Single motor electro wedge brake system using solenoid mechanism for implementing additional functions

The present invention provides an electro wedge brake (EWB) system that implements a main braking function by using power generated by one motor. Further, the electro wedge brake system implements various additional functions such as a function for maintaining a set clearance of a pad, a Fail-Safe function, and an EPB function, by using that the forward movement of a push rod shaft screwed using a NSL (Non-Self Locking) type screw is restrained or released on the basis of ON/OFF control of the solenoid mechanism interlocked with the main braking function motor. Accordingly, since only one motor is used to generate power, it is possible to reduce the number of parts and to simplify the structure.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is based on, and claims priority from, Korean Application Serial Number 10-2007-0062110, filed on Jun. 25, 2007, the disclosure of which is hereby incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention relates to a wedge brake system, and more particularly, to a single motor electro wedge brake system, which uses a solenoid mechanism to implement additional functions.

BACKGROUND OF THE INVENTION

In general, a brake system is used to decelerate, stop, or park a moving vehicle.

A friction brake, which converts kinetic energy into thermal energy by using a frictional force and radiates the thermal energy to the air, is generally used in the brake system. Pads press both sides of a disk, which rotates together with a wheel, with hydraulic pressure, so that the friction brake implements a braking function.

The hydraulic brake implements braking by pressing the pads against the disk using hydraulic pressure. For this reason, the hydraulic brake cannot help having a complicated structure including a master cylinder that is operated by a booster for increasing a force applied to a pedal to generate hydraulic pressure, hydraulic pressure lines connected to a wheel cylinder, and various devices that control and assist the cylinders and lines. Accordingly, improvement in the stability of the hydraulic brake is limited due to the complicated structure and deterioration in the reliability of a braking performance, which is caused by use of hydraulic pressure.

Therefore, an electro wedge brake system has been being developed and applied so as to have a simple structure unlike the hydraulic brake, improve the reliability of a braking performance, implement a parking brake function, improve the responsiveness and performance of an ABS (Anti Brake System), and optimally control an integrated chassis.

The electro wedge brake (EWB) uses the following method when braking. That is, brake pads are pressed against the disk by a wedge assembly that is operated by an actuator, and frictionize the disk so as to implement a braking function.

In this case, even though the EWB uses a motor using a voltage of 12 V, the EWB generates the same braking force as the hydraulic brake. The reason for this is that the EWB implements self-energizing using a wedge phenomenon. That is, as the actuator is driven, the wedge is moved to press the pads and a frictional force between the pad and the disk serves as an additional input force. Even though the power of the motor is small, it is possible to generate a large braking force due to the wedge effect, which is caused by the wedge structure.

In addition, whenever an engine is started, the EWB has a function for compensating a clearance of the pad, that is, a function for moving the wedge assembly toward the pad to adjust a clearance between the pad and the disk, which deviates from a set value due to abrasion, so as to always maintain a set clearance of the pad.

Further, the EWB also has a Fail-Safe function, that is, a function for releasing a braking force applied to the disk to prevent an abnormal operation of a vehicle occurring when a braking force is not released and continuously applied during brake-fail.

In addition, the EWB can implement an EPB (Electric Parking Brake) function.

The EWB implements various additional functions such as a function for maintaining a set clearance of a pad, a Fail-Safe function, and an EPB function in addition to a main braking function. For this reason, the entire structure of the EWB becomes complicated. In particular, since the EWB uses a motor for implementing a braking function and another motor for implementing various additional functions, the EWB requires at least two motors.

Since the EWB uses two motors to separately generate power, the size of the EWB cannot help being increased due to a space for a motor. The increase in size causes limitation in assembling the EWB at the wheel.

SUMMARY OF THE INVENTION

Embodiments of the present invention help overcome the above-mentioned problems and provide an electro wedge brake that implements a main braking function by using power generated from one motor. Further, the electro wedge brake implements various additional functions, such as a function for maintaining a set clearance of a pad, a Fail-Safe function, and an EPB function, by using a solenoid mechanism interlocked with a main braking motor. Accordingly, since the electro wedge brake uses only one motor, the size of the entire electro wedge brake can be reduced to improve the assembly property of the electro wedge brake. In addition, it is possible to reduce the number of parts related to the motion conversion, which are required when a motor is used. Therefore, it is possible to reduce manufacturing cost and weight of the electro wedge brake.

Embodiments of the present invention provide an electro wedge brake that implements a function for maintaining a set clearance of a pad, a Fail-Safe function, and an EPB function by using not a motor but a solenoid mechanism. Accordingly, it is possible to further simplify the structure for converting motion between related parts as compared to when a motor is used. Therefore, it is possible to easily design the electro wedge brake.

A single motor electro wedge brake system, which uses a solenoid mechanism to implement additional functions, includes an electric pedal, an ECU, wedge calipers, wedge actuator assemblies, and housings. The electric pedal is operated by a driver to brake a vehicle. ECU generates control signals by using information measured in the vehicle during braking of the vehicle. Each of the wedge calipers includes inner and outer pad assemblies and a torque member. The inner and outer pad assemblies cover a disk rotating together with a wheel and are provided on both sides of the disk to press the disk. The torque member performs an interlocking operation so that the outer pad assembly provided on the opposite side to the inner pad assembly is also moved toward the disk when the inner pad assembly is moved toward the disk. The wedge actuator assemblies convert torque, which is generated by one motor driven in normal and reverse directions by ECU, into an axial motion to move the inner pad assembly toward the disk. Further, the wedge actuator assemblies form a braking force by using a force applied to the disk that is generated using self-energizing depending on a wedge phenomenon caused by the movement of a wedge roller having a diameter. Furthermore, the wedge actuator assemblies implement a function for maintaining a set clearance of a pad, a Fail-Safe function, and an electric parking brake (EPB) function, by using that the forward movement of a push rod shaft screwed using a NSL (Non-Self Locking) type screw is restrained or released on the basis of ON/OFF control of the solenoid mechanism interlocked with the motor controlled by ECU. Each of the housings receives the wedge actuator assembly and is each fixed to the side of the wedge caliper.

