Brake apparatus for vehicle

A brake apparatus for a vehicle may include: a first driver and a second driver each configured to generate a driving force; a transfer gear part rotated by the driving force received from the first driver; a piston part configured to press or release a pad part according to the direction in which the piston part is moved forward or backward; a parking gear part rotated with the transfer gear part; a constraint part moved forward or backward by the driving force of the second driver, and configured to constrain the rotation of the parking gear part by being moved to one side during parking braking; and a locking part configured to transfer the driving force, generated by the second driver, to the constraint part, and to restrict the constraint part from moving to the other side during parking braking.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from and the benefit of Korean Patent Application No. 10-2021-0165353, filed on Nov. 26, 2021, which is hereby incorporated by reference for all purposes as if set forth herein.

BACKGROUND

Field

Exemplary embodiments of the present disclosure relate to a brake apparatus for a vehicle, and more particularly, to a brake apparatus for a vehicle, which generates a braking force by converting a pedal operation force of a driver into an electrical signal.

Discussion of the Background

In general, a brake apparatus for a vehicle refers to an apparatus which pushes a piston with a driving force such that a pad and a disk are pressed against each other, and brakes a vehicle by using the frictional force between the pad and the disk.

Among the brake apparatuses, EMB (Electro Mechanical Brake) refers to an apparatus which has a motor driving actuator directly mounted on a caliper without using hydraulic pressure, and presses a piston through a mechanism such as a gear or screw, thereby generating a braking force. The EMB can perform active braking and independent braking for each wheel, and thus implement various additional functions such as ABS, ESC, TCS and AEB as well as a main braking function, thereby implementing higher performance without hydraulic pressure transfer delay.

The conventional EMB secures quick responsiveness and high efficiency of the piston through a ball screw. However, such a ball screw cannot perform a self locking function capable of restricting its own rotation, due to the structural characteristics thereof. Thus, when power supplied to a motor is cut off, a braking force may be randomly released by a repulsive force between the pad and the piston.

The related art of the present disclosure is disclosed in Korean Patent Application Laid-Open No. 10-2010-0098846 published on Sep. 10, 2010 and entitled “Disk Brake Having Parking Function”.

SUMMARY

Various embodiments are directed to a brake apparatus for a vehicle, which can stably maintain a parking braking state.

In an embodiment, a brake apparatus for a vehicle may include: a first driver and a second driver each configured to generate a driving force; a transfer gear part rotated by the driving force received from the first driver; a piston part moved forward or backward in connection with a rotation of the transfer gear part, and configured to press or release a pad part according to a direction in which the piston part is moved forward or backward; a parking gear part rotated with the transfer gear part; a constraint part moved forward or backward by the driving force of the second driver, and configured to constrain a rotation of the parking gear part by being moved to one side during parking braking; and a locking part configured to transfer the driving force, generated by the second driver, to the constraint part, and to restrict the constraint part from moving to the other side during parking braking.

The constraint part may include: a body part configured to linearly reciprocate between the second driver and the parking gear part; a constraint member extending from the body part, and brought into surface contact with the parking gear part, as the body part is moved by a predetermined distance or more toward the parking gear part; and a guide part configured to abut on the constraint member, and to guide a movement of the body part.

The constraint member may include: a first constraint member brought into contact with one surface of the parking gear part; and a second constraint member spaced apart from the first constraint member so as to face the first constraint member, and brought into contact with another surface of the parking gear part.

The first constraint member and the second constraint member may be disposed in parallel to each other.

The first constraint member and the second constraint member may be spaced apart, by a width of the parking gear part, from each other.

The locking part may include: a first locking member connected to and rotated by an output shaft of the second driver; and a second locking member protruding from the constraint part, and configured to convert a rotational motion of the first locking member into a linear motion by being engaged with the first locking member.

The first locking member and second locking member may be engaged with each other, and when an operation of the second driver is stopped, the second locking member constrains a rotation of the output shaft of the second driver.

The first locking member may be provided in a shape of a worm gear.

Any one of the first locking member or the second locking member may be provided in a shape of a ball screw, and a remaining one of the first locking member of the second locking member may be provided in a shape of a nut screw.

