Abstract:
A power actuator for moving automotive closure panels between opened and closed positions. The actuator is particularly adapted for actuating the rear tailgate of a pickup truck type vehicle and includes an electric drive motor, a flexible cable assembly, and a strut assembly coupled to the hinge of the tailgate. Electrical control signals are applied to cause the opening and closing motion upon appropriate input electrical signals from vehicle mounted switches. The actuator assembly provides controlled opening rotational rate of the tailgate against the force of gravity through the application of a reduced electrical power level applied to the motor by a separate power source or by shunting the motor to an electrodynamic braking effect. Closing of the tailgate is caused by applying full power to the electric motor. The invention also involves the design of a hinge assembly which efficiently transfers torque between the vehicle body and closure panel, while allowing serviceability of the closure panel.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to an actuator assembly for automotive applications, and in particular, to such an assembly designed for moving a motor vehicle closure panel between opened and closed positions. In a preferred embodiment, the actuator assembly of the present invention is used to open and close the tailgate of a pickup truck type motor vehicle.  
       BACKGROUND AND SUMMARY OF THE INVENTION  
       [0002]     Motor vehicles are increasingly provided with convenience features to provide powered opening and closing of closure panels. Examples include rear hatches and lift gates of van and SUV type vehicles. Similarly, sliding doors of full size vans and mini-van type vehicles are now often provided with power actuators.  
         [0003]     Numerous designs of presently available products are used to provide such closure panel actuation. Examples of such systems are described by the assignees commonly owned U.S. Pat. Nos. 6,516,567; 5,784,833; 5,782,038; 6,553,719 and 6,324,788, which are hereby incorporated by reference. Several of these patents describe devices incorporating an electric motor actuator which transmits driving torque through a flexible cable to a lead screw type actuator unit. Through controlled rotation of the electric motor, opening and closing of the closure panel is provided.  
         [0004]     In addition to closure panels designed for allowing occupant ingress and egress for the vehicle, movable windows may also be power actuated. In addition to power window regulators which raise and lower door glass, flip-out vent windows, pick-up truck cab rear windows, or sail panel windows may also be provided with power actuators.  
         [0005]     The rear tailgates of pickup truck type motor vehicles have generally not been provided with power actuators for opening and closing the tailgates. However, increases in the strength and features integrated into pickup truck tailgates have led to their becoming increasingly heavy. Also, in the effort to make opening and closing of pickup truck tailgates convenient for a broad range of motor vehicle users, there is increasing interest in providing power actuation for pickup truck tailgates.  
         [0006]     The incorporation of power actuation for pickup truck tailgates and other motor vehicle closure panels should preferably be provided in a manner which enables convenient packaging of the actuator into the vehicle and further does not negatively affect manufacturability and servicing of the vehicle. It is further preferred to provide power actuation for existing designs of vehicles without requiring substantial reworking and redesign of the vehicle structure.  
       SUMMARY OF THE INVENTION  
       [0007]     The power actuator assembly in accordance with the present invention may be used for actuating various motor vehicle closure panels, but is especially implemented in the preferred embodiment to open and close a pickup truck tailgate.  
         [0008]     When opening and closing certain closure panels, such as a pickup truck tailgate, very different forces act on the tailgate and the actuator during the opening and closing motion. Since a pickup truck tailgate is hinged at its lower edge and raised between a generally horizontal open position to a vertical closed position, it is necessary to lift against the weight of the tailgate when closing it from the open position. Conversely, when the tailgate is dropped from its closed to the open position, the force of gravity urges the tailgate to move to the open position. A power actuator preferably will control the speed of the opening and closing movements of the tailgate. The actuator assembly in accordance with the present invention incorporates features to provide such controlled motion in both directions of movement of the tailgate.  
         [0009]     Another aspect of the present invention is a hinge system particularly adapted for use with a pickup truck tailgate while providing power actuation features. The hinge system efficiently transfer the driving torque of the actuator to the rear tailgate and further enables convenient assembly and servicing of the tailgate.  
