GEARBOX AND POWER UNIT

Abstract

A gear device (T) is provided in which an input gear (Gi) is configured to rotate with power from a power source (M), and a mating gear (Gc) is configured to rotate about an axis parallel to an axis of rotation of the input gear, wherein the input gear and the mating gear mesh with each other and are arranged in a gear housing (Ct), wherein the gear housing (Ct) comprises a first oil collection part (H1) which is capable of collecting oil scattered from the input gear (Gi), and the first oil collection part (H1) comprises an oil inlet opening (H1i) which, viewed from an axial direction of the input gear (Gi), is located on a front side in a forward direction of rotation of the input gear (Gi) on a common tangent of pitch circles of the input gear (Gi) and the mating gear (Gc).and wherein the gearbox housing (Ct) is provided with a lubrication target part which is to be lubricated by the oil collected by the first oil catcher part (H1). As a result, even when the input gear rotates at high speed, the oil which is vigorously ejected from the input gear after the input gear and the mating gear mesh can be efficiently collected by the first oil catcher part and supplied to the lubrication target part, and the oil scattered by the input gear can be effectively used to lubricate the lubrication target part.

Description

TECHNICAL FIELD

[0001] The present invention relates to a transmission device, in particular a transmission housing, which comprises an input gear configured to rotate about a first axis with power from a power source, and a counter gear configured to rotate about an axis parallel to a rotational axis of the input gear, wherein the input gear and the counter gear mesh with each other and are arranged in a transmission housing, wherein the transmission housing comprises therein in a lower part an oil reservoir which stores a transmission lubricating oil, and a power unit which comprises the transmission device and a motor. BACKGROUND STATE OF THE ART

[0002] The transmission device described above is known, for example, as disclosed in Patent Document 1 below. PRIOR ART DOCUMENTS PATENT DOCUMENTS

[0003] Patent Document 1: International Application WO 2019 / 202947 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] The power unit described in Patent Document 1 includes an auxiliary oil reservoir within a transmission case, which allows a reservoir oil to come into contact with a lower portion of an input gear, thereby easily introducing the oil into a specific lubrication target part (a fitting between an engine output shaft and a drive shaft).

[0005] However, since a large amount of the reservoir oil in the auxiliary oil reservoir is scattered when the input gear rotates at high speeds, there are possibilities that the oil cannot be effectively used for intended lubrication.

[0006] The present invention has been proposed in view of the above. An object of the present invention is to provide a transmission device capable of solving the above-described problem in conventional devices, and a power unit comprising the transmission device and a motor. 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 an input gear configured to rotate about a first axis with power from a power source;and a counter gear configured to rotate about an axis parallel to a rotational axis of the input gear, wherein the input gear and the counter gear mesh with each other and are arranged in a transmission case, the transmission case including an oil reservoir in a lower part therein that stores transmission lubricating oil, the transmission case including a first oil collecting part capable of collecting oil scattered from the input gear, and the first oil collecting part including an oil inlet port located on a common tangent of pitch circles of the input gear and the counter gear, viewed from an axial direction of the input gear, on a front side in a forward rotational direction of the input gear, and the transmission case is provided with a lubrication target part to be lubricated with the oil collected by the first oil collecting part.

[0008] In addition to the first feature, the present invention has a second feature in which the transmission case includes an input gear cover which covers the input gear and which is capable of storing an oil in a lower portion of an inner space of the input gear cover, and the first oil collecting part is arranged inside the input gear cover.

[0009] In addition to the first or second feature, the present invention has a third feature in which, in the transmission case, a final output gear configured to rotate about an axis identical to that of the input gear and transmit rotational power to a drive shaft is supported via a pair of final output gear bearings, a final output gear bearing is mounted on an intermediate housing coupled to an inner wall of the transmission case, and the inner wall forms the first oil collecting part together with the intermediate housing.

