Abstract:
A locking assembly for a differential of a motor vehicle, wherein corresponding drive axle shafts of the motor vehicle may be selectively positioned between a locked and an unlocked position by activation of a positioning assembly which is preferably, but not exclusively, a manual shifter mechanism. In the locked position, the differential locking assembly serves to interlock the corresponding axle shafts, such that the drive wheels associated therewith rotate in a synchronous manner, rather than relative to one another at different speeds. A locking gear assembly comprises a first locking gear, formed on one side gear of the differential and a second locking gear, formed on a locking member, wherein manipulation of the positioning assembly selectively positions the first and second locking gears into and out of intermeshing engagement with one another. A durable, high strength mounting assembly movably supports the locking member on a housing of the differential, such that the locking member rotates therewith and moves relative thereto when selectively disposed between the locked position and the unlocked position.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention is directed to a differential locking assembly, which may be manually actuated and which is specifically, but not exclusively, adaptable for use on a four wheel drive, off-road vehicle. 
     2. Description of the Related Art 
     A differential assembly, of the type found on motor vehicles, comprises a gear system which is generally structured to transfer power from a drive or propeller shaft to the output or drive axle shafts of the vehicle. The differential assembly typically incorporates a ring gear which is secured to a housing or carrier of the differential and rotatable therewith. Also the ring gear is disposed in intermeshing, driven engagement with the propeller or drive shaft. Torque or rotational force is transferred to the axle shafts and their and associated drive wheels. More particularly, the rotational or driving force is transferred from the drive shaft to the differential housing and eventually to the drive axles, which are splined to respectively disposed and rotationally interconnected side gears. The side gears are mounted within the differential housing and are rotationally interconnected by means of a spider gear assembly. The spider gear assembly typically comprises two spaced apart pinion gears, which are interconnected by a cross pin or like structure and which serve to rotationally interconnect each of the two side gears. 
     In operation, as the drive or propeller shaft rotates, it serves to rotate the ring gear which in turn rotates the differential housing to which the ring gear is securely attached. The two pinion gears, which define the spider gear assembly, rotationally interact with the two side gears, so as to rotate the output axle shafts and the drive wheels mounted on the outer ends thereof. When the motor vehicle is moving in a straight line direction, the ring gear and differential housing rotate together. In this straight line movement, the pinion gears of the spider gear assembly apply equal force to each of the side gears and their attached output axle shafts, as well as the respective wheels secured thereto. However, when the vehicle travels in a turning direction, the resistance against the rotation of one of the output axle shafts increases as the inner and outer wheels turn at different speeds. This difference in speed encourages the differential pinion gears of the spider gear assembly to rotate and turn the side gear on the axle encountering the increased resistance. 
     As generally described above, the structure and operation of a somewhat conventional differential serves an important purpose in the operation of a motor vehicle, especially when operating in a conventional, “on-road” environment. As set forth above, the use of the differential serves to transmit the driving torque from the drive shaft through the differential and apply such torque to either wheel substantially equally even though one wheel is rotating at a faster rate than the other, when the vehicle is involved in a turning maneuver. However, it is well recognized that in a number of situations it is highly desirable to lock the drive wheels of a vehicle so that they rotate synchronously. By locking the drive wheels of the vehicle to rotate at a synchronous speed, variations in traction of the drive wheels of the vehicle will not affect the rate of relative rotation between the drive wheels which are associated with the same axle. Therefore, the drive wheels associated with a common axle will rotate in unison even though there is variable traction, which normally causes slippage of one or other of the drive wheels. 
     It is well known that off-road vehicles, when encountering rough terrain, frequently have one or other of the drive wheels inadvertently disposed above or otherwise out of contact with the ground or surface over which the vehicle is traveling. The absence of a differential locking assembly in such situations would result in the free or non-contact wheel rotating while the opposite wheel, disposed in engaging relation with the surface, is absent rotational torque. Accordingly, there is a well recognized need and important use of differential locking assemblies capable of selectively locking the axle shafts of corresponding drive wheels, such that the wheels rotate synchronously regardless of their relative orientation or the amount of resistance being encountered. 
