Power transmission mechanism

Abstract

The invention provides a power transmission mechanism capable of improving lubrication inside a differential case. The power transmission mechanism (16) is provided with: a main shaft (28) provided with a drive gear (32) for setting a transmission stage; a differential gear (80) to which power is transmitted from the main shaft (28); and a housing (70) for housing the main shaft (28) and the differential gear (80). In a power transmission mechanism (16), (a) a differential gear (80) is disposed above a main shaft (28), and (b) a housing (70) has a housing cylinder section (74t) for storing lubricating oil (OIL) in order to introduce the lubricating oil (OIL) stirred up by a drive gear (32) into the differential gear (80). As a result of having the housing cylinder section (74t), it is possible to effectively introduce the lubricating oil (OIL) stored in the housing cylinder section (74t) into the differential housing (82) and improve the lubrication of the differential gear (80).

Description

TECHNICAL FIELD

[0001] The present application relates to a power transmission mechanism that includes a shaft provided with gears that set a shift stage, a differential gear that is transmitted power from the shaft, and a case that houses the shaft and the differential gear. BACKGROUND

[0002] A power transmission mechanism is known that includes a shaft provided with gears that set a shift stage, a differential gear that is transmitted power from the shaft, and a case that houses the shaft and the differential gear. For example, the technology described in Patent Document 1 is just such a power transmission mechanism. In the power transmission mechanism described in Patent Document 1, the lower portion of the differential case is submerged in lubricating oil that is accumulated in the bottom portion of the case. The lubricating oil that is accumulated in the bottom portion of the case is stirred up by a stirring plate that rotates together with the differential case, and the stirred-up lubricating oil is introduced from an opening portion formed in the differential case into the interior of the differential case to provide lubrication to the differential gear.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT DOCUMENTS

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-152266 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] However, in a power transmission mechanism that includes a shaft provided with gears that set a shift stage, a differential gear that is transmitted power from the shaft, and a case that houses the shaft and the differential gear, there is a structure in which the lower portion of the differential case is not submerged in lubricating oil that is accumulated in the bottom portion of the case. In the case of such a structure, the introduction of the lubricating oil that is stirred up into the interior of the differential case can become insufficient, i.e., the lubrication of the differential gear becomes insufficient.

[0008] The present application was made in light of the above-described circumstances, and aims to provide a power transmission mechanism that can improve the lubrication of the interior of the differential case.

[0009] MEANS FOR SOLVING THE PROBLEMS

[0010] The gist of the present application is that a power transmission mechanism includes a shaft provided with gears that set a shift stage, a differential gear that is transmitted power from the shaft, and a case that houses the shaft and the differential gear, wherein (a) the differential gear is disposed above the shaft, and (b) the case has an accumulation portion that accumulates lubricating oil that is stirred up by the gears in order to introduce the lubricating oil to the differential gear.

[0011] EFFECTS OF THE INVENTION

[0012] According to the power transmission mechanism of the present application, (a) the differential gear is arranged above the shaft, and (b) the housing has an accumulation portion that accumulates lubricating oil in order to introduce the lubricating oil stirred up by the gear to the differential gear. Even in the case where the differential gear is arranged above the shaft provided with the gear that stirs up the lubricating oil, the lubricating oil can be accumulated in the accumulation portion of the housing. Thus, in the case where the accumulation portion is provided, the lubricating oil accumulated in the accumulation portion can be effectively introduced into the inside of the differential gear housing to improve the lubrication of the differential gear, as compared with the case where the accumulation portion is not provided. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 is a schematic view that explains the schematic configuration of a vehicle on which the power transmission mechanism of the present application is mounted.

[0014] Figure 2 is a view that explains the arrangement of the main shaft, the auxiliary shaft, and a pair of drive shafts coupled to the differential gear, as viewed in the second axial direction.

[0015] Figure 3 is a view that explains the housing cylinder portion provided in the housing, and is a sectional view of the cutting line iii-iii shown in Figure 2 .

[0016] Figure 4 is a perspective view of the differential gear housing and the differential ring gear of the differential gear.

