Water pump shaft and water pump

Abstract

The present invention provides a water pump shaft which is used in a motor of a water pump including the motor, an impeller, a casing, and a frame, said water pump shaft comprising: a rotor shaft which is formed in a columnar shape, to which a rotor of the motor is fixed, and which constitutes a part of a power unit of the motor; and a pump shaft which is formed in a columnar shape, to a tip end of which the impeller is fixed, which constitutes a part that sends out a liquid inside the casing, and which is made of a material different from that of the rotor shaft. The water pump shaft has a fitting part in which the rotor shaft and the pump shaft are fitted. The rotor shaft and the pump shaft are coaxially disposed. The rotor shaft and the pump shaft are integrated by being fixed to each other via the fitting part.

Description

Water pump shaft and water pump

[0001] The present disclosure relates to a water pump shaft and a water pump, and more particularly to a structure of a water pump shaft.

[0002] Conventionally, an impeller is attached to the tip of the shaft used in a water pump. This impeller functions to pump water inside the pump casing. Because the impeller and the tip of the shaft are submerged in water, rust and corrosion prevention measures are essential near the tip of the shaft. One way to prevent rust and corrosion near the tip of the shaft is to use stainless steel as the material that makes up the entire shaft. However, when stainless steel is used as the shaft material, the material cost is higher than when iron is used as the shaft material.

[0003] Therefore, as a countermeasure against rust and corrosion near the tip of the shaft, it is considered to use multiple materials in the shaft construction. When constructing a shaft using multiple materials, a shaft processing method has been proposed in which different materials are integrated together (see, for example, Patent Document 1). The processing method of Patent Document 1 integrates shafts made of different materials using friction welding. The friction welding process of Patent Document 1 is a type of welding process in which different materials are brought into relative motion while being brought into contact and pressurized, and the generated frictional heat is used to weld the materials together. By using the friction welding process of Patent Document 1, for example, the shaft can be made of stainless steel only in the portions that will be submerged in water, thereby reducing material costs and providing countermeasures against rust and corrosion.

[0004] Japanese Unexamined Patent Publication No. 2-299784

[0005] The processing method of Patent Document 1 requires dedicated equipment and jigs for friction welding, which requires a large initial investment and is not suitable for small-lot production. Furthermore, the shaft becomes very hot during friction welding, which can cause some distortion of the shaft and burrs on the joining surface, which can require post-processing.

[0006] The present disclosure aims to solve the above-mentioned problems and to provide a water pump shaft and a water pump that can reduce initial investment, reduce the effects of thermal distortion, and eliminate the need for post-processing.

[0007] The shaft of the water pump according to the present disclosure is a shaft used in a motor for a water pump having a motor as a drive unit, an impeller that receives the output of the motor to rotate the liquid and apply centrifugal force to the liquid to move it, a casing that houses the impeller and has a water supply unit that serves as a flow path for the liquid, the water supply unit having an inlet at one end and an outlet at the other end, and a frame that connects the motor and the casing, the shaft comprising: a rotor shaft that is formed in a cylindrical shape and to which the motor rotor is fixed and that constitutes part of the motor's power unit; and a pump shaft that is formed in a cylindrical shape and to which the impeller is fixed at its tip and that constitutes the part inside the casing that pumps out the liquid, and is made of a material different from the rotor shaft, the shaft having a fitting portion that forms the part where the rotor shaft and the pump shaft are fitted together, the rotor shaft and the pump shaft are arranged coaxially, and the rotor shaft and the pump shaft are fixed to each other and integrated by the fitting portion.

[0008] The water pump of the present disclosure comprises a water pump shaft having the above-described configuration, a motor having the shaft, an impeller that receives the output of the motor to rotate the liquid and apply centrifugal force to the liquid to move the liquid, a water supply section that serves as a flow path for the liquid, a casing that has an inlet port at one end forming the water supply section and an outlet port at the other end, and that houses the impeller in an accommodation space formed in part of the water supply section, and a cylindrical frame that connects the motor and casing in the axial direction of the shaft.

[0009] The water pump of the present disclosure comprises a water pump shaft having the above-described configuration, a motor having the shaft, an impeller that receives output from the motor to rotate the liquid and apply centrifugal force to the liquid to move the liquid, a water supply section formed with a flow path through which the liquid flows, the water supply section having an inlet port at one end and an outlet port at the other end, and a casing that houses the impeller in an accommodation space formed in part of the water supply section, a cylindrical frame that connects the motor and the casing in the axial direction of the shaft, and a load side bearing that supports the pump shaft and a counter-load side bearing that supports the rotor shaft, when one direction along the axial direction of the shaft is the load side and the other direction along the axial direction of the shaft is the counter-load side, the load side bearing has a larger diameter than the counter-load side bearing, the rotor shaft is a common part, and the pump shaft attached to the rotor shaft can be changed to a pump shaft with a different outer diameter dimension.

[0010] According to the present disclosure, the water pump shaft and water pump can reduce initial investment, reduce the effects of thermal distortion, and eliminate the need for post-processing.

[0011] FIG. 1 is a schematic diagram showing an internal configuration of a water pump according to a first embodiment; FIG. 2 is a schematic diagram showing an example of a pump shaft used in the water pump according to the first embodiment, with a load side bearing attached; FIG. 3 is a schematic diagram showing an example of a pump shaft used in the water pump according to the first embodiment, with a load side bearing not attached; FIG. 4 is a schematic diagram showing an example of a rotor shaft used in the water pump according to the first embodiment, with a rotor fixed; FIG. 5 is a schematic diagram showing an example of a rotor shaft used in the water pump according to the first embodiment, with a rotor not fixed; FIG. 6 is a schematic diagram showing an example of a shaft used in the water pump according to the first embodiment, with the rotor shaft and the pump shaft fitted together; FIG. 7 is a schematic cross-sectional view of a shaft used in the water pump according to the first embodiment, with the rotor shaft and the pump shaft fitted together; FIG. 8 is a schematic diagram showing an example of a configuration of a water pump according to the first embodiment; FIG. 9 is a schematic diagram showing an example of a pump shaft used in the water pump according to the second embodiment, with a load side bearing not attached; FIG. 10 is a schematic diagram showing an example of a rotor shaft used in the water pump according to the second embodiment, with a rotor not fixed; FIG. 1 is a schematic diagram showing an example of a shaft used in a water pump according to a second embodiment, with the rotor shaft and the pump shaft fitted together; FIG. 2 is a schematic cross-sectional view of a shaft used in a water pump according to the second embodiment, with the rotor shaft and the pump shaft fitted together; FIG. 3 is a schematic cross-sectional view of a shaft used in a water pump according to a third embodiment, with the load side bearing not attached; FIG. 4 is a schematic cross-sectional view of a shaft used in a water pump according to a fourth embodiment, with the rotor shaft and the pump shaft fitted together;FIG. 10 is a cross-sectional schematic view of a shaft in a state where a rotor shaft and a pump shaft are fitted together, which is used in a water pump according to a fourth embodiment.

[0012] Hereinafter, embodiments will be described with reference to the drawings. Note that the forms of components shown in the specification are merely examples and are not limited to these descriptions. Furthermore, in the following drawings, including FIG. 1, the relative dimensional relationships and shapes of each component may differ from the actual ones. Furthermore, in the following drawings, identical symbols are used to denote identical or equivalent components, and this applies throughout the specification. Furthermore, to facilitate understanding, terms or orientations indicating directions are used as appropriate. However, these notations are used for the convenience of explanation and do not limit the placement, direction, or orientation of devices, instruments, or parts, etc. Examples of terms indicating directions or orientations include up, down, right, left, front, back, front, or back.

