Patent Publication Number: US-6669247-B2

Title: Vehicle door latch device

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a vehicle door latch device, and in particular to a latch device provided with power closing and power opening mechanisms of a door (including a hinged passenger door, a trunk lid, a glass hitch, a tailgate and the like). 
     2. Description of the Related Art 
     Conventionally, a door latch device provided with both a power closing mechanism and a power opening mechanism has been known. The known power closing mechanism causes a latch to be rotated to a full-latched position by a motor power after the latch is rotated to a half-latched position through engagement with a striker so that a door is displaced from a half-latched state to a full-latched state. Also, the known power opening mechanism causes the latch to be free to rotate by releasing a ratchet from the latch with a motor power. 
     A problem in such a conventional door latch device lies in that each of the power closing and the power opening mechanisms has own motor. Using two motors causes increase in cost of the latch device and increase in weight thereof. 
     Further, the vehicle door latch device provided with the power closing mechanism is conventionally provided with a safety mechanism which stops or invalidates operation of the power closing mechanism. The safety mechanism is provided with a function for releasing a connected state between the latch and the motor and a function for releasing the ratchet from the latch. 
     There is a drawback that the conventional safety mechanism is complicated and is increased in the number of parts. 
     SUMMARY OF THE INVENTION 
     In view of the above circumstances, an object of the present invention is to provide a door latch device where a power closing mechanism and a power opening mechanism can be operated by only one common motor. Since the power closing mechanism and the power opening mechanism shares one common motor, the door latch device of the present invention can be manufactured inexpensively in a small size and in a reduced weight. 
     Also, another object of the present invention is to provide a door latch device with a simplified structure, which stops or invalidates operation of a power closing mechanism. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front view of a door latch device according to the present invention; 
     FIG. 2 is a vertically sectional side view of the door latch device; 
     FIG. 3 is a front view of a pushing link of the door latch device; 
     FIG. 4 is a front view showing a state where a sector gear of the door latch device has been rotated in a door closing direction; 
     FIG. 5 is a front view showing a state where the sector gear has been rotated in a door opening direction; 
     FIG. 6 is a front view showing a state where an opening lever of the door latch device has been rotated with a first operating force; and 
     FIG. 7 is a front view showing a state where the opening lever has been moved with a second operation force. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An embodiment of the present invention will be explained with reference to the drawings. A door latch device  1  according to the present invention is provided with a latch body  4  comprising a base plate  2  and a cover plate  3 , such as that shown in U.S. Pat. No. 5,172,946. The door latch device  1  is mounted to a vehicle door (including a hinged passenger door, a trunk lid, a glass hatch, tailgate and the like). The device  1  shown in FIGS. 1 and 2 is particularly suitable for mounting on a tailgate  5 . 
     Well-known latch  6  and ratchet  7  are rotatably accommodated inside the latch body  4 . When moving the tailgate  5  in a door closing direction, the latch  6  is brought into contact with a striker  8  fixed to a vehicle body  8   a  and is rotated from an unlatched position to a half-latched position to be engaged with the striker  8  initially. The latch  6  is rotated from the half-latched position to a full latched position to be fully engaged with the striker  8  due to further movement of the tailgate  5 . The ratchet  7  is engaged with the latch  6  so as to keep engagement between the latch  6  and the striker  8 . 
     An upwardly projecting bracket  9  is fixed to the latch body  4 , and a motor unit  12  comprising a motor  10  and a reduction gear mechanism  11  is mounted to an upper portion of the bracket  9 . A sector gear  14  is pivoted to a central portion of the bracket  9  through a sector shaft  13 , and a gear portion  14 A of the sector gear  14  meshes with an output gear  15  of the motor unit  12 . The sector gear  14  being in a neutral position shown in FIG. 1 is rotatable in a clockwise direction (door closing direction) and in a counterclockwise direction (door opening direction) by power of the motor  10 . A sector switch  16  is provided on the bracket  9  in the vicinity of the sector gear  14 . When the sector gear  14  is rotated, a contact terminal  17  of the sector switch  16  is selectively brought into contact with one of two sensor pins  18  and  19 . 
