Power transmission device

Abstract

To provide a power transmission device capable of suppressing leakage of lubricating oil from a breather device and adjusting pressure in a case while simplifying the structure of the breather device.SOLUTION: In the power transmission device 16 in which the sub-shaft 52 is accommodated in the case 70 and the breather device 90 that allows the inside and the outside of the case 70 to communicate with each other is provided, (a) the sub-shaft 52 has a tubular shape extending in the direction of the second axis C2 and is disposed above the oil level position P1 of the lubricant OIL, (b) The intake and exhaust passage 92 provided between the sub-shaft 52 and the breather device 90 has the axial line extension portion 52i connected to the hollow portion C2 of the sub-shaft 52 and extending in the direction of the second axial line 92a, and the upward extension portion 92a bent and connected to the side opposite to the hollow portion 52i in the axial line extension portion 92b and extending upward.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a power transmission device in which a power transmission shaft is housed in a case and a breather device is provided to communicate between the inside and outside of the case. [Background technology]

[0002] There is known a power transmission device that houses a transmission in a case and is provided with a breather device that connects the inside and outside of the case. For example, the device described in Patent Document 1 is one such device. In the power transmission device described in Patent Document 1, air containing lubricating oil flows from the inside of the case into the breather device, and is separated into lubricating oil and air by a separation wall provided in a separation chamber of the breather device. The separated lubricating oil is returned to the inside of the case via a return oil passage, and the air can be exhausted to the outside of the case. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-119666 Summary of the Invention [Problem to be solved by the invention]

[0004] In the power transmission device described in Patent Document 1, the breather device has a complex configuration that includes a separation chamber, a return oil passage, etc. Therefore, there is a demand for a power transmission device that has a simple breather device configuration, yet can suppress leakage of lubricating oil from the breather device and adjust the pressure inside the case.

[0005] The present invention was made against the background of the above circumstances, and its purpose is to provide a power transmission device that has a breather device with a simple configuration, while suppressing leakage of lubricating oil from the breather device and capable of adjusting the pressure inside the case. [Means for solving the problem]

[0006] The gist of the present invention is a power transmission device in which a power transmission shaft is housed in a case and a breather device is provided to connect the inside and outside of the case, wherein (a) the power transmission shaft is cylindrical and extends axially and is located above the working oil level of the lubricating oil, and (b) an intake and exhaust path provided between the power transmission shaft and the breather device has an axial extension portion that is connected to a hollow portion of the power transmission shaft and extends in the axial direction, and an upward extension portion that is bent on the opposite side of the hollow portion of the axial extension portion and connects to it, extending upward. [Effects of the Invention]

[0007] According to the present invention, (a) the power transmission shaft is cylindrical and extends axially and is positioned above the working oil surface of the lubricating oil, and (b) the intake / exhaust passage provided between the power transmission shaft and the breather device has an axial extension connected to a hollow portion of the power transmission shaft and extending in the axial direction, and an upward extension bent on the opposite side of the hollow portion of the axial extension and extending upward. Air and lubricating oil are separated in the hollow portion of the power transmission shaft by gas-liquid separation caused by centrifugal force generated as the power transmission shaft rotates. Air and lubricating oil are separated in the intake / exhaust passage by gas-liquid separation caused by inertial collision. Thus, while the breather device has a simple configuration, the gas-liquid separation caused by centrifugal force due to rotation of the power transmission shaft and the gas-liquid separation caused by inertial collision in the intake / exhaust passage can be used to adjust the pressure inside the case while preventing lubricating oil from leaking from the breather device. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram illustrating a schematic configuration of a vehicle equipped with a power transmission device to which the present invention is applied. [Figure 2] 10 is a diagram illustrating the arrangement of a main shaft, a sub shaft, and a pair of drive shafts as viewed in the second axial direction. FIG. [Figure 3] 10A and 10B are diagrams illustrating the gas-liquid separation action due to rotation of the counter shaft and the gas-liquid separation action due to inertial collision in an intake / exhaust path provided between the breather device and the counter shaft. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that in the embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios and shapes of the various parts are not necessarily drawn accurately. [Example]

[0010] FIG. 1 is a schematic diagram illustrating the general configuration of a vehicle 10 equipped with a power transmission device 16 to which the present invention is applied. The vehicle 10 includes the power transmission device 16 in a power transmission path between an engine 12 and a pair of drive wheels 14. The engine 12 is a power source for traveling and is a well-known internal combustion engine. The vehicle 10 is, for example, a front-engine, rear-drive (FR) vehicle. The power transmission device 16 includes, in order from the engine 12 side, a clutch K1, a bevel gear pair 24, a transmission 26, and a differential gear 58. Of the power transmission device 16, the bevel gear pair 24, the transmission 26, and the differential gear 58 are housed in a case 70, which is a non-rotating member. One end of the clutch K1 is connected to the engine 12 via a propeller shaft 18, and the other end is connected to one of the bevel gear pair 24. The other end of the bevel gear pair 24 is connected to a main shaft 28 of the transmission 26, which will be described later.

