Liquefied gas pump

Abstract

This liquefied gas pump comprises: a rotary shaft made of stainless steel and rotatable around an axis; a casing that houses the rotary shaft; an impeller provided integrally with the rotary shaft in the casing and capable of pumping liquefied gas as the rotary shaft rotates; and an electric motor having a stator that is fixed to an inner peripheral surface of the casing and surrounds the rotary shaft, and a rotor that is provided inside the stator with a clearance therebetween and is integrally fixed to the rotary shaft, wherein the rotor has a sleeve made of alloy steel containing Ni and fitted onto the rotary shaft from the outer circumference, and a rotor core made of a plurality of electromagnetic steel plates stacked in the axial direction and fitted onto the sleeve from the outer circumference.

Description

Liquefied gas pump

[0001] The present disclosure relates to a liquefied gas pump. This application claims priority to Japanese Patent Application No. 2024-194172 filed in Japan on November 6, 2024, and incorporates its content herein by reference.

[0002] As a pump for boosting the pressure of a liquid, there is a vertical rotary pump. For example, Patent Document 1 discloses a technique for simplifying the structure, improving the reliability, and enhancing the efficiency of a pump for liquefied gas used in a low-temperature environment. In the pump for liquefied gas, the pump shaft (rotating shaft) and the motor shaft (rotor core) have an integrated structure made of the same material.

[0003] Japanese Patent Application Laid-Open No. 2006-170046

[0004] However, in order to balance the strength and magnetic properties of the rotating shaft and the rotor core, the rotating shaft and the rotor core may be composed of different materials according to their respective purposes. In this case, under low-temperature conditions such as liquefied gas, loosening may occur between the fitted rotating shaft and rotor core due to differences in the linear expansion coefficients. If the interference fit between the rotating shaft and the rotor core can be increased, this loosening can be suppressed, but it is difficult to implement because the strength of the rotating shaft and the rotor core is low.

[0005] The present disclosure provides a liquefied gas pump capable of firmly fixing the rotor of an electric motor to a rotating shaft even under low-temperature conditions.

[0006] The liquefied gas pump according to the present disclosure includes a rotating shaft that is rotatable about an axis and made of stainless steel, a casing that houses the rotating shaft, an impeller that is provided integrally with the rotating shaft within the casing and is capable of pumping liquefied gas as the rotating shaft rotates, a stator that is fixed to the inner peripheral surface of the casing and surrounds the rotating shaft, and an electric motor that has a rotor provided inside the stator with a clearance therebetween and fixed integrally to the rotating shaft. The rotor includes a sleeve made of alloy steel containing Ni and fitted to the rotating shaft from the outer peripheral side, and a rotor core made of electromagnetic steel sheets that are fitted to the sleeve from the outer peripheral side and stacked in a plurality in the axial direction.

[0007] According to the liquefied gas pump of this disclosure, the rotor of the electric motor can be firmly fixed to the rotating shaft even under low temperature conditions.

[0008] This is a schematic diagram showing the entire liquefied gas pump according to one embodiment of the present disclosure. This is an enlarged view of the main part of the liquefied gas pump according to the first embodiment of the present disclosure. This is an enlarged view of the main part of the liquefied gas pump according to the second embodiment of the present disclosure.

[0009] <First Embodiment> Hereinafter, the liquefied gas pump 1 according to the first embodiment of this disclosure will be described in detail with reference to Figures 1 and 2.

[0010] <Liquefied Gas Pump> As shown in Figure 1, the liquefied gas pump 1 is positioned so as to be suspended inside the sump 50. The liquefied gas pump 1 is a device for pressurizing a liquid as a fluid. In this embodiment, the liquefied gas pump 1 for pressurizing liquid hydrogen will be described. Note that the fluid is not limited to liquid hydrogen, but may be other liquids or gases. For example, liquefied natural gas (LNG) is one example.

[0011] In this disclosure, the first direction D1 and the second direction D2 are defined as follows. The first direction D1 and the second direction D2 are one side and the other side in the direction in which the axis O extends. In one embodiment of this disclosure, the direction in which the axis O extends is parallel to the vertical direction when the liquefied gas pump 1 is assembled. That is, the first direction D1 is the direction from below to above in the vertical direction. The second direction D2 is the direction from above to below in the vertical direction. Therefore, below, the first direction D1 may be described as the upward direction in the vertical direction, and the second direction D2 may be described as the downward direction in the vertical direction. Note that the liquefied gas pump 1 of this disclosure is not limited to a configuration in which the axis O and the vertical direction are parallel when the liquefied gas pump 1 is assembled, but also includes a configuration in which the axis O and the vertical direction intersect.

[0012] The sump 50 is capable of storing liquid. In this embodiment, the sump 50 is capable of storing liquid hydrogen. The sump 50 is, for example, a vacuum insulated container. That is, the sump 50 is an insulated structure having a bottomed cylindrical shape. The sump 50 has a liquid storage chamber 53 formed inside it. The liquid storage chamber 53 is capable of storing liquid hydrogen. The sump 50 has an outer peripheral flange 51 provided on its upper vertical side. The sump 50 is installed on a stand (not shown). The sump 50 has an upper flange provided on its upper vertical side. The upper flange is provided vertically above the outer peripheral flange 51. The upper flange and the outer peripheral flange 51 are arranged in contact with each other. The upper flange and the outer peripheral flange 51 are connected, for example, via bolts. The upper flange is positioned to maintain the airtightness of the sump 50. The upper flange can also be installed in a manner that suspends the liquefied gas pump 1.

[0013] The sump 50 has a supply pipe 60 and a gas discharge pipe 61 connected to its side. The supply pipe 60 is a pipe that allows liquid hydrogen to be supplied to the liquid storage chamber 53 from an external source. The gas discharge pipe 61 is a pipe that allows vaporized hydrogen from the liquid storage chamber 53 to be discharged to the outside of the sump 50. The gas discharge pipe 61 is located vertically above the supply pipe 60. The gas discharge pipe 61 may also be capable of discharging liquid hydrogen to the outside of the sump 50, as well as vaporized hydrogen.