The brake apparatus may further include an adjuster connected to the constraint part, and configured to limit a moving range of the constraint part toward the parking gear part.

The adjuster may include: a load application part configured to apply a load to the constraint part in an opposite direction of a moving direction of the constraint part in proportion to a moving distance of the constraint part; a measurement part configured to measure a current value of the second driver; and a control part configured to stop an operation of the second driver when the current value of the second driver, measured by the measurement part, exceeds a preset magnitude.

The load application part may be elastically deformable in a direction parallel to the moving direction of the constraint part.

The transfer gear part may include: a first transfer gear part rotated with an output shaft of the first driver; a second transfer gear part engaged and coupled with the first transfer gear part, and rotated in connection with a rotation of the first transfer gear part; and a third transfer gear part engaged and coupled with the second transfer gear part, rotated in connection with a rotation of the second transfer gear part, and configured to transfer a rotational force to the piston part.

The parking gear part may be connected to the output shaft of the first driver, and rotated at a same angular velocity as the first transfer gear part.

The parking gear part may have a polygonal cross-section.

The piston part may include: a ball screw connected to and rotated by the transfer gear part; a ball nut configured to linearly reciprocate in a longitudinal direction of the ball screw in connection with a rotation of the ball screw; and one or more rolling bodies arranged between the ball screw and the ball nut, and configured to come into rolling contact with the ball screw and the ball nut.

In accordance with the embodiment of the present disclosure, the brake apparatus for a vehicle may prevent the piston part from randomly separating from the pad part and losing a braking force, even though the operation of the driver is stopped by the constraint part during parking braking.

Furthermore, as the parking gear part is connected to the output shaft of the first driver and rotated at the same angular velocity as the first transfer gear part, it is possible to reduce the magnitude of a load applied to the constraint part, compared to when the parking gear part is connected to the second or third transfer gear part having a rotational force boosted by a gear ratio.

Furthermore, the brake apparatus may transfer a driving force, generated by the locking parking, to the constraint part. Simultaneously, when the operation of the second driver300is stopped, the brake apparatus may prevent the output shaft of the second driver from randomly rotating in the reverse direction, through a self locking operation, thereby more stably maintaining the parking braking state.

Furthermore, the brake apparatus may limit the moving range of the constraint part through the adjuster, thereby preventing damage to parts by a collision between the constraint part and the parking gear part during parking braking.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Hereinafter, a brake apparatus for a vehicle will be described below with reference to the accompanying drawings through various exemplary embodiments.

It should be noted that the drawings are not to precise scale and may be exaggerated in thickness of lines or sizes of components for descriptive convenience and clarity only. Furthermore, the terms as used herein are defined by taking functions of the invention into account and can be changed according to the custom or intention of users or operators. Therefore, definition of the terms should be made according to the overall disclosures set forth herein.

Throughout the specification, when one element is referred to as being “connected to” or “coupled to” another element, it may indicate that the one element is “directly connected or coupled to” the another element or the one element is “indirectly connected or coupled to” with still another element interposed therebetween. In this specification, when an element “includes or has” a component, it may indicate that the element does not exclude another component but can further include or have another component, unless referred to the contrary.

Through this specification, like reference numerals may represent the same components. Although like or similar reference numbers are not mentioned or described in a specific drawing, the reference numerals may be described with reference to other drawings. Furthermore, although a component is not represented by a reference numeral in a specific drawing, the component may be described with reference to other drawings. Furthermore, the number, shape and size of sub components included in the drawings of this application and the relative difference between sizes are set for convenience of description, and may not limit embodiments but may be set to various values.

FIG.1is a cross-sectional view schematically illustrating the configuration of a brake apparatus for a vehicle in accordance with an embodiment of the present disclosure,FIG.2is a front view schematically illustrating the configuration of the brake apparatus for a vehicle in accordance with the embodiment of the present disclosure, andFIG.3is a perspective view schematically illustrating the configuration of the brake apparatus for a vehicle in accordance with the embodiment of the present disclosure.

