GEARBOX

Abstract

A gear device is provided in which a large-diameter gear meshes with a pinion in a specific semi-circular region in which a tooth surface moves from a lower end of the large-diameter gear to an upper end thereof, in accordance with the forward rotation of the large-diameter gear, wherein the pinion (Gcp) and the large-diameter gear (Gf) each comprise a helical gear and are arranged such that, during the forward rotation of the large-diameter gear, oil is forced at the tooth surface from a mutual engagement section (40) to one side in an axial direction of the pinion, and a fluid boundary wall (Bc1), which is configured to counteract the oil forced from the engagement section to one side in the axial direction, is arranged on one side in the axial direction adjacent to an end face of teeth of the pinion (Gcp).wherein the fluid boundary wall (Bc1) is formed in a shape that allows a tooth tip section of the end face to be covered. Thus, the oil which, during the forward rotation of the large-diameter gear, is forced from the engagement section to one side of the pinion in the axial direction, is prevented by the fluid boundary wall, which opposes the forced oil, from flowing in that direction in the axial direction. So that the oil which accumulates at a point just in front of the fluid boundary wall flows more easily to a tooth section of the large-diameter gear, and it is possible to transport and scoop the oil through the large-diameter gear more easily, thereby increasing the amount of oil scooped to the upper section of the large-diameter gear.

Description

TECHNICAL FIELD

[0001] The present invention relates to a transmission device, in particular to a transmission device comprising a pinion and a large-diameter gear meshing with the pinion and having a larger diameter than the pinion, the pinion and the large-diameter gear being arranged in a transmission case, the transmission case including an oil reservoir in a lower part therein, which allows a reservoir oil to come into contact with a lower portion of the large-diameter gear. BACKGROUND STATE OF THE ART

[0002] The transmission device described above is known, for example, as disclosed in Patent Document 1 below, in which oil scooped by a large-diameter gear (for example, the final driven gear) is collected by a rib on an inner surface of a transmission case, and the collected oil is then guided to a bearing and others to be used for lubrication. PRIOR ART DOCUMENTS PATENT DOCUMENTS Patent document 1: Unexamined Japanese patent application 2016-89861 Patent document 2: Unexamined Japanese utility model application S53-37883 Microfilm Patent document 3: Unexamined Japanese patent application H7-54973 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0003] In the transmission device of Patent Document 1, the large-diameter gear is arranged such that it does not mesh with a counter pinion in a process of scooping oil from its lower end to its upper end. Accordingly, there is no concern that the amount of oil scooped by the large-diameter gear to a top of the gear will be reduced due to an oil dripping action at an engaging portion of the large-diameter gear and the counter pinion.

[0004] However, depending on the model of the transmission device and the vehicle installation conditions, the large-diameter gear may need to be designed in such a way that it meshes with the pinion during the oil-scooping process, as can be seen, for example, in the transmission device from patent document 2. In this case, there is a disadvantage that the large-diameter gear cannot scoop enough oil to the top of a gear ring, since some of the scooped oil falls off at the engagement point of the large-diameter gear and the pinion.

[0005] Furthermore, in transmission devices, when helical gears mesh with each other and rotate together, oil on its tooth surface is unevenly pushed from the meshing portion to one side in an axial direction of a tooth as a meshing position of each tooth moves from one end of the tooth to the other end in the axial direction. Such a phenomenon is known (see, for example, Patent Document 3). However, no technical method has yet been proposed to improve an oil scooping effect of the large-diameter gear by utilizing this phenomenon.

[0006] The present invention has been proposed in light of the above considerations. One objective of the present invention is to provide a transmission device capable of drawing sufficient oil to the upper surface of a final output gear using the phenomenon described above, even if the final output gear is configured to mesh with a pinion gear during the oil-drawing process. MEANS TO SOLVE THE PROBLEMS

[0007] To achieve the above-described object, the present invention has a first feature of providing a transmission device comprising a pinion gear; and a large-diameter gear meshing with the pinion gear and having a larger diameter than the pinion gear, wherein the pinion gear and the large-diameter gear are arranged in a transmission case, the transmission case including an oil reservoir in a lower part therein, which allows a reservoir oil to come into contact with a lower portion of the large-diameter gear, wherein the large-diameter gear meshes with the pinion gear in a specific semi-circumferential region in which a tooth surface moves from a lower end of the large-diameter gear to an upper end thereof in accordance with forward rotation of the large-diameter gear,wherein the pinion and the large-diameter gear each comprise a helical gear and are arranged such that, during forward rotation of the large-diameter gear, oil on the tooth surface is pressed from a mutual engagement portion to one side in an axial direction of the pinion, and wherein a fluid restriction wall configured to counteract the oil pressed from the engagement portion to the one side in the axial direction and prevent the oil from flowing to the one side in the axial direction is arranged on the one side in the axial direction adjacent to an end surface of teeth of the pinion, the fluid restriction wall being formed in a shape that allows a tooth tip portion of the end surface to be covered.

[0008] In addition to the first feature, the present invention has a second feature in which a width of the pinion in the axial direction is set such that a tooth portion of the pinion protrudes to the one side in the axial direction relative to the engagement portion.

[0009] In addition to the first or second feature, the present invention has a third feature in which the fluid confining wall comprises a shielded bearing or a sealed bearing which rotatably supports the pinion gear to the gear housing.

[0010] In addition to each of the first to third features, the present invention has a fourth feature in which a differential device is received in the gearbox housing and a differential housing which is rotatably mounted on the gearbox housing and which has an outer circumferential section on which the final output gear serving as the large diameter gear is fixed, and a differential gear mechanism which is received in the differential housing and which transmits a rotational force of the differential housing to a pair of drive shafts while enabling differential rotation, and the differential housing includes a window section which is arranged in a position offset to one side in the axial direction relative to the final output gear in order to allow communication with an interior and an exterior of the differential housing. EFFECTS OF THE INVENTION

[0011] According to the first feature, the large-diameter gear meshes with the pinion in the specific semi-circumferential region in which the tooth surface moves from the lower end of the large-diameter gear to the upper end thereof in accordance with the forward rotation of the large-diameter gear. The pinion and the large-diameter gear each comprise the helical gear and are arranged such that, during the forward rotation of the large-diameter gear, the oil on the tooth surface is pressed by the mutual engagement portion to one side in the axial direction of the pinion. The fluid limiting wall, which is configured to counteract the oil pressed by the engagement portion to one side in the axial direction and to prevent the oil from flowing to one side in the axial direction, is arranged on the one side in the axial direction adjacent to the end surface of teeth of the pinion.wherein the fluid restriction wall is formed in a shape that allows the tooth tip portion of the end surface to be covered. Thus, the oil pushed from the meshing portion of the large-diameter gear and the pinion toward one side of the pinion in the axial direction during forward rotation of the large-diameter gear is prevented from flowing toward that one side in the axial direction by the fluid restriction wall opposing the pushed oil, so that the oil accumulated at a location just before the fluid restriction wall flows more easily to a tooth portion of the large-diameter gear. This makes it possible to more easily transport the oil around and scoop up the oil by the large-diameter gear, thereby effectively increasing the amount of oil that the large-diameter gear scoops to its upper gear portion. As a result,Although a design allows the large-diameter gear to mesh with the pinion in a process of scooping the oil, it is possible to sufficiently supply the oil to the upper portion of the large-diameter gear.

