BACKGROUND OF THE INVENTION
1. Field of the Invention
A locking differential includes a pair of annular clutch members that are normally displaced apart to effect engagement between clutch teeth on the remote ends of the clutch members and corresponding gear teeth on the adjacent ends of a pair of side gears between which the clutch members are colinearly arranged. When one output shaft overruns the other by a predetermined amount, the clutch member associated with the overrunning output shaft is disengaged from its associated side gear. A retaining device retains the clutch members in the disengaged condition until the overrunning condition is terminated. In one embodiment, the retaining device is a cam arm and follower pin arrangement that is connected between the clutch members and operates in conjunction with a pair of friction rings. In a second embodiment, the retaining device comprises a pair of holdout rings that operate between the clutch members and the side gears.
2. Description of the Related Art
Locking differentials for motor vehicles are well known in the patented prior art, as evidenced, for example, by the patents to Schou U.S. Pat. No. 4,498,355, Zentmyer U.S. Pat. No. 5,413,015, Lewis U.S. Pat. No. 2,555,044, and Dissett U.S. Pat. No. 5,715,744, among others. In these known differentials, when the rotational velocity of one of the driven output shafts exceeds that of the other output shaft above a predetermined value, such as occurs during the turning of the vehicle, the overrunning shaft is automatically disengaged from the power train as long as the overrunning condition exists.
One drawback of the known differentials is the chattering of the clutch teeth during the engagement and disengagement that occurs when a clutch member is disengaged from the associated side gear. This results in tooth wear at the tips of the clutch teeth on the clutch and side gear members, which could possibly result in the failure of the differential.
The present invention was developed to provide an improved locking differential that avoids the above and other drawbacks of the known differentials.
BRIEF SUMMARY OF THE INVENTION
Accordingly, a primary object of the present invention is to provide a locking differential including retaining means for positively retaining the clutch member associated with an overrunning output shaft in the disengaged condition as long as the overrunning condition exists. In a first embodiment, the retaining means comprise cam means connected between the two clutch members. In a second embodiment, the retaining means comprise a pair of holdout rings that are selectively operable between the clutch members and their associated side gears, respectively. In each case, the retaining means is rotatably operated from an axially displaced intermediate condition to a final retaining condition by friction drag means.
According to a more specific object of the invention, the cam means includes a cam arm that is fixed at one end to one of the clutch members, said cam arm containing at its other end a generally T-shaped recess for receiving a cam follower pin that extends radially outwardly from the other clutch member, thereby to positively retain the overrunning clutch in the disengaged condition. In this embodiment, the friction drag means comprises a pair of resilient split friction rings that are respectively arranged concentrically between annular spacer members pinned to the side gears, and the inner circumferential surfaces of counterbores contained in the remote ends of the clutch members. Friction ring pins prevent rotational movement of the friction rings relative to their associated spacer members, and integral annular ribs on the friction rings cooperate with corresponding grooves contained in the clutch members, thereby to prevent relative axial displacement of the friction rings.
