Machine element or mechanism – Gearing – Plural power paths to and/or from gearing
Patent
1987-05-06
1989-04-18
Diehl, Dwight G.
Machine element or mechanism
Gearing
Plural power paths to and/or from gearing
74710, F16H 138
Patent
active
048216038
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to differential mechanisms for apportioning different driving torques between drive shafts in a motor vehicle.
According to the present invention, there is provided a differential mechanism comprising a gear carrier having means for mounting the gear carrier for rotation about an axis thereof, first and second output gears each being rotatable about its axis which coincides with the axis of the gear carrier, and at least one gear train comprising meshing toothed elements rotatably mounted in the gear carrier, the gear train meshing with both output gears to establish a drive path from one output gear to the other which includes in series along the drive path, in either order, both a worm-to-wormwheel and a wormwheel-to-worm mesh, the pitch circle diameters of the mesh between the output gears and the gear train being unequal.
Such an arrangement divides input torque applied to the gear carrier between the two output gears in proportion to the pitch circle diameters of the respective gears while at the same time forming a limited slip differential. Such a mechanism is particularly suitable for dividing the power from the gearbox of a four-wheel drive vehicle where, in view of the effective weight transference towards the rear axle during acceleration, it may be desirable, for example, to transmit one third of the available torque to the front axle and two thirds to the rear axle.
An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which:
FIG. 1 is an axial sectional view, longitudinally of the vehicle, of a transfer gearbox for dividing input torque between front and rear propeller shafts,
FIG. 2 shows the differential mechanism of FIG. 1 also in axial section but on an enlarged scale,
and FIG. 3 is a cross section on the line III--III of FIG. 2.
The transfer gearbox shown in FIG. 1 has a casing 1 comprising two outer casing parts 1a and 1b and an internal diaphragm wall 1c secured together by bolts (not shown). An input shaft 2 which in use is driven by the output of the vehicle gearbox (not shown) is mounted in bearings in the casing parts 1a and 1c and carries a gear 3 meshing with a further transfer gear 4 which is splined onto an extension sleeve 5 of a differential gear mechanism 6. A front output shaft 7 and a rear output shaft 8 are mounted in bearings respectively in the casing parts 1a and 1b and carry respective flanges 7a and 8a by which they may be coupled to a front propeller shaft and a rear propeller shaft (not shown) for driving front and rear axles respectively of a four-wheel drive vehicle.
The differential gear mechanism 6 is shown in detail in FIGS. 2 and 3. The differential mechanism 6 comprises a generally cylindrical gear carrier 10 comprising a front plate 10a formed integrally with the extension sleeve 5, a first tubular spacer 10b, a central body 10c, a second tubular spacer 10d and a rear end plate 10e, all of which are clamped together with a set of tie bolts 11 (FIG. 3). The back plate 10e is formed with a rearwardly projecting sleeve portion 12 by means of which it is supported in the bearing in the casing part 1a.
The front output shaft 7 is supported by bearings 13 and 14 in the extension sleeve 5 and is formed at its rear end with an integral helical gear 15. The front end of the rear output shaft 8 has splined onto it an output helical gear 16 of larger pitch circle diameter than the front output gear 15 (but of the same module and correspondingly larger number of teeth). The rear output gear 16 has a cylindrical extension 17 supported by means of a plain bearing in the extension sleeve 12.
Four identical worm gear members 18A, 18B, 18C and 18D are rotatably mounted on respective fixed pins 19A-19D which are longer than the worm gear members and are all parallel to the common axis of the output shaft 7 and 8 and of the gear carrier housing 10. The pins 19B and 19D have their forward ends supported in the front plate 10a and their rear ends in the central block 10c.
The rear end
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patent: 4667535 (1987-05-01), Knight
Diehl Dwight G.
Knight-Mechadyne Limited
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