Transmission

Abstract

Provided is a transmission device in which a large-diameter gear meshes with a pinion midway along a specific semiperimeter region in which a toothed surface moves toward the upper end of the large-diameter gear from the lower end thereof in conjunction with forward movement. The pinion (Gcp) and the large-diameter gear (Gf) are configured from helical gears, and are disposed such that oil on the toothed surface is pushed out from a meshing section (40) to one side of the pinion in the axial direction during the forward movement of the gears. A flow-regulating wall (Bc1) facing the oil that has been pushed out from the meshing section to the one side in the axial direction is disposed adjacent to the end surfaces on the one side in the axial direction of the teeth of the pinion (Gcp), and is formed in a shape capable of covering as far as the tooth tip portions of the end surfaces. Accordingly, the oil that has been pushed out from the meshing section to the one side of the pinion in the axial direction during the forward movement of the large-diameter gear is restricted from flowing towards the one side in the axial direction by the flow-regulating wall facing the oil, and thus more easily flows out to the toothed section-side of the large-diameter gear due to congestion at the front side of the flow-regulating wall; therefore, the oil is easily carried around and lifted up by the large-diameter gear, increasing the amount of oil pushed up to a gear upper section by the large-diameter gear.

Description

[Technical field]

[0001] The present invention relates to a transmission device, and more particularly to a transmission device in which a pinion and a large-diameter gear that meshes with the pinion and has a larger diameter than the pinion are arranged in a transmission case, and an oil reservoir is provided at the bottom of the transmission case to bring stored oil into contact with the lower part of the large-diameter gear. [Background technology]

[0002] The above-mentioned transmission device is already known, for example as disclosed in Patent Document 1 below, in which oil scooped up by a large diameter gear (e.g., a final driven gear) is captured by ribs on the inner surface of the transmission case and guided to the lubricated parts such as bearings to be used for lubrication. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2016-89861 [Patent Document 2] Microfilm of Japanese Utility Model Application Publication No. 53-37883 [Patent Document 3] Japanese Patent Publication No. 7-54973 Summary of the Invention [Problem to be solved by the invention]

[0004] In the transmission device of Patent Document 1, the large diameter gear is arranged so that it does not mesh with the counter pinion while it is scooping up the oil from its bottom end to its top end. Therefore, there is no need to worry about the amount of oil scooped up to the top of the large diameter gear being reduced by the oil-scraping effect of the meshing portion between the large diameter gear and the counter pinion.

[0005] However, depending on the model of the transmission device and the vehicle installation conditions, it may be necessary to adopt a layout in which the large diameter gear meshes with the pinion midway through scooping up the oil, as in the transmission device of Patent Document 2. In this case, the oil scooped up by the large diameter gear drops to a certain extent at the meshing portion between the large diameter gear and the pinion, which is inconvenient as it is not possible to scoop up the oil sufficiently to the top of the ring gear.

[0006] Furthermore, in a transmission, when helical gears mesh with each other and rotate in conjunction with each other, the meshing position of each tooth moves from one axial end to the other end of the tooth, and as a result, oil on the tooth surface is pushed out unevenly from the meshing portion to one axial side. This phenomenon is well known (see, for example, Patent Document 3). However, no technical means has yet been proposed that utilizes this phenomenon to improve the oil scraping effect of large diameter gears.

[0007] The present invention has been proposed in consideration of the above, and aims to provide a transmission device that utilizes the above phenomenon to enable oil to be sufficiently scooped up to the top of the final driven gear, even in a layout in which the final driven gear meshes with the pinion halfway through scooping up the oil. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, the present invention provides a transmission device in which a pinion and a large diameter gear that meshes with the pinion and has a larger diameter than the pinion are disposed within a transmission case, and an oil reservoir is provided at the bottom of the transmission case for bringing stored oil into contact with the lower part of the large diameter gear, the large diameter gear meshes with the pinion in the middle of a specific semi-circular region where a tooth surface of the large diameter gear moves from a lower end to an upper end thereof as the large diameter gear rotates in the forward direction, the pinion and the large diameter gear are both configured as helical gears and are arranged such that oil on the tooth surface is pushed out from a mutual meshing portion to one axial direction of the pinion during forward rotation of the large diameter gear, and a flow control wall that faces the oil pushed out from the meshing portion to the one axial direction side and restricts the flow of the oil in that one axial direction side is disposed adjacent to an end face of the teeth on that one axial side of the pinion, and is formed into a shape that can cover up to the tooth tips of the end face.

[0009] In addition to the first feature, the present invention has a second feature in that the axial width of the pinion is set so that the teeth of the pinion extend further to one side in the axial direction than the meshing portion.

[0010] Furthermore, in addition to the first or second feature, the present invention has a third feature in that the flow control wall is composed of a shielded bearing or a sealed bearing that rotatably supports the pinion on the transmission case.

[0011] In addition to any one of the first to third features, the present invention has a fourth feature in that a differential device including a differential case that is rotatably supported on the transmission case and has a final driven gear as the large diameter gear fixed to its outer periphery, and a differential gear mechanism that is housed within the differential case and transmits the rotational force of the differential case to a pair of drive shafts while allowing differential rotation, is housed within the transmission case, and the differential case has a window portion that is offset to one side in the axial direction from the final driven gear and communicates between the inside and outside of the differential case. Effect of the Invention

[0012] According to a first feature of the present invention, within a transmission case, a large diameter gear meshes with a pinion in the middle of a specific semi-circular region where the tooth surface moves from the lower end to the upper end of the large diameter gear as the large diameter gear rotates in the forward direction, and both the pinion and the large diameter gear are composed of helical gears and are arranged so that oil on the tooth surface is pushed out from the mutual meshing portion to one axial side of the pinion when the large diameter gear rotates in the forward direction, and a flow control wall that opposes the oil pushed out from the meshing portion to one axial side and restricts the flow of oil in that one axial direction is arranged adjacent to an end face of the teeth on that one axial side of the pinion and is formed in a shape that can cover up to the tooth tips of the end face. As a result, oil that is pushed out from the meshing portion between the large diameter gear and the pinion to one axial direction of the pinion when the large diameter gear rotates in the forward direction has its flow toward that one axial direction restricted by the flow restricting wall opposing it, causing it to become congested in front of the flow restricting wall and to tend to flow out toward the teeth of the large diameter gear. This makes it easier for the oil to be carried around and lifted by the large diameter gear, effectively increasing the amount of oil that the large diameter gear scoops up to the top of the gear. As a result, despite the layout in which the large diameter gear meshes with the pinion while it is scooping up the oil, it is possible to supply sufficient oil up to the top of the large diameter gear.

