Abstract:
A locking differential includes a pair of annular coaxially-arranged axially-spaced clutch members having adjacent faces that contain cam groove that receive a driving cross pin, cooperating locking lugs and grooves being provided on the adjacent faces of the clutch members for preventing relative rotation therebetween. The cross pin extends diametrically across a supporting sleeve that is non-rotatably mounted concentrically within the central chamber of the cylindrical housing of the differential, thereby permitting the differential to be retrofit into various differential casings.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This application is related to the pending patent application Ser. No. 09/422,945 filed Oct. 22, 1999, in the name of Tittjung, which is assigned to the same assignee as the present invention. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention relates to a locking differential that includes a pair of coaxially-arranged axially-spaced clutch members that are connected against rotation by cooperating locking lug and slot means contained on the adjacent faces of the clutch members. In a preferred embodiment, the adjacent faces of the clutch members also contain diametrically extending cam grooves that receive a driving cross pin the ends of which are supported by a tubular sleeve that is non-rotatably mounted concentrically within the cylindrical housing of the differential.  
           [0004]    2. Brief Description of the Prior Art  
           [0005]    Locking differentials for automotive vehicles are well known in the patented prior art, as evidenced by the patents to Lewis U.S. Pat. No. 2,555,044, Zentmyer U.S. Pat. No. 5,413,015, and Valente U.S. Pat. Nos. 5,590,572 and 5,727,430, and Dissett U.S. Pat. No. 5,715,733.  
           [0006]    In these known differentials, it is common to utilize a pair of annular coaxially-arranged axially-spaced clutch members arranged on opposite sides of a diametrically extending driving cross pin that extends within mating cam grooves contained in the adjacent faces of the clutch members. Spring means normally bias the clutch members apart, and a locking pin extends axially from one face into a recess contained in the adjacent face of the other clutch member, thereby to prevent relative rotational movement between the clutch members. The locking pins are generally separate components, used in connection with a plurality of biasing springs and spacer disks or plugs, thereby causing assembly of the differential to be relatively labor intensive and manually difficult.  
           [0007]    In the differential conversion market, it is common to retrofit one type of differential into the housing of another type of differential. For example, in certain automotive environments such as in high-performance all terrain four-wheel drive vehicles, it is desirable to substitute within a given casing a fully locking type differential for a limited slip differential. In one specific instance, it may be desired to retrofit within the differential housing of a limited slip differential mechanism of the fully locking type.  
         SUMMARY OF THE INVENTION  
         [0008]    Accordingly, a primary object of the present invention is to provide a fully locking differential mechanism that is adapted to be retrofit within the housing of another type of differential, use being made of a mounting sleeve adapted for insertion and non-rotatable connection within the housing, which mounting sleeve carries the diametrically arranged cross pin the differential mechanism.  
           [0009]    According to another object of the invention, the locking means for preventing relative rotation between the clutch members arranged on opposite sides of the cross pin comprises locking lugs that extend axially from one face of one clutch member into corresponding locking slots contained in the adjacent face of the other clutch member. In one embodiment, each clutch member contains a single locking lug and a single diametrically arranged locking slot operable to cooperate with a corresponding locking slot and locking lug on the adjacent face of the other clutch member. In a second embodiment, one clutch member carries two diametrically arranged locking lugs, and the other clutch member carries a corresponding pair of locking slots.  
