Abstract:
An axle disconnect assembly for a vehicle having an input shaft and a coaxially arranged output shaft. A collar is splined to one of the shafts and is slidable to selectively engage the other shaft to establish a positive driving connection between the input and output shafts. A movable piston engages the collar to selectively position the collar. A valve is in communication with the vehicle&#39;s existing oil pump and is controlled to selectively supply pressurized oil to opposite sides of the piston to selectively displace the piston thereby selectively controlling the position of the collar and the connection between the shafts.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is directed to a hydraulically actuated axle disconnect and is more particularly directed to an axle disconnect utilizing a vehicle&#39;s existing oil pump to provide pressurized lubricating oil as an actuating fluid, and integral with the engine oil pan. 
     2. Description of the Related Art 
     It is known to provide a part time four wheel drive vehicle that includes an axle disconnect mechanism in a front axle assembly. Such axle disconnect mechanisms include a vacuum motor and a shift fork assembly. The vacuum motor communicates with a vacuum source that is controlled by a two position solenoid valve. The fork shift assembly under control of the vacuum motor controls the axial shifting of a clutch collar between positions corresponding to coupled and uncoupled operating modes. 
     This conventional system has the drawback of an externally mounted vacuum motor that requires considerable extra space particularly when vehicle suspension travel is taken into account. The use of an externally mounted vacuum motor also necessitates the use of a fork shift assembly which adds to the cost and complexity of the prior art arrangement exemplified by this system. 
     It is also known that a part time four wheel drive vehicle may include an axle disconnect in the front axle assembly, wherein the axle disconnect is operated by a power shift mechanism. The power shift mechanism includes sealed envelopes in the form of expandable and contractible compartments that shift the axle disconnect into and out of engagement in response to a remote control valve. The sealed envelopes are offset from the axle housing. The shiftable drive gear couples and uncouples inner and outer drive shafts. 
     This power shift mechanism requires two sealed envelopes and numerous other parts operatively connecting the sealed envelopes with the shiftable drive gear. Moreover, such prior art axle disconnect systems do not provide a modular arrangement necessary for easy of manufacture, assembly and repair. Consequently these prior art arrangements are also complex and expensive to produce particularly when the difficulty of assembly is taken into account. 
     The need therefore exists for an axle disconnect arrangement and design that is simple in design, compact in construction and economical to package and manufacture. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an axle disconnect that improves upon the related art. 
     The present invention is directed to an axle disconnect assembly for a vehicle having an input shaft and a coaxially arranged output shaft. A collar is splined to one of the shafts and is slidable to selectively engage the other shaft to establish a positive driving connection between the input and output shafts. A movable piston engages the collar to selectively position the collar. A valve is in communication with the vehicle&#39;s existing oil pump and is controlled to selectively supply pressurized oil to opposite sides of the piston to selectively displace the piston thereby selectively controlling the position of the collar and the connection between the shafts. 
     These and other features of the present invention will become more apparent with reference to the following drawings and description associated therewith. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic plan view of a part time four wheel drive vehicle; 
     FIGS. 2 a  &amp;  2   b  are sectional views of the axle disconnect in different positions according to the present invention. 
     FIG. 3 is a plan view of the present axle disconnect assembly integral with an engine oil pan. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings and more particularly to FIG. 1, there is shown a schematic plan view of a part time four wheel drive vehicle  10  comprising engine  12 , transmission  14  and transfer case  16  mounted on a vehicle chassis (not shown). The engine  12  and transmission  14  are conventional and well known components as is the transfer case  16  which typically includes an input shaft, a main output shaft and an auxiliary output shaft. The main output shaft is drive connected to the input shaft by a clutch or the like in the transfer case  16  and customarily offset from the transfer case. The clutch is actuated by a suitable selector mechanism controlled by the vehicle driver. The internal details of the transfer case  16  and details of a selector mechanism are not shown because these are conventional and well known components. 
     The main output shaft is drivingly connected to a rear drive shaft  18  which in turn is drivingly connected to a rear differential of a rear drive axle  20  that drives rear wheels  22  in a well known manner. 
     The auxiliary output shaft is drivingly connected to a front drive shaft  24  which in turn is drivingly connected to a front differential of a front drive axle  26  for selectively driving front wheels  28 . 
     This invention relates to an auxiliary drive axle, such as the front drive axle  26  and more particularly to a axle disconnect for such a drive axle that is generally indicated by reference numeral  30  in FIG.  1 . 
     To disconnect input drive axle  30  stemming from a differential from an output shaft that is in driving connection with the wheels  28 . 
     FIGS. 2 a  &amp;  2   b  are directed to the axle disconnect assembly of the present invention. An input shaft  50  emerges from a differential assembly or other conventional gear assembly as in known in the art. The input shaft  50  is rotatably connected within an axle housing  54 . Similarly, the output shaft  52  is rotatably disposed within the axle housing  54  adjacent the input shaft  50 . In the preferred embodiment, the input shaft  50  has an extension  51  rotatably disposed within a bore  52  of the output shaft  52  to provide a more stable structure. An annular collar  56  is non rotatably and translatably disposed about the input shaft  50 . Preferably the collar  56  has internal splines engaging external splines formed on the end of the input shaft  50 . The collar  56  is able to translate between a first position which only engages the input shaft  50  and a second position to engage both the input shaft  50  and the output shaft  52 . The output shaft  52  also has external splines for engagement with the internal splines of the collar  56 . When in this second position, the collar  56  serves to provide a positive driving connection between the input  50  and output  52  shafts. 
