Fluid pump impeller

Abstract

An impeller (1) of a fluid pump according to the present invention comprises: an impeller body (10) having a first shroud (20) and a plurality of vanes (30) provided on the first shroud (20); and a second shroud (50) bonded to the impeller body (10) and arranged opposed to the first shroud (20) in a central axis direction across the plurality of vanes (30). The first shroud (20) has a boss part (40) protruding in the central axis direction. The second shroud (50) has a central hole (53) through which the boss part (40) is inserted in the central axis direction. By a combination of a recessed first groove part (41) formed on an outer peripheral surface of the boss part (40) and a recessed second groove part (54) formed on an inner peripheral surface of the central hole (53), a balance hole (B) penetrating in the central axis direction is constituted.

Description

[Technical Field]

[0001] The present invention relates to an impeller used in a fluid pump such as a water pump. [Background technology]

[0002] Conventionally, centrifugal fluid pumps have been widely known, which rotate an impeller formed with multiple blades inside a pump case to pressurize fluid drawn in through a suction port and send it out through a discharge port. Impellers include open impellers in which a shroud is provided only on one end of the blades, as well as closed impellers in which shrouds are provided on both ends of the blades so as to sandwich them from both sides (see, for example, Patent Document 1). Closed impellers have a higher pump efficiency than open impellers because a closed space is formed inside the impeller by both shrouds, preventing fluid from leaking out.

[0003] This closed impeller (hereinafter simply referred to as the impeller) is composed of an upper shroud, a lower shroud, and multiple blades disposed between the two shrouds. In a pump case in which the impeller is disposed, the pressure below the impeller is generally higher than the pressure above the impeller, resulting in an axial load (thrust load) acting on the impeller. Therefore, the lower shroud is provided with a circular balance hole penetrating the axial direction. This balance hole allows fluid to escape from the high-pressure side (the back surface of the lower shroud) to the low-pressure side (the front surface of the lower shroud). This reduces the axial pressure difference (thrust load) between the front and back surfaces of the lower shroud, preventing the impeller from floating up and interfering with the inner circumferential surface of the pump case. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2016 / 030928 Summary of the Invention [Problem to be solved by the invention]

[0005] However, because a closed impeller has a structure in which both ends of the blades are connected by upper and lower shrouds (disk portions), when it is integrally molded as an injection molded product, for example, so-called undercut portions are generated when the product is removed from a mold, which can make mass production difficult. For this reason, in recent years, a technology has been put into practical use to form a closed impeller by molding the upper shroud and the lower shroud separately and joining the two shrouds via multiple blades.

[0006] When the lower shroud is injection molded, a core pin is placed in the cavity to form a circular balance hole (through hole). The molten resin flowing inside the cavity splits into two flows around the core pin before merging. At this junction, the two flows (flows of molten resin) tend to form a cold shut, which is a boundary between the two flows that do not fuse. During impeller operation, cracks can form at these cold shuts, which can eventually grow into larger cracks and cause damage to the impeller.

[0007] The present invention has been made in view of the above-mentioned problems, and has an object to provide an impeller for a fluid pump that can prevent damage originating from a cold shut during injection molding. [Means for solving the problem]

[0008] In order to solve the above problem, the impeller of a fluid pump according to the present invention comprises an impeller body having a first shroud and a plurality of blades provided on the first shroud, and a second shroud joined to the impeller body and arranged opposite the first shroud in the central axis direction with the plurality of blades sandwiched between them, and is an impeller of a fluid pump that is driven to rotate around a central axis, wherein the first shroud has a boss portion that protrudes in the central axis direction, and the second shroud has a central hole into which the boss portion is inserted in the central axis direction, and a balance hole that penetrates in the central axis direction is formed by a combination of a first concave groove portion formed on the outer peripheral surface of the boss portion and a second concave groove portion formed on the inner peripheral surface of the central hole.

[0009] In addition, in the impeller of the fluid pump according to the present invention, it is preferable that the blades are integrally formed and connected to the outer periphery of the boss portion, and the first groove portion is formed between adjacent blades on the outer periphery of the boss portion.

[0010] In the impeller of the fluid pump according to the present invention, it is preferable that a balance hole having a circular cross section is formed by combining the first groove portion having a semicircular cross section and the second groove portion having a semicircular cross section.

[0011] In the impeller of the fluid pump according to the present invention, it is preferable that a drive shaft for rotating the impeller is coupled to the boss portion, and the impeller body is configured to be rotatable integrally with the drive shaft.

[0012] Furthermore, in the impeller of the fluid pump according to the present invention, it is preferable that the blade has a welding abutment on the tip side facing the second shroud in the central axis direction, the second shroud has a long groove into which the tip side of the blade is received, a welding receiving portion that abuts and joins with the welding abutment is formed on the inner surface of one side of the long groove, and a convex guide rib that protrudes into the long groove and presses the blade toward the one side is provided on the inner surface of the other side of the long groove. [Effects of the Invention]

[0013] In the impeller of the fluid pump according to the present invention, the balance hole has a divided structure and is formed by combining a first groove portion formed in the shroud body with a second groove portion formed in the second shroud. This makes it possible to form the balance hole without using a core pin during injection molding, and there is no risk of cold shut being formed around the balance hole. This makes it possible to prevent the cold shut from causing cracks in the impeller and resulting in damage.

[0014] Furthermore, according to the impeller of the fluid pump of the present invention, the boss portion to which the drive shaft of the fluid pump is connected is integrally molded on the impeller body side, so that even if an unforeseen event occurs in which the impeller body (blades) and the second shroud become separated and come apart while the impeller is operating, the impeller body (blades) can rotate integrally with the drive shaft and discharge a predetermined amount of fluid, thereby realizing a fail-safe function that prevents the fluid supply from being completely stopped.

[0015] Furthermore, with the impeller of the fluid pump according to the present invention, when the welding contact portion and the welding receiving portion are welded together, the convex guide rib formed in the long groove interferes with and presses against the blade, thereby reducing the contact area between the outer surface on the other side of the blade and the inner surface on the other side of the long groove, thereby making it possible to suppress the occurrence of burrs due to abnormal contact between the two. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 2 is a plan view showing the impeller according to the embodiment. [Figure 2] FIG. 2 is a bottom view showing the impeller. [Figure 3] FIG. 2 is a side view (partial cross-sectional view) showing the impeller. [Figure 4] FIG. 2 is an exploded perspective view of the impeller (as viewed from above). [Figure 5] FIG. 2 is an exploded perspective view of the impeller (as viewed from below). [Figure 6]FIG. 2 is a plan view showing an impeller body (excluding a bushing) of the impeller. [Figure 7] FIG. 4 is a plan view showing a second shroud of the impeller. [Figure 8] FIG. 3 is an enlarged view showing a main part of the second shroud. [Figure 9] FIG. 3 is a perspective view showing a main part of the second shroud. [Figure 10] 5A to 5C are diagrams for explaining a welding process for the impeller. [Figure 11] FIG. 4 is a view showing the blades of the impeller body and the long grooves of the second shroud. [Figure 12] 10 is a view showing a welded state between the weld contact portion of the blade and the weld receiving portion of the long groove. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0017] A preferred embodiment of the present invention will now be described with reference to the drawings. An impeller 1 according to one embodiment of the present invention is used, for example, in a water pump disposed in a cooling water circulation path of an engine to forcibly circulate cooling water. First, the overall configuration of the impeller 1 of this embodiment will be described with reference to FIGS. 1 to 12. For ease of explanation, the upper side in the axial direction (central axis direction) will be referred to as the "one end side" and the lower side in the axial direction (central axis direction) will be referred to as the "other end side" based on the installation posture of the impeller 1 shown in FIG. 3. Furthermore, hatching of cross-sectional portions has been omitted in FIGS. 3, 11, 12, etc., for ease of viewing. Furthermore, in each figure, the rotational direction of the impeller 1 is indicated by an arrow "X" as appropriate.

[0018] The impeller 1 is a so-called closed impeller that includes an impeller body 10 formed by a first shroud (upper shroud) 20 and a plurality of blades 30 integrally formed therewith, and a second shroud (lower shroud) 50 joined to the impeller body 10. The impeller 1 rotates in synchronization with the drive shaft (not shown) of the water pump, draws in cooling water from an intake port 23 formed in the impeller body 10, and discharges the cooling water from an outlet port 39, which is the space between the blades 30.

[0019] The impeller body 10 is formed as a one-piece molded product made of resin (preferably PPS resin), and is configured to include a first shroud 20, a plurality of blades 30, and a boss 40.

[0020] The first shroud 20 is formed in a truncated cone shape (approximately umbrella-shaped) whose diameter increases from one end to the other end in the axial direction. A front surface 21 of the first shroud 20 faces the inner surface of a pump case (not shown) that houses the impeller 1. A circular inlet (eye) 23 for introducing cooling water into the impeller 1 is formed axially through the center of the first shroud 20. A plurality of blades 30 (six blades 30 in this embodiment) are formed at equal intervals in the circumferential direction on a back surface 22 of the first shroud 20. A cylindrical boss 40 is integrally formed on the back surface 22 of the first shroud 20, with each blade 30 sandwiched between them. In this embodiment, the tapered (approximately umbrella-shaped) first shroud 20 allows the cooling water (cooling water introduced from the inlet 23) to flow smoothly along the back surface 22 of the first shroud 20.

[0021] Each blade 30 is formed in a plate shape curved along a centerline formed by a continuous series of convex and concave curves. The blades 30 are arranged radially around the axis, and the circumferential spacing between adjacent blades 30 gradually increases from the radially inner side to the radially outer side (i.e., toward the discharge direction of the cooling water). The blades 30 are also inclined so that their height gradually decreases from the radially inner side to the radially outer side in accordance with the tapered shape of the first shroud 20. This allows the cross-sectional area of the opening on the radially inner side (intake side) between adjacent blades 30 to be set approximately equal to the cross-sectional area of the opening on the radially outer side (discharge side), thereby making the internal flow velocity uniform.

[0022] Each blade 30 has a tip portion (blade tip portion) 31 formed on the other end side of the blade 30, a front outer surface (front outer surface in the rotation direction) 32 connected to the tip portion 31 and formed on the front side in the rotation direction, and a rear outer surface (rear outer surface in the rotation direction) 35 connected to the tip portion 31 and formed on the rear side in the rotation direction. Of two adjacent blades 30, a discharge path (discharge port 39) of cooling water is formed between the front outer surface 32 of one blade 30 and the rear outer surface 35 of the other blade 30. The tip portion 31 side of each blade 30 is formed so as to be receivable in a long groove 60 recessed on one end side of the second shroud 50.

[0023] The front outer surface 32 includes, in order from the tip end 31 side, a first outer surface 32a, a second outer surface 32b, and a third outer surface 32c. The first outer surface 32a and the rear outer surface 35 are each formed as an inclined surface with a gradient of approximately 2 degrees as they approach each other from one end side to the other end side in the axial direction. That is, the tip side of the blade 30 is slightly tapered from one end side to the other end side in a cross-sectional view. The corner between the tip end 31 of the blade 30 and the first outer surface 32a (the corner on the front side in the rotation direction) is configured as a portion (welding contact portion 33) to be welded to the second shroud 50. The second outer surface 32b extends in a direction approximately perpendicular to the first outer surface 32a and serves as a cover surface (burr outflow prevention surface) 34 for preventing outflow of burrs (excess molten resin) generated during welding.

[0024] The boss 40 is provided on the axis of the impeller body 10 and is a portion to which the aforementioned drive shaft (not shown) is coupled. The boss 40 is formed in a cylindrical shape extending toward the other end in the axis direction and is configured to be able to fit into a central hole 53 opened in the second shroud 50. A plurality of first grooves 41 penetrating in the axial direction are formed on the outer peripheral surface of the boss 40 at equal intervals in the circumferential direction. The first grooves 41 are formed in a semicircular cross section that is open radially outward. A bushing 42, which is a metal insert part, is attached to the axis of the boss 40.

[0025] The bushing (insert) 42 is made of a metal such as carbon steel or brass, and is embedded in the boss 40 of the first shroud 20 by insert molding. The bushing 42 has a shaft hole 42a into which the aforementioned drive shaft (not shown) is press-fitted, and is coupled to the drive shaft so as to be rotatable integrally with the drive shaft. The bushing 42 also has a detent portion 42b that bulges outward and has a polygonal cross-section (hexagonal cross-section in the illustrated example) with multiple corners 42c. The detent portion 42b prevents the bushing 42 from spinning freely relative to the boss 40 by virtue of the action of each corner 42c.

[0026] The second shroud 50 is a one-piece molded product made of resin (preferably PPS resin). The second shroud 50 is formed in a disk shape having approximately the same outer diameter as the first shroud 20. A circular center hole (combination center hole) 53 into which the boss 40 of the first shroud 20 is fitted is formed penetrating the second shroud 50 in the axial direction. Further, long grooves 60 extending radially from the center hole 53 are recessed on the front surface 51 side of the second shroud 50 at positions aligned with each blade 30. An ultrasonic horn H is brought into contact with a back surface 52 of the second shroud 50 during welding (see FIG. 10).

[0027] The long groove 60 is open at one end in the axial direction facing the impeller body 10, and is formed to be able to receive the tip side of the blade 30. The long groove 60 has a groove bottom 61 that faces the tip 31 of the blade 30 in the axial direction, a front inner surface (front inner surface in the rotation direction) 62 that is connected to the groove bottom 61 and formed on the front side in the rotation direction, and a rear inner surface (rear inner surface in the rotation direction) 65 that is connected to the groove bottom 61 and formed on the rear side in the rotation direction.

[0028] The front inner surface 62 has, in order from the groove bottom 61 side, a first inner surface 62a, a second inner surface 62b, and a third inner surface 62c. The first inner surface 62a is an inclined surface with a gradient of approximately 2 degrees in a direction away from the rear inner surface 65 from the other end side to one end side in the axial direction. The third inner surface 62c is an inclined surface or a vertical surface extending approximately parallel to the first inner surface 62a, and is further away from the rear inner surface 65 opposing the rotation direction than the first inner surface 62a. The second inner surface 62b connects between the first inner surface 62a and the third inner surface 62c, and is an inclined surface with a slight gradient (downward gradient) in a direction approaching the groove bottom 61 from the third inner surface 62c side toward the first inner surface 62a side. A corner (step portion of long groove 60) between first inner surface 62a and second inner surface 62b is configured as a portion (weld receiving portion 63) to be welded to weld contact portion 33 of blade 30. In addition, second inner surface 62b and third inner surface 62c form burr storage portion (space for storing burrs) 64 between themselves and second outer surface 32b of blade 30 (see FIG. 12).

[0029] The rear inner surface 65 is an inclined surface having a gradient of approximately 2 degrees in a direction away from the front inner surface 62 from the other end side to one end side in the axial direction. This rear inner surface 65 is formed as a guide surface that rubs against and guides the rear outer surface 35 of the blade 30 when welding to the blade 30. A plurality of triangular prism-shaped (wedge-shaped) guide ribs 66 are formed on the rear inner surface 65, each convex toward the front inner surface 62. The guide ribs 66 protrude into the long groove 60 (protrude in a direction approximately perpendicular to the insertion direction of the blade 30), and when the tip side of the blade 30 is inserted into the long groove 60, they come into contact with the rear outer surface 35 of the blade 30 and press the blade 30 toward the front inner surface 62 (weld-receiving portion 63). That is, the guide rib 66 reduces the contact between the rear outer surface 35 of the blade 30 and the rear inner surface 65 of the long groove 60 (reduces the contact area therebetween).

[0030] A plurality of second grooves 54 are formed at equal intervals in the circumferential direction on the inner peripheral surface of the central hole 53 of the second shroud 50, penetrating in the axial direction. The second grooves 54 have a semicircular cross-sectional shape that opens radially inward. The second grooves 54, which have a semicircular cross-sectional shape, are combined with the first grooves 41, which also have a semicircular cross-sectional shape, to form balance holes B, which have a circular cross-sectional shape and penetrate in the axial direction. The balance holes B are located between adjacent blades 30 near the intake ports 23 (on the side closer to the axis) and are connected to the cooling water discharge passages (discharge ports 39) formed between the blades 30. This balance hole B connects the front and back surfaces of the second shroud 50 (inside and outside the impeller 1), allowing cooling water to escape from the back surface 52 side (high-pressure side) of the second shroud 50 to the front surface 51 side (low-pressure side), thereby adjusting the pressure difference inside and outside the impeller 1 (pressure difference between the front and back surfaces of the second shroud 50).

[0031] Next, a method for manufacturing the impeller 1 of this embodiment will be described mainly with reference to Figures 10 to 12. In Figures 11 and 12, the positional relationship between the blades 30 and the second shroud 50 is shown upside down (upside down from Figure 10) to make it easier to understand the welding process.

[0032] In this embodiment, the impeller 1 is manufactured by joining an impeller body 10 and a second shroud 50, both made of resin, by ultrasonic welding.

[0033] To manufacture such an impeller 1, first, the impeller body 10 and the second shroud 50 are formed separately. The impeller body 10 is injection molded using a synthetic resin such as PPS resin. A metal bushing 42 is insert molded into the impeller body 10. Similarly, the second shroud 50 is injection molded using a synthetic resin such as PPS resin. Both the impeller body 10 and the second shroud 50 can be molded using an ordinary mold consisting of a fixed mold and a movable mold, without using a core pin, slide core, or the like.

[0034] Next, the impeller body 10 and the second shroud 50 are attached to a welding jig (not shown). The impeller body 10 and the second shroud 50 are attached to this welding jig in a vertically overlapping state, with the impeller body 10 placed on the lower side and the second shroud 50 placed on the upper side. At this time, the tip sides of the blades 30 are inserted into the long grooves 60 of the second shroud 50. Furthermore, when the impeller body 10 and the second shroud 50 are attached to the welding jig, the axial centers of the impeller body 10 and the second shroud 50 are aligned and oriented in the vertical direction.

[0035] Next, the ultrasonic horn H of the welding machine is brought into contact with the back surface of the second shroud 50, and ultrasonic vibrations and pressure are simultaneously applied to the impeller body 10 and the second shroud 50, which are overlapping in the vertical direction, thereby welding the impeller body 10 and the second shroud 50. Specifically, the tip portions 31 of the blades 30 of the impeller body 10 are received in the long grooves 60 of the second shroud 50, and with the weld abutting portions 33 of the blades 30 abutting the weld receiving portions 63 of the long grooves 60, ultrasonic vibrations are applied in the same direction while pressure is applied downward.

[0036] Here, when the second shroud 50 is pressed downward, the rear outer surface 35 of the blade 30 slides along the rear inner surface 65 of the long groove 60, and the rear outer surface 35 and the rear inner surface 65 act as guide surfaces when the weld abutment portion 33 is pressed into the weld receiving portion 63. At this time, a convex guide rib 66 is provided on the rear inner surface 65, and this guide rib 66 comes into contact with the rear outer surface 35 to press the blade 30 toward the weld receiving portion 63 (front inner surface 62). As a result, the front outer surface 32 (weld abutment 33) is pressed against the front inner surface 62 (weld receiving portion 63), which promotes welding between the weld abutment 33 and the weld receiving portion 63. Furthermore, the rear outer surface 35 is spaced from the rear inner surface 65, reducing the contact area between the rear outer surface 35 of the blade 30 and the rear inner surface 65 of the long groove 60. This reduces the amount of burrs that may result from contact between the two. The guide rib 66 is worn away by contact (friction) with the rear outer surface 35 of the blade 30 and is eventually made substantially flush with the rear inner surface 65. The ultrasonic vibrations from the ultrasonic horn H are propagated intensively to the contact portion between the weld abutment 33 and the weld receiving portion 63, generating frictional heat at the contact portion, which melts the contact portion and welds the impeller body 10 and the second shroud 50 together.

[0037] At this time, a shear joint is formed by the weld abutting portion 33 and the weld receiving portion 63, ensuring a wide welding area and improving the joining strength between the impeller body 10 and the second shroud 50. Furthermore, in a shear joint, only the actually molten surfaces of the weld abutting portion 33 and the weld receiving portion 63 are in contact with each other, making it difficult for air to be entrained during welding and preventing the occurrence of defects such as voids.

[0038] Burrs generated by welding between the weld contact portion 33 and the weld receiving portion 63 are covered by the second outer surface 32b (confined in the burr storage portion 64) and are prevented from flowing out of the long groove 60. This prevents burrs from entering the rotating portion of the impeller 1 and adversely affecting pump performance, and also eliminates the need for deburring work in the manufacturing process of the impeller 1.

[0039] The impeller 1 is completed by joining the impeller body 10 to the second shroud 50 in this manner. When the impeller body 10 and the second shroud 50 are integrated, a through hole with a circular cross section is formed by the combination of the first groove portion 41 of the impeller body 10 and the second groove portion 54 of the second shroud 50, and this through hole functions as a balance hole B.

[0040] As described above, according to the impeller 1 of this embodiment, each balance hole B has a divided structure, and the balance hole B having a circular cross section is formed by combining the first groove portion 41 having a semicircular cross section formed in the shroud body 10 with the second groove portion 54 having a semicircular cross section formed in the second shroud 50. This makes it possible to form the balance hole B without using a core pin during injection molding, and there is no risk of cold shut being formed around the balance hole B. This makes it possible to prevent the cold shut from causing cracks in the impeller 1 and resulting in damage.

[0041] Furthermore, according to the impeller 1 of this embodiment, the boss 40 to which the water pump drive shaft is connected is integrally molded on the impeller body 10 side, so that even if an unforeseen event occurs in which the connection between the impeller body 10 (vanes 30) and the second shroud 50 comes loose and separates while the impeller 1 is operating, the impeller body 10 (vanes 30) can rotate integrally with the drive shaft and discharge a predetermined amount of cooling water, thereby realizing a fail-safe function that prevents the supply of cooling water from being completely stopped.

[0042] Furthermore, according to the impeller 1 of this embodiment, when the welding contact portion 33 and the welding receiving portion 63 are welded together, the convex guide rib 66 formed in the long groove 60 interferes with and presses against the blade 30, thereby reducing the contact area between the rear outer surface 35 of the blade 30 and the rear inner surface 65 of the long groove 60, making it possible to suppress the generation of burrs due to abnormal contact between the two.

[0043] The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit of the present invention.

[0044] In the above embodiment, a water pump has been described as an example of a fluid pump, but the present invention is not limited to this configuration and may be applied to other fluid pumps, such as a fuel pump, an oil pump, a chemical pump, or an air pump. [Explanation of symbols]

[0045] 1 impeller 10 Impeller body 20 First Shroud 23 Intake port 30 Feathers 31 Tip 32 Front outer surface 33 Welding area 35 Posterior outer surface 39 Discharge port 40 Boss 41 First groove 42 Bush 50 Second Shroud 53 Center hole 54 Second groove 60 Nagamichi 61 Groove bottom 62 Front inner surface 63 Weld receiver 65 Back inner surface 66 Guide rib B Balance Hole H ultrasonic horn X rotation direction

Claims

1. An impeller for a fluid pump that is rotationally driven about a central axis, the impeller comprising: an impeller body having a first shroud and a plurality of blades provided on the first shroud; and a second shroud that is joined to the impeller body and disposed opposite the first shroud in a central axis direction with the plurality of blades interposed therebetween, the first shroud has a boss portion formed to protrude in the central axis direction, the second shroud has a central hole into which the boss portion is inserted in a central axis direction, A fluid pump impeller characterized in that a balance hole penetrating in the central axis direction is formed by the combination of a concave first groove portion formed on the outer peripheral surface of the boss portion and a concave second groove portion formed on the inner peripheral surface of the central hole.

2. The blade is integrally formed and connected to the outer periphery of the boss portion, 2. The impeller for a fluid pump according to claim 1, wherein the first groove portion is formed between adjacent blades on the outer peripheral surface of the boss portion.

3. 3. The impeller of claim 1, wherein a balance hole having a circular cross section is formed by combining the first groove portion having a semicircular cross section and the second groove portion having a semicircular cross section.

4. A drive shaft for rotating the impeller is coupled to the boss portion, 4. The impeller for a fluid pump according to claim 1, wherein the impeller body is configured to be rotatable integrally with the drive shaft.

5. the blade has a welding abutment portion on a tip side facing the second shroud in the central axis direction, the second shroud has a long groove into which a tip side of the blade is received, a weld receiving portion that abuts against and is joined to the weld abutting portion is formed on an inner surface on one side of the long groove; An impeller for a fluid pump as described in any one of claims 1 to 4, characterized in that a convex guide rib is provided on the inner surface of the other side of the long groove, protruding into the long groove and pressing the blades toward the one side.

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