[0013] According to the second feature, the axial width of the pinion is set so that the teeth of the pinion extend further to one side in the axial direction than the meshing portion. Therefore, when oil pushed out from the meshing portion to one side in the axial direction becomes congested in front of the flow control wall (particularly on the tooth surface of the pinion that extends further to one side in the axial direction than the meshing portion), some of the congested oil can be scattered from the pinion by centrifugal force and supplied to the surrounding lubricated parts.

[0014] According to the third feature, the flow control wall is composed of a shielded bearing or a sealed bearing that rotatably supports the pinion on the transmission case, so that the flow control wall can be easily and inexpensively constructed by utilizing a shielded bearing or a sealed bearing that has been commonly used up until now.

[0015] According to a fourth feature, a differential device including a differential case to which a final driven gear as a large diameter gear is fixed to its outer periphery, and a differential gear mechanism that differentially distributes the rotational force of the differential case to a pair of drive shafts is housed in a transmission case, and the differential case has a window portion that is offset to one axial side from the final driven gear and communicates between the inside and outside of the differential case. Therefore, the oil pushed out to one axial side of the pinion when the final driven gear rotates forward can be easily taken into the window portion of the differential case, thereby enhancing the lubricating effect on the differential gear mechanism in the differential case. [Brief description of the drawings]

[0016] [Figure 1] 1 is a general cross-sectional view of an embodiment of a power unit according to the present invention, taken along a line passing through the rotation axes of an input gear and a counter gear, as viewed from below (cross-sectional view taken along line 1X-1X in FIG. 2). [Diagram 2] FIG. 2 is a side view of the power unit as seen from the left side with the first half of the transmission case and the associated bearings omitted (a cross-sectional view taken along line 2X-2X in FIG. 1). [Diagram 3] 3 is a side view of the power unit as seen from the left side in a state in which the differential case and the final driven gear are further omitted from the state in FIG. 2 (a cross-sectional view taken along line 3X-3X in FIG. 1). [Figure 4] Fig. 4 is a side view of the power unit as seen from the left side in a state in which the intermediate case is further omitted from the state shown in Fig. 3 (a cross-sectional view taken along line 4X-4X in Fig. 1). [Diagram 5] 5 is a cross-sectional view showing the breather and the main part of the first oil capture portion (an enlarged cross-sectional view taken along line 5X-5X in FIG. 3). [Figure 6] Figure 6 is a cross-sectional view of the inside of the breather taken along the longitudinal direction of the breather as viewed from above (an enlarged cross-sectional view taken along line 6X-6X in Figure 4). [Figure 7] 7 is an enlarged perspective view of the breather and the first oil capture portion when the first case half and the intermediate case are removed from the second case half (a perspective view taken along the arrow 7X in FIG. 4). [Figure 8]8 is a cross-sectional view showing the layout of the second oil supply passage in the motor case (cross-sectional view taken along line 8X-8X in FIG. 4). [Figure 9] 9 is a right side view showing the main part of the second case half from the motor side with the motor case omitted (viewed from the arrow 9 in FIG. 1). [Figure 10] 10 is a perspective view showing the vicinity of the breather inlet and the opening of the first oil supply passage on the motor side of the second case half (an enlarged perspective view taken along the arrow 10X in FIG. 9). [Figure 11] FIG. 11 is an enlarged cross-sectional view taken along line 11X-11X of FIG. [Explanation of symbols]

[0017] Bc1: First counter bearing as a flow control wall Ct... Transmission case D...Differential device Dc...Differential case Dch... Window section Dg: Differential gear mechanism Gcp: Counter pinion as pinion Gf: Final driven gear as a large diameter gear T... Transmission device 15... Oil sump 40.....Meshing part 51,52 Drive shaft DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] 1 to 4, a power unit PU mounted on a vehicle, for example an automobile, includes an electric motor M as a power source, and a transmission device T that transmits the output of the motor M to left and right drive wheels. A metallic unit case C of the power unit PU is fixed and supported at an appropriate position on the vehicle body, and includes a transmission case Ct that forms the outer shell of the transmission device T, and a motor case Cm that forms the outer shell of the motor M.

[0019] Arranged in the space within the transmission case Ct, i.e., the transmission mechanism chamber 10, are a reduction gear R that reduces the output of the motor M, and a differential gear D that distributes the output of the reduction gear R to the left and right drive shafts 51, 52 (and thus the left and right drive wheels that rotate in conjunction with these shafts 51, 52) while allowing differential rotation.

[0020] In this specification and drawings, the front-rear, left-right, and up-down directions refer to the front-rear, left-right, and up-down directions when the power unit PU is mounted on the vehicle.

[0021] The motor case Cm is formed in a bowl shape having an outer end wall 21 and a cylindrical outer peripheral wall 22 connected to the outer periphery of the outer end wall 21, and is open on the transmission case Ct side. In the space inside the motor case Ct, i.e., the motor space 20, there are arranged a ring-shaped stator 24 fixed to the inner periphery of the outer peripheral wall 22 of the motor case Cm and having a plurality of coil groups 23 wound at intervals in the circumferential direction, a rotor 25 with a magnet (not shown) that cooperates with the stator 24 to generate a rotational driving force, and a motor output shaft 26 with the rotor 25 fixed to the outer periphery. The two ends of the motor output shaft 26 are supported by the transmission case Ct and the motor case Cm, respectively, via a pair of motor bearings Bm1 and Bm2. The motor output shaft 26 in the embodiment is formed hollow, and the right drive shaft 52 passes vertically through the hollow portion.

[0022] On the other hand, the transmission case Ct is divided into left and right first and second case halves 11, 12 that are detachably connected to each other. Of these, the left first case half 11 has a side wall 11s that covers the left side of the reduction gear device R and the differential device D, and a cylindrical outer circumferential wall 11o that is connected to the outer circumferential part of the side wall 11s and covers the outer circumferential side of the reduction gear device R and the differential device D.

[0023] The right-side second case half 12 has a cylindrical outer peripheral wall 12o that covers the outer peripheral side of the reduction gear R, and a partition wall 12s that is integrally connected to the entire circumference of the inner peripheral part of the axially middle part of the outer peripheral wall 12o and covers the right side of the reduction gear R. The partition wall 12s functions as a partition wall that separates the motor space 20 from the power mechanism chamber 10, with a left side surface 12si as one side surface of the partition wall 12s facing the power mechanism chamber 10 and a right side surface 12so as the other side surface facing the motor space 20.

[0024] Opposing end faces of the outer peripheral walls 11o, 12o of the first and second case halves 11, 12 are detachably joined to each other by a plurality of bolts b1, and a seal member (liquid gasket in this embodiment) is interposed between the opposing end faces to seal the gap. Opposing end faces of the outer peripheral wall 12o of the second case half 12 and the outer peripheral wall 22 of the motor case Cm are detachably joined to each other by a plurality of bolts b2, and a seal member (liquid gasket in this embodiment) is interposed between the opposing end faces to seal the gap.

