Abstract:
An annular actuator for moving a member axially to couple and un couple a drive member with a driven member of a vehicle drive train. The actuator encircles the drive and driven member. The actuator has a housing to which a diaphragm is mounted. A spring biases the diaphragm to move in one axial direction and withdrawal of air forces the diaphragm to move in the opposite axial direction. A shifting fork coupled to the diaphragm moves a clutch ring in the one axial direction to be coupled with only one of the drive and driven members and is coupled with both the drive and driven members when moved in the opposite direction. The actuator defines a sealed chamber that is totally non-rotatable with relative movement occurring between the shifting fork and the clutch ring.

Description:
This application is a continuation-in-part of U.S. application Ser. No. 08/953,278 filed Oct. 17, 1997, now U.S. Pat. No. 6,109,411, which is a continuation-in-part of U.S. application Ser. No. 08/651,384 filed May 22, 1996 and now U.S. Pat. No. 5,740,895. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to an actuator for initiating the shifting action of a clutch to affect engagement/disengagement of drive and driven shafts, and more particularly to such an actuator that is pneumatically actuated. 
     BACKGROUND OF THE INVENTION 
     In recent years it has become increasingly popular to provide vehicles with the ability to convert between two-wheel and four-wheel drive. As popularity has grown, so to have the many ways of affecting conversion. In one example there is a permanently driven drive line segment to the rear wheels of a vehicle, and a part-time driven drive line segment to the front wheels. The part-time drive line segment is simply disconnected/decoupled from the engine&#39;s drive shaft at the transmission or transfer case and that segment is rendered passive (undriven). There is often a second point of disconnection which may be at or near the differential (a center disconnect) or at both wheels. 
     There is a mechanical action that takes place to achieve each connection and disconnection as contemplated herein. Two shafts or drive line segments are in close relationship and a clutch ring that is permanently coupled to one shaft is slidable into engagement with the other shaft to couple (connect) the shafts and is slidable out of engagement with said other shaft to decouple (disconnect) the two shafts. 
     The sliding movement is achieved by what will here be referred to as an actuator. The actuator can be many types including, e.g., a shift lever, manual or electrically driven, it can be cam actuated and it can be pneumatic actuated. The present invention is directed to pneumatic actuators for clutch ring actuation. 
     Pneumatic actuators in general are not new. A pneumatic actuator is disclosed in U.S. Pat. No. 4,627,512, issued Dec. 9, 1986. This actuator was applied within a wheel hub for connecting/disconnecting the wheel from an axle. Another pneumatic actuator is disclosed in U.S. Pat. No. 5,044,479. One embodiment of this patent applies to the wheel hub of a vehicle and connects/disconnects an axle from the wheel hub, and another embodiment applied at a juncture between two axle portions located between the wheel hub and differential. 
     The pneumatic actuators as disclosed in these patents, and other similar actuators, function as claimed but they do have problems. In the &#39;512 patent, the air chamber is formed between components that have relative rotation making sealing difficult. Furthermore, the negative air pressure typically available for actuation, e.g., from the vehicle&#39;s exhaust manifold, is limited and the designs of both the &#39;512 patent and the &#39;479 patent can be inadequate to produce the desired actuation. 
     For the above reasons at least in part, the pneumatic actuator for the clutch ring has not gained a high degree of acceptance. The objective of the present invention is to provide an improved pneumatic actuator that avoids the above problems. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Whereas the clutch ring and components to be coupled are rotating, the annular actuator is designed to shift a non-rotating member (referred to as a fork) that is placed in contact with the rotating clutch ring. The contact between the rotating clutch ring and fork is designed to form a bearing that permits rotation of the clutch ring while the entire actuator remains static. 
     The annular configuration of the actuator which surrounds the juncture to be coupled enables the use of a greater surface area on which the air acts. Thus, the available air pressure (from the manifold) is being applied to the greater surface area and produces a greater accumulated force. Further, the force that is generated, because of its application at the greater radial distance from the clutch ring axis, produces greater torque and in combination with the greater surface area, the effective force applied to the clutch ring is substantially increased and adequately produces the desired clutch ring movement. 