[0012] According to the second feature, the width of the pinion in the axial direction is set such that the tooth portion of the pinion protrudes to the one side in the axial direction relative to the engaging portion, so that when the oil pushed from the engaging portion in the axial direction to the one side accumulates at a location short of the liquid confinement wall (specifically, at the tooth surface extending to the one side in the axial direction relative to the engaging portion of the pinion), a part of the accumulated oil is scattered away from the pinion with a centrifugal force, thereby allowing the oil to be supplied to the surrounding lubrication target parts.

[0013] According to the third feature, the fluid limiting wall includes the shielded bearing or the sealed bearing which rotatably mounts the pinion to the gearbox housing, so that the shielded bearing or the sealed bearing which has been commonly used can be used, making it possible to structure the fluid limiting wall simply and cost-effectively.

[0014] According to the fourth feature, the differential device is housed in the transmission case and includes the differential case having the outer peripheral portion to which the final driven gear serving as the large diameter gear is fixed;and the differential gear mechanism, which differentially distributes the rotational force of the differential housing to the pair of drive shafts while enabling differential rotation, and the differential housing includes the window section, which is arranged in a position offset to one side in the axial direction relative to the final output gear in order to allow communication between the interior and exterior of the differential housing, so that the oil forced to one side in the axial direction of the pinion during the forward rotation of the large-diameter gear can easily enter the window section of the differential housing and also increase the lubrication effect on the differential gear mechanism inside the differential housing. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a sectional view of an embodiment of a power unit according to the present invention, in which a cross-section extending through the axes of rotation of an input gear and a mating gear is viewed from below (sectional view along line 1X-1X in Fig. 2). Fig. Figure 2 is a side view of the power unit, viewed from the left, in a state where the first housing half of a gearbox housing and the bearings attached to it are omitted (cross-sectional view along line 2X-2X in Fig. 1). Fig. Fig. 3 is a side view of the power unit, viewed from the left side, in a state in which, in addition to the Fig. 2, a differential case and a final drive gear are omitted (cross-sectional view along line 3X-3X in Fig. 1). Fig. 4 is a side view of the power unit from the left side, in which, in addition to the one in Fig. In the state shown in Figure 3, an intermediate housing is omitted (cross-sectional view along line 4X-4X in Figure 3). Fig. 1). Fig. Figure 5 is a sectional view showing a main section of a vent and a first oil collection part (enlarged sectional view along line 5X-5X in Fig. 3). Fig. Figure 6 is a top-down sectional view of the interior of the vent in a cross-section along its longitudinal direction (enlarged sectional view along line 6X-6X in Fig. 4). Fig. Fig. 7 is an enlarged perspective view of the breather and the first oil collecting part in a state in which the first housing half body and the intermediate housing are removed from a second housing half body (from an arrow 7X in Fig. 4 (perspective view considered). Fig. Fig. 8 is a sectional view showing an arrangement of a second oil supply passage in an engine housing (sectional view taken along line 8X-8X in Fig. 4). Fig. Figure 9 is a right-hand view, viewed from the side where the motor is located, of a main section of the second housing half in a state where the motor housing is omitted (representation of an arrow 9 in Fig. 1). Fig. Figure 10 is a perspective view showing a vent inlet on a side surface of the second housing half on the side where the engine is located, and the vicinity of an opening of a first oil supply channel (from an arrow 10X in Fig. 9 (enlarged perspective view). Fig. 11 is an enlarged sectional view taken along line 11X-11X in Fig. 3. EXPLANATION OF REFERENCE SYMBOLS Bc1 first counter bearing as a fluid boundary wall CT gearbox housing D Differential device DC differential housing Roof window section Dg differential gear mechanism GCP counter-pinion as a pinion Gf final drive gear as a large diameter gear T Gearbox device 15 oil storage tanks 40 Intervention section 51, 52 Drive shafts MODE FOR EXECUTING THE INVENTION

[0015] Firstly, it includes in Fig. 1 to Fig. 4, a power unit PU mounted in a vehicle, for example, an automobile, includes an electric motor M as a power source and a transmission device T that transmits an output of the motor M to left and right drive wheels. A metal unit case C of the power unit PU is fixed and supported to a suitable portion of a vehicle body and includes a transmission case Ct serving as an outer shell of the transmission device T, and a motor case Cm serving as an outer shell of the motor M.

[0016] In a space within the transmission case Ct, i.e., in a transmission mechanism chamber 10, a reduction device R, which slows down the output of the motor M, and a differential device D are arranged. The differential device D distributes an output of the reduction device R to left and right drive shafts 51, 52 (and thus to left and right drive gears, which mesh with the shafts 51, 52 and rotate), while allowing differential rotation.

[0017] In the description and drawings, the directions front-rear, left-right, up-down refer to the directions front-rear, left-right, up-down in a state in which the power unit PU is mounted in the vehicle.

[0018] The motor housing Cm is configured such that it integrally comprises an outer end wall 21 and a tubular outer circumferential wall 22, which transitions into an outer circumferential section of the outer end wall 21, and has a shell-like body that is open towards the gearbox housing Ct. Within a space inside a motor housing Ct, i.e., in a motor chamber 20, are arranged a circular annular stator 24, which is fixed to an inner circumferential wall of the outer circumferential wall 22 of the motor housing Cm and which is wound in its circumferential direction by a plurality of coil groups 23 at intervals between them; a rotor 25, which includes a magnet (not shown) and which interacts with the stator 24 to generate a rotary driving force; and a motor output shaft 26, which fixes the rotor 25 to the outer circumferential section.Both end sections of the motor output shaft 26 are mounted on the gearbox housing Ct and the motor housing Cm, respectively, via a pair of motor bearings Bm1 and Bm2. Furthermore, in this embodiment, the motor output shaft 26 is hollow, and a drive shaft 52 extends vertically through a hollow section of the motor output shaft 26 on one right side.

[0019] The transmission case Ct is configured to be divided into first and second case half bodies 11, 12 on left and right sides, which are detachably coupled to each other. The first case half body 11, located on the left side, includes a side wall 11s covering left portions of the reduction device R and the differential device D, and a tubular outer peripheral wall 11o continuously provided on an outer peripheral portion of the side wall 11s and covering the outer peripheral sides of the reduction device R and the differential device D.

[0020] The second housing half body 12 on the right side includes a tubular outer peripheral wall 12o covering the outer peripheral side of the reduction device R, and a partition wall 12s integrally and continuously provided around an inner peripheral portion of an axially intermediate portion of the outer peripheral wall 12o and covering a right portion of the reduction device R. Further, the partition wall 12s functions as a partition wall separating the motor compartment 20 from the transmission mechanism chamber 10. A left surface 12si, which is one side surface of the partition wall 12s, faces the transmission mechanism chamber 10, and a right surface 12so, which is the other side surface, faces the motor compartment 20.