[0010] In addition to the third feature, the present invention has a fourth feature in which the intermediate housing includes a through hole configured to guide a portion of the oil collected by the first oil collecting portion to the one final driven gear bearing.

[0011] In addition to any of the first to fourth features, the present invention has a fifth feature in which a power unit comprises the transmission device according to any one of claims 1 to 4; and an engine serving as the power source, and in a unit case including a motor housing for the engine and the transmission case, an engine output shaft of the engine is rotatably supported via two or more engine bearings arranged axially at a distance, and the unit case includes an oil supply passage configured to supply the oil collected by the first oil collecting part to one engine bearing of the two or more engine bearings, the one engine bearing being located on a side axially farther from the transmission device.

[0012] In addition to the fifth feature, the present invention has a sixth feature in which the transmission case includes a second oil collecting part on the front side in the forward rotation direction of the counter gear relative to the first oil collecting part, the second oil collecting part is capable of collecting oil scattered from the counter gear, and the second oil collecting part communicates with the oil supply passage in the transmission case. EFFECTS OF THE INVENTION

[0013] According to the first feature, the transmission case includes the first oil collecting part capable of collecting the oil scattered from the input gear, and the oil inlet port of the first oil collecting part is located on the front side, viewed from the axial direction of the input gear, in the forward rotation direction of the input gear on the common tangent of the pitch circles of the input gear and the counter gear, and the transmission case is provided with the lubrication target part to be lubricated with the oil collected by the first oil collecting part, so that even when the input gear rotates at a high speed, the oil that forcefully splashes out from the input gear after the input gear and the counter gear mesh with each other can be efficiently collected by the first oil collecting part and supplied to the lubrication target part.This allows the oil spurting out of the input gear to be effectively used to lubricate the lubrication target part.

[0014] According to the second feature, the transmission case includes the input gear cover that covers the input gear and is capable of storing the oil in the lower portion of the internal space, and the first oil collecting part is disposed inside the input gear cover, so that it is possible to sufficiently scatter the oil from the input gear inside the input gear cover including the auxiliary oil reservoir for the input gear in the internal space and to more efficiently collect the scattered oil by the first oil collecting part inside the input gear cover, thereby further effectively lubricating the lubrication target part.

[0015] According to the third feature, in the transmission case, the final driven gear, which is configured to rotate about the axis identical to that of the input gear and transmit the rotational power to the input shaft, is supported via the pair of final driven gear bearings, wherein one of the pair of final driven gear bearings is attached to the intermediate case, which is coupled to the inner wall of the transmission case, and the inner wall forms the first oil collecting part together with the intermediate case, so that the intermediate case, which is a portion of the forming wall of the first oil collecting part, is also used as a supporting member for the one final driven gear bearing, and a device structure is accordingly simplified, which contributes to cost reduction.

[0016] According to the fourth feature, the intermediate housing includes the through hole that guides the portion of the oil collected by the first oil collecting portion to the one final driven gear bearing, so that the oil collected by the first oil collecting portion can be effectively used to lubricate the one final driven gear bearing. Furthermore, it is possible to form the oil introduction passage from the first oil collecting portion to the final driven gear bearing only by forming the through hole in the intermediate housing, which contributes to simplifying the oil passage structure.

[0017] According to the fifth feature, in the power unit including the transmission device and the motor, in the unit case, the motor output shaft of the motor is rotatably supported via two or more motor bearings arranged axially at the interval, and the unit case includes the oil supply passage configured to supply the oil collected by the first oil collecting part to one of the two or more motor bearings, the one motor bearing being located on the side axially farther from the transmission device, so that the oil scattered from the input gear and collected by the first oil collecting part can be more efficiently used to lubricate the one motor bearing being located on the side axially farther from the transmission device.

