Patent Publication Number: US-6042160-A

Title: Latch device for vehicle back door

Description:
FIELD OF THE INVENTION 
     The present invention relates to a latch device for a vehicle back door and particularly relates to a latch device for improving strength and rigidity of a housing thereof. 
     PRIOR ART 
     A housing of a latch device used in a vehicle back door is conventionally constructed by a main metal plate and a sub metal plate fixed to the main plate. A spatial portion for storing a latch which is engageable with a striker and a ratchet which is engageable with the latch for holding the engagement of the latch with the striker is provided within the housing. The main plate is formed by press drawing working into a vessel shape having upright front and rear walls, upright right-hand and left-hand walls, and a bottom wall. The sub plate is attached to the main plate so as to cover an upper opening of the vessel to define the spatial portion of the housing. A main notch portion and a sub notch portion for receiving the striker when the back door is closed are respectively formed in the bottom wall and the front wall. The strength of the housing thus formed substantially depends on strengths of the two metal plates. 
     FIG. 1 shows results obtained by tentatively giving a large load to the conventional latch device. As can be clearly seen from FIG. 1, when a striker A is pulled by a large load in the direction of an arrow B, a rear wall D of the main plate C which is originally flat as shown by a phantom line is greatly curved as shown by a solid line and a main notch portion E of the main plate C is greatly opened so that a latch F can be disengaged from a housing G. This problem can be overcome by arranging a reinforcing member within the housing as in a latch device of a vehicle swinging door. However, it is not realistic to add the reinforcing member to the latch device for the back door since the back door latch device must be manufactured at low cost. 
     FIGS. 2 and 3 show results of applying a large load to the striker A in a different direction. When the load is applied to the striker A in the direction of an arrow H, the main plate C is strongly pulled downward. As a result, a shift is caused between an attaching portion J of the main plate C and an attaching portion L of the sub plate K. It has become clear that this shift further promotes deformation of the main plate C. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of the present invention is to provide a back door latch device for improving the strength of a rear wall of a main plate. 
     Another object of the present invention is to provide a latch device for preventing a notch portion formed in the main plate from being opened by external force. 
     Another object of the present invention is to provide a latch device in which no shift is easily caused between an attaching portion of the main plate and an attaching portion of a sub plate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a plan view of the results of a strength test of a conventional back door latch device when a force in a direction B is applied to the latch. 
     FIG. 2 shows a sectional view through the latch of FIG. 1. 
     FIG. 3 shows the results of a strength test on the latch of FIG. 2 when a force in a direction H is applied to the latch. 
     FIG. 4 is a view showing a latch assembly according to the invention attached to a vehicle back door and a striker fixed to a vehicle body. 
     FIG. 5 is a plan view of the latch assembly of FIG. 4. 
     FIG. 6 is a bottom view of the latch assembly of FIG 4. 
     FIG. 7 is a plan view of a main metal plate of FIG. 4. 
     FIG. 8 is a longitudinal sectional view of the latch assembly of FIG. 4. 
     FIG. 9 is a front view of the latch assembly of FIG. 4. 
     FIG. 10 is a plan view of the striker of FIG. 4. 
     FIG. 11 is a cross-sectional view showing a state in which the latch is engaged with the striker of FIG. 4. 
     FIG. 12 is an enlarged sectional view of a main attaching portion and a sub attaching portion of FIG. 9. 
     FIG. 13 is a view showing a modified example of FIG. 12. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As shown in FIG. 4, a latch device of the present invention has a latch assembly 4 fixed to a back door or a trunk lid 3 of a vehicle and a striker 2 fixed to a vehicle body 1. A housing 50 of the latch assembly 4 is constructed by a substantially vessel-shaped main metal plate 12 and a metal sub plate 13 fixed to an upper portion of the main plate 12 so as to cover an upper opening of the main plate 12. A spatial portion 51 for storing a latch 14 which is engageable with the striker 2 and a ratchet 15 which is engageable with the latch 14 so as to hold the engagement of the latch 14 with the striker 2, is arranged within the housing 50. There is a case in which the latch assembly 4 is attached to the vehicle body 1. In this case, the striker 2 is naturally fixed to the back door 3. 
