WO2015092471A1

WO2015092471A1 - Differential arrangement and driven axle and automotive vehicle with improved lubrication

Info

Publication number: WO2015092471A1
Application number: PCT/IB2013/003167
Authority: WO
Inventors: Thomas BARILLOT
Original assignee: Volvo Truck Corporation
Priority date: 2013-12-20
Filing date: 2013-12-20
Publication date: 2015-06-25

Abstract

The invention relates to a differential arrangement (14) for a driven axle (2) of an automotive vehicle comprising: • a differential having a ring gear (22) and a. drive pinion (19), • an oil gutter (32), a radial section of which at least partly peripherally encases a corresponding radial section of the ring gear, characterized in that the differential arrangement (14) has a first (H1) and a second (H2) halves delimited by a first reference plane (P1) containing the ring gear rotation axis and perpendicular to the drive pinion axis (Y2), in that the drive pinion (19) meshes with the ring gear (24) at a meshing location in the first half of the differential arrangement (14), and in that the second extremity (32B) is located angularly along the circumference of the ring in the first half (H1) of the differential arrangement (14).

Description

DIFFERENTIAL ARRANGEMENT AND DRIVEN AXLE AND AUTOMOTIVE VEHICLE

WITH IMPROVED LUBRICATION

TECHNICAL FIELD

The invention concerns a differential arrangement for a driven axle and a driven axle.

BACKGROUND

A driven axle includes an axle housing having at least a central differential receiving portion. In the case of rigid axles, the axel housing may also have two lateral tubular wheel shaft receiving portions extending on each sides of the central differential receiving portion. A differential usually includes a ring gear which is in meshing engagement with a drive pinion gear. A rod may extend diametrically across the ring gear, so that it rotates with the ring gear. A pair of first conical gears is rotatably mounted on the rod. Each of the first two conical gears is in a meshing engagement with a second conical gear, where each second conical gear is mounted on the extremity of each lateral tubular wheel drive shaft.

It is known that the drive pinion, the ring gear and all of the gears of the differential have to be lubricated during operation. In particular, the meshing location between the drive pinion gear and the ring gear has to be lubricated carefully as it is a particularly important zone. Also, the drive pinion may be mounted on bearings which, due to their location, may be hard to lubricate.

In usual driven axles, the central differential receiving portion of the axle housing defines a sump for receiving oil. The ring gear is partially immersed in this sump so that the teeth of the ring gear are splashing in oil while the ring gear is spinning. The splashed oil allows dissipating frictional heat generated during the meshing engagement and minimizes the generation of steel shavings. However, even though this lubrication system is cost saving, a large amount of oil is necessary to ensure the lubrication of the whole differential, which leads to a relatively high level of the oil inside the sump. Thereupon, this amount of oil generates frictional forces which are opposed to the rotation of the ring gear. This effect is better known as "churning losses" or "splashing losses". This means that a part of the mechanical power which is received by the axle is consumed by the resistance of the lubricant to the rotation of the ring gear. To solve this drawback, US-A-5 505 112 discloses a driven axle including a differential arrangement having a gutter which encases a ring gear of the differential. This gutter extends around a lower portion of the ring gear. The ring gear has the largest diameter amongst all of the gears of the differential. The gutter comprises holes for draining oil from the sump. In operation, the oil level inside the gutter is lower than the level in the sump so that only the teeth of the ring gear are splashing in oil while the differential is running. It is expected that the total volume of oil which is splashed, especially towards the upper portion of the differential, will be reduced. This may affect the lubrication in this upper portion, especially in locations which are somewhat less exposed to oil splashing.

SUMMARY The invention intends to solve these drawbacks by proposing a differential arrangement which allows lubricating correctly the meshing engagement location between the drive pinion gear and the ring gear while using less oil than in prior art devices.

To this end, the invention concerns a differential arrangement for a driven axle of an automotive vehicle comprising:

· a differential having

- a ring gear defining a ring gear rotation axis, and

- a drive pinion having a pinion shaft extending along a drive pinion axis and a pinion gear engaging the ring gear for rotating the differential around the ring gear rotation axis,

· an oil gutter, a radial section of which at least partly peripherally encases a corresponding radial section of the ring gear, said gutter extending angularly around a part of the circumference of the ring gear around the ring gear rotation axis from a first angular extremity to a second angular extremity along a main rotation direction of the ring gear.

The differential arrangement has a first and a second halves delimited by a first reference plane containing the ring gear rotation axis and perpendicular to the drive pinion axis, in that the drive pinion meshes with the ring gear at a meshing location which is located on the first half of the differential arrangement.

According to an aspect of the invention, the second extremity of the gutter is located angularly along the circumference of the ring in the first half of the differential arrangement. Thanks to the invention, the oil gutter is able to guide the oil flow in the differential along the circumferential direction of the ring gear, way past the location at which the ring gear emerges out of the level of oil in the housing, and when oil reaches the second extremity of the gutter, oil may be expelled in a direction which favors oil projection on the drive pinion, preferably in the direction of the meshing location between the drive pinion gear and the ring gear and/or in the direction of the pinion bearings by which the drive pinion is joumalled with respect to the axle.

According to further aspects of the invention which are advantageous but not compulsory, such a differential arrangement may incorporate one or several of the following features:

- The second extremity may located angularly around the ring gear rotation axis at least 30°, or even more preferably at least 45°, past the first reference plane in the direction of the main rotation direction, in the first half of the differential arrangement. This allows oil to be channeled until even closer to the drive pinion, enhancing the part of oil susceptible of directly impacting the drive pinion, while minimizing the part of the oil flow which may impact the housing walls before arriving at the drive pinion.

- The first extremity may be located angularly around the ring gear rotation axis before the first reference plane in the direction of the main rotation direction, in the first half of the differential arrangement. This may ensure that the gutter extends long enough in a lower region of the housing, in an oil sump, so that some oil can enter in the channel to be guided by the gutter up the its second extremity.

