Abstract:
A vehicle seat assembly with a linear actuator is disclosed in which the actuator is used to adjust the relative position of two relatively movable components of the seat assembly. The actuator includes a first part attached to one of the seat assembly components in the form of a lead screw with an external helical screw thread. A second part of the actuator is attached to the other seat component that is relatively movable and includes a housing containing a spin nut threaded onto the lead screw. The second part further includes means for axially capturing the spin nut to prevent the spin nut from rotating along the lead screw and means for selectively releasing the spin nut from its axial capture to permit rotation about the lead screw and thereby relative movement of the actuator second part relative to the first part. A cam is mounted to the second part to selectively engage and release the spin nut from its axial capture.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     The present invention relates to vehicle seat assemblies and in particular to vehicle seat assemblies having an linear actuator for use as a seat adjuster and/or a recliner. 
     Manually adjustable vehicle seat assemblies typically include an adjuster for adjusting the fore and aft position of seat assembly relative to the vehicle and a recliner for adjusting the inclination of the seat back. Such mechanisms must be capable of withstanding the high loads that may be applied to the seat assembly during a vehicle collision. More and more vehicle seat assemblies are being developed with the seat belts mounted directly on the seat assembly rather than being mounted to the vehicle structure. This increases the seat belt comfort because the belt anchors are moved with the seat assembly during adjustment rather than being fixed to the vehicle structure. However, with the seat belts mounted to the seat assembly, the forces applied to the recliner and adjuster mechanisms during a vehicle collision are significantly increased. 
     Accordingly, it is an object of the present invention to provide a recliner mechanism and a seat adjuster mechanism that are capable of withstanding seat belt loads. 
     It is a further object of the present invention to provide such devices which, when under high loading conditions, act to &#34;lock up&#34;, making relative movement of seat components more difficult as opposed to failing under the high loads in a manner which increases the likelihood of seat component movement. 
     It is a feature of the present invention to provide a seat assembly with a seat adjuster mechanism or a recliner mechanism which relies upon friction to lock the movable seat components in place. When loaded, the mechanisms are designed to increase the normal force at the friction surfaces, thereby increasing the friction holding the seat components in place. 
     It is a further feature of the invention that the actuator of the present invention is infinitely variable in some embodiments to allow adjustment to any position desired. 
     The actuator includes a first part attached to one of the seat assembly components in the form of a lead screw with an external helical screw thread. A second part is attached to another seat component that is movable relative to the component attached to the first part. This second part includes an spin nut having a threaded bore that is threaded onto the lead screw and a housing for axially capturing the spin nut. The housing includes an end cap that is axially movable between a lock position in which the axial end walls of the spin nut are frictionally engaging the cap and the housing to prevent rotation of the nut along the lead screw and a release position in which the spin nut is freed for rotation. The end cap movement is controlled by a cam engaging an outer surface of the cap and an internal spring urging the end cap away from the housing. 
     Further objects, features and advantages of the invention will become apparent from a consideration of the following description and the appended claims when taken in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary side elevational view of the structure of the seat assembly of the present invention showing the infinitely variable linear actuator used as a recliner mechanism; 
     FIG. 2 is a front elevational view of the mechanism shown in FIG. 1; 
     FIG. 3 is a sectional view of the actuator shown in a locked position; 
     FIG. 4 is a sectional view of the actuator shown in a released position for seat back adjustment; 
     FIG. 5 is a fragmentary elevational view of the seat structure showing an alternative embodiment of the recliner mechanism; 
     FIG. 6 is a perspective view of the seat structure showing the actuator used as a seat adjuster; 
     FIG. 7 is a sectional view of an alternative embodiment of the actuator with a secondary locking latch shown with the mechanism shown in a locked position; 
     FIG. 8 is a sectional view of the mechanism of FIG. 7 shown in a released position; 
     FIG. 9 is a plan view of the mechanism shown in FIGS. 7 and 8; 
     FIG. 10 is a sectional view as seen from substantially the line 10--10 of FIG. 7; and 
     FIG. 11 is another embodiment of the actuator mechanism including a secondary inertia locking feature. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The seat assembly of the present invention, having an infinitely variable linear actuator for a recliner mechanism is shown in FIG. 1 and designatedgenerally as 10. Seat assembly 10 includes a base member 12 which is attachable to a vehicle floor. A seat member 14 is slidably mounted to thebase member 12 and includes a seat frame 16 comprised of a slide rail 18, slidably mounted to the base member 12, and a riser 20. A seat back or back member 22, having a back frame 24, is pivotally mounted to the riser 20 at a pivot joint 26. The pivotal connection of the back frame to the riser enables the back frame and hence the back member to be rotated relative to the seat member as shown by the phantom line positions of the back frame 24. This enables the inclination of the back member 22 relativeto the seat member 14 to be adjusted for the comfort of a seat occupant. Aninfinitely variable linear actuator 30 is used to hold or lock the back member in place relative to the seat member. 