Further, an auxiliary power supply circuit may be formed of an auxiliary battery in ECU, the motor of the wedge actuator assembly, and a solenoid.

Each of the wedge actuator assemblies may include a braking motor unit, a wedge braking unit, and a solenoid mechanism. The braking motor unit generates a braking force with power generated by the motor controlled by ECU. The wedge braking unit converts the torque of the motor into an axial motion to push the inner pad assembly against the disk. Further, the wedge braking unit converts the self-energizing, which is caused by the change in position of the wedge roller depending on the operation of the inner pad assembly from the disk, into an input force pressing the inner pad assembly against the disk. The solenoid mechanism is interlocked with the motor in order to implement a function for maintaining set clearances of the inner and outer pad assemblies, a Fail-Safe function against motor troubles, and an EPB function.

The braking motor unit may include a motor, a linear motion converter, and an interlocking rod. The motor is fixed to one side of the housing by a fixed bracket fixed to the housing and is controlled by ECU. The linear motion converter is fixed to an output shaft of the motor and moves forward and backward in an axial direction depending on the drive of the motor. The interlocking rod is fixed to the linear motion converter and moves depending on the axial movement of the linear motion converter.

The wedge braking unit may include a connecting rod, a wedge moving plate, a wedge base plate, and a wedge roller. The connecting rod is fixed to the motor so that an axial moving force caused by the drive of the motor is applied to the connecting rod. The wedge moving plate is moved by an integrally formed connecting rod so as to press the inner pad assembly, which is positioned on the opposite side to the outer pad assembly, that is, on the side of the disk, against the disk. The wedge base plate is arranged parallel to the wedge moving plate so as to face the wedge moving plate. The wedge roller is provided between rolling contact surfaces formed between the pair of plates and generates a frictional force during the movement of the wedge moving plate.

The solenoid mechanism may include an adjusting unit, a solenoid unit, and an EPB spring. The adjusting unit includes a push rod shaft fixed using a NSL (Non-Self Locking) type screw and is moved toward the disk in an axial direction when a function for maintaining a set clearance of a pad, a Fail-Safe function, and an electric parking brake function are implemented. The solenoid unit is turned on or off to operate the adjusting unit and releases or applies a restraining force. The EPB spring is fixed to the wedge moving plate moved by the motor so that the push rod shaft is restrained to maintain a parking braking performance during the operation of the electric parking brake.

When torque of the motor driven by ECU at the start of the engine is converted into a linear motion and the wedge moving plate generating a wedge effect by the wedge roller is moved, ECU turns off the solenoid of the solenoid unit so that the restraint of the adjusting unit, which maintains the contact between the pad and the disk, on the push rod shaft is released. Then, ECU drives the motor again to move the wedge moving plate so that the set clearance is secured between the pad and the disk, and turns on the solenoid so as to restrain the push rod shaft. After that, ECU drives the motor in a reverse direction to allow the wedge moving plate to return to an initial state, thereby implementing the function for maintaining the set clearance of the pad by using the solenoid mechanism.

The adjusting unit may include a supporting nut, a push rod shaft, a latch, front and rear bearings, and a spring. The supporting nut includes locking portions (grooves) formed on the outer periphery thereof and is fitted to position restraining portions of the housing. The push rod shaft includes a push rod screw formed on the outer periphery thereof so as to be screwed to the supporting nut in non-self locking type. The latch is formed on the outer periphery of a portion of the push rod shaft without the push rod screw. The front and rear bearings are disposed on the push rod shaft at the front and rear sides of the latch. One end of the spring is fixed to the supporting nut and the other end of the spring continuously applies an axial force to the front bearing.

The solenoid unit may include a solenoid and a switching lever. The solenoid is received at one side in the housing and turned on or off by ECU. The switching lever acts like a seesaw about a hinge shaft by a movable shaft protruding or retreating during the operation of the solenoid. The switching lever may include a press part, a latch contact part, and a contact portion. The press part is positioned so as to correspond to the moving path of the movable shaft of the solenoid. The latch contact part is bent from the end of the press part hinge-attached to the housing and rotates about a hinge point. The contact portion is formed on the outer surface of the latch contact part so as to be engaged with the latch formed on the push rod shaft.

In this case, the switching lever may include a contact slope inclined along the longitudinal direction of the press part so as to generate a force applied downward about the hinge point when a force is applied to the press part by the movable shaft of the solenoid.

The EPB spring may include a fixation portion, a connection portion, a connection portion, and a press portion. The fixation portion is fixed to the wedge moving plate. The connection portion is bent and extends so as to protrude from the fixation portion. The press portion is bent downward from an end of the connection portion and generates a force so as to restrain the axial movement of the push rod shaft when the solenoid is turned off.

The press portion of the EPB spring may press or push the rear bearing provided on the side of the latch of the push rod shaft so as to generate a restraining force. Alternatively, the press portion of the EPB spring may press or push an EPB spring positioning flange formed at the rear side of the latch of the push rod shaft.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a view of a single motor electro wedge brake system, which uses a solenoid mechanism to implement additional functions, according to an embodiment of the present invention. The single motor electro wedge brake system according to an embodiment of the present invention includes an electric pedal1, an ECU2, wedge calipers6, and wedge actuator assemblies10. Electric pedal1is operated by a driver to brake a vehicle. ECU2performs control in consideration of information about the vehicle when the vehicle is braked. Each of wedge calipers6presses a disk5, which rotates together with a wheel, to brake the vehicle. Each of wedge actuator assemblies10perform braking by pressing a pad against disk5using power, which is generated by one motor13controlled by ECU2, during the braking. Further, each of wedge calipers6includes a solenoid mechanism, which implements a function for maintaining a set clearance of a pad, a Fail-Safe function, and an EPB (Electric Parking Brake) function.

