CN109751279B

CN109751279B - Impeller for fan

Info

Publication number: CN109751279B
Application number: CN201811234311.9A
Authority: CN
Inventors: 永田武司
Original assignee: Nisshinbo Mechatronics Inc
Current assignee: Nisshinbo Mechatronics Inc
Priority date: 2017-11-01
Filing date: 2018-10-23
Publication date: 2022-04-05
Anticipated expiration: 2038-10-23
Also published as: JP6479934B1; JP2019085886A; KR20190049436A; CN109751279A

Abstract

The invention provides an impeller for a fan, which is a low-cost impeller with low noise and Nz factor elimination or reduction. A plurality of blade members formed in a cylindrical shape on a disc-shaped member to form a module, and the blade members of the module are joined to the disc-shaped member of another module; a fitting groove for fitting the tip of the blade member is formed on the opposite surface of the blade member on which the disc-shaped member is formed; a fitting groove formed at a position rotated in a clockwise direction when viewed from a direction of an opening of the fitting groove with reference to a position of the blade member on the disc-shaped member; the tip of the blade member is fitted in the fitting groove, and the components are coupled to each other.

Description

Impeller for fan

Technical Field

The present invention relates to an impeller used in a fan such as a tube fan.

Background

Recently, as a countermeasure for environmental problems or resource saving, there is an increasing demand for a lightweight, low-noise, and low-vibration impeller to improve the performance of a fan.

First, a structure of a conventional impeller will be described. As shown in fig. 12, the impeller 200 of the related art is composed of an assembly 202 of a plurality of impellers, a hub-side disc-shaped fixing plate 205, a shaft portion 206, and a hub portion 207. The assembly 202 is made up of a disc shaped member 203 and blades 204. The shaft 206 is attached to the disc-shaped member 203 of the assembly 202 at one end of the impeller 200. A hub-side disc-shaped fixing plate 205 is attached to the blade member side of the assembly at the other end of the impeller 200. The hub portion 207 is provided on the hub-side disc-shaped fixing plate 205. Hereinafter, the impeller is referred to as a "conventional impeller".

To achieve the low noise of the above-described prior art impeller, it is particularly desirable to eliminate or reduce the Nz sound. The Nz sound is a peak sound generated according to the number of blades and the number of rotations of the fan impeller. When Nz sound is generated, it is a peak of a specific frequency, and thus it is likely to be unpleasant. In order to reduce the Nz sound, patent document 1 discloses the following impeller.

Next, the impeller described in patent document 1 will be described. The blades of the impeller 300 have the shape shown in fig. 13, and a plurality of blades 304 are provided in a cylindrical shape on the block 302. Disclosed is an impeller which integrally forms blades which are twisted by relatively changing the angle between one end of a blade 304 fixed to a disc-shaped fixing plate 303 of a unit and the other end thereof, and connects a plurality of the units. However, the impeller of patent document 1 is complicated in the process and the mold for molding the assembly including the blades, and increases the cost of the impeller. Hereinafter, the above impeller is referred to as "current product".

Prior art documents

Patent document

Japanese patent laid-open publication H08-049689

Disclosure of Invention

Problems to be solved

The present invention is directed to overcoming the deficiencies of the prior art and providing an inexpensive impeller that has low noise and eliminates or reduces Nz factor.

Means for solving the problems

To achieve the above object, an impeller according to a first aspect of the present invention includes:

an impeller for a fan, wherein a plurality of blade members are formed in a cylindrical shape on a disc-shaped member to form a module, and the blade members of the module are joined to the disc-shaped member of another module;

the blade member of the impeller is made of a composite material of a synthetic resin material and glass fibers, the average thickness of the blade member of the impeller is in the range of 0.3mm to 0.8mm, and the glass fibers contained in the blade member are made to face the back surface of the blade member;

the plurality of blade members of the assembly are formed in a straight line;

a fitting groove for fitting the tip end of the blade member is formed in the same number as the number of the blade members on the surface opposite to the side of the blade member on which the disc-shaped member is formed;

the fitting groove is formed such that a center line position of the fitting groove is arranged at a position rotated by 1 to 7 degrees in a clockwise direction when viewed from a direction of an opening of the fitting groove with reference to a center position of a position of the blade member on the disc-shaped member;

when the tip end portion of the blade member is fitted into the fitting groove, the tip end portion of the blade member is twisted and deformed, and then fitted to each other, thereby coupling the respective components.

The impeller according to the first invention has the following effects:

in the impeller according to the first aspect of the present invention, the fitting groove of the disc-shaped member of the unit is provided so as to rotate clockwise by 1 to 7 degrees as viewed from the direction of the opening of the fitting groove with reference to the center position of the blade member, and the tip of the blade member is inserted into the fitting groove by twisting. Therefore, the material of the blade member (module) may be any material having flexibility such that no crack or the like occurs even when deformation such as twisting is applied. For example, by selecting a flexible synthetic resin and controlling the thickness of the blade member to the current level, the Nz sound can be suppressed to the same level as that of the current technology.

The fitting groove is formed at a position rotated in a clockwise direction by 1 to 7 degrees with reference to a center position of the blade member on the disc-shaped member. If the variation angle of the fitting groove is less than 1 degree, there is a possibility that the effect of reducing the Nz sound cannot be obtained. If the angle is greater than 7 degrees, the tip end of the blade may be locally deformed when the blade member is twisted in the fitting groove. The twist angle of the fitting groove is preferably 2 to 6 degrees. The optimal temperature is 3-5 degrees.

In the impeller according to the first aspect of the present invention, the blade member is made of a composite material of a synthetic resin material and glass fibers, and the average thickness of the blade member is controlled to be 0.3mm to 0.8 mm. Thus, the glass fibers contained in the blade member are made to face the inside of the surface of the blade member. By configuring the impeller in this way, the weight of the impeller can be reduced to less than half as compared with conventional and current products. Even if the blade member is made thin, the performance as an impeller is not degraded by the light weight, so that energy for driving the impeller can be saved. In particular, since the thickness of the blade member is reduced to half or less of the conventional one, the material cost is also reduced to half or less. In addition, the blade member of the present invention has a small average thickness of 0.3mm to 0.8mm, so that the weight can be reduced, and the strength of the blade member can be further improved by making the glass fiber in the composite material face the front and back surfaces of the blade member. Further, even if the tip of the blade member is twisted and fitted into the fitting groove in order to exhibit the effect of the present invention, the blade member is not cracked.

The impeller of the first invention has the structure that: a plurality of modules are formed, the same number of fitting grooves for fitting the tips of blade members as the number of blade members are formed on the opposite surface of the module from the side where the blade members of a disk-shaped member are formed, the positions of the fitting grooves are changed with respect to the positions of the blade members on the disk-shaped member, and the tips of the blade members are fitted in the fitting grooves to join the modules. Thus, the mold used for molding the impeller has a very simple structure as compared with a mold for manufacturing a conventional impeller described in patent document 1. The impeller of the invention thus becomes very inexpensive compared to prior art impellers.

In the impeller according to the first aspect of the present invention, the material of the blade member is a composite material, and the thickness of the blade member is made thin without reducing the strength of the blade member. In addition, it is very disadvantageous that the thickness of the blade member becomes thick for the reduction of Nz sound. However, according to the first aspect of the present invention, the tip of the fitting blade member is twisted in the fitting groove, and the level of Nz sound can be maintained at the same level as that of the impeller of the related art.

The fan impeller according to the second aspect of the present invention is the fan impeller according to the first aspect of the present invention, further including:

the bottom of the fitting groove has the same shape as the shape of the tip of the blade member to be fitted, and the portion of the fitting groove with which the tip of the blade member comes into contact when the blade member is inserted into the fitting groove is formed as an inclined surface whose inclination gradually changes from the center to the peripheral portion of the fitting groove.

According to the impeller of the second invention, the following effects are provided: the edge of the fitting groove on the opposite side of the blade member of the module having the disc-shaped member is formed with a smooth inclined surface. Therefore, when the blade member is inserted into the fitting groove, the tip end of the blade member can be smoothly fitted into the fitting groove while being torsionally deformed.

The fan impeller according to the third aspect of the present invention is the fan impeller according to the first or second aspect of the present invention, further including:

the blade member is made of a composite material of a synthetic resin material and glass fibers, and the resin composite material with the content of the glass fibers being 10-40% by weight is selected.

The impeller of the third invention is made of a composite material of a synthetic resin material and glass fibers, and the content of the glass fibers is 10-40% by weight of the resin composite material. Therefore, when the effect of the second invention is exhibited, the following effects are exhibited: even if the average thickness of the blade member of the impeller is controlled to be 0.3mm to 0.8mm, the strength of the blade member can be improved by disposing the glass fiber on the back surface of the blade member.

The fan impeller according to a fourth aspect of the present invention is the fan impeller according to any of the first through third aspects of the present invention, further including:

the blade member is made of a composite material of a synthetic resin material and glass fibers, and has a surface elastic coefficient (E') of 2.5X 10⁹Pa～1.2×10¹⁰Pa。

In the impeller according to the fourth aspect of the present invention, the blade member is made of a composite material of a synthetic resin material and glass fibers, and the blade member has a coefficient of elasticity (E') in the surface plane direction of 2.5 × 10⁹Pa～1.2×10¹⁰Pa of a resin material and glass fibers. Therefore, when the effect of the second invention is exhibited, the following effects are exhibited: that is, the impeller of the present invention can be manufactured to have a high coefficient of elasticity and a characteristic of easy restoration (restorability) by making the blade member thinner than when it is made thicker with the same composite material.

Drawings

FIG. 1 is a front view of an impeller of the present invention;

fig. 2 is an explanatory view of components and a fitting groove of an impeller of the present invention;

fig. 3 is an explanatory view of an embodiment of a fitting groove of the assembly;

fig. 4 is a detailed explanatory view of the sectional shape of the fitting groove;

fig. 5 is an explanatory view of a process of fitting the tip portion of the blade member to the fitting groove;

FIG. 6 is a graph showing the relationship between the torsion angle and the air volume;

FIG. 7 is a graph of torsion angle versus noise level;

FIG. 8 is a graph of the noise spectrum of the impeller of the present invention (torsion angle 1-2 degrees, torsion angle 6-7 degrees);

FIG. 9 is a graph of the noise spectrum of the impeller of the present invention (torsion angle 2-3 degrees, torsion angle 5-6 degrees);

FIG. 10 is a graph of the noise spectrum of the impeller (twist angle 3-5 degrees) according to the present invention;

FIG. 11 is a graph showing a noise spectrum of an impeller of a conventional product;

FIG. 12 is an explanatory view of a conventional product;

fig. 13 is an explanatory view of a current product (impeller of patent document 1).

The reference numbers illustrate:

1: impeller (the product of the invention)

2: assembly

3: disc-shaped member

4: blade component

5: disc-shaped fixing plate on side of shaft hub

6: shaft part

7: hub portion

8: tabling groove

200: impeller of comparative example (conventional product)

300: impeller of the prior art

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a front view of an impeller of the present invention; fig. 2 is an explanatory view of components and a fitting groove of an impeller of the present invention; fig. 3 is an explanatory view of an embodiment of a fitting groove of the assembly; fig. 4 is a detailed explanatory view of the sectional shape of the fitting groove; fig. 5 is an explanatory view of a process of fitting the tip portion of the blade member to the fitting groove; FIG. 6 is a graph showing the relationship between the torsion angle and the air volume; FIG. 7 is a graph of torsion angle versus noise level; FIG. 8 is a graph of the noise spectrum of the impeller of the present invention (torsion angle 1-2 degrees, torsion angle 6-7 degrees); FIG. 9 is a graph of the noise spectrum of the impeller of the present invention (torsion angle 2-3 degrees, torsion angle 5-6 degrees); FIG. 10 is a graph of the noise spectrum of the impeller (twist angle 3-5 degrees) according to the present invention; FIG. 11 is a graph showing a noise spectrum of an impeller of a conventional product; FIG. 12 is an explanatory view of a conventional product; fig. 13 is an explanatory view of a current product (impeller of patent document 1).

<1> Structure of impeller of the present invention

An impeller 1 shown in fig. 1 of the present invention is composed of a plurality of impeller assemblies 2 shown in fig. 2, a hub-side disc-shaped fixing plate 5, a shaft portion 6, and a hub portion 7. The shaft portion 6 is attached to the disc-shaped member 3 of the unit 2 at one end of the impeller 1. The hub-side disc-shaped fixing plate 5 is attached to the blade member side of the assembly at the other end of the impeller 1. The boss portion 7 is provided on the boss-side disc-shaped fixing plate 5.

<2> Structure of blade Member (Assembly 2)

The assembly 2 of the impeller 1 is composed of a disc-shaped member 3 and a blade member 4. The material is AS resin, ABS resin or PP resin. In addition, the composite material of the resin and the glass fiber can be selected. The resin and the like described herein are only examples, and any synthetic resin may be used as long as it can provide a molded article with a certain strength. In addition, the composite material of synthetic resin and glass fiber can be selected. The disc-shaped member 3 and the blade member 4 are integrally molded by extrusion molding, press molding, extrusion molding, or the like. The components 2 can be bonded by bonding such as ultrasonic welding. The hub-side disc-shaped fixing plate 5 may be joined to the blade member 4 of the assembly 2 at the hub-side end portion of the impeller 1 by an adhesive method such as ultrasonic welding.

In the present invention, a plurality of the components of the shape of fig. 2 are molded, unlike the blade components of the current product (please refer to fig. 13). That is, unlike the current product of fig. 13, the twist in the longitudinal direction of the bladeless section 4 is a straight line. These are joined by an adhesive method such as ultrasonic welding as described above to form the impeller.

The blade member 4 of the unit 2 of the impeller 1 has a thickness with a draft angle (draft angle) for molding. The blade member 4 has an average thickness of 0.3mm to 0.8 mm. Preferably 0.4mm to 0.6 mm. If the average thickness of the blade member is less than 0.3mm, moldability by molding becomes poor, and there is a possibility that molding failure occurs on the tip side of the blade member. If the average thickness of the blade member is greater than 0.8mm, it may be difficult to fit the blade member into a fitting groove provided in a disk-shaped member to be described later by twisting or the like.

<3> Material of blade Member (Assembly 2)

Next, the materials of the unit 2 of the impeller 1 and the hub-side disc-shaped fixing plate 5 will be described. The material can be synthetic resin such AS AS resin, ABS resin or PP resin. In the present invention, in order to fit the tip end of the blade member into a fitting groove provided in a disk-shaped fixing plate to be described later by deformation, it is necessary to provide the tip end of the blade member with a flexible average thickness.

In addition, the composite material of synthetic resin and glass fiber can be selected. In this case, the average thickness of the blade member is also preferably 0.3mm to 0.8mm, more preferably 0.4mm to 0.6 mm. If the average thickness of the blade member is less than 0.3mm, moldability by molding becomes poor, and there is a possibility that molding failure occurs on the tip side of the blade member. If the average thickness of the blade member is greater than 0.8mm, the glass fiber in the blade member does not face the surface or back surface of the blade member, and thus the elastic modulus (E') of the blade member may be lowered. The elastic modulus (E') will be described later. When the composite material is used, the content of the glass fiber is preferably 10 to 40% by weight, more preferably 10 to 30% by weight, of the whole. If the content of the glass fiber is greater than 40% by weight of the entire assembly, molding failure of the blade member of the assembly may occur. If the ratio is less than 10%, the strength of the blade member may be reduced.

In addition, the blade component of the impeller of the invention can be made of composite material of synthetic resin material and glass fiber, and the elastic coefficient (E') of the composite material is 2.5 multiplied by 10⁹Pa～1.2×10¹⁰Pa of a composite material. If the modulus of elasticity (E') of the composite is less than 2.5X 10⁹Pa, while it may be more than 1.2X 10 because it may not exhibit any low elastic modulus and may easily recover (recover)¹⁰Pa, molding failure of the blade member of the module occurs, and it is difficult to realize production.

The modulus of elasticity (E') was measured by preparing a test piece of a predetermined size from the molded blade member and measuring it with a viscoelasticity measuring instrument (RSA 3 manufactured by TA INSTRUMENTS). The measurement of the modulus of elasticity was carried out at a temperature rise rate of 7.2 ℃ and 7 minutes and a measurement frequency of 1 Hz. In addition, the modulus of elasticity was measured at 20 ℃.

Further, the elastic coefficient (E') of the composite material of the resin material and the glass fiber used for the blade member of the impeller of the present invention tends to be high when the thickness of the blade member is reduced and low when the thickness of the blade member is increased as shown in fig. 2. When the thickness is made to be 0.5mm to 2mm, the elastic modulus (E') becomes about half.

Further, when the oil content of the glass fiber is increased, the elastic modulus (E') tends to be increased. When the content of the glass fiber is increased to 10 to 40% by weight, the elastic modulus (E') becomes about three times.

<4> method for bonding modules

Next, a method of bonding modules will be described. When the components shown in fig. 2 are joined, a fitting groove 8 for fitting the tip end of the blade member is formed in the disk-shaped member 3 on the side where the blade member 4 is not formed, corresponding to the blade member of the joined components (see (c) in fig. 2). The tip ends of the blade members are fitted into the fitting grooves, and the impeller is joined and molded by an adhesive method such as ultrasonic welding. In the present invention, in order to improve the noise performance of the impeller, the shape of the fitting groove of the fitting blade member was studied. Next, an example of the fitting groove will be described with reference to fig. 3 to 5. As shown in fig. 2 (c), the fitting groove 8 is provided in plural on the disc-shaped member 3 of the module 2, but one (M portion in the drawing) will be described in detail. The rest are the same.

[ examples of the fitting grooves ]

The fitting groove will be described with reference to fig. 3 to 5 of the present embodiment. As shown in fig. 3, the fitting groove 8 of the present embodiment has a bottom portion having substantially the same shape as the tip portion of the blade member 4 of the unit, and is provided at a position on the disc-shaped member 3 where the shape of the tip portion of the blade member of the unit is projected on the disc-shaped member 3, and the position and the shape are varied in phase as follows. The modified method is shown in fig. 3. In fig. 3, the 1-point chain line is a shape obtained by projecting the shape of the tip portion of the blade member onto the disc-shaped member, and is substantially the same as the bottom portion of the fitting portion 8.

The center position of the shape of the 1-point chain line is set to 0. The center position 0 is also a center position on the center line of the fitting groove 8. The fitting groove 8 is rotated by 1 to 7 degrees about its central position 0. Fig. 3 is a view showing the disc-shaped member rotated clockwise with respect to the center position 0 of the fitting groove 8. If the variation angle of the fitting groove is less than 1 degree, there is a possibility that the effect of reducing the Nz sound cannot be obtained. If the angle is greater than 7 degrees, the tip end of the blade may be locally deformed when the tip end of the blade member is twisted in the fitting groove. The twist angle of the fitting groove is preferably 2 to 6 degrees. More preferably 3 to 5 degrees.

The cross-sectional shape of the fitting groove 8 is as shown in fig. 4. Fig. 4 shows the cross-sectional shapes of the grooves at positions a, B, C, D and E of the fitting groove shown in fig. 3 (a). In the figure, position A, position B, position C, position D and position E each correspond to section A-A through section E-E. The position C is a cross-sectional shape at the central position 0 of the fitting groove. The position a and the position B are the central position side of the disc-shaped member, and the position D and the position E are the outer peripheral position side of the disc-shaped member. The fitting groove 8 has an edge portion formed with an inclined portion T1 and an inclined portion T2. The inclined portion T1 is an inclined portion formed at an edge portion L1 (see fig. 3) of the fitting portion 8, and the inclined portion T2 is an inclined portion formed at an edge portion L2 (see fig. 3) of the fitting portion 8. The inclined portions T1 and T2 are point-symmetrical with respect to the center 0 of the fitting groove. The inclined portion T1 is inclined gradually from the slot center 0 toward the peripheral side of the disc-shaped member. The inclined portion T2 is inclined gradually from the slot center 0 toward the center side of the disc-shaped member.

The blade member 4 is formed linearly in the longitudinal direction, but the angle varies with respect to the fitting groove. Therefore, as shown in fig. 3 (a), when the blade member is fitted into the twisted fitting groove, first, both ends of the tip portion of the blade member come into contact with the inclined portions T1 and T2, and are smoothly and smoothly fitted into the fitting groove. Fig. 5 shows this state. Fig. 5 shows a case where the inclined portions T1 and T2 of the fitting groove are enlarged so that the blade is gently fitted in the fitting groove and contacts the bottom of the fitting groove. The fitting of the tip end portion of the blade member 4 into the fitting groove 8 is as shown in fig. 5

The sequence of (a) is completed. As described above, the tip end of the blade member is fitted into the fitting groove in a twisted state. In the state where the tip end portion of the blade member is fitted in the fitting groove, the tip end portions of the ridge line a and the ridge line B of the blade member in fig. 2 (d) are twisted. The blade member 4 is not twisted at portions 6 to 7 of the length L in the longitudinal direction. The center line of the blade member 4 in fig. 2 (d) is not twisted from the bottom to the tip. After the tip end portions of the blade members are fitted in the fitting grooves in this way, the fitting portions are joined by ultrasonic welding or the like.

<5> embodiment of impeller of the present invention

The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[ examples 1 to 6]

In this example, the module and the hub-side disk-shaped fixing plate were made of a composite material of AS resin having a glass fiber content of 20% by weight of the entire. The blade members of the assembly were shaped as shown in figure 2, with an average thickness of 0.4mm, a length of 79mm and a number of 35 sheets. In addition, the diameter of the assembly is 106mm at the outermost portion of the blade member 4. The component is formed by extrusion molding of the material. Further, the impeller shown in fig. 1 was produced by joining 8 units and the hub-side disk-shaped fixing plate 5 made of the same material as the unit 2 by ultrasonic welding. The impeller manufactured by the method has the overall length of 635mm, the diameter of 106mm and the overall weight of 385 gr.

In the present embodiment, the fitting groove 8 formed in the disc-shaped member is (a) in fig. 3 of the embodiment. The rotation angle θ of the blade member of the disc-shaped member with respect to the center position of the fitting groove is set to 1 degree, 2 degrees, 3 degrees, 4 degrees, 5 degrees, 6 degrees, and 7 degrees in the clockwise direction when viewed from the direction of the opening of the fitting groove. The above-described order of the torsion angle employed in examples 1 to 7.

Comparative examples 1 to 3

The impeller of this comparative example was produced in the same manner as in the example, except that the torsion angle θ of the fitting groove 8 was set to 0 degree, 7.5 degrees, and 10 degrees in the clockwise direction when viewed from the direction of the opening of the fitting groove. The weight of the impeller thus obtained was 385gr in the same manner as in example 1. The order of the twist angle was as in examples 1 to 3.

The impellers produced in the examples and comparative examples were compared by the following test.

[1] Air volume characteristic and noise level

The air volume characteristics of the impellers obtained in examples and comparative examples were evaluated as follows. The impeller manufactured as described above is incorporated into, for example, an indoor unit of an air conditioner, and the indoor unit of the air conditioner is attached to an air volume measuring device to measure an air volume (m)³7min) and the number of revolutions of the impeller. In addition, after the air conditioning indoor unit was mounted on the noise measurement chamber in a wall-mounted state, the noise level (db (a)) was measured. As a result of the measurement, the relationship between the twist angle and the air volume is shown in FIG. 6, and the relationship between the twist angle and the noise level at the same air volume is shownShown in fig. 7.

