Centrifugal fans and refrigeration systems

Abstract

This facilitates the manufacture of a resin-molded impeller in a centrifugal fan, in which multiple blades are arranged at unequal pitches. [Solution] The impeller (60) of the centrifugal fan (50) is integrally molded from resin, comprising a base plate (61), a shroud (62), and a plurality of blades (63). Each of the plurality of blades (63) extends in a curved manner from the inner circumference to the outer circumference in a cross section perpendicular to the axis of rotation (Ac). The circumferential pitch of the outer edges (63b) of adjacent blades (63) around the axis of rotation (Ac) is different on both sides of each blade (63) in that circumferential direction. The first surface (63p) of the inner end portion (63i) or the second surface (63s) of the outer portion (63r) of a pair of adjacent blades (63) differs in the presence or absence of a flat surface (68), or the area of ​​the flat surface (68).

Description

Technical Field

[0001] The present disclosure relates to a centrifugal fan and a refrigeration device.

Background Art

[0002] In refrigeration devices such as air conditioners, fans are used. As the fan, a centrifugal fan is known. The centrifugal fan includes an impeller and a fan motor. The impeller has a base plate attached to the fan motor, a shroud disposed axially spaced from the base plate along the rotation axis, and a plurality of blades provided between the base plate and the shroud. The plurality of blades are arranged at intervals in the circumferential direction centered on the rotation axis of the centrifugal fan.

[0003] In a centrifugal fan, when the fan motor is driven, the impeller rotates. Along with the rotation of the impeller, air is sucked in from the fan suction port formed in the center of the shroud, and air is blown out from between the blades to the outer peripheral side. In a centrifugal fan, it has been proposed to integrally mold the impeller by injection molding with the base plate, the shroud, and the plurality of blades made of resin. An example of a centrifugal fan having such a resin impeller is disclosed in Patent Document 1.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, in centrifugal fans, all the blades of the impeller are made of the same shape to improve airflow performance. Also, centrifugal fans generate noise due to the rotation of the impeller. This noise includes blade pitch noise, which is the sound of airflow cutting through the blades as they rotate. Blade pitch noise is also called NZ noise because its frequency is represented by the product of the fan speed (N) and the number of blades (Z) (N × Z). In centrifugal fans, it is conceivable to arrange multiple blades at unequal pitches to reduce this NZ noise.

[0006] However, in the aforementioned resin-molded impeller, if multiple blades are arranged at unequal pitches, it becomes difficult to avoid interference between the multiple slide molds that form the blades in the injection molding machine's mold when they slide in the drafting direction, which corresponds to the radially outward direction of the centrifugal fan, or interference between these slide molds and other parts of the mold. This necessitates a complex mold structure, leading to increased costs. Therefore, it is difficult to manufacture centrifugal fan impellers as resin-molded impellers.

[0007] The purpose of this disclosure is to facilitate the manufacture of a resin-molded impeller in which multiple blades are arranged at unequal pitches for a centrifugal fan. [Means for solving the problem]

[0008] A first aspect of this disclosure relates to a centrifugal fan (50). The centrifugal fan (50) comprises an impeller (60) that rotates around a predetermined axis of rotation (Ac). The impeller (60) has a base plate (61) that rotates around the predetermined axis of rotation (Ac), an annular shroud (62) provided at an axial distance from the base plate (61) along the axis of rotation (Ac), and a plurality of blades (63) arranged between the base plate (61) and the shroud (62) at intervals from each other in the circumferential direction with respect to the axis of rotation (Ac). The base plate (61), the shroud (62), and the plurality of blades (63) are integrally molded from resin. Each of the plurality of blades (63) has a cross-sectional shape that curves from the inner circumference to the outer circumference in a cross section perpendicular to the axis of rotation (Ac). Furthermore, each of the plurality of blades (63) has an inner edge (63a) which is the inner circumference edge of the blade (63), an outer edge (63b) which is the outer circumference edge of the blade (63), a first surface (63p) between the inner edge (63a) and the outer edge (63b) that faces outward from the curvature of the blade (63), and a second surface (63s) between the inner edge (63a) and the outer edge (63b) that faces inward from the curvature of the blade (63). The circumferential pitch of the outer edges (63b) of a pair of adjacent blades (63) differs from one another on both sides of each blade (63) in the circumferential direction. Furthermore, in a pair of adjacent blades (63), the first surface (63p) of the inner end portion (63i) near the inner edge (63a), or the second surface (63s) of the outer portion (63r) near the outer edge (63b), there is either a flat surface (68) extending in a direction intersecting the straight line connecting the outer edge (63b) of the blade (63) located forward in the rotational direction of the impeller (60) and the inner edge (63a) of the blade (63) located backward in the rotational direction of the impeller (60), or the area of ​​such flat surface (68) differs.

[0009] In the first embodiment, the circumferential pitch of the outer edges (63b) of adjacent blades (63) differs from that of each other on both sides in the circumferential direction of each blade (63). When multiple blades (63) are arranged with unequal pitches in this way, the NZ noise associated with the rotational movement of the impeller (60) is reduced. Furthermore, the first surface (63p) of the inner end (63i) or the second surface (63s) of the outer portion (63r) of adjacent pairs of blades (63) differs in the presence or absence of a flat surface (68), or the area of ​​the flat surface (68). The first surface (63p) of the inner end (63i) and the second surface (63s) of the outer portion (63r) of each blade (63) form the point where they are closest to other adjacent blades (63) in the rotational direction of the impeller (60). Therefore, the ejection direction (d2) of the slide mold (240) is constrained by the shape of the first surface (63p) of the inner end (63i) and the shape of the second surface (63s) of the outer portion (63r) of a pair of adjacent blades (63). The flat surface (68) formed on the first surface (63p) of the inner end (63i) or the second surface (63s) of the outer portion (63r) constitutes a surface that extends in the sliding direction of the slide mold (240) in the injection molding apparatus (200). Thus, if the presence or absence of a flat surface (68) on the first surface (63p) of the inner end (63i) or the second surface (63s) of the outer portion (63r) of a pair of adjacent blades (63), or if the area of ​​the flat surface (68) is different, the angles that the ejection direction (d2) of adjacent slide molds (240) makes with respect to the direction corresponding to the radial direction of the impeller (60) can be made different. This allows the ejection direction (d2) to be adjusted so that the multiple slide molds (240) that form the blades (63) in the mold (205) of the injection molding apparatus (200) do not interfere with each other, nor do the slide molds (240) interfere with other parts of the mold (205). Therefore, it is possible to easily manufacture an impeller (60) of a resin integral molding type in which multiple blades (63) are arranged at unequal pitches.

[0010] A second aspect of the present disclosure is a centrifugal fan (50) of the first aspect, wherein the plurality of blades (63) include a first blade (63A), a second blade (63B) adjacent to the first blade (63A), and a third blade (63C) adjacent to the first blade (63A) on the opposite side from the second blade (63B). The second blade (63B) is located behind the first blade (63A) in the direction of rotation. The third blade (63C) is located in front of the first blade (63A) in the direction of rotation. The pitch between the first blade (63A) and the third blade (63C) is shorter than the pitch between the first blade (63A) and the second blade (63B). The first blade (63A) and the third blade (63C) have flat surfaces (68) on the corresponding portions of the second surface (63s) of the outer portion (63r). The area of ​​the flat surface (68) on the second surface (63s) of the outer portion (63r) of the third blade (63C) is larger than the area of ​​the flat surface (68) on the second surface (63s) of the outer portion (63r) of the first blade (63A).

[0011] In the second embodiment, the pitch between the first blade (63A) and the third blade (63C) is shorter than the pitch between the first blade (63A) and the second blade (63B), and the area of ​​the flat surface (68) of the second surface (63s) of the outer portion (63r) of the third blade (63C) is larger than the area of ​​the flat surface (68) of the second surface (63s) of the outer portion (63r) of the first blade (63A). The shorter the pitch between adjacent blades (63), the stricter the restriction on the withdrawal direction (d2) of the corresponding slide type (240) between those adjacent blades (63). In contrast, the shorter the pitch between adjacent pairs of blades (63), the larger the area of ​​the flat surface (68) of the second surface (63s) of the outer portion (63r) of the blade (63) located on the front side in the rotational direction of that pair of blades (63), thereby easing the restriction on the withdrawal direction (d2) of the slide type (240). Therefore, the withdrawal direction (d2) of the slide type (240) corresponding to the space between the first blade (63A) and the second blade (63B) and the withdrawal direction (d2) of the slide type (240) corresponding to the space between the first blade (63A) and the third blade (63C) can be adjusted so that the two slide types (240) do not interfere with each other.

[0012] A third aspect of the present disclosure is a centrifugal fan (50) of the first or second aspect, wherein the plurality of blades (63) include a first blade (63A), a second blade (63B) adjacent to the first blade (63A), and a third blade (63C) adjacent to the first blade (63A) on the opposite side from the second blade (63B). The second blade (63B) is located behind the first blade (63A) in the direction of rotation. The third blade (63C) is located in front of the first blade (63A) in the direction of rotation. The pitch between the first blade (63A) and the third blade (63C) is shorter than the pitch between the first blade (63A) and the second blade (63B). The first blade (63A) and the second blade (63B) have flat surfaces (68) at corresponding portions of the first surface (63p) of the inner end portion (63i). The area of ​​the flat surface (68) on the first surface (63p) of the inner end portion (63i) of the first blade (63A) is larger than the area of ​​the flat surface (68) on the first surface (63p) of the inner end portion (63i) of the second blade (63B).

[0013] In the third embodiment, the pitch between the first blade (63A) and the third blade (63C) is shorter than the pitch between the first blade (63A) and the second blade (63B), and the area of ​​the flat surface (68) of the first surface (63p) of the inner end (63i) of the first blade (63A) is larger than the area of ​​the flat surface (68) of the first surface (63p) of the inner end (63i) of the third blade (63C). The shorter the pitch between adjacent blades (63), the stricter the restriction on the exit direction (d2) of the corresponding slide type (240) between those adjacent blades (63). In contrast, the shorter the pitch between adjacent pairs of blades (63), the larger the area of ​​the flat surface (68) of the first surface (63p) of the inner end (63i) of the blade (63) located on the front side in the rotational direction of that pair of blades (63), thereby easing the restriction on the withdrawal direction (d2) of the slide type (240). Therefore, the withdrawal direction (d2) of the slide type (240) corresponding to the space between the first blade (63A) and the second blade (63B) and the withdrawal direction (d2) of the slide type (240) corresponding to the space between the first blade (63A) and the third blade (63C) can be adjusted so that the two slide types (240) do not interfere with each other.

[0014] A fourth aspect of the present disclosure is a centrifugal fan (50) of any one of the first to third aspects, wherein the flat surface (68) is provided on the first surface (63p) of the inner end (63i) of the blade (63). The plurality of blades (63) include adjacent first blades (63A) and second blades (63B). In a cross section perpendicular to the axis of rotation (Ac) in the radial direction of the impeller (60), the line segment connecting the inner edge (63a) and the outer edge (63b) of the blade (63) is the cord line (Lc). The thickness of the inner end portion (63i) of the first blade (63A) in the direction perpendicular to the cord wire (Lc) and the thickness of the inner end portion (63i) of the second blade (63B) in the direction perpendicular to the cord wire (Lc) differ in corresponding parts depending on the presence or absence of the flat surface (68) or the area of ​​the flat surface (68).

[0015] In the fourth embodiment, a flat surface (68) is provided on the first surface (63p) of the inner end (63i) of the blade (63). The blade (63) has a cross-sectional shape that curves from the inner circumference to the outer circumference in a cross-section perpendicular to the axis of rotation (Ac). Therefore, the ejection direction (d2) of the slide mold (240) that forms the blade (63) in the mold (205) of the injection molding apparatus (200) is limited to a predetermined range by the shape of the inner end (63i) of the blade (63). In contrast, the thickness of the inner end (63i) of the first blade (63A) and the thickness of the inner end (63i) of the second blade (63B) differ in corresponding parts depending on the presence or absence of the flat surface (68) or the area of ​​the flat surface (68). The limiting range of the ejection direction (d2) of the slide mold (240) can be changed by making the thickness of the inner end (63i) of the blade (63) different. Therefore, the extraction direction (d2) of the slide mold (240) that forms the first surface (63p) of the first blade (63A) and the extraction direction (d2) of the slide mold (240) that forms the first surface (63p) of the second blade (63B) can be adjusted so that the two slide molds (240) do not interfere with each other.

[0016] A fifth aspect of the present disclosure is a centrifugal fan (50) of the fourth aspect, wherein the plurality of blades (63) include a third blade (63C) adjacent to the first blade (63A) on the opposite side from the second blade (63B). The second blade (63B) is located behind the first blade (63A) in the direction of rotation. The third blade (63C) is located in front of the first blade (63A) in the direction of rotation. The pitch between the first blade (63A) and the third blade (63C) is shorter than the pitch between the first blade (63A) and the second blade (63B). The thickness of the inner end portion (63i) of the first blade (63A) in the direction perpendicular to the cord wire (Lc) is thinner than the thickness of the inner end portion (63i) of the second blade (63B) in the direction perpendicular to the cord wire (Lc).

[0017] In the fifth embodiment, the pitch between the first blade (63A) and the third blade (63C) is shorter than the pitch between the first blade (63A) and the second blade (63B), and the thickness of the inner end (63i) of the first blade (63A) is thinner than the thickness of the inner end (63i) of the second blade (63B). The shorter the pitch between adjacent blades (63), the stricter the restriction on the exit direction (d2) of the slide type (240) between those adjacent blades (63). Conversely, the shorter the pitch between adjacent blades (63), the thinner the inner end (63i) of the blade (63) located on the rear side in the rotational direction among those adjacent blades (63), thereby easing the restriction on the exit direction (d2) of the slide type (240). Therefore, the withdrawal direction (d2) of the sliding type (240) corresponding to the space between the first blade (63A) and the second blade (63B), and the withdrawal direction (d2) of the sliding type (240) corresponding to the space between the first blade (63A) and the third blade (63C), can be adjusted so that the two sliding types (240) do not interfere with each other.

[0018] A sixth aspect of the present disclosure is a centrifugal fan (50) according to any one of the first to fifth aspects, wherein the second surface (63s) constitutes a negative pressure surface that receives negative pressure when the impeller (60) rotates. The flat surface (68) is provided on the second surface (63s) of the outer portion (63r) of the blade (63).

[0019] In the sixth embodiment, a flat surface (68) is provided on the second surface (63s) of the outer portion (63r) of the blade (63). The second surface (63s) constitutes the negative pressure surface of the blade (63). The shape of the negative pressure surface of the blade (63) does not significantly affect the airflow performance compared to the positive pressure surface. Therefore, it is possible to easily manufacture a resin-molded impeller (60) in which multiple blades (63) are arranged at unequal pitches, while suppressing a decrease in the airflow performance of the centrifugal fan (50).

[0020] A seventh aspect of this disclosure is a centrifugal fan (50) of any one of the first to sixth aspects, wherein the first surface (63p) constitutes a positive pressure surface that receives positive pressure when the impeller (60) rotates. More than 90% of the first surfaces (63p) of the plurality of blades (63) are the same shape as each other.

[0021] In the seventh embodiment, more than 90% of the first surfaces (63p) of the multiple blades (63) have the same shape. The first surfaces (63p) constitute the positive pressure surface of the blades (63). With this, by making the shapes of the first surfaces (63p) of the multiple blades (63) differ by less than 10%, the ejection direction (d2) can be adjusted so that the multiple slide molds (240) that form the blades (63) in the mold (205) of the injection molding apparatus (200) do not interfere with each other, or with the slide molds (240) and other parts of the mold (205). Furthermore, by having more than 90% of the first surfaces (63p) of the multiple blades (63) have the same shape, a decrease in the airflow performance of the centrifugal fan (50) can be suppressed.

[0022] An eighth aspect of the present disclosure is a centrifugal fan (50) according to the first to seventh aspects, wherein the outer edge (63b) of the blade (63) is inclined with respect to the rotation axis (Ac) such that it extends in a direction corresponding to the radially outward direction of the impeller (60) as it moves from the base plate (61) toward the shroud (62).

[0023] In the eighth aspect, the outer edge (63b) of the blade (63) is inclined with respect to the rotation axis (Ac), and extends in a direction corresponding to the outside in the radial direction of the impeller (60) as it goes from the base plate (61) toward the shroud (62), and has a skew angle. In the mold (205) for molding the impeller (60) having the blade (63) with such a skew angle, the first surface (63p) and the second surface (63s) molded by the slide mold (240) are long in the slide direction, and since the distance for removing the slide mold (240) from the impeller (60) when the mold (205) is opened is long, the restriction on the removal direction (d2) of the slide mold (240) becomes severe. Therefore, in the manufacturing method of the impeller (60), the technology of the present disclosure is particularly effective.

[0024] A ninth aspect of the present disclosure is a centrifugal fan (50) according to any one of the first to eighth aspects, wherein the number of the blades (63) is 6 or more. <​​​​​​​​​​In the tenth aspect, the refrigeration apparatus (1) includes a centrifugal fan (50). Since the impeller (60) of the centrifugal fan (50) is integrally formed of resin, compared with a centrifugal fan using an assembled impeller formed by integrating a base plate (61), a shroud (62), and a plurality of blades (63) which are separate components, the process of assembling the components can be omitted, making it suitable for mass production. Further, according to the centrifugal fan (50), compared with the case where a metal component is employed for at least one of the base plate (61), the shroud (62), and the plurality of blades (63), the centrifugal fan (50) can be lightened and the vibration during rotation of the centrifugal fan (50) can also be suppressed. This contributes to improving the energy efficiency in the refrigeration apparatus (1).

Brief Description of the Drawings

[0028] [Figure 1] FIG. 1 is a refrigerant circuit diagram illustrating the configuration of an air conditioner. [Figure 2] FIG. 2 is a perspective view showing the appearance of an indoor unit. [Figure 3] FIG. 3 is a view of the interior of the indoor unit as seen from the front side. [Figure 4] FIG. 4 is a view of the interior of the indoor unit as seen from the left side. [Figure 5] FIG. 5 is a perspective view illustrating the configuration of an indoor fan. [Figure 6] FIG. 6 is a cross-sectional view of the first centrifugal fan taken along line VI-VI of FIG. 5. [Figure 7] FIG. 7 is an exploded perspective view illustrating the main part configuration of the first centrifugal fan. [Figure 8] FIG. 8 is a perspective view illustrating the configuration of an impeller. [Figure 9] FIG. 9 is a plan view illustrating the configuration of an impeller. [Figure 10] FIG. 10 is a plan view illustrating the configuration of an impeller as seen through a shroud. [Figure 11] FIG. 11 is a side view illustrating the configuration of an impeller. [Figure 12]Figure 12 is a side view illustrating the configuration of the impeller on line XII-XII in Figure 11. [Figure 13] Figure 13 is a cross-sectional view of a molding apparatus including a mold for forming an impeller. [Figure 14] Figure 14 is a plan view illustrating the main parts of a mold in a closed state, seen through the fixed mold. For convenience, in Figure 14, the edges of the cavity where the base plate is formed are shown with a dashed line. [Figure 15] Figure 15 is a plan view showing an enlarged view of the main parts of the mold. [Figure 16] Figure 16 is a cross-sectional view showing the impeller in the state after the mold has been closed and in the state after the cavity inside the mold has been filled with resin during the manufacturing process. [Figure 17] Figure 17 is a plan view corresponding to Figure 14, showing the impeller formed inside the mold. For convenience, the edge of the base plate is shown as a dashed line in Figure 17. [Modes for carrying out the invention]

[0029] The embodiments of this disclosure will be described in detail below with reference to the drawings. The following embodiments will be described using as an example the application of the centrifugal fan according to this disclosure to an indoor unit of an air conditioning system. The drawings are intended to conceptually illustrate the technology of this disclosure. Therefore, in order to facilitate understanding of the technology of this disclosure, dimensions, ratios, or numbers may be exaggerated or simplified in the drawings.

[0030] In the following embodiments, the direction along the rotation axis of the centrifugal fan is referred to as the "axial direction," and the direction perpendicular to the axial direction is referred to as the "radial direction." Furthermore, the direction along the circumference of the rotation axis of the centrifugal fan is referred to as the "circumferential direction." The designations "first," "second," etc., are used to distinguish between the terms to which these designations are attached, and do not limit the number or order of these terms.

[0031] 《Embodiment》 In this embodiment, the centrifugal fan (50) according to the present disclosure will be described using as an example the case in which it is used in a floor-standing indoor unit (3). The indoor unit (3) is used in a refrigeration system. The refrigeration system in this embodiment is an air conditioning system (1). The air conditioning system (1) is a device that provides air conditioning to a large indoor space, such as a computer room where multiple servers or other computers are located, or a factory or warehouse; it is a so-called commercial air conditioner.

[0032] (1) Overall configuration of the air conditioning system As shown in Figure 1, the air conditioning system (1) is a paired air conditioning system comprising an outdoor unit (2) and an indoor unit (3). The outdoor unit (2) is installed outdoors. The indoor unit (3) is installed indoors. The outdoor unit (2) and the indoor unit (3) are connected to each other via a liquid connection pipe (4) and a gas connection pipe (5). This connection constitutes a refrigerant circuit (6).

[0033] The refrigerant circuit (6) is filled with refrigerant. The refrigerant circuit (6) mainly includes a compressor (22), an outdoor heat exchanger (11), an expansion valve (25), a four-way switching valve (26), and an indoor heat exchanger (23). The compressor (22), outdoor heat exchanger (11), expansion valve (25), four-way switching valve (26), and indoor heat exchanger (23) are connected by piping. The refrigerant circuit (6) performs the refrigeration cycle by circulating the refrigerant.

[0034] The compressor (22), indoor heat exchanger (23), expansion valve (25), and four-way directional valve (26) are included in the indoor unit (3). The compressor (22) draws in low-pressure gaseous refrigerant, compresses it, and discharges the compressed refrigerant. The refrigerant filled in the refrigerant circuit (6) circulates due to the operation of the compressor (22). The expansion valve (25) reduces the pressure of the refrigerant. The four-way directional valve (26) switches the direction of circulation of the refrigerant in the refrigerant circuit (6).

[0035] The four-way directional valve (26) is in the first state (shown by the solid line in Figure 1) during cooling operation. When the four-way directional valve (26) is in the first state, the refrigerant flows through the refrigerant circuit (6) in the direction indicated by the solid arrow. The four-way directional valve (26) is in the second state (shown by the dashed line in Figure 1) during heating operation. When the four-way directional valve (26) is in the second state, the refrigerant flows through the refrigerant circuit (6) in the direction indicated by the dashed arrow.

[0036] The indoor unit (3) further includes an indoor fan (48). The indoor fan (48) rotates under the drive of a first fan motor (53) and transports indoor air so that it passes through the indoor heat exchanger (23). The indoor fan (48) in this embodiment is composed of two centrifugal fans (50). The indoor heat exchanger (23) exchanges heat between the air transported by the indoor fan (48) and the refrigerant flowing inside it.

[0037] The outdoor heat exchanger (11) is included in the outdoor unit (2). The outdoor unit (2) further includes an outdoor fan (12). The outdoor fan (12) rotates under the drive of a second fan motor (13) and transports outdoor air so that it passes through the outdoor heat exchanger (11). The outdoor heat exchanger (11) exchanges heat between the air transported by the outdoor fan (12) and the refrigerant flowing inside.

[0038] The air conditioning unit (1) provides air conditioning to the target space, which is the indoor space (IS). The air conditioning unit (1) performs both cooling and heating operations.

[0039] Cooling operation is the operation to cool the air in the indoor space (IS). In cooling operation, with the four-way switching valve (26) in the first state, the outdoor fan (12), compressor (22), and indoor fan (48) are operated, the outdoor heat exchanger (11) functions as a heat radiator, and the indoor heat exchanger (23) functions as an evaporator. The air transported by the indoor fan (48) is cooled in the indoor heat exchanger (23) and supplied to the indoor space (IS).

[0040] Heating operation is an operation that heats the air in the indoor space (IS). In heating operation, the four-way switching valve (26) is set to the second state, and the outdoor fan (12), compressor (22), and indoor fan (48) are operated, with the outdoor heat exchanger (11) functioning as an evaporator and the indoor heat exchanger (23) functioning as a radiator. The air transported by the indoor fan (48) is heated in the indoor heat exchanger (23) and supplied to the indoor space (IS).

[0041] (2) Indoor unit The indoor unit (3) will be explained with reference to Figures 2 to 4. In the following explanation, terms such as "up," "down," "front," "back," "left," and "right" refer to the directions of the arrows shown in Figures 2 to 4. In Figures 3 and 4, the airflow in the indoor unit (3) is indicated by dashed white arrows.

[0042] The indoor unit (3) is a floor-standing indoor unit and is installed on the floor (FL) of the indoor space (IS). The indoor unit (3) comprises a casing (21), an indoor heat exchanger (23), a drain pan (40), an electrical component box (45), a compressor (22), an expansion valve (25), a four-way switching valve (26), and an indoor fan (48). In Figures 3 and 4, the expansion valve (25) and the four-way switching valve (26) are not shown.

[0043] (2-1) Casing The casing (21) is formed in a generally rectangular box shape. The casing (21) houses the indoor heat exchanger (23), drain pan (40), electrical equipment box (45), compressor (22), and indoor fan (48). The casing (21) is placed on the floor (FL) and fixed to the floor by fasteners via fittings (not shown). The casing (21) is constructed by combining metal or resin plates. The casing (21) has a top plate (21a), a bottom plate (21b), a front plate (21c), a rear plate (21d), a left side plate (21e), and a right side plate (21f).

[0044] The top plate (21a) and bottom plate (21b), the front plate (21c) and rear plate (21d), and the left side plate (21e) and right side plate (21f) are opposite each other. The top plate (21a) forms the upper surface of the casing (21). The bottom plate (21b) forms the lower surface of the casing (21). The front plate (21c) forms the front surface of the casing (21). The rear plate (21d) forms the rear surface of the casing (21). The left side plate (21e) forms the left side of the casing (21). The right side plate (21f) forms the right side of the casing (21).

[0045] The front plate (21c) is divided into three sections vertically. The front plate (21c) consists of an upper plate (21g), an intermediate plate (21h), and a lower plate (21i). The upper plate (21g), intermediate plate (21h), and lower plate (21i) are arranged in this order from the top to the bottom of the front plate (21c), and are each detachable from the casing body (CB). The casing body (CB) is the part of the casing (21) excluding the front plate (21c). An operation panel (30) for operating the air conditioning unit (1) is provided on the intermediate plate (21h).

[0046] The casing (21) has an intake port (31) and an outlet port (32). The intake port (31) is an opening for drawing air from the indoor space (IS) into the casing (21). Multiple intake ports (31) are provided on the intermediate plate (21h) of the front plate (21c), avoiding the control panel (30). Each intake port (31) is made up of, for example, a slit extending in the left-right direction. Multiple intake ports (31) are arranged parallel to each other with a gap between them in the vertical direction.

[0047] The air outlets (32) are openings for blowing out air that has undergone heat exchange within the casing (21) into the interior space (IS). Two air outlets (32) are provided on the top plate (21a). The two air outlets (32) are the first air outlet (32a) and the second air outlet (32b). The first air outlet (32a) and the second air outlet (32b) open with a gap between them in the left-right direction. The first air outlet (32a) and the second air outlet (32b) are each composed of, for example, rectangular openings.

[0048] A frame-like section (35) is provided on the upper surface of the top plate (21a). The frame-like section (35) surrounds the two air outlets (32) and forms a connection port (36) that protrudes upward from the top plate (21a). The frame-like section (35) is constructed by combining multiple metal fittings, such as L-shaped long angles. A duct (100) is connected to the connection port (36) made up of this frame-like section (35) to transport the air blown out from each air outlet (32) to various locations in the interior space (IS).

[0049] Furthermore, a first opening (37) and a second opening (38) are formed in the left panel (21e) and the right panel (21f), respectively. The first opening (37) is located at the top of the casing (21) and is used when performing maintenance on the indoor fan (48). The second opening (38) is located at the bottom of the casing (21) and is used when performing maintenance on the electrical equipment box (45) and the compressor (22). The first opening (37) and the second opening (38) are normally covered by a cover (39), and the cover (39) is removed and the openings are opened during maintenance.

[0050] An air passage (AP) is formed inside the casing (21). The air passage (AP) is a passage that extends from multiple intake ports (31) to the first outlet (32a) and the second outlet (32b). The air passage (AP) has a right-side passage (Pa) and a left-side passage (Pb). The right-side passage (Pa) is a passage that is drawn into the first centrifugal fan (50A) and reaches the first outlet (32a), and is located on the right side inside the casing (21). The left-side passage (Pb) is a passage that is drawn into the second centrifugal fan (50B) and reaches the second outlet (32b), and is located on the left side inside the casing (21).

[0051] (2-2) Indoor heat exchanger The indoor heat exchanger (23) is positioned in the air passage (AP) within the casing (21). The indoor heat exchanger (23) is fixed to the casing (21) so that substantially all of the air flowing through the air passage (AP) passes through it. In this example, the indoor heat exchanger (23) is positioned vertically behind the intermediate plate (21h) and is installed in a forward-tilting position so that it protrudes forward as it goes upward. The lower part of the indoor heat exchanger (23) is located on the rear side of the casing (21) and is fixed to a bracket (24) attached to the rear plate (21d). The indoor heat exchanger (23) is a fin-and-tube type air heat exchanger.

[0052] (2-3) Drain pan The drain pan (40) consists of a first drain pan (40a) and a second drain pan (40b).

[0053] The first drain pan (40a) is fixed to the bracket (24) together with the indoor heat exchanger (23) and is positioned below the bottom of the indoor heat exchanger (23). The first drain pan (40a) receives water (condensation) that has condensed on the surface and around the indoor heat exchanger (23). A discharge pipe (41) is provided at one end of the first drain pan (40a) in the left-right direction (the left end in the example shown in Figure 3). The discharge pipe (41) extends downward from the bottom of the first drain pan (40a) and drains the water in the first drain pan (40a) downward.

[0054] The second drain pan (40b) is located in the lower part of the casing (21). The second drain pan (40b) faces almost the entire surface of the bottom plate (21b) of the casing (21), and is installed in a forward-sloping position such that its front edge is slightly above its rear edge. Although not shown in the figures, a drain channel (42) is formed at the rear of the second drain pan (40b) so as to extend in the left-right direction. The water collected in the first drain pan (40a) and the second drain pan (40b) is collected in the drain channel (42) and discharged outside or elsewhere via a drain hose.

[0055] (2-4) Electrical component box The electrical component box (45) is located on the right side of the lower part of the casing (21). The electrical component box (45) is fixed to a stand member (46) attached to the casing (21) and is positioned above the second drain pan (40b). The electrical component box (45) is a box that is generally rectangular in shape and houses predetermined electrical components. These electrical components include control boards that control equipment such as the indoor fan (48) and compressor (22) and receive signals from various sensors.

[0056] (2-5) Compressor The compressor (22) is installed on the second drain pan (40b) in a position that does not overlap with the electrical component box (45) when viewed from the front. The compressor (22) is located on the left side in the lower part of the casing (21). The compressor (22) is a variable displacement compressor. The compressor (22) is configured to have a variable rotation speed via inverter control by a control board in the electrical component box (45), and to be able to change the volume of refrigerant being compressed.

[0057] (2-6) Indoor fan The two centrifugal fans (50) that make up the indoor fan (48) are a first centrifugal fan (50A) and a second centrifugal fan (50B). Both the first centrifugal fan (50A) and the second centrifugal fan (50B) are turbo fans and are located in the upper half of the interior of the casing (21). In this embodiment, the first centrifugal fan (50A) and the second centrifugal fan (50B) are attached to the top plate (21a) of the casing (21) and are located above the indoor heat exchanger (23), and are positioned downstream of the indoor heat exchanger (23) in the airflow.

[0058] The first centrifugal fan (50A) is located on the right side of the upper part of the casing (21). The second centrifugal fan (50B) is located on the left side of the upper part of the casing (21). A first fan motor (53) is located between the first centrifugal fan (50A) and the second centrifugal fan (50B). The first fan motor (53) is a double-shaft motor in which the drive shaft (53b) extends from the motor body (53a) to both the left and right sides. The first fan motor (53) is shared by both the first centrifugal fan (50A) and the second centrifugal fan (50B).

[0059] The first centrifugal fan (50A) is connected to a drive shaft (53b) extending to the right of the first fan motor (53). The second centrifugal fan (50B) is connected to a drive shaft (53b) extending to the left of the first fan motor (53). Both the first centrifugal fan (50A) and the second centrifugal fan (50B) are rotated by the drive of the first fan motor (53). The axis of the drive shaft (53b) coincides with the rotation axes (Ac) of the first centrifugal fan (50A) and the second centrifugal fan (50B). The rotation axes (Ac) of the first centrifugal fan (50A) and the second centrifugal fan (50B) extend in the left-right direction. That is, the left-right direction in this embodiment corresponds to the axial direction along the rotation axis (Ac).

[0060] (2-6-1) First centrifugal fan The first centrifugal fan (50A) is a double-suction centrifugal fan. As shown in Figures 5 and 6, the first centrifugal fan (50A) comprises a first impeller (60A), a second impeller (60B), a first fan casing (54), a first bell mouth (80A), and a second bell mouth (80B). The first impeller (60A) and the second impeller (60B) are connected to the drive shaft (53b) of the first fan motor (53) via a first connecting component (70), and are arranged in this order from the side closest to the first fan motor (53) toward the side away from it. That is, the first impeller (60A) is located on the left side, and the second impeller (60B) is located on the right side.

[0061] The first impeller (60A) and the second impeller (60B) have essentially the same components. The first impeller (60A) and the second impeller (60B) each have a base plate (61), a shroud (62), and a number of blades (63). The first impeller (60A) is provided such that the fan intake port (66) formed in the shroud (62) opens to one side in the axial direction, in this example to the left. The second impeller (60B) is provided such that the fan intake port (66) formed in the shroud (62) opens to the other side in the axial direction, in this example to the right.

[0062] As shown in Figure 7, the first impeller (60A) and the second impeller (60B) are integrated in a back-to-back configuration with their base plates (61) facing each other via a first connecting component (70). The first connecting component (70) connects the first impeller (60A) and the second impeller (60B) and also receives the drive shaft (53b). The first connecting component (70) has a boss portion (71) and a flange portion (72). The boss portion (71) is a cylindrical portion through which the insertion hole (73) passes. The flange portion (72) is formed in an annular shape that protrudes outward from the boss portion (71).

[0063] The boss portion (71) is inserted through the shaft hole (64) of the second impeller (60B). The flange portion (72) is sandwiched between the base plate (61) of the first impeller (60A) and the base plate (61) of the second impeller (60B). Both base plates (61) are fastened together to the flange portion (72) with bolts (75) and nuts (76). A pin hole (74) is also formed in the boss portion (71). The pin hole (74) penetrates the boss portion (71) radially. The drive shaft (53b) is inserted through the insertion hole (73) of the boss portion (71). A retaining pin (77) is inserted into the drive shaft (53b) through the pin hole (74). In this way, the drive shaft (53b) is fixed to the first connecting component (70).

[0064] The first impeller (60A) and the second impeller (60B) are integrated via the first connecting component (70) and have a mirror-symmetric structure or shape relative to each other. The blades (63) of the first impeller (60A) and the blades (63) of the second impeller (60B) are positioned with a half-pitch offset from each other in the circumferential direction of the impeller (60). When the first centrifugal fan (50A) is viewed from the axial direction, the blades (63) of the second impeller (60B) correspond to the adjacent blades (63) of the first impeller (60A), and the blades (63) of the first impeller (60A) correspond to the adjacent blades (63) of the second impeller (60B).

[0065] As shown in Figures 5 and 6, the first fan casing (54) houses the first impeller (60A) and the second impeller (60B). The first fan casing (54) is formed in a box shape with an open top. The first fan casing (54) has a first upper opening (55) that is open upward. A first mounting piece (56) is provided on the periphery of the first upper opening (55) of the first fan casing (54), protruding outwards. The first mounting piece (56) is attached to the top plate (21a) of the casing (21). The first fan casing (54) is fixed to the top plate (21a) of the casing (21) with the first upper opening (55) corresponding to the first air outlet (32a).

[0066] A first side opening (57) is formed on the left side wall (54a) of the first fan casing (54). A second side opening (58) is formed on the right side wall (54b) of the first fan casing (54). The first side opening (57) and the second side opening (58) are formed, for example, in a circular shape. The first side opening (57) corresponds to the fan intake port (66) of the first impeller (60A). The inner diameter of the first side opening (57) is larger than the inner diameter of the fan intake port (66) of the first impeller (60A). On the other hand, the second side opening (58) corresponds to the fan intake port (66) of the second impeller (60B). The inner diameter of the second side opening (58) is larger than the inner diameter of the fan intake port (66) of the second impeller (60B).

[0067] The first bell mouth (80A) is fitted into the first side opening (57) of the first fan casing (54). The first bell mouth (80A) is located on the intake side of the first impeller (60A) and is a component that guides air from outside the first centrifugal fan (50A) to the first impeller (60A). The second bell mouth (80B) is fitted into the second side opening (58) of the first fan casing (54). The second bell mouth (80B) is located on the intake side of the second impeller (60B) and is a component that guides air from outside the first centrifugal fan (50A) to the second impeller (60B).

[0068] The same bell mouth (80) is used for both the first bell mouth (80A) and the second bell mouth (80B). The bell mouth (80) is a metal component and has a rim portion (81) and a cylindrical portion (82). The rim portion (81) is formed in the shape of an annular plate. The rim portion (81) of the first bell mouth (80A) is fixed to the periphery of the first side opening (57) on the left side wall (54a) of the first fan casing (54). The rim portion (81) of the second bell mouth (80B) is fixed to the periphery of the second side opening (58) on the right side wall (54b) of the first fan casing (54).

[0069] The cylindrical portion (82) of the bell mouth (80) is formed in a cylindrical shape that protrudes into the interior of the first fan casing (54) from the inner peripheral edge of the rim portion (81). The cylindrical portion (82) constitutes an air vent (83) through which air flows. The tip of the cylindrical portion (82) of the first bell mouth (80A) is inserted into the fan intake port (66) of the first impeller (60A) with a predetermined gap between it and the peripheral edge of the fan intake port (66). The tip of the cylindrical portion (82) of the second bell mouth (80B) is inserted into the fan intake port (66) of the second impeller (60B) with a predetermined gap between it and the peripheral edge of the fan intake port (66).

[0070] In the first centrifugal fan (50A), when the first fan motor (53) is driven, the first impeller (60A) and the second impeller (60B) rotate together, drawing in air from the vents (83) of the first bell mouth (80A) and the second bell mouth (80B) located on both sides of the first fan casing (54). The air drawn in from the vents (83) of the first bell mouth (80A) passes through the first impeller (60A), and the air drawn in from the vents (83) of the second bell mouth (80B) passes through the second impeller (60B). The air that has passed through the first impeller (60A) and the second impeller (60B) is blown out from the first upper opening (55) to the first outlet (32a).

[0071] (2-6-2) Second centrifugal fan The second centrifugal fan (50B) is a single-inlet centrifugal fan. As shown in Figure 5, the second centrifugal fan (50B) includes a third impeller (60C), a second fan casing (84), and a third bell mouth (80C). The third impeller (60C) is provided such that the fan intake port (66) formed in the shroud (62) opens to one side in the axial direction, in this example to the left. The third impeller (60C) is connected to the drive shaft (53b) of the first fan motor (53) via a second connecting component (not shown). The second connecting component is similar to the first connecting component (70).

[0072] The second fan casing (84) houses the third impeller (60C). The second fan casing (84) is formed in a box shape with an open top. The second fan casing (84) has a second upper opening (85) that is open upward. A second mounting piece (86) is provided on the periphery of the second upper opening (85) of the second fan casing (84), protruding outwards. The second mounting piece (86) is attached to the top plate (21a) of the casing (21). The second fan casing (84) is fixed to the top plate (21a) of the casing (21) with the second upper opening (85) aligned with the second air outlet (32b).

[0073] A third side opening (not shown) is formed in the left side wall (84a) of the second fan casing (84). The third side opening is formed, for example, in a circular shape. The third side opening corresponds to the fan intake port (66) of the third impeller (60C). The inner diameter of the third side opening is larger than the inner diameter of the fan intake port (66) of the third impeller (60C). The third bell mouth (80C) is fitted into the third side opening of the second fan casing (84). The third bell mouth (80C) is positioned on the intake side of the third impeller (60C) and is a component that guides air from outside the second centrifugal fan (50B) to the third impeller (60C). Although not shown, a hole is formed in the right side wall (84b) of the second fan casing (84) through which the drive shaft (53b) is inserted.

[0074] The third bell mouth (80C) uses the same metal bell mouth (80) as the first bell mouth (80A) and the second bell mouth (80B). The rim portion (81) of the third bell mouth (80C) is fixed to the periphery of the third side opening on the left side wall (84a) of the second fan casing (84). The cylindrical portion (82) of the third bell mouth (80C) protrudes into the interior of the second fan casing (84). The tip of the cylindrical portion (82) is inserted into the fan intake port (66) of the third impeller (60C) with a predetermined gap between it and the periphery of the fan intake port (66).

[0075] In the second centrifugal fan (50B), when the first fan motor (53) is driven, the third impeller (60C) rotates and draws air in through the vent (83) of the third bell mouth (80C) located on the left side of the second fan casing (84). The air drawn in through the vent (83) of the third bell mouth (80C) passes through the third impeller (60C) and is blown out through the second upper opening (85) to the second outlet (32b). The air blown out from the second outlet (32b) flows through the duct (100) together with the air blown out from the first outlet (32a) and is transported to various locations in the interior space (IS).

[0076] (3) Impeller configuration The first impeller (60A) and the second impeller (60B) use impellers (60) that have the same configuration as the first impeller (60A), except that the orientation of the blades (63) is different. The third impeller (60C) uses the same impeller (60) as the first impeller (60A). The configuration of this impeller (60) is shown in Figures 8 to 12, using the first impeller (60A) as an example. The impeller (60) rotates around a predetermined axis of rotation (Ac) that coincides with the axis of the drive shaft (53b). The impeller (60) is a single-piece molded resin part. The base plate (61), shroud (62), and multiple blades (63) are integrally molded from resin.

[0077] The base plate (61) is formed in a disc shape. The base plate (61) is the hub of the impeller (60) and is positioned substantially coaxially with the drive shaft (53b) of the first fan motor (53). An axle hole (64) is formed in the central part of the base plate (61). The drive shaft (53b) is inserted through the axle hole (64) via a first connecting component (70) or a second connecting component. In addition, a plurality of fastening holes (65) (three fastening holes (65) in the example shown in Figure 8, etc.) are formed around the axle hole (64) of the base plate (61). The plurality of fastening holes (65) are holes through which bolts (75) are inserted and are provided at equal intervals in the circumferential direction of the axle hole (64).

[0078] The shroud (62) is formed in an annular shape. The shroud (62) is positioned opposite the base plate (61) at a distance from the base plate (61) in the axial direction (left-right in this example) along the axis of rotation (Ac). The shroud (62) is also positioned substantially coaxially with the base plate (61). In this example, the outer diameter of the shroud (62) is larger than the outer diameter of the base plate (61). The outer diameter of the shroud (62) may be equal to the outer diameter of the base plate (61), or it may be smaller than the outer diameter of the base plate (61). The shroud (62) has a fan intake port (66). The fan intake port (66) is an opening that draws air into the interior of the first impeller (60A). The inner peripheral edge of the shroud (62) protrudes away from the base plate (61), forming the fan intake port (66).

[0079] Multiple blades (63) are provided between the base plate (61) and the shroud (62). The multiple blades (63) are spaced apart from each other in the circumferential direction around the axis of rotation (Ac), that is, in the direction of rotation of the impeller (60). In this example, the impeller (60) has six blades (63). Each of the multiple blades (63) is located in the region near the outer edge of the base plate (61). Each blade (63) is provided upright in the direction in which the base plate (61) and the shroud (62) face each other. Each blade (63) has a cross-sectional shape that curves from the inner circumference to the outer circumference in a cross section perpendicular to the axis of rotation (Ac).

[0080] Each of the multiple blades (63) has an inner edge (63a) and an outer edge (63b). The inner edge (63a) is the edge located on the inner circumference side of the blade (63). The inner edge (63a) is located on the front side in the direction of rotation of the impeller (60) and corresponds to the inner circumference of the fan intake (66) in a plan view of the impeller (60). The outer edge (63b) is the edge located on the outer circumference side of the blade (63). The outer edge (63b) is located on the rear side in the direction of rotation of the impeller (60) and corresponds to the outer circumference edge of the shroud (62) in a plan view of the impeller (60). The inner edge (63a) and the outer edge (63b) extend in a direction inclined with respect to the axis of rotation (Ac).

[0081] The inner edge (63a) is inclined to extend outward in the radial direction of the impeller (60) and backward in the rotational direction as it moves from the base plate (61) towards the shroud (62). The inner edge (63a) is curved to form a convex shape forward in the rotational direction, and is more curved on the shroud (62) side than on the base plate (61) side. The outer edge (63b) is inclined to extend outward in the radial direction of the impeller (60) and backward in the rotational direction as it moves from the base plate (61) towards the shroud (62). The outer edge (63b) is formed in a generally straight shape.

[0082] One end of each blade (63) in the axial direction is connected to the shroud (62) side of the base plate (61). The other end of each blade (63) in the axial direction is connected to the base plate (61) side of the shroud (62). In a cross section perpendicular to the rotation axis (Ac) of the impeller (60), the line segment connecting the inner edge (63a) and the outer edge (63b) of the blade (63) is the chord line (Lc). An example of the chord line (Lc) is shown in Figure 10. The length of the chord line (Lc) is the chord length (L). The chord length L is approximately constant throughout the entire axial direction of the blade (63).

[0083] The inner edge (63a) and outer edge (63b) have skew angles β1 and β2, respectively. The skew angle β1 of the inner edge (63a) is the angle formed by the line connecting the base plate (61) side end of the inner edge (63a) to the axis of rotation (Ac) and the line connecting the shroud (62) side end to the axis of rotation (Ac) in a plan view of the impeller (60). The skew angle β1 of the inner edge (63a) is, for example, 5° to 15°. The skew angle β2 of the outer edge (63b) is the angle formed by the line connecting the base plate (61) side end of the outer edge (63b) to the axis of rotation (Ac) and the line connecting the shroud (62) side end to the axis of rotation (Ac) in a plan view of the impeller (60). The skew angle β2 of the outer edge (63b) is, for example, 5° to 15°.

[0084] The thickness of each blade (63) gradually increases from the inner edge (63a) towards the outer edge (63b) in a cross-section perpendicular to the axis of rotation (Ac), and then decreases. The thickness of each blade (63) is the thickness in the direction perpendicular to the cord wire (Lc) of the blade (63). Each blade (63) has a teardrop shape, with the thickness being greatest near the inner edge (63a). The portion of each blade (63) near the inner edge (63a) has a relatively large curvature compared to other portions. This portion with relatively large curvature severely restricts the exit direction (d2) of the slide mold (240), so the area of ​​this portion may be small or absent by providing a flat surface (68), which will be described later.

[0085] Each blade (63) further has a first surface (63p) and a second surface (63s). The first surface (63p) constitutes a positive pressure surface that receives positive pressure when the impeller (60) rotates. The first surface (63p) faces the outside of the curvature of the blade (63) between the inner edge (63a) and the outer edge (63b), faces forward in the direction of rotation of the impeller (60), and faces the outer circumference of the impeller (60). The second surface (63s) constitutes a negative pressure surface that receives negative pressure when the impeller (60) rotates. The second surface (63s) faces the inside of the curvature of the blade (63) between the inner edge (63a) and the outer edge (63b), faces rearward in the direction of rotation of the impeller (60), and faces the rotation axis (Ac) side of the impeller (60).

[0086] A fan outlet (67) is formed between the outer edge of the base plate (61) and the outer edge of the shroud (62). The fan outlet (67) is an opening that blows air out from the impeller (60) to the outside. In the impeller (60), the portion of the space between the base plate (61) and the shroud (62) where the blades (63) are arranged constitutes a fan flow path (Pf). The fan flow path (Pf) is an annular flow path that is continuous with the fan outlet (67) and is partitioned by multiple blades (63). The fan flow path (Pf) between adjacent blades (63) widens from the rotation axis (Ac) side of the impeller (60) toward the outer edge.

[0087] In the impeller (60), multiple blades (63) are arranged at unequal pitches to reduce the NZ tone. The pitch between adjacent blades (63) refers to the circumferential pitch between the outer edges (63b) of the blades (63). The pitches between adjacent blades (63) differ from each other on both sides in the circumferential direction of each blade (63). In this embodiment, the six blades (63) are arranged at three different pitches. The six blades (63) include two first blades (63A), two second blades (63B), and two third blades (63C).

[0088] The first blade (63A) and the second blade (63B) are adjacent to each other in the circumferential direction. The second blade (63B) is located behind the first blade (63A) in the direction of rotation. The first blade (63A) is also adjacent to the third blade (63C) in the circumferential direction. The third blade (63C) is adjacent to the first blade (63A) on the opposite side from the second blade (63B) and is located in front of the first blade (63A) in the direction of rotation. The third blade (63C) is also adjacent to the second blade (63B) and is located behind the second blade (63B) in the direction of rotation.

[0089] As shown in Figure 10, the two first blades (63A), the two second blades (63B), and the two third blades (63C) are each positioned 180 degrees apart in the circumferential direction and are point-symmetrically located at radially corresponding positions across the axis of rotation (Ac). The pitch between the first blades (63A) and the third blades (63C) is shorter than the pitch between the first blades (63A) and the second blades (63B). The pitch between the second blades (63B) and the third blades (63C) is shorter than the pitch between the first blades (63A) and the second blades (63B).

[0090] In a plan view of the fan intake port (66) of the impeller (60) from the front, the line connecting the outer edge (63b) of the first blade (63A) and the axis of rotation (Ac) is defined as the first line (L1), the line connecting the outer edge (63b) of the second blade (63B) and the axis of rotation (Ac) is defined as the second line (L2), and the line connecting the outer edge (63b) of the third blade (63C) and the axis of rotation (Ac) is defined as the third line (L3). The first blade (63A), the second blade (63B), and the third blade (63C) are arranged at pitches such that the first line (L1) and the third line (L3), the first line (L1) and the second line (L2), and the second line (L2) and the third line (L3) form different angles with respect to each other.

[0091] For example, the first blade (63A) and the third blade (63C) are positioned at a pitch such that the angle α1 between the first line (L1) and the third line (L3) is 60°. The first blade (63A) and the second blade (63B) are positioned at a pitch such that the angle α2 between the first line (L1) and the second line (L2) is 69°. The second blade (63B) and the third blade (63C) are positioned at a pitch such that the angle α3 between the second line (L2) and the third line (L3) is 51°. Thus, the spacing between the first blade (63A) and the third blade (63C) is narrower than the spacing between the first blade (63A) and the second blade (63B), and wider than the spacing between the second blade (63B) and the third blade (63C).

[0092] In an impeller (60) in which multiple blades (63) are arranged at unequal pitches, there are areas where the spacing between adjacent blades (63) is narrower compared to an impeller (60) in which the same number of blades (63) are arranged at equal pitches. In areas where the spacing between adjacent blades (63) is narrower, the sliding direction of the slide type (240) located between the cavities (C) forming those two blades (63) becomes more restricted, and the slide types (240) are more likely to interfere with each other. Therefore, arranging multiple blades (63) at unequal pitches results in a localized reduction in the pitch of the blades (63), which becomes a factor that makes interference between adjacent slide types (240) more apparent.

[0093] Therefore, in the impeller (60) of this embodiment, the shapes of adjacent blades (63) are partially different from each other. The first blade (63A), the second blade (63B), and the third blade (63C) have different shapes in their corresponding parts. Here, "corresponding parts" means the parts in which the coordinate values ​​of each axis correspond in a three-dimensional coordinate system for each blade (63) represented by three axes: an axis along the cord wire (Lc) of the blade (63), an axis perpendicular to the cord wire (Lc), and an axis extending in the axial direction. In this embodiment, the meaning of different blade (63) shapes includes cases where the surface shape of the blade (63) is slightly different to the extent that it cannot be recognized by visual inspection alone.

[0094] The parts of the first feather (63A), second feather (63B), and third feather (63C) that differ in shape from each other are the inner end portion (63i) (the part with dot hatching in Figures 10 to 12), which is the part of the feather (63) closer to the inner edge (63a) and in this example includes the inner edge (63a), and the second surface (63s) of the outer portion (63r), which is the part of the outer portion (63r) closer to the outer edge (63b) (the part shown by a thick line in Figure 10, and the part with mesh hatching in Figures 11 and 12). Here, the inner end portion (63i) refers to the part of the feather (63) that is 10% from the inner edge (63a) relative to the cord length L. The outer portion (63r) refers to the part of the feather (63) that is 30% from the outer edge (63b) relative to the cord length L.

[0095] The first surface (63p) of the inner end (63i) and the second surface (63s) of the outer portion (63r) of each blade (63) are the points that are closest to the adjacent blades (63) on both sides in the rotational direction of the impeller (60). Therefore, the shapes of the first surface (63p) of the inner end (63i) and the second surface (63s) of the outer portion (63r) of each blade (63) are dominant factors that restrict the withdrawal direction (d2) of the slide mold (240) that forms the first surface (63p) of one of a pair of adjacent blades (63) and the second surface (63s) of the other blade (63) in the mold (205) that forms the impeller (60). In this embodiment, the shapes of the first surface (63p) of the inner end portion (63i) and the second surface (63s) of the outer portion (63r) of each blade (63) are devised in order to adjust the extraction direction (d2) of the slide type (240).

[0096] In this embodiment, the portion of the first surface (63p) of each inner end (63i) of the first blade (63A), second blade (63B), and third blade (63C) that has a different shape is, strictly speaking, the first surface (63p) of the portion of each inner end (63i) of the blade (63) excluding the end on the shroud (62) side (see Figure 11). Also, the portion of the second surface (63s) of each outer portion (63r) of the first blade (63A), second blade (63B), and third blade (63C) that has a different shape is, strictly speaking, the second surface (63s) of the outer portion (63r) of the blade (63) on the end on the shroud (62) side (see Figure 12).

[0097] Where adjacent pairs of blades (63) have different shapes, the area of ​​the flat surface (68) differs. The flat surface (68) is a flat surface that extends in a direction intersecting the straight line connecting the outer edge (63b) of one blade (63) located forward in the direction of rotation and the inner edge (63a) of the other blade (63) located backward in the direction of rotation, in a plan view of the impeller (60). The direction in which the flat surface (68) extends in a plan view of the impeller (60) corresponds to the release direction (d2) of the slide type (240). The area of ​​the flat surface (68) differs depending on the angle it makes with respect to the radial direction of the impeller (60).

[0098] In this embodiment, the first blade (63A), second blade (63B), and third blade (63C) each have a flat surface (68) on the first surface (63p) of the inner end (63i) and the second surface (63s) of the outer portion (63r), and the area of ​​the flat surface (68) differs in the corresponding parts. The area of ​​the flat surface (68) of the inner end (63i) and outer portion (63r) of each blade (63) increases as the pitch between adjacent blades (63) in the rotational direction of the impeller (60) decreases.

[0099] Specifically, the area of ​​the flat surface (68) at the inner end (63i) of the first blade (63A) is larger than the area of ​​the flat surface (68) at the inner end (63i) of the second blade (63B), and the area of ​​the flat surface (68) at the outer part (63r) of the first blade (63A) is larger than the area of ​​the flat surface (68) at the outer part (63r) of the second blade (63B). Furthermore, the area of ​​the flat surface (68) at the inner end (63i) of the third blade (63C) is larger than the area of ​​the flat surface (68) at the inner end (63i) of the first blade (63A), and the area of ​​the flat surface (68) at the outer part (63r) of the third blade (63C) is larger than the area of ​​the flat surface (68) at the outer part (63r) of the first blade (63A).

[0100] Where adjacent blades (63) have different shapes, their thicknesses differ. That is, the thickness of the inner end (63i) of the first blade (63A), the thickness of the inner end (63i) of the second blade (63B), and the thickness of the inner end (63i) of the third blade (63C) differs in corresponding areas according to the area of ​​the flat surface (68). Also, the thickness of the outer part (63r) of the first blade (63A), the thickness of the outer part (63r) of the second blade (63B), and the thickness of the outer part (63r) of the third blade (63C) differs in corresponding areas according to the area of ​​the flat surface (68).

[0101] The thickness of the inner end portion (63i) of the first blade (63A), the second blade (63B), and the third blade (63C) is the thickness of the inner end portion (63i) in a direction perpendicular to the cord wire (Lc) of the blade (63). The thickness of the outer portion (63r) of the first blade (63A), the second blade (63B), and the third blade (63C) is the thickness of the outer portion (63r) in a direction perpendicular to the cord wire (Lc) of the blade (63). The thickness of the inner end portion (63i) and the outer portion (63r) of each blade (63) becomes thinner in areas where the blades (63) have different shapes as the pitch between adjacent blades (63) in the direction of rotation of the impeller (60) becomes shorter.

[0102] Specifically, in the corresponding parts of the first wing (63A) and the second wing (63B), the thickness of the inner end (63i) of the first wing (63A) is thinner than the thickness of the inner end (63i) of the second wing (63B), and the thickness of the outer part (63r) of the first wing (63A) is thinner than the thickness of the outer part (63r) of the second wing (63B). Also, in the corresponding parts of the first wing (63A) and the third wing (63C), the thickness of the inner end (63i) of the third wing (63C) is thinner than the thickness of the inner end (63i) of the first wing (63A), and the thickness of the outer part (63r) of the third wing (63C) is thinner than the thickness of the outer part (63r) of the first wing (63A).

[0103] The difference in thickness at the points where the shape of the inner end portion (63i) of the first blade (63A), second blade (63B), and third blade (63C) differs is, for example, approximately 0.3 mm or more and 0.7 mm or less. The difference in thickness at the points where the shape of the second surface (63s) of the outer portion (63r) of the first blade (63A), second blade (63B), and third blade (63C) differs is, for example, approximately 0.1 mm or more and 0.3 mm or less. More than 90% of the first surface (63p) of the first blade (63A), second blade (63B), and third blade (63C) are the same.

[0104] More specifically, of the area of ​​the first surface (63p) of the first blade (63A), second blade (63B), and third blade (63C), the area of ​​portions that are the same shape as each other accounts for 90% or more. In this specification, "same shape as each other" means that the cross-sectional shape, curvature distribution, and projected contour are the same or substantially the same. Preferably, the area of ​​portions that are the same shape as each other of the first surface (63p) of multiple blades (63), i.e., the area of ​​portions that are the same shape as each other of the area of ​​the first surface (63p), accounts for 95% or more.

[0105] As the impeller (60) rotates, air is drawn in through the fan intake (66) and blown out through the fan outlet (67). The air passing through the impeller (60) flows from the inside to the outside in the radial direction of the fan flow path (Pf). Each blade (63) increases the air pressure due to the change in the rotational velocity of the airflow between the inner edge (63a) and the outer edge (63b), and the difference in peripheral velocities between the inner edge (63a) and the outer edge (63b). As a result, the impeller (60) pressurizes the air drawn in through the fan intake (66) and blows it out through the fan outlet (67).

[0106] The first impeller (60A) and the third impeller (60C) are each configured as impellers (60) for clockwise rotation. In the first impeller (60A), the inner edge (63a) of each blade (63) is located clockwise forward of the outer edge (63b) of the blade (63). The second impeller (60B) is configured as an impeller (60) for counterclockwise rotation. In the second impeller (60B), the inner edge (63a) of each blade (63) is located counterclockwise forward of the outer edge (63b) of the blade (63). The first impeller (60A) and the second impeller (60B) are connected to the drive shaft (53b) of the same first fan motor (53) via a first connecting component (70) to form a double-suction centrifugal fan.

[0107] (4) Manufacturing of impellers The impeller (60) is formed by injection molding. The injection molding apparatus (200) shown in Figure 13 is used to form the impeller (60).

[0108] (4-1) Injection molding equipment The injection molding apparatus (200) comprises a mold (205), an injection machine and an opening / closing mechanism (both not shown), and a control unit (250). The opening / closing mechanism is a mechanism for opening, closing, and clamping the mold (205). The injection molding apparatus is configured to form a cavity (C) for molding the impeller (60) by closing the mold (205), and to inject molten resin (R) sent from the injection machine into the cavity (C).

[0109] (4-1-1) Mold The mold (205) comprises a fixed mold (210), a movable mold (230), and a plurality of sliding molds (240). The fixed mold (210) is an example of a first mold. The movable mold (230) is an example of a second mold.

[0110] The fixed mold (210) is attached to the fixed plate (212). The side of the fixed mold (210) facing the movable mold (230) has a third molding surface (214). The third molding surface (214) is the surface of the base plate (61) opposite to the shroud (62), that is, the surface that molds the outer surface facing the outside of the impeller (60). The central part of the third molding surface (214) is provided with a cylindrical portion (216) for forming an axial hole (64) and a projection (not shown) for forming a retaining hole (65). In addition, the fixed mold (210) has a plurality of gates (218). Each gate (218) is an opening for injecting molten resin (R), which is the raw material for the impeller (60), into the cavity (C), and opens onto the third molding surface (214). Each gate (218) in this example is a direct gate.

[0111] A resin channel (220) is provided in the fixed mold (210). The resin channel (220) consists of a hot runner (221) and a sprue (222). The hot runner (221) has a plurality of branch channels (223) and a common channel (224). A branch channel (223) is provided for each gate (218). Each branch channel (223) extends from the gate (218) in the mold opening direction and communicates with the gate (218). The common channel (224) extends in a direction perpendicular to the branch channels (223) and connects the ends of each branch channel (223) opposite to the gate (218), and communicates with a plurality of branch channels (223). The sprue (222) extends from the common channel (224) of the hot runner (221) in the mold opening direction, passes through the fixed plate (212), and communicates with the nozzle of the injection machine.

[0112] The fixed type (210) is further provided with multiple needle valves (225). A needle valve (225) is provided for each gate (218). Each needle valve (225) consists of a needle (226) and a first actuator (227). The needle (226) is housed in a branch passage (223). The first actuator (227) is a device that moves the needle (226) forward and backward relative to the gate (218), and is provided on the fixed plate (212), with the part of the needle (226) opposite to the gate (218) connected to it. Each gate (218) opens and closes in accordance with the forward and backward movement of the needle (226). In addition, although not shown, the fixed type (210) is provided with a cooling channel through which a cooling liquid such as water flows.

[0113] The movable mold (230) comprises a base block (231), a center mold (238), and a plurality of inner cores (239). The base block (231) is attached to the movable plate (233) via a spacer block (232). The spacer block (232) has a housing chamber (234) inside. The housing chamber (234) houses the ejector plate (235). The ejector plate (235) supports a plurality of arms (236) that penetrate the base block (231) in an inclined position with respect to the mold opening direction. The plurality of arms (236) extend from the ejector plate (235) toward the fixed mold (210) side from a position corresponding to the outer circumference of the impeller (60) to a position closer to the axis of rotation (Ac), that is, closer to the cylindrical portion (216).

[0114] The base block (231) has a fourth molding surface (237). The fourth molding surface (237) molds the surface of the shroud (62) opposite to the base plate (61), that is, the surface facing the outside of the impeller (60). Although not shown, the base block (231) is also provided with a cooling channel through which a cooling liquid such as water flows. The center mold (238) is positioned in the base block (231) at a location corresponding to the inside of the impeller (60). Multiple inner cores (239) are positioned around the center mold (238) and are arranged to surround the center mold (238). The center mold (238) and each inner core (239) are elements that mold the portion of the base plate (61) on the shroud (62) side that is closer to the center than the blades (63). Each inner core (239) also forms a portion of the negative pressure surface (63s) of each blade (63), specifically the portion on the inner edge (63a) side.

[0115] Each inner core (239) is connected to an arm (236). The ejector plate (235) changes the degree of inclination of the arm (236) in conjunction with the opening and closing operation of the mold (205). When the mold (205) is closed, the ejector plate (235) reduces the degree of inclination of each arm (236) with respect to the mold opening direction, and the multiple inner cores (239) are displaced so as to spread radially toward the outer circumference of the impeller (60). On the other hand, when the mold (205) is opened, the ejector plate (235) increases the degree of inclination of each arm (236) with respect to the mold opening direction, and the multiple inner cores (239) are displaced so as to converge toward a position corresponding to the rotation axis (Ac) of the impeller (60) (the direction of displacement is shown by arrows in Figure 17).

[0116] Multiple slide molds (240) are arranged between the fixed mold (210) and the movable mold (230), spaced apart from each other, surrounding the third molding surface (214) and the fourth molding surface (237). As shown in Figure 14, a slide mold (240) is provided for each pair of adjacent blades (63). In other words, there are six slide molds (240) in this example. Each slide mold (240) has a first molding surface (241) and a second molding surface (243). The first molding surface (241) is the surface that molds the other part of the negative pressure surface (63s) of one of the adjacent blades (63), specifically the outer edge (63b) side. The second molding surface (243) is the surface that molds the positive pressure surface (63p) of the other blade (63) of the adjacent blades (63).

[0117] Each slide mold (240) is provided to slide in the return direction (d1) corresponding to the rotation axis (Ac) side of the impeller (60) and in the withdrawal direction (d2) corresponding to the outer circumference side of the impeller (60). A second actuator (245) is connected to each slide mold (240). Multiple slide molds (240) slide in the return direction (d1) or the withdrawal direction (d2) by the drive of the second actuator (245). The slide molds (240) slide in the return direction (d1) between the fixed mold (210) and the movable mold (230), thereby closing the mold (205) and forming a cavity (C).

[0118] As shown in Figure 15, the cavity (C) includes multiple blade cavities (Cf) for forming each of the multiple blades (63). The multiple blade cavities (Cf) include two first blade cavities (Cf1), two second blade cavities (Cf2), and two third blade cavities (Cf3). The first blade cavity (Cf1) is the part of cavity (C) that forms the first blade (63A). The second blade cavity (Cf2) is the part of cavity (C) that forms the second blade (63B). The third blade cavity (Cf3) is the part of cavity (C) that forms the third blade (63C).

[0119] The pitch between the first blade cavity (Cf1) and the third blade cavity (Cf3) in the direction corresponding to the circumferential direction of the impeller (60) is shorter than the pitch between the first blade cavity (Cf1) and the second blade cavity (Cf2) in the direction corresponding to the circumferential direction of the impeller (60). The pitch between the second blade cavity (Cf2) and the third blade cavity (Cf3) in the direction corresponding to the circumferential direction of the impeller (60) is shorter than the pitch between the first blade cavity (Cf1) and the second blade cavity (Cf2) in the direction corresponding to the circumferential direction of the impeller (60).

[0120] The multiple slide types (240) consist of two first slide types (240A), two second slide types (240B), and two third slide types (240C). The first slide type (240A) is a slide type (240) located between the first blade cavity (Cf1) and the second blade cavity (Cf2). The second slide type (240B) is a slide type (240) located between the first blade cavity (Cf1) and the third blade cavity (Cf3). The third slide type (240C) is a slide type (240) located between the second blade cavity (Cf2) and the third blade cavity (Cf3).

[0121] In a pair of adjacent slide molds (240), the outer surface portion (242) that forms the portion of the first molding surface (241) closer to the outer edge (63b) of the blade (63) and the inner surface portion (244) that forms the portion of the second molding surface (243) closer to the inner edge (63a) of the blade (63) have different sliding surface areas (246). The sliding surface (246) is a surface that extends parallel to the sliding direction of the slide mold (240) and constitutes the surface that forms the flat surface (68) of the blade (63). The first slide mold (240A), the second slide mold (240B), and the third slide mold (240C) of this embodiment each have a slide surface (246) (shown as a thick line in Figure 8) on the outer surface portion (242) of the first molding surface (241) and the inner surface portion (244) of the second molding surface (243), respectively, and the area of ​​the slide surface (246) differs in the corresponding parts.

[0122] The area of ​​the sliding surfaces (246) of the inner surface (244) and outer surface (242) of the sliding type (240) increases as the pitch of the blade cavities (Cf) located on both sides of the sliding type (240) decreases. Specifically, the area of ​​the sliding surface (246) of the inner surface (244) of the second sliding type (240B) is larger than the area of ​​the sliding surface (246) of the inner surface (244) of the first sliding type (240A), and the area of ​​the sliding surface (246) of the outer surface (242) of the second sliding type (240B) is larger than the area of ​​the sliding surface (246) of the outer surface (242) of the first sliding type (240A). Furthermore, the area of ​​the sliding surface (246) of the inner surface portion (244) of the third slide type (240C) is larger than the area of ​​the sliding surface (246) of the inner surface portion (244) of the second slide type (240B), and the area of ​​the sliding surface (246) of the outer surface portion (242) of the third slide type (240C) is larger than the area of ​​the sliding surface (246) of the outer surface portion (242) of the second slide type (240B).

[0123] The end of each slide mold (240) in the return direction (d1) abuts against the inner core (239). Due to the arrangement of multiple blades (63) of the impeller (60) to be molded at unequal pitches, the boundary positions between the inner core (239) and the end of the slide mold (240) in the direction along the cord line (Lc) of the blade cavity (Cf) are different for the first blade cavity (Cf1), the second blade cavity (Cf2), and the third blade cavity (Cf3). Each slide mold (240) has an outer edge trim line (247) that molds the outer edge (63b) of the blade (63) as the edge of the first molding surface (241) and the second molding surface (243).

[0124] The outer peripheral trim lines (247) of adjacent slide molds (240), specifically the first slide mold (240A) and the second slide mold (240B), the second slide mold (240B) and the third slide mold (240C), and the first slide mold (240A) and the third slide mold (240C), are lines that form the outer edge (63b) of the common blade (63). The outer peripheral trim lines (247) on the first molding surface (241) and the second molding surface (243) of each slide mold (240) are inclined with respect to the mold opening direction so as they extend from the cavity portion where the base plate (61) is formed toward the cavity portion where the shroud (62) is formed, in a direction corresponding to the radially outward direction of the impeller (60), so as they form the skew angle β2 of the corresponding outer edge (63b).

[0125] Each slide mold (240) has a movable part (248) that forms the surface of the shroud (62) on the base plate (61) side on the outer circumference of the impeller (60). The slide mold (240) is configured so that the movable part (248) can be displaced to avoid interference between the molded product in the cavity (C) and the movable mold (230) when the mold is opened. The shape of the first molding surface (241) in each slide mold (240) is mirror-image to the shape of the negative pressure surface (63s) on the corresponding blade (63) of the impeller (60) to be molded, and the shape of the second molding surface (243) is mirror-image to the shape of the positive pressure surface (63p) on the corresponding blade (63) of the impeller (60) to be molded.

[0126] In this embodiment, more than 90% of the second molding surfaces (243) of the multiple slide molds (240) have the same shape. Preferably, more than 95% of the portions of the second molding surfaces (243) of the multiple slide molds (240) have the same shape. More specifically, of the area of ​​the second molding surfaces (243) of the first slide mold (240A), the second slide mold (240B), and the third slide mold (240C), the area of ​​portions with the same shape is 90% or more, and preferably 95% or more.

[0127] (4-1-2) Control Unit The control unit (250) is a controller based on a well-known microcomputer. The control unit (250) has a processor and memory. The memory stores various programs and data. The processor reads and executes programs from the memory and controls the molding operation of the impeller (60) in the injection molding apparatus (200). The control unit (250) is electrically connected to each first actuator (227) of the multiple needle valves (225), the injection machine and the opening / closing mechanism. The control unit (250) controls the timing of injecting molten resin (R) from each gate (218) when the mold (205) is closed and a cavity (C) is formed inside the mold (205).

[0128] (4-2) Impeller molding process A method for manufacturing an impeller (60) using an injection molding apparatus (200) includes a mold clamping step, a molding step, and a mold opening step as molding steps. The mold clamping step, molding step, and mold opening step are performed in this order.

[0129] First, in the clamping step, the opening and closing mechanism of the mold (205) is operated to bring the fixed mold (210) and the movable mold (230) closer together, and each second actuator (245) is operated to slide the multiple slide molds (240) in the return direction (d1). In this way, as shown in Figure 16(a), the fixed mold (210), the movable mold (230), and each slide mold (240) are in a predetermined positional relationship on the closed side, and the mold (205) is closed, forming a cavity (C) inside the mold (205). Furthermore, pressure is applied to the closed mold (205) with toggles and cylinders to clamp the mold (205).

[0130] In the next molding step, the injection machine is operated, and the first actuator (227) of each needle valve (225) is operated to retract the needle (226) corresponding to each gate (218), thereby opening each gate (218). As shown in Figure 16(b), the molten resin (R) supplied from the injection machine to the resin flow path (220) in the mold (205) is injected from each gate (218) into the cavity (C), filling the cavity (C) with resin (R). When the cavity (C) is filled with resin (R), the injection of resin (R) from the injection machine is stopped, and the first actuator (227) of each needle valve (225) is operated to advance the needle (226) corresponding to each gate (218), thereby closing each gate (218). The resin (R) filled in the cavity (C) solidifies as the mold (205) cools. By cooling and solidifying the resin (R), an impeller (60) consisting of a base plate (61), a shroud (62), and multiple blades (63) is formed into a cavity (C).

[0131] Then, in the mold opening step, the opening and closing mechanism of the mold (205) is operated to separate the fixed mold (210) and the movable mold (230) from each other, and each second actuator (245) is operated to slide the multiple slide molds (240) in the withdrawal direction (d2) as shown in Figure 17. In this way, the mold (205) is opened with the fixed mold (210), the movable mold (230), and each slide mold (240) in a predetermined positional relationship on the opening side. At this time, each inner core (239) is displaced so as to move closer to each other toward a position corresponding to the rotation axis (Ac) of the impeller (60) by changing the degree of inclination of the arm (236), thereby avoiding interference with the shroud (62) of the impeller (60). Once the mold (205) is opened, it becomes possible to remove the impeller (60) from the mold (205).

[0132] After removing the impeller (60) from the mold (205), if there are burrs on the impeller (60), post-processing such as removing the burrs is performed. In this way, the impeller (60) can be manufactured using the injection molding apparatus (200).

[0133] (5) Features of the Embodiment In this embodiment of the centrifugal fan (50), the circumferential pitch of the outer edges (63b) of adjacent blades (63) differs from that of each other on both sides in the circumferential direction. When multiple blades (63) are arranged with unequal pitches in this way, the NZ noise associated with the rotational movement of the impeller (60) is reduced. Furthermore, the area of ​​the flat surface (68) differs between the first surface (63p) of the inner end (63i) and the second surface (63s) of the outer portion (63r) of a pair of adjacent blades (63). The first surface (63p) of the inner end (63i) and the second surface (63s) of the outer portion (63r) of each blade (63) form the point where they are closest to other adjacent blades (63) in the rotational direction of the impeller (60). Therefore, the ejection direction (d2) of the slide mold (240) is constrained by the shape of the first surface (63p) of the inner end (63i) and the shape of the second surface (63s) of the outer portion (63r) of an adjacent pair of blades (63). The flat surface (68) formed on the first surface (63p) of the inner end (63i) or the second surface (63s) of the outer portion (63r) constitutes a surface that extends in the sliding direction of the slide mold (240) in the injection molding apparatus (200). Thus, if the area of ​​the flat surface (68) on the first surface (63p) of the inner end (63i) or the second surface (63s) of the outer portion (63r) of an adjacent pair of blades (63) is different, the angle that the ejection direction (d2) of adjacent slide molds (240) makes with respect to the direction corresponding to the radial direction of the impeller (60) can be made different. This allows the ejection direction (d2) to be adjusted so that the multiple slide molds (240) that form the blades (63) in the mold (205) of the injection molding apparatus (200) do not interfere with each other, nor do the slide molds (240) interfere with other parts of the mold (205). Therefore, it is possible to easily manufacture an impeller (60) of a resin integral molding type in which multiple blades (63) are arranged at unequal pitches.

[0134] In this embodiment of the centrifugal fan (50), the pitch between the first blade (63A) and the third blade (63C) is shorter than the pitch between the first blade (63A) and the second blade (63B), and the area of ​​the flat surface (68) of the second surface (63s) of the outer portion (63r) of the third blade (63C) is larger than the area of ​​the flat surface (68) of the second surface (63s) of the outer portion (63r) of the first blade (63A). The shorter the pitch between adjacent blades (63), the stricter the restriction on the exit direction (d2) of the corresponding sliding type (240) between those adjacent blades (63). In contrast, the shorter the pitch between adjacent pairs of blades (63), the larger the area of ​​the flat surface (68) of the second surface (63s) of the outer portion (63r) of the blade (63) located on the front side in the rotational direction of that pair of blades (63), thereby easing the restriction on the withdrawal direction (d2) of the slide type (240). Therefore, the withdrawal direction (d2) of the slide type (240) corresponding to the space between the first blade (63A) and the second blade (63B) and the withdrawal direction (d2) of the slide type (240) corresponding to the space between the first blade (63A) and the third blade (63C) can be adjusted so that the two slide types (240) do not interfere with each other.

[0135] In the centrifugal fan (50) of this embodiment, the area of ​​the flat surface (68) of the first surface (63p) of the inner end (63i) of the third blade (63C) is larger than the area of ​​the flat surface (68) of the first surface (63p) of the inner end (63i) of the first blade (63A). The shorter the pitch of a pair of adjacent blades (63), the larger the area of ​​the flat surface (68) of the first surface (63p) of the inner end (63i) of the blade (63) located on the front side in the rotational direction of that pair of blades (63), thereby easing the restriction on the release direction (d2) of the slide type (240). Therefore, the withdrawal direction (d2) of the sliding type (240) corresponding to the space between the first blade (63A) and the second blade (63B), and the withdrawal direction (d2) of the sliding type (240) corresponding to the space between the first blade (63A) and the third blade (63C), can be adjusted so that the two sliding types (240) do not interfere with each other.

[0136] In this embodiment of the centrifugal fan (50), a flat surface (68) is provided on the first surface (63p) of the inner end (63i) of the blade (63). The blade (63) has a cross-sectional shape that curves from the inner circumference to the outer circumference in a cross-section perpendicular to the axis of rotation (Ac). Therefore, the exit direction (d2) of the slide mold (240) that forms the blade (63) in the mold (205) of the injection molding apparatus (200) is limited to a predetermined range by the shape of the inner end (63i) of the blade (63). On the other hand, the thickness of the inner end (63i) of the first blade (63A) and the thickness of the inner end (63i) of the second blade (63B) differ in corresponding parts depending on the presence or absence of the flat surface (68) or the area of ​​the flat surface (68). The limiting range of the cutting direction (d2) of the slide mold (240) can be changed by varying the thickness of the inner end portion (63i) of the blade (63). Therefore, the cutting direction (d2) of the slide mold (240) that forms the first surface (63p) of the first blade (63A) and the cutting direction (d2) of the slide mold (240) that forms the first surface (63p) of the second blade (63B) can be adjusted so that the two slide molds (240) do not interfere with each other.

[0137] In the centrifugal fan (50) of this embodiment, the pitch between the first blade (63A) and the third blade (63C) is shorter than the pitch between the first blade (63A) and the second blade (63B), and the thickness of the inner end (63i) of the first blade (63A) is thinner than the thickness of the inner end (63i) of the second blade (63B). The shorter the pitch between adjacent blades (63), the stricter the restriction on the exit direction (d2) of the sliding type (240) between those adjacent blades (63). Conversely, the shorter the pitch between adjacent blades (63), the thinner the inner end (63i) of the blade (63) located on the rear side in the rotational direction among those adjacent blades (63), thereby easing the restriction on the exit direction (d2) of the sliding type (240). Therefore, the withdrawal direction (d2) of the sliding type (240) corresponding to the space between the first blade (63A) and the second blade (63B), and the withdrawal direction (d2) of the sliding type (240) corresponding to the space between the first blade (63A) and the third blade (63C), can be adjusted so that the two sliding types (240) do not interfere with each other.

[0138] In this embodiment of the centrifugal fan (50), a flat surface (68) is provided on the second surface (63s) of the outer portion (63r) of the blade (63). The second surface (63s) constitutes the negative pressure surface of the blade (63). The shape of the negative pressure surface of the blade (63) does not significantly affect the airflow performance compared to the positive pressure surface. Therefore, it is possible to easily manufacture a resin-molded impeller (60) in which multiple blades (63) are arranged at unequal pitches, while suppressing a decrease in the airflow performance of the centrifugal fan (50).

[0139] In this embodiment of the centrifugal fan (50), more than 90% of the first surfaces (63p) of the multiple blades (63) have the same shape. The first surfaces (63p) constitute the positive pressure surface of the blades (63). By making the shapes of the first surfaces (63p) of the multiple blades (63) differ by less than 10%, the ejection direction (d2) can be adjusted so that the multiple slide molds (240) that form the blades (63) in the mold (205) of the injection molding apparatus do not interfere with each other, or with the slide molds (240) and other parts of the mold (205). Furthermore, by having more than 90% of the first surfaces (63p) of the multiple blades (63) have the same shape, a decrease in the airflow performance of the centrifugal fan (50) can be suppressed.

[0140] In the centrifugal fan (50) of this embodiment, the outer edge (63b) of the blade (63) is inclined with respect to the axis of rotation (Ac), and extends in a direction corresponding to the radially outward direction of the impeller (60) as it moves from the base plate (61) toward the shroud (62), thus having a skew angle. In a mold (205) for forming an impeller (60) having such a skew angle blade (63), the first surface (63p) and the second surface (63s) formed by the slide mold (240) are long in the sliding direction, and the distance for removing the slide mold (240) from the impeller (60) when the mold (205) is opened is long, thus severely restricting the removal direction (d2) of the slide mold (240). Therefore, the technology of this disclosure is particularly effective in the manufacturing method of the impeller (60).

[0141] In this embodiment, the centrifugal fan (50) has six blades (63). If the number of blades (63) is five or less, the workload per blade (63) is relatively large, resulting in increased noise during airflow. There is also concern that the static pressure characteristics of the impeller (60) will deteriorate. When the static pressure characteristics of the impeller (60) deteriorate, the required rotational speed becomes larger for the required airflow, thus increasing the shaft power. In contrast, if the number of blades (63) is six or more, the noise associated with the rotational operation of the impeller (60) can be suitably suppressed while ensuring the static pressure characteristics of the impeller (60) and reducing the shaft power. In particular, having six blades (63) is suitable for ensuring the performance of the impeller (60) and for making the molding method of this example feasible.

[0142] The air conditioning system (1) of this embodiment includes a centrifugal fan (50). Since the impeller (60) of the centrifugal fan (50) is made of integrally molded resin, it is suitable for mass production because it eliminates the assembly process of parts compared to centrifugal fans that use an assembled impeller made by integrating separate parts such as a base plate (61), a shroud (62), and multiple blades (63). Furthermore, with this centrifugal fan (50), the weight of the centrifugal fan (50) can be reduced and vibrations during rotation of the centrifugal fan (50) can be suppressed compared to cases where at least one of the base plate (61), shroud (62), and multiple blades (63) is made of metal. This contributes to improving the energy efficiency of the air conditioning system (1).

[0143] Other embodiments The number of blades (63) of the impeller (60) may be five or fewer, or seven or more. However, as described above, it is preferable to have six or more blades in order to reduce the shift in the center of gravity and axial wobble of the impeller (60), allow for a margin of error for manufacturing tolerances, and effectively suppress noise associated with the rotational movement of the impeller (60). The pitch of adjacent blades (63) may differ for all sets of blades (63). If multiple blades (63) have unequal pitches, that is, if the pitch of adjacent blades (63) differs on both sides in the circumferential direction of each blade (63), the number of blades (63) can be any number.

[0144] In the impeller (60), the presence or absence of flat surfaces (68) or the area of ​​the flat surfaces (68) differing between adjacent blades (63) may be limited to the first surface (63p) of the inner end (63i), or limited to the second surface (63s) of the outer portion (63r). From the viewpoint of suppressing a decrease in the air blowing performance of the impeller (60), it is preferable to limit it to only the second surface (63s) of the outer portion (63r), or to a relatively small area of ​​the first surface (63p) of the inner end (63i).

[0145] In the impeller (60), the first surface (63p) of the inner end portion (63i) or the second surface (63s) of the outer portion (63r) of some adjacent blades (63) may differ in whether or not they have a flat surface (68). For example, the first surface (63p) of each inner end portion (63i) of the first blade (63A) and the third blade (63C), and the second surface (63s) of each outer portion (63r) of the second blade (63B) and the third blade (63C), each have a flat surface (68) as in the above embodiment, but one or both of the second surface (63s) of the outer portion (63r) of the first blade (63A) and the first surface (63p) of the inner end portion (63i) of the second blade (63B) may not have a flat surface (68). In short, the presence or absence of a flat surface (68) or a difference in the area of ​​the flat surface (68) on the first surface (63p) of the inner end (63i) or the second surface (63s) of the outer portion (63r) of a pair of adjacent blades (63) is sufficient to allow adjustment of the removal direction (d2) of the slide molds (240) in the mold (205) of the injection molding apparatus (200) that forms the impeller (60) so that adjacent slide molds (240) do not interfere with each other or with other parts of the mold (205).

[0146] The first centrifugal fan (50A) and the second centrifugal fan (50B) may both be double-suction centrifugal fans or single-suction centrifugal fans. The first centrifugal fan (50A) and the second centrifugal fan (50B) may be located in the lower half of the interior of the casing (21). The centrifugal fan (50) forming the indoor fan (48) may be one or three or more.

[0147] The indoor unit (3) may be configured to be wall-mounted. The indoor unit (3) may be positioned on the front side of the ceiling surface and suspended from the ceiling surface. The indoor unit (3) may be positioned on the back side of the ceiling surface and suspended from the ceiling beams. Any installation method can be adopted for the indoor unit (3).

[0148] The air conditioning system (1) does not have to be a pair type having one outdoor unit (2) and one indoor unit (3), but may be an outdoor multi-type having multiple outdoor units (2) or an indoor multi-type having multiple indoor units (3).

[0149] The air conditioning system (1) does not have to be a separate type having an indoor unit (3) and an outdoor unit (2), but may be an integrated type having only an indoor unit and no outdoor unit (2). In this case, the indoor unit has a heat source side heat exchanger, etc.

[0150] The spaces to which the air conditioning system (1) provides air conditioning are not limited to indoor spaces (IS) such as computer rooms, factories, and warehouses. The spaces to which the air conditioning is provided may also be spaces in shops or buildings, or indoor spaces in residences.

[0151] The air conditioning system (1) does not need to be equipped with a four-way switching valve (26) in the refrigerant circuit (6). In this case, the air conditioning system (1) may be configured as a heater capable of performing only heating operations. The air conditioning system (1) may be configured as a cooler capable of performing only cooling operations. Furthermore, the air conditioning system (1) may be configured to perform dehumidification and ventilation operations.

[0152] In the above embodiment, an air conditioning system (1) was used as an example of a refrigeration system in which a centrifugal fan (50) is used, but the invention is not limited to this. Refrigeration systems in which a centrifugal fan (50) according to this disclosure can be used may also include water heaters, chiller units, cooling devices for cooling the air inside a storage unit, etc. Cooling devices, for example, cool the air inside refrigerators, freezers, containers, etc.

[0153] While embodiments and variations have been described above, it will be understood that a variety of modifications to the form and details are possible without departing from the spirit and scope of the claims. Furthermore, these embodiments and variations may be combined or substituted as appropriate, as long as they do not impair the functions covered by this disclosure. [Industrial applicability]

[0154] As described above, this disclosure is useful for centrifugal fans and refrigeration systems equipped therewith. [Explanation of Symbols]

[0155] 1. Air conditioning system (refrigeration system) 50 centrifugal fan 60 Impeller 61 Base plate 62 Shroud 63 feathers 63A First Wing 63B Second feather 63C Third feather 63a inner edge 63b Outer edge 63i inner end 63r outer part 63p page 1 63s 2nd page 68 Flat surface AC rotation axis Lc cord wire

Claims

1. It is equipped with an impeller (60) that rotates around a predetermined axis of rotation (Ac), The impeller (60) comprises a base plate (61), an annular shroud (62) provided at an axial distance from the base plate (61) along the rotation axis (Ac), and a plurality of blades (63) arranged between the base plate (61) and the shroud (62) at intervals from each other in the circumferential direction with respect to the rotation axis (Ac). The base plate (61), the shroud (62), and the plurality of blades (63) are integrally molded from resin. Each of the aforementioned multiple blades (63) is, The cross-sectional shape has a curved shape extending from the inner circumference to the outer circumference in a cross-section perpendicular to the rotation axis (Ac), The inner edge (63a), which is the inner circumference edge of the blade (63), The outer edge (63b) is the outer edge of the blade (63), Between the inner edge (63a) and the outer edge (63b), there is a first surface (63p) facing the outside of the curvature of the blade (63), The blade (63) has a second surface (63s) between the inner edge (63a) and the outer edge (63b) that faces the inside of the curvature of the blade (63), The plurality of blades (63) include a first blade (63A), a second blade (63B) adjacent to the first blade (63A), and a third blade (63C) adjacent to the first blade (63A) on the opposite side from the second blade (63B). The second blade (63B) is located behind the first blade (63A) in the direction of rotation. The third blade (63C) is located in front of the first blade (63A) in the direction of rotation. The circumferential pitch of the outer edges (63b) of the first blade (63A) and the third blade (63C) is shorter than the circumferential pitch of the outer edges (63b) of the first blade (63A) and the second blade (63B). The first blade (63A) and the third blade (63C) each have a flat surface (68) on the corresponding portion of the second surface (63s) of the outer portion (63r) near the outer edge (63b) of the impeller (60), extending in a direction intersecting the straight line connecting the outer edge (63b) of the third blade (63C) and the inner edge (63a) of the first blade (63A) in a plan view of the impeller (60), wherein the area of ​​the flat surface (68) on the second surface (63s) of the outer portion (63r) of the third blade (63C) is larger than the area of ​​the flat surface (68) on the second surface (63s) of the outer portion (63r) of the first blade (63A), or The second surface (63s) of the outer portion (63r) of the third blade (63C) has the flat surface (68), while the second surface (63s) of the outer portion (63r) of the first blade (63A) does not have the flat surface (68). Centrifugal fan.

2. comprising an impeller (60) that rotates around a predetermined axis of rotation (Ac), The impeller (60) comprises a base plate (61), an annular shroud (62) provided at an axial distance from the base plate (61) along the rotation axis (Ac), and a plurality of blades (63) arranged between the base plate (61) and the shroud (62) at intervals from each other in the circumferential direction with respect to the rotation axis (Ac). The base plate (61), the shroud (62), and the plurality of blades (63) are integrally molded from resin. Each of the aforementioned multiple blades (63) is, The cross-sectional shape has a curved shape extending from the inner circumference to the outer circumference in a cross-section perpendicular to the rotation axis (Ac), The inner edge (63a), which is the inner circumference edge of the blade (63), The outer edge (63b) is the outer edge of the blade (63), Between the inner edge (63a) and the outer edge (63b), there is a first surface (63p) facing the outside of the curvature of the blade (63), The blade (63) has a second surface (63s) between the inner edge (63a) and the outer edge (63b) that faces the inside of the curvature of the blade (63), The plurality of blades (63) include a first blade (63A), a second blade (63B) adjacent to the first blade (63A), and a third blade (63C) adjacent to the first blade (63A) on the opposite side from the second blade (63B). The second blade (63B) is located behind the first blade (63A) in the direction of rotation. The third blade (63C) is located in front of the first blade (63A) in the direction of rotation. The circumferential pitch of the outer edges (63b) of the first blade (63A) and the third blade (63C) is shorter than the circumferential pitch of the outer edges (63b) of the first blade (63A) and the second blade (63B). The first blade (63A) and the second blade (63B) each have a flat surface (68) on the corresponding portion of the first surface (63p) of the inner end portion (63i) near the inner edge (63a), which extends in a direction intersecting the straight line connecting the outer edge (63b) of the first blade (63A) and the inner edge (63a) of the second blade (63B) in a plan view of the impeller (60), and the area of ​​the flat surface (68) on the first surface (63p) of the inner end portion (63i) of the first blade (63A) is larger than the area of ​​the flat surface (68) on the first surface (63p) of the inner end portion (63i) of the second blade (63B), or The first surface (63p) of the inner end portion (63i) of the first blade (63A) has the flat surface (68), while the first surface (63p) of the inner end portion (63i) of the second blade (63B) does not have the flat surface (68). Centrifugal fan.

3. In the centrifugal fan described in claim 2, In a cross-section of the impeller (60) perpendicular to the axis of rotation (Ac), the line segment connecting the inner edge (63a) and the outer edge (63b) of the blade (63) is the cord line (Lc). The thickness of the inner end portion (63i) of the first blade (63A) in the direction perpendicular to the cord wire (Lc) and the thickness of the inner end portion (63i) of the second blade (63B) in the direction perpendicular to the cord wire (Lc) differ in corresponding parts depending on the presence or absence of the flat surface (68) or the area of ​​the flat surface (68). Centrifugal fan.

4. In the centrifugal fan described in claim 3, The thickness of the inner end portion (63i) of the first blade (63A) in the direction perpendicular to the cord wire (Lc) is thinner than the thickness of the inner end portion (63i) of the second blade (63B) in the direction perpendicular to the cord wire (Lc). Centrifugal fan.

5. In the centrifugal fan described in claim 1, The second surface (63s) constitutes a negative pressure surface that receives negative pressure when the impeller (60) rotates. Centrifugal fan.

6. In the centrifugal fan according to claim 1 or 2, The first surface (63p) constitutes a positive pressure surface that receives positive pressure when the impeller (60) rotates. More than 90% of the first surfaces (63p) of the plurality of feathers (63) are the same shape as each other. Centrifugal fan.

7. In the centrifugal fan according to claim 1 or 2, The outer edge (63b) of the blade (63) is inclined with respect to the rotation axis (Ac) such that it extends in a direction corresponding to the radially outward direction of the impeller (60) as it moves from the base plate (61) toward the shroud (62). Centrifugal fan.

8. In the centrifugal fan according to claim 1 or 2, The number of blades (63) is six or more. Centrifugal fan.

9. A centrifugal fan (50) according to claim 1 or 2, Refrigeration equipment.

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