- The first extremity and the second extremity of the gutter are located on the first half of the ring gear. This translates in the gutter extending at least 180° around the second half of the ring gear which is located opposite the meshing location. Such configuration allows both that enough oil is picked up in the gutter by the rotation the ring gear and that it is discharged towards an area where the expelled oil has the most chance of coming into contact with the meshing location and/or with the drive pinion bearings. Preferably though, the gutter extends even more than 180°, such as at least 240°.

- The second extremity of the oil gutter may be configured so as to expel oil in the direction of the drive pinion, when the ring gear is rotating in its main rotation direction.

Preferably, oil is expelled in the direction of at least one of the meshing location and/or or of the drive pinion shaft, i.e. of at least one of the drive pinion bearings.

- The gutter may have at least one oil intake opening which is located on a wall portion. It may be on a lateral wail portion having an internal surface facing towards the teeth of ring gear and an external surface facing away from the ring gear. Such openings may allow oil to enter the gutter. - Said opening may face towards the exterior of the oil gutter in a direction which is rearwardly oriented compared to a forward motion direction of the ring gear. Such orientation of the gutter openings may tend to favor oil entry in the gutter rather than oil exit when the ring gear rotates in the gutter is its forward motion.

- The differential arrangement may have a lower half and an upper half delimited by a second reference plane, containing the ring gear rotation axis and perpendicular to the first reference plane. The first extremity may then be located in the lower half of the differential arrangement while the second extremity may be located in the upper half of the differential arrangement.

- The differential arrangement may comprise a differential carrier for carrying the differential, and the gutter may be fitted to the differential carrier, so that the differential carrier, together with the differential and the gutter as a unit, can be removably attached to an axle housing. This may ease considerably the assembly of the driven axle. In such an arrangement, the carrier, the differential and the gutter can be removed and attached as one unit from the housing. Also, the gutter can be mounted with tight installation tolerances with respect to the ring gear, thus minimizing the distance between the gutter wall portions and the ring gear.

- Typically, the differential arrangement may have a housing which is a central differential receiving portion of an axle housing. The central differential receiving portion may have a main opening through which the differential can be mounted, and the, differential carrier may be removably attached to the axle housing at the main opening.

- In some embodiments, the first extremity of the gutter is located above an oil level in the axle housing, especially during operation. This may allow limiting the quantity of oil in contact with the ring gear, thus limiting churning losses.

- The main rotation direction of the ring gear typically corresponds to a forward direction of travel of an automotive vehicle having a driven axle equipped with the differential arrangement.

- The first extremity may be located below the meshing location where the drive pinion meshes with the ring gear. This allows that the gutter does not interfere with the drive pinion, even if the gutter is arranged very close to the gutter, for example between 2 and 20 mm, for example equal to 5 mm.

- the housing may comprise a central differential receiving portion of an axle housing having also two lateral tubular wheel drive shaft receiving portions, wherein the central differential receiving portion has a main opening through which a differential can be mounted. In such a design, the central differential receiving portion of the axle housing may define a sump for receiving oil, and the gutter may comprise a lower portion which extends in the sump.

According to another aspect of the invention, the invention concerns a differential arrangement for a driven axle of an automotive vehicle comprising:

• a differential having

- a ring gear defining a ring gear rotation axis, and

• an oil gutter, a radial section of which at least partly peripherally encases a corresponding radial section of the ring gear, said gutter extending angularly around a part of the circumference of the ring gear around the ring gear rotation axis from a first angular extremity to a second angular extremity along a main rotation direction of the ring gear, where the gutter may have at least one oil intake opening which is located on a wall portion, said opening facing towards the exterior of the oil gutter in a direction which is rearwardly oriented compared to a forward motion direction of the ring gear. In such arrangement, if those openings are located in a part of the arrangement where oil is present in operation, i.e. in a lower part of the gutter which extends below the level of oil in the housing, it may allow a limited entry of oil in the gutter, enough to ensure that the proper quantity of oil is expelled from the second extremity of the gutter. The rearward orientation may also limit flow turbulences due to the flow of oil through the opening and to its contact with the rotating ring gear. Such a differential arrangement may additionally have one or several of the features already discussed above, taken individually or in combination.

Such openings may be formed by a cutout of the lateral wall portion having a flange portion attached to the lateral wall portion by a border portion. The flange portion may be bent outwardly of the gutter, away from the ring gear, and the border portion may be located at a forward extremity of the flange when considering the main rotation direction of the ring.

The invention further relates to an automotive vehicle having a driven axle, wherein said automotive vehicle has a main forward direction of travel, and wherein the driven axle comprises a differential arrangement having any of the preceding features. The differential arrangement is preferably mounted on the vehicle such that upon movement of the vehicle along main forward direction of travel, the ring gear rotates in its main rotation direction.

Such an automotive vehicle may have an axle housing having a central differential receiving portion in which the differential is received. The central differential receiving portion may have a lower portion defining a sump for receiving oil by gravity, and the ring gear may comprise a lower portion which extends in the sump. Upon rotation of the ring gear along its main rotation direction corresponding to forward movement of the vehicle, a part of the ring gear in meshing contact with the drive pinion may move downwards towards the sump. The first extremity of the gutter may be located below the meshing location where the drive pinion meshes with the ring gear, while the second extremity of the gutter may be located above said meshing location.

According to some embodiments of the invention, a differential arrangement is provided comprising:

· a differential having

- a ring gear defining a ring gear rotation axis, and

· an oil gutter, a radial section of which at least partly peripherally encases a corresponding radial section of the ring gear, said gutter extending angularly around a part of the circumference of the ring gear around the ring gear rotation axis from a first angular extremity to a second angular extremity,

wherein the differential arrangement has a first and a second halves delimited by a first reference plane containing the ring gear rotation axis and perpendicular to the drive pinion axis, and wherein the drive pinion meshes with the ring gear at a meshing location which is located on the first half of differential arrangement,

characterized in that the gutter extends over more than 180°, preferably more than 240°, around the ring gear axis, along the second half of the differential arrangement, and the first extremity and the second extremity of the gutter are located on the first half of the differential arrangement.