     Numerous attempts have been made to establish an efficient, durable, high strength locking assembly which may be applied to a variety of vehicles. Such differential locking assemblies are available for both manual and “automatic” activation. In the latter category of automatic activation assemblies, sensing devices are incorporated within the differential so as to automatically activate an associated locking structure and thereby dispose the associated axle shafts into a synchronous, locked mode. While assumed to be functional for their intended purpose, such “automatic” activation assemblies are not particularly applicable or desirable for use in the four wheel drive, “off-road” vehicles, which are specifically designed and structured to travel over extremely rough terrain. In such an environment, the manual actuation of a differential lock is preferable and generally considered to be both more reliable and durable. 
     Accordingly, there is a significant need in the field of differential locking assemblies for a high strength, durable and consistently operative locking assembly which is particularly, but not exclusively, adaptable for use in off-road, four wheel drive vehicles. The design and structure of such an improved and preferred differential locking assembly should be such as to be readily adaptable for an “after market” application, such that off-road vehicles, of the type described above, can be easily adapted to include an improved differential locking assembly having all of the attributes which are necessary to endure the rigors of off-road operation. 
     SUMMARY OF THE INVENTION 
     The present invention is directed towards a locking assembly for the differential of a motor vehicle and is particularly, but not exclusively, adaptable for use on “off-road”, vehicles of the type which are structured or modified to travel over extremely rough terrain. As a result of the vehicle operating in such a harsh environment, it is not uncommon for one of the drive wheels of an associated axle to be lifted or positioned out of contact with the ground or other surface over which the vehicle is traveling. In such instances, the operation of a conventional differential will deliver rotational torque or driving force to the wheel which is not in contact with the surface. For obvious reasons, such a situation is highly undesirable and will significantly affect the efficient and desired operation of the vehicle. 
     Accordingly, the present invention is directed towards a locking assembly which is preferably, but not exclusively, manually actuated so as to selectively dispose the locking assembly into a either a locked position or an unlocked position, at the will of the operator. When in the locked position, both drive wheels associated with a common axle will be locked so as to rotate in synchronous relation to one another, thereby overcoming the conventional operation of the differential. 
     More specifically, the differential locking assembly of the present invention is structured to function with cooperative components of a differential, such as, but not limited to the type produced and made commercially available by the Dana Corporation of Toledo, Ohio. As such, a differential housing or carrier has a ring-gear fixedly secured thereto so as to rotate therewith. Also in substantially conventional fashion, the ring gear is rotationally driven by its interconnection with the drive shaft of the vehicle. Such interconnection also serves to rotate the differential housing. Two side gears are mounted within the differential housing and normally rotate relative thereto. The side gears are secured in driving relation to co-extensive axle shafts of an axle assembly, wherein the outer end of each axle shaft is secured to a separate drive wheel. The inner end of each axle shaft is secured, by a splined engagement, with respective ones of the aforementioned side gears. A spider gear assembly, comprising spaced apart pinion gears and an interconnecting cross pin, serves to rotationally interconnect the side gears and is cooperatively structured therewith to define the operational workings of the differential. 
     Structural features of the differential locking assembly of the present invention include a locking member mounted on the differential housing so as to rotate therewith and move relative thereto, into and out of the aforementioned locked end unlocked positions. In addition, the locking assembly of the present invention includes a locking gear assembly which is disposed and structured to establish a locking interconnection of both of the axle shafts of an associated drive axle. As a result, both drive wheels of the associated drive axle are locked into synchronous rotation with one another regardless of their respective orientations relative to the ground or other surface over which the vehicle is traveling. 
     The aforementioned locking gear assembly is structured to be durable, strong, reliable and perform consistently, particularly in the harsh environment in which off-road vehicles are intended to operate. In order to provide such reliable and durable performance, the locking gear assembly includes a first locking gear integrally formed on an outer face of one of the side gears. The locking gear assembly also includes a second locking gear integrally formed on a corresponding or confronting surface or face of the locking member. As set forth above, the locking member is selectively positionable or slidable on the differential housing as it rotates therewith. Therefore, the first and second locking gears may be selectively disposed into intermeshing engagement with one another, as the differential housing rotates, to define the aforementioned locked position or selectively disposed out of engagement with one another to define the aforementioned unlocked position. Additional structural features, as set forth in greater detail hereinafter, are attributable to the first and second locking gears in order to assure their durability and consistently reliable performance under the aforementioned harsh operating conditions. 
