Lubrication structure for a speed reducer

Abstract

Lubrication structure for a speed reducer, wherein the lubrication structure comprises: a housing (20) in which a lubricating oil supply object is provided between an internally formed side wall (20b1) and a rotation axis (26a); a reduction gear (26) provided inside the housing (20), the reduction gear (26) being connected to an output shaft (12) of a drive source (11) and being configured to rotate about the rotation axis (26a); a collecting container (35) adapted to receive a portion of a lubricating oil accumulated at a bottom in the housing (20) and carried by the reduction gear (26); an oil passage (34) provided on the side wall (20b1), the oil passage (34) being designed to guide the lubricating oil carried by the reduction gear (26) to the collecting container (35); a rib (39) formed on the side wall (20b1) so as to extend radially from a position near a rear wall side of the oil passage (34); a groove (40) provided at an end edge (39a) of the rib (39) of the side wall (20b1), wherein lubricating oil collected by the rib (39) is introduced into the groove (40), and the groove (40) is in communication with the lubricating oil supply object, so that the lubricating oil carried by the reduction gear (26) is supplied to the lubricating oil supply object via the rib (39) without passing through the collecting container (35); and at least one additional rib (39b) which is formed radially in front of the rib (39) in a direction of rotation of the reduction gear (26), wherein the side wall (20b1) is formed with a bevelled shape so that it approaches the rotation axis (26) when the side wall (20b1) moves away from the reduction gear (26) and the rib (39) for guiding the lubricating oil, which has not reached the oil passage (34) due to a low entrainment height in the lubricating oil entrained by the reduction gear (26) and is collected with the aid of the additional ribs (39b), is formed to a radially inner side.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The invention relates to a lubricating structure for a speed reducer, and more particularly, to a lubricating structure for a speed reducer having a reduction gear rotating in mesh with an output shaft of a drive source and provided inside a casing, which guides lubricating oil accumulated at a bottom in the casing to a receiver by carrying the lubricating oil (upward) by means of the reduction gear, and then supplies the lubricating oil from the receiver to a lubricating oil supply object, such as a lubricated object or a cooled object. 2. Description of the state of the art

[0002] Since lubricating oil is not supplied to lubricated parts until lubricating oil accumulates in a catch tank, it takes time for lubricating oil to be supplied. Therefore, in order to quickly supply lubricating oil to a lubricating oil supply object, a structure is provided (see, for example, Japanese Patent Application Publication No. 2012-172779 (JP 2012-172779 A)). In the structure, an opening is provided on the top of a catch tank for supplying entrained lubricating oil to the catch tank, a supply port is provided below the opening for supplying lubricating oil from the catch tank to the lubricating oil supply object, and a guide member is provided between the opening and the supply port for guiding lubricating oil from the opening to the supply port.This makes it possible to quickly supply lubricating oil to the lubricating oil supply object by guiding the lubricating oil to the supply port with the aid of the guide element before the oil level in the collecting container reaches the supply port. DE 10 2011 001 950 A1, JP 2006 - 275 164 A, JP 2011 - 021 656 A, JP 2012 - 172 779 A, ​​EP 1 544 510 A2, JP H06 - 72 168 A, JP H11 - 48 806 A, and JP H05 - 106710 A disclose further lubrication structures. SUMMARY OF THE INVENTION

[0003] However, in the above-described structure according to JP 2012-172779 A, ​​even if the guide member is provided, only lubricating oil in the entrained lubricating oil guided from the opening of the receiver tank to the supply port can be used, and moreover, since lubricating oil must pass through the receiver tank, it takes time for the lubricating oil to be supplied to the lubricating oil supply object.

[0004] The invention provides a lubrication structure for a speed reducer with which it is possible to quickly supply entrained lubricating oil to a lubricating oil supply object without passing through a collecting container.

[0005] In one aspect of the invention, a lubrication structure for a speed reducer according to claim 1 is provided.

[0006] In this configuration, the lubricating oil carried by the reduction gear is quickly supplied to the lubricating oil supply object via the rib without passing through the catch tank. Even if lubricating oil is carried by the reduction gear, it is possible to supply lubricating oil that has not reached the catch tank in the conventional way and has drained to the bottom of the housing to the lubricating oil supply object, thus making efficient use of the lubricating oil.

[0007] Furthermore, by restricting the circulation of lubricating oil at the auxiliary rib, it is possible to collect lubricating oil that has not reached the oil passage due to a low drag height in the lubricating oil carried by the reduction gear. Lubricating oil collected by the auxiliary rib flows along the auxiliary rib and the tapered wall surface of the side wall to the rotation axis. Lubricating oil that has reached the rib via the auxiliary rib is restricted from circulation by the rib and flows along the rib to the rotation axis, and the lubricating oil is then supplied to the lubricating oil supply object for lubrication. Therefore, the auxiliary rib improves the collection of lubricating oil that has not reached the oil passage due to a low drag height in the lubricating oil carried by the reduction gear, making it possible to supply the lubricating oil to the lubricating oil supply object.