[0025] The bottom of the transmission case Ct functions as an oil reservoir 15 that stores lubricating oil. The oil level L of the oil stored in the oil reservoir 15 is set to a level at which the lower part of a final driven gear Gf (described later) is immersed and in contact with the oil when the motor M (and therefore the reduction gear R and the differential D) are stopped (see FIGS. 2 to 4).

[0026] An oil return passage 16 for returning oil from the motor space 20 to the power mechanism chamber 10 is formed penetrating the lower part of the partition wall 12s of the second case half 12. The motor space 20 and the power mechanism chamber 10 are in communication with each other via this oil return passage 16.

[0027] Next, an example of the reduction gear R will be described with reference mainly to FIGS.

[0028] The gear transmission mechanism G, which is composed of a gear train and functions as a reduction gear R, includes, for example, an input gear Gi fixed (in this embodiment, spline-fitted and circlip-fastened) to the outer periphery of the inner end of the motor output shaft 26 that protrudes into the transmission mechanism chamber 10, a counter shaft 14 located rearward and above the rotation axis Xi of the input gear Gi and having a parallel rotation axis Xc, a counter gear Gc fitted and fixed (in this embodiment, spline-fitted and circlip-fastened) to the counter shaft 14 and meshing with the input gear Gi, a counter pinion Gcp fixed (in this embodiment, formed integrally) to the outer periphery of the counter shaft 14 at a position spaced to the left of the counter gear Gc, and a final driven gear Gf arranged on the same axis as the input gear Gi, formed with a larger diameter than the counter pinion Gcp, and meshing with the counter pinion Gcp.

[0029] The final driven gear Gf in the embodiment is positioned so as to mesh with the counter pinion Gcp in the middle of a specific semi-circular region (a semi-circular region to the right of the rotation axis Xi in FIG. 2) in which the tooth surface of the final driven gear Gf moves from the lower end to the upper end as the final driven gear Gf rotates in the forward direction (counterclockwise in FIG. 2).

[0030] One end of the counter shaft 14 is rotatably supported by the side wall 11s of the first case half 11 via a first counter bearing Bc1, and the other end is rotatably supported by the partition wall 12s of the second case half 1 via a second counter bearing Bc2. In particular, in this embodiment, the first counter bearing Bc1 is configured as a shielded bearing as is clear from FIG.

[0031] That is, the first counter bearing Bc1, like conventionally known shielded bearings, comprises an outer race 101 and an inner race 102 each having a circular ring shape, a plurality of balls 103 interposed between the opposing peripheral surfaces of the races 101, 102, and a circular ring-shaped plate shield 104 made of synthetic resin or metal located between one axial end (right end) of the races 101, 102, and the shield 104 is fixed to one of the inner and outer races 101, 102 (for example, the outer race 101) and is adjacent to and faces the other of the inner and outer races (for example, the inner race 102) with a small clearance between them.

[0032] As the first counter bearing Bc1, a sealed bearing (not shown since it is well known in the art) may be used instead of the above-mentioned shielded bearing. In this sealed bearing, a contact-type rubber or synthetic resin seal is used instead of the above-mentioned non-contact shield 104. This contact-type seal is fixed to either one of the inner or outer races 101, 102 (e.g., the outer race 101) and is in slidable contact with the other one (e.g., the inner race 102).

[0033] In particular, in this embodiment, by opening the left side of the shielded bearing or sealed bearing that constitutes the first counter bearing Bc1, the shielded bearing or sealed bearing can be lubricated by oil flowing from the right end side of the counter shaft 14 through its hollow portion to the left end side.

[0034] Each of the gears Gi, Gc, Gcp, and Gf of the gear transmission mechanism G is composed of a helical gear. In Fig. 1, each helical tooth is conveniently shown as a cross section along the tooth trace. The final driven gear Gf functions as a large diameter gear and is fixed concentrically to the outer periphery of the differential case Dc (described later) by an appropriate fixing means (e.g., bolt connection, welding, etc.).

[0035] During operation of the reduction gear device R, the counter gear Gc has a larger diameter than the input gear Gi, so primary reduction is performed between the two gears Gc and Gi. The final driven gear Gf, which serves as a large-diameter gear, has a larger diameter than the counter pinion Gcp, so secondary reduction is performed between the two gears Gf and Gcp. The counter gear Gc and the counter pinion Gcp may be formed integrally.

[0036] When the motor M is rotated in the forward direction to move the car forward, the gears Gi, Gc, Gcp, and Gf rotate in the forward direction in conjunction with the motor M, as shown by the white arrows in Figures 2 and 4. In this case, the forward rotation direction of the input gear Gi and the final driven gear Gf is the same as the forward rotation direction of the motor M, and the forward rotation direction of the counter gear Gc and the counter pinion Gcp is opposite to the forward rotation direction of the motor M.

[0037] Incidentally, the counter pinion Gcp and the final driven gear Gf are disposed so that, when these gears rotate forward, the oil on the tooth surface is pushed out from the meshing portion 40 to one axial side (the left side in this embodiment) of the counter pinion Gcp as they mesh with each other. This arrangement is naturally related to the twist angle (i.e., the direction of the tooth trace) of the helical gear teeth of the counter pinion Gcp and the final driven gear Gf, which are twisted with respect to the respective axes.

[0038] According to the above-mentioned arrangement of the counter pinion Gcp and the final driven gear Gf, when the two mesh with each other, as the meshing position moves from the right end to the left end in the axial direction of the teeth, the oil on the tooth surface is pushed out toward the left in the axial direction from the meshing portion 40 as shown by the dotted arrow in Figure 1.

[0039] In contrast, in this embodiment, a first counter bearing Bc1 made of a shielded bearing is used as a flow control wall that controls the flow of oil to the axial left side in opposition to the oil pushed out to the axial left side from the meshing portion 40. In this case, as is clear from Fig. 1, the first counter bearing Bc1 is disposed adjacent to the axial left end face of the teeth of the counter pinion Gcp, and is formed in a shape that can cover up to the tooth tips of the left end face of the teeth (i.e., a diameter larger than that of the counter pinion Gcp).

[0040] The axial width of the counter pinion Gcp in the embodiment is set so that the teeth of the counter pinion Gcp extend a predetermined length s (see FIG. 1) to the left in the axial direction beyond the meshing portion 40 with the final driven gear Gf. Alternatively, another embodiment can be implemented in which the extension length s of the teeth of the counter pinion Gcp to the left in the axial direction from the meshing portion 40 is set to zero or very small.

[0041] Next, the differential device D will be described mainly with reference to Figures 1 and 2. The differential device D includes a differential case Dc having bearing boss portions Dca, Dcb integrally formed at both axial ends of a body portion, and a differential gear mechanism Dg that is housed within the body portion of the differential case Dc and transmits the rotational force of the differential case Dc to a pair of drive shafts 51, 52 while allowing differential rotation.

