Electric disk brake

Disclosed herein is an electric disk brake including: a carrier in which a pair of pad plates for pressing both sides of a rotating disk together with wheels are installed to make advance and retreat; a caliper housing that is slidably installed in the carrier and has a cylinder in which a piston is installed to make advance and retreat due to brake hydraulic pressure; an adjuster disposed in the piston; a push rod that is installed in the cylinder and is screw-coupled to the adjuster; a ramp unit that is installed to penetrate the rear of the cylinder, converts a rotation motion into a rectilinear motion by receiving a rotation force from an actuator that generates a parking brake force, and presses the push rod toward the piston; and an elastic member that is disposed in a spring case formed between an inner circumferential surface of the cylinder and the push rod and provides an elastic force to the push rod, further including a connector having one end coupled to a rotating ramp plate of the ramp unit so that the connector is rotated together with the rotating ramp plate, and having the other end connected to a final output gear among a plurality of gears configured to decelerate a rotation force generated from the actuator so that the rotation force is transferred only in a direction in which a brake force is generated in the rotating ramp plate, wherein at least one hole is spaced by a predetermined distance apart from a center of the connector in a radial direction and is formed in an arc shape, and protrusions are formed in the final output gear to penetrate the at least one hole and to rotate, and the connector includes: a first coupling part that penetrates a center of the final output gear and is coupled to the rotating ramp plate; and a second coupling part, which extends from the first coupling part in a radial direction and in which the at least one hole is formed in the radial direction of a center of the second coupling part.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No. 10-2014-0073246, filed on Jun. 17, 2014 in the Korean Intellectual Property Office, the disclosure of which is incorporated in its entirety herein by reference.

BACKGROUND

Embodiments of the present invention relate to an electric disk brake, and more particularly, to an electric disk brake that is easily capable of easily controlling an actuator when a parking brake force is released from the electric disk brake and of preventing damage of components caused by releasing an excessive parking brake force.

2. Description of the Related Art

Disk brakes are devices that forcibly compress a frictional pad on both sides of a rotating disk together with wheels of a vehicle so that rotation of the disk is stopped, thereby braking the vehicle. These disk brakes include parking brakes that electrically operate during parking and maintain the vehicle in a stopped state.

In general, an electric disk brake includes a pair of pad plates that are disposed on both sides of a disk and generate a brake force by compressing the disk, a carrier that supports the pair of pad plates, a caliper housing that is slidably installed in the carrier so as to press the pair of pad plates and has a piston moved by a brake hydraulic pressure, and an actuator that operates the piston using a mechanical mechanism.

Such an electric disk brake includes a so-called ball in ramp (BIR) type electric disk brake including a fixed ramp plate fixedly installed in the caliper housing, a rotating ramp plate that rotates by an operation of a parking cable, balls that are installed between the fixed ramp plate and the rotating ramp plate and make a forward movement of the rotating ramp plate when the rotating ramp plate is rotated, a push rod that is disposed adjacent to the rotating ramp plate and pushes the piston, an adjuster screw-coupled to the push rod, and a spring that restores the push rod to its original position.

The BIR type electric disk brake is generally referred to as a BIR caliper type and is disclosed in U.S. Patent Publication No. 2012/029214 and Korean Patent Publication No. 10-2013-0034605. According to the disclosure, the BIR type electric disk brake is configured in such a way that, as a rotation force generated by a motor of an actuator is transferred to the rotating ramp plate of a ramp unit using a decelerator (gear assembly), a rotation motion is converted into a rectilinear motion and pushes the push rod, and the push rod pushes the piston together with the adjuster so that a frictional pad can closely contact the disk and a parking brake force can be generated.

In this case, the rotating ramp plate is directly connected to a final output gear among gears of the decelerator, receives the rotation force, and is rotated in a direction in which the parking brake force is applied to the rotating ramp plate, or is rotated in a direction in which the parking brake force is released from the rotating ramp plate.

However, when an excessive rotation force is transferred to the rotating ramp plate when the parking brake force is released, the balls may escape from the ramp unit, or an excessive load may be applied to internal components so that the internal components may be damaged.

Patent Document

SUMMARY

Therefore, it is an aspect of the present invention to provide an electric disk brake in which a rotating ramp plate that converts a rotation motion into a rectilinear motion and a connector that connects a final output gear transferring a rotation force to the rotating ramp plate are disposed and the rotation force is transferred only in a direction in which a parking brake force is generated, using the connector so that, even when an excessive rotation force is generated in the rotating ramp plate when the parking brake force is released from the rotating ramp plate, the rotation force is not transferred to the rotating ramp plate.

