Patent Publication Number: US-6341448-B1

Title: Cinching latch

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims priority of U.S. Provisional Application No. 60/055,296, filed on Aug. 13, 1997, the contents of which are hereby incorporated by reference and is a continuation of Ser. No. 09/132,906, filed Aug. 12, 1998, now U.S. Pat. No. 6,125,583. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is related to a power sliding mini-van door, and in particular, to a motor which can be used to drive both a power drive assembly and a lock cinching assembly of the door. 
     2. Background of the Related Art 
     Conventional systems for automatically opening and closing a sliding door in a vehicle include a power drive assembly for moving the door and a latch assembly for cinching the door so that the door can be moved into a fully locked position. A first motor drives the power drive assembly and a second motor drives the latch assembly. The use of these multiple motors leads to a number of difficulties. For example, the use of the multiple motors increases the cost of the system and further necessitates additional corresponding circuitry to be added to the system, thereby further increasing costs. Moreover, the increase in components as a result of using multiple motors results in an undesirable increase in the weight of the door. 
     When the door of the vehicle is being opened or closed, it will often encounter an obstacle which will resist or hinder the door&#39;s movement. This obstacle can be, for example, a user of the vehicle. Thus, it is desirable for a system which automatically opens or closes the door to be able to reverse direction upon the detection of the obstacle. Unfortunately, these detection systems can fail, sometimes without previous notification of its defective state being provided to the vehicle&#39;s users. Accordingly, it would be desirable to have at least two systems to detect obstacles of the door&#39;s movement in case one of the systems fails. 
     In conventional systems, changes in motor speed are a direct function of the effective voltage of an input signal. When the opening or closing of the door is initiated, the rapidly changing input signal causes an in-rush current. This in-rush current is known to demagnetize motor magnets, which reduces horsepower and is detrimental to the life of any motor. Thus, it would be desirable to reduce or eliminate the in-rush current. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to use a single motor to drive both the power drive assembly and a latch assembly of a vehicle door. This will decrease the number of required parts and hence, simplify and lower the cost of manufacture, while reducing the weight of the door. 
     This object is achieved by providing power sliding door for a motor vehicle that comprises a door structure, a power drive assembly, a latch assembly, and a single motor for operating both the latch assembly and the power drive assembly. The door structure is mounted on a track associated with the motor vehicle, the door structure being movable along the track between opened and closed positions. The power drive assembly is connected with the door and capable of being driven to move the door along the track between the opened and closed positions. The latch assembly is mounted on the door and movable between latched and unlatched positions. The single motor is mounted on the door structure operatively connected with both the power drive assembly and the latch assembly. The motor drives the power drive assembly and thus enables the power drive assembly to move the door along the track between the opened and closed positions. The motor assists movement of the latch assembly to the latched position after the power drive assembly moves the door to the closed position. 
     It is another object of the present invention to provide two systems for detecting an obstacle to the door&#39;s movement. One of two systems includes at least one Hall effect sensor to measure the speed of the motor. If the detected speed is less than a predetermined threshold, then it is assumed that an obstacle is in the way of the door and hence, the direction of the motor is reversed. The second system of the present invention includes a tape switch mounted on the edge of the door. The tape switch has two electrical strips which will contact each other if the tape switch contacts an obstacle and will provide a signal to reverse the direction of the motor. These two systems operate independently of one another. Therefore, if one of the systems fails, the other would still enable the motor to reverse direction upon detection of an obstacle. Thus, the safety of all users of the vehicle is maintained. 
     It is another object of the invention to include a controller to provide a signal to the motor which slowly ramps up the effective voltage, and hence the speed of the motor, when the opening or closing of the door is initiated. This will reduce or eliminate the in-rush current caused by a rapid start sequence. Thus, the life and performance of the motor is enhanced. 
     These and other objects, features and characteristics of the present invention, will be more apparent upon consideration of the detailed description and appended claims with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partial exterior elevational view of a mini-van incorporating the power sliding door of the present invention; 
     FIG. 2 is a partial inboard elevational view of a passenger side mini-van power sliding door, with the paneling removed, and in accordance with the principles of the present invention; 
     FIG. 3 is an inboard plan view of an actuating brain plate incorporated in the power sliding door of the present invention, with the actuator in a neutral position; 
     FIG. 4 is an inboard plan view of the actuating brain plate shown in FIG. 3, with the actuator retracted and a lower assembly disengage cable tensioned; 
     FIG. 5 is an inboard plan view of the actuating brain plate shown in FIG. 3, with the actuator extended, and a lower assembly engage cable tensioned; 
     FIG. 6 is an inboard perspective view of a motor drive control assembly incorporated in the power sliding door of the present invention; 
     FIG. 7 is a front view of the motor drive control assembly shown in FIG. 6; 
     FIG. 8 is a side view of the motor drive control assembly shown in FIG.  6 . 