[0018] According to the sixth feature, the transmission case includes the second oil collecting part on the front side in the forward rotation direction of the counter gear relative to the first oil collecting part, the second oil collecting part being capable of collecting oil scattered from the counter gear, and the second oil collecting part communicating with the oil supply passage in the transmission case, so that it is possible to efficiently collect the oil scattered not only from the input gear but also from the counter gear using the second oil collecting part and then combine the collected oils with the oil in the oil supply passage from the first oil collecting part. Thus, it is possible to more efficiently lubricate the one engine bearing located on the side axially farther from the transmission device. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Fig. 1 is an overall sectional view of an embodiment of a power unit according to the present invention, in which a cross section extending through rotational axes of an input gear and a counter gear is viewed from below (sectional view taken along line 1X-1X in Fig. 2). Fig. Fig. 2 is a side view of the power unit, viewed from a left side, in a state in which a first case half body of a transmission case and bearings attached thereto are omitted (cross-sectional view taken 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. Figure 4 is a side view of the power unit viewed from the left side, in which, in addition to the Fig. 3, an intermediate housing is omitted (cross-sectional view along line 4X-4X in Fig. 1). Fig. 5 is a sectional view showing a main portion of a breather and a first oil collecting part (enlarged sectional view taken along line 5X-5X in Fig. 3). Fig. 6 is a top sectional view of an interior of the breather in a cross section along its longitudinal direction (enlarged sectional view taken 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 considered perspective view). 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. Fig. 9 is a right side view of a main portion of the second casing half body, viewed from a side where the motor is located, in a state in which the motor casing is omitted (shown by an arrow 9 in Fig. 1). Fig. 10 is a perspective view showing a breather inlet on a side surface of the second casing half body on the side where the engine is located, and the vicinity of an opening of a first oil supply passage (indicated by 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 Bf1, Bf2 first and second differential bearing as final drive gear bearing Bm1, Bm2 engine mounts C Unit housing cm engine housing CT gearbox housing Gc counter gear Gf final drive gear Gi input gear H1, H2 first and second oil collecting part M engine PU power unit T Gear device Xi axis of rotation of the input gear Xc axis of rotation of the counter gear, parallel to the axis of rotation of the input gear 12s partition wall as an inner wall 15 oil storage tanks 26 Engine output shaft 51, 52 drive shafts 70 Input gear cover 80 intermediate housings 85 third oil channel as a through hole 90 second oil supply channel as the oil supply channel MODE FOR CARRYING OUT THE INVENTION

[0019] First of all, 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.

[0020] 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.

[0021] 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.

[0022] The motor housing Cm is configured to integrally comprise an outer end wall 21 and a tubular outer peripheral wall 22 which is continuous with an outer peripheral portion of the outer end wall 21, and to have a shell-like body open toward the transmission case Ct. In a space within a motor housing Ct, i.e., a motor compartment 20, there are disposed a circular annular stator 24 which is fixed to an inner peripheral wall of the outer peripheral wall 22 of the motor housing Cm and which is wound by a plurality of coil groups 23 at intervals therebetween in its circumferential direction; a rotor 25 which includes a magnet (not shown) and which cooperates with the stator 24 to generate a rotational driving force; and a motor output shaft 26 which fixes the rotor 25 to the outer peripheral portion.Both end portions of the motor output shaft 26 are supported on the transmission case Ct and the motor case Cm, respectively, via a pair of motor bearings Bm1 and Bm2. Furthermore, in the embodiment, the motor output shaft 26 is formed hollow, and a drive shaft 52 extends vertically on a right side through a hollow portion of the motor output shaft 26.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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).

[0027] An oil return passage 16 is formed in a lower portion of the partition wall 12s of the second housing half-body 12. This passage allows oil to return from the engine compartment 20 to the transmission mechanism chamber 10 to permeate the transmission mechanism chamber. The engine compartment 20 and the transmission mechanism chamber 10 communicate with each other via the oil return passage 16.

[0028] Next, an example of the reduction device R will be described with reference to mainly Fig. 1 to Fig. 4 described.