     Other structural features incorporated within the differential locking assembly of the present invention include to a mounting assembly which movably supports the locking member on the differential housing so that it selectively moves relative thereto, between the aforementioned locked position and unlocked position. The mounting assembly comprises a plurality of transversely elongated cams of predetermined number, collectively arranged in a predetermined configuration so as to engage an equal number of correspondingly dimensioned and configured apertures formed in the locking member. Movable support of the locking member on the differential housing is thereby accomplished and failure and breakage due to stress placed on the locking member, such as when it is selectively disposed in the locked position, is significantly reduced or eliminated. The noticeable reduction in stress failures of the subject locking assembly is due, at least in part, to the equal distribution of forces which the mounting assembly may accommodate due its structure, disposition and cooperative engagement with both the differential housing and the locking member. 
     Another structural feature of the present invention is the inclusion of a positioning assembly which may be selectively activated to assume either the locked position or the unlocked position. It is well known in the structural design and operation of other locking assemblies to provide for either the manually or “automatic” activation thereof. Under certain pre-established operating conditions, conventional differential lockers will be automatically activated to lock the drive wheels of a vehicle into synchronous rotation with one another. Typically, such automatic activation assemblies include hydraulic, pneumatic and/or electric modes of operation. While such automatic activation assemblies are generally considered to be operative for their intended function, they frequently are not designed to effectively operate with off-road, four wheel drive vehicles. Therefore, the differential locking assembly of the present invention is specifically, but not exclusively, adaptable for manual activation. Therefore, the positioning assembly of the present invention preferably comprises a manual shifter mechanism, connected by a drive cable, of the type well known and used extensively in modern day motor vehicles, to a fork-type shifter. The fork shifter selectively engages the locking member and moves it in a direction which is coaxial to the axis of rotation of the differential housing and the corresponding side gear. Operative interconnection of the manual shifter, located within the passenger compartment of the vehicle, and the locking member by the aforementioned drive cable, serves as a reliable and efficient structure for selectively positioning the locking member. The locking member need only be moved a relatively small distance relative to the one side gear on which the first locking gear is formed, in order to position the locking member into the aforementioned locked position. In addition, a plurality of biasing springs are disposed between the differential housing and the locking member so as to normally bias the locking member and the first and second locking gears, as set forth above, out of engagement with one another or into the unlocked position. Certain mechanical linkages associated with the manual shifter readily overcome this biasing force allowing the locking member to be easily disposed into the locked position, as described. 
     Therefore, the differential locking assembly of the present invention is preferably, but not exclusively, manually actuated for disposition in either a locked position or an unlocked position and includes specific structural components that assure durability, reliability and consistent operational characteristics, especially when the vehicle is operating under the extremely harsh environment of off-road conditions. 
     These and other objects, features and advantages of the present invention will become more clear when the drawings as well as the detailed description are taken into consideration. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a fuller understanding of the nature of the present invention, reference should be had to the following detailed description taken in connection with the accompanying drawings in which: 
     FIG. 1 is a front view in partial phantom of an assembled differential of a motor vehicle including the locking assembly of the present invention. 
     FIG. 2 is a exploded view in partial phantom of the various components comprising the differential and associated locking assembly of the present invention. 
     FIG. 3 is an exploded perspective view of the various components of the differential locking assembly of the present invention in partially assembled form. 
     FIG. 4A is a front view of a locking member associated with the locking assembly of the present invention. 
     FIG. 4B is a side view of the embodiment of FIG.  4 A. 
     FIG. 4C is a rear view of the embodiment of FIGS. 4A and 4B. 
     FIG. 5A is a front view of one side gear associated with the locking assembly of the present invention. 
     FIG. 5B is a side view of the embodiment of FIG.  5 A. 
     FIG. 5C is a rear view of the embodiment of FIGS. 5A and 5B with a normally operative gear section deleted for purposes of clarity. 
     FIG. 6A is a partially schematic side view in cutaway showing features of the locking assembly of the present invention disposed in an unlocked position. 