     A right end portion  21  of a pushing link  20  (FIG. 3) is pivoted to a proximal portion side of the sector gear  14  via a pin  22 . The substantially horizontally elongated pushing link  20  is provided at its central lower portion with an vertically extending abutting portion  23  and it is also provided at its left side portion with a substantially horizontally elongated gently curved guide slot  24 . A front end portion of a guide pin  25  extending in a front-and-rear direction is slidably inserted into the guide slot  24 . When the sector gear  14  is rotated from the neutral position in the clockwise direction, the pushing link  20  is moved to a left side while its left side portion is being guided by the guide pin  25 . A rear end portion of the guide pin  25  is inserted into a vertical groove or slot  26  formed in the bracket  9 . The pin  25  is slidable in a vertical direction within the vertical groove  26 . 
     A latch lever  27  provided above the latch body  4  is rotated together with the latch  6  as one piece. The latch  6  and the latch lever  27  have a common rotating shaft or latch shaft  28 . A latch switch  40  is disposed in the vicinity of the latch lever  27 . By contact of the latch switch  40  with the latch lever  27 , the half-latched position of the latch  6  is detected. 
     A front end  29  of the latch lever  27  is positioned in the vicinity of the abutting portion  23  of the pushing link  20 . When the pushing link  20  is moved leftward by power of the motor  10 , the abutting portion  23  abuts on the front end  29  of the latch lever  27  to rotate the latch  6  toward the full-latched position via the latch lever  27 . The mechanism for rotating the latch lever  27  (latch  6 ) by the motor power of the motor  10  is called “power closing mechanism”. The power closing mechanism is actuated when the latch switch  40  detects the half-latched position of the latch  6 . 
     The cover plate  3  of the latch body  4  has an upwardly extending sub-plate  30 , and a ratchet lever  32  is pivoted to the sub-plate  30  via a shaft  31 . A first arm  33  of the ratchet lever  32  extends inside the latch body  4  through a gap between the base plate  2  and the cover plate  3  so as to be engageable with a distal end  34  of the ratchet  7 . 
     A short second arm  35  of the ratchet lever  32  has a rearward bent portion  36  which is engageable with an upper face  21 A of the right end portion  21  of the pushing link  20 . When the sector gear  14  is rotated from the neutral position in the counterclockwise direction by power of the motor  10 , the upper face  21 A of the right end portion  21  abuts on the bent portion  36  to rotate the ratchet lever  32  about the shaft  31  in the counterclockwise direction. The first arm  33  of the ratchet lever  32  then abuts on the distal end  34  of the ratchet  7  to rotate the ratchet  7 , thereby the ratchet  7  is released from the latch  6  and the tailgate  5  is opened. The mechanism for rotating the ratchet  7  by the motor power of the motor  10  is called “power opening mechanism”. It should be noted that the power opening mechanism and the power closing mechanism has only one common motor  10 . 
     An opening lever  37  is disposed on a left side of the ratchet lever  32 . The opening lever  37  is rotatably supported at a front end of the guide pin  25 . The opening lever  37  is provided at its right end with a pushing portion  39  which is engageable with a third arm  38  of the ratchet lever  32 . It is desirable that an operation arm  41  of the opening lever  37  is connected to a key cylinder (not shown) of the tailgate  5 . 
     Operation of the door latch device of the present invention will be explained below. 
     When the tailgate  5  is manually moved in the closing direction, the latch  6  is rotated from the unlatched position to the half-latched position due to the initial engagement with the striker  8 , and the latch switch  40  then detects displacement of the latch  6  to the half-latched position. Simultaneously, the ratchet  7  is engaged with the latch  6  to keep the initial engagement of the latch  6  and the striker  8 . 