[0029] 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 driven gear Gf arranged on a coaxial line relative to the input gear Gi, which has a larger diameter than the counter pinion Gcp and which meshes with the counter pinion Gcp;

[0030] The final driven gear Gf is arranged in the embodiment such that it meshes with the counter pinion Gcp in a specific semi-circumferential region (right semi-circumferential region with respect to the rotation axis Xi in 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.

[0031] 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.

[0032] 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.

[0033] As the first thrust bearing Bc1, a sealed bearing (not shown as conventionally known) may be used instead of the above-described shielded bearing. In this sealed bearing, a contact seal made of rubber or synthetic resin is used instead of the above-described non-contact shield 104. 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).

[0034] 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.

[0035] 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).

[0036] 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.

[0037] 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.

[0038] 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.

[0039] Further, according to the above-described arrangement of the counter pinion Gcp and the final driven gear Gf, in accordance with the movement of the meshing position from a right end to a left end in an axial direction of the teeth, when the gears mesh with each other, the oil on the tooth surface is pressed from the engaging portion 40 to an axially left side in a biased manner as shown by a dashed arrow in Fig. 1 shown.

[0040] In contrast, in the embodiment, the first thrust bearing Bc1, which in the embodiment comprises a shielded bearing, is used as a fluid limiting wall that opposes the oil pushed toward the axially left side by the above-described engaging portion 40 to prevent the pushed oil from flowing to the axially left side. In this case, as shown in Fig. 1, the first counter bearing Bc1 is arranged adjacent to axially left end surfaces of the teeth of the counter pinion Gcp and formed in such a shape that tooth tip portions of the left end surfaces of the teeth can be covered (ie, a larger diameter than that of the counter pinion Gcp).

[0041] In addition, in the counter pinion Gcp in the embodiment, its axial width is set such that a tooth portion of the counter pinion Gcp has a specific length s (see Fig. 1) extending to the axially left side relative to the engagement portion 40 with the final driven gear Gf. Instead of this setting, another embodiment may also be possible in which the length s of the tooth portion of the counter pinion Gcp extending from the above-described engagement portion 40 to the axially left side is set to zero or a negligible length.

[0042] Next, the differential device D will be described mainly with reference to the Fig. 1 and Fig. 2. The differential device D includes the differential case Dc, which integrally includes bearing boss parts Dca, Dcb at both axial end portions of a body part of the differential case Dc; and a differential gear mechanism Dg, which is housed in the body part of the differential case Dc and which transmits a rotational force of the differential case Dc to the pair of drive shafts 51, 52 while allowing differential rotation.

[0043] 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.

[0044] Furthermore, the differential case Dc is rotatably supported on the transmission case Ct along the rotational axis Xi of the input gear Gi. In parallel, the drive shafts 51, 52, which are rotatably fitted to the inner peripheries of the left and right bearing bosses Dca, Dcb of the differential case Dc, are also supported on the transmission case Ct via the transmission case Ct and the first and second differential bearings Bf1, Bf2. Furthermore, an intermediate portion of the right drive shaft 52 is supported on the engine case Cm via a bearing Bd.

[0045] In a mating surface of the bearing boss portion Dca on the left side and the drive shaft 51 and a mating surface of the bearing boss portion Dcb on the right side and the drive shaft 52, a helical groove is formed, which is capable of providing a screw pumping performance to supply oil scattered within the transmission case Ct into the differential case Dc.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] The unit case C (specifically, the transmission case Ct) includes a first oil collecting part H1 capable of collecting oil scattered from the input gear Gi; an input gear cover 70 having an upwardly open rear part, allowing the counter gear Gc and the input gear Gi to mesh with each other, and covering the input gear Gi; and a breather BR, allowing an interior of the unit case C to communicate with the outside air while preventing the oil from splashing out toward the outside air. Next, specific structures of the first oil collecting part H1, the input gear cover 70, and the breather BR will be described with reference to Fig. 5 to Fig. 11 described.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] For a more detailed description of how 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 communication channel forming wall W4 located immediately below the breather chamber forming wall W3 and integrally connecting a front portion of the input gear surrounding wall W1 with a front part of the outer peripheral wall 12o of the second housing half-body 12. Each front end surface (left end surface) of the input gear surrounding wall W1, the breather chamber forming wall W3, and the communication channel forming wall W4 is located on the same plane as the corresponding mating surface of the outer peripheral wall 11o of the first housing half-body 11 and the outer peripheral wall 12o of the second housing half-body 12.

