US20130280090A1

US20130280090A1 - Fan device

Info

Publication number: US20130280090A1
Application number: US13/804,300
Authority: US
Inventors: Sumio Sato; Yoichi Kawai
Original assignee: Minebea Co Ltd
Current assignee: Minebea Co Ltd
Priority date: 2012-04-23
Filing date: 2013-03-14
Publication date: 2013-10-24
Also published as: JP5993602B2; JP2013224632A; CN203239630U

Abstract

A structure that rigidly connects a shaft and a hub in a fan device with a motor, ensuring the squareness of the shaft in relation to the hub, and not worsening the flowability of the resin that constitutes the hub during injection molding, is provided. The fan device includes an approximately cylindrical hub 117 with a bottom and made of resin, vanes 118 positioned at an outer circumference of the hub 117, a shaft 113 attached to the bottom of the hub 117, and a reinforcing plate 115 for reinforcing the bottom of the hub 117. The shaft 113 is connected to the reinforcing plate 115, and a through hole 115 b filled with the resin for making the hub 117 is provided on the reinforcing plate.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a fan device with a motor having a special structure for fixing a shaft.
2. Description of Related Art
Japanese Patent Application Laid-open No. H11-132193 discloses a structure in which a shaft supporting a rotor rotatably and a fastening interventional part fitted to the shaft are surrounded by a boss part of an impeller made of synthetic resin formed by injection molding, as a means for firmly fixing a boss part of a rotor and a shaft of a fan device.
In the structure disclosed in Japanese Patent Application Laid-open No. H11-132193, the fastening interventional part is integrally molded inside of the boss part, and therefore, the dimension of the fastening interventional part in radial direction is limited by the boss part, resin shrinkage is generated around the fastening interventional part and the hub when the impeller are injection-molded, squareness of the shaft in relation to the upper surface of the hub is worsened, and rotation balance of the entire rotor is deteriorated. In addition, there is a problem in that flowability of the resin during injection molding is worsened when the fastening interventional part is enlarged, since the fastening interventional. part is located inside of the boss part.
In view of such circumstances, an object of the present invention is to provide a structure for rigidly connecting the shaft and the hub in a fan device with motor, in which the squareness of the shaft is ensured, and in which the flowability of the resin which constitutes the hub is not worsened during injection molding.

SUMMARY OF THE INVENTION

In a first aspect of the invention, a fan device includes an approximately cylindrical hub with a bottom and made of a resin, vanes positioned at the outer circumference of the hub, a shaft attached to the bottom of the hub, and a reinforcing plate for reinforcing the bottom of the hub, in which the shaft is connected to the reinforcing plate, and an through hole filled with the resin forming the hub is provided on the reinforcing plate.
According to the first aspect of the invention, squareness of the shaft is ensured by the reinforcing plate. When the hub is formed by injection molding using the resin as a raw material, the resin flows to the back side of the reinforcing plate through the through hole, and therefore, the problem in which flowability of the resin in injection molding is worsened can be solved, even when the reinforcing plate is enlarged.
In a second aspect of the invention, a boss part is provided at the center part of the bottom of the hub in which the boss part has a thickness in axial direction greater than the thickness of the bottom of the hub at a position located in an outside radial direction, and the reinforcing plate is extended in a radial direction to the outside of the boss part.
According to the second aspect of the invention, the effect in which the bottom of the hub is reinforced by the reinforcing plate is further increased, since the reinforcing plate is extended to the outside of the hub when viewed from axial direction. In addition, flowability of the resin during formation of the hub does not become worse, even when the reinforcing plate is made larger, because the through hole is provided on the reinforcing plate.
In a third aspect of the invention, one of the surfaces of the reinforcing plate is exposed to the outside or the inside of the hub, According to the third aspect of the invention, during the injection molding process using the resin as raw material, one of the surfaces of the reinforcing plate may be contacted with an inner surface of a die for reinforcing the hub. Thus, the squareness of the shaft connected to the reinforcing plate with respect to the hub is easily ensured, and the accuracy can be increased.
In a fourth aspect of the invention, position of the through hole is used as an injection gate for forming the hub, when viewed from an axial direction. According to the fourth aspect of the invention, the resin injected in the die runs into the through hole, and as a result, injection pressure of the resin loaded to the reinforcing plate is reduced so that deformation and displacement of the reinforcing plate within the die during injection molding are prevented. In addition, the resin injected in the die easily reaches to the through hole of the reinforcing plate, and therefore, flowability of the resin to the back side of the reinforcing plate viewed from the direction injecting the resin can be improved.
In a fifth aspect of the invention, multiple through holes are further provided, and the multiple through holes are arranged at positions which are in point symmetry with respect to the rotation center of the shaft, when viewed from the axial direction. According to the fifth aspect of the invention, superior weight balance in rotating can be obtained.
In a sixth aspect of the invention, the reinforcing plate has a shape which is in point symmetry with respect to the rotation center of the shaft, when viewed from the axial direction. According to the sixth aspect of the invention, superior weight balance in rotating can be obtained.
In a seventh aspect of the invention, a cylindrical part that extends in the axial direction to which the shaft is fitted is provided on the reinforcing plate. According to the seventh aspect of the invention, a part of the shaft supported in the axial direction by the reinforcing plate becomes longer, and the area of the fitting part of the reinforcing plate and the shaft is increased. Therefore, the squareness of the shaft with respect to the reinforcing plate is more easily ensured, and the connecting strength between the reinforcing plate and the shaft can be further improved.
According to the present invention, a structure for rigidly connecting a shaft and a hub in a fan device with a motor, in which the squareness of the shaft is ensured, and in which the flowability of the resin that constitutes the hub during injection molding is not worsened, can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of an embodiment of an axial flow fan device.

FIG. 2A is a top view of an impeller viewed from axial direction.

FIG. 2B is a cross sectional view thereof viewed from a direction perpendicular to the axis.

FIG. 3A is a top view of a reinforcing plate viewed from axial direction.

FIG. 3B is a cross sectional view thereof viewed from a direction perpendicular to the axis.

FIG. 4A is a top view of a modified embodiment of an impeller, viewed from axial direction.

FIG. 4B is a cross sectional view thereof viewed from a direction perpendicular to the axis.

FIG. 4C is a cross sectional view of a forming state using an injection die.

FIG. 5A is a bottom view of a modified embodiment of an impeller, viewed from axial direction.

FIG. 5B is a cross sectional view thereof when viewed from a direction perpendicular to the axis.

FIG. 5C is a cross sectional view of a forming state using an injection die.

FIG. 6A is a top view of a modified embodiment of the reinforcing plate viewed from axial direction.

FIG. 6B is a cross sectional view thereof when viewed from a direction perpendicular to the axis.

FIG. 7A is a top view of a modified embodiment of the reinforcing plate viewed from axial direction.

FIG. 7B is a cross sectional view thereof when viewed from a direction perpendicular to the axis.

PREFERRED EMBODIMENT OF THE INVENTION

1. First Embodiment

Structure

FIG. 1 shows a cross-sectional view of an axial flow fan device 100 viewed from a direction perpendicular to the rotational axis. FIG. 2A shows a top view of an impeller 122 of the axial flow fan device 100 of FIG. 1 viewed from the axial direction and FIG. 2B shows a cross-sectional view of the same viewed from a direction perpendicular to the axis. FIG. 2A shows a situation in which FIG. 2B is viewed from an upper direction.
The axial flow fan device 100 has a casing 101. The casing 101 has an approximately cylindrical shape, and a rotor 125 is rotatably arranged therein. The casing 101 supports a motor base 103 by a plurality of motor base supporting members 102 which are support ribs extending toward the axis center direction. The motor base 103 has a cylindrical bearing housing 104 which extends toward the axial direction. The casing 101, the motor base supporting members 102, the motor base 103, and the bearing housing 104 are formed as an integrally molded part.
A stator core 105 is fixed to the outer circumference of the bearing housing 104. The stator core 105 is formed by layered steel plates, and has a plurality of protruding poles (not shown) radially arranged when viewed from the axial direction. Although detailed explanation is omitted, the shape of the stator core 105 is same as the stator core of a conventional outer rotor type brushless motor. A resin insulator 106 is attached to the stator core 105. A stator coil (driving coil) 107 is coiled around each of multiple salient poles of the stator core 105 via the insulator 106. The stator core 105, the insulator 106, and the stator coil 107 form a stator 108 of an outer rotor type motor. Metallic terminal pins 109 are embedded in the insulator 106. One end of a winding wire of the stator coil 107 is tangled and connected to the terminal pin 109. The tip of the terminal pin 109 is connected to a circuit board 110. A driving circuit for generating the driving current in the stator coil 107 is formed on the circuit board 110.
Bearings 111 and 112 are attached inside of the bearing housing 104. The bearings 111 and 112 support a shaft 113 which is the rotating axis member in a rotatable condition. The bearings 111 and 112 are a sliding bearing or a rolling bearing, and include a lubricant in order to reduce friction accompanied by rotating of the shaft 113. The shaft 113 is cylindrical and metallic, and a resin hub 117 is fixed to the upper part thereof. The hub 117 is of approximately cylindrical shape having a bottom, and consists of a boss part 119, a circular plate part 120, and a cylindrical part 121. Here, the boss part 119 and the circular plate part 120 form the bottom part, and the cylindrical part 121 forms the cylindrical part of the approximately cylindrical shape having a bottom.
In the bottom part of the hub 117 having an approximately cylindrical shape with a bottom, the boss part 119 corresponds to the part that is thicker in the axial direction than the circular plate part 120 that is at outside radial direction. The circular plate part 120 is a part outside (distancing direction from the axis center) of the boss part 119, and has a flat circular ring shape having even thickness. The cylindrical part 121 is a part of a cylinder extending from the periphery of the circular plate part 120 along the axial direction, and vanes 118 are integrally formed at the outer circumference thereof. The shaft 113, the hub 117, a reinforcing plate 115 (explained later) embedded in the hub 117, and the vanes 118 form an impeller 122.
The reinforcing plate 115 is embedded inside of the hub 117. FIG. 3A shows a top view in which the reinforcing plate is viewed from the axial direction, and FIG. 3B shows a cross-sectional view in which the reinforcing plate is viewed from a direction perpendicular to the axis. The reinforcing plate 115 is made of a metal, has an approximately circular shape, and has a larger outer diameter than that of the boss part 119. That is, the outer edge of the reinforcing plate 115 extends to the outside of the boss part 119 in a radial direction. A fitting hole 115 a, in which the shaft 113 is fitted, is formed at the center of the reinforcing plate 115, and through holes 115 b are formed at six positions along a circle around the fitting hole 115 a, The six through holes 115 b are arranged at positions which are point-symmetric with respect to the rotation center. It is desirable that there be multiple through holes 115 b, but the number is not limited to six.
In a condition in which the shaft 113 is fitted in the fitting hole 115 a, the hub 117 is formed so that the hub 117 is integrated with the shaft 113 and the reinforcing plate 115, by the injection molding method using resin as a raw material. The hub 117 is produced as follows. First, the shaft 113 is inserted in the fitting hole 115 a of the reinforcing plate 115, and then the assembled body is arranged in a die. Then, a resin that is heated and made fluid is injected into the die so as to form the hub 117 and the vanes 118 integrated to the hub 117 (that is, to form impeller 122). In this case, the through holes 115 b function as pathways through which the resin flows. Furthermore, at the step in which the hub 117 is formed, the resin forming the hub 117 fills the through holes 115 b, and thus a structure in which the connection between the shaft 113 and the reinforcing plate 115, and the reinforcing plate 115 itself are covered with the resin can be obtained.
Furthermore, in this example, among the through holes 115 b at six positions, the through holes 115 b at three positions which are indicated by reference numeral 126 in FIG. 2 are utilized as injection gates. The resin is injected from upper side of FIG. 2B through the injection gates 126 into the die.
A spring 116 is arranged between the boss part 119 and the bearing 112 so as to absorb backlash of the shaft 113 along the axial direction. A rotor yoke 123 having cylindrical shape formed by a thin steel plate is arranged inside of the cylindrical part 121 of the hub 117, and a rotor magnet 124 having cylindrical shape (ring shape) is arranged inside of the rotor yoke 123. The rotor magnet 124 has plural magnetic poles at an inner circumferential surface thereof along a circumferential direction and is arranged in a condition such that polarity of the magnetic poles facing the axis center is alternately reversed. The inner circumference of the rotor magnet 124 and the outer circumference of the stator 108 are facing via a small gap. The rotor 125 is composed of the impeller 122, the rotor yoke 123 and the rotor magnet 124.
As mentioned so far, the axial flow fan device 100 has a structure in which the vanes of the axial flow fan are formed at the rotor part of the outer rotor type brushless motor. That is, in the axial flow fan device 100, the rotor 125 rotates around the stator 108 fixed to the bearing housing 104 of the motor base 103. In the rotor 125, the resin hub 117 is fixed to the shaft 113, and the hub 117 is reinforced from the inside thereof by the reinforcing plate 115 attached to the shaft 113. In addition, the vanes 118 are arranged at the outer circumference of the hub 117. The rotor magnet 124 is attached inside of the hub 117, and by switching the polarity of driving current applied in the stator coil 107 which is a driving coil arranged in the stator 108, the magnetic attractive force and the magnetic repulsive force which act between the stator coil 107 and the rotor magnet 124 are switched, then the rotor 125 rotates around the shaft 113 working as the rotational axis. By rotating the rotor 125, vanes 118 also rotate, and then the movement of air along the axial direction (axial flow) occurs.

Advantages

Since the shaft 113 is fitted in the fitting hole 115 a of the reinforcing plate 115, and since the outer diameter of the reinforcing plate 115 is greater than that of the boss part 119, squareness of the shaft 113 in relation to the hub 117 can be favorably maintained. Furthermore, since the reinforcing plate 115 forms the core of the central part of the hub 117, rigidity of the hub 117 in the vicinity of the shaft 113 is increased. As a result, thickness of the hub 117 in the axial direction can be reduced, and thus sinking and thermal shrinkage after resin molding can be favorably controlled.
Since the through hole 115 b is formed on the reinforcing plate 115, even in the case in which an outer diameter of the reinforcing plate 115 is large, resin can be tightly filled to the back side of the reinforcing plate 115 viewed from the resin injection side. Therefore, filling defects in resin rarely occur during injection molding, and uniformity of the hub 117 can be maintained. On the other hand, in a case in which the through hole 115 is not arranged, the flow path of the resin which is to fill the back part of the reinforcing plate 115 becomes longer, and the probability of occurring defects during filling of the resin may increase.
By positioning an injection gate that is the filling inlet for resin on the through hole 115 b of the reinforcing plate 115, the injection pressure of resin is not directly applied to the reinforcing plate, and thus the deformation of the reinforcing plate 115 during injection molding can be prevented. As a result, the deterioration of the squareness of the shaft due to the injection pressure of the resin during the injection molding can be prevented.

2. Second Embodiment

FIG. 4A is a top view showing an impeller 122 viewed from an axial direction, FIG. 4B is a cross-sectional view viewed from a direction perpendicular to the axis, and FIG. 4C is a cross-sectional view showing a forming condition using an injection molding die. FIG. 4A corresponds to the configuration viewed from upper side of FIG. 4B.
In this example, the position of the reinforcing plate 115 in the hub 117 differs from the case of FIGS. 1 and 2B. That is, one of the surfaces of the reinforcing plate 115 (the upper surface in FIG. 4B) is exposed on the surface at outside of the hub 117 in the axial direction. This structure is prepared according to the condition shown in FIG. 4C. FIG. 4C shows the dies 410 and 402. By combining the dies 401 and 402, the die 404 with a cavity 403 is obtained for forming the hub 117 with the vanes 118 integrated to the hub 117 (that is, the impeller 122).
In the case of present example, the upper end part of the shaft 113 in the figure FIG. 4B is fitted to the center of the reinforcing plate 115. Then, as shown in FIG. 4C, the integrated member consisting of the shaft 113 and the reinforcing plate 115 is contacted to the surface of the die 401 in the cavity 403, and the resin is injected from the injection nozzle 405 into the cavity 403 utilizing the position of the through hole 115 b formed in the reinforcing plate 115 viewed from the axial direction as the injection gate, so as to obtain the impeller 122 shown in FIG. 4B.
In the structure shown in FIG. 4B, the reinforcing plate 115 can be set to contact the die surface, and the injection molding can be performed maintaining this condition. Therefore, squareness of the shaft 113 with respect to the hub 117 can be improved further.

