TECHNICAL FIELD

The present invention relates to an axle for a vehicle.

BACKGROUND ART Heavy vehicles are provided with a driven rear axle that is adapted to power the vehicle. Some vehicles are provided with more than one driven or non-driven rear axles. Further, vehicles are provided with one or more front axles which may also be driven or non-driven.

The main task of a driven rear axle is to transmit driving power from the engine out to the driving wheels. The rear axle comprise a rear axle housing, normally made of cast-iron, and helical gears that angle the driving power 90°. The driving power is then transmitted to the driving shafts and on to the wheels.

The input shaft of a driven rear axle is referred to as the pinion. It is journalled in two taper roller bearings in front and in a straight roller bearing at the rear. The rear bearing has the task of keeping the pinion in place against the crown wheel. The driving power is transmitted from the pinion to the crown wheel, which is fitted to the differential housing. Due to the fact that the pinion and crown wheel rotate at a 90° angle to each other, the driving power can be transmitted to the driving wheels via the drive shafts.

The rear axle housing is further provided with a differential which adapts the speed of the driving wheels at the same time as retaining the total driving power. The differential allows the drive wheels to travel with different speeds when the vehicle turns without putting excessive stress on the drive shafts. The differential is fitted in a differential housing in the rear axle housing. The rear axle is normally provided with a differential lock by which the drive shafts can be locked to each other, bypassing the differential. The drive shafts are connected to the drive wheels.

The rear axle housing is cast in iron and is provided with hollow axle beams. The axel housing is provided with a plurality of different attachment positions, adapted to hold e.g. an anti-roll bar, a V-stay, shock absorbers, suspension components etc, but also smaller components such as the differential switch, cables and tubing. The shape of the rear axle housing is thus relatively complicated and thus difficult to manufacture. Although several attachment means can be cast with the rear axle housing, some components such as the air suspension member adapted to hold the air suspension bellows are however to large and complicated to cast together with the rear axle housing. The air suspension member is thus produced separately and attached to the rear axle housing with fastening means. To produce a complete cast rear axle housing is difficult and there are only a few manufacturer that has the knowledge and the facilities to produce such large and complicated components. With a modular axle housing design, it will be easier to find a suitable manufacturer. Further, the attachment of external components such as the air suspension member adds weight and reduces ground clearance for the vehicle.

It is also possible to weld a rear axle housing from several preformed parts. Such a solution is however time consuming and is not suitable for heavy vehicles, where high loads are present, especially for vehicles used in construction sites and in rough terrain. The same applies to non-driven rear axle housings and also to driven front axles, which are often manufactured in the same way. Non-driven front axles may also be cast.

US 7 585 032 discloses a modular front axle assembly comprising a first tube assembly and a second tube assembly interconnected by a centre section. The axle assemblies may be provided with different centre sections, such that a non-driving front axle includes a sleeve interconnecting the first and the second tube assemblies. A driving front axle includes a differential housing interconnecting the first and second tube assemblies.

JP 2004 291 926 discloses an axle housing intended to replace a welded axle housing. The axle housing comprises a right axle member, a central banjo-shaped part and a left axle member. The axle members are formed of a pipe member through a hydro-form and are welded to the central part. With this arrangement, the axle housing can be formed through a hydro- form with a reduced number of parts which reduces the number of welded parts.

In these documents, different solutions for a modular axle housing are described. These solutions may work well for some applications. There is however room for improvements.

DISCLOSURE OF INVENTION

An object of the invention is therefore to provide an improved axle housing which allows for a weight reduction of the axle housing. A further object of the invention is to provide an improved axle housing which allows for an improved ground clearance. A further object of the invention is to provide an improved axle housing which is modular and assembled from several smaller parts. A further object of the invention is to provide an improved axle housing having an integrated air suspension member. A further object of the invention is to provide an improved axle housing which is cost effective to produce.

The solution to the problem according to the invention is described in the characterizing part of claim 1. The other claims contain advantageous further developments of the inventive axle housing. In a axle housing for an axle assembly for a vehicle, comprising a central section and two hollow axle beams, the object of the invention is achieved in that each axle beam comprises a mid section and an outer section, where the mid section is fixedly attached to the central section, where the outer section is fixedly attached to the mid section and where the mid section comprises suspension attachment means.

By this first embodiment of the axle housing according to the invention, an axle housing which is manufactured from several sections is provided, where a suspension attachment is integrated in a mid section. The sections are attached to each other in order to create an axle housing. One section comprises a suspension member such that a complete rear axle housing with an integrated suspension member is obtained.

In a development of the inventive axle housing, the central section of the axle housing is adapted for holding a pinion, a crown wheel and a differential and the two hollow axle beams are adapted to hold two drive shafts. In this way, a driven axle housing is obtained.