In such embodiments, the gutter may extend over more than 30° around the ring gear axis along the first half of the differential arrangement, either on the side of the first extremity of the gutter, on the side of the second extremity of the gutter or on both sides. The invention also concerns a driven axle comprising an axle housing having a central differential receiving portion, wherein the central differential receiving portion has a front opening through which a differential can be mounted. The axle also has a differential carrier for holding the differential, the differential carrier being removably attached to the axle housing at the front opening. The differential comprises a ring gear. According to the invention, the driven axle comprises a U profiled oil gutter, in section by a radial plane, a radial section of which encases a corresponding radial section of the ring gear, said gutter extending around a part of the circumference of the ring gear, and said gutter being fitted to the differential carrier.

Thanks to this aspect of invention, the differential and the gutter for lubricating the differential can be mounted as one unit in the central portion of the axle housing, together with the carrier, which eases considerably the assembly of the driven axle.

According to a further aspect of the invention, which is advantageous but not compulsory the central differential receiving portion of the axle housing defines a sump for receiving oil and the gutter comprises a lower portion which extends in the sump.

Such a driven axle may additionally have one or several of the features already discussed above, taken individually or in combination.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained in correspondence with the annexed figures, and as an illustrative example, without restricting the object of the invention. In the annexed figures:

- figure 1 is an exploded perspective view of a driven axle according to the invention, illustrating a housing and a differential arrangement,

- figure 2 is a longitudinal vertical sectional view of the driven axle of figure 1 in the assembled state,

- figure 3 is a transversal horizontal sectional view, at higher scale, along line Ill-Ill of figure 2,

- figure 4 is a perspective view of a gutter belonging to the differential arrangement of figure 1 , and

- figure 5 is a front view of the differential arrangement of figure 1 when looking in the direction of arrow V of Figure 1 , without the axle housing. DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF INVENTION Figure 1 represents a driven axle 2. More precisely, the driven axle is here a rigid axle which supports a pair of wheels. Such an axle can typically be used to support the rear wheels of a vehicle, such as a truck. However, such an axle can equip other automotive vehicles, including construction equipment machines. Moreover, the invention can also be implemented on a driven axle with independent wheels suspensions. Also, the invention will be described in the context of an axle to be mounted on rear wheels of the vehicle. However, such can axle could also be mounted to support front driven wheels of the vehicles.

Here below, the terms "vertical", "horizontal", "high" and "low" should be interpreted in relation to an orientation of the differential arrangement as shown on figure 3, and which will be detailed below.

The driven axle will be hereinafter described in a case where it is located at the rear of a vehicle. In such a case, it may receive drive power from an engine of a vehicle through a propulsion shaft extending in a longitudinal direction of the vehicle. In the case of a rear axle, the propulsion shaft would be located in front of the axle. In the case of rear tandem or tridem axles, the axle according to the invention can be the first or second or the third of the set of axles. In such a case, the propulsion shaft may be an intermediate propulsion shaft extending between two successive axles. However, the invention can also be implemented on an axle to be mounted as a front axle of the vehicle. In such a case, the axle may receive its drive power from a propulsion shaft extending longitudinally rearwards from the axle.

The driven axle 2 comprises an axle housing 6 which is hollow and extends along a horizontal axis X2, which would typically be transverse to a vehicle longitudinal axis. The housing 6 has a central differential receiving portion 12 and, in the case of a rigid axle, two lateral tubular wheel drive shaft receiving portions 8 and 10 which extend along axis X2 from the central differential portions. The two lateral tubular wheel drive shaft receiving portions 8 and 10 delimit each an opening at their free end, respectively referenced 08 and 010, through which the drive shafts of the wheels can be engaged. Thus, in this example, X2 may also denote the axis of rotation of the rear wheels of the vehicle.

In the following, the invention will be described in the context of an axle having a removable carrier for carrying the differential. However, some aspects of the invention may be implemented in an axle design having a differential carrier which is integral with the differential housing, and where the differential is mounted in the housing through an aperture to be closed by a differential cover.

In the shown embodiment, the central differential receiving portion 12 has a front opening 012 through which a differential 18 can be mounted. The term front opening here corresponds to the case of a rear axle receiving drive power from a propulsion shaft extending in front of the axel. Such front opening 012 would in fact be turned towards the rear in the case of a front axle. The front opening 012 may extend in a substantially vertical and transverse plane. The front opening may be circular, as in the example shown, or of other shapes, such as in the shape of a square, a rectangle or of an ellipsoid.

The differential 8 belongs to the differential arrangement 14 and is supported by a differential carrier 16. The differential carrier 16 may be designed to form a cap for the closing the opening 012. The differential carrier may thus be complementary to the central portion 12 of the housing 6 to form an enclosed volume, which can be roughly spherical, in which the differential assembly 14 is received. The carrier may thus comprise a wall portion 162 having a peripheral contour 164 matching the contour of the front opening 012. The wall portion 162 may have an internal surface 166, which may be generally concave, turned towards the enclosed volume. It may also have an exterior surface 168, which may be generally convex, turned towards the exterior of the axle. The carrier 16 holds the differential 18 but does not support the wheel shafts, as they are received in the tubular portions 8 and 10 of the housing 6. The drive pinion 19 comprises a drive pinion shaft 15 which is to be connected to a powered propulsion shaft, driven by the engine of the vehicle. Preferably, especially in the case of a removable carrier 16, the differential 8 is held exclusively by the carrier 16 or by a part which may remain fitted to the carrier when the carrier is removed from the axle housing. Thus, the differential 18 is preferably not held by the axle housing.

As shown figure 1 , the differential 18 of the differential arrangement 14 can be introduced inside the central portion 12 of the housing 6 by a linear motion F1. More precisely, the differential carrier 16 may be attached to the periphery of the opening 012 by means of bolts, studs, or other removable fasteners which are not represented on the drawings. The linear motion F1 is performed along a longitudinal axis Y2 which is perpendicular to the axis X2 of the housing 6. Therefore, using this differential arrangement 14, the differential 18 can be mounted in one part in the housing 6, which makes the driven axle 2 easy and comfortable to assemble and disassemble as compared to a driven axle wherein each component has to be mounted separately.