[0056] Specifically, the input gear surrounding wall W1 is continuously provided with a protruding portion W1a extending upward from its lower open end, thereby preventing the oil from flowing out of the auxiliary oil reservoir 71. Further, the input gear surrounding wall W1 includes, at an inner peripheral edge of the front end surface (left end surface), a positioning step portion W1s extending in the circumferential direction and recessed by a step deeper than the front end surface.

[0057] On the other hand, the intermediate case 80 includes a disc-like case body 81 corresponding to the input gear surrounding wall W1, and an upwardly projecting portion 82 continuously and integrally provided at a portion of an upper half of the case body 81 and extending upward in a substantially fan-shaped manner. On an outer surface (left side) of the case body 81, a stepped cylindrical annular boss portion 81b is integrally provided in a projecting manner and fittingly fixes an outer race of the second differential bearing Bf2 on the right side. The case body 81 includes, on its inner surface (right side), an upper arcuate projection 81a provided at a portion closer to an outer peripheral portion of the case 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.

[0058] 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. 4, an end surface of the greater width has a shallow groove 12g which extends along an upper edge of the upwardly projecting portion 82 and which is adjacent to the upwardly projecting portion 82. A portion of a sealing element (e.g., a liquid seal) to be used between the connecting end surfaces of the first and second housing half-bodies 11, 12 can be held in the groove 12g.

[0059] The intermediate housing 80 is fixed to the partition wall 12s of the second housing half body 12 by allowing the above-described arcuate projection 81a to be fitted onto the positioning step portion W1s of the input gear surrounding wall W1 (see Fig. 1, Fig. 5) and by coupling an inner surface of the outer peripheral portion of the housing body 81 with the input gear surrounding wall W1 on an outer side of the arcuate 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 wall 12s (specifically, by an inner periphery of the input gear surrounding wall W1, the left surface 12si of the partition wall 12s, and an inner surface of the housing body 81).

[0060] 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).

[0061] 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.

[0062] As from Fig. 4, the second casing half body 12 of the transmission case Ct includes a second oil collecting part H2 located at a front side in the forward rotation direction of the counter gear Gc relative to the first oil collecting part H1, and capable of collecting the oil scattered from the counter gear Gc. The second oil collecting part H2 is formed of a concave surface provided on the left surface 12si of the partition wall 12s in a region between the breather BR and a front portion of the counter gear Gc in the front-rear direction, and between a front portion of the outer peripheral wall 12o of the second casing half body 12 and the front portion of the input gear surrounding wall W1 in the up-down direction. The second oil collecting part H2 has its opening at a rear end serving as an oil inlet port H2i adjacent to and facing the front portion of the counter 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.

[0063] 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. 10, an open end of the first oil supply passage 17, which is open to the engine compartment 20 (i.e., a side on which the right surface 12so of the partition wall 12s is located), is located in a position corresponding to a cutout-like slit 18s provided in a stepped cylindrical annular projection portion 18 provided on the right surface 12so in a projecting manner and which fittingly fixes an outer race of the first engine bearing Bm1. The right surface 12so includes a shallow oil groove 19 provided in a depressed manner, which is depressed and extends radially inward from the open end of the first oil supply passage 17 through the slit 18s.

[0064] 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.

