screw pump

Abstract

To provide a screw pump having a screw that reduces manufacturing costs and wear. [Solution] The screw pump 1 comprises a plurality of screws 10, 20 that rotate having helical teeth 12a, 22a, and a case that houses the plurality of screws 10, 20. The plurality of screws 10, 20 mesh with each other and transfer liquid by rotating simultaneously. At least screw 10 of the plurality of screws 10, 20 is a first screw having a shaft 14 and a resin screw rotor 12 integrated with the shaft 14. The first ends 14a, 24a of the ends of the shafts 14, 24 of the screws 10, 20 protrude from the resin screw rotors 12, 22, and the first ends 14a, 24a are configured to be supported by the case. The shafts 14, 24 are hollow shafts having hollow sections 14g, 24g.

Description

Technical Field

[0001] The present disclosure relates to a screw pump.

Background Art

[0002] Conventionally, a two-axis screw pump has been known. The two-axis screw pump has a drive screw that is rotationally driven by a drive source, and a driven screw that meshes with the drive screw and is rotated by the rotation of the drive screw. The screw pump can transfer materials with viscosities ranging from low to high as the transferred material.

[0003] Patent Document 1 discloses a two-axis screw pump. In the screw pump disclosed in Patent Document 1, the drive screw (male screw in Patent Document 1) and the driven screw (female screw in Patent Document 1) are made of an iron-based metal material.

[0004] Patent Document 2 discloses a two-axis screw pump (fuel pump in Patent Document 1). In the screw pump disclosed in Patent Document 2, the drive screw and the motor shaft of the drive motor are connected via a clutch element that is an independent component. Thereby, by manufacturing one long drive screw and cutting the drive screw according to the size (pump output) of the screw pump and attaching a clutch element to the end, the driving force of the drive motor can be transmitted to the drive screw. Thus, it is not necessary to manufacture separate drive screws according to the size of the screw pump, and one drive screw can be used to correspond to screw pumps of various sizes.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] To reduce the manufacturing cost of screw pumps, it is conceivable to use resin, which is a less expensive material than metal. In the screw pump disclosed in Patent Document 1, both the driving screw and the driven screw are manufactured from iron-based metal materials, so there is room for improvement in order to reduce manufacturing costs.

[0007] However, if both the drive screw and the driven screw (hereinafter, when referring to both the drive screw and the driven screw collectively, simply referred to as the screw) are manufactured from resin, there is a risk of voids forming inside the screw during the screw molding process. Furthermore, if warping or distortion occurs in the screw due to variations in the cooling rate of the resin during cooling, there is a risk that the screw may come into contact with the screw housing case during rotation and wear down, indicating room for improvement.

[0008] Therefore, there is a need for a screw pump that has a screw that reduces manufacturing costs and wear. [Means for solving the problem]

[0009] One embodiment of the screw pump according to the present disclosure comprises a plurality of screws having helical teeth having a predetermined pitch and rotating about their respective rotational axes, and a case housing the plurality of screws, wherein the plurality of screws are arranged in a meshed state with each other and rotate simultaneously to transfer liquid, and at least one of the plurality of screws is a first screw having a shaft arranged coaxially with the rotational axis and a resin screw rotor made of resin integrated with the shaft, wherein the first end of the shaft of the first screw, which is located on the opposite side of the direction of liquid transfer, protrudes from the resin screw rotor, and the first end protruding from the resin screw rotor is supported by the case, and the shaft is a hollow shaft having a hollow portion.

[0010] The screw pump of this embodiment is configured so that thrust loads can be received at the ends of the shafts of multiple screws. Therefore, even without using dedicated bearings to receive thrust loads, the frictional force that the ends of the shafts exert on the case when the multiple screws rotate can be reduced, thereby suppressing screw wear. In addition, since the first screw has a resin screw rotor, manufacturing costs can be reduced compared to when the entire screw is made of metal. Furthermore, since the shaft has a hollow section, the shaft can be made lighter. [Brief explanation of the drawing]

[0011] [Figure 1] This is a partial cross-sectional view showing a screw pump according to the first embodiment. [Figure 2] This is a cross-sectional view showing the drive shaft of the drive screw. [Figure 3] This is a disassembled cross-sectional view of a screw pump. [Figure 4] This is a perspective view illustrating the method for removing a screw from a mold. [Figure 5] This is a partial cross-sectional view showing a screw pump according to the second embodiment. [Figure 6] This is a partially enlarged cross-sectional view showing the driving screw and driven screw of a screw pump according to the third embodiment. [Figure 7] This is a partially enlarged cross-sectional view showing a screw pump according to the fourth embodiment. [Figure 8] This is a partially enlarged cross-sectional view showing a screw pump according to the first modified example of the fourth embodiment. [Figure 9] This is a partially enlarged cross-sectional view showing a screw pump according to a second modified example of the fourth embodiment. [Modes for carrying out the invention]

[0012] The embodiments of the screw pump according to this disclosure will be described in detail below with reference to the drawings. The embodiments described below are illustrative examples for illustrating the screw pump, and the screw pump of this disclosure is not limited to these embodiments. Therefore, the screw pump according to this disclosure can be implemented in various forms without departing from its essence.

[0013] [First Embodiment] [Screw pump configuration] As shown in Figures 1 to 3, the screw pump 1 of the first embodiment is a twin-screw pump having a drive screw 10 (an example of a screw) and a driven screw 20 (an example of a screw). The screw pump 1 is used to transfer (pump) cooling water (an example of a liquid), such as long-life coolant (LLC), for cooling automobile engines, etc. The screw pump 1 consists of a drive screw 10, a driven screw 20, a case 30, and a drive source 40. The drive screw 10 and the driven screw 20 are housed in the case 30. The drive source 40 is partly located outside the case 30 and transmits rotational driving force to the drive screw 10.