[0021] Facing end surfaces of the outer peripheral walls 11o, 12o of the first and second housing half-bodies 11, 12 are detachably connected to each other with a plurality of bolts b1, and a sealing member (a liquid seal in the embodiment) for sealing a gap between the facing end surfaces is interposed therebetween. Facing end surfaces of the outer peripheral wall 12o of the second housing half-body 12 and the outer peripheral wall 22 of the motor housing Cm are detachably connected to each other with a plurality of bolts b2, and a sealing member (a liquid seal in the embodiment) for sealing a gap between the facing end surfaces is interposed therebetween.

[0022] A lower part within the transmission case Ct functions as an oil reservoir 15, which stores oil for lubrication. An oil surface L of the oil stored in the oil reservoir 15 is set to such a level that a lower portion of a final driven gear Gf described below is immersed in and in contact with the stored oil in a stop state of the engine M (i.e., the reduction device R and the differential device D) (see Fig. 2 to 4).

[0023] In a lower section of the partition 12s of the second housing half 12, an oil return channel 16 is formed, which returns oil from the engine compartment 20 to the transmission mechanism chamber 10 in order to pass through it. The engine compartment 20 and the transmission mechanism chamber 10 communicate with each other via the oil return channel 16.

[0024] Next, an example of the reduction device R will be described with reference to mainly Fig. 1 to Fig. 4 described.

[0025] A transmission mechanism G, which is formed of a gear train and functions as the reduction device R, includes, for example, an input gear Gi fixed (in the embodiment by a spline and a snap ring) to an outer periphery of an inner end portion of the motor output shaft 26 that bulges into the transmission mechanism chamber 10; a counter shaft 14 located on a rear upper side relative to a rotation axis Xi of the input gear Gi and including a rotation axis Xc parallel thereto; a counter gear Gc fitted and fixed on the counter shaft 14 (in the embodiment by a spline and a snap ring retainer) to mesh with the input gear Gi; a counter pinion Gcp fixed (in the embodiment integrally) to an outer periphery of the counter shaft 14 at a position spaced to the left from the counter gear Gc;and a final output gear Gf, which is arranged on a coaxial line relative to the input gear Gi, which has a larger diameter than the mating gear Gcp and which meshes with the mating gear Gcp.;

[0026] In this embodiment, the final output gear Gf is arranged such that it engages with the mating pinion Gcp in a specific semicircular area (right semicircular area with respect to the axis of rotation Xi). Fig. 2) meshes, in which a tooth surface in accordance with a forward rotation of the final driven gear Gf (rotation in a counterclockwise direction in Fig. 2) from a lower end of the final driven gear Gf to an upper end thereof.

[0027] One end portion of the countershaft 14 is rotatably supported on the side wall 11s of the first housing half-body 11 via the first counter bearing Bc1, and the other end portion of the countershaft 14 is rotatably supported on the partition wall 12s of the second housing half-body 1 via the second counter bearing Bc2. In particular, in the embodiment, as shown in Fig. 1, the first counter bearing Bc1 is formed from a shielded bearing.

[0028] That is, similar to conventionally known shielded bearings, the first thrust bearing Bc1 includes an outer race 101 and an inner race 102 each having a circular annular shape, a plurality of balls 103 interposed between facing peripheries of both races 101, 102, and a resin or metal shield 104 having a circular annular plate shape and located in an axial direction between one end (right end) of the outer race 101 and one end (right end) of the inner race 102. The shield 104 is fixed to one of the inner race 101 and the outer race 102 (for example, the outer race 101) and is adjacent to and facing the other of the inner race 101 and the outer race 102 (for example, the inner race 102) at a small distance.

[0029] As the first counter bearing Bc1, a sealed bearing (which is conventionally known but not shown) can be used instead of the shielded bearing described above. In this sealed bearing, a contact seal made of rubber or synthetic resin is used instead of the non-contact shield 104 described above. This contact seal is fixed to one of the inner and outer races 101, 102 (for example, the outer race 101) and is in sliding contact with the inner and outer races 101, 102 (for example, the inner race 102).

[0030] Specifically, in the embodiment, a left side of the shielded bearing or the sealed bearing serving as the first counter bearing Bc1 is open, thereby allowing the shielded bearing or the sealed bearing to be lubricated with oil flowing from a right end side of the counter shaft 14 to a left end side through its hollow portion.

[0031] The gears Gi, Gc, Gcp, Gf of the gear transmission mechanism G are each formed of helical gears. Fig. In Figure 1, helical teeth of each helical gear are shown in a cross-sectional view along their tooth trace for convenience. The final driven gear Gf functions as a large-diameter gear and is concentrically fixed to an outer peripheral portion of a differential case Dc described below by a suitable fastening means (for example, such as a screw coupling, welding, or the like).

[0032] During operation of the reduction device R, primary deceleration is performed between the two gears Gc and Gi due to a relationship between the diameters of the counter gear Gc, which is larger than that of the input gear Gi. Due to a relationship between the diameters of the final output gear Gf, which is larger than that of the counter gear Gcp, secondary deceleration is performed between the two gears Gf and Gcp. Note that the counter gear Gc and the counter pinion Gcp may be integrally formed.

[0033] Furthermore, when the motor M rotates in a forward direction to move a vehicle forward, each of the gears Gi, Gc, Gcp, Gf described above rotates in the forward direction in conjunction with this rotation. The forward direction of rotation is indicated by hollow arrows in Fig. 2 and Fig. 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 a forward rotation direction of the counter gear Gc and the counter pinion Gcp is a direction opposite to the forward rotation direction of the motor M.

[0034] The counter pinion Gcp and the final driven gear Gf are arranged such that, during the forward rotations of these gears, in accordance with a mutual meshing between the counter pinion Gcp and the final driven gear Gf, the oil on the tooth surface is forced from an engaging portion 40 to one side (left side in the embodiment) in an axial direction of the counter pinion Gcp. Obviously, this arrangement relates to a helix angle of the helical gear teeth (i.e., a tooth track orientation) that has a helical shape with respect to an axis of both the counter pinion Gcp and the final driven gear Gf.

[0035] Furthermore, according to the arrangement of the counter pinion Gcp and the final output gear Gf described above, in accordance with the movement of the engagement position from a right end to a left end in an axial direction of the teeth when the gears mesh, the oil is forced at the tooth surface from the engagement section 40 to an axially left side in a preloaded manner, as indicated by a dashed arrow in Fig. 1 shown.

[0036] In contrast, in this embodiment, the first counter bearing Bc1, which in this embodiment comprises a shielded bearing, is used as a fluid boundary wall that counteracts the oil pushed towards the axially left side by the engagement section 40 described above, in order to prevent the forced oil from flowing towards the axially left side. In this case, as shown in Fig. As can be seen in Figure 1, the first counter bearing Bc1 is arranged adjacent to the axially left end faces of the teeth of the counter pinion Gcp and is formed in such a way that tooth tip sections of the left end faces of the teeth can be covered (i.e. a larger diameter than that of the counter pinion Gcp).

[0037] Furthermore, in the embodiment, the axial width of the counter pinion Gcp is defined such that a tooth section of the counter pinion Gcp has a specific length s (see Fig. 1) which extends to the axially left side relative to the engagement section 40 with the final output gear Gf. Instead of this setting, another embodiment may also be possible in which the length s of the tooth section of the counter pinion Gcp, which extends from the engagement section 40 described above to the axially left side, is set to zero or a negligible length.

