Lubrication structure for a speed reducer

Abstract

Lubrication structure for a speed reducer, wherein the lubrication structure comprises: a housing (20); a first reduction gear pair (14) provided inside the housing (20) and configured for meshing rotation with an output shaft (12) of a drive source, the first reduction gear pair (14) comprising a first drive gear and a first output gear meshing with the first drive gear; a second reduction gear pair (16) provided inside the housing (20) and arranged to be offset in a rotational axis direction of the first reduction gear pair (14) with respect to the first reduction gear pair (14), the second reduction gear pair (16) having a second drive gear and a second driven gear that is in engagement with the second drive gear and has a lower rotational speed than the first driven gear; a first collecting container (32) arranged inside the housing (20); a second collecting container (35) arranged inside the housing (20); a partition member (20d) which is a component of the housing (20), the partition member (20d) having a partition wall (20d1) which divides an interior of the housing (20) into a first accommodating space (20A) in which the first reduction gear pair (14) is accommodated, and a second accommodating space (20B) in which the second reduction gear pair (16) is accommodated; a first oil passage (33) communicating with the first receiving space (20A), the first oil passage (33) being configured to guide lubricating oil accumulated at a bottom in the housing (20) and carried by the first driven gear to the first collecting tank (32); a second oil passage (34) communicating with the second receiving space (20B), the second oil passage (34) being adapted to guide lubricating oil accumulated at the bottom of the housing (20) and carried by the second driven wheel to the second collecting container (35); and a connecting port (36) provided in the separating member (20d) and connecting the first oil passage (33) to the second oil passage (34).

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, inside a housing, a first reduction gear pair that rotates a drive source in meshing engagement with an output shaft, and a second reduction gear pair that is arranged (offset) with respect to the first reduction gear pair in a rotational axis direction of the first reduction gear pair and that has a lower rotational speed than the first reduction gear pair, and with which it is possible to reduce a stirring loss in a high rotational speed range of the drive source by increasing lubricating oil held in catch tanks by providing two catch tanks such that lubricating oil accumulated at a bottom inside the housing is led to the first catch tank by entraining the lubricating oil with the aid of the first reduction gear pair,and the lubricating oil is also fed to the second collecting container by entraining the lubricating oil with the help of the second pair of reduction gears., 2. Description of the state of the art

[0002] A structure is known in which lubricating oil accumulated at a bottom inside a housing is divided by a partition provided in the housing, and the divided portions of the lubricating oil are respectively directed to a first collecting tank and a second collecting tank (see, for example, JP 2010 - 223 376 A). Other lubrication structures for speed reducers are known from JP 2006 - 307 908 A, JP 2012 - 189 176 A, and US 2008 / 0 128 208 A1. SUMMARY OF THE INVENTION

[0003] However, since a first oil passage that supplies lubricating oil to the first catch tank and a second oil passage that supplies lubricating oil to the second catch tank are separated from each other by the partition wall provided in the housing as described above, when the first catch tank and / or the second catch tank become full of lubricating oil and have no space to contain (receive) the lubricating oil, the entrained lubricating oil flows backward and returns to the bottom of the housing. This may reduce the efficiency of entrainment of the lubricating oil.

[0004] The invention provides a lubrication structure for a speed reducer with which it is possible, even if one of the two collecting containers, to which carried lubricating oil is respectively led and which respectively receives lubricating oil, becomes full of lubricating oil and has no space to receive lubricating oil, to guide (direct) excess lubricating oil to the other collecting container, which still has space to receive lubricating oil.