The single motor electro wedge brake system further includes an auxiliary battery4. The auxiliary battery4is used as a spare battery for ECU2and motors13and solenoids41of actuator assemblies10.

Further, when a parking brake is operated, the single motor electro wedge brake system receives signals so that ECU2perceives a parking brake conversion state. For example, a parking brake button, which generates separate electric signals corresponding to portions of a driver's seat and supplies the signals to ECU2, is used.

The single motor electro wedge brake system further includes housings60in which wedge actuator assemblies10are received, respectively. Each of housings60is fixed to wedge caliper6.

In this case, wedge caliper6and housing60may be fixed to each other in various ways. For example, housing60may have a guide that protrudes and is inserted into wedge caliper6. Accordingly, the housing is fixed to the wedge caliper.

ECU2performs a control required for braking on the basis of information about a pushing distance of electric pedal1to be operated and information about an attitude of a vehicle obtained from a yaw moment sensor3provided in the vehicle.

In addition, various sensors are provided to wedge caliper6and wedge actuator assembly10fixed to the wedge caliper, so that measurement signals are transmitted to ECU2. For example, pad abrasion sensing sensors, which sense an increase of a clearance between disks5depending on the increase of a set clearance of the pad so as to always maintain a set clearance, and load sensors, which are used to prevent wheel jamming occurring when a pad is pressed against disk5by a wedge roller during the braking, may be provided to the wedge caliper and the wedge actuator assembly.

Further, wedge caliper6includes inner and outer pad assemblies7and8that cover disk5rotating together with the wheel, are provided on both sides of disk5to press disk5.

Wedge caliper6includes a torque member for performing an interlocking operation (the operation of a general caliper type brake) so that outer pad assembly8provided on the opposite side to the inner pad assembly is also moved toward disk5when inner pad assembly7is pressed against disk5.

Further, each of wedge actuator assemblies10includes a braking motor unit11, a wedge braking unit16, and a solenoid mechanism. Braking motor unit11generates a braking force with power, which is generated by one motor13controlled by ECU2. Wedge braking unit16is interlocked with braking motor unit11so as to press pad assemblies7and8against disk5at one side of wedge caliper6. The solenoid mechanism implements a function for maintaining set clearances of pad assemblies7and8, a Fail-Safe function against motor troubles, and an EPB (Electric Parking Brake) function.

Furthermore, braking motor unit11generates power, which is used to implement the brake function, by the control of ECU2during the braking. Braking motor unit11operates wedge braking unit16, which presses inner pad assembly7provided on one side of disk5, by using one motor13provided on one side of housing60, which is fixed to the side of wedge caliper6, as a power source.

For this purpose, as shown inFIG. 2, braking motor unit11includes motor13, a linear motion converter14, and an interlocking rod15. Motor13is fixed to one side of housing60fixed to the side of wedge caliper6by a fixed bracket12that is fixed to housing60, and is controlled by ECU2. Linear motion converter14is fixed to an output shaft of motor13, and moves forward and backward in an axial direction depending on the drive of the motor. Interlocking rod15is fixed to linear motion converter14, and moves depending on the axial movement of linear motion converter14.

In this case, when a rotating shaft of linear motion converter14is rotated by the drive of motor13, the linear motion converter moves forward and backward according to the rotational direction of the rotating shaft due to the fact that the linear motion converter is engaged with threads formed on the outer periphery of the rotating shaft. This structure is generally applied to an EWB (electro wedge brake) of a vehicle.

For example, although an interlocking rod15of a linear motion converter14shown inFIG. 2Bhas a slight difference in shape, the interlocking rod moves forward and backward in an axial direction of a motor13by the drive of the motor. Further, a method of generating a shaft pulling force in an electric parking brake (EPB) is a method using still another structure.

Further, interlocking rod15diagonally crosses housing60and is positioned on the side opposite to motor13. Interlocking rod15moves together with linear motion converter14, which moves in the axial direction depending on the drive of motor13. Further, interlocking rod15is composed of a pair of upper and lower pieces so that a moving force caused by linear motion converter14becomes uniform.

The reason for the diagonal arrangement of interlocking rod15is to utilize a space in housing60, and housing60is made more compact by reducing the space in housing60, which is occupied by interlocking rod15.

Further, wedge braking unit16includes a connecting rod18, a wedge moving plate17, a wedge base plate20, and a wedge roller19. Connecting rod18is fixed to motor13so that an axial moving force caused by the drive of motor13is applied to the connecting rod. Wedge moving plate17is moved by an integrally formed connecting rod18so as to press inner pad assembly7, which is positioned on the opposite side to outer pad assembly8, that is, on the side of disk5, against disk5. Wedge base plate20is arranged parallel to wedge moving plate17so as to face wedge moving plate17. Wedge roller19is provided between rolling contact surfaces17aand20a, which are formed between the pair of plates17and20, and generates a frictional force.

Connecting rod18is fixed to an end of interlocking rod15, which moves in an axial direction by linear motion converter14moved depending on the drive of motor13, and moves the wedge plate17in a direction where interlocking rod15is moved.

Further, connecting rod18extends perpendicular to the surface of the wedge moving plate at upper and lower portions of wedge moving plate17, and is fixed to the end of interlocking rod15by bolts or the like.

