Power transmission device

Abstract

To provide a power transmission device that can reduce a pressure difference between the inside and the outside of a case while restraining oil from evaporating.SOLUTION: A power transmission device according to the present invention comprises a gear mechanism for transmitting power, oil to be supplied to the gear mechanism, and a case housing the gear mechanism and the oil, and is used in a vacuum atmosphere. A breather plug for adjusting pressure inside the case is provided in the case. The breather plug comprises: a housing communicating with the inside and the outside of the case, and forming a flow passage having a labyrinth structure; and a movable lid covering an opening of the housing on the outside of the case.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a power transmission device. [Background technology]

[0002] Patent Document 1 discloses a differential device in which the inside of a differential cover is filled with oil. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-257214 Summary of the Invention [Problem to be solved by the invention]

[0004] When a power transmission device such as a differential gear is moved from the atmosphere into a vacuum, or when the temperature inside the power transmission device rises due to continuous operation, there is a concern that the pressure difference between the inside and outside of the case housing the gear mechanism that transmits power of the power transmission device may increase. Therefore, one possible means of reducing this pressure difference is to provide a breather plug. However, in a vacuum, a challenge arises: how to prevent the oil contained in the power transmission device case to lubricate the gear mechanism from evaporating from the inside of the case to the outside through the breather plug.

[0005] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a power transmission device that can reduce the pressure difference between the inside and outside of the case while suppressing oil evaporation. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the power transmission device of the present invention is a power transmission device that includes a gear mechanism that transmits power, oil that is supplied to the gear mechanism, and a case that houses the gear mechanism and the oil, and is used in a vacuum atmosphere, wherein a breather plug that adjusts the pressure inside the case is provided in the case, and the breather plug has a housing that communicates with the inside and outside of the case and forms a flow path with a labyrinth structure, and a movable lid that covers the opening of the housing on the outside side of the case. [Effects of the Invention]

[0007] The power transmission device according to the present invention has the advantage of being able to reduce the pressure difference between the inside and outside of the case while suppressing evaporation of oil. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a reducer, which is a power transmission device according to an embodiment. [Figure 2] FIG. 2 is a diagram showing an example of the shape of a breather plug provided in the reducer according to the embodiment. [Figure 3] FIG. 3 is a diagram showing the breather plug according to the embodiment in a state before pressure reduction. [Figure 4] FIG. 4 is a diagram showing a state in which the breather plug according to the embodiment is being depressurized. [Figure 5] FIG. 5 is a diagram showing the breather plug according to the embodiment in a state after pressure reduction. [Figure 6] FIG. 6 is a diagram showing another example of the shape of the breather plug provided in the reducer according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A power transmission device according to an embodiment of the present invention will be described below, but the present invention is not limited to the present embodiment.

[0010] FIG. 1 is a diagram showing a schematic configuration of a reducer 1, which is a power transmission device according to an embodiment. The reducer 1 according to the embodiment is a power transmission device, and is, for example, a compound planetary reducer used in an in-wheel motor. The reducer 1 is configured by connecting a planetary gear mechanism to an input shaft 11 and an output shaft 12 inside a case 10. The reducer 1 is configured with a sun gear 13 provided on the input shaft 11, a carrier 18 connected to the input shaft 11, a pinion shaft 15 supported by the carrier 18, a first pinion gear 14a rotatably supported on the pinion shaft 15 and meshing with the sun gear 13 on the radially inner side, a first ring gear 16 meshing with the first pinion gear 14a on the radially outer side of the first pinion gear 14a, and a second ring gear 19 meshing with a second pinion gear 14b integral with the first pinion gear 14a on the radially outer side of the second pinion gear 14b. First ring gear 16 is fixed to case 10. Second ring gear 19 is rotatably supported by a bearing provided in case 10. Second ring gear 19 has a ring gear flange 17, which is connected to output shaft 12. Oil used to lubricate various gears of the planetary gear mechanism is stored inside case 10, and oil seals 20 and 21 are provided between input shaft 11 and case 10, and between output shaft 12 and case 10, respectively.

[0011] The reducer 1 according to the embodiment is used, for example, in a vacuum atmosphere outside the reducer 1. A breather plug 3 that adjusts the pressure inside the reducer 1 (case 10) is provided in the case 10 of the reducer 1. The breather plug 3 is preferably attached to the case 10 of the reducer 1 on the top surface of the case 10, where the environmental temperature outside the reducer 1 is lower depending on the characteristics of the usage environment.