In accordance with one aspect of the present invention, an electric disk brake includes: a carrier in which a pair of pad plates for pressing both sides of a rotating disk together with wheels are installed to make advance and retreat; a caliper housing that is slidably installed in the carrier and has a cylinder in which a piston is installed to make advance and retreat due to brake hydraulic pressure; an adjuster disposed in the piston; a push rod that is installed in the cylinder and is screw-coupled to the adjuster; a ramp unit that is installed to penetrate the rear of the cylinder, converts a rotation motion into a rectilinear motion by receiving a rotation force from an actuator that generates a parking brake force, and presses the push rod toward the piston; and an elastic member that is disposed in a spring case formed between an inner circumferential surface of the cylinder and the push rod and provides an elastic force to the push rod, further including a connector having one end coupled to a rotating ramp plate of the ramp unit so that the connector is rotated together with the rotating ramp plate, and having the other end connected to a final output gear among a plurality of gears configured to decelerate a rotation force generated from the actuator so that the rotation force is transferred only in a direction in which a brake force is generated in the rotating ramp plate, wherein at least one hole may be spaced by a predetermined distance apart from a center of the connector in a radial direction and may be formed in an arc shape, and protrusions may be formed in the final output gear to penetrate the at least one hole and to rotate, and the connector may include: a first coupling part that penetrates a center of the final output gear and is coupled to the rotating ramp plate; and a second coupling part, which extends from the first coupling part in a radial direction and in which the at least one hole is formed in the radial direction of a center of the second coupling part.

The connector may be configured so that the final output gear is rotated in a direction in which a parking brake force is generated and the protrusions rotate from a time when the protrusions contact a distal end of one side of the at least one hole to transfer a rotation force to the rotating ramp plate.

The protrusions may rotate toward a distal end of the other side of the at least one hole when the final output gear is rotated in a direction in which the parking brake force is released, and as the rotating ramp plate rotates in an opposite direction like rotating in a direction in which the parking brake force is generated, the connector may be rotated together with the rotating ramp plate so that contact between the protrusions and a distal end of the other side of the at least one hole is prevented.

The ramp unit may include: a fixed ramp plate having an opened front and fixedly installed in the cylinder; a rotating ramp plate that is disposed in the fixed ramp plate, penetrates the rear of the fixed ramp plate and the rear of the cylinder, is coupled to the connector and rotates by a transferred rotation force; and a plurality of balls that are interposed between the rotating ramp plate and the push rod and allow the push rod to make a forward movement when the rotating ramp plate is rotated.

DETAILED DESCRIPTION

Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The following embodiment is proposed to sufficiently convey the spirit of the invention to one of ordinary skill in the art. The invention is not limited by the proposed embodiment but may be embodied in different shapes. In the drawings, for clarity, illustration of unrelated parts to description is omitted, and for understanding, sizes of components may be slightly exaggerated.

FIG. 1is an exploded perspective view schematically illustrating an electric disk brake in accordance with an embodiment of the present invention, andFIG. 2is a side cross-sectional view of assembling ofFIG. 1.

Referring toFIGS. 1 and 2, an electric disk brake100in accordance with an embodiment of the present invention includes a carrier110in which a pair of pad plates111and112for pressing both sides of a rotating disk D together with wheels (not shown) are installed to make advance and retreat, a caliper housing120that is slidably installed in the carrier110and has a cylinder122in which a piston123is installed to make advance and retreat due to brake hydraulic pressure, an adjuster130that prevents the pad plates111and112from being far away from the disk D and maintains a constant distance between the pad plates111and112, a push rod140that is screw-coupled to the adjuster130, a ramp unit150that supports the push rod140so as to prevent rotation of the push rod140and is installed in the cylinder122, a spring case160that forms a predetermined accommodation space between an inner side surface of the cylinder122and the push rod140, an elastic member164disposed in the spring case160, an actuator170that generates a parking brake force, and a connector180that conveys the parking brake force to the ramp unit150.

The carrier110is fixed to a knuckle of a vehicle using a mounting bolt (not shown), and the caliper housing120is slidably fastened on both ends of the carrier110using a guide rod (not shown). Also, the pair of pad plates111and112are disposed in a center of the carrier110to be spaced by a predetermined distance apart from each other and to be slidable in a direction in which they face each other.