Referring toFIGS.1and3, a brake apparatus1for a vehicle in accordance with an embodiment of the present disclosure includes a caliper body part10, a pad part20, a housing100, a first driver200, a second driver300, a transfer gear part400, a piston part500, a parking gear part600, a constraint part700, a locking part800, and an adjuster900.

The caliper body part10is fixed to a vehicle body through a torque member2, and supports the pad part20, the housing100, and the piston part500which will be described below. The caliper body part10is slidably coupled to the torque member2in a direction parallel to the axial direction of a brake disk (not illustrated) through guide pins connected to both sides thereof. The caliper body part10is movably supported by the torque member2through the guide pins connected to both sides thereof. The caliper body part10is slid in the direction parallel to the axial direction of the brake disk by a reaction force which is generated as the piston part500to be described below presses the pad part20.

The caliper body part10in accordance with the embodiment of the present disclosure includes a bridge part11, a finger part12, and a cylinder part13.

The bridge part11forms the upper exterior of the caliper body part10. The bridge part11in accordance with the embodiment of the present disclosure may be formed in the shape of a plate whose inner surface is spaced apart by a predetermined distance from the outer circumferential surface of the brake disk, while facing the outer circumferential surface of the brake disk. The specific shape and area of the bridge part11may be variously changed in design depending on the size of the brake disk or the like.

The finger part12forms the front exterior of the caliper body part10, and presses or releases the pad part20, which will be described below, in connection with the sliding movement of the caliper body part10. The finger part12in accordance with the embodiment of the present disclosure is vertically extended downward from the front end of the bridge part11. The finger part12has an inner surface facing the pad part20which is disposed outside the brake disk in a widthwise direction of the vehicle, between the pair of pad parts20.

The cylinder part13forms the rear exterior of the caliper body part10, and movably supports the piston part500which will be described below. The cylinder part13in accordance with the embodiment of the present disclosure is vertically extended downward from the rear end of the bridge part11. The cylinder part13is formed in a hollow cylindrical shape whose one side is open. The open side of the cylinder part13faces the pad part20which is disposed inside the brake disk in the widthwise direction of the vehicle, between the pair of pad parts20.

The pair of pad parts20are disposed so as to face the brake disk which is rotated with a wheel of the vehicle. The pair of pad parts20are disposed so as to face both side surfaces of the brake disk, respectively, with the brake disk interposed therebetween. The pad part20is supported by the caliper body part10so as to slide in the direction parallel to the center axis of the brake disk. The pad part20is pressed against or separated from the brake disk by a pressing force applied from the caliper body part10and the piston part500which will be described below, and thus generates or removes a braking force for the vehicle. A friction pad made of a material with a high frictional coefficient, such as rubber, may be attached to one surface of the pad part20facing the brake disk. The specific shape of the pad part20is not limited to that illustrated inFIGS.1and2, but may be variously changed in design as long as the pad part20can be pressed against the brake disk and apply a braking force to the vehicle.

The housing100is coupled to the caliper body part10, and supports the first driver200, the second driver300, the transfer gear part400, the parking gear part600, and the constraint part700, which will be described below. The housing100in accordance with the embodiment of the present disclosure is coupled to the rear surface of the caliper body part10, or specifically the rear surface of the cylinder part13. The housing100may be detachably coupled to the cylinder part13through bolting or the like, or integrated with the cylinder part13through welding or the like. The housing100is formed in a hollow shape, and has an internal space in which the first driver200, the transfer gear part400, the parking gear part600, and the constraint part700can be installed. The housing100may be opened/closed so that the components installed therein can be easily managed.

The first driver200is coupled to and supported by the housing100, and generates a driving force by using power received from the outside. The first driver200may be electrically connected to a battery of the vehicle or the like, and receive power. The first driver200in accordance with the embodiment of the present disclosure may be exemplified as various types of electric motors which generate a rotational force by using received power.

The second driver300is coupled to and supported by the housing100, and generates a driving force by using power received from the outside. The second driver300may be electrically connected to the battery of the vehicle or the like, and receive power. The second driver300in accordance with the embodiment of the present disclosure may be exemplified as various types of electric motors which generate a rotational force by using received power. The second driver300may have an output shaft disposed in a direction perpendicular to an output shaft of the first driver200. The operation state of the second driver300may be controlled by a control part930which will be described below.