     The actuator 30 includes a first part 32 pivotally attached at a pivot joint 36 to a recliner arm 34 of the back frame 24. The recliner arm extends downward from the pivot joint 26 that attaches the back frame to the riser. The first part 32 is allowed to pivot about a horizontal transverse axis but is not allowed to pivot about the axis 52 described below. 
     A second part 38 of the actuator is pivotally attached to the riser througha mounting bracket 40. The actuator 30 includes an internal mechanism, shown in FIGS. 3 and 4 which operates to lock the first part 32 relative to the second part 38, thus locking the back frame 24 to the seat frame 16, preventing relative motion therebetween. The second part 38 of the actuator includes a housing 42 having an end wall 43 at one end with a central aperture 45 therethrough. The opposite end 47 of the housing is open. An end cap 44 with a central aperture 49 is positioned in the open end so as to close the housing. A pair of mounting flanges 46 extend from the housing 42 and are coupled to the mounting bracket 40 at the pivot joint 48. This allows the second part 38 of the actuator to pivot relativeto the seat frame 16 about a horizontal transverse axis 50. 
     The actuator 30 comprises a central linear axis 52 which passes through thepoints of attachment 36 and 48 of the actuator to the back frame 24 and seat frame 16 respectively. The attachment of a first part 32 to the recliner arm 34 of the seat frame comprises an eyelet 54 formed at one endof a shaft 56 which extends along axis 52. The eyelet 54 comprises a circular aperture 58 and its attachment to the recliner arm 34 is made by a circular pivot pin (not shown) being passed through the aperture 58 and a corresponding aperture in the recliner arm 34. 
     The shaft 56 is formed on its exterior surface with a threaded portion comprising a plurality of threads extending in the helical fashion around the outside of the shaft over a significant portion of its length as illustrated. The shaft 56 is operatively coupled with a complementary threaded portion 60 of an annular element 62 (FIGS. 3 and 4). The annular element 62 has its threaded portion 60 on its central bore which is concentric with the axis 52. In its preferred form, element 62 is of a circular outside diameter with spaced axial end walls or end faces 64 and 66 disposed in planes at a right angle to the axis 52. 
     The housing 42 includes a bore 68 at the closed end of the housing forming a recess 70 of a diameter less than that portion of the housing containingthe annular element 62. The end cap 44 includes a cylindrical flange 72 extending into the housing 42 forming a recess 74 within the end cap that is similar to the recess 70. 
     Disposed within each recess is a circular array of bearings 76, an annular bearing race 78 and a yieldable resilient annular member 80. These membersassist in positioning the annular element 62 within the housing 42. As illustrated, the yieldable resilient annular elements 80 are in the form of spring washers sometimes referred as Belleville washers. 