           [0010]    Owing to the use of the locking lugs and slots, the use of dowel-type locking pins and the associated machining of the holes therefore are eliminated, thereby reducing the number of parts and machining steps, whereby the overall cost of the clutch members is reduced. The resulting locking lug and slot design is more robust and durable, than the prior weak dowel pins, which often fail through use. Another advantage of the invention is that by the use of the locking lugs and slots; more space is provided for accommodating four biasing springs, rather than the two springs of the prior art. In the embodiment wherein each clutch member carries at least one locking lug and at least one locking slot, the further advantage is achieved that a pair of identical clutch members can serve as the clutch members of the differential, whereby the inventory of the types of clutch members required for production is reduced to one. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    Other objects and advantages of the invention will become apparent from a study of the following specification when viewed in the light of the accompanying drawings, in which:  
         [0012]    [0012]FIGS. 1 and 2 are longitudinal sectional and prospective views, respectively, of a limited slip differential of the prior art;  
         [0013]    [0013]FIG. 3 is a longitudinal sectional view of the improved differential of the present invention, and FIG. 4 is a similar sectional view displaced by 90° about the axis of the differential;  
         [0014]    [0014]FIGS. 5 and 6 are end and side elevation views, respectively, of the sleeve member of the invention of FIGS. 3 and 4;  
         [0015]    [0015]FIGS. 7 and 8 are perspective views illustrating the clutch member of the prior art and a first embodiment of the clutch member of the present invention, respectively;  
         [0016]    [0016]FIG. 9 is an end view of the clutch member of FIGS. 3, 4, and  8 , and FIGS.  10 - 13  are sectional and side views taken along lines  10 - 10 ,  11 - 11 ,  12 - 12 , and  13 - 13 , respectively, of FIG. 9;  
         [0017]    [0017]FIG. 14 is a right-hand end view of the clutch member of FIG. 11, and FIG. 15 is a diagrammatic enlarged view of the clutch portion A of the FIG. 9;  
         [0018]    [0018]FIG. 16 is a longitudinal sectional view of a second embodiment of the invention wherein the mounting sleeve of FIGS. 3 and 4 has been eliminated; and  
         [0019]    [0019]FIGS. 17 and 18 are perspective views of a further embodiment of a pair of clutch members of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0020]    Referring first more particularly to FIGS. 1 and 2, it is known in the prior art, as shown, for example, by the illustrated A. P. SURETRAC differential produced by Automotive Products plc, to provide a limited slip differential having an outer casing  2  in which is rotatably mounted a housing  4  containing a central chamber for receiving a gearing arrangement including side gears  6  that are keyed with the left and right output shafts  8  and  10 , respectively. The side gears  6  are connected by follower gears  12  that are rotatably mounted on a transverse shaft  14 . The housing  4  is rotatably driven from drive shaft  18  via pinion gear  20  and a ring gear  22  that is bolted to the housing  4 . The side gears are supported for rotation relative to the housing  4  by needle bearing means  22 , and Belleville washer means  24 .  
         [0021]    As best shown in FIG. 2, the inner circumferential surface of the housing  4  provided with a plurality of longitudinally extending splines  30  that are engaged by corresponding splines  32  carried by the follower ring  34 . In this limited slip differential, when one output shaft  8  or  10  overruns the other output shaft (such as might occur during the vehicle making a turn), the output shafts remain connected via the side gear  6  and the follower gear  12 .  
         [0022]    In accordance with the present invention, the differential mechanism of the apparatus of FIGS. 1 and 2 may be replaced by a fully locking differential mechanism as illustrated in FIGS. 3 and 4. To this end, use is made of a tubular mounting sleeve  40  having a plurality of circumferentially spaced longitudinally-extending splines  40   a  that engage the internal circumferential splines  30  on the inner surface of the housing  4 , thereby to prevent relative rotation between the sleeve  40  and the housing  4 . The sleeve  40  contains a pair of diametrically arranged openings  42  that receive the end portions  44   a  and  44   b  of the cross pin  44 , as shown in FIG. 4. Arranged on opposite sides of the cross pin  44  are a pair of coaxially-arranged axially-spaced annular clutch members  46  and  48 . The adjacent faces of the clutch members  46  and  48  contain cam grooves  50  that are diametrically arranged for receiving the driving cross pin  44 . The clutch members  46  and  48  are arranged in concentrically spaced relation about a pair of side gears  54  and  56  that are internally splined for non-rotational connection with the output shafts  8  and  10 . The remote ends of the clutch members  46  and  48  contain counter bores  60  and  62  that receive friction clutch packs  64  and  66 , respectively. As known in the art, the clutch packs  64  and  66  include annular friction disks that are arranged in a stack, a first set of alternate frictions disks being externally splined against rotation relative to the splined inner circumferential surface of the associated clutch member (FIG. 14), and the remaining alternate friction disks being internally splined for non-rotational connection with the associated side gear. Thus, as will be described in greater detail below, when either of the clutch members  46  or  48  is axially displaced outwardly relative to the drive cross pin  44 , the associated friction pack  64  or  66  will be compressed, thereby to non-rotatably connect the clutch member with the associated side gear.  
         [0023]    As is known in the art, the clutch members  46  and  48  and normally biased axially apart by a plurality of circumferentially arranged compression springs  70 . As shown in FIG. 9, each face of the clutch member contains four bores  72  for receiving the ends of four compression springs  70 , respectively.  
         [0024]    In accordance with a characterizing feature of the invention, rotation of the clutch members  46  and  48  relative to each other is prevented by the cooperation between locking lugs  78  that extend axially from one face of the clutch member into a corresponding locking slot or groove  80  contained in the opposing adjacent face of the other clutch member. As shown in FIG. 9, the radian angle ∝ subtended by the locking lug  78  is less than the radian angle β defined by the locking slot  80 . Thus, a slight angular adjustment between the clutch members is permitted, as will be described below. In the illustrated embodiment, the angle ∝ is 26.5°, and the angle β is 35°.  