[0013] Embodiment 1. [Configuration of water pump 100] Figure 1 is a schematic diagram showing the internal configuration of a water pump 100 according to embodiment 1. The water pump 100 is a device for transporting liquid such as water, and is used for circulating the liquid. The water pump 100 is, for example, a circulation pump, and is a line pump in which an inlet 34 and an outlet 35 (described later) are aligned with the piping.

[0014] The water pump 100 includes a motor 10, an impeller 20, a casing 30, and a frame 40. More specifically, the water pump 100 includes the motor 10, which is a drive unit, and the impeller 20, which receives the output of the motor 10 to rotate the liquid and impart centrifugal force to the liquid, thereby moving the liquid. In other words, the water pump 100 includes the motor 10, which has a shaft 15 (described below), and the impeller 20, which receives the output of the motor 10 to rotate the liquid and impart centrifugal force to the liquid, thereby moving the liquid.

[0015] The water pump 100 has a casing 30 that houses the impeller 20 therein, has a water supply section 38 formed therein that serves as a flow path for liquid, and has an inlet 34 formed at one end that forms the water supply section 38 and an outlet 35 formed at the other end. The water pump 100 has a casing 30 that houses the impeller 20 in an accommodation space 31 formed in a part of the water supply section 38, and has a water supply section 38 formed therein that serves as a flow path for liquid, and has an inlet 34 formed at one end that forms the water supply section 38 and an outlet 35 formed at the other end.

[0016] The water pump 100 is formed in a cylindrical shape and has a frame 40 that connects the motor 10 and the casing 30 in the axial direction of the shaft 15 .

[0017] (Motor 10) Motor 10 is the drive unit of water pump 100, and is driven to rotate impeller 20 and transport liquid. Motor 10 has rotor 11, which rotates to transmit power to impeller 20 via shaft 15 (described later), and stator 12, which generates a force to rotate rotor 11.

[0018] The motor 10 also has a motor case 13 that houses the rotor 11 and the stator 12, and a shaft 15 fixed to the rotor 11. The motor 10 also has a load side bearing 14 and a counter-load side bearing 16 that support the shaft 15 and receive the load of the rotor 11. One side along the axial direction of the shaft 15 is referred to as the load side, and the other side along the axial direction of the shaft 15 is referred to as the counter-load side. The load side is the side of the motor 10 on which a load is applied and on which the impeller 20 is attached, and the counter-load side is the side of the motor 10 opposite the load side and on which the impeller 20 is not attached.

[0019] The stator 12 is formed in an annular shape when viewed in the axial direction of the shaft 15. The stator 12 is formed in a hollow cylindrical shape. The stator 12 is fixed inside the motor case 13. The stator 12 is made up of, for example, an iron core and a wound coil. The iron core is made up of, for example, multiple thin electromagnetic steel plates stacked along the axial direction of the shaft 15.

[0020] The rotor 11 is rotatably disposed in the hollow portion of the stator 12. The rotor 11 is composed of, for example, an iron core and a plurality of magnets. The iron core is composed of, for example, a plurality of thin electromagnetic steel plates laminated along the axial direction of the shaft 15. The magnets are, for example, permanent magnets.

[0021] In the motor 10, the rotor 11 rotates due to magnetic action generated when power is supplied from an external power source to the wound coils that make up the stator 12. A shaft 15 connected to an impeller 20 is fixed to the rotor 11.

[0022] The motor case 13 forms the outer shell of the motor 10. The motor case 13 is formed in a cylindrical shape. The motor case 13 houses the stator 12 and the rotor 11 inside, and the stator 12 is fixed inside. The motor case 13 and the frame 40 are fixed together with fasteners such as bolts.

[0023] The shaft 15 is a rod-shaped or columnar member. The shaft 15 is fixed to the rotor 11 at the center of the rotor 11, penetrating the rotor 11 in the axial direction of the shaft 15. The shaft 15 is fixed to the rotor 11 with its upper portion inserted into the rotor 11. The shaft 15 is connected to and fixed to the impeller 20 at its lower portion. The shaft 15 rotates when the rotor 11 rotates. The shaft 15 transmits the rotational force of the rotor 11 to the impeller 20, causing the impeller 20 to rotate. A detailed configuration of the shaft 15 will be described later.

[0024] The load side bearing 14 and the anti-load side bearing 16 are annular members provided around the shaft 15. The load side bearing 14 and the anti-load side bearing 16 are, for example, ball bearings, and rotatably support the shaft 15. More specifically, the load side bearing 14 rotatably supports a pump shaft 15a (described later), and the anti-load side bearing 16 rotatably supports a rotor shaft 15b (described later). In the axial direction of the shaft 15, if the motor 10 side is the upper part and the impeller 20 side is the lower part, the load side bearing 14 is provided near the center of the shaft 15, and the anti-load side bearing 16 is provided near the upper part of the shaft 15.

[0025] The load side bearing 14 is disposed between the rotor 11 and the frame 40 in the axial direction of the shaft 15. The load side bearing 14 is also disposed above the impeller 20. The anti-load side bearing 16 is disposed above the rotor 11 in the axial direction of the shaft 15. That is, in the axial direction of the shaft 15, the load side bearing 14 is located below the rotor 11, and the anti-load side bearing 16 is located above the rotor 11. The load side bearing 14 and the anti-load side bearing 16 are provided on both sides of the rotor 11 in the axial direction of the shaft 15.

[0026] (Impeller 20) The impeller 20 is housed in a housing space 31 of a casing 30, which will be described later, and has a plurality of blades 21. When viewed in the axial direction of the shaft 15, the blades 21 extend in a radial direction centered on the shaft 15. The blades 21 are plate-shaped members, and are formed, for example, in an arc shape when viewed in the axial direction of the shaft 15. The blades 21 are not limited to being formed in an arc shape, and may be formed in other shapes, such as a straight line when viewed in the axial direction of the shaft 15.

[0027] Liquid is sucked into the impeller 20 through a blade inlet 22 formed in the center, and is discharged from an outer slit 23 by centrifugal force generated by the rotation of the impeller 20. The blade inlet 22 is an opening formed in the impeller 20, faces an inlet 31a of the casing 30 (described later), and communicates with an inlet-side pipe 32 of the casing 30. As the impeller 20 rotates, it applies pressure to the liquid flowing in the accommodation space 31. At this time, the liquid in the accommodation space 31 rotates and flows through the accommodation space 31, and is sent to the discharge port 35 side.

[0028] (Casing 30) The casing 30 is hollow and allows a liquid to flow inside. The casing 30 forms a liquid flow path between one pipe (not shown) connected to the casing 30 and another pipe (not shown) connected to the casing 30. In this liquid flow path within the casing 30, pressure is applied to the liquid, such as water, by the impeller 20 described above, and the liquid is sent from one pipe to the other pipe.

[0029] The casing 30 is formed with an accommodation space 31, an inlet-side pipe section 32, an outlet-side pipe section 33, a suction port 34, and a discharge port 35. The casing 30 also includes an inlet-side connection section 36 and an outlet-side connection section 37. The casing 30 has a water supply section 38 formed therein, which has the suction port 34 at one end and the discharge port 35 at the other end, through which a liquid flows. The impeller 20 is accommodated in the accommodation space 31 formed in part of the water supply section 38. The water supply section 38 forms a fluid passage through which the liquid flows within the casing 30. The water supply section 38 is formed by the accommodation space 31, the inlet-side pipe section 32, the outlet-side pipe section 33, the suction port 34, and the discharge port 35.