     FIGS. 9-13 are graphical representations of the voltage waveforms of the motor drive control assembly, for determining the speed of the motor drive and for detecting the presence of an obstacle in the door travel path; 
     FIG. 14 is a schematic representation of the motor and hall effect sensors used in the obstacle detection arrangement in the power sliding door of the present invention; 
     FIG. 15 is a sectional view taken through the line  15 — 15  in FIG. 2 of a tape sensor used for obstacle detection in the power sliding door of the present invention; 
     FIG. 16 is a sectional view of the tape sensor of FIG.  15  and illustrating two pinch points for obstacle detection; 
     FIG. 17 is a perspective view of the lower drive assembly of the power sliding door of the present invention; 
     FIG. 18 is a partial plan view of the lower drive assembly of FIG.  17  and positioned at the rear end of the track rail; 
     FIG. 19 is a sectional view of the vehicle track assembly to which the door of the present invention is mounted; 
     FIG. 20 is a partial plan view of the lower drive assembly with the clutch assembly engaged; 
     FIG. 21 is an overhead plan view similar to that in FIG. 20, but with the clutch assembly disengaged; 
     FIG. 22 is a plan view of the door track rail system in mounted relation with a conventional mini-van floor and door sill, and the lower drive assembly at the forward end of the track rail; 
     FIG. 23 is an inboard side rear perspective view of the door latch assembly with portions of the door cut away for clarity of illustration; 
     FIG. 24 is a front perspective view of the latch assembly with the cover plate omitted for clarity of illustration; 
     FIG. 25 is a plan view of the latch assembly, with the cover plate omitted, and in the full open position; 
     FIG. 26 is a plan view of the latch assembly similar to FIG. 25, but shown in the secondary latching position; 
     FIG. 27 is a plan view of the latch assembly similar to FIG. 25, but showing the power cinch cable in a cinching mode; 
     FIG. 28 is a plan view of the latch assembly similar to FIG. 25, but shown in the primary latching position; 
     FIG. 29 is a perspective view of a coupler for coupling the ratchet and the cinching arm of the latch assembly. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Referring now more particularly to the drawings, there is shown in FIG. 1 a partial exterior elevational view of a mini-van which incorporates a power sliding door, generally indicated at  10 , in accordance with the present invention. The door  10  is shown mounted on vehicle track  204 . FIG. 2 is a partial inboard elevational view of the passenger side power-sliding mini-van door  10 , embodying the principles of the present invention. The mini-van door  10  generally comprises a lower drive assembly  14  cooperable with a track assembly for moving the door between opened and closed positions, a brain plate actuating assembly  16  for door actuation, a motor and gear assembly  18  for automated door opening and closing, a microprocessor  20  for system logic and actuation control, and an electro-mechanically actuated cable controlled latch assembly, generally indicated at  22 . The brain plate actuating assembly  16  is mounted below the door window  23  in a recessed section of the door frame  24 . The microprocessor  20  is a computer chip programmed to control the logic and sequence of operation. The microprocessor  20  receives feedback information from various electrical components and processes the information through its software providing output signals that operate the system. As shown in FIG. 2, the brain plate actuating assembly  16  includes an electrically operated linear actuator  36  rigidly mounted to the door frame  24 , forwardly of a mounting plate  30  (relative to the fore-aft vehicle direction). The linear actuator  36  has an electrically actuated motor  35  that is electrically connected, as at  37 , to receive the output signal from microprocessor  20  which is mounted within a motor assembly housing  107  (see FIG.  5 ). In FIG. 3, the linear actuator  36  is shown in a neutral or central position, as will be described in greater detail later. 
     A movable cylindrical extension rod  52  is connected to and driven for movement by the electrical motor  35 . The extension rod  52  is movable along its longitudinal axis between extended and retracted positions. The extension rod  52  is protected by a flexible accordion sheath  55  that covers the interconnecting area between the electrical motor  35  and the extension rod  52 , thereby protecting the linear actuator  36  from dirt or debris. The distal end of the extension rod  52  has a centrally located aperture  56  extending vertically therethrough. 
     The brain plate actuating assembly  16  also comprises a linkage assembly, shown at  50 , for operatively connecting the actuator  36  with the lower drive assembly  14  and latch assembly  22 . The linkage assembly  50  includes a generally flat triangular or sector shaped actuating plate  32 , which is pivotally attached by pivot pin  58  to the mounting plate  30 . An arcuate outer edge  61  defines the size and general shape of the actuating plate  32 . At the upper pivotal corner is a longitudinal protrusion  60  extending upwardly. A small oval shaped bumper  62  is attached to the upper end of the longitudinal protrusion  60  and extends laterally outwardly therefrom. 
     A tab  64  extends downwardly from the lower corner of the actuating plate  32 . The tab  64  extends through the aforementioned aperture  56  in the rod  52  of the linear actuator  36 . The tab  64  coacts with linear actuator  36  to pivot the actuating plate  32  in the desired direction. At the opposite upper corner of actuating plate  32  is a cable engaging end bracket  66 . A lower assembly engaging cable  48  has a ball end  49  constructed and arranged to engage bracket  66 . 
     The brain plate assembly  16  also mounts one end of a door unlatching rod assembly  40 . More particularly, rod assembly  40  comprises a rod member  190  and a rod clamp  42  that also functions as a rod lever. More particularly, the rod clamp  42  is fixed to rod member  190 , and has a pin  43  which is received in a slot  45  in the mounting plate  30 . When the rod clamp  42  is moved to the left in the figures, it carries with it the end of latch rod  190 , as pin  43  rides within slot  45 . The opposite end of latch rod  190  extends to the latch assembly  22 , as will be described in greater detail later. A rod spring  38  is connected between the mounting plate  30  and the rod clamp  42 , biasing the rod clamp  42  and the latch rod  190  towards the right or a stand-by position in FIGS. 3-5. 
     Fixed to the actuating plate  32 , directly above tab  64 , is a cylindrical guide pin  74  which extends inwardly toward the door frame  24 . The guide pin  74  passes through a longitudinal slot  76 , in the forward end of an elongate connecting link  26 . The opposite or rearward end of connecting link  26  is pivotally connected to an L-shaped pivot link  28  by a connecting pin  84 . 
