Synchronized Hub Clutch

This invention relates to hub clutches for the front wheels of a four-wheel drive vehicle.

To operate a typical manual hub clutch, the vehicle operator must manually turn the hubs at each front wheel to an engaged or disengaged position. However, to do this, the vehicle operator must leave the cab of the vehicle. A remotely controlled hub clutch mechanism is disclosed in U.S. Application Ser. No. 56,483 filed July 11, 1979, however, to prevent damage to the clutch teeth of this hub clutch mechanism the mechanism may be engaged only when the vehicle is stopped to assure synchronization of the clutch teeth. Automatic free wheeling hub clutches are engaged or disengaged by over-running clutch arrangements which operate automatically in response to the relative rotation of portions of these clutch assemblies when the vehicle is in motion. Such automatic free wheeling hubs are not entirely reliable because they may inadvertenly cut in or out of engagement at undesirable times under certain driving conditions such as loss of traction due to road conditions or when a wheel loses contact with the road surface. Such automatic hub clutches also tend to become noisy during operation as a result of wear. Accordingly, a remotely controlled manual hub clutch mechanism which may be operated while the vehicle is in motion is desired.

A synchronized hub clutch mechanism for the front wheels of a four-wheel-drive vehicle includes a pair of meshable, toothed coupling members mounted for rotation with the vehicle wheel hub and axle, respectively. The vehicle operator engages and disengages the coupling members by movement of a linkage connected to one of the coupling members. A clutch ring with a first friction surface rotates with the wheel hub. A blocking ring rotates with the axle and includes a second friction surface which is engageable with the first friction surface to equalize the rotation speed of the axle and wheel hub so that the coupling members may be engaged and disengaged while the vehicle is in motion.

An advantage of this invention is that a manually operated, positively acting hub clutch mechanism is synchronized so that the hub clutch may be engaged and disengaged while the vehicle is in motion or at rest.

FIG. 1 is a sectional view of applicant's hub clutch in a disengaged position;

FIG. 2 is a sectional view of applicant's hub clutch in an engaged position .

A vehicle hub assembly 10 includes a non-rotating housing 12 fixed relative to the vehicle (not shown). Axle or shaft 14 is rotatably and coaxially mounted in the housing 12 by bearing 16 in bearing race 17. Wheel support member or wheel hub member 20 is rotatably and coaxially mounted on housing 12 by bearings 22. Cap 26 fits onto wheel hub 20 to protect the interior of the hub assembly 10 from the environment.

An engageable and disengageable driving connection between axle 14 and wheel hub 20 is provided by clutch mechanism 28. Clutch mechanism 28 includes a sliding toothed coupling member 30 and a fixed toothed coupling member 32. Sliding coupling member 30 includes internal splines 34 for matching engagement with external splines 36 on axle member 14 and coupling teeth 35 for coupling with fixed coupling member 32. The splines 34, 36 are oriented to permit axial translation of the coupling member 30 with respect to axle member 14, but to prevent rotation of coupling member 30 relative to axle member 14. Coupling member 30 includes a flange-shaped member 37 extending therefrom. A plurality of axially extending chamfered bores 41 extend through flange 37. Fixed coupling member 32 includes outer splines 38 for matching engagement with inner splines 40 of wheel hub 20 and coupling teeth 39 for coupling with coupling teeth 35 of sliding coupling member 30. The engaging edges of coupling teeth 35 and 39 are rounded for smooth coupling. The splines 38, 40 mate so that coupling member 32 rotates with wheel hub 20. Return spring 42 is biased to urge sliding coupling member 30 away from fixed coupling member 32 and out of coupling engagement therewith. Needle bearing 44 and washer 45 permits relative rotation between the spring 42 and inner coupling member 30.

A clutch ring 48 coaxially surrounds axle 14 and is splined at 49 for rotation with fixed coupling member 32. Shim 50 axially spaces clutch ring 48 apart from fixed coupling member 32. Clutch ring 48 includes an inwardly facing frustoconical clutch surface 52. A blocking ring 56 coaxially surrounds axle 14 and sliding coupling member 30. Blocking ring 56 includes an outwardly facing frustoconical clutch surface 58 which is engageable with clutch surface 52 of ring 48. A plurality of stepped pins 60 extend axially from ring 56 and may be received in axial bores 41 of member 37. Stepped pins 60 include smaller and larger diameter portions 62 and 64 interconnected by an annular chamfered abutment surface 65. The smaller diameter portions 62 of pins 60 have a relatively large clearance with the walls of bores 41 to permit a predetermined amount of relative rotation between blocking ring 56 and sliding coupling member 30 when pin portions 62 are received by bores 41, as best shown in FIG. 1. The relatively smaller clearance between the walls of bores 41 and the larger diameter portions 64 of pins 60 maintains blocking ring 56 and sliding coupling member 30 in a substantially fixed relative position when pin portions 64 are received by bores 41, as best shown in FIG. 2.