[0014] The drive screw 10 is a screw that rotates when the rotational driving force generated by the drive source 40 is transmitted. The drive screw 10 is composed of a drive rotor 12 (an example of a resin screw rotor) and a drive shaft 14 (an example of a shaft and a metal shaft). The drive rotor 12 and the drive shaft 14 are integrated. The drive rotor 12 is made of a low moisture-absorbing resin such as polyketone (POK) or polyacetal (POM). The drive shaft 14 is made of an iron-based metal material such as carbon steel. That is, the drive screw 10 of the present embodiment is a composite material screw (an example of a first screw) composed of a resin-made drive rotor 12 and a metal-made drive shaft 14.

[0015] The drive screw 10 is formed by insert molding the drive rotor 12 so as to be coaxial with the rotation axis X of the drive shaft 14. The drive rotor 12 has spiral teeth 12a having a predetermined pitch P formed in a spiral shape. The spiral teeth 12a of the drive rotor 12 are composed of three threads.

[0016] In at least a part of the portion of the drive shaft 14 covered by the drive rotor 12, a recess 14c or a protrusion 14d is formed on the outer peripheral surface. Specific examples of the recess 14c are the D cut shown in Fig. 2(a) and a plurality of concave grooves shown in Fig. 2(b). A specific example of the protrusion 14d is a convex portion protruding in the radially outward direction from the outer peripheral surface of the drive shaft 14 shown in Fig. 2(c). The recess 14c and the protrusion 14d have a predetermined length along the rotation axis X. By forming the recess 14c and the protrusion 14d on the drive shaft 14, the drive shaft 14 and the drive rotor 12 rotate integrally.

[0017] Both the first end portion 14a (an example of an end portion) in the direction along the rotation axis X of the drive shaft 14 of the drive screw 10 and the second end portion 14b (an example of an end portion) on the side opposite to the first end portion 14a protrude from the drive rotor 12.

[0018] The driven screw 20 is a screw that rotates along with the rotation of the driving screw 10. That is, the driving screw 10 and the driven screw 20 rotate simultaneously. The driven screw 20 includes a driven rotor 22 (an example of a resin screw rotor) and a driven shaft 24 (an example of a shaft and a metal shaft). The driven rotor 22 and the driven shaft 24 are integrated. The same material as that of the driving rotor 12 and the driving shaft 14 is used for the driven rotor 22 and the driven shaft 24. That is, the driven screw 20 of the present embodiment is also a composite material screw (an example of the first screw).

[0019] The driven screw 20 is formed by insert molding the driven rotor 22 so as to be coaxial with the rotation axis Y of the driven shaft 24. The driven rotor 22 has helical teeth 22a formed in a helical shape opposite to the helical direction of the helical teeth 12a of the driving rotor 12. The helical teeth 22a have the same predetermined pitch P as the helical teeth 12a of the driving rotor 12. The helical teeth 22a of the driven rotor 22 are composed of two threads.

[0020] At least a part of the portion of the driven shaft 24 covered by the driven rotor 22 has a concave portion 24c or a convex portion 24d formed on the outer peripheral surface, similar to the driving shaft 14 (see FIG. 2). Although FIG. 2 shows the cross sections of the driving rotor 12 and the driving shaft 14, the driven shaft 24 also has the same cross-sectional shape.

[0021] A first end portion 24a (an example of an end portion) and a second end portion 24b (an example of an end portion) on the side opposite to the first end portion 24a in the direction along the rotation axis Y of the driven shaft 24 of the driven screw 20 both protrude from the driven rotor 22.

[0022] The case 30 includes a lid portion 32, a main body portion 34, and a delivery portion 36. The main body portion 34 has a cylindrical shape made of metal such as an aluminum alloy or resin, and houses the driving screw 10 and the driven screw 20 in an internal space. At this time, the driving screw 10 and the driven screw 20 are arranged such that the helical teeth 12a and the helical teeth 22a mesh with each other.

[0023] The lid portion 32 has a plate-like shape made of metal such as aluminum alloy, and is joined to one end of the cylindrical main body portion 34 by adhesive or other means, thereby sealing one end of the main body portion 34. An O-ring (not shown) is placed at the joint between the main body portion 34 and the lid portion 32, thereby preventing cooling water that has flowed into the main body portion 34 from leaking out of the joint.

[0024] An inlet 32a, which is a through-hole for allowing cooling water to flow from the outside into the internal space of the main body 34, is formed in the center of the lid 32. The inner surface 32b of the lid 32 faces the drive screw 10 and the driven screw 20. The first end 14a of the drive shaft 14 of the drive screw 10 and the first end 24a of the driven shaft 24 of the driven screw 20 are supported by the inner surface 32b of the lid 32. In this embodiment, "supported" is a concept that includes both cases in which the first ends 14a and 24a are in contact with the inner surface 32b of the lid 32 and cases in which there is a small gap between them. When the first end 14a and the first end 24a are supported by the inner surface 32b, one of the following is possible: (1) both the first end 14a and the first end 24a are in contact with the inner surface 32b of the lid 32; (2) both the first end 14a and the first end 24a have a gap between them; or (3) one of the first end 14a and the first end 24a is in contact with the inner surface 32b of the lid 32 and the other has a small gap between them.

[0025] The discharge section 36 has a cylindrical shape made of metal such as aluminum alloy, and a discharge port 36a extends from its side for discharging cooling water to the outside. The discharge section 36 is joined to the main body 34 at the end opposite to the lid 32. Similar to the lid 32, an O-ring (not shown) is placed at the joint between the main body 34 and the discharge section 36, thereby preventing cooling water that has flowed into the main body 34 from leaking out at the joint. On the side of the discharge section 36 opposite to the main body 34, the drive motor 42 of the drive source 40 is located, sealing the end of the discharge section 36. A sealant (not shown) is placed at the joint between the drive motor 42 and the discharge section 36. This prevents cooling water circulating in the internal space of the discharge section 36 from leaking out at the joint. Furthermore, the internal space of the discharge section 36 is in communication with the internal space of the main body section 34 and the internal space of the discharge port 36a, and the cooling water that flows into the main body section 34 of the case 30 from the inlet 32a of the lid section 32 can circulate through the internal space of the main body section 34, the internal space of the discharge section 36, and the internal space of the discharge port 36a.