     A connecting spring  34  is attached between the mounting plate  30  at an aperture  78  and the lower side of the connecting link  26  at an aperture  80  in a mid-portion thereof. The spring  34  is tensioned slightly, thereby biasing the connecting link  26  downwardly in a stand-by condition. 
     The L-shaped pivot link  28  is pivotally mounted at a corner between a short leg portion  82  and a stem  92  thereof to the mounting plate  30  by a pivot pin  86 . The ball end  87  of a disengaging cable  88  is received and held in place by a bracket  90 , which extends laterally from the top edge of the stem  92  of the L-shaped pivot link  28 . With the stem  92  of the pivot link  28  held the stand-by condition in FIG. 3, a slight amount of slack is provided for the disengage cable  88 . The distal end of stem  92  of the pivot link  28  is pivotally attached to a slotted, lost motion link member  29  by a hinge pin  94 . 
     The lost motion link member  29  connects the L-shaped link  28  with a second linkage arm  95  disposed in parallel and adjacent relation with actuating plate  32  (i.e., behind plate  32  in FIGS.  3 - 5 ), and is mounted for common pivotal movement around the pivot pin  58 . The linkage arm  95  is operably connected to both inside and outside manual door handles (not shown), and has a laterally extending pin  96  received within a longitudinal slot  98  in the link member  29 . The linkage arm  95  further includes an elongate extension  99  similar to extension  60  of first actuating plate  32 , and similarly has a bumper (not shown) that is adapted to engage the rod/clamp  42  of the rod assembly  40 . 
     Cable sheaths  100  and  102  are fixedly attached to bracket  104 , which is fixed to mounting plate  30 . Engage cable  48  passes through an opening  101  in the bracket  104  and disengage cable  88  passing through opening  103  in the bracket. 
     When the inside or outside handle is manually moved to unlatch the door, the linkage arm  95  is pivoted in an unlatching sense (in a counterclockwise direction in the figures) so that the extension  99  moves the rod clamp  42  to the left against the bias of spring  38 . As a result, the latch rod  190  is moved to the left to unlatch door latch assembly  22 . In addition, such pivotal movement of the linkage arm  95  causes the pin  96  to ride upward within slot  98  until the link member  29  is moved upwards to cause the L-shaped link  28  to pivot in a disengaging sense (in a clockwise direction in the figures) around hinge pin  86 . Bracket  90  is thus raised to tension disengage cable  88 , which is turn disengages the clutch assembly  184  of lower assembly  14 , as will be described in conjunction with FIG.  21 . In this manner, the door  10  can be manually opened with no resistance from motor  108 , as will also be described. 
     During this manual mode of operation, the aforementioned pivotal movement of L-shaped link  28  has no effect on actuating plate  32  or actuator  36 , as link  26  simply slides relative thereto (e.g., in FIG.  3 ), with the actuator and actuating plate  32  remaining in the neutral position. 
     To automatically disengage the clutch  184  of lower assembly  14  without unlocking latch assembly  22  (e.g., during the cinching mode for latch assembly  22 , as will be described), the microprocessor  20  electrically signals the linear actuator  36  to retract, as shown in FIG.  4 . The actuating plate  32  is pivoted from the neutral position in the clockwise direction or disengaging sense and releases any tension from the engage cable  48 . The guide pin  74  of the actuating plate  32  pulls the connecting link  26 , which in turn pulls the short leg  82  of the L-shaped pivot link  28  and pivots the L-shaped pivot link  28  clockwise about the pivot pin  86 . The stem  92  of the pivot link  28  pivots upwardly so that bracket  90  tensions the disengage cable  88 . In this mode of operation, the latch rod  190  is not activated. In addition, the lost motion connection between link  29  and actuating plate  32  via pin  96  and slot  98  prevents the outside or inside door handles (which are functionally connected via pin  96 ) from being moved in the door unlocking direction. 
     To effect automatic opening of the door  10 , the microprocessor  20  electrically signals the linear actuator  36  to extend rod  52 , as shown in FIG.  5 . Movement of tab  64  to the right causes actuating plate  32  to pivot counterclockwise in an engaging sense. The connecting spring  34  prevents a significant amount of pivotal movement of L-shaped pivot link  28  to avoid tensioning of disengage cable  88 . By extending rod  52 , the actuator  36 , pivots the actuating plate  32  thereby moving the cable bracket  66  upward, applying tension to the engage cable  48 . The elongated portion  60  pivots with actuating plate  32  and moves bumper  62  into engagement with the rod clamp  42 . This pulls latch rod  190 , thereby unlatching the latch assembly  22 . 
     The motor and gear assembly  18  comprises an electric motor  108  of standard configuration, latch assembly a gear train  110  mounted within a housing  107  fixed to door frame  24 , a cable pulley  114 , a flexible drive shaft  116  extending from a distal end of a rigid motor shaft  118 , and an electromechanical clutch  112  for coupling the cable pulley  114  with the latch assembly gear train  110 . The cable pulley  114  controls a cable  154  for cinching latch assembly  22 , and the flexible drive shaft  116  is used to drive the power drive assembly  14 . 
     The electric motor  108 , as shown in FIGS. 6 and 7, is mounted on top of the housing  107 . A motor shaft  118  extends from the motor  108  and has screw-like helical threads  122  on the surface thereof forming a wormgear type structure that meshes with teeth  124  of a first gear  126  of latch assembly gear train  110 . 
