition, the troublesome operation (hydraulic pressure operation) of once supplying the hydraulic pressure to the hydraulic pressure chamber 16 and releasing the axial force applied from the piston 15 to the screw portion becomes unnecessary, and the parking brake can be released quickly. it can.

  Incidentally, the expression for loosening the screw is generally represented by T = F × d / 2 × tan (ρ−β). Here, T is the rotational torque, F is the axial force, d is the effective diameter of the threaded portion, ρ is the friction angle of the screw, β is the screw lead angle, and the axial force F is applied if a screw with ρ = β is used. Even so, the rotational torque T is zero. Since the male screw 22 and the female screw 24 in the above embodiment are square screws, the rotational torque is almost zero, and a large motor torque is not required for releasing the parking brake as described above. The male screw 22 and the female screw 24 can be, for example, ball screws instead of the square screws, and the same effect can be obtained in this case.

  Here, if the electric motor 28 breaks down during the parking brake, an appropriate rotating jig is engaged with the extended end portion 40a of the rotating shaft 40 protruding to the outside of the housing 18 to rotate from the outside. The shaft 40 is forcibly rotated. As a result, the shaft 23 rotates through the gear mechanism 26, the nut 25 moves directly through the screw mechanism, moves away from the piston 15, and the parking brake is released. Also in this case, no special rotational force is required for the rotation of the shaft 23 for the reason described above, and the rotating shaft 40 is rotated, so that the parking brake can be easily released manually.

1 is a cross-sectional view showing the overall structure of a disc brake as one embodiment of the present invention. It is a front view which shows this disc brake as a partial cross section. It is sectional drawing which expands and shows a part of screw mechanism which comprises this disc brake. It is a perspective view which shows the whole structure of this disc brake.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Disc rotor, 2, 3 pad 4 Caliper, 5 Carrier 10 Caliper main body, 13 Cylinder 15 Piston, 19 Housing 20 Parking brake mechanism 22 Male screw (square screw), 23 Shaft 24 Female screw (square screw), 25 Nut 26 Gear mechanism 28 Electric motor 40 Rotating shaft, 40a Extending end of tip of rotating shaft 41 Worm, 43 Worm wheel

Claims (3)

  A pair of pads disposed on both sides of the disk and a piston slidably disposed in the bottomed cylinder are propelled by introducing hydraulic pressure into the cylinder, and the pair of pads are used as a disk. A caliper that generates a braking force when pressed and an electric motor provided outside the cylinder operate as a drive source, and a piston that is propelled by supplying hydraulic pressure into the cylinder is mechanically released after the hydraulic pressure in the cylinder is released. In the disc brake including a parking brake mechanism that holds the brake at a braking position, the parking brake mechanism includes a speed reduction mechanism that increases a rotational torque of the electric motor and a rotation that is increased by the speed reduction mechanism. A rotation-linear motion conversion mechanism that converts and presses the piston in the propulsion direction, the speed reduction mechanism is a non-reversible gear mechanism, and the rotation-linear motion conversion mechanism is acceptable. Disc brake characterized by comprising from screw mechanism.   The gear mechanism includes a worm fixed to a rotating shaft of an electric motor and a worm wheel meshed with the worm. The screw mechanism has one end connected to the worm wheel and a square screw formed on the other end. 2. The disc brake according to claim 1, wherein the disc brake includes: a shaft having a square screw engaging with a square screw of the shaft on an inner surface thereof, and being prevented from rotating by the piston. The disc brake according to claim 2, wherein a tip end portion of the rotating shaft of the electric motor extends through the caliper to the outside.

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