[0038] Next, the differential device D will be described mainly with reference to the Fig. 1 and Fig. 2 described. The differential device D comprises the differential housing Dc, which integrally includes bearing hub parts Dca, Dcb at both axial end sections of a body part of the differential housing Dc; and a differential gear mechanism Dg, which is received in the body part of the differential housing Dc and which transmits a rotational force of the differential housing Dc to the pair of drive shafts 51, 52 while enabling differential rotation.

[0039] The bearing hub portion Dca on a left side of the differential case Dc is supported via a first differential bearing Bf1 on the side wall 11s of the first case half body 11, and the bearing hub portion Dcb on a right side of the differential case Dc is supported via a second differential bearing Bf2 on an intermediate case 80 described below, which is fixed to the partition wall 12s of the second case half body 12. The first and second differential bearings Bf1, Bf2 are an example of a pair of bearings for a final driven gear.

[0040] Furthermore, the differential housing Dc is rotatably mounted on the gearbox housing Ct on the axis of rotation Xi of the input gear Gi. Parallel to this, the drive shafts 51, 52, which are rotatably fitted onto the inner circumferences of the left and right bearing hub sections Dca, DCB of the differential housing Dc, are also mounted on the gearbox housing Ct via the gearbox housing Ct and the first and second differential bearings Bf1, Bf2. Additionally, an intermediate section of the right drive shaft 52 is mounted on the motor housing Cm via a bearing Bd.

[0041] A helical groove is formed in a mating surface of the bearing hub part Dca on the left side and the drive shaft 51 and a mating surface of the bearing hub part Dcb on the right side and the drive shaft 52, which is capable of providing a screw pumping action to guide oil scattered within the gearbox housing Ct into the differential housing Dc.

[0042] On an outer periphery of the body part of the differential case Dc, the final driven gear Gf comprising a ring gear is fixed (with the bolt b4 in the embodiment) in a position offset to an axial right side from a central portion of the body part. Further, the differential case Dc includes two or more window portions Dch (two in the embodiment) in the body part, which are provided in a position offset to the axial left side relative to the final driven gear Gf. The window portions Dch are symmetrically arranged with a pinion shaft 33 interposed therebetween, and function as an operation port for gear mounting or as an oil inflow port between an outer side and an inner side of the differential case Dc.

[0043] From the relationship in which the window portions Dch are arranged in a manner offset to the axially left side relative to the final driven gear Gf, the axial position of the window portions Dch is arranged to partially coincide with the tooth portion of the counter pinion Gcp extending to the axially left side from the engaging portion 40 with the final driven gear Gf, as shown in Fig. 1 is evident.

[0044] Although an example of the differential case Dc is integrally configured in the embodiment, the differential case Dc may be configured to be divided into two or more case members which are mutually coupled.

[0045] Next, the differential gear mechanism Dg will be described. The differential gear mechanism Dg includes a pair of side gears 31 housed in the differential case Dc and rotatable about the same axis as the differential case Dc; two or more pinions 32 meshing with both side gears 31; and the pinion shaft 33 fixed to the differential case Dc and supporting the pinions 32 rotatably about their axes perpendicular to the rotational axis of the side gears 31. An inner periphery of a center hole of each of the left and right side gears 31 is locked and coupled (in the embodiment, by spline engagement) to an outer periphery of an inner end portion of each of the first and second drive shafts 51, 52.

[0046] The structure and function of the differential gear D are well known, and thus further description is omitted. However, the rotational drive force from the engine M is input into the differential case Dc through the reduction device R and then from the final driven gear Gf. The differential device D distributes and transmits the rotational drive force to the first and second drive shafts 51, 52 while enabling differential rotation.

[0047] The unit housing C (in particular the gear housing Ct) comprises a first oil collection section H1, which is capable of collecting oil scattered from the input gear Gi; an input gear cover 70, which includes an upwardly open rear portion that allows the mating gear Gc and the input gear Gi to mesh with each other, and which covers the input gear Gi; and a vent BR, which allows the interior of the unit housing C to communicate with the outside air while preventing oil from splashing out into the outside air. Next, specific structures of the first oil collection section H1, the input gear cover 70, and the vent BR are described with reference to Fig. 5 to Fig. 11 described.

[0048] As from Fig. 4, in the first oil collecting part H1, an oil inlet port H1i is located on a front side in the forward rotational direction of rotation of the input gear Gi on a common tangent of pitch circles of the input gear Gi and the counter gear Gc in a side view (that is, viewed from an axial direction of the input gear Gi). Accordingly, after the input gear Gi, which rotates together with the engine M at high speeds, meshes with the counter gear Gc, the oil remaining on the tooth surface is forcibly sprayed upward in a direction of the above-described common tangent due to centrifugal force and moves into the oil inlet port H1i, so that the oil is efficiently collected by the first oil collecting part H1.The oil collected by the first oil collecting part H1 can be supplied to a lubrication target part located in both the transmission case Ct and the motor case Cm, as described below.

[0049] On the other hand, the input gear cover 70 includes the rear upwardly open part, which enables the mutual engagement between the counter gear Gc and the input gear Gi, and has an internal space, a lower portion of which functions as an auxiliary oil reservoir 71 capable of storing oil for the input gear Gi. In an upper portion of the internal space of the input gear cover 70, the first oil collecting part H1 is located, and the opening, i.e., the oil inlet port H1i, faces an engagement portion in which the counter gear Gc and the input gear Gi mesh with each other.

[0050] The above-described first oil collecting part H1, the input gear cover 70 and the breather BR are formed by the second housing half body 12 and the intermediate housing 80, which serves as a cover detachably coupled to the partition wall 12s.

[0051] For a more detailed description, as Fig. 4, the left surface 12si of the partition wall 12s is integrally provided with an upper arcuate input gear surrounding wall W1 surrounding the input gear Gi over half its circumference or more; an oil collecting part forming wall W2 extending slightly downward from an upper inner circumference of the input gear surrounding wall W1 and further extending in a circumferential direction of the input gear Gi while changing its direction to a side where the counter gear Gc is located; a breather chamber forming wall W3 spaced upward from the input gear surrounding wall W1 and extending substantially along an inner circumference of the outer peripheral wall 12o of the second casing half body 12;and a wall W4 forming a communication channel, which is located directly below the wall W3 forming the vent chamber and integrally connects a front section of the wall W1 surrounding the input gear with a front part of the outer circumferential wall 12o of the second housing half-body 12. Each front end face (left end face) of the wall W1 surrounding the input gear, the wall W3 forming the vent chamber, and the wall W4 forming the communication channel is on the same plane as the corresponding matching face of the outer circumferential wall 11o of the first housing half-body 11 and the outer circumferential wall 12o of the second housing half-body 12.

[0052] In particular, the wall W1 surrounding the input gear is continuously provided with a projecting portion W1a, which extends upwards from its lower open end, thereby preventing oil from flowing out of the auxiliary oil reservoir 71. Furthermore, the wall W1 surrounding the input gear includes, at an inner circumferential edge of the front end face (left end face), a positioning step section W1s, which extends circumferentially and which is recessed by a step that is deeper than the front end face.