     Having established a viable pneumatic actuator for a surrounding clutch ring, the inventors turned to the reduction of cost. The diaphragm that is used as the movable wall is made of material that conforms and seals against metal objects. Placing the diaphragm in an opening that needs otherwise to be sealed allows the diaphragm to serve dual purposes. Cost is also reduced by providing the other wall half of the air chamber from an existing component of the vehicle where available, the diaphragm forming the movable wall half. 
     Previously the other half (the fixed wall half) of a conventional air chamber had to be machined at the interface where the diaphragm had to grip the metal material. This is because a cast part is provided with tapered surfaces and machining was used to remove the taper. An elastomeric material such as a diaphragm will slide off a tapered surface. In one embodiment of the invention, the inventors cast into the elastomeric material a bendable metal stay that when properly placed is swagged at its end to provide mechanical gripping and holding of the diaphragm. Also, the elastomeric material is formed with a peripheral bead or beads that are collapsed against the tapered surface to assist gripping against the tapered surfaces. 
     With the increased surface area of the diaphragm and thus greater effective force applied by the intake manifold, the return spring force can also be increased to insure more reliable engagement and disengagement. 
     Having thus achieved a far more efficient air actuated clutch ring actuator, all or most of the actuators heretofore provided along the drive line are advantageously replaced with the present annular actuator. Those skilled in the art will appreciate the advantages and the numerous applications for the above pneumatic actuator upon reference to the following detailed description having reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an annular actuator of the present invention; 
     FIG. 2 is an exploded view of the annular actuator of FIG. 1; 
     FIG. 3 is a cross sectional view of the annular actuator of FIG. 1 as applied to a wheel hub showing the engaged position; 
     FIG. 4 is a view similar to FIG. 3 but showing the disengaged position; 
     FIG. 5 is a view of an annular actuator similar to that of FIG. 1 but applied to a differential; and, 
     FIG. 6 is a view of a pair of annular actuators similar to that of FIG.  1  and FIG. 5 but applied to a transfer case. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1-4 illustrate one embodiment of an annular actuator  10  of the present invention. Referring to FIGS. 1 and 2, the actuator  10  has a housing  12  that is arranged to be fixedly mounted in a non-rotative manner. The actuator  10  is circular in configuration and has a center opening (bore)  14 . A defined gas chamber  22  is formed within the housing  12  including a pliable diaphragm  40  which defines a movable wall of the chamber  22 . The diaphragm  40  is biased axially outwardly by a biasing member such as a spring  30  which expands the chamber  22 . The diaphragm  40  is moved axially inwardly by withdrawing a media from the defined chamber  22  which contracts the chamber. 
     Refer now to the exploded view of FIG. 2 of the actuator  10 . The housing  12  of the actuator  10  is preferably molded and is circular in configuration resembling a ring like structure. The housing  12  has its center opening  14  defined by an inner wall  18  extending from a base portion  20 . An outer circular wall  16  also extended from the base portion  20  in combination with the inner wall  18  and the base portion  20  define the fixed wall portion of the interior vacuum or gas chamber (cavity)  22 . 
     The inner surface  28  of the wall  16  typically has a slight taper resulting from the molding operation. A port  24  communicates with the chamber  22  and is provided to input or exhaust air from the defined chamber  22 . As shown in the figure, the outer wall  16  extends from the base portion  20  a greater distance than the inner wall  18 . Projecting tabs  29  are provided to facilitate mounting the housing  12  to a member of a vehicle chassis. 
     A spring  30  is sized to fit within the chamber  22  between the walls  18  and  16  with one end of the spring  30  being in abutment with the base portion  20  of the housing  12 . A piston  34  that is ring like in structure abuts the spring  30  when the components of the actuator  10  are assembled. The piston  34  has multiple bores  36  that are spaced and configured to receive posts or pins  70  of a shifting fork  68  as will be later explained. 