[0026] In the delivery section 36, a support section 36b is positioned opposite the second end 24b of the driven shaft 24 of the driven screw 20, and is capable of contacting the second end 24b. In other words, the driven screw 20 is housed in the case 30 in a position where the driven shaft 24 is sandwiched between the inner surface 32b of the lid section 32 and the inner surface 36c of the support section 36b. At this time, although not shown in Figure 1, the length of the driven shaft 24 of the driven screw 20 is slightly shorter (for example, 0.5 mm) than the distance between the inner surface 32b of the lid section 32 and the inner surface 36c of the support section 36b. Therefore, the driven screw 20 is movable along the rotation axis Y direction within the range until the end of the driven shaft 24 contacts either the inner surface 32b or the inner surface 36c of the support section 36b.

[0027] An engaging portion 12b is positioned at the end of the helical teeth 12a on the second end 14b side of the drive shaft 14 in the drive rotor 12 of the drive screw 10. The engaging portion 12b is formed simultaneously with the molding of the helical teeth 12a of the drive rotor 12 and is part of the drive rotor 12. In other words, the engaging portion 12b is formed by insert molding, and the helical teeth 12a and the engaging portion 12b are integrally formed. In this embodiment, the second end 14b of the drive shaft 14 protrudes from the engaging portion 12b.

[0028] As shown in the cross-sectional view AA of Figure 3 and in Figure 4, the engaging portion 12b has a cylindrical outer shape, and multiple engaging recesses 12c, which are depressions extending from the side surface (outer edge of the circle) toward the center (direction of the rotation axis X), are formed along the circumferential direction (direction of rotation) (in this embodiment, three are spaced at 120-degree intervals). The engaging recesses 12c are formed in a direction along the rotation axis X, extending from the engaging surface 12d of the engaging portion 12b to the boundary between the engaging portion 12b and the helical teeth 12a.

[0029] The drive source 40 comprises a drive motor 42, a motor shaft 44, and an engaged portion 46. The drive motor 42 generates rotational driving force when power is supplied. The motor shaft 44 rotates due to the rotational driving force of the drive motor 42. The engaged portion 46 is attached to the motor shaft 44 on the opposite side from the drive motor 42 and rotates together with the motor shaft 44. In other words, the rotational driving force of the drive motor 42 is transmitted to the engaged portion 46 via the motor shaft 44.

[0030] As described above, the drive motor 42 of the drive source 40 is connected to the side of the case 30 opposite to the side of the delivery section 36 that is connected to the main body 34, and the drive motor 42 closes the end of the delivery section 36.

[0031] As shown in the BB cross-sectional view of Figure 3, the engaged portion 46 has a cylindrical outer shape and has a plurality of engaged projections 46b (three at 120-degree intervals in this embodiment) extending from the engaged surface 46a, which is the end opposite to the side attached to the motor shaft 44. The engaged projections 46b have the same shape as the engaged recess 12c of the engaged portion 12b in a plan view (see Figure 3). In addition, a bottomed hole 46c is formed in the center of the engaged portion 46, extending from the engaged surface 46a toward the motor shaft 44, into which the second end 14b of the drive shaft 14 of the drive screw 10 fits. The bottomed hole 46c has a hole bottom surface 46d. With the engaged projections 46b of the engaged portion 46 fitted into the engaged recess 12c of the engaged portion 12b, the engaged portion 12b (drive screw 10) is configured to be movable relative to the engaged portion 46 (drive source 40) both in the circumferential direction and in the direction along the rotation axis X. In other words, the dimensions of the engaging recess 12c of the engaging portion 12b and the engaged projection 46b of the engaged portion 46 are set so that they can move both in the circumferential direction and in the direction along the rotation axis X. However, it is preferable that the gap between the engaging recess 12c and the engaged projection 46b be as small as possible, within the range in which the drive screw 10 can move smoothly in the direction along the rotation axis X when the engaged projection 46b of the engaged portion 46 is fitted into the engaging recess 12c of the engaging portion 12b.

[0032] The length of the motor shaft 44 of the drive source 40 is set such that, with the drive motor 42 joined to the delivery section 36 of the case 30, the engaged projection 46b of the engaged portion 46 fits into the engaged recess 12c of the engaged portion 12b of the drive rotor 12 of the drive screw 10. At this time, the second end 14b of the drive shaft 14 fits into the bottomed hole 46c of the engaged portion 46, with a small gap between it and the bottom surface 46d of the hole. Also, at this time, there is a larger gap between the engaged surface 12d of the engaged portion 12b and the engaged surface 46a of the engaged portion 46 than the gap between the end face of the second end 14b and the bottom surface 46d of the hole.

[0033] Thus, the drive screw 10 is housed in the case 30 in a position where the drive shaft 14 is sandwiched between the inner surface 32b of the lid portion 32 and the bottom surface 46d of the closed hole 46c of the engaged portion 46. At this time, although not shown in Figure 1, the length of the drive shaft 14 of the drive screw 10 is slightly shorter (for example, 0.5 mm) than the distance between the inner surface 32b of the lid portion 32 and the bottom surface 46d of the closed hole 46c of the engaged portion 46. For this reason, the drive screw 10 is movable along the rotation axis X direction within the range until the end of the drive shaft 14 contacts either the inner surface 32b or the bottom surface 46d of the closed hole 46c of the engaged portion 46. The engaging portion 12b and the engaged portion 46 are configured such that even when the end face of the second end 14b of the drive shaft 14 is in contact with the bottom surface 46d of the hole, there is a gap between the engaging surface 12d of the engaging portion 12b and the engaged surface 46a of the engaged portion 46.

