GB2399323A

GB2399323A - A live axle particularly for urban buses with low floors

Info

Publication number: GB2399323A
Application number: GB0405771A
Authority: GB
Inventors: Luciano Bologna; Riccardo Sorbini
Original assignee: Graziano Trasmissioni SpA
Current assignee: Dana Graziano SRL
Priority date: 2003-03-13
Filing date: 2004-03-15
Publication date: 2004-09-15
Anticipated expiration: 2024-03-15
Also published as: GB0405771D0; GB2399323B

Abstract

The live axle (1) comprises a rigid support casing or axle housing (2), including an intermediate tubular portion (3) and a first and second housing end portion (4, 5), and a differential (6) fitted in the casing (2) at a first housing end portion (4) and capable of the split transfer of torque from a power input device (7) accessible from the outside of the casing (2) with two half-shafts (8, 9) which are connected to respective speed reducers (16, 17), fitted respectively in one and the other housing end portion (4, 5) of the casing or axle housing (2). The differential (6) comprises a crown wheel (11) which extends transversely to the half-shafts (8, 9) and which is partially immersed in a lubricant provided in the support casing or axle housing (2). A balance pipe (40) extends between the housing end portions (4, 5) of the casing or axle housing (2), to balance out at least in part a difference between the levels and the temperatures of the lubricant contained in the housing end portions (4, 5) of the support casing or axle housing (2).

Description

1 2399323

A LIVE AXLE PARTICULARLY FOR URBAN BUSES WITH LOW FLOORS

The present invention relates to a live axle, particularly for urban buses with low floors.

More specifically, the subject of the invention is a live axle of the inverted portal type comprising: a rigid support casing or axle housing, including an intermediate tubular portion and a first and second housing end portion, a differential, fitted in the casing at a first of its housing end portions and capable of the split transfer of drive torque from a power input device accessible from the outside of the casing with two half-shafts which are connected to respective speed reducers, fitted respectively in one and the other housing end portion of the casing; the differential comprising a crown wheel which extends transversely to said half-shafts and which is partially immersed in a lubricant provided in the support casing or axle housing.

In live axles of this type produced according to prior art, the rotation of said crown wheel of the differential is liable in operation to cause a flow of lubricant towards a housing end portion of the casing. This represents a disadvantage since it tends to create an accumulation of lubricant in an end portion of the axle housing and the quantity of lubricant effectively available in the other end portion of the axle housing is correspondingly reduced.

A purpose of the present invention is therefore to produce a live axle of the above- mentioned type which enables the disadvantage described above to be overcome.

This and other purposes are achieved according to the invention with a live axle of the type specified above, characterised in that it comprises at least one balance pipe which extends between the housing end portions of the casing or axle housing and is capable of balancing out at least in part a difference between the levels and the temperatures of the lubricant contained in the above-mentioned housing end portions.

The balance pipe which extends between the housing end portions of the casing or axle housing also enables the difference in temperature of the lubricant contained in said I housing end portions to be balanced out.

Other characteristics and advantages of the invention will become clear from the following detailed description which is given purely by way of non-limiting example, with reference t to the appended drawings in which: Figure 1 is a view in front elevation of a live axle according to the present invention; Figure 2 is a plan view from above of the live axle according to Figure 1; Figures 3 and 4 are sectional views substantially along the lines III-III and IV-IV respectively in Figure 1; Figure 5 is a view at an enlarged scale, essentially along the section line V-V in Figure 3; Figure 6 shows at an enlarged scale a detail of Figure 4; Figure 7 is a partial sectional view substantially along the line VII-VII in Figure 3; :: Figure 8 is a section similar to that in Figure 4 and shows a variant embodiment; and Figure 9 is a sectional view along the line IX-IX in Figure 8.

In the drawings, the number I is used to indicate as a whole a drive axle according to the invention. This axle is of the inverted portal type and comprises a rigid support casing or: axle housing, indicated as a whole by the number 2.

