Power transmission device

Abstract

To provide a power transmission device capable of reducing wear of a sliding part in vacuum atmosphere.SOLUTION: A power transmission device is used in vacuum atmosphere, and comprises an oxygen supply pipe that communicates the inside and outside of a case of a speed reducer. At one end of the oxygen supply pipe arranged outside the case, an oxygen supply port is formed. At the other end of the oxygen supply pipe arranged inside the case, an oxygen discharge port is formed. The oxygen discharge port is immersed in lubricant stored in an oil pan in the case.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a solid lubrication type rolling bearing for use in a vacuum environment such as outer space. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-106559 Summary of the Invention [Problem to be solved by the invention]

[0004] The method using a solid lubricant as disclosed in Patent Document 1 can lubricate the sliding parts but cannot cool them, which makes it particularly disadvantageous for use in equipment with a high sliding load or a high number of sliding movements, or in a vacuum environment where heat dissipation is difficult.

[0005] It is also possible to use a liquid lubricating oil instead of a solid lubricant, but in a vacuum environment, the film-forming reaction of the anti-wear agent in the lubricating oil is less likely to proceed, which may result in increased wear in the sliding parts.

[0006] The present disclosure has been made in view of the above, and has an object to provide a power transmission device that can reduce wear of sliding parts in a vacuum atmosphere. [Means for solving the problem]

[0007] The power transmission device according to the present disclosure is used in a vacuum atmosphere and includes an oxygen supply pipe that connects the inside and outside of a reducer case, with an oxygen supply port formed at one end of the oxygen supply pipe that is located outside the case, and an oxygen outlet formed at the other end of the oxygen supply pipe that is located inside the case, and the oxygen outlet immersed in lubricating oil stored in an oil pan inside the case. [Effects of the Invention]

[0008] According to the present disclosure, by supplying oxygen to the lubricating oil, a protective coating is regenerated on the gear surface inside the case even in a vacuum atmosphere, thereby reducing friction during sliding and achieving a longer service life. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view showing an example of the configuration of a power transmission device according to an embodiment. [Figure 2] FIG. 2 is a front view showing an example of the configuration of the outlet of the oxygen supply pipe shown in part A of FIG. [Figure 3] FIG. 3 is a graph showing an example of elements detected on the gear surface after sliding in air and in vacuum. [Figure 4] FIG. 4 is a graph showing an example of the relationship between the amount of oxygen in the power transmission device according to the embodiment and the thickness of the protective coating. DETAILED DESCRIPTION OF THE INVENTION

[0010] A power transmission device according to an embodiment of the present disclosure will be described with reference to the drawings. Note that the components in the following embodiments include those that are easily replaceable by those skilled in the art, or those that are substantially identical.

[0011] The configuration of a power transmission device according to an embodiment will be described with reference to Figures 1 and 2. The power transmission device is a compound planetary speed reducer used in, for example, an in-wheel motor. The power transmission device is used in a vacuum environment such as outer space, or in an oxygen-poor environment.

[0012] The power transmission device 1 includes a case 11, a sun gear 12, a pinion gear 13, a front ring gear 14, a rear ring gear 15, a shaft 16, bearings 17, 18, 19, 20, 21, and 22, an oxygen supply pipe 23, and an oil pan 24.

[0013] Case 11 accommodates the components that make up the reducer. Sun gear 12 meshes with pinion gear 13. Sun gear 12 is supported by bearings 17. Pinion gear 13 meshes with sun gear 12, front ring gear 14, and rear ring gear 15.

[0014] The front ring gear 14 meshes with the pinion gear 13. The rear ring gear 15 meshes with the pinion gear 13. The rear ring gear 15 is supported by bearings 19, 21, and 22. The shaft 16 extends in the axial direction and is supported by a bearing 18.

[0015] The oxygen supply pipe 23 is for supplying external oxygen into the case 11. The oxygen supply pipe 23 is formed in a cylindrical shape and communicates with the inside and outside of the case 11. An oxygen supply port 231 is formed at one end of the oxygen supply pipe 23 located outside the case 11. An oxygen outlet 232 is formed at the other end of the oxygen supply pipe 23 located inside the case 11 (see part A in FIG. 1).

[0016] The discharge port 232 is immersed in the lubricating oil O stored in the oil pan 24 inside the case 11. The discharge port 232 has a mesh structure as shown in Fig. 2. The oil pan 24 is provided on the radially outer side of the case 11. The oil pan 24 stores the lubricating oil O.