[0034] The screw pump 1 of this embodiment is configured such that the end face of the drive shaft 14 of the drive screw 10 and the end face of the driven shaft 24 of the driven screw 20 can receive thrust loads (loads acting in the direction along the rotation axis X,Y). The end faces of the first end 14a and second end 14b of the drive shaft 14, and the first end 24a and second end 24b of the driven shaft 24, are stronger than the resin drive rotor 12, and their diameter (area) is smaller than the diameter (area) of the drive rotor 12 and driven rotor 22. Therefore, even without using dedicated bearings to receive thrust loads, the frictional force that the end faces of the drive shaft 14 and the end faces of the driven shaft 24 exert on the inner surface 32b of the cover portion 32, the inner surface 36c of the support portion 36b, and the bottom surface 46d of the hole of the engaged portion 46 can be reduced when the drive screw 10 and driven screw 20 rotate, thereby suppressing wear of the drive screw 10 and driven screw 20. Furthermore, when the drive screw 10 and driven screw 20 rotate, cooling water penetrates between the end faces of the drive shaft 14 and driven shaft 24 and their inner surfaces, forming a thin film. This further reduces friction and suppresses wear.

[0035] Furthermore, in the screw pump 1, the drive screw 10 is provided with a first end 14a protruding from the drive rotor 12, and the driven screw 20 has a first end 24a protruding from the driven rotor 22. As a result, there is space for the cooling water that flows into the internal space of the main body 34 from the inlet 32a of the lid 32 of the case 30 to enter and spread radially outward without resistance. Therefore, compared to a configuration in which the first ends 14a and 24a are absent (or short) and the drive rotor 12 and driven rotor 22 are in contact (close) with the lid 32, the inflow resistance when the cooling water flows in from the inlet 32a when the screw pump 1 is operated, and the flow resistance when the cooling water flows through the internal space of the main body 34 can be reduced, thereby increasing the operating efficiency of the screw pump 1.

[0036] [Screw pump operation] Next, the operation of the screw pump 1 will be described. In this embodiment of the screw pump 1, cooling water that flows in from the inlet 32a of the lid 32 of the case 30 is transferred from the main body 34 toward the discharge section 36 by the rotation of the drive screw 10 and the driven screw 20, and discharged from the discharge port 36a. At this time, the drive screw 10 rotates as the rotational driving force of the drive motor 42 of the drive source 40 is transmitted in the order of motor shaft 44, engaged part 46, and engaged part 12b. The driven screw 20 receives rotational driving force from the cooling water transferred by the rotation of the drive screw 10 and rotates together with the drive screw 10. This is because the drive screw 10 and the driven screw 20 are arranged with the helical teeth 12a of the drive rotor 12 and the helical teeth 22a of the driven rotor 22 meshed together.

[0037] As the drive screw 10 and driven screw 20 rotate, negative pressure is generated in the internal space of the main body 34, and cooling water outside the screw pump 1 is drawn into the internal space of the main body 34 of the case 30 through the inlet 32a. The cooling water in the space between the helical teeth 12a of the drive screw 10 and the helical teeth 22a of the driven screw 20, and in the space between the helical teeth 12a and 22a and the main body 34 is then pressurized and pumped towards the discharge section 36 as the drive screw 10 and driven screw 20 rotate. The cooling water that reaches the discharge section 36 is discharged to the outside through the discharge port 36a.

[0038] [Method for manufacturing a drive screw] Next, the manufacturing method of the drive screw 10 used in the screw pump 1 of this embodiment will be explained with reference to Figure 4. In this embodiment, the drive screw 10 and the driven screw 20 are manufactured by the same method, so below, only the manufacturing method of the drive screw 10 will be explained, and the manufacturing method of the driven screw 20 will be mentioned as necessary.

[0039] As described above, the drive screw 10 is manufactured by so-called insert molding, in which resin is supplied with the drive shaft 14 placed in the molding die 50 (hereinafter also simply referred to as the die) to form the drive rotor 12.

[0040] From a manufacturing cost perspective, it is preferable to form the entire drive screw, including the drive shaft, out of resin. However, when the entire drive screw is formed out of resin, the cooling rate differs between the surface and the interior of the resin as the molten resin supplied to the mold cools and hardens, with the cooling rate being slower inside the resin. As a result, sink marks may occur on the surface of the helical teeth, potentially preventing the drive screw from achieving the required shape and precision. Furthermore, if voids occur inside, it may also cause problems in terms of strength. Therefore, in this embodiment, an iron-based metal material is used for the drive shaft 14. This allows the heat inside the resin to be released to the outside via the drive shaft 14, making the internal cooling rate equivalent to the surface heat dissipation rate. This suppresses sink marks and voids, enabling the manufacture of a highly precise and high-strength drive screw 10.

[0041] When forming the drive rotor 12 (helical teeth 12a) by resin molding, using a mold divided into two parts may cause burrs to form on the mating surfaces of the two molds. If burrs form on the helical teeth 12a as a result of using two molds to manufacture the helical teeth 12a, the burrs may detach due to collisions between the driven rotor 22 and the helical teeth 22a, or due to the flow of the cooling water, and may be mixed into the cooling water as foreign matter. Therefore, when molding the drive rotor 12, a mold divided into two parts is not usually used for the part in which the helical teeth 12a are formed, but rather one mold (first mold 51 in this embodiment) is used for molding. Therefore, in order to remove the drive screw 10 from the first mold 51 after molding the drive rotor 12, it is necessary to rotate either the drive screw 10 or the first mold 51 along the helical teeth 12a.

[0042] In this embodiment, the mold 50 is composed of a first mold 51 that forms the helical teeth 12a of the drive rotor 12 and a second mold 52 that forms the engaging portion 12b. The first mold 51 has a cylindrical shape and has a helical groove 51a formed inside that will become the helical teeth 12a after molding. A gear 51b is also formed on the side surface of the first mold 51, coaxial with the central axis of the first mold 51. The second mold 52 has an engaging groove 52a formed therein that will become the engaging portion 12b after molding. Since the mating surface between the first mold 51 and the second mold 52 is the boundary between the helical teeth 12a and the engaging portion 12b, there is no risk of burrs falling off even if they occur.

