Abstract:
An integrated gas strut actuator strut assembly particularly adapted for providing power actuation of a motor vehicle lift gate or other opening closure. The system integrates the function of a counterbalancing gas spring and that of a electrically powered actuator. The system incorporates a strut assembly including a gas charged cylinder, and internal plunger and a threaded rod. Rotation of the threaded rod through a cable drive system causes the internal plunger to be advanced or retracted within the cylinder. Another feature of the invention are various embodiments of couplers between the gas cylinder plunger and rod and connectors for the assembly to the vehicle.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims priority to provisional patent application Ser. No. 60/604,147 filed Aug. 24, 2004. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     This invention relates to an assembly for controlling the motion of a body closure panel, such as found in motor vehicles. More particularly, this invention relates to an integrated gas spring and actuator assembly, which in one embodiment, is especially adapted for rear hatch doors of motor vehicles.  
         [0003]     Motor vehicles have closure panels to allow ingress and egress from the vehicle, to provide access to vehicle compartments for the movement of cargo and passengers, and for servicing the vehicle. Certain types of motor vehicles, for example, sport utility vehicles and mini vans frequently include a large rear hatch or lift gate. These panels can be quite large and include the backline glass. Some of these panels span the entire height and width of the rear area of the vehicle. In order to reduce effort for the opening and closing of these panels, counterbalancing springs are used. The current predominant form of counterbalancing springs are so-called gas springs or gas struts which are gas filled cylinders, typically attached to the left and right-hand sides of the panel opening, with their ends attached to the vehicle body and door. In addition to counterbalancing the weight of the door to ease opening and closing, gas spring devices further incorporate internal damping to control the rate at which the doors open and close. Gas spring struts are also found in other body closure panels, such as the hoods covering the vehicle engine compartment.  
         [0004]     A recent innovation to improve the convenience of use of hatch doors, is a provision of remote electric powered actuators. The system allows the vehicle operator to open and close the hatch panel, simply by controlling an electrical switch. One type of electric actuator incorporates an electric motor, gear reducer and cable connected with an actuator strut. The actuator strut includes an internal threaded rod and nut, and rotation of the lead screw causes the nut to move along the length of the lead screw which is coupled to the door for controlling its motion. These power actuators perform well and are valued features in motor vehicles. An example of such a system is provided with reference to U.S. Pat. No. 6,516,567 which is owned by the assignee of this invention and is hereby incorporated by reference.  
         [0005]     Motor vehicle components suppliers are constantly striving to improve their products. With respect to the system described by the previously noted U.S. Pat. No. 6,516,567, the motor vehicle lift gate incorporates three strut devices, including gas spring struts on both the left and right-hand side of the vehicle opening, with the actuator strut positioned on one side of the opening. This invention provides a device which combines the functions of a gas spring strut with a power actuator. This approach eliminates one component from the rear hatch opening of the vehicle. In addition to the esthetic improvements, this integration further reduces the number of components required for the vehicle.  
       SUMMARY OF THE INVENTION  
       [0006]     In accordance with one embodiment of this invention, an integrated spring actuator strut assembly is provided which incorporates a gas strut cylinder having an actuator drive nut. Rather than a smooth plunger rod as is typically found in gas struts, a threaded rod is used. The threaded rod end abuts the gas spring plunger. The threaded rod is caused to rotate through activation of a drive motor through a cable, as in the case of prior art lift actuators as previously described.  
         [0007]     In some applications, it may be desired to employ an existing design of a gas strut without significantly modifying its internal components. Certain types of presently available gas springs utilized compressed gas on two sides of the moving plunger. This is principally provided to enable automatic temperature compensation for the gas struts, providing them with consistent performance over a range of temperatures. In accordance with another aspect of this invention, an alternate embodiment of an integrated spring strut assembly is described having an external thread on the outside of the gas strut cylinder which meshes with an internally threaded nut which is caused to rotate by a drive system.  
         [0008]     Another feature of this invention is a means of conveniently connecting a subassembly with the threaded rod to the cylinder subassembly. This is advantageous since it would permit parts to be separately supplied by a gas strut manufacturer, and a manufacturer of the remaining elements of the power actuator.  
         [0009]     In the traditional gas strut system, a ball-and-socket arrangement is typically used to attach the ends of the strut to the vehicle mounting points. Ball-and-socket joints allow a degree of relative movement between the components as the lift gate undergoes its opening and closing motion. In the case of a power actuator, however, it is important to monitor the rotated position of the threaded rod which is translated directly to a position of the lift gate. However, if a significant amount of lost motion is present in the attachments of the strut of the vehicle, precise relationship between the rotated position of the threaded rod and closure panel position is lost. In accordance with another feature of this invention, several embodiments of mounting systems for the integrated spring actuator assembly are provided.  