[0014] The liquefied gas pump 1 is located inside the sump 50. The liquefied gas pump 1 comprises a casing 10, a rotating shaft 20, an electric motor 30, an inducer 21, an impeller 22, and a bearing device 40.

[0015] <Casing> The casing 10 forms the outer shell of the liquefied gas pump 1. The casing 10 has a hollow shape. The casing 10 may be composed of a single component or may be composed of multiple components assembled together. The casing 10 is capable of housing the electric motor 30, inducer 21, impeller 22, and bearing device 40 inside. The upper end of the casing 10 is connected to the upper flange and is suspended and supported inside the sump 50. The casing 10 has a cylindrical shape centered on an axis O that extends along the vertical direction, but is not limited to this. In addition, although both the sump 50 and the casing 10 spread out around the axis O, the centers of the sump 50 and the casing 10 may be offset from each other.

[0016] The casing 10 is provided with a suction section 11 at its lower end. The suction section 11 is formed to communicate with the liquid storage chamber 53. Liquid hydrogen stored in the liquid storage chamber 53 can flow through the suction section 11. The casing 10 is also provided with a discharge section 12 at its upper end. The discharge section 12 is connected to a discharge pipe 62 that extends to the outside of the sump 50. The suction section 11 may also be directly connected to piping extended from the supply pipe 60 or the like. In other words, liquid hydrogen may be introduced directly from the piping to the suction section 11 without first being stored in the liquid storage chamber 53.

[0017] <Rotational Axis> The rotational shaft 20 is a rod-shaped member extending along the axis O. The rotational shaft 20 and the casing 10 are arranged concentrically with respect to the axis O. The rotational shaft 20 is supported by a bearing device 40 so as to be rotatable relative to the casing 10 around the axis O. In this embodiment, the rotational shaft 20 is made of stainless steel. More specifically, the rotational shaft 20 is made of SUS316L. However, it is not limited to this. The inducer 21, the impeller 22, and the rotor 36 of the electric motor 30 are fixed to the rotational shaft 20. Hereinafter, the radial direction of the rotational shaft 20 will be simply referred to as the radial direction, and the circumferential direction of the rotational shaft 20 will be simply referred to as the circumferential direction. The direction in which the axis O extends will be referred to as the axial direction.

[0018] <Bearing Device> The bearing device 40 is a component that supports the rotating shaft 20 so that it can rotate around axis O relative to the casing 10. The bearing device 40 is fixedly installed inside the casing 10. The bearing device 40 includes a radial bearing 41, a thrust bearing 44, and a thrust disc 45.

[0019] The radial bearing 41 is positioned to withstand the radial load of the rotating shaft 20. That is, the radial bearing 41 is positioned concentrically with the rotating shaft 20 and is provided to cover the rotating shaft 20 from its outer circumferential surface. Multiple radial bearings 41 are provided. In this embodiment, a first radial bearing 42 and a second radial bearing 43 are provided. The first radial bearing 42 is positioned vertically above the casing 10. The second radial bearing 43 is positioned vertically below the casing 10. The radial bearing 41 is not limited in type. For example, the radial bearing 41 may be a rolling bearing, a sliding bearing, or a magnetic bearing. Also, the first radial bearing 42 and the second radial bearing 43 may be bearings of the same type or bearings of different types.

[0020] The thrust bearing 44 and thrust disc 45 are arranged to withstand the load in the axial direction of the rotating shaft 20. The thrust disc 45 is fixed to the outer circumference of the rotating shaft 20. The thrust disc 45 is a disc shape that is provided to expand the diameter of the rotating shaft 20 in the radial direction while fixed to the rotating shaft 20. The thrust disc 45 is rotatable integrally with the rotating shaft 20. The thrust disc 45 is also movable integrally with the rotating shaft 20 in the axial direction. The thrust bearing 44 is provided to sandwich the thrust disc 45 in the axial direction.

[0021] In this embodiment, the thrust bearing 44 is a hydrostatic bearing. Preferably, the thrust bearing 44 is a non-contact type bearing. For example, the thrust bearing 44 may be a magnetic bearing. However, the thrust bearing 44 is not limited to a non-contact type bearing. Furthermore, the thrust bearing 44 is positioned vertically above the first radial bearing 42 and the second radial bearing 43. However, the position of the thrust bearing 44 is not limited to this. The thrust bearing 44 may be positioned between the first radial bearing 42 and the second radial bearing 43, or vertically below the first radial bearing 42 and the second radial bearing 43.

[0022] <Inducer and Impeller> The inducer 21 and impeller 22 are provided so as to be able to pump liquid hydrogen as the rotating shaft 20 rotates. The inducer 21 and impeller 22 are fixed to the rotating shaft 20 and are provided as a single unit. The inducer 21 and impeller 22 are rotatable together with the rotating shaft 20. In addition, the inducer 21 and impeller 22 are movable together with the rotating shaft 20 in the axial direction. Multiple impellers 22 are provided and are spaced apart in the axial direction. The impeller 22 includes a first-stage impeller 23, a second-stage impeller 24, and a third-stage impeller 25. Note that the number of impellers 22 is not limited to three. The number of impellers 22 may be two or fewer, or four or more.

[0023] The inducer 21 is located at the lower end of the rotating shaft 20. The first stage impeller 23 is provided integrally with the inducer 21. Specifically, the first stage impeller 23 is positioned vertically above the inducer 21. The inducer 21 and the first stage impeller 23 are located in the suction section 11 of the casing 10. The second stage impeller 24 and the third stage impeller 25 are positioned vertically above the first stage impeller 23. Specifically, the second stage impeller 24 and the third stage impeller 25 are positioned vertically above the first stage impeller 23, sandwiching the second radial bearing 43. Note that the inducer 21 may be omitted.

