ASSEMBLY INCORPORATING SAME

The invention relates to optimisation of lubricant levels in driven vehicle axles that contain gear transmissions and shaft bearings.

To improve the efficiency of vehicle transmissions it has been attempted to reduce churning losses caused by rotating elements that are immersed to a substantial extent in a liquid lubricant, such as lubricating oil. Various proposals have been made by which part of the lubricating oil is deviated to a buffer reservoir, from which it is returned with a controlled delay to the elements to be lubricated. Usually a collecting reservoir that receives an overflow of excess lubricant returns this lubricant back to a common sump via a restricted orifice. Such restrictions hold a serious risk of becoming clogged up by contaminations in the oil, after which proper lubrication can become completely interrupted. Furthermore the excess lubricating oil, while being splash-fed to the collecting reservoir, may have difficulty in reaching bearings that also require lubrication. There have also been proposals to arrange for an oil level that depends on the load of the transmission. Such load depending system often requires pump devices or valves and auxiliary control systems, which substantially add to the complication and costs. Common to many of these known devices are also oil retaining receptacles that retain a small enough amounts of oil in the direct proximity of bearings to ensure lubrication thereof. To form such oil retaining receptacles auxiliary structural elements are affixed adjacent to the bearing locations in transmission housings. While such retaining receptacles or reservoirs can be made relatively cheaply from sheet metal or plastic, they constitute auxiliary parts that add to the assembly effort and costs. Moreover such components are critical to the performance of vehicle transmissions that function with reduced oil levels, and inadvertent omissions in manufacture or repair can have dire consequences.

Accordingly it is an object of the present invention to propose an improved transmission housing, in particular transmission housing improvements that are applicable to driven vehicle axles. In particular it is an object of the present invention to capture lubricating oil in critical locations reliably and efficiently. In a more general sense it is thus an object of the invention to overcome or ameliorate at least one of the disadvantages of the prior art. It is also an object of the present invention to provide alternative structures which are less cumbersome in assembly and operation and which moreover can be made relatively inexpensively. Alternatively it is an object of the invention to at least provide a useful choice in proposing an alternative solution.

To this end the invention proposes a gear transmission housing and drive axle assembly incorporating same, as defined in the appended claims. More in particular the invention proposes a gear transmission housing that has an outer fluid barrier adapted to define a fluid sealed interior for accommodating an amount of fluid lubricant not exceeding a predefined level and at least one rotatable gear wheel adapted to be partly immersed in the amount of fluid lubricant for causing splash distribution of the fluid lubricant when the at least one gear wheel is rotated in the fluid sealed interior, the housing further including at least one bearing seat positioned above the predefined fluid level in the fluid sealed interior for receiving a shaft bearing, and a collecting reservoir in fluid communication with the bearing seat and defining at least one upstanding wall member, wherein the at least one upstanding wall member is integrally formed on the transmission housing. Such a gear transmission housing can be cost efficiently manufactured and assembled, while in use it may substantially reduce driving losses through oil churning. The advantages are best obtained when the at least one upstanding wall member is integrally formed by casting and/or when the at least one upstanding wall member is integrally formed when machining/forming the bearing seat.

When preferred the gear transmission housing can also include a removable gear carrier. Such an arrangement is convenient in assembly, in adjustment, and in servicing or repair. In general the at least one wall member can be formed into a fluid retaining upstanding wall upon attachment of an auxiliary removable component, carrying a complementary upstanding wall member, to the housing. In such a case the removable auxiliary component can also be attached to the gear carrier. This arrangement is advantageous when the removable auxiliary component is a bearing cap, which can simplify the mounting and demounting of bearings.

It is particularly advantageous to have a drive axle assembly incorporating the gear transmission housing according to the invention. It is then preferred that the at least one rotatable gear wheel is a ring gear, and wherein the drive axle assembly further comprises a driving gear pinion, drivingly engaging the ring gear. It is then further preferred that the shaft bearing is associated with the driving gear pinion.

In an advantageous embodiment the ring gear can be associated with at least one further bearing seat collection reservoir in fluid

communication with the at least one further bearing seat defining a further upstanding wall member. In a practical arrangement the ring gear will be associated with a differential carrier, and the differential carrier will be rotatably arranged between a pair of opposite further bearing seats.

In a particular advantageous arrangement, when the drive axle assembly includes a removable gear carrier, the bearing seat may be located on the gear carrier. In particular the arrangement may then be such that the pair of opposite further bearing seats is also located on the gear carrier.

