JP6577694B2 - Impeller and axial flow fan provided with the impeller - Google Patents

Description

The present invention relates to an impeller and an axial fan provided with the impeller.

  An axial blower may generate a large vibration during operation at a specific rotation speed (rotation 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.

  In addition, 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, compared to the case of the rivet type in which the boss plate is riveted, the rivet type can be easily changed in thickness because the boss plate and the blade are separate. On the other hand, in the welding impeller, since the thickness of one blade is uniform, there is a high possibility that a large stress acts on the blade attachment portion due to a large amplitude at the time of resonance.

  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. Japanese Patent Laid-Open No. 4-203296 (Patent Document 1) describes a method of mounting an inclusion having a damping action on the impeller attached to the drive shaft.

JP-A-4-203296

  In the above-mentioned Patent Document 1, no consideration is given to the resonance with respect to the change in the operating rotational speed of the axial blower, and there is a problem in applying variable speed operation simply by reducing the vibration.

  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. There is a case.

  In an example of a conventional solution to this problem, there is a method of increasing the natural frequency by increasing the plate thickness of the member and avoiding the resonance frequency. However, in the impeller of a steel plate welded structure, the cost is low. For this reason, since a steel plate with a uniform thickness is used, increasing the plate thickness increases the weight, which increases the centrifugal force and increases the stress generated at the base of the blade, resulting in product reliability. There was a problem that would decrease.

  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 above object is achieved by an impeller in which a plurality of blades are attached to the outer peripheral surface of a cup-shaped boss member, and a steel plate is partially provided on each of the plurality of blades.

  ADVANTAGE OF THE INVENTION According to this invention, there is no possibility that an abnormal vibration and excessive stress will generate | occur | produce at the time of variable speed operation, and a highly reliable axial-flow fan can be provided.

It is the side view and front view of an axial-flow fan of the Example in this invention. It is a figure which shows the AA cross section of FIG. It is a figure which shows the modification of the shape of a steel plate. It is a figure which shows the modification of the shape of a steel plate.

  Hereinafter, examples will be described with reference to the drawings.

  First, FIG. 1 shows an axial blower of the present embodiment. 1A is a side view with a partial cross section, and FIG. 1B is a front view. In FIG. 1, 1 is an electric motor, 2 is a rotating shaft, 3 is an impeller, 4 is a blade, 5 is a boss member, 6 is a hub member, 7 is a washer, 8 is a bolt, and 9 is a steel plate. It is.

  Here, the electric motor 1 is an induction motor that is driven at a variable speed by, for example, a VVVF (variable voltage variable frequency) inverter power supply. A propeller-type impeller 3 is attached to the rotary shaft 2 of the electric motor 1. Is configured. 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 figure, attached to the outer peripheral surface of the boss member 5 made in a substantially cup shape. Is provided with a hub member 6 having a short cylindrical shape for attaching the impeller 3 to the rotating shaft 2 of the electric motor 1. 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. .

  This axial-flow fan can obtain a large air volume and a high static pressure as compared with a general household ventilation fan using an impeller formed of resin. Further, the material of the impeller is required to be made of a steel plate in relation to the use environment, the use temperature, and the like, and the impeller is required to have a strong strength.

  Next, the impeller 3 will be described in detail. FIG. 2 shows the impeller 3 in detail, and is a view of the cross section of FIG. In FIG. 2, the blade 4 is formed by pressing a metal plate, for example, a steel plate, into a predetermined plane shape, for example, and then superposing the steel plate 9 and joining them by, for example, laser welding or spot welding. , It is formed into a predetermined curved surface shape.

  The boss member 5 is also made of, for example, a steel plate, and is also formed into a cup shape by pressing. The blade 4 is welded to the outer peripheral surface of the boss member 5 to complete the impeller 3.

  The feature of this embodiment is that a steel plate 9 is provided on the blade 4.

Here, the natural frequency f is generally expressed as Equation (1) in relation to the weight M and the spring constant K.

f = √ (K / M) (1)

Therefore, when this is applied to the impeller, the spring constant K corresponds to the ease of twisting or bending of the blade 4, and the spring constant K becomes higher as it is less likely to twist or bend. Therefore, as the thickness of the blade 4 increases, the spring constant K increases and the natural frequency f increases. However, if the thickness is increased, the weight of the blade 4 also increases, so that the natural frequency f is lowered. Therefore, in order to increase the natural frequency f, it is necessary to suppress the increase in weight while making it difficult to be twisted or bent.

  Therefore, in this embodiment, by providing the steel plate partly on the blade, the thickness of the blade 4 is substantially increased, the natural frequency f is increased, and the operating frequency of the axial fan is increased. The natural frequency can be set at a frequency higher than the variable range, thereby avoiding the resonance phenomenon. In the direction of lower natural frequency, the operating frequency of the axial flow fan is changed by inverter control, etc., the demand for lowering the rotation speed as much as possible and reducing the power consumption is increasing, and Since it is common for a low frequency to become a resonance frequency when integrated with the housing, the possibility of resonance at a low frequency increases, and it is desirable to avoid it.

  Therefore, in this embodiment, the shape of the steel plate 9 is such that, as shown in FIG. 1 (b), the front edge and the rear edge at the root portion of the blade 4, which is the attachment portion of the blade 4 to the boss member 5. In the radial direction along the center of the impeller, it is arranged from a position having the same diameter (for example, 100 mm or more) as the boss member 5 in the central portion of the impeller to a position having the same diameter as the outer diameter of the impeller (for example, 200 mm or more). That is, it is made difficult to bend by reinforcing with a steel plate from the base to the tip of the blade 4, and the blade 4 is disposed only at the center portion of the front edge portion and the rear edge portion of the blade 4. Thereby, the natural frequency can be increased by making the blade 4 difficult to be twisted or bent, and at the same time suppressing an increase in weight.

  Moreover, the modification of the shape of the steel plate 9 is shown in FIG. FIG. 3 shows only one of the plurality of blades in FIG. 1 (b), and shows the relationship between the blades and the steel plate. As shown in FIG. 3, from the viewpoint of making it difficult to twist, the steel plate is disposed at the root portion of the blade 4, which is the attachment portion of the blade 4 to the boss member 5, and is provided at the distal end in the radial direction of the blade 4. It is good also as a shape which suppressed the increase in the weight so that it may not exist.

  Moreover, the further modification of the shape of the steel plate 9 is shown in FIG. FIG. 4 shows only one of a plurality of blades taken out and displayed as in FIG. 3, and shows the relationship between the blades and the steel plate. As shown in FIG. 4, by arranging the steel plate only in the portion where the stress generated at the base portion of the blade 4 is large, it is difficult to be twisted or bent, to reduce the weight, and to reduce the natural frequency. May be high.

  Further, in FIG. 1A, when the impeller rotates, the wind flows from the right side to the left side, but since the pressure is high on the left side of the blade, that is, the downstream side, pressure fluctuation occurs when the steel plate 9 is joined to this side. Therefore, the increase in noise is suppressed as much as possible by joining the steel plate to the right side of the blade, that is, the upstream side.

  In addition, since the steel plate 9 is divided | segmented from the blade 4, there exists an advantage that each board thickness can be changed. For example, the natural frequency can be increased by increasing the thickness of the steel plate 9 (for example, about 2.3 mm or more), and the increase in weight can be suppressed by reducing the thickness of the blade 4 (for example, about 2.3 mm or less). can do.

  Furthermore, by reducing the thickness of the blade 4, it is possible to reduce the weight as compared to before adding the steel plate.

  Therefore, according to the present embodiment, the steel plate is partially provided on the blade, and the increase in weight is suppressed while the natural frequency is increased, and the resonance frequency is avoided. Therefore, since the resonance phenomenon can be avoided even when the variable speed operation is performed, there is no possibility that abnormal vibration or excessive stress occurs during the variable speed operation, and a highly reliable axial flow fan can be provided. It also has the effect of being able to respond to energy conservation awareness.

  Although the embodiments have been described above, the present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described.

1: electric motor 2: rotating shaft 3: impeller 4: blade (blade) 5: boss member
6: Hub member, 7: Washer (washer), 8: Bolt, 9: Steel plate

Claims (3)

An impeller in which a plurality of blades having a uniform plate thickness are attached to the outer peripheral surface of a cup-shaped boss member,
Each of the plurality of blades is provided with a steel plate from the root to the tip in the radial direction from the center of the front edge and the rear edge at the root portion which is the attachment portion of the blade to the boss member,
And an impeller, wherein the steel sheet plate which is arranged only in the central portion of the leading and trailing edges of the front Stories blade. The impeller according to claim 1,
An impeller characterized in that the steel plate is joined to the upstream surface of the blade through which wind flows with the impeller attached. The impeller according to claim 1 or 2,
An axial blower characterized by comprising an electric motor for rotating the impeller.

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