[0024] As the rotating shaft 20 rotates, the inducer 21 and impeller 22 rotate together. As a result, the liquid hydrogen in the liquid storage chamber 53 is drawn into the suction section 11 by the inducer 21. The drawn-in liquid hydrogen is pressurized by one stage by the first-stage impeller 23. The pressurized liquid hydrogen is supplied to the second-stage impeller 24 through the flow path 70 provided in the casing 10. The liquid hydrogen is pressurized by two stages by the second-stage impeller 24. The pressurized liquid hydrogen is supplied to the third-stage impeller 25 through the flow path 71 provided in the casing 10. The liquid hydrogen is pressurized by three stages by the third-stage impeller 25. The pressurized liquid hydrogen is supplied to the discharge section 12 through the flow path 72 provided in the casing 10. The liquid hydrogen supplied to the discharge section 12 is discharged to the outside of the sump 50 from the discharge pipe 62. Furthermore, it is preferable that multiple flow paths 70, 71, and 72 are provided radially outside the impeller 22, spaced apart in the circumferential direction. In addition, other paths through which liquid hydrogen flows may be provided besides the above-mentioned flow paths 70, 71, and 72.

[0025] <Electric Motor> The electric motor 30 is a component for rotating the rotating shaft 20 around the axis O. As shown in Figure 2, the electric motor 30 is installed inside the casing 10. The electric motor 30 has a rotor 36 and a stator 31.

[0026] The rotor 36 is a component that receives power to rotate the rotating shaft 20 around axis O and rotates the rotating shaft 20. The rotor 36 is integrally fixed to the rotating shaft 20. Specifically, the rotor 36 is fixed to the outer circumferential surface of the rotating shaft 20. The rotor 36 has a sleeve 37 and a rotor core 38.

[0027] The sleeve 37 is positioned concentrically with the rotating shaft 20. The sleeve 37 has a cylindrical shape extending in the axial direction. The sleeve 37 is fixed to the outer circumferential surface of the rotating shaft 20. Specifically, the sleeve 37 is fitted to the rotating shaft 20 from the outer circumferential side with a first overlap. The rotor core 38 can be fixed to the outer circumferential surface of the sleeve 37. The sleeve 37 is made of a material with higher strength than the rotor core 38. The sleeve 37 in this embodiment is made of alloy steel containing Ni. The proportion of Ni in the alloy steel constituting the sleeve 37 is preferably 2% to 16% by mass relative to the alloy steel, more preferably 6% to 12%, and optimally 9%. Furthermore, the coefficient of linear expansion of the sleeve 37 is smaller than the coefficient of linear expansion of the rotating shaft 20.

[0028] Here, the statement that the linear expansion coefficient of the sleeve 37 is smaller than that of the rotating shaft 20 is specifically as follows: The sleeve 37 and the rotating shaft 20 are subjected to temperature changes by a fluid (liquid hydrogen in this embodiment). The sleeve 37 and the rotating shaft 20 change in size according to their linear expansion coefficients due to the temperature change. At this time, the change in size of the rotating shaft 20 is greater than that of the sleeve 37. Furthermore, with the sleeve 37 and the rotating shaft 20 placed separately in liquid hydrogen, the difference obtained by subtracting the diameter of the outer surface of the rotating shaft 20 from the diameter of the inner surface of the sleeve 37 is smaller than the first overlap.

[0029] The rotor core 38 is arranged concentrically with the rotating shaft 20 and the sleeve 37. The rotor core 38 is provided inside the stator 31, with a clearance between it and the stator 31. The rotor core 38 has an overall cylindrical shape that extends in the axial direction. The rotor core 38 is fixed to the outer circumferential surface of the sleeve 37. Specifically, the rotor core 38 is fitted into the sleeve 37 from the outer circumferential side with a second overlap. The second overlap is smaller than the first overlap. Furthermore, the coefficient of thermal expansion of the rotor core 38 is approximately the same as that of the sleeve 37. That is, the coefficient of thermal expansion of the rotor core 38 is smaller than that of the rotating shaft 20.

[0030] Here, the condition that the linear expansion coefficients of the rotor core 38 and the sleeve 37 are similar is defined as follows: The rotor core 38 and the sleeve 37 are subjected to temperature changes by a fluid (liquid hydrogen in this embodiment). Due to the temperature change, the size of the rotor core 38 and the sleeve 37 changes according to their linear expansion coefficients. With the rotor core 38 and the sleeve 37 placed separately in liquid hydrogen, the difference obtained by subtracting the diameter of the outer surface of the sleeve 37 from the diameter of the inner surface of the rotor core 38 is smaller than the second overlap. This state is described as the linear expansion coefficients of the rotor core 38 and the sleeve 37 being similar.

[0031] The rotor core 38 is composed of multiple layers of electromagnetic steel sheets stacked in the axial direction. The rotor core 38 may also have a support member on its outer circumferential surface. Furthermore, the rotor core 38 is provided to be shorter than the sleeve 37 in the axial direction, but is not limited to this. The rotor core 38 may be the same length as the sleeve 37 in the axial direction, or it may be longer than the sleeve 37.

[0032] The stator 31 is fixed to the inner circumferential surface of the casing 10. The stator 31 is arranged concentrically with the rotating shaft 20 and the rotor 36. The stator 31 is cylindrical in shape. The stator 31 is arranged to surround the rotating shaft 20 and the rotor 36 from the radially outer side. In other words, the stator 31 is facing the rotor 36 with a radial gap between them. The stator 31 has a stator core 32 and a coil 35.

[0033] The stator core 32 has a yoke and teeth. The yoke is cylindrical with an axis O. The yoke is fixed to the inner surface of the casing 10 with its outer surface fixed thereto. The teeth are provided so as to protrude from the inner surface of the yoke. Multiple teeth are formed, spaced apart from each other in the circumferential direction. Multiple coils 35 are provided, corresponding to each tooth. The coils 35 are wound around each tooth. Therefore, multiple coils 35 are provided, spaced apart in the circumferential direction.