[0005] In one aspect of the invention, a lubricating structure for a speed reducer is provided. The lubricating structure comprises: a housing; a first reduction gear pair provided inside the housing, the first reduction gear pair being configured for meshed rotation with an output shaft of a drive source and including a first drive gear and a first driven gear meshed with the first drive gear; a second reduction gear pair provided inside the housing and arranged to be offset from the first reduction gear pair in a rotational axis direction of the first reduction gear pair, the second reduction gear pair including a second drive gear and a second driven gear meshed with the second drive gear and having a lower rotational speed than the first driven gear; a first receptacle disposed inside the housing;a second collecting container disposed inside the housing; a partition member that is a component of the housing, the partition member having a partition wall that divides an interior of the housing into a first receiving space in which the first reduction gear pair is housed and a second receiving space in which the second reduction gear pair is housed; a first oil passage (oil passage) communicating with the first receiving space, the first oil passage being configured to guide (conduct) lubricating oil that has accumulated at a bottom in the housing and is carried (picked up, scooped up, swirled up) by the first driven gear (upward) to the first collecting container;a second oil passage communicating with the second receiving space, the second oil passage being configured to guide lubricating oil collected at the bottom of the housing and carried upward by the second driven gear to the second collecting tank; and a connecting port provided in the partition member and connecting the first oil passage to the second oil passage.

[0006] In this configuration, the first oil passage, which supplies entrained lubricating oil to the first catch tank, and the second oil passage, which supplies entrained lubricating oil to the second catch tank, communicate with each other via the connecting port provided in the partition member. That is, of the two catch tanks, i.e., the first catch tank and the second catch tank, each of which supplies entrained lubricating oil and each stores lubricating oil, even if one of the catch tanks becomes full of lubricating oil and has no space to store lubricating oil, excess lubricating oil is supplied to the other catch tank, which still has space to store lubricating oil, thus improving the efficiency of entrainment of lubricating oil.

[0007] In the above aspect, the housing may include the partition member, a first sub-housing portion fixed to one side of the partition member and having a first side wall defining the first accommodating space, and a second sub-housing portion fixed to the other side of the partition member and having a second side wall defining the second accommodating space, the first oil passage may be radially defined by an outer periphery of a first oil passage wall (oil passage wall) extending from the first side wall and an outer peripheral wall of the first sub-housing portion, and the second oil passage may be radially defined by an outer periphery of a second oil passage wall (oil passage wall) extending from the second side wall and an outer peripheral wall of the second sub-housing portion.It is therefore possible to define the first oil passage and the second oil passage merely by connecting and fixing the first sub-housing portion and the second sub-housing portion to the separating member.

[0008] In the above aspect, the second sub-housing portion may include a weir on the outer periphery of the second oil passage wall, and the weir may allow the lubricating oil entrained to the second oil passage to be guided to the connection port. Therefore, it is possible to guide entrained lubricating oil from the second oil passage to the first oil passage.

[0009] In the above aspect, the weir may be an ejector pin seat of the second sub-casing section. Therefore, the ejector pin seat required at the time of casting the second sub-casing section can also be used as a weir, eliminating the need to form the weir itself.

[0010] In the above aspect, the second collecting tank may be radially defined by the outer periphery of the second oil passage wall, an outer periphery of a tank wall extending from the partition wall, the outer peripheral wall of the second sub-housing portion, and an outer peripheral wall of the partition member. Therefore, it is possible to define the second collecting tank merely by connecting and fixing the second sub-housing portion to the partition member.

[0011] In the above aspect, the second collecting container may have a discharge hole at the bottom thereof, and the discharge hole may be configured to discharge lubricating oil. Therefore, it is possible to return lubricating oil accumulated in the second collecting container to the bottom of the housing.