[0042] The left bearing boss portion Dca of the differential case Dc is supported by the side wall 11s of the first case half 11 via a first differential bearing Bf1, and the right bearing boss portion Dcb is supported by an intermediate case 80 (described later) fixed to the partition wall 12s of the second case half 12 via a second differential bearing Bf2. The first and second differential bearings Bf1, Bf2 are an example of a pair of final driven gear bearings.

[0043] Thus, the differential case Dc is rotatably supported by the transmission case Ct on the rotation axis Xi of the input gear Gi. At the same time, the drive shafts 51, 52 rotatably fitted into the inner peripheries of the left and right bearing bosses Dca, Dcb of the differential case Dc are also supported by the transmission case Ct via the transmission case Ct and the first and second differential bearings Bf1, Bf2. Furthermore, the middle portion of the right drive shaft 52 is also supported by the motor case Cm via another bearing Bd.

[0044] Further, on one of the fitting surfaces between the left and right bearing boss portions Dca, Dcb and the drive shafts 51, 52, a spiral groove capable of exerting a screw pump action to guide scattered oil in the transmission case Ct into the differential case Dc is formed.

[0045] The final driven gear Gf, which is a ring gear, is fixed (by bolt b4 in this embodiment) to the outer periphery of the body of the differential case Dc at a position offset axially to the right from the center of the body. In addition, a plurality of windows Dch (two in this embodiment) are provided in the body of the differential case Dc at a position offset axially to the left from the final driven gear Gf. The windows Dch are symmetrically arranged with respect to the pinion shaft 33, and function as work holes for gear assembly or as oil circulation holes between the inside and outside of the differential case Dc.

[0046] In addition, since the window portion Dch is offset axially to the left with respect to the final driven gear Gf, the axial position of the window portion Dch is arranged so that, as is clear from Figure 1, part of the axial position of the tooth portion of the counter pinion Gcp extending axially to the left from the meshing portion 40 with the final driven gear Gf.

[0047] In the embodiment, the differential case Dc is configured as an integral unit, but the differential case Dc may be configured as separate units including a plurality of case elements that are joined together.

[0048] Next, the differential gear mechanism Dg will be described. It includes a pair of side gears 31 housed within the differential case Dc and rotatable about the same axis relative to the differential case Dc, a plurality of pinion gears 32 meshing with both side gears 31, and a pinion shaft 33 fixed to the differential case Dc and supporting the pinion gears 32 rotatably about an axis perpendicular to the rotation axis of the side gears 31. The outer peripheries of the inner ends of first and second drive shafts 51, 52 are interlocked and connected (spline-fitted in this embodiment) to the inner peripheries of the center holes of the left and right side gears 31.

[0049] The structure and function of the differential device D are well known in the art, so further explanation will be omitted, but the rotational driving force input from the motor M through the reduction gear R to the final driven gear Gf and then to the differential case Dc is distributed and transmitted to the first and second drive shafts 51, 52 while allowing differential rotation.

[0050] Meanwhile, the unit case C (specifically, the transmission case Ct) is equipped with a first oil capture section H1 capable of capturing oil scattered from the input gear Gi, an input gear covering section 70 that has an upwardly rearward opening that allows the counter gear Gc and the input gear Gi to mesh with each other and covers the input gear Gi, and a breather BR that communicates the inside of the unit case C with the outside air while preventing oil from being blown out to the outside air. Next, specific structures of the first oil capture section H1, the input gear covering section 70, and the breather BR will be described with reference to Figs. 5 to 11 as well.

[0051] As is clear from Fig. 4, the first oil capture section H1 has an oil inlet H1i located on the common tangent to the pitch circles of the input gear Gi and the counter gear Gc, on the forward side of the input gear Gi in the forward rotation direction, in a side view (i.e., when viewed from the axial direction of the input gear Gi). Therefore, after the input gear Gi, which rotates at high speed in conjunction with the motor M, meshes with the counter gear Gc, the oil remaining on the tooth surface is forcefully scattered upward in the common tangent direction by centrifugal force and jumps into the oil inlet H1i, and is efficiently captured in the first oil capture section H1. The oil captured in the first oil capture section H1 can be supplied to the lubricated parts present in the transmission case Ct and the motor case Cm, as described later.

[0052] On the other hand, the input gear covering part 70 has an open part facing upward toward the rear to allow the counter gear Gc and the input gear Gi to mesh with each other, and the lower part of the internal space thereof functions as an auxiliary oil reservoir 71 capable of storing oil for the input gear Gi. A first oil capture part H1 is located in the upper part of the internal space of the input gear covering part 70, and its opening part, i.e., an oil inlet port H1i, faces the meshing part side between the counter gear Gc and the input gear Gi.

[0053] The first oil capture portion H1, the input gear covering portion 70 and the breather BR are formed by the second case half 12 and an intermediate case 80 serving as a lid detachably coupled to the partition wall 12s of the second case half 12.

[0054] More specifically, as can be seen in Figure 4, on the left side surface 12si of the partition 12s, there are integrally provided a major arc-shaped input gear surrounding wall W1 that surrounds the input gear Gi over more than half its circumference, an oil capture portion forming wall W2 that extends downward from the upper inner circumference of the input gear surrounding wall W1 and then turns toward the counter gear Gc and extends in the circumferential direction of the input gear Gi, a breather chamber forming wall W3 that is spaced upward from the input gear surrounding wall W1 and extends approximately along the inner circumference of the outer peripheral wall 12o of the second case half 12, and a communication passage forming wall W4 that connects the upper part of the input gear surrounding wall W1 and the front part of the outer peripheral wall 12o of the second case half 12 directly below the breather chamber forming wall W3. The leading end faces (left end faces) of the input gear surrounding wall W1, the breather chamber forming wall W3 and the communication passage forming wall W4 are located on the same plane as the mating faces of the outer peripheral walls 11o, 12o of the first and second case halves 11, 12.

[0055] In particular, the input gear surrounding wall W1 is provided with a return portion W1a extending upward from its lower opening end, thereby suppressing the outflow of oil from within the auxiliary oil reservoir 71. Also, a positioning step W1s extending circumferentially is formed on the inner peripheral edge of the tip end face (left end face) of the input gear surrounding wall W1, the positioning step W1s being recessed one step from the tip end face.

[0056] On the other hand, the intermediate case 80 includes a disk-shaped case body 81 corresponding to the input gear surrounding wall W1, and an upper overhang 82 that is integrally connected to the upper half of the case body 81 and expands upward in a roughly fan shape. A stepped cylindrical annular boss 81b for fitting and fixing the outer race of the right second differential bearing Bf2 is integrally formed and protruded from the outer surface (left side) of the case body 81. A major arc-shaped protrusion 81a that extends along the input gear surrounding wall W1 and can be fitted into the positioning step W1s is integrally formed and protruded from the inner surface (right side) of the case body 81 near the outer periphery.