[0034] <Effects and Effects> In the liquefied gas pump 1 described above, a sleeve 37 made of alloy steel containing Ni is fitted to a rotating shaft 20 made of stainless steel from the outer circumference. A rotor core 38 made of electromagnetic steel sheet is fitted to the sleeve 37 from the outer circumference. That is, the rotating shaft 20 and the rotor core 38 are not in direct contact but are connected via the sleeve 37. Furthermore, the first interference fit between the rotating shaft 20 and the sleeve 37 is greater than the second interference fit between the sleeve 37 and the rotor core 38. Moreover, the coefficients of thermal expansion of the sleeve 37 and the rotor core 38 are smaller than the coefficient of thermal expansion of the rotating shaft 20. In addition, the coefficients of thermal expansion of the sleeve 37 and the rotor core 38 are approximately the same.

[0035] The rotating shaft 20 is made of stainless steel, and its coefficient of thermal expansion is greater than that of the electrical steel sheet that makes up the rotor core 38. Therefore, under low temperature conditions, the rotating shaft 20 contracts more than the rotor core 38. Consequently, in order to ensure that the rotating shaft 20 and the rotor core 38 do not loosen under low temperature conditions, a large overlap is required. However, since the rotor core 38 is made of electrical steel sheet, it has low strength, making it difficult to allow a large overlap when attaching it to the rotating shaft 20. More precisely, if the rotor core 38 is attached to the rotating shaft 20 with a large overlap, the strength of the rotor core 38 may not be sufficient, and wear may occur. Here, a sleeve 37 is provided so as to be sandwiched between the rotating shaft 20 and the rotor core 38. Since the sleeve 37 has higher strength than the rotor core 38, a large overlap can be applied to the rotating shaft 20. In addition, the sleeve 37 has a coefficient of thermal expansion similar to that of the rotor core 38. Therefore, even if the overlap of the rotor core 38 is small relative to the sleeve 37, loosening can be suppressed even under low temperature conditions.

[0036] With this configuration, loosening does not occur between the rotating shaft 20 and the sleeve 37 even under low-temperature conditions such as those of liquid hydrogen. Furthermore, loosening does not occur between the sleeve 37 and the rotor core 38. Therefore, the rotating shaft 20 and the rotor core 38 can be formed as a single unit that does not loosen even under low-temperature conditions. Accordingly, with the liquefied gas pump 1 of this embodiment, the rotor 36 of the electric motor 30 can be firmly fixed to the rotating shaft 20 even under low-temperature conditions. Moreover, the liquefied gas pump 1 of this embodiment is applicable to liquid hydrogen, which has an even lower temperature than LNG.

[0037] Thus, according to this embodiment, even though the rotating shaft 20 and the rotor core 38 are made of different materials, it is possible to suppress the occurrence of loosening due to temperature changes. Furthermore, it is possible to achieve the above-mentioned effects while balancing the strength of the rotating shaft 20 and the magnetic properties of the rotor core 38.

[0038] <Second Embodiment> Next, the liquefied gas pump 1a according to the second embodiment of this disclosure will be described in detail with reference to Figure 3. The liquefied gas pump 1a according to the second embodiment is further equipped with a holder 80 and a key 90 compared to the liquefied gas pump 1 according to the first embodiment. Also, the configuration of the rotating shaft 20a and the electric motor 30a according to the second embodiment differs from that of the first embodiment. Note that the configuration of the liquefied gas pump 1a according to the second embodiment, other than that described below, is the same as the configuration of the liquefied gas pump 1 according to the first embodiment.

[0039] <Rotating shaft> The rotating shaft 20a of the second embodiment differs from the rotating shaft 20 of the first embodiment in some structural aspects near the electric motor 30a. The rotating shaft 20a has a groove formed therein so that a key 90 can be attached (details will be described later). The rotating shaft 20a has a rotating shaft main portion 26 and an enlarged diameter portion 27.

[0040] The main rotating shaft portion 26 is the part that extends along the axis O. The enlarged diameter portion 27 is formed when the main rotating shaft portion 26 is enlarged radially outward. The enlarged diameter portion 27 is formed extending in a part of the direction in which the main rotating shaft portion 26 extends. Specifically, the enlarged diameter portion 27 is formed in a range that faces radially opposite the second fixing portion 82b of the second holder 80b, which will be described later.

[0041] <Electric Motor> The electric motor 30a of the second embodiment has a stator 31 and a rotor 36a. The stator 31 is the same as in the first embodiment, so its description is omitted. The rotor 36a of the second embodiment has a sleeve 37a and a rotor core 38a. The sleeve 37a and rotor core 38a differ from the first embodiment in that grooves are formed to allow the key 90 to be attached (details will be described later). In addition, the sleeve 37a is in contact with the enlarged diameter portion 27 at its lower end face in the vertical direction.

[0042] The sleeve 37a is fitted to the rotating shaft 20a with a third engagement allowance. The rotor core 38a is fitted to the sleeve 37a with a fourth engagement allowance. The fourth engagement allowance is set to be larger than the third engagement allowance. The third engagement allowance is, for example, 10 micrometers or more and 20 micrometers or less. The fourth engagement allowance is, for example, 40 micrometers or more and 50 micrometers or less.

[0043] <Holder> The holder 80 is arranged concentrically with the rotating shaft 20a. The holder 80 is cylindrical in shape and extends in the axial direction. The holder 80 is formed to face the sleeve 37a from the outer circumference. The holder 80 is also fitted to the rotating shaft 20a from the outer circumference. That is, the holder 80 is attached to the rotating shaft 20a and the sleeve 37a from the outer circumference. The holder 80 is made of the same material as the rotating shaft. That is, the holder 80 is made of stainless steel (SUS316L). The holder 80 has a holder body 81 and a fixing part 82.

[0044] The holder body 81 is the part of the holder 80 that is fitted to the rotation axis 20a. In other words, the holder body 81 is fitted to the rotation axis 20a from the outer peripheral side. The holder body 81 is fitted to the rotation axis 20a with a fifth interference fit. The fifth interference fit is set to be smaller than, for example, the third interference fit. The fifth interference fit is, for example, 10 micrometers or more and 30 micrometers or less. The holder body 81 is in contact with the sleeve 37a at the end face on the side facing the sleeve 37a in the axial direction.

[0045] The fixing part 82 is the part of the holder 80 that faces the sleeve 37a from the outer peripheral side. The fixing part 82 is connected to the holder body 81 in the axial direction. The fixing part 82 may be fitted or in contact with the sleeve 37a from the outer peripheral side. The fixing part 82 of the second embodiment will be described as being in contact with the sleeve 37a. Also, the outer peripheral surfaces of the holder body 81 and the fixing part 82 may be flush with each other, or one may have a larger diameter in the radial direction than the other.

[0046] The holder 80 of the second embodiment has a first holder 80a disposed on the upper side in the vertical direction of the sleeve 37a and a second holder 80b disposed on the lower side in the vertical direction of the sleeve 37a. The first holder 80a has a first holder body 81a and a first fixing part 82a. The second holder 80b has a second holder body 81b and a second fixing part 82b.

[0047] The first holder body 81a and the second holder body 81b are as described for the above holder body 81. Specifically showing some configurations, the first holder body 81a is in contact with the sleeve 37a at the end face on the lower side in the vertical direction. Also, the second holder body 81b is in contact with the sleeve 37 at the end face on the upper side in the vertical direction.

[0048] The first fixing part 82a and the second fixing part 82b are as described for the above fixing part 82. Specifically showing some configurations, the first fixing part 82a faces the sleeve 37a on the upper side in the vertical direction of the sleeve 37a. Also, the second fixing part 82b faces the sleeve 37a on the lower side in the vertical direction of the sleeve 37a.

[0049] <Key> The key 90 is provided such that torque transmission is possible even when the surface pressure of the fitted portion disappears. The key 90 is provided at least between the rotary shaft 20a and the sleeve 37a, between the sleeve 37a and the rotor core 38a, and between the rotary shaft 20a and the holder body 81 (81a, 81b). The key 90 is formed of, for example, the same material as the rotary shaft 20a and the holder 80. That is, the key 90 of the present disclosure is formed of SUS316L. The key 90 of the second embodiment includes a first key 91, a second key 92, a third key 93, and a fourth key 94.

[0050] Each key 90 is arranged in a part of the circumferential direction. Each key 90 of the second embodiment is arranged one by one in the circumferential direction. Note that a plurality of keys 90 may be arranged in the circumferential direction. In addition, key grooves for providing the key 90 are appropriately formed at the locations where the key 90 is provided. The key grooves will be described in detail in the description of each of the following keys 90.

[0051] The first key 91 is arranged between the rotary shaft 20a and the first holder 80a. The first key 91 is formed shorter than the first holder body 81a in the axial direction. First inner key groove 91a and first outer key groove 91b are formed to enable the arrangement of the first key 91.

[0052] The first inner key groove 91a is formed in the rotary shaft 20a. The first inner key groove 91a is formed by the rotary shaft 20a being recessed inward in the radial direction. The first outer key groove 91b is formed in the first holder 80a. The first outer key groove 91b is formed by the first holder body 81a being recessed outward in the radial direction. The first outer key groove 91b is formed to penetrate to the lower side in the vertical direction of the first holder body 81a.

[0053] The second key 92 is arranged between the rotary shaft 20a and the second holder 80b. The second key 92 is formed shorter than the second holder body 81b in the axial direction. Second inner key groove 92a and second outer key groove 92b are formed to enable the arrangement of the second key 92.

[0054] The second inner keyway 92a is formed on the rotating shaft 20a. The second inner keyway 92a is formed by recessing the rotating shaft 20a radially inward. The second outer keyway 92b is formed on the second holder 80b. The second outer keyway 92b is formed by recessing the second holder body 81b radially outward. The second outer keyway 92b is formed to penetrate the second holder body 81b vertically upward.

[0055] The third key 93 is positioned between the rotating shaft 20a and the sleeve 37a. The third key 93 is positioned on the lower side of the extension of the sleeve 37a in the vertical direction. Furthermore, the third key 93 is positioned so as not to extend vertically downward beyond the sleeve 37a. A third inner key groove 93a and a third outer key groove 93b are formed to accommodate the third key 93.

[0056] The third inner keyway 93a is formed on the rotating shaft 20a. The third inner keyway 93a is formed by recessing the rotating shaft 20a radially inward. The third outer keyway 93b is formed on the sleeve 37a. The third outer keyway 93b is formed by recessing the sleeve 37a radially outward. The third outer keyway 93b is formed to penetrate the sleeve 37a vertically downward.

[0057] The first key 91, the second key 92, and the third key 93 are rectangular prisms. However, they are not limited to this shape; for example, they may have a shape in which the corners of the rectangular prism are rounded off.

[0058] The fourth key 94 is positioned between the sleeve 37a and the rotor core 38a. A fourth inner key groove 94a and a fourth outer key groove 94b are formed to accommodate the fourth key 94.

[0059] The fourth inner keyway 94a is formed in the sleeve 37a. The fourth inner keyway 94a is formed by recessing the sleeve 37a radially inward. The fourth outer keyway 94b is formed in the rotor core 38a. The fourth outer keyway 94b is formed by recessing the rotor core 38a radially outward. The fourth outer keyway 94b is formed by penetrating the rotor core 38a vertically.

[0060] The fourth key 94 has a main body portion 95, a first extension portion 96, and a second extension portion 97. The main body portion 95 is the main part of the fourth key 94. The main body portion 95 is formed to be shorter than the sleeve 37a and the rotor core 38a in the axial direction. The main body portion 95 has a rectangular parallelepiped shape.

[0061] The first extension portion 96 is the part that extends vertically downward from the main body portion 95. The vertically downward end face of the first extension portion 96 is flush with the rotor core 38a. The first extension portion 96 is in contact with the sleeve 37a on the radially inward-facing surface. Also, the radially outward-facing surface of the first extension portion 96 is flush with the main body portion 95.

