WO2019064879A1

WO2019064879A1 - Axial fan

Info

Publication number: WO2019064879A1
Application number: PCT/JP2018/028349
Authority: WO
Inventors: 雅俊大林; 正岡部; 悠輔齋藤; 中田　佑希
Original assignee: 日本電産コパル電子株式会社
Priority date: 2017-09-26
Filing date: 2018-07-27
Publication date: 2019-04-04
Also published as: TW201915343A; JP2019060280A

Abstract

An axial fan (10) comprises: a shaft (11), which is a rotating shaft; an air dynamic pressure bearing (34) that through air dynamic pressure minimizes radial shifting of the shaft (11); a metal frame (13) having a circular surface in the middle of which is provided a first hole through which the shaft (11) passes, and having a cylindrical shape closed at one end; and a resinous impeller (2) which covers the frame such that the frame (13) is accommodated in the interior, and which is centered between the shaft (11) and the inner side of a second hole provided to the center of the circular surface.

Description

Axial fan

The present invention relates to axial fans.

In general, various axial fans are known. For example, in an outer rotor type blower fan, it is disclosed that an adjustment member which makes the natural frequency of the device mounting portion be different is provided to suppress the occurrence of resonance (see Patent Document 1).

However, in the case of an axial flow fan in which a resin-made impeller is covered on a cylindrical metal rotor holder, a crack may occur in the impeller. This is because the rotor holder generates heat when the axial flow fan operates, and the linear expansion coefficients of metal and resin are different. In particular, in the case of such a fan, since centering is performed at the contact portion between the side surface forming the outer periphery of the rotor holder and the impeller, no extra gap can be provided at this contact portion, and such a crack It becomes easy to occur.

Patent No. 6183995

An object of embodiments of the present invention is to provide an axial flow fan having improved durability in consideration of thermal expansion.

An axial flow fan according to an aspect of the present invention has a shaft which is a rotating shaft, an air dynamic pressure bearing which suppresses fluctuation in the radial direction of the shaft by air dynamic pressure, and a first hole through which the shaft passes And a metal frame of a shape in which one end of a cylindrical shape is closed by a circular surface provided on the frame, and the frame is covered at the center of the circular surface so as to accommodate the frame inside. A resin impeller is provided which is centered between the inside of the second hole and the shaft.

FIG. 1 is a perspective view showing a configuration of an axial flow fan according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the configuration of the axial flow fan according to the embodiment. FIG. 3 is a perspective view showing the configuration of the motor main body according to the embodiment. FIG. 4 is a perspective view showing the configuration from the lower side of the impeller according to the embodiment. FIG. 5 is a perspective view showing a state in which the impeller according to the embodiment is attached to the motor main body. FIG. 6 is a perspective view showing a configuration in which the outer frame according to the embodiment is vertically cut.

(Embodiment)
FIG. 1 is a perspective view showing the configuration of an axial fan 10 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the configuration of the axial flow fan 10 according to the embodiment.

The axial fan 10 is used, for example, as a cooling fan for cooling the server. The axial fan 10 includes a motor body 1, an impeller 2 and an outer frame 3.

FIG. 3 is a perspective view showing the configuration of the motor main body 1 according to the embodiment.

The motor body 1 is divided into a rotating body that rotates and a stationary portion that is stationary with respect to the rotation of the rotating body.

The rotating body of the motor main body 1 includes a shaft 11, a shaft holder 12, a frame 13, and a magnet 14. The shaft holder 12 and the frame 13 form a rotor holder.

The stationary portion of the motor body 1 is configured of a substrate 15, a plurality of coils 16, a core 17, and a plurality of support members 18.

The shaft 11 is a rotating shaft of a rotating body, and has a cylindrical shape. The shaft 11 is made of metal such as iron.

The shaft holder 12 is ring-shaped, the front surface is flat, and the back surface is shaped to fit in the hole of the frame 13. The shaft holder 12 is joined in a state in which the upper portion of the shaft 11 is fitted in the center hole of the surface. The bottom portion of the shaft holder 12 is joined to the top of the frame 13. By selecting the material of the shaft holder 12 that is close to the metal of the material of the frame 13 and the linear expansion coefficient thereof, the shift between the shaft holder 12 and the frame 13 due to thermal expansion is suppressed. Specifically, when the frame 13 is made of iron, the shaft holder 12 is preferably made of brass or steel. Brass is more suitable for the shaft holder 12 because it is less likely to rust than steel.

The frame 13 has a shape in which a hole from which the shaft 11 protrudes is provided at the center on a circular surface (upper surface) that closes one end of the cylindrical shape. The hole in the upper surface of the frame 13 is closed in such a manner that the gap formed between the shaft 11 and the frame 13 is covered by the shaft holder 12 when the shaft 11 passes through. The frame 13 is made of metal such as iron. The frame 13 is formed by pressing.

The magnet 14 is a permanent magnet for providing a function as a rotor of the motor body 1. The magnet 14 has a cylindrical shape and is attached to the inside of the frame 13.

The substrate 15 is in the shape of a disk having a hole at its center through which the shaft 11 passes. A control circuit for driving the motor body 1 is mounted on the substrate 15. The substrate 15 is provided with a sensor 151 for detecting the rotational position of the rotor. The substrate 15 may be used for a sensorless motor in which the sensor 151 is not provided. Further, the substrate 15 may be attached to the outer frame 3 instead of the motor body 1. Such a configuration is used, for example, for a sensorless motor in which the sensor 151 is not provided.

The coil 16 and the core 17 are provided inside the frame 13. The coils 16 are wound around the core 17 and circumferentially equally spaced around the shaft 11. The coil 16 and the core 17 have a function as a stator of the motor body 1. The core 17 may be composed of any number of members. For example, the core 17 may be formed by stacking thin plates in the rotational axis direction to suppress eddy current loss.

The plurality of support members 18 include a member for supporting the rotating body to rotate with respect to the stationary portion of the motor body 1 and a member for supporting the stationary portion of the motor body 1 to be fixed to the outer frame 3 . For example, the support member 18 is a member for disposing the coil 16 and the core 17 or a rod-like member which is fixed to the outer frame 3 by penetrating the small hole provided in the substrate 15.

FIG. 4 is a perspective view showing the configuration from the lower side of the impeller 2 according to the embodiment. FIG. 5 is a perspective view showing a state in which the impeller 2 according to the embodiment is attached to the motor body 1.

The impeller 2 is made of resin such as plastic. The impeller 2 has a shape in which a plurality of blades 22 are provided on an impeller main body 21 having a shape in which one end of a cylindrical shape is closed. The impeller main body 21 has a shape in which a hole in which the outer peripheral surface of the shaft holder 12 is fitted is provided at the center on a circular surface (upper surface). The periphery of the hole on the upper surface of the impeller body 21 has a sufficient thickness to prevent cracks due to thermal expansion. The inner shape of the impeller body 21 is such that the frame 13 fits from the top. Inside the impeller main body 21 may be provided a recess for applying an adhesive for bonding to the frame 13. When the blades 22 rotate, they are shaped to flow air in the direction of the rotation axis. The impeller 2 is attached to the frame 13 so that the outer shape of the shaft holder 12 fits in the hole on the upper surface. By fitting the outer shape of the shaft holder 12 in the hole on the upper surface of the impeller 2, the motor main body 1 is in a centered state. The inner peripheral surface of the impeller main body 21 and the outer peripheral surface of the frame 13 are bonded with an adhesive.

FIG. 6 is a perspective view showing a configuration in which the outer frame 3 according to the embodiment is vertically cut.

The outer frame 3 includes a cup portion 31, a plurality of stationary blades (ribs) 32, an outer portion 33, a bearing sleeve 34, and a magnetic bearing 35.

The cup portion 31 is disposed at the center of the bottom portion of the outer frame 3. The cup portion 31 is a place where the motor body 1 is mounted. The motor body 1 is mounted on the bottom of the cup portion 31 such that the impeller 2 is on top. The substrate 15 is arranged to be fixed to the inside of the cup portion 31. The outer shape of the cup portion 31 is one size larger than the outer shape of the substrate 15. Therefore, when the motor body 1 is mounted, there is a slight gap between the vertically extending outer edge on the outer periphery of the cup portion 31 and the substrate 15. When the substrate 15 is attached to the outer frame 3, the substrate 15 is bonded to the outer edge of the cup portion 31, and a slight gap is formed on the inner periphery of the hole at a position where the shaft 11 penetrates the hole at the center. Provided as.

The stationary wings 32 are provided at equal intervals around the cup portion 31 so as to connect the outer peripheral surface of the cup portion 31 and the inner peripheral surface of the outer portion 33. The stationary wing 32 is shaped in such a way that the wind passes between the two adjacent stationary wings 32 in the direction of the rotation axis according to the rotation of the rotating body. The stationary wing 32 is formed in a thin shape with a flexible material such as a resin to secure the flow characteristics of air.

The outer portion 33 is a portion covering the outermost side of the axial flow fan 10. The outer shape portion 33 has a shape in which a square flange portion provided with a hole for attaching the axial flow fan 10 to a mounting location is attached to both ends of a cylindrical shape portion in which the motor body 1 is accommodated.

A bearing sleeve 34 is provided at the center of the cup portion 31. The bearing sleeve 34 is cylindrical in shape. The motor body 1 is mounted such that the shaft 11 is inserted into the bearing sleeve 34. The bearing sleeve 34 is an air dynamic pressure bearing for suppressing the fluctuation of the shaft 11 in the radial direction. When the shaft 11 rotates, the air dynamic pressure around the shaft 11 keeps the gap between the shaft 11 and the bearing sleeve 34 constant, whereby the fluctuation of the shaft 11 is suppressed. Therefore, when the shaft 11 rotates, the shaft 11 and the bearing sleeve 34 are kept in non-contact with each other.

The magnetic bearing 35 is provided at a portion located on the bottom surface of the bearing sleeve 34. The magnetic bearing 35 is mainly composed of permanent magnets. The magnetic bearing 35 suppresses the fluctuation of the shaft 11 in the thrust direction by utilizing the attractive force or the repulsive force due to the magnetism of the permanent magnets. Therefore, the shaft 11 and the magnetic bearing 35 are kept in non-contact with each other. In addition, as long as it is a bearing which suppresses that the shaft 11 is fluctuate | varied to a thrust direction, not only the magnetic bearing 35 but any thing may be used. As in the case of the magnetic bearing 35, as long as it is a non-contact type bearing in which the shaft 11 is kept non-contacting, it has good durability and is suitable for high-speed rotation, it may be a contact type.

Next, centering of the axial fan 10 will be described.

As shown in FIGS. 1 and 2, a portion where the outer peripheral surface of the upper portion of the shaft holder 12 contacts the inside of the hole of the upper surface of the impeller 2 is the centering point SN of the axial flow fan 10. At the time of manufacture of the axial fan 10, centering adjustment is performed so that the center of the rotation axis of the shaft 11 is at a desired position at the centering position SN.

Since the manufacture of the axial flow fan 10 is performed at normal temperature, it is necessary to take into consideration that each component is thermally expanded by the heat generated by the operation of the axial flow fan 10. The influence of the thermal expansion is smaller at the centering point SN inside the hole of the upper surface whose diameter is smaller than the inner peripheral surface of the impeller 2. For example, if a gap of 50 to 150 μm is required between the inner peripheral surface of the impeller 2 and the outer peripheral surface of the frame 13 in consideration of thermal expansion, the outer peripheral surface of the shaft holder 12 as the centering location SN and the impeller 2 The gap between the top of the hole and the inside of the hole may be 0-50 μm.

By performing the centering adjustment at the centering position SN, it is not necessary to center at the contact portion between the inner peripheral surface of the impeller 2 and the outer peripheral surface of the frame 13, so the gap at this portion is the impeller 2 and the frame 13. In consideration of the difference in the linear expansion coefficient of the above, it can be made wide enough not to cause a crack. Further, by setting the centering position SN inside the hole on the upper surface having a diameter smaller than the inner peripheral surface of the impeller 2, the width of the gap that needs to be secured in consideration of thermal expansion may be narrow. Accuracy can be increased.

Next, an example of a method of correcting mass imbalance of the rotor of the axial fan 10 will be described.

The shaft holder 12 is provided around the top of the shaft 11. The material of the shaft holder 12 is brass which has a relatively high specific gravity and is easy to cut. Therefore, by cutting the shaft holder 12, mass imbalance correction of the negative balance method is performed. Here, although the method of making a circular hole with a drill and performing a mass unbalance correction is described as an example, what may be used and how cutting may be carried out.

First, the mass balance of the rotor of the axial fan 10 is measured. Based on this measurement result, the location and depth at which the shaft holder 12 is drilled are determined. According to this determination result, the shaft holder 12 is bored with a drill. The location and depth of the hole can be determined mechanically by using a conventionally known method. Therefore, from the measurement of the mass balance, the location and depth of the hole may be determined, and the process of performing the mass imbalance correction process on the shaft holder 12 may be automated.

In addition, the correction method of mass unbalance may be performed not only the above-mentioned method but how. For example, mass imbalance correction of the positive balance method may be performed. As a specific example, a groove may be provided around the upper portion of the shaft 11, and an adhesive with a heavy specific gravity may be applied to the groove to perform mass imbalance correction.

According to the present embodiment, the impeller is centered by centering location SN where the outer peripheral surface of the shaft holder 12 in which the shaft 11 is fitted in the center hole and the inside of the hole on the upper surface of the impeller 2 contact. There is no need to center between the inner circumferential surface of the second frame and the outer circumferential surface of the frame 13. Therefore, the gap between the inner peripheral surface of the impeller 2 and the outer peripheral surface of the frame 13 can be secured widely considering the thermal expansion. As a result, it is possible to prevent the occurrence of cracks in the impeller 2 due to the difference in coefficient of linear expansion between the resin which is the material of the impeller 2 and the metal which is the material of the frame 13.

In addition, since the diameter of the centering portion SN of the impeller 2 is smaller than the diameter of the inner peripheral surface of the impeller 2, the magnitude of the change due to the thermal expansion also becomes smaller. Therefore, by performing centering at the centering position SN, the width of the gap in consideration of thermal expansion can be reduced as compared to the case where centering is performed on the inner peripheral surface of the impeller 2, so the centering accuracy is high. can do.

Furthermore, by adopting a non-contact type air dynamic bearing as the bearing of the shaft 11, it is possible to make the highly durable axial flow fan 10 suitable for high speed rotation as compared with the contact type ball bearing. . Furthermore, by adopting a non-contact type magnetic bearing as the thrust bearing, it is possible to make the axial flow fan 10 suitable for higher speed rotation and excellent in durability.

Further, by providing the cuttable shaft holder 12, mass imbalance correction of the rotating body by the negative balance method can be facilitated.

In addition, you may comprise as follows as a modification of this embodiment. Without providing the shaft holder 12, the hole in the upper surface of the frame 13 is burred so as to fit the shaft 11 and vertically raised around the hole. The hole on the upper surface of the impeller 2 is made smaller so as to fit on the outer peripheral surface of the burred hole of the frame 13. In such a configuration, the contact point between the inside of the hole on the upper surface of the impeller 2 and the outer peripheral surface of the burred hole of the frame 13 is taken as a centering point SN. Thus, as in the present embodiment, in consideration of thermal expansion, the gap between the inner peripheral surface of the impeller 2 and the outer peripheral surface of the frame 13 can be made wider. Therefore, the occurrence of a crack due to the difference between the linear expansion coefficients of the two materials can be suppressed, and the durability can be improved. Further, as compared with the case where centering is performed on the inner peripheral surface of the impeller 2, centering can be performed at a portion having a smaller diameter, so that centering accuracy can be increased.

The present invention is not limited to the above-described embodiment, and the constituent elements may be deleted, added or changed. Further, by combining or exchanging the constituent elements in a plurality of embodiments, a new embodiment may be made. Even if such an embodiment differs directly from the above-described embodiment, the description of the same principle as the present invention is omitted as it is described as the embodiment of the present invention.

Claims

A shaft that is a rotating shaft,
An air dynamic pressure bearing that suppresses the radial fluctuation of the shaft by the air dynamic pressure;
A metal frame having a shape in which one end of a cylindrical shape is closed by a circular surface provided at the center with a first hole through which the shaft passes;
The frame is covered with the frame so as to accommodate the frame inside, and a resin-made impeller is provided which is centered between the inside of the second hole provided at the center of the circular surface and the shaft. An axial fan characterized by
The gap between the outer circumferential surface of the frame and the inner circumferential surface of the impeller is wider than the gap centered between the inside of the second hole of the impeller and the shaft. Axial fan described.
A ring-shaped member is joined in a state in which the shaft is fitted in a third hole, and is provided to close the first hole of the frame, and an outer peripheral surface and an inner side of the second hole of the impeller The axial flow fan according to claim 1, further comprising a shaft holder centered between the two.
The axial flow fan according to claim 3, wherein the shaft holder is made of brass.
The axial flow fan according to any one of claims 1 to 4, further comprising a magnetic bearing that suppresses a fluctuation in a thrust direction of the shaft by magnetism.
The axial flow fan according to claim 3 or 4, wherein the shaft holder is provided to correct mass imbalance of the rotating body by cutting.
An air dynamic pressure bearing is provided which suppresses the radial fluctuation of the shaft which is the rotating shaft by the air dynamic pressure,
A resin impeller is mounted on the frame so as to internally accommodate a metal frame having a shape in which one end of the cylindrical shape is closed by a circular surface provided at the center with a first hole through which the shaft passes. Cover,
A method of manufacturing an axial flow fan, comprising centering between the shaft and the inside of a second hole provided at the center of the circular surface of the impeller.