         [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 area of a motor vehicle including a lift gate shown in an opened position with the integrated spring actuator strut assembly according to this invention mounted to the vehicle;  
         [0012]      FIG. 2  is an elevational view of the integrated spring actuator strut assembly according to a first embodiment of this invention;  
         [0013]      FIG. 3  is a cross-sectional view taken longitudinally through the assembly of  FIG. 2 ;  
         [0014]      FIG. 4  is first embodiment of a coupler between the threaded rod and strut plunger of an integrated spring actuator strut assembly according to this invention showing the coupler elements assembled;  
         [0015]      FIG. 5  is a cross-sectional view similar to  FIG. 4  but showing the coupler in a disengaging position;  
         [0016]      FIG. 6  is a cross-sectional view of a second embodiment of a coupler between the threaded rod and strut plunger showing the elements assembled;  
         [0017]      FIG. 7  is a cross-sectional view similar to  FIG. 6  showing the coupler in a disengaging position;  
         [0018]      FIG. 8  is a cross-sectional view of a third embodiment of a coupler between the threaded rod and strut plunger showing the elements assembled;  
         [0019]      FIG. 9  is a cross-sectional view similar to  FIG. 8  showing the coupler in a disengaging position;  
         [0020]      FIG. 10  is an elevational view of an integrated spring actuator strut assembly in accordance with a second embodiment of this invention;  
         [0021]      FIG. 11  is a longitudinal cross-sectional view of the assembly of  FIG. 10  taken along line  11 - 11  of  FIG. 10 ;  
         [0022]      FIG. 12  is an elevational view of a first embodiment of a ball stud attachment in accordance with this invention for connecting the integrated spring actuator strut assembly to a vehicle;  
         [0023]      FIG. 13  is a cross-sectional view through the ball stud of  FIG. 12  taken along line  13 - 13  of  FIG. 12 ; and  
         [0024]      FIG. 14  is an elevational view of a ball stud attachment in accordance with a second embodiment of this invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0025]      FIG. 1  illustrates motor vehicle  10  of a mini van or sport utility type. Motor vehicle  10  includes a rear hatch door or lift gate  12  shown in an open position in the figure. A conventional gas spring strut  14  is provided on the right-hand side of the lift gate opening  16 . The left-hand side of the lift gate opening  16  includes integrated spring actuator strut assembly  18  according to this invention. An actuator is used including an electric drive motor  20  which rotates cable  22  through gear reducer  24 . Additional references and descriptions of drive motor  20 , cable  22 , and gear reducer  24  may be obtained by reference to the previously noted U.S. Pat. No. 6,516,567.  
         [0026]     Preferably, electric drive motor  20  and gear reducer  24  are hidden behind interior trim panels of the vehicle. Cable  22  passes through an opening in the trim (not shown) to connect with integrated spring strut assembly  18 . In addition to permitting hidden placement of system drive components, cable  22  also allows strut assembly  18  to move during the motion of opening and closing of lift gate  12 .  
         [0027]     Now with reference to  FIG. 2 , a more detailed illustration of the components of strut assembly  18  is provided. Strut assembly  18  includes hollow case or cylinder  26  which is preferably formed from tube stock. Upper lift gate mount  28  is formed at the top of cylinder  26  and allows the device to be fixed to lift gate  12  of the vehicle. Various attachment approaches may be utilized, including one of the ball-and-socket arrangements described below. Threaded rod  30  extends from cylinder  26  and is mounted for rotation to lower vehicle mount  32 , which also attaches to the vehicle body through a ball-and-socket arrangement. An internal bearing  33  at lower vehicle mount  32  allows threaded rod  30  to freely rotate. Cylinder  26  defines longitudinal axis Z.  
         [0028]      FIG. 3  provides a cross-sectional view through strut assembly  18 , showing internal components. Nut  34  is positioned at the bottom open end of cylinder  26  and forms internal threads which mate with the external threads of rod  30 . Nut  34  is fixed to cylinder  26  so that it does not rotate or move longitudinally within the cylinder. Nut  34  can be mounted to cylinder  26  by various means including the use of pins  36  as illustrated in the figure. Various other attachment approaches could be implements, including fusion bonding, adhesives, or through deformation of nut  34  or cylinder  26 . Internal plunger  38  is movable within cylinder  26  and is acted upon by gas within closed gas chamber  40 . Compression of the gas within chamber  40  provides the desired counterbalancing effect in the manner of a conventional gas spring strut. A mechanical stop in the form of inward shoulder  42  prevents plunger  38  from escaping from within cylinder  26 . Cylinder  26 , rod  30  and plunger  38  are coaxially located on longitudinal axis Z.  
