Abstract:
A vehicle having an endgate counter balance for use with an endgate of the vehicle, and a method of operating, is disclosed. The endgate counterbalance may include a hinge arm extending from the hinge, an energy storage device and a crank mechanism connected between the hinge arm and the energy storage device. The endgate counterbalance is configured to create a cross-over position for the endgate between closed and fully open where the endgate counterbalance does not exert a rotational bias on the endgate.

Description:
BACKGROUND OF INVENTION 
     The present invention relates generally to vehicle endgates, and more particularly to a counterbalance for a vehicle endgate. 
     Conventional pickup trucks have an endgate that pivots from a vertical closed position rearward and downward to a horizontal open position for ease in loading and unloading cargo from the bed of the pickup. For some people, however, the amount of effort required to lift the endgate from its open position in order to close it is undesirably high. Thus, some pickup manufacturers have added mechanisms to assist in lifting the tailgate from its open position while one is closing the endgate. 
     For example, some have added torsion rods or vertically extending gas cylinders connected to the endgate hinge assembly. These devices store energy as the endgate is moved from its closed position to its fully open position, with the energy being used to assist a person when closing the endgate. While the torsion rod provides assist with lift effort, it does not provide any damping effect, which may be desirable when moving the endgate between its open and closed positions. The gas cylinder also has drawbacks in that it may interfere with the tail lamp housing, creating a packaging problem within the vehicle. Moreover, neither of these designs assists with maintaining the endgate (and hinge) in a position desirable for removal of the endgate from (and reassembly of the endgate to) the vehicle. 
     SUMMARY OF INVENTION 
     An embodiment contemplates an endgate counter balance for use with an endgate of a vehicle having a hinge about which the endgate pivots between a closed position and a fully open position. The endgate counterbalance may comprise a hinge arm, an energy storage device and a crank mechanism. The hinge arm may extend from the hinge and be pivotally fixed relative to the endgate. The energy storage device may have a first end and a second end configured to mount to vehicle structure, and be configured to store and dissipate potential energy as the first end is moved relative to the second end. The crank mechanism may include a hinge pivot link, having a first leg and a second leg, and a crank pivot link, having a first leg, a second leg and a pivot location at an intersection of the first and second pivot legs of the crank pivot link. The first leg of the hinge pivot link is pivotally attached to the hinge arm, the second leg of the hinge pivot link is pivotally attached to the first leg of the crank pivot link, the second leg of the crank pivot link is pivotally attached to the energy storage device, and the pivot location is configured to pivotally mount to the vehicle structure. 
     An embodiment contemplates a vehicle including vehicle structure having an endgate with a hinge pivotally mounted thereto and movable between a closed position and a fully open position. The vehicle also has an endgate counterbalance including a hinge arm extending from the hinge and pivotally fixed relative to the endgate; an energy storage device having a first end and a second end configured to mount to vehicle structure, the energy storage device configured to store and dissipate potential energy as the first end is moved relative to the second end; and a crank mechanism pivotally connected between the hinge arm and the energy storage device. The endgate counterbalance is configured to provide no rotational bias to the endgate when the endgate is in a cross-over position between the closed position and the fully open position and to provide a rotational bias to the endgate when the endgate is not in the cross-over position. 
     An embodiment contemplates a method of moving an endgate of a vehicle between a closed position and a fully open position, the method comprising the steps of: inducing a zero rotational bias by an endgate counterbalance on the vehicle endgate when the vehicle endgate is in a cross-over position located between the closed position and the fully open position; inducing a rotational bias away from the closed position by the endgate counterbalance when the endgate is located between the cross-over position and the closed position; and inducing a rotational bias away from the open position by the endgate counterbalance when the endgate is located between the cross-over position and the fully open position. 
     An advantage of an embodiment is that the endgate counterbalance assists with lifting the endgate during a closing event by reducing the effort during the initial portion of endgate travel from its horizontal while also assisting in reducing potential squeak and rattle issues by preloading latches that keep the endgate in its closed position. An embodiment may also include the provision for damping during endgate opening and also during the last portion of motion into the fully closed position. 
     An advantage of an embodiment is that the endgate counterbalance provides a cross-over position when partially opened that allows for easier removal and re-installation of the endgate to the vehicle. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a side view looking inboard at a portion of a pickup truck. 