[0065] On the other hand, the intermediate housing 80 includes a third oil supply passage 85, which guides the part of the oil collected by the first oil collecting part H1 to a surrounding part of the second differential bearing Bf2. As shown in 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.

[0066] As can be seen from the Fig. 4 and Fig. As shown in Fig. 7, the first oil communication passage 91 is defined between the second housing half body 12 and the intermediate housing 80, and extends in the front-rear direction while passing between the breather chamber forming wall W3 and a front portion of the input gear surrounding wall W1 and the communication passage forming wall W4. At the first oil communication passage 91, a through oil passage 12sh penetrating the partition wall 12s in the front-rear direction has an open front end and a rear end open to an innermost portion located at a front side of the first oil collecting part H1.

[0067] Accordingly, of the oil collected by the first oil collecting part H1, except for the oil flowing toward the first and third oil supply passages 17, 85, the oil flows through the through oil passage 12sh into a portion of the first communicating oil passage 91. The first communicating oil passage 91 communicates with a second communicating oil passage 92 provided axially on the outer peripheral wall 12o of the second housing half body 12. As shown in 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.

[0068] Furthermore, the through oil passage 12sh, the first communicating oil passage (specifically, a front half portion), the second communicating oil passage 92, and the first and second communicating oil passages 93, 94, which are connected in series, cooperate to form a second oil supply passage 90, which supplies the part of the oil collected by the first oil collecting portion H1 to the second engine mount Bm2 on the right side. A portion in the second oil supply passage 90 and the above-described second oil collecting portion H2 communicate with each other via a rear portion of the first communicating oil passage 91. Accordingly, the oil collected by the second oil collecting portion H2 is also supplied to the second engine mount Bm2 via the second oil supply passage 90.

[0069] In the above-described fixed state of the intermediate housing 80, a breather chamber 60 of the breather BR is defined by the intermediate housing 80 and the second housing half body 12 (specifically, by an upper surface of the breather chamber forming wall W3, a lower surface of a wider front portion of the outer peripheral wall 12o of the second housing half body 12, the left surface 12si of the partition wall 12s, and an inner surface of the upwardly projecting portion 82).

[0070] The breather chamber 60 is shielded from the gear mechanism chamber 10 by the intermediate housing 80 and communicates with outside air via an exhaust cylinder 61 fixed to the front portion of the outer peripheral wall 12o of the second housing half body 12. Similar to conventionally known breathers, the breather chamber 60 includes, on its inner wall (particularly, on the left surface 12si of the partition wall 12s), two or more baffles 62 provided in a protruding manner to form a labyrinth within the breather chamber 60 and prevent the oil from splashing out (see Fig. 4, Fig. 6 and Fig. 7).

[0071] 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.

[0072] 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.

[0073] As can be seen from the Fig. 6, Fig. 9 and Fig. As can be seen from Fig. 10, the right surface 12so of the partition wall 12s in the embodiment is provided with a protruding wall 12t that protrudes toward the engine compartment 20 and surrounds the inlet 60i of the breather chamber 60. Even if the oil within the engine compartment 20 is slightly scattered, provision of the protruding wall 12t makes it possible to effectively prevent the scattered oil from entering the breather chamber 60.

[0074] As from Fig. 2, at least a portion of the breather chamber 60 is arranged to overlap the final driven gear Gf when viewed from an axial direction of the final driven gear Gf. Since such an arrangement can prevent the breather chamber 60 from projecting greatly axially outward toward the final driven gear Gf, it is advantageous for making the transmission case Ct (and thus the unit case C) more radially compact.

[0075] Fig. 1 clearly shows an arrangement in which the counter gear Gc is axially disposed between the intermediate housing 80 and the partition wall 12s. From this arrangement, it can be seen that the breather chamber 60 defined between the intermediate housing 80 and the partition wall 12s is located in a position where it partially overlaps with the counter gear Gc when viewed radially outward from the rotational axis Xc of the counter gear Gc. Since this arrangement can prevent the breather chamber 60 from protruding greatly to an axially outer side with respect to the counter gear Gc, it is also advantageous for making the transmission case Ct (and thus the unit case C) more axially compact.