         [0010]     Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates from the subsequent description of the preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a pictorial view of the rear corner area of a pickup truck type motor vehicle shown in a partially cut-away form and showing the actuator assembly in accordance with the present invention;  
         [0012]      FIG. 2  is a cross-sectional view taken along line  2 - 2  of  FIG. 1  showing the internal construction of the strut assembly component of the present invention;  
         [0013]      FIG. 3  is pictorial view similar to  FIG. 1 , but showing the rear tailgate in its open position;  
         [0014]      FIG. 4  is an enlarged pictorial view taken from  FIG. 3  showing in greater detail the components of the tailgate hinge assembly of the present invention; and  
         [0015]      FIG. 5  is an exploded view of the hinge assembly shown in  FIG. 4 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]     With particular reference to  FIG. 1 , an actuator assembly in accordance with this invention is shown and generally designated by reference number  10 . Actuator assembly  10  is shown installed in a pickup truck type motor vehicle including bed side  12 , tailgate  14 , and bed load floor  16 . Bed side  14  forms a hollow interior cavity between outer side sheet metal skin  18  and inner side panel  20 . Similarly, tailgate  14  is formed from welded or bonded together sheet metal panels including outer and inner tailgate panels  22  and  24 , respectively.  
         [0017]     Tailgate  14  is pivotable about hinge assembly  26  between its generally vertical closed position shown in  FIG. 1  to an open generally horizontal position as shown in  FIG. 3 .  FIGS. 4 and 5  provide more illustrations of the hinge assembly  26 , described in more detail below.  
         [0018]     Tailgate latch assembly  32  is provided for latching the tailgate  14  in its closed locked position. As shown, latch assembly  32  includes a laterally projecting latch rod  34  which engages with receiving socket  36  formed by bed side  12 . Latch assembly  32  further includes latch handle  38  which, when grasped and lifted, pulls latch rod  34  from its engagement with socket  36  to enable the tailgate  14  to be moved from its closed position, to its open position. Except for details of hinge assembly  26 , the previously described components are generally of conventional configurations and are found in motor vehicle pickup truck tailgate assemblies which are manually operated.  
         [0019]     In accordance with a principal feature of the present invention, actuator assembly  10  is provided to enable powered movement of tailgate  14  between its opened and closed positions. Actuator assembly principally comprises electric motor actuator  42 , flexible torsional cable assembly  44 , and strut assembly  46 .  
         [0020]     Electric motor actuator  42  includes electric motor  50  which is coupled to flexible torsional cable assembly  44  through transmission  52  and clutch assembly  54 . Transmission assembly  52  provides the desired gear reduction between the rotational speed of the rotating armature of electric motor  50  and the desired rotational speed and torque to be delivered to flexible torsional cable assembly  44 . Clutch assembly  54  is provided to enable electric motor  50  to be selectively coupled and decoupled from cable assembly  44 . Clutch assembly  54  couples the transmission  52  to the cable assembly  44  when the motor  50  is energized, and decouples while the motor is not powered. In another configuration of clutch assembly  54 , the clutch“grounds” the rotation of cable assembly  44  to assert motion of the tailgate  14 . The transmission  52 , clutch assembly  54  and strut assembly form a force transmission assembly for converting rotational movement of motor  50  to motion of tailgate  14 . Although flexible cable assembly  44  is described, it is within the scope of this invention to provide a rigid coupling between the components by eliminating the flexible cable. Moreover, other mechanical linkages may be provided for coupling motor  50  to the tailgate  14 , such as linear drives, pulley arrangements and equivalent systems.  
         [0021]     Flexible torsional cable assembly  44  includes a non-rotating outer casing  60  and an inner rotatable core  62 . Flexible torsional cable assembly  44  provides the ability to mount electric motor actuator  42  remotely from strut assembly  46 , thus increasing packaging and mounting flexibility.  
         [0022]     Strut assembly  46  includes tubular housing  64  and extendible tube  66 . Strut housing  64  is mounted to the vehicle by vehicle mounting bracket  68 . The end of tube  66  protruding from housing  64  includes through bore  70  for mounting to hinge assembly  26 .  FIG. 2  provides additional detail of the internal construction of strut assembly  46 . As shown in that figure, flexible cable inner core  62  is coupled with rotatable screw rod  72 . Screw rod  72  is maintained in position within housing  64  by bushings  74 . Rotation of cable core  62  causes screw rod  72  to rotate within bushing  74 . Nut  78  meshes with the threads of screw rod  72  and is fixed to tube  66 . When tube  66  is attached to clevis arm  92  of hinge assembly  26 , it cannot rotate and therefore rotation of cable inner core  62  causes the position of nut  78  to change along the length of screw rod  72 . This action causes retraction and extension of tube  66  from housing  64 . This motion is coupled to the tailgate  14  via clevis arm  92  and hinge assembly  26  to cause it to move between its opened and closed positions.  