         FIG. 2  is a side view of a portion of a pickup truck, including part of an endgate and an endgate counterbalance. 
         FIG. 3  is a perspective view looking aft and inboard at a portion of a pickup truck. 
         FIG. 4  is a side view of an endgate and endgate counterbalance, in an endgate closed position. 
         FIG. 5  is a side view of a portion of an endgate and endgate counterbalance, in an endgate open position. 
         FIG. 6  is a schematic side view of the geometry for a portion of the endgate and endgate counterbalance, in the endgate closed position. 
         FIG. 7  is a schematic side view similar to  FIG. 6 , but illustrating the endgate in a partially open, cross-over position. 
         FIG. 8  is a schematic side view similar to  FIG. 6 , but illustrating the endgate in a fully open position. 
         FIG. 9  is a side view of an endgate counterbalance according to a second embodiment. 
         FIG. 10  is a side view of a portion of vehicle structure and an endgate counterbalance according to a third embodiment. 
         FIG. 11  is a perspective view, on a reduced scale, of the embodiment of  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a portion of a vehicle (pickup truck) body, indicated generally at  20 , is shown. The body  20  includes a box  22  having a box bed  24  (i.e., the floor of the box  22 ), which can be seen located inboard of a wheel well opening  26  in a rear quarter panel  28 . The rear quarter panel  28  also includes a brake light opening  30  and a recess  32  within which a bumper (not shown) extends. The pickup body  20  has an endgate  34  mounted at the rearmost portion of the box  22 . 
     Referring now to  FIGS. 1-5 , the endgate  34  is shown in both a vertical, closed position ( FIGS. 1-4 ) and a horizontal, fully open position ( FIG. 5 ). The endgate  34  has an aft (outer) surface  36  and a forward (inner) surface  38 . A conventional latch assembly (not shown) may be employed to hold the endgate  34  in its closed position, and a conventional cable assembly (not shown) may be employed to hold the endgate  34  in its fully open position. The endgate  34  also includes a pair of hinges  40  (only one shown) pivotally connected to box side hinge structure  41  and defining a pivot axis  44  about which the endgate  34  pivots. When referring herein to two components being pivotally connected, this means that they are connected together but can pivot relative to one another. Such an arrangement may be achieved, for example, when the components have aligned holes, with a rivet or bolt extending through the holes, thus holding the components together while allowing them to pivot about the rivet/bolt axis. 
     A hinge arm  42  extends laterally from the hinge  40  and is pivotally fixed relative to the endgate  34 . The hinge arm  42  includes a crank attachment hole  46  for pivotally connecting to a crank mechanism  48  of an endgate counterbalance  50 . 
     The crank mechanism  48  includes an L-shaped hinge pivot link  52  and an L-shaped crank pivot link  54 . The hinge pivot link  52  includes a first pivot hole  56 , through a first leg  60 , that pivotally connects to the crank attachment hole  46  and a second pivot hole  58 , through a second leg  62 , that pivotally connects to a first pivot hole  64  in a first leg  66  of the crank pivot link  54 . The crank pivot link  54  also includes a body pivot hole  68  located at an intersection of the first leg  66  and a second leg  70 . The body pivot hole  68  is used to pivotally mount the crank pivot link  54  to structure  72 , which is fixed relative to the body  20 . The second leg  70  includes a second hole  74  that pivotally connects to a first end  78  of an energy storage device  80 , which is also part of the endgate counterbalance  50 . 
     The energy storage device  80  in the first embodiment is a gas strut, which includes a rod  82 . The first end  78  of the rod  82  is attached to the crank mechanism  48  with the rod  82  extending through box side structure  88 , and telescopically mounting in a gas cylinder  84 . The gas cylinder  84  is pivotally mounted to a mounting bracket  86  that mounts to vehicle structure under the box bed  24 . The crank mechanism  48  allows the gas strut  80  to extend forward in a generally horizontal orientation. Thus, packaging concerns relating to a vertically mounted gas strut and tail lamp assembly (not shown) are avoided. Moreover, in the case of a gas strut, this particular energy storage device  80  also provides a damping function while one is pivoting the endgate  34 . 