     Particular reference to FIG. 3, the end cap 44 is shown in a locked position in which it is forced into the housing 42 by a cam lever 82, described in greater detail below. In the locked position of the end cap, the yieldably resilient annular elements 80 are both compressed to the point that the end 84 of the cylindrical flange 72 contacts an outer annular portion of the axial end wall 66 of the annular element 62. Likewise, the shoulder 86 formed in the housing by smaller diameter bore 68, contacts an outer annular portion of the end wall 64 of the annular element 62. The friction between the two end walls 64 and 66 and the shoulder 86 and cylindrical flange 72 prevents rotation of the annular element 62 within the housing 42 about the axis 52. The mounting of the first part 32 to the recliner arm 34 prevents rotation of the first part 32 about the axis 52 while the mounting of the second part 38 to the seat frame 16 precludes rotation of the second part relative to the axis 52. Therefore, with the annular element 62 being prevented from rotating, the first and second parts of the actuator 30 are fixed in position relative to one another which in turn fixes the back frame 2 in position relative to the seat frame 16. 
     With reference to FIG. 4, the end cap 44 is shown in a release position in which it has been partially withdrawn from the open end of the housing 42.This has been permitted by rotation of the cam lever 82 decreasing the distance between pivot joint 48 and the cam surface 87 along the directionof axis 52. This enables the yieldably resilient annular elements 80 to move the end cap 44 axially toward the pivot joint 48. This disengages thecylindrical flange 72 from the annular element and also disengages the annular element from the shoulder 86 in the housing 42. 
     Each array of bearings comprises a retainer which serves to retain individual bearing balls. It is these bearing balls which provide rolling contact with the corresponding race 78 and the corresponding end wall 64 or 66 of the annular element 62. In this way, the bearing balls serve to facilitate free rotation of the element 66 between the walls which axiallycapture it when the mechanism is in an unlocked condition as shown in FIG. 4. In the unlocked condition, when axial forces are applied to the actuator 30, the threaded coupling between the shaft 56 and the annular element 62 enables the annular element 62 to rotate about the axis 52. This in turn causes translation of the first part 32 relative to the second part 38 thus changing the distance between the pivot joint 36 and the pivot joint 48. 
     The cam lever 82 is a forked lever having two legs 88 extending from a center portion 90. The cam lever is forked to provide a center clearance for the shaft 56 to extend therethrough. The two legs 88 are each pivotally mounted to the flanges 46 by the pivot joint 48. A pair of bias springs 92, each coupled to one of the legs 88 of the cam lever, acts to bias the cam lever to the locked position shown in FIG. 3. A control wire 94 is connected to the center portion 90, opposite the pivot joint 48 fromthe bias spring 92, and serves to limit the rotational travel of the cam lever in the direction of rotation urged by the springs 92. 
     The cam lever 82 has an irregular shaped cam surface 87. The axial distancebetween the pivot joint 48 and the cam surface varies depending upon the rotational position of the cam lever. In the locked position of the cam lever, the axial distance between the pivot joint 48 and the cam surface 87 is greater than when the cam lever is in the unlocked position shown inFIG. 4. As a result, in the locked position, the end cap 44 is positioned further from the pivot joint 48 than in the unlatched position shown in FIG. 4. 
     A hand operated control lever (not shown) is coupled to the control wire 94in a conventional manner to pull on the wire 94 in the direction of the arrow 96 of FIG. 4 to unlock the actuator 30. When the wire 94 is pulled, the cam lever is rotated to the release position, enabling the annular element 62 to spin. This enables adjustment of the back frame 24 relative to the seat frame. Upon release of the lever, the bias springs 92 will automatically return the actuator to the locked position. During a vehiclecollision, if forces are applied to the seat back in a direction to rotate the seat back forward, the shaft 56 will be placed in tension causing the annular element 62 to be forced against the shoulder 86 with a greater force than applied by the end cap and cam. This increases the frictional force at that interface and thereby increases the resistance to rotation of the annular element 62 tending to &#34;lock-up&#34; the actuator during a period of high loading. If the seat back is loaded in the opposite direction, placing the shaft 56 in compression, the annular element 62 will be forced against the cylindrical flange 72 thus increasing the friction at that interface and increasing the resistance to rotation of the annular element. 