[0043] In this embodiment, a jig 60 is used to remove the drive screw 10, whose drive rotor 12 has been molded, from the mold 50. As shown in Figure 4, the jig 60 is composed of a gripping portion 62, a shaft portion 64, and a holding portion 66. The gripping portion 62, shaft portion 64, and holding portion 66 are integrated. The gripping portion 62 is the handle of the jig 60. The worker removing the drive screw 10 from the mold 50 operates the jig 60 using the gripping portion 62. The shaft portion 64 extends from the gripping portion 62, and the holding portion 66 is positioned at its tip. The holding portion 66 has a base plate 66a and a plurality of holding protrusions 66b (three in this embodiment, spaced 120 degrees apart) extending from the base plate 66a on the opposite side of the shaft portion 64. The holding protrusions 66b have a cylindrical shape.

[0044] To remove the drive screw 10 from the mold 50, first, the second mold 52 is removed to expose the engagement portion 12b. Then, the retaining projection 66b of the holding portion 66 of the jig 60 is fitted into the engagement recess 12c of the engagement portion 12b. The distance from the center of the base plate 66a of the jig 60 to the outer circumferential surface of the retaining projection 66b is approximately equal to the distance from the rotation axis X to the innermost circumferential surface of the engagement recess 12c of the engagement portion 12b. Therefore, when the retaining projection 66b of the holding portion 66 of the jig 60 is fitted into the engagement recess 12c of the engagement portion 12b, the retaining projection 66b can hold the engagement recess 12c without moving in the circumferential direction relative to the engagement recess 12c.

[0045] With the engaging portion 12b held by the jig 60, a motor (not shown) having a gear formed or attached to its rotating shaft is positioned so that the gears mesh with the gear 51b of the first mold 51, and the motor is rotated to rotate the gear 51b in the direction of the arrow. As a result, the drive screw 10, whose engaging portion 12b is held by the jig 60, does not rotate, and only the first mold 51 rotates along the helical teeth 12a, allowing the drive screw 10 to be removed from the first mold 51.

[0046] In the drive screw 10 removed from the first mold 51, the engaging portion 12b used to hold the drive screw 10 during removal is not removed by cutting or other means, but is used to engage with the engaged portion 46 of the drive source 40. Thus, in the screw pump 1 of this embodiment, the engaging portion 12b serves both as the part used to hold the drive screw 10 when removed from the mold 50 and as the part used to engage with the engaged portion 46 of the drive source 40. Therefore, compared to the case where separate parts are used for holding and engaging, there is no need to remove the engaging portion 12b from the drive screw 10 by cutting or other means and attach a separate part to engage with the engaged portion 46, thus reducing parts costs and assembly man-hours, and making it possible to suppress the manufacturing cost of the screw pump 1.

[0047] Similar to the drive screw 10, the driven screw 20 has an engagement portion formed during insert molding, and the engagement portion is held by the jig 60 and removed from the first mold 51. The driven screw 20 is then obtained by removing the engagement portion by cutting or other means.

[0048] [Second Embodiment] Next, the configuration of the screw pump 1 according to the second embodiment will be described with reference to Figure 5. In this embodiment, the shape of the drive rotor 12 of the drive screw 10 and the shape of the driven rotor 22 of the driven screw 20 are different from those of the first embodiment. Otherwise, it has the same configuration as the first embodiment. Therefore, in the description of this embodiment, the same reference numerals are used for parts with the same configuration as the first embodiment, and detailed explanations of similar configurations are omitted.

[0049] Specifically, in the screw pump 1 of this embodiment, the number of helical teeth 12a of the drive rotor 12 of the drive screw 10 and the number of helical teeth 22a of the driven rotor 22 of the driven screw 20 are reversed. That is, the helical teeth 12a are composed of 2 teeth, and the helical teeth 22a are composed of 3 teeth.

[0050] [Modified versions of the first and second embodiments] Next, the configuration of the screw pump 1 according to the modified versions of the first and second embodiments will be described. In this modified version, the material of the drive rotor 12 of the drive screw 10 is different from that of the first and second embodiments. Otherwise, it has the same configuration as the first and second embodiments. Therefore, in the description of this modified version, the same reference numerals are used for parts with the same configuration as the first and second embodiments, and detailed explanations of similar configurations are omitted.

[0051] In this modified example, the drive rotor 12 of the drive screw 10 is made of an iron-based metal material such as carbon steel. The drive rotor 12 in this modified example is an example of a metal screw rotor. In other words, the drive screw 10 in this modified example is a metal screw (an example of a second screw) consisting of a metal drive rotor 12 and a metal drive shaft 14. Therefore, an engaging portion 12b is arranged at the end of the helical teeth 12a on the second end 14b side of the drive shaft 14 of the drive screw 10 in this modified example, and by engaging with the engaged portion 46 of the drive source 40, the rotational driving force of the drive source 40 is transmitted to the drive screw 10. The shape of the screw pump 1 in this modified example is the same as in Figures 1 and 5. In addition to the drive screw 10, the driven rotor 22 of the driven screw 20 may also be made of metal. In this case, the driven rotor 22 is an example of a metal screw rotor, and the driven screw 20 is a metal screw (an example of a second screw).

[0052] [Third Embodiment] Next, the configuration of the screw pump 1 according to the third embodiment will be described with reference to Figure 6. The configuration according to this embodiment is applicable to the first embodiment, the second embodiment, and its modified versions. In this embodiment, the shapes of the drive shaft 14 and the driven shaft 24 differ from those of the first embodiment, the second embodiment, and its modified versions. Otherwise, it has the same configuration as the first embodiment, the second embodiment, and its modified versions. Therefore, in the description of this embodiment, the same reference numerals are used for parts with the same configuration as the first embodiment, the second embodiment, and its modified versions, and detailed descriptions of similar configurations are omitted.

[0053] While the drive shaft 14 and driven shaft 24 in the first embodiment, the second embodiment, and their variations were solid shafts, the drive shaft 14 and driven shaft 24 in this embodiment are hollow shafts with internal space. That is, the drive shaft 14 and driven shaft 24 each have hollow sections 14g and 24g, respectively. Figure 6 shows the drive shaft 14 and driven shaft 24 of the second embodiment shown in Figure 5 replaced with the drive shaft 14 and driven shaft 24 of this embodiment. By having hollow sections 14g and 24g in the drive shaft 14 and driven shaft 24, the drive shaft 14 and driven shaft 24 can be made lighter.

[0054] [Fourth Embodiment] Next, the configuration of the screw pump 1 according to the fourth embodiment will be described with reference to Figure 7. The configuration according to this embodiment is applicable to the first embodiment, the second embodiment, its modified form, and the third embodiment. In this embodiment, the drive shaft 14 and the driven shaft 24 have the same hollow portions 14g and 24g as in the third embodiment, and differ from the first embodiment, the second embodiment, its modified form, and the third embodiment in that the drive shaft 14 and the driven shaft 24 have first communication holes 14h and 24h (both examples of communication holes) in order to circulate cooling water through the hollow portions 14g and 24g. Otherwise, it has the same configuration as the third embodiment. Therefore, in the description of this embodiment, the same reference numerals are used for parts with the same configuration as in the first embodiment, the second embodiment, its modified form, and the third embodiment, and detailed explanations of similar configurations are omitted.

[0055] In this embodiment, the second ends 14b, 24b of the drive shaft 14 and the driven shaft 24 have first communication holes 14h, 24h that connect the outside of the drive shaft 14 and the driven shaft 24 to the hollow portions 14g, 24g. The first communication holes 14h, 24h are formed along the radial direction. Since an engaging portion 12b is arranged at the second end 14b of the drive shaft 14, a second communication hole 14i is formed in the engaging portion 12b that connects to the first communication hole 14h. That is, the delivery portion 36 communicates with the hollow portion 14g of the drive shaft 14 via the first communication hole 14h and the second communication hole 14i, and communicates with the hollow portion 24g of the driven shaft 24 via the first communication hole 24h.

[0056] As described above, the cooling water flows in from the inlet 32a of the lid 32 of the case 30, is transferred from the main body 34 toward the discharge section 36 by the rotation of the drive screw 10 and the driven screw 20, and is discharged from the discharge port 36a. Therefore, the water pressure of the cooling water is higher near the discharge section 36 than near the lid 32. For this reason, as in this embodiment, if first communication holes 14h, 24h are formed in the second ends 14b, 24b of the drive shaft 14 and the driven shaft 24, a portion of the cooling water near the discharge section 36 flows from the second communication hole 14i through the first communication hole 14h, enters the hollow section 14g of the drive shaft 14, and flows through the hollow section 14g toward the lid 32. Furthermore, some of the cooling water near the discharge section 36 flows through the first communication hole 24h, enters the hollow section 24g of the driven shaft 24, and flows through the hollow section 24g toward the lid section 32.

[0057] Since the lower ends of the hollow sections 14g and 24g are open at the first ends 14a and 24a (see Figure 6), the cooling water that has flowed through the hollow sections 14g and 24g flows out from the lower ends of the hollow sections 14g and 24g to the outside of the drive shaft 14 and driven shaft 24. At this time, due to the water pressure acting on the cover 32, the first ends 14a of the drive shaft 14 and 24a of the driven shaft 24 float slightly above the inner surface 32b of the cover 32, creating a small gap between the first ends 14a and 24a and the inner surface 32b. As a result, the frictional force between the drive shaft 14 and the driven shaft 24 and the inner surface 32b is reduced compared to the case where the first ends 14a of the drive shaft 14 and 24a of the driven shaft 24 are in contact with the inner surface 32b, thereby suppressing wear.

[0058] [First modified example of the fourth embodiment] Next, the configuration of the screw pump 1 according to the first modified example of the fourth embodiment will be described with reference to Figure 8. In this modified example, the shape of the inner surface 32b of the cover portion 32, which is in contact with the first end 14a of the drive shaft 14 and the first end 24a of the driven shaft 24, is different from that of the fourth embodiment. Otherwise, it has the same configuration as the fourth embodiment. Therefore, in the description of this modified example, the same reference numerals are used for parts with the same configuration as the fourth embodiment, and detailed explanations of similar configurations are omitted.

[0059] As shown in Figure 8, the inner surface 32b of the lid 32 has two recesses 32c formed therein, into which the first end 14a of the drive shaft 14 and the first end 24a of the driven shaft 24 fit. The depth of the recesses 32c is greater than the gap created when the drive shaft 14 and driven shaft 24 float due to the flow of cooling water in the hollow sections 14g and 24g. Therefore, even if the drive shaft 14 and driven shaft 24 float, they will not come out of the recesses 32c, and the positioning of the drive screw 10 and driven screw 20 and the lid 32 can be performed while reducing the frictional force between the drive shaft 14 and driven shaft 24 and the inner surface 32b.

[0060] [Second modified example of the fourth embodiment] Next, the configuration of the screw pump 1 according to the second modified example of the fourth embodiment will be described with reference to Figure 9. In this modified example, the recesses for positioning the drive shaft 14 and the driven shaft 24 are different from those in the first modified example of the fourth embodiment. Otherwise, it has the same configuration as the first modified example of the fourth embodiment. Therefore, in the description of this modified example, the same reference numerals are used for parts with the same configuration as the first modified example of the fourth embodiment, and detailed explanations of similar configurations are omitted.

[0061] As shown in Figure 9, two support members 28 are fixed to the inner surface 32b of the lid 32 by means of adhesive or other methods, and recesses 28a are formed in each support member 28. The first end 14a of the drive shaft 14 and the first end 24a of the driven shaft 24 fit into the two recesses 28a, respectively. The depth of the recesses 28a is greater than the gap created when the drive shaft 14 and driven shaft 24 float due to the flow of cooling water in the hollow sections 14g and 24g. Therefore, even if the drive shaft 14 and driven shaft 24 float, they will not come out of the recesses 28a. According to this embodiment, the positioning of the drive screw 10 and driven screw 20 and the lid 32 can be performed without processing the lid 32, while reducing the frictional force between the drive shaft 14 and driven shaft 24 and the inner surface 32b using the support members 28.

[0062] [Other Embodiments] Embodiments of this disclosure may be configured as follows, in addition to the embodiments and modifications described above (those having the same functions as the embodiments are given the same numbers and reference numerals as the embodiments).

[0063] (1) In the screw pump 1 of each embodiment and each modified example described above, cooling water was used as the liquid to be transferred, but this is not limited to this. Instead of cooling water, insulating oil such as paraffin may be transferred. In this case, it is not necessary to use a low-hygroscopic resin as the material for the drive rotor 12 and the driven rotor 22, and an inexpensive resin material that is hygroscopic, such as nylon (PA66), can be used.

[0064] (2) In the above embodiments and modifications, the engaged projection 46b and the engaged recess 12c are assumed to have the same shape in plan view, but they do not have to be the same shape as long as the drive screw 10 is configured to be movable in both the circumferential direction (rotational direction) and along the rotation axis X relative to the drive source 40.

[0065] (3) In each of the above embodiments and modifications, the number of engaged protrusions 46b of the drive source 40 and the number of engaged recesses 12c of the drive rotor 12 was three, but it may be two or fewer or four or more.

[0066] (4) In each of the above embodiments and modifications, the screw pump 1 had two shafts, but it may be composed of three or more shafts.

[0067] (5) In the above embodiment, both the drive screw 10 and the driven screw 20 were formed by insert molding, but the driven screw 20 may be formed by a different manufacturing method or material than insert molding.

[0068] (6) In the first to third embodiments described above, the drive shaft 14 and the driven shaft 24 were solid, but they may be hollow.

[0069] (7) In each of the second modifications of the first to fourth embodiments described above, the drive shaft 14 and the driven shaft 24 were made of metal, but they may be made of resin or other materials. For example, if the drive shaft 14 and the driven shaft 24 are made of resin, the resin constituting the drive shaft 14 and the driven shaft 24 may be the same resin as the resin constituting the drive rotor 12 and the driven rotor 22, or it may be a different resin. If the drive shaft 14 and the driven shaft 24 are made of resin and are made of a different resin than the drive rotor 12 and the driven rotor 22, the drive screw 10 and the driven screw 20 can be formed by two-color molding.

[0070] In the screw pump 1 described in the above embodiment, the following configuration can be envisioned.

[0071] <1> One embodiment of the screw pump (1) comprises a plurality of screws (10, 20) having helical teeth (12a, 22a) with a predetermined pitch (P) and rotating around their respective rotation axes (X, Y), and a case (30) housing the plurality of screws (10, 20), wherein the plurality of screws (10, 20) are arranged in a meshed state with each other, and at least one of the plurality of screws (10, 20) is integrated with a shaft (14, 24) which is arranged to be coaxial with the rotation axis (X, Y), and the shaft (14, 24) The first screw (10, 20) has a resin screw rotor (12, 22) made of resin, and the first ends (14a, 24a) of the shaft (14, 24) of the first screw (10, 20) that are located on the opposite side of the liquid transfer direction protrude from the resin screw rotor (12, 22), and the first ends (14a, 24a) that protrude from the resin screw rotor (12, 22) are supported by the case (30), and the shaft (14, 24) is a hollow shaft having a hollow section (14g, 24g).

[0072] According to this embodiment, the screw pump (1) is configured so that thrust loads can be received at both ends (14a, 14b, 24a, 24b) of the shafts (14, 24) of the multiple screws (10, 20). Therefore, even without using dedicated bearings for receiving thrust loads, the frictional force that the ends (14a, 14b, 24a, 24b) of the shafts (14, 24) exert on the case (30) when the multiple screws (10, 20) rotate can be reduced, thereby suppressing wear. In addition, since the first screw (10, 20) has a resin screw rotor (12, 22), manufacturing costs can be reduced compared to the case where the entire screw is made of metal material. Furthermore, since the shafts (14, 24) have hollow sections (14g, 24g), the shafts (14, 24) can be made lighter.

[0073] <2> the above <1> In the screw pump (1) described above, the shaft is preferably a metal hollow shaft (14, 24), and the first screw (10, 20) is preferably composed of a resin screw rotor (12, 22) that is insert-molded into the metal hollow shaft (14, 24).

[0074] If the shaft is a hollow metal shaft (14, 24), the ends (14a, 14b, 24a, 24b) of the hollow metal shaft (14, 24) are stronger than the resin screw rotor (12, 22), and their diameter (area) is smaller than that of the resin screw rotor (12, 22). Therefore, even without using a dedicated bearing to receive the thrust load, the frictional force that the ends (14a, 14b, 24a, 24b) of the hollow metal shaft (14, 24) exert on the case (30) during the rotation of the first screw (10, 20) can be further reduced, thereby suppressing wear.

[0075] Furthermore, when the entire screw (10,20) is formed from resin, the cooling rate differs between the surface and the interior of the resin as the molten resin supplied into the mold cools and hardens, with the cooling rate being slower inside the resin. As a result, sink marks and other defects may occur on the surface of the resin screw rotor (12,22), potentially preventing the screw (10,20) from achieving the required shape and precision. Additionally, the occurrence of voids inside the resin may pose a strength problem. Therefore, according to this embodiment, an iron-based metal material is used as the metal hollow shaft (14,24). This allows the heat inside the resin to be released to the outside through the metal hollow shaft (14,24), making it possible to make the internal cooling rate equivalent to the surface heat dissipation rate. This suppresses sink marks and voids, enabling the manufacture of a first screw (10,20) with high precision and high strength.

[0076] <3> the above <1> or <2> In the screw pump (1) described above, it is preferable that at least one of the plurality of screws (10,20) is a second screw (10,20) having a metal hollow shaft (14,24) arranged to be coaxial with the rotation axis (X,Y) and a metal screw rotor (12,22) integrated with the metal hollow shaft (14,24).

[0077] According to this embodiment, at least one of the multiple screws (10,20) is a second screw (10,20) having a metal hollow shaft (14, 24) arranged coaxially with the rotation axis (X,Y) and a metal screw rotor (12, 22) integrated with the metal hollow shaft (14, 24). Therefore, the second screw (10,20) can be manufactured with high strength.