3. Third Embodiment

FIG. 5A is a bottom view of another embodiment of impeller 122 for forming another rotor viewed from the axial direction, FIG. 5B is the cross-sectional view viewed from a direction perpendicular to the axis, and FIG. 5C is the cross-sectional view showing the forming condition using an injection molding die. FIG. 5A shows the condition viewed from the lower side of FIG. 5B. In addition, FIG. 5A shows multiple rib parts 119 a radially formed at the outer edge part of the boss part 119. The rib parts 119 a are arranged in order to maintain strength of the boss part 119 and to release the stress generated at the boss part 119 during the injection molding.
In this example, the position of the reinforcing plate 115 in the hub 117 differs from the case of FIGS. 1 and 2. That is, one of the surfaces of the reinforcing plate 115 (the lower surface in FIG. 5B) is exposed on the surface at inside of the hub 117 in the axial direction (the surface at the stator side). This structure is prepared according to the condition shown in FIG. 5C. FIG. 5C shows the dies 401 and 402. By combining the dies 401 and 402, the die 404 with a cavity 403 is obtained for forming the hub 117 and the vanes 118 integrated to the hub 117 (that is, the impeller 122).
In the case of present example, the reinforcing plate 115 is fitted near the end part of the shaft 113 in a manner that the lower surface of the reinforcing plate 115 can contact the surface of the die 402 in the cavity 403. Then, as shown in FIG. 5C, the reinforcing plate 115 is contacted to the surface of the die 402 in the cavity 403, and the resin is injected from the injection nozzle 405 into the cavity 403 utilizing the position of the through hole 115 b formed in the reinforcing plate 115 viewed from the axial direction as the injection gate, so as to obtain the impeller 122 shown in FIG. 5B.
In the structure shown in FIG. 5B, the reinforcing plate 115 can be set to contact the die surface, and the injection molding can be performed maintaining this condition. Therefore, squareness of the shaft 113 with respect to the hub 117 can be improved further.

4. Modification 1

FIG. 6A is a top view showing another example of a reinforcing plate viewed from the axial direction, and FIG. 6B is a cross-sectional view viewed from a direction perpendicular to the axis. FIG. 6A shows a reinforcing plate 601. The reinforcing plate 601 has a right-hexagonal shape when viewed from the axial direction. A fitting hole 601 a to hold the shaft is arranged at a center of the reinforcing plate 601, and rectangular through holes 601 b are arranged at six positions along a circumference around the fitting hole 601 a. The through holes 601 b correspond to the through holes 115 b in FIG. 2A. The six through holes 601 b are arranged at the point-symmetric positions with respect to the fitting hole 601 a which is the rotation center in order to maintain the weight balance during rotation. A right-hexagonal reinforcing plate 601 is exemplified here. However, the reinforcing plate can be of another polygonal shape, such as a right-pentagon or a right-octagon. Furthermore, a shape which is not a right-polygon can be employed, as long as it is a shape which can maintain weight balance during rotating, that is, any shape which is point-symmetric with respect to the rotation center of the shaft (center of the fitting hole 601 a). Furthermore, the through hole is not limited to a rectangle, and any shape such as a polygonal shape or a star shape can be employed.