The transfer gear part400is rotated by a driving force received from the first driver200, and transfers the driving force generated from the first driver200to the piston part500to be described below.

The transfer gear part400in accordance with the embodiment of the present disclosure includes a first transfer gear part410, a second transfer gear part420, and a third transfer gear part430.

The first transfer gear part410is connected to the output shaft of the first driver200, and rotated with the output shaft of the first driver200. The first transfer gear part410in accordance with the embodiment of the present disclosure may be formed in the shape of a hollow helical gear or spur gear which has teeth provided on the outer circumferential surface thereof. The first transfer gear part410has a central portion inserted onto and supported by the output shaft of the first driver200. The central axis of the first transfer gear part410is disposed coaxially with the output shaft of the first driver200. During an operation of the first driver200, the first transfer gear part410is rotated at the same angular velocity as the output shaft of the first driver200.

The second transfer gear part420is engaged and coupled with the first transfer gear part410, and rotated in connection with the rotation of the first transfer gear part410.

The second transfer gear part420in accordance with the embodiment of the present disclosure may include a plurality of second transfer gears421.

The second transfer gear421may be formed in the shape of a hollow helical gear or spur gear which has teeth provided on the outer circumferential surface thereof. The plurality of second transfer gears421are sequentially engaged and coupled from the first transfer gear part410toward the third transfer gear part430which will be described below. In this case, the outer circumferential surfaces of the second transfer gears421may be each directly engaged with the outer circumferential surface of the neighboring second transfer gear421, or engaged with the neighboring second transfer gear421through a separate small-diameter gear. The second transfer gear421disposed at one end among the plurality of second transfer gears421is engaged and coupled with the first transfer gear part410. The center axes of the plurality of second transfer gears421are disposed in parallel to the central axis of the first transfer gear part410. The diameters of the plurality of second transfer gears421may have an ascending relationship from the first transfer gear part410toward the third transfer gear part430. Thus, the plurality of second transfer gears421may boost the magnitude of the rotational force transferred from the first transfer gear part410to the third transfer gear part430.FIG.2illustrates that two second transfer gears421are provided. However, the number of the second transfer gears421is not limited thereto, but may be changed in design to various values such as three and four.

The third transfer gear part430is engaged and coupled with the second transfer gear part420. The third transfer gear part430is rotated in connection with the rotation of the second transfer gear part420, and transfers a rotational force to the piston part500which will be described below. The third transfer gear part430in accordance with the embodiment of the present disclosure may be formed in the shape of a hollow helical gear or spur gear which has teeth provided on the outer circumferential surface thereof. The third transfer gear part430has an outer circumferential surface engaged and coupled with the second transfer gear421disposed at the other end among the plurality of second transfer gears421. In this case, the outer circumferential surface of the third transfer gear part430may be directly engaged with the outer circumferential surface of the second transfer gear part420, or engaged with the second transfer gear part420through a separate small-diameter gear. The central axis of the third transfer gear part430is disposed in parallel to the central axis of the second transfer gear part420. The third transfer gear part430may have a central axis connected to the piston part500which will be described below, and transfer a rotational force to the piston part500when rotated on the central axis thereof. The third transfer gear part430has a larger diameter than the second transfer gear part420. Thus, when the second transfer gear part420is rotated, the third transfer gear part430may be rotated at a lower angular velocity than the second transfer gear part420, and boost the magnitude of the rotational force transferred to the piston part500.

The piston part500is movably installed on the caliper body part10. The piston part500is moved forward or backward in connection with the rotation of the transfer gear part400. The piston part500applies or removes a braking force while pressing or releasing the pad part20against or from the brake disk according to the direction in which the piston part500is moved forward or backward.

The piston part500in accordance with the embodiment of the present disclosure includes a ball screw510, a ball nut520, a rolling body530, and a piston member540.