This casing or axle housing 2 includes an intermediate tubular portion 3, the opposite ends 3a and 3b of which are flanged, and are connected to respective housing end portions 4 and of the casing or axle housing (this can be seen in particular in Figure 4, for example).

The axle I comprises a geared differential indicated as a whole by the number 6 (Figures 4, and 7), fitted in the casing or axle housing at its first housing end portion 4, and intended for the split transfer of drive torque from a power input device 7 (Figures 2, 4 and 7) to two halfshafts 8 and 9 (Figure 4).

In the embodiment shown by way of example, the power input device 7 is connected in rotation to a bevel pinion 10 which meshes with a crown wheel 11, which is integral with the cage 12 of the differential 6 and is coaxial with the half-shaft 9. In a manner known in itself, respective gear wheels or sun gears 13 and 14 are keyed to the two hall:shafts 8 and 9 and mesh with bevel or planet gears 15 (Figures 4, 5 and 7).

As can be seen in particular in Figure 4, the half-shafts 8 and 9 are connected to respective geared speed reducers 16 and 17, which are fitted respectively in one and the other housing end portion 4 and 5 of the support casing or axle housing 2.

In a manner known in itself, in operation the reduction units 16 and 17 cause rotation of the wheel carriers 18 and 19 respectively associated with them (Figures 1 and 2).

In a manner also known in itself, respective brake operating cylinders 20 and 21 are connected to the housing end portions 4 and 5 of the axle housing 2. Moreover, extending from each of said housing end portions of the axle housing are respective pairs of arms 22, 23 and 24, 25 respectively which connect to the suspension (Figures 1 to 3).

With reference to Figures 4 to 7, in the right-hand end housing structure 4 of the axle there are substantially formed two contiguous chambers, indicated as 30 and 31, separated by a transverse wall 32 through which the half-shaft 8 passes. The differential 6 is housed in the chamber 30. The right-hand reduction unit 16 is housed in the chamber 31.

At the top, the chamber 30 has an opening 33 (Figure 5) which is closed by a cover 34, secured by means of screws 35 (see also Figure 2) As can be seen in Figure 5, the cover 34 has an upper wall 36 and, at a distance from it, a lower wall 37, between which a passage 38 is formed. Adjacent to the periphery of the crown wheel 11 of the differential 6, the lower wall 37 of the cover 34 has a slot 37a through which the chamber 30 communicates with the passage 38 formed inside the cover 34.

At the opposite end, the passage 38 in the cover 34 communicates with a passage 39 made in the wall 32 of the portion 4 of the axle housing. This passage 39 opens into the chamber 31 where, as can be seen in Figure 4, the reduction unit 16 is fitted.

In operation, due to the effect of the rotation imparted to the power input device 7, the crown wheel 11 of the differential 6 is caused to rotate.

The ring gear 11 is partially immersed in lubricating oil, and its rotation tends to cause a flow of lubricating oil which, drawn from the intermediate tubular portion 3 of the axle housing, tends to cause an accumulation of lubricant in the end portion 4 of the axle housing. In particular, a portion of the flow of lubricant caused by rotation of the crown wheel 11 finds its way into the passage 38 in the cover 34 (Figure 5) through the slot 37a in this cover, and then via the passage 39 reaches the chamber 31 where the right-hand reduction unit 16 is located. This flow of oil descends to the base of the chamber 31 into which, as shown in Figures 4 and 6, there extends a first end 40a, cut in a step, of a balance pipe 40, which advantageously extends through the intermediate tubular portion 3 of the axle housing 2. The other end 40b of the pipe 40 (Figure 4) emerges at the chamber 41 formed in the end portion 5 of the axle housing, at the left-hand reduction unit 17.