According to another object of the invention, the retaining means comprises a pair of holdout rings that connected for angular displacement relative to the clutch members, which holdout rings have radially outwardly flange portions that carry a plurality of axially extending lugs adjacent the side gears, such that when one of the clutch members is in the disengaged condition upon the overrunning of the associated output shaft, the associated holdout ring is slightly angularly displaced so that the lugs engages the tips of the teeth of the side gears, thereby to positively retain the clutch member associated with the overrunning shaft in the disengaged condition. In this embodiment, the friction drag effect is provided by resiliently outwardly biased segments of the body portion of each holdout ring.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and advantages of the invention will become more apparent from a study of the following specification, when viewed in the light of the accompanying drawings, in which:
FIGS. 1 and 2 are sectional and side elevation views, respectively, of a locking differential of the prior art;
FIG. 3 is a longitudinal sectional view of a first embodiment of the improved locking differential of the present invention,
FIG. 4 is a sectional view taken along the line 4-4 of FIG. 3, and
FIG. 5 is a left hand end view of the differential of FIG. 3;
FIG. 6 is a sectional view taken along line 6-6 of FIG. 7, and
FIG. 7 is a detailed view of the cam and pin arrangement of FIG. 5 when in the normal locking condition;
FIGS. 8-10 are front, side and rear views, respectively, of one of the side gears of FIG. 3, and
FIG. 11 is a sectional view taken along line 11-11 of FIG. 8;
FIGS. 12 and 13 are side and end views, respectively, of one of the helical compression springs of FIG. 3;
FIGS. 14-17 are front, side and rear views, respectively, of one of the clutch members of FIG. 3, and FIG. 17 is a sectional view taken along line 17-17 of FIG. 16;
FIGS. 18 and 19 are left hand end and side elevation views, respectively, of the spring cap member of FIG. 3;
FIG. 20 is a sectional view of the annular spacer member taken along line 20-20 of FIG. 21, and
FIG. 21 is a right hand end view of the spacer member;
FIGS. 22 and 23 are left hand end and side elevation views, respectively, of the spring pin;
FIG. 24 is a sectional view of the friction ring taken along line 24-24 of FIG. 25, and
FIG. 25 is a right hand end view of the friction ring;
FIG. 26 is a sectional view of the cam arm taken along line 26-26 of FIG. 27, and
FIG. 27 is a top plan view of the cam arm;
FIG. 28 illustrates the cam arm and pin means when in the retaining disengaged condition;
FIG. 29 is a further sectional view corresponding to FIG. 3;
FIG. 30 is a sectional view of a second embodiment of the invention, and
FIG. 31 is a corresponding section view taken at right angles to FIG. 30,
FIG. 32 and 33 are end views of the clutch member and the side gear, respectively, and
FIG. 34 is an end view of the other end of a modified version of the clutch member of FIG. 32;
FIG. 35 is an end view of one end of the holdout ring,
FIG. 36 is a sectional view taken along line 36-36 of FIG. 35, and
FIG. 37 is an end view of the other end of the holdout ring; and
FIGS. 38-40 are schematic detailed views illustrating the operation of the locking differential of FIGS. 30 and 31 when in the normal driving condition, with one output shaft in the overrunning condition, and with the other output shaft in the over running condition, respectively.
DETAILED DESCRIPTION OF THE INVENTION
Referring first to FIGS. 1 and 2, as illustrated and described in the prior Dissett U.S. Pat. No. 5,715,733, the disclosure of which is incorporated herein, the known locking differential includes an outer housing 2 that is rotatably driven from the drive shaft 4 via pinion 6 and ring gear 8. A pair of output shafts are normally rotatably driven at the same speed by the housing via transverse drive rod 14 having end portions 14a and 14b supported in corresponding openings contained in the housing; a pair of annular clutch members 16 and 18 the adjacent faces of which contain diametrically extending grooves that receive the drive rod; and a pair of side gears 20 and 22 that are non-rotatably splined to the output shafts 10 and 12, respectively. The clutch members are mounted for axial sliding displacement on annular spacer members 24 and 26, which clutch members are normally biased apart by compression springs 28 and 30 that react on spring pins 32 and 34, respectively, thereby to effect locking engagement between circular arrangements of clutch teeth on the clutch members and corresponding circular arrangements of clutch teeth on the side gears, respectively. A plurality of support washers 36 are provided for reducing friction and wear between the rotating components. Access openings 38 are provided in the clutch members to afford access to the compression springs and pins.
As is known in the locking differential art, the output shafts are normally driven at the same rotational velocity. In the event that the rotational velocity of one output shaft exceeds that of another by a given value, as might occur during a turn, for example, the cooperation between the drive rod 14 and the wall of the groove contained in the clutch member associated with the overrunning output shaft, together with the com-out configuration of the clutch teeth and the side gear teeth, causes the clutch member to be axially displaced in a direction to disengage the clutch teeth thereof from the corresponding clutch teeth of the associated side gear, thereby to place the overrunning shaft in a free-wheeling condition. When the rotational velocity of the overrunning shaft is reduced to that of the other output shaft, the associated clutch member is spring-biased toward its initial engaged condition with the associated side gear, whereupon both output shafts are again driven at the same rotational velocity by the drive shaft 4.