     The first gear  126  is axially coextensive with and connected for rotation with second gear  138  by any conventional means. The second gear  138  is a solid disc-like structure, smaller in diameter than the first gear  128 , and also has teeth  140  extending circumferentially along its outer edge. A mounting shaft  142  passes axially through the first gear  126  and the second gear  138  and connects them for rotation with one another. Mounting shaft  142  is rotatably mounted to the gear housing  107 . Third gear  144  is preferably a solid disc that has a diameter larger than both the first gear  126  and the second gear  138 , and has teeth  146  extending circumferentially along its outer edge. The teeth  146  of gear  144  mesh with the teeth  140  of the second gear  138 . Third gear  144  is axially mounted for rotation on a shaft  148 , which is in turn mounted at a first end to the gear housing  107 . An intermediate portion of the shaft  148  is fixed to the gear  144  so as to rotate therewith. The second end of shaft  148  is received within the input end of the electromechanical clutch  112 . The output end of the electromagnetic clutch is connected with the shaft  149  of a cable pulley  114 . During the cinching operation for latch  22 , the microprocessor  20  sends a signal to engage the electromechanical clutch  112 , so that the gear  144  becomes rotatably coupled to the cable pulley  114  to drive the cable pulley  114  in a clockwise direction or a latching sense. The type of electromechanical clutch  112  contemplated herein is manufactured by Reel Precision Mfg. of Saint Paul, Minn., part # ED30CCW8MM-12, and is disclosed in U.S. Pat. Nos. 4,263,995 and 5,183,437, hereby incorporated by reference. The distal end  128  of motor shaft  118  has an axial opening having a square cross-section adapted to receive one end of the flexible drive shaft  116 , which also has a square cross section. The motor shaft  118  is connected to the flex drive shaft  116  so that the motor shaft  118  drivingly rotates the flex driver shaft  116 . The flex drive shaft  116  extends downwardly through an aperture  130  in the bottom of the gear housing  107  and continues downwardly to the lower drive assembly  14 . 
     This arrangement in accordance with the present invention allows the same motor  108  to be used for multiple tasks. More specifically, the motor  108  is used for both driving the lock cinching pulley  114  via latch assembly gear train  110  and also for driving the lower drive assembly  14  via flexible drive shaft  116 . Both the gear train  110  and the flexible drive shaft  116  operate whenever the motor  108  is spinning, either in the forward direction or reverse direction. A clutch  184  on the lower drive assembly  14  (described later in greater detail) can be disengaged to disengage the operative connection between the drive shaft  116  and the gears on lower drive assembly  14  which move the door  10  along track  204 . This is done, for example, when the motor  108  is being used to cinch latch  22  via cable pulley  114  into the fully locked or primary latching position. The latch assembly gear train  110 , on the other hand, can be disengaged from cable pulley  114  by disengagement of electromechanical clutch  112  when the motor  108  is functioning to drive the lower assembly  14 . 
     As shown in FIG. 6, cinch cable  154  has a ball end  152  thereof positioned within a slot  156  in cable pulley  114  and leads out from the housing  107  through a slot  160 . After the electromechanical clutch  112  is magnetically engaged, the motor  108  drives gear train  110  so that cable pulley  114  turns clockwise in a latching sense, and the cinch cable  154  is pulled to cinch the latch assembly  22  into the primary latched position. 
     Mounted within the motor  108  are two hall effect sensors  162 , shown. schematically in FIG.  14 . The hall effect sensors  162  monitor the rpm of the motor  108  and are set up to provide a quadrature offset for measuring the speed and direction of motor  108  when driving the lower assembly  14 . The two hall effect sensors  162  provide on and off (high/low) voltage output signals in response to motor displacement, which are then evaluated and processed by the microprocessor  20 . By using a ¼ offset (90° displacement) between the two hall effect sensors  162 , two output signals (one from each sensor) enable the motor speed to be monitored with twice the resolution in comparison with a single sensor. Referring to FIGS. 9-13, the frequency of the on/off signals from sensors  162  establish a reference time used to determine motor speed. If only one sensor were used, it would be necessary for ½ t to elapse to determine whether the high or low signal remained high or low for a period of time greater than-the ½ t reference period. Because a quadrature system is used in accordance with the invention, it is only necessary to wait ¼ t (e.g., between two high signals of the two sensors) to determine whether the motor is moving more slowly than the threshold speed. 
     When the motor  108  is detected as moving more slowly than the threshold speed during door closing (i.e., during the motor  108  effecting driving movement of lower assembly  14  via flex drive cable  116 ), it is assumed by microprocessor  20  that an obstruction is in the way of the door and thus reverses the motor  108  direction to reverse the direction of door movement. This is the primary mode for obstacle detection. 
     As can be appreciated by those skilled in the art, changes in motor speed are a direct function of the effective voltage (V eff ). As can be appreciated from FIG. 11, where V effective is ½V, the voltage signal is high for 50% of the time, and low for 50% of the time. As time increases for the high signal portion of the cycle, the effective voltage increases. In accordance with the present invention, when initiating opening or closing of the door  10 , it is preferable to have the microprocessor  20  slowly ramp up the effective voltage, and hence the speed of the motor  108  (e.g., to Veffective=¾V as shown in FIG. 12, and then to Veffective=⅞V as shown in FIG. 13) in order to reduce or eliminate in-rush current caused by a rapid start sequence. In-rush current is known to demagnetize motor magnets, which reduces horsepower and is detrimental to the life of any motor. 