The tube 40 creates a "communicating vessels" situation between the end portions of the axle housing 2 and in operation balances out at least in part a difference between the levels of lubricant contained in the end portions 4 and 5 of the support casing or axle housing 2 caused by the effect of the pumping action deriving from rotation of the crown wheel 11 of the differential 6.

The lubricating oil present inside the casing portion 4 containing the components in rotation such as the differential 6, the bevel pinion 10 and the crown wheel 11, because of the vigorous beating to which it is subjected by these rotating components, tends to reach temperatures substantially higher than those which may be found inside the housing portion 5.

The balance pipe which extends between the housing end portions of the casing or axle housing is therefore also able to balance out a difference in temperature of the lubricant contained in the above-mentioned housing end portions.

With reference to Figures 4, 5 and 7, the opposite ends of the cage 12 of the differential with epicyclic gearing 6 are supported in rotation by means of respective tapered roller bearings 50 and 51.

A threaded adjustment ring 52 is arranged axially in series with the bearing 51, at the end 3a of the intermediate tubular portion 3 of the axle housing 2.

On the other hand, the other bearing support 50 is advantageously fitted radially and axially inside an associated threaded adjustment ring or bush 53, screwed into a corresponding thread arranged in a passage 54 produced in the wall 32 which separates the chamber 30 of the differential 6 from the chamber 31 in which the reduction unit 16 is located. The fact that the bearing support 50 is fitted into the adjustment ring 53 enables the differential unit 6 and the power input 7 to be brought as close as possible to the chamber 31 of the reduction unit 16, thus minimising the space occupied by the differential 6 at the right-hand end of the axle.

The ring 53 has a plain external portion to ensure adequate location of the bearing 50 in the seating and a threaded portion to allow axial movement and therefore adjustment of the bearings 50 and 51 of the differential 6.

The two rings 52 and 53 have internal teeth 71 and 72 to allow them to be turned separately or simultaneously by means of a suitable tool, and, as the two rings have the same thread pitch, to allow axial movement of the differential 6 to give the operating clearance required between the flanks of the teeth of the crown wheel 11 and of the pinion 10.

Advantageously, as can be seen in Figure 7 only, in the wall 32 which separates the chamber 30 of the differential from the chamber 31 of the reduction unit 16 there is produced a channel or passage 60 such as to allow lubrication of the bearing 50, on the side of this bearing facing the reduction unit 16, and of the bearing 70 on the side of this bearing facing the differential.

Figures 8 and 9 illustrate a variant embodiment in which the balancing action provided through the balance pipe 40 is made more effective in operation.

A variant embodiment according to Figures 8 and 9 largely corresponds to the embodiment already described with reference to Figures 1-7.

Consequently, in Figures 8 and 9 the reference numbers already used previously are assigned to parts and components already described.

With reference to Figures 8 and 9, in the variant embodiment the end 40a of the balance pipe 40 has a side inlet opening, indicated by 40c, facing substantially upwards.

In the vicinity of this inlet opening 40c of the balance pipe a side wall 30a of the chamber of the differential forms a surface 30b inclined downwards in the manner of a chute (Figure 9). This inclined surface 30b is able in operation to convey towards the inlet opening 40c of the balance pipe a part of the flow of lubricating oil centrifuged by the effect of rotation of the crown wheel 11 of the differential 6.

As can be seen in Figure 8 in particular, the crown wheel 11 of the differential has substantially tapering teeth, so that in operation it is liable to generate a centrifugal flow of lubricating oil in directions having a component transverse to the axis of this crown wheel and a longitudinal component, that is parallel to said axis. Advantageously, as can be seen in figure 8, the inlet opening 40c of the balance pipe 40 has a longitudinal extension greater than the axial extension of the crown wheel 11 of the differential, in particular on the side facing the vertex of this crown wheel. Consequently, in operation the inlet opening 40c provides effective collection of the flow of oil centrifuged by said crown wheel 11 of the differential. l

Naturally, the principle of the invention remaining the same, the forms of embodiment and details of construction may be varied widely with respect to what has been described and À illustrated purely by way of non-limiting example, without thereby departing from the scope of the invention, as defined in the appended claims.

