Rotor shaft

Abstract

To remove the risk of inhibiting liquefaction of a working fluid in a heat-dissipation portion during low-speed rotation or tilting of a rotor.SOLUTION: A rotor shaft 1 forming a rotor R of a rotary electric machine M includes a rotor core 11 and rotor shafts 12 and 13 on a common center axis, the rotor core 11 has a boiling part S1 filled with a working fluid F, and one of the rotor shafts 12 has an intermediate part S2 communicating with the boiling part S1 and a condensation part S3 communicating with the intermediate part S2. In the boundary between the boiling part S1 and the intermediate part S2, the inner diameter R2a of the intermediate part S2 is set smaller than the inner diameter R of the boiling part S1, so as to prevent inflow of the working fluid F from the boiling part S1 to the condensation part S3 due to the step between the boiling part S1 and the intermediate part S2 and to realize stable operation even when a rotational speed or posture of the rotor R changes.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a rotor shaft that constitutes a rotor of a rotating electrical machine, and more particularly to a rotor shaft having a boiling cooling function. [Background technology]

[0002] A conventional rotor shaft with a boiling cooling function is described, for example, in Patent Document 1. Patent Document 1 describes a configuration in which a heat pipe is housed inside a rotatably supported shaft-shaped container. The heat pipe has a heat receiving portion as the main portion, an intermediate portion connected to one end of the heat receiving portion, and a heat dissipation portion communicating with the intermediate portion. The heat receiving portion and the intermediate portion have a constant inner diameter along the axial direction, and a wick for holding a working fluid is disposed on their inner circumferential surfaces. The heat dissipation portion protrudes outside the rotor and has a tapered structure in which the inner diameter gradually decreases from the intermediate portion to the tip.

[0003] The rotor shaft absorbs heat generated by the rotor in the heat receiving section, vaporizes the working fluid held in the wick, and cools the rotor with the heat of vaporization.The rotor shaft then radiates the heat from the heat receiving section to the outside in the heat radiating section, and causes film condensation in which the inner surface of the heat radiating section is covered with a liquid film of the working fluid, liquefying the vapor, and then returns the liquid to the heat receiving section by centrifugal force and the tapered structure, repeating this cycle. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-102616 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the conventional rotor shaft described above, when the centrifugal force acting on the liquid in the heat dissipation section becomes dominant over gravity when the rotor rotates at low speed, the liquid may not adhere to the inner wall of the heat dissipation section, which may hinder good film condensation. Also, in the rotor shaft described above, when the rotor rotates at low speed and the heat dissipation section is tilted downward, the working fluid may accumulate between the heat receiving section and the heat dissipation section, causing the liquid film in the heat dissipation section to become thick and hindering film condensation.

[0006] The present invention has been made in consideration of the above-mentioned conventional situation, and aims to provide a rotor shaft that has a boiling cooling function due to its structure with a boiling section and a condensing section, and that prevents the flow of working fluid from the boiling section to the condensing section, thereby achieving stable operation even when the rotation speed or attitude of the rotor changes. [Means for solving the problem]

[0007] The rotor shaft according to the present invention constitutes a rotor for a rotating electric machine and includes a rotor core and a rotor shaft connected to both ends of the rotor core, arranged coaxially. The rotor core has a boiling portion therein, which is a cylindrical space filled with a working fluid. One of the rotor shafts has an intermediate portion therein, which is a cylindrical space communicating with the boiling portion, and a condensing portion therein, which is also a cylindrical space communicating with the intermediate portion. The rotor shaft is characterized in that, at the boundary between the boiling portion and the intermediate portion, the inner diameter of the intermediate portion is smaller than the inner diameter of the boiling portion. [Effects of the Invention]

[0008] By adopting the above-mentioned configuration, the rotor shaft of the present invention has a step formed between the boiling section with a large inner diameter and the middle section with a small inner diameter in a rotor shaft equipped with a boiling cooling function, thereby preventing the flow of working fluid from the boiling section to the condensation section and achieving stable operation even when the rotor rotation speed or attitude changes. [Brief explanation of the drawings]

[0009] [Figure 1]1A is a cross-sectional explanatory view showing a first embodiment of a rotor shaft, and FIG. 1B is a cross-sectional view taken along line AA in FIG. 1A. [Figure 2] 1A is a cross-sectional view showing a rotor shaft rotating at high speed in a horizontal position, and FIG. 1B is a cross-sectional view showing a rotor shaft rotating at low speed in an inclined position. [Figure 3] 1A is a cross-sectional view showing a rotor shaft according to a second embodiment, and FIG. 1B is a cross-sectional view showing a rotor shaft according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] First Embodiment The rotor shaft 1 shown in Fig. 1(A) constitutes the rotor R of a motor M, which is a rotating electrical machine. Note that Fig. 1(A) is a cross-sectional view of the motor with one half of the stator S omitted, and Fig. 1(B) is a cross-sectional view taken along the line AA in Fig. 1(A).

