Abstract: Disclosed are a parking actuator and an electromechanical brake including the same. The parking actuator, which is connected to a brake actuator that performs braking of a vehicle, includes a parking gear connected to the brake actuator to be rotatable together, a parking lever having one side hingedly fixed and the other side engaged with the parking gear, a parking motor provided to generate power, a power conversion unit including a spindle member rotating by receiving a rotational driving force of the parking motor and a nut member screwed to the spindle member to move forward or backward, and a pressing unit installed on the nut member to press the parking lever by the nut member moved forward or backward.

Abstract: A wheel hub drive for a vehicle, having: a drive housing; a hub output mounted rotatably relative to the drive housing; a wheel brake for the hub output that has a stationary and a rotating braking partner, the stationary braking partner being connected to the drive housing for conjoint rotation therewith, and the rotating braking partner being connected to the hub output. The two braking partners are frictionally connected in a braking state, A parking brake for fixing the hub output relative to the drive housing. The stationary and rotating brake partners being movable relative to one another when the parking brake is actuated and being frictionally connected to one another in a parked state. The has a ramp mechanism for converting a rotary movement into a linear movement in order to transfer a parking force to the stationary and/or rotating brake partner.

Abstract: In an electric parking brake device configured in such a way that a parking brake state resulting from pulling of a brake cable is released by loosening the brake cable, the brake cable is formed by twisting together a plurality of wires in such a way as to generate a twisting force in a fixed direction when pulled, and the direction in which the twisting force generated by the brake cable in a pulled state acts on a screw shaft is set to be the same direction as the direction in which a nut is rotated to loosen the brake cable. This makes it possible to reduce an operating sound and to reduce wear of members constituting a rotation restricting device.

Abstract: In some examples, a brake assembly includes an actuator assembly configured to cause the translation of a piston to compress a disc stack. The actuator assembly is configured to generate a first torque around a motor axis using a motor and generate a second torque from the first torque using a harmonic drive. The actuator assembly may include a gear set configured to cause a linear actuator to translate the piston using the second torque. In some examples, the actuator is configured to translate the piston along a compression axis different from the motor axis.

Abstract: A longitudinal end of the nut has: at least one blocking face forming a means for blocking a rotation of the nut along a longitudinal axis of the nut, and at least one transmission face forming a means for transmitting a force directed along the axis. The blocking face or at least one of the blocking faces and the transmission face or at least one of the transmission faces have at least one common edge, and the blocking face or at least one of the blocking faces is concave.

Abstract: A motor including a support unit, a first rotating part, a second rotating part, a rotor and a stator is disclosed. The support unit includes an axle and a bearing coupled with the axle. The first rotating part is fit around the axle and is coupled with the bearing. The second rotating part is coupled with the first rotating part. The rotor is coupled with the second rotating part. The stator is connected to the support unit.

Abstract: An electric motor-driven brake apparatus has speed reduction mechanisms transmitting rotational force of an electric motor, a ball screw mechanism converting rotational force of the speed reduction mechanisms into a thrust, a piston propelled by the ball screw mechanism, and a caliper movably supporting the piston. The ball screw mechanism has a base nut non-rotatably supported relative to the caliper. The ball screw mechanism further has a push rod receiving rotational force from the speed reduction mechanisms. The push rod is movable relative to the base nut in the axial direction of the push rod. Consequently, it is possible to reduce the axial length of the cylinder portion of the caliper body, and hence possible to attain a size reduction. Accordingly, it is possible to improve the mountability of the electric motor-driven brake apparatus 1 onto vehicles.

Abstract: A parking brake apparatus for a vehicle includes a pair of pressing units receiving power from a driving unit, and pressing a brake pad; and a load transmission unit installed between the pair of pressing units, connected to each of the pair of pressing units, and transmitting a pressing load of any one of the pair of pressing units to the other pressing unit, wherein the load transmission unit comprises a pair of ring gear sections, and the pair of ring gear sections are meshed with each other.

Abstract: A brake system that includes a brake caliper, a motor, and a torque distributing assembly configured to distribute torque from the motor to a first brake piston and/or to a second brake piston. The torque distributing assembly includes a gear set that includes gears that are configured to rotate about an axis. One of the first brake piston and the second brake piston is configured to move along the same axis during a brake apply or a brake release.