[0053] On the other hand, the intermediate housing 80 comprises a disk-shaped housing body 81, which corresponds to the wall W1 surrounding the input gear, and an upwardly projecting section 82, which is provided continuously and integrally on a section of an upper half of the housing body 81 and which extends upwards in a substantially fan-like manner. On an outer surface (left side) of the housing body 81, a stepped cylindrical annular hub portion 81b is integrally provided in a projecting manner and appropriately secures an outer race of the second differential bearing Bf2 on the right side. The housing body 81 includes on its inner surface (right side) an upper arc-shaped projection 81a, which is provided in a section closer to an outer circumferential section of the housing body 81.The upper arcuate projection 81a is integrally provided in a protruding manner so as to extend along the input gear surrounding wall W1 and to be fittable to the positioning step portion W1s.

[0054] The left end surface of the outer peripheral wall 12o of the second housing half body 12 is formed such that its portion corresponding to the wall W3 forming the breather chamber has a larger width. As shown in Fig. 2 to Fig. As can be seen in Figure 4, an end surface of the greater width has a shallow groove 12g, which extends along an upper edge of the upwardly projecting section 82 and which is adjacent to the upwardly projecting section 82. A section of a sealing element (e.g., a liquid seal) to be used between the connecting end surfaces of the first and the second housing half-body 11, 12 can be held in the groove 12g.

[0055] The intermediate housing 80 enables the arc-shaped projection 81a described above to be fitted onto the positioning step section W1s of the wall W1 surrounding the input gear (see Fig. 1, Fig. 5) and is fixed to the partition 12s of the second housing half-body 12 by coupling an inner surface of the outer circumferential section of the housing body 81 with the wall W1 surrounding the input gear on an outer side of the arc-shaped projection 81a (see Fig. 1, Fig. 3, Fig. 5 and Fig. 6) with a bolt b3. In such a fixed state of the intermediate housing 80, the input gear cover 70 is defined by the intermediate housing 80 and the partition 12s (in particular by an inner circumference of the wall W1 surrounding the input gear, the left surface 12si of the partition 12s and an inner surface of the housing body 81).

[0056] Furthermore, in the above-described fixed state of the intermediate housing 80, an upper surface (right end surface) of the arcuate projection 81a of the inner surface of the housing body 81 faces adjacent to the front end surface (left end surface) of the oil collecting part forming wall W2. Accordingly, the first oil collecting part H1 is defined by the housing body 81 and the partition wall 12s (specifically, the oil collecting part forming wall W2 and the left surface 12si of the partition wall 12s).

[0057] In the embodiment, the front end surfaces (left end surfaces) of the protruding part W1a and the oil collecting part forming wall W2 are adjacent to and facing each other relative to the inner surface of the case body 81 with a small gap (for example, 0.5 millimeters), but may abut against the inner surface of the case body 81.

[0058] As from Fig. As can be seen in Figure 4, the second housing half 12 of the gearbox housing Ct includes a second oil collection element H2, which is located on a front side in the forward direction of rotation of the mating gear Gc relative to the first oil collection element H1 and is capable of collecting the oil scattered by the mating gear Gc. The second oil collection element H2 is formed from a concave surface located on the left surface 12si of the partition 12s in an area between the breather BR and a front section of the mating gear Gc in the front-to-back direction, and between a front section of the outer circumferential wall 12o of the second housing half 12 and the front section of the wall W1 surrounding the input gear in the top-to-bottom direction. The opening at a rear end of the second oil collection element H2 serves as an oil inlet H2i, which is adjacent to and facing the front section of the mating gear Gc.In addition, the second oil collecting part H2 has a front end portion which communicates directly with a rear end of a first communicating oil passage 91 described below.

[0059] In a portion of the partition wall 12s forming a side wall portion of the first oil collecting part H1, a first oil supply passage 17 is formed in a through-hole shape so as to guide a part of the oil collected by the first oil collecting part H1 to a surrounding portion of a first engine mount Bm1 on the left side. As shown in FIGS. Fig. 9 and Fig. As can be seen in Figure 10, an open end of the first oil supply channel 17, which is open towards the engine compartment 20 (i.e., a side on which the right surface 12so of the partition 12s is located), is in a position corresponding to a cut-out slot 18s provided in a stepped cylindrical annular projection 18, which is provided on the right surface 12so in a projecting manner and which appropriately secures an outer bearing race of the first engine bearing Bm1. The right surface 12so includes a shallow oil groove 19 provided in a recessed manner, which extends radially inwards from the open end of the first oil supply channel 17 through the slot 18s.

[0060] As described above, the part of the oil collected by the first oil collecting part H1 passes through the first oil supply passage 17 and is guided to the first engine mount Bm1 via the slit 18s and the oil groove 19.

[0061] On the other hand, the intermediate housing 80 includes a third oil supply channel 85, which directs the portion of the oil collected by the first oil collection part H1 to a surrounding part of the second differential bearing Bf2. As shown from Fig. 3 and Fig. As can be seen from Fig. 11, the third oil supply passage 85 is formed of a slit-like through-hole that radially extends beyond the above-described arcuate protrusion 81a on the inner surface (right side) of the housing body 81 and axially penetrates the housing body 81. As described above, the portion of the oil collected by the first oil collecting portion H1 flows through the third oil supply passage 85 and flows along outer peripheral portions of the second differential bearing Bf2 and the second drive shaft 52.

[0062] As can be seen from the Fig. 4 and Fig. As can be seen in Figure 7, the first oil communication channel 91 is defined between the second housing half-body 12 and the intermediate housing 80 and extends in the front-to-back direction, running between the wall W3 forming the vent chamber and a front section of the wall W1 surrounding the input gear and the wall W4 forming the communication channel. On the first oil communication channel 91, a through-flow oil channel 12sh, which penetrates the partition wall 12s in the front-to-back direction, has an open front end and a rear end that opens to an innermost section located at a front face of the first oil collection part H1.

[0063] Accordingly, with the exception of the oil flowing towards the first and third oil supply channels 17, 85, the oil collected by the first oil collection section H1 flows through the through-flow oil channel 12sh into a section of the first communicating oil channel 91. The first communicating oil channel 91 communicates with a second communicating oil channel 92, which is provided axially on the outer circumferential wall 12o of the second housing half-body 12. As can be seen from Fig. 8, the second communicating oil passage 92 communicates with the second engine mount Bm2 on the right side via a series of first and second communicating oil passages 93, 94 extending in the outer and inner peripheral walls 21, 22 of the engine housing Cm.

[0064] Furthermore, the through-flow oil passage 12sh, the first communicating oil channel (in particular a front half-section), the second communicating oil channel 92, and the first and second communicating oil channels 93, 94, which are connected in series, work together to form a second oil supply channel 90, which carries the portion of the oil collected by the first oil catch section H1 to the second engine mount Bm2 on the right side. A section in the second oil supply channel 90 and the second oil catch section H2 described above communicate with each other via a rear section of the first communicating oil channel 91. Accordingly, the oil collected by the second oil catch section H2 is also carried via the second oil supply channel 90 to the second engine mount Bm2.

[0065] In the fixed state of the intermediate housing 80 described above, a vent chamber 60 of the vent BR is defined by the intermediate housing 80 and the second housing half-body 12 (in particular by an upper surface of the wall W3 forming the vent chamber, a lower surface of a wider front section of the outer circumferential wall 12o of the second housing half-body 12, the left surface 12si of the partition 12s and an inner surface of the upwardly projecting section 82).