[0008] In the above aspect, the lubricating oil supply object may include a bearing that supports the reduction gear on the housing, and an oil seal provided adjacent to the bearing and sealing an interior of the housing from an exterior. The groove may be recessed in an inner periphery of a bearing hole provided in the housing and in a step wall formed between the bearing and the oil seal. A portion of the groove formed in the bearing hole may have a greater width than the rib. The groove may be provided in a width direction (transverse direction) of the rib at a center of the rib. Therefore, even when the reduction gear rotates in the reverse direction, for example, when the vehicle moves backward, as well as when the vehicle moves forward, it is possible to supply lubricating oil from the rib into the groove.Since it is possible to supply lubricating oil to the bearing that supports the reduction gear on the housing and the oil seal provided next to the bearing and sealing the inside of the housing from the outside by means of the groove, it is not necessary to form a special oil passage.

[0009] In the above aspect, the reduction gear may be attached to a differential case containing a differential gear that drives a pair of axles for rotation. Therefore, the invention is applicable to a vehicle having a differential case. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention are described below with reference to the accompanying drawings, in which like reference numerals designate like elements, and wherein: Fig. Figure 1 is a schematic diagram illustrating the schematic configuration of a rear axle of a vehicle to which the invention is applied; Fig. 2 is a front view showing an opening side of a first split case portion (first split case portion) of a transaxle case according to an embodiment of the invention; Fig. 3 is a front view showing an opening side of a second split case portion (second split case portion) of the rear axle case according to the embodiment of the invention; Fig. 4 is a front view showing, in the rear axle housing according to the embodiment of the invention, a side of a partition member facing the second split housing portion; Fig. 5 is a front view showing only the opening side of the second sub-housing portion according to the embodiment of the invention; and Fig. 6 is a longitudinal sectional view of the rear axle of the vehicle to which the invention is applied, with a part cut away. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0011] An embodiment of the invention will be described in more detail with reference to the accompanying drawings. In the following embodiment, the drawings may be modified or simplified, and the size ratio, shape, and the like of individual sections are not always drawn accurately. Like reference numerals denote like or corresponding elements in the drawings referenced below.

[0012] Fig. 1 is a schematic diagram illustrating the configuration of a rear axle 10 in an electric four-wheel drive vehicle to which the invention is applied. The rear axle 10 is a two-axle electric drive system for a vehicle. The rear axle 10 includes an electric motor 11 as a drive source, a first reduction gear pair 14, a second reduction gear pair 16, and a differential gear unit 19 in a rear axle housing (transaxle housing) 20 (which is an example of a housing). The first reduction gear pair 14 is provided between an output shaft 12 of the electric motor 11 and a countershaft (countershaft) 13 in parallel with the output shaft 12. The second reduction gear pair 16 is provided between the countershaft 13 and a differential case 15 in parallel with the countershaft 13 and concentric with the electric motor 11.The differential gear unit 19 includes the differential gear 17 provided inside the differential case 15. The differential gear unit 19 drives a pair of rear axles 18 for rotation using the torque transmitted from the electric motor 11 via the first reduction gear pair 14 and the second reduction gear pair 16.

[0013] A rotor 11a of the electric motor 11 is connected to the center portion of the output shaft 12. A pair of bearings 21 are mounted at both ends of the output shaft 12 (i.e., one bearing 21 is mounted at each end of the output shaft 12). The output shaft 12 is therefore rotatably supported on the rear axle housing 20 by the pair of bearings 21.

[0014] The first reduction gear pair 14 consists of a counter drive gear 22 with a small diameter and a counter driven gear 23 with a large diameter. The counter drive gear 22 is integrally connected to the distal end side of one end of the output shaft 12. The counter driven gear 23 is integrally fixed to one end side of the counter shaft 13 in a state where the counter driven gear 23 is in mesh with the counter drive gear 22. The output shaft 12 and the counter shaft 13 parallel to the output shaft 12 correspond to the rotating shafts of the first reduction gear pair 14. Therefore, the rotation axis direction of the first reduction gear pair 14 represents the axial direction of the output shaft 12 or the counter shaft 13, and the horizontal direction in Fig. 1 corresponds to the direction of rotation of the first reduction gear pair 14.

[0015] The countershaft 13 is provided at the front of the vehicle relative to the concentric output shaft 12 and the differential case 15, the countershaft drive gear 22, and a final driven gear 26 (which is an example of a reduction gear), which in turn is connected to the output shaft 12 and the differential case 15. The countershaft driven gear 23 is thus arranged at the frontmost side in the rear axle housing 20. A pair of bearings 24 are mounted at both ends of the countershaft 13 (i.e., one bearing 24 is mounted at each end of the countershaft 13). The countershaft 13 is rotatably supported on the rear axle housing 20 via this pair of bearings 24.