The pair of pad plates111and112are classified into an inner pad plate111that is disposed to contact the piston123that will be described later and has an inner side surface to which a frictional pad113is attached, and an outer pad plate112that is disposed to contact a finger part121that will be described later and has an inner side surface to which a frictional pad114is attached. In this case, the disk D has a shape of a disk that rotates together with the wheels (not shown) of the vehicle. The disk D rotates in a state in which a part of the disk D is inserted between the pair of pad plates111and112.

The caliper housing120includes the finger part121that operates the outer pad plate112and the cylinder122having the piston123disposed therein so that the cylinder122may slide due to brake hydraulic pressure. In this case, a hydraulic duct (not shown) is formed on one end of the caliper housing120so that the brake hydraulic pressure may be supplied to the cylinder122through the hydraulic duct.

The finger part121is formed to be bent from the front to a lower side of the caliper housing120so as to surround the outer pad plate112from outside. Thus, as the caliper housing120slides from the carrier110due to a reaction force caused by movement of the piston123and is moved to the right when a brake operation is performed, the outer pad plate112is pushed by the finger part121toward the disk D and presses the disk D.

The cylinder122is formed in the rear of the caliper housing120so that the brake hydraulic pressure formed in a master cylinder (not shown) may be transferred to the cylinder122. The piston123is installed in the cylinder122to make advance and retreat. That is, the piston123installed in the cylinder122makes advance and retreat in the cylinder122due to the brake hydraulic pressure. The push rod140and the ramp unit150that will be described later are installed in the cylinder122in addition to the piston123.

The piston123is disposed to have a shape of a cup having one opened side, and a head part133of the adjuster130that will be described later is inserted into and contacts an inner center of the piston123.

The adjuster130includes the head part133that is installed in the piston123inserted into the cylinder122and contacts the piston123and a rod134that extends from the head part133and has a screw thread formed on an outer circumferential surface of the rod134. In this case, the head part133is inserted into and contacts an inside of the piston123through the opened side of the piston123, as described above.

The adjuster130prevents the pad plates111and112from being far away from the disk D as the frictional pads113and114attached to the pair of pad plates111and112are worn out, and maintains a constant distance between the pad plates111and112. Washers128and138are installed at an inner side surface of the piston123and a rear wall of the head part133, respectively, and a washer spring139is disposed between the washers128and138. That is, the adjuster130is disposed in contact with the piston123due to an elastic force of the washer spring139installed between the inner side surface of the piston123and the head part133. Thus, the washer spring139presses the adjuster130toward a tip end of the piston123so that the adjuster130and the piston123are always in contact with each other even though the frictional pads113and114of the pad plates111and112are worn out by friction with the disk D and a position of the piston123is moved to the inner pad plate111.

The push rod140installed in the cylinder122is screw-coupled to the rear of the adjuster130, i.e., the rod134. Thus, the adjuster130coupled to the piston123makes a forward movement together when the piston123makes a forward movement due to the brake hydraulic pressure. In this case, the push rod140screw-coupled to the adjuster130makes a forward movement together. Thus, the adjuster130and the push rod140are configured so that a distance between screw-coupled screw threads may be reduced. That is, although a distance between screw threads of the adjuster130and the push rod140generally exists, the adjuster130is pressed in a forward direction (left side) of the piston123so that the distance between the screw threads may be reduced and movements of the adjuster130and the push rod140may occur simultaneously.

The push rod140has a hollow center part so that the push rod140may be screw-coupled to the adjuster130, and a screw thread is formed on an inner circumferential surface of the push rod140, and a flange part142is disposed in the rear of the push rod140and extends toward an inner circumferential surface of the cylinder122. The push rod140is supported on the ramp unit150that will be described later, and rotation of the push rod140is prevented. A rotation prevention structure of the push rod140will be described again.

As the push rod140is screw-coupled to the adjuster130in a state in which rotation of the push rod140is prevented, the adjuster130may be moved in a lengthwise direction of the push rod140. That is, when the frictional pads113and114are worn out and the piston123is moved, the adjuster130is rotated from the push rod140due to characteristics of the adjuster130in which the adjuster130closely contacts the piston123due to the washer spring139, and is moved by a movement distance of the piston123and is maintained in close contact with the piston123. Thus, a constant distance between the pad plates111and112pressed by the disk D and the piston123is maintained.

Meanwhile, a plurality of coupling protrusions144are formed on the flange part142of the push rod140and are spaced by a predetermined distance apart from each other along an outer circumferential surface of the flange part142and protrude outwardly. As the coupling protrusions144are inserted into coupling grooves154formed in a fixed ramp plate151of the ramp unit150, rotation of the push rod140is prevented, and the coupling protrusions144are coupled to the ramp unit150.