         [0025]    In accordance with an important feature of the invention, the cam grooves  50  have a generally V-shaped configuration and include side walls  50   a  and  50   b  that are generally planar but are skewed by the angle γ, as shown in FIG. 15. FIG. 15 is an enlarged diagrammatic view of the portion A of FIG. 9. As shown in FIG. 15, the wall surfaces  50   a  and  50   b  are inclined at an angle of 30° relative to the face of the associated clutch member  48 , and the skew angle γ is 4.25° relative to the center line of the cross pin.  
         [0026]    Operation In operation, assume that the limited slip differential of FIGS. 1 and 2 has been disassembled and the housing sections  4   a  and  4   b  are disconnected by unbolting the fastening bolts  5 . The differential mechanism is axially removed from the housing section  4   a  by axially sliding the follower carrier  34  relative to the housing  4 , thereby removing the cross shaft  14 , pinions  12 , side gear  6 , and associated bearings from the chamber contained in housing  4 . The fully locking differential of FIGS. 3 and 4 is then inserted within the chamber contained in housing section  4   a,  whereupon the housing sections  4   a  and  4   b  are again bolted together by the bolts  5 , and the driven output shafts  8  and  10  are inserted axially within the housing  4  into splined non-rotatable connection with the side gears  54  and  56 , respectively.  
         [0027]    Owing to the fact that the angle β of the groove  80  is larger than the ∝ of the locking lug  78 , there is a limited amount of angular play between the two clutch members  46  and  48 . Furthermore, owing to the skew angle γ between the wall surfaces  50   a  and  50   b  of the cam groove  50 , that is, when the full differential assembly is in a neutral position so that the cross pin does not make contact with either of the side walls  50   a  and  50   b  of the cam groove  50 , there is a specific amount of clearance and play in the unit. The cross pin rotates around and touches the V-slot surfaces of the cam groove, and starts to run up the ramps of the V-slots. This forces the clutch members  46  and  48  to separate axially outwardly, and eliminates the aforementioned end play. Once the end play is eliminated, the two clutch packs lock up, thereby permitting torque to flow to both axles. The point where the end play is eliminated can be measured by the angle γ (in this case, at an skewing angle of 4.25°).  
         [0028]    The condition described above simulates a vehicle being driven in a straight ahead mode or a straight reverse mode. When the vehicle begins to make a turn in either direction, the outside faster running wheel and the clutch member associated therewith pulls forward of the ramps  50   a  or  50   b,  thereby allowing the end play to return on that side, deactivating the associated clutch pack to the non-compressed condition, thereby allowing the outside wheel to be driven at ground speed. This mode is operable for left- and right-hand turns, and for forward and reverse operation.  
         [0029]    Referring now to FIG. 7, it will be seen that in the prior art clutch member  48 , a single dowel locking pin  278  projects from one face of the clutch member, which face contains a diametrically arranged bore  279  for receiving the dowel locking pin of the associated clutch member. A pair of diametrically arranged bores  272  are provided for receiving two biasing compression springs. As shown in FIG. 8, the clutch member  48  of the present invention, on the other hand, contains four bores  72  for receiving four biasing compression springs, thereby to allow a more even axial displacement of the clutch members.  
         [0030]    According to the modified embodiment of the invention shown in FIG. 16, the mounting sleeve  40  of the embodiment of FIGS. 3 and 4 is omitted, and the cross pin  144  has end portions  144   a  and  144   b  extend within through bores  145  contained in the housing  104 . Otherwise, the operation of the second embodiment of the differential is identical to that of the embodiment of FIGS. 3 and 4.  
         [0031]    Referring now to FIGS. 17 and 18, according to another modification of the invention, the clutch member  346  is provided with two diametrically opposed locking lugs  378 , and the opposing face of the second clutch member  348  contains a pair of corresponding locking grooves or slots  380 . This embodiment is easier to produce from a manufacturing standpoint, has less material waste, and thus is cheaper to produce.  
         [0032]    While specific examples of the radian angles of the locking slots and locking lugs have been set forth, it is apparent that a certain degree of variation of these angles is permitted. Similarly, the skew angle of the side walls of the V-shaped drive groove may be varied as desired.  
         [0033]    While in accordance with the provisions of the Patent Statutes the preferred forms and embodiments of the invention have been illustrated and described, it will be apparent to those skilled in the art that various changes may be made without deviating from the inventive concepts set forth above.