GB2280481A

GB2280481A - Drive unit for four wheel drive has shifting sleeve within a sun gear of one planetary gearing

Info

Publication number: GB2280481A
Application number: GB9414819A
Authority: GB
Inventors: Klaus Lippitsch
Original assignee: Steyr Daimler Puch AG
Current assignee: Steyr Daimler Puch AG
Priority date: 1993-07-22
Filing date: 1994-07-22
Publication date: 1995-02-01
Anticipated expiration: 2014-07-22
Also published as: GB2280481B; GB9414819D0; AT405728B; DE4421606A1; ATA146493A

Description

1 - 2280481 FOUR WHEEL DRIVE UNIT WITH ANCILLARY RANGE BOX The invention

relates to a drive unit for four-wheel driven vehicles with a main gearbox and a subsequent range box, the casing of which contains a first planetary gearing serving as a range box and a second planetary gearing serving as a central differential, where an annular gear of the first planetary gearing is driven from the main gearbox and the second planetary gearing comprises an annular gear and a sun gear, each being drivingly connected with either of the driven axles, and a planet carrier being united with that of the first planetary gearing, the sun gear of the first planetary gearing being drivingly connectable to either the planet carrier or the casing by means of a shifting coupling.

Such a drive unit is known from EP-A 151 711. Planet carrier and shifting sleeve for the range box of this drive unit are arranged in such a way as to necessitate three concentric hollow shafts and as to entail a very bulky unit, especially in the axial direction.

Furthermore, the arrangement of the shifting device is unsatisfactory as the shifting sleeve is poorly accessible. The problems of accessibility and bulk are aggravated, if locking of the second planetary gearing which serves as central differential is to be added.

2 It is therefore the object of the invention, to resolve in a drive unit of the above mentioned kind the said problem of bulk and to provide a shifting mechanism of utmost simplicity, easy action and good acessibility, even if additional means for locking of the central differential are required.

According to the invention, this is achieved in that the shifting coupling comprises a shifting sleeve arranged within the sun gear and provided with at least one first set of splines which engage a set of inside splines of the sun gear of the first planetary gearing, the shifting sleeve further selectively engaging either a set of splines of the casing or a set of splines of the planet carrier, and in that to this end, the planet carrier is designed as a disk with the splines at its inner perimeter and disposed between the planet pinions of the two planetary gearings, the coupling being shiftable by means of a shifting device disposed on one side of the first planetary gearing.

In this way, the annular gear of the first planetary gearing can be lodged within the gear wheel driven from the main gearbox, the latter always being very large due to the required transmission ratio. Therefore, the two planetary gearings which can be very close to one another thanks to their common planet carrier, do not need more space in transverse direction than a conventional front axle differential. The shifting sleeve with the splines housed in the center of the planetary gearings and within the sun gears needs very little space in transverse direction, as it replaces the shifting sleeves and actuation contrivances arranged in the casing necessary according to the state of the art. The plate- shape of the planet carrier allows a further simplification and reduction of bulk in transverse direction. It also shortens the shifting stroke of the range box. The shifting device actuating the shifting sleeve can be arranged outside the casing on the side of the first planetary 3 gearing, not occupying ans casing space at all and being easily accessible from the side of the main gearbox.

In an advantageous embodiment of the invention enabling the central differential to be locked also in the off-road range, the shifting coupling rotatably journals an annulus provided with a set of outer splines, selectably engaging either the set of splines of the planet carrier or the set of inner splines of the sun gear of the second planetary gearing (claim 2). This arrangement allows shifting both planetary gearings with one single sleeve and actuating device. This offers the additional advantage that the sequence of the various shifting positions corresponds to the necessities of gradually worsening road conditions.

In an advantageous development of the invention, the splines of the casing are arranged on an element extending into the shifting sleeve and cooperating with a second set of splines within the shifting coupling (claim 3). This further shortens the shifting stroke and improves guidance of the shifting sleeve in axial direction.

The arrangement of the elements of the two planetary gearings and their linkup with the driving and driven elements of the vehicle according to the invention enables identical layout of the correponding gears of the two planetary gearings (claim 4) while safeguarding a suitable stepping of the range box and of a reasonable ratio of torque distribution between front and rear axle. The advantage of the higher number of identical parts is obvious.

