1. Field of the Invention
The present invention relates to a door locking apparatus for a motor vehicle and more particularly to a locking mechanism of a door locking apparatus.
2. Prior Arts
The door locking apparatus comprises a latch plate engaging with a striker secured to the vehicle body, a detent lever engaging with a pawl of the latch plate to hold an engagement condition with the latch plate, an operating lever for operating the detent lever in the direction of disengaging with the pawl of the latch plate when an outer handle or inner handle is operated and a locking mechanism for disabling a disengagement with the pawl even when the outer or inner handle is operated.
With respect to the locking mechanism, a so-called "idle lock type" locking mechanism has been generally used. This type of the locking mechanism is constituted such that an unlocking condition where the operating lever is connected with the detent lever is changed over to a locking condition where the operating lever is disconnected with the detent lever by use of a lock lever. The changeover from the unlocking condition to the locking condition of the lock lever is performed by operating an inner lock lever from inside of the vehicle or turning a key from outside of the vehicle.
When the locking mechanism of the door locking apparatus is in the locking condition, it is constituted such that the door will not open from outside of the vehicle. This causes a problem that a passenger trapped in a car can not be rescued readily due to the broken locking mechanism when the vehicle has a collision, especially when it has a side impact. Further, even if the locking mechanism is in the unlocking condition, there is a possibility that the locking mechanism turns to the locking condition due to an external force applied to the engaging mechanism between the inner lock lever and the lock lever, resulting in taking time to rescue the passenger.
Japanese Utility Model Application Laid-open No. Jitsu-Kai-Hei 4-98972 discloses a technique in which a door lock switch is provided with an impact sensing device for changing over the locking mechanism to the unlocking condition, when a large impact is given to the vehicle body, by returning a movable contact to a fixed contact side. Further, Japanese Utility Model Application Laid-open No. Jitsu-Kai-Hei 6-32648 discloses a technique in which, when an impact is detected by an impact sensor, a control section raises a signal for operating an actuator and the locking mechanism is changed over into the unlocking condition by the operation of this actuator.
However, these prior arts need expensive components such as an impact sensor, an impact sensing mechanism, and an electrically operated actuator and the like. Further, these techniques have an uncertainty about such cases where an impact by collision or a deformation of the body or the door may cause a disconnection in the electrical circuits or other electrical failures.