[0076] As can be seen from the Fig. 8 and Fig. As can be seen in Fig. 9, the inlet 60i of the breather chamber 60 faces the stator 24, which is fixed to the engine housing Cm, at a relatively close distance. As described above, by arranging the inlet 60i of the breather chamber 60 adjacent to and facing the stator 24, which does not rotate within the engine compartment 20, it is possible to more effectively prevent the oil from penetrating the breather chamber 60 through the engine compartment 20 using the stator 24.

[0077] 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.

[0078] 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.

[0079] Furthermore, during transmission of the gear transmission mechanism G, particularly during forward rotation of the engine M (when a vehicle starts to move forward), the input gear Gi, the counter gear Gc, the counter pinion Gcp and the final driven gear Gf rotate in a direction indicated, for example, by 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] Furthermore, in the embodiment, the transmission case Ct includes the input gear cover 70 covering the input gear Gi and 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 input gear oil reservoir 71 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.

[0084] The second differential bearing Bf2 on the right side in the embodiment is attached to the intermediate housing 80, which is coupled to the partition wall 12s of the transmission case Ct, and the partition wall 12s defines the first oil collecting part H1 together with the intermediate housing 80. That is, since the intermediate housing 80, which is a portion of the molded wall of the first oil collecting part H1, is also used as a bearing member for the second differential bearing Bf2, a device structure is simplified accordingly, and thus a cost reduction is achieved.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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 in accordance with the forward rotation of the final driven gear Gf from the lower end of the final driven gear Gf toward its upper end. Both the counter pinion Gcp and the final driven gear Gf, which is a helical gear, are arranged such that the oil on the tooth surface of the mutual engagement portion 40 during the forward rotation of the final driven gear Gf flows to an axially left side of the counter pinion Gcp (ie, in the direction indicated by the dashed arrow in Fig. 1 direction). In addition, as can be seen from Fig. 1, the first counter bearing Bc1 is a shielded bearing as a fluid barrier that prevents oil from flowing to the left side opposite to the oil pushed to the axially left side by the engagement portion 40. The first counter bearing Bc1 is disposed adjacent to the axially left tooth end of the counter pinion Gcp and is shaped such that the tooth tip portions of the end surfaces can be covered.

[0090] Accordingly, during the forward rotation of the final driven gear Gf, the oil pushed toward the axially left side of the counter pinion Gcp from the meshing portion 40 of the final driven gear Gf and 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 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 while scooping up the oil, it becomes possible to sufficiently supply the oil to the upper portion of the final driven gear Gf.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] Unlike the present embodiment in which the shielded bearing (first counter bearing Bc1) also functions as the fluid restriction wall, a variety of variations are applicable as the above-described fluid restriction wall. For example, a modified example is also possible in which a flat washer is held between the tooth portion 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 fluid restriction wall. Alternatively, another modified example is also possible in which an annular flange-like projecting wall formed integrally with an outer peripheral portion of the counter shaft 14 and interposed between the tooth portion of the counter pinion Gcp and the first counter bearing Bc1, which is not a shielded bearing, can be used as the fluid restriction wall.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] In the embodiment described above, the transmission device T includes, in addition to the reduction device R, the differential device D, in which an output of the reduction device R, that is, a torque of the final driven gear Gf, is distributed to the 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 locked and coupled to a single drive shaft via a lock 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).

[0102] 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.

[0103] 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 extending portion of the tooth portion of the counter pinion Gcp is located at a position axially coincident with or close to the second differential bearing Bf2, so that it is also possible to increase an oil supply amount to the second differential bearing Bf2 because the oil, which is pushed by the extending portion of the tooth portion and which accumulates on the near side of the fluid confinement wall, is scattered with the centrifugal force.

