GB2061844A - Motor vehicle drive axle - Google Patents

Abstract

A drive axle has the axes of rotation of the wheel carrying hubs 48 offset from the axis of the output shafts 26, 27 of a differential gearing at the centre of the axle, the hubs being connected to the differential by way of universally jointed shafts 41. The hubs may be steerable, and the shafts incorporate a facility for plunge, e.g., by a sliding spline arrangement. <IMAGE>

Description

SPECIFICATION Axles This invention relates to a portal axle, i.e., a drive axle in which the axes of rotation of the wheel carrying hubs are offset from the axis of the output shaft of a differential gearing located at or near the centre of the axle. The axle centre may be offset either upwardly from the hub axes to give good ground clearance, or downwardly to obtain a low floor height in the vehicle in which the axle is to be used. The invention has been developed in relation to a portal axle in which the hubs are steerable.

Hitherto, it has been usual for portal axles to include, adjacent each hub, gearing to provide for transmission from straight shafts extending outwardly from the differential to the offset axes of the hubs. For steerable hubs it is then necessary to provide a universal joint in the hub input shaft, and a plunge facility (e.g., by way of a sliding sun pinion shaft in the case of a reduction geared hub) to accommodate plunge resulting from steering movement. This is a relatively complex, and hence expensive, arrangement, and it is the object of the present invention to provide an improved construction.

According to the invention, we provide a portal axle in which transmission from the differential to the hubs is by way of universally jointed shafts.

Preferably the shafts are of variable length, e.g., by way of sliding spline connections. In the case of an axle with steerable hubs, such provision acccommodates plunge arising from steering movement of the hubs and also, providing the plunge provision is sufficiently great, facilitates drive head removal in the manner to be described hereafter. In an axle with steerable hubs, universal joints are necessary for steering movement and thus are available for use in the universally jointed shafts.

The invention will now be described by way of example with reference to the accompanying drawing, which is a part vertical and part horizontal section through part of an axle embodying the invention.

The illustrated axle comprises a main casing part 10 at the centre of the axle, and further casing parts at the ends of the axle and connected to the part 10 by bearing means providing for steering swivelling movement of the end parts. One such further casing part is shown at 11, connected to the part 10 by bearings 12, 1 3 for steering movement about a vertical axis 14. In the drawing, those parts to the right of line 1 5 are shown in horizontal section (plan) and those to the left of line 1 5 in vertical section (elevation).

The main casing part 10 accommodates a drive head comprising a removeable casing part 1 6 supporting, in bearings 17, an input shaft 1 8 with a drive flange 1 9 and a pinion 20 engaging crown wheel 21. The crown wheel 21 drives the outer member 22 of a bevel gear differential gearing with planet bevels 23 and bevel side gears 24, 25 formed integrally with internally splined sleeves 26, 27 respectively. The sleeves 26, 27 of the side gear are rotatably mounted in the outer member 22 of the differential gearing, the latter being carried in taper roller bearings 28 supported in the removeable casing part 16.

The casing part 10 receives, in a bore 29, a bearing housing 30 carrying a bearing 31 supporting a stub shaft 32 which has an externally splined end portion 33 engaging in the sleeve 26 and at its opposite end is formed as the yoke 34 of a hookes universal joint. The bearing housing 30 is retained within bore 29 by a locking screw 35 with a lock nut 36. An aperture 37 in casing 10, with a removeable cover plate 38, provides for access to the bearing housing 30.

The other yoke 39 of the universal joint of which yoke 34 forms part is connected to a shaft 41 incorporating a sliding spline arrangement to allow for length variation, the yoke 39 being connected to the inner member 40 of the spline arrangement. The outer member 42 is connected to one yoke 43 of a further hookes joint, the other yoke 44 of that joint being connected to the input of a reduction hub assembly.

The end of the steerable casing part 11 has connected to it, by bolts 45, a hub body 46 which supports, on external bearings 47, a rotatable member 48 having a flange 49 with studs 50 for wheel attachment, The member 48 is bolted to a planet carrier 51 carrying planet gears 52 on pins 53, the planet gears meshing externally with a stationary annulus gear 54 fixed to the hub body 46. The planet gears 52 also mesh with a sun gear 55 formed integrally with a shaft 56 connected to joint yoke 44 and supported in a bearing 57.

Oil seals 58, 59 provide for retention of oil in the hub assembly which, by virtue of the arrangement of its planetary gearing, constitutes a reduction hub.

The use of shaft 41 and its associated universal joints provides for transmission between the offset axes of the output shafts of the differential gearing and the input shafts of the hubs. The sliding spline arrangement incorporated in the shaft accommodates plunge arising from steering movement of the hubs, and, because a universal joint must be provided for such steering movement in any event, the arrangement represents an appreciable economy over that usually adopted hitherto in portal axles, with drop gears.

The sliding spline arrangement incorporated in shaft 41 also serves another purpose, which is in facilitating removal of the drive head assembly from the centre of the axle should this be desired. In the arrangement illustrated, for removal of the drive head which constitutes the casing part 1 6 and the differential gearing and associated parts carried thereby, it is necessary to disengage the stub shaft 33 (and the corresponding shaft on the opposite side of the differential) from the sleeve of the differential side gear.

To effect such removal, the locking screw 36 must be disengaged from the bearing housing 30. The bearing housing, and with it the stub shaft 33 and joint yoke 34 can then be moved to the left, which is done by removal of cover plate 38 and insertion of a bar or like member 60 into an aperture in the bearing housing 30 to move the latter. When this has been done, what ever bolts or like fastenings are provided to retain the drive head can be removed, followed by removal of the drive head itself. Of course, a similar arrangement to the moveable bearing housing 30 would be provided for the output shaft (part of which is shown at 61) on the opposite side of the differential.

Such an arrangement removes the necessity of removing the hubs or other axle components if servicing of the drive head is required.

The principle of incorporating variable length output shafts to permit disengagement from the drive head for removal thereof is applicable to axles in general, and not only to a portal axle as described above.

Means for locking the differential gearing may be incorporated in the axle, and this means comprises a sleeve 62 slidably splined to shaft 61 and having an end portion 63 formed with internal dogs for engagement with corresponding dogs 64 at the end of sleeve 27. To lock the differential, sleeve 62 is moved to the left, this movement being effected by a fork 65 engaging with a grooved end 66 of the sleeve and moveable by a selector rod 67 slidably mounted in a removeable casing part 68. If the casing part 68 is removed, this permits manual alignment of shaft 61 with the interior of sleeve 27 if the axle is being reassembled after replacement of the drive head assembly. This facility is particularly valuable if the end of shaft 61 is a relatively great distance from its support bearing assembly.

Instead of using a sliding spline arrangement in shaft 41, plunge capability could be achieved by the use of a plunging type of constant velocity ratio universal joint at one end of the shaft.

Claims (4)

1. A portal axle in which transmission from the differential to the hubs is by way of universally jointed shafts.

2. An axles according to Claim 1, in which the hubs are steerable and said shafts and universal joints provide for plunge.

3. An axle according to Claim 2 in which said shaft incorporates a sliding spline arrangement.

4. An axle substantially as hereinbefore described with reference to and as shown in the accompanying drawing.