         [0023]      FIG. 1  illustrates the mounting of electric motor actuator  42  within the internal cavity formed by vehicle bed side  12 . Electric motor actuator  26  is mounted to the vehicle structure via bracket  80 . Flexible torsional cable assembly  44  is routed through the internal cavity of bed side  12  to connect with strut assembly  46  as previously described. Strut assembly  46  passes through end panel  82  such that tube  66  engages with hinge assembly  26 . Electronic control unit (ECU) controller  84  applies electrical power to electric motor actuator  42  to cause it to undergo the desired actuation. ECU controller is coupled with the vehicle&#39;s power bus and further receives signals from one or more sensors and switches used in connection with actuator assembly  10 . Tailgate close switch  86  is conveniently positioned for access by the vehicle operator near tailgate  14  and is electrically connected with ECU controller  84 .  
         [0024]     Now with reference to  FIGS. 4 and 5 , additional details of the components comprising hinge assembly  26  are illustrated. Hinge assembly  26  includes extending clevis arm  92  which has a clevis attachment arrangement for receiving a pin (not shown) which passes through clevis arms  96  and tube  66  through bore  70 . The opposite end of clevis arm  92  forms an internally splined bore  96 . A pair of inner and outer support brackets  102  and  104  are provided which each include an internal passageway for receiving pressed-in bearing sleeves  103  and  105 , respectively. Support brackets  102  and  104  are mounted via their mounting flanges to panel  106  which is part of the pickup truck bed side structure.  
         [0025]     Hinge drive shaft  108  passes through the bearing sleeves  103  and  105  of inner and outer support brackets  102  and  104  and forms a protruding splined end which matches with the splined bore  98  of clevis arm  92  to enable torsional forces to be transferred between these components. Lever arm  110  is attached near an end of drive shaft  108  and is preferably welded or otherwise bonded to the driveshaft. On the end of driveshaft  108  opposite spline  112 , drive head  114  is formed. Drive head  114  fits within a socket of drive cup  116  which in turn includes a protruding head  118  which fits within a similarly shaped aperture  120  of tailgate bracket  122 . Tailgate bracket  122  and drive cup  116  are preferably affixed to one another, for example by welding or an interference fit. Bracket  122  is fastened to tailgate  14  using suitable fasteners.  
         [0026]      FIG. 4  illustrates hinge assembly  26  mounted to the vehicle and shows the engagement between driveshaft lever arm  110  and tailgate bracket  122  which includes a projecting flange  124  which engages with lever arm  110 .  FIG. 4  also illustrates the orientation of bracket  122  in its connection with tailgate  14 . The interaction between tailgate bracket  122  and driveshaft lever arm  110  allows tosional loads exerted by actuator assembly  10  to be coupled to tailgate  14  without imposing excessive localized stresses on the tailgate or components of hinge assembly  26 . This arrangement of hinge assembly  26  allows portions of the hinge assembly to be disassembled to permit installation and removal of the tailgate  14  since drive cup  116  and lever arm  110  can be decoupled from the tailgate by pulling both components away from their engagement with tailgate bracket  122 .  
         [0027]     Once the entire hinge assembly  26  is assembled to the tailgate  14 , it is still easily removable. During such servicing steps, the tailgate  14  would be removed by detaching the fasteners used for affixing tailgate bracket  122  to the tailgate. Thereafter, clevis arm  92  may be removed from driveshaft  108 , allowing the driveshaft to slide out from its support bushings and removed. The support brackets  102  and  104  may also be removed by removing the associated fasteners.  
         [0028]     In operation of actuator assembly  10 , extension of strut tube  66  exerts a downward force of clevis arm  92  which closes tailgate  14  from its opened to its closed position. Conversely, opening of the tailgate from its closed position causes rotation of the clevis arm  92  and retraction of strut tube  66 .  