Wedge roller19is provided between the pair of plates17and20facing each other, and has a cylindrical shape. The wedge roller causes a wedge phenomenon where self-energizing is performed by a frictional force generated depending on the operation of plates17and20, and then applies an input force to press the pad.

For this purpose, wedge roller19is positioned between rolling contact surfaces17aand20aincluding a plurality of grooves, which has V-shaped cross sections and is formed on the surfaces of the pair of plates17and20facing each other. Rolling contact surfaces17aand20aincluding the plurality of grooves, which has V-shaped cross sections, and wedge roller19generate a frictional force. Further, rolling contact surfaces17aand20amake one plate (wedge plate17) move toward the pad depending on the change in position of wedge roller19.

Wedge base plate20is stationary with respect to wedge moving plate17, which is moved by power of motor13. For this purpose, wedge base plate20is formed using a part of housing60fixed to the side of wedge caliper6.

The solenoid mechanism, which implements various additional functions in addition to a main braking function implemented using braking motor unit11and wedge braking unit16during the operation of the EWB, includes an adjusting unit30, a solenoid unit40, and an EPB spring50. Adjusting unit30is fixed using a NSL (Non-Self Locking) type screw, and is moved toward disk5in an axial direction when a pad compensating function, a Fail-Safe function, and an electric parking brake function are implemented. Solenoid unit40is turned on or off to operate adjusting unit30, and releases or applies a restraining force. EPB spring50restrains adjusting unit30to maintain a parking braking performance during the operation of the electric parking brake.

In this case, as shown inFIG. 3A, adjusting unit30includes a supporting nut32, a push rod shaft31, a pair of front and rear bearings33and34, and a spring35. Supporting nut32has locking portions32a(grooves) formed on the outer periphery thereof and is fitted to position restraining portions60aof housing60. Push rod shaft31has a push rod screw31bformed on the outer periphery thereof so as to be screwed to supporting nut32, and is moved in an axial direction by the rotation thereof. Front and rear bearings33and34are disposed on the push rod shaft at the front and rear sides of a latch31a, which is formed on the outer periphery of a portion of push rod shaft31without push rod screw31b. One end of spring35is fixed to supporting nut32, and the other end of the spring continuously applies an axial force to front bearing33.

Further, push rod shaft31and supporting nut32use a NSL (Non-Self Locking) type screw, that is, a screw having a large lead angle. Accordingly, when a force is applied to the push rod shaft in an axial direction, the push rod shaft is automatically rotated due to the large lead angle and is moved in the axial direction.

A needle bearing, which withstands an axial force and does not restrain rotation, is used as front bearing33. A thrust bearing is used as rear bearing34.

During the initial assembling, spring35is provided between supporting nut32and front bearing33so as to continuously apply a force to front bearing33.

Further, adjusting unit30is disposed at the central portion of base plate20of wedge braking unit16so that a force applied by push rod shaft31is applied to wedge base plate20.

Solenoid unit40includes a solenoid41that is received at one side in housing60and turned on or off by ECU2, and a switching lever43that operates like a seesaw about a hinge shaft by a movable shaft42protruding or retreating during the operation of solenoid41.

Switching lever43includes a press part44that is positioned so as to correspond to the moving path of movable shaft42of solenoid41, and a latch contact part45that is bent from the end of press part44hinge-attached to housing60and rotates about a hinge point.

In this case, switching lever43is generally supported by a spring so as to return to an initial position when the pressing of solenoid41is released.

Press part44has a contact slope44ainclined along the longitudinal direction of press part44so as to generate a force applied downward about the hinge point when a force is applied to the press part by movable shaft42of solenoid41.

In addition, a contact portion45ais formed on the outer surface of the latch contact part45so as to be engaged with latch31aformed on push rod shaft31of adjusting unit30.

Accordingly, as shown inFIG. 3B, in adjusting unit30and solenoid unit40, solenoid41is disposed in the axial direction of push rod shaft31of adjusting unit30. Further, switching lever43, which operates like a seesaw about the hinge shaft, is assembled so as to be engaged with latch31aof push rod shaft31. As a result, as long as solenoid41is not turned off, the axial movement of push rod shaft31is restrained.

If solenoid41is disposed parallel to the axial direction of the push rod shaft31of adjusting unit30, it is possible to improve the space utilization of the entire housing60including solenoid41.

Further, the solenoid unit, which restrains and releases the push rod shaft of the adjusting unit, may be modified in various ways. For example, as shown inFIG. 4A, a solenoid401of a solenoid unit460may be positioned perpendicular to push rod shaft31of adjusting unit30.

Since solenoid401protrudes, the position of solenoid401deteriorates the space utilization of the entire housing60including solenoid401. However, load required in solenoid401becomes smaller than when the solenoid is disposed parallel to the axial direction of the push rod shaft.

As shown inFIG. 4B, solenoid unit400includes solenoid401that is received at one side in housing60and turned on or off by ECU2, and a switching lever403that angularly moves about a hinge shaft by a movable shaft402protruding or retreating during the operation of solenoid401.

Switching lever403includes a press part404that is positioned so as to correspond to the moving path of movable shaft402of solenoid401, and a latch contact part405that is perpendicularly formed at the end of press part404and hinge-attached to housing60at the end thereof.

In this case, a contact portion405aprotrudes from latch contact part405so as to be engaged with latch31aformed on push rod shaft31of adjusting unit30.

In addition, switching lever403is generally supported by a spring so as to return to an initial position when the pressing of solenoid401is released.

The above-mentioned modification of solenoid unit400causes the entire shape of housing60to be changed. That is, as shown inFIG. 5, a braking motor unit11, which generates a braking force with power generated from one motor13controlled by ECU2, is positioned at one side in housing60forming an entire appearance. Further, adjusting unit30is positioned in front of wedge braking unit16at a central portion of housing60, and solenoid unit400is positioned at the other side in housing60so that housing60partially protrude.