     The elastomeric pliable diaphragm  40  previously mentioned is configured to fit the housing  12  of the actuator  10 . A rim  42  of the diaphragm  40  is sized to fit within the bore  14  (fitted against wall  18 ) of the housing  12 . The rim  42  is reinforced by a metallic ring  44  that is molded integral with the rim  42 . Upon installation, the rim  42  is press fit into the bore  14  which provides a seal (between the wall  18  and the diaphragm  40 ) to seal the chamber  22  of the housing  12 . The end  45  of the ring  44  may be swaged over (see FIG. 3) to assure retention of the rim  42  in the bore  14 . The outer diameter  50  of the diaphragm  40  has a projecting bead  52  formed around its periphery. A ring  54  molded integral with the diaphragm  40  (FIG. 3) supports the bead  52  and acts as a compression member to compress the bead  52  against the inner surface  28  of the housing  12  upon installation. When the diaphragm  40  is installed on the housing  12 , the bead  52  will be in compressive contact with the inner surface  28  of the wall  16  which provides a seal (between the wall  16  and the bead  52  of the diaphragm  40 ) to seal the chamber  22  of the housing  12 . A base portion  56  of the diaphragm  40  has multiple bores  58  that mate with the bores  36  of the piston  34 . 
     A circular shifting fork  68  is mountable to the diaphragm  40  and the piston  34 . The fork  68  has posts  70  extending from a base portion  69  that will extend through the bores  58  of the diaphragm  40  and fit in the matching bores  36  of the piston  34 . The diaphragm  40  is thus sandwiched between the piston  34  and the shifting fork  68 . The pins  70  of the fork  68  are fixedly mounted in the bores  36  of the piston  34  in a conventional manner such as by welding. The fork  68  has a projecting L-shaped arcuate section  74  extending from the base portion  69  that is configured to reside in a groove  82  of a clutch ring  80 . 
     A circular clutch ring  80  has a peripheral groove  82  that will receive the formed section  74  of the shifting fork  68 . The groove  82  and the formed section  74  provide a bearing section such that the clutch ring  80  may rotate relative to the shifting fork  68 . The clutch ring  80  has internal splines  84  that are matable with splines of a drive and driven member of a vehicle. 
     Refer now to FIGS. 3 and 4 of the drawings which illustrate the annular actuator applied to a wheel hub. The housing  12  of the actuator is fixedly mounted to a knuckle  100  of the vehicle. An air line  102  is coupled to the port  24  of the housing  12  with the air line  102  being connected to an air source such as an intake manifold. The actuator is assembled as previously described with the clutch ring  80  being rotatable relative to the fork  68 . As shown, the L-shaped section  74  of the fork  68  fits in the groove  82  of the clutch ring  80 . The internal splines  84  of the clutch ring  80  are permanently engaged with splines  106  on axle  108 . A coupler  112  having internal splines  113  is mounted on the wheel hub spindle  116  with the internal splines  113  of the coupler  112  being mated with the splines  114  of the wheel hub spindle  116 . The coupler  112  has external splines  118  that are alignable with the splines  106  of the axle  108 . The coupler  112  being in splined engagement with the hub spindle  116  rotates with the hub spindle  116 . 
     The spring  30  of the actuator being captive between the base  20  and the piston  34  urges the assembly of the piston  34 , diaphragm  40  and fork  68  to move axially away from the base  20  of the housing  12 . This will move the clutch ring  80  axially along the splines  106  of the axle  108  and will urge the clutch ring  80  into engagement with the splines  118  of the coupler  112 . This positions the clutch ring  80  in engagement with both the axle  108  and the coupler  112  (FIG. 3) and since the coupler  112  is in splined engagement with the hub spindle  116 , the hub spindle  116  will be forced to rotate with the axle  108 . 
     When air is withdrawn from the housing  12  via port  24 , negative air pressure generated within the chamber  22  of the housing  12  will force the assembly of the piston  34 , the diaphragm  40  and the fork  68  toward the base  20  of the housing  12 . Negative air pressure is sufficient to compress the spring  30  and thus the clutch ring  80  will be moved out of engagement with the coupler  112  to be only engaged with the axle  108  as shown in FIG.  4 . 
     A benefit of the assembly as described above and which will be observed from FIG. 4 is that the diaphragm  40  provides a seal as between the axle  108  and knuckle  100  which protects the wheel end from contamination. 