The ramp unit150includes the fixed ramp plate151fixedly installed in the cylinder122, a rotating ramp plate156that is coupled to the connector180connected to the actuator170that will be described later and rotates by a transferred rotation force, and a plurality of balls158interposed between the push rod140and the rotating ramp plate156.

The fixed ramp plate151has a shape of a cylinder, the front of which is opened. The flange part142of the push rod140is disposed in the fixed ramp plate151, and the coupling grooves154are formed so that the coupling protrusions144of the flange part142may be inserted into the coupling grooves154, as described above.

Meanwhile, the fixed ramp plate151is installed in the cylinder122so that rotation of the fixed ramp plate151may be prevented. According to the drawings, rotation prevention protrusions155are formed in the rear of the fixed ramp plate151and protrude outwardly, and rotation prevention grooves125that correspond to the rotation prevention protrusions155are formed in the cylinder122in positions corresponding to the rotation prevention protrusions155. Thus, as the rotation prevention protrusions155are inserted into the rotation prevention grooves125, rotation of the fixed ramp plate151is prevented, and rotation of the push rod140coupled to the fixed ramp plate151is also prevented.

The rotating ramp plate156includes an axial part156bthat penetrates the rear of the fixed ramp plate151and the rear of the cylinder122and protrudes toward an outside of the caliper housing120and a pressing part156athat is disposed in the fixed ramp plate151and extends from an end of the axial part156bin a radial direction. In this case, the axial part156bthat protrudes toward the outside of the caliper housing120is coupled to the connector180that will be described later, and a rotation force is transferred to the axial part156busing the connector180.

Meanwhile, unexplained reference numeral159is a bearing that is interposed between the rotating ramp plate156and the fixed ramp plate151and supports rotation of the rotating ramp plate156.

The plurality of balls158are interposed on opposite surfaces of the rotating ramp plate156and the push rod140, and guide grooves (not shown) that support the plurality of balls158are formed in the opposite surfaces. The guide grooves are formed to be inclined so that, as the rotating ramp plate156is rotated, the balls158are moved along the inclined grooves and allow the push rod140to make a rectilinear motion. A configuration of making a rectilinear motion of the push rod140using the balls158is a well-known technology that is generally used, and thus, a detailed description thereof will be omitted.

The spring case160is configured to form a predetermined accommodation space between the push rod140and the inner side surface of the cylinder122. In detail, one end of the spring case160is fixed onto the inner side surface of the cylinder122using a snap ring162, and the elastic member164that restores the push rod140to its original position so as to restore the piston123is disposed in the spring case160.

One end of the elastic member164is supported on one side surface of the spring case160, and the other end of the elastic member164is supported on the flange part142of the push rod140so that the elastic member164may be configured to provide an elastic force to the push rod140in a movement direction of the piston123.

The actuator170includes a motor172that generates a brake force, a decelerator including a plurality of gears so as to decelerate a rotation force of the motor172, and a housing171that accommodates the motor172and the decelerator and is installed at an outside of the caliper housing120.

The decelerator has a two-stage deceleration structure in which a plurality of gears are engaged so as to decelerate the rotation force of the motor172that rotates forward and reverse by power applied to the decelerator. According to the drawings, the decelerator that has a two-stage worm wheel deceleration structure includes a first worm174coupled to a rotation shaft173of the motor172, a first worm wheel175engaged with the first worm174, a second worm176that has the same axis as that of the first worm wheel175and is rotated by the first worm wheel175, and a second worm wheel177that rotates while being engaged with the second worm176. In this case, the second worm wheel177is a gear that outputs a decelerated rotation force, and hereinafter, is referred to as a final output gear177.

Meanwhile, the decelerator of the electric disk brake according to the present invention has a worm wheel deceleration structure. However, the present invention is not limited thereto, and various gear assembling structures including a spur gear assembling structure to which the rotation force of the motor172may be transferred, may be employed. That is, the decelerator decelerates the rotation force using various gear assembling structures, and any gear assembling structure that may transfer the rotation force using the final output gear177may be employed.

According to an embodiment of the present invention, the connector180installed in the final output gear177is provided to transfer the rotation force to the rotating ramp plate156of the ramp unit150. The connector180is configured to transfer the rotation force to the rotating ramp plate156only in one direction using the final output gear177, and an assembling structure of the connector180is illustrated inFIG. 3.