[0017] In the power transmission device 1 according to the embodiment, lubrication is performed using lubricating oil O, which is expected to have a cooling effect, as a lubricant for parts that slide under high load and high frequency in a vacuum environment such as outer space. It is generally believed that the lubricating effect of lubricating oil O on the sliding parts of each gear and each bearing is achieved by the anti-wear agent contained in lubricating oil O reacting with oxygen to form a protective film on the sliding parts, thereby preventing wear on the sliding parts.

[0018] On the other hand, in a vacuum environment such as outer space, the absence of oxygen in the atmosphere can worsen the reaction of the anti-wear agent in the lubricating oil O, which requires oxygen molecules, and this can lead to increased wear in the sliding parts.

[0019] Figure 3 shows an example of elements detected on the gear surface after sliding in air and vacuum. Specifically, Figure 3 shows the results of an analysis of the gear's surface layer (15 nm) using hard X-ray photoelectron spectroscopy (HAXPES). As shown in Figure 3, in a vacuum, the proportion of P, the main component of the anti-wear agent, is smaller than in air, and the amount of iron (Fe), a component that makes up the base (gear material), is higher, making it difficult for a protective coating to form.

[0020] Therefore, in the power transmission device 1 according to the embodiment, an oxygen supply pipe 23 is provided that communicates the inside and outside of the case 11, thereby supplying oxygen from outside the atmosphere to the sliding parts (sliding parts of each gear and each bearing) during operation of the power transmission device 1. This promotes the reaction of the anti-wear agent in the lubricating oil O and promotes the formation of a protective film.

[0021] 1, in the power transmission device 1, an outlet 232 for oxygen generated externally (for example, by a water electrolysis device) is installed on the wall surface of the oil pan 24. Furthermore, as shown in FIG. 2, by making the outlet 232 have a mesh structure, the oxygen bubbles are made finer (the surface area is increased), making it easier for the oxygen to dissolve in the lubricating oil O.

[0022] Here, Fig. 4 shows an example of the relationship between the amount of oxygen in the power transmission device 1 according to the embodiment and the thickness of the protective coating. As shown in Fig. 4, when the amount of oxygen in the device is high, a thick protective coating is formed on the base (iron) just as in the atmosphere. Once formed, the protective coating does not disappear immediately, but is gradually consumed by repeated sliding.

[0023] In this way, the protective coating made by the anti-wear agent is gradually consumed by sliding, so by supplying oxygen into the lubricating oil O at the appropriate time, a new protective coating can be generated and its thickness can be maintained. Furthermore, by supplying oxygen into the lubricating oil O at the appropriate time, the maximum effect (generation of the protective coating) can be achieved with the minimum amount of oxygen. This improves reliability for long-term operation in a vacuum atmosphere. Furthermore, maintaining a protective coating with an appropriate thickness can extend the life of the sliding parts.

[0024] The supply of oxygen to the lubricating oil O can be controlled by, for example, a motor control ECU (Electronic Control Unit) mounted on the vehicle. In this case, the timing of supplying oxygen to the lubricating oil O may be controlled based on, for example, the mileage of the vehicle, which is closely related to the consumption of the protective coating.

[0025] According to the power transmission device of the embodiment described above, by supplying oxygen to the lubricating oil O, a protective coating is regenerated on the sliding parts inside the case 11 (for example, the surfaces of each gear, each bearing, etc.) even in a vacuum atmosphere, thereby reducing friction during sliding and achieving a longer life.

[0026] Further advantages and modifications will readily occur to those skilled in the art. Thus, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. [Explanation of symbols]

[0027] 1 Power transmission device 11 cases 12 Sun gear 13 Pinion gear 14 Front ring gear 15 Rear ring gear 16 shaft 17,18,19,20,21,22 Bearings 23 Oxygen supply piping 231 Supply port 232 Outlet 24 Oil pan O Lubricating oil

Claims

[Claim 1] Used in a vacuum environment, an oxygen supply pipe communicating with the inside and outside of the reducer case; an oxygen supply port is formed at one end of the oxygen supply pipe disposed outside the case; an oxygen outlet is formed at the other end of the oxygen supply pipe disposed inside the case, The oxygen exhaust port is immersed in lubricating oil stored in an oil pan inside the case. Power transmission device.

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