Further advantageous aspects of the invention will become clear from the appended description and in reference to the accompanying drawings, in which:

Figure 1 is a driven rear axle assembly, with included final drive, suitable for a commercial or heavy duty vehicle;

Figure 2 is a final drive gear carrier for use with the rear axle assembly of Figure 1; Figure 3 is a partial cross section of a pinion bearing arrangement in the final drive carrier of Figure 2, according to the direction III-III as indicated in Figure 1;

Figure 4 is a rear view of the final drive gear carrier with gear elements mounted therein;

Figure 5 is the final drive gear carrier of Figure 2 viewed from a direction opposite to that of Figure 2; and

Figure 6 is an example of a bearing cap that is part of the final drive gear carrier as illustrated in Figure 4.

In Figure 1 a driven rear axle 1 for a motor vehicle is shown. The rear axle 1 includes a rear axle housing 3, in the form of a banjo-shaped body. Exiting from opposite ends of the banjo housing 3 are left hand and right hand half shafts 5, 7 that is use connect operatively to the wheels driving the motor vehicle (not shown but conventional). Also associated with the opposite ends of the banjo housing 3 are left hand and right hand mounting flanges 9, 11 for connecting the rear axle 1 to the axle guidance and suspension means of the vehicle (not shown but conventional). The axle 1, as shown in Figure 1, is further provided with a final drive gear carrier 13 and a pinion shaft bearing unit 15.

In Figures 2 and 5 the final drive gear carrier 13 is shown without gears being mounted therein as viewed from opposite directions. In contrast Figures 3 and 4 illustrate gear and bearing elements in position in the gear carrier 13. Generally the final drive gear carrier 13 as shown in Figure 2 has a mounting flange 17 for its attachment to the banjo axle housing 3 and a forward opening 19 for receiving the pinion shaft bearing unit 15. Also shown in Figure 2 is that the gear carrier 13 has an innermost pinion shaft bearing seat 21 for receiving a ball or roller bearing 23 as shown in Figure 3. Integrally formed in the gear carrier 13 and coinciding with the pinion shaft bearing seat 21 is an upstanding wall 25. When reference is now had to the partial cross section shown in Figure 3, it is seen that the pinion bearing unit 15 is mounted in the gear carrier 13. The pinion bearing unit 15 carries the outer and inner races 27, 29 of a front tapered roller bearing 31, as well as the outer and inner races 33, 35 of a rear tapered roller bearing 37. Both inner races 29, 35 of the front and rear tapered roller bearings 31, 37 locate a pinion shaft 39 of a gear pinion 41. A rearward end 43 of the pinion shaft 39 is rotatably journalled in ball bearing 23. Ball bearing 23 is held in the bearing seat 21. The bearing seat 21 is machined in an integral portion of the gear carrier 13, that can conveniently be obtained by casting, moulding, sintering, or like non-material removing shaping techniques. The machining of the bearing seat 21 can carried out in a conventional manner and no further machining or shaping is required to obtain the upstanding wall 25. In use the upstanding wall 25 will prevent lubrication oil that has reached the bearing 23 by splash distribution from flowing away from the lower anti-friction rollers of bearing 23. The opposite forward end of the pinion shaft 39 receives a driving flange 45 attached by a nut 47 engaging a screw threaded forward end of the pinion shaft 39. Thereby the inner races 29, 35 of the tapered roller bearings 31, 37 are firmly located between a boss of the driving flange 45 and the pinion gear 41. A rotatable fluid seal 49 is interposed between the rotating outer circumference of the driving flange 45 and the stationary pinion bearing unit 15 and ensures that lubricating oil cannot escape from the axle 1 when the drive gear carrier 13 and the axle housing 3 are assembled into a fully operational rear axle 1. In this regard the axle housing 3 (see Figure 1) defines an outer fluid barrier, which assembled with gear carrier 13 and pinion bearing unit 15 forms a fluid sealed interior for accommodating an amount of fluid lubricant and gear and bearing elements.

In Figure 4 a rear view of the final drive gear carrier shows gear elements such as a differential case 50 and a ring gear 52 mounted therein. The ring gear 52 is driven by the gear pinion 41 (shown in Figure 3) and rotates the differential case 50 on which it is mounted. The differential case 50 contains differential gears and distributes driving torque between the left and right hand half shaft driving shafts 5, 7 (shown in Figure 1). This arrangement however is conventional in driving axles and thus well known to the skilled person.

In Figure 5 a rear perspective view of the final drive gear carrier 13 illustrates the presence of laterally spaced left and right hand bearing seats 51, 53. These bearing seats 51, 53 are provided to accommodate bearings that can carry the differential case 50 and the ring gear 52 between them. For clarity the differential housing and ring gear are deleted from Figure 5, but these parts are conventional and need no further explanation beyond what has been shown in Figure 4. The ring gear when in position will rotate within a shallow cavity 55 provided in the gear carrier 13, and be driven by the pinion gear 41. For easy mounting of the differential case and its opposite end bearings, the left hand and right hand bearing seats 51, 53 are each formed with a respective removable left hand and right hand bearing caps 57, 59. Formed at the bottom portion of each of the left and right hand bearing seats 51, 53 is an upstanding wall 61, which is composed of a first complementary wall section 61A on the gear carrier 13 and a second complementary wall section 61B on one of the left and right hand bearing caps 57, 59.