[0078] <4> the above <3> In the screw pump (1) described above, a drive source (40) is further provided, which has an engaged portion (46) that generates rotational driving force and transmits the rotational driving force to one of the second screws (10, 20) (10), wherein the metal screw rotor (12) of the second screw (10) has an engaged portion (12b) at one end (14b) in the direction along the rotation axis (X), and it is preferable that the rotational driving force of the drive source (40) is transmitted to the second screw (10) by the engaged portion (46) of the drive source (40) engaging with the engaged portion (12b) of the metal screw rotor (12).

[0079] According to this embodiment, by engaging the engaged portion (46) of the drive source (40) with the engaged portion (12b) of the metal screw rotor (12), the rotational driving force of the drive source (40) can be reliably transmitted to the second screw (10).

[0080] <5> the above <1> from <4> In the screw pump (1) described in any one of the above, the shaft is preferably a metal hollow shaft (14, 24), and the metal hollow shaft (14, 24) has a second end (14b, 24b) located opposite to the first end (14a, 24a) and has a communication hole (14h, 24h) that connects to a hollow section (14g, 24g) and into which liquid flows.

[0081] The water pressure of the liquid is higher at the second end (14b,24b) of the hollow metal shaft (14,24) than at the first end (14a,24a). Therefore, if a connecting hole (14h,24h) is formed at the second end (14b,24b) of the hollow metal shaft (14,24), some of the liquid near the second end (14b,24b) will flow through the connecting hole (14h,24h), enter the hollow portion (14g,24g) of the hollow metal shaft (14,24), and flow through the hollow portion (14g,24g) towards the first end (14a,24a). Finally, it will flow out of the hollow metal shaft (14,24) from the first end (14a,24a). At this time, the water pressure acting on the case (30) causes the first ends (14a, 24a) of the hollow metal shafts (14, 24) to float slightly above the case (30), creating a small gap between the first ends (14a, 24a) and the case (30). This reduces the frictional force between the hollow metal shafts (14, 24) and the case (30) compared to when the first ends (14a, 24a) of the hollow metal shafts (14, 24) are in contact with the case (30), thereby suppressing wear.

[0082] <6> the above <5> In the screw pump (1) described above, the case (30) has a recess (32c), and it is preferable that the first end (14a, 24a) fits into the recess (32c).

[0083] According to this embodiment, the case (30) has a recess (32c), and the first ends (14a, 24a) fit into the recess (32c), so that the frictional force between the hollow metal shafts (14, 24) and the case (30) can be reduced while positioning the screws (10, 20) and the case (30).

[0084] <7> the above <5> In the screw pump (1) described above, a support member (28) is further provided which is fixed to the case (30), and the support member (28) has a recess (28a), and it is preferable that the first end (14a, 24a) fits into the recess (28a).

[0085] According to this embodiment, the support member (28) fixed to the case (30) has a recess (28a), and the first end portions (14a, 24a) fit into the recess (28a). Therefore, without processing the case (30), the positioning of the screws (10, 20) and the case (30) can be performed by the support member (28) while reducing the frictional force between the metal hollow shafts (14, 24) and the case (30). [Industrial applicability]

[0086] This disclosure can be used in screw pumps. [Explanation of Symbols]

[0087] 1: Screw pump, 10: Drive screw (screw, first screw, second screw), 12: Drive rotor (resin screw rotor, metal screw rotor), 12a: Helical teeth, 12b: Engaging part, 14: Drive shaft (shaft, metal shaft, hollow shaft, metal hollow shaft), 14a: First end (end), 14b: Second end (end), 14g: Hollow part, 14h: First communication hole (communication hole), 20: Driven screw (screw, first screw) 22: Driven rotor (resin screw rotor, metal screw rotor), 22a: Helical teeth, 24: Driven shaft (shaft, metal shaft, hollow shaft, metal hollow shaft), 24a: First end (end), 24b: Second end (end), 24g: Hollow section, 24h: First communication hole (communication hole), Support member: 28, Recess: 28a, 30: Case, Recess: 32c, 40: Drive unit, 46: Engaged part, P: Pitch, X: Rotation axis, Y: Rotation axis

Claims

1. Multiple screws, each having helical teeth with a predetermined pitch and rotating around its respective axis of rotation, A case for housing multiple screws, Multiple screws are arranged in a meshed state and rotate simultaneously to transfer liquid. At least one of the plurality of screws is a first screw having a shaft arranged to be coaxial with the axis of rotation and a resin screw rotor made of resin integrated with the shaft. The first end of the shaft of the first screw, which is located on the side opposite to the direction of liquid transfer, protrudes from the resin screw rotor. The first end protruding from the resin screw rotor is configured to be supported by the case, The aforementioned shaft is a hollow shaft having a hollow section, which is a screw pump.

2. The aforementioned shaft is a metal hollow shaft, The screw pump according to claim 1, wherein the first screw is composed of the resin screw rotor that is insert-molded into the metal hollow shaft.

3. The screw pump according to claim 1, wherein at least one of the plurality of screws is a second screw having a metal hollow shaft arranged coaxially with the rotation axis and a metal screw rotor integrated with the metal hollow shaft.

4. The device further comprises a drive source having an engaged portion that generates rotational driving force and transmits the rotational driving force to one of the second screws, The metal screw rotor of the second screw has an engaging portion at the second end, which is located on the opposite side of the first end. The screw pump according to claim 3, wherein the rotational driving force of the drive source is transmitted to the second screw by the engagement of the engaged portion of the drive source with the engagement portion of the metal screw rotor.

5. The aforementioned shaft is a metal hollow shaft, The screw pump according to any one of claims 1 to 4, wherein the metal hollow shaft has a communication hole at a second end located opposite to the first end, which is connected to the hollow portion and through which the liquid flows into the hollow portion.

6. The aforementioned case has a recess, The screw pump according to claim 5, wherein the first end fits into the recess.

7. The case further comprises a support member fixed to the aforementioned case, The support member has a recess, The screw pump according to claim 5, wherein the first end fits into the recess.

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