Referring now to FIGS. 3, 4, and 29, according to the present invention, the output shafts 60 and 62 are non-rotatably splined to the colinearly-arranged axially-spaced annular side gears 64 and 66 the adjacent faces of which are provided with a circular arrangement of side gear teeth 112 (FIG. 8) that normally are in engagement with a corresponding circular arrangement of clutch teeth 110 (FIG. 14) on the remote ends of the clutch members 68 and 70 that are colinearly arranged between the side gears. The adjacent faces of the clutch members contain diametrically-extending drive grooves 72 and 74 that receive the diametrically-extending drive rod 76 the ends of which are supported by the housing H (FIG. 5). The remote ends of the clutch members contain counterbores 71 (FIGS. 14 and 17) that receive annular spacer members 78 and 80 that are colinearly arranged relative to the side gears 64 and 66 and to which they are non-rotatably connected by the spacer pins 82 and 84, respectively, that extend axially from bores 85 (FIGS. 20 and 21) contained in the remote ends of the spacer members. Arranged concentrically between the spacer members and the clutch members are a pair of resilient split friction rings 86 and 88 that are resiliently biased radially outwardly toward frictional engagement with the inner circumferential surfaces of counterbores contained in the remote ends of the clutch members 68 and 70, respectively. Friction ring pins 90 extend radially outwardly from radial bores 92 (FIG. 20) contained in the spacer members 78 and 80, which friction pins extend into the gaps G (FIG. 25) of the split friction rings 86 and 88, thereby to prevent the rotation of the friction rings relative to the spacer members 78 and 80, respectively. The split friction rings are provided on their outer circumferential surfaces with integral ribs 86a and 88a that respectively extend radially outwardly into corresponding grooves 94 (FIG. 17) contained in the inner circumferential surfaces of the clutch members 68 and 70, thereby to prevent axial displacement of the friction rings relative to their associated clutch members.
The clutch members 68 and 70 are normally biased apart by compression springs 100 that react with first ends of limit pins 102 via spring caps 104 having body portions 104a (FIG. 19) that extend concentrically within the adjacent ends of the associated compression springs. The compression springs 100 are supported at one end within the oversize bores 104 (FIG. 5) contained in the opposed faces of the clutch members. Similarly, the limit pins 102 are supported at their other ends within bores 106 also contained in the clutch member opposed faces. As shown in FIGS. 14, 15 and 17, the clutch members are provided at one end with a circular arrangement of clutch teeth 110 that are normally in driving engagement with a corresponding circular arrangement of side gear teeth 112 (FIGS. 8, 9 and 10) on the side gears 64 and 66.
Referring now to FIGS. 6 and 7, in accordance with a characterizing feature of the present invention, cam arm and follower pin means are provided for maintaining in a disengaged condition the clutch member associated with an output shaft having a rotational velocity that exceeds that of the other output shaft by a predetermined value, as occurs, for example, during the turning operation of a vehicle. To this end, a rigid generally-rectangular cam arm 120 is secured at a first end 120a (FIG. 27) within a recess 122 contained in the outer peripheral surface of the clutch member 70. The second end 120b of the cam arm slidably extends into a corresponding recess 124 contained in the outer peripheral surface of the other clutch member 68. This second cam arm end contains a generally T-shaped cam opening 126 that receives a cam follower pin 130 that extends radially outwardly from a radially-inwardly extending bore 132 (FIGS. 5 and 16) contained in one or more of the recesses 124 provided in the outer circumferential surface of the clutch member.
As best shown in FIG. 27, the cam opening 126 has a first recess 126a adjacent the free extremity 120c of the cam member, and second and third recesses 126b and 126c contained in a plane that extends transversely of the axis of rotation of the output shafts, which plane is spaced axially inwardly of the first recess 126a.
Operation
In operation, during normal operation of the vehicle (FIG. 29), the output shafts 60 and 62 are driven at the same rotational velocity from the drive shaft via the pinion and ring gears (not shown), housing H (FIG. 5), drive rod 76, clutch members 68 and 70, and side gears 64 and 66. Assuming that the drive rod 76 is driven in the direction shown by the arrow, the clutch members 68 and 70 are displaced outwardly by the driving torque as shown by the arrows, thereby effecting engagement between the clutch teeth 110 of the clutch members and the side gear teeth 112 of the side gears, as shown in FIG. 7. Cam pin 130 is positioned in the locking recess 126a of the cam opening 126 contained in the cam arm 120, and the clutch members 68 and 70 are locked together to prevent any relative angular displacement therebetween.