[0066] The vent chamber 60 is shielded from the transmission mechanism chamber 10 by the intermediate housing 80 and communicates with the outside air via an outlet cylinder 61 fixed to the front section of the outer circumferential wall 12o of the second housing half-body 12. Similar to conventionally known vents, the vent chamber 60 comprises, on its inner wall (particularly on the left surface 12si of the partition 12s), two or more deflector plates 62, which are arranged in a manner described above to form a labyrinth within the vent chamber 60 and to prevent oil from splashing out (see Figure 1). Fig. 4, Fig. 6 and Fig. 7).

[0067] As from Fig. As can be seen in Figure 6, a communication channel 63, which enables communication between the breather chamber 60 and the engine compartment 20, is formed such that it axially penetrates the partition wall 12s. An opening of the communication channel 63 is open toward the right surface 12so of the partition wall 12s and forms an inlet 60i of the breather chamber 63 facing the engine compartment 20.

[0068] The breather chamber 60 is in a communication state to communicate with the engine compartment 20 (and thus the transmission mechanism chamber 10) through the inlet 60i. Accordingly, when an air pressure in the engine compartment 20 is higher than atmospheric pressure, the air in the breather chamber 60 flows from the inlet 60i through the communication passage 63 and is discharged to outside air through the exhaust cylinder 61.

[0069] As can be seen from the Fig. 6, Fig. 9 and Fig. As can be seen in Figure 10, the right surface 12so of the partition 12s in this embodiment is provided with a projecting wall 12t, which extends towards the engine compartment 20 and surrounds the inlet 60i of the vent chamber 60. Even if the oil is slightly scattered within the engine compartment 20, the provision of the projecting wall 12t effectively prevents the scattered oil from entering the vent chamber 60.

[0070] As from Fig. As can be seen in Figure 2, at least one section of the vent chamber 60 is arranged such that, viewed from an axial direction of the final output gear Gf, it overlaps the final output gear Gf. Since such an arrangement can prevent the vent chamber 60 from projecting significantly outwards axially towards the final output gear Gf, it is advantageous for making the gearbox housing Ct (and thus the unit housing C) more radially compact.

[0071] Fig. Figure 1 clearly shows an arrangement in which the mating gear Gc is positioned axially between the intermediate housing 80 and the partition 12s. From this arrangement, it is evident that the vent chamber 60, defined between the intermediate housing 80 and the partition 12s, is in a position where, looking radially outward from the axis of rotation Xc of the mating gear Gc, it partially overlaps the mating gear Gc. Since this arrangement prevents the vent chamber 60 from protruding significantly towards an axially outer side with respect to the mating gear Gc, it is also advantageous for making the gearbox housing Ct (and thus the unit housing C) more axially compact.

[0072] As can be seen from the Fig. 8 and Fig. As can be seen in Figure 9, the inlet 60i of the vent chamber 60 is located at a relatively close distance to the stator 24, which is fixed to the motor housing Cm. As described above, by arranging the inlet 60i of the vent chamber 60 adjacent to and facing the stator 24, which does not rotate within the motor chamber 20, it is possible to prevent oil from entering the vent chamber 60 through the motor chamber 20 more effectively using the stator 24.

[0073] Next, an operation in the embodiment will be described. In the power unit PU including the transmission device T according to the present invention, upon input of the rotational drive force from the engine output shaft 26 to the input gear Gi in accordance with the operation of the engine M, the rotational drive force is decelerated in two stages by the reduction device R within the transmission device T and transmitted to the final driven gear Gf. The differential device D distributes the rotational drive force of the final driven gear Gf to the first and second drive shafts 51, 52 while allowing differential rotation, and the rotational drive force is further transmitted from the first and second drive shafts 51, 52 to the left and right drive gears.

[0074] In the stop state of the engine M, a certain amount of oil is stored in the oil reservoir 15 located in the lower part inside the transmission case Ct, and a part of the oil that has been scattered and flowed downward within the transmission mechanism chamber 10 in accordance with the previous operation of the engine M is also stored in the auxiliary oil reservoir 71 in the input gear cover 70.

[0075] Furthermore, during a transmission of the gear mechanism G, in particular during the forward rotation of the motor M (when a vehicle begins to move forward), the input gear Gi, the mating gear Gc, the counter pinion Gcp and the final output gear Gf rotate in a direction which can be seen, for example, in the hollow arrows in the Fig. 2 and Fig. 4. In accordance with this rotation, the oil within the oil reservoir 15 is scooped up by the final driven gear Gf, which is located at the lowest position and has the largest diameter, and then scatters to various parts within the gear mechanism chamber 10.

[0076] The transmission case Ct in the embodiment includes the first oil collecting part H1, which is capable of collecting the oil from the input gear Gi rotating at high speeds. As also shown in Fig. 4, the oil inlet port H1i of the first oil collecting part H1 is located on the front side in the forward rotation direction of the input gear Gi on the common tangent of the pitch circles of the input gear Gi and the counter gear Gc. This enables the first oil collecting part H1 to efficiently collect the oil that scatters upward from the input gear Gi after the input gear Gi and the counter gear Gc mesh with each other during rotation of the input gear Gi at high speeds, and to supply the collected oil to various lubrication target parts located within the unit case C.

[0077] That is, the part of the oil collected by the first oil collecting part H1 is supplied to the first engine bearing Bm1 on the left side (i.e., closer to the transmission device T) through the first oil supply passage 17 penetrating the partition wall 12s on a right side of the first oil collecting part H1. A part of the other oil, i.e., the oil different from that collected by the first oil collecting part H1, is supplied to the second differential bearing Bf2 on the right side or a surrounding area of ​​the second drive shaft 52 through the slit-hole-like third oil supply passage 85 provided on the case body 81 of the intermediate case 80. In addition, the remaining oil of the above-described other oil (i.e.,the oil which just flows around the inlets of the first and third oil supply passages 17, 85) enters the through hole 12sh which is open to the innermost portion of the first oil collecting part H1, and is then supplied to the second engine mount Bm2 on the right side (ie, far from the transmission device T) through the second oil supply passage 90.

[0078] As described above, the oil collected by the first oil collecting part H1 efficiently lubricates lubrication target parts inside and outside the transmission case Ct, that is, each of the bearings Bm1, Bm2, Bf2 and others described above.

[0079] Furthermore, in the embodiment, the transmission case Ct includes the input gear cover 70 covering the input gear Gi, which is capable of storing the oil in the lower portion of the internal space, and the first oil collecting part H1 is disposed inside the input gear cover 70. Accordingly, within the input gear cover 70, which includes the auxiliary oil reservoir 71 for the input gear at its inner bottom, it is possible to sufficiently scatter the oil from the input gear Gi with centrifugal force and effectively collect the scattered oil by the first oil collecting part H1 facing the oil inlet port H1i inside the input gear cover 70, thereby further effectively lubricating the above-described lubrication target parts.

[0080] The second differential bearing Bf2 on the right side in this embodiment is attached to the intermediate housing 80, which is coupled to the partition 12s of the gearbox housing Ct, and the partition 12s, together with the intermediate housing 80, defines the first oil collection element H1. That is, since the intermediate housing 80, which is a section of the molded wall of the first oil collection element H1, is also used as a bearing element for the second differential bearing Bf2, the device structure is simplified accordingly, thus achieving a cost reduction.