[0062] The second extension portion 97 is the portion that extends radially outward from the vertically lower end of the first extension portion 96. The second extension portion 97 is in contact with the rotor core 38a at its vertically upper end. The second extension portion 97 is formed so that its vertically lower end does not come into contact with the second holder 80b. The second extension portion 97 is formed so that it does not protrude radially outward from the rotor core 38a.

[0063] The fourth key 94 may have a shape that is chamfered as appropriate. For example, the main body 95 may have a rectangular parallelepiped shape, but the vertex facing the fourth inner key groove 94a may be chamfered.

[0064] <Cooled and Uncooled Conditions> The following describes the clearance for the liquefied gas pump 1a described above, both during cooling and uncooled conditions. Cooling refers to the state in which liquid hydrogen fills the liquefied gas pump 1a and it is stable at a low temperature. Uncooled refers to the state in which liquid hydrogen does not fill the inside of the liquefied gas pump 1a.

[0065] The first surface S1, second surface S2, third surface S3, fourth surface S4, fifth surface S5, and sixth surface S6 are defined as follows, with respect to surfaces that are fitted together or in contact with each other. The first surface S1 is the surface to which the rotating shaft 20a and the sleeve 37a are fitted. The first surface S1 is fitted with a third interference fit when not cooled. The second surface S2 is the surface to which the sleeve 37a and the rotor core 38a are fitted. The second surface S2 is fitted with a fourth interference fit when not cooled. The third surface S3 is the surface to which the rotating shaft 20a and the first holder 80a (first holder body 81a) are fitted. The third surface S3 is fitted with a fifth interference fit when not cooled. The fourth surface S4 is the surface to which the rotating shaft 20a and the second holder 80b (second holder body 81b) are fitted. The fourth surface S4 is fitted with a fifth overlap when not cooled. The fifth surface S5 is the surface to which the sleeve 37a and the first holder 80a (first fixing part 82a) are fitted. The fifth surface S5 is in contact with each other when not cooled. The sixth surface S6 is the surface to which the sleeve 37a and the second holder 80b (second fixing part 82b) are fitted. The sixth surface S6 is in contact with each other when not cooled.

[0066] During cooling, the following changes occur compared to the uncooled state. The first surface S1 is fitted more loosely than the third surface during cooling. This is because the linear expansion coefficient of the sleeve 37a is smaller than that of the rotating shaft 20a. The second surface S2 is fitted with approximately the same tightness as the fourth surface during cooling. This is because the linear expansion coefficients of the sleeve 37a and the rotor core 38a are similar. The third surface S3 and the fourth surface S4 are fitted with approximately the same tightness as the fifth surface during cooling. This is because the rotating shaft 20a and the holder 80 are made of the same material. The fifth surface S5 and the sixth surface S6 are fitted with the fixing part 82 (first fixing part 82a, second fixing part 82b) pressing the sleeve 37a radially inward during cooling. This is because the linear expansion coefficient of the sleeve 37a is smaller than that of the fixing part 82 (first fixing part 82a, second fixing part 82b).

[0067] As described above, the sleeve 37a is fitted to the rotating shaft 20a with a third engagement allowance when not cooled, and is fitted to the rotating shaft 20a more loosely when cooled than when not cooled. The fixing portion 82 (first fixing portion 82a, second fixing portion 82b) is in contact with the sleeve 37a when not cooled, and presses the sleeve 37a radially inward when cooled. The sleeve 37a may also be configured not to fit with the rotating shaft 20a when cooled (the surface pressure is released).

[0068] <Assembly Method of Liquefied Gas Pump> The assembly method (assembly procedure) for the liquefied gas pump 1a of the second embodiment, particularly near the electric motor 30a, will be explained.

[0069] First, a preparation process is carried out. In the preparation process, the rotating shaft 20a, sleeve 37a, rotor core 38a, first holder 80a, second holder 80b, and key 90 are prepared.

[0070] After the preparation process is performed, the sleeve mounting process is carried out. In the sleeve mounting process, the third key 93 is positioned in the third inner keyway 93a, and then the sleeve 37a is inserted onto the rotating shaft 20a from the first direction D1 to the second direction D2 and shrink-fitted. At this time, the end of the sleeve 37a on the second direction D2 side is in contact with the rotating shaft 20a (enlarged diameter portion 27), and the position of the sleeve 37a in the axial direction can be determined.

[0071] After the sleeve mounting process is performed, the rotor core mounting process is performed. In the rotor mounting process, the fourth key 94 is positioned in the fourth inner key groove 94a, and then the rotor core 38a is inserted into the sleeve 37a from the first direction D1 to the second direction D2 and shrink-fitted. At this time, the end of the rotor core 38a on the second direction D2 side is in contact with the fourth key 94 (second extension portion 97), so that the position of the rotor core 38a in the axial direction can be determined.

[0072] The holder mounting process is performed after the sleeve mounting process is completed. In the holder mounting process, the holder 80 is shrink-fitted onto the rotating shaft 20a and the sleeve 37a. The first holder 80a is inserted into the rotating shaft 20a and the sleeve 37a from the first direction D1 to the second direction D2 after the first key 91 is positioned in the first inner keyway 91a and then shrink-fitted. The second holder 80b is inserted into the rotating shaft 20a and the sleeve 37a from the second direction D2 to the first direction D1 after the second key 92 is positioned in the second inner keyway 92a and then shrink-fitted. At this time, the first holder 80a and the second holder 80b are in contact with the axial ends of the sleeve 37a, respectively, so that their axial positions can be determined.

[0073] <Effects> In the liquefied gas pump 1a described above, the holder 80 is attached to the rotating shaft 20a and the sleeve 37a from the outer circumference. The holder 80 is fitted to the rotating shaft 20a with the holder body 81 and faces (contacts) the sleeve 37a with the fixing part 82. With this configuration, even if the third interference fit is set small, the holder 80 contracts more than the sleeve 37 under low temperature conditions, so the sleeve 37a is held by the holder 80. Therefore, it is possible to prevent the sleeve 37a from coming off the rotating shaft 20a. In other words, by providing the holder 80, it is permissible to reduce the interference fit between the sleeve 37a and the rotating shaft 20a.