Abstract: Disk brake systems including disk brake systems that are motor actuated are discussed. As a part of these brake systems, various piston assemblies are also discussed, including piston assemblies that include a piston; a spindle; a ball screw assembly within the piston, wherein the spindle forms a lead screw with an interior surface of the ball screw assembly and the ball screw assembly and the lead screw are configured for the lead screw to move linearly followed by the ball screw assembly moving linearly to move the piston upon application of the brake. Additional embodiments of piston assemblies that include ball ramp actuators are also discussed.

Abstract: An electromechanical brake caliper comprising a caliper body comprising a housing containing a piston and a member for driving a mechanism for moving the piston. The driving member comprises a threaded body and a head comprising a face supported on a bottom of the housing, the supported face being provided with a non-friction coating.

Abstract: Disclosed herein is an electronic disc brake. The electronic disc brake according to one embodiment of the present disclosure includes a disc configured to be rotated with a wheel, a caliper housing configured to operate pad plates installed at both sides of the disc, and an actuator including a piston provided in the caliper housing and configured to press the pad plates to bring the pad plates into contact with the disc, a spindle rotatably installed in the caliper housing to move the piston forward and backward, a motor configured to rotate the spindle, and a speed reduction apparatus configured to transmit a rotational force of the motor to the spindle, wherein the speed reduction apparatus includes a power connecting unit connected to the motor, a bracket provide above the motor and configured to support the power connecting unit, and a speed reduction gear unit configured to sequentially connect the power connecting unit and the spindle.

Abstract: A brake apparatus for vehicle may include: a pair of pressurization units configured to receive driving force from a drive unit and pressurize a brake pad; and a load transmitting unit installed between the pair of pressurization units and coupled to the pair of pressurization units to transmit a pressurizing load of any one of the pair of pressurization units to another one of the pair of pressurization units.

Abstract: A parking brake mechanism achieves a parking brake function using a friction material operation mechanism driven by a main brake motor. The parking brake mechanism includes a parking brake motor provided coaxially with one of rotational shafts transmitting a torque from the main brake motor to the friction material operation mechanism. A linear motion mechanism moves a rotor of the motor and an engaging mechanism. The engaging mechanism includes a rotor-side engaging portion and a housing-side engaging portion engaging with each other when the rotor is moved linearly to a predetermined position by the linear motion mechanism. Engagement of the engaging mechanism achieves a pressing force holding function of holding an angle of the rotational shaft against a reaction force of the pressing force of a friction material.

Abstract: A brake system comprising: (a) a rotor; and (b) two or more brake assemblies in communication with the rotor, the two or more brake assemblies each including: (i) a caliper; (ii) a piston assembly located within the caliper; and (iii) a motor gear unit in communication with the caliper and configured to move the piston assembly to create a braking force; wherein one or more both of the piston assemblies are moved during a service brake apply or release; and wherein one or both of the piston assemblies are moved during a parking brake apply or release.

Abstract: In a method for controlling a parking brake in a vehicle, in order to set a clearance between the brake pad and the brake disk, a supply voltage is first applied to an electric motor, after which the supply voltage is switched off before the brake pad comes into contact with the brake disk.

Abstract: A brake system including a motor; a rotary to linear stage mechanism; and a torque locking mechanism. The rotary to linear stage mechanism in communication with the motor. The torque locking mechanism in communication with the motor. The torque locking mechanism comprises an electromagnet and a permanent magnet. During a brake apply the motor is adapted to move the rotary to linear stage mechanism so that at least one brake pad or at least one brake shoe is moved against a surface to create a clamp force. The electromagnet and the permanent magnet are adapted to cooperate to maintain the created clamp force.

Abstract: The electric brake device includes an electric motor, a brake rotor, a friction pad, a conversion mechanism, a braking force command section, a braking force estimation section, a controller, and a power supply device. The controller includes: a power determination section to determine whether an amount of remaining power that can be supplied from a power supply device to the electric motor has become equal to or less than a determined value; and a residual pressure cancellation section to cancel a residual pressure of a braking force by driving the electric motor in a direction opposite to a brake pressing direction such that an estimated value of the braking force obtained by the braking force estimation section becomes equal to or less than a set value, when the power determination section determines that the amount of remaining power has become equal to or less than the determined value.