As shown figure 2, the differential 18 includes a drive pinion 19 which comprises the drive pinion shaft 5 and a pinion gear 20. The drive pinion 9 is supported and guided in rotation around its axis Y2 with respect to the carrier 16 by at least two pinion bearings 44, preferably conical bearings, which are supported internally on the drive pinion shaft 15 and externally in the carrier. A front extremity of the drive pinion shaft extends outside of the enclosed volume, through the wall portion 162 of the carrier, and may be equipped with a connector for its mechanical connection to the propulsion shaft. The pinion gear 20, which is preferably located at the opposite extremity of the drive pinion shaft 15, here the rear extremity, cooperates with a ring gear 22 for rotating the differential 18 around a ring gear rotation axis X24 which is parallel, in practice coincident, with the axis X2 of rotation of the wheels. To this end, the ring gear 22 is fixed on a differential case 24 and is engaged with the pinion gear 20. In a well-known manner, the differential case 24 is carried by the carrier 26 so as to be able to rotate with respect to the carrier 26 around the transverse axis X24. The carrier 16 may comprise a pair of bearing legs 161 which extend each in a plane perpendicular to axis X24 of the differential case 24, on each side of the differential case. The bearing legs are spaced apart along axis X24. They extend from the internal surface 166 of the carrier wall portion 162, towards the interior of the enclosed volume. The bearing legs 161 may be integral with the wall portion 162 or may be affixed thereto, for example by welding or by screws. Bearing caps 163 may be bolted on the bearing legs to hold differential bearings 165 thanks to which the differential case 24 is rotatably carried with respect to the carrier 16 around axis X24.

The drive pinion 19 is conical. It may form with the ring gear 22 a spiral bevel gear, or a hypoid gear.

For the purpose of this invention, the notion of "vertical" is intrinsic to the differential arrangement 14 and is defined to qualify a first reference plane P1 containing the ring gear rotation axis X24 and perpendicular to the drive pinion axis Y2. Similarly, the notion "horizontal" and is intrinsic to the differential arrangement 14 and is defined to qualify a second reference plane P2 which contains the rotation axis X24 of the differential casing 24 and perpendicular to the first reference plane P1 , thus parallel to the axis Y2 of the drive pinion 19. It is acknowledged that the axis X24 and Y2 may not be coincident, for example in the case of hypoid gears, but that does not prevent from defining the intrinsic horizontality as above. In figure 3, the axis Y2 of the drive pinion 19 is represented as horizontal.

It is also acknowledged that, when fitted on a vehicle, the pinion drive axis Y2 may be at a certain angle with respect to the horizontal as defined by gravity. In common cases, this angle is fairly small, for example less than 10 degrees, or less than 5 degrees. Therefore, in a configuration in which the driven axle is incorporated into a vehicle lying on a flat and horizontal surface (with respect to gravity), such as the ground, the intrinsic horizontality may not correspond to the horizontality as defined by gravity. However, in a common installation such as found on a truck, the first reference plane P1 can usually be considered as essentially vertical, and the second reference plane P2 can usually be considered as essentially horizontal. In the shown example of a differential, a rod 26 is fixedly secured in rotation to the differential case 24 and extends diametrically across the differential case 24, along an axis Y26 which is perpendicular to the axis X24 of rotation of the differential case 24 and of the ring gear 22. The rod 26 supports a first pair of conical gears 28A and 28B. The conical gears 28A and 28B are mounted in rotation on the rod 26 and are engaged with two second conical gears 30A and 30B. The two second conical gears 30A and 30B are arranged transversally on both sides of the differential case 24, with regards to the axis X24. These second conical gears 30A and 30B are each adapted to be fixed to an extremity of each of the wheel drive shafts. To this end, the conical gears 30A and 30B may be hollow and the internal surface of their hollow part may be adapted to mesh with the extremity of the wheel shafts. Thus, the conical gears 30A and 30B are rotating rigidly with the wheel drive shafts around the axis X2. So, the differential 18 includes the drive pinion 19, the ring gear 22, the differential case 24, the rod 26 and the conical gears 28A and 28B.

When the differential 18 is running, the rotation of the drive pinion shaft 15 implies the rotation of the ring gear 22 and of the differential case 24 around the axis X24. Consequently, the rotation of the first conical gears 28A and 28B around the wheel ring gear rotation axis X24 implies the rotation of the second conical gears 30A and 30B around the axis X2 of rotation of the wheel shafts.

When the vehicle is moving in a straight line, the conical gears 28A and 28B do not rotate around themselves, that is around the axis X26. This means that the first wheel shaft engaged in the tubular portion 10 and the second wheel shaft engaged in the tubular portion 8 rotate at the same speed. However, when the vehicle makes a turn, the external wheels are rotating faster than the internal wheels. This difference of rotation speed between the external wheels and the internal wheels implies the rotation of conical gears 28A and 28B around the axis Y26. This rotation of the conical gears 28A and 28B allows the left wheel shaft and the right wheel shaft rotating at a different speed, which is the main function of the differential.

As shown on figure 1 , the central differential receiving portion 12 delimits, in a low portion, a sump S12 for receiving oil. Indeed, different parts of the differential 18 need to be lubricated in order to, on the one hand, dissipate the frictional heat resulting from the engagement between the gears and, on the other hand, prevent a premature wear of the teeth of the gears. On figure 3, an example of the level of oil present in the sump S12 is marked with a dashed line L1. This level of oil L1 is representative of the level of oil in the sump 12 when the vehicle is at rest on a horizontal surface. The differential arrangement 14 includes an oil gutter 32, visible on figures 2 to 5. The gutter 32 is received inside the enclosed volume delimited by the central portion of the axle housing and by the carrier 16. The gutter is preferably fitted on the carrier 16.