         [0029]     Drive end  44  of rod  30  abuts and engages plunger  38 . In operation, rod  30  rotates and moves longitudinally relative to nut  34 , driving plunger  38  to move within gas chamber  40 . It is desirable to reduce the level of torque loads acting on plunger  38  caused by rotation of rod  30 . Therefore, in a preferred embodiment, an anti-friction thrust bearing would be provided between these components. The embodiment illustrated in  FIG. 3  incorporates roller thrust bearing  46  for this purpose. An outer cover tube  45  encloses rod  30  for esthetic improvements and to shield the rod from contamination, or having items wrap around it.  
         [0030]     When an operator of motor vehicle  10  desires to open or close the lift gate  12 , drive motor  20  is actuated to cause rotation of rod  30 . Rod  30  rotates and threads into and out of nut  34 , forcibly moving plunger  38  within gas chamber  40 . This action changes the distance between upper lift gate mount  28  and lower body mount  32 , thus causing the lift gate  12  position to be changed. A desirable feature is to permit the motor vehicle operator to manually open and close lift gate  12 . In such instances, manual movement of lift gate  12  will cause a change in the separation between vehicle mounts  28  and  32 . This motion forcibly causes rod  30  to rotate within nut  34 . This “free-wheeling” motion is accommodated through provision of a clutch within gear reducer  24  or drive motor  20 . In this way, the system can be “back-driven” as desired to permit such manual operation. This manual override feature is also known as described by the previously noted U.S. Pat. No. 6,516,567.  
         [0031]     Another feature of this invention relates to the coupling between rod drive end  44  and plunger  38 . Several embodiments of coupler designs for these components are described herein. Convenience, quick, or “snap” attachment between these components is desired to permit the components of strut subassembly  41 , which includes cylinder  26 , plunger  38 , nut  34 , and upper mount  28 ; and actuator subassembly  43  components, including rod  30  and the connected components, to be conveniently combined. Moreover, it is desired to permit these assemblies to be disassembled conveniently for warranty repair or component replacement in a manner which would not require the entire assembly  18  to be replaced as a unit. Convenient attachment between strut subassembly  41  and actuator subassembly  43  also provide the ability for separate manufacturers to supply them.  
         [0032]     A first embodiment of such a releasable coupler  47  is described with reference to  FIG. 4 . As illustrated, retainer  48  is coupled with plunger  38  (not shown in  FIG. 4 ) and includes an internal hollow socket  50 . In this embodiment, rod drive end  44  includes groove  52 . Socket  50  incorporates engagement elements in the form of inwardly deflecting fingers or tabs  54 . Insertion of drive end  44  into socket  50  causes fingers  54  to be initially deflected in a radially outward manner, and further insertion causes them to snap into position engaging with groove  52 . Once assembled in this manner, the parts are locked together and the rod  30  can exert pushing and pulling forces on plunger  38 . As mentioned previously, it is desirable to further allow these components to be disassembled as required. Release ring  56  is provided to enable such disconnection. In the normal position of release ring  56 , it is retracted relative to drive end  44 . When it is desired to disassemble these components, release ring  56  is pushed toward drive end  44  as shown in  FIG. 5 , causing engagement with fingers  54  and retracting them from their position in engagement within groove  52 . This allows the actuator subassembly  43  and strut subassembly  41  to be disassembled.  
         [0033]     With reference to  FIG. 6 , a second embodiment of a coupler  60  is shown. In this instance, retainer  62  includes a projecting barrel or tube which is split to form a number of engagement elements in the form of fingers  64  with inwardly directed teeth or barbs  66 . Insertion of rod drive end  68  causes the barbs  66  to initially be deformed in a radially outward direction until they can snap into engagement with groove  70 . Coupler  60  further incorporates release ring or bushing  76 . Release bushing  76  includes a forward edge which is conically tapered. As shown in  FIG. 7 , depressing release bushing  76  into engagement with fingers  64  causes them to be expanded in a radially outward direction, releasing the interengagement between barbs  66  and grooves  70 . This embodiment of coupler  60  further incorporates an anti-friction thrust bearing in the form of ball  72  which contacts bearing plate  74 . Since the contact between ball  72  and bearing plate  74  is essentially point contact, very little torque is transmitted between these elements.  