[0011] The motor M comprises a rotor R arranged on the axis and a stator S arranged on the outer periphery of the rotor R, with bearings B, B interposed between the rotor R and the stator S. The rotor R comprises a rotor shaft 1 and a magnet 2 fixed to its outer periphery. The stator S comprises a housing 3 and a coil 4 arranged on its inner periphery.

[0012] The rotor shaft 1 is equipped with a hollow rotor core 11 with magnets 2 arranged on its outer circumferential surface, and rotor shafts 12 and 13 connected to both ends of the rotor core 11, all on the same axis. The rotor shafts 12 and 13 have large diameter portions 12A and 13B on the rotor core 11 side and small diameter portions 12B and 13B on the opposite side of the rotor core 11, and at least one of the rotor shafts 12 (left in FIG. 1) has a hollow shape with the tip of the small diameter portion 12B closed.

[0013] The rotor shaft 1 has a boiling portion S1, which is a cylindrical space filled with a working fluid F, inside the rotor core 11. The rotor shaft 1 also has, in one hollow rotor shaft 12, a middle portion S2, which is a cylindrical space communicating with the boiling portion S1, inside the large diameter portion 12A, and a condensing portion S3, which is a cylindrical space communicating with the middle portion S2, inside the small diameter portion 12B. As a result, the boiling portion S1, the middle portion S2, and the condensing portion S3 are arranged coaxially and communicate with each other, and are arranged concentrically with the axis C of the rotor shaft 1, as shown in FIG. 1(B).

[0014] Furthermore, the rotor shaft 1 is rotatably held by bearings B at the large diameter portions 12A and 13A of both rotor shafts 12 and 13, and a cooler 5 is disposed on the outside of the small diameter portion 12B of one rotor shaft 12, which forms the condenser section S3. The illustrated cooler 5 is a water jacket that includes piping 7 for circulating a cooling liquid 6 and rotatably passes through the small diameter portion 12B of the rotor shaft 12 while ensuring watertightness, and may also include fins for heat dissipation.

[0015] The rotor shaft 1 has a boiling portion S1 with a constant inner diameter R1 along the axis C, and an inner diameter R2a of the intermediate portion S2 at the boundary between the boiling portion S1 and the intermediate portion S2 is smaller than the inner diameter R1 of the boiling portion S1 (R1>R2a). In the illustrated example, the inner diameter R2a of the intermediate portion S2 is approximately one-third of the inner diameter R1 of the boiling portion S1, but is not particularly limited thereto, and an appropriate value can be determined based on the volume of the boiling portion S1, the volume of the working fluid F, etc.

[0016] Further, as a more preferred embodiment, the rotor shaft 1 has an inner diameter R2b of the hollow portion S2 that is greater than or equal to the inner diameter R3a of the condensation portion S3 (R2b≧R3a) at the boundary between the intermediate portion S2 and the condensation portion S3, and gradually increases toward the boiling portion S1 side. That is, the intermediate portion S2 has a configuration in which the inner diameter R2a on the boiling portion S1 side is larger than the inner diameter R2b on the condensation portion S1 side (R2b<R2a), and has a tapered structure in which the inner diameter gradually increases from the condensation portion S1 to the boiling portion S1.

[0017] Furthermore, as a more preferred embodiment, the rotor shaft 1 has a configuration in which the inner diameter of the condensation portion S3 is the same along the direction of the axis C or gradually increases toward the intermediate portion R2 side (the inner diameter R3b of the tip portion≦the inner diameter R3a of the intermediate portion S2 side). That is, the condensation portion S3 may have a constant inner diameter along the direction of the axis C or a tapered structure in which the inner diameter gradually increases from the tip portion to the intermediate portion S2.

