Power transmission apparatus

This application claims the priority benefit of Japan application serial no. 2017-099925, filed on May 19, 2017. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

1. Field of the Invention

The disclosure relates to a power transmission apparatus mounted on a vehicle and used for transmitting power from a drive source such as an engine to a drive wheel.

2. Description of Related Art

A power transmission apparatus is used for transmitting power from a drive source such as an engine to a drive wheel in a vehicle. For example, as shown in Patent Document 1, a power transmission apparatus includes: a gear mechanism, including a drive bevel gear (pinion gear), integrally rotating with a drive shaft extending along a front-to-rear direction of the vehicle, and a driven bevel gear (ring gear), engaged with the drive bevel gear; a rotating shaft, disposed orthogonal to the drive shaft, and integrally rotating with the driven bevel gear; and left and right oil pressure clutches, disposed between left and right ends of the rotating shaft and axles connected to a pair of drive wheels.

In the power transmission apparatus of Patent Document 1, in an axial direction of the rotating shaft, a gear chamber used for accommodating the gear mechanism is disposed in the center, and clutch chambers used for accommodating the left and right oil pressure clutches are respectively disposed at two sides of the gear chamber. Moreover, the power transmission apparatus includes an oil pump, and the oil pump conveys oil stored in the gear chamber to the left and right oil pressure clutches. By using the oil pump, oil sucked from the gear chamber in the center is supplied to piston chambers of the clutches, and then are discharged into the clutch chambers at the two sides. The oil discharged into the clutch chambers returns to the gear chamber in the center through a communicating hole that communicates the clutch chambers and the gear chamber. That is, the power transmission apparatus is a structure that circulates oil between the gear chamber in the center and the left and right clutch chambers.

In addition, in the power transmission apparatus of in Patent Document 1, the gear chamber in the center is provided with a gear accommodating portion and a strainer accommodating portion, the gear accommodating portion is provided with the driven bevel gear (ring gear) disposed on the rotating shaft, and the strainer accommodating portion is provided with an oil strainer connected to the oil pump. Moreover, the prior structure is that a communicating hole is formed on a wall portion between the right clutch chamber and the gear accommodating portion of the gear chamber, and the right clutch chamber directly communicates with the gear accommodating portion by using the communicating hole.

However, this structure has the following risk: when the power transmission apparatus transmits power to the drive wheels, a situation may occur that oil in the right clutch chamber is forced and introduced into the gear accommodating portion through the communicating hole due to rotation of the driven bevel gear (ring gear). Therefore, there is the following risk: An oil surface in the right clutch chamber excessively decreases, and a volume of oil required for lubricating the right clutch is not ensured.

[Patent Document 1]: Japanese Laid-open No. 2014-194242

The power transmission apparatus of an embodiment of the disclosure is a power transmission apparatus ( 100 ) mounted on a vehicle, and characterized by including: a rotating shaft ( 4 ), extending along a width direction of the vehicle, and used for transmitting power to a pair of drive wheels of the vehicle; gears ( 2 , 3 ), disposed on the rotating shaft ( 4 ), and used for transmitting power to the rotating shaft ( 4 ); clutches ( 5 R, 5 L), used for disconnecting or connecting the power respectively transmitted from the rotating shaft ( 4 ) to the pair of driving wheels; a gear chamber ( 15 ), used for accommodating the gears ( 2 , 3 ); a pair of clutch chambers ( 16 , 17 ), disposed respectively adjacent to two sides of the gear chamber ( 15 ) in an axial direction of the rotating shaft ( 4 ), and used for respectively accommodating one of the pair of clutches ( 5 R or 5 L); an oil pump ( 7 ), used for pumping and conveying oil stored in the gear chamber ( 15 ) to the pair of clutches ( 5 R, 5 L); and an oil strainer ( 66 ), disposed in the gear chamber ( 15 ) and connected to the oil pump ( 7 ), where the gear chamber ( 15 ) includes a gear accommodating portion ( 15 a ) used for accommodating the gear ( 3 ) and a strainer accommodating portion ( 15 b ) used for accommodating the oil strainer ( 66 ); the gear accommodating portion ( 15 a ) and the strainer accommodating portion ( 15 b ) are disposed abreast in the axial direction; and one clutch chamber ( 16 ) of the pair of clutch chambers ( 16 , 17 ) adjacent to the strainer accommodating portion ( 15 b ) only directly communicates with the strainer accommodating portion ( 15 b ) of the gear accommodating portion ( 15 a ) and the strainer accommodating portion ( 15 b ), and the one clutch chamber ( 16 ) communicates with the gear accommodating portion ( 15 a ) only by using the strainer accommodating portion ( 15 b ).

FIGS. 1A and 1B are diagrams of an exterior structure of a power transmission apparatus according to an embodiment of the disclosure, FIG. 1A is a top view, and FIG. 1B is a side view.

FIG. 2 is a perspective view of an exterior structure of a power transmission apparatus.

FIG. 3 is a sectional view (a sectional view along A-A of FIG. 1A ) of a power transmission apparatus.

FIG. 4 is a sectional view (a sectional view along B-B of FIG. 1B ) of a power transmission apparatus.

FIGS. 5A and 5B are perspective views (partial sectional views) of an interior structure of left and right clutch chambers and a gear chamber, FIG. 5A is a diagram of the left clutch chamber and a gear accommodating portion of the gear chamber, and FIG. 5B is a diagram of the right clutch chamber and a strainer accommodating portion of the gear chamber.

FIG. 6 is a perspective view (a partial sectional view) of an interior structure of a gear chamber (a gear accommodating portion and a strainer accommodating portion).

FIG. 7 is a sectional view of a communicating hole formed between a position near a bottom portion of a right clutch chamber and a position near a bottom portion of a gear chamber (a strainer accommodating portion).