[0016] As in Fig. 1, the second reduction gear pair 16 is arranged to be offset in the rotational axis direction of the first reduction gear pair 14. The second reduction gear pair 16 consists of a final drive gear 25 with a small diameter and the final driven gear 26 with a large diameter. The final drive gear 25 is integrally connected to the other end of the counter shaft 13. The final driven gear 26 is arranged to be offset from the counter drive gear 22 in the axial direction of the output shaft 12. The final driven gear 26 is mounted on the outer peripheral portion of the differential case 15 and integrally fixed in a state where the final driven gear 26 is engaged with the final drive gear 25.

[0017] A pair of bearings 27 are mounted on the outer peripheries of the two axial ends of the differential case 15 (i.e., one bearing 27 is mounted on each outer periphery of the corresponding axial end of the differential case 15). The final drive gear 26 is therefore integrally fixed to the differential case 15, and the differential case 15 is rotatably supported on the rear axle housing 20 by this pair of bearings 27.

[0018] The differential gear 17 is of the general type known as a bevel gear. The differential gear 17 includes a pair of side gears 28 and a pair of pinions 30. The side gears 28 are arranged opposite each other along the rotational axis inside the differential case 15. The pair of pinions 30 are rotatably supported between this pair of side gears 28 via a pinion shaft 29 and are each in engagement with the pair of side gears 28. The pinion shaft 29 is fixed to the differential case 15 in a state where the pinion shaft 29 is perpendicular to the rotational axis of the differential case 15.

[0019] The pair of rear axles 18 are each integrally connected to the pair of side gears 28. The differential gear unit 19, which includes the differential case 15 and the differential gear 17, drives the pair of rear axles 18 for rotation by transmitting the torque from the electric motor 11 through the first reduction gear pair 14 and the second reduction gear pair 16, while allowing a speed difference between the pair of rear axles 18. One rear axle of the pair of rear axles 18 is inserted into the hollow cylindrical output shaft 12 and connected to one rear wheel of the pair of rear wheels 31 on a left side of the vehicle.

[0020] As in Fig. 1, the rear axle housing 20 is formed of four sections in the axial direction of the rear axles 18. A partition member 20d, which is a component of the rear axle housing 20, has a cylindrical shape and includes a partition wall 20d1 (see Fig. 4) which divides the interior of the rear axle housing 20 into a first receiving space 20A and a second receiving space 20B. The first reduction gear pair 14 is housed in the first receiving space 20A. The second reduction gear pair 16 is housed in the second receiving space 20B. The rear axle housing 20 further comprises a cylindrical first section 20a of the divided housing (first sub-housing section 20a), a flap-shaped second section 20b of the divided housing (second sub-housing section 20b), and a flap-shaped third section 20c of the housing (third sub-housing section 20c). The first sub-housing section 20a is on one side (left side in Fig. 1) of the separating element 20d and has a first side wall 20a1 (see Fig. 2) which defines the first receiving space 20A. The second sub-housing section 20b is on the other side (right side in Fig. 1) of the separating element 20d and has a second side wall 20b1 (see Fig. 1, Fig. 3 and Fig. 5, which is an example of a side wall) that defines the second receiving space 20B. The third sub-housing section 20c essentially houses the electric motor 11. The first sub-housing section 20a, the second sub-housing section 20b, the third sub-housing section 20c and the separating element 20d, which are the components of the rear axle housing 20, are connected to one another via screws (not shown) in a manner as shown in Fig. 1. These sub-housing sections 20a, 20b, 20c and the separating element 20d are made of a light metal casting, for example, by aluminum die-casting or the like. One of the above-described bearings 21 and one of the above-described bearings 27 is mounted on the separating element 20d.

[0021] The counter driven gear 23 and the final driven gear 26 are configured to rotate to supply lubricating oil to the lubricated portions by entraining (picking up, scooping up, or stirring up) the lubricating oil accumulated at the bottom of the rear axle housing 20. That is, according to the present embodiment, a drag lubrication system is used in the rear axle 10. The drag lubrication system is designed to supply lubricating oil to the lubricated portions by entraining the lubricating oil accumulated at the bottom inside the rear axle housing 20. The lubricated portions include, for example, meshing portions of the first reduction gear pair 14 and the second reduction gear pair 16, gear meshing portions, and rotational sliding portions of the differential gear 17, the bearings 21, 24, 27, and the like.

[0022] The rear axle housing 20 has a first collecting container 32 for receiving a portion of the entrained lubricating oil to reduce the oil level position of the lubricating oil accumulated at the bottom inside the rear axle housing 20, with the aim of reducing the stirring resistance of the lubricating oil at the counter driven gear 23, which stirring resistance increases with the vehicle speed V. As shown in Fig. 2 and Fig. As shown in Figure 3, the first collecting container 32 is arranged above (or along) the sub-housing sections 20a, 20b, 20c and the partition member 20d such that lubricating oil is collected at a position higher than the oil level H1 (oil level H1) at the bottom of the rear axle housing 20. The oil level H1 is the height of the lubricating oil accumulated at the bottom of the rear axle housing 20 when the vehicle is stopped.