[0104] In the above-described embodiment, the intermediate housing 80 also functions as a means for forming the breather chamber 60 together with the partition wall 12s, as a means for forming the input gear cover 70, and as a means for supporting the second differential bearing Bf2. However, the intermediate housing 80 may also function as any two of these means, or it may be used exclusively as any one of these means.

[0105] In the above-described embodiment, each gear Gi, Gc, Gcp, Gf of the gear transmission mechanism G of the transmission device T is formed of a helical gear. However, of these gears Gi, Gc, Gcp, Gf, at least one gear pair (for example, a gear pair of the input gear Gi and the counter gear Gc, or a gear pair of the final driven gear Gf and the counter pinion Gcp) that mesh with each other may each be formed of a spur gear.

[0106] 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.

Claims

[1] Transmission device comprising: an input gear (Gi) adapted to rotate with power from a power source (M); and a counter gear (Gc) which is arranged to rotate about an axis (Xc) parallel to a rotational axis (Xi) of the input gear (Gi), wherein the input gear (Gi) and the counter gear (Gc) mesh with each other and are arranged in a transmission housing (Ct), the transmission housing (Ct) comprising therein in a lower part an oil reservoir (15) which stores a transmission lubricating oil, wherein the transmission case (Ct) comprises a first oil collecting part (H1) capable of collecting oil scattered from the input gear (Gi), and the first oil collecting part (H1) comprises an oil inlet opening (H1i) located on a front side in a forward rotational direction of the input gear (Gi) on a common tangent of pitch circles of the input gear (Gi) and the counter gear (Gc), viewed from an axial direction of the input gear (Gi), and wherein the transmission case (Ct) is provided with a lubrication target part to be lubricated with the oil collected by the first oil collecting part (H1). [2] A transmission device according to claim 1, wherein the transmission case (Ct) includes an input gear cover (70) covering the input gear (Gi) and capable of storing an oil in a lower portion of an inner space of the input gear cover (70), and the first oil collecting part (H1) is disposed inside the input gear cover (70). [3] Transmission device according to claim 1 or 2, wherein in the transmission housing (Ct) a final output gear (Gf) which is adapted to rotate about an axis identical to that of the input gear (Gi) and to transmit a rotational force to a drive shaft (51, 52) is mounted via a pair of final output gear bearings (Bf1, Bf2), wherein a final drive gear bearing (Bf2) is mounted on an intermediate housing (80) which is coupled to an inner wall (12s) of the transmission housing (Ct), and wherein the inner wall (12s) forms the first oil collecting part (H1) together with the intermediate housing (80). [4] A transmission device according to claim 3, wherein the intermediate housing (80) comprises a through hole (85) adapted to guide a portion of the oil collected by the first oil collecting part (H1) to the one final output gear bearing (Bf2). [5] Power unit comprising: the transmission device (T) according to one of claims 1 to 4; and a motor (M) which serves as the power source, wherein in a unit housing (C) comprising a motor housing (Cm) for the motor (M) and the gear housing (Ct), a motor output shaft (26) of the motor (M) is rotatably mounted via two or more motor bearings (Bm1, Bm2) which are arranged axially at a distance, and wherein the unit housing (C) comprises an oil supply channel (90) which is adapted to supply the oil collected by the first oil collecting part (H1) to one engine bearing (Bm2) of the two or more engine bearings (Bm1, Bm2), the one engine bearing (Bm2) being located on a side which is axially further away from the transmission device (T). [6] The power unit according to claim 5, wherein the transmission case (Ct) includes a second oil collecting part (H2) on a front side in a forward rotation direction of the counter gear (Gc) relative to the first oil collecting part (H1), the second oil collecting part (H2) being capable of collecting an oil scattered from the counter gear (Gc), and the second oil collecting part (H2) communicating with the oil supply passage in the transmission case (Ct).

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