JP2008014153A - Axial flow blower - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an axial flow blower which precludes the generation of abnormal vibrations and excessive stress even in variable speed operation. <P>SOLUTION: In an impeller 3 of an axial flow blower which keeps a blade 4 on the periphery of a cup-like boss member 5, a vibration damping member 9 with a sandwich structure is provided to the inner peripheral surface of the boss member 5 so as to reduce stress and vibrations produced during resonance. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an axial blower using a propeller-shaped impeller, and more particularly to an axial blower suitable when an impeller in which blades formed by metal plate are welded to a boss portion are used.

  An axial blower may generate a large vibration during operation at a specific rotation speed (rotational speed). This is a resonance phenomenon caused by the fact that the resonance frequency of the impeller of the axial fan is equal to the operating frequency of the axial fan. In the case of a propeller-type impeller, the blade is cantilevered. Especially remarkable.

  Here, in a propeller-shaped impeller, when the part is struck in order to know the stress applied to the part, the relationship between the stress σ and the time t at this time is attenuated as shown in FIG. Show properties. If the attenuation coefficient at this time is ζ, the resonance magnification is ½ζ.

  By the way, such propeller-type impellers are generally equipped with metal plate blades attached to the bosses, except in the case of relatively small fans and the like. At this time, welding is used to attach the blades. In the so-called welding impeller, the damping coefficient ζ tends to be smaller than in the case of riveting. In this case, the resonance magnification increases, so the amplitude at the time of resonance increases and a large stress is applied to the blade. There is a high possibility of working on the mounting part.

Therefore, in the conventional axial flow fan, it is necessary to operate at an operation frequency that avoids the resonance frequency, and when the axial flow fan is designed, the operation frequency and the eigenvalue do not overlap. At this time, a method of interposing a member having a damping effect on the attachment of the impeller to the drive shaft is also known as a prior art (see, for example, Patent Document 1).
JP-A-4-203296

  In the above prior art, consideration has not been given to the change in the rotational speed of the axial blower, and there has been a problem in applying variable speed operation.

  In recent years, energy conservation awareness has increased, and there is an increasing demand to operate with reduced power consumption by changing the operating frequency of the axial blower by inverter control, etc., and reducing power consumption as much as possible. Since the setting differs depending on the user, it is necessary to assume a wide range of operating frequencies.

  However, as already explained, since the impeller of an axial flow fan always has a natural frequency, there is a possibility that the operation frequency of the axial flow fan and the natural frequency of the axial flow fan overlap when corresponding to a wide range of operation frequencies. In this case, a resonance phenomenon occurs, abnormal vibration and excessive stress occur, and the reliability of the product is remarkably lowered. Therefore, the conventional technology has a problem in applying variable speed operation. It is.

  An object of the present invention is to provide an axial blower that is free from the occurrence of abnormal vibration or excessive stress even during variable speed operation.

  The object is to provide an axial blower having a propeller-shaped impeller in which a plurality of blades are attached to the outer peripheral surface of a cup-shaped boss member, wherein a damping member is provided on the inner peripheral surface of the boss member, and the impeller Reduction of vibration and stress due to resonance between the vibration frequency unique to the impeller and the operating frequency of the impeller is achieved as provided by the damping member.

  At this time, the above-mentioned object is also achieved by the damping member being a sandwich structure member in which a synthetic resin layer is sandwiched between two steel plates, and the damping member bends the plate-like member into a wave shape. The above object can also be achieved by using a molded corrugated plate member.

  According to the above means, the resonance is suppressed by the vibration damping member located in the center of the impeller and inside the boss member to which the blade is attached, and the stress generated during the resonance phenomenon can be suppressed. If a certain member is deformed due to resonance, friction due to structural deviation occurs in the member, and this causes the deformation to be damped. At this time, the damping member is made so that the damping due to the friction is increased. Therefore, vibration is suppressed and stress can be reduced.

  The damping member may be a damping steel plate in which a synthetic resin is sandwiched between steel plates, or a corrugated plate member may be used, and any of these members is provided inside the boss member. Here, in the case of a corrugated member, a reduction in stress and vibration generated during resonance can be obtained at the contact portion between the inner surface portions of the boss member.

  According to the present invention, there is no possibility that abnormal vibration or excessive stress is generated even during variable speed operation, so that an axial fan with higher reliability and higher performance than the prior art can be provided.

  Hereinafter, an axial blower according to the present invention will be described in detail with reference to embodiments shown in the drawings. First, FIG. 1 shows an axial blower according to an embodiment of the present invention, in which (a) of FIG. 1 is a side view with a partial cross section, and (b) is a front view. In these drawings, 1 is an electric motor, 2 is a rotating shaft, 3 is an impeller, 4 is a blade (blade), 5 is a boss member, 6 is a hub member, 7 is a washer (washer), 8 is a bolt, and 9 Represents a damping material.

  2 shows the impeller 3 in more detail. At this time, FIG. 2A is a front view, FIG. 2B is a back view, that is, FIG. 1A viewed from the left side. Here, the electric motor 1 is, for example, an induction motor that is driven at a variable speed by, for example, a VVVF (variable voltage variable frequency) inverter power supply. A propeller-shaped impeller 3 is attached to the rotary shaft 2 of the induction motor. The main part of At this time, although not shown, there is a casing provided with a substantially cylindrical member called a duct or shroud covering the periphery of the impeller 3, and the electric motor 1 is held by the casing.

  Next, the impeller 3 has a plurality of blades 4, for example, eight as shown in the drawing, attached to the periphery of a boss member 5 made in a substantially cup shape. A hub member 6 having a short cylindrical shape for attaching the impeller 3 to the rotating shaft 2 of the electric motor 1 is provided. Therefore, the impeller 3 can be attached to the rotary shaft 2 by fitting the hole of the hub member 6 to the rotary shaft 2 and then fastening the bolt 8 to the rotary shaft 2 via the washer 7. .

  The blade 4 will be described in more detail. First, the blade 4 is formed by pressing a metal plate, for example, a steel plate, into a predetermined plane shape, for example, by pressing, and then forming a predetermined curved shape. The boss member 5 is also made of, for example, a steel plate, and is formed into a cup shape by press working. The blade 4 is welded to the outer peripheral surface of the boss member 5 to complete the impeller 3. However, in this embodiment, the boss member 5 is further provided with a vibration damping member 9.

  Here, the damping member 9 is a member called a damping steel plate having a sandwich structure in which a synthetic resin layer such as polyvinyl chloride is sandwiched between two steel plates, and this is a synthetic resin sandwiched therein. This is a member in which friction loss due to displacement deformation appears strongly due to the viscosity of this, and in this embodiment, this is attached to the inner peripheral surface of the boss member 5 and attached over the entire circumference of the inner peripheral surface. Thus, deformation of the cup-shaped boss member 5 is suppressed.

  Then, next, operation | movement of this embodiment is demonstrated. Now, assuming that the axial flow fan according to this embodiment is operated at a variable speed and is in a terrible resonance state, the stress appearing at this time is concentrated mainly on the attachment portion of the blade 4 and the boss member 5, and as a result, The boss member 5 tends to be deformed on the circumferential portion. However, at this time, the boss member 5 has a damping member 9, which is attached to the inner surface of the circumferential portion of the boss member 5.

  Therefore, the vibration damping member 9 effectively exhibits a vibration damping function against the deformation appearing on the circumferential portion of the boss member 5 and attenuates the vibration. As a result, the blade 4 is deformed. Therefore, even when resonating, excessive stress does not occur. Therefore, according to this embodiment, noise and vibration are increased even when variable speed operation is performed. There is no fear and it can respond to energy saving awareness.

  Further, according to this embodiment, even when the impeller 3 in which the blade 4 is welded to the boss member 5 is used as the impeller, so-called welding impeller, there is no risk of noise and vibration associated with variable speed operation. Therefore, the cost reduction by using the welding impeller can be enjoyed.

  Next, another embodiment of the present invention will be described with reference to FIG. In the embodiment described above, the case where a damping structure steel plate having a sandwich structure is used as the damping member 9 has been described. However, in the embodiment of FIG. 3, a plate-like member such as a metal plate is corrugated as the damping member. A vibration damping member 10 made of a so-called corrugated plate is used, and the other configuration is the same as that of the embodiment described with reference to FIGS.

  The damping member 10 using this corrugated plate is also attached to the inner peripheral surface of the boss member 5 over the entire circumference of the inner peripheral surface, and when the cup-like boss member 5 is deformed, it becomes wavy. Since the bent part is bent and a loss appears, deformation of the boss member 5 is suppressed.

  Therefore, according to the embodiment of FIG. 3, it is possible to eliminate the possibility of increasing noise and vibration in the case of variable speed operation, to respond to energy saving awareness, and to enjoy the cost reduction by using the welding impeller. it can.

It is the side view and front view which show one Embodiment of the axial-flow fan by this invention. It is the side view and front view which show the impeller in one Embodiment of the axial-flow fan by this invention. It is the side view and front view which show the impeller in other one Embodiment of the axial-flow fan by this invention. It is explanatory drawing which shows an example of the vibration which appears in the impeller of an axial-flow fan.

Explanation of symbols

1: Electric motor 2: Rotating shaft (axis of electric motor 1)
3: Impeller 4: Blade (blade)
5: Boss member 6: Hub 2
7: Washer (washer)
8: Bolt 9: Damping member (Damping member with sandwich structure)
10: Damping member (damping member of corrugated plate)

Claims (3)

In the axial blower including a propeller-shaped impeller in which a plurality of blades are attached to the outer peripheral surface of a cup-shaped boss member,
A damping member is provided on the inner peripheral surface of the boss member,
An axial blower characterized in that vibration and stress reduction due to resonance between the vibration frequency unique to the impeller and the operation frequency of the impeller are provided by the damping member. In the axial blower according to claim 1,
The axial blower according to claim 1, wherein the vibration damping member is a member having a sandwich structure in which a synthetic resin layer is sandwiched between two steel plates. In the axial blower according to claim 1,
An axial-flow fan, wherein the damping member is a corrugated member obtained by bending a platy member into a corrugated shape.

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