[0023] In order to reserve the top side of the rear axle housing 20 for a place for attaching a spare wheel or a vehicle storage battery, in the present embodiment, the first collecting container 32 is arranged on the rearmost side of the rear axle housing 20 (on the vehicle rear side with respect to the first reduction gear pair 14 and the second reduction gear pair 16, with the counter shaft 13, that is, the bottom side in Fig. 1, the left side in Fig. 2 and Fig. 4 and the right side in Fig. 3 and Fig. 5), as an example of a position where the first catch tank 32 prevents overlap with both the first reduction gear pair 14 and the second reduction gear pair 16 in the vertical direction. That is, as the position where the first catch tank 32 is arranged, the position where the first catch tank 32 prevents overlap with both the first reduction gear pair 14 and the second reduction gear pair 16 in the vertical direction constitutes a zone (area) in which the first catch tank 32 does not overlap with at least a portion above the highest position of both the first reduction gear pair 14 and the second reduction gear pair 16 in the height direction, even if the first catch tank 32 overlaps with an area above the first reduction gear pair 14 and the second reduction gear pair 16.Since most of the lubricating oil carried by the counter driven gear 23 of the first reduction gear pair 14 is sprayed (fed) upward and backward as indicated by arrow A in . Fig. 2, the first collecting container 32 is arranged at a position where the first collecting container 32 can efficiently hold the entrained lubricating oil, that is, at the rearmost side of the rear axle housing 20.

[0024] Therefore, the lubricating oil taking-up operation of the counter driven gear 23, which has a higher speed and a higher lubricating oil taking-up performance (i.e., a larger take-up amount) than the final driven gear 26 of the second reduction gear pair 16, is smoothly accomplished.Lubricating oil accommodated in the first reservoir 32 is supplied from a lubricating oil supply port (not shown) provided in the first reservoir 32 to another lubricated portion, overflows from the first reservoir 32 as a result of accumulation of lubricating oil at or above a predetermined amount, or is supplied from a discharge port (not shown) provided at the bottom of the first reservoir 32 as naturally discharged oil to portions requiring lubrication, such as bearings and oil seals, which are not immersed in lubricating oil due to a decrease in the oil level position at the bottom in the rear axle housing 20. Therefore, lubricating oil is returned to the bottom inside the rear axle housing 20.

[0025] A first oil passage 33 is provided in the first sub-housing section 20a of the rear axle housing 20. The first oil passage 33 carries lubricating oil, which is carried by the counter driven gear 23 of the first reduction gear pair 14, to the first collecting tank 32, as indicated by arrow A in Fig. 2. On the other hand, a second oil passage 34 (corresponding to an oil passage) is provided in the second sub-housing portion 20b of the rear axle housing 20. The second oil passage 34 carries lubricating oil carried by the final driven gear 26 of the second reduction gear pair 16 to a second collecting tank 35, as indicated by arrow B in Fig. 3. As in Fig. 1, the second oil passage 34 is arranged such that it is directed relative to the first oil passage 33 in the axial direction of the counter shaft 13 (i.e., to the right in Fig. 1), that is, the rotating shaft of the counter driven gear 23 of the first reduction gear pair 14. The arrangement position of the second oil passage 34 is also a position that is offset relative to the first oil passage 33 in the axial direction of the output shaft 12 (that is, to the right in Fig. 1), that is, the rotating shaft of the counter drive gear 22 of the first reduction gear pair 14. That is, the second oil passage 34 is arranged such that it is offset from the first oil passage 33 in the rotational axis direction of the first reduction gear pair 14.

[0026] As in Fig. As shown in Figure 2, the first oil passage 33 is formed in the outer periphery of a first oil passage wall 20a2 extending from the first side wall 20a1 of the first sub-housing portion 20a. The first oil passage 33 is radially defined by the outer periphery of the first oil passage wall 20a2 and an outer peripheral wall 20a3 of the first sub-housing portion 20a. The first oil passage 33 carries lubricating oil entrained by the counter driven gear 23 to the first catch tank 32.

[0027] As in Fig. 3, the second oil passage 34 is formed on the outer periphery of a second oil passage wall 20b2 extending from the second side wall 20b1 of the second sub-housing portion 20b. The second oil passage 34 is radially defined by the outer periphery of the second oil passage wall 20b2 and an outer peripheral wall 20b3 of the second sub-housing portion 20b. The second oil passage 34 carries lubricating oil entrained by the final driven gear 26 to the second catch tank 35. As shown in Fig. 3 to Fig. 5, the second catch tank 35 is provided at a position higher than the level H1 at the bottom in the rear axle housing 20 compared to the first catch tank 32 to receive entrained lubricating oil and reduce the oil level position of the lubricating oil accumulated at the bottom in the rear axle housing 20.