Meanwhile, one end of EPB spring50, which is used to implement an electric parking brake function, is fixed to wedge braking unit16. The other end of the EPB spring is positioned at latch31aof push rod shaft31of adjusting unit30. Accordingly, when solenoid41is turned off during the operation of the parking brake, one end of EPB spring50restrains push rod shaft31. As a result, when solenoid41is turned off, the EPB spring restrains adjusting unit30.

For this purpose, as shown inFIG. 6, EPB spring50includes a fixation portion51that is screwed to wedge moving plate17of wedge braking unit16, a connection portion52that is bent and extends so as to protrude from fixation portion51, and a press portion53that is bent downward from the end of connection portion52and restrains the axial movement of push rod shaft31when solenoid41is turned off.

As an example of the restraint of push rod shaft31using EPB spring50, press portion53of EPB spring50restrains rear bearing34positioned at the side surface of latch31aof push rod shaft31. That is, press portion53is positioned at rear bearing34and applies a strong force to rear bearing34, so that the movement of push rod shaft31is restrained.

In this case, EPB spring50is moved together with wedge moving plate17, which is moved by motor13so as to generate a final braking force, during the parking braking. Accordingly, press portion53of EPB spring50is positioned at rear bearing34, and presses rear bearing34due to its own strong electric force so as to restrain the movement of push rod shaft31.

Further, in order to improve the restraining force of push rod shaft31, EPB spring50may be composed of a pair of pieces restraining push rod shaft31at upper and lower portions of the push rod shaft.

Meanwhile, EPB spring50may be modified in various ways to perform a similar operation. For example, as shown inFIG. 7, a connection portion152extends to wedge braking unit16so as to protrude from a fixation portion151of an EPB spring150. Further, a press portion153, which is bent downward from the end of connection portion152, is positioned at latch31aof push rod shaft31.

Accordingly, when solenoid41is turned off during the operation of the EPB, press portion153of EPB spring150is engaged with latch31aof push rod shaft31so as to restrain the axial movement of push rod shaft31.

The restraint of the axial movement of push rod shaft31, which is performed using the EPB spring, may be performed by the modification of push rod shaft31. That is, as shown inFIGS. 8A and 8B, an EPB spring positioning flange31cis formed to have a large diameter at the rear side of latch31aof push rod shaft31, and press portion53or153of EPB spring50or150is positioned at EPB spring positioning flange31c.

Accordingly, during the operation of the EPB, press portion53or153of EPB spring50or150restrains EPB spring positioning flange31cof push rod shaft31. As a result, when solenoid41is turned off, the axial movement of push rod shaft31is restrained.

The operation of the single motor electro wedge brake system according to the embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

The electro wedge brake (EWB) system according to the embodiment of the present invention implements a main braking function by using power generated from one motor13. Further, the electro wedge brake system implements various additional functions such as a function for maintaining a set clearance of a pad, a Fail-Safe function, and an EPB function, by using that the forward movement of push rod shaft31screwed using a NSL (Non-Self Locking) type screw is restrained or released on the basis of ON/OFF control of the solenoid mechanism interlocked with the main braking function motor13. Accordingly, since only one motor13is used to generate power, it is possible to reduce the number of parts and to simplify the structure.

In addition, the electro wedge brake according to the embodiment of the present invention implements a function for maintaining a set clearance of a pad, a Fail-Safe function, and an EPB function by using a solenoid mechanism. For this reason, it is possible to reduce the number of parts related to power conversion and operation, which are required when a motor is used. Therefore, it is possible to easily design the electro wedge brake.

Since the electro wedge brake system uses one motor13and implements a function for maintaining a set clearance of a pad, a Fail-Safe function, and an EPB function except for the main braking by using a solenoid mechanism, it is possible to obtain these various characteristics of the present invention.

Accordingly, in the EWB according to the embodiment of the present invention, as shown inFIG. 1, a wedge caliper6including inner and outer pad assemblies7and8is provided at disk5that is rotated together with a wheel. Further, a wedge actuator assembly10, which is controlled by ECU2receiving operational information of electric pedal1, is provided in housing60, and is fixed to the side of wedge caliper6.

That is, wedge actuator assembly10includes one motor13controlled by ECU2, and wedge braking unit16. Wedge braking unit16has a wedge structure that generates an input force pressing the pad due to self-energizing while moving the pad as the torque of the motor is converted into an axial moving force by linear motion converter14. In this case, the self-energizing is caused by the change in position of the wedge roller depending on the operation of wedge roller19with respect to the pad.

In addition, wedge actuator assembly10includes adjusting unit30positioned at the central portion of wedge braking unit16. Adjusting unit30performs an adjustment function for maintaining a clearance between disk5and the pad when the pad is abraded. Further, adjusting unit30includes a NSL (Non-Self Locking) type screw interlocked with solenoid41so as to implement the Fail-Safe function for releasing the pressing of wedge braking unit16when motor13is broken down in a braking state.

Further, adjusting unit30includes EPB spring50, which restrains the movement with respect to adjusting unit30while solenoid41is turned off, so as to perform the EPB function of the electric brake during the braking.

The operation, which is performed by the EWB according to the embodiment of the present invention using one motor13, will be classified into the main braking function and the various additional functions, such as a function for maintaining a set clearance of a pad, a Fail-Safe function, and an EPB function, and will be described in detail below.

In the main braking function of the present invention, when ECU2generates control signals by analyzing information about a pushing distance of electric pedal1and information about a moving vehicle obtained from various sensors, motor13controlled by ECU2is driven and linear motion converter14generates an axial moving force in the axial direction, that is, in a direction where the linear motion converter protrudes from motor13(braking against forward movement) or retreats toward motor13(braking against backward movement) depending on the rotational direction of motor13.