[0081] Furthermore, since the intermediate housing 80 includes the through-hole, i.e., the slit-like third oil supply passage 85, which guides the part of the oil collected by the first oil collecting portion H1 to the second differential bearing Bf2, the oil collected by the first oil collecting portion H1 can be effectively used to also lubricate the second differential bearing Bf2 and the like. Since it is possible to form an oil introduction passage from the first oil collecting portion H1 to the second differential bearing Bf2 merely by providing the through-hole-like third oil supply passage 85 in the intermediate housing 80, the oil passage structure is simplified.

[0082] In the power unit PU in the embodiment, the unit case C includes, on the front side in the forward rotation direction of the counter gear Gc relative to the first oil collecting part H1, the second oil collecting part H2, which is capable of collecting the oil scattered from the counter gear Gc. The second oil collecting part H2 communicates with the first oil supply passage 90 in the second case half body 12.

[0083] Accordingly, it is possible to more efficiently collect not only the oil scattered from the input gear Gi but also the oil scattered radially outward by centrifugal force from the counter gear Gc using the second oil collecting part H2, and then combine the collected oils with the oil in the first oil supply passage 90 from the first oil collecting part H1 toward the second engine mount Bm2. Accordingly, it is possible to more efficiently lubricate the second engine mount Bm2, which is located farther away from the transmission device T, using not only the first oil collecting part H1 but also the second oil collecting part H2.

[0084] In this case, when an orientation of a helical shape of the helical teeth of the counter gear Gc is set such that the oil scatters while being biased to the axially right side relative to the gear teeth, particularly during the forward rotation of the engine M, it is possible to more efficiently collect the scattered oil from the counter gear Gc by the second oil collecting part H2 located axially right on a front upper outer periphery of the counter gear Gc.

[0085] In the embodiment, the final driven gear Gf as the large diameter gear meshes with the counter pinion Gcp in a specific semi-circumferential region (a semi-circumferential region behind the rotation axis Xi in Fig. 2), in which the tooth surface moves from the lower end of the final output gear Gf towards its upper end in accordance with the forward rotation of the final output gear Gf. Both the mating pinion Gcp and the final output gear Gf, which is a helical gear, are arranged such that the oil at the tooth surface of the mutual engagement section 40, during the forward rotation of the final output gear Gf, flows to an axially left side of the mating pinion Gcp (i.e., into the area indicated by the dashed arrow in Fig. 1 (in the specified direction) is pressed. Furthermore, as shown, it includes... Fig. As can be seen in Figure 1, the first counter bearing Bc1 is a shielded bearing acting as a fluid boundary wall, which prevents the oil from flowing to the left side in the opposite direction to the oil being forced to the axially left side by the engagement section 40. The first counter bearing Bc1 is arranged adjacent to the axially left tooth end of the mating pinion Gcp and is shaped such that the tooth tip sections of the end faces can be covered.

[0086] Accordingly, during the forward rotation of the final driven gear Gf, the oil pushed from the meshing portion 40 of the final driven gear Gf and the counter pinion Gcp to the axially left side of the counter pinion Gcp is prevented from flowing to the axially left side by the first counter bearing Bc1 (shielded bearing as the fluid confinement wall) opposing the pushed oil. This allows the oil accumulated at a location just before the bearing Bc1 to flow more easily to a tooth portion of the final driven gear Gf. This makes it possible to more easily transport this oil and scoop up the oil through the final driven gear Gf, effectively increasing the amount of oil that the gear Gf scoops up to its upper gear portion.As a result, although such a configuration allows the final driven gear Gf to mesh with the counter pinion Gcp in a process of scooping up the oil, it becomes possible to sufficiently supply the oil to the upper portion of the final driven gear Gf.

[0087] As from Fig. 1, in particular, the axial width of the counter pinion Gcp in the embodiment is set such that the tooth portion of the pinion Gcp extends to the axially left side relative to the above-described engaging portion 40. Accordingly, when the oil pushed from the above-described engaging portion 40 to the axially left side accumulates on a proximal side of the first thrust bearing Bc1 serving as the fluid confinement wall (specifically, on the tooth surface extending to the axially left side relative to the engaging portion 40 of the counter pinion Gcp), it is possible to scatter a part of the accumulated oil radially outward from the counter pinion Gcp with the centrifugal force to supply the oil to the surrounding lubrication target parts.

[0088] In this case, since the side wall 11s of the first case half body 11 (particularly, the bowl-shaped portion surrounding the differential case Dc) includes on its inner periphery a plurality of oil guide ribs (not shown) in a projecting manner, the oil scattered from the counter pinion Gcp and adhering to an inner surface of the side wall 11s can also be efficiently guided and supplied to the first differential bearing Bf1 on the left side.

[0089] In the embodiment, the fluid restriction wall that performs fluid restriction of the oil pushed from the above-described engaging portion 40 to the axially left side to accumulate on the near side is formed by the first counter bearing Bc1, which is the shielded bearing that supports the counter pinion Gcp to the transmission case Ct. Accordingly, the shielded bearing having an oil seal function, which is commonly used, is utilized, making it possible to simply structure the above-described fluid restriction wall at low cost.

[0090] Unlike the present embodiment, in which the shielded bearing (first counter bearing Bc1) also acts as the fluid boundary wall, a variety of variations can be used as the fluid boundary wall described above. For example, a modified example is also possible in which a flat disk is held between the toothed section of the counter pinion Gcp and the first counter bearing Bc1, which is not a shielded bearing, and this flat disk is used as the fluid boundary wall. Alternatively, another modified example is also possible in which an annular, flange-like projecting wall, which is integrally formed with an outer circumferential section of the counter shaft 14 and inserted between the toothed section of the counter pinion Gcp and the first counter bearing Bc1, which is not a shielded bearing, can be used as the fluid boundary wall.

[0091] Alternatively, another modified example is also possible in which a radially flat bearing (e.g., a needle bearing) is used as the first counter bearing Bc1, this radially flat bearing being located in a fitting portion between the counter shaft 14 and the side wall 11s of the first housing half body 11. In this modified example, the side wall 11s has its inner wall closer or adjacent to a left end surface of the tooth portion of the counter pinion Gcp, and the inner wall of the side wall 11s can be used as the fluid confinement wall.

[0092] As from Fig.1, the differential case Dc of the differential device D in the embodiment includes the window portion Dch, which is arranged in a position offset to the axially left side relative to the final driven gear Gf and which enables communication with the inside and outside of the differential case Dc. Accordingly, when the above-described oil pressed to the axially left side onto the tooth surface of the counter pinion Gcp during forward rotation of the final driven gear Gf is scattered by centrifugal force, the oil is easily introduced into the window portions Dch. Accordingly, since the oil scattered from the counter pinion Gcp is efficiently supplied to the differential gear mechanism Dg within the differential case Dc through the window portions Dch, a lubricating effect on the differential gear mechanism Dg can also be increased.