[0012] Here, there is a concern that the pressure difference between the inside of the reducer 1 (internal pressure P1) and the outside of the reducer 1 (external pressure P2) may increase when the reducer 1 according to the embodiment is moved from the atmosphere to a vacuum or due to an increase in the temperature inside the reducer 1 accompanying continuous operation. This increase in pressure difference may, for example, cause the oil seals 20 and 21 to be pressed against the input shaft 11 and the output shaft 12, resulting in increased wear and a deterioration in sealing performance. One method for reducing the pressure difference between the internal pressure P1 of the reducer 1 and the external pressure P2 of the reducer 1 is to use a breather plug 3, but suppressing oil evaporation through the breather plug 3 in a vacuum poses a challenge. Therefore, the reducer 1 according to the embodiment is provided with a breather plug 3 that can reduce the internal pressure P1 of the reducer 1 while suppressing oil evaporation through the breather plug 3. When the pressure difference between the internal pressure P1 of the reducer 1 and the external pressure P2 of the reducer 1 is large, the breather plug 3 opens a valve 33 to reduce the internal pressure P1 of the reducer 1. The valve 33 may be forced to open using a drive mechanism.

[0013] 2 is a diagram showing an example of the shape of the breather plug 3 provided in the reducer 1 according to the embodiment. The breather plug 3 has a housing 32 having large and small cylindrical portions that communicate between the case interior 101 and the case exterior 102, and a movable lid 31 having a cylindrical shape with a bottom that fits over the large-diameter cylindrical portion of the housing 32 and covers the opening of the housing 32 on the case exterior 102 side. A flow path 320 is formed in the small-diameter cylindrical portion of the housing 32, and has a labyrinth structure portion 360 in which a labyrinth-shaped weir portion 36 is provided.

[0014] The breather plug 3 also includes a valve 33 disposed inside the lid 41 and a coil spring 34 serving as an elastic member. The valve 33 includes a flange portion 331 and a cylindrical portion 322. The flange portion 331 can abut against an abutment portion 321 provided on the edge (end face) of the opening of the small-diameter cylindrical portion of the housing 32 on the case exterior 102 side. The cylindrical portion 322 is disposed in a bottomed cylindrical retaining member 35 provided on the bottom surface of the lid 41, with the end opposite the flange portion 331 in the axial direction, with the coil spring 34 compressed and deformed. The coil spring 34 biases the cylindrical portion 332 of the valve 33, applying an elastic force to the valve 33 in a direction that presses the flange portion 331 of the valve 33 against the abutment portion 321 of the housing 32. When the internal pressure P1 of the reducer 1 (inside the case 101) becomes equal to or greater than a predetermined pressure P3, the valve 33 opens the space between the inside 101 of the case and the outside 102 of the case, allowing gas to flow from the inside 101 of the case to the outside 102 of the case through the flow path 320 of the housing 32.

[0015] Fig. 3 is a diagram showing the state of the breather plug 3 according to the embodiment before pressure reduction. In the breather plug 3 according to the embodiment, when the internal pressure P1 of the reducer 1 (interior 101 of the case) is greater than the external pressure P2 of the reducer 1 (exterior 102 of the case) and is less than the predetermined pressure P3 at which the valve 33 operates, the elastic force of the coil spring 34 causes the flange portion 331 of the valve 33 to abut against the abutment portion 321 of the housing 32, as shown in Fig. 3. This causes the breather plug 3 to achieve a closed state of the valve 33, in which the interior 101 of the case is isolated from the exterior 102 of the case.

[0016] FIG. 4 is a diagram showing a state of the breather plug 3 according to the embodiment during pressure reduction. In the breather plug 3 according to the embodiment, when the pressure difference between the internal pressure P1 and the external pressure P2 of the reducer 1 (inside the case 101) is large and the internal pressure P1 of the reducer 1 (inside the case 101) is greater than the predetermined pressure P3 at which the valve 33 operates, the flange portion 331 of the valve 33 moves in a direction away from the abutting portion 321 of the housing 32 against the elastic force of the coil spring 34, as shown in FIG. 4 . As a result, in the breather plug 3, a gap is generated between the flange portion 331 and the abutting portion 321, and the valve 33 is opened, opening the case interior 101 and the case exterior 102. Gas containing oil components evaporated from the case interior 101 is discharged to the case exterior 102 through the flow path 320 of the housing 32, the gap between the flange portion 331 and the abutting portion 321, and the gap between the inner circumferential surface of the lid 31 and the outer circumferential surface of the housing 32. As a result, the internal pressure P1 of the reducer 1 (inside the case 101) is reduced.