     FIG. 6B is a partially schematic side view in cutaway similar to that of FIG. 6A with a locking assembly of the present invention disposed in a locked position. 
     FIG. 6C is a schematic representation in partial cutaway showing the relative positions of a first and second locking gear when the locking assembly of the present is in an unlocked position. 
     FIG. 6D is a schematic representation similar to the embodiment of FIG. 6C with the locking assembly of the present invention in a locked position. 
    
    
     Like reference numerals refer to like parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As shown in the accompanying drawings, the present invention is directed towards a differential locking assembly, generally indicated as  10 , and structured for use on a motor vehicle. The locking assembly  10  is particularly, but not exclusively, adapted for use on a four wheel drive, off-road vehicle due at least partially to its durability, reliability and consistent operating characteristics especially when performing in the harsh environment typically encountered by off-road vehicles. 
     More specifically, and as best shown in FIG. 2, a differential with which the locking assembly  10  is utilized includes two side gears  12  and  14 . The side gears  12  and  14  are mounted within a differential carrier or housing  16  which is to be considered a part of the locking assembly of the present invention. The side gears  12  and  14  are rotationally interconnected by a somewhat conventional spider gear assembly. The spider gear assembly is more specifically defined by two spaced apart pinion gears  18  and  20  interconnected by an elongated cross pin  22 , wherein all of such components are movably mounted within the differential housing  16 . An end cap or cover member  24  is secured in overlying at least partially covering relation to one end of the differential housing  16  and is attached to the outwardly extending peripheral flange  26  by means of a plurality of bolts or like connectors (not shown for purposes of clarity) passing through the mounting apertures  28 . Similarly, an oppositely disposed end cap or cover member  30  is attached by connectors  32  in overlying covering relation to an opposite end of the differential housing  16 , as will be explained in greater detail hereinafter. 
     The respective cover members  24  and  30 , as well as the two side gears  12  and  14  include centrally disposed openings sufficiently dimensioned and configured to allow the passage of at least a portion of respective axle shafts  32  and  34  there through. The axle shafts are operatively connected to the differential, as well as the locking assembly  10  associated therewith, as best shown in FIG.  1 . Naturally, the opposite or outer ends of each of the axle shafts  32  and  34  have corresponding drive wheels (not shown) mounted thereon. The inner ends of each of the axle shafts  32  and  34 , as represented in phantom lines in FIG. 1, are attached in driving interconnection with the respective side gears  12  and  14 , through a splined engagement  36 , of the type shown in FIG.  3 . 
     In addition to the above, the differential includes a somewhat, conventional ring gear  34  with which the differential locking assembly of the present invention is operatively associated. The ring gear  34  is fixedly mounted on the differential housing  16  so as to be exteriorly accessible for interconnection to a drive pinion  37  associated with the drive shaft  38 . Accordingly, as also shown in FIG. 1, the various components of the differential locking assembly  10 , as well as certain operative components of the differential with which the locking assembly  10  is operatively associated, are housed within a casing  40 . The casing  40  may be of conventional design or may be structurally modified to incorporate the various components of the differential locking assembly  10 , including a drive cable  84 , to be described in greater detail hereinafter. 
     Due to the fixed mounting or attachment of the ring gear  34  to the differential housing  16 , driving rotation of the ring gear  34  will cause rotation of the differential housing  16 . Rotation of the differential housing  16  will thereby cause relative rotation of the spider assembly, defined by the pinion gears  18  and  20 , within the interior of the differential housing  16 . The two side gears  12  and  14  which are drivingly attached to the axle shafts  32  and  34  respectively, are thereby forced into rotation upon the rotation of the differential housing  16 . 
     Other structural components of the locking assembly  10  of the present invention include a locking member generally indicated as  42  in FIG.  2  and shown in detail in FIGS. 4A,  4 B and  4 C. The locking member  42  may be more specifically defined by a locking gear plate including a central opening or aperture  44  of sufficient dimension to allow passage therethrough of axle shaft  34  into a splined connection with the one side gear  14 , as at  36 . In addition, the central opening or aperture  44  is further dimensioned and configured to accommodate the inwardly disposed placement of the hub  46  of the cover member  30 , such that an outer hub portion  48  of the one side gear  14  is received therein. 