[0018] From the above, for the rotor shaft 1, the inner diameter R1 of the boiling portion S1, the inner diameter R2a on the boiling portion S1 side of the intermediate portion S2, the inner diameter R2b on the condensation portion 3 side of the intermediate portion S2, the inner diameter R3a on the intermediate portion S2 side of the condensation portion S3, and the inner diameter R3b of the tip portion of the condensation portion S3 have a relationship of R1>R2a>R2b≧R3a≧R3b.

[0019] In the above relationship of the inner diameter sizes, at the boundary between the intermediate portion S2 and the condensation portion S3, the case where the inner diameter R2b of the intermediate portion S2 is equal to the inner diameter R3a of the condensation portion S3, and both the intermediate portion S2 and the condensation portion S3 are tapered structures, or the case where a step occurs between the intermediate portion S2 and the condensation portion S3 is included. When both are tapered structures, it is also possible to set their inclinations at the same angle or different angles.

[0020] Furthermore, as a more preferred embodiment, as shown in Fig. 1(B), the rotor shaft 1 can adopt a configuration in which the volume V1 of the working fluid F filled in the boiling portion S1 is smaller than the reference volume V2 calculated based on the difference between the inner diameter R1 of the boiling portion S1 and the inner diameter R2a of the intermediate portion S2 and the axial length of the boiling portion S1 (V1<V2).

[0021] In this case, the volume V1 of the working fluid F includes an amount that allows the liquid level (shown by a virtual line in FIG. 1) to reach a depth near the opening edge of the middle portion S2 in the boiling portion S1. However, the volume V of the working fluid is an amount necessary for boiling cooling, and also takes into account the inclination of the vehicle body if the motor M is mounted on a vehicle, and as an example, is an amount that provides a depth of less than half the reference volume V2 as shown in the illustrated example.

[0022] When the motor M is driven, the rotor shaft 1 having the above configuration forms a liquid film of the working fluid F on the inner surface of the boiling section S1 due to centrifugal force, as shown in Figure 2(A), and the heat generated by the rotor R is absorbed by the boiling section S1, vaporizing the working fluid F, and the heat of vaporization cools the rotor R.

[0023] The rotor shaft 1 then introduces steam from the boiling section S1 through the intermediate section S2 to the condensing section S3, where it dissipates heat and liquefies the steam by causing film condensation in which the inner surface of the condensing section S3 is covered with a liquid film of the working fluid F, and then passes the liquid through the intermediate section S2 and returns it to the boiling section S1, repeating this cycle.

[0024] At this time, a step is formed in the rotor shaft 1 between the boiling section S1, which has a relatively large inner diameter R1, and the intermediate section S2, which has a relatively small inner diameter R2a. As a result, even when the rotation speed of the rotor R decreases and the rotor shaft 1 is tilted so that the condensation section S3 is on the lower side as shown in Figure 2(B), the step structure prevents the working fluid F in the boiling section S1 from flowing into the intermediate section S2 or the condensation section S3.

[0025] In this way, the rotor shaft 1 equipped with the boiling cooling function prevents the working fluid F from flowing from the boiling section S1 to the condensation section S3 by the step formed between the boiling section S1 and the intermediate section S2, thereby realizing stable operation even when the rotation speed or posture of the rotor R changes.

[0026] Furthermore, the rotor shaft 1 has a tapered structure in which the hollow section S2 gradually increases in inner diameter in the direction from the condensation section S3 to the boiling section S1. Therefore, the centrifugal force generated during rotation can promote the flow of the working fluid F liquefied in the condensation section S3 back to the boiling section S1, thereby achieving further improvement in operational stability.

[0027] Furthermore, the condensation section S3 of the rotor shaft 1 has a tapered structure in which the inner diameter is constant along the axial direction or gradually increases in the direction from the tip to the intermediate section S2. This allows the centrifugal force generated when the rotor shaft 1 rotates to promote the flow of the working fluid F liquefied in the condensation section S3 toward the intermediate section S2, and combined with the effect of the tapered structure of the intermediate section S2 described above, this further promotes the flow of the working fluid F back to the boiling section S1, thereby achieving further improvement in operational stability.

[0028] Furthermore, by setting the volume V1 of the working fluid F to a value smaller than the reference volume V2, the rotor shaft 1 can ensure sufficient volume in the boiling section S1, thereby preventing the working fluid F from overflowing and flowing toward the condensation section S3.

