Centrifugal fan and blower having the same

A centrifugal fan includes a plurality of blades, a first wall disposed at first axial ends of the blades, and a second wall disposed at second axial ends of the blades and having a shaft portion at a center. At least one of the first wall and the second wall has a cutout portion configured to control balance.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Applications No. 2007-171520 filed on Jun. 29, 2007 and No. 2007-334107 filed on Dec. 26, 2007 the disclosure of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a centrifugal fan and a blower having the same, which is, for example, used for a vehicle air conditioning apparatus.

BACKGROUND OF THE INVENTION

In a conventional blower, it is known to control balance of a fan so as to cancel vibrations between the fan and a motor as rotational members. The balance is controlled by adding a balance weight to the fan or reducing an excess weight from the fan. Controlling the balance by adding the balance weight is, for example, referred to as a plus balance control, and controlling the balance by reducing the excess weight is, for example, referred to as a minus balance control.

In general, the minus balance control is put into practice at a relatively low cost because the balance weight needs not to be added. As an example of the minus balance control, if a cutout portion is formed on a fan blade, which serves to force air out, air flow will be disturbed by the cutout portion. As a result, air blowing efficiency will be reduced and noise will be increased.

SUMMARY OF THE INVENTION

The present invention is made in view of the foregoing matter, and it is an object of the present invention to provide a centrifugal fan having a structure of a minus balance control, capable of suppressing a decrease in air blowing efficiency and an increase in noise. It is another object of the present invention to provide a blower having a centrifugal fan having a structure of a minus balance control, capable of suppressing a decrease in air blowing efficiency and an increase in noise.

According to a first aspect of the present invention, a centrifugal fan includes a plurality of blades, a first wall disposed at first axial ends of the blades, and a second wall disposed at second axial ends of the blades and having a shaft portion at a center. The first wall has a cutout portion configured to control balance.

Accordingly, the balance is controlled by the cutout portion formed on the first wall. That is, the balance is controlled without cutting a portion of the blade, which serves to force air out. Therefore, it is less likely that air blowing efficiency will be reduced and noise will be increased due to the cutout portion.

According to a second aspect of the present invention, a centrifugal fan includes a plurality of blades, a first wall disposed at first axial ends of the blades, and a second wall disposed at second axial ends of the blades and having a shaft portion at a center. The second wall has a cutout portion configured to control balance.

Accordingly, the balance is controlled by the cutout portion formed on the second wall. That is, the balance is controlled without cutting a portion of the blade, which serves to force air out. Therefore, it is less likely that air blowing efficiency will be reduced and noise will be increased due to the cutout portion.

For example, the centrifugal fan is employed to a blower and is housed in a casing. In a case where the first wall of the centrifugal fan has a first projection that projects from the first axial ends of the blades toward a bell mouth portion of the casing to form a labyrinth-like structure between the bell mouth portion and the first wall, the cutout portion can be formed on the first projection. As another example, in a case where the centrifugal fan has a second projection that projects from the first wall or the second wall in a radially outward direction toward the air passage of the casing for facilitating generation of rotational flow of air in the casing, the cutout portion can be formed on the second projection. As further another example, in a case where the second wall of the centrifugal fan has a projection that projects from the second axial ends of the blades in an axially outward direction and forms a labyrinth-like structure with the casing, the cutout portion can be formed on the projection. Accordingly, the cutout portion is formed on the portion other than blades, and will not directly interfere with air flow path.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. Hereinafter, like components are designated by like reference characters, and a description thereof is not repeated.

First Embodiment

Referring toFIGS. 1 and 2, a blower generally has an electric motor1, a centrifugal fan (hereinafter, simply referred to as the fan)2, and a scroll casing (hereinafter, simply referred to as the casing)3. The electric motor1has a rotation shat11. The fan2is made of a resin and is housed in the casing3. The fan2is driven by the electric motor1to generate air. The casing3is made of a resin, and has a scroll passage31through which the air generated by the fan2flows.

