JP2003232296A - Blower fan - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a blower fan reducing electromagnetic vibration sound without using an elastic body and moreover dispensing with marked enlargement of a hub part diameter. <P>SOLUTION: A hub 11 of this blower fan 10a is formed in concentric double structure of an outer hub 11a provided with fan blades 12, and an inner hub 11b provided with a boss 14 fitted to a shaft 2 of a fan driving motor 1. The outer hub 11a and inner hub 11b are connected at one end part side by an annular connecting part 19, and an annular space 20 is formed between the inner peripheral surface of the outer hub 11a and the outer peripheral surface of the inner hub 11b. A boss 14 is projected toward the fan driving motor 1 from an end wall 13 provided at the other end of the inner hub 11b. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a structure of a blower fan.

[0002]

Blower fans are indispensable for air conditioners, electric fans, ventilation fans, cooling devices for radiators of automobiles, and the like. 4 to 6 show an example of a conventional blower fan. The blower fan shown here is of a type called a propeller fan. 1 is a fan drive motor,
2 is the shaft. The fan driving motor 1 is arranged with the shaft 2 standing upright, and a blower fan 10 which is an injection molded product of synthetic resin is attached to the tip (upper end) of the shaft 2.

At the center of the blower fan 10 is a hub 11 having a cup-like shape. A plurality of fan blades 12 radially protrude from the outer peripheral surface of the hub 11. At the center of the end wall 13 of the hub 11, a boss 14 that is fitted to the shaft 2 from the outside is formed in the direction of the fan driving motor 1. The outer peripheral surface of the boss 14 and the inner peripheral surface of the hub 11 are connected by a plurality of spoke-shaped ribs 15 as shown in FIG.

The tip of the shaft 2 has a much thinner male screw portion 3
It has become. The blower fan 10 is fixed to the shaft 2 by fitting the boss 14 onto the shaft 2 and then screwing and tightening the nut 4 onto the male screw portion 3.

The torque is transmitted from the shaft 2 to the blower fan 10 by the following mechanism. First, the flat surface portion 5 is provided on the side surface of the tip portion of the shaft 2, and the shaft 2 and the male screw portion 3 are provided.
Both have a D-shaped cross section as seen in FIG. A flat surface portion 16 that engages with the flat surface portion 5 of the shaft 2 is provided on the inner surface of the central hole of the boss 14 (see FIG. 5). A flat portion 18 that engages with the flat portion 5 of the male screw portion 3 is provided in a center hole of a washer 17 that is insert-molded on the end wall 13 of the blower fan 10. In this way, the flat portions are engaged with each other at the male and female fitting portions, whereby torque is transmitted. The position where the washer 17 engages with the stepped portion between the shaft 2 and the male screw portion 3 is the fitting limit of the boss 14.

Generally, a fan produces noise when it rotates, and various attempts have been made to reduce the noise.

In the plastic centrifugal fan described in JP-A-61-116097, a first inner boss ring fixed on a shaft and a second boss ring for supporting a rotor disk with fan blades. And are connected by an elastic arm so that the slot ripple frequency of the electric motor is not transmitted to the fan blades.

In the propeller-type blower described in JP-A-61-275597, a propeller-type blower in which a blade body composed of a boss and metal blades is fixed to a motor shaft by a spinner is used. An elastic body is sandwiched between the blades to prevent the blade body from resonating due to the vibration caused by the electric motor.

In the blower disclosed in Japanese Unexamined Patent Publication No. 4-86398, the boss portion of the impeller fixed to the output shaft of the motor and the hub holding the impeller are made of an elastic body having a plurality of holes. Another elastic piece is inserted into the hole so as to prevent the vibration of the output shaft of the motor from being transmitted to the impeller so that the impeller does not resonate.

In the blower described in Japanese Patent Laid-Open No. 4-203296, when fixing the fan to the rotor of the electric motor with a fan cap, a vibration damping layer in which a damping layer is laminated with a steel plate is provided between the fan and the fan cap. By interposing a steel plate, the vibration force generated by the rotor is reduced and the noise is reduced.

In the fan for an air conditioner described in Japanese Patent Laid-Open No. 7-103191, a centrifugal blower fan is sandwiched by two anti-vibration rubbers made of two plate materials sandwiching rubber, and the centrifugal blower fan and a fan motor drive. A gap is formed between the shafts so that the vibration generated in the fan motor does not directly propagate to the centrifugal blower fan.

The noise generated by the blower is roughly classified into fluid noise generated by the fan and electromagnetic vibration noise generated by the fan driving motor as a vibration source. In the case of electromagnetic vibration sound, the level of a specific frequency rises, and it feels jarring. 4 to 6
The blower fan with the conventional structure as shown in (1) transmits this electromagnetic vibration sound properly. A general means used to reduce electromagnetic vibration noise is to attach a fan via an elastic body, and the above-mentioned conventional techniques often belong to this category.

When an elastic body is used to reduce electromagnetic vibration noise, if the elastic body is soft, the fan swirls,
The vibration of the blower becomes large. If the elastic body is made hard to prevent this, the vibration isolation performance of the electromagnetic excitation force deteriorates. In addition, the elasticity of the elastic body changes with the passage of time, so that the desired vibration damping effect may not be obtained after long-term use.

In the fan for an air conditioner described in Japanese Unexamined Patent Publication No. 10-318190, a plurality of openings are provided in the torque transmitting portion from the boss portion of the fan to the blade portions so as to have a spring effect, and the fan and the motor are provided. When the natural frequency of the vibration system and the electromagnetic excitation force of the motor resonate, the vibration is absorbed by the spring action of the blower boss.

Since the structure described in Japanese Patent Laid-Open No. 10-318190 does not sandwich the elastic body, it is not necessary to pay attention to the physical properties and durability of the elastic body. However, when an opening is provided in the torque transmission part from the boss part of the fan to the blade part and the spring effect of the remaining spoke-shaped part is used, the spoke part is not long enough to obtain a sufficient spring effect. Do not. In other words, the spring effect cannot be produced unless the diameter of the hub portion where the blade protrudes is considerably large. This is a big constraint in designing the fan.

[0016]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a blower fan that can reduce electromagnetic vibration noise without using an elastic body and that does not require the hub portion to have a large diameter. . At the same time, it is an object of the present invention to have a structure in which the shaft of the motor to which the blower fan is attached can be shortened.

[0017]

In order to achieve the above object, the blower fan of the present invention has the following structure.

(1) In a blower fan provided with a boss fitted to a shaft of a motor at the center of a hub having a plurality of fan blades protruding from an outer peripheral surface, the hub is an outer hub provided with the fan blades. , A concentric double structure with the inner hub provided with the boss, while connecting one end of the outer hub and one end of the inner hub with an annular connecting portion,
An annular space is formed between the inner peripheral surface of the outer hub and the outer peripheral surface of the inner hub.

According to this structure, the spring effect can be generated in the double structure portion of the outer hub and the inner hub.

(2) In the blower fan as described above,
The inner hub has an end wall at the end facing the fan driving motor, and the boss projects from the center of the end wall toward the motor.

According to this structure, since the boss and the motor come close to each other, the shaft of the motor can be shortened.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the blower fan of the present invention will be described below with reference to FIGS. This blower fan 1
Since the structure of 0a has a considerable part in common with the conventional structure shown in FIGS. 4 to 6, common components are denoted by the same reference numerals as those used in the description of the conventional structure, and description thereof will be omitted.

The blower fan 10a of the present invention is characterized by the structure of the hub 11. That is, the hub 11 has an outer hub 11a having a fan blade 12 and an inner hub 11b having an end wall 13 and a boss 14 arranged concentrically with each other.
It has a concentric double structure. One ends (upper ends) of the outer hub 11a and the inner hub 11b are connected by an annular connecting portion 19. An annular space 20 is formed between the inner peripheral surface of the outer hub 11a and the outer peripheral surface of the inner hub 11b.
The annular space 20 does not have the spoke-like ribs that existed in the conventional structure.

The upper end of the inner hub 11b is connected to the connecting portion 19, and the end wall 13 is provided at the lower end of the inner hub 11b located on the opposite side of the connecting portion 19. Therefore, the end wall 13 is closer to the fan driving motor 1 as compared with the conventional structure. Since the boss 14 projects from the center of the end wall 13 toward the fan driving motor 1, the boss 14 itself also approaches the fan driving motor 1. Correspondingly, the length of the shaft 2 is shorter than that of the conventional structure.

When transmitting the torque from the shaft 2 to the blower fan 10a, the flat portion 16 may be eliminated from the inner surface of the central hole of the boss 14 and the torque may be transmitted only through the washer 17.

The operation of the blower fan 10a according to the present invention is as follows. First, let us consider the general noise generation mechanism of a fan. When a fan drive motor rotates a blower fan having a conventional structure, the electromagnetic excitation force of the fan drive motor propagates to the blower fan. Noise is generated due to the vibration of a fan blade having a particularly large area among the blower fans. This vibration system consists of two masses, a blower fan and a motor rotor, placed on both sides of the fan drive motor shaft. Since the shaft acts as a torsion spring, "two masses, one torsion spring" vibration It becomes a system.

In the above vibration system, resonance occurs when the natural frequency in the rotating direction is in the vicinity of an integral multiple of the fundamental frequency (twice the power supply frequency, that is, 100 Hz or 120 Hz) of the electromagnetic excitation force, and the resonance occurs. The electromagnetic vibration sound of the double frequency component increases.

However, in the blower fan 10a of the present invention, since the hub 11 has a double structure of the outer hub 11a and the inner hub 11b, the fan blade 12 and the outer hub 11a are formed.
Constitutes a first mass, the inner hub 11b, the end wall 13 including the washer 17, and the boss 14 constitute a second mass,
The rotor of the fan drive motor constitutes the third mass.
Speaking of springs, the shaft 2 acts as a torsion spring, and the dual structure portion of the outer hub 11a and the inner hub 11b also acts as a spring, so that a torsional vibration system of "three masses, two springs" is obtained. If the blower fan 10a is made of synthetic resin, the torsional vibration generated in the double structure portion of the outer hub 11a and the inner hub 11b is greatly attenuated, and the vibration energy is absorbed. Therefore, fan blade 12
Vibration energy transmitted to the vehicle is reduced, and noise is reduced.

FIGS. 7 and 8 show the results of measuring the noise levels of the blower fan having the conventional structure (FIGS. 4 to 6) and the blower fan having the structure of the present invention (FIGS. 1 to 3). FIG. 7 shows the measurement result of the conventional structure, and FIG. 8 shows the measurement result of the structure of the present invention. The number of rotations was set in three stages of 750 rpm, 900 rpm, and 1000 rpm. At each stage, the structure of the present invention has a lower noise level. Further, the noise level of the conventional structure has a sharp peak in the low frequency region, but the structure of the present invention does not have such a peak.

In the case of the blower fan 10 having the conventional structure, if the distance from the fan driving motor 1 is large, for example, if the depth of the unit in the outdoor unit of the air conditioner is long, it is necessary to lengthen the shaft 2. On the other hand, in the blower fan 10a of the present invention, the boss 14 projects toward the fan driving motor 1 from the end wall 13 closer to the fan driving motor 1 as compared with the conventional structure, so that the length of the shaft 2 is reduced. It can be made shorter than the conventional structure.

Although the propeller fan is taken as the blower fan in the above-described embodiments of the present invention and the conventional structure, the present invention can be applied to other types of fans such as a centrifugal fan. In addition, various modifications can be made and implemented without departing from the spirit of the invention.

[0032]

The present invention has the following effects.

(1) In a blower fan provided with a boss fitted to the shaft of a motor at the center of a hub having a plurality of fan blades protruding from the outer peripheral surface, the hub is an outer hub provided with the fan blades. , A concentric double structure with the inner hub provided with the boss, while connecting one end of the outer hub and one end of the inner hub with an annular connecting portion,
Since the annular space is formed between the inner peripheral surface of the outer hub and the outer peripheral surface of the inner hub, the spring effect can be generated in the double structure portion of the outer hub and the inner hub. Can be absorbed. Since the spoke-shaped portion does not obtain the spring effect, it is not necessary to provide long spoke portions in order to obtain a sufficient spring effect, and it is not necessary to increase the hub diameter.

(2) In the blower fan as described above,
Since the inner hub has a bottom wall portion at the end facing the fan driving motor, and the boss projects toward the motor from the center of the bottom wall portion, the boss and the motor approach each other. The motor shaft can be shortened. As a result, the cost required for manufacturing, transporting, and storing the shaft can be reduced. Further, the tip of the shaft is eccentric, though slightly, due to a shaft manufacturing error and a motor assembly error. This eccentricity is amplified if the shaft is long, but the degree is small if the shaft is short. Therefore, the whirling of the blower fan is small, which also contributes to noise reduction.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a blower fan according to an embodiment of the present invention.

FIG. 2 is a bottom view of a hub portion of the blower fan.

FIG. 3 is a partial perspective view showing a structure of a hub portion of the blower fan.

FIG. 4 is a sectional view of a conventional blower fan.

FIG. 5 is a bottom view of a hub portion of a conventional blower fan.

FIG. 6 is a front view of a motor shaft tip and washer in a conventional blower fan structure.

FIG. 7 is a graph of a noise level of a blower fan having a conventional structure.

FIG. 8 is a graph of the noise level of the blower fan having the structure of the present invention.

[Explanation of symbols]

1 Fan drive motor 2 shafts 10a blower fan 11 hubs 11a outer hub 11b inner hub 12 fan blades 13 End wall 14 Boss 19 Connection 20 ring space

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Claims (2)

[Claims] 1. A blower fan having a hub having a plurality of fan blades protruding from an outer peripheral surface and having a boss fitted to a shaft of a motor in the center of the hub, wherein the hub is an outer hub having the fan blades.
A concentric double structure with an inner hub provided with the boss, wherein one end of the outer hub and one end of the inner hub are connected by an annular connecting portion, and an inner peripheral surface of the outer hub and an outer periphery of the inner hub are connected. A blower fan characterized by forming an annular space with the surface. 2. The inner hub has an end wall at the end facing the fan driving motor, and the boss projects from the center of the end wall toward the motor. The blower fan according to item 1.