[0028] The second collecting container 35 is radially formed by the outer circumference of the second oil passage wall 20b2, a container wall 20d2 (see Fig. 4) extending from the partition wall 20d1 of the partition member 20d, the outer peripheral wall 20b3 of the second sub-housing portion 20b and an outer peripheral wall 20d3 (see Fig. 4) of the partition member 20d. The second catch tank 35 is defined in the axial direction by the second side wall 20b1 of the second sub-housing portion 20b and the partition wall 20d1 of the partition member 20d. The second catch tank 35 has an outlet hole 35a at its bottom. The outlet hole 35a discharges lubricating oil. Lubricating oil supplied to the second catch tank 35 is naturally discharged through the outlet hole 35a and returned to the bottom inside the rear axle housing 20.

[0029] As in Fig. 1, the second catch tank 35 is provided in the rotational axis direction of the counter driven gear 23 at a position within the protruding portion of the receiving space of the counter driven gear 23 on the outer peripheral side of the final drive gear 25. In this way, the second catch tank 35 is provided in the dead space of the speed reducer unit including the first reduction gear pair 14 and the second reduction gear pair 16, so that it is possible to increase the total capacity of the catch tank with the first catch tank 32 without increasing the size of the speed reducer unit.

[0030] As in Fig. 4, the partition wall 20d1 of the separating element 20d has a window 36 as a connection port that connects the first oil passage 33 to the second oil passage 34. As shown in Fig. 3, the second sub-housing portion 20b has a weir 37 on the outer periphery of the second oil passage wall 20b2. The weir 37 allows lubricating oil, which is entrained to the second oil passage 34, to be guided to the window 36. The weir 37 is provided by using a push-out pin seat, which is generally provided for easily removing the second sub-housing portion 20b from a mold (casting die) at the time of casting the second sub-housing portion 20b. The weir 37 is provided on a downstream side near a position corresponding to the window 36 of the second oil passage 34. As shown in Fig. 3, the weir 37 guides a part of the flow (indicated by arrow B) of the lubricating oil entrained to the second oil passage 34 such that the part of the flow of entrained lubricating oil changes its direction towards the window 36 and enters the first oil passage 33 as indicated by arrow C. As shown in Fig. 4, a guide wall 38 extending from the partition wall 20d1 of the partition member 20d connects the container wall 20d2 to the outer peripheral wall 20d3 and guides lubricating oil, which is guided as indicated by the arrow C, to the window 36.

[0031] Through the window 36 provided in the separating element 20d, the second oil passage 34, which carries entrained lubricating oil to the second collecting container 35, is connected to the first oil passage 33, which carries entrained lubricating oil to the first collecting container 32. Therefore, from the two collecting containers 32, 35, that is, the first collecting container 32 and the second collecting container 35, to each of which entrained lubricating oil is carried and each receives lubricating oil, even if the second collecting container 35 becomes full of lubricating oil first and has no space to hold (receive) lubricating oil, excess lubricating oil is led through the window 36 to the first collecting container 32, which still has space to hold (receive) lubricating oil, as indicated by the arrow C in Fig. 3, so that it is possible to improve the efficiency of lubricating oil entrainment. Even if the first catch tank 32 initially becomes full of lubricating oil and has no space to receive the lubricating oil, excess lubricating oil flows from the first oil passage 33 through the window 36 into the second oil passage 34 and is guided to the second catch tank 35, which still has space to receive the lubricating oil, so that it is possible to improve the efficiency of lubricating oil entrainment.

[0032] As in Fig. 5, a rib 39 is provided. The rib 39 extends from a position near the rear wall side of the second oil passage 34 on the inner wall side of the second side wall 20b1 of the second split case portion 20b, that is, the underside of the second oil passage wall 20b2, to an inner peripheral portion 20b4, that is, a rotation axis 26a side of the final driven gear 26, that is, a rotation axis 15a side of the differential case 15, in the second side wall 20b1. A groove 40 is provided in the second side wall 20b1. The groove 40 is provided so as to face an end edge 39a of the rib 39. Lubricating oil trapped by the rib 39 is introduced into the groove 40. The groove 40 communicates with lubricating oil supply objects.The lubricating oil supply objects are the bearing 27 that supports the final driven gear 26 on the second sub-housing portion 20b, and an oil seal 41 that seals the interior of the second sub-housing portion 20b from the exterior. The lubricating oil supply objects are provided on the second side wall 20b1 near the rotational axis 26a of the final driven gear 26. Thus, the bearing 27 and the oil seal 41, which are the lubricating oil supply objects, are provided on the second sub-housing portion 20b between the internally formed second side wall 20b1 and the rotational axis 26a. The rib 39 is formed on the second side wall 20b1 to extend radially and guide entrained lubricating oil to a radially inner side.