Abstract: In a differential limiting device for a vehicle, when rotary motion of an electric motor is converted by a screw mechanism into linear motion of a nut member in a direction of a first axis C1 of a side gear shaft, and a piston mounted on the nut member is moved in a direction opposite to a direction to depress frictional engagement elements, the piston and a clutch drum are relatively non-rotatably engaged. Therefore, differential rotation of a pair of side gears is mechanically limited. Thus, rotation of one electric motor makes it possible to generate differential limiting torque for limiting differential rotation of the pair of side gears in a rear-wheel differential device.

Abstract: It is an object of the present invention to improve seal performance in an electric linear motion actuator configured to linearly drive a linear motion member due to the rotation of a rotary shaft. The linear motion member is constituted by a cylindrical member slidably fitted in a housing, and a pressing member coupled to the distal end portion of the cylindrical member so as to close the opening of the distal end of the cylindrical member. The portion of the pressing member coupled to the cylindrical member is located inside of a boot sealing the space between the distal end portion of the housing and the distal end portion of the linear motion member.

Abstract: A setting device, particularly a motor vehicle parking brake includes a remotely-operated drive, a hollow shaft, a spindle shaft and an elastic element. The hollow shaft is driven by the remotely-operated drive so that the hollow shaft rotates. The spindle shaft moves relative to the hollow shaft within the hollow shaft due to the rotation of the hollow shaft. The spindle shaft is connected to a brake cable such that the spindle shaft can apply and release the brake as it moves in different directions within the hollow shaft. The elastic element is loaded due to movement of the hollow shaft as the hollow shaft is driven in an attempt to release the brake while the brake cable is blocked.

Abstract: The present disclosure provides an actuator assembly comprising a ballnut having a helical track, an actuator drive unit (“ADU”) housing having an ADU track, and a ballscrew. In various embodiments, the ballscrew comprises a first translation bearing track, wherein the helical track and the first translation bearing track form a first translation bearing raceway in which a plurality of first translation bearing balls having a first diameter are disposed, and a second translation bearing track, wherein the helical track and the second translation bearing track form a second translation bearing raceway in which a plurality of second translation bearing balls having a second diameter are disposed, wherein the first diameter and the second diameter are not equal.

Abstract: Rotational motion of a shaft member rotationally driven by a motor is converted by a screw member into translational motion of a pressing member. An outer periphery of a cap member is brought into slide contact with a first cylindrical part of the pressing member so that the cap member is relatively movable in an axial direction of the pressing member and is relatively unrotatable about its axis. An inner periphery of the cap member is brought into slide contact with a second cylindrical part of the shaft member so that the cap member is relatively movable in an axial direction of the shaft member and is relatively rotatable about its axis. The first cylindrical part, the second cylindrical part, and the cap member partition a storage chamber connected to one end of the screw member, and a lubricant for lubricating the screw member is filled inside the storage chamber.

Abstract: An arrangement contains a brake piston for operating at least one disk brake pad and a nut-and-screw unit for producing an axial thrust, from the rear to the front, of the piston containing a nut arranged in the piston's interior, and secured thereto to prevent rotation, and mounted therein to slide axially, whose front axial end face interacts with an internal section facing the piston's front wall to push the piston axially towards the front when the screw is rotatably driven in the unscrewing direction, and the screw containing a front section screwed into the nut, an intermediate radial flange and a rear section, wherein the piston screw contain centering elements that interact with one another when the screw is in a predetermined front axial mounting position in relation to the piston in order to center the rear section of the screw radially in relation to the piston.

Abstract: A park brake system for an electric motor actuator is provided. The system may comprise a wrap spring that may rotatably engage the shaft. In this regard, the system may be configured to exert a radial force on a shaft of the electric motor actuator to lock the actuator. Moreover, in various embodiments, the system may be bi-stable.

Abstract: A disc brake for a commercial vehicle includes a brake caliper which extends over a brake disc, a brake application device which is arranged in the brake caliper for pressing brake pads against the brake disc, and at least one adjustment spindle which is rotatably mounted in a bridge via a threaded coupling. A wear adjusting device is positioned in the brake caliper by which a wear-induced change of the clearance between the brake pad and the brake disc can be substantially compensated for via an axial movement of the adjusting spindle. The disc brake is designed such that the adjusting spindle has at least one axial groove on an outer side, the length of the groove being limited in the direction of the brake application device. A stop, which is axially fixed relative to the bridge, engages into the axial groove in a relatively displaceable manner.