[0030] The accommodation space 31 is a space formed inside the casing 30, and accommodates the impeller 20. The accommodation space 31 forms a columnar space, with an inlet 31a formed in the lower surface portion and an outlet 31b formed in the side surface portion. When viewed in the axial direction of the shaft 15, the side surface of the accommodation space 31 forms part of a spiral shape that winds from the center outward, for example.

[0031] The inlet portion 31a is an opening formed on the surface opposite to the side where the motor 10 is disposed. The inlet portion 31a is an inlet for liquid flowing into the accommodation space 31 from the inlet-side pipe portion 32, and is the end portion of the inlet-side pipe portion 32 on the liquid outlet side. The inlet portion 31a is formed at a position opposite to the portion where the blade inlet portion 22 of the impeller 20 is formed.

[0032] The inlet-side pipe section 32 is a section that forms a pipe line between the suction port 34 and the inlet section 31a of the accommodation space 31. The suction port 34 is formed at one end of the inlet-side pipe section 32, and the inlet section 31a of the accommodation space 31 is formed at the other end. The axial direction of the section of the inlet-side pipe section 32 on the inlet section 31a side is along the shaft 15, and the axial direction of the section of the inlet-side pipe section 32 on the suction port 34 side is along the radial direction of the shaft 15. In other words, the inlet-side pipe section 32 is formed so that the pipe axis is curved.

[0033] The suction port 34 is an opening formed on the side surface of the casing 30. The suction port 34 is connected to the accommodation space 31 via the inlet-side pipe portion 32. The liquid flowing through one of the pipes connected to the casing 30 passes through the suction port 34, flows into the inlet-side pipe portion 32, and then flows into the accommodation space 31 through the inlet-side pipe portion 32.

[0034] The outlet portion 31b is an opening formed in the radial direction relative to the shaft 15. The outlet portion 31b is an outlet for the liquid flowing out from the accommodation space 31 to the outlet-side pipe portion 33, and is the end portion on the inlet side of the liquid in the outlet-side pipe portion 33. The outlet portion 31b is formed in a position opposite to the portion of the impeller 20 where the slit 23 is formed.

[0035] The outlet-side pipe portion 33 is a portion that forms a pipe line between the discharge port 35 and the outlet portion 31b of the accommodation space 31. The discharge port 35 is formed at one end of the outlet-side pipe portion 33, and the outlet portion 31b of the accommodation space 31 is formed at the other end. The outlet-side pipe portion 33 extends, for example, along the radial direction of the shaft 15.

[0036] The discharge port 35 is an opening formed on the side surface of the casing 30. The discharge port 35 is in communication with the storage space 31 via the outlet-side pipe portion 33. The liquid flowing out from the storage space 31 flows into the outlet-side pipe portion 33 and passes through the discharge port 35 into the other pipe connected to the casing 30.

[0037] The discharge port 35 is an opening formed on the side surface of the casing 30 opposite the suction port 34 across the accommodation space 31. Note that the casing 30 is not limited to a structure in which the discharge port 35 and the suction port 34 are formed on side surfaces opposite each other. The casing 30 may be formed so that the discharge port 35 and the suction port 34 are positioned radially from the shaft 15 as the center when viewed in the axial direction of the shaft 15.

[0038] The inlet side connecting portion 36 is a flange-shaped portion at the suction port 34. One of the pipes through which the liquid flowing into the casing 30 flows is connected to the inlet side connecting portion 36. The outlet side connecting portion 37 is a flange-shaped portion at the discharge port 35. The other of the pipes through which the liquid flowing out of the casing 30 flows is connected to the outlet side connecting portion 37. The inlet side connecting portion 36 and the outlet side connecting portion 37 form the side surfaces of the casing 30.

[0039] The casing 30 has an inlet 34 at one end in the direction of flow of the liquid passing through it, and an outlet 35 at the other end. As the impeller 20 rotates, the liquid inside the water pump 100 flows from the inlet 34 to the outlet 35. At this time, the impeller 20 and the tip 15c of the shaft 15 to which the impeller 20 is attached are placed underwater in the accommodation space 31 or the like and are immersed in the liquid. For this reason, rust and corrosion prevention measures are essential for the tip 15c of the shaft 15 and the like.

[0040] (Frame 40) The frame 40 is a columnar member extending in the axial direction of the shaft 15. The frame 40 has a portion formed in a cylindrical shape, and is disposed between the motor 10 and the casing 30 in the axial direction of the motor 10 to connect the motor 10 and the casing 30. An upper portion of the frame 40 supports the load-side bearing 14 in the axial direction of the shaft 15.

[0041] With the motor 10 side defined as the upper part and the impeller 20 side defined as the lower part in the axial direction of the shaft 15, the frame 40 is provided on the upper part of the casing 30. The motor 10 is also disposed on the upper part of the frame 40. The frame 40 connects the lower part of the motor 10 to the upper part of the casing 30. The lower part of the frame 40 is fixed to the upper part of the casing 30 by fasteners such as bolts. The upper part of the frame 40 is fixed to the lower part of the motor 10 by fasteners such as bolts.

[0042] An upper annular portion 41 is formed on the upper part of the frame 40. The upper annular portion 41 is a flange-shaped portion that extends radially when viewed in the axial direction of the shaft 15. The upper annular portion 41 is formed, for example, in an annular shape. The upper annular portion 41 is fixed to the motor case 13 by fasteners such as bolts.

[0043] A lower annular portion 43 and a lower insertion portion 44 are formed at the bottom of the frame 40. The lower annular portion 43 is a flange-shaped portion that extends radially when viewed in the axial direction of the shaft 15. The lower annular portion 43 is formed, for example, in an annular shape. The lower annular portion 43 engages with the top of the casing 30, and the lower annular portion 43 and the casing 30 are fixed together by fasteners such as bolts.

[0044] The lower insertion portion 44 is formed lower than the lower annular portion 43 and is a cylindrical portion of the casing 30. The lower insertion portion 44 is inserted into an upper opening 30a formed in the casing 30 and fitted to the casing 30.

[0045] A frame shaft hole 45 is formed in the center of the frame 40 when viewed in the axial direction of the shaft 15. The frame shaft hole 45 is a through-hole that passes through the frame 40 in the axial direction of the shaft 15. The opening diameter of the frame shaft hole 45 is larger than the diameter of the shaft 15. In the water pump 100, the shaft 15 is inserted through the frame shaft hole 45 and passes through the frame 40.

[0046] (Detailed Structure of Shaft 15) The shaft 15 is one of the components used in the motor 10 of the water pump 100. The shaft 15 includes a pump shaft 15a and a rotor shaft 15b. The shaft 15 is made up of at least two components, the pump shaft 15a and the rotor shaft 15b. The shaft 15 is made up of a combination of the pump shaft 15a and the rotor shaft 15b.

[0047] Before the pump shaft 15 a and the rotor shaft 15 b are combined, the shaft 15 is divided into two parts, the pump shaft 15 a and the rotor shaft 15 b. The shaft 15 is integrally configured by combining the pump shaft 15 a and the rotor shaft 15 b and fixing them to each other.

[0048] In the axial direction of the shaft 15, if the motor 10 side is the upper part and the impeller 20 side is the lower part, within the water pump 100, the rotor shaft 15b is located relatively at the upper part of the shaft 15, and the pump shaft 15a is located relatively at the lower part of the shaft 15.