     The actuator can embody an inertia locking feature by virtue of the construction which has already been described. This would be particularly useful in the event that inertia loads are encountered when the end cap 44is in a condition other than a fully locked condition. For example, if the mechanism is not fully locked and the vehicle is involved in a sudden deceleration, such as panic braking or a collision, the application of inertia forces arising out of the deceleration can be effective to cause the element 62 to be urged axially within its axial capture so that one ofits end walls forcefully abuts the corresponding axial confining surface 84or 86, depending on the direction of inertia forces. Hence, such inertia forces can be effective to lock element 62 against rotation and thereby resist collapse or extension of the actuator which might otherwise occur. Such inertia locking capability is created by a suitable selection of the yieldability of the annular elements 80 since they must yield to permit the inertia locking action to take place. 
     The actuator 30 is shown in a alternative installation for use as a recliner mechanism. The actuator 30 is in all respects identical to the actuator shown and described in FIGS. 1 through 4. It is the seat assemblyitself that differs between the embodiment shown in FIGS. 1 through 4 and the embodiment shown in FIG. 5. Identical elements are given the same reference numerals while elements that have been modified are given the same reference numeral with the lower case &#34;a&#34; as a suffix. The back frame24a is in the form of a closed section beam 97 with the actuator 30 mountedwithin the beam. The beam 97 is used when a shoulder belt is mounted to theseat back to provide added strength to accommodate the belt loads. The two flanges 46 of the actuator are pivotally mounted to the side walls 98 and 100 of the beam 24a. The actuator 30 is mounted to the seat assembly with the first part 32 pivotally mounted to the seat frame 16a at the pivot joint 102 while the second part 38 of the actuator is mounted to the back frame 24a through the pivot joint 104. 
     With reference to FIG. 6, the infinitely variable actuator 30 is shown in use as a seat adjuster to lock the seat in the fore and aft adjusted position. Components of the seat assembly in FIG. 6 identical to those in FIGS. 1-4 are given the same reference numerals while those components that are similar to that disclosed in FIGS. 1-4 are given the same reference numeral with the suffix &#34;b&#34;. In most respects, the actuator 30 of FIG. 6 is identical to the actuator 30 in FIGS. 1-4. The first part of the actuator 32b is a screw shaft 56b that is mounted at its two axial ends to the base member 12b through mounting flanges 106 extending laterally from the base member 12b. Shaft 56b is not rotatable about the axis 52. The second part 36b of the actuator is mounted to the seat frame 16b through a mounting flange 108. As in the previous embodiments, the first part 32b is fixed from rotating about the axis 52. 
     The seat frame 16b is slidably mounted to the base member 12b for fore and aft sliding motion in the direction of arrow 110. With the base part 12b fixed to a vehicle floor pan, movement of the seat frame 16b accomplishes fore and aft adjustment of the seat assembly within the motor vehicle. With the actuator 30 in a locked condition, the annular element 62 within the second part 38b is fixed from rotating and thereby prevents movement of the seat frame 16b relative to the base part 12b. When the wire 94 is pulled by rotation of the release lever 112 in the direction of arrow 114,the cam lever 82 is rotated about the pivot 48, releasing the frictional capture of the annular element 62 allowing the element to rotate and the seat frame 16b to move relative to the base part 12b. 
     The seat assembly would typically include a second actuator 30 mounted to abase frame 12b and seat frame 16b at the opposite lateral side of the seat assembly. A second wire 94 can be coupled to the actuator 30 at the opposite side of the seat assembly and actuated by the release lever 112 for simultaneous release of the two actuators 30. 
     An alternative embodiment of the actuator, is shown in FIGS. 7-10 and designated generally as actuator 30c. As before, identical components are given the same reference numeral while modified components are given the same numeral with the suffix &#34;c&#34;. The operation of actuator 30c is the same as actuator 30 described in detail above. Actuator 30c includes an additional secondary locking mechanism to prevent rotation of the annular element 62c. The secondary locking mechanism requires that the actuator beused positioned with the axis 52 oriented vertically. 
     The secondary locking mechanism includes a pair of lock levers 116 and 118 rotatably mounted to the mounting flanges 46 at the pivot joint 48. The locking levers 116 and 118 are forked so as to be positioned on both sidesof the shaft 56 as shown in FIG. 9. The locking levers 116 and 118 are generally C-shaped and are mounted at their upper ends at the pivot joint 48. The lower ends of the locking levers form pawl portions 120 having a plurality of teeth 122. The housing 42c  includes openings 124 on oppositesides adjacent to the annular element 62c. The pawl portions 120 of the twolocking levers extend through the openings 124. 