The ball screw510is connected to and rotated by the transfer gear part400. The ball screw510in accordance with the embodiment of the present disclosure is formed in substantially a rod shape, and rotatably installed in the cylinder part13. The longitudinal direction of the ball screw510is set in parallel to the longitudinal direction of the cylinder part13. The ball screw510has a rear end connected to the third transfer gear part430, and axially rotated on the central axis thereof, when the third transfer gear part430is rotated. The ball screw510has a groove formed on the outer circumferential surface thereof, such that a half of the circumference of the rolling body530to be described below is seated in the groove. Such a groove is extended helically in the longitudinal direction of the ball screw510, and provides a cyclic path of the rolling body530.

The ball nut520is linearly reciprocated in the longitudinal direction of the ball screw510in connection with the rotation of the ball screw510. The ball nut520in accordance with the embodiment of the present disclosure may be formed in a hollow cylindrical shape to cover the outer circumferential surface of the ball screw510. The ball nut520has an inner circumferential surface which is spaced apart by a predetermined distance from the outer circumferential surface of the ball screw510while facing the outer circumferential surface of the ball screw510. When the ball screw510is rotated, the ball nut520is linearly reciprocated from front to rear in the longitudinal direction of the ball screw510by the cyclic movement of the rolling body530which will be described below. The ball nut520has a groove formed on the inner circumferential surface thereof, such that the other half of the circumference of the rolling body530to be described below is seated in the groove. Such a groove is extended helically in the longitudinal direction of the ball nut520, and provides the cyclic path of the rolling body530.

The rolling body530is provided between the ball screw510and the ball nut520, and has both sides that come into rolling contact with the ball screw510and the ball nut520, respectively. The rolling body530in accordance with the embodiment of the present disclosure is formed in substantially a spherical shape, and installed between the ball screw510and the ball nut520. The entire circumference of the rolling body530comes into rolling contact with the grooves formed on the outer circumferential surface of the ball screw510and the inner circumferential surface of the ball nut520. The rolling body530is cyclically moved along the grooves when the ball screw510is rotated, and converts the rotational motion of the ball screw510into the linear reciprocation of the ball nut520.

The piston member540is linearly reciprocated with the ball nut520, and presses or releases the pad part20depending on the moving direction. The piston member540in accordance with the embodiment of the present disclosure is slidably installed in the cylinder part13. The piston member540has a rear end coupled to the front end of the ball nut520, and is linearly reciprocated in the longitudinal direction of the cylinder part13with the ball nut520. As the ball nut520is moved forward, the front end of the piston member540is brought into contact with the pad part20, and presses the pad part20toward the brake disk. As the ball nut520is moved backward, the piston member540is separated from the pad part20and releases the pad part20.

The parking gear part600is rotated with the transfer gear part400. More specifically, the parking gear part600may be connected to the output shaft of the first driver200, and rotated at the same angular velocity as the first transfer gear part410. Thus, the parking gear part600may reduce the magnitude of a load applied to the constraint part700which will be described below, compared to when the parking gear part600is connected to the second or third transfer gear part420or430having a rotational force boosted by a gear ratio. The parking gear part600in accordance with the embodiment of the present disclosure is fitted onto an end of the output shaft of the first driver200, and rotated with the first transfer gear part410. The central axis of the parking gear part600is disposed coaxially with the output shaft of the first driver200. The parking gear part600may have a polygonal cross-section. Thus, when brought into contact with the constraint part700which will be described, the parking gear part600may be locked and coupled to the constraint part700and thus prevented from rotating relative to the constraint part700.FIG.2illustrates that the parking gear part600has a hexagonal cross-section. However, the parking gear part600is not limited thereto, but may be changed in design in various shapes such as a rectangular or octagonal shape.

The constraint part700is moved forward or backward in connection with the driving force of the second driver300. During parking braking, the constraint part700is moved toward one side, i.e. the parking gear part600by the driving force of the second driver300, and constrains the rotation of the parking gear part600. Thus, although the operation of the first driver200is stopped during parking braking, the constraint part700may prevent a loss in braking force, which occurs when the piston part500is randomly separated from the pad part20.

FIG.4is an expanded view schematically illustrating the configuration of the constraint part in accordance with the embodiment of the present disclosure, andFIG.5is a front view schematically illustrating the configuration of the constraint part in accordance with the embodiment of the present disclosure.