     Another structural feature of the present invention is the inclusion of a mounting assembly which serves to connect and support the locking member  42  to the differential housing  16 . The mounting assembly is structured to facilitate rotation of the locking member  42  with the differential housing  16 , while at the same time allowing selective positioning or movement of the locking member  42  on and relative to the differential housing  16 . Relative movement there between occurs as the locking member  42  is selectively disposed between a locked position and an unlocked position. In one embodiment of the present invention the mounting assembly comprises a plurality of cams  50  integrally or otherwise fixedly formed on the differential housing,  16  as best shown in FIGS. 2 and 3. The cams  50  are disposed in equally spaced apart relation to one another so as to collectively form a substantially annular configuration. Further, each of the cams  50  has a substantially elongated transverse configuration relative to the central axis of rotation of the differential housing  16  and side gears  12  and  14 . The cams  50  are preferably four in number and are positioned and configured, as set forth above, in order to best distribute and accommodate the stress and force placed on the differential housing  16  and locking member  42  as the locking assembly is selectively disposed into and out of the locked position. In order to accommodate such selective disposition of the locking member  42 , the mounting assembly further comprises a plurality of receiving apertures  52  integrally formed in and correspondingly disposed, dimensioned and configured relative to the array of cams  50 . More specifically, each of the receiving apertures  52  are dimensioned to movably receive one of the cams  50  therein, such that the locking member  42  may be axially displaced towards and away from the housing  16  as it is supported on the cams  50 . 
     Selective displacement or positioning of the locking member  42  is accomplished by a positioning assembly including a fork-type shifter generally indicated as  60 , to be described in greater detail hereinafter. With further regard to FIG. 3, the cover member  30  is secured in covering or overlying relation to an outer face  43  of the locking member  42  by virtue of a plurality of bolts or like connectors  32  passing through connecting apertures  33  formed in the body of the cover member  30  as shown. In order to further increase the durability and reliable operational characteristics of the locking assembly  10 , the connectors  32  pass through the connecting apertures  33  into threaded engagement or like attachment to the cams  50  by open ended slots or channels  54 . Accordingly, it should be apparent that the thickness or width of the locking member  42  and accordingly the receiving aperture  52  is less than the outwardly extending protrusion of each of the cams  50 . Therefore, the locking member  42  may slide or be otherwise movable on the plurality of cams  50  towards and away from the differential housing  16  through activation of the fork shifter  60 , as part of the positioning assembly, to be described in greater detailed hereinafter. 
     Other structural features associated with the mounting and selective movement of the locking member  42  is the provision of a plurality of biasing springs  56  which are interposed between the differential housing  16 , as shown in FIG. 3, and an exposed, inner face or surface of the locking member  42 . The positioning of the biasing springs  56 , in this manner serves to normally exert a biasing force on the locking member  42  which tends to position it in the unlocked position, as will also be described in greater detail. Moving engagement between the fork shifter  60  and the locking member  42  is accomplished through the provision of a continuously configured peripheral groove or channel  58  formed about the outer periphery of the locking member  42 . An inner engaging bracket or segment  62  of the fork shifter  60  is disposed and configured to engage the peripheral groove  58 . Lateral movement of the fork shifter, in accordance with a directional arrows  65  and  66  of FIG. 6A and 6B, cause selective positioning of the locking member  42  into the unlocked position (FIGS. 6A and 6C) or the locked (FIGS.  6 B and  6 D). 
     Yet another structural feature of the present invention is the provision of a locking gear assembly specifically structured to accomplish a secure locking engagement between the locking member  42  and the one side gear  14 , to define the aforementioned locked position of the differential locking assembly  10  of the present invention. More specifically, the side gear  14 , which also may be referred to as the locking side gear, includes a somewhat conventionally disposed and structured gear set  15  which is intended to rotationally engage the pinion gears  18  and  20 , defining the spider gear assembly as set forth above. This interior gear set  15  is equivalent to a correspondingly disposed gear set formed on the other side gear  12  (not shown for purposes of clarity). The first and second side gears  12  and  14  are thereby rotationally interconnected to one another by means of the pinion gears  18  and  20 . 