[0049] The pump shaft 15a is formed in a columnar shape, and an impeller 20 is fixed to a tip end 15c, constituting a portion that pumps liquid inside the casing 30. The pump shaft 15a shown in Fig. 3, which will be described later, has five columnar portions with different outer diameters, but the number of columnar portions may be one or more.

[0050] The rotor shaft 15b is formed in a columnar shape, to which the rotor 11 of the motor 10 is fixed, and constitutes a part of the power unit of the motor 10. The rotor shaft 15b is formed in, for example, a cylindrical shape. The rotor shaft 15b may include a conical or truncated conical portion.

[0051] The pump shaft 15a and the rotor shaft 15b are made of different materials.

[0052] The tip 15c of the pump shaft 15a and other parts are contained underwater inside the casing 30, and therefore, the pump shaft 15a is made of a material such as stainless steel to provide rust and corrosion protection. However, the pump shaft 15a may be made of a material other than stainless steel as long as it is a material that can be used to provide rust and corrosion protection and that can ensure the strength required to form a pump shaft.

[0053] The rotor shaft 15b is made of a relatively inexpensive material such as iron. However, the rotor shaft 15b may be made of a material other than iron as long as it is suitable for forming a shaft fixed to the rotor 11 and has the strength required for forming a pump shaft. In order to reduce the manufacturing cost of the water pump 100, it is desirable that the rotor shaft 15b be made of a relatively inexpensive material.

[0054] As shown by the dashed line in Figure 1, the shaft 15 has a fitting portion 150 that forms the portion where the rotor shaft 15b and the pump shaft 15a are fitted together. The rotor shaft 15b and the pump shaft 15a are arranged coaxially on the shaft 15, and the rotor shaft 15b and the pump shaft 15a are fixed to each other and integrated by the fitting portion 150. The load side end of the rotor shaft 15b of the shaft 15 is inserted into the anti-load side end of the pump shaft 15a. That is, the lower end of the rotor shaft 15b of the shaft 15 is inserted into the upper end of the pump shaft 15a.

[0055] FIG. 2 is a schematic diagram showing an example of a pump shaft 15a used in the water pump 100 according to the first embodiment, with the load-side bearing 14 attached. FIG. 3 is a schematic diagram showing an example of a pump shaft 15a used in the water pump 100 according to the first embodiment, with the load-side bearing 14 not attached. Note that the internal structure is indicated by dashed lines in FIGS. 2 and 3 . Also, in FIG. 3 , the center line indicating the center of the shaft 15 is indicated by a dashed-dotted line. As shown in FIGS. 1 to 3 , the pump shaft 15a has a first fitting portion 151 that constitutes the fitting portion 150.

[0056] The first fitting portion 151 is formed in a cylindrical shape with a bottom that is recessed from the anti-load side toward the load side in the axial direction of the pump shaft 15a. That is, the first fitting portion 151 is formed in a cylindrical shape with a bottom that is recessed from the upper end side toward the lower end side in the axial direction of the pump shaft 15a. The first fitting portion 151 has a hollow portion 151c that forms a hollow portion. In the portion that forms the hollow portion 151c, the first fitting portion 151 has an outer peripheral wall 151a that forms a side wall of the outer peripheral surface and an inner peripheral wall 151b that forms a side wall of the inner peripheral surface.

[0057] The outer diameter of the first fitting portion 151 of the pump shaft 15a is larger than, for example, the inner diameter of the load-side bearing 14. The load-side end face of the first fitting portion 151 of the pump shaft 15a in the axial direction of the shaft 15 is caught on the load-side bearing 14, preventing the pump shaft 15a from moving toward the load side.

[0058] An impeller 20 is fixed to a tip 15c of the pump shaft 15a. The tip 15c of the pump shaft 15a is the end of the load side of the shaft 15 and also forms the lower end of the shaft 15. The tip 15c of the pump shaft 15a and a portion close to the tip 15c are portions that are immersed in the liquid inside the casing 30.

[0059] Fig. 4 is a schematic diagram showing an example of a rotor shaft 15b used in the water pump 100 according to embodiment 1, with the rotor 11 fixed thereto. Fig. 5 is a schematic diagram showing an example of a rotor shaft 15b used in the water pump 100 according to embodiment 1, with the rotor 11 not fixed thereto. As shown in Figs. 1, 4, and 5, the rotor shaft 15b has a second fitting portion 152 that, together with a first fitting portion 151, constitutes the fitting portion 150.

[0060] The second fitting portion 152 is formed in a columnar shape to be inserted into the first fitting portion 151. For example, at least a portion of the second fitting portion 152 in the circumferential direction or the axial direction is formed in a cylindrical shape.

[0061] Fig. 6 is a schematic diagram showing an example of the shaft 15 used in the water pump 100 according to the first embodiment, in which the rotor shaft 15b and the pump shaft 15a are fitted together. Fig. 7 is a schematic cross-sectional view of the shaft 15 used in the water pump 100 according to the first embodiment, in which the rotor shaft 15b and the pump shaft 15a are fitted together. Fig. 7 is an example of a schematic cross-sectional view of the shaft 15 cut perpendicular to the axial direction of the shaft 15. The fitting portion 150 will be described with reference to Figs. 1, 6, and 7.

[0062] 1, 6, and 7, the shaft 15 has a fitting portion 150 in which the second fitting portion 152 of the rotor shaft 15b is inserted into the first fitting portion 151 of the pump shaft 15a, and the second fitting portion 152 and the first fitting portion 151 are fitted together. By fitting the second fitting portion 152 of the rotor shaft 15b into the first fitting portion 151 of the pump shaft 15a, the rotor shaft 15b and the pump shaft 15a are fixed to each other and integrated.

[0063] The shaft 15 has a fitting structure in which the first fitting portion 151 and the second fitting portion 152 have a preset fitting tolerance between the hole diameter of the first fitting portion 151 and the shaft diameter of the second fitting portion 152. As the fitting tolerance here, for example, the gap between the first fitting portion 151 and the second fitting portion 152 is set to 40 μm to 50 μm on one side, and the smaller the gap, the better.

[0064] An example of the structure of the fitting portion 150 will be described using Figures 6 and 7. Note that the structure of the fitting portion 150 is not limited to the structure shown in Figures 6 and 7. As shown in Figures 2 and 3 and Figures 6 and 7, the shaft 15 may have a setscrew 155. That is, the fitting portion 150 may have a setscrew 155.

[0065] 2, 3, 6, and 7, the first fitting portion 151 of the pump shaft 15a has a threaded hole 151d formed in its side surface, through which a setscrew 155 is inserted. The setscrew 155 is a screw used to fasten objects by pressing the tip of the threaded portion against a mating member. The setscrew 155 fastens the first fitting portion 151 to the second fitting portion 152, and thereby fastens the pump shaft 15a to the rotor shaft 15b. The setscrew 155 is inserted into the threaded hole 151d.

[0066] The rotor shaft 15b and the pump shaft 15a are fixed to each other by a set screw 155 that is inserted into the screw hole 151d and has its tip abutting against the D-cut surface 15d. Although there is one screw hole 151d and one set screw 155 shown in Fig. 7, there may be one or more screw holes 151d and one or more set screws 155.

[0067] 4, 5, 6, and 7, the second fitting portion 152 of the rotor shaft 15b has a D-cut surface 15d formed on its side surface. The D-cut surface 15d is a portion obtained by cutting a part of the outer peripheral surface of a cylinder into a flat shape, and is a flat surface formed on part of the outer peripheral surface of a cylinder when a part of a circle when viewed in the axial direction is cut along a straight line to form a cross-sectional shape. In other words, the D-cut surface 15d is a portion obtained by cutting the outer peripheral portion of a cylindrical shaft to form a flat surface with one straight side in a planar shape, like the letter D.

[0068] As shown in Figure 7, the first fitting portion 151 has a cylindrical portion with a threaded hole 151d formed in its side surface, through which a setscrew 155 is inserted. The first fitting portion 151 defines a cylindrical hole extending in the axial direction inside. The inner peripheral wall 151b of the first fitting portion 151 defines a hollow portion of the cylinder. The inner peripheral wall 151b of the first fitting portion 151 defines the inner peripheral surface of the first fitting portion 151. The first fitting portion 151 is fixed to the D-cut surface 15d of the second fitting portion 152 with the setscrew 155.

[0069] [Operation of Water Pump 100] The operation of water pump 100 will now be described. In water pump 100, motor 10 drives rotor 11 to rotate, which in turn rotates impeller 20 connected to shaft 15. Casing 30 has a suction port 34 formed at one end of a refrigerant flow path formed in casing 30, and a discharge port 35 formed at the other end. As impeller 20 rotates, liquid in water pump 100 flows from suction port 34 to discharge port 35, thereby transporting the liquid in casing 30.

[0070] At this time, the fluid flowing from the piping connected to the inlet-side connector 36 passes through the suction port 34, and the liquid that has passed through the suction port 34 flows inside the inlet-side pipe 32. The liquid that has flowed through the inlet-side pipe 32 passes through the inlet 31a and flows into the accommodation space 31. The liquid that has flowed into the accommodation space 31 passes through the blade inlet 22 of the impeller 20 and is subjected to centrifugal force due to the rotation of the impeller 20. The liquid that has been subjected to centrifugal force is then discharged from the slit 23 of the impeller 20, moves along the inner surface of the spiral shape of the accommodation space 31, passes through the outlet 31b, and flows into the outlet-side pipe 33. The liquid that has flowed into the outlet-side pipe 33 passes through the discharge port 35 and is discharged into the piping connected to the outlet-side connector 37.

[0071] 8 is a schematic diagram showing an example of the configuration of the water pump 100 according to embodiment 1. The water pump 100 has a load-side bearing 14 that supports the pump shaft 15a and an anti-load-side bearing 16 that supports the rotor shaft 15b. As described above, one direction along the axial direction of the shaft 15 is the load side, and the other direction along the axial direction of the shaft 15 is the anti-load side.

[0072] In the water pump 100, the rotor shaft 15b is attached to the non-load side bearing 16, and the pump shaft 15a is attached to the load side bearing 14. The water pump 100 has the rotor shaft 15b as a common component, and the pump shaft 15a attached to the rotor shaft 15b can be changed to a pump shaft 15a with a different outer diameter.

[0073] As shown in FIG. 8 , the water pump 100 can be modified or replaced, for example, by changing the pump shaft 15a, where the outer diameter of the portion where the load-side bearing 14 is attached, to a pump shaft 15a where the outer diameter of the portion where the load-side bearing 14 is attached, that is, a diameter D1, and another pump shaft 15a where the outer diameter of the portion where the load-side bearing 14 is attached to that is a diameter D2. For example, the water pump 100 uses the rotor shaft 15b as a common component, and the pump shaft 15a attached to the rotor shaft 15b can be changed to a pump shaft 15a with a different outer diameter. The load-side bearing 14 of the water pump 100 has a larger diameter than the non-load-side bearing 16. It is conceivable to increase the diameter of the pump shaft 15a when it is desired to increase the output of the water pump 100 without changing the external shape of the water pump 100.

[0074] 8 shows two types of pump shafts 15a, one with a diameter D1 and the other with a diameter D2, but the pump shafts 15a may be three or more types formed with different diameter sizes. That is, the water pump 100 and the shaft 15 may have one type of pump shaft 15a, or may have multiple pump shafts 15a formed with different diameter sizes.

[0075] As will be described later, the diameter of the load-side bearing 14 of the water pump 100 may be changed. The water pump 100 can use the pump shaft 15a corresponding to the diameter of the load-side bearing 14 to be used, from among a plurality of pump shafts 15a formed with different outer diameters.

[0076] [Operation and Effects of Shaft 15 and Water Pump 100] The shaft 15 includes a rotor shaft 15b and a pump shaft 15a. The rotor shaft 15b is formed in a cylindrical shape, and the rotor 11 of the motor 10 is fixed to the rotor shaft 15b, constituting part of the power section of the motor 10. The pump shaft 15a is formed in a cylindrical shape, and the impeller 20 is fixed to a tip end 15c, constituting a section that pumps liquid inside the casing 30, and is made of a different material from the rotor shaft 15b. The shaft 15 has a fitting portion 150 that forms the portion where the rotor shaft 15b and the pump shaft 15a are fitted together. The rotor shaft 15b and the pump shaft 15a are arranged coaxially in the shaft 15, and the rotor shaft 15b and the pump shaft 15a are fixed to each other and integrated by the fitting portion 150.

[0077] The shaft 15 is divided into two parts: a rotor shaft 15b, which is attached to the rotor 11 and serves as the power unit, and a pump shaft 15a, which is attached to the impeller 20 and pumps water. The pump shaft 15a and the rotor shaft 15b are fitted together. The shaft 15 can be easily manufactured by integrating dissimilar metal components without the need for dedicated equipment and jigs, as in friction welding. This reduces initial investment. Furthermore, the shaft 15 can be manufactured by integrating dissimilar metal components without using friction welding, which can heat the shaft during processing. This reduces the effects of thermal distortion and eliminates the need for post-processing. Therefore, the shaft 15 of the water pump 100 and the water pump 100 equipped with the shaft 15 can reduce initial investment and eliminate the effects of thermal distortion and the need for post-processing.

[0078] Furthermore, the shaft 15 has a rotor shaft 15b and a pump shaft 15a arranged coaxially, and the rotor shaft 15b and the pump shaft 15a are fixed to each other and integrated by a fitting portion 150. The shaft 15 has a two-piece structure consisting of the rotor shaft 15b, which is attached to the rotor 11 and serves as the power unit, and the pump shaft 15a, which is attached to the impeller 20 and pumps water, and the pump shaft 15a and the rotor shaft 15b are fitted together. Therefore, the shaft 15 can be easily obtained as an integrated shaft made of dissimilar metal parts without using dedicated equipment or jigs, and the portion that will be submerged can be protected against rust and corrosion without using dedicated equipment or jigs.

[0079] A characteristic of water pumps is that a load is applied downward during operation, so the diameter of the load-side bearing must be changed depending on the load.When changing the specifications of the load-side bearing diameter depending on the load during operation, it is necessary to change the shaft to one with an outer diameter that corresponds to the inner diameter of the load-side bearing being used.

[0080] The shaft 15 is constructed in two parts, the rotor shaft 15b and the pump shaft 15a, so that the rotor shaft 15b can be a common part and the pump shaft 15a can be a replaceable part. Therefore, it is easy to use pump shafts 15a with different outer diameters corresponding to the inner diameter of the load-side bearing 14, which changes depending on the load on the water pump 100.

[0081] The shaft 15 has a structure in which the pump shaft 15a and the rotor shaft 15b each have a bearing, and by changing the shaft dimensions on one side in response to changes in the bearing specifications, the shafts can be easily used interchangeably. In other words, since the shaft 15 can easily be used with pump shafts 15a having different outer diameters, the load-side bearing 14 with different diameters can be easily changed and used interchangeably depending on the load on the water pump 100.

[0082] The pump shaft 15a also has a first fitting portion 151 that constitutes the fitting portion 150. The rotor shaft 15b also has a second fitting portion 152 that, together with the first fitting portion 151, constitutes the fitting portion 150. The first fitting portion 151 is formed in a cylindrical shape with a bottom that is recessed in the axial direction of the pump shaft 15a. The second fitting portion 152 is formed in a columnar shape that is inserted into the first fitting portion 151. This configuration of the shaft 15 allows for easy production of an integrated shaft from dissimilar metal components without the need for dedicated equipment and jigs, such as friction welding, thereby reducing initial investment. Furthermore, this configuration of the shaft 15 allows for production of an integrated shaft from dissimilar metal components without the need for friction welding, which generates high temperatures during processing. This reduces the effects of thermal distortion and eliminates the need for post-processing. This configuration also allows for easy use of pump shafts 15a with different outer diameters that correspond to the inner diameter of the load-side bearing 14, which changes depending on the load applied to the water pump 100.

[0083] In addition, the hole diameter of the first fitting portion 151 and the shaft diameter of the second fitting portion 152 are configured to have a fitting tolerance that is set in advance, so that the axial misalignment of the shaft 15 can be kept within the fitting tolerance.

[0084] The fitting portion 150 also has a setscrew 155. The first fitting portion 151 of the pump shaft 15a has a threaded hole 151d formed in its side surface, through which the setscrew 155 is inserted. The second fitting portion 152 of the rotor shaft 15b has a D-cut surface 15d formed in its side surface. The rotor shaft 15b and the pump shaft 15a are fixed to each other by the setscrew 155 inserted in the threaded hole 151d. The tip of the setscrew 155 abuts against the D-cut surface 15d, and the setscrew 155 prevents the second fitting portion 152 from moving relative to the first fitting portion 151.

[0085] The shaft 15 can prevent the rotor shaft 15b from spinning freely relative to the pump shaft 15a by contacting the D-cut surface 15d of the second fitting portion 152 with the set screw 155. Therefore, the shaft 15 can firmly fasten the rotor shaft 15b and the pump shaft 15a by contacting the D-cut surface 15d of the second fitting portion 152 with the set screw 155.

[0086] The water pump 100 has a fitting portion 150 that forms the portion where the rotor shaft 15b and the pump shaft 15a are fitted together. In the water pump 100, the rotor shaft 15b and the pump shaft 15a are arranged coaxially, and the fitting portion 150 fixes the rotor shaft 15b and the pump shaft 15a to each other and integrates them.

[0087] The water pump 100 has a load side bearing 14 that supports the pump shaft 15a and a non-load side bearing 16 that supports the rotor shaft 15b. In the water pump 100, the non-load side bearing 16 is attached to the rotor shaft 15b, and the load side bearing 14 is attached to the pump shaft 15a. The water pump 100 has the rotor shaft 15b as a common component, and the pump shaft 15a attached to the rotor shaft 15b can be changed to a pump shaft 15a with a different outer diameter.

[0088] As mentioned above, when changing the diameter specifications of the load side bearing of a water pump depending on the load during operation, it is necessary to change the shaft to one with an outer diameter that corresponds to the inner diameter of the load side bearing being used.

[0089] When the diameter specifications of the load side bearing 14 of the water pump 100 are changed in accordance with the load during operation, it is sufficient to change the pump shaft 15a, which has an outer diameter corresponding to the inner diameter of the load side bearing 14 used. In other words, when the diameter specifications of the load side bearing 14 of the water pump 100 are changed in accordance with the load during operation, it is not necessary to change the entire shaft 15, which has an outer diameter corresponding to the inner diameter of the load side bearing 14 used, and it is sufficient to change only the pump shaft 15a.

[0090] The water pump 100's pump output varies depending on the required flow rate or head. In the water pump 100, the operating load on the load-side bearing 14 varies depending on the pump output. When manufacturing water pumps 100 with different outputs, the rotor shaft 15b can be used as a common component even when changing the diameter of the load-side bearing 14, eliminating the need to change the rotor shaft 15b. When changing the specifications of the load-side bearing 14, the water pump 100 requires only changing the pump shaft 15a with the corresponding outer diameter, allowing the rotor shaft 15b to be a common component, making it easy to use for different applications. The water pump 100 allows for easy replacement of the shaft on which the load-side bearing 14 is attached, which is different from the various types of water pumps whose bearing diameter changes depending on the load applied during operation. This allows for a shaft structure suitable for multiple models to be obtained at a lower cost than preparing multiple shafts.

[0091] The water pump 100 includes a shaft 15. Therefore, the water pump 100 can achieve the same effects as the shaft 15 described above. For example, as described above, the water pump 100 can reduce initial investment and reduce the effects of thermal distortion, eliminating the need for post-processing. Furthermore, the water pump 100 can easily obtain an integrated shaft 15 made of dissimilar metal components without the need for dedicated equipment or jigs, and the portion that will be submerged can be protected against rust and corrosion without the need for dedicated equipment or jigs.

[0092] The load side bearing 14 of the water pump 100 has a larger diameter than the anti-load side bearing 16. The water pump 100 uses the rotor shaft 15b as a common component, and the pump shaft 15a attached to the rotor shaft 15b can be changed to a pump shaft 15a with a different outer diameter. In the water pump 100, the diameter of the load side bearing 14 is larger than the diameter of the anti-load side bearing 16, allowing the diameter of the pump shaft 15a to be larger than the rotor shaft 15b. By allowing the diameter of the pump shaft 15a to be larger than the rotor shaft 15b, the water pump 100 can increase the output of the water pump 100 compared to when the pump shaft 15a has a diameter smaller than the diameter of the rotor shaft 15b.

[0093] Second Embodiment. Figure 9 is a schematic diagram showing an example of a pump shaft 15a used in a water pump 100 according to a second embodiment, with the load-side bearing 14 not attached. Figure 10 is a schematic diagram showing an example of a rotor shaft 15b used in a water pump 100 according to a second embodiment, with the rotor 11 not fixed. Figure 11 is a schematic diagram showing an example of a shaft 15 used in a water pump 100 according to a second embodiment, with the rotor shaft 15b and the pump shaft 15a fitted together. Figure 12 is a schematic cross-sectional view of a shaft 15 used in a water pump 100 according to a second embodiment, with the rotor shaft 15b and the pump shaft 15a fitted together. Figure 12 is an example of a schematic cross-sectional view of the shaft 15 cut perpendicular to the axial direction of the shaft 15. The fitting portion 150 will be described using Figures 9 to 12. Note that parts having the same configuration as those in the water pump 100 according to the first embodiment are designated by the same reference numerals, and their description will be omitted. In the water pump 100 according to the second embodiment, the configuration of the fitting portion 150 is different from the configuration of the fitting portion 150 of the water pump 100 according to the first embodiment.

[0094] The shaft 15 of the water pump 100 according to the second embodiment includes a key 153 in the fitting portion 150. The key 153 is a rod-shaped mechanical element that is inserted between the rotating body and the shaft of the machine to secure them together. The key 153 is, for example, a square bar-shaped piece of iron. The shape and material of the key 153 are not limited to a square bar shape and iron, and other shapes and materials may be used as long as they can reliably secure the rotating body and the shaft together and ensure strength. The key 153 is a rod-shaped mechanical element that is inserted between the pump shaft 15a and the rotor shaft 15b of the shaft 15 to secure them together.

