Vehicle door latch device with one-motion door opening mechanism and antitheft mechanism

#The present invention relates to a vehicle door latch device, and more particularly to a vehicle door latch device provided with a one-motion door opening mechanism and an antitheft mechanism.

#A conventional vehicle door latch device is provided with a lock lever which is displaceable, by an unlocking operation and a locking operation of an inside lock button of the door, between an unlocked position where an opening operation of an outside open handle of the door is transmitted to a ratchet so as to open the door and a locked position where the opening operation of the outside open handle is not transmitted to the ratchet. Because the inside lock button to which the lock lever should be connected is disposed on an interior surface of the door in the exposed state, an antitheft performance of the lock button is not so high. For example, it is quite easy to operate the lock button by breaking a door glass from outside the vehicle to illegally change the lock lever to the unlocked position. To invalidate such an illegal access to the lock button, a number of antitheft mechanisms have been developed.

#The typical antitheft mechanism has a free-play mechanism provided between the inside lock button and the lock lever (e.g., U.S. Pat. No. 5,538,298). The free-play mechanism can absorb an unlocking movement of the lock button so as not to transmit the unlocking movement to the lock lever. That is, no external force is applied to the lock lever even if the lock button is operated to unlock illegally. This free-play type antitheft mechanism effectively invalidates the illegal access to the inside lock button.

#FIG. 1 is a front view of a latch assembly of a door latch device according to the present invention;

#FIG. 2 is a rear view of the latch assembly in a locked state;

#FIG. 3 is a side view showing an interior side of the latch assembly;

#Referring to FIG. 1, a vehicle door latch device in accordance with the present invention comprises a latch assembly 1 which is attached to a vehicle door (not shown) and a striker 2 which is fixed to a vehicle body (not shown). The latch assembly 1 has a latch 3 which is engaged with the striker 2 when the door is closed, and a ratchet 4 which holds the engagement between the latch 3 and the striker 2. The latch 3 is rotatably received by a latch shaft 7 in a recess 6 formed in the front surface of a synthetic resin latch body 5, and the ratchet 4 is rotatably received in the recess 6 by a ratchet shaft 8.

#The latch 3 is urged clockwise in FIG. 1 by a spring force of the latch spring 9. When the door is in an open position, the latch 3 is located in an unlatched position or open position as shown in FIG. 1 by the spring force of the latch spring 9. The ratchet 4 is urged counterclockwise by a spring force of a ratchet spring 10 to be brought into contact with the latch 3. When the door is moved toward a full-closed position, the striker 2 enters a horizontal passage 11 formed in the latch body 5 to be brought into contact with a U-shaped groove 12 of the latch 3, and the latch 3 is then rotated counterclockwise against the latch spring 9. When the latch 3 is rotated up to a half-latched position, the ratchet 4 is engaged with a first step 13 of the latch 3 and the door reaches a half-closed position. Further, when the latch 3 comes to a full-latched position, the ratchet 4 is engaged with a second step 14 of the latch 3 and the door is held in the full-closed position.

#The ratchet 4 has a ratchet pin 16 projecting onto the rear side of the latch body 5 through an opening 15 of the latch body 5. To the front surface of the latch body 5, a metal cover plate 17 for covering the recess 6 is fixed. The cover plate 17 is partially shown in FIG. 1.