     However, the locking gear assembly of the present invention includes a first locking gear generally indicated as  70  integrally formed on an outer face or surface  72  of the one locking side gear  14 . The plurality of teeth  71  defining the first locking gear  70  are preferably provided in a predetermined number, such as fourteen, which is equal to the number of closed gear pockets  74  formed on and at least partially defining a blind gear assembly  76 . The blind gear assembly  76  defines a second locking gear of the aforementioned locking assembly. The term “blind gear assembly”, referring to the second locking gear  76  is meant to describe the structural configuration of the closed gear pockets  74  which do not communicate with or protrude through the outer face  43  of the locking member  42 . To the contrary the plurality of closed gear pockets  74  are alternately formed adjacent outwardly extending gear teeth  78 , and are accessible only from the inner face or surface  45  of the locking gear member  42 . The formation of an equal number of fourteen teeth  71  and  78  and an equal number of gear pockets  74  facilitates the movable intermeshing of the side gear  14  and the locking member  42 , while maintaining a sufficient strength of the respective components. The respective number of teeth may of course vary and still be within the intended spirit and scope of the present invention. Accordingly, as shown in FIG. 2 the first locking gear  70 , integrally formed on the side gear  14 , is disposed in somewhat confronting relation to the second locking gear  76 , integrally formed on the inner face  45  of the locking member  42 . When assembled and in the unlocked position of FIGS. 6A and 6C, the first and second locking gears  70  and  76  are disposed in spaced apart but confronting relation to one another. To the contrary when the first locking gear  70  and the second locking gear  76  are in the locked position of FIGS. 6B and 6D, they are disposed in confronting intermeshing engagement with one another. Locking engagement between the plurality of gear teeth  71  and the closed gear pockets  74  of the first and second locking gears  70  and  76  respectively, are facilitated by applicable dimensioning of the closed gear pockets  74  so as to receive the gear teeth  71  therein. Further, intermeshing engagement is facilitated by forming the outer exposed surfaces  73  and  75  respectively of each of the gear teeth  71  and  78  to include a multi-faceted or multi-sided configuration or other such configuration, such as a curved, beveled or rounded configuration, which will best facilitate sliding, intermeshing engagement with one another. 
     With primary reference to FIG. 6A through 6D, the differential locking assembly  10  of the present invention incorporates a positioning assembly generally indicated as  80  which includes the fork shifter  60  as described above and which serves to engage the locking member  42  by virtue of the peripheral groove or channel  58  formed therein. Moreover, the positioning assembly  80  includes a manually activated shifter mechanism  82  disposed within the passenger compartment of the motor vehicle. The manual shifter  82  is connected to the fork shifter  60  by any appropriate linkage, but preferably by means of the drive cable  84 , as referred to above. Selective movement of the shifter  82  in an appropriate direction as indicated by directional arrows  84  and  85  will respectively serve to position the differential locking assembly  10  of the present invention, into the unlocked position of FIGS. 6A and 6C or the locked position of FIG. 6B and 6D due to the corresponding positioning of the locking member  42  as represented by directional arrow  65  and  66 . 
     Therefore, it should be apparent that the selective positioning of the locking member  42  into the locked position of FIGS. 6B and 6D will serve to lock the one side gear  14  to the locking member  42 , and thereby force the one side gear to rotate with the differential housing  16 . The differential housing  16  is forced to rotate because of the driving engagement of the ring gear  44  with the drive shaft  38 . Therefore, a locked interconnection will occur between both side gears  12  and  14  due to their interconnection with the spider gear assembly, as set forth above. This in turn will force both drive wheels attached to the opposite ends of the axle shafts  32  and  34 , to be synchronized and rotate at the same speed. Such synchronized rotation will be established regardless of the resistance on either one or both of the drive wheels, associated with the drive axles  32  and  34 , and regardless of either one of the drive wheels are engaging the ground or other surface over which the vehicle is traveling. 
     Since many modifications, variations and changes in detail can be made to the described preferred embodiment of the invention, it is intended that all matters in the foregoing description and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense. Thus, the scope of the invention should be determined by the appended claims and their legal equivalents. 
     Now that the invention has been described,