[0095] A key groove 151f is formed in the inner peripheral wall 151b of the first fitting portion 151 of the pump shaft 15a. The key groove 151f is formed to extend along the axial direction of the shaft 15. The key groove 151f is recessed from the inner peripheral side toward the outer peripheral side in the radial direction of the shaft 15. The key groove 151f is formed in a shape that fits with the key 153.

[0096] A key 153 that fits into the key groove 151f is attached to the outer peripheral wall 152a of the second fitting portion 152 of the rotor shaft 15b. The key 153 is formed to extend along the axial direction of the shaft 15. The key 153 is provided on the rotor shaft 15b so as to protrude from the inner peripheral side toward the outer peripheral side in the radial direction of the shaft 15. The key 153 is formed in a shape that fits into the key groove 151f. The key 153 is formed, for example, in a rectangular parallelepiped shape. The key 153 is fitted into the key groove 151f of the pump shaft 15a.

[0097] The key 153 is, for example, a parallel key such as a sunken key. However, the key 153 is not limited to a parallel key, and may be any other type of key as long as it can ensure the functionality and strength required for the shaft 15 of the motor 10 used in the water pump 100.

[0098] For example, an axial key groove 153a is formed in the outer peripheral wall 152a of the second fitting portion 152 of the rotor shaft 15b. The axial key groove 153a is formed to extend along the axial direction of the shaft 15. The axial key groove 153a is recessed from the outer peripheral side toward the center in the radial direction of the shaft 15. The axial key groove 153a is formed in a shape that fits with a key 153. The key 153 is fitted into the axial key groove 153a of the rotor shaft 15b and attached to the rotor shaft 15b.

[0099] [Operation and Effects of Shaft 15 and Water Pump 100] A key groove 151f is formed in the inner peripheral wall 151b of the first fitting portion 151 of the pump shaft 15a. A key 153 that fits into the key groove 151f is attached to the outer peripheral wall 152a of the second fitting portion 152 of the rotor shaft 15b. This structure of the shaft 15 enables the rotor shaft 15b and the pump shaft 15a to be firmly fastened together. This structure of the shaft 15 also prevents the rotor shaft 15b from spinning freely relative to the pump shaft 15a.

[0100] The water pump 100 includes a shaft 15. Therefore, the water pump 100 can achieve the same effects as the shaft 15 described above.

[0101] Third Embodiment. Figure 13 is a schematic diagram showing an example of a pump shaft 15a used in a water pump 100 according to a third embodiment, with the load-side bearing 14 not attached. Figure 14 is a schematic diagram showing an example of a rotor shaft 15b used in a water pump 100 according to a third embodiment, with the rotor 11 not fixed. Figure 15 is a schematic diagram showing an example of a shaft 15 used in a water pump 100 according to a third embodiment, with the rotor shaft 15b and the pump shaft 15a fitted together. Figure 16 is a schematic cross-sectional view of a shaft 15 used in a water pump 100 according to a third embodiment, with the rotor shaft 15b and the pump shaft 15a fitted together. Figure 16 is an example of a schematic cross-sectional view of the shaft 15 cut perpendicular to the axial direction of the shaft 15. The fitting portion 150 will be described using Figures 13 to 16. Note that parts having the same configuration as those in the water pumps 100 according to the first and second embodiments are designated by the same reference numerals, and their description will be omitted. In the water pump 100 according to the third embodiment, the configuration of the fitting portion 150 is different from the configuration of the fitting portion 150 of the water pumps 100 according to the first and second embodiments.

[0102] The shaft 15 of the water pump 100 according to the third embodiment has a fastening structure with a screw at the fitting portion 150. The shaft 15 of the water pump 100 according to the third embodiment has a structure in which the rotor shaft 15b and the pump shaft 15a are fastened together by forming a male thread 152d at the tip of the rotor shaft 15b and a female thread 151g at the hollow portion 151c of the pump shaft 15a.

[0103] As shown in FIG. 13 , a female thread 151g is formed on the inner circumferential wall 151b of the first fitting portion 151 of the pump shaft 15a. The female thread 151g is a groove cut into the inner circumferential wall 151b, which is the inside of the hole, so as to fit with the male thread 152d of the rotor shaft 15b. The pump shaft 15a is formed, for example, in a cylindrical shape. The female thread 151g is formed on the end opposite the tip end 15c in the axial direction of the shaft 15, that is, on the anti-load side. In other words, the female thread 151g is formed on the upper end of the pump shaft 15a in the axial direction of the shaft 15.

[0104] As shown in Figure 14, a male thread 152d is formed on the outer peripheral wall 152a of the second fitting portion 152 of the rotor shaft 15b. The male thread 152d is a thread with a spiral groove cut into the outside of the rotor shaft 15b. The rotor shaft 15b is formed, for example, in a cylindrical shape. The male thread 152d is formed at the end of the shaft 15 on the load side in the axial direction. In other words, the male thread 152d is formed at the lower end of the rotor shaft 15b in the axial direction of the shaft 15.

[0105] 15 and 16 , the shaft 15 has a first fitting portion 151 and a second fitting portion 152 fastened together by fitting the female thread 151g and the male thread 152d together, thereby fixing the rotor shaft 15b and the pump shaft 15a to each other. The female thread 151g of the first fitting portion 151 and the male thread 152d of the second fitting portion 152 are threaded in the direction opposite to the rotational direction of the motor 10 that constitutes the water pump 100. This configuration of the shaft 15 prevents loosening of the fastened portion between the rotor shaft 15b and the pump shaft 15a.

[0106] [Operation and Effects of the Shaft 15 and the Water Pump 100] A female thread 151g is formed on the inner peripheral wall 151b of the first fitting portion 151 of the pump shaft 15a. A male thread 152d is formed on the outer peripheral wall 152a of the second fitting portion 152 of the rotor shaft 15b. When the female thread 151g and the male thread 152d are fitted together, the first fitting portion 151 and the second fitting portion 152 of the shaft 15 are fastened together, thereby fixing the rotor shaft 15b and the pump shaft 15a to each other. This structure of the shaft 15 enables the rotor shaft 15b and the pump shaft 15a to be firmly fastened together. This structure of the shaft 15 also prevents the rotor shaft 15b from spinning freely relative to the pump shaft 15a. Furthermore, this configuration of the shaft 15 eliminates the need for parts such as setscrews or keys, thereby reducing the number of parts.

[0107] The water pump 100 includes a shaft 15. Therefore, the water pump 100 can achieve the same effects as the shaft 15 described above.

[0108] Fourth Embodiment. Figure 17 is a schematic diagram showing an example of a shaft 15 used in a water pump 100 according to a fourth embodiment, with the rotor shaft 15b and the pump shaft 15a fitted together. Figure 18 is a schematic cross-sectional view of the shaft 15 used in a water pump 100 according to the fourth embodiment, with the rotor shaft 15b and the pump shaft 15a fitted together. Figure 18 is an example of a schematic cross-sectional view of the shaft 15 cut perpendicular to the axial direction of the shaft 15. The fitting portion 150 will be described using Figures 17 to 18. Note that parts having the same configuration as those in the water pumps 100 according to the first to third embodiments are denoted by the same reference numerals, and their description will be omitted. The water pump 100 according to the fourth embodiment has a different configuration of the fitting portion 150 from the fitting portion 150 of the water pumps 100 according to the first to third embodiments.