     A hydraulically actuated piston  58  is provided to actuate the collar  56  between the first disconnect position and the second connected position. The piston  58  is slidably shiftable within a hydraulic chamber. The hydraulic chamber is defined by a sleeve  66  mounted about the axle housing  54 . Pressurized fluid is provided to first and second opposite ends  60 / 62  of the chamber to act upon respective first and second ends of the piston  58  to force the piston to move between the first and second positions. When pressurized fluid is supplied to the first end  60  of the chamber, the piston  58  is forced to the right as shown in FIG. 2 b . Consequently, the collar  56  is simultaneously forced to the right to engage both the input  50  and output  52  shafts to form the positive connection there between. When pressurized fluid is supplied to the second opposite end  62  of the chamber, the piston  58  and collar  56  is forced to the left thereby disconnecting the collar  56  from the output shaft  52  and allowing relative rotation of the output shaft  52  with respect to the input shaft  54 . Such disconnect removes the powerline drive to the output shaft  52  and consequently to a wheel body attached to the output shaft  52 . Thus it can be seen that actuation/shifting of the piston  58  within the chamber provides the ability to selectively establish a connection between the input  50  and outputs  52  shafts as well as a disconnect there between. 
     As can be further seen in FIGS. 2 a  &amp;  2   b , the sleeve  66  is mounted about the external surface of the axle housing  54  to define the hydraulic chamber there between. As previously mentioned, the piston  58  is disposed within the chamber, between the sleeve  66  and axle housing  54  and is translatable between the first connect position (as shown in FIG. 2 a ) and the second disconnect position (as shown in FIG. 2 b ). In order to provide a seal between the first end of the chamber  60  and the second end of the chamber  62 , a pair of seals are disposed one each in an annular recess formed in the piston  58  adjacent each end thereof. These seals provide a seal between the sleeve  66  and the piston  58 . Similarly, a pair of annular seals are disposed one each in a pair of annular recessed formed in the outer surface of the axle housing  54  to form a seal between the piston  58  and the axle housing  54 . Such an arrangement separates the first end of the chamber  60  from the second end  62  such that when pressurized fluid is supplied to the first end  60  of the chamber, the piston  58  is forced to the second end  62  and the input  50  and output  52  shafts are connected. When pressurized fluid is supplied to the second end of the chamber  62 , the piston  58  is forced to the first end of the chamber  60  to disconnect the input  50  and output  52  shafts. 
     Rather than provide a separate and additional hydraulic circuit and pump, the present invention contemplates the use of a vehicle&#39;s existing lubricating oil pump  84  to provide pressurized fluid to actuate the pistons. Pressurized fluid from the vehicle&#39;s oil pump  84  is simply fed to a valve body  80  via passage  84   a  for selective delivery to each of the first, and second ends of the chamber. A controller  82  is provided to control the valve body  80  in accordance with a desired connect/disconnect mode for the input  50  and output  52  shafts. The valve body  80  may be any type of controllable valve device capable selectively delivering pressurized fluid to one of two separate flow paths. The controller  82  simply controls the valve  80  to deliver pressurized fluid to either of these flowpaths. 
     The controller  82  may interact or be incorporated into the vehicle&#39;s electronic control unit or may be separate to interact with a manual switch. When four wheel drive is desired, the controller  82  acts in a connect mode and controls the valve  80  to deliver pressurized fluid from the oil pump  84  to the first end of the chamber  60  via flowpath  70 . The valve body  80  simultaneously connects the second end of the chamber  62  via flow path  72  to an exhaust circuit  74  leading to an oil sump  76  or other reservoir for the lubricating oil. Consequently, the piston  58  together with the collar  56  is forced to the right to interconnect the input  50  and output  52  shafts. Similarly, when two wheel drive is desired, the controller  82  shifts the valve body  80  to direct pressurized fluid to the second end of the chamber  62  via flowpath  72  and simultaneously establish communication of the first end of the chamber  60  with the exhaust circuit  74  leading to the sump or reservoir. Consequently, the piston  58  and collar  56  are forced to disconnect the input  50  and output  52  shafts and remove positive drive to the output shaft  52  and connected wheel body. 
     Of course, it is noted that FIGS. 2 a  &amp;  2   b  only depicts the disconnect assembly leading to one output shaft  52  leading to one of the wheels  28  as is in the preferred embodiment. However, two disconnects assemblies could be employed to disconnect each wheel  28  from the driveline. In such an arrangement a second disconnect assembly is arranged on an opposite side of the differential  26  to simultaneously disconnect or connect each or the output shafts leading to the wheels  28 . However, a single controller would be employed to control each disconnect assembly. 
     FIG. 3 depicts the disconnect assembly of the present invention in its preferred arrangement. FIG. 3 depicts an engine&#39;s oil pan  90  with the axle disconnect and axle assembly  92  directly attached thereto. The differential axle assembly  92  is secured to one side of the oil pan  90 . A first shaft emerges from the differential  90 , (previously referred to as the disconnect input shaft  520  and passes through the oil pan to an opposite side and engages the disconnect assembly of the present invention. The outer sleeve  66  of the disconnect assembly is shown on the opposite side of the oil pan from the differential/axle assembly  92 . The valve body  80  and flowpaths  70 / 72  are also depicted. In this arrangement, the oil passage  84 a leads directly from the oil pump and the exhaust circuit  74  leads directly to the oil filter  94 . This arrangement provides only a single disconnect that selectively disconnects output shaft  52  from the differential assembly  92 . The opposite axle shaft  52   a  remains connected to the differential/axle assembly  92 . 
     While the foregoing invention has been shown and described with reference to a preferred embodiment, it will be understood by those possessing skill in the art that various changes and modifications may be made without departing from the spirit and scope of the invention 
     For example, while the aforementioned embodiment has been described for a wheel end disconnect, the disconnect assembly may be employed to disconnect separate portions of a drive shaft.