Subsequently, the axial moving force of linear motion converter14caused by motor13moves interlocking rod15fixed to linear motion converter14, and the movement of interlocking rod15causes wedge braking unit16fixed to the end thereof to be continuously and linearly moved together with the pad. As wedge braking unit16is moved, a force for pressing the pad against disk5is generated due to the wedge structure using wedge roller19.

That is, wedge moving plate17connected to connecting rod18and inner pad assembly7fixed to the side of the disk are moved by an axial moving force, which is converted by motor13, with respect to wedge base plate20integrally formed with housing60.

For this reason, wedge roller19, which is positioned at the central portion between rolling contact surfaces17aand20aof the moved wedge moving plate17and the fixed wedge base plate20, generates a frictional force due to the movement of wedge moving plate17as shown inFIG. 9A.

After that, as wedge moving plate17is moved forward, wedge roller19is moved from the central portion between rolling contact surfaces17aand20ato the outside as shown inFIGS. 9B and 9C. The movement of wedge roller19with respect to rolling contact surfaces17aand20acauses wedge moving plate17to be further separated from wedge base plate20.

Accordingly, wedge moving plate17is linearly moved and causes a clearance due to the change in position of wedge roller19. The clearance between wedge moving plate17and wedge base plate20causes a wedge effect of wedge roller19where inner pad assembly7generates an input force pressing disk5.

Subsequently, when braking is released, ECU2drives motor13in a reverse direction and allows wedge moving plate17to return to the initial position by linear motion converter14, interlocking rod15, and connecting rod18as shown inFIGS. 9D and 9E. Accordingly, wedge roller19also returns to the central position between rolling contact surfaces17aand20a. Therefore, a force pressing wedge moving plate17against disk5is released and a braking force is also released.

Further, even when a vehicle moving backward is braked, a vehicle is braked in the same manner as when a vehicle moving forward is braked. That is, ECU2, which receives a signal of electric pedal1and perceives the reversing of a vehicle, drives motor13in a reverse direction (forward moving is referred to as driving in a normal direction).

Then, if linear motion converter14, interlocking rod15, and connecting rod18are pulled toward motor13by the reverse drive of motor13, wedge moving plate17pulls inner pad assembly7in the same direction.

The pulling movement of wedge moving plate17causes wedge roller19, which is positioned at the central portion between rolling contact surfaces17aand20aof the moved wedge moving plate17and the fixed wedge base plate20, to move as shown inFIGS. 9F and 9Gby a frictional force due to the movement of wedge moving plate17.

That is, since wedge roller19is moved to the outside of rolling contact surfaces17aand20a, wedge moving plate17is further separated from wedge base plate20. The clearance between wedge moving plate17and the wedge base plate causes an input force of inner pad assembly7, which presses disk5. Therefore, a braking force is generated.

Subsequently, when the braking is released, ECU2drives motor13in a normal direction and allows wedge roller19to return to the central position between rolling contact surfaces17aand20aas shown inFIG. 9E, thereby releasing the braking force.

Meanwhile, various additional functions of the EWB are implemented by adjusting unit30, which is positioned at the central portion of wedge braking unit16and includes an NSL type screw interlocked with solenoid41. The various additional functions will be classified and described below.

First, the Fail-Safe function releases the pressing of wedge braking unit16when wheel jamming of wedge roller19occurs or motor13is broken down in the braking state. The Fail-Safe function will be described. ECU2turns off solenoid41and releases the restraint on adjusting unit30. Accordingly, a force, which is applied to disk5by the pad and wedge braking unit16, is released to prevent a vehicle from abnormally operating due to an undesired braking force.

That is, as shown inFIG. 10A, switching lever43is engaged with latch31aof push rod shaft31, so that solenoid41turned on in a normal braking state restrain push rod shaft31. Accordingly, push rod shaft31supports wedge roller19, which is in the braking state. For this reason, a wedge effect of wedge roller19where an input force pressing disk5is generated is not released and a braking state is maintained.

However, if ECU2perceives the broken-down of motor13or wheel jamming, ECU2turns off solenoid41to separate switching lever43from latch31aand releases the restraint of push rod shaft31, as shown inFIG. 10B, even though ECU2perceives as a Fail-Safe state.

Due to the release of the restraint of push rod shaft31, a force is applied to push rod shaft31by spring35, and the force applied by spring35moves forward push rod shaft31while rotating push rod shaft31that is fixed using supporting nut32and the NSL type screw.

As described above, when the restraining force of solenoid41is released, a reaction force is applied from the pad (inner pad assembly7) to push rod shaft31moved forward by the force of spring35.

That is, a reaction force, which is transmitted through inner pad assembly7and wedge moving plate17and wedge roller19and wedge base plate20, is applied to push rod shaft31. Push rod shaft31to which a reaction force is applied is moved toward supporting nut32, and releases the wedge effect of wedge roller19for maintaining the braking force between the pad and disk5. Accordingly, the state of a vehicle is converted into a Fail-Safe state where undesired braking is abnormally performed during braking.

The release or restraint of solenoid41with respect to push rod shaft31is different depending on the structure of the switching lever. InFIG. 3, when the state of solenoid41is converted from a turning-on state to a turning-off state, movable shaft42of solenoid41is retreated and a force pressing switching lever43is released, that is, a downward moving force, which is caused by the contact between the contact slope of switching lever43and movable shaft42of solenoid41, is released.

Subsequently, as press part44is lifted, the contact part45of switching lever43to which a force is not applied by solenoid41is rotated about the hinge point and separated from latch31aof push rod shaft31. Therefore, the engagement between switching lever43and latch31ais released.

