Electromechanical brake system and control method thereof

1. An electromechanical brake system, comprising:

a pair of pad plates to which a brake pad is attached, respectively, to press a disc that rotates with a wheel;

a carrier on which the pair of pad plates are installed;

a caliper housing slidably installed on the carrier;

a piston movably installed in forward and backward direction inside the caliper housing;

a power transfer part configured to press the pair of pad plates onto the disc by moving the piston;

a brake actuator comprising a drive motor configured to provide a rotational force of the drive motor to the piston, and a reduction gear part configured to decelerate the rotational force of the drive motor and transmit the decelerated rotational force to the power transfer part;

a parking actuator connected to the brake actuator to maintain a parking braking state of a vehicle;

a force sensor configured to detect a clamping force due to a contact between the disc and the brake pad; and

a controller configured to control the brake actuator and the parking actuator,

wherein the controller is configured to control the parking actuator based on the clamping force detected through the force sensor,

wherein the parking actuator comprises:

a parking gear; and

a parking lever having one side hinged and another side provided to be engaged with the parking gear;

wherein the parking gear is concentric with the reduction gear and is connected to the reduction gear such that the parking gear is integrally rotatable together with the reduction gear.

2. The electromechanical brake system of claim 1 , wherein the parking actuator comprises:

a parking motor configured to generate power;

a power conversion part comprising a spindle member configured to rotate by receiving a rotational driving force of the parking motor, and a nut member screwed with the spindle member to move forward and backward; and

a pressing part installed on the nut member and configured to press the parking lever by forward and backward movement of the nut member.

3. The electromechanical brake system of claim 2 , wherein the controller is configured to control the parking actuator, when the clamping force detected through the force sensor reaches a target clamping force in a parking apply mode.

4. The electromechanical brake system of claim 3 , wherein, when the clamping force detected through the force sensor reaches the target clamping force, the controller is configured to engage the parking lever with the parking gear by rotating the parking motor of the parking actuator in one direction to perform a parking-on operation.

5. The electromechanical brake system of claim 4 , wherein, when the clamping force detected through the force sensor is lower than the target clamping force after the parking-on operation is completed, the controller is configured to separate the parking lever from the parking gear by rotating the parking motor of the parking actuator in an opposite direction to perform a parking-off operation, and

when the clamping force detected through the force sensor reaches the target clamping force, the controller is configured to perform the parking-on operation again.

6. The electromechanical brake system of claim 5 ,

wherein one surface of the parking lever facing the parking gear is provided with lever gear teeth meshing with gear teeth of the parking gear and the opposing surface of the parking lever is provided with a pressing surface bent to be gradually pressed by the pressing member when the pressing member moves forward,

wherein the parking actuator further comprises a stepped surface formed from the pressing surface in a stepped manner such that the stepped surface prevents the nut member from moving forward excessively.

7. The electromechanical brake system of claim 6 , wherein the force sensor is disposed between the power transfer part and the brake actuator.

8. A control method of an electromechanical brake system according to claim 1 , the control method comprising:

detecting a clamping force due to a contact between the disc and the brake pad through a force sensor; and

controlling the parking actuator based on the clamping force detected through the force sensor.

9. The control method of claim 8 , wherein the controlling of the parking actuator operates the parking actuator for a parking-on operation, when the clamping force detected through the force sensor reaches a target clamping force in a parking apply mode.

10. The control method of claim 9 , wherein the controlling of the parking actuator

when the clamping force detected through the force sensor is lower than the target clamping force after the parking-on operation with respect to the parking actuator is completed, operates the parking actuator for a parking-off operation, and

when the clamping force detected through the force sensor reaches the target clamping force, operates the parking actuator for the parking-on operation again.