BACKGROUND AND PRIOR ART

The invention pertains to a synchronisation device for a gearbox according to the preamble of patent claim 1, a gearbox with such a synchronisation device according to the preamble of patent claim 7, and a vehicle with such a gearbox according to the preamble of patent claim 9.

A gearbox contains a large number of interacting components, which impact the geometrical shape and weight of the gearbox. In the event the gearbox is mounted in a vehicle, the length and weight of the gearbox will impact the length and weight of the entire vehicle. The number of components also impacts the function of the gearbox. Synchronised gearboxes, which con- tain a large number of gear steps, sometimes comprise several synchronisation rings, their task being to achieve a synchronous shifting between different gear steps.

A gearbox of double coupling type comprises a first and second main shaft on which a number of cogwheels are arranged. Such a gearbox also comprises a first and a second side shaft on which a number of cogwheel elements are arranged. The cogwheels on the first and second main shafts interact with the cogwheel elements on the first and the second side shafts, when connection and disconnection of shafts, cogwheels and cogwheels elements occurs synchronously with the help of synchronisation rings. Synchronisation rings impact on the length of the gearbox, which entails that the weight of the gearbox increases.

In relevant cases, the gearbox is completed with a retarder and a range gearbox, which also comprise synchronisation rings.

The document EP-B 1-2322822 pertains to a double coupling gearbox, which comprises two main shafts and two side shafts, on which a number of cogwheels and cogwheel elements are arranged. SUMMARY OF THE INVENTION

Despite prior art, there is a need to develop a synchronisation device for a gearbox, so that the gearbox and thus the vehicle, in which the gearbox is mounted, may be designed to be shorter and with a lower weight, which would entail a cost saving in manufacturing both the gearbox and the vehicle and a saving of fuel in the operation of the vehicle. If the vehicle's fuel consumption may be reduced there is also potential for reducing emissions from the vehicle.

The objective of the present invention is thus to provide a synchronisation device for a gear- box, which entails a limited length distribution of the gearbox.

Another objective of the invention is to provide a synchronisation device for a gearbox, which entails a low weight of the gearbox. Another objective of the invention is to provide a synchronisation device for a gearbox, which entails an increased service life of the gearbox.

These objectives are achieved with a synchronisation device for a gearbox of the type mentioned above, which is characterised by the features specified in patent claim 1.

By replacing the synchronisation rings with synchronisation devices, which comprise a brake element between the first and the second brake wheels, the first and the second shafts may be braked down to a suitable speed, so that a synchronous shifting between the gear steps may be carried out in the gearbox.

According to one embodiment of the invention, the brake element may consist of a multi- plate brake, which may be controlled pneumatically or hydraulically. At least one speed sensor may be connected to the first and the second shafts to detect the speed of the first and the second shafts and in order thus to determine the control of the synchronisation devices when shifting between different gears is to be carried out.

By manoeuvring the synchronisation device, according to one embodiment of the invention, the speed of the input shaft of a range gearbox may be controlled, so that shifting between the different gears in the range gearbox may occur without any impact and need for synchronisation rings.

As an example, a traditional double coupling gearbox with eight synchronisation rings may be replaced by four synchronisation devices according to the invention. Thus the size, weight and manufacturing cost of the gearbox may be reduced with the help of the proposed invention. By combining a double coupling gearbox with a range gearbox, a very large number of gear steps may be obtained, which entails increased manoeuvrability of a vehicle. When the double coupling gearbox is combined with a range gearbox, the synchronisation rings of the range gearbox may be omitted, which entails reduced size, weight and manufacturing cost of the range gearbox. An increased service life of the double coupling gearbox and the range gearbox may also be expected.

The above specified objectives are achieved also with a gearbox of the type mentioned above, which is characterised by the features specified in patent claim 7.

The above specified objectives are achieved also with a vehicle of the type mentioned above, which is characterised by the features specified in patent claim 9. Other features and advantages of the invention are set out in the example descriptions below.

BRIEF DESCRIPTION OF DRAWINGS

Below is a description, as an example, of a preferred embodiment of the invention with refer- ence to the enclosed drawings, in which:

Fig. 1 shows, in a schematic side view, a vehicle comprising a gearbox according to the present invention,

Fig. 2 shows a partial view of the gearbox comprising a synchronisation device according to the present invention,

Fig. 3 shows a partial view of the gearbox according to Fig. 2 in another section plane, and

Fig. 4 shows a partial view of the gearbox, according to the present invention, equipped with a range gearbox. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

Fig. 1 shows a vehicle 1 in a schematic side view, the vehicle 1 of which is equipped with a combustion engine 2, which drives the driving wheels 4 of the vehicle 1 via a gearbox 6 according to the present invention. The gearbox 6 is connected to the driving wheels 4 via a conventional transmission comprising, among others, a propeller shaft 8.