Claims

À 1. A live axle (1), particularly for urban buses with low floors, in particular a live axle (1) of the inverted portal type, comprising: a rigid support casing or axle housing (2), including an intermediate tubular portion (3) and a first and second housing end portion (4, 5), a differential (6) fitted in the casing (2) in a first housing end portion (4) and capable of the split transfer of drive torque from a power input device (7) accessible from the outside of said casing (2) with two half-shafts (8, 9) which are connected to respective speed reducers (16, 17) fitted respectively in one and the other housing end portion (4, 5) of the casing or axle housing (2); the differential (6) comprising a crown wheel (11) which extends transversely to said half-shafts (8, 9) and which is partially immersed in a lubricant provided in the support casing or axle housing (2) ; the live axle being characterized in that it comprises at least one balance pipe (40) which extends between the housing end portions (4, 5) of the casing or axle housing (2) and is capable of balancing out at least in part a difference between the levels and the temperatures of the lubricant contained in said housing portions (4, 5) of the support casing or axle housing (2).
2. A live axle according to claim 1, in which said balance pipe (40) runs inside the above-mentioned intermediate tubular portion (3) of the axle housing (2).
3. A live axle according to claim 1 or 2, in which in said first end portion (4) of the casing or axle housing (2) a collecting passage or duct (38) is produced which has an intake opening (37a) adjacent to said crown wheel (11) of the differential (6) and is capable of conveying a flow of lubricant towards the intake of said balance pipe (4o)
4. A live axle according to claim 3, in which said collecting passage or duct (38) is produced in a removable cover (34) which closes an opening (33) arranged in a wall of said first end portion (4) of the casing or axle housing (2).
5. A live axle according to claim 4, in which in said first end portion (4) of the casing or axle housing (2) are formed a first chamber (30) in which the differential (6) is fitted and a second chamber (31) in which a speed reducer (16) is fitted; said first and second chamber (30, 31) being separated by an intermediate dividing wall (32) in which is produced at least one passage (39) which places said collecting passage or duct (38) in communication with said second chamber (31); the above mentioned balance pipe having an intake end (40a) which extends into the lower part of said second chamber (31).
6. A live axle according to claim 5, in which the differential (6) is of the epicyclic gearing type and comprises a cage (12) which has one end supported rotatably in an opening (54) arranged in said intermediate dividing wall (32); said end of the cage (12) being inserted into a bearing support (50) which is fitted axially and radially inside a threaded adjustment ring or bush (53) screwed into a correspondingly threaded portion of said opening (54).
7. A live axle according to claim 6, in which in said intermediate wall (32) is produced a lubrication passage (60) which places the chamber (30) of the differential (6) in communication with an area facing the side of said support or bearing (50) which faces the opposite way to the differential (6).
8. A live axle (1) according to any one of the preceding claims, characterized in that: the end (40a) of the balance pipe (40) which runs near the above-mentioned crown wheel (11) of the differential (6) has a side inlet opening (40c) adjacent to said crown wheel (11), and in that; adjacent to said side inlet opening (40c) of the balance pipe (40) a side wall (30a) of a chamber (30) containing the differential (6) forms a surface inclined downwards (30b) in the manner of a chute, able in operation to convey towards said inlet opening (40c) part of the flow of lubricating oil generated by the effect of the rotation of said crown wheel (11).
9. A live axle according to claim 8, in which said crown wheel (11) has substantially tapering teeth so that in operation it is liable to generate a centrifugal flow of lubricant in directions having a component transverse to the axis of said ring gear (11) and a longitudinal component, that is parallel to said axis, and in which the inlet opening (40c) of the balance pipe (40) has a longitudinal extension greater than the axial extension of said ring gear (41), in particular on the side facing the vertex of said ring gear ( 1 1).