JP2564889B2 - Axial fan - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an axial fan that is suitable for a dryer for drying hair and that sends air in the axial direction of a moving blade.

[Prior Art] In recent years, downsizing of OA equipment and home electric appliances has been advanced, and a blower that is small and has high efficiency, large air volume and low noise is also required.

In general, as blowers, there are Shirotsuko type and mixed flow type fans. In these, there is no member such as a motor, a circuit component or a heater, which is a resistance to the flow of wind, between the moving blades and the outlet pipe of the blower, or even if they are present, the required pressure P-air volume Q characteristics can be obtained. It consumes a lot of power and has low efficiency, and it is difficult to cope with miniaturization.

In addition, there is an axial fan that blows air in the axial direction of the moving blade as one that consumes less power, has high efficiency, and can be easily adapted to miniaturization. However, even in this case, it is hard to say that the wind flow is smooth in the type in which a member that acts as a resistance to the flow of the wind is interposed between the moving blade and the outlet pipe of the blower,
The pressure P-air flow Q characteristic deteriorates. That is, as shown in FIG. 16, the wind flow W1 in the case A, which has a tubular shape and has one end side as a suction port and the other end side as a discharge port, has a wind flow W1 between the moving blade B and the discharge port of the blower. Due to the resistance member, the parallel state with the axis cannot be maintained and stall occurs on the moving blade B surface, and in the range indicated by X, part of the flow W2 is in the opposite direction, and in the range indicated by Y, both flows W1, W2
Collide with each other to generate a vortex W3. Therefore, this collision causes noise (turbulent noise) or a decrease in wind pressure or air volume.

In order to solve such a problem, a thin-walled cylindrical body having an outer diameter smaller than the inner diameter of the case is arranged between the suction port and the moving blade (Actual No. 50-20326 and No. 35).
-32077). These are characterized in that the main stream discharged from the thin-walled cylinder and the backflow generated near the tip of the moving blade are prevented from separating and colliding with each other, and a part of the backflow is re-engaged in the main stream. is there. However, in the case of Japanese Utility Model Publication No. 50-20326, in order to re-engage all of the backflow into the mainstream, the case has a suction port side end surface of the thin-walled cylinder so that the backflow is attracted by the viscosity of the mainstream. The axial length from the inlet to the end face of the suction port must be formed to be a certain length or more, and as a result, it is difficult to form the axial fan in a small size without lowering the efficiency. Also, in the case of Japanese Utility Model Publication No. 35-32077, since the end surface of the thin-walled cylinder on the suction port side is located near the suction port end surface, a part of the backflow portion flows out into the atmosphere, and the air volume is not improved much. I can't expect.

[Problems to be Solved by the Invention] In the conventional axial fan, the size of the case is reduced by forming the thin cylindrical body so that the axial length from the suction port side end surface to the suction port end surface is a certain length or more. It was not possible to achieve a sufficient effect when the thin-walled cylindrical body was arranged such that the end surface on the suction port side was located near the end surface on the suction port.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an axial fan that does not reduce the air volume and has low noise.

[Means for Solving the Problems] In order to solve the above problems, an axial fan according to the present invention includes a motor and a rotor blade that is coaxially attached to a rotation shaft of the motor for sending air in the axial direction. And a case in which a member including a motor and a moving blade is housed and fixed between the one end side of which is a suction port and the other end side of which is a discharge port, which serves as a resistance to the flow of wind between the discharge port and the moving blade. In the axial fan in which the member is interposed, a thin-walled cylindrical body having an outer diameter smaller than the inner diameter of the case is disposed between the suction port and the moving blade, and a large-diameter portion and a thin-walled cylindrical body joined to one end of the case. A bell mouth with a straight tubular small diameter part that enters the inside of the is installed, and the case, thin cylinder and bell mouth form a double flow path structure that causes the backflow generated near the tip of the rotor blade to flow in the mainstream direction. It is configured to be.

[Operation] In the axial flow fan of the present invention, the backflow generated in the vicinity of the tip of the moving blade is sucked by the double flow path structure part by the case, the thin-walled cylindrical body and the bellmouth to surely separate it from the main flow, and the swirl backflow It is possible to prevent flow turbulence and energy loss due to collision and interference of the suction main flow, reduce turbulent noise in the moving blade part due to turbulence on the upstream side, and reliably collect backflow components to suppress air flow reduction, wind power Improve the characteristics. In addition, the bell mouth, which forms a dual flow channel structure, introduces air in the atmosphere to reduce loss and turbulence, and exhibits an acoustic insertion loss function against noise near the tip of the rotor blade. This contributes to noise reduction.

[Embodiment] A first embodiment in which the axial fan of the present invention is applied to a hair dryer will be described below with reference to FIGS. 1 to 3.

FIG. 1 is a side sectional view of the hair dryer taken along the central axis line, showing only one side of the substantially symmetrical axis line.

Reference numeral 1 denotes a substantially cylindrical plastic case having one end as a suction port 1a and the other end as a discharge port (not shown). Inside the case 1 between the suction port 1a and the discharge port, for example, a motor 2 such as a brushless motor of about 16000 rpm, a guide vane 3 located around the motor 2, and a resistance of wind flow such as a circuit part and a heater are provided. The member 4 is accommodated and fixed. The rotary shaft of the motor 2 projects to the suction port 1a side, and a moving blade 5 that sends air in the axial direction, that is, to the discharge port side is coaxially attached to this. The outer diameter of the moving blade 5 is slightly smaller than the inner diameter of the case 1, and a gap g exists between them. Therefore, the member 4 serving as a resistance against the flow of the wind is interposed between the outlet and the moving blade 5.

Reference numeral 6 denotes a thin-walled cylindrical body having an outer diameter smaller than the inner diameter of the case 1 and further smaller than the outer diameter of the moving blade 5, and the axial flow is preferably shorter than that between the suction port 1a and the moving blade 5. With respect to the outer diameter of the thin-walled cylindrical body 6, it is desirable that the space between the thin-walled cylindrical body 6 and the inner diameter of the case 1 be 10 times or less the gap g. Therefore, a space S1 is formed between the case 1 and the thin-walled cylindrical body 6. Further, since the thin-walled cylindrical body 6 is fixed to the case 1, an appropriate number of thin-walled ribs 6a, 6 extending radially to the inner peripheral surface of the case 1 are provided on the outer periphery thereof.
, are formed and fixed to the case 1 by press fitting or adhesion. In addition to the method of forming the thin-walled cylindrical body 6 separately from the case 1, the thin-walled cylindrical body 6 may be molded integrally with the case 1.

Reference numeral 7 is a suction part net provided in the preceding stage of the suction port 1a.

Reference numeral 28 is a bell-shaped mouthpiece having a substantially trumpet shape, in which the large diameter portion 28a has an outer diameter substantially equal to that of the case 1, and the small diameter portion 28b is formed in a straight tube shape smaller than the inner diameter of the thin cylindrical body 6. The outer diameter of the straight tubular portion is set such that the gap between the straight tubular portion and the thin-walled cylindrical body 6 is substantially equal to the gap between the case 1 and the thin-walled cylindrical body 6. Further, if the length of the straight tubular portion is at least half the axial length of the thin-walled cylindrical body 6, better results can be obtained in both noise characteristics and air volume characteristics. Further, the bell mouth 28 may be formed so that the ratio of the diameter D of the large diameter portion 28a and the inner diameter d of the small diameter portion 28b, that is, the suction bell mouth diameter ratio d / D is about 0.6 to 0.7.

The bell mouth 28 has the large diameter portion 28a in the case 1
It suffices that the small-diameter portion 28b having a straight tubular shape is joined to one end of the thin-walled cylindrical body 6 by sandwiching or adhering, and at least half overlaps with the thin-walled cylindrical body 6 in the axial direction. Therefore, the space S2 can be formed between the thin cylindrical body 6 and the small diameter portion 28b.

In such an axial flow fan, as shown in FIG. 3, the wind flow W1 in the case 1 is parallel to the axis by the member 4 which acts as a resistance against the wind flow interposed between the moving blade 5 and the discharge port. The state cannot be maintained, and a part of the flow becomes a reverse flow (reverse swirl flow) W2 in the vicinity of the tip of the moving blade 5 on the suction port 1a side, that is, in the range indicated by X. By the way, this flow (backflow) W2 is a space formed between the case 1 and the thin cylindrical body 6.
Since it flows through S1, it is suppressed from being separated from the flow (main flow) W1 and colliding with it.

Then, the flow (backflow) W2 is the large diameter portion 28a of the thin-walled cylindrical body 6.
When it reaches the vicinity of the side, it changes its direction along the curvature between the large diameter portion 28a and the small diameter portion 28b, becomes a flow in the substantially same direction as the flow (main flow) W1, and joins the flow (main flow) W1 again. As a result, the axial fan of the present embodiment causes the bellmouth 28 to more reliably collect the flow (backflow) W2 of the flow (mainstream) W1, and further shuts off the noise of the rotor blade 5 to perform the present embodiment. It is possible to reduce the noise by about 4 to 6 db as compared with the axial fan of the example (excluding the additional example 1 described later) in which the thin cylindrical body 6 and the bell mouth 28 are removed from the axial fan.

Note that the Applicant, just in case, removes the thin-walled cylindrical body 6 and the bell mouth 28 from the axial flow fan of the present embodiment, and the axial flow fan (supplementary example 1) configured as in the above-described conventional example and the present embodiment. Two types of axial flow fans (an additional test example 2) configured as in the other conventional example except that Bellmouth 28 was removed from the example axial flow fan were manufactured and additional test experiments were conducted. Comparative examples 1 and 2 will be described below. 4 and 5 are drawings relating to the additional test example 2, and FIG. 6 is a drawing comparing the additional test example 1 and the additional test example 2 with respect to the pressure P-air volume Q characteristic. Further, FIG. 16 which is a drawing of the conventional example is used as a drawing of the additional test example 1.

In the additional test example 2, a part of the wind flow W1 becomes a reverse flow (backward swirl flow) W2 in the range indicated by X. This flow (backflow) W2 flows in the space S1 so as to be separated from the flow (main flow) W1. Then, when the flow (backflow) W2 reaches the vicinity of the end face on the suction port 1a side of the thin-walled cylindrical body 6, it is attracted by the viscosity of the flow (main flow) W1 sucked from the suction port 1a, and most of it flows again ( Main stream) Join W1. As a result, the additional test example 2 can suppress the generation of vortices and reduce the turbulent noise component by about 1 to 2 db as compared with the additional test example 1. However, the axial flow fan of the present embodiment has about 4 to 6 db. The noise was not reduced. Further, in the additional test example 2, the air volume is increased by 3 to 5% as compared with the case where the moving blade 5 of the additional test example 1 is set to have substantially the same number of revolutions, but a part of the backflow is discharged from the suction port 1a. It was difficult to expect more air flow. Further, from FIG. 6, it was found that the fall of the wind pressure due to the generation of the vortex was considerably large in the additional test example 1 and was reduced in the additional test example 2.

7 and 8 show a modification of the first embodiment, in which the length of the small diameter portion 28b of the bell mouth 28 is increased.

Next, a second embodiment in which the axial fan of the present invention is applied to a hair dryer will be described with reference to FIGS. 9 to 11.

FIG. 9 is a side sectional view of a main part of the hair dryer cut along the central axis line, showing only one side of the substantially symmetrical axis line. This is one in which fins described later are added to the first embodiment, and other parts are the same as in the first embodiment,
Therefore, the same members are designated by the same reference numerals and detailed description thereof will be omitted.

As shown in FIG. 10, a plurality of fins 39, 39, ... Which extend in a substantially axial direction and are inclined while being slightly curved with respect to the axis are provided on the outer peripheral surface of this thin cylindrical body 36. That is, the plurality of fins 39 are provided in the space S1 between the case 1 and the thin-walled cylindrical body 36.

FIG. 11 shows a part of the thin-walled cylindrical body 36 which is expanded, and the slightly curved fin 39 has a curvature capable of smoothly accepting the swirling flow W2 flowing backward. In the present embodiment, seven fins 39 are provided throughout the axial direction of the thin-walled cylindrical body 36, but the axial length may be shorter than this, and the number is preferably about 10.