[2] Nz sound

Comparing the levels of Nz factor in the noise spectrogram when the noise characteristics of [1] are measured on a flat scale. The product of the present invention shows the conditions of the twist angle pairs (twist angle 1-2 degrees, twist angle 6-7 degrees), (twist angle 2-3 degrees, twist angle 5-6 degrees) and (twist angle 3-5 degrees) in fig. 8-10. A prior art noise spectrum plot is shown in fig. 11.

<6> evaluation of Performance of examples and comparative examples

Fig. 6 shows a relationship between the torsion angle and the air flow rate. When the twist angle increases from 0 degrees, the twist angle becomes almost the same up to 7 degrees, but when the twist angle exceeds 7 degrees, the twist angle tends to decrease rapidly. Stable air volume can be ensured in the inventive products of examples 1 to 7.

Fig. 7 shows the relationship between the torsion angle and the noise score. In the invention products of examples 1 to 7 (the twist angle is between 1 degree and 7 degrees), the noise level is 55.8dB (A) to 56.2dB (A), which is a level not affecting the use of the fan. The most preferable state is when the twist angle is 3 to 5 degrees. In comparative examples 1 to 3, the values are values exceeding 56.5dB (A), which are levels affecting the use of the fan.

Fig. 8 to 10 show the level of Nz sound reduction of the inventive products (examples 1 to 7) in noise spectrum diagrams. Fig. 11 shows the level of Nz tones in the prior art as a noise spectrum diagram. In the figure, portions labeled "Nz sound" and "2 Nz" indicate intensity (level) as Nz sound.

Fig. 8 is a noise spectrum diagram of the product of the invention at torsion angles of 1-2 degrees and 6-7 degrees. Fig. 9 is a noise spectrum diagram of the product of the invention at torsion angles of 2-3 degrees and 5-6 degrees. Fig. 10 is a noise spectrum diagram of the product of the invention at a torsion angle of 3-5 degrees. The comparison between the noise spectrogram of the above inventive product and fig. 11, which is the noise spectrogram of the prior art, is as follows:

the noise levels of Nz and 2Nz sounds in the noise spectrogram of the product (embodiment) of the present invention are lower than those of the prior art. In the same invention product, it was found that when the twist angle is set to 3 to 5 degrees, the noise level of Nz sound and 2Nz sound is the lowest.

Claims

1. An impeller for a fan, wherein a plurality of blade members are formed in a cylindrical shape on a disc-shaped member to form a module, and the blade members of the module are joined to the disc-shaped member of another module;

a plurality of blade members of the assembly are molded in a straight line, and the thickness of the blade members is provided with a draft angle for molding;

when the tip end portion of the blade member is fitted into the fitting groove, the center line position of the blade member is fitted in a state where the blade member is not twisted, and a portion of 6 to 7 in the length of the blade member in the longitudinal direction is not twisted and the remaining portion is twisted, and both ends of the blade member are twisted and deformed at the tip end portion of the blade member and then fitted to each other to join the respective units.

2. The impeller for the fan as claimed in claim 1, wherein: the bottom of the fitting groove has the same shape as the shape of the tip of the blade member to be fitted, and the portion of the fitting groove with which the tip of the blade member comes into contact when the blade member is inserted into the fitting groove is formed as an inclined surface whose inclination gradually changes from the center to the peripheral portion of the fitting groove.

3. The impeller for the fan as claimed in claim 1 or 2, wherein: the blade member is made of a composite material of a synthetic resin material and glass fibers, and the resin composite material with the content of the glass fibers being 10-40% by weight is selected.

4. The impeller for the fan as claimed in claim 1 or 2, wherein: the blade member is made of a composite material of a synthetic resin material and glass fibers, and has a surface elastic coefficient (E') of 2.5X 10⁹Pa～1.2×10¹⁰Pa。

5. The impeller for the fan as claimed in claim 3, wherein: the blade member is made of a composite material of a synthetic resin material and glass fibers, and has a surface elastic coefficient (E') of 2.5X 10⁹Pa～1.2×10¹⁰Pa。