         [0029]     In accordance with a principal feature of the present invention, ECU controller  84  provides controlling functions for actuator assembly  10 . When tailgate  14  is in its closed position, as shown in  FIG. 1 , when it is desired to open the tailgate, the operator engages latch handle  38  begins to move the tailgate open. This motion drives motor  50  to rotate, which provides a motor armature housing and input to ECU controller  84 . In some implementations of this invention, a position encoder may be incorporated into clutch assembly  54  to provide output of cable rotation whether or not the clutch is engaged. In the “opening” mode of operation, ECU controller  84  then applies an average power to the electric motor which is less than the higher power level used to lift the tailgate, as will be described in more detail below. This reduced power may be provided by a reduced DC constant voltage application to motor  50  or by a chopped or pulse width modulated higher level voltage having a reduced effective level. Moreover, this applied power for providing a braking effect can be provided by “shunting” the motor power leads, in effect creating a braking effect through electrical potential generated by driven rotation of the motor. In the case of such motor shunting, the generated electrical potential is proportional to the motor speed, and therefore the braking effect is dynamically varied. In any case however, the reduced power level is less than that needed to positively drive tailgate  14  to the down or opened position and acts to provide a braking effect.  
         [0030]     It has been found that energizing electric motor  50  to a reduced power level, enables the motor to exert an electrodynamic braking effect when it is “over driven”, or driven by the tailgate motion.  
         [0031]     The weight of tailgate  14  and it being hinged at its lower edge results in there not being a need for power actuation to open the tailgate. However, a means for slowing its opening operation is desired. The gravity forces acting on tailgate  14 , urging it to the opened position, are transmitted through strut assembly  46  and causes rotation of cable core  62  and the rotating armature of the electric motor  50  acting through clutch assembly  54  and transmission  52 . The electodynamic braking effect provided by the electric motor  50  slows the downward motion of the tailgate. This is desirable to produce a controlled opening motion rather than simply allowing the tailgate  14  to drop under its own weight.  
         [0032]     Once tailgate  14  reaches its full opened position, it reaches the horizontal position which is mechanically limited by cables  126 . ECU controller  84  de-energizes the electric motor  50  once a predetermined number of rotations of the motor armature occurs. Electric motor  50  includes well known features to output its rotational position, which can be achieved by electrical artifacts resulting from rotation of the armature, or by an integrated shaft encoder, such as conventional Hall effect devices. Moreover, as mentioned previously, the rotation signal may also be produced by clutch assembly  54 .  
         [0033]     When the operator desires to move the tailgate  14  from its opened to closed position, close switch  86  is actuated which sends a control signal to ECU controller which applies full power to be applied to electric motor  50  to cause it to rotate in a direction to cause extension of strut assembly  46 . The electrical power applied to electric motor  50  in this mode of operation is a full power level associated with the desired average voltage to produce the desired tailgate closing torque acting on hinge assembly  26 . The average electrical power applied in this mode of operation is referred to as the full power application. The electodynamic braking effect produced when lowering the tailgate  14  causes the application of a reduced average power applied to the electric motor  50  (or by self generated power by shunting the motor, as described previously). The reduced power level is preferably significantly less than the full power level. For reference, full power may be provided by application to motor  50  about 12-13 VDC, equivalent to battery power on the vehicle electrical supply bus. For such vehicles, the reduced power level may be provided by applying to motor  50  voltage in the range of 4-8 VDC in applied externally, or by the power generated through shunting of the motor. Another approach to modulate power is to control electrical current applied to motor  50  in a manner which provides two or more power levels, as described previously.  
         [0034]     In the mode of closing tailgate  14 , actuator assembly  10  will raise the tailgate until it reaches a position where latch assembly  32  engages with bed side  12 . At this position, the current to electric motor  50  is interrupted.  
         [0035]     It is contemplated that several types of latch assemblies  32  may be used in connection with this invention. In a conventional latch, tailgate  14  moves directly to its final latched position. In so-called cinching-type latches, a secondary, partially opened position is reached at which point the latch assembly includes a mechanism for powered cinching of the tailgate  14  to a fully closed and locked position. In the case of a cinching-type lock, actuator assembly  10  may be de-energized once the secondary position is reached, providing for final movement under the operation of the cinching latch unit.  
         [0036]     Power actuated closure panels for motor vehicles typically require a so-called anti-pinch features which causes the powered actuator to stop or reverse operation when the closure panel hits an obstacle. For example, if the tailgate  14  encounters and obstacle in its opening movement, an increase in load on electric motor  50  is detected through monitoring current or other electrical parameters acting on the electric motor. ECU controller  84  then will either interrupt the application of power to the motor or reverse polarity to move the tailgate in the opposite position, away from the obstacle. A similar operation occurs in the tailgate closing direction of movement.  
         [0037]     While the above description constitutes the preferred embodiment of the present invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims.