JPH04304948A - Cooling device for rotating shaft - Google Patents

Abstract

PURPOSE:To increase the amount of heat transport by increasing the amount of the return flow of the heat medium of a heat pipe which cools a rotating shaft. CONSTITUTION:The axial space 1A of a heat pipe 1 provided within a rotating shaft 10 and having a heat medium enclosed therein is larger in diameter at its portion to be heated than at its portion to be cooled, and both of the portions are communicated with each other by a tapered portion and the heat medium condensed is allowed to flow by centrifugal force from the small diameter portion to be cooled to the large diameter portion to be heated.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling device for a rotating shaft of a motor for rotating the main shaft of a machine tool, an engine shaft, or the like.

0002

[Prior Art] A heat pipe is sometimes used to cool the rotating shaft of a motor used to rotate the main shaft of a conventional machine tool. A certain straight, double-tube structure is used.

0003

[Problems to be Solved by the Invention] The temperature of the rotating shaft of a motor increases mainly due to heat generation in the rotor and stator as well as heat generation in the bearings, causing problems such as seizure of the bearings and thermal expansion of the shaft length. In order to intensively and efficiently release this heat from a partial region in the longitudinal direction of the shaft, a heat pipe may be used within the rotating shaft as described above. However, heat pipes used in conventional rotating shafts are designed with restrictions on the outermost diameter and have a straight double-tube structure in order to pass bolts on the central shaft, so heat pipes are enclosed in a heat medium. The axial cross-sectional area of the space becomes small and is not sufficient to transport all the heat generated by the rotating shaft in the axial direction. Therefore,
There is a problem in that it cannot be used for rotating shafts that are subject to high heat loads.

The present invention is an attempt to solve the above-mentioned problems in the conventional cooling device for a rotating shaft using a heat pipe.

[0005]

[Means for Solving the Problems] The present invention provides a cooling device for a rotating shaft in which a heat pipe for cooling is provided inside the rotating shaft. The diameter of the heated portion of the space is increased, the diameter of the cooled portion of the space is decreased, and a tapered portion connects the space.

[0006]

[Operation] In the present invention, when the rotating shaft rotates, the heating medium in the heat pipe inside the rotating shaft is subjected to centrifugal force, and flows toward the larger radius in the tapered part of the space of the heat pipe that accommodates the heating medium. try For this reason, in the axial direction of the heat pipe, the heat medium liquid condensed on the inner surface of the cooled part of the space forming the heat pipe with a small inner diameter,
The air flows back to the inner surface of the heated portion of the space forming a heat pipe with a large radius.

[0007] The limit of the heat transport capacity of the heat pipe used for the rotating shaft is determined by the amount of heat medium sealed in due to the cross-sectional area of the space in which the heat medium is accommodated, and is therefore determined by the maximum recirculation flow rate of the heat medium. The recirculation flow rate of the heat medium is determined by the difference in water head between the liquid on the condensing surface and the evaporating surface of the heat pipe.In conventional straight heat pipes, this difference in water head was determined only by the difference in liquid film thickness. In contrast, in the present invention, since the small-diameter heating side and the large-diameter cooling side are connected by a tapered part, the flow caused by centrifugal force due to the difference in inner diameter is replaced by a flow due to the difference in liquid film thickness. , the reflux flow rate is further increased and therefore the maximum heat transport amount is increased.

[0008]

[Embodiment] An embodiment of the present invention is shown in FIG. Rotating axis 1
A rotor 4 is attached to the outer periphery of the rotor 4.
A rotating shaft 10 is supported by bearings 6, 6 on both sides. A stator 5 is provided surrounding the rotor 4, and the rotor 4 and stator 5 form a motor, and a rotating shaft 10 is rotated by the action of the motor. The right end of the rotating shaft 10 in FIG. 1 protrudes outward from the bearing 6, and the outer periphery of the rotary shaft 10 is cooled by applying water or air flow 7 from the outside. A space 1A is formed in the rotating shaft 10, which is concentric with the axis of the rotating shaft 10 and extends in the axial direction from the portion where the water or air flow hits to near the other bearing, and the heating medium 3 is in the space 1A. The heat pipe 1 is configured by being sealed. Space 1A is the water or air flow 7
It has a small diameter on the side it touches, and a large diameter on the opposite side, and is formed into a truncated conical shape that tapers smoothly linearly in the axial direction of the rotating shaft 10.

In this embodiment, the heat generated by the rotor 4 and the stator 5 heats and evaporates the liquid heat medium in the space 1A in this portion to form the vapor portion 3. On the other hand, the evaporated heat medium is cooled and condensed in the part where the water or air flow hits (the end part in Figure 1), and the liquid phase part 2
form.

In this embodiment, the inner surface of the space A where the heating medium condenses has a small diameter, and the inner surface of the space A where the heating medium evaporates has a large diameter. Since the heating medium forming the condensed liquid phase portion 2 is subjected to centrifugal force when the rotating shaft rotates, it tends to flow through the tapered portion in the direction of the larger diameter. In addition to the water head difference due to the difference in the liquid film between the cooled part and the heated part, the condensed heat medium is added with the force due to this centrifugal force, and the condensed heat medium moves leftward along the inner surface of the space 1A in FIG. Move to.

Therefore, in this embodiment, the flow rate of the circulating heat medium can be increased, and thereby the amount of heat transport can be increased.

FIG. 2 shows a rotary shaft with a motor to which the heat pipe according to the present embodiment is attached and a rotary shaft with a motor to which a conventional heat pipe is attached so that the temperature of the cooling side end is 100°C. While adjusting the cooling strength, the rotor,
The results of measuring the temperature at point A of the bearing in FIG. 1 when the heat load on the stator side is changed at a constant rotation speed are shown. Note that the axial length of these rotating shafts is 350 mm,
Methanol was used as the heat medium, and the inner diameter of the heat pipe (the maximum inner diameter in this example) was 40 mmφ.

FIG. 2 shows that the rotary shaft according to this embodiment has a higher thermal load from the rotor, which causes the bearing temperature to rise rapidly, and therefore has a higher critical thermal load that causes bearing seizure.

Although the above-mentioned embodiment has a linear tapered portion, in the present invention, a tapered portion other than a linear portion can be provided, and a smooth portion is preferable.
Further, the cross section of the space forming the heat pipe perpendicular to the rotation axis can also have a shape other than circular.

[0015]

Effects of the Invention The present invention increases the diameter of the heated portion of the space forming the heat pipe that accommodates the heat medium and extends in the axial direction of the rotating shaft, and decreases the diameter of the cooled portion, and creates a tapered shape between them. By connecting the parts, the centrifugal force causes the heating medium to flow from the part to be cooled to the part to be heated, increasing the circulation flow rate of the heating medium and increasing the amount of heat transport. Can be done.

[0016] Therefore, seizure of the bearing and the like can be prevented and thermal expansion of the rotating shaft can be reduced.

[Brief explanation of drawings]

FIG. 1 is a structural diagram of an embodiment of the present invention.

FIG. 2 is a graph showing the effect of reducing the amount of bearing temperature rise according to the same example.

[Explanation of symbols]

1 Heat pipe 1A Heat pipe space 2 Liquid phase part of heating medium 3. Steam part of heating medium 4 Motor rotor 5 Motor stator 6 Bearing 7 Water or air flow 10 Rotation axis

Claims (1)

[Claims] 1. A cooling device for a rotating shaft in which a heat pipe for cooling is provided inside the rotating shaft, wherein the heat pipe is formed in a space extending in the axial direction within the rotating shaft containing a heat medium, and 1. A cooling device for a rotating shaft, characterized in that the diameter of a portion to be heated is increased, the diameter of a portion of the space to be cooled is decreased, and a tapered portion connects the two.