[0017] When the valve 33 is open, the temperature T1 of the wall surface of the labyrinth structure portion 360 is lower than the temperature T2 inside the reducer 1 (inside the case 101). Therefore, the gas flowing through the flow path 320 of the housing 32 is cooled by the wall surface of the labyrinth structure portion 360, the oil component contained in the gas becomes liquid, and the oil 4 is separated from the gas. As a result, the breather plug 3 according to this embodiment can prevent the oil 4 from evaporating from the inside of the reducer 1 (inside the case 101) through the breather plug 3 and being discharged to the outside of the reducer 1 (outside the case 102) and being lost. In addition, the weir portion 36 of the labyrinth structure portion 360 is inclined toward the bottom surface of the case 10, making it easier for the oil 4 to fall from the weir portion 36 toward the bottom surface of the case 10. This allows the oil 4 adhering to the wall surface of the labyrinth structure portion 360 (flow path 320) and the weir portion 36 to be smoothly returned to the inside of the reducer 1 (inside the case 101) under low gravity.

[0018] 5 is a diagram showing a state of the breather plug 3 according to the embodiment after pressure reduction. In the breather plug 3 according to the embodiment, when the internal pressure P1 of the reducer 1 (inside the case 101) is reduced and the pressure difference between the internal pressure P1 of the reducer 1 (inside the case 101) and the external pressure P2 of the reducer 1 (outside the case 102) is smaller than before pressure reduction shown in FIG. 3 or when the pressure difference between the internal pressure P1 of the reducer 1 (inside the case 101) and the external pressure P2 of the reducer 1 (outside the case 102) becomes substantially zero, the flange portion 331 of the valve 33 abuts against the abutment portion 321 of the housing 32 due to the elastic force of the coil spring 34, as shown in FIG. 5. As a result, in the breather plug 3, a closed state of the valve 33 is achieved in which the case interior 101 and the case exterior 102 are blocked from each other.

[0019] As described above, the reducer 1 according to the embodiment is provided with the breather plug 3, thereby making it possible to reduce the pressure difference between the inside of the reducer 1 (inside the case 101) and the outside of the reducer 1 (outside the case 102), which occurs when the reducer 1 is moved from the atmosphere to a vacuum, for example. In particular, since the flow path 320 of the breather plug 3 has the labyrinth structure portion 360, when a gas containing oil components flows through the flow path 320, the gas is cooled by the wall surface of the labyrinth structure portion 360, causing the oil components to become liquid, and it is possible to prevent the oil 4 from evaporating and being discharged to the outside of the reducer 1 (outside the case 102).

[0020] In this way, the reducer 1 according to the embodiment can reduce the pressure difference between the inside of the reducer 1 (inside the case 101) and the outside of the reducer 1 (outside the case 102) while suppressing the evaporation of the oil 4.

[0021] 6, the breather plug 3 provided in the reducer 1 according to the embodiment may have a structure in which a labyrinth structure portion 360 having a labyrinth shape and provided with a dam portion 36 and a lid 31 are integrated or fastened together via a connecting portion 37. In this case, the wall surfaces of the lid 31 and the labyrinth structure portion 360 are preferably made of a material with high thermal conductivity, such as copper or aluminum. [Explanation of symbols]

[0022] 1 Reducer 3 Breather plug 4. Oil 10 cases 31 Lid 32 Housing 33 Valve 34 coil spring 35 Retaining member 36 Weir 37 Connecting part 101 Inside the case 102 Case exterior 320 Flow path 331 Flange 332 Cylinder 360 Labyrinth structure

Claims

[Claim 1] a gear mechanism for transmitting power; Oil supplied to the gear mechanism; a case that accommodates the gear mechanism and the oil; Equipped with A power transmission device used in a vacuum atmosphere, A breather plug for adjusting the pressure inside the case is provided in the case, The breather plug is a housing communicating with the inside and outside of the case and forming a flow path with a labyrinth structure; a movable lid that covers an opening on the housing's case exterior side; A power transmission device comprising:

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