     The annular element 62c is provided with axially extending teeth 126 about its periphery which are engagable with the teeth 122 of the locking levers. The forked arms 117 and 119 on the locking levers each include a downwardly projecting cam portion 128 which rests upon the top surface 130of the end cap 44. When the end cap is in the locked position as shown in FIG. 7, the end cap 44 is pushed away from the pivot joint 48 a sufficientdistance that the two locking levers, due to gravitational forces, are rotated to a position in which the teeth 122 of the locking levers engage the teeth 126 of the annular element 62c, thus preventing rotation of the annular element. 
     When the end cap 44 is moved to an unlocked position as shown in FIG. 8 upon rotation of the cam lever 82, the top surface 130 of the end cap 44 exerts an upward force on the locking levers at the cam portions 128. Due to the horizontal offset between the cam portions 128 and the pivot joint 48, this upward force causes a rotation of the locking levers 116 and 118 about the pivot joint 48, withdrawing the pawl portions 120 of the lockinglevers from the annular element 62c and out of engagement with the teeth 126 of the annular element 62c. This frees the annular element 62c for rotation about the actuator axis 52 allowing the first part 32 of the actuator 30c  to move relative to the second part 38c. Upon release of thepawl wire 94 and return of the cam lever 82 to the locked position, gravitywill return the locking levers 116 and 118 to engagement with the annular element 62c. 
     A last embodiment of the actuator 30 is shown in FIG. 11 designated generally as 30d. Like actuator 30c, actuator 30d is intended for use withthe central axis 52 oriented vertically. Actuator 30d includes a secondary locking mechanism having a single locking lever 132. Locking lever 132 is generally C-shaped but is mounted at its center for rotation at the pivot joint 48 and has two pawl portions 120d with teeth engagable with the teeth 126d of the annular element 62d. The locking lever 132 extends in opposite directions from the pivot joint 148 with the pawl portions 120d engagable on opposite sides of the annular element 62d. 
     In addition to being oriented vertically, the actuator 30d should also be oriented with the locking lever 132 extending in the direction of anticipated loading applied to the seat assembly into which the actuator 30d is installed. The anticipated loading direction is indicated by the arrow 134. When used as a seat assembly recliner, the loading direction will be in the fore and aft direction Without any load being applied to the seat assembly, the locking lever 132 will be positioned with the two pawl portions 120d spaced from the annular element 62d. During loading in the direction of arrow 134, the inertia of the locking lever 132 will cause it to rotate in one direction or the other about the pivot joint 48.This will cause one of the two pawl portions 120d to move into the housing 42d where the teeth of the pawl portion will engage the teeth 126d of the annular element 62d. The engagement between the teeth of the pawl portion and the annular element will prevent rotation of the annular element. 
     Because the locking lever 132 is normally not in locking engagement with the annular element 62d, there is no need for the locking lever to rotate upon unlocking of the actuator 30d when the end cap 44 is raised to an unlocked position. Accordingly, there are no cam portions on the locking lever 132 similar to the cam portions 128 of the locking levers in the actuator 30c. 
     The seat assembly of the present invention includes a linear actuator used as either a recliner mechanism or a seat adjuster mechanism. The linear actuator operates by frictional engagement with a spin nut to prevent the spin nut from rotating along a lead screw to hold the seat components in their adjusted positions. By using frictional engagement to prevent rotation of the spin nut, the actuator is made to lock-up upon axial loading by increasing the frictional forces acting on the spin nut and thus increasing its resistance to rotation. By providing the actuator witha cam action release lever, the actuator can be released with the use of a simple pull cable in a manner well know in manually adjustable seat assemblies. 
     It is to be understood that the invention is not limited to the exact construction illustrated and described above, but that various changes andmodifications may be made without departing from the spirit and scope of the invention as defined in the following claims.