FIG. 8 is a sectional view (a sectional view along P-P of FIG. 3 ) of an interior structure of a gear chamber, a strainer chamber, and a right clutch chamber.

The disclosure is directed to provide a power transmission apparatus that can prevent oil from being forced and introduced into a gear chamber along with rotation of a gear, thereby, preventing an oil surface of the clutch chamber from excessively decreasing, so as to ensure a volume of oil required for lubricating a clutch.

The power transmission apparatus of an embodiment of the disclosure is a power transmission apparatus ( 100 ) mounted on a vehicle, and characterized by including: a rotating shaft ( 4 ), extending along a width direction of the vehicle, and used for transmitting power to a pair of drive wheels of the vehicle; gears ( 2 , 3 ), disposed on the rotating shaft ( 4 ), and used for transmitting power to the rotating shaft ( 4 ); clutches ( 5 R, 5 L), used for disconnecting or connecting the power respectively transmitted from the rotating shaft ( 4 ) to the pair of driving wheels; a gear chamber ( 15 ), used for accommodating the gears ( 2 , 3 ); a pair of clutch chambers ( 16 , 17 ), disposed respectively adjacent to two sides of the gear chamber ( 15 ) in an axial direction of the rotating shaft ( 4 ), and used for respectively accommodating one of the pair of clutches ( 5 R or 5 L); an oil pump ( 7 ), used for pumping and conveying oil stored in the gear chamber ( 15 ) to the pair of clutches ( 5 R, 5 L); and an oil strainer ( 66 ), disposed in the gear chamber ( 15 ) and connected to the oil pump ( 7 ), where the gear chamber ( 15 ) includes a gear accommodating portion ( 15 a ) used for accommodating the gear ( 3 ) and a strainer accommodating portion ( 15 b ) used for accommodating the oil strainer ( 66 ); the gear accommodating portion ( 15 a ) and the strainer accommodating portion ( 15 b ) are disposed abreast in the axial direction; and one clutch chamber ( 16 ) of the pair of clutch chambers ( 16 , 17 ) adjacent to the strainer accommodating portion ( 15 b ) only directly communicates with the strainer accommodating portion ( 15 b ) of the gear accommodating portion ( 15 a ) and the strainer accommodating portion ( 15 b ), and the one clutch chamber ( 16 ) communicates with the gear accommodating portion ( 15 a ) only by using the strainer accommodating portion ( 15 b ).

According to the power transmission apparatus of the disclosure, the one clutch chamber of the pair of clutch chambers adjacent to the strainer accommodating portion only directly communicates with the strainer accommodating portion, and the one clutch chamber communicates with the gear accommodating portion only by using the strainer accommodating portion. Therefore, the problem is avoided that oil is introduced from the one clutch chamber into the gear accommodating portion of the gear chamber due to rotation of the driven bevel gear. Therefore, an oil surface of the one clutch chamber is prevented from excessively decreasing, so as to avoid insufficiency of a volume of oil required for lubricating the clutch.

In addition, the power transmission apparatus may further include a wall portion ( 38 ) used for isolating the one clutch chamber ( 16 ) from the strainer accommodating portion ( 15 b ), and the one clutch chamber ( 16 ) communicates with the strainer accommodating portion ( 15 b ) by using a communicating hole ( 38 a ) near bottom portions ( 16 a , 15 d ) of the one clutch chamber ( 16 ) and the strainer accommodating portion ( 15 b ) and formed on the wall portion ( 38 ).

According to this structure, the one clutch chamber communicates with the strainer accommodating portion by using the communicating hole near the bottom portions of the one clutch chamber and the strainer accommodating portion and formed on the wall portion. Therefore, when oil for exchanging in the power transmission apparatus is exchanged, the oil is ensured to be discharged from the one clutch chamber to the gear chamber (strainer accommodating portion) by using the communicating hole. Therefore, the oil is prevented from being left in the one clutch chamber when the oil is exchanged, so as to pursue to facilitate the oil exchange operation. Especially, in the disclosure, the one clutch chamber is not in direct communication with the gear accommodating portion of the gear chamber, consequently, the following undesirable situation may occur: when oil for exchanging in the power transmission apparatus is exchanged, the oil cannot be smoothly discharged from the one clutch chamber to the gear chamber. However, because the communicating hole is included, the undesirable situation may be effectively avoided.

In addition, the power transmission apparatus may be that boundary portions ( 15 c ) of the gear accommodating portion ( 15 a ) and the strainer accommodating portion ( 15 b ) are in communication with each other; and the strainer accommodating portion ( 15 b ) is disposed at a side closer to a center in the axial direction of the rotating shaft ( 4 ) than the gear accommodating portion ( 15 a ) disposed.

In addition, symbols in the parentheses are shown for referring to the reference numerals of each element in the following embodiments.

According to the power transmission apparatus of the disclosure, the oil can be prevented from being forced and introduced from the clutch chamber into the gear chamber along with the rotation of the gear, thereby preventing the oil surface of the clutch chamber from excessively decreasing, so as to ensure the volume of the oil required for lubricating the clutch.

The following describes embodiments of the disclosure with reference to the accompanying drawings. FIGS. 1A and 1B are diagrams of an exterior structure of a power transmission apparatus according to an embodiment of the disclosure, FIG. 1A is a top view, and FIG. 1B is a side view. FIG. 2 is a perspective view of an exterior structure of a power transmission apparatus. FIG. 3 and FIG. 4 are sectional views of the power transmission apparatus, FIG. 3 is a sectional view along A-A of FIG. 1A , and FIG. 4 is a sectional view along B-B of FIG. 1B .