     The latch 14 and the ratchet 15 are rotatably attached to the housing 50 by shafts 24 and 26, respectively. In FIG. 5, the latch 14 is biased by the resilient force of a spring 27 in a counterclockwise direction, and the ratchet 15 is biased by the resilient force of a spring 28 in a clockwise direction. 
     The main plate 12 is formed by press drawing working into a vessel shape having an upright front wall 16, an upright rear wall 17, an upright right-hand wall 18, an upright left-hand wall 19, and a bottom wall 52. A main notch portion 20 and a sub notch portion 20a for receiving the striker 2 when the back door 3 is closed, are respectively formed in the bottom wall 52 and the front wall 16. 
     A short hook 37 at an upper portion of the front wall 16 is angled to extend forward and is engaged with a slit 36 formed in the sub plate 13. 
     As clearly shown in FIGS. 5 and 6, the upright rear wall 17 is not formed in the shape of a flat wall, but is formed in the shape of an arc wall swelling backward. Therefore, great forward deformation of the rear wall 17 is prevented even when a strong external force is applied to the striker 2 forward, i.e., in the direction of an arrow B. 
     The main plate 12 has a main right-hand attaching portion 29 which is angled to extend horizontally from an upper portion of the upright right-hand wall 18, and a main left-hand attaching portion 30 which is angled to extend horizontally from an upper portion of the upright left-hand wall 19. The sub plate 13 has a sub right-hand attaching portion 32 corresponding to the right-hand attaching portion 29 and a sub left-hand attaching portion 33 corresponding to the left-hand attaching portion 30. The right-hand attaching portions 29, 32 and the left-hand attaching portions 30, 33 are fixed to the back door 3 by using bolts 53 and nuts 54 (see FIG. 12). 
     Holes 31 through which the bolts 53 are inserted are formed in the main attaching portions 29 and 30, holes 34 through which the bolts 53 are inserted are formed in the sub attaching portions 32, 33. As shown in FIG. 12, a diameter of each of the holes 31 is set to be slightly smaller than that of each of the holes 34. Each of the holes 31 has a ring-shaped flange 55 integrally formed with the main attaching portions 29, 30 which is inserted into a corresponding one of the holes 34. A length of the flange 55 is set to be shorter than thickness of the sub attaching portions 32, 33. The engagements between the ring-shaped flanges 55 and the holes 34 prevent generation of the shift explained with reference to FIGS. 2 and 3. FIG. 13 shows a modified example in which the flange 55 extends into each of the holes 34 of the sub attaching portions 32, 33. In the example of FIG. 13, the use of a nut can be omitted by forming a screw groove in each of the flange 55 and a hole 34. 
     As shown in FIGS. 4, 10 and 11, the striker 2 has a metal base plate 5 fixed to the vehicle body 1 by a screw or bolt 9, and a substantially U-shaped rod 6 fixed to the base plate 5. A bent wall 7 is formed in an end portion of the base plate 5 and angled to substantially extend in parallel to the front wall 16. The bent wall 7 does not come in contact with the front wall 16 even when the back door 3 is closed. At least two metal studs 11 projecting toward the front wall 16 are fixed to the bent wall 7. Concave portions or holes 35 for respectively receiving the studs 11 when the back door 3 is closed are formed on both sides of the sub notch portion 20a of the front wall 16. When the studs 11 are respectively engaged with the holes 35 by closing the back door, it is very difficult to widen the front wall 16 leftward and rightward with the sub notch portion 20a as a center. Thus, the bottom wall 52 is prevented from widening leftward and rightward with the main notch portion 20 as a center. 
     The foregoing discussion discloses and describes merely exemplary embodiment of the present invention only. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that various changes, modifications and variations can be made therein without departing from the spirit and scope of the invention as defined in the following claims.