[0057] Incidentally, the left end face of the outer peripheral wall 12o of the second case half 12 has a wide portion corresponding to the breather chamber forming wall W3, and on that wide end face, as is clear from Figures 2 to 4, a shallow groove 12g extending along the upper edge of the upward protrusion 82 is provided adjacent to the upward protrusion 82. The groove 12g is designed to hold a portion of a seal material (e.g., a liquid gasket) applied between the joining end faces of the first and second case halves 11, 12.

[0058] The intermediate case 80 is fixed to the partition 12s of the second case half 12 (see FIGS. 1, 3, 5, and 6) by fitting the major arc-shaped convex portion 81a of the intermediate case 80 into the positioning step portion W1s of the input gear surrounding wall W1 (see FIGS. 1 and 5) and connecting the inner peripheral portion of the case body 81 to the input gear surrounding wall W1 with bolts b3 outside the major arc-shaped convex portion 81a. With the intermediate case 80 in this fixed state, the input gear covering portion 70 is defined by the intermediate case 80 and the partition 12s (specifically, by the inner peripheral surface of the input gear surrounding wall W1, the left side surface 12si of the partition 12s, and the inner surface of the case body 81).

[0059] Moreover, when the intermediate case 80 is in a fixed state, the top surface (right end surface) of the major arc-shaped convex portion 81a on the inner surface of the case body 81 closely faces the tip surface (left end surface) of the oil capture portion forming wall W2. As a result, the case body 81 and the partition wall 12s (specifically, the oil capture portion forming wall W2 and the left side surface 12si of the partition wall 12s) define a first oil capture portion H1.

[0060] In addition, in the embodiment, the tip surfaces (left end surfaces) of the return portion W1a and the oil capture portion forming wall W2 are close to and face the inner surface of the case main body 81 with a small gap (e.g., 0.5 mm) between them, but they may also abut against the inner surface of the case main body 81.

[0061] As shown in Fig. 4, the second case half 12 of the transmission case Ct has a second oil capture portion H2 capable of capturing oil scattered from the counter gear Gc, located forward of the first oil capture portion H1 in the forward rotation direction of the counter gear Gc. The second oil capture portion H2 is formed by a concave surface provided on the left side surface 12si of the partition wall 12s in an area sandwiched in the front-rear direction between the breather BR and the upper portion of the counter gear Gc, and sandwiched in the up-down direction between the upper portion of the outer peripheral wall 12o of the second case half 12 and the upper portion of the input gear surrounding wall W1. The rear end opening of the second oil capture portion H2 serves as an oil inlet port H2i that faces and is adjacent to the upper portion of the counter gear Gc, and the front end portion directly communicates with the rear end of a first communication oil passage 91, which will be described later.

[0062] A first oil supply passage 17 is formed in the partition wall 12s in the form of a through hole in a portion of the partition wall 12s that serves as the side wall of the first oil catcher H1, and guides a portion of the oil caught in the first oil catcher H1 to the periphery of the first motor bearing Bm1 on the left side. As is clear from Figures 9 and 10, the opening end of this first oil supply passage 17 on the motor space 20 side (i.e., the right side surface 12so side of the partition wall 12s) is located at a position corresponding to a notched slit 18s provided in a stepped cylindrical annular boss portion 18 that protrudes from the right side surface 12so and fits and fixes the outer race of the first motor bearing Bm1. A shallow oil groove 19 is recessed in the right side surface 12so, extending radially inward from the opening end of the first oil supply passage 17 through the slit 18s.

[0063] Thus, a portion of the oil captured in the first oil capture portion H1 passes through the first oil supply passage 17, and further passes through the slit 18s and the oil groove 19, to be guided to the first motor bearing Bm1.

[0064] Meanwhile, the intermediate case 80 is provided with a third oil supply passage 85 that guides a portion of the oil captured by the first oil capture portion H1 to the periphery of the second differential bearing Bf2. As is clear from Figs. 3 and 11, this third oil supply passage 85 is configured as a slit-shaped through-hole that extends radially across the major arc-shaped convex portion 81a on the inner surface (right side surface) of the case body 81 and penetrates the case body 81 in the axial direction. Thus, a portion of the oil captured by the first oil capture portion H1 flows through the third oil supply passage 85 to the second differential bearing Bf2 and the outer periphery of the second drive shaft 52.

[0065] 4 and 7, a first communication oil passage 91 is defined between the second case half 12 and the intermediate case 80, extending in the front-rear direction through an upper portion of the input gear surrounding wall W1, the communication passage forming wall W4, and the breather chamber forming wall W3. A front end of a through oil passage 12sh penetrating the partition wall 12s in the front-rear direction opens in the middle of this first communication oil passage 91, and a rear end of the through oil passage 12sh opens in a deep inner portion recessed forward of the first oil capture portion H1.

[0066] Therefore, the oil captured in the first oil capture portion H1, excluding the oil that has flowed out to the first and third oil supply passages 17 and 85, flows through the through oil passage 12sh into the middle of the first communication oil passage 91. The first communication oil passage 91 communicates with a second communication oil passage 92 in the axial direction provided in the outer peripheral wall 12o of the second case half 12, and the second communication oil passage 92 communicates with the second motor bearing Bm2 on the right side through a series of first and second communication oil passages 93 and 94 that pass through the outer peripheral wall 22 and end wall 21 of the motor case Cm, as is clear from FIG.

[0067] Thus, the through oil passage 12sh, the first connecting oil passage 91 (particularly the front half), the second connecting oil passage 92, and the first and second connecting oil passages 93, 94, which are connected in series, cooperate with each other to form a second oil supply passage 90 that guides a portion of the oil captured in the first oil capture section H1 to the right-side second motor bearing Bm2. The middle part of this second oil supply passage 90 and the above-mentioned second oil capture section H2 are mutually connected via the rear half of the first connecting oil passage 91. Therefore, the oil captured in the second oil capture section H2 is also guided to the second motor bearing Bm2 via the second oil supply passage 90.

[0068] When the intermediate case 80 is in the fixed state, the breather chamber 60 of the breather BR is defined by the intermediate case 80 and the second case half 12 (specifically, by the upper surface of the breather chamber forming wall W3, the lower surface of the wide upper part of the outer peripheral wall 12o of the second case half 12, the left side surface 12si of the partition 12s, and the inner surface of the upper protrusion 82).