     When the initial engagement (half-latched state) is detected, the power closing mechanism is actuated. That is, the motor  10  that is a member of the power closing mechanism rotates in the closing direction to rotate the sector gear  14  in the clockwise direction in FIG.  1 . Then, the pushing link  20  connected to the sector gear  14  via the pin  22  is moved leftward, and the abutting portion  23  of the pushing link  20  is brought into contact with the front end  29  of the latch lever  27  to rotate the latch lever  27  as shown in FIG. 4, thereby the latch  6  is rotated from the half-latched position to the full-latched position via the latch lever  27  and the tailgate  5  is closed by power of the motor  10 . 
     The rotation of the motor  10  in the closing direction is controlled by time, a load current value of the motor  10  or the like. When the latch  6  is displaced into the full-latched position by the motor  10 , the motor  10  is rotated in the opening direction until the contacting terminal  17  of the sector switch  16  comes in contact with the sensor pin  18  of the sector gear  14 , and the sector gear  14  is returned to the neutral position. 
     In order to conduct emergent stopping of the closing operation of the tailgate  5  effected by the power of the motor  10 , the operation arm  41  of the opening lever  37  is moved upward in FIG.  4 . Then, the opening lever  37  is rotated about the guide pin  25  in the clockwise direction and the pushing portion  39  of the opening lever  37  pushes the third arm  38  of the ratchet lever  32  downward so as to rotate the ratchet lever  32  about the shaft  31  in the counterclockwise direction, as shown in FIG. 6, thereby the first arm  33  of the ratchet lever  32  abuts on the distal end  34  of the ratchet  7  to rotate the ratchet  7 , so that the latch  6  is released from the ratchet  7 . The force or power applied for rotating the opening lever  37  about the guide pin  25  in the clockwise direction by moving the operating lever  4  upward is hereinafter referred to as “first operating force”. 
     In the state shown in FIG. 6, the latch  6  is put in a state where it has been released from the restraint of the ratchet lever  7 . However, the abutting state of the abutting portion  23  of the pushing link  20  and the latch lever  27  is still maintained, and this means that the connection between the latch  6  and the motor  10  has not been released yet. Therefore, the latch  6  cannot return back towards the unlatched position in the state shown in FIG.  6 . 
     For this reason, in the state shown in FIG. 6, the operating arm  41  of the opening lever  37  is further lifted by a second operating force in order to cancel the connection state between the latch  6  and the motor  10 . That is, when applying the second operating force to the opening lever  37 , the opening lever  37  is moved upward using the third arm  38  of the ratchet lever  32  as a fulcrum, as the ratchet lever  32  is positioned at a mechanical rotation limit position. The guide pin  25  is then moved upwardly along the vertical groove  26  and the pushing link  20  is rotated about the pin  22  in the clockwise direction as shown in FIG. 7, thereby the abutting portion  23  of the pushing link  20  is disengaged from the front end  29  of the latch lever  27 , so that the connection state of the latch  6  and the motor  10  is cancelled. As a result, the front end  29  of the latch lever  27  returns back from the solid line position to an imaginary line position (unlatched position) and the tailgate  5  is opened. Since the second operating force acts in the substantially same direction as the first operating force, an operator must not distinguish the first operating force and the second operating force from each other. Therefore, when he/she lifts up the operating arm  41  simply, the first operating force and the second operating force serve necessarily in a sequential manner. 
     In the closed state of the tailgate, when the motor  10  is rotated in the opening direction by a door opening switch of a remote controller or an actuation switch provided near to a driver&#39;s seat, the sector gear  14  is rotated from the neutral position in the counterclockwise direction, the right end portion  21  of the pushing link  20  is then moved upward to abut on the bent portion  36  of the ratchet lever  32 , and the ratchet lever  32  is rotated about the shaft  31  in the counterclockwise direction. Then, the first arm  33  is brought into contact with the distal end  34  of the ratchet  7  to rotate the ratchet  7 , so that the latch  6  is released from the ratchet  7  and the tailgate  5  is opened. 
     In the above embodiment, the present invention has been explained as the latch device for the tailgate, but the power closing mechanism and the power opening mechanism are also applicable to various latch device for a vehicle door including a swinging type door and a sliding type door. When these doors is each provided with an opening handle, such a structure may be employed that the opening lever  37  is connected to the opening handle.