Patent ID: 12234874

DETAILED DESCRIPTION

Like reference numerals refer to like elements throughout the specification. This specification does not describe all the elements of the embodiments, and duplicative contents between general contents or embodiments in the technical field of the present disclosure will be omitted. The terms ‘part,’ ‘module,’ ‘member,’ and ‘block’ used in this specification may be embodied as software or hardware, and it is also possible for a plurality of ‘parts,’ ‘modules,’ ‘members,’ and ‘blocks’ to be embodied as one component, or one ‘part,’ ‘module,’ ‘member,’ and ‘block’ to include a plurality of components according to embodiments.

Throughout the specification, when a part is referred to as being “connected” to another part, it includes not only a direct connection but also an indirect connection, and the indirect connection includes connecting through a wireless network.

Also, when it is described that a part “includes” an element, it means that the element may further include other elements, not excluding the other elements unless specifically stated otherwise.

Throughout the specification, when a member is described as being “on” another member, this includes not only a case in which a member is in contact with another member but also a case in which another member is present between the two members.

The terms ‘first.’ ‘second,’ etc. are used to distinguish one element from another element, and the elements are not limited by the above-mentioned terms. The singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

In each step, an identification numeral is used for convenience of explanation, the identification numeral does not describe the order of the steps, and each step may be performed differently from the order specified unless the context clearly states a particular order.

FIG.1is a configuration view of an electronic parking brake (EPB) of an electronic parking brake system according to an embodiment.

Referring toFIG.1, an electronic parking brake10may include a carrier110on which a pair of pad plates111and112are installed to be movable forward or backward to press a brake disk100rotating together with a wheel of a vehicle, a caliper housing120provided with a cylinder123slidably installed on the carrier110and in which a piston121is installed to move forward or backward by a braking hydraulic pressure, a power conversion unit130that presses the piston121, and a motor actuator140to transmit a rotational force to the power conversion unit130using a motor M.

The pair of pad plates111and112include the inner pad plate111disposed to contact the piston121and the outer pad plate112disposed to contact a finger portion122of the caliper housing120. The pair of pad plates111and112are installed on the carrier110fixed to a vehicle body so as to be movable forward or backward toward opposite sides of the brake disk100. In addition, a brake pad113is attached to one surface of each of the pad plates111and112facing the brake disk100.

The caliper housing120is slidably installed on the carrier110. More specifically, the caliper housing120includes the cylinder123provided at a rear portion and in which the power conversion unit130is installed and the piston121is provided to be movable forward and backward, and the finger portion122provided at a front portion and formed to be bent in a downward direction to operate the outer pad plate112. The finger portion122and the cylinder123are formed integrally.

The piston121is provided in a cylindrical form having a cup shape to be slidably inserted into the cylinder123. The piston121presses the inner pad plate111toward the brake disk100by an axial force of the power conversion unit130to which the rotational force of the motor actuator140is transmitted. Accordingly; when the axial force of the power conversion unit130is applied, the piston121moves forward toward the inner pad plate111to press the inner pad plate111, and the caliper housing120operates in a direction opposite to the piston121by a reaction force, so that the finger portion122presses the outer pad plate112toward the brake disk100to perform braking.

The power conversion unit130may serve to press the piston121toward the inner pad plate111by the rotational force transmitted from the motor actuator140.

The power conversion unit130may include a nut member131installed so as to be disposed in the piston121and in contact with the piston121, and a spindle member135screwed to the nut member131.

The nut member131may be disposed in the piston121in a state in which rotation is restricted to be screwed with the spindle member135.

The nut member131may include a head portion132provided to be in contact with the piston121, and a coupling portion133formed to extend from the head portion132and having female threads formed on an inner circumferential surface thereof to be screwed with the spindle member135.

The nut member131may move in a forward direction or a backward direction depending on the rotation direction of the spindle member135to serve to press and release the piston121. In this case, the forward direction may be a moving direction in which the nut member131approaches the piston121. The backward direction may be a moving direction in which the nut member131becomes away from the piston121. In addition, the forward direction may be a moving direction in which the piston121approaches the brake pad113. The backward direction may be a moving direction in which the piston121becomes away from the brake pad113.