     FIGS. 15 and 16 is a cross section taken through the line  15 — 15  in FIG. 2 of an elongate tape switch  164  positioned along the leading edge  166  of the door  10 . The tape switch  164  operates as a secondary or back-up mode of obstacle detection in the event of failure of the first mode of detection. The tape switch  164  is preferably of a conventional type, which consists of two metallic tape strips  168  that are mounted in spaced relation within a tubular resilient, rubber housing  170 . The strips  168  of tape switch  164  are electrically connected to the microprocessor  20 . If the two tape strips  168  come in contact with one another during door movement towards the closed position within the vehicle frame, as when an obstacle is encountered, the microprocessor  20  senses that an object is interfering with door travel and sends a signal to the motor  108  to stop the door  10  from further movement in the forward direction and causes motor  108  to reverse direction and move the door rearwardly to the opened position. 
     It can be appreciated from FIG. 16 that with the tape switch  164  attached to the door&#39;s leading edge  166 , two spaced pinch points  172  and  174  can be readily detected. More specifically, as the door  10  approaches the closed position, any obstacle located at two separate pinch points, including a first pinch point between the leading edge  166  of the door  10  and a rear edge or corner  172  of the vehicle&#39;s B-pillar  180  and a second pinch point between the leading edge  166  of the door  10  and a rear edge  178  of a front passenger door  176  can be detected. The ability to detect an obstacle at two separate pinch points or at any position during the door&#39;s movement toward its closed position is enabled by the fact that the tape switch is mounted on the leading edge of the door  10  rather than on one of the stationary edges  172  or  178 . The ability to mount the tape switch on the door  10  is enabled by the fact that the door  10  itself is electrified. Moreover, because the tape switch is mounted on the door itself, rather than one or more of the opposite edges  172  or  178  forming the pinch points, the tape switch is not limited to obstacle detection at such pinch points. Rather, the tape switch will detect any obstacle it encounters at any point in the door&#39;s path of movement toward its closed position. 
     Shown in FIG. 17, is the lower drive assembly  14  which mounts the door  10  on a track rail  204  (see FIG. 18) fixed to the vehicle body. The drive assembly  14  comprises a mounting structure  182 , a clutch assembly  184 , a gear drive assembly  186 , and a track rail guide assembly  188 . The mounting structure  182  has an L-shaped mounting bracket  192  mounted on the door frame  24  with any conventional attaching hardware. The bracket  192  has a bottom leg  194  extending outwardly in a perpendicular manner from the door frame  24 . The mounting structure  182  further includes an arm portion  198  connected with the bracket  192 . The arm portion  198  supports the clutch assembly  184 , the gear drive assembly  186  and the track rail guide assembly  188 . 
     As illustrated in FIGS.  18 , 19  and  20 , the track rail guide assembly  188  is pivotally attached to the end of the arm structure  198  by a pivot pin  200  and has a generally flattened U-shape bracket  202  of the guide assembly  188  extending beneath the track  204 . Rollers  206  are attached by vertical pins  208  at the ends of the legs of bracket  202 . Between the legs of bracket  202  is generally rectangular shaped extension  210  that allows a large roller  212  to be attached by a horizontally extending pin  214 . The large roller  212  extends axially from pin  214  and rotates orthogonally to rollers  206 . The track rail guide assembly  188  provides a means of flexibly but securely holding the lower drive assembly  14  to the track  204  during operation. Rollers  206  ride along the inside surface  218  of a vertically extending wall  216  of the track rail  204 , while the large roller  212  runs along a surface  205  of the vehicle body immediately beneath the track  204 . Since the guide assembly  188  is pivotally attached to the arm structure  198 , the rollers  206  and  212  are capable of following a bend of the track  204  thereby maintaining constant engagement with the surface  216  of track  204  and surface  205  of the vehicle body. Track  204  may thus be contoured to any desired shape while maintaining pinion gear  220  in geared engagement with teeth  248 . 
     Gear drive assembly  186  comprises a power drive gear train, including the pinion gear  220 , an input worm gear  222 , and a plurality of intermediate gears  226 ,  232 , and  240  for coupling the worm gear  222  with the pinion gear  220 . 
     The worm gear  222  receives its driving input  222  from the flexible drive shaft  116  connected with the motor  108 . The worm gear  222  is provided with screw gear teeth  122  that mesh with teeth  224  of the first drive gear  226 . 
     First drive gear  226  is a disc structure with teeth  224  extending circumferentially along its outer edge. The first gear  226  rotates about shaft  228 , which is affixed at one end to a drive assembly cover plate  230  that is mounted to the arm structure  198 . Connecting member  234  is commonly mounted on shaft  228  and connects first drive gear  226  and second drive gear  232  for rotation with one another. Second drive gear  232  is commonly mounted and rotates about shaft  228 , and has a diameter approximately half that of first drive gear  226 . The teeth  236  of second drive gear  232  are meshed with teeth  238  of the third drive gear  240 . The third drive gear  240  is positioned on the same plane as second drive gear  232  and the pinion gear  220 . The third drive gear  240  is supported and rotates about shaft  242 , which is affixed to clutch assembly mounting plate  244 , as will be described in greater detail later. 
     It can be appreciated that the construction and gearing arrangement of the gear drive assembly  186 , particularly the use of worm gear  222  driven by the flexible drive shaft  116 , converts a high speed, low torque input to provide a low speed, high torque output to operate the door  10 . 