[0074] Specifically, even if the surface pressure on the first surface S1 decreases during cooling, the sleeve 37a is held by the holder 80 on the fifth surface S5 and the sixth surface S6, preventing it from coming off the rotating shaft 20a. Furthermore, the holder 80 is fitted onto the rotating shaft 20a on the third surface S3 and the fourth surface S4, which allows for a more secure retention of the sleeve 37a on the rotating shaft 20a.

[0075] Furthermore, the state in which the sleeve 37a and the rotor core 38a are fitted together is the same as in the first embodiment. Therefore, by using the sleeve 37a, even if the amount of tightening of the rotor core 38a with respect to the sleeve 37a is reduced, the occurrence of loosening between the rotating shaft 20a and the rotor core 38a can be suppressed.

[0076] Furthermore, the holder 80 is made of stainless steel. Because the holder 80 and the rotating shaft 20a are made of the same material, the clamping force between the holder 80 and the rotating shaft 20a can be reduced.

[0077] The sleeve 37a is fitted to the rotating shaft 20a with a third level of tension when not cooled, and is fitted more loosely than the third level of tension when cooled. The fixing part 82 (first fixing part 82a, second fixing part 82b) is in contact with the sleeve 37a when not cooled, and presses the sleeve 37a radially inward when cooled. With this structure, the sleeve 37a is securely held by the rotating shaft 20a. Furthermore, with this structure, a third level of tension is also permissible when cooled, such that there is no surface pressure between the sleeve 37a and the rotating shaft 20a.

[0078] Furthermore, the liquefied gas pump 1a of the second embodiment is equipped with a key 90. Therefore, torque can be reliably transmitted regardless of the expansion and contraction of the rotating shaft 20a, sleeve 37a, rotor core 38a, and holder 80 due to temperature changes. Specifically, the third key 93 allows for a third level of tightening so that the surface pressure between the sleeve 37a and the rotating shaft 20a is eliminated during cooling.

[0079] <Other Embodiments> Although one embodiment of the present disclosure has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment and may include design changes and the like that do not depart from the gist of the present disclosure.

[0080] For example, the rotors 36, 36a according to one embodiment may further include permanent magnets. For example, a plurality of permanent magnets may be provided inside the rotor cores 38, 38a at circumferential intervals.

[0081] Furthermore, in the second embodiment, the first holder 80a and the second holder 80b may be provided in a configuration where only one of them is present.

[0082] Furthermore, in the second embodiment, the configuration near the electric motor 30a may be reversed in the axial direction. That is, the configuration of the part shown in Figure 3 may be reversed in the first direction D1 and the second direction D2.

[0083] Furthermore, in the second embodiment, the holder 80 is not limited to being made of the same material as the rotating shaft 20a. For example, it may be made of a material having a similar coefficient of thermal expansion.

[0084] Furthermore, in the second embodiment, the key 90 may not be provided. For example, only the third key 93 may be provided. Moreover, for example, if the surface pressure of the first surface S1 is not released even during cooling, the third key 93 may not be provided.

[0085] <Note> The liquefied gas pumps 1 and 1a described in each embodiment can be understood, for example, as follows.

[0086] (1) The liquefied gas pumps 1 and 1a according to the first embodiment include a rotating shaft 20 and 20a made of stainless steel that is rotatable around axis O, a casing 10 that houses the rotating shafts 20 and 20a, an impeller 22 that is integrally provided with the rotating shafts 20 and 20a within the casing 10 and capable of pumping liquefied gas as the rotating shafts 20 and 20a rotate, a stator 31 fixed to the inner circumferential surface of the casing 10 and surrounding the rotating shafts 20 and 20a, and the stator 31 The motors 30, 30a are provided on the inside of the stator 31 with a clearance between them and the rotors 36, 36a which are integrally fixed to the rotating shafts 20, 20a. The rotors 36, 36a have sleeves 37, 37a made of alloy steel containing Ni that are fitted onto the rotating shafts 20, 20a from the outer circumference, and rotor cores 38, 38a made of electromagnetic steel sheets stacked in the axial direction and fitted onto the sleeves 37, 37a from the outer circumference.

[0087] According to the above configuration, sleeves 37 and 37a made of Ni-containing alloy steel are fitted to the rotating shafts 20 and 20a made of stainless steel from the outer circumference. Rotor cores 38 and 38a made of electromagnetic steel sheet are fitted to the sleeves 37 and 37a from the outer circumference. The rotating shafts 20 and 20a and the rotor cores 38 and 38a have different coefficients of thermal expansion. Also, because the rotor cores 38 and 38a have low strength, a large overlap cannot be taken. The rotating shafts 20 and 20a and the rotor cores 38 and 38a are fitted via sleeves 37 and 37a, which have a coefficient of thermal expansion similar to that of the rotor cores 38 and 38a, but have higher strength than the rotor cores 38 and 38a. This makes it possible to suppress loosening of the rotating shafts 20 and 20a and the rotor cores 38 and 38a, which may occur under low temperature conditions.

[0088] (2) The liquefied gas pump 1 according to the second embodiment is the liquefied gas pump 1 of (1), wherein the sleeve is fitted to the rotating shaft with a first interference fit, and the rotor core is fitted to the sleeve with a second interference fit smaller than the first interference fit.

[0089] According to the above configuration, the first interference fit between the rotating shaft 20 and the sleeve 37 is greater than the second interference fit between the sleeve 37 and the rotor core 38. By fitting the sleeve 37, which has higher strength than the rotor core 38, to the rotating shaft 20 with a large interference fit, the sleeve 37 and the rotating shaft 20 can be fitted more securely even under low temperature conditions. In other words, by fitting the rotating shaft 20 and the rotor core 38 via the sleeve 37, loosening of the rotating shaft 20 and the rotor core 38, which may occur under low temperature conditions, can be suppressed.