[0029] Furthermore, in a rotating electric machine (motor M) equipped with the above-mentioned rotor shaft 1, the rotor shaft 1 acts as a heat pipe with a boiling cooling function, regardless of the rotation speed, inclination, etc., and the rotor R can be cooled efficiently.

[0030] 3A and 3B are diagrams illustrating second and third embodiments of a rotor shaft according to the present invention. In the following embodiments, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed descriptions thereof will be omitted.

[0031] Second Embodiment 3(A) has the same basic configuration as the first embodiment, and the boiling portion S1 has an annular body 21 that protrudes from the periphery of the intermediate portion S2 in the direction of the axis C. The material of the annular body 21 is not limited, but it may be made of metal similar to that of the rotor core 1, for example, and is disposed concentrically with the opening of the intermediate portion S2 within the boiling portion S1.

[0032] The rotor shaft 1 having the above configuration provides the same functions and effects as the first embodiment, and the annular body 21 can more reliably prevent the working fluid F from flowing toward the intermediate section S2 without impeding the flow of the working fluid F liquefied in the condensation section S3 back to the boiling section 1.

[0033] <Third embodiment> The rotor shaft 1 shown in FIG. 3(B) has the same basic configuration as that of the first embodiment, and The boiling section S1 has an annular body 22 that extends from the peripheral edge of the intermediate section S2 over the entire length in the direction of the axis C. The annular body 22 is, for example, a network structure or a porous structure, and is permeable to the working fluid F.

[0034] The rotor shaft 1 having the above configuration allows the working fluid F vaporized in the boiling section S1 to pass through the annular body 22 and be introduced into the intermediate section S2 and the condensation section S3, and allows the working fluid F liquefied in the condensation section S3 to return to the boiling section S1 and be passed through the annular body 22.

[0035] The rotor shaft 1 having the above configuration provides the same functions and effects as the first embodiment, and does not impede the flow of the working fluid F liquefied in the condensation section S3 back to the boiling section S1, and the annular body 22 more reliably prevents the working fluid F from flowing toward the intermediate section S2, thereby achieving further improvement in operational stability.

[0036] The configuration of the rotor shaft according to the present invention is not limited to the above-described embodiments, and can be modified as appropriate within the scope of the present invention. [Explanation of symbols]

[0037] 1 rotor shaft 11 Rotor core 12,13 Rotor shaft 21,22 Cycloids M motor (rotating electric machine) S stator S1 Boiling part S2 middle part S3 Condenser R rotor R1 Inner diameter of boiling part R2a, R2b Inner diameter of middle part R3a, R3b Inner diameter of condensation section V1 Volume of working fluid V2 Reference volume

Claims

1. A rotor shaft constituting a rotor of a rotating electric machine, a rotor core and a rotor shaft connected to both ends of the rotor core, the rotor core being coaxially arranged; the rotor core has a boiling portion therein which is a cylindrical space filled with a working fluid, and one of the rotor shafts has an intermediate portion therein which is a cylindrical space communicating with the boiling portion, and a condensation portion therein which is a cylindrical space communicating with the intermediate portion, A rotor shaft, characterized in that, at a boundary between the boiling portion and the intermediate portion, the inner diameter of the intermediate portion is smaller than the inner diameter of the boiling portion.

2. 2. The rotor shaft according to claim 1, wherein the inner diameter of the hollow portion at the boundary between the intermediate portion and the condensation portion is equal to or greater than the inner diameter of the condensation portion and gradually increases toward the boiling portion.

3. 3. The rotor shaft according to claim 2, wherein the inner diameter of the condensation section is constant along the axial direction or gradually increases toward the intermediate section.

4. 4. The rotor shaft according to claim 3, wherein the volume of the working fluid filled in the boiling portion is smaller than a reference volume calculated based on the difference between the inner diameter of the boiling portion and the inner diameter of the intermediate portion and the axial length of the boiling portion.

5. 5. The rotor shaft of claim 4, wherein the boiling portion comprises an annular body projecting axially from the periphery of the intermediate portion.

6. 6. The rotor shaft according to claim 5, wherein the annular body is permeable to the working fluid and is disposed axially across the boiling portion.

7. A rotating electric machine comprising: a rotor including the rotor shaft according to any one of claims 1 to 6; and a stator corresponding to said rotor.

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