[0011] The transmission 26 is a parallel two-shaft transmission that includes a main shaft 28 and a countershaft 52 that are arranged horizontally and parallel to each other. The transmission 26 achieves multiple gear stages (speed stages) by slowing or speeding up the rotation of the main shaft 28 at a predetermined gear ratio γ (also referred to as a speed ratio) γ (= rotational speed of the main shaft 28 / rotational speed of the countershaft 52). The main shaft 28 is rotatably disposed about a first axis C1, and the countershaft 52 is rotatably disposed about a second axis C2. The first axis C1 direction and the second axis C2 direction are horizontally extending in the same direction. The second axis C2 corresponds to the "axis" in this invention. The countershaft 52 includes a main rotation shaft portion 54 and a gear rotation shaft portion 56, which are connected by a spline engagement portion 52s so as not to rotate relative to each other. An output gear 56g provided on the gear rotation shaft portion 56 meshes with a final gear 58a provided on the differential gear 58, thereby connecting the countershaft 52 and the differential gear 58. The differential gear 58 and the pair of drive wheels 14 are connected via a pair of drive shafts 20. The pair of drive shafts 20 are arranged rotatably about a third axis C3, and the third axis C3 and the second axis C2 are parallel to each other.

[0012] The transmission 26 includes a plurality of gear pairs 30. Each gear pair 30 includes a drive gear 32 fixed to the main shaft 28 so as not to rotate relative to the main shaft 28, and a driven gear 34 that is constantly meshed with the drive gear 32, is rotatable relative to the main rotary shaft portion 54, and is immovable in the second axis C2 direction. The plurality of gear pairs 30 are provided, in order from one side to the other in the first axis C1 direction (= second axis C2 direction), as a reverse gear pair 30a, a second-speed gear pair 30b, a first-speed gear pair 30c, a fourth-speed gear pair 30d, a fifth-speed gear pair 30e, a sixth-speed gear pair 30f, and a third-speed gear pair 30g. The gear ratio γ decreases from first gear pair 30c to second gear pair 30b, third gear pair 30g, fourth gear pair 30d, fifth gear pair 30e, and sixth gear pair 30f. Reverse gear pair 30a has an intermediate gear 36 between the drive gear 32 and the driven gear 34 that meshes with both of them to reverse the direction of rotation. Hereinafter, unless otherwise specified, reverse gear pair 30a to third gear pair 30g will be referred to as "gear pair 30." When the drive gear 32 of a gear pair 30 rotates, the driven gear 34 rotates at a rotational speed corresponding to the gear ratio γ of that gear pair 30.

[0013] In the direction of the second axis C2, the transmission 26 includes switching mechanisms 40 on one side of the driven gear 34 of the reverse gear pair 30a, between the driven gears 34 of the second-speed gear pair 30b and the first-speed gear pair 30c, between the driven gears 34 of the fourth-speed gear pair 30d and the fifth-speed gear pair 30e, and between the driven gears 34 of the sixth-speed gear pair 30f and the third-speed gear pair 30g. The switching mechanisms 40 are each provided on the main rotation shaft portion 54 of the countershaft 52 so as to be non-rotatable relative to the main rotation shaft portion 54 and movable in the direction of the second axis C2. Each switching mechanism 40 has a switching meshing tooth 42 at a position facing the driven gear 34 in the direction of the second axis C2. Each of the driven gears 34 has gear-side meshing teeth 44 that can mesh with the switching meshing teeth 42 at a position facing the switching mechanism 40 in the direction of the second axis C2. The switching mechanism 40 having the switching meshing teeth 42 and the driven gear 34 having the gear-side meshing teeth 44 form a dog clutch 50, which is a meshing clutch.

[0014] The shift mechanism 60 includes shift forks 62 that fit into the switching mechanism 40, a shift barrel 64, and a shift actuator 66. The shift barrel 64 is formed with shift grooves 68 that define the movement positions of the switching mechanism 40 in the direction of the second axis C2 via the shift forks 62. The transmission 26 changes gears by switching the engagement and disengagement states of the dog clutch 50 as the switching mechanism 40 moves to specific positions in the direction of the second axis C2 in accordance with the rotational position of the shift barrel 64. For example, when the driven gear 34 of the reverse gear Rev and the countershaft 52 are connected via the switching mechanism 40, the reverse gear Rev is established in the transmission 26. The same applies to the first gear 1st to the sixth gear 6th.

