GB1592250A

GB1592250A - Compact gearbox for a motor vehicle

Info

Publication number: GB1592250A
Application number: GB41753/77A
Authority: GB
Original assignee: Automobiles M Berliet SA
Current assignee: Automobiles M Berliet SA
Priority date: 1977-06-30
Filing date: 1977-10-07
Publication date: 1981-07-01
Also published as: FR2396213A1; NL7712492A; FR2396213B1; SE7801043L; IT1086038B

Description

(54) A COMPACT GEARBOX FOR A MOTOR VEHICLE (71) We, AUTOMOBILES M. BER LIET of 30 quai Claude Bernard, Lyon 7" (Rhone), France, a French Joint Stock Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention concerns a compact gearbox for a motor vehicle and in particular for lorries.

Modern lorries, which are fitted with high-performance engines, demand the use of gearboxes comprising several ratios. This allows advantage to be taken of the power installed at all running speeds of the vehicle.

However, such boxes are bulky. They are becoming more and more difficult to accommodate within the space reserved for them on the chassis. It is well known that this problem is at its greatest in the case of road tractor units with a short wheel base, above all if these tractors must take an automatic braking device mounted in the transmission in addition to the gearbox.

One of the aims of the inventors has therefore always been to seek solutions which lead to gearboxes which are compact and as short as possible.

The present invention has therefore the aim of achieving a compact and short gearbox which nevertheless has a relatively high number of ratios.

The invention provides a gearbox for a motor vehicle comprising: an input shaft; an output shaft co-axial with the input shaft; and only two intermediate shafts parallel to the output shaft, the two intermediate shafts being situated on the same side of the output shaft, and carrying gears by means of which these intermediate shafts are able to engage on the one hand with each other and on the other hand with the input shaft and the output shaft, the arrangement being such that for some speeds, the transmission is carried out solely by means of the first intermediate shaft, whilst for slower speeds and reverse speeds the transmission is carried out by means of both the intermediate shafts.

Preferably all the synchronising rings of the gearbox are situated on the output shaft, which carries the largest diameter gears, the cones designed to co-operate with the said rings being placed inset within the gears, which allows the overall bulk of the gearbox to be reduced longitudinally, when compared to conventional gearboxes.

The gearbox may include a power takeoff shaft parallel to the output shaft, the power take-off shaft and the output shaft being placed on either side of the two intermediate shafts, whilst the power takeoff shaft carries a gear which can slide so as to mesh either with a gear on the first intermediate shaft or with a gear on the second intermediate shaft.

The attached drawing given by way of non-limiting example, will allow the characteristics of the invention to be better understood.

Figure 1 is a diagrammatic side view of a road tractor fitted with a gearbox according to the invention.

Figure 2 is a perspective view of the gearbox.

Figure 3 is a diagrammatic end view of the gearbox.

Figure 4 is a diagrammatic side view of the gearbox.

Figures 5 to 13 are simplified diagrammatic view of the gearbox showing the possible positions of engagement of the different gear ratios.

The gearbox according to the invention is intended particularly to be fitted to a road tractor of the type shown in Figure 1. It is known that on such a vehicle the engine 1 is in general accommodated at the front, and below the driving cabin 2. From the engine the kinematic chain of the transmission of the drive towards the wheels 3 comprises for example, in order; the clutch 4, the gearbox 5, a two-speed transfer unit relay 6 and two universal joints 7 interposed in the transmission shaft 8 and the differential 9. It will be seen that this kinematic chain extends longitudinally in the tractor, and it will be understood that it would be advantageous to reduce the length of the gearbox S in order to achieve a shorter tractor.

The gearbox according to the invention includes, as is shown in Figures 2 and 3, an input shaft 10, an output shaft 11, co-axial with the input shaft 10, two intermediate shafts 12 and 13 parallel to the shaft 11 and located on the same side of this latter, and finally a power take-off shaft 14 parallel to the shaft 11. The shafts 11 and 14 are situated on either side of the intermediate shafts 12 and 13.