Abstract: An axle assembly having two hubs, each for connection to a wheel, a housing for differential gears and a mounting arrangement for a braking system for braking a connected wheel. The housing has a depression formed therein. The depression is configured so as to accommodate: (a) when the mounting arrangement has a drum brake mounted thereon, movement of a slack adjuster of the drum brake in a direction away from one of the hubs nearest the drum brake so as to allow detachment of the slack adjuster; and/or (b) when the mounting arrangement has a disc brake mounted thereon, an air chamber of the braking system, wherein the air chamber is capable of being partially accommodated within the depression.

Abstract: Disclosed herein is a electric caliper brake with a parking function. The electric caliper brake includes a caliper submodule to apply pressure to a piston to press the disc by converting rotational motion into rectilinear motion through the received rotation power, an actuator submodule to produce braking force to perform the braking function and parking function, and a self-locking module to transfer the braking force by connecting the caliper submodule to the actuator submodule.

Abstract: An electro-mechanical brake assembly comprising a brake disk stack having a center axis; and a plurality electro-mechanical actuators for applying braking pressure to the brake disk stack. The actuators are circumferentially arranged around the center axis, and each actuator includes a housing, a linearly movable ram, a screw for linearly moving the ram, a nut mounted for rotation in the housing and operatively engaged with the screw such that rotation of the nut effects linear movement of the screw for urging the ram into forceful engagement with the brake disk stack, an electric motor for rotating the nut, and an anti-rotation device for preventing rotation of the screw relative to the housing when the nut is rotated to effect linear movement of the screw. The foregoing arrangement provides for greater stroke than prior art actuators without sacrificing durability and performance.

Abstract: The invention relates to a disc brake for a motor vehicle having a housing, a piston which is movable in the housing along a longitudinal axis and a nut-spindle arrangement which acts on the piston or can be brought into engagement with this, wherein the nut-spindle arrangement is arranged in the housing and is workingly supported via a bearing arrangement on a support surface of the housing. In order to increase the service life of the bearing arrangement, the support surface is formed by a defined contact surface which projects with respect to an adjacent housing region and against which the bearing arrangement bears.

Abstract: A method of determining a status of a brake actuator of a brake assembly includes sensing one or more activations of the brake actuator, storing the one or more activations in a computer memory, sensing a depth of a parameter of the one or more activations, storing the depth of the parameter of the one or more activations in the computer memory, and determining a status of the brake actuator based on the depth of the parameter of the one or more activations.

Abstract: A caliper parking brake including: caliper housing having one end on which a cylinder is formed and the other end on which a fork is formed to face the cylinder; brake force input terminal rotatably mounted on an end of the cylinder by a parking cable; brake force switching terminal installed within the cylinder on a common axis so as to rotate together with the brake force input terminal; brake force output terminal directly connected to the brake force switching terminal on a common axis; and a brake terminal that is disposed between the fork and the brake force output terminal and stops rotation of a brake disc using the brake force output by the brake force output terminal, wherein the brake force output terminal compensates for abrasion that occurs in the fork and a frictional pad of the piston by moving an initial position of the piston forward.

Abstract: A brake actuator has a motor that provides input rotation in first and second directions. A reducer couples to the motor and reduces the input rotation into an output rotation to be applied to a brake screw of a progressive cavity pump drive. A sensor measures rotational speed of the drive shaft. In manual operation, an operator can view an indication of the rotational speed and can manually operate the motor accordingly to control rotation of the shaft. In automated operation, a controller automatically controls the motor based on the rotational speed measured by the sensor. The controller can also use a torque sensor to detect the torque applied to the brake screw, a displacement sensor to detect displacement of the brake screw, and/or a current sensor to detect the current consumption of the motor.

Abstract: An electric braking apparatus is provided and includes an electromechanical actuator (EMA) configured to apply an axial load on a brake stack and a damping end-stop. The damping end-stop is configured to transmit torque into the EMA and includes an end cap, a screw disposed such that a longitudinal axis about which the screw is rotatable extends through the end cap, a nut threadably engaged with the screw and movable with the end cap relative to the screw with screw rotation and a spring element anchored on the end cap to resist the screw rotation beyond a predefined position.

Abstract: An aircraft brake system electromechanical actuator is provided. The actuator is configured with features that allow the electric motor to be a line replaceable unit. One such feature is a foreign-object-damage shield that inhibits dust, debris, and/or other particulate contaminants from entering the electromechanical actuator during electric motor removal and replacement.