The casing3has a suction port32at a first axial end. The suction port32is open in an axial direction of the fan2. Further, the casing3has a bell-mouth33on a perimeter of the suction port32. The bell-mouth33extends toward an inner periphery of the fan2for conducting air from the suction port32into the fan2.

The fan2has a plurality of blades21, a side wall22, and a main wall23. The blades21are arranged on a periphery of the rotation shaft11. The blades21, for example, have a plate shape. The side wall22has an annular shape. First axial ends211of the blades21, which are closer to the suction port32, connect to the side wall22, and second axial ends212of the blades21, which are further from the suction port32, connect to the main wall23. In other words, the first axial ends211of the blades21are connected to each other through the side wall22, and the second axial ends212of the blades21are connected to each other through the main wall23. The side wall22is located adjacent to the suction port32of the casing3. The main wall23is located further than the side wall22with respect to the suction port32in the axial direction.

The main wall23connects to the rotation shaft11at its center. That is, the main wall23has a shaft portion to be coupled to the rotation shaft11at the center thereof. A driving force of the electric motor1is transmitted to the fan2through the rotation shaft11and the main wall23. As driven by the electric motor1, the fan2suctions air from its first axial end in the axial direction and blows the air in a radial direction of the fan2, which is perpendicular to an axis of the rotation shaft11.

The side wall22has an aerodynamic cross-sectional shape for facilitating the air flow between the blades21. The side wall22has a cross-sectional shape such that a cross-sectional area of an air passage between the blades21reduces from an inner side toward an outer side with respect to the radial direction. For example, the side wall22has a substantially arc shape in a cross-section.

The side wall22has a side-wall first projection221. The side-wall first projection221has an annular shape and projects from the first axial ends211of the blades21in an axially outward direction. For example, the side-wall first projection221has a cylindrical shape that is coaxial with the rotation shaft11. The fan2is housed in the casing3such that the side-wall first projection221is disposed in or adjoined with the bell-mouth33of the casing3. As such, a labyrinth-like structure, such as a maze-shaped clearance is provided between the side-wall first projection221and the bell-mouth33. The labyrinth-like structure restricts the air blown by the fan2from flowing back toward the suction port32through the clearance between the bell-mouth33and the side wall22.

To cancel vibrations between the electric motor1and the fan2as the rotational members, that is, to control the balance of the fan, the side-wall first projection221has a cutout portion A at a part, as a balance control structure, as shown inFIG. 2. For example, the cutout portion A is provided by partly recessing an axial end of the side-wall first projection221.

In this case, the balance can be controlled without forming cutout portions on the blades21, which serves to force the air out. That is, the cutout portion A as the balance control structure is formed at a position without directly interfering with an air flow path. Thus, it is less likely that air-blowing efficiency will be reduced and noise will be increased due to the balance control structure.

The balance control structure is achieved by using the side-wall first projection221, which is provided for restricting the backflow of the air toward the suction port32. Thus, it is easy to control the balance without largely changing the shape of the fan2and the like.

Second Embodiment

Referring toFIGS. 3 and 4, in the fan2of the present embodiment, the side wall22has a side-wall second projection222. The side-wall second projection222projects from radially outer ends213of the blades21in a radially outside direction and has an annular shape. For example, the side-wall second projection222has a flange shape being generally flat and extending in a direction perpendicular to the axis of the rotation shaft11, that is, in the radial direction. Further, the side-wall second projection222is configured to facilitate generation of a rotational flow of the air in the casing3.

In the present embodiment, the balance control structure is provided by forming the cutout portion A at a part of the side-wall second projection222, as shown inFIG. 4. For example, the cutout portion A is provided by partly recessing a radially outer edge of the side-wall second projection222. In this case, the balance control structure is achieved without forming the cutout portions on the blades21, which serve to force the air out. It is less likely that the air-blowing efficiency will be reduced and the noise will be increased due to the balance control structure.