Referring toFIG. 3, the connector180is configured so that one end of the connector180is coupled to the rotating ramp plate156so as to rotate together with the rotating ramp plate156and the other end of the connector180is connected to the final output gear177and the connector180transfers the rotation force to the rotating ramp plate156. In more detail, the connector180includes a first coupling part181that penetrates a center of the final output gear177and is coupled to the rotating ramp plate156, a second coupling part182that extends from the first coupling part181in the radial direction, and holes188that are spaced by a predetermined distance apart from each other in the radial direction based on a center of the second coupling part182. In this case, the second coupling part182is placed at an outside of the final output gear177. Also, at least one or more holes188are formed in the second coupling part182.

In order to transfer the rotation force to the rotating ramp plate156using the above-described connector180, pin-shaped protrusions178are disposed in the final output gear177so as to penetrate the holes188. The protrusions178are rotated along the holes188together when the final output gear177is rotated. Thus, as illustrated inFIG. 4, the rotation force is transferred to the connector180from a time when the protrusions178are rotated along the holes188and contact a distal end of one side of the holes188when the final output gear177is rotated in one direction (a direction in which the final output gear177generates a parking brake force). That is, the rotating ramp plate156coupled to the connector180is rotated together with the connector180.

Meanwhile, the holes188are formed in the connector180, and the protrusions178are disposed in the final output gear177so that the rotation force is transferred to the rotating ramp plate156only in one direction. However, the present invention is not limited thereto, and protrusions that are formed in the second coupling part182of the connector180and protrude toward the final output gear177, and arc-shaped holes through which the protrusions pass are formed in the final output gear177so that the rotation force may be transferred to the rotating ramp plate156only in one direction using the connector180.

As described above, the electric disk brake100according to an embodiment of the present invention is configured to transfer the rotation force only in the direction in which the parking brake force is generated, using the connector180. In more detail, referring toFIGS. 5 and 6, when the final output gear177is rotated in a direction in which the parking brake force is released, the protrusions178are rotated toward a distal end of the other side of the holes188so that the rotation force may not be transferred to the connector180. In this case, the connector180is rotated together with the rotating ramp plate156as the rotating ramp plate156rotates in an opposite direction like rotating in the direction in which the parking brake force is generated. That is, even when the final output gear177is rotated in the direction in which the parking brake force is released, the protrusions178are rotated in the other-side direction of the holes188, and the connector180is rotated in the same direction as a rotation direction of the final output gear177, and contact between the holes188and the protrusions178is not performed so that power may not be transmitted to the rotating ramp plate156using the protrusions178. This is because self-locking is not possible due to characteristics of the ramp unit150and a rotation force is generated in the rotating ramp plate156in a direction in which the rotating ramp plate156is brake-released due to loads applied to the frictional pads113and114when the brake force is released from the rotating ramp plate156and the rotating ramp plate156and the connector180are rotated together by the push rod140pressed by the elastic member164.

As a result, the electric disk brake100according to an embodiment of the present invention is configured so that a rotation force may be transferred to the electric disk brake100only in a direction in which a parking brake force is generated, using a coupling structure of the connector180and even when an excessive rotation force is generated in the rotating ramp plate156when the parking brake force is released from the rotating ramp plate156, the rotation force may not be transferred to the rotating ramp plate156and damage of the ramp unit150may be prevented.

As described above, an electric disk brake according to an embodiment of the present invention includes a connector that connects a final output gear of a decelerator and a rotating ramp plate of a ramp unit that converts a rotation motion into a rectilinear motion, and a rotation force is transferred to the rotating ramp plate only in a direction in which a parking brake force is generated, using the connector so that, even when an excessive rotation force is generated in the rotating ramp plate in a direction in which the parking brake force is released from the rotating ramp plate, escape of balls or damage of components can be prevented.

This is because arc-shaped holes are formed in the connector in a circumferential direction and rotating protrusions are inserted into the holes together with a final output gear and rotate along the holes. That is, when the parking brake force is applied to the rotating ramp plate, the protrusions rotate along the holes and contact a distal end of one side of the holes so as to transfer the rotation force to the connector, and when the parking brake force is released, the protrusions rotate in an opposite direction to a direction in which the parking brake force is applied to the rotating ramp plate, and rotate along the holes, and as the rotating ramp plate rotates in the opposite direction like rotating in a direction in which the parking brake force is generated, the connector is rotated together with the rotating ramp plate so that the rotation force when the parking brake force is released, may not be transferred to the rotating ramp plate. Thus, control of an actuator that generates the parking brake force can be easily performed.