     FIG. 5 illustrates a similar annular actuator  10 ′ as applied to a differential assembly  130 . The actuator  10 ′ is provided to disconnect at least one of the axles of the assembly  130  indicated as  132   a ,  132   b  in the drawing. Basically a drive shaft  134  is rotatably driven to provide motive power to the wheels of the vehicle coupled to the axles  132 . A pinion  140  mounted on the end of the drive shaft  134  is in mesh with a ring gear  142  that is mounted to a rotatable carrier  144 . Rotation of the drive shaft  134  will thus rotate the pinion  140  which will cause rotation of the ring gear  142  and the carrier  144 . Spider gears  146  are rotatably supported on the carrier  144  and are coupled to the axles  132  with one spider gear  146   a  being coupled to the left axle portion  132   b  and the other spider gear  146   b  being coupled to the right axle  132 . The spider gears  146   a  and  146   b  are in mesh with spider gears  148   a  and  148   b  that are rotatably supported on the carrier  144 . As is known, the differential assembly  130  allows one wheel (of the vehicle wheels connected to the axles) to overrun or run faster than the other wheel such as is required when going around a corner. 
     The actuator  10 ′ is applied to at least one axle ( 32   a ,  32   b ) to provide for coupling that axle to the drive train of the vehicle or uncouple the axle from the drive train of the vehicle. When uncoupled, both axles are free to turn independent of drive shaft  134  to avoid driving the drive shaft  134  when the drive shaft is uncoupled at the transfer case. 
     As shown in FIG. 5, one axle is split to provide an axle portion  132   a  and an axle portion  132   b . A spider gear  146   a  is mounted on the end of the axle portion  132   b  and is rotatably supported in the carrier  144 . The axle portion  132   a  is aligned with the axle portion  132   b  and is supported on bearings  150  interposed between the axle portions  132   a  and  132   b . Splines  152  are formed on the axle portion  132   a  and splines  154  are formed on the end of the axle portion  132   b.    
     The actuator  10 ′ is fixedly mounted to the housing of the differential assembly  130  such that a clutch ring  80  surrounds the axle portions  132   a  and  132   b . The clutch ring  80  is normally biased by the spring  30  of the actuator  10 ′ to be in engagement with both the axle portions  132   a  and  132   b . The internal splines  84  of the clutch ring  80  will be in engagement with the splines  152  of the axle portion  132   a  and the splines  154  of the axle portion  132   b . When air is withdrawn from the housing of the actuator  10 ′, the spring  30  will be compressed by the action of the diaphragm  40  and the piston  34  to thus move the clutch ring  80  out of engagement with the splines  154  on the axle portion  132   b . This will disconnect the axle portion  132   a  from the axle portion  132   b.    
     Disconnecting the axle portion  132   b  from the axle portion  132   a  in effect disconnects the wheel coupled to the axle portion  132   a  from the drive line of the vehicle. When the drive shaft  134  is uncoupled from the power line of the vehicle such as by shifting the transfer case into a neutral position and the vehicle is propelled along the roadway, the wheel coupled to the right axle  132  will simply rotate its spider gear  46   b  which is in mesh with the spider gears  148   a  and  148   b  and the only rotation of elements will be the right axle  132 , the spider gears  146 , the spider gears  148  and the axle portion  132   b . The large mass of the carrier  144  will resist rotation and thus rotation will not be imparted to the drive shaft  134 . It will be understood that this condition is permitted because axle portion  132   b  is allowed to rotate in a direction opposite to that of axle portion  132   a.    
     FIG. 6 illustrates a four-wheel drive transfer case  170 . The transfer case  170  is of the type that is shiftable to provide two-wheel drive or four-wheel drive for a vehicle. The transfer case also has gearing to provide a high and low range output to the front and rear wheels of the vehicle. 
     The transfer case has an input shaft  172  that is rotatably driven by the vehicle engine to provide the motive power for the vehicle wheels. The input shaft  172  may be coupled directly to an output shaft  174  or may be coupled to the output shaft  174  through a gear train which will provide the low range of the transfer case. The shaft  174  provides a rotative power for one set of wheels of the vehicle and in this example the shaft  174  provides rotative power to the rear wheels of the vehicle. The shaft  174  is further connectable and un connectable from an auxiliary shaft  176 . The shaft  176  provides a motive power for the front wheels of the vehicle. The transfer case  170  thus is arranged to provide motive power to the rear wheels only of the vehicle or to provide motive power to the front and rear wheels of the vehicle. Additionally the transfer case  170  is shiftable between a high range and low range for both front and rear wheels. 
