Seat slide apparatus for vehicle

A seat slide apparatus for a vehicle, comprising:

• a first rail including a pair of flanges arranged side by side in a width direction where an end of each of the pair of flanges is formed with a plurality of locking protrusions;
• a second rail connected to the first rail to be relatively movable;
• a lock member connected to the second rail to rotate about an axis extending in the width direction, the lock member formed with a locking portion configured to receive the locking protrusion to fit into the locking portion, the lock member selectively locking and restricting relative movement between the first rail and the second rail by the locking protrusion removably fitting into the locking portion in response to rotational movement of the lock member;
• a pair of resilient members rotationally biasing the lock member in a direction to lock and restrict the relative movement between the first rail and the second rail;
• and
• an operation member configured to transmit an operational force to the lock member for releasing the first rail and the second rail from a locked and restricted state to allow the relative movement between the first rail and the second rail, wherein
• the lock member connects to the second rail to be rotatable about a retaining shaft positioned at the axis extending in the width direction, the retaining shaft fixed to either one of the second rail and the lock member and rotationally supports the other one of the second rail and the lock member, wherein
• each of the pair of resilient members includes a shaft biasing portion biasing the retaining shaft in a direction opposite to a direction of biasing the lock member and includes a first and a second end portions arranged at positions arranging the shaft biasing portion between the first and the second end portions where the first end portion is locked and restrained to the lock member and the second end portion is locked and restrained to the second rail, wherein
• a first resilient member of the pair of resilient members includes a stress concentrating portion concentrating stress greater than the stress at a second resilient member of the pair of resilient members, the stress concentrating portion arranged on the shaft biasing portion at one side in the direction of the relative movement between the first rail and the second rail, and wherein
• the first rail is provided with a plurality of engaging portions arranged next to each other and aligning in a direction of the relative movement between the first rail and the second rail, the engaging portions configured to engage with the stress concentrating portion of the first resilient member released from the retaining shaft.