[0033] At least one additional rib 39b, in which Fig. 5, three additional ribs 39b are provided radially next to the rib 39 in the direction of rotation of the final driven gear 26 in front of the rib 39. As in Fig. 6, the second side wall 20b1 is formed with a tapered shape so that a tapered portion 20b7 is provided that approaches the rotational axis 26a of the final driven gear 26 as the tapered portion 20b7 moves away from the final driven gear 26. A part of the differential case 15 is provided so as to face the tapered portion 20b7 of the second side wall 20b1, and a tapered clearance 20b8 (see Fig. 6) is formed between the part of the differential case 15 and the chamfered portion 20b7.

[0034] As in Fig. 5 and Fig. 6, the groove 40 includes a groove 40a and a groove 40b. The groove 40a is recessed into the inner periphery of a bearing hole 20b5 for the bearing 27 provided on the second split housing portion 20b. The groove 40b is recessed into a step wall 20b6 formed between the bearing 27 and the oil seal 41. The groove 40a, which is recessed into the inner periphery of the bearing hole 20b5 for the bearing 27, has a greater width than the rib 39. The groove 40 is provided substantially at the center in the width direction (transverse direction) of the rib 39. The groove 40 supplies lubricating oil to the bearing 27 and the oil seal 41, which are the lubricating oil supply objects. After the lubricating oil has lubricated the bearing 27 and the oil seal 41, the lubricating oil is returned to the bottom inside the rear axle housing 20.By providing the groove 40 substantially at the center in the width direction of the rib 39, it is possible to introduce lubricating oil from the rib 39 into the groove 40 when the final driven gear 26 rotates in the reverse direction, for example, when the vehicle moves backward, as well as when the vehicle moves forward.

[0035] Since the rib 39 is provided in the second sub-housing portion 20b, lubricating oil having a low entrainment height in the lubricating oil entrained by the final driven gear 26 and not having reached the second oil passage 34 passes near the rear wall side of the second oil passage 34, that is, the underside of the second oil passage wall 20b2, as shown by the arrow D in Fig. 5. This lubricating oil flow indicated by arrow D is limited by the rib 39 on the circumference. Lubricating oil flows along the rib 39 to the rotation axis 26a and is supplied from the outer peripheral side to the bearing 27 for lubrication, and also flows into the groove 40a formed in the inner peripheral portion of the bearing hole 20b5. Lubricating oil that has flowed into the groove 40a passes through the groove 40b formed in the step wall 20b6 and is supplied to the bearing 27 from the rear side (right side in Fig. 6) of the bearing 27, which is the lubricating oil supply object, for lubrication, and is supplied to the oil seal 41, which is the lubricating oil supply object, for lubrication.

[0036] By providing the auxiliary ribs 39b in front of the rib 39 in the rotational direction of the final driven gear 26, it is also possible to collect, with the aid of the auxiliary ribs 39b, lubricating oil that has a low drag height in the lubricating oil entrained by the final driven gear 26 and that has not reached the second oil passage 34. Lubricating oil entrained by the final driven gear 26 and caused to flow along the rotational axis 26a toward the tapered portion 20b7 of the second side wall 20b1 flows into the tapered clearance 20b8 formed between the tapered portion 20b7 and the outer periphery of the differential case 15. A part of the lubricating oil restricted from circulating by the auxiliary ribs 39b flows toward the rotation axis 26a along the auxiliary ribs 39b and the wall surface of the tapered portion 20b7, and is supplied to the bearing 27 from the outer peripheral side for lubrication.Lubricating oil that has reached the rib 39 via the auxiliary ribs 39b and the lubricating oil that has flowed between the last auxiliary rib 39b and the rib 39 is restricted from circumferentially flowing by the rib 39, flows along the rib 39 toward the rotation axis 26a, and is supplied to the bearing 27, and further flows into the groove 40a formed in the inner peripheral portion of the bearing hole 20b5. Lubricating oil that has flowed into the groove 40a flows through the groove 40b formed in the step wall 20b6 and is supplied to the bearing 27 from the rear side (right side in FIG. Fig. 6) of the bearing 27, which is the lubricating oil supply target, for lubrication, and is also supplied to the oil seal 41, which is the lubricating oil supply target, for lubrication. In this way, part of the lubricating oil carried by the final driven gear 26 is directly supplied to the bearing 27 or the oil seal 41, which are the lubricating oil supply targets, without passing through the second reservoir 35 or the first reservoir 32, thus enabling rapid lubrication. Since the lubricating oil carried by the final driven gear 26 is supplied to the bearing 27 or the oil seal 41, which are the targets of the lubricating oil supply, by means of the rib 39 and the groove 40, it is not necessary to form a special oil passage.