The invention will now be described and commented with reference to the drawings which show:

Fig. 1: A schematic view of one embodi-ment of the invention; Fig.2: The drive unit according to the invention in a first operating position; 4 Fig-3: The drive unit according to the invention in a second operating position; Fig.4: The drive unit according to the invention in a third operating position; Fig.5: The drive unit according to the invention in a fourth operating position; Fig-6: The drive unit according to the invention in a fifth operating position; Fig-7: The design of the embodiment according to fig.1 In figure 1, an engine 1, a coupling 2 and the main gearbox 3 are not shown in detail. A gear wheel 4 of the main gearbox meshes with a drive gear 5 which is already part of the range box summarily indicated by 6. In a conventional front-wheel driven vehicle, the drive gear 5 would carry the front axle differential. In order to derive the subject four- wheel driven version therefrom, the range gear is fitted instead of the front axle differential.

The range box 6 is only sketched in fig.1 and shown in more detail in fig. 7, parts with numbers over 50 being only shown in fig.7. The range box 6 is__accomodated in a casing 7 secured to a main gearbox casing (not shown). The drive gear 5 is drivingly connected, by means of threaded bolts 50, with a bell 8 and a bearing flange 51 which are journalled in the casing 7 by means of bearings 52,53. Within the drive gear 5 and the bell 8, are accomodated a first planetary gearing 9 serving as a range gearing and a second planetary gearing 10 serving as a central differential.

The first planetary gearing 9 comprises an annular gear 11, here designed in one part with the drive gear 5, a planet carrier 12 with planet pinions 13 and a sun gear 14. The planet carrier 12 is shared between both planetary gearings 9,10 and comprises preferably three journalling pins 54, a disk 55 arranged between the planet pinions of both planetary gearings, and possibly two outer shroud rings 56. The sun gear 14 of the h 1 first planetary gearing is journalled by means of a bearing 57 in a bearing flange 51 and can be coupled to various elements, as described later.

The second planetary gearing 10 comprises an annular gear 16 coupled to a trumpet 58 which is journalled in the bell 8 by means of bearings 59,60, planet pinions 17 jounalled on the planet carrier common to both planetary gearings and a sun gear 18 drivingly connected with the front axle drive shaft 23 by means of a set of splines 62. The trumpet 58 is drivingly connected with a rear axle drive shaft 20 by means of a set of splines 61.

Both drive shafts 20,23 (only fig.1) are hollow shafts projecting from the casing 7. The rear axle drive shaft 20 drives a cardan shaft 22 leading to the rear wheels (not shown) by means of a meshing pair of bevel gears 21. The front axle drive shaft 23 is drivingly connected with the front axle differential 24 and further with a right hand side wheel drive shaft 25 and by means of a link shaft 26 through the range box 6 with a left hand side wheel drive shaft 27.

Within the sun gears 14,18 of both planetary gearings 9,10, an axially shiftable tubular shifting sleeve 30 is arranged and provided at their (in fig 1 and 7) left extremity with a groove 31 engaged by a shifting fork 65. The latter can be shifted by means of a lever 66, for example. The tubular shifting sleeve 30 bears a first outwardly directed set of splines 32 and a second inwardly directed set of splines 33. on the other extremity of the shifting sleeve 30 which protrudes inside the planetary gearings 9,10, a ring 34 with a further set of outwardly directed splines 35 is journalled.

The sets of splines 32,33,35 of the shifting sleeve 30 are designed to cooperate with one or more sets of matching splines: The inner circumference of the sun gear 14 of the first planetary gearing is provided with a set of inwardly directed spli- 6 nes 36, the casing 7 or a part 70 of the casing coupled with it, in the described embodyment an inwardly turned collar, is provided with an outer set of splines 37, the disk 55 constituting the planet carrier with an inwardly directed set of splines 38 and at last the sun gear 18 of the second planetary gearing 10 with a set of inwardly directed splines 39.

Fig.7 shows in dotted line that the front part 71 of the shifting sleeve 30 can be omitted in a simplified embodiment, if the central differential need not be lockable. The splines 39 of the sun gear 18 can then be omitted as well. Furthermore, a different embodiment can be created by replacing the part 70 (in through lines) by part 72 of the casing (drawn in dotted line) provided with an inner set of splines 73 (instead of the outer set of splines 37, in through lines). In this case, the second set of splines 33 of the shifting sleeve 30 can be omitted and the first set of splines must extend further outside.

When identical dimensions are chosen for the gears in both planetary gearings 9,10, reasonable conditions can be maintained thanks to the disposition of the elements of the planetary gearings according to the. invention. If for instance a range ratio step of 1:1,55 is chosen for the off-the-road range, the resulting distribution of torque between front axle and rear axle is 60:40, which is well within the desirable range.