Further, inFIG. 4showing the modification of the solenoid, solenoid401is turned off and a force applied by movable shaft402is released in the axial direction of switching lever403. Accordingly, switching lever403angularly moves about the hinge point, and contact part405is separated from latch31aof push rod shaft31. As a result, the engagement between switching lever403and latch31ais released.

Meanwhile, the function for maintaining a set clearance of a pad among various additional functions implemented by the EWB is a function for always maintaining a clearance that is set between the pad and disk5at initial assembling, and may be implemented in various ways. For example, the function for maintaining a set clearance may be implemented in the following manner. That is, an adjustment for maintaining the set clearance is performed by adjusting a clearance between the pad and disk5whenever an engine is started. Alternatively, ECU2detects pad abrasion and compensation is then performed to maintain a set clearance between the pad and disk5.

When the adjustment for maintaining an initial set clearance between disk5and the pad is performed in the starting of the engine, as shown inFIG. 12, the engine is started and ECU2drives motor13. The drive of motor13causes wedge moving plate17to move by linear motion converter14, interlocking rod15, and connecting rod18, like the main braking. Therefore, inner and outer pad assemblies7and8come in close contact with the both surfaces of disk5.

That is, if wedge moving plate17of wedge braking unit16is moved together with inner pad assembly7by the driving force of motor13, as shown inFIG. 11A, wedge roller19positioned between rolling contact surfaces17aand20ais moved by the frictional force between wedge moving plate17and the wedge base plate, like the main braking where push rod shaft31is restrained by solenoid41. Due to the movement of wedge moving plate17, inner and outer pad assemblies7and8come in close contact with the both surfaces of disk5.

Since inner and outer pad assemblies7and8come in close contact with the both surfaces of disk5as described above, clearances between inner and outer pad assemblies7and8and disk5do not exceed the set clearance. Therefore, as shown inFIG. 11B, ECU2turns off solenoid41and then releases the solenoid restraining force of push rod shaft31.

The release of the restraining force of push rod shaft31allows push rod shaft31, which is an NSL type screw, to move in an axial direction. That is, while push rod shaft31is loosened from supporting nut32by the axial moving force that is applied by spring35provided between supporting nut32and push rod shaft31, push rod shaft31is moved forward.

In this case, push rod shaft31is moved forward until the push rod shaft protrudes from supporting nut32by a distance A. The distance A is a clearance required for push rod shaft31to come in contact with and support wedge base plate20so that inner and outer pad assemblies7and8coming in close contact with the both surfaces of disk5are maintained. The distance A is changed depending on the specification of the single motor electro wedge brake.

As described above, wedge base plate20, wedge roller19, and wedge moving plate17are maintained as shown inFIG. 11B. Further, after push rod shaft31, which is moved forward, comes in contact with wedge base plate20, ECU2drives motor13again to move wedge moving plate17so that the set clearance is secured between the pad and disk5.

In this case, when a clearance between the pad and disk5is larger than the set clearance, ECU2drives motor13(referred to as normal rotation) to further move wedge moving plate17so that the clearance between the pad and disk5corresponds to the set clearance.

However, when the clearance between the pad and disk5is smaller than the set clearance, ECU2drives motor13(referred to as reverse rotation) to pull wedge moving plate17(movement in an opposite direction to the moving direction when braking) so that the clearance between the pad and disk5corresponds to the set clearance.

The control of the drive of motor13, which is performed by ECU2, allows the clearance between the pad and disk5to always correspond to the set clearance whenever the adjustment is performed.

Subsequently, ECU2turns on solenoid41and allows switching lever43to be engaged with latch31aso that the state of push rod shaft31, which is moved forward by a distance A, is converted into the stationary state as shown inFIG. 11C. That is, since movable shaft42of solenoid41allows switching lever43to rotate about the hinge point, the contact portion45ais engaged with latch31a.

After the state of push rod shaft31is converted into a stationary state by solenoid41as described above, ECU2converts the states of wedge base plate20, wedge roller19, and wedge moving plate17into the initial states by driving motor13in the reverse direction as shown inFIG. 11C. Accordingly, clearances between inner and outer pad assemblies7and8and disk5do not exceed the set clearance. Therefore, it is possible to maintain a constant braking force by the wedge effect of wedge roller19, which is implemented during the braking.

The starting of the engine and processes for maintaining a clearance of a pad are not performed at the same time. Further, when ECU2perceives pad abrasion, processes for maintaining a clearance are also similarly performed. However, except for only whether the starting of the engine and the drive of motor13are performed at the same time, all of the processes are similarly performed by a procedure shown inFIG. 12.

That is, if ECU2determines that the pad is abraded and the clearance between the pad and disk5is more than the set clearance on the basis of information from a sensor for measuring the amount of the pad abrasion, ECU2drives motor13to allow inner and outer pad assemblies7and8to come in close contact with the both surfaces of disk5, similar at the start of the engine.

Accordingly, wedge roller19positioned on the rolling contact surface20aof wedge base plate20is moved together with wedge moving plate17as shown inFIG. 11B. As a result, clearances between inner and outer pad assemblies7and8and disk5do not exceed the set clearance.

Subsequently, ECU2turns off solenoid41and allows push rod shaft31to move forward in the axial direction by spring35. After that, ECU drives motor13again to move wedge moving plate17so that the close contact is secured between the pad and disk5.

After performing the above-mentioned operations, as shown inFIG. 11C, ECU2turns on solenoid41to convert the state of push rod shaft31into a stationary state and drives motor13in the reverse direction so as to be in the initial state. For this reason, since the set clearance is again maintained between disk5and the pad, it is possible to maintain a constant braking force during braking.