[0017] EXPLANATION OF REFERENCE NUMERALS

[0018] 14r: right wheel (drive wheel), 16: power transmission mechanism, 20r: right wheel drive shaft (drive shaft), 28: main shaft (shaft), 32: drive gear (gear), 70: housing, 74t: housing cylinder portion (accumulation portion), 80: differential gear, 82: differential gear housing, 82b: small diameter portion (differential cylinder portion), 82d: helical groove (groove), 82o: opening portion (opening portion), OIL: lubricating oil, S: gap DETAILED DESCRIPTION

[0019] Hereinafter, an embodiment of the present application will be explained in detail with reference to the drawings. Note that in the embodiment, the drawings are appropriately simplified or modified, and the size ratio and shape of each portion are not necessarily accurately depicted.

[0020] EMBODIMENT

[0021] Figure 1is a schematic diagram illustrating an outline structure of a vehicle 10 equipped with a power transmission mechanism 16 to which the present application is applied. The vehicle 10 is provided with the power transmission mechanism 16 in a power transmission path between an engine 12 and a left and right pair of drive wheels 14. The left and right pair of drive wheels 14 are a left wheel 141 and a right wheel 14r. The engine 12 is a power source for running, and is a known internal combustion engine. The vehicle 10 is a vehicle of, for example, an FR (Front Engine Rear Drive) system. The power transmission mechanism 16 is provided with, in order from the engine 12 side, a clutch Kl, a bevel gear pair 24, a transmission 26, and a differential gear 80. The bevel gear pair 24, the transmission 26, and the differential gear 80 in the power transmission mechanism 16 are housed in a case 70 that is a non-rotating member. One of the clutch Kl is linked to the engine 12 via a propeller shaft 18, and the other is linked to one of the bevel gear pair 24. The other of the bevel gear pair 24 is linked to a main shaft 28 of the transmission 26 described later.

[0022] The transmission 26 is a parallel two-shaft type transmission provided with the main shaft 28 and a countershaft 52 that are arranged parallel to and horizontally to each other, and a plurality of gear stages (transmission stages) are established by reducing or increasing the rotation of the main shaft 28 at a predetermined gear ratio γ (also referred to as a transmission ratio γ). The gear ratio γ is the ratio of the rotational speed of the main shaft 28 to the rotational speed of the countershaft 52 (=rotational speed of the main shaft 28 / rotational speed of the countershaft 52). The main shaft 28 is arranged so as to be rotatable about a first axis CI, and the countershaft 52 is arranged so as to be rotatable about a second axis C2. The first axis CI direction and the second axis C2 direction are the same direction in which they extend horizontally. The countershaft 52 and the differential gear 80 are linked by an output gear 52g provided to the countershaft 52 meshing with a differential ring gear (final stage gear) 84 provided to the differential gear 80. The differential gear 80 is linked to the left and right pair of drive wheels 14 via a left and right pair of drive shafts 20. The left and right pair of drive shafts 20 are arranged so as to be rotatable about a third axis C3 that is parallel to the second axis C2. The left and right pair of drive shafts 20 are a left wheel drive shaft 20l and a right wheel drive shaft 20r.

[0023] The transmission 26 has a plurality of gear pairs 30. The gear pairs 30 each have a drive gear 32 that is fixedly provided to the main shaft 28 so as not to rotate relatively, and a driven gear 34 that is always engaged with the drive gear 32, is provided to the countershaft 52 so as to be able to rotate relatively and not to move in the second axis C2 direction. The reverse gear pair 30a, the second gear pair 30b, the first gear pair 30c, the fourth gear pair 30d, the fifth gear pair 30e, the sixth gear pair 30f, and the third gear pair 30g are provided in this order from one side of the first axis Cl direction (= the second axis C2 direction) toward the other side as the plurality of gear pairs 30. The gear ratio γ decreases from the first gear pair 30c to the second gear pair 30b, the third gear pair 30g, the fourth gear pair 30d, the fifth gear pair 30e, and the sixth gear pair 30f. The reverse gear pair 30a has an intermediate gear 36 that is engaged with both the drive gear 32 and the driven gear 34 in order to reverse the rotation direction. Hereinafter, the reverse gear pair 30a to the third gear pair 30g will be referred to as "gear pair 30" without particular distinction. When the drive gear 32 of the gear pair 30 rotates, the driven gear 34 rotates at a rotational speed corresponding to the gear ratio γ of the gear pair 30.

[0024] In the second axis C2 direction, the transmission 26 has the switching mechanisms 40 between the driven gears 34 of the reverse gear pair 30a, the second gear pair 30b, and the first gear pair 30c, between the driven gears 34 of the fourth gear pair 30d and the fifth gear pair 30e, and between the driven gears 34 of the sixth gear pair 30f and the third gear pair 30g, respectively. The switching mechanisms 40 are provided to the countershaft 52 so as to not rotate relatively and to be able to move in the second axis C2 direction, respectively. The switching mechanisms 40 have the switching engagement teeth 42 at positions facing the driven gears 34 in the second axis C2 direction, respectively. The driven gears 34 have the gear-side engagement teeth 44 that are able to engage with the switching engagement teeth 42 at positions facing the switching mechanisms 40 in the second axis C2 direction, respectively. The switching mechanism 40 having the switching engagement teeth 42 and the driven gear 34 having the gear-side engagement teeth 44 constitute the dog clutch 50 as an engagement clutch.

[0025] The shift mechanism 60 has a shift fork 62, a shift drum 64, and a shift actuator 66 that respectively engage with the switching mechanism 40. The shift drum 64 has shift grooves 68 that respectively define the moving positions of the switching mechanism 40 in the second axis C2 direction via the shift fork 62. The switching mechanism 40 is moved to the defined positions in the second axis C2 direction according to the rotational position of the shift drum 64, whereby the disconnecting / connecting state of the dog clutch 50 is switched to change the transmission 26. For example, when the driven gear 34 of the reverse gear stage Rev is connected to the countershaft 52 via the switching mechanism 40, the reverse gear stage Rev is formed in the transmission 26. The same applies to the first gear stage Ist to the sixth gear stage 6th. The drive gear 32 and the driven gear 34 are gears that set the gear stage.

[0026] Figure 2 FIG. 6 is a view that explains the arrangement of the main shaft 28, the countershaft 52, and the left and right pair of drive shafts 20 that are connected to the differential gear 80, as viewed in the second axis C2 direction. In FIG. 6, the housing 70 (the third housing portion 76 described later) is shown only with the outer edge portion to which a fastening tool such as a bolt is fastened. Figure 2

[0027] For example, the lubricating oil OIL for lubricating the gears is stored in the bottom portion of the housing 70. The lubricating oil OIL functions as a coolant in addition to lubrication. The drive gear 32 that is fixed to the main shaft 28 is in a position where the lubricating oil OIL can be stirred up. The "position where the lubricating oil OIL can be stirred up" is a position where the actual working oil surface of the lubricating oil OIL stored in the bottom portion of the housing 70 can be stirred up. The "actual working oil surface" is the height position of the oil surface of the lubricating oil OIL in the usual state of the lubricating oil OIL stored in the bottom portion of the housing 70. The "usual state" is a driving state that continues for a relatively long time, unlike a temporary state at the time of sudden acceleration or deceleration of the vehicle 10, at the time of driving on a sloping road, at the time of sharp turning, and the like. On the other hand, the countershaft 52 is arranged above the direction of the plumb line with respect to the main shaft 28 (hereinafter, simply referred to as "above"). Thus, the driven gear 34 provided to the countershaft 52 is not in a position where the lubricating oil OIL can be stirred up. Similarly, the differential gear 80 and the left and right pair of drive shafts 20 connected to the differential gear 80 are arranged above with respect to the main shaft 28. Thus, the differential ring gear 84 provided to the differential gear 80 is not in a position where the lubricating oil OIL can be stirred up. The lubricating oil OIL is stirred up by the drive gear 32, whereby the lubricating oil OIL is used for lubrication of the gears and bearings inside the housing 70. Furthermore, the lubricating oil OIL adhering to the gears (for example, the driven gear 34) inside the housing 70 is further scattered around by rotation of the gears.

[0028] ​For example, in the vehicle 10 in which the propeller shaft 18 and the clutch K1 are disposed at relatively low positions in the direction of the vertical line and the rotation center lines of the pair of left and right drive wheels 14 are disposed at relatively high positions in the direction of the vertical line, the main shaft 28, the auxiliary shaft 52, and the differential gear 80 become configurations that use Figure 2 the configuration described above.

[0029] Figure 3 is a view that describes the housing cylinder portion 74t of the housing 70, is Figure 2 a cross-sectional view taken along the cutting line iii-iii shown in Fig. 1.

[0030] The housing 70 is a casting made of, for example, an aluminum alloy, and has, for example, a first housing portion 72, a second housing portion 74, and a third housing portion 76.

[0031] The first housing portion 72 is a bottomed cylindrical member, and has an opening on the left wheel 14l side in the third axis C3 direction. The second housing portion 74 is a cylindrical member, and has openings on the right wheel 14r side and the left wheel 14l side in the third axis C3 direction, respectively. The third housing portion 76 is a bottomed cylindrical member, and has an opening on the right wheel 14r side in the third axis C3 direction. The first housing portion 72 and the second housing portion 74 are joined in one body in a manner in which the opening on the left wheel 14l side in the first housing portion 72 and the opening on the right wheel 14r side in the second housing portion 74 are brought into register, by a fastening tool such as a bolt. The second housing portion 74 and the third housing portion 76 are joined in one body in a manner in which the opening on the left wheel 14l side in the second housing portion 74 and the opening on the right wheel 14r side in the third housing portion 76 are brought into register, by a fastening tool such as a bolt.

[0032] The second housing portion 74 has a cylindrical housing cylinder portion 74t on its inner side. The housing cylinder portion 74t is formed so that its inner peripheral surface faces the outer peripheral surface of the right wheel drive shaft 20r with a gap S therebetween. The right wheel 14r and the right wheel drive shaft 20r correspond to the "drive wheel" and the "drive shaft" in the present application, respectively. The housing cylinder portion 74t has a function of storing the lubricating oil OIL stirred up by the drive gear 32 in the gap S so as to be introduced into the differential gear 80. The housing cylinder portion 74t corresponds to the "storing portion" in the present application. For example, when the main shaft 28 is rotated during vehicle running, the drive gear 32 fixed to the main shaft 28 stirs up the lubricating oil OIL and scatters it around. Also, the lubricating oil OIL adhering to the driven gear 34 is scattered around by rotating the driven gear 34 provided to the pinion shaft 52. For example, an introduction oil passage 74in is provided in the housing cylinder portion 74t so as to make the lubricating oil OIL easily enter the gap S. The introduction oil passage 74in is, for example, a through hole provided in the lower portion of the housing cylinder portion 74t. In this way, the lubricating oil OIL stirred up by the drive gear 32 enters and is stored in the gap S directly or indirectly through the path of the hollow arrow. The main shaft 28 and the drive gear 32 correspond to the "shaft" and the "gear" in the present application, respectively.

[0033] The differential gear 80 is transmitted power from the main shaft 28 via the pinion shaft 52 in the transmission 26. The differential gear 80 is a differential gear which receives power transmitted from the output gear 52g of the transmission 26, and transmits driving torque equal to each other to the left and right pair of drive shafts 20 while allowing a proper rotational speed difference between the left and right pair of drive shafts 20.

[0034] The differential gear 80 has a differential housing 82, a differential ring gear 84, a pair of differential pinion gears 86, and a pair of differential half shaft gears 88.

[0035] The differential housing 82 is configured by joining a plurality of members with fastening tools such as bolts. The differential housing 82 is rotatable about the third axis line C3 and has a hollow portion in the inside thereof. The differential housing 82 has a large diameter portion 82a and a small diameter portion 82b which protrudes from the large diameter portion 82a to the right wheel 14r side in the third axis line C3 direction. Both the large diameter portion 82a and the small diameter portion 82b are cylindrical. The right wheel 14r side of the small diameter portion 82b in the third axis line C3 direction becomes an opening portion 82r. The left wheel 14l side of the large diameter portion 82a in the third axis line C3 direction becomes an opening portion 82l. On the left wheel 14l side of the small diameter portion 82b in the third axis line C3 direction, the outer edge of the small diameter portion 82b is connected to the outer edge of the large diameter portion 82a.

[0036] The differential ring gear 84 is disc-shaped and centered on the third axis C3, with gear teeth on its outer periphery. The inner periphery of the differential ring gear 84 forms a through hole extending along the third axis C3. With the large-diameter portion 82a of the differential housing 82 inserted into the through hole of the differential ring gear 84, the differential ring gear 84 and the differential housing 82 are connected as one unit using bolts or other fastening tools.

[0037] A pair of differential pinions 86 and a pair of differential half-shaft gears 88 are both housed within a cavity inside the differential housing 82. When the vehicle 10 is traveling straight, the pair of differential pinions 86 do not rotate independently; the rotation of the differential housing 82 causes the pair of differential half-shaft gears 88 to rotate via the pair of differential pinions 86. When the vehicle 10 is turning, the pair of differential pinions 86 rotate independently; the rotation of the differential housing 82 transmits equal driving torque to the pair of differential half-shaft gears 88 via the pair of differential pinions 86, allowing for a suitable speed difference.

[0038] Figure 4 This is a perspective view of the differential housing 82 and the differential ring gear 84 of the differential gear 80.

[0039] Although Figure 4 Although not shown in the figure, a drive shaft 20r for the right wheel is inserted into the inner circumference of the small diameter portion 82b of the differential housing 82, and a drive shaft 20l for the left wheel is inserted into the opening 82l of the large diameter portion 82a of the differential housing 82.

[0040] A spiral groove 82d is provided on the inner circumferential surface of the small diameter portion 82b. The spiral groove 82d is a groove arranged in a direction that, when the vehicle 10 is moving forward, facilitates the introduction of lubricating oil 74t from the outside to the inside of the differential housing 82 in response to the rotation of the right wheel drive shaft 20r. The small diameter portion 82b and the spiral groove 82d correspond to the "differential cylinder portion" and "groove" in this invention, respectively. In the direction of the third axis C3, the clearance S between the housing cylinder portion 74t and the right wheel drive shaft 20r (refer to...) Figure 3 It is close to the front end of the opening 82r side of the small diameter portion 82b of the differential housing 82.

[0041] In the direction of the third axis C3, the large-diameter portion 82a has an opening 82o for discharging lubricating oil only on the opposite side of the small-diameter portion 82b (see reference). Figure 3 For example, multiple openings 82o are provided at equal angular intervals. The openings 82o are equivalent to the "openings" in this invention.

[0042] According to the present embodiment, the power transmission mechanism 16 includes: the main shaft 28 provided with the drive gear 32 that sets the shift stage; the differential gear 80 that is transmitted power from the main shaft 28; and the housing 70 that houses the main shaft 28 and the differential gear 80. In the power transmission mechanism 16, (a) the differential gear 80 is arranged above the main shaft 28, and (b) the housing 70 has the housing cylindrical portion 74t that stores the lubricating oil OIL in order to introduce the lubricating oil OIL stirred up by the drive gear 32 to the differential gear 80. Even in the case where the differential gear 80 is arranged above the main shaft 28 provided with the drive gear 32 that stirs up the lubricating oil OIL, the lubricating oil OIL can be stored in the housing cylindrical portion 74t of the housing 70. Thus, in the case where the housing 70 has the housing cylindrical portion 74t, the lubricating oil OIL stored in the housing cylindrical portion 74t can be effectively introduced into the inside of the differential gear housing 82, compared with the case where the housing 70 does not have the housing cylindrical portion 74t, thereby improving the lubrication of the differential gear 80.

[0043] According to the present embodiment, the housing cylindrical portion 74t is a cylindrical shape that faces the right-wheel drive shaft 20r across the gap S. Thus, since the lubricating oil OIL is stored in the gap S, the lubricating oil OIL can be effectively introduced into the inside of the differential gear housing 82.

[0044] According to the present embodiment, (a) the differential gear housing 82 has the small-diameter portion 82b that faces the right-wheel drive shaft 20r, and (b) the helical groove 82d that introduces the lubricating oil OIL from the housing cylindrical portion 74t to the inside of the differential gear housing 82 in correspondence with the rotation of the right-wheel drive shaft 20r is provided to the inner peripheral portion of the small-diameter portion 82b. In the case where the helical groove 82d is provided, compared with the case where the helical groove 82d is not provided, in correspondence with the rotation of the right-wheel drive shaft 20r, the lubricating oil OIL stored in the housing cylindrical portion 74t is easily introduced into the inside of the differential gear housing 82 via the helical groove 82d. Thus, the lubricating oil OIL can be effectively introduced into the inside of the differential gear housing 82.

[0045] According to the present embodiment, the differential gear housing 82 has the opening portion 82o that discharges the lubricating oil OIL only on the side opposite to the side of the housing cylindrical portion 74t to which the lubricating oil OIL is introduced. In the third axis C3 direction, the lubricating oil OIL is introduced into the inside of the differential gear housing 82 from the side of the housing cylindrical portion 74t and is discharged from the opening portion 82o of the differential gear housing 82 provided only on the side opposite to the side of the housing cylindrical portion 74t. Also, in the radial direction around the third axis C3, the lubricating oil OIL is introduced into the inside of the differential gear housing 82 from the inner peripheral portion side of the radial direction in which the housing cylindrical portion 74t is provided and is discharged to the outer peripheral portion side of the radial direction in which the opening portion 82o is provided. Thus, the lubricating oil OIL can be supplied to the inside of the differential gear housing 82 as a whole in the differential gear 80.

[0046] Note that the above is an embodiment of the present application, and the present application can be implemented in various forms to which various changes and modifications based on the knowledge of those skilled in the art are applied, without departing from the spirit of the present application.

[0047] In the foregoing embodiment, the small-diameter portion 82b has the spiral groove 82d on the inner peripheral portion, but the present application can also be applied to a form in which the spiral groove 82d is not provided. Even in the form in which the spiral groove 82d is not provided, the lubricating oil OIL can be introduced into the inside of the differential case 82 through the gap S between the inner peripheral portion of the small-diameter portion 82b and the outer peripheral portion of the right-wheel drive shaft 20r. In such a form, compared to the case where the case cylinder portion 74t is not provided, in the case where the case cylinder portion 74t is provided, the lubricating oil OIL accumulated in the case cylinder portion 74t can be effectively introduced into the inside of the differential case 82, and the lubrication of the differential gear 80 can be improved.

[0048] In the foregoing embodiment, the large-diameter portion 82a has the opening portion 82o on the side opposite to the side of the case cylinder portion 74t, but the present application is not limited to this form. For example, the present application can also be applied to a form in which the opening portion 82o is provided on both the side opposite to the side of the case cylinder portion 74t and the side of the case cylinder portion 74t of the large-diameter portion 82a. In the case of such a form, in the third axis C3 direction, the lubricating oil OIL is introduced into the inside of the differential case 82 from the side of the case cylinder portion 74t and is discharged from the opening portion 82o of the differential case 82. In such a form, compared to the case where the case cylinder portion 74t is not provided, in the case where the case cylinder portion 74t is provided, the lubricating oil OIL accumulated in the case cylinder portion 74t can be effectively introduced into the inside of the differential case 82, and the lubrication of the differential gear 80 can be improved.

[0049] In the foregoing embodiment, the right wheel 14r and the right-wheel drive shaft 20r correspond to the "drive wheel" and the "drive shaft" in the present application, respectively, and the inner peripheral surface of the case cylinder portion 74t faces the outer peripheral surface of the right-wheel drive shaft 20r with the gap S therebetween, but the present application is not limited to this form. For example, it can also be a form in which the left wheel 14l and the left-wheel drive shaft 20l correspond to the "drive wheel" and the "drive shaft" in the present application, respectively, and the inner peripheral surface of the case cylinder portion 74t faces the outer peripheral surface of the left-wheel drive shaft 20l with the gap therebetween.

[0050] In the foregoing embodiment, the tubular housing tubular portion 74t corresponds to the "accumulation portion" of the present application, but the present application is not limited to this form. As long as it has the function of accumulating the lubricating oil OIL introduced to the differential gear 80 by the driving gear 32, the structure corresponding to the "accumulation portion" of the present application can not necessarily be tubular. For example, in the foregoing embodiment 1, it can also be a form in which a slit extending in the third axis C3 direction is formed in the lower portion of the housing tubular portion 74t.

[0051] In the foregoing embodiment, the vehicle 10 is an FR mode vehicle, but the present application can also be applied to a FF (Front Engine Front Drive) mode, MR (Midship Engine Rear Drive) mode, and four-wheel drive mode vehicle.

Claims

1. A power transmission mechanism having a shaft provided with a gear that sets a shift stage, a differential gear that is transmitted power from the shaft, and a case that houses the shaft and the differential gear, the power transmission mechanism characterized in that, the differential gear is disposed above the shaft, the case has an accumulation portion that accumulates lubricating oil stirred up by the gear in order to introduce the lubricating oil to the differential gear.

2. The power transmission mechanism according to claim 1, characterized in that, the accumulation portion is a tubular shape that faces a drive shaft across a gap, the drive shaft linking between the differential gear and a drive wheel.

3. The power transmission mechanism according to claim 1 or 2, characterized in that, a differential case of the differential gear has a differential tubular portion that faces the drive shaft, a groove is provided at an inner peripheral portion of the differential tubular portion, the groove introducing the lubricating oil from the accumulation portion to an inside of the differential case in correspondence with rotation of the drive shaft.

4. The power transmission mechanism according to claim 1 or 2, characterized in that, the differential case of the differential gear has an opening portion that discharges the lubricating oil only at a side opposite to the accumulation portion into which the lubricating oil is introduced.

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