[0015] 2 is a diagram illustrating the arrangement of the main shaft 28, the counter shaft 52, and the pair of drive shafts 20 as viewed from the direction of the second axis C2. The case 70 is formed by integrally assembling multiple case members together with fasteners such as bolts. In FIG. 2, only the outer edge of the case 70 where the fasteners are fastened is shown.

[0016] For example, lubricating oil OIL, such as ATF (Automatic Transmission Fluid), is stored in the bottom of the case 70. Oil level position P1 is the height of the lubricating oil OIL stored in the bottom of the case 70 in a normal state. The normal state is a relatively long-lasting driving state, as opposed to temporary states such as sudden acceleration / deceleration of the vehicle 10, driving on an incline, or making a sharp turn, as described below. Oil level position P1 corresponds to the "actual oil level" in this invention. The drive gear 32 fixed to the main shaft 28 is located in a position where it can scoop up the lubricating oil OIL, which is at oil level position P1. On the other hand, the countershaft 52 and the driven gear 34 mounted on the countershaft 52 are not located in a position where it can scoop up the lubricating oil OIL, which is at oil level position P1. The lubricating oil OIL is scooped up by the drive gear 32, and is used to lubricate the gears and bearings in the case 70. Furthermore, when a gear (for example, the driven gear 34) inside the case 70 rotates, the lubricating oil adhering to the gear is further scattered around.

[0017] 3 is a diagram illustrating the gas-liquid separation action due to the rotation of the countershaft 52 and the gas-liquid separation action due to inertial collision in the intake / exhaust path 92 provided between the breather device 90 and the countershaft 52. FIG. 3 is a cross-sectional view taken along the line iii-iii shown in FIG. 2.

[0018] The main rotating shaft 54 ​​and the gear rotating shaft 56 are each tubular (e.g., cylindrical) and extend in the direction of the second axis C2, and are positioned above the oil level P1 of the lubricating oil OIL. The main rotating shaft 54 ​​has a hollow portion 54i on the side near the second axis C2. The main rotating shaft 54 ​​is provided with a plurality of through holes 54h that penetrate from the hollow portion 54i to the outer periphery. The gear rotating shaft 56 has a hollow portion 56i on the side near the second axis C2. The hollow portion 52i of the countershaft 52 includes the hollow portion 54i and the hollow portion 56i, which are connected in the direction of the second axis C2. The countershaft 52 and the hollow portion 52i correspond to the "power transmission shaft" and the "hollow portion," respectively, in this invention.

[0019] The countershaft 52 is supported by the case 70 via a plurality of bearings 80. For example, when the transmission 26 is assembled to be housed within the case 70, an opening 70o is provided in the case 70 on an extension of the countershaft 52 in the direction of the second axis C2 of the countershaft 52. The cover 72 is connected to the case 70 with fasteners to close the opening 70o. For example, a cylindrical passage is integrally formed with the cover 72 by, for example, casting. This cylindrical passage is an intake / exhaust passage 92 provided between the breather device 90 and the countershaft 52. The breather device 90 is a well-known breather device that connects the inside and outside of the case 70. The intake / exhaust passage 92 functions as an exhaust passage when the pressure inside the case 70 is higher than the pressure outside the case 70, and as an intake passage when the pressure inside the case 70 is lower. When the cover 72 is assembled to the case 70 with fasteners, one end of the intake / exhaust passage 92 is positioned to be inserted into the hollow portion 52i of the countershaft 52. In this way, the intake and exhaust passages 92 are formed when the cover 72 is cast without increasing the number of manufacturing steps. Furthermore, the intake and exhaust passages 92 are formed so that, when the cover 72 is assembled, the countershaft 52 and one end of the intake and exhaust passages 92 overlap in the direction of the second axis C2. The breather device 90 is attached to the other end of the intake and exhaust passages 92. In this way, the intake and exhaust passages 92 are provided between the countershaft 52 and the breather device 90. The intake and exhaust passages 92 have an axial extension 92a and an upward extension 92b. The axial extension 92a is a portion connected to the hollow portion 52i of the countershaft 52 and extending in the direction of the second axis C2. The upward extension 92b is a portion of the axial extension 92a that is bent to the opposite side from the hollow portion 52i and extends upward. The bent portion 92c is a connection portion between the axial extension 92a and the upward extension 92b. In this embodiment, the axial extension portion 92a extends in the direction of the second axis C2 from the hollow portion 52i of the countershaft 52 toward the bent portion 92c. The upward extension portion 92b extends upward in the vertical direction from the bent portion 92c toward the breather device 90. In this manner, the intake / exhaust path 92 is bent 90 degrees at the bent portion 92c.