As shown in FIG. 4 and the like, a power transmission apparatus 100 is configured as a differential mechanism used for allocating rotation of a drive shaft 1 to left and right wheels (not shown). The drive shaft 1 is connected to a rear end of a propeller shaft not shown, and drive power from a drive source (engine) not shown is transmitted to the drive shaft 1 . The power transmission apparatus 100 includes: a drive bevel gear (pinion gear) 2 , used for integrally rotating with the drive shaft 1 ; a driven bevel gear (ring gear) 3 , engaged with the drive bevel gear 2 ; a center shaft (rotating shaft) 4 , disposed orthogonal to the drive shaft 1 , and connected to the driven bevel gear 3 in a manner of integrally rotating with the driven bevel gear 3 ; left and right oil pressure clutches 5 L and 5 R, disposed at the left and right of the center shaft 4 ; left and right axles 6 L and 6 R, used for respectively transmitting drive power transmitted by the left and right oil pressure clutches 5 L and 5 R to the left and right wheels (not shown); an oil pump (an electric oil pump) 7 , used for supplying hydraulic oil (oil) to each piston chamber 59 L and 59 R of the left and right oil pressure clutches 5 L and 5 R; and left and right pressure regulating valves 8 L and 8 R, used for regulating pressure of oil discharged from each piston chamber 59 L and 59 R. In addition, the power transmission apparatus 100 includes a center case 9 used for accommodating the differential mechanism, and side cases 58 L and 58 R used for respectively accommodating the left and right oil pressure clutches 5 L and 5 R. As shown in FIG. 1A and FIG. 2 , the center case 9 is divided, by using a center of a front-to-rear direction, into two parts, namely, a front case 9 a and a rear case 9 b . The front case 9 a and the rear case 9 b are connected to each other in the front-to-rear direction, and are integrally fixed by means of being secured by a bolt 96 . The left and right side cases 58 L and 58 R are integrally fixed at openings at left and right ends of the center case 9 by means of being secured by a bolt 97 (referring to FIG. 1A ). In addition, an axial direction of a rotating shaft or an axial direction in the following descriptions represents an axial direction of the center shaft 4 (a left-to-right direction in FIG. 1A ). The following further describes each structure.

The driven bevel gear 3 is mounted at an outer periphery of the center shaft 4 disposed on a common axis of the left axel 6 L and the right axel 6 R. Therefore, when the drive shaft 1 is driven to rotate by using the engine and the propeller shaft, the drive power is transmitted from the drive bevel gear 2 and the driven bevel gear 3 to the center shaft 4 , so as to enable the center shaft 4 to rotate.

The center case 9 is internally provided with a gear chamber 15 disposed at a center of the axial direction of the center shaft 4 . In addition, the left and right side cases 58 L and 58 R are respectively internally provided with a pair of clutch chambers 16 and 17 disposed at two sides of the gear chamber 15 . Therefore, a casing of the power transmission apparatus 100 is of a structure of three chambers, that is, including the gear chamber 15 and the pair of clutch chambers 16 and 17 .

The gear chamber 15 includes a gear accommodating portion 15 a and a strainer accommodating portion 15 b , the gear accommodating portion 15 a is a chamber provided with the driven bevel gear 3 , and the strainer accommodating portion 15 b is a chamber provided with a part of the drive bevel gear 2 and the oil strainer 66 . The gear accommodating portion 15 a is located on a left side in the gear chamber 15 , and adjacent to a right side of the left clutch chamber 17 . On the other hand, the strainer accommodating portion 15 b is located on a right side in the gear chamber 15 , and adjacent to a left side of the right clutch chamber 16 . The gear accommodating portion 15 a and the strainer accommodating portion 15 b communicate with each other at a boundary portion 15 c therebetween (referring to FIG. 4 and FIG. 6 ), and the gear accommodating portion 15 a and the strainer accommodating portion 15 b form the gear chamber 15 .

As shown in FIG. 3 and the like, the left and right clutch chambers 16 and 17 are respectively provided with the oil pressure clutch 5 L and the oil pressure clutch 5 R. The right oil pressure clutch 5 R in the right clutch chamber 16 includes: a clutch drum (clutch housing) 41 R, approximately in a shape of a cylinder, and connected to a right end portion of the center shaft 4 ; a clutch hub 43 R, spline-connected to an end portion of the right axel 6 R at an inner peripheral side of the clutch drum 41 R; and a friction binding portion 42 R, formed by means of alternately laminating multi-layers of friction material (plate) along the axial direction in the clutch drum 41 R. In addition, a position adjacent to the friction binding portion 42 R is provided with: a piston housing 44 R, integrally formed with the right side case 58 R; a cylinder piston 45 R, accommodated in the piston housing 44 R; and a return spring 47 R, used for applying a force to the cylinder piston 45 R. The piston housing 44 R is internally provided with a piston chamber 59 R, and the hydraulic oil is introduced between the piston chamber 59 R and the cylinder piston 45 R. In addition, although detailed descriptions are omitted, the oil pressure clutch 5 L disposed in the left clutch chamber 17 is of a same structure as the oil pressure clutch 5 R (Numerals of elements of the oil pressure clutch 5 L are marked with a suffix L).

As shown in FIG. 4 and the like, the electric oil pump 7 includes a motor portion 71 and a pump portion 72 . The motor portion 71 generates rotating power, and the pump portion 72 pumps the hydraulic oil (oil) sucked from the oil strainer 66 to the left and right oil pressure clutches 5 L and 5 R by using the rotating power. The pump portion 72 is of a structure of double pumps, that is, left and right internally connected gear pumps (oil pumps) 74 L and 74 R are serially connected to each other on a pump shaft 73 . Oil lines (not shown) extending to a downstream side to communicate with the left and right piston chambers 59 L and 59 R of the left and right oil pressure clutches (clutch apparatuses) 5 L and 5 R are connected to the oil pumps 74 L and 74 R. Therefore, the left internally connected gear pump 74 L pumps oil to the piston chamber 59 L of the left oil pressure clutch 5 L, and the right internally connected gear pump 74 R pumps oil to the piston chamber 59 R of the right oil pressure clutch 5 R.