     The operation of the endgate counterbalance  50  of  FIGS. 1-5  will be discussed with reference to schematic  FIGS. 6-8 . The phantom lines in  FIGS. 6-8  extend between the various pivot points of the endgate counterbalance  50 . With the endgate  34  in its closed position ( FIG. 6 ), the hinge arm  42  extends downward in a generally vertical direction. This position of the hinge arm  42  positions the links  52 ,  54  of the crank mechanism  48  so that the gas strut (energy storage device)  80  is somewhat compressed. This compression produces a bias in the endgate opening direction. By having this bias, the endgate  34  preloads the latch assembly (not shown) that holds the endgate  34  closed, thus reducing the potential for squeak and rattle. Moreover, during the last portion of the closing movement to the fully closed position, the endgate counterbalance, having this opening direction bias, will feel as if this last part of the motion is being damped, creating a desirable feel for the person closing the endgate  34 . 
     As the endgate  34  begins to open, the hinge arm  42  will pivot the crank attachment hole  46  forward and upward, actuating the crank mechanism  48  such that the gas strut  80  moves toward its uncompressed position. The endgate  34 , then, will reach a cross-over position (shown in  FIG. 7 ) where the endgate counterbalance  50  does not exert a bias in either the opening or closing direction. Pivoting of the endgate  34  in either direction from this position will create a bias back toward this position. The cross-over position allows for greater ease in removal and installation of the endgate  34  from the body  20  since, when the endgate  34  is removed, the biases of the endgate counterbalance will tend to hold the hinge assemblies and locating features (not shown) in place. 
     As the endgate  34  is rotated past the cross-over position toward the full open position (shown in  FIG. 8 ), the hinge arm  42  will pivot into a generally horizontal position. This pivoting will cause the crank mechanism  48  to again compress the gas strut  80 , creating a bias in the endgate closing direction. Thus, when one lifts up on the endgate  34  to close it, the endgate counterbalance  50  will assist by initially biasing the endgate toward the closed position. Moreover, with the energy storage device  80  being a gas strut, the motion will be damped, creating a desirable feeling for the person moving the endgate  34 . 
       FIG. 9  illustrates a second embodiment. Since this embodiment is similar to the first, similar element numbers will be used for similar elements, but employing 100-series numbers. In this embodiment, the energy storage device  180  employed is a spring. While not providing all of the damping effect of a gas strut, it may reduce the cost of the overall endgate counterbalance  150 . In this embodiment, the hinge  140  still includes a hinge arm  142  that is pivotally connected to the first leg  160  of the hinge pivot link  152 . Also, the second leg  162  of the pivot link  152  still pivotally connects to the first leg  166  of the crank pivot link  154 , which pivotally connects to structure  172  at the body pivot hole  168 . Also, the second leg  170  of the crank pivot link  154  connects to a first end of the spring  180 . However, the L-shape of the crank pivot link  154  may be more of a closed angle to accommodate the connection of the forward end  186  of the spring  180  to vehicle structure (not shown in  FIG. 9 ). The endgate counterbalance  150  still functions to provide for a cross-over position, thus allowing for the same functionality as the first embodiment. 
       FIGS. 10-11  illustrate a third embodiment. Since this embodiment is similar to the first, similar element numbers will be used for similar elements, but employing 200-series numbers. In this embodiment, the energy storage device is a torque rod  280  extending horizontally under the box bed  224 . While not providing all of the damping effect of a gas strut, it has less sensitivity to temperature changes than the gas strut. The hinge  240  still includes the hinge arm  242  that is pivotally connected to the hinge pivot link  252 . Also, the hinge pivot link  252  still pivotally connects to the first leg  266  of the crank pivot link  254 , which pivotally connects to structure  272  at the body pivot hole  268 . The second leg  270  of the crank pivot link  254  connects to the first end of the torque rod  280 . However, the torque rod  280  then extends through the center of the body pivot hole  268  before extending toward a second end (not shown) that is rotationally fixed to vehicle structure (not shown). The endgate counterbalance  250  still functions to provide for a cross-over position, thus allowing for the same functionality as the first and second embodiments. 
     While certain embodiments of the present invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims.