Fan and method of manufacturing the same

Abstract

To provide a fan capable of adjusting an unbalance amount with a simple configuration.SOLUTION: A fan includes a boss to which a rotating shaft of a motor is fixed, and a blade group which is constituted by a plurality of blades radially extending from the boss. The blade group has a recession or a protrusion, and the recession or the protrusion is arranged on a circumference concentric with the boss. A surface of the recession or a surface of the protrusion has a molding surface.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a balanced fan and a method for manufacturing the fan. [Background technology]

[0002] A known fan used to cool an automobile radiator is one in which a boss and multiple blades are integrally molded from resin. The boss is located at the center of the fan. A rotating shaft of a motor is fixed to the boss. The multiple blades extend radially from the boss. Wind is generated when the fan rotates due to the motor.

[0003] Even when molding using the same mold, the center of gravity of the fan may deviate from the center of rotation depending on the molding environment conditions such as room temperature and humidity, or the lot of material. When the center of gravity of the fan deviates from the center of rotation, the fan becomes unbalanced. If there is a large deviation between the center of rotation and the center of gravity, that is, if the amount of unbalance is large, vibrations and noise will occur during the rotation of the fan. Therefore, balance adjustments are made so that the amount of unbalance of the fan falls within a specified value.

[0004] Techniques for adjusting the balance of fans are disclosed in Patent Documents 1 to 3. The technique in Patent Document 1 adjusts the balance by setting the mounting bracket to which the motor's rotating shaft is fixed at a position eccentric from the center of the boss according to the amount of imbalance. The technique in Patent Document 2 adjusts the balance by embedding a weight according to the amount of imbalance in a predetermined position on the boss. The technique in Patent Document 3 adjusts the balance by providing multiple protrusions on a ring connecting the tips of multiple blades and cutting the protrusions according to the amount of imbalance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2001-145934 A [Patent Document 2] Japanese Patent Application Publication No. 6-317293 [Patent Document 3] JP 2003-113798 A Summary of the Invention [Problem to be solved by the invention]

[0006] In the balance adjustment by eccentricity of the mounting bracket described in Patent Document 1, the amount of eccentricity allowed for the mounting bracket is small. Since the amount of unbalance that can be corrected is small, it may not be possible to deal with a large amount of unbalance. The dimensions of the fan are determined based on the seating surface of the mounting bracket. If the amount of eccentricity of the mounting bracket is changed, the position of the mounting bracket will shift, causing the dimensional accuracy to be affected. In addition, in the technology of Patent Document 1, an eccentric mechanism for adjusting the amount of eccentricity of the mounting bracket is provided in the mold, but since this eccentric mechanism is a combination of multiple parts, variations are likely to occur when the amount of eccentricity of the mounting bracket is changed. There is a risk that the parallelism of the seating surface of the mounting bracket to the mold will be disturbed.

[0007] The balance adjustment using weights described in Patent Document 2 increases the number of parts because weights are used. Also, the technology in Patent Document 2 has low productivity because it requires placing weights in predetermined positions in the mold every time a fan is molded.

[0008] The balance adjustment method described in Patent Document 3 corrects the amount of imbalance by partially changing the weight of the fan. The technology in Patent Document 3 requires multiple protrusions to be molded on the ring in advance, which increases the amount of resin used. Also, a process of cutting off the protrusions is required every time the fan is molded, which reduces productivity. Furthermore, if the ring has protrusions, there is a risk that the protrusions will interfere with surrounding components. An example of a surrounding component is a cover that covers the fan.

[0009] It is an object of the present invention to provide a fan that can adjust the amount of unbalance with a simple configuration. It is another object of the present invention to provide a method for manufacturing a fan that can easily adjust the amount of unbalance. [Means for solving the problem]

[0010] (1) A fan according to one aspect of the present invention comprises: a boss portion to which a rotating shaft of a motor is fixed; a blade group consisting of a plurality of blades extending radially from the boss portion, The set of blades has a concave portion or a convex portion, the recess or the protrusion is disposed on a circumference concentric with the boss portion, The surface of the recess or the surface of the protrusion has a molding surface.

[0011] (2) In the fan described in (1) above, the vane set has a flash line formed by a parting line of a die; The joints are arranged at intervals on a circumference concentric with the boss portion, The recessed portion or the protruding portion may be located between adjacent ones of the joint grooves.

[0012] (3) A method for manufacturing a fan according to one aspect of the present invention includes the steps of: 1. A method for manufacturing a fan including a boss portion to which a rotating shaft of a motor is fixed, and a blade group including a plurality of blades extending radially from the boss portion, comprising: A step of preparing a mold including a first mold and a second mold that is combined with the first mold; attaching a plurality of auxiliary molds to one of the first mold and the second mold; and injecting molten resin into a cavity formed between the first mold and the second mold to integrally mold the boss portion and the set of blades. each of the auxiliary dies is disposed in a portion of the cavity where the blade set is molded; At least one of the plurality of auxiliary dies has a convex portion or a concave portion on a surface in contact with the cavity, each of the protruding portions or the recessed portions is disposed on a circumference concentric with the boss portion in a state in which the plurality of auxiliary dies are attached; In the step of attaching the plurality of auxiliary molds, at least one of the plurality of auxiliary molds is replaced with an auxiliary mold having a different height of the convex portion or a different depth of the concave portion. Effect of the Invention

[0013] The fan of (1) above can adjust the amount of imbalance by the recess or protrusion provided on the blade group. When the blade group has a recess, it does not interfere with surrounding members. In addition, since the surface of the recess or the surface of the protrusion has a molding surface, the recess or the protrusion is integrally molded with the blade group. The molding surface is described in detail below, but typically refers to a surface to which the mold surface of a metal mold is transferred. In other words, the surface of each of the recess or the protrusion does not have a processed surface formed by cutting or cutting. Since the recess or the protrusion is integrally molded with the blade group, the surface of the recess or the surface of the protrusion is not processed in such a way that the constituent material of the fan is removed. Therefore, the above fan has high productivity.

[0014] The fan of (2) above can be manufactured by the fan manufacturing method of (3) above, with excellent productivity.

[0015] In the above fan manufacturing method (3), the amount of imbalance can be easily adjusted by attaching an auxiliary mold having a different height of the convex portion or a different depth of the concave portion to the mold. It is only necessary to replace the auxiliary mold, and there is no need to modify the mold according to the amount of imbalance. Therefore, the productivity of the fan is also excellent. When an auxiliary mold having a convex portion is used, a concave portion can be integrally molded with the group of blades. When an auxiliary mold having a concave portion is used, a convex portion can be integrally molded with the group of blades. According to the above fan manufacturing method, a concave portion having a depth corresponding to the height of the convex portion of the auxiliary mold is molded. Alternatively, according to the above fan manufacturing method, a convex portion having a height corresponding to the depth of the concave portion of the auxiliary mold is molded. The above fan manufacturing method has high productivity because it is possible to integrally mold concave portions of different depths or convex portions of different heights with the group of blades. The reason for the high productivity is that after molding the fan, a processing step of cutting a concave portion in the group of blades or cutting a convex portion previously molded is not required. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic perspective view of a fan according to the first embodiment. [Diagram 2] FIG. 2 is a schematic front view of the fan according to the first embodiment. [Diagram 3] FIG. 3 is a schematic cross-sectional view taken along line III-III shown in FIG. [Figure 4] FIG. 4 is an enlarged schematic cross-sectional view of part IV shown in FIG. [Diagram 5] FIG. 5 is a schematic cross-sectional view showing a mold used in the method for producing the fan according to the first embodiment. [Figure 6] FIG. 6 is an enlarged schematic cross-sectional view of a portion VI shown in FIG. [Figure 7] FIG. 7 is a schematic diagram illustrating the arrangement of an auxiliary mold used in the method for manufacturing a fan according to the first embodiment. [Figure 8] FIG. 8 is a schematic diagram illustrating the flow of molten resin in a mold used in the method for manufacturing the fan according to the first embodiment. [Figure 9]FIG. 9 is a schematic partial perspective view of the fan according to the first embodiment as viewed from behind. [Figure 10] FIG. 10 is a schematic cross-sectional view showing another example of an auxiliary mold used in the method for manufacturing a fan according to embodiment 1. As shown in FIG. [Figure 11] FIG. 11 is a schematic front view of the fan according to the second embodiment. [Figure 12] FIG. 12 is a schematic cross-sectional view taken along line XII-XII shown in FIG. [Figure 13] FIG. 13 is a schematic cross-sectional view showing a mold used in the method for producing the fan according to the second embodiment. [Figure 14] FIG. 14 is an enlarged schematic cross-sectional view of a portion XIV shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] A specific example of a fan and a method of manufacturing a fan according to an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals. For ease of explanation, the drawings may show some components in an exaggerated or simplified manner. The dimensional ratios of the parts in the drawings may also differ from the actual ratios.

[0018] [Embodiment 1] <Fan> A fan 1 according to the first embodiment will be described with reference to Figs. 1 to 4. The fan 1 includes a boss 2 and a blade group 3g consisting of a plurality of blades 3. The fan 1 in this embodiment is made of resin. The boss 2 and the blade group 3g are integrally molded. The fan 1 is, for example, a fan for cooling a radiator. The application of the fan 1 is not limited to a fan for cooling a radiator. The fan 1 may be a vehicle fan mounted on an automobile. The vehicle fan is, for example, a fan for cooling an electronic control unit (ECU) or a fan for cooling a drive motor of an electric vehicle or the like. One of the features of the fan 1 according to the first embodiment is that, as shown in Figs. 2 and 4, a plurality of recesses 5 are provided at intervals from each other on a circumference concentric with the boss 2 in the blade group 3g. The configuration of the fan 1 will be described in detail below.

[0019] (Boss part) The boss portion 2 is located at the center of the fan 1, as shown in Figures 1 and 2. The boss portion 2 is attached to the motor 100 shown in Figure 3. In this example, the boss portion 2 is shaped like a cap. The boss portion 2 has a disk portion 21 and a cylindrical portion 22. The cylindrical portion 22 protrudes from the back surface of the disk portion 21. The back surface here refers to the surface facing the motor 100.

[0020] A rotating shaft of a motor 100 shown in FIG. 3 is fixed to the boss portion 2. The boss portion 2 is placed over the motor 100. The disk portion 21 is arranged parallel to a plane perpendicular to the rotating shaft of the motor 100. A shaft hole 23 into which the rotating shaft of the motor 100 is inserted is formed at the center of the boss portion 2, i.e., the center of the disk portion 21. In other words, the center of the boss portion 2 is the rotation center of the fan 1. In the boss portion 2 of this example, a mounting bracket 25 shown in FIG. 3 is embedded in the center of the disk portion 21. The rotating shaft is fixed to the mounting bracket 25. The mounting bracket 25 has a shaft hole 23.

[0021] (Feather) A plurality of blades 3 extend radially from the boss portion 2. Specifically, each blade 3 protrudes in a direction away from the outer circumferential surface of the cylindrical portion 22. The direction away from the center of the boss portion 2 is defined as the "radial direction". The root portion of each blade 3 is connected to the cylindrical portion 22. In this example, each blade 3 is disposed at equal intervals. The number of blades 3 is, for example, three or more. The number of blades 3 may further be five or more, or six or more. In this example, the number of blades 3 is seven.

[0022] The blade group 3g of this example has an outer peripheral ring portion 4 that connects the tips of adjacent blades 3. The tips of the blades 3 are the ends far from the boss portion 2. The shape of the outer peripheral ring portion 4 is annular. The outer peripheral ring portion 4 of this example has a cylindrical portion 41 and a flange portion 42. The tips of each blade 3 are joined to the inner peripheral surface of the cylindrical portion 41. The flange portion 42 protrudes from the outer peripheral surface of the cylindrical portion 41. The flange portion 42 of this example is provided at a first end of the cylindrical portion 41. The first end of the cylindrical portion 41 is the end close to the front. The tips of the blades 3 may protrude radially beyond the outer peripheral ring portion 4. Specifically, the tips of each blade 3 may protrude partially from the outer peripheral surface of the cylindrical portion 41. The outer peripheral ring portion 4 is not an essential component of this embodiment. In this embodiment, all components of the fan 1 other than the boss portion 2 are considered to constitute the blade group 3g.

[0023] (recess) As shown in FIG. 2, the blade group 3g of this example has a plurality of recesses 5. At least one recess 5 is sufficient. In this example, the recess 5 is provided in the outer peripheral ring portion 4. Specifically, as shown in FIG. 4, the recess 5 is provided in the flange portion 42 located at the tip of the blade 3. The recess 5 is provided in the back surface 4b of the flange portion 42. Unlike this example, the recess 5 may be provided on the surface of the flange portion 42 opposite to the back surface 4b, that is, the front surface 4f. The back surface 4b of the flange portion 42 is disposed so as to face a peripheral member such as a cover (not shown). The front surface 4f of the flange portion 42 is disposed so as to face, for example, a radiator (not shown).

[0024] As shown in FIG. 2, the recesses 5 are arranged at intervals on the circumference of a concentric circle with the boss portion 2. The center of the concentric circle is the center of the boss portion 2. The concentric circle exists on an xy plane perpendicular to the z-axis along the axis of the boss portion 2. "Arranged on the circumference of the concentric circle" does not necessarily mean that the geometric center of each recess 5 is located on the circumference of the concentric circle, but includes that at least a part of each recess 5 overlaps on the circumference of the concentric circle. In this example, the recesses 5 are arranged at equal intervals on the circumference of the concentric circle. The radius of the concentric circle is the average value of the radius of the inscribed circle tangent to the recess 5 closest to the center of the boss portion 2 and the radius of the circumscribed circle tangent to the recess 5 farthest from the center of the boss portion 2.

[0025] In this example, one recess 5 is provided at a position corresponding to the tip of each blade 3. The recess 5 in this example is located approximately on the center line C of the blade 3. That is, the number of recesses 5 is 7, which is the same as the number of blades 3. The number of recesses 5 may be the same as the number of blades 3, or may be different from the number of blades 3. The number of recesses 5 may be less than the number of blades 3, or may be more than the number of blades 3. For example, the number of recesses 5 may be one less than the number of blades 3. That is, among the multiple blades 3, one blade 3 may not have a recess 5 at its tip. When the recess 5 is located approximately on the center line C of the blade 3 as in this example, the area of ​​the portion where the recess 5 is formed is relatively large, so that the recess 5 is easily provided. "Located approximately on the center line C of the blade 3" includes the case where at least a part of the recess 5 is located on the extension line of the center line C. If at least a part of the recess 5 overlaps with the extension line of the center line C, the recess 5 is considered to be located on the center line C. In this example, the geometric center of recess 5 is located on an extension of center line C. Unlike this example, two or more recesses 5 may be provided at positions corresponding to the tips of each blade 3. Also, recesses 5 may be provided in flange portion 42 located between adjacent blades 3.

[0026] The recesses 5 may be provided on some of the multiple blades 3, or on all of the blades 3. The recesses 5 are disposed between the tip and the base of the blade 3. Because the blade 3 has a large area, it is easy to provide a recess 5 with a large opening.

[0027] The recesses 5 are integrally molded with the outer circumferential ring portion 4 of the blade group 3g, and the surfaces of all the recesses 5 have a molded surface. The surface of the recesses 5 refers to the inner circumferential surface of the recesses 5. Since the surface of the recesses 5 has a molded surface, the recesses 5 maintain the molded state. The molded surface refers to the surface onto which the mold surface of the mold is transferred. In other words, the molded surface refers to the surface onto which the mold surface of the mold is transferred, and which has not been subjected to processing that partially removes the constituent material of the fan. In this embodiment, the recesses 5 are not formed by machining such as cutting after molding. The surface of the recesses 5 does not have a processed surface.

[0028] The above-mentioned processed surface is a result of machining or hand machining. Mechanical machining includes, for example, grinding, cutting, or cutting. In general, a number of streaky grinding marks, cutting marks, or cutting marks remain on a processed surface by machining. In addition, for example, when a previously molded convex portion is broken by hand, a fracture surface is formed on the surface of the remaining convex portion. There are no grinding marks, cutting marks, cutting marks, or fracture surfaces on the molded surface.

[0029] The shape of the recess 5 is, for example, a truncated cone, a truncated pyramid, a cylindrical shape, or a prismatic shape. In this embodiment, the shape of the recess 5 is a truncated cone, and the opening is a circle. As shown in FIG. 4, the inner peripheral surface of the recess 5 in this embodiment has an inclined surface in which the inner diameter decreases from the opening toward the bottom. When the inner peripheral surface of the recess 5 has an inclined surface, it is easier to reduce wind noise generated when the fan 1 rotates, compared to when the inner peripheral surface is a vertical surface.

[0030] The size of the opening of the recess 5 and the depth of the recess 5 are selected from a range that can ensure the mechanical strength of the portion where the recess 5 is formed. The size of the opening of the recess 5 is represented by the diameter of the opening of the recess 5. In this example, the diameter φ of the opening of the recess 5 shown in FIG. 4 is, for example, 4 mm or more and 20 mm or less. The diameter φ of the opening of the recess 5 may further be 5 mm or more and 15 mm or less. When the shape of the opening of the recess 5 is non-circular, the diameter of the opening of the recess 5 is regarded as the diameter of a circle having an area equal to the area of ​​the opening. The depth of the recess 5, i.e., the distance from the opening to the bottom surface, may be smaller than the diameter φ of the opening of the recess 5. The depth of the recess 5 is, for example, 0.2 mm or more and 3 mm or less. The depth of the recess 5 may further be 0.2 mm or more and 2 mm or less.

[0031] Unlike the present embodiment, for example, it is also possible to provide a plurality of recesses 5 in the disk portion 21 of the boss portion 2. When the blade set 3g has a plurality of recesses 5 as in the present embodiment, it is easier to make the boss portion 2 smaller than when the boss portion 2 has a plurality of recesses 5.

[0032] The multiple recesses 5 are for adjusting the amount of imbalance of the fan 1. The depth of each recess 5 is set according to the amount of imbalance. The amount of imbalance here means the amount of imbalance relative to the standard state. The standard state refers to a state in which there are no recesses 5, or the recesses 5 are molded under the condition that the opening size and depth of all the recesses 5 are the same. The amount of imbalance is expressed by the product of the mass of the fan 1 and the deviation of the center of gravity from the center of rotation. The thickness of the portion in which the recesses 5 are formed varies depending on the depth of the recesses 5. The greater the depth of the recesses 5, the thinner the portion in which the recesses 5 are formed becomes, and therefore the lighter the weight of the portion in which the recesses 5 are formed becomes. In the fan 1 of this example, the depth of at least one recess 5 among the multiple recesses 5 is different so that the deviation of the center of gravity from the center of rotation becomes smaller than that in the standard state.

[0033] The farther the recess 5 is located from the center of the boss 2, i.e., the center of rotation, the easier it is to achieve the effect of reducing the deviation between the center of rotation and the center of gravity. This is because the greater the distance from the center of the boss 2 to the recess 5, the greater the displacement of the center of gravity due to the difference in weight caused by the depth of the recess 5. When the recess 5 is provided at the tip of each blade 3 as in this example, it is possible to reduce the deviation of the center of gravity even if the depth of the recess 5 is small, compared to when the recess 5 is provided in the boss 2.

[0034] <Fan manufacturing method> A method for manufacturing a fan according to the embodiment will now be described. Here, the method for manufacturing fan 1 according to the above-mentioned embodiment 1 will be described with reference to Figures 5 to 9. The method for manufacturing fan 1 includes a first step, a second step, and a third step, which will be described below. The first step is to prepare a mold. The second step is to attach the auxiliary mold to the metal mold. The third step is to mold the fan using a mold. Each step will be described in detail below.

[0035] (first step) In the first step, a mold 7 shown in FIG. 5 is prepared. The mold 7 is a mold for injection molding. The mold 7 includes a first mold 71 and a second mold 72 that is combined with the first mold 71. The first mold 71 in this example is a movable mold. The second mold 72 in this example is a fixed mold. The first mold 71 is attached to a movable plate of a molding machine (not shown). The second mold 72 is attached to a fixed plate of a molding machine (not shown). The first mold 71 can be opened and closed with respect to the second mold 72. As shown in FIG. 5, when the first mold 71 is closed, a cavity 70 is formed between the first mold 71 and the second mold 72. The cavity 70 is a space in which the fan 1 is molded. The first mold 71 has a first mold surface that molds the back surface of the fan 1. The second mold 72 has a second mold surface that molds the front surface of the fan 1. The second mold surface faces the first mold surface. When the fan 1 is molded, the first mold 71 is closed. After fan 1 is molded, first mold 71 is opened, and fan 1 is removed from mold 7. When fan 1 is removed from mold 7, second mold 72 moves away from the fixed plate, and the runner is discharged from between second mold 72 and the fixed plate.

[0036] Either the first mold 71 or the second mold 72 has a plurality of auxiliary molds 8, which will be described later. In this example, the first mold 71 has the auxiliary molds 8.

[0037] (Second process) In the second step, multiple auxiliary dies 8 are attached to either the first mold 71 or the second mold 72. The auxiliary dies 8 in this example are attached to the first mold 71 as shown in Figs. 5 and 6. The auxiliary dies 8 have a nested structure that is fitted into the first mold 71. The first mold 71 with the multiple auxiliary dies 8 attached has parting lines at the boundaries between the first mold 71 and each auxiliary die 8. In this example, the auxiliary dies 8 are fixed to the first mold 71 by bolts 85. The auxiliary dies 8 are freely attachable to and detachable from the first mold 71 when the second mold 72 is open. The bolts 85 are disposed outside the cavity 70. A counterbore is provided on the surface of the auxiliary die 8 facing the second mold 72 to accommodate the head of the bolt 85.

[0038] Each of the multiple auxiliary dies 8 is disposed in a portion of the cavity 70 where the blade set 3g is molded. Specifically, as shown in Fig. 6, the auxiliary dies 8 are disposed in a portion where the flange portion 42 of the outer peripheral ring portion 4 is molded. As shown in Fig. 7, the auxiliary dies 8 are disposed at positions corresponding to the tips of the respective blades 3. Fig. 7 shows the arrangement of the auxiliary dies 8 in a simplified manner.

[0039] At least one of the auxiliary dies 8 has a convex portion 81 on the surface that contacts the cavity 70. In this example, each auxiliary die 8 has a convex portion 81 on the surface that contacts the cavity 70. As shown in FIG. 6, the auxiliary die 8 in this example has a convex portion 81 on the surface that molds the back surface 4b of the flange portion 42. In this example, as shown in FIG. 7, each auxiliary die 8 has one convex portion 81. The convex portion 81 is located approximately on the center line C of the blade 3. When the multiple auxiliary dies 8 are attached to the first mold 71, each of the convex portions 81 is arranged at intervals from one another on the circumference of a circle concentric with the boss portion 2. The convex portions 81 are arranged at equal intervals.

[0040] The protrusions 81 are for forming the above-mentioned recesses 5 in the blade group 3g. When the fan 1 is formed in the third step described later, the recesses 5 corresponding to the protrusions 81 are formed. In this example, a plurality of recesses 5 are formed in the back surface 4b of the flange portion 42. The number of protrusions 81 corresponds to the number of the above-mentioned recesses 5. The number of protrusions 81 in this example, i.e., the number of auxiliary molds 8, is 7, which is the same as the number of blades 3. Unlike this example, when recesses 5 are provided on the front surface 4f of the flange portion 42, an auxiliary mold 8 having a protrusion 81 is attached to the second mold 72. By attaching a plurality of auxiliary molds 8 to the second mold 72, a plurality of recesses 5 are formed on the front surface 4f of the flange portion 42.

[0041] The shape of the protrusion 81 corresponds to the shape of the recess 5 described above. The shape of the protrusion 81 in this example is a truncated cone shape. The protrusion 81 has a height corresponding to the depth of the recess 5 described above. The height of the protrusion 81 is, for example, 0.2 mm or more and 3 mm or less. The height of the protrusion 81 may further be 0.2 mm or more and 2 mm or less. The height of the protrusion 81 is selected from a range that can ensure the mechanical strength of the portion where the recess 5 is formed and does not hinder the flow of molten resin in the third step described later. The outer peripheral surface of the protrusion 81 in this example has an inclined surface whose outer diameter becomes smaller toward the tip. Since the outer peripheral surface of the protrusion 81 has an inclined surface, it is easy to remove the protrusion 81 from the recess 5 after the fan 1 is molded. When the protrusion 81 is located approximately on the center line C of the blade 3 as in this example, the protrusion 81 is less likely to hinder the flow of molten resin. "Located approximately on the center line C of the blade 3" includes a case where at least a part of the protrusion 81 is located on an extension of the center line C. If at least a portion of the convex portion 81 overlaps with an extension of the center line C, the convex portion 81 is considered to be located on the center line C. In this example, the geometric center of the convex portion 81 is located on the extension of the center line C.

[0042] In the second step, at least one of the auxiliary molds 8 is replaced with an auxiliary mold 8 having a different height of the convex portion 81. Specifically, the auxiliary mold 8 is replaced according to the amount of imbalance described above. For example, auxiliary molds 8 having the same height of the convex portion 81 are attached to the first mold 71 to manufacture a fan in a standard state in which all the recesses 5 have the same depth. The amount of imbalance of the fan in the standard state is measured. From the measured amount of imbalance, the depth of each recess 5 in which the amount of imbalance falls within a specified value is calculated. The height of each convex portion 81 is determined based on the calculated depth of each recess 5. An auxiliary mold 8 having a convex portion 81 of the determined height is attached to the first mold 71. If the determined height of the convex portion 81 is the same as the height of the convex portion 81 when the fan in the standard state is molded, the auxiliary mold 8 does not need to be replaced. If the determined height of the convex portion 81 is different from the height of the convex portion 81 when the fan in the standard state is molded, the auxiliary mold 8 is replaced.

[0043] (Third step) In the third step, molten resin is injected into the cavity 70 of the mold 7 to integrally mold the boss portion 2 and the blade group 3g. This step produces the fan 1 in which the boss portion 2 and the blade group 3g are integrally molded with resin. The second mold 72 in this example is provided with a gate (not shown) for injecting molten resin into the cavity 70. In this example, the position of the gate is set at a position in the cavity 70 that corresponds to the boss portion 2. That is, the molten resin injected into the cavity 70 flows in the order of the boss portion 2, the blades 3, and the outer peripheral ring portion 4.

[0044] In this example, the molten resin that flows from the boss 2 toward the tip of each blade 3 branches into two at the tip of each blade 3 as shown by the dashed arrows in Figure 8, and then joins at the outer ring 4 located between adjacent blades 3. A weak part called a weld line may occur at the part where the molten resin joins. In this example, since the recess 5 is located at the tip of each blade 3, the recess 5 and the weld line are formed at a misaligned position. Since the recess 5 does not overlap the weld line, it is easy to ensure the mechanical strength of the part where the recess 5 is formed.

[0045] In addition, because the auxiliary molds 8 have a nested structure, there are gaps between the first mold 71 and each auxiliary mold 8. When molten resin is injected into the cavity 70, the air inside the cavity 70 can escape through these gaps. This makes it easier to prevent molding defects such as insufficient resin filling.

[0046] On the surface of the molded fan 1, a matching line is formed by the parting line between the first mold 71 and each auxiliary mold 8. The matching lines are arranged at intervals on the circumference of a circle concentric with the boss portion 2, corresponding to the arrangement of the auxiliary molds 8 shown in FIG. 7. A pair of matching lines is formed for each auxiliary mold 8. In this example, as shown in FIG. 9, a matching line 50 is formed on the back surface 4b of the flange portion 42 and the outer circumferential surface of the cylindrical portion 41. Although only a part of the outer circumferential ring portion 4 is shown in FIG. 9, the matching line 50 is actually formed on the remaining part of the outer circumferential ring portion 4 not shown in FIG. 9. The recess 5 is located between a pair of adjacent matching lines 50. The fan 1 having such a matching line 50 can be manufactured by the manufacturing method of the fan of this embodiment, and therefore has excellent productivity.

[0047] {Variation} A modified example of the auxiliary die 8 will be described with reference to FIG. 10. The auxiliary die 8 shown in FIG. 10 is attached to a push rod 9 provided in the first die 71. The push rod 9 is a member that pushes up the molded fan 1 from the first die 71. By attaching the auxiliary die 8 to the push rod 9, it is easier to secure a space for arranging the auxiliary die 8 compared to a case in which the push rod 9 and the auxiliary die 8 are arranged in different positions. The auxiliary die 8 of this example is connected to the tip of the push rod 9 by a bolt 95. The bolt 95 is arranged in a direction perpendicular to the axis of the push rod 9. The head of the bolt 95 is housed in a countersunk provided on the outer circumferential surface of the auxiliary die 8. The auxiliary die 8 is attached and detached by pushing up the push rod 9. Specifically, this is done in a state in which the auxiliary die 8 comes out of the first die 71 and the head of the bolt 95 is exposed.

[0048] [Embodiment 2] <Fan> A fan 1a according to a second embodiment will be described with reference to Figures 11 and 12. The fan 1a according to the second embodiment differs from the fan 1 according to the first embodiment described above in that a plurality of protrusions 6 are provided at intervals from one another on a circumference concentric with the boss portion 2 in the blade set 3g. The fan 1a of the second embodiment has protrusions 6 instead of the recesses 5 described in the first embodiment. The following description will focus on the differences from the first embodiment. Descriptions of configurations common to the first embodiment will be omitted.

[0049] (Convex part) As shown in FIG. 11, the blade group 3g of this example has a plurality of protruding portions 6. At least one protruding portion 6 is sufficient. The protruding portion 6 is provided on the outer peripheral ring portion 4. Specifically, the protruding portion 6 is provided on the flange portion 42 located at the tip of the blade 3. The protruding portion 6 is provided on the front surface 4f of the flange portion 42. Unlike this example, the protruding portion 6 may be provided on the back surface 4b of the flange portion 42. In general, the clearance between the front surface 4f of the flange portion 42 and the radiator (not shown) is larger than the clearance between the back surface 4b of the flange portion 42 and the cover (not shown). Therefore, even if the protruding portion 6 is provided on the front surface 4f of the flange portion 42, the protruding portion 6 is unlikely to interfere with the radiator.

[0050] If the protrusion 6 provided on the blade group 3g is within the range of an envelope rectangle in the vertical section of the blade group 3g, it is easy to avoid interference with surrounding members such as a cover or a radiator. The above-mentioned envelope rectangle is a rectangle Er shown in FIG. 3. As shown in FIG. 3, the above-mentioned envelope rectangle is the smallest rectangle that surrounds the blade group 3g in the vertical section of the fan with two vertical lines V1 and V2 along the central axis of the fan and two horizontal lines H1 and H2 perpendicular to the central axis of the fan. The vertical section of the fan is a section along the central axis of the fan. The vertical line V1 and the horizontal line H1 pass through the intersection point between the front of the base part of the blade 3 and the outer circumferential surface of the cylindrical part 22 of the boss part 2. The vertical line V2 is in contact with the outer circumferential surface of the blade group 3g. In this example, the outer circumferential surface of the blade group 3g is the outer circumferential surface of the flange part 42 of the outer circumferential ring part 4. The horizontal line H2 is in contact with the back surface of the cylindrical part 41.

[0051] The multiple protrusions 6 are arranged at intervals on a circumference concentric with the boss portion 2, similar to the recessed portion 5 described above. In this example, one protrusion 6 is provided at a position corresponding to the tip of each blade 3. The protrusion 6 in this example is located approximately on the center line C of the blade 3. The number of protrusions 6 may be the same as the number of blades 3, or may be different from the number of blades 3. The number of protrusions 6 may be less than the number of blades 3, or may be more than the number of blades 3. For example, among the multiple blades 3, one blade 3 may not have a protrusion 6 at its tip. Unlike this example, a protrusion 6 may be provided on a flange portion 42 located between adjacent blades 3.

[0052] The protrusions 6 may be provided on some of the multiple blades 3, or on all of the blades 3. The protrusions 6 are disposed between the tip and the base of the blade 3. Since the blade 3 has a large area, it is easy to provide large protrusions 6.

[0053] The protrusions 6 are integrally molded with the outer peripheral ring portion 4 of the blade set 3g, and the surfaces of all of the protrusions 6 have a molded surface. Since the surfaces of the protrusions 6 have a molded surface, the protrusions 6 maintain their molded state. In other words, after molding, the protrusions 6 have not been subjected to mechanical processing such as cutting or processing such as bending by hand. The surfaces of the protrusions 6 do not have a processed surface.

[0054] The shape of the protrusion 6 is, for example, a truncated cone, a truncated pyramid, a cylindrical shape, or a prismatic shape. In this example, the shape of the protrusion 6 is a truncated pyramid, and the shape of the top surface is generally rectangular. As shown in FIG. 12, the cross section of the protrusion 6 is a trapezoid that tapers away from the flange portion 42. In FIG. 12, the boundary between the front surface 4f of the flange portion 42 and the protrusion 6 is indicated by a dashed line. The cross section of the protrusion 6 is a cross section perpendicular to the front surface 4f of the flange portion 42. The top surface of the protrusion 6 is a flat surface that is generally parallel to the front surface 4f of the flange portion 42. The outer peripheral surface of the protrusion 6 has an inclined surface as shown in FIG. 12. The outer peripheral surface of the protrusion 6 is connected to the front surface 4f of the flange portion 42. When the outer peripheral surface of the protrusion 6 has an inclined surface, it is easier to reduce wind noise generated when the fan 1a rotates, compared to when the outer peripheral surface is a vertical surface.

[0055] The size and height of the protrusion 6 can be appropriately selected. The size of the protrusion 6 is expressed by the product of the length and width of the protrusion 6. In this example, the length L of the protrusion 6 shown in FIG. 11 is, for example, 5 mm or more and 40 mm or less. The length L of the protrusion 6 may further be 10 mm or more and 40 mm or less. The length L of the protrusion 6 refers to the length along the circumference of the flange portion 42. The width W of the protrusion 6 shown in FIG. 12 is, for example, 4 mm or more and 20 mm or less. The width W of the protrusion 6 may further be 5 mm or more and 15 mm or less. The width W of the protrusion 6 refers to the length along the diameter of the flange portion 42. The length L and width W of the protrusion 6 are measured at the boundary between the protrusion 6 and the front surface 4f. The height H of the protrusion 6 shown in FIG. 12, that is, the distance from the front surface 4f of the flange portion 42 to the top surface, is, for example, 0.2 mm or more and 3 mm or less. The height H of the protrusion 6 may further be 0.2 mm or more and 2 mm or less.

[0056] Unlike the present embodiment, for example, it is also possible to provide a plurality of protrusions 6 on the disk portion 21 of the boss portion 2. When the blade set 3g has a plurality of protrusions 6 as in the present embodiment, it is easier to make the boss portion 2 smaller than when the boss portion 2 has a plurality of protrusions 6.

[0057] The multiple protrusions 6 are for adjusting the amount of imbalance of the fan 1a. The height of each protrusion 6 is set according to the amount of imbalance relative to the standard state. The standard state here refers to a state in which the fan 1a is molded under the condition that there are no protrusions 6 or that all of the protrusions 6 are the same size and height. The amount of imbalance is expressed by the product of the mass of the fan 1a and the deviation of the center of gravity from the center of rotation. The thickness of the portion in which the protrusions 6 are formed varies depending on the height of the protrusions 6. The greater the height of the protrusions 6, the thicker the portion in which the protrusions 6 are formed becomes, and therefore the heavier the portion in which the protrusions 6 are formed becomes. In the fan 1a of this example, the height of at least one of the multiple protrusions 6 is different so that the deviation of the center of gravity from the center of rotation is smaller than that in the standard state.

[0058] The farther the protrusion 6 is disposed from the center of the boss 2, i.e., the center of rotation, the easier it is to achieve the effect of reducing the deviation between the center of rotation and the center of gravity. This is because the greater the distance from the center of the boss 2 to the protrusion 6, the greater the displacement of the center of gravity due to the difference in weight caused by the height of the protrusion 6. When the protrusion 6 is provided at the tip of each blade 3 as in this example, the deviation of the center of gravity can be reduced even if the height of the protrusion 6 is smaller, compared to when the protrusion 6 is provided on the boss 2.

[0059] <Fan manufacturing method> A method for manufacturing a fan 1a according to embodiment 2 will be described with reference to Figures 13 and 14. The method for manufacturing the fan 1a comprises the first to third steps described above, as in embodiment 1. An auxiliary die 8a used when manufacturing the fan 1a of embodiment 2 has a different configuration from the auxiliary die 8 described in embodiment 1. The following description will focus on the differences from embodiment 1. Descriptions of configurations common to embodiment 1 will be omitted.

[0060] The auxiliary die 8a is attached to either the first die 71 or the second die 72. In this example, the auxiliary die 8a is attached to the second die 72. The auxiliary die 8a has a nested structure that is fitted into the second die 72. The auxiliary die 8a is fixed to the second die 72 by a bolt 85. The auxiliary die 8a is freely attachable to and detachable from the second die 72. The bolt 85 is disposed outside the cavity 70. A countersunk hole is provided on the surface of the auxiliary die 8a facing the first die 71 to accommodate the head of the bolt 85.

[0061] Similar to the auxiliary mold 8 described above, a plurality of auxiliary molds 8a are disposed in the portions of the cavity 70 where the set of blades 3g are molded. Specifically, as shown in Fig. 14, the auxiliary molds 8a are disposed in the portions where the flange portion 42 of the outer peripheral ring portion 4 is molded. The auxiliary molds 8a are disposed at positions corresponding to the tips of the blades 3, respectively.

[0062] At least one of the auxiliary dies 8a has a recess 82 on the surface that contacts the cavity 70. In this example, each auxiliary die 8a has a recess 82 on the surface that contacts the cavity 70. As shown in FIG. 14, the auxiliary die 8a in this example has a recess 82 on the surface that molds the front surface 4f of the flange portion 42. In this example, each auxiliary die 8a has one recess 82. The recess 82 is located approximately on the center line C of the blade 3. When the multiple auxiliary dies 8a are attached to the second mold 72, each of the recesses 82 is disposed at intervals from one another on a circumference concentric with the boss portion 2. The recesses 82 are disposed at equal intervals.

[0063] The recesses 82 are for forming the above-mentioned protrusions 6 on the blade group 3g. When the fan 1a is formed in the above-mentioned third step, the protrusions 6 corresponding to the recesses 82 are formed. In this example, a plurality of protrusions 6 are formed on the front surface 4f of the flange portion 42. The number of recesses 82 corresponds to the number of the above-mentioned protrusions 6. The number of recesses 82 in this example, that is, the number of auxiliary molds 8a, is 7, which is the same as the number of blades 3. Unlike this example, when the protrusions 6 are provided on the back surface 4b of the flange portion 42, the auxiliary mold 8a having the recesses 82 is attached to the first mold 71. By attaching a plurality of auxiliary molds 8a to the first mold 71, a plurality of protrusions 6 are formed on the back surface 4b of the flange portion 42.

[0064] The shape of the recess 82 corresponds to the shape of the protrusion 6 described above. The shape of the recess 82 in this example is a truncated pyramid. The recess 82 has a depth corresponding to the height of the protrusion 6 described above. The depth of the recess 82 is, for example, 0.2 mm or more and 3 mm or less. The depth of the recess 82 may further be 0.2 mm or more and 2 mm or less. The depth of the recess 82 can be selected as appropriate. The inner surface of the recess 82 in this example has an inclined surface that narrows from the opening toward the bottom. Since the inner surface of the recess 82 has an inclined surface, it is easy to remove the protrusion 6 from the recess 82 after the fan 1a is molded.

[0065] In the second step described above, at least one of the auxiliary dies 8a is replaced with an auxiliary die 8a having a different depth of the recess 82. Specifically, the auxiliary die 8a is replaced according to the amount of imbalance described above. For example, auxiliary dies 8a having the same depth of the recess 82 are attached to the second mold 72 to manufacture a fan in a standard state in which all the protrusions 6 have the same height. The amount of imbalance of the fan in the standard state is measured. From the measured amount of imbalance, the height of each protrusion 6 at which the amount of imbalance falls within a specified value is calculated. The depth of each recess 82 is determined based on the calculated height of each protrusion 6. An auxiliary die 8a having a recess 82 of the determined depth is attached to the second mold 72. If the determined depth of the recess 82 is the same as the depth of the recess 82 when the fan in the standard state is molded, the auxiliary die 8a does not need to be replaced. If the determined depth of the recess 82 is different from the depth of the recess 82 when the fan in the standard state is molded, the auxiliary die 8a is replaced.

[0066] The present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0067] In the above-described embodiment, a plurality of recesses 5 or a plurality of protrusions 6 are provided on the flange portion 42 of the outer peripheral ring portion 4 in the blade set 3g. The recesses 5 or protrusions 6 may be provided on the outer peripheral surface or the inner peripheral surface of the cylindrical portion 41. The recesses 5 or protrusions 6 may be provided on both the flange portion 42 and the cylindrical portion 41. The recesses 5 or protrusions 6 may be provided on the front or rear surface of the blade 3 in a region close to the tip.

[0068] The plurality of recesses 5 or the plurality of protrusions 6 are preferably provided in the outer peripheral region of the blade group 3g. The outer peripheral region of the blade group 3g is a region close to the tip of the blade 3. The outer peripheral region of the blade group 3g is a range from the outer periphery of the envelope circle of the blade group 3g to 25% or less of the radius of the envelope circle, further 20% or less, particularly 15% or less. In other words, the outer peripheral region is a range of 75% or more of the radius of the envelope circle of the blade group 3g, further 80% or more, particularly 85% or more. Even if the recesses 5 or protrusions 6 are smaller when the recesses 5 or protrusions 6 are provided closer to the outer periphery of the blade group 3g than when the recesses 5 or protrusions 6 are provided closer to the inner periphery, the amount of imbalance can be effectively adjusted. The envelope circle of the blade group 3g is a circle that constitutes the outer peripheral edge of the outer peripheral ring portion 4 when each blade 3 is only inside the outer peripheral ring portion 4. When the tip of each blade 3 protrudes outside the outer peripheral ring portion 4, it is an envelope circle of the outer peripheral ends of the multiple blades 3. When there is no outer peripheral ring portion 4, it is an envelope circle of the outer peripheral ends of the multiple blades 3. [Explanation of symbols]

[0069] 1,1a Fan 2 Boss 21 disk portion, 22 cylindrical portion 23 Shaft hole 25 Mounting bracket 3 feathers, 3g feather group 4 Outer ring 41 cylindrical portion, 42 flange portion 4b back, 4f front 5. Recess 50 Matching muscles 6 Convex 7. Mold 71 first mold, 72 second mold, 70 cavity 8,8a auxiliary type 81 Convex 82 Recess 85 volts 9 Extrusion Rod 95 volts 100 Motor C center line φ diameter L length, W width, H height Er rectangle V1, V2 vertical lines, H1, H2 horizontal lines

Claims

1. a boss portion to which a rotating shaft of a motor is fixed; a blade group consisting of a plurality of blades extending radially from the boss portion, The set of blades has a concave portion or a convex portion, the recess or the protrusion is disposed on a circumference concentric with the boss portion, The surface of the recess or the surface of the protrusion has a molding surface. fan.

2. The set of blades has a joint line formed by a parting line of a mold, The joints are arranged at intervals on a circumference concentric with the boss portion, The fan according to claim 1 , wherein the recessed portion or the protruding portion is located between adjacent ones of the joint grooves.

3. 1. A method for manufacturing a fan including a boss portion to which a rotating shaft of a motor is fixed, and a blade group including a plurality of blades extending radially from the boss portion, comprising: A step of preparing a mold including a first mold and a second mold that is combined with the first mold; attaching a plurality of auxiliary molds to one of the first mold and the second mold; and a step of injecting molten resin into a cavity formed between the first mold and the second mold to integrally mold the boss portion and the set of blades. each of the auxiliary dies is disposed in a portion of the cavity where the blade set is molded; At least one of the plurality of auxiliary dies has a convex portion or a concave portion on a surface in contact with the cavity, each of the protruding portions or the recessed portions is disposed on a circumference concentric with the boss portion in a state in which the plurality of auxiliary dies are attached; In the step of attaching the plurality of auxiliary molds, at least one of the plurality of auxiliary molds is replaced with an auxiliary mold having a different height of the convex portion or a different depth of the concave portion. How the fan is manufactured.

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