     The clutch assembly  184 , the operation of which is described in conjunction with FIGS. 20 and 21, incorporates gears  220  and  240  of the drive assembly  186 , which are simply disengaged or engaged as part of the clutch operation. In FIGS. 20 and 21, various components, such as gears  222  and  232  have been omitted for sake of clarity of illustration. The clutch assembly  184  also includes the aforementioned mounting plate  244 , a pivot link  250  that has a cable connecting opening  252  on one end and a link pin  254  on the other. The pivot link  250  pivots about a centrally disposed pivot pin  256 , which is connected at opposite ends between the drive assembly cover plate  230  and arm structure  198 . An L-shaped link  258  is pivotally attached to the pivot link  250  by the link pin  254  at the corner  260  of the legs of the L-shaped link  258 . A shorter leg  262  of the L-shaped link  258  has a cable connecting opening  264 . The stem  266  of the L-shaped link  258  is pivotally attached to the clutch mounting plate  244  by a pivot pin  268 . The clutch mounting plate  244  is pivotally supported by shaft  228  which also serves as the axis of rotation for the first and the second gears  226  and  232 , respectively. The clutch assembly  184  further includes a stop member  269  fixed to the pivot link  250  by pin  256 . The stop member  269  has an irregular shape that includes a straight edge  271  which is disposed in abutting relation with an adjacent straight edge  273  formed on the shorter leg  262  of the L-shaped link  258  when the clutch assembly is in the engaged position as shown in FIG.  20 . The straight edge  273  of the L-shaped link  258  has a curved or arcuate edge  275  about corner  260  in order to create an “over center” condition with the stop member  269  as will be described. 
     As shown in FIG. 20, the engage cable  48  attaches to the connecting opening  252  of pivot link  250 , and the disengage cable  88  attaches to the connecting opening  264  of the link  258 . In an engaged condition, the linkage gears  226 ,  232 , and  240  form a driving connection between the worm gear  222  and pinion gear  220 . When the disengage cable  88  is pulled by retracting the linear actuator  36  of the brain plate assembly  16  (see FIG.  4 ), the leg  262  of the L-shaped link  258  is pulled. As a result, the link pin  254  is also pulled, causing the link  250  to pivot in a counterclockwise direction, or disengage sense, about pin  256  in the view shown. During this movement of links  250  and  258 , the curved edge  275  of link  258  travels about the straight edge  271  of stop member  269 . The force of engagement between edges  275  and  271  increases as the curved edge  275  is forced further into engagement with surface  271 , until eventually the “over-center” position is reached. Continued pulling of cable  88  causes the engagement between the edges to go beyond the “over-center” position, and thereafter the force of engagement between the edges  275  and  271  gradually lessens. This “over-center” arrangement enables the clutch assembly to remain virtually locked in the disengaged position (as shown in FIG. 21) even after the tension in cable  88  is relieved. 
     In moving the links  250  and  258  in the aforementioned manner, the clutch mounting plate  244  is pivoted (in a counterclockwise direction or disengaging sense in the figures) about shaft  228  as a result of movement of the L-shaped link  258  at pivot pin  268 . Pivotal movement of the mounting plate  244  in this manner causes the gear  240  to be moved out of mesh with the pinion gear  220 . As a result, the clutch assembly  184  is disengaged, and the motor  108  is no longer capable of driving the lower assembly  14  to effect door movement. 
     The purpose of disengaging clutch assembly  184  is to disconnect the motor  108  from the rack and pinion connection  220 ,  221  when the door  10  is to operate in manual mode. As a result, the door  10  can be manually moved along track  204  without the load of motor  108  and without inflicting unnecessary wear on the motor  108  and the entire drive system. 
     FIG. 22 illustrates the general curvature at the front portion of track  204 . The track  204  is mounted to the vehicle body  268  in the bottom of a door sill  270 , under the vehicle floor  274 . The track teeth  248  are the most outboard portion of the track. The track  204  extends from the rear of the door sill  270  linearly forward curving inboard near the front end  272 . This shape is a common travel path for sliding doors found on mini-vans. 
     Shown in FIG. 23 is a perspective view of the latch assembly  22  comprising a latch housing  292  mounted to the vehicle door frame  24  by a plurality of fasteners  279 . The housing  292  defines a mouth  293  which receives a door latch striker mounted to a door opening frame in conventional fashion. 
     In FIGS. 24 and 25, a portion of the latch housing  292  has been omitted to better reveal interior components of latch assembly  22 . The latch assembly  22  includes a spring biased (spring not shown) pawl or locking arm member  306 , and a spring biased (spring not shown) striker retaining member or ratchet  286 . The ratchet  286  is mounted for rotation about a pivot pin  288 , which defines a pivot axis generally at  290  (see FIG.  25  and is spring biased in the clockwise direction or open condition (as seen in the figures) in conventional fashion. The pivot pin  288  is attached at opposite ends thereof to the latch assembly housing  292 . The housing  292  has a cutout that forms the opening  293  for receiving a door striker  296  (see FIGS.  25 - 28 ). The ratchet  286  has a slot  294  as is conventional with latches. As is also conventional, the door striker  296  fits into the slot  294  and engages a leading surface portion  297  of the ratchet, causing the ratchet  286  to rotate in a clockwise direction or latching sense against the spring biasing direction, thereby trapping the door striker  294  within the mouth  293 . 
     The pawl  306  is pivotally mounted at a center portion to the housing  292  by a pin  310 . Pawl  306  is conventionally spring biased (spring not shown in Figures) for rotation to engage the ratchet  286 . Latch rod  190  is connected to ratchet  186  in a well known manner to rotate pawl  306  to release ratchet  286 . The ratchet  286  has a flat edge  308  or first lock engaging surface as shown, which is sized to accept a latching end  309  or retaining member engaging surface of locking arm  306 . Flat edge  308  acts as an abutment for the pawl  306  in order to lock and hold the ratchet  286  in a primary locking position as shown in FIG.  28 . The ratchet  286  also has a second flat edge  312  or second lock engaging surface of the same size and shape as the flat edge  308 . This second flat edge  312  also accepts the latching end  309  of the pawl  306 . This is the initial latching position for the ratchet  286 . During the door closing operation, the lower assembly  14  moves the door  10  until the ratchet  286  engages the door striker  296  and is rotated counterclockwise into the initial latching position as shown in FIG.  26 . Movement of the ratchet  286  into the primary position is accomplished by a cinching process, as will be described. 
     The aforementioned cinch cable  154 , described in conjunction with FIG. 6, enters the latch assembly&#39;s housing  292  through a cable guide  316  (see FIG.  24 ). The cable guide  316  is attached to the latch housing  292  or any adjacent portion of the door  10  in any conventional manner. The cable guide  316  is of a two part construction including a first part  318  having an arcuate groove  324  extending therethrough. The groove  324  provides an approximately 90° change in direction for the cinch cable  154 . A second part  320  of the cable guide has substantially the same peripheral configuration as the first part, but has an arcuate ridge  322  received into the groove  324 . The ridge  322  has a height which extends only partially into groove  324 , to close-off the groove, leaving sufficient room for cable  154 . The cable guide  316  is preferably made from a hardened plastic, teflon, or resin material, and advantageously functions to properly orient the cinch cable  154  and align it with a cable cinch arm  326 . This construction is more cost-effective than conventional pulley assemblies which could also be used to accomplish the same function. 
     The cinch arm  326  is an elongated member that pivots around a common axis of rotation with ratchet  286 . One end of arm  326  has an aperture  328  which enables the arm  326  to be mounted for pivotal movement about pivot pin  288 . 
     The ratchet  286  and cable cinch arm  326  are connected together by a coupler member  304 , shown in FIG.  29 . The coupler  340  enables the ratchet  286  and the cinch arm  326  to be connected at the common pivots, thus allowing the latch assembly  22  to be of a smaller configuration than conventional arrangements in which a cinch arm is connected to the periphery of the ratchet. 
     The coupler  340  is a cylinder with an aperture  336  extending centrally therethrough. To be connected with coupler  340 , as shown in FIG. 24, the generally hook shaped ratchet  286  has an aperture  298  through the central portion thereof. The aperture  298  is generally circular with two rectangular portions  300  extending radially outwardly in opposed relation to each other. Portions  300  are sized and shaped to accept bottom extending elements  302  of the coupler  340 . The central portion of the cylindrical coupler  340 , generally indicated at  340 , acts as a spacer between the ratchet  286  and the cinch arm  326 . Extending upwardly from the top flange  342  of coupler  340  is an upper extending element  330  sized to receive the aperture  328  in the cable cinch arm  326 . The aperture  336  fits down over a shaft  288 , thereby providing a pivotal operating point for the ratchet  286  and cable cinch arm  326  allowing them to rotationally coact within the confines of a relatively smaller latch assembly. 
     The opposite end of the cinch arm  326  is folded back upon itself forming parallel walls through which the cinch cable  154  extends. A U-shaped notch  332  is provided in each of the walls and in axial alignment with one another. The notch is shaped into the back edge of the parallel walls and accepts and holds a ball end  334  of the cinch cable  154 . 
     FIG. 25 shows the latch assembly  22  in a full open position with the ratchet opening  294  ready to receive the striker  296 . The cinch arm  326  extends outwardly and the pawl  306  is biased against the ratchet  286 . A first contact switch  344  has an outwardly biased pin member  343  thereof engaged and depressed by the cam surface  345  of the ratchet  286 . When depressed, switch  344  sends a signal to microprocessor  20  indicating that latch assembly  22  is unlocked. Also, in FIG. 25, the cinch cable  154  is in a relatively relaxed condition. 
     FIG. 26 shows the latch assembly  22  in the initial position. The latch assembly  22  is moved into this condition as a result of the lower assembly  14  moving the door  10  towards the closed position. The striker  296 , as shown in FIG. 26, has entered the mouth  293  in the housing  292  and has engaged the surface  297  of the ratchet  286 , thus causing the ratchet  286  to pivot about the pivot pin  288  until the locking arm  306  is able to move inwardly (counterclockwise) under spring force against a surface  307  of the ratchet  286  after the latching end  309  passes flat edge  312  of the ratchet. When the ratchet  286  is rotated into the initial position, a recessed portion  347  of the cam surface  345  of ratchet  286  releases pin member  343  of the first contact switch  344 . The switch  344  sends a signal to the microprocessor  20 , indicating the initial position has been reached. Microprocessor  20  responsively then sends appropriate signals to stop the lower assembly  14  from moving the door  10  any further by momentarily stopping motor  108  and disengaging the clutch assembly  184  of the lower assembly  14 . The microprocessor  20  responsively energizes cinching clutch  112  to be engaged to initiate the cinching process. 
     Referring to FIG. 6, after the microprocessor  20  causes the cinching clutch  112  on the motor and gear assembly  18  to engage the cable pulley  114 , motor  108  is energized so that the worm gear  118  begins to rotate causing the cinch cable  154  to be pulled or tensioned. Referring to FIG. 27, as the cinch cable  154  is tensioned, the cinch arm  326  is caused to rotate counterclockwise or in a cinching sense and, through the coupler  304 , the ratchet  286  is also rotated counterclockwise. As the ratchet  286  is rotated, the striker  296  is maneuvered relatively further into the latch assembly  22 , thereby pulling the periphery of the door  10  into sealing engagement with the resilient peripheral door seal strip around the door frame which seals the passenger compartment from the external environment. 
