JPH0773529B2 - Axial fan - Google Patents

Description

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

[Conventional technology]

In recent years, OA equipment and home appliances have been downsized, and there is a demand for a blower that is small, highly efficient, and has a large air volume and low noise.

As a general blower, there are sirocco type and mixed flow type fans. These are between the blade and the blower outlet of the blower,
There is no intervening member such as a motor, a circuit component, or a heater that becomes a resistance to the flow of air, or even if it is intervening, the required pressure P-air volume Q characteristic can be obtained, but the current consumption is large and the efficiency is low. It is difficult to respond to miniaturization.

Further, there is an axial fan that blows air in the axial direction of the moving blade as a device that consumes less current, 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 a type in which a member that resists the flow of wind is interposed between the moving blade and the blowout port of the blower,
The pressure P-air flow Q characteristic deteriorates.

The reason why the air flow is not smooth in the conventional axial fan is as follows. That is, as shown in FIG. 4, the wind flow W1 in the case A, which is cylindrical and has one end side as the suction port Aa and the other end side as the blowing port, has a wind flow W1 between the moving blade B and the blower port of the blower. Due to the flow resistance member (including the motor and the moving blade itself), the parallel state with the axis cannot be maintained, and stall occurs on the moving blade B surface. A part of the flow W2 is in the opposite direction in the range indicated by X, and both flows W1 and W2 collide in the range indicated by Y to generate a vortex W3. Therefore, due to this collision, noise (turbulent noise) is generated, or the wind pressure or air volume is reduced.

Therefore, the inventors of the present application have conducted extensive research in order to obtain an axial fan with low air flow and low noise.
In 63-94380 (Japanese Patent Laid-Open No. 2-5799), the result was proposed. In itself, 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 to form a space between the case and the thin-walled cylindrical body. A bell mouth, which is joined to the suction port and has a straight tubular small diameter part that enters the inside of the thin-walled cylinder, forms a space between the thin-walled cylindrical body and the straight tubular small-diameter part. And the like.

In the case where the thin cylindrical body is arranged, the main flow that is blown out and the reverse flow generated near the tip of the moving blade can be separated, the collision of both is reduced, and the case where the bell mouth is attached to form the return path is , The backflow is surely recovered to the mainstream, and the collision between the mainstream and the backflow is eliminated near the suction port,
Therefore, it was possible to suppress the decrease in the air volume and to reduce the noise.

[Problems to be Solved by the Invention]

Even after making the above proposal, the inventors of the present application have examined whether or not there is an element capable of further reducing noise while adopting such a basic configuration. As a result, it was found that the relationship between the small diameter part of the bell mouth and the inner diameter of the case affects noise.

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 in which the air volume does not decrease and the noise can be further reduced.

[Means for Solving the Problems]

In order to solve such a problem, the axial fan of the present invention,
A thin cylinder is placed inside the case, and a bell mouth is joined to the suction port of the case.
When D ₁ and the inner diameter of the straight tubular small-diameter portion of the bell mouth are D ₂ , the relationship of 0.5D ₁ ≦ D ₂ ≦ 0.8D ₁ is established.

[Operation] According to the present invention, the thin-walled cylindrical body reduces the collision of the main flow with the back flow generated near the tip of the moving blade, and the bell mouth and the recirculation passage reliably collect the back flow, and the vicinity of the suction port. There is no collision between the main flow and the back flow in the above, and in addition, by having a special relationship between the inner diameter of the case and the inner diameter of the small diameter part of the bell mouth, the air flow becomes extremely good, so the air volume does not decrease. Moreover, the noise can be further reduced.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS.

Reference numeral 1 denotes a substantially cylindrical plastic case having one end as a suction port 1a and the other end 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 motor at about 16,000 rpm, guide vanes 3 located around the motor 2, and a flow of wind such as a circuit portion and a heater. The member 4 serving as the resistance of is accommodated and fixed. The rotation shaft of the motor 2 projects toward the suction port 1a, and
A moving blade 5 having a plurality of blades for sending air in the axial direction, that is, to the outlet 1b side is coaxially attached.

In this embodiment, the inner diameter of the case 1 is about 50 mm and 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. Further, the member 4 serving as a resistance against the flow of wind is interposed between the blowout port 1b 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 has an axial length shorter than that between the suction port 1a and the moving blade 5. . Regarding the outer diameter of this, it is desirable that the space between this and the inner peripheral surface of the case 1 be 10 times or less of the above-mentioned gap g, so that a space S1 is formed between the case 1 and the thin cylindrical body 6. In order to fix this to the case 1, an appropriate number of thin ribs 6a, 6 are formed on the outer peripheral surface thereof to extend radially to the inner peripheral surface of the case 1.
are formed, and they are fixed to the case 1 by press fitting or bonding.

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. Furthermore, the end surface 6b of the thin-walled cylindrical body 6 on the suction port 1a side is located inside the end surface of the case 1, that is, the inner edge of the suction port 1a so that a space can be formed between the thin cylindrical body 6 and a bell mouth described later. To do so.

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

8 is a bell mouth, which has a roughly trumpet shape and has a large diameter portion.
8a has an outer diameter substantially equal to that of the case 1, and the small diameter portion 8b is formed in a straight tubular shape smaller than the inner diameter of the thin cylindrical body 6. In this embodiment, the small diameter portion 8b has an inner diameter of about 30 mm.
A space S2 is formed between the thin cylindrical body 6 and the thin cylinder 6, and the radial widths of the spaces S1 and S2 are substantially equal. Further, the bell mouth 8 has an axial length of about 40 mm and the small diameter portion 8b has a length of about 30 mm.
The bell mouth 8 has a large-diameter portion 8a attached to one end of the case 1, that is, an edge of the suction opening 1a by sandwiching or adhering, and a small-diameter portion 8b enters the inside of the thin-walled cylindrical body 6 and extends in the axial direction. Overlaps with the thin-walled cylinder 6. It is desirable that this amount of overlap be at least half the axial length of the thin-walled cylindrical body 6.

In such an axial fan, as shown in FIG. 2, a wind flow 1W in the case 1 is conventionally formed by a member 4 or a motor 2 or a moving blade 5 which acts as a resistance to the wind interposed between the moving blade 5 and the outlet 1b. As in the example, the state parallel to the axis cannot be maintained, and a part of the flow in the opposite direction (reverse swirling flow) W2 near the tip of the moving blade 5 on the suction port 1a side, that is, in the range indicated by X Becomes This flow (backflow) W2 flows through the space S1, is then turned by the bell mouth 8 to flow through the space S2, and merges with the flow (main flow) W1 after passing through the inner end surface of the small diameter portion 8b. The flow (backflow) W2 is recovered and the air volume does not decrease. That is, these spaces S1 and S2 form a return path. Further, the thin cylindrical body 6 separates the flow (main flow) W2 and the flow (backflow) W2 from each other so that they do not collide with each other, thereby suppressing the generation of vortices. Will be done.

FIG. 3 shows the inner diameter D _{1 of the} case ₁ and the small diameter portion of the bell mouth 8.
It shows how the relationship of the inner diameter D ₂ of 8b affects noise. This measurement was obtained by changing the air flow rate (Q = 0.57 m ³ / min) and the axial length of the above member while changing D ₁ and D ₂ . And in FIG. 3, the horizontal axis is D ₂ / D ₁ ,
The vertical axis represents noise [dB (A)]. According to this measurement result, when the relationship of 0.5D ₁ ≦ D ₂ ≦ 0.8D ₁ is satisfied, the noise is the axial flow obtained by removing the thin-walled cylindrical body 6 and the bell mouth 8 from the axial flow fan of this embodiment. 4 to 6 than a fan
[DB (A)] becomes lower.

〔The invention's effect〕

Since the axial fan of the present invention is configured as described above, the thin-walled cylindrical body reduces the collision of the main flow with the reverse flow generated near the tips of the moving blades, and the bell mouth and the return passage ensure the recovery of the reverse flow component. At the same time, there is no collision between the main flow and the back flow near the suction port, and in addition, by having a special relationship between the inner diameter of the case and the inner diameter of the small diameter part of the bell mouth, the wind flow becomes extremely good. Therefore, the air volume does not decrease and the noise can be further reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the present invention, FIG. 2 is an explanatory view of wind flow, and FIG. 3 shows how the relationship between a case and a bell mouth affects noise. The characteristic diagram shown in FIG. 4 is an explanatory diagram of the flow of wind in the conventional example. 1 ... Case, 1a ... Suction port, 1b ... Blowout port,
2 ... Motor, 3 ... Guide vane, 4 ... Member that acts as resistance to wind flow, 5 ... Moving vane, 6 ... Thin cylindrical body, 7 ... Suction net, 8 ... Bell mouth, 8a …… Large diameter part, 8b…
… Small diameter part, D ₁ …… Case inner diameter, D ₂ …… Bell mouth small diameter part inner diameter, S1, S2 …… Space (return path).

Claims (1)

[Claims] Claim: What is claimed is: 1. A motor, a rotor blade coaxially attached to a rotating 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 of which is a blowing port. A case in which a member including a motor and a moving blade is housed and fixed, a thin-walled cylindrical body having an outer diameter smaller than the inner diameter of the case and disposed between the suction port and the moving blade, and a large diameter portion of the suction port of the case. The bell-mouth has a small diameter portion of a straight tube attached to the inside of the thin-walled cylindrical body, and a member serving as a resistance to the flow of wind is interposed between the outlet and the moving blade, and between the case and the thin-walled cylindrical body, in axial flow fan to form a return path by the space between the small diameter portion of the thin-walled cylindrical body and the bell mouth, when the inner diameter of the case and D _1, the inner diameter of the small diameter portion of the bellmouth and D _2, 0.5D ₁ ≦ D ₂ An axial fan having a relationship of ≤ 0.8D ₁ .