The balance control structure is achieved by using the side-wall second projection222that is provided for facilitating the rotational flow of the air in the casing3. It is easy to control the balance without largely changing the shape of the fan2and the like.

Third Embodiment

Referring toFIGS. 5 and 6, in the fan2of the present embodiment, an entirety of the side wall22has a flange shape that is substantially flat and extends in the radial direction. The side wall22has the side-wall second projection222that projects from the radially outer ends213of the blades21in the radially outside direction. The side-wall second projection222serves to facilitate the generation of the rotational flow of the air in the casing3.

In the present embodiment, the balance control structure is provided by the cutout portion A formed on a part of the side-wall second projection222, as shown inFIG. 6. For example, the cutout portion A is provided by recessing a part of the side-wall second projection222. In this case, the balance control structure is achieved without forming the cutout portions on the blades21, which serve to force the air out. It is less likely that the air-blowing efficiency will be reduced and the noise will be increased due to the balance control structure.

The balance control structure is achieved by using the side-wall second projection222that is provided for facilitating the rotational flow of the air in the casing3. It is easy to control the balance without largely changing the shape of the fan2and the like.

Fourth Embodiment

Referring toFIGS. 7 and 8, in the fan2of the present embodiment, the balance control structure is provided by using the main wall23.

The main wall23has a main-wall first projection231that projects from the second axial ends212of the blades21in the axially outward direction and has an annular shape. For example, the main-wall first projection231has a cylindrical shape that is coaxial with the rotation shaft11.

The casing3has a casing inner projection34and a casing outer projection35. The casing inner projection34and the casing outer projection35project from a surface of the casing3in the axial direction, the surface facing the main-wall first projection231. The casing inner projection34and the casing outer projection35have a cylindrical shape that is coaxial with the rotation shaft11. The casing inner projection34is located on an inner side of the casing outer projection35with respect to the radial direction, and is coaxial with the casing outer projection35. Thus, an annular groove36is provided between the casing inner projection34and the casing outer projection35.

The main-wall first projection231is disposed in the annular groove36such that a labyrinth-like structure, such as a maze-shaped clearance is provided between the casing inner projection34, the casing outer projection35and the main-wall first projection231. The labyrinth-like structure restricts the air from passing through a clearance between the casing3and the main wall23of the fan2.

In the present embodiment, the balance control structure is provided by the cutout portion A formed on a part of the main-wall first projection231, as shown inFIG. 8. For example, the cutout portion A is provided by partly recessing an axial end of the main-wall first projection231. In this case, since the balance control structure is provided without forming the cutout portions on the blades21, which serve to force the air out, it is less likely that the air-blowing efficiency will be reduced and the noise will be increased due to the balance control structure.

The balance control structure is provided by using the main-wall first projection231that is provided for restricting the air from passing through the casing3and the main wall23of the fan2. It is easy to control the balance without largely changing the shape of the fan2and the like.

Fifth Embodiment

Referring toFIGS. 9 and 10, in the fan2of the present embodiment, the main wall23has a main-wall second projection232that projects from radially outer edges213of the blades21in the radially outward direction. The main-wall second projection232has an annular shape. For example, the main-wall second projection232has a flange shape being generally flat and extending in the radially outward direction. The main-wall second projection232serves to facilitate the generation of the rotational flow of the air in the casing3.

In the present embodiment, the balance control structure is provided by the cutout portion A formed on a part of the main-wall second projection232, as shown inFIG. 10. For example, the cutout portion A is provided by partly recessing a radially outer end of the main-wall second projection232. In this case, since the balance control structure is provided without forming the cutout portions on the blades21, which serve to force the air out, it is less likely that the air-blowing efficiency will be reduced and the noise will be increased due to the balance control structure.

The balance control structure is provided by using the main-wall second projection232that is provided for facilitating the generation of the rotational flow in the casing3. It is easy to control the balance without largely changing the shape of the fan2and the like.