As in the shown embodiment, this gutter may have a U profile, when viewed in section in a radial plane containing the axis of the ring gear X24, and may comprise a peripheral portion joining two lateral wall portions. The peripheral portion is substantially cylindrical around axis X32 while the two lateral wall portions are substantially annular discs around axis X32. However, as shown in the figures, the U profile may be more complex. As shown on figure 4, the gutter 32 extends angularly around the ring gear 22 along an annulus centered on an axis X32 which, in an assembled configuration of driven axle 2, is preferably coincident with the rotation axis X24 of the ring gear 22.

For ease of construction and/or of assembly, the gutter 32 can be made out of two parts 320 and 322. In the shown embodiment, each of the two parts extend around the axis X32, one part 302 above the second reference plane P2, which contains axis X32, and the other part 322 below the second reference plane P2. The two parts are two separate physical entities, the part 322 constituting a lower part while the part 320 constitutes an upper part. Using a two part oil gutter facilitates its assembly around the ring gear 22. The cut plane of the gutter 32 which results in a gutter made out of two parts 320 and 322 is radial to the axis X32 so that oil flowing inside the gutter 32 is not likely to escape through a joint between the parts 320 and 322, or only in small quantities. In a non-represented variant, the two parts could be separated along a cut plane taken perpendicular to the axis X32 and cutting the gutter approximately between the two walls of the gutter. However, in such a design would result in a peripheral joint extending along the entire angular extent of the gutter. In order to limit oil could flow through such joint, some care would be needed in the design of the joint between the two parts to limit or inhibit the flow of oil through the joint. A role of the gutter is to channel oil around the ring gear 22.

The gutter 32 may comprise a first pair of fixation brackets 36A and 36B which are for example arranged on the external surface of one lateral wall portion of the gutter and a second pair of fixation brackets 38A and 38B which are arranged on the external surface of the other wall portion of the gutter 32. The fixation brackets 36A and 38A may be arranged on the upper part 320 of the gutter 32 while the fixation brackets 36B and 38B may be arranged on the lower part 322 of the gutter 32. In the assembled configuration, the fixation brackets are fixedly attached to the carrier 16. The brackets may be attached for example to one of the bearing caps 163, as for example brackets 38A, 38B shown on Figure 5, or to a bearing leg 161 , or to the wall portion 162 of the differential carrier 16. The gutter 32 is preferably removably fitted on the carrier 16, for example with mechanical fasteners such as bolts, screws, braces, clamps or rivets. Being fixedly mounted on the differential carrier 16, the gutter 32 is held in position within the differential arrangement 14, and has therefore a fixed position with respect to the ring gear axis X24.

As shown on figure 2, a radial section of the gutter 32, taken in a plane containing the axis X24, encases a corresponding radial section of the ring gear 22. This gutter 32 extends around a part of the circumference of the ring gear 22. More precisely, the gutter 32 extends angularly from a first angular extremity 32A to a second angular extremity 32B around the axis X24 of the differential case. The extremities of the gutter can be determined as the ends of the gutter where the gutter stops being capable of performing it oil channeling role, i.e. where the radial U section ends. Preferably, the oil gutter is continuous between its first and second ends, in that the U profile in radial section is uninterrupted between the first and second ends, or at least substantially uninterrupted as in the shown example where, at the joint portion between the two parts 320, 322 of the gutter, the U section profile might be slightly interrupted. At any such interruption, the flow of oil susceptible to escape from the channel is preferably minimal, preferably less than 20 % of the flow in the gutter before the interruption, more preferably less than 10 %.

The radial distance between the gutter 32 and the ring gear 22 may be chosen between 2 mm and 20 mm, for example equal to 5 mm so as to minimize the risk of contact while keeping the oil flow at high speed, and optimize the dynamic lubrication.

Considering the first reference plane P1 which is perpendicular to the axis Y2 of the drive pinion 19 and contains the rotation axis X24 of the ring gear 22, this plane P1 delimits a first half H1 and a second half H2 of the differential arrangement 14. The drive pinion 19 meshes with the ring gear 22 at a meshing location which is located in the first half HL

As visible on the Figures, the second extremity 32B of the gutter is located angularly along the circumference of the ring gear 22 past a high point A of the gutter in the main rotation direction F2 of the ring gear 22. In other words, the second extremity 32B of the gutter 32 is located in the first half H1 of the differential arrangement 14.

In the shown example, both the first extremity 32A and the second extremity 32B of the gutter 32 are located in the first half H1 of the differential arrangement 4.

Thus, the gutter 32 extends angularly over more than 180°, preferably more than 240° around the rotation axis X24, as shown by angle a32 between extremities 32A and 32B.

In the same way, considering the second reference plane P2 which contains the rotation axis X24 of the ring gear 22 and which is parallel to axis Y2 of the drive pinion 19, this plane P2 delimits a lower half H3 and an upper half H4 of the ring gear 22. The first extremity 32A of the gutter 32 is arranged in the lower half H3 while the second extremity 32B of the gutter 32 is arranged in the upper half H4.

F2 denotes a main rotation direction of the spinning motion of the ring gear 22, that is preferably the rotation direction of the ring gear 22 when the vehicle is moving in a forward direction. With such main rotation direction, a part of the ring gear 22 in meshing contact with the drive pinion 20 moves downwards towards the sump, i.e. clockwise in the representation of figure 3.

The point A denotes a high point of the gutter 32 and of the ring gear 22. This point A is included in the plane P1 and represents the highest point of the section of the ring gear 22 along the plane P1. This high point A is defined in relation to the orientation of a differential assembly as represented on figure 3 In figure 3, where the axis of the drive pinion is represented as horizontal.

One can note that, in the hypoid gear of Figure 3, the axis Y2 of the drive pinion 19 is located below the second reference plane P2.

The second extremity 32B of the gutter 32 is located angularly around the ring gear rotation axis past the first reference plane in the direction of the main rotation direction, in the first half H1 of the differential arrangement.