5. Modification 2

FIG. 7A is a top view showing another example of a reinforcing plate viewed from the axial direction, and FIG. 7B is a cross-sectional view viewed from a direction perpendicular to the axis. FIG. 7A shows a reinforcing plate 701. The reinforcing plate 701 is different from the reinforcing plate 115 in FIG. 3A in that the fitting hole 701 a to which the shaft is fitted has a cylindrical part 701 c extending along the axial direction, so that the contact area with the shaft is considerably increased. According to the structure, squareness with respect to the reinforcing plate 105 can be maintained more securely, and the reinforcing plate 105 and the shaft 113 can be joined more securely. It should be noted that in this example, circular through holes 701 b, which function in a similar manner to the through holes 115 b, are provided.

6. Modification 3

In each of the embodiments explained above, a structure in which the shaft and the reinforcing plate are joined by an interference fit is desirable. For example, the inner diameter of the fitting hole 115 a can be made smaller than the outer diameter of the fitting part of the shaft, and the shaft can be fitted in the fitting hole 115 a by press fitting. In this way, the shaft 113 and the reinforcing plate 115 can be connected more securely. In addition, by welding the shaft 113 and the reinforcing plate 115, the shaft 113 and the reinforcing plate 115 can be fixed securely.

Other Modifications

Although an example of the present invention employed in an axial flow fan device has been explained above, the present invention can also be employed in a centrifugal flow fan device or the like.
The scope of the present invention is not limited to the embodiments described above, and the present invention includes any modification that those skilled in the art can conceive. That is, various additions, modifications, and partial omissions can be made to the invention without departing from the scope and spirit of the present invention.

EXPLANATION OF REFERENCE NUMERALS

100 . . . axial flow fan device, 101 . . . casing, 102 . . . motor base supporting part, 103 . . . motor base, 104 . . . bearing housing, 105 . . . stator core, 106 . . . insulator, 107 . . . stator coil, 108 . . . stator, 109 . . . terminal pin, 110 . . . circuit board, 111 . . . bearing, 112 . . . bearing, 113 . . . shaft, 115 . . . reinforcing plate, 115 a . . . fitting hole, 115 b . . . through hole, 115 c . . . cylindrical part, 116 . . . spring, 117 . . . hub, 118 . . . vane, 119 . . . boss part, 119 a . . . rib part, 120 . . . circular plate part, 121 . . . cylindrical part, 122 . . . impeller, 123 . . . rotor yoke, 124 . . . rotor magnet, 125 . . . rotor, 126 . . . injection gate, 401 . . . die, 402 . . . die, 403 . . . cavity, 404 . . . die, 405 . . . injection nozzle, 601 . . . reinforcing plate, 601 a . . . fitting hole, 601 b . . . through hole, 701 . . . reinforcing plate, 701 a . . . fitting hole, 701 b . . . through hole, 701 c . . . cylindrical part.

Claims

What is claimed is:

1. A fan device comprising:

an approximately cylindrical hub with a bottom and made of a resin;

vanes positioned at an outer circumference of the hub;

a shaft attached to the bottom of the hub; and

a reinforcing plate for reinforcing the bottom of the hub;

wherein the shaft is connected to the reinforcing plate, and a through hole filled with the resin forming the hub is provided on the reinforcing plate.

2. The fan device according to claim 1, wherein a boss part is provided at the center part of the bottom of the hub in which the boss part has a thickness in an axial direction greater than the thickness of the bottom of the hub at a position located in an outside radial direction, and the reinforcing plate is extended in a radial direction to the outside of the boss part.

3. The fan device according to claim 1, wherein one of the surfaces of the reinforcing plate is exposed to the outside or the inside of the hub.

4. The fan device according to claim 1, wherein a position of the through hole is used as an injection gate for forming the hub, when viewed from an axial direction.

5. The fan device according to claim 1, wherein multiple through holes are further provided, and the multiple through holes are arranged at positions that are in point symmetry with respect to the rotation center of the shaft, when viewed from an axial direction.

6. The fan device according to claim 1, wherein the reinforcing plate has a shape that is in point symmetry with respect to the rotation center of the shaft, when viewed from an axial direction.

7. The fan device according to claim 1, wherein a cylindrical part that extends in an axial direction to which the shaft is fitted is provided on the reinforcing plate.