[0069] The breather chamber 60 is shielded from the power mechanism chamber 10 by the intermediate case 80, and is connected to the outside air through an exhaust pipe 61 fixed to the upper part of the outer peripheral wall 12o of the second case half 12. Also, a plurality of baffle plates 62 (see FIGS. 4, 6 and 7) that form a labyrinth in the breather chamber 60 and suppress the blowing out of oil are protruded from the inner wall of the breather chamber 60 (specifically, the left side surface 12si of the partition wall 12s) in the same manner as in conventionally known breathers.

[0070] 6, a communication passage 63 that communicates between the breather chamber 60 and the motor space 20 is formed so as to penetrate the partition wall 12s in the axial direction. An opening of the communication passage 63 that opens to the right side surface 12so of the partition wall 12s serves as an inlet 60i of the breather chamber 63, and the inlet 60i faces the motor space 20.

[0071] The breather chamber 60 is in communication with the motor space 20 (and therefore the power train chamber 10) through the inlet 60i. Therefore, when the air in the motor space 20 becomes higher than the atmospheric pressure, it flows through the breather chamber 60 from the inlet 60i via the communication passage 63 and is discharged to the outside air through the exhaust pipe 61.

[0072] 6, 9, and 10, a protruding wall 12t is provided on the right side surface 12so of the partition wall 12s in the embodiment, protruding toward the motor space 20 and surrounding the inlet 60i of the breather chamber 60. Due to the provision of this protruding wall 12t, even if a small amount of oil is splashed inside the motor space 20, the splashed oil can be effectively prevented from entering the breather chamber 60.

[0073] 2, at least a portion of the breather chamber 60 is arranged to overlap with the final driven gear Gf when viewed from the axial direction of the final driven gear Gf. This arrangement prevents the breather chamber 60 from protruding significantly radially outward from the final driven gear Gf, which is advantageous in making the transmission case Ct (and therefore the unit case C) more compact in the radial direction.

[0074] 1 clearly shows that the counter gear Gc is sandwiched between the intermediate case 80 and the partition wall 12s in the axial direction, and from this arrangement, it is clear that the breather chamber 60 defined between the intermediate case 80 and the partition wall 12s is located in a position that partially overlaps with the counter gear Gc when viewed radially outward from the rotation axis Xc of the counter gear Gc. This arrangement prevents the breather chamber 60 from protruding significantly axially outward from the counter gear Gc, which is advantageous in making the transmission case Ct (and therefore the unit case C) more compact in the axial direction.

[0075] 8 and 9, the inlet 60i of the breather chamber 60 faces the stator 24, which is fixed within the motor case Cm, at a relatively close distance. By bringing the inlet 60i of the breather chamber 60 close to and facing the non-rotating stator 24 within the motor space 20 in this manner, it is possible to more effectively prevent oil from entering the breather chamber 60 from the motor space 20 by utilizing the stator 24.

[0076] Next, the operation of the embodiment will be described. In the power unit PU including the transmission device T according to the present invention, when a rotational driving force is input from the motor output shaft 26 to the input gear Gi as the motor M operates, the rotational driving force is reduced in two stages by the reduction gear R in the transmission device T and transmitted to the final driven gear Gf. The rotational driving force of the final driven gear Gf is then distributed by the differential device D to the first and second drive shafts 51, 52 while allowing differential rotation, and is further transmitted from the first and second drive shafts 51, 52 to the left and right drive wheels.

[0077] In addition, when the motor M is stopped, a predetermined amount of oil is stored in the oil reservoir 15 at the bottom of the transmission case Ct, and the auxiliary oil reservoir 71 in the input gear covering portion 70 also stores a portion of the oil that splashed and flowed down inside the transmission mechanism chamber 10 during the previous operation of the motor M.

[0078] Thus, during transmission of the gear transmission mechanism G, particularly when the motor M is rotating in the forward direction (when the vehicle is moving forward), the input gear Gi, counter gear Gc, counter pinion Gcp and final driven gear Gf rotate, for example, in the direction of the white arrows in Figures 2 and 4. As a result of this rotation, the oil in the oil sump 15 is scooped up by the lowest and largest-diameter final driven gear Gf, and is scattered throughout the transmission mechanism chamber 10.

[0079] Incidentally, the transmission case Ct of the embodiment has a first oil capture portion H1 capable of capturing oil scattered from the input gear Gi rotating at high speed, and an oil inlet H1i of the first oil capture portion H1 is located on the front side in the forward rotation direction of the input gear Gi on a common tangent to the pitch circles of the input gear Gi and the counter gear Gc, as is clear from Fig. 4. This makes it possible to efficiently capture oil scattered upward from the input gear Gi after it meshes with the counter gear Gc during high speed rotation of the input gear Gi by the first oil capture portion H1 and supply it to parts to be lubricated located at various locations within the unit case C.

[0080] That is, a part of the oil captured in the first oil capture portion H1 is supplied to the first motor bearing Bm1 on the left side (i.e., closer to the transmission device T) via the first oil supply passage 17 penetrating the partition wall 12s on the right side of the first oil capture portion H1. Another part of the oil captured in the first oil capture portion H1 is supplied to the second differential bearing Bf2 on the right side and the periphery of the second drive shaft 52 via the third oil supply passage 85 in the form of a slit hole provided in the case body 81 of the intermediate case 80. Furthermore, the remainder of the other oil (i.e., the oil that has passed through the inlets of the first and third oil supply passages 17 and 85) enters the through hole 12sh that opens to the innermost part of the first oil capture portion H1, and is supplied to the second motor bearing Bm2 on the right side (i.e., farther from the transmission device T) via the second oil supply passage 90.

[0081] The oil trapped in the first oil trap portion H1 in this manner efficiently lubricates the parts to be lubricated inside and outside the transmission case Ct, that is, the bearings Bm1, Bm2, Bf2, etc.

[0082] Moreover, the transmission case Ct of the embodiment has an input gear covering portion 70 that covers the input gear Gi and can store oil in the lower part of the internal space, and a first oil capture portion H1 is disposed within the input gear covering portion 70. As a result, in the input gear covering portion 70 having the input gear auxiliary oil reservoir 71 at its inner bottom portion, oil is sufficiently scattered from the input gear Gi by centrifugal force, and the scattered oil can be efficiently captured by the first oil capture portion H1 whose oil inlet port H1i faces the input gear covering portion 70, so that the lubricated parts can be lubricated more effectively.

[0083] In addition, the second differential bearing Bf2 on the right side of the embodiment is attached to an intermediate case 80 joined to a partition wall 12s of the transmission case Ct, and the partition wall 12s defines the first oil capture portion H1 in cooperation with the intermediate case 80. In other words, the intermediate case 80, which is a wall forming part of the first oil capture portion H1, also serves as a support member for the second differential bearing Bf2, thereby simplifying the structure of the device and reducing costs.