In Figure 6 an example of the right hand bearing cap 59 is shown detached from the gear carrier 13. The upstanding complementary second wall section 61B is clearly visible. Furthermore the right hand bearing cap 59 has mounting holes 63, 65, 67, 69 for fastener elements, such as screw studs or bolts, and recessed 71, 73 for receiving registering pins.

As with the bearing seat 21 for the pinion shaft bearing 23, the bearing seats 51, 53 for the differential case can be machined as usual with the also unmachined bearing caps 57, 59 in position. No additional cutting or shaping being required to form the upstanding walls 61. In use the ring gear 52, shown in Figure 4 will be rotated within the shallow cavity 55 and distribute lubricating oil, contained in the axle housing 3 between the teeth of the pinion gear 41 and the teeth of the ring gear 52 itself. This type of splash lubrication, while adequate for the final drive gears, does not ensure proper lubrication of all bearings, when not at least a bottom portion of these bearings is also immersed below the lubricating oil level. The upstanding walls 25 and 61 at the respective pinion bearing seat 21 and laterally spaced differential case bearing seats 51, 53 ensure that the relevant bearings are nonetheless sufficiently immersed in lubricating oil. Thereby the level of lubricating oil in contact with the ring gear 52 can be significantly lowered and the total volume of lubricating oil in the axle housing 3 that is subject to churning by the ring gear substantially reduced. Reducing the churning of oil increases the mechanical efficiency of the vehicle. Collecting reservoirs as add-on elements to bearing locations, in accordance with the prior art, have been found cumbersome in assembly and difficult in ensuring proper fitment and reliability. Therefore the solution according to the invention of forming these collecting reservoirs by integrally formed

upstanding walls is cost saving and secure.

Thus a gear transmission housing is described that can be composed of a rear axle housing 3, a final drive gear carrier 13, and a pinion bearing unit 15. This gear transmission housing has an outer fluid barrier, formed by the rear axle housing 3 that is adapted to define a fluid sealed interior for accommodating an amount of fluid lubricant not exceeding a predefined level. The gear transmission housing (3, 13, 15) also accommodates at least one rotatable gear wheel, such as ring gear 52, which is adapted to be partly immersed in the amount of fluid lubricant for causing splash distribution of the fluid lubricant when the at least one gear wheel 52 is rotated in the fluid sealed interior. The gear transmission housing further includes at least one bearing seat, such as a innermost pinion shaft bearing 21, or bearing seats 51, 53 for a differential case 50. The at least one bearing seat is positioned above the predefined fluid level in the fluid sealed interior for receiving a shaft bearing, such as a low friction bearing 23. A collecting reservoir is in fluid communication with the bearing seat and defines at least one upstanding wall member 25 or 61, as the case may be. The at least one upstanding wall member 25; 61 is integrally formed on the transmission housing 3, 13, 15. A drive axle assembly 1 can advantageously incorporate the gear transmission housing 3, 13, 15.

While the invention has been described in reference to a vehicle drive axle, it will be clear to the skilled person that the invention can also be usefully applied to gear transmissions, of any kind that employ splash lubrication, or in which long periods of non-use hold a risk that lubricant is drained from locations that that should never be starved from lubrication.

It is thus believed that the operation and construction of the present invention will be apparent from the foregoing description and drawings appended thereto. It will be clear to the skilled person that the invention is not limited to any embodiment herein described and that modifications are possible which should be considered within the scope of the appended claims. Also kinematic inversions are considered inherently disclosed and to be within the scope of the invention. In the claims, any reference signs shall not be construed as limiting the claim. The term 'comprising' and 'including' when used in this description or the appended claims should not be construed in an exclusive or exhaustive sense but rather in an inclusive sense. Thus the expression 'comprising' as used herein does not exclude the presence of other elements or steps in addition to those listed in any claim. Furthermore, the words 'a' and 'an' shall not be construed as limited to 'only one', but instead are used to mean 'at least one', and do not exclude a plurality. Features that are not specifically or explicitly described or claimed may be auxiliarily included in the structure of the invention within its scope. Expressions such as: "means for ..." should be read as: "component configured for ..." or "member constructed to ..." and should be construed to include equivalents for the structures disclosed. The use of expressions like: "critical", "preferred", "especially preferred" etc. is not intended to limit the invention. Additions, deletions, and modifications within the purview of the skilled person may generally be made without departing from the spirit and scope of the invention, as is determined by the claims.