In the orientation of Figure 3, the means that it is located past the high point A of the gutter 32 in the main rotation direction F2 of the ring gear 22. This means the second extremity 32B is located in a quarter of the circle, which is contained both in the first half H1 and in the upper half H4 of the ring gear 22. So, the extremity 32B is located at an angle with the plane P1 which is positive around the main rotation direction of the ring gear. Preferably, however the second extremity 32B is located angularly around the ring gear rotation axis X24 at least 30°, or even preferably, as shown in figure 3 at least 45°, past the first reference plane P1 in the direction of the main rotation direction, in the first half of the differential arrangement.

In the shown embodiment, the first extremity of the gutter is located in a quarter of the circle, which is contained both in the first half H1 and in the lower half H3 of the ring gear 22. Therefore, in the shown embodiment, the gutter 32 extends angularly around the axis X24 over more 180°, preferably more than 240°. In other words, the value of angle a32 is preferably larger than 180°, more preferably larger than 240°. On figure 3, the gutter 32 extends clockwise from a four o'clock position to a two o'clock position.

The gutter 32 can be made of a folded sheet. It can also be made by casting. The gutter 32 can be made of metal but it can also be made of another material, such as plastic or composite material including fiber reinforced resin. When the differential 18 rotates around its axis, the ring gear 22 will tend to evacuate the oil contained in the gutter though the second extremity of the gutter. As shown on figure 3, the level L1 of the oil received in the sump S1 is preferably below the first extremity 32A of the gutter 32, at least during operation of the differential, so oil is not entrained by the ring gear 22 into the first extremity of the gutter. Therefore, oil is mainly located at the exterior of the gutter 32. However, a lower portion of the gutter 32 extends in the sump S12 and the external surfaces of this low portion are in touch with oil in the sump S12.

The gutter may have one or several oil intake openings 34.

Such openings may be located on the external surface of the lower half 322 of the gutter 32, in a portion of the gutter which remains immersed in the oil or the oil sump 12 during operation. The openings are preferably on at least one lateral wall portion thereof to limit the tendency of oil escaping the gutter through the opening due to the centrifugal force when oil is circulated in the gutter by the rotation of the ring gear 22. The openings 34 may be arranged on the lateral wall portion of the gutter which faces the teeth of the ring gear. Those lateral wall portions have an internal surface facing towards the ring gear 22 and an external surface facing away from the ring gear 22.

The openings 34 may be arranged near the peripheral circumference of the lateral wall portion of the gutter 32.

These oil intake openings 34 may present the form of "fish scales" or "gill slits", as shown in Figure 4. Preferably, those scales or slits are oriented so as to favor entry of oil in the gutter rather that exit of oil in the gutter, when the ring gear is rotated in its main rotation direction F2. In other words, the gutter may have at least one oil intake opening which is located on a wall portion, said opening facing towards the exterior of the oil gutter in a direction which is rearwardly oriented compared to a forward motion direction of the ring gear.

For example, the openings may be formed by an arcuate cutout of the lateral wall portion in the shape of a U, leaving a flange portion 341 which remains attached to the lateral wall portion by a border portion 342 at the extremities of the branches of the U.

In the shown design, the flange portion 341 is bent outwardly of the gutter, away from the ring gear along axis X24, and the border portion 342 of the U shaped flange 341 by which it is attached to the lateral wall portion is located at a forward extremity of the flange when considering the main rotation direction F2 of the ring 22. As an alternative, the flange portion 341 could be bent outwardly of the gutter, towards the ring gear along axis X24, and the border portion 342 of the U shaped flange 341 by which it is attached to the lateral wall portion would then be preferably located at a rearward extremity of the flange when considering the main rotation direction F2 of the ring 22.

In the shown example, the openings 34, at least at their widest location near the free end of the flange 341 , face towards the exterior of the oil gutter in a tangential direction which is rearwardly oriented compared to the rotation direction F2 of the ring gear 22.

When the ring gear 22 is rotating around its axis X24 along its main rotation direction, oil contained in the sump S12 tends to be sucked through the openings 34 inside the gutter 32 by the rotation of the ring gear inside the gutter, this being eased by the orientation of the openings 34 with regards to the main spinning motion F2 of the ring gear 22. This particular orientation allows, similarly to a pump, taking profit from the spinning motion of the ring gear 22 to draw oil from the sump S12. Openings facing in the same direction than the main spinning motion F2 of the ring gear 22 would not allow draining enough oil inside the gutter 32 and the suction of oil inside the gutter 32 would not be facilitated by the spinning motion of the ring gear 22.

The openings 34 may be made quite small in comparison with round holes.

Consequently, only a small amount of oil flows into the gutter 32. Therefore, the rotation, of the ring gear 22 is not impaired as much as it would be if the ring gear 22 was immersed directly in the sump S12. The amount of oil penetrating inside the gutter 32 is, nonetheless, sufficient to provide a good lubrication of the teeth of the gears.

Moreover, the openings 34 produce, with a form of "fish scales" or "gill slits" oriented rearwardly, less turbulence in the oil flow than with round holes thanks to the oil being channeled in the proper direction prior to coming in contact with the ring gear. This minimizes the resistance generated by oil inside the gutter 32.

Once sucked from the sump S12, oil is guided by the gutter 32 along a circumferential direction around the axis X24. More precisely, oil flows inside the gutter 32 in the same direction than direction F2 of the rotation of the ring gear 22, that is from the first extremity 32A to the second extremity 32B, or from one of the openings 34 to the second extremity 32B. Centrifugal forces tend to force oil flowing against the peripheral portion of the gutter 32. Preferably, the second extremity 32B of the gutter 32 is arranged so as to expel oil in direction of regions which are normally considered hard to lubricate. For instance, the pinion teeth, the pinion bearings 44, the pinion gear 20 and/or the pinion shaft 15 are normally considered hard to lubricate.