Further, if the set clearance of the pad is maintained when ECU2perceives the pad abrasion, it is convenient to maintain the clearance of the pad and to find out the time to replace the pad. That is, when the pad is abraded over a predetermined level, the perception of the pad abrasion by ECU2can be used as information for informing a driver of the time to replace the pad.

Meanwhile, as the state of solenoid41is converted into a turning-off state, the function for maintaining braking, which is implemented by the EWB during the operation of the electric parking brake, is implemented by restraining push rod shaft31with EPB spring50.

That is, when ECU2perceives the conversion into the parking braking state (a method of transmitting a signal to ECU by using a button or methods similar thereto are used), ECU2turns off solenoid41to allow switching lever43to be separated from latch31a, thereby releasing the restraint of push rod shaft31.

As the restraint is released by solenoid41as described above, push rod shaft31to which the force of spring35is applied is loosened from supporting nut32and moved forward. The forward movement of push rod shaft31causes rear bearing34to push wedge base plate20. Accordingly, wedge moving plate17at which wedge roller19is positioned and inner pad assembly7fixed thereto are pushed against disk5.

Subsequently, when the pad and disk5come in contact with each other due to the forward movement of push rod shaft31, which is caused by turning-off solenoid41, ECU2drives motor13to maintain the braking force.

That is, if wedge moving plate17is moved by the sequential operations of linear motion converter14, interlocking rod15, and connecting rod18, which are caused by the drive of motor13, wedge moving plate17pushes inner pad assembly7against disk5.

As wedge moving plate17is moved as described above, wedge roller19is moved by wedge moving plate17and a frictional force. The movement of wedge roller19generates an input force pressing wedge moving plate17against disk5.

As shown inFIG. 13B, the movement of wedge roller19causes wedge moving plate17, which is moved by a distance B by push rod shaft31, to move by a distance C. Accordingly, inner pad assembly7fixed to wedge moving plate17presses disk5. As a result, a parking brake force is generated.

The wedge moving plate is further moved during the parking braking, as compared to the main braking. That is, for example, as shown inFIGS. 13A and 13B, a moving distance B of wedge moving plate17, which is moved due to the movement of wedge roller19, is 2 mm maximum during the main braking. Further, a moving distance C of wedge moving plate17is larger than the moving distance B by 0.8 mm during the parking braking, and a parking brake force is maintained. The additional movement is caused by the axial movement of wedge moving plate17, which is moved by motor13.

In this case, the above-mentioned distance (2 mm or 0.8 mm) is different depending on the design specification of the wedge caliper. The value of the distance is not limited to a specific value, and is only an example.

As described above, the pad is further moved by motor13to perform the parking braking, and push rod shaft31is also moved forward. Then, push rod shaft31, which is moved forward, maintains a restraining force by EPB spring50instead of solenoid41that is turned off.

That is, if EPB spring50is moved together with wedge moving plate17that is moved by motor13, press portion53of EPB spring50is positioned on rear bearing34of push rod shaft31.

The movement of EPB spring50allows press portion53to press rear bearing34due to its own electric force. Further, the force of EPB spring50is converted into the restraining force applied to push rod shaft31to which a restraining force is not applied by solenoid41, and restrains the movement of push rod shaft31, thereby maintaining the braking force generated due to the operation of the parking brake.

Meanwhile, the restraint of push rod shaft31, which is performed using the EPB spring, may be similarly performed by various modifications of the EPB spring. That is, according to the structure where press portion153of EPB spring150is bent inward, as shown inFIG. 7, if EPB spring150and wedge moving plate17are moved by motor13after the initial parking braking, press portion153of EPB spring150restrains the side of rear bearing34of push rod shaft31. Accordingly, the movement of push rod shaft31is restrained, so that a braking force caused by the operation of the parking brake is maintained.

Further, inFIGS. 8A and 8Billustrating another modification where a parking brake force is maintained using the EPB spring, EPB spring50restrains EPB spring positioning flange31cthat is formed at the rear side of latch31aof push rod shaft31.

That is, if EPB spring50or150and wedge moving plate17moved by motor13are moved so as to generate a parking brake force, press portion53or153of EPB spring50or150is positioned at EPB spring positioning flange31cof push rod shaft31. Accordingly, push rod shaft31, which is moved forward, is restrained by press portion53or153pressing EPB spring positioning flange31c.

In this case, EPB spring50having press portion53, which is bent outward, presses EPB spring positioning flange31cof push rod shaft31from above to below. Further, EPB spring150having press portion153, which is bent inward, presses EPB spring positioning flange31cof push rod shaft31from side. Therefore, the restraint is maintained so that the parking braking state is maintained.

As described above, according to the present invention, an electro wedge brake (EWB) uses one motor to generate power, which is used to perform main braking during braking. The electro wedge brake uses a solenoid mechanism interlocked with the motor, so as to implement various additional functions, such as a function for maintaining a set clearance of a pad, a Fail-Safe function, and an EPB function. Accordingly, since only one motor for generating power is used, the size of the entire electro wedge brake can be reduced to improve the assembly property of the electro wedge brake.

Further, according to the present invention, the electro wedge brake implements various additional functions, such as a function for maintaining a set clearance of a pad, a Fail-Safe function, and an EPB function, by using one motor. For this reason, it is possible to reduce the number of parts related to the motion conversion, which are required when a motor is used. Therefore, it is possible to reduce manufacturing cost and weight of the electro wedge brake.

Furthermore, according to the present invention, the electro wedge brake system implements a function for maintaining a set clearance of a pad, a Fail-Safe function, and an EPB function by using not a motor but a solenoid mechanism. Accordingly, it is possible to more simplify the structure for converting motion between related parts as compared to when a motor is used. Therefore, it is possible to easily design the electro wedge brake.