JP2002201944A - Axial fan - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress noise and the lowering of fan efficiency by eliminating the effect of back flow on suction air flow in an axial fan. SOLUTION: This axial fan comprises a ring 5 for connecting the tip parts of vanes 4 to each other having a bell mouth 7 formed at the suction side end part thereof, and a shroud 6. When a vane diameter is Df, the tip part diameter of the bell mouth 7 is Dr, the inner diameter of the shroud on the inside of the bell mouth 7 is Dsr, and the discharge angle of the back flow is α, the axial fan has the relation of 1.07<=Dr/Df<=1.09, Dr>=Dsr, and >0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an axial flow fan used for cooling a radiator of an automobile, and more particularly to an axial flow fan in which backflow of a fan is prevented from being sucked into intake air to prevent noise increase and fan efficiency reduction. Regarding fans.

[0002]

2. Description of the Related Art An axial fan used for cooling a radiator of an automobile is provided with a plurality of blades radially on a boss portion rotated by a drive source such as an engine or a motor, and blows the air in the axial direction by the rotation of the blades. It has become. Generally, an axial fan has a phenomenon in which a part of air blown from a downstream side flows backward from a blade periphery to an upstream side (intake side), and if such a backflow is large, the air blowing efficiency is reduced and noise is increased, so it is preferable. Absent.

[0003] Conventionally, therefore, a method has been adopted in which the blade tips are connected to each other by a ring, and a cylindrical shroud is disposed facing the outside of the ring in the radial direction to suppress backflow.
Further, in order to enhance the effect of suppressing the backflow, a method of forming a labyrinth seal portion between the outer surface of the ring and the inner surface of the shroud has been adopted. On the other hand, a bell mouth whose cross section is formed in an arc shape on the intake side of the ring is aimed at suppressing turbulence (turbulence) of intake air, which is a main cause of noise generation and reduction of fan efficiency in an axial fan. Is often provided.

FIGS. 3A and 3B show an example of an axial fan for cooling a radiator mounted on an automobile and a fan shroud thereof. FIG. 3A is a sectional view, and FIG. 3B is a front view in the AA direction. The axial fan 1 has a drive shaft 2 rotated by a crankshaft or a fan motor of an engine (not shown), and a plurality of blades 4 radially provided on a boss 3 fixed to the drive shaft 2. 3A, the air is blown from the left side to the right side. The tip of each wing 4 is connected to each other by a ring 5,
An annular shroud 6 is disposed facing the outside of the ring 5 in the radial direction.

[0005] At the end of the ring 5 on the intake side, there is provided a bell mouth 7 having an arc-shaped cross section and curved in the radial direction. On the other hand, the shroud 6 is connected to the cylindrical connecting body 8 at the flange portion 12, and the connecting body 8 is fixed to the radiator 9. The outer peripheral surface of the ring 5 and the inner peripheral surface of the cylindrical body 11 in the shroud 6 are opposed to each other with a slight gap so as not to contact each other, and a part of the air blows from the downstream side through a passage 10 formed in the gap. Backflow to the intake side.
When such a bell mouth 7 is provided on the intake side of the axial fan 1, the air on the intake side including the backflow is sucked into the axial fan 1 with turbulence suppressed to some extent. However, since the turbulence itself is not completely eliminated, it is to be understood that the bellmouth 7 is only a means for avoiding noise generation and a decrease in fan efficiency to some extent.

[0006] Since the backflow is a major cause of turbulence in the suction airflow, a method of forming a labyrinth seal portion in the passage 10 to reduce the absolute amount of the backflow is recommended as described above. However, even if the labyrinth seal portion is formed, the backflow cannot be completely eliminated, so that it is difficult to suppress the noise and the decrease in the fan efficiency to a practical level only by combining the labyrinth seal portion and the bell mouth 7. There are many.

On the other hand, there has been proposed an attempt to suppress the influence of the backflow by other means to improve noise generation and reduction in fan efficiency. Japanese Patent Application Publication No. 7-501593 discloses a method of arranging a large number of stators at predetermined intervals in a backflow passage formed between a ring and a shroud of an axial fan, or an inlet or an outlet thereof. . Generally, the backflow has a component in the direction in which the blade rotates, and it has been found that when the backflow having the rotation direction component is drawn into the axial fan from the intake side, turbulence is generated. Therefore, the technique disclosed in the above publication rectifies the backflow with a large number of stays, thereby reducing the rotational direction component and suppressing the occurrence of turbulence.

[0008]

However, the method proposed in Japanese Patent Publication No. Hei 7-501593 has a complicated structure and a high cost. In addition, the weight increases accordingly, which is disadvantageous when mounted on an automobile or the like. Accordingly, an object of the present invention is to avoid noise and a decrease in fan efficiency due to backflow, and to provide a new axial fan for that purpose.

[0009]

That is, an axial fan according to the present invention is an axial fan in which a plurality of blades are radially provided on a boss portion, a ring connecting the tips of the blades to each other,
A shroud opposed to the ring in the radial direction is provided, and a bell mouth formed at the intake end of the ring is provided. The wing diameter is Df, the tip diameter of the bell mouth is Dr, and the shroud inside the bell mouth is provided. When the inner diameter is Dsr and the outflow angle of the backflow is α, 1.07 ≦ Dr / Df ≦ 1.0
9, characterized by having a relationship of Dr ≧ Dsr, α> 0.

Here, each diameter is a diameter centered on the rotation axis of the boss portion, and α is an outflow angle of the backflow R with respect to a reference line parallel to the rotation axis. Unlike the backflow rectification proposed in Japanese Patent Publication No. Hei 7-501593, the axial flow fan of the present invention moves the backflow ejected to the suction side away from the suction area of the blast by using the above-described configuration. The feature is that the generation of turbulence is effectively suppressed by this. There is no technical idea in the past that the noise and the reduction in the fan efficiency are suppressed by preventing the turbulent backflow as the intake air as much as possible.

[0011]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a partially enlarged view of a blade of an axial fan of the present invention, and a main part of an axial fan (not shown) is configured in the same manner as FIG. The arrow F indicates the direction of air flow of the axial flow fan, and the tips of the blades 4 are connected to each other by a short cylindrical ring 5, and a bell mouth 7 having an arc-shaped cross section is provided at the intake end of the ring 5. The ring 5 and the bell mouth 7 are made of resin, for example, and can be integrally formed by molding.

The shroud 6 includes a cylindrical body 11 and a flange 1.
2, which can be integrally formed by molding a resin. In this example, the intake side of the cylindrical body 11 is formed in a crank shape, so that the backflow R passes through the space 13 formed obliquely and inside the bell mouth 7. In the figure, Df is the blade diameter, Dr is the tip diameter of the bell mouth, Dsr is the shroud inside diameter inside the bell mouth,
α is the outflow angle of the backflow, and the measurement standard of those diameters is as described above.

As described above, the axial flow fan of the present invention discharges the backflow away from the intake portion of the blast, thereby effectively suppressing the turbulent flow. The R ejection position and direction. Considering the ejection position of the backflow R from the relationship with the radial direction, the tip position of the bell mouth 7, that is, the tip diameter D of the bell mouth
r, and given the relative relationship with wing 4, D
It is affected by the ratio between r and the blade diameter Df. It was also found that the direction of the backflow, that is, the outflow angle α of the backflow, is greatly affected by the ratio of the tip diameter of the bell mouth to the diameter Dr and the inner diameter Dsr of the shroud inside the bell mouth.

In particular, the outflow angle α of the latter
The backflow R entering horizontally at 0 is regulated by the inner diameter of the shroud inside the bellmouth (that is, the inner diameter of the horizontal portion closest to the bellmouth 7 of the cylindrical body 11) Dsr, enters the space 13, and slopes inside the bellmouth 7. To change the direction, and the jet is blown off by the centrifugal force, so that the relative relationship between Dr and Dsr greatly affects.

It is preferable that the backflow is more radially outward from the blade diameter Df and that the outflow angle α is larger because the backflow is farther from the suction portion of the airflow. The latter outflow angle α must be at least larger than zero. It is. However, if the jetting position is excessively moved, the external dimensions of the axial fan become large, so that there is a practical limit.

FIG. 2 shows data of the noise level SPL (dB) with respect to the change of the tip diameter Dr of the bell mouth, which was tested on an axial fan having a blade diameter Df of 340 mm. In the experiment, the relationship between the tip diameter Dr of the bell mouth and the inner diameter Dsr of the shroud inside the bell mouth was maintained at Dr ≦ Dsr, and Dr was gradually increased. As can be seen from FIG. 2, the noise is large in the range of Dr / Df <1.05,
In the range of Dr / Df = 1.05 to 1.07, the noise level does not decrease so much, and the noise level sharply drops from Dr / Df ≧ 1.07.

Further, in the range of Dr / Df> 1.09, the effect of lowering the noise level tends to be saturated, and on the contrary, it is disadvantageous in terms of dimensional restrictions. According to experiments, it was confirmed that the reduction effect of the noise level and the reduction of the fan efficiency tended to be proportional. As Dr / Df is increased under the condition of Dr ≦ Dsr, the outflow angle α of the backflow R
Is getting bigger. From these experimental results and the above-mentioned reasons, 1.07 ≦ Dr / Df ≦ 1.09, Dr ≧ Ds
It is understood that the range of r, α> 0 is a preferable range in terms of suppression of noise, suppression of reduction in fan efficiency, and suppression of size.

In the above embodiment, the labyrinth seal portion is not formed between the ring 4 and the shroud 6. However, the present invention relates to a method in which an annular rib is provided on the inner surface of the shroud at right angles to its axis. Obviously, the present invention can be applied to a case where a labyrinth seal portion is provided.

[0019]

As described above, in the axial flow fan of the present invention, the blade diameter Df, the tip diameter Dr of the bell mouth, the shroud inner diameter Dsr inside the bell mouth, and the outflow angle α of the backflow are specified in the claims. , The backflow is released away from the intake part of the blast, and the turbulence of the suction is effectively suppressed, thereby obtaining a low noise level and high fan efficiency despite the simple structure. it can.

[Brief description of the drawings]

FIG. 1 is a partially enlarged view of a blade tip portion in an axial fan according to the present invention.

FIG. 2 shows the tip diameter D of a bell mouth for an axial fan.
The figure showing the experimental data of the noise level SPL (dB) at the time of changing r.

FIG. 3 is a view showing an axial fan for cooling a radiator mounted on an automobile.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Axial fan 2 Drive shaft 3 Boss part 4 Blade 5 Ring 6 Shroud 7 Bell mouth 8 Connecting body 9 Radiator 10 Passage 11 Tubular body 12 Flange part 13 Space

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3H033 AA02 AA15 BB02 BB08 CC01 CC04 DD10 DD27 EE06 EE08 3H034 AA02 AA15 BB02 BB08 CC01 CC04 DD05 DD25 EE06 EE08

Claims (1)

[Claims] 1. An axial fan 1 having a plurality of blades 4 radially provided on a boss portion 3 and a ring 5 connecting the tips of the blades 4 to each other, and a radially outer side of the ring 5 opposed to each other. A shroud 6 and a bell mouth 7 formed at the end of the ring 5 on the intake side are provided. The wing diameter is Df, the tip diameter of the bell mouth 7 is Dr, the inner diameter of the shroud inside the bell mouth 7 is Dsr, When the outflow angle is α,
An axial fan characterized by having a relationship of 07 ≦ Dr / Df ≦ 1.09, Dr ≧ Dsr, α> 0.