JP2751741B2 - Axial fan - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an axial fan for blowing air in the axial direction of a moving blade suitable for a hair dryer or the like.

[0002]

2. Description of the Related Art In recent years, miniaturization of OA equipment and home electric appliances has progressed, and a blower having a small size, high efficiency, a large air volume and low noise has been required. Further, as general blowers, there are sirocco type fans and mixed flow type fans. In these, there is no intervening member, such as a motor, a circuit component or a heater, which acts as a resistance to the flow of air, between the rotor blade and the outlet of the blower.
Although characteristics can be obtained, current consumption is large and efficiency is low, and it is difficult to cope with miniaturization.

On the other hand, there is an axial fan that blows air in the axial direction of the moving blade as one that consumes less current, has high efficiency, and can easily cope with miniaturization. But even in this one,
In a type in which a member that acts as a resistance to the flow of the wind is interposed between the rotor blade and the outlet, it is difficult to say that the flow of the wind is smooth, and the characteristics of the pressure P and the flow rate Q are reduced.

The reason why the flow of wind is not smooth in the conventional axial fan is as follows. That is, as shown in FIG. 5 , the wind flow W1 in the case A having a cylindrical shape, one end of which is a suction port Aa, and the other end of which is an outlet, is a wind flow W1 between the rotor blade B and the outlet. Due to the member (including the motor and the moving blade itself) that resists the flow of air, the stall occurs on the moving blade B surface because the parallel state with the axis cannot be maintained. Then, in the range indicated by X, a part of the flow becomes the opposite flow W2, and in the range indicated by Y, both flows collide to generate a vortex W3. Therefore, this collision generates noise (turbulent noise),
The wind pressure or volume decreases.

Therefore, the applicant of the present application has found that the air volume does not decrease,
In addition, we continued our research to obtain an axial fan with low noise, and proposed the results in Japanese Patent Application No. 63-94380. As shown in FIG. 6 , a thin cylindrical body C having an outer diameter smaller than the inner diameter of the case A is disposed between the suction port Aa and the rotor blade B, and an outer diameter sufficiently smaller than the inner diameter of the thin cylindrical body C as shown in FIG. The bell mouth D composed of the straight pipe part Da and the enlarged diameter part Db connected to the straight pipe part Da is inserted so that the straight pipe part Da enters the inside of the thin-walled cylindrical body C. The end of the enlarged diameter portion Db is joined to the suction port Aa so as to surround the straight pipe portion Da of the mouse D. As a result, a space serving as a return path is formed between the case A and the thin cylindrical body C, and between the thin cylindrical body C and the straight pipe portion Da of the bell mouth D. Therefore, the collision between the main flow W1 and the backflow W2 of the wind is eliminated. , The backflow W2 can also be recovered.

[0006]

SUMMARY OF THE INVENTION The above-mentioned proposal proposed by the present applicant improves the flow of air from an axial fan so that the collision between the main stream W1 and the backflow W2 is eliminated and the backflow W2 can be recovered. However, if the distance between the rotor blade B and the thin-walled cylindrical body C was increased to a certain extent or more, the noise sometimes increased again.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to avoid the collision of the mainstream and the backflow wind, to recover the backflow, and to reduce the axial flow with low noise. To provide fans.

[0008]

SUMMARY OF THE INVENTION In order to solve the above problem, an axial flow fan according to the present invention has a motor and a plurality of blades attached to a rotating shaft of the motor to send air in an axial direction. A rotor blade, a case in which a cylindrical member is formed and one end side is a suction port, and the other end side is a blowout port and a member including a motor and a rotor blade is accommodated and fixed therebetween, and a resistance of wind flow between the blowout port and the rotor blade. In the axial fan provided with a bell mouth at the suction port, and further provided with a thin-walled cylindrical body surrounding the bell mouth between the moving blade and the suction port, the length of the chord of the blade is provided. Is set to L, the distance a between the opposed ends of the rotor blade and the thin cylindrical body is set to 0 <a <0.3 L.

[0009]

According to this construction, the distance a between the rotor blade and each of the opposed ends of the thin cylinder is within a specific range, so that there is no collision between the main flow and the backflow and the backflow is recovered. And noise can be reduced.

[0010]

BRIEF DESCRIPTION based on an embodiment of applying the axial flow fan to the hair dryer of the present invention in FIGS.

Reference numeral 1 denotes a substantially cylindrical plastic case having one end serving as a suction port 1a and the other end serving as a blowout port 1b. Inside the case 1 between the inlet 1a and the outlet 1b, for example, a motor 2 such as a brushless DC motor of about 25,000 rpm, a guide vane 3 located around the motor 2, and a wind of a circuit section and a heater. A member 4 that acts as a flow resistance is accommodated and fixed. The rotating shaft 2a of the motor 2 protrudes toward the suction port 1a, and a moving blade 5 having a plurality of blades for sending wind in the axial direction, that is, toward the blowing port 1b is coaxially attached thereto. In the present embodiment, the inner diameter of the case 1 is about 35 mm, and the outer diameter of the rotor blade 5 is slightly smaller than the inner diameter of the case 1, and a gap g exists between them. It is preferable that the gap g be equal to or less than 2.5% of the outer diameter of the bucket 5. FIG.
(B), the chord of each blade of the rotor blade 5, the end face of the suction port side, i.e., blowout or suction port side et al
And inclined upward toward the mouth side, the length L of that is in the present embodiment is of a approximately 30 mm.

Reference numeral 6 denotes a bell mouth, which comprises a small-diameter straight pipe portion (in the present embodiment, an inner diameter of about 25 mm) 6a and a wide-diameter portion 6b whose section expands in a curved shape from the straight pipe portion 6a. Is joined to the suction port 1a by sandwiching or bonding. 7
Is a protection net, which is attached to the suction port 1a so as to face the enlarged diameter portion 6b of the bell mouth 6.

8 is a thin-walled cylindrical body, the inner diameter of which is a straight pipe
The outer diameter of the rotor blade 5 is larger than the outer diameter of the rotor blade 5 as well as smaller than the inner diameter of the case 1.
More specifically, the shape of the thin cylindrical body 8 is preferably set such that the distance between the thin cylindrical body 8 and the inner peripheral surface of the case 1 is 10 times or less the gap g described above. A space S1 is formed between them. Also, a thin cylindrical body
8 on Case 1 to secure it to Case 1.
An appropriate number of thin ribs 8a, 8a,... Extending radially to this are formed, and these are fixed to the case 1 by press-fitting or bonding. The number of the thin ribs 8a, 8a,... Is set to be relatively prime to the number of blades in order to reduce interference noise with the rotor blade 5. The thin-walled cylindrical body 8 surrounds the straight pipe portion 6a of the bell mouth 6, and a space S2 similar to the space S1 described above is provided between them, between the suction port side end face and the enlarged diameter portion 6b. Space
Set to form S3. The axial length of the thin cylindrical body 8 is 0.5 L to 2 L with respect to the length L of the chord of the blade.
A degree is desirable. The distance a between the opposed ends of the rotor blade 5 and the thin cylindrical body 8 is set to 0 <a <0.3 L.

As shown in FIG. 3 , the flow (main flow) W1 of the wind in the case 1 in such an axial flow fan is caused by the presence of the member 4 serving as a wind resistance, the motor 2 and the moving blade 5, as shown in FIG.
As in the conventional example, the state parallel to the axis cannot be maintained,
In the vicinity of the tip of the rotor blade 5 on the suction port side, a part of the flow becomes a reverse flow (reverse flow = reverse swirling flow) W2. This backflow component W2
Flows through the space S1, the space S3, and then the space S2, and merges into the main stream W1 as if sucked.

[0015] The inventors have for the distance a between the opposite ends of the rotor blade 5 and the thin cylindrical member 8, was carried out sequentially increased to noise measurements it from zero, the measurement results as shown in FIG. 4 was gotten. In the figure, the horizontal axis is distance a and the vertical axis is noise. From this result, when the distance a is very small,
That about 2.5dB noise than if you do not come larger than 0.3L is low,
Then, it was found that when the distance a was smaller than 0.3 L, there was an effect on noise reduction.

[0016]

According to the axial flow fan of the present invention, since the distance a between the rotor blade and each of the opposed ends of the thin cylinder is within a specific range, there is no collision between the main flow and the reverse flow. In addition to collecting the backflow, the noise can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIGS. 2A and 2B are explanatory views illustrating a moving blade, wherein FIG.
FIG. 1B is a cross-sectional view of the AA.

FIG. 3 is an explanatory diagram illustrating the flow of the wind.

FIG. 4 shows the distance between the rotor blades and the opposed ends of the thin-walled cylinder.
FIG. 4 is a characteristic diagram showing noise and measurement results.

FIG. 5 is an explanatory diagram illustrating a conventional flow of wind.

FIG. 6 The wind flow of what the applicant has proposed earlier
FIG.

[Explanation of symbols]

 1 Case 2 Motor 3 Guide vane 4 Wind resistance material 5 Moving blade L Length of blade of moving blade 6 Bellmouth 6a Straight tube of bellmouth 6b Enlarged diameter of bellmouth 7 Protection net 7 Thin-walled cylinder a Distance between blade and thin-walled cylinder 4 W1 Main stream of wind W2 Backflow of wind S1, S2, S3 Space where backflow flows

Continuation of the front page (51) Int.Cl. ⁶ identification symbol FI // A45D 20/12 A45D 20/12 Z (58) Investigation field (Int.Cl. ⁶ , DB name) F04D 29/54 F04D 29/66 F04D 25/08 A45D 20/12

Claims (1)

(57) [Claims] A motor having a plurality of blades attached to a rotating shaft of the motor for sending wind in an axial direction;
A case in which a member having a motor and a moving blade is accommodated and fixed between the outlet and the moving blade, and a member interposed between the blowing port and the moving blade is interposed therebetween. In the axial flow fan provided with a bell mouth at the suction port, and further provided with a thin cylindrical body surrounding the bell mouth between the rotor blade and the suction port, the length of the chord of the blade is L. In this case, the axial flow fan is characterized in that the distance a between the rotor blade and each of the opposed ends of the thin cylinder is 0 <a <0.3 L.