Abstract: A brake includes a brake shoe, an actuating element for pressing the brake shoe against a brake disc, and at least one lever disposed such that it increases the braking force applied by the brake shoe to the brake disc by deflecting a tangential force acting on the brake shoe during braking. The actuating element comprises at least one brake disc side part, an actuator side part, and a coupling part disposed between the brake disc side part and the actuator side part, wherein the coupling part can be pivoted relative to the brake disc side part and/or the actuator side part.

Abstract: An electronic brake device for use with a wheel of a bicycle provides, among other features, wireless, remote disengagement of a wheel brake. A brake coupled to a housing is movable between an engaged position and a disengaged position. The housing includes a receiver configured to receive a command signal, and a processor operative to identify the received command signal. If the command signal is identified as a first command signal, the processor outputs a first control signal. An electric motor is operatively coupled to the brake to selectively move the brake from the engaged position in which the wheel of the bicycle is being braked to the disengaged position in which the wheel of the bicycle is free of any brake contact in response to the first control signal. Measured movement of the brakes between fully braked or fully disengaged positions are possible in the disclosed arrangement.

Abstract: A combined electromechanical vehicle brake has a hydraulically activated operating brake and an electromechanically activated parking brake apparatus. A hydraulic operating pressure chamber in a brake housing is delimited by a brake piston that can be loaded by hydraulic pressure to carry out operating braking actions. The brake piston can be activated along a longitudinal piston axis to achieve a braking effect. The parking brake apparatus acts upon the brake piston by a gear unit because the gear unit converts the rotational movement of an electromechanical actuator into a translational movement, causing the brake piston to be activated to carry out parking brake processes and remain in the activated position. The gear unit has a threaded spindle and a threaded nut that contact one another via a plurality of rolling elements. A spring element allows the rolling elements to slip when the gear unit is activated in the unloaded state.

Abstract: An electromechanical brake includes a pair of pad plates provided with a friction pad to apply pressure to a disc, a carrier to support the pad plates, a caliper housing supported movably back and forth on the carrier to apply pressure to the pad plates; and a presser to apply pressure to the pad plates. The presser includes a pressing member to apply pressure to one of the pad plates, a driving motor to operate the pressing member, a gear assembly disposed between the driving motor and the pressing member to transfer rotational force of the driving motor to the pressing member. The gear assembly includes an input shaft connected to a motor, an external gear coupled to the input shaft such that the external gear eccentrically rotates, and a stationary internal gear and a rotational internal gear meshed with the external gear such that the external gear revolves, while rotating. The rotational internal gear includes an output shaft in the center thereof and the output shaft is connected to the pressing member.

Abstract: Disclosed herein are a decelerator in which a first deceleration unit of a planet gear type is provided inside a second deceleration unit of a cycloid type so as to apply eccentric rotation force to the second deceleration unit, and a motor brake with the same. The decelerator restricts an increase in the axial thickness of a motor and achieves an effectively increased deceleration ratio, and the motor brake equipped with the decelerator restricts an increase of the overall length thereof due to the decelerator, achieving enhanced space utility.

Abstract: A brake caliper of a disk brake, includes a housing having a bore hole, in which an axially displaceable piston is arranged, and a shaft for actuation, which is supported so that it is rotatable and axially displaceable in the housing, and an adjusting device having a spindle to compensate for brake lining wear, an axial bearing being provided between the spindle and the shaft. For an improved wear resistance, it is proposed according to the invention that the axial bearing be integrally formed from a homogeneous material matrix.

Abstract: A brake apparatus for restraining rotation of a wheel of a vehicle by application of a brake that is to be activated for causing a friction member, to be pressed against a brake rotor, through a piston that is movable in an axial direction of the piston. The brake apparatus includes: (a) a power drive device; (b) a driven member that is to be moved, by the power drive device, relative to the piston in the axial direction; and (c) an engaging portion that is provided in one of the driven member and the piston, such that the piston is held in engagement with the driven member through the engaging portion. The engaging portion is disposed such that, during release of the application of the brake, the piston is movable rearwardly while being held in engagement with the driven member through the engaging portion.