In the event that the rotational velocity of one output shaft exceeds that of the other above a predetermined amount (as indicated by the arrow in FIG. 28), the drive rod 76 is displaced up the wall of the corresponding groove 74, and the clutch member 70 associated with the overrunning side gear 66 splined to the overrunning output shaft is cammed out by the cooperation between the side gear teeth and the clutch teeth, and is axially displaced toward the other clutch member, thereby to effect disengagement of the clutch teeth 110 from the side gear clutch teeth 112. Cam follower pin 130 is now axially displaced within the opening 126 to an intermediate released position between the second and third positions 126b and 126c. Owing to the frictional drag produced by the friction rings 86 and 88, the clutch members are relatively slightly rotatably angularly displaced, as limited by the limit pins 102, thereby to cause the cam pin 130 to enter retaining recess 126c. The clutch members 68 and 70 is then retained in the disengaged condition as long as the output shaft overrunning condition exists. When the rotational velocity of the overrunning shaft is reduced to that of the other output shaft, the clutch members are rotationally returned by frictional drag to their initial relative positions. Owing to the force of the driving rod 76 and the biasing force produced by the compression springs 100, the clutch members are axially displaced apart toward the initial driving condition of FIG. 7, whereupon the cam pin 130 is returned to the cam locking recess 126a. Of course, in the event that the other output shaft was to be in an overrunning condition, the operation would be reversed and the cam follower pin 130 in the retaining condition would be contained in the recess 126b.
In this embodiment, the drive tooth height on the clutch teeth on the clutch and side gear members may be increased to prevent tooth tip interference with the root of the mating side gear teeth, and to prevent compressive loading at the face of the drive teeth.
Referring now to FIGS. 30 and 31, according to a second embodiment of the invention, the retaining means includes a pair of annular resilient holdout rings 220 and 222 arranged concentrically within the clutch members 168 and 170, respectively. The holdout rings, which are axially split to define a gap 224, include tubular body portions that are provided at their remote ends with outwardly directed integral flange portions 220a and 222a that extend within corresponding counterbores contained in the outermost remote end walls of the clutch members, respectively. On their remote end surfaces, the flange portions are provided with a circular arrangement of axially projecting lugs 226. The body portion of each holdout ring contains a plurality of longitudinal slots 225 that define a plurality of resilient body segments that are biased radially outwardly into frictional engagement with the inner circumferential surface of the associated clutch member. At their adjacent ends, the holdout rings contain grooves 228 that receive the drive rod 176.
As shown in FIG. 38, when the vehicle is driven in the forward direction, the driving torque is equally distributed and both output shafts are driven at the same rotational velocity by the clutch members 168 and 170 and the side gears 164 and 166. In this condition, the lugs on the holdout rings extend between the side gear teeth 210. In the event of a left turn, the side gear 166 and the clutch member 170 speed up relative to the drive rod 176, and the clutch teeth 212 are disengaged from the side gear teeth 210. The holdout ring 222 is frictionally dragged relative to the clutch member 170 to the illustrated holdout position in which the lugs 226 engage the tips of the side gear teeth 210, thereby to positively maintain the clutch member in the disengaged condition as long as the overrunning condition exists. When the turn is completed, the components are returned to their initial condition of FIG. 28.
In the event of a right hand turn (FIG. 40), the clutch teeth 212 of the clutch member 168 are disengaged from the side gear teeth 210 of the side gear 164, and the holdout ring 220 is frictionally dragged and angularly rotated to the illustrated holdout position in which the holdout ring lugs 226 engage the tips of the side gear teeth 210. Thus, the clutch member 168 is positively maintained in the disengaged condition by the holdout ring 220 as long as the overrunning condition exists.
In this embodiment, to obtain the proper holdout ring operation, the lengths of the side gear teeth are preferably longer and extend radially inwardly to a greater extent than clutch teeth 212.
While in accordance with the provisions of the Patent Statutes, we have illustrated and described the best form and embodiments of the invention now known to us, it is apparent that changes may be made without deviating from the inventive concepts set forth above.
Patent Application
20090011890