The spindle member135may include a shaft portion136provided to pass through the rear portion of the caliper housing120to be rotated by the rotational force transmitted from the motor actuator140, and a flange portion137formed to extend in a radial direction from the shaft portion136. One side of the shaft portion136may be rotatably installed through a rear side of the cylinder123, and the other side of the shaft portion136may be disposed in the piston121. In this case, one side of the shaft portion136passing through the cylinder123is connected to an output shaft of a speed reducer142to receive the rotational force of the motor actuator140.

The motor actuator140may include an electric motor141and the speed reducer142.

The electric motor141may press or release the piston121by moving the nut member131forward or backward by rotating the spindle member135.

The speed reducer142may be provided between an output side of the electric motor141and the spindle member135.

Through the configuration as described above, the electronic parking brake10may move the nut member131by rotating the spindle member135in one direction using the motor actuator140to press the piston121in a parking operation mode. The piston121pressed by the movement of the nut member131presses the inner pad plate111to come the brake pad113into close contact with the brake disk100, thereby generating a clamping force.

In addition, the electronic parking brake10rotates the spindle member135in the opposite direction using the motor actuator140in a parking release mode, so that the nut member131pressed against the piston121may move backward. The pressing against the piston121may be released by the backward movement of the nut member131. When the pressing against the piston121is released, the clamping force generated by the brake pad113being separated from the brake disk100may be released.

FIG.2is a control block diagram of the electronic parking brake system according to an embodiment, andFIG.3is a circuit diagram for driving the EPB of the electronic parking brake system according to an embodiment.

Referring toFIGS.2and3, the electronic parking brake system may include a controller200configured to perform overall control.

An H-bridge210that is a motor driving circuit for driving the electric motor141of the EPB10is electrically connected to an output side of the controller200. For example, the EPB10may be provided on a left rear wheel and/or a right rear wheel.

The H-bridge210may rotate the electric motor141in the forward or backward direction in response to a control signal of the controller200. For example, the H-bridge210may include four switching elements FET1to FET4to rotate the electric motor141in the forward or backward direction.

The controller200supplies a motor power supply B+ to the electric motor141by controlling each of the switching elements FET1to FET4of the H-bridge210to be turned on or off, thereby rotating the electric motor141in the forward or backward direction.

The first switching element FET1on a high side and the second switching element FET2on a low side in a half-bridge on one side of the H-bridge210are connected in series. A drain of the first switching element FET1is connected to the motor power supply B+, and a source of the second switching element FET2is grounded.

Also, the third switching element FET3on the high side and the fourth switching element FET4on the low side in the half-bridge on the other side of the H-bridge210are connected in series. A drain of the third switching element FET3is connected to the motor power supply B+, and a source of the fourth switching element FET4is grounded.

One side of the electric motor141is connected to a midpoint between the first switching element FET1and the second switching element FET2, and the other side of the electric motor141is connected to a midpoint between the third switching element FET3and the fourth switching element FET4.

A warning device220may be electrically connected to the output side of the controller200.

The warning device220may warn a driver of a motor failure related to the lock of the electric motor141. When a plurality of the H-bridges210is provided, the warning device220may warn the driver of information related to stop of the operation of the motor driving circuit in response to the electric motor141in which the motor lock has occurred. The warning device220is implemented as a visual configuration such as a warning lamp or an audible configuration such as a buzzer that is installed at a suitable place inside the vehicle, so that the warning lamp or buzzer may be operated in response to a control signal of the controller200to warn the driver of the motor lock. A speaker may be used as the warning device220of an audible configuration, and as such a speaker, a speaker of a car audio system provided inside the vehicle or a separate speaker provided at a suitable place inside the vehicle may be used.

The controller200may receive a terminal voltage VM of the electric motor141. The controller200may recognize the voltage of the electric motor141by receiving a terminal voltage signal of the electric motor141. The controller200may also receive the voltage of the electric motor141through a voltage sensor provided to detect the voltage of the electric motor141.