         [0034]     A third embodiment of coupler  80  is shown with reference to  FIG. 8 . In this instance, retainer  82  includes engagement elements in the form of fingers  86  having inwardly directed barbs  88 , similar to those described in connection with coupler  60 . In a similar fashion, depressing rod drive end  90  into retainer  82  causes fingers  86  to be expanded outwardly until barbs  88  engage with groove  92 . This embodiment of a coupler differs from the previously embodiments in that nut  94  is modified to incorporate a projecting conical extension  96 . Coupler  80  can be disengaged simply by advancing nut  94  to a position causing conical end  96  to engage with fingers  86 , causing them to expand in a manner similar to the previous embodiments.  
         [0035]     An alternate embodiment of integrated spring actuator strut assembly  102  is shown with reference to  FIGS. 10 and 11 . This second embodiment differs from strut assembly  18  in that gas strut cylinder  104  is of generally conventional internal construction, utilizing internal plunger  106  and a smooth rod  108  which passes through collar  110 . In this embodiment, however, the external surface of cylinder  104  forms threads  112  to perform the function of the threaded rod in the prior embodiment. The projecting end at the top of the figures would be affixed to an upper lift gate vehicle mount (not shown). The opposite lower end of rod  108  is mounted to base plate  114  which in turn is affixed to a lower vehicle mount (not shown). Housing  116  is also affixed to base plate  114  and forms an open cylinder providing mounting locations for bearings  118  and  120 . Outer nut carrier tube  122  is journaled for rotation within housing  116  via bearings  118  and  120 . Outer nut carrier tube  122  extends to its top end where nut  124  is positioned. Nut  124  has internal threads which mate with the external threads of strut cylinder  104 .  
         [0036]     A cable (not shown) drives pinion gear  126 , which in turn mates with drive gear  128 , mounted to outer nut carrier tube  122 . Rotation of pinion gear  126  causes rotation of drive gear  128  and, consequently, rotates outer nut carrier tube  122 . This rotation causes the threaded position of nut  124  to move along the outer surface of strut cylinder  104 . Cylinder  104  is constrained from rotating due to its connection to the lift gate and an upper vehicle mount (not shown). As in the first embodiment, this motion causes the open position of lift gate  12  to move as desired. The release clutch provided in the drive system described previously would also be used in this embodiment to allow manual actuation of the device. Integrated spring actuator strut assembly  102  allows the internal construction of the gas spring elements with cylinder  104  to be of conventional construction. This permits automatic temperature compensation features to be preserved as well as allowing some carry-over parts to be used for the assembly.  
         [0037]     A still further alternative embodiment of an integrated spring actuator assembly is not illustrated, but would simply reverse the configuration shown in  FIGS. 10 and 11  with the motor causing rotation of strut cylinder  104 , while nut  124  would remain in a fixed position.  
         [0038]     Now with reference to  FIGS. 12, 13 , and  14 , various embodiments of ball-and-socket type connectors are described which may be used for attaching the strut assemblies of this invention to a vehicle at upper lift gate mount  28  and lower vehicle mount  32 . As mentioned previously, it is important to establish an accurate relationship between the rotated position of the internally threaded components (nuts  34  or  124 ) and the externally threaded components (rod  20  or cylinder  104 ) and the extended distance between the upper and lower vehicle mounts  28  and  32 . Conventional ball-and-socket arrangements allow a high degree of angular lost motion to occur at the joint, which causes a drop in accuracy in that correlation.  FIGS. 12 and 13  illustrate a first embodiment of a connector assembly  130  which includes socket  132  and ball stud  134 . This design approach constrains rotation about the Z axis illustrated in  FIG. 12  through use of anti-rotation clip  136  installed within socket  132 . Anti-rotation clip  136  includes a pair of projecting tabs  138  which engage with ball stud collar  140 . The engagement between tabs  138  and collar  140  defines a limited degree of angular rotation about the Z axis which is the axis about which the relative rotation between the internally and externally threaded components occurs. Connector assembly  130  however continues to provide the desired degree of angular motion desired to accommodate the change in orientation of the system components as the lift gate  12  is moved between its opened and closed positions.  
         [0039]      FIG. 14  illustrates a second embodiment of a connector assembly  144 . In this embodiment, socket  146  integrally defines projecting walls  148  which engage with ball stud collar  140  in a manner similar to that described in connection with connector assembly  130 . This embodiment also constrains lost motion about the Z axis. In the case of both connector assemblies  130  and  144 , allowed relative rotation about the orthogonal X and Y axes is greater than that allowed about the Z axis.  
         [0040]     Throughout this specification, gas spring type devices are described as providing a force applying mechanism for counterbalancing the weight of the vehicle lift gate. However, it is within the scope of this invention to implement other types of force applied or damping mechanisms. For example, mechanical springs, hydraulic fluid or other systems could be implemented in connection with the mechanical drive systems described herein.  
         [0041]     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.