     An actuator  10   a  provides the shift mechanism for shifting the transfer case between the high range and low range and additionally, another actuator  10   b  is provided to shift the transfer case between two-wheel drive and four-wheel drive. 
     Actuator  10   a  is fixedly mounted to the housing  171  of the transfer case  170 . A clutch ring  80   a  is permanently and slidably mounted on splines  180  of output shaft  174  and is slidably movable between engagement with either the splines  184  of gear  182  or splines  188  of gear  186 . (It is shown in the intermediate position for convenience of illustration only.) Gear  182  is fixedly mounted to and directly driven by the input shaft  172 . Gear  186  is rotatably mounted on the output shaft  174  and is indirectly and permanently driven by gear  182  as will be explained. The spring  30  of the actuator  10   a  normally biases the clutch ring  80   a  into engagement with the splines  188  on the gear  186 . When air is withdrawn from the chamber of the actuator  10   a , the diaphragm and piston in combination will compress the spring  30  and the clutch ring  80   a  will be moved out of engagement with splines  188  and into engagement with the splines  184  on the gear  182 . This latter position of the clutch ring  80   a  couples the input shaft  172  directly to the output shaft  174  causing input shaft  172  and the output shaft  174  to rotate in unison. 
     The indirect permanent driving connection between gear  186  and gear  182  is now explained. An auxiliary shaft  196  has a gear  198  fixedly mounted thereon and in mesh with the gear  182  mounted to the input shaft  172 . Another gear  200  which is integral with and thus fixedly mounted on the axillary shaft  196  is in mesh with the gear  186  rotatably mounted on the output shaft  174 . The gear  182  in mesh with the gear  198  rotates the shaft  196  and thus the gear  200 . This produces indirect (gear reduction) rotation of the gear  186  whenever input shaft  172  is rotated. Thus, when the clutch ring  80   a  has been moved into engagement with the splines  184  of the gear  182 , the gear  186  drives the output shaft  174  but at a reduced rate as compared to the direct drive as previously described. 
     When the actuator  10   a  is in static state, that is the pressure within the chamber of the actuator  10   a  is at ambient pressure, the spring  30  will force the clutch ring  80   a  to move along the splines  180  on the output shaft  174  and into engagement with the splines  188  on the gear  186 . This will couple the gear  186  with the shaft  174 . The clutch ring  80   a  will, however, be out of engagement with the splines  184  on the gear  182 . The input shaft  172  will rotate at a different rate than the output shaft  174  due to the gear ratio of the gear  182  in mesh with the gear  198  and in turn the gear  200  in mesh with the gear  186 . This provides for the low range setting. That is, the output shaft  174  will rotate at a lesser rate than the input shaft  172 . 
     Another actuator  10   b  is fixedly mounted to the housing of the transfer case and strategic to the output shaft  174 . A gear  199  is rotatively mounted on the output shaft  174  and drive chain  202  is coupled to gear  199 . The drive chain  202  is also coupled to a gear  204  on output shaft  176  which is coupled to the front drive train of the vehicle. Actuator  10   b  includes a clutch ring  80   b  that is slidably movable on splines  206  of a gear  208 . Gear  208  is fixedly mounted to output shaft  174 . When air is withdrawn from the chamber of actuator  10   b , the spring  30  will be compressed and the clutch ring  80   b  will only be engaged with splines  206  of gear  208 . This isolates the drive mechanism from shaft  176  and the vehicle is in two wheel drive mode. 
     When the negative air pressure of the chamber of the actuator  10   b  is released the spring  30  will urge the clutch ring  80   b  to slide on the splines  206  to become engaged with the splines  201  of gear  199 . This couples the output shaft  174  to the front wheel drive shaft  176 . This provides for four-wheel drive mode. 
     Those skilled in the art will recognize that modifications and variations may be made without departing from the true spirit and scope of the invention. The invention is therefore not to be limited to the embodiments described and illustrated but is to be determined from the appended claims.