The controller200may be referred to as an electronic control unit (ECU).

The controller200may include a processor201and a memory202.

The memory202may store a program for processing or controlling the processor201and various data for the operation of the electronic parking brake system.

The memory202may include a non-volatile memory such as a flash memory, a read only memory (ROM), and an erasable programmable read only memory (EPROM), as well as a volatile memory such as S-RAM and D-RAM.

The processor202may control the overall operation of the electronic parking brake system.

The controller200having the above configuration may perform the parking operation mode or the parking release mode by an operation signal of a parking switch operated by the driver or an operation signal generated by the program related to the operation of the electronic parking brake.

In the parking operation mode, the controller200may perform a parking operation (Parking Apply) of generating a clamping force required for parking by making close contact of the brake pad of the wheel with the brake disk using EPB10.

In the parking release mode, the controller200may perform a Parking Release of releasing the generated clamping force by releasing the brake pad in close contact with the brake disk of the wheel using the EPB10.

The controller200may determine a clamping force required for parking, determine a target current according to the determined clamping force, and control the electric motor141of the EPB10according to the determined target current.

The controller200may determine whether the motor lock occurs based on a back electromotive force of the electric motor141in a motor lock inspection mode.

FIG.4is a circuit operation diagram when a motor rotates in a forward direction in the electronic parking brake system according to an embodiment.

Referring toFIG.4, in the parking operation mode, the controller200may rotate the electric motor141in the forward direction by turning on the first switching element FET1and the fourth switching element FET4of the H-bridge210and turning off the second switching element FET2and the third switching element FET3of the H-bridge210. Arrows shown inFIG.4indicate current flows flowing through the first switching element FET1, the electric motor141, and the fourth switching element FET4.

FIG.5is a circuit operation diagram when the motor rotates in a backward direction in the electronic parking brake system according to an embodiment.

Referring toFIG.5, in the parking release mode, the controller200may, in contrast to the parking operation mode, rotate the electric motor141in the backward direction by turning on the second switching element FET2and the third switching element FET3of the H-bridge210and turning off the first switching element FET1and the fourth switching element FET4of the H-bridge210. Arrows shown inFIG.5indicate current flows flowing through the third switching element FET3, the electric motor141, and the second switching element FET2.

In the parking operation mode in which the electric motor141rotates in the forward direction by the H-bridge210, the forward rotation of the electric motor141may be decelerated through the speed reducer142to rotate the spindle member135in one direction with a large force. When the spindle member135rotates in one direction, the nut member131may move in an axial direction. When the nut member131presses the piston121, the two brake pads113may press the brake disk100to brake the wheel. The operation in the parking release mode may be opposite to the operation in the parking operation mode.

FIG.6is a circuit operation diagram when a motor lock is inspected in the electronic parking brake system according to an embodiment.

Referring toFIG.6, in the motor lock inspection mode, the controller200operates the electric motor141in a free wheel state by turning off the first switching element FET1and the third switching element FET3on the high side of the H-bridge210and turning on the second switching element FET2and the fourth switching element FET4on the low side of the H-bridge210. An arrow shown inFIG.6indicates a current flow flowing through the second switching element FET2, the electric motor141, and the fourth switching element FET4. The direction of the arrow is indicated clockwise, but counterclockwise is also possible. On the other hand, the first switching element FET1and the third switching element FET3on the high side may be turned on, and the second switching element FET2and the fourth switching element FET4on the low side may be turned off.

Therefore, a winding of the electric motor141is short-circuited by the H-bridge210turning on only the elements on the high side or the low side, and the current is recirculated and slowly attenuated depending on an inductor/resistance time constant of the electric motor141. Because this method short-circuits the back electromotive force of the electric motor141, the electric motor141is rapidly braked. The recirculated current is dissipated as heat through a resistance of the inductor and a resistance of the two switching elements.

The controller200may recognize the voltage VM of the electric motor141by detecting a voltage from the winding of one side of the electric motor141.

The controller200monitors the back electromotive force (back EMF) of the electric motor141in the motor lock inspection mode.