[0084] Moreover, because the intermediate case 80 has a through hole, i.e., a slit-shaped third oil supply passage 85, that guides a portion of the oil captured in the first oil capture portion H1 to the second differential bearing Bf2, the oil captured in the first oil capture portion H1 can also be effectively used to lubricate the second differential bearing Bf2, etc. Also, by simply opening the through hole-shaped third oil supply passage 85 in the intermediate case 80, an oil introduction passage can be formed from the first oil capture portion H1 to the second differential bearing Bf2, simplifying the oil passage structure.

[0085] In the power unit PU of the embodiment, the unit case C has a second oil capture portion H2 capable of capturing oil scattered from the counter gear Gc, located forward of the first oil capture portion H1 in the forward rotation direction of the counter gear Gc, and the second oil capture portion H2 is connected to the first oil supply passage 90 in the second case half 12.

[0086] As a result, not only the oil scattered from the input gear Gi but also the oil scattered radially outward from the counter gear Gc due to centrifugal force can be efficiently captured in the second oil capture portion H2, and the captured oil can be merged with the oil in the first oil supply passage 90 flowing from the first oil capture portion H1 to the second motor bearing Bm2. Therefore, by utilizing not only the first oil capture portion H1 but also the second oil capture portion H2, the second motor bearing Bm2 on the side farther from the transmission device T can be more efficiently lubricated.

[0087] In this case, when the direction of the twisted shape of the helical teeth of the counter gear Gc is set so that oil scatters from the gear teeth toward the right in the axial direction, particularly when the motor M is rotating in the forward direction, the second oil capture portion H2, located toward the right in the axial direction on the upper outer periphery of the counter gear Gc, can more efficiently capture the oil that scatters from the counter gear Gc.

[0088] In the embodiment, the final driven gear Gf as a large diameter gear meshes with the counter pinion Gcp in the middle of a specific half-periphery region (a half-periphery region rearward of the rotation axis Xi in FIG. 2) where the tooth surface of the final driven gear Gf moves from the lower end to the upper end as the final driven gear Gf rotates forward, and the counter pinion Gcp and the final driven gear Gf, each of which is made up of a helical gear, are arranged so that oil on the tooth surface is pushed out from the mutual meshing portion 40 to the axial left side of the counter pinion Gcp (i.e., the direction of the dotted arrow in FIG. 1) when the final driven gear Gf rotates forward. Moreover, the first counter bearing Bc1 made of a shielded bearing as a flow control wall that opposes the oil pushed out from the meshing portion 40 to the axial left side and controls the flow of the oil to the left side is arranged adjacent to the end face of the teeth on the axial left side of the counter pinion Gcp as is clear from FIG. 1, and is formed in a shape that can cover up to the tooth tip portion of the end face.

[0089] As a result, the oil pushed out from the meshing portion 40 between the final driven gear Gf and the counter pinion Gcp to the axial left side of the counter pinion Gcp during forward rotation of the final driven gear Gf is restricted from flowing toward the axial left side by the first counter bearing Bc1 (a shielded bearing as a flow restriction wall) facing it, and becomes congested in front of the bearing Bc1 and tends to flow out to the teeth side of the final driven gear Gf, so that the oil is easily carried around and lifted by the final driven gear Gf, effectively increasing the amount of oil that the gear Gf scoops up to the top of the gear. As a result, despite the layout in which the final driven gear Gf meshes with the counter pinion Gcp while scooping up the oil, it is possible to supply sufficient oil to the top of the final driven gear Gf.

[0090] 1, the axial width of the counter pinion Gcp in the embodiment is set so that the teeth of the pinion Gcp extend axially leftward beyond the meshing portion 40. As a result, when the oil pushed out axially leftward from the meshing portion 40 becomes congested in front of the first counter bearing Bc1 serving as a flow restricting wall (particularly on the tooth surface of the counter pinion Gcp extending axially leftward beyond the meshing portion 40), a part of the congested oil can be scattered radially outward from the counter pinion Gcp by centrifugal force and supplied to the surrounding lubricated parts.

[0091] In this case, multiple oil guide ribs (not shown) are protruded from the inner surface of the side wall 11s of the first case half 11 (particularly the bowl-shaped portion surrounding the differential case Dc), so that when oil splashed from the counter pinion Gcp adheres to the inner surface of the side wall 11s, it can be efficiently guided and supplied to the first differential bearing Bf1 on the left side.

[0092] In the embodiment, the flow control wall for restricting the flow of the oil pushed out from the meshing portion 40 to the left in the axial direction at the front side and causing congestion is constituted by the first counter Bc1 made of a shielded bearing that supports the counter pinion Gcp on the transmission case Ct. This makes it possible to easily and inexpensively construct the flow control wall by using a shielded bearing with an oil seal function that has been commonly used up until now.

[0093] As for the flow restriction wall, in addition to the present embodiment in which the shielded bearing (first counter bearing Bc1) is also used, various other variations are possible. For example, a modification in which a flat washer is sandwiched between the teeth of the counter pinion Gcp and the first counter bearing Bc1, which is not a shielded bearing, and this flat washer is used as the flow restriction wall can be implemented. Alternatively, another modification in which an annular flange-shaped protruding wall is integrally formed on the outer periphery of the counter shaft 14, and this protruding wall is interposed between the teeth of the counter pinion Gcp and the first counter bearing Bc1, which is not a shielded bearing, so that it can be used as the flow restriction wall can be implemented.

[0094] Alternatively, it is also possible to implement yet another modified example in which a radially flat bearing (e.g., a needle bearing) is used as the first counter bearing Bc1 and installed at the fitting portion between the side wall 11s of the first case half 11 and the counter shaft 14, and the inner wall of the side wall 11s is brought close to or adjacent to the left end face of the tooth portion of the counter pinion Gcp, thereby making it possible to use the inner wall of the side wall 11s as a flow control wall.

[0095] Furthermore, as is clear from Fig. 1, the differential case Dc in the differential device D of the embodiment has a window portion Dch that is offset axially leftward from the final driven gear Gf and communicates the inside and outside of the differential case Dc. This makes it easier for the oil pushed out axially leftward on the tooth surface of the counter pinion Gcp during forward rotation of the final driven gear Gf to be taken into the window portion Dch when it is scattered by centrifugal force. Therefore, the scattered oil from the counter pinion Gcp is efficiently supplied to the differential gear mechanism Dg in the differential case Dc through the window portion Dch, thereby improving the lubrication effect on the differential gear mechanism Dg.

[0096] In the embodiment, the unit case C, particularly the second case half 12, has a partition 12s whose left side surface 12si faces the transmission mechanism chamber 10 and whose right side surface 12so faces the motor space 20, and a breather chamber 60 is defined by the left side surface 12si of this partition 12s and an intermediate case 80 serving as a lid connected to the left side surface 12si, and an inlet 60i of the breather chamber 60 opens to the right side surface 12so of the partition 12s and can communicate with the motor space 20.