Referring toFIGS.1to5, the constraint part700in accordance with the embodiment of the present disclosure includes a body part710, a constraint member720, and a guide part730.

The body part710is disposed between the second driver300and the parking gear part600. The body part710receives a driving force generated by the second driver300through the locking part800which will be described below, and linearly reciprocates between the second driver300and the parking gear part600. The body part710in accordance with the embodiment of the present disclosure is formed in substantially a rod shape, and disposed between the second driver300and the parking gear part600. The longitudinal direction of the body part710is set in parallel to the output shaft of the second driver300.

The constraint member720is extended from the body part710. As the body part710is moved by a predetermined distance or more toward the parking gear part600, the constraint member720is brought into surface contact with the parking gear part600, thereby constraining the rotation of the parking gear part600.

The constraint member720in accordance with the embodiment of the present disclosure includes a first constraint member721and a second constraint member722.

The first constraint member721is extended from the body part710. As the body part710is moved by a predetermined distance or more toward the parking gear part600, the first constraint member721is brought into contact with one surface of the parking gear part600.

The first constraint member721in accordance with the embodiment of the present disclosure may be formed in the shape of a rod which is bent and extended from the front end of the body part710toward the parking gear part600. As the body part710is moved by a predetermined distance or more toward the parking gear part600, the inner surface of the first constraint member721is brought into contact with an outer surface of the parking gear part600. In this case, since the parking gear part600has a polygonal cross-section, the inner surface of the first constraint member721is brought into surface contact with any one surface (bottom surface inFIG.3) of the outer surfaces of the parking gear part600.

The second constraint member722is extended from the body part710, and spaced apart by a predetermined distance from the first constraint member721while facing the first constraint member721. As the body part710is moved by a predetermined distance or more toward the parking gear part600, the second constraint member722is brought into contact with another outer surface of the parking gear part600.

The second constraint member722in accordance with the embodiment of the present disclosure may be formed in the shape of a rod which is bent and extended from the front end of the body part710toward the parking gear part600. The inner surface of the second constraint member722is disposed in parallel to the inner surface of the first constraint member721, while facing the inner surface of the first constraint member721. The inner surface of the second constraint member722is spaced apart, by the width of the parking gear part600, from the inner surface of the first constraint member721. Therefore, the space into which the parking gear part600may be inserted may be provided between the inner surfaces of the first and second constraint members721and722.

As the body part710is moved by a predetermined distance or more toward the parking gear part600, the inner surface of the second constraint member722is brought into contact with an outer surface of the parking gear part600. Since the parking gear part600has a polygonal cross-section, the inner surface of the second constraint member722is brought into surface contact with a surface (top surface inFIG.3) parallel to the outer surface of the parking gear part600brought into contact with the first constraint member721. Thus, the second constraint member722may be brought into surface contact with the parking gear part600at two surfaces with the first constraint member721, thereby more stably constraining the rotation of the parking gear part600.

The guide part730abuts on the constraint member720, and guides the movement of the body part710. The guide part730in accordance with the embodiment of the present disclosure may be formed in the shape of a pair of plates which are extended from the housing100and have inner surfaces spaced apart from each other while facing each other, or a hollow pipe fixed to the housing100. The guide part730is extended in a longitudinal direction thereof, corresponding to the longitudinal direction of the body part710. Both inner surfaces of the guide part730are disposed in parallel to the outer surfaces of the first and second constraint members721and722, while facing the outer surfaces of the first and second constraint members721and722. Both inner surfaces of the guide part730abut on the outer surfaces of the first and second constraint members721and722, respectively, and slidably support the first and second constraint members721and722. Thus, the guide part730may guide the body part710to linearly reciprocate along a preset path.

The locking part800is provided between the second driver300and the constraint part700, and transfers the driving force generated by the second driver300to the constraint part700. The locking part800restricts from the output shaft of the second driver300from rotating in the reverse direction such that the constraint part700is moved to the other side, during parking braking. That is, the locking part800functions as a medium that transfers power between the second driver300and the constraint part700. Simultaneously, when the operation of the second driver300is stopped, the locking part800functions to restrict the output shaft of the second driver300from randomly rotating in the reverse direction, through a self locking operation.