Sixth Embodiment

Referring toFIG. 11, in the present embodiment, the balance control structure is provided by multiple cutout portions A formed on the side-wall second projection222.

The side-wall second projection222has the plural cutout portions A, each having a semi-circular shape, for example. The cutout portions A are disposed adjacent to each other in a circumferential direction of the fan2. For example, the cutout portions A are arranged continuously in the circumferential direction, such that the part of the side-wall second projection222has a serrated portion.

The air separating from the side wall22after flowing through the vicinity of the side wall22is likely to be disturbed, that is, cause wake turbulence. In the case where the cutout portions A are arranged adjacent to each other in the circumferential direction, the cutout portions A serves as a serration that restricts generation of the wake turbulence of the air separated from the side wall22. Therefore, noise of the fan2is reduced.

Here, the shape of the cutout portions A is not limited to the semi-circular shape. The cutout portions A can have any other shapes, such as V-shape, U-shape and edged U-shape and the like.

Seventh Embodiment

Referring toFIG. 12, in the present embodiment, the balance control structure is provided by the cutout portion A formed on the part of the side-wall second projection222. The cutout portion A has a shape different from that of the second embodiment shown inFIG. 4.

In a case where it is necessary to increase the size of the cutout portion to control the balance, the length of the cutout portion A in the circumferential direction can be increased. For example, the cutout portion A can have a shape that the length in the circumferential direction is larger than a depth in the radial direction.

Eighth Embodiment

Referring toFIG. 8, in the present embodiment, the balance control structure is provided by the cutout portion A formed on the part of the side-wall second projection222. The cutout portion A has a shape different from that of the second embodiment shown inFIG. 4.

In the second embodiment, the cutout portion A is formed by recessing the radially outer edge of the side-wall second projection222. In the present embodiment, on the other hand, the cutout portion A is formed as an opening or a through hole, as shown inFIG. 8.

Ninth Embodiment

Referring toFIG. 14, in the present embodiment, the balance control structure is provided by multiple cutout portions A formed on the main-wall second projection232.

The cutout portions A are arranged along the radially outer edge of the main-wall second projection232, and adjacent to each other in the circumferential direction. For example, the cutout portions A have the semi-circular shape. The cutout portions A can be arranged continuously in the circumferential direction as the serrated portion.

The air separated from the main wall23after flowing through the vicinity of the main wall23is likely to be disturbed and cause the wake turbulence. In the case where the cutout portions A are arranged adjacent to each other in the circumferential direction, the cutout portions A serve as the serration that restricts the wake turbulence of the air separated from the main wall23. As such, the noise is reduced.

Here, the shape of the cutout portions A is not limited to the semi-circular shape. The cutout portions A can have any other shapes such as V-shape, U-shape, edged U-shape and the like.

Tenth Embodiment

Referring toFIG. 15, in the present embodiment, the balance control structure is provided by the cutout portion A formed on the part of the main-wall second projection232. The cutout portion A has a shape, such as, a size, different from that of the fifth embodiment shown inFIG. 10.

In the case where it is necessary to increase the side of the cutout portion A to control the balance, the length of the cutout portion A in the circumferential direction can be increased. For example, the cutout portion A can have a shape that the length in the circumferential direction is greater than the depth in the radial direction.

In the above embodiments, the cutout portion A is provided by the recess, the opening, the through hole and the like. The cutout portion A can be formed by various methods. For example, the cutout portion A can be formed when the fan2is molded. As another example, the cutout portion A can be formed by removing a part of the fan2other than the blades21, such as by cutting, punching or the like.

Exemplary embodiments of the present embodiment are described above as the first to tenth embodiments. However, the above embodiments can be employed in various combinations. For example, the size, the shape and/or number of the cutout portion A of the side-wall first projection221shown inFIG. 2can be modified as the ways shown inFIGS. 11,12and/or13.

Additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader term is therefore not limited to the specific details, representative apparatus, and illustrative examples shown and described.