In a further development, an air suspension attachment is integrated in the mid sections. By providing the mid sections with an integrated suspension member, an axle assembly with an air suspension member is obtained, which has a reduced weight and an improved ground clearance compared with a conventional axle housing having a traditional suspension member attached to the rear axle housing.

One advantage of the inventive axle housing is that a rear axle housing with an integrated air suspension member can be obtained. This has the advantage that the weight of the rear axle assembly can be reduced for a rear axle with the same stiffness, since the fastening means for the air suspension member can be left out. A further advantage is the attachment of the air suspension member to the rear axle housing is more rigid with reduced tolerances, since all air suspension members will be mounted in the same way. A further advantage of an integrated air suspension member is that the regular air suspension extends under the rear axle housing since it is mounted underneath the rear axle housing. The ground clearance with an integrated air suspension member is thus improved. A further advantage is that the sections making up the axle housing are smaller and thus easier to manufacture. In this way, the different sections can be produced by different suppliers and they can also be produced by using different production methods and/or by using different materials. It is also possible to provide a section with a more complicated design, since each section is produced separately.

The axle housing may be manufactured from cast iron or forged steel. Different sections may also be manufactured by either material. The manufacturing process depend e.g. on the requirements of the axle housing. The sections may be welded together. When welding is used to attach the sections to each other, the flanges bearing on each other may be provided with a bevel in order to optimize the flanges for welding. It is also possible to bolt or press fit the sections to each other.

BRIEF DESCRIPTION OF DRAWINGS The invention will be described in greater detail in the following, with reference to the attached drawings, where

Fig. 1 shows a view of a known conventional rear axle housing with a mounted air suspension member,

Fig. 2 shows a view of a rear axle housing with an air suspension member according to the invention, and

Fig. 3 shows a view of an unassembled rear axle housing according to the invention, Fig. 4 shows a view of a mid section with a leaf spring member rear axle housing according to the invention, and

Fig. 5 shows a view of a non-driven front axle housing according to the invention. MODES FOR CARRYING OUT THE INVENTION

The embodiments of the invention with further developments described in the following are to be regarded only as examples and are in no way to limit the scope of the protection provided by the patent claims. In the described example, a driven rear axle housing is used to exemplify the inventive axle housing. Driven and non-driven front and rear axle housings will also display the same advantages.

Fig. 1 shows a prior art rear axle housing 40 adapted for an air suspension. The rear axle housing is made from cast iron and the central housing and the axle beams 41 are cast in one piece. An air suspension member 42 is attached to the lower side of the axle beam with shackles that engage with protruding attachment shoulders 46 integrated in the cast rear axle housing in a known manner. The air suspension member 42 comprises a front air suspension attachment leg 43 and a rear air suspension attachment leg 44, to which the air suspension bellows 45 are mounted. In order to provide a secure and stable attachment of an air suspension member to the rear axle housing, the attachment section of the air suspension member is relatively large and extends well below the axle beam. This impedes the ground clearance of the vehicle. The size and weight of the air suspension member and the fastening shackles adds weight to the vehicle. Further, the attachment of the air suspension member to the axle beam may flex some during high loads, which may affect the stability of the vehicle.

Such a known rear axle housing is widely used for heavy vehicles, such as trucks, buses and construction vehicles. One problem with this type of rear axle housing is that it is relatively difficult to produce such large cast pieces. This also makes it difficult to introduce changes to the rear axle housing, which in turn makes the production inflexible. Further, the machining of the rear axle housing is difficult due to the large size of the rear axle housing.

Figures 2 and 3 show a rear axle housing according to the invention. The inventive rear axle housing 1 comprises a central section 2, a first axle beam 3 and a second axle beam 4. On the shown rear axle housing, the first axle beam 3 will be positioned on the left side of the vehicle when the rear axle housing is mounted on a vehicle, and the second axle beam 4 will be positioned on the right side of the vehicle. The first axle beam 3 comprises a first mid section 5 and a first outer section 7. The second axle beam 4 comprises a second mid section 6 and a second outer section 8. The axle beams 3, 4 are hollow such that a drive shaft can be lead through the axle beams. The drive shaft can further be suspended in roller bearing elements in an axle beam.

Apart from the fact that the central section of the rear axle housing is not necessarily positioned exactly in the centre of the rear axle housing, the rear axle housing is substantially symmetrical with regards to the right and left sides. Thus, only the first axle beam 3, i.e. the axle beam on the left side, will be described in detail. The central section is preferably cast.