[0093] The unit case C in the embodiment, specifically, the second case half body 12, includes the partition wall 12s, of which the left surface 12si faces the transmission mechanism chamber 10 and the right surface 12so faces the engine compartment 20. The left surface 12si of the partition wall 12s and the intermediate case 80 serving as a cover, which is coupled to the left surface 12si, define the breather chamber 60. The inlet 60i of the breather chamber 60 is open to the right surface 12so of the partition wall 12s and can communicate with the engine compartment 20.

[0094] Accordingly, since the inlet 60i of the breather chamber 60 has a communicating configuration that is not directly open to the transmission mechanism chamber 10 and that communicates with the transmission mechanism chamber 10 through the engine compartment 20, the oil scattered from each gear of the gear transmission mechanism G within the transmission case Ct can be effectively prevented from entering the breather chamber 60. This can reduce a risk of oil splashing out of the breather chamber 60.Moreover, since the breather chamber 60 is defined by the left surface 12si of the partition wall 12s of the transmission case Ct and the intermediate case 80 serving as the lid coupled thereto, it is also possible to easily obtain a hollow structure of the breather chamber 60 separated from the transmission mechanism chamber 10 without complicating the structure of the partition wall 12s of the transmission case Ct and its molding process, thus achieving a cost reduction accordingly.

[0095] Although the embodiment of the present invention has been described above, the present invention is not limited to the embodiment, and various design modifications may be made thereto without departing from the gist of the present invention.

[0096] For example, in the above-described embodiment, the gear transmission mechanism G of the transmission device T comprises a so-called two-axis gear transmission mechanism in which the input gear Gi and the final driven gear Gf (and thus the drive shafts 51, 52), which rotate about the axis different from the axis Xc of the counter gear Gc, are arranged on a coaxial line thereof. However, in the present invention, a so-called three-axis gear transmission mechanism may be employed in which the input gear Gi, the counter gear Gc, and the final driven gear Gf (and thus the drive shafts 51, 52) rotate about three different axes.

[0097] In the embodiment described above, the transmission device T comprises, in addition to the reduction device R, the differential device D, in which an output from the reduction device R, i.e., a torque from the final output gear Gf, is distributed via the differential device D to the pair of drive shafts 51, 52 (and thus to the left and right drive wheels). However, in the present invention, the differential device D can be omitted, and the final output gear Gf can be locked and coupled to a single drive shaft via a locking mechanism without a differential function. In this case, the drive shaft can rotate to drive a single drive wheel (for example, a rear wheel of a motorcycle).

[0098] In the above-described embodiment, the transmission device T is applied to a transmission device for a vehicle (e.g., an automobile). However, the transmission device T of the present invention may be applicable to a transmission device in other machine devices other than vehicles.

[0099] In the above-described embodiment, during the forward rotation of the final driven gear Gf, the counter pinion Gcp and the final driven gear Gf, in which the orientation of the helical shapes of the helical teeth of both gears Gcp, Gf (in other words, helix angles) are set such that the oil on the tooth surface Gcp is pushed from the engaging portion 40 to the axially left side of the counter pinion in accordance with the mutual engagement between the counter pinion Gcp and the final driven gear Gf. However, in the present invention, the orientation of the helical shapes of the helical teeth of both gears Gcp, Gf may be set to an orientation opposite to that in the embodiment.In this case, since the oil on the tooth surface is pressed from the engaging portion 40 to the axially right side of the counter pinion Gcp in accordance with the mutual engagement between the counter pinion Gcp and the final driven gear Gf in the above-described forward rotation, the fluid restricting wall adjacent to the tooth end surface on the axially right side of the counter pinion Gcp is provided in a protruding manner annularly on an outer periphery of the counter shaft 14, and the axial width of the counter pinion Gcp is set such that the tooth portion of the counter pinion Gcp extends from the above-described engaging portion 40 to the axially right side.In this setting, an extension section of the tooth section of the counter pinion Gcp is in a position that coincides axially with or is close to the second differential bearing Bf2, so that it is also possible to increase the oil supply quantity to the second differential bearing Bf2, since the oil which is forced through the extension section of the tooth section and which accumulates on the near side of the fluid boundary wall is dispersed by centrifugal force.

[0100] In the embodiment described above, the intermediate housing 80 also acts as a means of forming the vent chamber 60 together with the partition 12s, as a means of forming the input gear cover 70, and as a means of supporting the second differential bearing Bf2. However, the intermediate housing 80 can also act as any two of these means, or it can be used exclusively as any one of these means.

[0101] In the above-described embodiment, each gear Gi, Gc, Gcp, Gf of the gear transmission mechanism G of the transmission device T is configured by a helical gear. However, the input gear Gi and the counter gear Gc may be spur gears.

[0102] In the above embodiment, the motor M is described as the power source of the power unit PU, but an internal combustion engine may also be used as the power source. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2016-89861

[0002] JP 53-37883

[0002] JP 7-54973

[0002]

Claims

[1] Transmission device comprising: a pinion (Gcp); and a large diameter gear (Gf) meshing with the pinion (Gcp) and having a larger diameter than the pinion (Gcp), wherein the pinion (Gcp) and the large-diameter gear (Gf) are arranged in a gear housing (Ct), the gear housing (Ct) comprising therein in a lower part an oil reservoir (15) which allows a reservoir oil to come into contact with a lower portion of the large-diameter gear (Gf), wherein the large-diameter gear (Gf) meshes with the pinion (Gcp) in a specific semi-circumferential region in which a tooth surface moves from a lower end of the large-diameter gear (Gf) to an upper end thereof in accordance with forward rotation of the large-diameter gear (Gf), wherein the pinion (Gcp) and the large-diameter gear (Gf) each comprise a helical gear and are arranged such that, during forward rotation of the large-diameter gear (Gf), an oil on the tooth surface is pressed from a mutual engagement portion (40) to one side in an axial direction of the pinion (Gcp), and wherein a fluid restriction wall (Bc1) configured to oppose the oil pushed from the mutual engagement portion (40) to the one side in the axial direction and prevent the oil from flowing to the one side in the axial direction is disposed on the one side in the axial direction adjacent to an end face of teeth of the pinion gear (Gcp), the fluid restriction wall (Bc1) being formed in a shape allowing a tooth tip portion of the end face to be covered. [2] A transmission device according to claim 1, wherein a width of the pinion (Gcp) in the axial direction is set such that a tooth portion of the pinion (Gcp) protrudes to the one side in the axial direction relative to the engagement portion (40). [3] A transmission device according to claim 1 or 2, wherein the fluid limiting wall (Bc1) comprises a shielded bearing or a sealed bearing (Bc1) which rotatably supports the pinion gear (Gcp) on the transmission case (Ct). [4] Transmission device according to one of claims 1 to 3, wherein a differential device (D) is accommodated in the transmission case (Ct) and comprises: a differential case (Dc) which is rotatably supported on the transmission case (Ct) and which has an outer peripheral portion to which the final driven gear (Gf) serving as the large-diameter gear is fixed; and a differential gear mechanism (Dg) which is housed in the differential case (Dc) and which transmits a rotational force of the differential case (Dc) to a pair of drive shafts (51, 52) while allowing differential rotation, and wherein the differential case (Dc) includes a window portion (Dch) disposed in a position offset to one side in the axial direction relative to the final drive gear (Gf) to enable communication with an interior and an exterior of the differential case (Dc).

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