The ejection of oil at the outlet of the second extremity 32B is represented on figure 3 by an arrow F3 representing the mean direction of oil being expelled. The mean direction of oil F3 expelled from the gutter depends mainly on the position of the end of the second extremity 32B and on the shape of the gutter at the extremity. In the example of the an annular gutter 32 shown on the figures, the mean direction of oil F3 can be considered to be parallel to a tangent to the peripheral portion of the gutter at the second extremity 32B. Thus, the location of the second extremity 32B can determine the mean direction of oil expelled from the gutter. In the example of figure 3, the tangent to the peripheral portion of the gutter at the second extremity 32B is oriented towards the drive pinion. It even intersects the drive pinion 19, here in the region of the pinion shaft 15 in the region of the bearing 44. In an embodiment having a more extended gutter, it could intersect the pinion gear 20.

Moreover, oil flowing along the gutter 32 is expelled at high speed which improves the efficiency of the lubrication.

In practice, oil may not flow entirely in direction of the meshing region between the pinion gear 20 and the ring gear 22. More precisely, some of the oil flow may have a different trajectory out of the gutter 32. For example, some of the oil entrained by the ring gear in the gutter may fall down, due to gravity, globally in a centripetal direction with regards to the axis X24 when it arrives approximately at the high point A of the ring gear 32. This divergent oil flow is represented on figure 3 by arrow F4 and allows lubricating the differential bearings, the conical gears 28A and 28B and the other conical gears 30A and 30B. Therefore, the whole differential 18 is lubricated using a minimum amount of oil.

In a non-represented alternative embodiment, the gutter 32 may be devoid of openings 34 in its peripheral or lateral wall portions, but the level of oil L1 inside the sump S12 is higher than a wall portion of the gutter, so that some of the oil spills over from the sump into the oil gutter 32. In other words, the excess of oil above the gutter 32 flows inside the gutter 32.

In another non-represented alternative embodiment, the gutter 32 may be asymmetric, for example asymmetric around axis X24. For instance, the gutter 32 can present a larger section, for example larger along the transverse direction and/or larger section along the radial direction with respect to axis X24, at the second extremity 32B than at the first extremity 32A. This would allow having a minimal volume of oil entrained between the ring and the gutter in the lower section of gutter, while having a relatively lower speed of oil expelled. With an inverse design, i.e. with a the gutter 32 having a smaller section, for example smaller along the transverse direction and/or smaller section along the radial direction with respect to axis X24, at the second extremity 32B than at the first extremity or than at a median angular zone of the gutter, a relatively higher speed of oil expelled may be obtained. The speed of oil expelled may, together with the shape of the second extremity 32B, impact the part, of the arrangement which will be best sprayed with the expelled oil. In another non-represented alternative embodiment, the gutter 32 may be equipped, in the upper half 320, with deflectors for diverting a part of the oil flow towards the center of the differential 18, that is along the direction F4. Conical gears 28A, 28B, 30A and 30B can consequently be lubricated using the same oil gutter 32. Such deflectors can consist of suitable shapes formed on an internal surface of at least one of the lateral wall portions, such internal surface facing the ring gear 22.

In another non-represented alternative embodiment, some oil retainers can be installed within the differential 18, especially within the differential case 24, to ensure lubrication in regions hard to lubricate during transitory phase. Indeed, dynamic oil lubrication takes place when the ring gear 22 starts running, which means that the period before the ring gear 22 reaches its stationary rotation speed constitutes a transitory phase during which lubrication may be not as efficient as necessary. The most concerned regions are the regions hard to lubricated, such as the meshing location between the pinion gear 20 and the ring gear 22.

In another non-represented alternative embodiment, the openings 34 may be arranged on the peripheral wall portion of a lower part of the gutter 32. In that case, the internal surface of the openings faces towards the centre of the ring gear 22. However, this configuration eases the emptying of the gutter 32 due to gravity and centrifugal effect in comparison with the configuration represented on the figures.

In another non-represented alternative embodiment, the extremity 32B of the gutter

32 may divided in two branches, one diverting the oil flow towards the pinion 19 and the other diverting the flow towards the centre of the differential 18.

The technical features of the different embodiments and alternative embodiments of the invention described here above can be combined together to generate new embodiments of the invention.

Claims

1. Differential arrangement (14) for a driven axle (2) of an automotive vehicle comprising:

• a differential having

- a ring gear (22) defining a ring gear rotation axis (X24), and

- a drive pinion (19) having a pinion shaft (15) extending along a drive pinion axis (Y2) and a pinion gear (20) engaging the ring gear for rotating the differential around the ring gear rotation axis (X24),

• an oil gutter (32), a radial section of which at least partly peripherally encases a corresponding radial section of the ring gear, said gutter extending angularly around a part of the circumference of the ring gear around the ring gear rotation axis (X24) from a first angular extremity (32A) to a second angular extremity (32B) along a main rotation direction (F2) of the ring gear,

characterized in that the differential arrangement (14) has a first (H1) and a second (H2) halves delimited by a first reference plane (P1) containing the ring gear rotation axis and perpendicular to the drive pinion axis (Y2), in that the drive pinion (19) meshes with the ring gear (24) at a meshing location which is located on the first half of the differential arrangement (14), and in that the second extremity (32B) is located angularly along the circumference of the ring in the first half (H1) of the differential arrangement (14).

2. Differential arrangement (14) according to claim 1 , characterized in that the second extremity (32B) is located angularly around the ring gear rotation axis (X24) at least 30° past the first reference plane (P1 ) in the direction of the main rotation direction, in the first half (H1) of the differential arrangement (14).

3. Differential arrangement (14) according to claim 2, characterized in that the second extremity (32B) is located angularly around the ring gear rotation axis (X24) at least 45° past the first reference plane (P1) in the direction of the main rotation direction, in the first half (H1) of the differential arrangement (14).

4. Differential arrangement (14) according to any preceding claim, characterized in that the first extremity (32B) is located angularly around the ring gear rotation axis (X24) before the first reference plane (P1) in the direction of the main rotation direction, in the first half (H1) of the differential arrangement (14).