FIG.6is an exploded perspective view schematically illustrating the configuration of the locking part in accordance with the embodiment of the present disclosure.

Referring toFIGS.4to6, the locking part800in accordance with the embodiment of the present disclosure includes a first locking member810and a second locking member820.

The first locking member810is connected to and rotated by the output shaft of the second driver300. The first locking member810in accordance with the embodiment of the present disclosure may be formed in the shape of a worm gear which has gear teeth formed helically on the outer circumferential surface thereof and extended in the longitudinal direction thereof. The central axis of the first locking member810is located coaxially with the output shaft of the second driver300. The first locking member810is connected to the output shaft of the second driver300, and rotated on the central axis thereof with the output shaft of the second driver300, during the operation of the second driver300.

The second locking member820protrudes from the constraint part700, and is engaged with the first locking member810so as to convert a rotational motion of the first locking member810into a linear motion of the constraint part700. Through a self locking force which is generated when the second locking member820is engaged with the first locking member810, the second locking member820constrains the rotation of the output shaft of the second driver300, when the operation of the second driver300is stopped. The second locking member820in accordance with the embodiment of the present disclosure may be formed in the shape of a rack gear which protrudes from the rear bottom surface of the body part710, and is engaged and coupled with the first locking member810.

FIG.7is a cross-sectional view schematically illustrating the configuration of a locking part in accordance with another embodiment of the present disclosure.

Referring toFIG.7, any one of the first and second locking members810and820in accordance with the another embodiment of the present disclosure may be provided in the shape of a bolt screw, and the other of the first and second locking members810and820may be provided in the shape of a nut screw.FIG.7illustrates that the first locking member810is provided in the shape of a bolt screw, and the second locking member820is provided in the shape of a nut screw. On the contrary, however, the first locking member810may be provided in the shape of a nut screw, and the second locking member820may be provided in the shape of a bolt screw.

The adjuster900is connected to the constraint part700, and limits the moving range of the constraint part700toward the parking gear part600. Thus, the adjuster900may prevent damage to the parts, which may be caused by a collision between the constraint part700and the parking gear part600during parking braking.

FIG.8is a block diagram schematically illustrating the configuration of the adjuster in accordance with the embodiment of the present disclosure.

Referring toFIGS.4and8, the adjuster900in accordance with the embodiment of the present disclosure includes a load application part910, a measurement part920, and the control part930.

The load application part910applies a load to the constraint part700in the opposite direction of the moving direction of the constraint part700in proportion to the moving distance of the constraint part700. That is, as the constraint part700approaches the parking gear part600, the load application part910may linearly increase the magnitude of a load applied to the second driver300, thereby inducing an increase in current value of the second driver300. The load application part910in accordance with the embodiment of the present disclosure may be formed in the shape of a coil spring which can be elastically deformed in a direction parallel to the moving direction of the constraint part700. Both sides of the load application part910may be fixed to and supported by the rear end of the body part710and the inner surface of the housing100, respectively. In this case, the load application part910is extended in the longitudinal direction thereof as the constraint part700is moved toward the parking gear part600, and applies a tensile force to the constraint part700.

FIG.9is a front view schematically illustrating that a load application part in accordance with another embodiment is installed.

Referring toFIG.9, the load application part910in accordance with the another embodiment of the present disclosure may have both sides fixed to and supported by the front end of the constraint member720and the inner surface of the housing100, respectively. More specifically, the load application part910may be provided as a pair of load application parts whose one sides are fixed to the front end of the first constraint member721and the front end of the second constraint member722, respectively. In this case, the load application part910applies a pressing force to the constraint part700while compressed in the longitudinal direction thereof as the constraint part700is moved toward the parking gear part600. The installation positions of the load application part910are not limited to those illustrated inFIGS.4and9, but can be variously changed in design as long as the load application part910can apply a load to the constraint part700in the opposite direction of the moving direction of the constraint part700in proportion to the moving distance of the constraint part700.