The controller200may determine the motor lock based on the back electromotive force of the electric motor141generated while the electric motor141operates in the free wheel state in the motor lock inspection mode.

The controller200may determine the motor lock based on a slope of the motor back electromotive force generated while the electric motor141operates in the free wheel state in the motor lock inspection mode.

FIG.7is a flowchart of a control method of the electronic parking brake system according to an embodiment.

Referring toFIG.7, a control method of the electronic parking brake system according to an embodiment may include turning off the first switching element FET1and the third switching element FET3on the high side of the H-bridge210and turning on the second switching element FET2and the fourth switching element FET4on the low side of the H-bridge210in order for the electric motor141to be in the free wheel when inspecting the motor lock (300), detecting the motor back electromotive force (302), determining whether the slope of the motor back electromotive force is equal to or greater than a preset slope (304), determining that the motor is normal when the slope of the motor back electromotive force is not equal to or greater than the preset slope (306), determining that the motor lock occurs when the slope of the motor back electromotive force is equal to or greater than the preset slope (308), and warning of the motor lock (310).

FIG.8is a graph illustrating a normal motor back electromotive force and a motor back electromotive force when the motor lock occurs in the electronic parking brake system according to an embodiment.

Referring toFIG.8, the controller200converts the parking operation mode in which the electric motor141is driven or the parking release mode to the motor lock inspection mode in which the electric motor141operates in the free wheel state.

The controller200converts the parking operation mode or the parking release mode to the motor lock inspection mode by turning off the first switching element FET1and the third switching element FET3on the high side and turning on the second switching element FET2and the fourth switching element FET4on the low side.

When the controller200converts the parking operation mode or parking release mode to the motor lock inspection mode, in the cases of the normal state in which the electric motor141is not locked and the locked state in which the electric motor141is locked, the back electromotive forces of the electric motor141generated in the parking operation mode and the parking release mode appear differently. More specifically, the changes in the slopes of the back electromotive forces of the electric motor appear differently.

Because the electric motor141operates in the free wheeled state in the case of the normal state in which the electric motor141is not locked, the motor back electromotive force decreases relatively gently.

However, because the electric motor141does not operate in the free wheel state in the case of the state in which the electric motor141is locked, the motor back electromotive force decreases relatively steeply.

When a slope ΔV/Δt of the motor back electromotive force between a time point t1and a time point t2is greater than the preset slope, the controller200may determine that the motor lock occurs and determine as a motor lock failure. As such, the motor lock failure may be determined only by the slope of the motor back electromotive force without using a current sensor.

FIG.9is a circuit diagram for driving an EPB of an electronic parking brake system according to another embodiment.

Referring toFIG.9, the electronic parking brake system according to another embodiment may additionally include a current sensor230electrically connected to the input side of the controller200.

The current sensor230may detect a current flowing through the electric motor141of the EPB10. The current sensor230may detect a current supplied to the electric motor141from the motor power supply B+.

One side of the current sensor230is connected to a source terminal of the second switching device FET2and the fourth switching device FET4on the low side, and the other side of the current sensor230is grounded.

The current sensor230may detect a current on a circuit in which the current sensor230is installed by using a shunt resistor or a Hall sensor. The current sensor230may use various methods capable of detecting a motor current other than the shunt resistor or the Hall sensor. The current sensor230may transmit information on the detected current to the controller200.

When the motor current detected through the current sensor230in the parking operation mode or the parking release mode is higher than a preset current, and the slope of the motor back electromotive force in the motor lock inspection mode is greater than the preset slope, the controller200may determine that the motor lock occurs and determine as the motor lock failure.

As is apparent from the above, according to an embodiment of the disclosure, a motor lock can be reliably detected without a current sensor, so that a product can be miniaturized and a manufacturing cost can be reduced.

Further, while the method of using the current sensor detects a motor lock only during motor operation, according to an embodiment of the disclosure, a situation in which the motor lock occurs immediately after the motor operation can be detected.

Further, according to another embodiment of the disclosure, when used with the current sensor, a failure can be detected more reliably.