[0012] In the above aspect, the drive source may be an electric motor, the first reduction gear pair may be provided between the output shaft and a countershaft (countershaft) parallel to the output shaft, the second reduction gear pair may be provided between the countershaft and a differential case which is parallel to the countershaft and houses a differential gear configured to drive a pair of axles for rotation, the first output gear may be a first countershaft output gear which is the gear with a larger diameter among the first reduction gear pair and is fixed to the countershaft, the second output gear may be a final output gear fixed to the differential case,and the second collecting container may be provided in a rotational axis direction of the counter driven gear at a position within a protruding portion of a receiving space of the counter driven gear on an outer peripheral side of the second drive gear. Therefore, the invention is applicable to a vehicle having at least the pair of electrically driven axles. In this way, it is possible to provide the second collecting container in the dead space of the speed reducer unit including the first reduction gear pair and the second reduction gear pair, making it possible to increase the total capacity of the collecting container with the first collecting container without increasing the size of the speed reducer unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] 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

[0014] 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.

[0015] 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.

[0016] 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.

[0017] The first reduction gear pair 14 consists of a counter drive gear 22 (which is an example of a first drive gear) with a small diameter and a counter driven gear 23 (which is an example of a first driven gear) 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.

[0018] 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 in turn is connected to the output shaft 12 and the differential case 15. The countershaft driven gear 23 is therefore 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.

[0019] 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 (which is an example of a second drive gear) with a small diameter and the final driven gear 26 (which is an example of a second driven gear) 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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 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.

[0024] 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 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 (picking up, scooping up, or swirling up) 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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 is provided in the second sub-housing section 20b of the rear axle housing 20. The second oil passage 34 carries lubricating oil, which is carried by the final driven gear 26 of the second reduction gear pair 16, to a second collecting container 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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 an ejector 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.

[0034] 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.

[0035] 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 side of the final driven gear 26, that is, a rotation axis 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 inside of the second sub-housing portion 20b from the outside.The lubricating oil supply objects are provided on the second side wall 20b1 near the rotation axis of the final driven gear 26.

[0036] 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 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.

[0037] 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.

[0038] 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 axis 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.

[0039] 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 axis 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 axis 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 extending by the rib 39, flows along the rib 39 toward the axis, 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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, inside the rear axle casing 20 (which is an example of a casing), the first reduction gear pair 14 that rotates in mesh with the output shaft 12 of the electric motor 11 (which is an example of a drive source), and the second reduction gear pair 16 that is arranged to be offset from the first reduction gear pair 14 in a rotational axis direction of the first reduction gear pair 14. The first reduction gear pair 14 includes a first drive gear and a first driven gear that meshes with the first drive gear. The second reduction gear pair 16 includes a second drive gear and a second driven gear.which is in engagement with the second drive gear and has a lower speed than the first driven gear. The rear axle 10 further comprises the first collecting container 32 arranged inside the rear axle housing 20, the second collecting container 35 arranged inside the rear axle housing 20, the partition element 20d, which is a component of the rear axle housing 20 and which forms the partition wall 20d1, which divides the interior of the rear axle housing 20 into the first receiving space 20A in which the first reduction gear pair 14 is housed, and the second receiving space 20B in which the second reduction gear pair 16 is housed, the first oil passage 33, which communicates with the first receiving space 20A and leads lubricating oil, which has accumulated at the bottom in the rear axle housing 20 and is carried by the first driven gear, to the first collecting container 32, the second oil passage 34,which communicates with the second receiving space 20B and leads lubricating oil accumulated at the bottom of the rear axle housing 20 and carried by the second driven gear to the second collecting tank 35, and the window 36 (which is an example of a connecting port) provided in the partition member 20d and connects the first oil passage 33 to the second oil passage 34. The first oil passage 33, which carries carried lubricating oil to the first collecting tank 32, and the second oil passage 34, which carries carried lubricating oil to the second collecting tank 35, communicate with each other via the window 36 provided in the partition member 20d. With this configuration, the two collecting tanks 32, 35, that is, the first collecting tank 32 and the second collecting tank 35, each of which carries carried lubricating oil and each of which receives lubricating oil,Even if one of the collecting tanks becomes full of lubricating oil and has no space to hold the lubricating oil, the excess lubricating oil is led to the other collecting tank, which still has space to hold the lubricating oil, so that it is possible to improve the efficiency of lubricating oil collection.