The first axle beam 3 comprises the first mid section 5 and the first outer section 7. The mid section 5 comprises in the shown example a front air suspension attachment leg 9 and a rear air suspension attachment leg 10 integrated with an intermediate axle section 11 , where the intermediate axle section is integrated with the front and rear air suspension attachment legs, forming a compact and light air suspension solution. The front air suspension attachment leg 9 is provided with a front air bellows attachment seat 12 and the rear air suspension attachment leg 10 is provided with a rear air bellows attachment seat 13. The air bellows 45 are attached to the air bellows attachment seats in a known manner. The air suspension attachment legs are dimensioned for the intended use and load. The mid sections may be cast or forged. Depending on the type of air suspension used and the axle arrangement of the vehicle, the mid section may be provided with either a front or a rear air bellows attachment leg. The mid section may also be provided with attachment means for a reaction rod or another suspension component.

The first outer section 7 comprises attachment means for the hub, the brake etc. The attachment means of the outer section 7 is identical to the attachment means of an outer section of a conventional rear axle housing, and are not further described. The outer sections are preferably cast, even though it would be possible to forge them.

The central section 2, the mid sections 5, 6 and the outer sections 7, 8 are attached to each other in a fixedly manner. One suitable method to attach the sections to each other is welding. If a welding method using filler material is used, the edges of the sections may be provided with a bevel 14 in order to facilitate the welding process. The edges may also be provided with flanges 15 adapted to position the sections to each other prior to the welding. The sections may also be attached to each other by press fit. The sections are in this case provided with flanges 15 that will provide a secure press fit. The surfaces of the flanges are preferably machined in order to obtain the required tolerances. In the shown example, the central section and the outer sections are provided with flanges extending towards the mid section. The mid section is provided with corresponding indentations. The sections may then be pressed together by an axial force. In one example, the mid section is heated before the sections are assembled. When the mid section cools down, a secure press fit is obtained. It would also be possible to provide the mid section with flanges and to cool the mid section before the assembly. It is further possible to bolt the sections together. When bolts are used to attach the sections together, the sections should comprise flanges that take up vertical and horizontal forces, such that the bolts are not subjected to shearing forces. Bolting is preferably combined with press fit. Fig. 3 shows a view of an unassembled rear axle housing comprising a central section 2, outer sections 7, 8 and mid sections 5, 6 as described above, where the mid sections are provided with an air suspension attachment section. Fig. 4 shows a mid section 20 adapted for the attachment of a leaf spring. The mid section is thus provided with an upper bearing surface 21 for the leaf spring. The mid section is further provided with protruding attachment shoulders 22 adapted for the fastening of the shackles that holds the leaf spring. By using different mid sections adapted for different spring members, a flexible modular axle housing assembly is obtained, which can easily be adapted for different suspensions.

In a development of the inventive rear axle housing, mid sections having different dimensions can be used. In this way, it is possible to provide different rear axle housings in an easy and cost effective way. The mid sections may e.g. have differently dimensioned front and/or rear air suspension attachment legs in order to fit different types of rear axle arrangements, such as single axle or bogie axle arrangements. It is further possible to use different outer sections adapted for e.g. different types of brakes.

The mid section may be adapted both for driven and non-driven axle housings. In this way, a bogie assembly for a truck can be obtained by using the same components. For a 6x4 assembly with two driven rear axles, the same central section is used for both rear axles. For a 6x2 rear axle assembly, with one driven axle, different central sections are used for the two rear axles. Fig. 7 shows an example of a non-driven front axle housing according to the invention. The axel housing comprises a straight hollow central section 30, a first mid section 31 , a second mid section 32, a first outer section 33 and a second outer section 34. The mid sections are preferably provided with suspension attachment means, in the shown example protruding attachment shoulders 35 adapted to hold leaf spring attachment shackles. The outer sections are adapted for the attachment of steering knuckles, e.g. by using king pins.

The invention is not to be regarded as being limited to the embodiments described above, a number of additional variants and modifications being possible within the scope of the subsequent patent claims.

REFERENCE SIGNS

1 : Rear axle housing

2: Central section

3: First axle beam

4: Second axle beam

5: First mid section

6: Second mid section

7: First outer section

8: Second outer section

9: Front air suspension attachment leg

10: Rear air suspension attachment leg

11 : Intermediate axle section

12: Front air bellows attachment

13: Rear air bellows attachment 14: Bevel

15: Flange

20: Mid section

21 : Bearing surface

22: Shoulder

30: Central section

31 : First mid section

32: Second mid section

33: First outer section

34: Second outer section

35: Shoulder

40: Rear axle housing

41 : Axle beam

42: Air suspension member

43: Front air suspension attachment leg

44: Rear air suspension attachment leg

45: Air bellows

46: Attachment shoulder