5. Differential arrangement (14) according to claim 4, characterized in that the gutter extends over more than 180° around the ring gear axis (X24), along the second half (H2) of the differential arrangement (14), and in that the first extremity (32A) and the second extremity (32B) of the gutter (32) are located in the first half (H1) of the differential arrangement (14).

6. Differential arrangement (14) according to any preceding claim, characterized in that the gutter extends over more than 240° around the ring gear axis (X24).

7. Differential arrangement (14) according to any previous claim, characterized in that the second extremity (32B) of the oil gutter (32) is configured so as to expel oil in the direction (F3) of the drive pinion (19), when the ring gear (22) is rotating in its main rotation direction (F2).

8. Differential arrangement (14) according to claim 7, characterized in that the second extremity (32B) of the oil gutter (32) is configured so as to expel oil in the direction of the pinion shaft (15) when the ring gear (22) is rotating in its main rotation direction (F2).

9. Differential arrangement according to any previous claim, characterized in that the differential arrangement (14) has a lower half (H3) and an upper half (H4) delimited by a second reference plane (P2), containing the ring gear rotation axis (X24) and perpendicular to the first reference plane (P1) and in that the first extremity (32A) is located in the lower half of the differential arrangement (14) while the second extremity (32B) is located in the upper half of the differential arrangement (14).

10. Differential arrangement according to claim 9, characterized in that an upper portion (320) of the gutter (32) includes at least one deflector, for diverting the oil flow towards the centre of the ring gear (22).

11. Differential arrangement according to any previous claim, characterized in that the gutter (32) has at least one oil intake opening (34) which is located on a wall portion and facing towards the exterior of the oil gutter in a direction which is rearwardly oriented compared to the main rotation direction (F2) direction of the ring gear.

12. Differential arrangement according to any previous claim, characterized in that the differential arrangement comprises a differential carrier (16) for carrying the differential (18), in that the gutter (32) is fitted to the differential carrier (16), and in that the differential carrier (18), together with the differential (18) and the gutter (32) as a unit, is removably attached to an axle housing (6)

13. Differential arrangement according to claim 12, characterized in that it has a housing which is a central differential receiving portion ( 2) of an axle housing, wherein the central differential receiving portion has a main opening (012) through which the differential (18) can be mounted, and in that the differential carrier (16) is removably attached to the axle housing at the main opening (012).

14. Differential arrangement according to claim 13, characterized in that the axle housing (6) has also two lateral tubular wheel drive shaft receiving portions (10, 12) rigidly connected to the central differential receiving portion (12).

15. Differential arrangement according to any of claims 12 to 14, characterized in that the first extremity (32B) of the gutter (32) is located above an oil level in the axle housing (6).

16. Differential arrangement according to any previous claim, characterized in that the main rotation direction of the ring gear (22) corresponds to a forward direction of travel of an automotive vehicle having a driven axle (2) equipped with the differential arrangement.

17. Automotive vehicle having a driven axle (2), wherein said automotive vehicle has a main forward direction of travel, characterized in that the driven axle comprises a differential arrangement according to any preceding claim.

18. Automotive vehicle according to claim 17, characterized in that that, upon movement of the vehicle along main forward direction of travel, the ring gear (22) rotates in its main rotation direction.

19. Automotive vehicle, characterized in that the driven axle (2) has an axle housing

(6) having a central differential receiving portion (12) in which the differential is received, in that the central differential receiving portion (12) has a lower portion defining defines a sump (S12) for receiving oil by gravity, and in that ring gear comprises a lower portion which extends in the sump, and in that, upon rotation of the ring gear along its main rotation direction corresponding to forward movement of the vehicle, a part of the ring gear (22) in meshing contact with the drive pinion moves downwards towards the sump (S12), and in that the first extremity (32A) of the gutter (32) is located below the meshing location where the drive pinion (19) meshes with the ring gear (22), while the second extremity (32A) of the gutter (32) is located above said meshing location.

20. Differential arrangement (14) comprising:

• a differential having

- a ring gear (22) defining a ring gear rotation axis (X24), and

• an oil gutter (32), a radial section of which at least partly peripherally encases a corresponding radial section of the ring gear, said gutter extending angularly around a part of the circumference of the ring gear around the ring gear rotation axis (X24) from a first angular extremity (32A) to a second angular extremity (32B)

wherein the differential arrangement (14) has a first (H1) and a second (H2) halves delimited by a first reference plane (P1) containing the ring gear rotation axis (X24) and perpendicular to the drive pinion axis (Y2), and wherein the drive pinion (19) meshes with the ring gear (22) at a meshing location which is located on the first half (H1) of differential arrangement (14),

characterized in that the gutter extends over more than 180° around the ring gear axis (X24), along the second half (H2) of the differential arrangement (14), and in that the first extremity (32A) and the second extremity (32B) of the gutter (32) are located on the first half (H1) of the differential arrangement (14).

21. Differential arrangement, characterized in that the gutter (32) extends over more than 240° around the ring gear axis (X24),

22. Differential arrangement according to claim 20, characterized in that the gutter (32) extends over more than 30° around the ring gear axis (X24) along the first half (H1) of the differential arrangement (14).

23. Driven axle (2) comprising:

an axle housing (6) having a central differential receiving portion (12), wherein the central differential receiving portion has a front opening (012) through which a differential (18) can be mounted, a differential carrier (16) for holding the differential, the differential carrier being removably attached to the axle housing at the front opening,

the differential (18) comprising a ring gear (22).

characterized in that it comprises a U profiled oil gutter (32), a radial section of which encases a corresponding radial section of the ring gear (22), said gutter extending around a part of the circumference of the ring gear, and said gutter being fitted to the differential carrier (16).

24. Driven axle according to claim 23, characterized in that the central differential receiving portion (12) of the axle housing (6) defines a sump (S12) for receiving oil, and in that the gutter (32) comprises a lower portion which extends in the sump.

25. Differential arrangement according to claim 23 or 24 characterized in that the axle housing (6) has also two lateral tubular wheel drive shaft receiving portions (10, 12) rigidly connected to the central differential receiving portion (12).