[0037] As in Fig. 2 and Fig. 3, in a state where the vehicle is stopped, the counter driven gear 23 of the first reduction gear pair 14 and the final driven gear 26 of the second reduction gear pair 16 are arranged at the level at which at least substantially the lower half of the counter driven gear 23 of the first reduction gear pair 14 and the lower half of the final driven gear 26 of the second reduction gear pair 16 are immersed in lubricating oil accumulated at the bottom in the rear axle housing 20. The level H1 shown in the Fig. 2 and the Fig. 3, indicated by a dot-dash line, indicates the level of lubricating oil accumulated at the bottom of the rear axle housing 20 during a vehicle stop. The rotor 11a of the electric motor 11 is also positioned at the level at which at least substantially the lower half of the rotor 11a of the electric motor 11 is immersed in lubricating oil accumulated at the bottom of the rear axle housing 20 during a vehicle stop.

[0038] When the vehicle starts moving, the amount of lubricating oil accumulated at the bottom of the rear axle housing 20 increases with increasing vehicle speed, and the level of the lubricating oil begins to gradually decrease from the level H1. In a state where the vehicle speed is substantially 50 kilometers per hour, the level of the lubricating oil accumulated at the bottom of the rear axle housing 20 is the level H2, which is indicated by the dot-dash line in the Fig. 2 and the Fig. 3, and even the lowermost portion of the counter driven gear 23 of the first reduction gear pair 14 is almost not immersed in lubricating oil. On the other hand, the lower end of the final driven gear 26 of the second reduction gear pair 16 remains immersed in lubricating oil.

[0039] Even when the vehicle speed reaches substantially 50 kilometers per hour, and therefore, it becomes difficult for the intermediate driven gear 23, which has a higher lubricating oil absorption capacity than the final driven gear 26, to pick up lubricating oil from the ground in the rear axle housing 20, the state in which it is possible to pick up lubricating oil through the final driven gear 26 is maintained. Structurally, the rotation of the final driven gear 26 is smaller than that of the intermediate driven gear 23; however, when the vehicle speed is substantially 50 kilometers per hour, the rotation of the final driven gear 26 also increases, so that it is possible to pick up lubricating oil from the ground in the rear axle housing 20 using only the final driven gear 26.

[0040] As described above, the rear axle 10 (which is an example of a lubricating structure of a speed reducer) according to the present embodiment includes the rear axle housing 20 (which is an example of a housing), the final driven gear 26 (which is an example of a reduction gear), the second catch tank 35 (which is an example of a catch tank), the second oil passage 34 (which is an example of an oil passage), the rib 39, and the groove 40. In the rear axle housing 20, the lubricating oil supply objects are provided between the internally formed second side wall 20b1 (which is an example of a side wall) and the rotational axis 26a of the final driven gear 26. The final driven gear 26 is provided inside the rear axle housing 20 and is connected to the output shaft 12 of the electric motor 11 (which is an example of a drive source). The final drive gear 26 rotates around the rotation axis 26a.The second catch tank 35 receives a portion of the lubricating oil collected at the bottom of the rear axle housing 20 and carried by the final driven gear 26. The second oil passage 34 is provided in the second side wall 20b1 and guides the lubricating oil carried by the final driven gear 26 to the second catch tank 35. The rib 39 is formed on the second side wall 20b1 to extend radially and guides the carried lubricating oil to a radially inner side. The groove 40 is provided at the end edge 39a of the rib 39 of the second side wall 20b1. The lubricating oil collected by the rib 39 is introduced into the groove 40. The groove 40 communicates with the lubricating oil supply objects. The lubricating oil carried by the final drive gear 26 is therefore quickly supplied to the lubricating oil supply objects via the rib 39 without passing through the second collecting container 35.Even if lubricating oil is carried away from the final driven gear 26, it is possible to supply the lubricating oil that has not reached the second catch tank 35 in a conventional manner and that has drained to the bottom in the rear axle housing 20 to the lubricating oil supply object, so that it is possible to use lubricating oil efficiently.

[0041] As described above with reference to the rear axle 10 (which is an example of a lubricating structure of a speed reducer) according to the present embodiment, at least one auxiliary rib 39b is formed radially in front of the rib 39 in the rotational direction of the final driven gear 26, and the second side wall 20b1 is formed in a tapered shape so that it approaches the rotational axis 26a of the final driven gear 26 as the second side wall 20b1 moves away from the final driven gear 26. Consequently, it is also possible to restrict lubricating oil from circulating and to collect lubricating oil that has not reached the second oil passage 34 due to a small drag height in the lubricating oil dragged by the final driven gear 26 by means of the auxiliary ribs 39b.Lubricating oil trapped by the auxiliary ribs 39b flows along the auxiliary ribs 39b and the tapered wall surface of the second side wall 20b1 to the rotation axis 26a. Lubricating oil that has reached the rib 39 via the auxiliary ribs 39b is restricted from circumferential movement by the rib 39 and flows along the rib 39 to the rotation axis 26a. The lubricating oil is then supplied to the lubricating oil supply objects for lubrication. Therefore, the auxiliary ribs 39b enhance the trapping of lubricating oil that has not reached the second oil passage 34 due to a small drag height in the lubricating oil entrained by the final driven gear 26, making it possible to supply the lubricating oil to the lubricating oil supply objects.