The measurement part920measures the current value of the second driver300. The measurement part920in accordance with the embodiment of the present disclosure may be connected to the second driver300, and exemplified as various types of current sensors which can measure the magnitude of a current flowing through the second driver300during the operation of the second driver300.

The control part930may be an electric circuitry (e.g., a processor, an ASIC (Application Specific Integrated Circuit), a DSP (Digital Signal Processor), a DSPD (Digital Signal Processing Device), a PLD (Programmable Logic Device), a FPGA (Field Programmable Gate Array), a microcontroller, microprocessor) that executes instructions of software which thereby performs various functions described hereinafter. The control part930stops the operation of the second driver300when the current value of the second driver300, measured by the measurement part920, exceeds a preset magnitude. The present current value at which the control part930stops the operation of the second driver300can be changed in design to various values in the range of current values measured by the measurement part920at the point of time that the first constraint member721and the second constraint member722are brought into surface contact with the parking gear part600. Thus, the control part930may prevent the constraint member720from excessively moving toward the parking gear part600and colliding with the parking gear part600or prevent an unnecessary load from being applied to the second driver300. The control part930in accordance with the embodiment of the present disclosure may include a communication unit configured to receive data on the current value measured by the measurement part920through a wired or wireless method, and an electronic control unit configured to compare the current value measured by the measurement part920to the preset current value and adjust the operation state of the second driver300.

Hereafter, an operation process of the brake apparatus for a vehicle in accordance with the embodiment of the present disclosure will be described in detail.

FIGS.10and11are operation diagrams schematically illustrating an operation process of the brake apparatus for a vehicle in accordance with the embodiment of the present disclosure.

Referring toFIGS.10and11, the first driver200generates a driving force to rotate the transfer gear part400, during a parking braking operation of the vehicle.

The driving force generated by the first driver200is transferred to the ball screw510of the piston part500after sequentially passed through the first transfer gear part410, the second transfer gear part420, and the third transfer gear part430.

As the ball screw510is rotated on the central axis thereof, the ball nut520is moved forward through the cyclic movement of the rolling body530.

The piston member540is moved forward with the ball nut520and brought into contact with the pad part20, and generates a parking braking force by pressing the pad part20toward the brake disk.

Then, as a sufficient parking braking force is generated, the second driver300generates a driving force, and the constraint part700is moved toward the parking gear part600in connection with the driving force of the second driver300.

More specifically, as the output shaft of the second driver300is rotated, the first locking member810is also rotated on the central axis thereof with the output shaft of the second driver300.

The second locking member820engaged with the first locking member810converts the rotational motion of the first locking member810into a linear motion, and moves the body part710toward the parking gear part600.

As the body part710is moved by a predetermined distance or more toward the parking gear part600, the inner surfaces of the first and second constraint members721and722are brought into contact with the outer surfaces of the parking gear part600.

The load application part910applies a load to the constraint part700in the opposite direction of the moving direction of the constraint part700, i.e. the direction in which the constraint part700is away from the parking gear part600, in proportion to the moving distance of the constraint part700.

Thus, as the constraint part700approaches the parking gear part600, the magnitude of the load applied to the second driver300linearly increases. Such an increase in the load raises the current value of the second driver300.

The control part930stops the operation of the second driver300, as the current value of the second driver300, measured by the measurement part920, exceeds the preset magnitude.

When the operation of the second driver300is stopped, the first locking member810and the second locking member820constrain the reverse rotation of the second driver300by using a self locking force generated by the frictional force therebetween.

Therefore, the constraint member720may not collide with the parking gear part600, but maintain the surface contact with the parking gear part600.

Then, the generation of the driving force by the first driver200is stopped, and a rotational force acting in the opposite direction of the rotational force transferred during parking braking is transferred to the parking gear part600by a reaction force generated between the piston member540and the pad part20.

The constraint member720offsets such a rotational force by using a locking coupling force with the parking gear part600, thereby constraining the rotation of the parking gear part600.

As the rotation of the parking gear part600is constrained, the rotations of the output shaft of the first driver200and the transfer gear part400may also be constrained to maintain the parking braking state.