[0097] As a result, the inlet 60i of the breather chamber 60 does not open directly to the power mechanism chamber 10, but communicates with the power mechanism chamber 10 via the motor space 20, so that it is possible to effectively prevent oil scattered from each gear of the gear transmission mechanism G in the transmission case Ct from entering the breather chamber 60, thereby reducing the risk of oil blowing out from the breather chamber 60. Moreover, since the breather chamber 60 is defined by the left side surface 12si of the partition wall 12s of the transmission case Ct and the intermediate case 80 connected thereto as a lid, the hollow structure of the breather chamber 60 isolated from the power mechanism chamber 10 can be easily obtained without significantly complicating the structure of the partition wall 12s of the transmission case Ct or the molding process thereof, thereby reducing costs.

[0098] Although the embodiment of the present invention has been described above, the present invention is not limited to the embodiment, and various design modifications are possible without departing from the gist of the present invention.

[0099] For example, in the above embodiment, the gear transmission mechanism G of the transmission device T is a so-called two-shaft type gear transmission mechanism in which the input gear Gi and the final driven gear Gf (thus the drive shafts 51, 52) which rotate around an axis different from the axis Xc of the counter gear Gc are arranged on the same axis, but in the present invention, the gear transmission mechanism G may be a so-called three-shaft type gear transmission mechanism in which the input gear Gi, the counter gear Gc, and the final driven gear Gf (thus the drive shafts 51, 52) are rotated around three different axes.

[0100] In the above embodiment, the transmission device T is equipped with a differential device D in addition to the reduction device R, and the rotational torque of the output part of the reduction device R, i.e., the final driven gear Gf, is distributed to a pair of drive shafts 51, 52 (and thus to the left and right drive wheels) via the differential device D. However, in the present invention, the differential device D may be omitted, and the final driven gear Gf may be interlocked and connected to a single drive shaft via an interlocking mechanism without a differential function, and in this case the drive shaft is capable of rotating and driving a single drive wheel (for example, the rear wheel of a motorcycle).

[0101] In the above embodiment, the transmission device T is implemented as a transmission device for a vehicle (for example, an automobile), but the transmission device T of the present invention may be implemented as a transmission device for various mechanical devices other than a vehicle.

[0102] In addition, in the above embodiment, the direction of the twisted shape of the helical teeth of both gears Gcp, Gf (in other words, the twist angle) is set so that when the final driven gear Gf rotates forward, the counter pinion Gcp and the final driven gear Gf mesh with each other, and oil on the tooth surface is pushed out from the meshing portion 40 to the axial left side of the counter pinion Gcp. However, in the present invention, the direction of the twisted shape of the helical teeth of both gears Gcp, Gf may be set in the opposite direction to that in the embodiment. In this case, during the forward rotation, the counter pinion Gcp and the final driven gear Gf mesh with each other, and oil on the tooth surface is pushed out from the meshing portion 40 to the axial right side of the counter pinion Gcp, so a flow control wall adjacent to the end face of the teeth on the axial right side of the counter pinion Gcp is provided in an annular shape protruding from the outer periphery of the counter shaft 14, and the axial width of the counter pinion Gcp is set so that the teeth of the counter pinion Gcp extend to the axial right side from the meshing portion 40. According to this setting, the extending portion of the teeth of the counter pinion Gcp is in a position that coincides with or is close to the second differential bearing Bf2 in the axial direction, so that the oil pushed out to the extending portion of the teeth and stuck in front of the flow control wall is scattered by centrifugal force, and the amount of oil supplied to the second differential bearing Bf2 can be increased.

[0103] In addition, in the above embodiment, the intermediate case 80 is shown as being used as a means for forming the breather chamber 60 in cooperation with the partition 12s, a means for forming the input gear covering portion 70, and a means for supporting the second differential bearing Bf2, but it may also be used as a means for only two of these means, or it may be dedicated to any one of these means.

[0104] In the above embodiment, the gears Gi, Gc, Gcp, and Gf of the gear transmission mechanism G of the transmission device T are configured as helical gears, but the input gear Gi and the counter gear Gc may be configured as spur gears.

[0105] In the above embodiment, the motor M is used as the power source of the power unit PU, but an internal combustion engine may also be used as the power source.

Claims

1. Pinion (Gcp), a large-diameter gear (Gf) meshing with the pinion (Gcp) and having a larger diameter than the pinion (Gcp); a differential case (Dc) to which the large-diameter gear (Gf) is fixed at an outer periphery thereof; a window portion (Dch) that communicates the inside and outside of the differential case (Dc); and a differential gear mechanism (Dg) that is housed in the differential case (Dc) and transmits a rotational force of the differential case (Dc) to a pair of drive shafts (51, 52) while allowing differential rotation; is disposed in a transmission case (Ct), and an oil reservoir (15) is provided at the bottom of the transmission case (Ct) to bring the stored oil into contact with the lower part of the large-diameter gear (Gf), The large-diameter gear (Gf) meshes with the pinion (Gcp) in the middle of a specific half-circumference region in which a tooth surface of the large-diameter gear (Gf) moves from the lower end to the upper end of the large-diameter gear (Gf) as the large-diameter gear (Gf) rotates in the normal direction, The pinion (Gcp) and the large-diameter gear (Gf) are both configured as helical gears, and are arranged such that oil on the tooth surfaces of the mutual meshing portion (40) is pushed out to one axial side of the pinion (Gcp) when the large-diameter gear (Gf) rotates forward. a flow control wall (Bc1) which faces the oil pushed out from the meshing portion (40) to the one axial direction side and controls the flow of the oil in the one axial direction side is disposed adjacent to an end face of a tooth on the one axial direction side of the pinion (Gcp) and is formed in a shape capable of covering up to the tooth tip portion of the end face, The flow control wall (Bc1) is composed of a shielded bearing or a sealed bearing (Bc1) that rotatably supports the pinion (Gcp) on the transmission case (Ct), A transmission device characterized in that the window portion (Dch) is arranged so as to coincide with a part of the pinion (Gcp) in the axial direction.

2. 2. The transmission device according to claim 1, wherein an axial width of the pinion (Gcp) is set so that a tooth portion of the pinion (Gcp) extends beyond the meshing portion (40) to one side in the axial direction.

3. A transmission device as described in claim 1 or 2, characterized in that the portion of the pinion (Gcp) includes the end face of the tooth on one axial side of the pinion (Gcp).

4. The pinion (Gcp) is fixed to the outer periphery of a rotating shaft (14) rotatably supported by the shielded bearing or the sealed bearing (Bc1), The rotating shaft (14) has a hollow portion communicating with both ends of the rotating shaft (14), The transmission device according to any one of claims 1 to 3, characterized in that one axial side of the shielded bearing or the sealed bearing (Bc1) is open and communicates with the hollow portion.

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