[0090] (3) The liquefied gas pump 1a according to the third embodiment is the liquefied gas pump 1a of (1), further comprising holders 80, 80a, and 80b made of stainless steel, wherein the sleeve 37a is fitted to the rotating shaft 20a with a third overlap, the rotor core 38a is fitted to the sleeve 37a with a fourth overlap that is larger than the third overlap, and the holders 80, 80a, and 80b have a holder body 81, 81a, and 81b fitted to the rotating shaft 20a from the outer circumference, and a fixing portion 82, 82a, and 82b facing the sleeve 37a from the outer circumference.

[0091] According to the above configuration, the sleeve 37a is covered from the outer circumference by the holders 80, 80a, and 80b. The holder bodies 81, 81a, and 81b are fitted onto the rotating shaft 20a from the outer circumference. Therefore, the sleeve 37a is maintained in a state attached to the rotating shaft 20a. Consequently, it is possible to prevent the sleeve 37a from coming off the rotating shaft 20a.

[0092] (4) The liquefied gas pump 1a relating to the fourth embodiment is the liquefied gas pump 1a of (3), wherein the sleeve 37a is fitted to the rotating shaft 20a with the first tightening allowance when not cooled by the liquefied gas, and is fitted to the rotating shaft 20a more loosely when cooled by the liquefied gas than when not cooled, and the fixing parts 82, 82a, and 82b face the sleeve 37a when not cooled by the liquefied gas, and press the sleeve 37a radially inward when cooled by the liquefied gas.

[0093] With the above configuration, the sleeve 37a is securely held by the rotating shaft 20a. Furthermore, this structure allows for a third level of clamping force such that the surface pressure between the sleeve 37a and the rotating shaft 20a is eliminated during cooling.

[0094] (5) The liquefied gas pump 1a according to the fifth embodiment is the liquefied gas pump 1a according to (3) or (4), further comprising keys 90, 91, 92, 93, and 94 provided in at least one of the following locations: between the rotating shaft 20a and the sleeve 37a, between the sleeve 37a and the rotor core 38a, and between the rotating shaft 20a and the holder bodies 81, 81a, and 81b.

[0095] With the above configuration, torque can be reliably transmitted regardless of the expansion and contraction of the rotating shaft 20a, sleeve 37a, rotor core 38a, and holder 80 due to temperature changes.

[0096] (6) The liquefied gas pumps 1, 1a relating to the sixth aspect are the liquefied gas pumps 1, 1a of (1) to (4), wherein the liquefied gas is liquid hydrogen.

[0097] According to the liquefied gas pump of this disclosure, the rotor of the electric motor can be firmly fixed to the rotating shaft even under low temperature conditions.

[0098] 1 Liquefied gas pump 10 Casing 11 Suction section 12 Discharge section 20 Rotating shaft 21 Inducer 22 Impeller 23 First stage impeller 24 Second stage impeller 25 Third stage impeller 30 Electric motor 31 Stator 32 Stator core 35 Coil 36 Rotor 37 Sleeve 38 Rotor core 40 Bearing device 41 Radial bearing 42 First radial bearing 43 Second radial bearing 44 Thrust bearing 45 Thrust disc 50 Sump 51 Outer flange 53 Liquid storage chamber 60 Supply pipe 61 Gas discharge pipe 62 Discharge pipe 70, 71, 72 Flow path 1a Liquefied gas pump 20a Rotating shaft 26 Main part of rotating shaft 27 Enlarged diameter section 30a Electric motor 36a Rotor 37a Sleeve 38a Rotor core 80 Holder 81 Holder body 82 Fixing part 80a First holder 81a First holder body 82a First fixing part 80b Second holder 81b Second holder body 82b Second fixing part 90 Key 91 First key 91a First inner keyway 91b First outer keyway 92 Second key 92a Second inner keyway 92b Second outer keyway 93 Third key 93a Third inner keyway 93b Third outer keyway 94 Fourth key 94a Fourth inner keyway 94b Fourth outer keyway 95 Body part 96 First extension part 97 Second extension part S1 First surface S2 Second surface S3 Third surface S4 Fourth surface S5 Fifth surface S6 Sixth surface D1 First direction D2 Second direction О Axis

Claims

1. A liquefied gas pump comprising: a rotating shaft made of stainless steel that is rotatable about an axis; a casing that houses the rotating shaft; an impeller integrally mounted on the rotating shaft within the casing and capable of pressurizing liquefied gas as the rotating shaft rotates; a stator fixed to the inner circumferential surface of the casing and surrounding the rotating shaft; and a rotor provided inside the stator with a clearance from the stator and integrally fixed to the rotating shaft, wherein the rotor comprises: a sleeve made of alloy steel containing Ni that is fitted onto the rotating shaft from the outer circumference; and a rotor core made of electromagnetic steel sheets stacked in the axial direction and fitted onto the sleeve from the outer circumference.

2. The liquefied gas pump according to claim 1, wherein the sleeve is fitted to the rotating shaft with a first overlap, and the rotor core is fitted to the sleeve with a second overlap smaller than the first overlap.

3. A liquefied gas pump according to claim 1, further comprising a holder made of stainless steel, wherein the sleeve is fitted onto the rotating shaft with a third overlap, the rotor core is fitted onto the sleeve with a fourth overlap that is larger than the third overlap, and the holder has a holder body fitted onto the rotating shaft from the outer circumference, and a fixing portion facing the sleeve from the outer circumference.

4. The liquefied gas pump according to claim 3, wherein the sleeve is fitted to the rotating shaft by the third tightening allowance when not cooled by the liquefied gas, and is fitted to the rotating shaft more loosely than when not cooled when cooled by the liquefied gas, and the fixing portion faces the sleeve when not cooled by the liquefied gas, and presses the sleeve radially inward when cooled by the liquefied gas.

5. The liquefied gas pump according to claim 3 or 4, further comprising a key provided in at least one of the following locations: between the rotating shaft and the sleeve, between the sleeve and the rotor core, and between the rotating shaft and the holder body.

6. The liquefied gas pump according to any one of claims 1 to 4, wherein the liquefied gas is liquid hydrogen.

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