In such an axial flow fan, the swirling flow W2 that has flowed backward by the fin 39 can be rectified in the axial direction in addition to the same operation as in the first embodiment, and the air flow rate can be further increased by 3 to 4%.

FIG. 12 shows the flow state of the swirling flow W2 when there is no fin 39.

13 and 14 show a modification of the second embodiment, in which the former is provided with fins 39a, 39a, ... In parallel to the axial direction, and the latter is only the space S1 between the case 1 and the thin cylindrical body 36. Not only in the thin cylindrical body 36 and in the space S2 of the small diameter portion 28b of the bell mouth 28.
9b is provided parallel to the axial direction. That is, in the second embodiment, the space between the case 1 and the thin-walled cylindrical body 36, or the thin-walled cylindrical body
A plurality of fins 39a, 39b are provided in at least one of the spaces between the 36 and the small diameter portion 28b of the bell mouth 28. These modified examples have a slightly lower air flow than those shown in FIGS. 9 to 11, but are still 2-3%.
It is possible to increase the air volume of.

FIG. 15 is a sectional view of a hair dryer to which the second embodiment is applied.

[Advantages of the Invention] In the axial fan of the present invention, the backflow generated in the vicinity of the tip of the moving blade flows through the double flow path structure portion, and thus is prevented from being separated from the main flow flowing through the bell mouth and colliding. As a result, the turbulent flow noise is reduced, and the back flow is more surely collected into the main stream by the bell mouth, so that the reduction in the air volume can be suppressed.
Further, the bell mouth, which constitutes the double channel structure, exhibits an acoustic insertion loss function for noise near the tip of the moving blade and contributes to noise reduction.

[Brief description of drawings]

FIG. 1 is a side sectional view of the first embodiment, FIG. 2 is a perspective view of an essential part thereof, FIG. 3 is an explanatory view of its action, FIG. FIG. 6 is a diagram for explaining its operation, FIG. 6 is a wind pressure-air flow rate characteristic diagram of additional test examples 1 and 2, FIG. 7 is a cross-sectional view of a main part of a modified example of the first embodiment, and FIG. FIG. 9 is a side sectional view of a second embodiment, FIG. 10 is a perspective view of relevant parts, FIG. 11 is an explanatory view of its operation, and FIG. FIG. 13 is a perspective view of a main part of a modified example thereof, FIG. 14 is a perspective view of a main part of another modified example, and FIG. 15 is a perspective view of a hair dryer to which the second embodiment is applied. FIG. 16 is a side sectional view of the conventional example and the additional test example 1. 1 ... Case, 1a ... Suction port, 2 ... Motor, 3 ...
… Guiding blades, 4… members that act as resistance, 5… moving blades, 6,36…
… Thin-walled cylinder, 7 …… Suction part net, 28 …… Bell mouth, 28a …… Large diameter part, 28b …… Small diameter part, 39,39a, 39b ……
Fin, W1 ... Main stream, W2 ... Backflow, g ... Gap, S1, S2
……space.

Front Page Continuation (72) Inventor Yuzo Okuhira, 1048, Kadoma, Kadoma City, Osaka Prefecture, Matsushita Electric Works, Ltd. (56) References B1) Actual Public Sho 35-32077 (JP, Y1) Actual Public Sho 50-20326 (JP, Y1)

Claims (1)

(57) [Claims] Claim: What is claimed is: 1. A motor, a rotor blade coaxially attached to a rotation shaft of the motor for sending air in an axial direction, and a tubular shape, one end side of which is a suction port and the other end side is a discharge port, and between them. In an axial fan in which a member including a motor and moving blades is housed and fixed, and a member that acts as a resistance to the flow of wind between the discharge opening and the moving blades is interposed, the case between the suction opening and the moving blades is While disposing a thin-walled cylinder having an outer diameter smaller than the inner diameter, a bell mouth having a large-diameter portion joined to one end of the case and a straight tubular small-diameter portion that enters the inside of the thin-walled cylindrical body is provided, and a case, An axial-flow fan that has a double-flow passage structure in which a backflow generated near the tip of a moving blade is made to flow in the mainstream direction by a thin-walled cylindrical body and bellmouth.