Left and right pressure regulating valves 8 L and 8 R are linear solenoid valves (electromagnetic pressure regulating valves). As shown in FIG. 1A , FIG. 1B , FIG. 2 , and the like, the left and right pressure regulating valves 8 L and 8 R of this embodiment are mounted by means of inserting into mounting holes (not shown) formed on the side cases 58 L and 58 R, and are approximately symmetrically disposed in right beside each piston chamber 59 L and 59 R of the left and right oil pressure clutches 5 L and 5 R. Therefore, oil lines 67 L and 67 R from the left and right piston chambers 59 L and 59 R to the left and right pressure regulating valves 8 L and 8 R are respectively formed by using the shortest distances. In addition, the oil lines 67 L and 67 R between the piston chambers 59 L and 59 R and the pressure regulating valves 8 L and 8 R are provided with filters (secondly filter: purification component) 40 L and 40 R used for removing little foreign matter contained in the hydraulic oil flowing on the oil lines 67 L and 67 R.

In addition, the side cases 58 L and 58 R are internally provided with lube oil lines 60 L and 60 R used for introducing oil ejected from the pressure regulating valves 8 L and 8 R into the inside of the oil pressure clutches 5 L and 5 R. That is, in the power transmission apparatus 100 of this embodiment, the oil ejected from the pressure regulating valves 8 L and 8 R are directly introduced into the inside of the oil pressure clutches 5 L and 5 R by using the lube oil lines 60 L and 60 R, rather than by using an oil line (an axis oil line) formed inside the center shaft 4 , and then the introduced oil are stirred by means of rotation of clutch hubs 43 L and 43 R, so as to lubricate rotating slide portions of the oil pressure clutches 5 L and 5 R.

In addition, the oil strainer 66 is disposed near a bottom portion 15 d (referring to FIG. 3 ) of the gear chamber 15 . A lower surface of the oil strainer 66 is provided with a suction opening 66 a used for sucking hydraulic oil, so as to suck hydraulic oil stored in the bottom portion 15 d in the gear chamber 15 through the suction opening 66 a.

In addition, the left and right piston chambers 59 L and 59 R are provided with oil pressure sensors 90 L and 90 R used for detecting oil pressure of oil in the piston chambers 59 L and 59 R. The oil pressure sensors 90 L and 90 R are mounted by means of inserting a sensor portion at a root portion into another mounting hole (not shown) formed on the side cases 58 L and 58 R. The oil pressure sensors 90 L and 90 R detect the oil pressure in the piston chambers 59 L and 59 R by the sensor portions disposed in the piston chambers 59 L and 59 R through the mounting holes. In addition, covers (protection components) 95 L and 95 R are provided to cover at least one part of the pressure regulating valves 8 L and 8 R and the oil pressure sensors 90 L and 90 R that are exposed from the side cases 58 L and 58 R.

FIGS. 5A and 5B are perspective views (partial sectional views) of an interior shape of the left and right clutch chambers 16 and 17 and the gear chamber 15 , FIG. 5A is a diagram of an upper interior shape of the left clutch chamber 17 and the gear accommodating portion 15 a of the gear chamber 15 , and FIG. 5B is a diagram of an upper interior shape of the right clutch chamber 16 and the strainer accommodating portion 15 b of the gear chamber 15 . In addition, FIG. 5A is a diagram of an exterior portion (inner surfaces of the center case 9 (the rear case 9 b ) and the left side case 58 L) of a part X 1 shown in FIG. 2 , and FIG. 5B is a diagram of an exterior portion (inner surfaces of the center case 9 (the rear case 9 b ) and the right side case 58 R) of a part X 2 shown in FIG. 2 .

As shown in FIG. 5A , the left clutch chamber 17 accommodates the clutch drum 41 L of the oil pressure clutch 5 L. In addition, the left clutch chamber 17 communicates with the gear accommodating portion 15 a of the adjacent gear chamber 15 by using a communicating hole 35 a formed on an isolation wall (wall portion) 35 . Moreover, in this embodiment, a portion in the left side case 58 L forming the left clutch chamber 17 opposite to an outer periphery of an upper side of the clutch drum 41 L is provided with an inclined wall 52 disposed opposite to an outer peripheral surface of the clutch drum 41 L. An inner surface 52 a of the inclined wall 52 forms an inclined surface inclined to the following direction: in two sides with respect to a rotating direction R 1 (a traveling direction of the outer peripheral surface of the clutch drum 41 L when the clutch drum 41 L rotates) of the clutch drum 41 L, one side (the right side of the figure) close to the gear chamber 15 (the gear accommodating portion 15 a ) is set to an inner side of the traveling direction, and the other side (the left side of the figure) away from the gear chamber 15 is set to a front side. In addition, the inclined wall 52 and the inclined surface 52 a are formed at a position opposite to a portion (a portion rotating toward a rising direction during rotation) that is closer to the front side in the rotating direction R 1 of the clutch drum 41 L than an upper end (a top portion) of the clutch drum 41 L is. In addition, the communicating hole 35 a is formed on an isolation wall 35 in approximately right beside the gear chamber 15 of the inclined wall 52 (the inclined surface 52 a ). The inclined wall 52 (the inclined surface 52 a ) is formed as a surface facing toward the communicating hole 35 a.

In addition, in this embodiment, a protruding rib 37 facing toward the inside of the left clutch chamber 17 and protruding toward a horizontal direction is formed at a position on the isolation wall 35 lower than the communicating hole 35 a . The rib 37 includes a plate portion protruding from a surface of the left clutch chamber 17 of the isolation wall 35 toward the horizontal direction (toward the left side of the figure). That is, the rib 37 is formed as a protrusion at a lower side of the communicating hole 35 a and extending from the isolation wall 35 to the left side. In addition, the communicating hole 35 a and the rib 37 are formed at a position opposite to an upper side of a half (an upper half part) of the clutch drum 41 L. In addition, an end portion of the rib 37 extends to near an end surface (an end surface in the axial direction) of the gear chamber 15 of the clutch drum 41 L. Therefore, an oil storage portion 37 a used for temporarily storing (keeping) oil lifted by the clutch drum 41 L is formed at an upper surface of the rib 37 .

In the left clutch chamber 17 , when the clutch drum 41 L rotates, oil stored in a bottom portion 17 a (referring to FIG. 3 ) of the left clutch chamber 17 is stirred by using the clutch drum 41 L. The stirred oil is lifted upward along the outer peripheral surface of the clutch drum 41 L and along the rotating direction R 1 of the clutch drum 41 L. In this case, because the inclined wall 52 (the inclined surface 52 a ) of the structure is included, the oil lifted along the outer peripheral surface of the clutch drum 41 L collides with the inclined wall 52 (the inclined surface 52 a ). The oil splashes at the inclined surface 52 a toward the communicating hole 35 a . Therefore, as shown by an arrow S 1 in FIG. 5A , most of the oil splashed at the inclined surface 52 a is introduced into the gear chamber 15 through the communicating hole 35 a . In this way, the oil in the left clutch chamber 17 can return to the gear chamber 15 (the gear accommodating portion 15 a ) by means of oil lift generated by means of the rotation of the clutch drum 41 L.

In addition, the rib 37 is formed in the left clutch chamber 17 , therefore, the rib 37 may be used for holding some of the oil splashed at the inclined surface 52 a toward the gear chamber 15 . That is, before reaching the communicating hole 35 a , some of the oil splashed at the inclined surface 52 a toward the gear chamber 15 constantly drops due to its own weight. In this case, the rib 37 may be used for holding the constantly dropping oil and introducing the oil into the communicating hole 35 a . Thereby, more oil is ensured to be oil that returns from the left clutch chamber 17 to the gear chamber 15 (the gear accommodating portion 15 a ) through the communicating hole 35 a.

In addition, as shown in FIG. 5B , the right clutch chamber 16 accommodates the clutch drum 41 R of the oil pressure clutch 5 R. In addition, the right clutch chamber 16 communicates with the strainer accommodating portion 15 b of the adjacent gear chamber 15 by using a communicating hole 34 a formed on the isolation wall (wall portion) 34 . Moreover, in this embodiment, an outer peripheral side of the clutch drum 41 R in the right side case 58 R forming the right clutch chamber 16 is provided with an inclined wall 51 disposed opposite to an outer peripheral surface of the clutch drum 41 R. An inner surface 51 a of the inclined wall 51 forms an inclined surface inclined to the following direction: in two sides with respect to a rotating direction R 2 (a traveling direction of the outer peripheral surface of the clutch drum 41 R when the clutch drum 41 R rotates) of the clutch drum 41 R, one side (the left side of the figure) close to the gear chamber 15 is set to an inner side (an upper side) of the traveling direction, and the other side (the right side of the figure) away from the gear chamber 15 is set to a front side (a lower side). In addition, the communicating hole 34 a is formed on the isolation wall 34 lower than the location right beside the gear chamber 15 of the inclined wall 51 (the inclined surface 51 a ). The inclined wall 51 (the inclined surface 51 a ) is formed as a surface facing toward the isolation wall 34 and communicating hole 34 a.

In addition, in this embodiment, a protruding rib 36 facing toward the inside of the right clutch chamber 16 and protruding toward a horizontal direction is formed at a position on the isolation wall 34 lower than the communicating hole 34 a . The rib 36 includes a plate portion protruding from a surface of the right clutch chamber 16 of the isolation wall 34 toward the horizontal direction (toward the right side of the figure). That is, the rib 36 is formed as a protrusion at a lower side of the communicating hole 34 a and extending from the isolation wall 34 to the right side. In addition, the communicating hole 34 a and the rib 36 are formed at a position at a lower side (a lower position) than the inclined wall 51 , and opposite to an upper side of a half (an upper half part) of the clutch drum 41 R. In addition, an end portion of the rib 36 extends to near an end surface (an end surface at the left side of the axial direction) of the gear chamber 15 of the clutch drum 41 R. Therefore, an oil storage portion 36 a used for temporarily storing (keeping) oil lifted by the clutch drum 41 R is formed at an upper surface of the rib 36 .

In the right clutch chamber 16 , when the clutch drum 41 R rotates, oil stored in a bottom portion 16 a (referring to FIG. 3 ) of the right clutch chamber 16 is lifted by using the clutch drum 41 R. The lifted oil splashes upward along the outer peripheral surface of the clutch drum 41 R and along the rotating direction R 2 of the clutch drum 41 R. In this case, because the inclined wall 51 (the inclined surface 51 a ) of the structure is included, the oil lifted along the outer peripheral surface of the clutch drum 41 R collides with the inclined wall 51 (the inclined surface 51 a ). The oil splashes at the inclined surface 51 a toward the isolation wall 34 . When colliding with the isolation wall 34 , the splashed oil flows downward along a surface of the isolation wall 34 , so as to reaching the communicating hole 34 a . In this way, the oil is introduced into the gear chamber 15 through the communicating hole 34 a . Therefore, as shown by an arrow S 2 in FIG. 5B , the oil splashed at the inclined surface 51 a is introduced into the gear chamber 15 (the strainer accommodating portion 15 b ) through the communicating hole 34 a . In this way, the oil in the right clutch chamber 16 can return to the gear chamber 15 by means of oil lift generated by means of the rotation of the clutch drum 41 R.

In addition, the rib 36 is formed in the right clutch chamber 16 , therefore, the rib 36 may be used for holding some oil flowing downward along the surface of the isolation wall 34 , and introducing the oil into the communicating hole 34 a . Thereby, more oil is ensured to be oil that returns from the right clutch chamber 16 to the gear chamber 15 through the communicating hole 34 a.

FIG. 6 is a perspective view (a partial sectional view) of an interior shape of the gear chamber 15 (the gear accommodating portion 15 a and the strainer accommodating portion 15 b ), and is a diagram of an interior portion (inner surfaces of the rear case 9 b of the center case 9 ) of a part Y shown in FIG. 2 . As shown in FIG. 6 , a protruding portion 33 that protrudes an inner surface of the strainer accommodating portion 15 b is formed at a boundary portion 15 c between the inner surface of the strainer accommodating portion 15 b of the gear chamber 15 and the gear accommodating portion 15 a . The protruding portion 33 is formed at a position opposite to a portion rotating toward a rising direction when the driven bevel gear 3 in the gear accommodating portion 15 a rotates. In addition, the protruding portion 33 is in a shape of an inclined surface inclined in such a manner that a height position of a lower side surface 33 a becomes higher in a direction farther away from the boundary portion 15 c . That is, the protruding portion 33 can introduce, by means of making the lower side surface 33 a be in the shape described above, most of the oil lifted along with the rotation of the driven bevel gear 3 (not shown in FIG. 6 ) from the gear accommodating portion 15 a to the strainer accommodating portion 15 b as shown by an arrow S 3 . The driven bevel gear 3 rotates in the gear accommodating portion 15 a about a rotating direction R 3 shown in FIG. 6 . Therefore, as shown by the arrow S 3 , the oil lifted by means of the rotation of the driven bevel gear 3 that rotates in the gear accommodating portion 15 a can be effectively separated from the driven bevel gear 3 , and be actively introduced into the strainer accommodating portion 15 b closer to the center in the gear chamber 15 . Thereby, a volume of oil left in the gear accommodating portion 15 a can be reduced, and a volume of the oil introduced from the left clutch chamber 17 into the gear chamber 15 (the gear accommodating portion 15 a ) through the communicating hole 35 a described above can be ensured to be more. Based on the above, the oil moving to the left clutch chamber 17 is enabled to effectively return to the strainer accommodating portion 15 b of the gear chamber 15 by using the operation of the power transmission apparatus 100 , so as to pursue the rationalization of the oil surface (the volume of the oil) of each component inside the power transmission apparatus 100 .

FIG. 7 is a perspective view (a sectional view) of the communicating hole 34 b formed between the bottom portion 16 a of the right clutch chamber 16 and the bottom portion 15 d of the gear chamber 15 (the strainer accommodating portion 15 b ). In addition, FIG. 7 is a diagram of an interior portion (the inner surfaces of the center case 9 and the right side case 58 R) of a part Z shown in FIG. 2 . As shown in FIG. 7 , in the center case 9 , besides the communicating hole 34 a , a communicating hole 34 b (another communicating portion) is additionally formed at a height position near a lower end of the isolation wall 34 . The communicating hole 34 b communicates the bottom portion 15 d of the strainer accommodating portion 15 b of the gear chamber 15 or a position near the bottom portion 15 d with the bottom portion 16 a of the right clutch chamber 16 or a position near the bottom portion 16 a that are separated by the isolation wall 34 .

In addition, FIG. 7 shows an oil surface L 1 of the right clutch chamber 16 and an oil surface L 2 of the strainer accommodating portion 15 b of the gear chamber 15 when the power from the engine is transmitted to the left and right wheels by using the power transmission apparatus 100 (when the clutch drum 41 R, or the drive bevel gear 2 , the driven bevel gear 3 , and the like rotate). As shown in FIG. 7 , when the power transmission apparatus 100 transmits the power to the left and right wheels, oil circulates in the components of the power transmission apparatus 100 . Therefore, compared with the oil surface L 2 of the strainer accommodating portion 15 b , the oil surface L 1 of the right clutch chamber 16 is in a higher position. In this case, it is ideal to set the position (the height position) of the communicating hole 34 b at a position higher than the oil surface L 2 of the gear chamber 15 (the strainer accommodating portion 15 b ) when the power is transmitted to left and right wheels. If such a setting is applied, when the power transmission apparatus 100 transmits the power to the left and right wheels, as shown by an arrow S 4 in FIG. 7 , the oil stored in the bottom portion 16 a of the right clutch chamber 16 is enabled to effectively return to the strainer accommodating portion 15 b through the communicating hole 34 b . Therefore, by using this structure, oil moving to the right clutch chamber 16 along with the operation of the power transmission apparatus 100 is enabled to effectively return to the strainer accommodating portion 15 b of the gear chamber 15 , so as to pursue the rationalization of the oil surface (the volume of the oil) of each component inside the power transmission apparatus 100 .

FIG. 8 is a perspective view (a partial sectional view) of the bottom portion 15 d of the gear chamber 15 and the bottom portion 16 a of the right clutch chamber 16 . In addition, FIG. 8 is a diagram of a part corresponding to a sectional view indicated by P-P of FIG. 3 . As shown in FIG. 8 , in this embodiment, the right clutch chamber 16 does not directly communicate with the gear accommodating portion 15 a of the gear chamber 15 due to the isolation of the wall portion 39 of the center case 9 . On the other hand, the right clutch chamber 16 communicates with the strainer accommodating portion 15 b of the gear chamber 15 . That is, a communicating hole (a communicating portion) 38 a formed by a through hole is provided, the through hole runs through a front end of the right clutch chamber 16 , a front end of the strainer accommodating portion 15 b of the gear chamber 15 and a position near a lower end of a wall portion 38 , and the communicating hole 38 a is used for communicating the right clutch chamber 16 with the strainer accommodating portion 15 b of the gear chamber 15 .