[0042] As described above with reference to the rear axle 10 (which is an example of a lubricating structure of a speed reducer) according to the present embodiment, the lubricating oil supply objects are the bearing 27 that supports the final driven gear 26 on the rear axle housing 20, and the oil seal 41 that is provided adjacent to the bearing 27 and seals the inside of the rear axle housing 20 from the outside. The groove 40 is recessed into the inner periphery of the bearing hole 20b5 provided in the rear axle housing 20 and into the step wall 20b6 formed between the bearing 27 and the oil seal 41. The portion of the groove 40 formed in the bearing hole 20b5 has a greater width than the rib 39, and the groove 40 is provided substantially at the center in the width direction of the rib 39.Therefore, even when the final driven gear 26 rotates in the reverse direction, for example, when the vehicle is moving backward, as well as when the vehicle is moving forward, it is possible to introduce lubricating oil from the rib 39 into the groove 40. Since it is possible to supply lubricating oil to the bearing 27 supporting the final driven gear 26 on the rear axle housing 20 and the oil seal 41 provided adjacent to the bearing 27 and sealing the interior of the rear axle housing 20 from the exterior by means of the groove 40, it is not necessary to form a special oil passage.

[0043] As described above with reference to the rear axle 10 (which is an example of a lubrication structure of a speed reducer) according to the present embodiment, the final driven gear 26 is fixed to the differential case 15, which contains the differential gear 17 that drives the pair of rear axles 18 (which are examples of axles) for rotation. Therefore, the invention is applicable to a vehicle having the differential case 15.

[0044] It is explicitly emphasized that all features disclosed in the description and / or the claims are to be considered separate and independent of each other for the purpose of the original disclosure as well as for the purpose of limiting the claimed invention, regardless of the feature combinations in the embodiments and / or the claims. It is explicitly stated that all range specifications or specifications of groups of units disclose every possible intermediate value or subgroup of units for the purpose of the original disclosure as well as for the purpose of limiting the claimed invention, in particular also as a limit of a range specification.

Claims

[1] Lubrication structure for a speed reducer, wherein the lubrication structure comprises: a housing (20) in which a lubricating oil supply object is provided between an internally formed side wall (20b1) and a rotation axis (26a); a reduction gear (26) provided inside the housing (20), the reduction gear (26) being connected to an output shaft (12) of a drive source (11) and being configured to rotate about the rotation axis (26a); a collecting container (35) adapted to receive a portion of a lubricating oil accumulated at a bottom in the housing (20) and carried by the reduction gear (26); an oil passage (34) provided on the side wall (20b1), the oil passage (34) being designed to guide the lubricating oil carried by the reduction gear (26) to the collecting container (35); a rib (39) formed on the side wall (20b1) so as to extend radially from a position near a rear wall side of the oil passage (34); a groove (40) provided at an end edge (39a) of the rib (39) of the side wall (20b1), wherein lubricating oil collected by the rib (39) is introduced into the groove (40), and the groove (40) is in communication with the lubricating oil supply object, so that the lubricating oil carried by the reduction gear (26) is supplied to the lubricating oil supply object via the rib (39) without passing through the collecting container (35); and at least one additional rib (39b) which is formed radially in front of the rib (39) in a direction of rotation of the reduction gear (26), wherein the side wall (20b1) is formed with a bevelled shape so that it approaches the rotation axis (26) when the side wall (20b1) moves away from the reduction gear (26) and the rib (39) for guiding the lubricating oil, which has not reached the oil passage (34) due to a low entrainment height in the lubricating oil entrained by the reduction gear (26) and is collected with the aid of the additional ribs (39b), is formed to a radially inner side. [2] A lubricating structure according to claim 1, wherein the lubricating oil supply object comprises a bearing (27) supporting the reduction gear (26) on the housing (20), and an oil seal (41) provided adjacent to the bearing (27) and sealing an inside of the housing (20) from an outside. [3] Lubricating structure according to claim 2, wherein the groove (40) is recessed in an inner circumference of a bearing hole (20b5) provided in the housing (20) and in a step wall (20b6) formed between the bearing (27) and the oil seal (41), a portion of the groove (40) formed in the bearing hole (20b5) has a greater width than the rib (39), and the groove (40) is provided in a width direction of the rib (39) at a center of the rib (39). [4] A lubricating assembly according to any one of claims 1 to 3, wherein the reduction gear (26) is fixed to a differential case (15) having a differential gear (17) driving a pair of axles (18) for rotation.

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