Fig. 2 shows a partial view of the gearbox 6 comprising a synchronisation device 10 accord- ing to the present invention. The synchronisation device 10 comprises a first brake wheel 12 for engagement with a first cogwheel 14 on a first shaft 16, and a second brake wheel 18 for engagement with a second cogwheel 20 on a second shaft 22. The first cogwheel 14 is arranged to drive the first brake wheel 12 and the second cogwheel 20 is arranged to drive the second brake wheel 18. The synchronisation device 10 also comprises a brake element 24 in the form of a multi-plate brake 24, which is arranged between the first and the second brake wheels 12, 18. The task of the multi-plate brake 24 is to reduce the speed difference between the first and the second shafts 16, 22 by exerting a brake torque between the first and the second brake wheels 12, 18. In the event of a predetermined speed difference between the first and the second shafts 16, 22, or when the first and the second shafts 16, 22 stand still or rotate with the same speed, there is a shifting between different gear steps in the gearbox 6. In order to detect the speed of the first and the second shafts 16, 22, at least one speed sensor 26 is arranged at the first and the second shafts 16, 22. As an alternative, the first and the second shafts 16, 22 may be equipped with one speed sensor each. With knowledge about the speed of the first and the second shafts 16, 22, the first and the second shafts 16, 22 may, with the help of the synchronisation device 10, be braked down to a speed and a speed difference which allows synchronous shifting between two gear steps in the gearbox 6.

The first brake wheel 12 is arranged on a first brake shaft 28 and the second brake wheel 18 is arranged on a second brake shaft 30, which brake shafts 28, 30 are coaxially and rotatably journalled in the gearbox 6. The first and the second brake shafts 28, 30 are connected with the multi-plate brake 24. The first and the second brake wheels 12, 18 are equipped with teeth 32 for engagement with the respective first and second cogwheels 14, 20. Thus, the brake wheels 12, 18 will, according to the displayed embodiment, be designed as cogwheels or ring gears. _

The gearbox 6 is, according to the example embodiment displayed, a double coupling gearbox, where the first and the second shafts 16, 22 are coaxially arranged in relation to each other. The first and the second shafts 16, 22 may alternately be connected and disconnected from the combustion engine's 2 driving shaft 36 with a coupling device 34. The first cogwheel 14 is, according to the embodiment shown in Fig. 2, arranged on the first shaft 16 and the second cogwheel 20 is arranged on the second shaft 22.

Fig. 3 shows a partial view of the gearbox 6 according to Fig. 2, but in a different section plane. Fig. 3 shows that the first and the second cogwheels 14, 20 are in engagement with the respective first and second cogwheel elements 38, 40 which are rotatably journalled on a side shaft 42. By braking down the first and the second shaft 16, 22 to a suitable speed, the cogwheel elements 38, 40 may on the side shaft 42 be connected and disconnected with the side shaft 42 through manoeuvring sleeves 44, which are controlled by manoeuvring forks that are not shown. Thus different gears may be obtained in the gearbox 6. In a double coupling gearbox 6 more than one side shafts 42 are arranged depending on the number of gear steps. Only one side shaft 42, however, is shown on the figures. In the event several side shafts 42 are arranged in the gearbox 6, preferably more synchronisation devices 10 are arranged in the gearbox 6 according to the invention. As an example, a traditional double coupling gearbox with eight synchronisation rings may be replaced by four synchronisation devices 10 according to the invention. Thus the size, weight and manufacturing cost of the gearbox 6 may be reduced.

By combining the double coupling gearbox 6 with a range gearbox 46, a very large number of gear steps may be obtained, which entails increased manoeuvrability of the vehicle 1. When the double coupling gearbox 6 is combined with a range gearbox 46 the synchronisation rings of the range gearbox 46 may be omitted, which entails reduced size, weight and manufacturing cost of the range gearbox 46. An increased life of the double coupling gearbox 6 and the range gearbox 46 may also be expected when traditional synchronisation rings are replaced with synchronisation devices 10 according to the invention.

Fig. 4 shows a partial view of the gearbox according to the invention. A range gearbox 46 is arranged at the output shaft of the gearbox 6. The range gearbox 46 comprises a planetary gear 48 with a sun wheel 50, a planetary wheel holder 52 on which a planetary wheel 54 is journalled, and an axially shiftable ring wheel 56. According to the embodiment shown in Fig. 4, the first shaft 16 consists of the sun wheel 50 in the range gearbox 46, the sun wheel 50 of which is in engagement with the synchronisation device's 10 first brake wheel 12. The second shaft 22 consists of the planetary wheel holder 52, which is journalled on the first shaft 16. The planetary wheel holder 52 is in engagement with the second brake wheel 18, so that the synchronisation device 10 is designed to control the sun wheel 50 and the planetary wheel holder 52 to a speed difference, which allows the ring wheel 56 to be brought into engagement with the planetary wheel holder 52 or with a gearbox house 58 arranged around the range gearbox 46, depending on whether the range gearbox 46 is to be shifted to a low or a high gear. The axial shifting of the ring wheel 56 is achieved with a manoeuvring fork which is not shown.

The components and features specified above may within the framework of the invention be combined between different embodiments specified.