For the detailed description which follows, reference should be made to the diagrammatic Figure 4 in which the three shafts 10, 12 and 13 have been brought into the same plane with the object of facilitating comprehension.

A gear 15 is fixed to the input shaft 10, and three gears 16, 17 and 18 are fitted so as to turn freely on the output shaft 11. The output shaft 11 includes in addition a sliding splined sleeve 19 with driving dogs which allows the shaft 11 to be coupled either with the input shaft 10 or with the gear 16, and another sliding splined sleeve 20, likewise with driving dogs, which allows the shaft 11 to be coupled either to the gear 17 or to the gear 18. The sleeves 19 and 20 are connected with synchronising rings 21 which co-operate with the cones 22 inset within the gears 15, 16, 17, 18.

The intermediate shaft 12 is fixed to a gear 23 which meshes permanently with the gear 15, and a gear 24, whilst a cluster of three gears 25, 26, 27 is mounted to turn freely around the shaft 12. A sliding splined sleeve with driving dogs 28 allows the three gears 25, 26, 27, which mesh permanently with the gears 16, 17, 18 respectively, to be coupled simultaneously with the shaft 12.

The intermediate shaft 13 is fixed to a gear 29 which meshes permanently with the gear 24. Two gears 30 and 31 are fitted so as to turn freely on the shaft 13 on either side of a sliding sleeve with driving dogs 32 which allows the shaft 13 to be coupled to one or the other of these two gears. The gear 30 meshes permanently with the gear 17 of the output shaft 11, and the gear 31 meshes permanently with the gear 27 of the intermediate shaft 12.

A gear 33, which is fixed in rotation on the power take-off shaft 14, can move along the shaft so as to engage either with the gear 25 of the intermediate shaft 12 or with the gear 30 of the intermediate shaft 13.

The operation is as follows.

In the simplified diagrammatic views S to 13 which illustrate the various engagement positions of the gearbox according to the invention, the configuration adapted for Figure 4 has been retained, and a small oblique stroke symbolises each connection made between a shaft and a gear or between two co-axial shafts, and a thick stroke shows the path of the transmission of movement.

A first slow speed is obtained (Figure 5) by connecting the gear 31 with the shaft 13 by means of the sleeve 32, and the gear 17 with the output shaft 11 by means of the sleeve 20.

A second slow speed is obtained (Figure 6) by connecting the gear 31 with the shaft 13 by means of the sleeve 32, and the gear 18 with the output shaft 11 by means of the sleeve 20.

A first normal speed is obtained (Figure 7) by connecting the gear 26 with the shaft 12 by means of the sleeve 28, and the gear 17 with the shaft 11 by means of the sleeve 20.

A second normal speed is obtained (Figure 8) by connecting the gear 27 with the shaft 12 by means of the sleeve 28, and the gear 18 with the output shaft 11 by means of the sleeve 20.

A third normal speed is obtained (Figure 9) by connecting the input shaft 10 directly to the output shaft 11 by means of the sleeve 19.

A fourth normal speed is obtained (Figure 10) by connecting the gear 25 with the shaft 12 by means of the sleeve 28, and the gear 16 with the shaft 11 by means of the sleeve 19.

A first reverse speed is obtained (Figure 11) by connecting the gear 30 with the shaft 13 by means of the sleeve 32, and the gear 18 with the shaft 11 by means of the sleeve 20.

A second reverse speed is obtained (Figure 12) by connecting the gear 31 with the shaft 13 by means of the sleeve 32, and the gear 17 with the shaft 11 by means of the sleeve 20.

Finally, a parking brake is obtained by connecting the gear 31 with the shaft 13 by means of the sleeve 32, the gear 27 with the shaft 12 by means of the sleeve 28, and also the gear 18 with the shaft 11 by means of the sleeve 20 (Figure 13).