A non-rotating cylindrical sleeve 66 is coaxially mounted around rotatable shaft or axle 14 in the annular space between axle 14 and housing 12. The outboard end of sleeve 66 includes tabs 68 which engage a washer 70 and a needle bearing 72 adjacent sliding coupling member 30 so that coupling member 30 may freely rotate relative to non-rotating sleeve 66. Slots 74 in housing cooperate with tabs 68 to prevent rotation of sleeve 66. The inboard end of sleeve 66 terminates in flange 76. Pins 78 extend from actuation plate 80 through bores 82 in bearing race 17 and engage flange 78. Actuation plate 80 may be connected to a linkage including a bell crank such as is described in U.S. Application Ser. No. 56,483, filed July 11, 1979, so that the coupling members 30 and 32 may be engaged and disengaged by the vehicle operator from the cab or operator's compartment of the vehicle (not shown). Similarly, the sleeve 66 may be replaced with a hydraulic linkage, such as is also disclosed in Application Ser. No. 56,483.

Applicant's hub clutch mechanism operates as follows: First, assume the transfer case (not shown) is shifted so that the vehicle is in the two-wheel drive mode. In this situation, the front drive shaft (not shown) and the front axle, including axle member 14 are disengaged from the transmission (not shown). The hub assembly, one of which is associated with each of the front wheels (not shown) is in the state shown in FIG. 1 with coupling member 30 disengaged from coupling member 32 by return spring 42. If the vehicle were to move in this condition, the wheel hub 20 would freely rotate on housing 12. But since clutch mechanism 28 is disengaged, axle member 14 would not be forced to rotate with wheel hub 20. Thus, axle member 14, bearings 16, the front differential gear (not shown), and the front drive shaft would not be subject to wear.

The vehicle may be shifted from the two-wheel drive mode to the four-wheel drive mode while the vehicle is at rest or in motion by shifting the transfer case to four-wheel drive and by engaging clutch mechanism 28. Shifting the transfer case to four-wheel drive engages the front wheel drive shaft, as well as the rear drive shaft, with the vehicle transmission. Engaging clutch mechanism 28 couples wheel hub 20 to the front drive shaft through axle member 14 and the front differential gear.

The hub clutch mechanism 28 is engaged by applying a force to plate 80 which shifts actuation plate 80, sleeve 66, and sliding coupling member 30 to the left from the disengaged position shown in FIG. 1 to the position shown in FIG. 2. Shifting plate 80 to the left also moves sleeve 66 and sliding coupling member 30 to the left against the bias of return spring 42 thus preventing engagement of teeth 35 and 39. The movement of sliding coupling member 30 to the left causes engagement of clutch surfaces 52 and 58 of clutch and blocking rings 48 and 56. If this movement is accomplished while the vehicle is in motion, then it is possible for the wheel hub 20 and the shaft 14 to rotate at different speeds. This rotation speed differential and the friction between clutch surfaces 52 and 58 loads small diameter portion 62 of pins 60 against the walls of bores 41 in flange 37 so that abutment 65 engages flange 37 and prevents further leftward movement of sliding coupling member 30, thus preventing engagement of teeth 35 and 39. Eventually, the friction between clutch surfaces 52 and 58 equalizes the rotation speeds of coupling members 30 and 32. Equalization of the rotation speeds unloads the pins 60 from against the walls of bores 41 so that the large diameter pin portions 64 may enter bores 41 and so that coupling member 30 may continue its leftward movement. As coupling member 30 continues to the left, coupling teeth 35 mesh with coupling teeth 39 of fixed coupling member 32 and bores 41 pass over abutments 65 and receive large diameter portions 64 of pins 60. At this point coupling members 30 and 32 are meshed, the hub clutch mechanism is in the coupled position and torque may be transferred between the shaft 14 and the wheel hub 20.

When it is desired to uncouple the applicant's hub clutch mechanism, the operator terminates the force which urges plate 80, sleeve 66 and coupling member 30 to the left. With this force removed return spring 42 moves sliding coupling member 30 to the right and out of meshing engagement with fixed coupling member 32 and into the uncoupled position shown in FIG. 1. With the hub clutch uncoupled, the wheel hub 20 may freely rotate without forcing shaft 14 to also rotate. In this manner, the applicant's hub clutch may be engaged and disengaged while the vehicle is in motion or at rest.