Assuming that a wall portion 39 between the right clutch chamber 16 and the gear accommodating portion 15 a of the gear chamber 15 is provided with a communicating hole or the like to enable the right clutch chamber 16 and the gear accommodating portion 15 a of the gear chamber 15 directly communicate with each other, oil in the right clutch chamber 16 may be forced and introduced into the gear accommodating portion 15 a of the gear chamber 15 through the communicating hole due to the rotation of the driven bevel gear 3 , causing a risk of excessively decreasing of the oil surface in the right clutch chamber 16 . In view of this risk, in this embodiment, the right clutch chamber 16 is not in direct communication with the gear accommodating portion 15 a of the gear chamber 15 . Therefore, oil may be prevented from being introduced due to the rotation of the driven bevel gear 3 , so as to effectively prevent the oil surface in the right clutch chamber 16 from excessively decreasing.

On the other hand, in this embodiment, a communicating hole communicating the right clutch chamber 16 with the gear accommodating portion 15 a of the gear chamber 15 is not provided, consequently, the following undesirable situation may occur: when oil in the power transmission apparatus 100 is exchanged, the oil cannot be smoothly discharged from the right clutch chamber 16 to the gear chamber 15 through the communicating hole. However, in view of this, in this embodiment, the communicating hole 38 a communicating the right clutch chamber 16 with the strainer accommodating portion 15 b of the gear chamber 15 is provided, and a diameter of the communicating hole 38 a is set to be a larger diameter, so as to ensure to discharge the oil from the right clutch chamber 16 to the gear chamber 15 when the oil is exchanged.

The following simply describes flowing and actions of oil in a power transmission apparatus 100 of this embodiment. In the power transmission apparatus 100 , oil stored in a bottom portion 15 d of a gear chamber 15 (a strainer accommodating portion 15 b ) is sucked from an oil strainer 66 into left and right oil pumps 74 L and 74 R by means of rotation of an oil pump 7 (the left and right oil pumps 74 L and 74 R) driven by a motor portion 71 . The oil sucked into the left and right oil pumps 74 L and 74 R is introduced into left and right piston chambers 59 L and 59 R of left and right oil pressure clutches (clutch apparatuses) 5 L and 5 R at a downstream side. Pressure of the oil introduced into the left and right piston chambers 59 L and 59 R is regulated by left and right pressure regulating valves 8 L and 8 R disposed at a downstream side of each flowing direction of oil of the left and right oil pressure clutches 5 L and 5 R. The oil flowing out of the left and right pressure regulating valves 8 L and 8 R is supplied to the inside of the oil pressure clutches 5 L and 5 R by using lube oil lines 60 L and 60 R extending from the left and right pressure regulating valves 8 L and 8 R to the downstream side, to lube the oil pressure clutches 5 L and 5 R and the like. The oil supplied to the oil pressure clutches 5 L and 5 R is stored in bottom portions 16 a and 17 a of clutch chambers 16 and 17 . The oil stored in the bottom portions 16 a and 17 a of the clutch chambers 16 and 17 returns to the gear chamber 15 through communicating holes 34 a and 35 a by means of lift generated by rotation of the clutches 5 L and 5 R.

As described above, driven by the motor portion 71 , the left and right oil pumps 74 L and 74 R eject oil. However, if the left and right pressure regulating valves 8 L and 8 R are open, the oil ejected from the left and right oil pumps 74 L and 74 R directly passes through the left and right piston chambers 59 L and 59 R. Therefore, the left and right oil pressure clutches 5 L and 5 R are not connected. On the other hand, if the left and right pressure regulating valves 8 L and 8 R are closed in a specific degree, oil pressure of the left and right piston chambers 59 L and 59 R at an upstream side increases, and the left and right oil pressure clutches 5 L and 5 R are connected with specific connecting force, to transmit drive power to left and right axles 6 L and 6 R.

As described above, according to the power transmission apparatus 100 of this embodiment, inclined walls 51 and 52 facing toward the communicating holes 34 a and 35 a that communicate the clutch chambers 16 and 17 with the gear chamber 15 are disposed on inner surfaces in the clutch chambers 16 and 17 opposite to outer peripheral surfaces of clutch drums 41 L and 41 R (the clutches 5 L and 5 R). Therefore, when the clutch drums 41 L and 41 R (the clutches 5 L and 5 R) rotate, the oil in the clutch chambers 16 and 17 is lifted along the outer peripheral surfaces of the clutch drums 41 L and 41 R and along the rotating directions of the clutch drums 41 L and 41 R. In this case, because inclined surfaces 51 a and 52 a are included, the oil lifted along the outer peripheral surfaces of the clutch drums 41 L and 41 R collides with the inclined surfaces 51 a and 52 a . The oil colliding with the inclined surfaces 51 a and 52 a splashes at the inclined surfaces 51 a and 52 a toward the communicating holes 34 a and 35 a . Therefore, most of the oil splashed at the inclined surfaces 51 a and 52 a is introduced into the gear chamber 15 through the communicating holes 34 a and 35 a . In this way, the oil in the clutch chambers 16 and 17 can be effectively introduced into (return to) the gear chamber 15 by means of oil lift generated by the rotation of the clutches 5 L and 5 R.

In addition, in the power transmission apparatus 100 , because ribs 36 and 37 protruding from the wall portions 34 and 35 lower than the communicating holes 34 a and 35 a toward the inside of the clutch chambers 16 and 17 are included, the ribs 36 and 37 may be used for holding some of the oil splashed at the inclined surfaces 51 a and 52 a toward the communicating holes 34 a and 35 a . That is, before reaching the communicating holes 34 a and 35 a , some of the oil splashed at the inclined surfaces 51 a and 52 a constantly drops due to its own weight. In this case, the ribs 36 and 37 may be used for holding the constantly dropping oil and introducing the oil into the communicating holes 34 a and 35 a . Thereby, more oil is ensured to be oil that returns from the clutch chambers 16 and 17 to the gear chamber 15 through the communicating holes 34 a and 35 a.

In addition, in the power transmission apparatus 100 , because the oil pump 7 used for conveying the oil stored in the gear chamber 15 to the clutch chambers 16 and 17 is included, there is a risk that the oil surface of the gear chamber 15 decreases due to the operation of the oil pump 7 . However, according to the power transmission apparatus 100 of this embodiment, because the inclined surfaces 51 a and 52 a of the structure are included, the oil in the clutch chambers 16 and 17 can be introduced into (return to) the gear chamber 15 by means of the oil lift generated by the rotation of the clutches 5 L and 5 R. Therefore, the oil surface of the gear chamber 15 is effectively prevented from decreasing.

In addition, in the power transmission apparatus 100 , the gear chamber 15 accommodates the driven bevel gear 3 disposed on a center shaft 4 and the oil strainer 66 connected to the oil pump 7 , therefore, especially in a situation in which a volume of the oil returning to the gear chamber 15 is not sufficient, there is a risk that the oil is mixed with the air (air bubble) because the oil stored in the gear chamber 15 is stirred due to the rotation of the driven bevel gear 3 . Therefore, there is a risk of generating the aeration, that is, a risk of sucking oil mixed with the air into the oil strainer 66 from a suction opening 66 a . In view of this risk, in the power transmission apparatus 100 of this embodiment, because the inclined surfaces 51 a and 52 a of the structure are included, the volume of the oil returning from the clutch chambers 16 and 17 to the gear chamber 15 can be ensured to be sufficient. Therefore, the oil surface of the gear chamber 15 may be prevented from excessively decreasing, and the risk of generating the aeration is effectively reduced.

In addition, in the power transmission apparatus 100 , the gear chamber 15 includes the gear accommodating portion 15 a accommodating the driven bevel gear 3 and the strainer accommodating portion 15 b accommodating the oil strainer 66 , the gear accommodating portion 15 a and the strainer accommodating portion 15 b are disposed adjacent to each other in an axial direction of the center shaft 4 , and boundary portions 15 c of the gear accommodating portion 15 a and the strainer accommodating portion 15 b are in communication with each other. Moreover, the strainer accommodating portion 15 b is disposed at a side closer to a center in the axial direction of the center shaft 4 than the gear accommodating portion 15 a disposed.

In addition, the structure may be that a protruding portion 33 is formed on an inner surface of the strainer accommodating portion 15 b near the boundary portion 15 c , the protruding portion 33 includes an inclined surface 33 a , and the inclined surface 33 a is inclined in such a manner that that its position becomes closer to a far side of the rotating direction of the driven bevel gear 3 in a direction farther away from the boundary portion 15 c.

According to this structure, the oil lifted along with the rotation of the driven bevel gear 3 that rotates in the gear accommodating portion 15 a can be introduced into the strainer accommodating portion 15 b . Therefore, oil in the gear accommodating portion 15 a can be effectively separated from the driven bevel gear 3 , and be actively conveyed to the strainer accommodating portion 15 b accommodating the oil strainer 66 in the gear chamber 15 . In terms of the result, a volume of oil left in the gear accommodating portion 15 a can be reduced, therefore, a volume of the oil introduced from the clutch chamber 17 into the gear accommodating portion 15 a through the communicating hole 35 a can be ensured to be more. Based on the above, the oil moving to the clutch chamber 17 along with the operation of the power transmission apparatus 100 is enabled to effectively return to the strainer accommodating portion 15 b , so as to pursue the rationalization of the volume of the oil of each component inside the power transmission apparatus 100 .

In addition, in the power transmission apparatus 100 , a communicating hole 34 b formed on an isolation wall 34 between the right clutch chamber 16 and the strainer accommodating portion 15 b of the gear chamber 15 is further included, and the communicating hole 34 b is formed at a position on the isolation wall 34 lower than the communicating hole 34 b and the rib 36 .

According to this structure, because the communicating hole 34 b is included, the oil stored in the bottom portion 16 a of the clutch chamber 16 is enabled to return to the gear chamber 15 (the strainer accommodating portion 15 b ) through the communicating hole 34 b . Therefore, the oil surface of the gear chamber 15 (the strainer accommodating portion 15 b ) is effectively prevented from decreasing, so as to pursue further rationalization of the volume of the oil of each component inside the power transmission apparatus 100 .

In addition, in the power transmission apparatus 100 , the communicating hole 34 b is formed at a position higher than the oil surface L 2 of the gear chamber 15 when the power transmission apparatus 100 operates.

According to this structure, when the power transmission apparatus 100 operates, the oil stored in the bottom portion 16 a of the clutch chamber 16 is enabled to return to the gear chamber 15 through the communicating hole 34 b . Therefore, by using this structure, the oil moving to the clutch chamber 16 along with the operation of the power transmission apparatus 100 is enabled to effectively return to the gear chamber 15 , so as to pursue the rationalization of the volume of the oil of each component inside the power transmission apparatus 100 .

In addition, in the power transmission apparatus 100 , the clutch chamber is a pair of clutch chambers 16 and 17 respectively disposed at two sides of the gear chamber 15 in the axial direction of the center shaft 4 , the communicating hole is a pair of communicating holes 34 a and 35 a , respectively disposed at the pair of clutch chambers 16 and 17 , and the inclined surface is a pair of inclined surfaces 51 a and 52 a respectively disposed at the pair of clutch chambers 16 and 17 .

According to this structure, in the power transmission apparatus 100 in which the two sides of the gear chamber 15 are respectively provided with the clutch chambers 16 and 17 , the oil introduced into the clutch chambers 16 and 17 at the two sides is enabled to effectively return to the gear chamber 15 in the center by using the communicating holes 34 a and 35 a and the inclined surfaces 51 a and 52 a . Therefore, the oil surface of the gear chamber 15 can be effectively prevented from decreasing, so as to pursue the optimum of the oil surface of each component inside the power transmission apparatus 100 .

The foregoing describes the embodiments of the disclosure, but the disclosure is not limited to the embodiments, and a plurality of variants may be made within the range of the claims, and the technical concept set forth in the specification and accompanying drawings.