[0020] Although lubricating oil O is not actively supplied to the hollow portion 52i, lubricating oil O may flow in through an opening in the hollow portion 52i. For example, when the rotational speed of the drive gear 32 increases while the vehicle is running, the lubricating oil O is vigorously agitated and foamed, and the pressure inside the case 70 increases. This may cause the oil level of the lubricating oil to become higher than the oil level position P1. When air containing foamed lubricating oil O flows into the hollow portion 52i, the air and the lubricating oil O are separated in the hollow portion 52i by gas-liquid separation caused by centrifugal force generated as the countershaft 52 rotates. Specifically, the lubricating oil O, which has a relatively high specific gravity, moves toward the outer periphery of the countershaft 52 due to centrifugal force, while the air, which has a relatively low specific gravity, remains near the second axis C2 of the countershaft 52, thereby separating the air and the lubricating oil. The separated lubricating oil OIL passes through the through-hole 54h and is discharged from the hollow portion 52i of the counter shaft 52 to the outside of the counter shaft 52. The separated lubricating oil OIL flows in the direction of arrow F1 and is discharged from the hollow portion 52i of the counter shaft 52.

[0021] When the pressure inside the case 70 increases relative to the pressure outside the case 70, causing air containing lubricating oil to flow from the hollow portion 52i into the intake / exhaust path 92 in the direction of arrow F2a, the air containing lubricating oil collides with the bent portion 92c due to inertia. Hereinafter, a collision due to inertia will be referred to as "inertial collision." The air and lubricating oil are separated by the gas-liquid separation caused by this inertial collision. Specifically, the lubricating oil, which has a relatively high specific gravity, remains at the bent portion 92c due to inertial collision, while the air, which has a relatively low specific gravity, does not remain at the bent portion 92c but flows toward the upward extension portion 92b in the direction of arrow F2b. The separated lubricating oil is returned to the hollow portion 52i of the countershaft 52 through the axial extension portion 92a. The oil level position P2 is a height position at which the lubricating oil level can temporarily reach its highest point during sudden acceleration / deceleration of the vehicle 10, driving on an incline, or making a sharp turn. The length of the upward extension 92b is determined so that the attachment position of the breather device 90 is above the oil level position P2, thereby preventing the lubricating oil from leaking from the breather device 90 even if the oil level of the lubricating oil temporarily rises.

[0022] According to this embodiment, (a) the countershaft 52 is cylindrical and extends along the second axis C2, and is positioned above the oil level P1 of the lubricating oil. (b) The intake / exhaust passage 92, which is provided between the countershaft 52 and the breather device 90, has an axial extension 92a connected to the hollow portion 52i of the countershaft 52 and extending along the second axis C2, and an upward extension 92b that bends and connects to the axial extension 92a on the opposite side of the hollow portion 52i and extends upward. Air and lubricating oil are separated in the hollow portion 52i of the countershaft 52 by a gas-liquid separation effect due to centrifugal force generated as the countershaft 52 rotates. Furthermore, air and lubricating oil are separated in the intake / exhaust passage 92 by a gas-liquid separation effect due to inertial collision. In this way, the breather device 90 has a simple configuration, and the pressure inside the case 70 can be adjusted while suppressing leakage of lubricating oil from the breather device 90 by the centrifugal force caused by the rotation of the countershaft 52 and the gas-liquid separation action caused by inertial collision in the intake and exhaust path 92.

[0023] The above-described embodiments of the present invention are merely examples, and the present invention can be embodied in various forms with various modifications and improvements based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

[0024] In the above-described embodiment, the intake / exhaust path 92 is bent at the bent portion 92c by 90 degrees, but this is not limited thereto. As long as the gas-liquid separation effect due to inertial collision functions, the bend angle may exceed 90 degrees or may be less than 90 degrees. In the above-described embodiment, the upward extension portion 92b extends upward from the bent portion 92c in a vertical direction, but this is not limited thereto. The upward extension portion 92b may extend upward from the bent portion 92c in a direction other than a vertical direction. In the above-described embodiment, the vehicle 10 is an FR vehicle, but the present invention is also applicable to FF (Front Engine Front Drive) vehicles, MR (Midship Engine Rear Drive) vehicles, and four-wheel drive vehicles. [Explanation of symbols]

[0025] 16: power transmission device, 52: countershaft (power transmission shaft), 52i: hollow portion (hollow portion), 70: case, 90: breather device, 92: intake and exhaust path, 92a: axial extension portion, 92b: upper extension portion, C2: second axial line (axial line), OIL: lubricating oil, P1: oil level position (actual oil level)

Claims

[Claim 1] A power transmission device in which a power transmission shaft is housed in a case and a breather device is provided to communicate between the inside and outside of the case, the power transmission shaft is cylindrical and extends in an axial direction, and is disposed above an actual oil level of the lubricating oil; The intake and exhaust path provided between the power transmission shaft and the breather device has an axial extension portion connected to a hollow portion of the power transmission shaft and extending in the axial direction, and an upward extension portion bent on the opposite side of the axial extension portion from the hollow portion and connected to the axial extension portion, and extending upward. A power transmission device characterized by:

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