[0044] As described above with respect to the rear axle 10 (which is an example of a lubricating structure for a speed reducer) according to the above embodiment, the rear axle housing 20 includes the partition member 20d, the first sub-housing portion 20a fixed to one side of the partition member 20d and having the first side wall 20a1 defining the first accommodating space 20A, and the second sub-housing portion 20b fixed to the other side of the partition member 20d and having a second side wall 20b1 defining the second accommodating space 20B. The first oil passage 33 is radially defined by the outer periphery of the first oil passage wall 20a2 extending from the first side wall 20a1 and the outer periphery wall 20a3 of the first sub-housing portion 20a, and the second oil passage 34 is radially defined by the outer periphery of the second oil passage wall 20b2.extending from the second side wall 20b1 and the outer peripheral wall 20b3 of the second sub-housing portion 20b. Therefore, it is possible to define the first oil passage 33 and the second oil passage 34 simply by connecting and securing the first sub-housing portion 20a and the second sub-housing portion 20b to the separator 20d.

[0045] As described above with respect to the rear axle 10 (which is an example of a lubrication structure for a speed reducer) according to the above embodiment, the second split case portion 20b includes the weir 37 on the outer periphery of the second oil passage wall 20b2, and the weir 37 allows the lubricating oil entrained to the second oil passage 34 to be guided to the window 36. Therefore, it is possible to guide entrained lubricating oil from the second oil passage 34 to the first oil passage 33.

[0046] As described above with reference to the rear axle 10 (which is an example of a lubrication structure for a speed reducer) according to the above embodiment, the weir 37 is the ejector pin seat of the second split housing portion 20b. Therefore, the ejector pin seat required at the time of molding the second split housing portion 20b is also used as the weir 37, so it is not necessary to form the weir 37 itself.

[0047] As described above with respect to the rear axle 10 (which is an example of a lubrication structure for a speed reducer) according to the above embodiment, the second catch tank 35 is radially defined by the outer periphery of the second oil passage wall 20b2, the outer periphery of the tank wall 20d2 extending from the partition wall 20d1, the outer peripheral wall 20b3 of the second split case portion 20b, and the outer peripheral wall 20d3 of the partition member 20d. Therefore, it is possible to define the second catch tank 35 merely by connecting and fixing the second split case portion 20b to the partition member 20d.

[0048] As described above with respect to the rear axle 10 (which is an example of a lubrication structure for a speed reducer) according to the above embodiment, the second reservoir 35 has an outlet hole 35a at its bottom, and the outlet hole 35a discharges lubricating oil. Therefore, it is possible to return the lubricating oil stored in the second reservoir 35 to the bottom of the rear axle housing 20.

[0049] As described above with respect to the rear axle 10 (which is an example of a lubrication structure for a speed reducer) according to the above embodiment, the drive source is the electric motor 11, the first reduction gear pair 14 is provided between the output shaft 12 and the counter shaft 13 in parallel with the output shaft 12, the second reduction gear pair 16 is provided between the counter shaft 13 and the differential case 15, which is parallel to the counter shaft 13 and houses the differential gear 17 that drives the pair of axles 18 for rotation, the first output gear is the counter driven gear 23, which is the gear with a larger diameter of the first reduction gear pair 14 and is fixed to the counter shaft 13, the second output gear is the final driven gear 26, which is fixed to the differential case 15,and the second collecting container 35 is located 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 second drive wheel. Therefore, the application is applicable to a vehicle having at least the pair of electrically driven axles 18. In this way, it is possible to provide the second collecting container 35 in the dead space of the speed reducer unit with 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 collecting container with the first collecting container 32 without increasing the size of the speed reducer unit.

