Brake apparatus for vehicle

1. A brake apparatus for a vehicle, comprising:

a screw bar positioned in a caliper body, and rotated by power received from a motor module, the screw bar including a first portion formed in a rod shape and a second portion which has a larger diameter than the first portion;

a nut configured to be engaged and coupled with a male screw thread on an outer surface of the first portion of the screw bar, and moved toward a brake disk by the rotation of the screw bar;

a piston formed in a pillar shape having a hollow portion configured to cover an outer surface of the nut which has one end integrated with an inside of the piston and protrudes from the one end toward to an open end of the piston and configured to be moved with the nut,

wherein the first portion of the screw bar is inserted into the open end of the piston and the second portion is not inserted into the open end of the piston,

the piston has a length L 1 to cover the outer surface of the nut coupled with the first portion of the screw bar and another outer surface of the first portion of the screw bar which does not have the male screw thread there on, the nut has a length L 2 which is shorter than the length L 1 ; and

a first brake pad connected to the piston, and moved with the piston so as to pressurize the brake disk,

wherein the first brake pad includes a first back plate includes a plurality of first coupling grooves formed therein,

a first friction member made of elastic material includes a plurality of first coupling protrusions coupled to the plurality of first coupling grooves, respectively, so that the first friction member is detachably coupled to the first back plate,

wherein the nut, the piston and the first brake pad are formed as one body and moved together toward the brake disk.

2. The brake apparatus of claim 1 , wherein the nut includes a nut hole having a female screw thread formed therein, the female screw thread being engaged and coupled with the male screw thread of the first portion of the screw bar.

3. The brake apparatus of claim 2 , wherein

the first back plate formed as one body with the piston, and disposed on one side of the brake disk; and

the first friction member coupled to the first back plate, and configured to pressurize the brake disk.

4. The brake apparatus of claim 1 , further comprising a second brake pad coupled to the caliper body so as to face the first brake pad, and contacted with the brake disk.

5. The brake apparatus of claim 4 , wherein the second brake pad comprises:

a second back plate coupled to the caliper body, and disposed on the other side of the brake disk; and

a second friction member coupled to the second back plate, and contacted with the brake disk.

6. The brake apparatus of claim 5 , wherein the second friction member is detachably coupled to the second back plate.

7. The brake apparatus of claim 6 , wherein the second back plate has a plurality of second coupling grooves formed therein, and

the second friction member includes a plurality of second coupling protrusions coupled to the plurality of second coupling grooves, respectively.