Impeller manufacturing method

Abstract

The impeller for a centrifugal fan, which has multiple blades arranged at unequal pitches, is integrally molded from resin. [Solution] In the method for manufacturing an impeller, a mold (5) having a fixed mold (10), a movable mold (30), and a plurality of slide molds (40) is used. Each slide mold (40) has a first molding surface (41) that forms the negative pressure surface (63s) of the blade (63) and a second molding surface (43) that forms the positive pressure surface (63p) of the blade (63), and is provided to slide in the return direction (d1) corresponding to the rotation axis (Ac) side of the impeller (60) and the withdrawal direction (d2) corresponding to the outer circumference side of the impeller (60). The outer surface portion (42) of the first molding surface (41) or the inner surface portion (44) of the second molding surface (43) of a pair of adjacent slide molds (40) differ in the presence or absence of a slide surface (46) that extends parallel to the sliding direction of the slide mold (40), or the area of ​​the slide surface (46).

Description

Technical Field

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[0003]

[0001] The present disclosure relates to a method for manufacturing an impeller.

Background Art

[0002] Fans are used in refrigeration devices such as air conditioners. As a 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 at a distance from the base plate in the axial direction 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, the impeller rotates by driving the fan motor. Along with the rotational operation of the impeller, air is sucked in from a fan suction port formed at 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 removal direction corresponding to the outer circumference of the impeller, 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 integrally mold a centrifugal fan impeller, in which multiple blades are arranged at unequal pitches, using resin. [Means for solving the problem]

[0008] A first aspect of this disclosure relates to a method for manufacturing an impeller. This method for manufacturing an impeller comprises a base plate that rotates around a predetermined axis of rotation, an annular shroud provided at an axial distance from the base plate along the axis of rotation, and a plurality of blades arranged between the base plate and the shroud at intervals from each other in the circumferential direction centered on the axis of rotation, wherein each of the plurality of blades 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, and the circumferential pitch of the outer edges of adjacent blades is different on both sides of each blade in the circumferential direction. The impeller manufacturing method uses a mold comprising: a first mold for forming the surface of the base plate opposite to the shroud; a second mold for forming the surface of the shroud opposite to the base plate, the surface of the base plate on the shroud side, and a portion of the negative pressure surface facing the inside of the curvature of the plurality of blades; and a plurality of slide molds provided for each pair of adjacent blades, for forming the other portion of the negative pressure surface of one of the blades and the positive pressure surface facing the outside of the curvature of the other blade, wherein each of the plurality of slide molds has a first molding surface for forming the negative pressure surface of one blade and a second molding surface for forming the positive pressure surface of the other blade, and is slidable in the return direction corresponding to the rotation axis side of the impeller and in the withdrawal direction corresponding to the outer circumference side of the impeller. The impeller manufacturing method includes a mold clamping step of closing the mold to form a cavity and clamping the mold by bringing the first mold and the second mold closer together and sliding the plurality of slide molds in the return direction; a molding step of filling the cavity with molten resin and cooling and solidifying the resin to form the impeller, which integrates the base plate, the shroud, and the plurality of blades; and a mold opening step of sliding the plurality of slide molds in the removal direction and separating the first mold and the second mold from each other to open the mold.Furthermore, in a pair of adjacent slide molds, the outer surface portion that forms the edge of the outer circumference of the blade on the first molding surface, or the inner surface portion that forms the edge of the inner circumference of the blade on the second molding surface, differ in the presence or absence of a sliding surface extending parallel to the sliding direction of the slide mold, or the area of ​​such sliding surface.

[0009] In the first embodiment, the outer surface of the first molding surface or the inner surface of the second molding surface of a pair of adjacent slide molds differs in the presence or absence of a sliding surface extending parallel to the sliding direction of the slide mold, or the area of ​​such a sliding surface. The outer surface of the first molding surface or the inner surface of the second molding surface of the slide mold forms the point where the negative pressure surface of one adjacent blade formed by the first molding surface and the positive pressure surface of the other adjacent blade formed by the second molding surface are closest. Therefore, the release direction of the slide mold is constrained by the shape of the outer surface of the first molding surface and the shape of the inner surface of the second molding surface. If the presence or absence of a sliding surface or the area of ​​the sliding surface differs on the outer surface of the first molding surface or the inner surface of the second molding surface, the angles that the release directions of adjacent slide molds make with respect to the direction corresponding to the radial direction of the impeller can be made different. This allows the release direction of the slide molds to be adjusted so that multiple slide molds do not interfere with each other, or between the slide molds and other parts of the mold. Therefore, an impeller for a centrifugal fan, in which multiple blades are arranged at unequal pitches, can be integrally molded from resin.

[0010] A second aspect of this disclosure is a method for manufacturing an impeller according to the first aspect, wherein the sliding surface is provided on the outer surface portion of the first molded surface.

[0011] In the second embodiment, the sliding surface is provided on the outer surface of the first molded surface. This imposes constraints on the negative pressure surface regarding the blade shape in the slide's withdrawal direction. As a result, the shape of the positive pressure surface of the blade can be maintained as much as possible while considering the airflow performance of the impeller. The shape of the negative pressure surface of the blade has less impact on the airflow performance of the impeller compared to the positive pressure surface. Therefore, even when integrally molding an impeller for a centrifugal fan with multiple blades arranged at unequal pitches, a decrease in airflow performance can be suppressed.

[0012] A third aspect of the present disclosure is a method for manufacturing an impeller according to the first or second aspect, wherein the outer peripheral trim lines that form the outer peripheral edges of the blades on the first and second molding surfaces are inclined with respect to the mold opening direction of the first and second molds such that they extend in a direction corresponding to the radially outward direction of the impeller as they move from the base plate toward the shroud.

[0013] In the third embodiment, the outer peripheral trim lines of the first and second molding surfaces are inclined with respect to the axis of rotation, and the shroud side protrudes further outward in the radial direction of the impeller than the base plate side. This allows for the integral molding of an impeller in which the outer peripheral edges of the blades have a skew angle. In a mold for molding such an impeller with a skew angle, the positive pressure surface and negative pressure surface formed by the slide mold are long in the sliding direction, and the distance from which the slide mold is removed from the impeller when the mold is opened is long, thus severely restricting the direction in which the slide mold can be removed. Therefore, the technology of this disclosure is particularly effective in a method for manufacturing such an impeller.

[0014] A fourth aspect of the present disclosure is a method for manufacturing an impeller according to any one of the first to third aspects, wherein the cavity includes a plurality of blade cavities for forming each of the plurality of blades. The plurality of blade cavities includes a first blade cavity for forming a first blade among the plurality of blades, a second blade cavity for forming a second blade adjacent to the first blade, and a third blade cavity for forming a third blade adjacent to the first blade on the opposite side from the second blade. The plurality of slide molds include a first slide mold located between the first blade cavity and the second blade cavity, and a second slide mold located between the first blade cavity and the third blade cavity. The pitch in the circumferential direction between the first blade cavity and the third blade cavity is shorter than the pitch in the circumferential direction between the first blade cavity and the second blade cavity. The first slide mold and the second slide mold each have the slide surface at corresponding portions of the outer surface of the first molding surface or the inner surface of the second molding surface. The area of ​​the slide surface of the second slide mold is larger than the area of ​​the slide surface of the first slide mold.

[0015] In the fourth embodiment, the pitch between the first blade cavity and the third blade cavity is shorter than the pitch between the first blade cavity and the second blade cavity, and the area of ​​the sliding surface of the second slide type is larger than the area of ​​the sliding surface of the first slide type. The shorter the pitch between adjacent blade cavities, the stricter the restriction on the removal direction of the slide type located between those adjacent blade cavities. Conversely, the shorter the pitch between adjacent blade cavities, the larger the area of ​​the sliding surface of the slide type located between those adjacent blade cavities, thereby easing the restriction on the removal direction of that slide type. This allows the removal direction of the first slide type and the removal direction of the second slide type to be adjusted so that they do not interfere with each other.

[0016] The fifth aspect of the present disclosure is a method for manufacturing an impeller according to any one of the first to fourth aspects, wherein 90% or more of said second molding surfaces in said plurality of slide molds have the same shape, which is a method for manufacturing an impeller.

[0017] In the fifth aspect, 90% or more of the second molding surfaces in the plurality of slide molds have the same shape. As a result, 90% or more of the positive pressure surfaces in the plurality of blades are molded into the same shape. According to this, since the ratio of the different shapes of the positive pressure surfaces in the plurality of blades can be suppressed to less than 10%, it is possible to suppress a decrease in the blowing performance while integrally molding an impeller for a centrifugal fan in which the plurality of blades are arranged at unequal pitches.

Brief Description of the Drawings

[0018] [Figure 1] FIG. 1 is a perspective view illustrating the configuration of an impeller. [Figure 2] FIG. 2 is a plan view illustrating the configuration of an impeller. [Figure 3] FIG. 3 is a plan view illustrating the configuration of an impeller through a shroud. [Figure 4] FIG. 4 is a side view illustrating the configuration of an impeller. [Figure 5] FIG. 5 is a cross-sectional view illustrating the configuration of an impeller taken along line V-V of FIG. 4. [Figure 6] FIG. 6 is a cross-sectional view of a molding apparatus including a mold for molding an impeller. [Figure 7] FIG. 7 is a plan view illustrating a main part of the mold in a mold-closed state through a fixed mold. In FIG. 7, for the sake of convenience, the edge of the cavity for molding the base plate is shown by a two-dot chain line. [Figure 8] FIG. 8 is a plan view showing an enlarged main part of the mold. In FIG. 8, for the sake of convenience, the edge of the cavity portion for molding the base plate is shown by a two-dot chain line. [Figure 9] FIG. 9 is a cross-sectional view showing a state where the mold is closed and a state where the cavity in the mold is filled with resin in the manufacturing process of the impeller. [Figure 10]FIG. 10 is a plan view corresponding to FIG. 8 in a state where an impeller is formed in a mold. In FIG. 10, for convenience, the edge of the base plate is indicated by a two-dot chain line.

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the following embodiments, a case of manufacturing an impeller having six blades will be described as an example of the method for manufacturing an impeller according to the present disclosure. Note that the drawings are for conceptually explaining the technology of the present disclosure. Therefore, in the drawings, dimensions, ratios, or numbers may be exaggerated or simplified for ease of understanding of the technology of the present disclosure.

[0020] In the following embodiments, the direction along the rotation axis of the impeller is referred to as the "axial direction", and the direction perpendicular to the axial direction is referred to as the "radial direction". Further, the direction along the circumference around the rotation axis of the impeller is referred to as the "circumferential direction". Also, the descriptions such as "first", "second",... are used to distinguish the terms to which these descriptions are given, and do not limit even the number or order of those terms.

[0021] 《Embodiment》 The manufacturing method of the impeller (60) of this embodiment is used to integrally mold the impeller (60) shown in FIG. 1 used for a centrifugal fan. The impeller (60) in this example is for a turbo fan.

[0022] -Configuration of the impeller- The impeller (60) has a base plate (61), a shroud (62), and a plurality of blades (63). The impeller (60) is an integrally molded resin product. That is, the base plate (61), the shroud (62), and the plurality of blades (63) are integrally molded with resin. Although not shown, the drive shaft of a fan motor is connected to the base plate (61) of the impeller (60) via a connecting component. The impeller (60) rotates by the drive of the fan motor.

[0023] 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 of the fan motor. An axle hole (64) is formed in the center of the base plate (61). The drive shaft is inserted through the axle hole (64) via a connecting component. In addition, a plurality of fastening holes (65) (three fastening holes (65) in the example shown in Figure 2, etc.) are formed around the axle hole (64) of the base plate (61). The plurality of fastening holes (65) are holes through which bolts for fixing the connecting component are inserted and are provided at equal intervals in the circumferential direction of the axle hole (64).

[0024] The shroud (62) is formed in an annular shape. The shroud (62) is positioned opposite the base plate (61) at an axial distance from the base plate (61) 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 or 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 impeller (60). The inner peripheral edge of the shroud (62) protrudes away from the base plate (61), forming the fan intake port (66).

[0025] 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).

[0026] 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 (rotation axis (Ac) side) of the blade (63). The inner edge (63a) is located on the front side in the rotational direction 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 (outside in the radial direction of the impeller (60)). The outer edge (63b) is located on the rear side in the rotational direction 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 rotation axis (Ac).

[0027] 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.

[0028] 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 3. 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).

[0029] 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°.

[0030] 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 (40), so the area of ​​this portion may be small or absent by providing a flat surface (68), which will be described later.

[0031] Each blade (63) further has a positive pressure surface (63p) and a negative pressure surface (63s). The positive pressure surface (63p) is the surface that receives positive pressure when the impeller (60) rotates. The positive pressure 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 negative pressure surface (63s) is the surface that receives negative pressure when the impeller (60) rotates. The negative pressure surface (63s) faces the inside of the curvature of the blade (63) between the inner edge (63a) and the outer edge (63b), faces backward in the direction of rotation of the impeller (60), and faces the rotation axis (Ac) side of the impeller (60).

[0032] 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.

[0033] The impeller (60) has multiple blades (63) 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 pitch between adjacent blades (63) is different on both sides of each blade (63) in the circumferential direction. 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).

[0034] 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.

[0035] As shown in Figure 3, 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 third blades (63C).

[0036] 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.

[0037] 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).

[0038] 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 (40) located between the cavities (C) forming those two blades (63) becomes more restricted, and the slide types (40) 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 (40) more apparent.

[0039] 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.

[0040] The parts of the first blade (63A), second blade (63B), and third blade (63C) that differ in shape from each other are the positive pressure surface (63p) of the inner end portion (63i) (the part with dot hatching in Figures 3 to 5), which is the part of the blade (63) closer to the inner edge (63a) and in this example includes the inner edge (63a), and the negative pressure surface (63s) of the outer portion (63r) (the part shown by a thick line in Figure 10, the part with mesh hatching in Figures 4 and 5), which is the part of the blade (63b). Here, the inner end portion (63i) refers to the part of the blade (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 blade (63) that is 30% from the outer edge (63b) relative to the cord length (L).

[0041] The positive pressure surface (63p) of the inner end (63i) and the negative pressure surface (63s) of the outer portion (63r) of each blade (63) are the points where they are closest to adjacent blades (63) on both sides in the rotational direction of the impeller (60). Therefore, the shapes of the positive pressure surface (63p) of the inner end (63i) and the negative pressure surface (63s) of the outer portion (63r) of each blade (63) are dominant factors that restrict the withdrawal direction (d2) of the slide mold (40) that forms the positive pressure surface (63p) of one of a pair of adjacent blades (63) and the negative pressure surface (63s) of the other blade (63) in the mold (5) that forms the impeller (60). In this embodiment, the shapes of the positive pressure surface (63p) of the inner end portion (63i) and the negative pressure 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 (40).

[0042] In this embodiment, the areas where the positive pressure surface (63p) of each inner end (63i) of the first blade (63A), second blade (63B), and third blade (63C) has a different shape are, strictly speaking, the positive pressure surface (63p) of each inner end (63i) of the blade (63) excluding the end on the shroud (62) side (see Figure 4). Also, the areas where the negative pressure surface (63s) of each outer portion (63r) of the first blade (63A), second blade (63B), and third blade (63C) has a different shape are, strictly speaking, the negative pressure surface (63s) of the outer portion (63r) of the blade (63) on the shroud (62) side (see Figure 5).

[0043] 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 (40). The area of ​​the flat surface (68) differs depending on the angle it makes with respect to the radial direction of the impeller (60).

[0044] In this embodiment, the first blade (63A), second blade (63B), and third blade (63C) each have a flat surface (68) on the positive pressure surface (63p) of the inner end (63i) and the negative pressure 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.

[0045] 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).

[0046] 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).

[0047] 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.

[0048] 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).

[0049] The difference in thickness at the points where the shape of the inner ends (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 negative pressure surface (63s) of the outer portions (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 positive pressure surfaces (63p) of the first blade (63A), second blade (63B), and third blade (63C) are the same.

[0050] More specifically, of the area of ​​the positive pressure surfaces (63p) of the first blade (63A), second blade (63B), and third blade (63C), the area of ​​portions with the same shape is 90% or more. In this specification, "same shape" means that the cross-sectional shape, curvature distribution, and projected contour are the same or substantially the same. Preferably, the area of ​​portions with the same shape of the positive pressure surfaces (63p) of multiple blades (63), i.e., the area of ​​portions with the same shape of the positive pressure surfaces (63p), is 95% or more of the area of ​​the positive pressure surfaces (63p).

[0051] 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).

[0052] -Manufacturing of impellers- The impeller (60) is formed by injection molding. The injection molding apparatus (1) shown in Figure 6 is used to form the impeller (60).

[0053] <Injection molding equipment> The injection molding apparatus (1) comprises a mold (5), an injection machine and an opening / closing mechanism (both not shown), and a control unit (50). The opening / closing mechanism is a mechanism for opening, closing, and clamping the mold (5). The injection molding apparatus is configured to form a cavity (C) for molding an impeller (60) by closing the mold (5), and to inject molten resin sent from the injection machine into the cavity (C).

[0054] <Mold> The mold (5) comprises a fixed mold (10), a movable mold (30), and a plurality of sliding molds (40). The fixed mold (10) is an example of a first mold. The movable mold (30) is an example of a second mold.

[0055] The fixed mold (10) is attached to the fixed plate (12). The side of the fixed mold (10) facing the movable mold (30) has a third molding surface (14). The third molding surface (14) 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 (14) is provided with a cylindrical portion (16) for forming an axial hole (64) and a projection (not shown) for forming a retaining hole (65). In addition, the fixed mold (10) has a plurality of gates (18). Each gate (18) 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 (14). Each gate (18) in this example is a direct gate.

[0056] A resin channel (20) is provided in the fixed mold (10). The resin channel (20) consists of a hot runner (21) and a sprue (22). The hot runner (21) has a plurality of branch channels (23) and a common channel (24). A branch channel (23) is provided for each gate (18). Each branch channel (23) extends from the gate (18) in the mold opening direction and communicates with the gate (18). The common channel (24) extends in a direction perpendicular to the branch channels (23) and connects the ends of each branch channel (23) opposite to the gate (18), and communicates with a plurality of branch channels (23). The sprue (22) extends from the common channel (24) of the hot runner (21) in the mold opening direction, passes through the fixed plate (12) and communicates with the nozzle of the injection machine.

[0057] The fixed type (10) is further provided with multiple needle valves (25). A needle valve (25) is provided for each gate (18). Each needle valve (25) consists of a needle (26) and a first actuator (27). The needle (26) is housed in a branch passage (23). The first actuator (27) is a device that moves the needle (26) forward and backward relative to the gate (18), and is provided on the fixed plate (12), with the part of the needle (26) opposite to the gate (18) connected to it. Each gate (18) opens and closes in accordance with the forward and backward movement of the needle (26). In addition, although not shown in the figures, the fixed type (10) is provided with a cooling channel through which a cooling liquid such as water flows.

[0058] The movable mold (30) comprises a base block (31), a center mold (38), and a plurality of inner cores (39). The base block (31) is attached to the movable plate (33) via a spacer block (32). The spacer block (32) has a housing chamber (34) inside. The housing chamber (34) houses the ejector plate (35). The ejector plate (35) supports a plurality of arms (36) that penetrate the base block (31) in an inclined position with respect to the mold opening direction. The plurality of arms (36) extend from the ejector plate (35) toward the fixed mold (10) toward a position corresponding to the outer circumference of the impeller (60) toward a position closer to the axis of rotation (Ac), that is, toward the cylindrical portion (16).

[0059] The base block (31) has a fourth molding surface (37). The fourth molding surface (37) 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 (31) is also provided with a cooling channel through which a cooling liquid such as water flows. The center mold (38) is positioned in the base block (31) at a location corresponding to the inside of the impeller (60). Multiple inner cores (39) are positioned around the center mold (38) and are arranged to surround the center mold (38). The center mold (38) and each inner core (39) 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 (39) is also an element that molds a portion of the negative pressure surface (63s) of each blade (63), specifically the portion on the inner edge (63a) side.

[0060] Each inner core (39) is connected to an arm (36). The ejector plate (35) changes the degree of inclination of the arm (36) in conjunction with the opening and closing operation of the mold (5). When the mold (5) is closed, the ejector plate (35) reduces the degree of inclination of each arm (36) with respect to the mold opening direction, and the multiple inner cores (39) are displaced so as to spread radially toward the outer circumference of the impeller (60). On the other hand, when the mold (5) is opened, the ejector plate (35) increases the degree of inclination of each arm (36) with respect to the mold opening direction, and the multiple inner cores (39) 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 10).

[0061] Multiple slide molds (40) are arranged between the fixed mold (10) and the movable mold (30), spaced apart from each other, surrounding the third molding surface (14) and the fourth molding surface (37). As shown in Figure 7, a slide mold (40) is provided for each pair of adjacent blades (63). In other words, there are six slide molds (40) in this example. Each slide mold (40) has a first molding surface (41) and a second molding surface (43). The first molding surface (41) 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 (43) is the surface that molds the positive pressure surface (63p) of the other blade (63) of the adjacent blades (63).

[0062] Each slide mold (40) is provided so as to be slidable 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 (45) is connected to each slide mold (40). Multiple slide molds (40) slide in the return direction (d1) or the withdrawal direction (d2) by the drive of the second actuator (45). The slide molds (40) slide in the return direction (d1) between the fixed mold (10) and the movable mold (30), thereby closing the mold (5) and forming a cavity (C).

[0063] As shown in Figure 8, 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).

[0064] 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).

[0065] The multiple slide types (40) include two first slide types (40A), two second slide types (40B), and two third slide types (40C). The first slide type (40A) is a slide type (40) located between the first blade cavity (Cf1) and the second blade cavity (Cf2). The second slide type (40B) is a slide type (40) located between the first blade cavity (Cf1) and the third blade cavity (Cf3). The third slide type (40C) is a slide type (40) located between the second blade cavity (Cf2) and the third blade cavity (Cf3).

[0066] In a pair of adjacent slide molds (40), the outer surface portion (42) that forms the portion of the first molding surface (41) near the outer edge (63b) of the blade (63) and the inner surface portion (44) that forms the portion of the second molding surface (43) near the inner edge (63a) of the blade (63) have different areas of slide surface (46). The slide surface (46) is a surface that extends parallel to the sliding direction of the slide mold (40) and constitutes the surface that forms the flat surface (68) of the blade (63). In this embodiment, the first slide mold (40A), the second slide mold (40B), and the third slide mold (40C) each have slide surfaces (46) (shown as thick lines in Figure 8) on the outer surface portion (42) of the first molding surface (41) and the inner surface portion (44) of the second molding surface (43), respectively, and the areas of the slide surfaces (46) in the corresponding parts are different.

[0067] The area of ​​the sliding surfaces (46) of the inner surface (44) and outer surface (42) of the slide type (40) increases as the pitch of the blade cavities (Cf) located on both sides of the slide type (40) decreases. Specifically, the area of ​​the sliding surface (46) of the inner surface (44) of the second slide type (40B) is larger than the area of ​​the sliding surface (44) of the inner surface (44) of the first slide type (40A), and the area of ​​the sliding surface (46) of the outer surface (42) of the second slide type (40B) is larger than the area of ​​the sliding surface (46) of the outer surface (42) of the first slide type (40A). Furthermore, the area of ​​the sliding surface (46) of the inner surface portion (44) of the third slide type (40C) is larger than the area of ​​the sliding surface (46) of the inner surface portion (44) of the second slide type (40B), and the area of ​​the sliding surface (46) of the outer surface portion (42) of the third slide type (40C) is larger than the area of ​​the sliding surface (46) of the outer surface portion (42) of the second slide type (40B).

[0068] The end of each slide mold (40) in the return direction (d1) abuts against the inner core (39). 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 (39) and the end of the slide mold (40) 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 (40) has an outer peripheral trim line (47) that molds the outer edge (63b) of the blade (63) as the edge of the first molding surface (41) and the second molding surface (43).

[0069] The outer peripheral trim lines (47) of adjacent slide molds (40), specifically the first slide mold (40A) and the second slide mold (40B), the second slide mold (40B) and the third slide mold (40C), and the first slide mold (40A) and the third slide mold (40C), are lines that form the outer edge (63b) of the common blade (63). The outer peripheral trim lines (47) on the first molding surface (41) and the second molding surface (43) of each slide mold (40) 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).

[0070] Each slide mold (40) has a movable part (48) 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 (40) is configured so that the movable part (48) can be displaced to avoid interference between the molded product in the cavity (C) and the movable mold (30) when the mold is opened. The shape of the second molding surface (43) in each slide mold (40) is mirror-image to the shape of the positive pressure surface (63p) on the corresponding blade (63) of the impeller (60) to be molded.

[0071] In this embodiment, more than 90% of the second molding surfaces (43) of the multiple slide molds (40) have the same shape. Preferably, more than 95% of the portions of the second molding surfaces (43) of the multiple slide molds (40) have the same shape. More specifically, of the area of ​​the second molding surfaces (43) of the first slide mold (40A), the second slide mold (40B), and the third slide mold (40C), it is preferable that the area of ​​portions with the same shape accounts for more than 90% and more than 95%.

[0072] <Control Unit> The control unit (50) is a controller based on a well-known microcomputer. The control unit (50) 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 (1). The control unit (50) is electrically connected to each first actuator (27) of the multiple needle valves (25), the injection machine and the opening / closing mechanism. With the mold (5) closed and a cavity (C) formed inside the mold (5), the control unit (50) controls the timing of injecting molten resin (R) from each gate (18).

[0073] <Impeller molding process> A method for manufacturing an impeller (60) using an injection molding apparatus (1) 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.

[0074] First, in the clamping step, the opening and closing mechanism of the mold (5) is operated to bring the fixed mold (10) and the movable mold (30) closer together, and each second actuator (45) is operated to slide the multiple slide molds (40) in the return direction (d1). In this way, as shown in Figure 9(a), the fixed mold (10), the movable mold (30), and each slide mold (40) are in a predetermined positional relationship on the closed side, the mold (5) is closed, and a cavity (C) is formed inside the mold (5). Furthermore, pressure is applied to the closed mold (5) with toggles and cylinders to clamp the mold (5).

[0075] In the next molding step, the injection machine is operated, and the first actuator (27) of each needle valve (25) is operated to retract the needle (26) corresponding to each gate (18), thereby opening each gate (18). As a result, as shown in Figure 9(b), the molten resin (R) supplied from the injection machine to the resin flow path (20) in the mold (5) is injected from each gate (18) into the cavity (C), filling the cavity (C). When the cavity (C) is filled with resin (R), the injection of resin (R) from the injection machine is stopped, and the first actuator (27) of each needle valve (25) is operated to advance the needle (26) corresponding to each gate (18), thereby closing each gate (18). The resin (R) that has filled the cavity (C) solidifies as the mold (5) 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).

[0076] Then, in the mold opening step, the opening and closing mechanism of the mold (5) is operated to separate the fixed mold (10) and the movable mold (30) from each other, and each second actuator (45) is operated to slide the multiple slide molds (40) in the withdrawal direction (d2) as shown in Figure 10. In this way, the fixed mold (10), the movable mold (30), and each slide mold (40) are in a predetermined positional relationship on the opening side, and the mold (5) is opened. At this time, each inner core (39) 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 (36), thereby avoiding interference with the shroud (62) of the impeller (60). When the mold (5) is opened, it becomes possible to remove the impeller (60) from the mold (5).

[0077] After removing the impeller (60) from the mold (5), 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 (1).

[0078] -Features of the Embodiment- In the manufacturing method of the impeller (60) of this embodiment, in the mold (5) of the injection molding apparatus (1) used to form the impeller (60), the area of ​​the sliding surface (46) extending parallel to the sliding direction of the sliding mold (40) differs between the outer surface (42) of the first molding surface (41) or the inner surface (44) of the second molding surface (43) of a pair of adjacent sliding molds (40). The outer surface (42) of the first molding surface (41) or the inner surface (44) of the second molding surface (43) of the sliding mold (40) forms the point where the negative pressure surface (63s) of one of the adjacent blades (63) formed by the first molding surface (41) and the positive pressure surface (63p) of the other blade (63) formed by the second molding surface (43) are closest. Therefore, the ejection direction (d2) of the slide mold (40) is constrained by the shape of the outer surface (42) of the first molding surface (41) and the shape of the inner surface (44) of the second molding surface (43). If the area of ​​the slide surface (46) differs between the outer surface (42) of the first molding surface (41) and the inner surface (44) of the second molding surface (43), the angles that adjacent slide molds (40) make with respect to the direction corresponding to the radial direction of the impeller (60) can be made different. This allows the ejection direction (d2) of the slide molds (40) to be adjusted so that multiple slide molds (40) do not interfere with each other or with other parts of the mold (5). Thus, an impeller (60) for a centrifugal fan, in which multiple blades (63) are arranged at unequal pitches, can be integrally molded from resin.

[0079] In the manufacturing method of the impeller (60) of this embodiment, the sliding surface (46) of each slide mold (40) is provided on the outer surface portion (42) of the first molding surface (41). This imposes constraints on the shape of the blades (63) in the extraction direction (d2) of the slide mold (40) on the negative pressure surface (63s). This makes it possible to maintain the shape of the positive pressure surface (63p) of the blades (63) as much as possible, taking into account the airflow performance of the impeller (60). The shape of the negative pressure surface (63s) of the blades (63) does not have as much effect on the airflow performance of the impeller (60) as the shape of the positive pressure surface (63p). Therefore, even when integrally molding an impeller (60) for a centrifugal fan in which multiple blades (63) are arranged at unequal pitches, it is possible to suppress a decrease in airflow performance.

[0080] In the manufacturing method of the impeller (60) of this embodiment, in each slide mold (40), the outer peripheral trim lines (47) of the first molding surface (41) and the second molding surface (43) are inclined with respect to the rotation axis (Ac), and the shroud (62) side protrudes further outward in the radial direction of the impeller (60) than the base plate (61) side. As a result, an impeller (60) having a skew angle β2 on the outer edge (63b) of the blades (63) can be integrally molded. In a mold (5) for molding such an impeller (60) having a skew angle β2, the positive pressure surface (63p) and negative pressure surface (63s) formed by the slide mold (40) are long in the sliding direction, and the distance from which the slide mold (40) is removed from the impeller (60) when the mold (5) is opened is long, so the restriction on the removal direction (d2) of the slide mold (40) becomes strict. Therefore, the technology of this disclosure is particularly effective in a method for manufacturing such an impeller (60).

[0081] In the manufacturing method of the impeller (60) of this embodiment, the pitch between the first blade cavity (Cf1) and the third blade cavity (Cf3) is shorter than the pitch between the first blade cavity (Cf1) and the second blade cavity (Cf2), and the area of ​​the sliding surface (46) of the second slide mold (40B) is larger than the area of ​​the sliding surface (46) of the first slide mold (40A). The shorter the pitch between adjacent blade cavities (Cf), the stricter the restriction on the withdrawal direction (d2) of the slide mold (40) located between those adjacent blade cavities (Cf). Conversely, the shorter the pitch between adjacent blade cavities (Cf), the larger the area of ​​the sliding surface (46) of the slide mold (40) located between those adjacent blade cavities (Cf), thereby easing the restriction on the withdrawal direction (d2) of the slide mold (40). This allows the extraction direction (d2) of the first slide type (40A) and the extraction direction (d2) of the second slide type (40B) to be adjusted so that the two slide types (40) do not interfere with each other.

[0082] In the manufacturing method of the impeller (60) of this embodiment, more than 90% of the second molding surfaces (43) of the multiple slide molds (40) have the same shape. As a result, more than 90% of the positive pressure surfaces (63p) of the multiple blades (63) are molded to the same shape. This allows the proportion of the positive pressure surfaces (63p) of the multiple blades (63) that have different shapes to be kept to less than 10%, so that even when integrally molding an impeller (60) for a centrifugal fan in which multiple blades (63) are arranged at unequal pitches, a decrease in airflow performance can be suppressed.

[0083] In the manufacturing method of the impeller (60) of this embodiment, the mold (5) of the injection molding apparatus (1) has six slide molds (40), and an impeller (60) having six blades (63) is manufactured. If the number of blades (63) is five or less, the workload per blade (63) is relatively large, so there is a tendency for abnormal noise during airflow to increase. There is also concern that the static pressure characteristics of the impeller (60) will decrease. If the static pressure characteristics of the impeller (60) decrease, the required rotational speed will increase relative to 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.

[0084] Other embodiments In the mold (5) of the injection molding apparatus (1), the area of ​​the sliding surface (46) of each slide mold (40) may be limited to the outer surface (42) of the first molding surface (41), or to the inner surface (44) of the second molding surface (43). From the viewpoint of suppressing a decrease in the air blowing performance of the impeller (60), it is preferable that the area of ​​the sliding surface (46) of the slide mold (40) may be limited to either the outer surface (42) of the first molding surface (41), or a relatively small area of ​​the inner surface (44) of the second molding surface (43).

[0085] In the mold (5) of the injection molding apparatus (1), the outer surface portion (42) of the first molding surface (41) or the inner surface portion (44) of the second molding surface (43) of some adjacent slide molds (40) may differ in whether or not they have a slide surface (46). For example, the outer surface portion (42) of the first molding surface (41) and the inner surface portion (44) of the second molding surface (43) of the second slide mold (40B) and the third slide mold (40C) have a slide surface (46) as in the above embodiment, while the outer surface portion (42) of the first molding surface (41) and the inner surface portion (44) of the second molding surface (43) of the first slide mold (40A) may not have a slide surface (46). In short, the goal is to adjust the ejection direction (d2) of the slide molds (40) so that they do not interfere with each other or with other parts of the mold (5) by having a slide surface (46) or a slide surface (46) different on the outer surface (42) of the first molding surface (41) or the inner surface (44) of the second molding surface (43) of adjacent slide molds (40).

[0086] 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 suitably suppress the noise associated with the rotational operation of the impeller (60) while ensuring the static pressure characteristics of the impeller (60) and reducing shaft power. The pitch of adjacent blades (63) may be different for all sets of blades (63). If multiple blades (63) have unequal pitches, that is, if the pitch of adjacent blades (63) is different on both sides in the circumferential direction of each blade (63), the number of blades (63) can be any number.

[0087] In the mold (5) of the injection molding apparatus (1), the area of ​​the slide surface (46) on the outer surface portion (42) of the first molding surface (41) of each slide mold (40) may be the same for all slide molds (40), i.e., the first slide mold (40A), the second slide mold (40B), and the third slide mold (40C). In this case, the area of ​​the flat surface (68) on the outer surface portion (42) of each blade (63) will be the same for the first blade (63A), the second blade (63B), and the third blade (63C).

[0088] 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]

[0089] As described above, this disclosure is useful for manufacturing an impeller. [Explanation of Symbols]

[0090] 5. Mold 10 Fixed type (First mold) 30. Movable type (second mold) 40 Slide type 40A Type 1 Slide 40B Type 2 Slide 41 1st molding surface 42 External surface part 43 Second molding surface 44 Inner side part 46 Sliding surface 47 Outer perimeter border line 60 Impeller 61 Base plate 62 Shroud 63 feathers 63A First Wing 63B Second feather 63C Third feather 63p pressure side 63s suction side AC rotation axis C Cavity Cf Feather Cavity Cf1 First Wing Cavity Cf2 Second Wing Cavity Cf3 Third Wing Cavity d1 Return direction d2 extraction direction R resin

Claims

1. A method for manufacturing an impeller (60) comprising: a base plate (61) that rotates around a 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), wherein 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), and the circumferential pitch of the outer edges of adjacent blades (63) is different on both sides of each blade (63) in the circumferential direction, A first mold (10) for forming the surface of the base plate (61) opposite to the shroud (62), A second mold (30) for forming the surface of the shroud (62) opposite to the base plate (61), the surface of the base plate (61) on the shroud (62) side, and a portion of the negative pressure surface (63s) facing the inside of the curvature in the plurality of blades (63), The device has a plurality of sliding molds (40) provided for each pair of adjacent blades (63), which form the other part of the negative pressure surface (63s) of one of the pair of blades (63), and the positive pressure surface (63p) facing the outside of the curve of the other blade (63), Each of the plurality of slide molds (40) has a first molding surface (41) for forming the negative pressure surface (63s) of one blade (63) and a second molding surface (43) for forming the positive pressure surface (63p) of the other blade (63), and uses a mold (5) that is slidable in the return direction (d1) corresponding to the rotation axis (Ac) side of the impeller (60) and the withdrawal direction (d2) corresponding to the outer circumference side of the impeller (60), A clamping step in which the first mold (10) and the second mold (30) are brought closer to each other, and the plurality of slide molds (40) are each slid in the return direction (d1) to close the mold (5) and form a cavity (C), thereby clamping the mold (5), A molding step in which the base plate (61), the shroud (62), and the plurality of blades (63) are integrally formed impeller (60) is formed by filling the cavity (C) with molten resin (R) and cooling and solidifying the resin (R), The process includes a mold opening step in which the plurality of slide molds (40) are each slid in the removal direction (d2), and the first mold (10) and the second mold (30) are separated from each other, thereby opening the mold (5). The cavity (C) includes a plurality of blade cavities (Cf) for forming each of the plurality of blades (63), The plurality of blade cavities (Cf) include a first blade cavity (Cf1) for forming a first blade (63A) among the plurality of blades (63), a second blade cavity (Cf2) for forming a second blade (63B) adjacent to the first blade (63A), and a third blade cavity (Cf3) for forming a third blade (63C) adjacent to the first blade (63A) on the opposite side from the second blade (63B). The plurality of slide molds (40) include a first slide mold (40A) located between the first blade cavity (Cf1) and the second blade cavity (Cf2), and a second slide mold (40B) located between the first blade cavity (Cf1) and the third blade cavity (Cf3), The pitch in the direction corresponding to the circumferential direction between the first blade cavity (Cf1) and the third blade cavity (Cf3) is shorter than the pitch in the direction corresponding to the circumferential direction between the first blade cavity (Cf1) and the second blade cavity (Cf2). The first slide mold (40A) and the second slide mold (40B) each have a slide surface (46) extending parallel to the sliding direction of the slide mold (40) at corresponding portions of the outer surface portion (42) of the first molding surface (41) that molds the area near the outer edge of the blade (63) or the inner surface portion (44) of the second molding surface (43) that molds the area near the inner edge of the blade (63), and the area of ​​the slide surface (46) of the second slide mold (40B) is larger than the area of ​​the slide surface (46) of the first slide mold (40A), or In the second slide mold (40B), the outer surface portion (42) of the first molding surface (41) or the inner surface portion (44) of the second molding surface (43) has the slide surface (46), whereas in the first slide mold (40A), the outer surface portion (42) of the first molding surface (41) and the inner surface portion (44) of the second molding surface (43) do not have the slide surface (46). A method for manufacturing an impeller.

2. In the method for manufacturing an impeller according to claim 1, The sliding surface (46) is provided on the outer surface portion (42) of the first molding surface (41), A method for manufacturing an impeller.

3. In the method for manufacturing an impeller according to claim 1, The outer edge trim lines (47) that form the outer edge of the blade (63) on the first molding surface (41) and the second molding surface (43) are inclined with respect to the mold opening direction between the first mold (10) and the second mold (30) such that they extend in a direction corresponding to the radially outward direction of the impeller (60) as they move from the base plate (61) toward the shroud (62). A method for manufacturing an impeller.

4. In the method for manufacturing an impeller according to any one of claims 1 to 3, More than 90% of the second molding surfaces (43) in the plurality of slide molds (40) are the same shape as each other. A method for manufacturing an impeller.

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