It will be realised therefore that this gearbox presents six forward speeds and two reverse speeds in a very reduced overall bulk. In the width, the gears of the two intermediate shafts 12 and 13 are overlapped with one another. In the length, the gearbox is no longer than a conventional gearbox with four forward and one reverse speeds, in spite of its 12 gears.

It will be noticed in addition that the gears of the two intermediate shafts 12 and 13 are used simultaneously for the slow speeds and the reverse speeds, whilst for the normal speeds the intermediate shaft 13 is never used, but only the intermediate shaft 12.

Owing to a careful choice of the spacing of the shafts and the gear ratios, the synchronisation may be carried out solely on the shaft 11 which carries the large gears.

The cones 22 may be located within these gears and without the cone diameter being too much reduced, hence effective synchronisation is obtained. In the case of the use of the rear relay 6, the location of the synchronisation component is advantageous in that it allows inertias to be reduced.

The drive take-up shaft 14 is accessible at each of its ends, which is very advantageous.

In addition, a rapid speed is available by bringing the gear 33 to engage with the gear 25 of the shaft 12, and a slow speed by bringing the gear 33 to engage with the gear 30 of the shaft 13.

WHAT WE CLAIM IS: 1. A gearbox for a motor vehicle comprising: an input shaft; an output shaft co-axial with the input shaft; and only two intermediate shafts parallel to the output shaft, the two intermediate shafts being situated on the same side of the output shaft, and carrying gears by means of which these intermediate shafts are able to engage on the one hand with each other, and on the other hand with the input shaft and the output shaft, the arrangement being such that for some speeds, the transmission is carried out solely by means of the first intermediate shaft, whilst for slower speeds and reverse speeds the transmission is carried out by means of both the intermediate shafts.

2. A gearbox according to claim 1, in which all the synchronisation rings of the box are located on the output shaft, which carries the largest diameter gears, the cones intended to co-operate with the said rings being placed inset within the gears.

3. A gearbox according to Claim 1 or Claim 2, including a power take-off shaft parallel to the output shaft, the power take-off shaft and the output shaft being located on either side of the two intermediate shafts, whilst the power take-off shaft carries a gear which can slide so as to engage either with a gear of the first intermediate shaft or with a gear of the second intermediate shaft.

4. A gearbox constructed and arranged substantially as herein described, with reference to the accompanying drawings.

5. A motor vehicle having a gearbox as claimed in any one of the preceding claims.

6. A motor vehicle constructed and arranged substantially as herein described, with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. It will be noticed in addition that the gears of the two intermediate shafts 12 and 13 are used simultaneously for the slow speeds and the reverse speeds, whilst for the normal speeds the intermediate shaft 13 is never used, but only the intermediate shaft 12. Owing to a careful choice of the spacing of the shafts and the gear ratios, the synchronisation may be carried out solely on the shaft 11 which carries the large gears. The cones 22 may be located within these gears and without the cone diameter being too much reduced, hence effective synchronisation is obtained. In the case of the use of the rear relay 6, the location of the synchronisation component is advantageous in that it allows inertias to be reduced. The drive take-up shaft 14 is accessible at each of its ends, which is very advantageous. In addition, a rapid speed is available by bringing the gear 33 to engage with the gear 25 of the shaft 12, and a slow speed by bringing the gear 33 to engage with the gear 30 of the shaft 13. WHAT WE CLAIM IS:

1. A gearbox for a motor vehicle comprising: an input shaft; an output shaft co-axial with the input shaft; and only two intermediate shafts parallel to the output shaft, the two intermediate shafts being situated on the same side of the output shaft, and carrying gears by means of which these intermediate shafts are able to engage on the one hand with each other, and on the other hand with the input shaft and the output shaft, the arrangement being such that for some speeds, the transmission is carried out solely by means of the first intermediate shaft, whilst for slower speeds and reverse speeds the transmission is carried out by means of both the intermediate shafts.