[0109] The shaft 15 of the water pump 100 according to the fourth embodiment has a fitting portion 150 that includes a shrink-fit fastening structure. The shaft 15 is fastened by shrink fitting between a first fitting portion 151 of the pump shaft 15a and a second fitting portion 152 of the rotor shaft 15b. The shaft 15 is fixed between the pump shaft 15a and the rotor shaft 15b by shrink fitting. For example, the shaft 15 may be configured such that the hole diameter of the first fitting portion 151 of the pump shaft 15a is smaller than the shaft diameter of the second fitting portion 152 of the rotor shaft 15b, thereby forming an interference fit. After heating the pump shaft 15a, the rotor shaft 15b is inserted and fixed by shrink fitting.

[0110] [Effects of the shaft 15 and the water pump 100] The shaft 15 is fastened by shrink fitting between the first fitting portion 151 of the pump shaft 15a and the second fitting portion 152 of the rotor shaft 15b. This structure of the shaft 15 allows for a strong fastening between the rotor shaft 15b and the pump shaft 15a. This structure of the shaft 15 prevents the rotor shaft 15b from spinning freely relative to the pump shaft 15a. Furthermore, this configuration of the shaft 15 eliminates the need for parts such as setscrews or keys, thereby reducing the number of parts. Furthermore, this configuration of the shaft 15 eliminates the need for threading, such as female and male threads, simplifying the processing compared to when threading is required.

[0111] The water pump 100 includes a shaft 15. Therefore, the water pump 100 can achieve the same effects as the shaft 15 described above.

[0112] The shaft 15 of the water pump 100 and the water pump 100 have been described above based on the embodiments, but the shaft 15 of the water pump 100 and the water pump 100 are not limited to the configurations of the above-described embodiments. Each of the above-described first to fourth embodiments can be implemented in combination with one another. The configuration of the shaft 15 of the water pump 100 and the water pump 100 described above is merely an example, and other components may be included, or some components may be omitted. In short, the shaft 15 of the water pump 100 and the water pump 100 are within the scope of design modifications and application variations that would normally be made by a person skilled in the art, as long as they do not deviate from the technical concept thereof.

[0113] 10 Motor, 11 Rotor, 12 Stator, 13 Motor case, 14 Load side bearing, 15 Shaft, 15a Pump shaft, 15b Rotor shaft, 15c Tip portion, 15d D-cut surface, 16 Non-load side bearing, 20 Impeller, 21 Blade portion, 22 Blade inlet portion, 23 Slit, 30 Casing, 30a Opening, 31 Housing space, 31a Inlet portion, 31b Outlet portion, 32 Inlet side pipe portion, 33 Outlet side pipe portion, 34 Suction port, 35 Discharge port, 36 Inlet side connection portion, 37 Outlet side connection portion, 38 Water supply portion, 40 Frame, 41 Upper annular portion, 43 Lower annular portion, 44 Lower insertion portion, 45 Frame shaft hole portion, 100 Water pump, 150 Fitting portion, 151 First fitting portion, 151a Outer peripheral wall, 151b inner peripheral wall, 151c hollow portion, 151d screw hole, 151f keyway, 151g female screw, 152 second fitting portion, 152a outer peripheral wall, 152d male screw, 153 key, 153a shaft side keyway, 155 set screw.

Claims

1. A shaft used in a motor of a water pump having a motor as a drive unit, an impeller that receives output from the motor to rotate the liquid and apply centrifugal force to the liquid to move it, a casing that houses the impeller and has a water supply unit that serves as a flow path for the liquid, the water supply unit having an inlet at one end and a discharge outlet at the other end, and a frame that connects the motor and the casing, the shaft comprising: a cylindrical rotor shaft to which the rotor of the motor is fixed and that constitutes part of the power unit of the motor; and a cylindrical pump shaft to which the impeller is fixed at its tip and that constitutes the part inside the casing that pumps out the liquid, the pump shaft being made of a different material from the rotor shaft; and a fitting portion that forms the part where the rotor shaft and the pump shaft are fitted together, the rotor shaft and the pump shaft being arranged coaxially and fixed to each other by the fitting portion to form an integrated unit.

2. A water pump shaft as described in claim 1, wherein the pump shaft has a first fitting portion that constitutes the fitting portion, the rotor shaft has a second fitting portion that constitutes the fitting portion together with the first fitting portion, the first fitting portion is formed in a cylindrical shape with a bottom that is recessed in the axial direction of the pump shaft, and the second fitting portion is formed in a columnar shape that is inserted into the first fitting portion.

3. A water pump shaft as described in claim 2, wherein the fitting portion further has a setscrew, the first fitting portion of the pump shaft has a cylindrical portion on its side surface with a threaded hole through which the setscrew is inserted, the second fitting portion of the rotor shaft has a D-cut surface on its side surface, and the first fitting portion has a cylindrical hole formed therein, and the rotor shaft and the pump shaft are fixed to each other by the setscrew inserted into the threaded hole and abutting the D-cut surface.

4. A water pump shaft as described in claim 2, wherein a key groove is formed on the inner peripheral wall of the first fitting portion of the pump shaft, and a key that fits into the key groove is attached to the outer peripheral wall of the second fitting portion of the rotor shaft.

5. A water pump shaft as described in claim 2, wherein a female thread is formed on the inner peripheral wall of the first fitting portion of the pump shaft, and a male thread is formed on the outer peripheral wall of the second fitting portion of the rotor shaft, and the first fitting portion and the second fitting portion are fastened together by fitting the female thread and the male thread together, thereby fixing the rotor shaft and the pump shaft to each other.

6. The shaft of a water pump according to claim 2, wherein the first mating portion of the pump shaft and the second mating portion of the rotor shaft are fastened together by shrink fitting.

7. A water pump shaft as set forth in any one of claims 2 to 5, wherein the first fitting portion and the second fitting portion have a fitting structure in which the hole diameter of the first fitting portion and the shaft diameter of the second fitting portion have a preset fitting tolerance.

8. A water pump comprising: a water pump shaft according to any one of claims 1 to 7; a motor having said shaft; an impeller that receives output from said motor to rotate a liquid and apply centrifugal force to the liquid to move the liquid; a casing that is formed with the water supply section that serves as a flow path for the liquid, the casing having an inlet at one end forming said water supply section and an outlet at the other end, and that houses the impeller in a storage space formed in part of said water supply section; and a frame that is formed in a cylindrical shape and connects the motor and the casing in the axial direction of the shaft.

9. A water pump comprising: a water pump shaft according to any one of claims 1 to 6; a motor having said shaft; an impeller that receives output from said motor to rotate a liquid and apply centrifugal force to the liquid to move the liquid; a casing that is formed with the water supply section that serves as a flow path for the liquid, the casing having the suction port at one end that forms the water supply section and the discharge port at the other end, and that houses the impeller in an accommodation space formed in part of the water supply section; a cylindrical frame that connects the motor and the casing in the axial direction of the shaft; and a load side bearing that supports the pump shaft and an anti-load side bearing that supports the rotor shaft, when one direction along the axial direction of the shaft is the load side and the other direction along the axial direction of the shaft is the anti-load side, wherein the load side bearing has a larger diameter than the anti-load side bearing, and the rotor shaft is a common part, and the pump shaft attached to the rotor shaft can be changed to a pump shaft with a different outer diameter.

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