     In FIG. 28, latch cinching is complete. The cinch arm  326  has rotated the ratchet  286  to the primary position. The flat edge  308  on the ratchet  296  is engaged by the latching end  309  of the pawl  306 , thereby locking and holding the latch assembly  22 , and therefore the door  10 , in a fully closed position. A second contact switch  346  has a pin member  351  which is actuated by being depressed by a protruding portion  349  of the cam surface  345  of ratchet  286 , thus sending a signal to the microprocessor  20  indicating that the latch assembly  22  is in the primary position. The microprocessor  20  then responsively signals the motor  108  to stop further cinching, and disengages the cinching clutch  112  so that the pulley  114  then releases the tension from the cinch cable  154 . 
     In order to release the latch assembly  22 , the microprocessor  20  sends a signal to the brain plate actuating assembly  16 , causing linear actuator  36  to extend. The latch rod  190  is pulled, causing the pawl  306  to rotate against the bias of the lock arm spring in a clockwise direction or a releasing sense away from the ratchet  286  flat edges  308  and  312 . As a result, the ratchet spring (not shown) causes the ratchet  286  to rotate in a clockwise direction or releasing sense to the full opened position as shown. Because the cinching clutch  112  connected with the cinch pulley  114  is disengaged at this point, the ratchet urges the arm  326  and cable  154  attached thereto into the stand-by position as shown in FIG.  25 . 
     SYSTEM LOGIC 
     With the door  10  fully shut and at rest, the lower drive assembly  14  is disengaged, the latch assembly  22  is in the primary position, and the motor and gear assembly  18  is shut off with the cinching clutch  112  disengaged. The door  10  can now be opened by activating an electronic switch either manually or remotely. Upon receiving a signal to open the door  10 , the microprocessor  20  releases the latch assembly  22  and engages the lower drive assembly  14 . More specifically, microprocessor  20  sends a signal to the linear actuator  36  of the brain plate actuating assembly  16 , which extends actuator rod  52 . The bumper  62  contacts rod clamp  42 , thus moving the rod clamp and the latch rod  190  connected thereto to the left in the figures. This unlatches the latch assembly  22 , and causes the engage cable  48  to be tensioned to ensure that clutch assembly  184  of lower drive assembly  14  engages the drive gears to be driven by motor  108 . 
     The motor  108  begins to rotate the flexible drive shaft  116 , slowly building up speed by increasing the effective voltage to avoid in-rush current in the motor. The drive shaft  116  drives the gears of the lower drive assembly  14 . As pinion gear  220  of the lower drive assembly  14  turns, it drives the door  10  along the track system  216 , drawing the door open. As the door  10  reaches the end of the track system  216  it hits a travel switch  350  (see FIG.  22 ), whereby the microprocessor  20  responsively stops motor  108  to stop travel of the door  10 . The lower drive assembly  14  remains engage, now holding the door  10  in the full open position. 
     In manual mode of door opening operation, the inner or outer door handle (not shown) is engaged and moved, thus causing the plate  95  of brain plate assembly  16  to pivot in a counterclockwise direction or unlatching sense. This action tensions disengage cable  88  to disengage clutch assembly  184  of lower assembly  14  and moves latch rod  190  to unlock door latch assembly  22 . The door is then manually moved to the opened position. When the door reaches the full opened positioned, a contact trip switch  352  is engaged, sending a signal to microprocessor  20 . The microprocessor  20  then sends a signal to the actuator  36 , causing extension rod  52  to extend and the engage cable  48  to engage the lower assembly clutch  184  to maintain the door  10  in the fully opened position. 
     To close the door  10 , the microprocessor  20  extends the extension rod  52  of the brain plate actuating assembly  16 , pulling the engage cable  48 , engaging the lower drive assembly  14 . The microprocessor  20  then slowly starts the motor  108 , which draws the door  10  closed until the initial position of the latch assembly  22  is reached as detected by latch switch  344 . The microprocessor  20  now momentarily stops, and then instantaneously reverses the motor  108  in order to prevent friction lock-up between the clutch gears of lower assembly  14 , before such gears are disengaged. At substantially the same time, the microprocessor  20  sends a signal to the linear actuator  36  to disengage the clutch gears of the lower drive assembly  14 . With the lower drive assembly  14  disengaged, the microprocessor  20  sends a signal to the cinching clutch  112  to engage the cable pulley  114  and energizes the motor  108  to continue rotation in the aforementioned reverse direction to cause the gears in assembly  18  to rotate the pulley  114  in a direction that will pull on the cinch cable  154 . As a result, the arm  326  and ratchet  286  of the latch assembly  22  will cinch the latch into the primary latching position. Once the latch assembly  22  is in the primary position, the latch switch  346  sends a signal to the microprocessor  22 , which releases the tension on the cable pulley  114  and shuts the motor  108  off. 
     To close the door  10  in manual mode, the inside or outside door handle is lifted so that the disengage cable  88  is tensioned to release the clutch assembly  184  of the lower arm assembly  14 . The door  10  can then be manually moved to the closed position. The momentum imparted to the door in normal operation is sufficient to cause the latching ratchet  286  to hit the door striker and rotate the ratchet into the primary position. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications to the embodiments may be made without departing from the spirit or scope of the invention as described by the appended claims.