Patent ID: 7766398

Claim:
A door lock system comprising: a door handle disposed and operable from outside of a door for opening/closing the door; a lock mechanism including a switching lever, the switching lever capable of moving between a neutral position and a locking position and between the neutral position and an unlocking position, wherein the lock mechanism is configured to prevent opening of the door by operation of the door handle when the switching lever is moved from the neutral position to the locking position, and allows opening of the door by operation of the door handle when the switching lever is moved from the neutral position to the unlocking position; a key cylinder that is disposed on the door handle and that rotates according to a key operation and includes a cylinder returning spring that keeps the key cylinder at a normal position when no key operation is performed; a link unit that receives a key operation force when the key cylinder is rotated according to the key operation and conveys the key operation force to the switching lever of the lock mechanism to thereby move the switching lever between the neutral position and the locking position and between the neutral position and the unlocking position; a holding unit that biases the switching lever to the neutral position when the link unit does not receive the key operation force; and a housing for housing the switching lever, wherein the holding unit is a lever returning spring interposed between the housing and the switching lever, the link unit is a torque cable interposed between the key cylinder and the switching lever, and the lever returning spring has a spring constant that is smaller than that of the cylinder returning spring in the key cylinder, wherein the switching lever comprises a spring working piece that engages with the lever returning spring when the lever returning spring has been moved to the locking position or the unlocking position.