Now, the operation of the drive unit according to the invention will be described with respect to figures 2 to 6:

Fig.2: Off-the-road range, central differential locked: The shifting sleeve 30 is in its outermost position (see also fig.7), its first set of splines 32 engages the inner set of splines 36 of the sun gear 14, its second set of splines 33 engages the splines 37 of the casing 7; the splines 35 of the ring 34 rotatably journalled on the shifting sleeve 30 engage the splines 38 of the planet carrier 12 and the inner set of splines 39 of the sun gear 18. In this way, the sun gear 14 is 7 coupled with the housing and the sun gear 18 with the planet carrier 12. Rotation of the drive gear 5 is demultiplied to the slower rotation of the planet carrier 12 in the first planetary gearing 9 by immobilising the sun gear 14. The second planetary gearing 10 is rotated as a whole due to the sun gear 18 being locked against the planet carrier 12.

Fig.3: Off-the-road range, central differential open: When the shifting sleeve 30 is translated in an inwardly direction into the next position, its splines 32,33 remain engaged with splines 36 of the sun gear 14 and with splines 33 of the casing 7, but the set of splines 35 on the rotatable ring 34 is disengaged from the splines 38 of the planet carrier 12. This changes nothing in the first planetary gearing, but the second planetary gearing 10 is unlocked due to the released planet carrier 12. The torque therefore is distributed among front axle and rear axle at the ratio determined by the chosen number of teeth of the planetary gearing.

Fig.4: Neutral position: When shifting the sleeve 30 further inside, its second set of splines 33 is disengaged from the splines 37 of the casing 7. No torque is transmitted, as the sun gear 14 of the first planetary gearing rotates freely together with the sleeve 30.

Fig.5: Road range, central differenmtial open: In the next position of the shifting sleeve 30, its first set of splines 32 engages the inner set of splines 36 of the sun gear 14 of the first planetary gearing and the inner set of splines 38 of the planet carrier 12. The rotatably journalled ring 34 is now in completely disengaged position. Thanks to the sun gear 14 being coupled with the planet carrier 12, the first planetary gearing rotates as a whole, corresponding to the road range. In the second planetary gearing, the splines 39 of the sun gear 18 are not coupled with the planet carrier 12 (without regard to the rotatable ring 34 engaging the sun gear or not), the central differential is effective.

8 Fig.6: Road range, central differential locked: In the innermost position of the shifting sleeve 30, its first set of splines 32 engages the splines 36,39 of both sun gears 14,18 and the splines 38 of the planet carrier 12. Both planetary gearings now rotate as a whole, in other words the first does not demultiply and the second is not effective.

From the foregoing, it is apparent that the sequence of the various shifting positions of the shifting sleeve 30 and with it also the positions of a selecting lever within reach of the driver is in line with driving requirements. When leaving a solid road, the driver will first shift to the unlocked off-theroad range which is the next position, then with road conditions further deteriorating into the next position corresponding to off-the-road range and locked central differential.

a 9 Cl ai ms A drive unit for a four-wheel driven vehicle with a main gearbox and a subsequent range box, the casing of which contains a first planetary gearing serving as a high/low gear and a second planetary gearing serving as a central differential, wherein an annular gear of the first planetary gearing is driven from the main gearbox and the second planetary gearing comprises an annular gear and a sun gear, each being drivingly connected with either of the driven axles, and a planet carrier being integral with the planet carrier of the first planetary gearing, the sun gear of the first planetary gearing being drivingly connectable to either the planet carrier or the casing by means of a shifting coupling, characterised in that the shifting coupling comprises a shifting sleeve arranged within the sun gear provided with at least one first set of splines and engaging a set of inside splines of the sun gear of the first planetary gearing, the shifting sleeve further selectively engaging either a set of splines of the casing or a set of splines of the planet carrier, the planet carrier being designed as an annular disk with the splines at its inner perimeter and being arranged between the planet pinions of the two planetary gearings, the coupling being shiftable by means of a device arranged on one side of the first planetary gearing.

Claims

2. A drive unit according to Claim 1, characterised in that the shifting

coupling rotatably journals an annulus provided with a set of outer splines, selectively engaging either the set of splines of the planet carrier or the set of inner splines of the sun gear of the second planetary gearing.

3. A drive unit according to Claim 1 or 2, wherein the splines of the casing are arranged on a member extending into the shifting sleeve and cooperating with a second set of splines within the shifting coupling.

4. A drive unit according to Claim 1, 2 or 3 wherein both planetary gearings have identical gears.

5. A drive unit substantially as herein described with reference to the accompanying drawings.

"4 1