Claims

[1] Lubrication structure for a speed reducer, wherein the lubrication structure comprises: a housing (20); a first reduction gear pair (14) provided inside the housing (20) and configured for meshing rotation with an output shaft (12) of a drive source, the first reduction gear pair (14) comprising a first drive gear and a first output gear meshing with the first drive gear; a second reduction gear pair (16) provided inside the housing (20) and arranged to be offset in a rotational axis direction of the first reduction gear pair (14) with respect to the first reduction gear pair (14), the second reduction gear pair (16) having a second drive gear and a second driven gear that is in engagement with the second drive gear and has a lower rotational speed than the first driven gear; a first collecting container (32) arranged inside the housing (20); a second collecting container (35) arranged inside the housing (20); a partition member (20d) which is a component of the housing (20), the partition member (20d) having a partition wall (20d1) which divides an interior of the housing (20) into a first accommodating space (20A) in which the first reduction gear pair (14) is accommodated, and a second accommodating space (20B) in which the second reduction gear pair (16) is accommodated; a first oil passage (33) communicating with the first receiving space (20A), the first oil passage (33) being configured to guide lubricating oil accumulated at a bottom in the housing (20) and carried by the first driven gear to the first collecting tank (32); a second oil passage (34) communicating with the second receiving space (20B), the second oil passage (34) being adapted to guide lubricating oil accumulated at the bottom of the housing (20) and carried by the second driven wheel to the second collecting container (35); and a connecting port (36) provided in the separating member (20d) and connecting the first oil passage (33) to the second oil passage (34). [2] Lubricating structure according to claim 1, wherein the housing (20) comprises the separating element (20d), a first sub-housing section (20a) which is fastened to one side of the separating element (20d) and has a first side wall (20a1) which defines the first receiving space (20A), and a second sub-housing section (20b) which is fastened to the other side of the separating element (20d) and has a second side wall (20b1) which defines the second receiving space (20B), the first oil passage (33) is radially defined by an outer periphery of a first oil passage wall (20a2) extending from the first side wall (20a1) and an outer peripheral wall (20a3) of the first sub-housing portion (20a), and the second oil passage (34) is radially defined by an outer periphery of a second oil passage wall (20b2) extending from the second side wall (20b1) and an outer peripheral wall (20b3) of the second sub-housing portion (20b). [3] A lubricating structure according to claim 2, wherein the second split case portion (20b) has a weir (37) on the outer periphery of the second oil passage wall (20b2), and the weir (37) enables the lubricating oil entrained to the second oil passage (34) to be guided to the connecting port (36). [4] A lubrication assembly according to claim 3, wherein the weir (37) is an ejector pin seat of the second sub-housing portion (20b). [5] A lubricating structure according to any one of claims 2 to 4, wherein the second collecting tank (35) is radially defined by the outer periphery of the second oil passage wall (20b2), an outer periphery of a tank wall (20d2) extending from the partition wall (20d1), the outer peripheral wall (20b3) of the second split housing portion (20b) and an outer peripheral wall (20d3) of the partition member (20d). [6] A lubricating structure according to any one of claims 1 to 5, wherein the second collecting container (35) has an outlet hole (35a) at the bottom thereof, and the outlet hole (35a) is configured to discharge lubricating oil. [7] Lubricating structure according to one of claims 1 to 6, wherein the drive source is an electric motor (11), the first reduction gear pair (14) is provided between the output shaft (12) and a countershaft (13) parallel to the output shaft (12), the second pair of reduction gears (16) is provided between the countershaft (13) and a differential housing (15) which is parallel to the countershaft (13) and accommodates a differential gear (17) designed to drive a pair of axles (18) for rotation, the first output gear is a countershaft output gear (23) which is the gear with a larger diameter of the first reduction gear pair (14) and is fixed to the countershaft (13), the second output gear is a final output gear (26) which is fixed to the differential housing (15), and the second collecting container (35) is provided in a rotational axis direction of the counter driven gear (23) at a position within a projecting portion of a receiving space of the counter driven gear (23) on an outer peripheral side of the second drive gear.

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