Abstract: A ball-and-ramp mechanism of a thrust generator includes a rotary ramp member and a rectilinear ramp member, each having a plurality of sloped grooves sloped along a circumferential direction and having an arcuate diametrical cross-section, and a spherical member interposed between the sloped grooves of the ramp members to transmit force from the rotary ramp member to the rectilinear ramp member. Each of the sloped grooves has regions varying in the curvature radius of the diametrical cross-section in a track area where the spherical member contacts the sloped groove. Accordingly, it is possible to improve the durability of the rotary ramp member and the rectilinear ramp member.

Abstract: A motor driven brake system including a parking brake, in particular, a motor driven parking brake system in which a parking brake is implemented using a compact motor and a plurality of disks and friction pads mutually fractionized or released by the compact motor, so that it is possible to reduce operating noise of a solenoid as compared with that of an existing solenoid and to prevent a phenomenon that although a power failure of the compact motor occurs during driving, the braking power of the motor driven brake system is not released.

Abstract: In a method for controlling an electronic parking brake system and an electronic parking brake system, a travel-optimized method is used to achieve the released state of the parking brake system. When the parking brake is applied, travel-force values are detected and a plausibility check is run, the values being used to arrive at a first optimized position when the brake is released. If the residual force applied to the brake exceeds a threshold value, the parking brake is released even more until the value remains just under the threshold value or until a maximum defined release travel is achieved.

Abstract: A disc brake is arrangeable in a space that accommodates a brake caliper having an application device. The brake caliper is held slidably with guiding elements on a brake carrier, which is fastened with screws to an axle connection at the vehicle. The caliper straddles a brake disc, against which brake pads can be pressed on either side while braking. At least the brake pad on the application side is mounted movably in the direction of the brake disc in a pad shaft of the brake carrier. A device for the visual identification of the wear of a brake pad and/or brake disc is constructed so that for identifying wear, a pointer element, extending in the opposite direction to the brake disc, is connected at least at one screw.

Abstract: A brake mechanism is constituted to have: an electromotive actuator which suppresses a rotation of a disk by moving a first pad toward a second pad to sandwich and press the disk between the first pad and the second pad; a pressing force setting section outputting a set signal to set a pressing force of the pad to the disk; a plurality of piezoelectric elements provided at different places from each other in the first pad or the second pad, the plurality of piezoelectric elements detecting a stress of the pad; a signal processing part which processes electric signals obtained from the plurality of piezoelectric elements and generates a detection signal of a pressing force, the detection signal corresponding to a pressing force of the pad to the disk; and a computing part which obtains a deviation between the set signal and the detection signal, computes an operation signal of the electromotive actuator based on the deviation, and then outputs the operation signal.

Abstract: An arrangement contains a brake piston for operating at least one disk brake pad and a nut-and-screw unit for producing an axial thrust, from the rear to the front, of the piston containing a nut arranged in the piston's interior, and secured thereto to prevent rotation, and mounted therein to slide axially, whose front axial end face interacts with an internal section facing the piston's front wall to push the piston axially towards the front when the screw is rotatably driven in the unscrewing direction, and the screw containing a front section screwed into the nut, an intermediate radial flange and a rear section, wherein the piston screw contain centering elements that interact with one another when the screw is in a predetermined front axial mounting position in relation to the piston in order to center the rear section of the screw radially in relation to the piston.

Abstract: A stationary shaft supports a fluid-tight rotatable drum which receives an elongated flexible restraining member. The shaft has a threaded portion which receives an actuating nut connected to rotate with the drum through a detent mechanism. Spaced compression springs extend axially between the nut and a stack of interfitting annular brake disks and brake plates, with the disks splined to the shaft and the plates rotatable with the drum. The stack is immersed in an oil-shear cooling fluid that contacts the drum, and the nut and springs are effective to compress the stack with increasing force in response to rotation of the drum for progressively increasing the resistance torque on the drum as the restraining member is pulled from the drum. The detent mechanism limits the compression force on the stack and the tension force on the restraining member while the drum continues to rotate.

Abstract: Disclosed is an electric disc brake capable of reducing noise and vibration while expanding the life span of the product. The electric disc brake includes a caliper housing to press friction pads provided at both sides of a disc against the disc, a cylinder installed in the caliper housing, a piston moving back and forth in the cylinder to press the friction pads, a driving device generating driving force with respect to the piston, and a volume compensation part communicated with the cylinder to compensate for an increment of a volume of the cylinder according to movement of the piston.