WO2011115238A1

WO2011115238A1 - Canned electric rotating machine

Info

Publication number: WO2011115238A1
Application number: PCT/JP2011/056512
Authority: WO
Inventors: Hiroyuki Kato
Original assignee: Ebara Corporation
Priority date: 2010-03-15
Filing date: 2011-03-14
Publication date: 2011-09-22
Also published as: JP2011193662A; JP5457236B2

Abstract

A canned electric rotating machine is suitable for use in an electric motor for driving a seal-less pump (non-seal pump) having a rotor chamber filled with a high-pressure pump working liquid. The canned electric rotating machine includes a cylindrical frame (11), a stator (17) having a stator core (17a) and a stator winding (17b) and housed in the cylindrical frame (11), a can (21) configured to enclose the stator (17), and a rotor (20) rotatably provided in a space surrounded by the can (21). The can (21) comprises a first layer (21a) composed of resin and a second layer (21b) composed of a thin metal plate, and a bellows (21c) or a diaphragm is provided at an end portion of the second layer (21b).

Description

DESCRIPTION

Title of Invention

CANNED ELECTRIC ROTATING MACHINE

Technical Field

[0001] The present invention relates to a canned electric rotatingmachine in which a stator is enclosed by a can, and more particularly to a canned electric rotating machine suitable for use in an electric motor for driving a seal-less pump (non-seal pump) having a rotor chamber filled with a high-pressure pump working liquid.

Background Art

[0002] Conventionally, in a high-voltage canned electric motor, whose stator comprising a stator core and a stator winding is enclosed by a can, for driving a seal-less pum ^ (non-seal pump), particularly in a large-scale canned induction motor, having several thousands of output power (KW) and four to six poles in the number of poles, whose rotor chamber is filled with a pump working liquid having a high-pressure of one to two kg/mm², it is required that eddy-current loss caused by magnetic flux passing through the can is reduced, the motor can withstand high internal pressure and the motor has high airtightness

(gastightness) .

[0003] In this canned induction motor, it is desirable that the can made of insulting material such as resin material is used to reduce can loss (eddy-current loss) . Further, as a structure for withstanding a high-pressure pump working liquid which fills the rotor chamber, it may be conceivable that fiber-reinforced plastic (FRP) is used for a can constituent material . Furthermore, since the rotor chamber is filled with a high-pressure pump working liquid, when the rotor is rotated at high speed, the pump working liquid flows over the surface of the can at the same circumferential velocity as the rotor, thus causing erosion of the surface. of the can made of FRP due to fluid friction and abrasion of the can. As the abrasion of the can progresses, airtightness of the can may deteriorate. Therefore, in the case where FRP is used for the can, it is necessary to take countermeasure against erosion .

[0004] Further, the pump working liquid flows in the rotor chamber at high circumferential velocity, thus causing fluid friction loss in a gap between the can and the rotor. This fluid friction loss becomes a large amount of loss depending on the length of the gap along the can and the rotor. Therefore, in a general cooling method such as a cooling method utilizing forced-fluid circulation in the rotor chamber, it is necessary to reduce the fluid friction loss because of limitations in cooling efficiency.

[0005] Further, in the case where the above high-voltage induction motor is used for driving a cooling pump having a seal-less structure in a nuclear reactor, because the pump working liquid becomes high temperature, the high-voltage induction motor requires heat resistance and radiation resistance .

[0006] As a canned motor which employs FRP for a can, there have been a permanent magnet synchronous electric motor having heat resistance and pressure resistance disclosed in Japanese Laid-open Patent Publication 05-153749 and a canned motor having an improved gastightness disclosed in Japanese Laid-open Patent Publication 2001-231213.

Summary of Invention

Technical Problem

[0007] As a canned electric rotating machine which can ensure pressure resistance and heat resistance against a high-pressure and high-temperature pump working liquid which fills a rotor chamber, erosion resistance of the can composed of FRP against high-speed flow of the pump working liquid, and radiation resistance, Japanese patent application serial No.2010-27016 was filed. In this patent application, there has been proposed a can having a plural-layer structure comprising a first layer, disposed at an outer diameter side, composed of FRP which is resistant to pressure deformation and buckling, and a second layer, disposed at an inner diameter side, composed of a thin metal plate which has excellent liquidtightness and excellent erosion resistance. The high-strength resin and the metal have respective linear expansion coefficients which differ greatly. For example, polyether ether ketone (PEEK) and inconel are different in linear expansion coefficient by four times or more. Even in the case where there is no temperature difference between the first layer of FRP and the second layer of thin metal plate, as operating temperature becomes high, the resin part tends to be relatively longer than the metal part. Further, because the thin metal plate part produces heat by eddy current, internal fluid is circulated along the can to cool the can and motor components. However, it is difficult to keep the part from the thin metal part to the motor frame at the same temperature, thus causing difference in thermal expansion in the part from the thin metal part to the motor frame.

[0008] The present invention has been made in view of the above circumstances. It is therefore an object of the present invention to provide a canned electric rotating machine having a plural-layer structured can comprising a resin layer and a thin metal plate layer which can absorb difference in thermal expansion between a resin part, a thin metal plate part and a motor frame to prevent an excessive stress from being produced in each part.

Solution to Problem

[0009] In order to achieve the above object, according to a first aspect of the present invention, there is provided a canned electric rotating machine comprising: a cylindrical frame; a stator housed in the cylindrical frame, the stator comprising a stator core and a stator winding provided on the stator core; a can configured to enclose the stator; and a rotor rotatably provided in a space surrounded by the can; wherein the can comprises a first layer composed of resin and a second layer composed of a thin metal plate, and a bellows or a diaphragm is provided at an end portion of the second layer.

[0010] In a preferred aspect of the present invention, a spring mechanism is provided to press the first layer against the cylindrical frame at a location where the first layer faces the cylindrical frame in an axial direction of the cylindrical frame.

[0011] In a preferred aspect of the present invention, end pieces are connected to respective end portions of the cylindrical frame in an axial direction of the cylindrical frame, and both end portions of the second layer are connected to the respective end pieces.

[0012] In a preferred aspect of the present invention, both end portions of the first layer in an axial direction of the first layer faces the respective end pieces.

[0013] In a preferred aspect of the present invention, an elastic 0 ring is inserted into a gap between the cylindrical frame and the first layer at a location where the spring mechanism is provided.

[0014] In a preferred aspect of the present invention, the bellows is a cylindrical bellows.

[0015] In a preferred aspect of the present invention, a split-ring type stiffening ring is provided between a root portion at an outer diameter side of the bellows and an inner diameter side of the cylindrical frame facing the root portion.

[0016] In a preferred aspect of the present invention, the diaphragm comprises a bellows which extends in a radial direction thereof.

[0017] In a preferred aspect of the present invention, the diaphram faces an end surface of the cylindrical frame in an axial direction of the cylindrical frame, and a stiffening ring is provided between the root portion at the cylindrical frame side of the bellows constituting the diaphram and an end surface of the cylindrical frame in an axial direction of the cylindrical frame facing the root portion.

[0018] In a preferred aspect of the present invention, the bellows or the diaphragm comprises a thin metal plate which is thicker than the thin metal plate of the second layer.

[0019] In a preferred aspect of the present invention,, a body portion comprising a thin metal plate which is thicker than the thin metal plate of the second layer is continuously provided on said bellows or the diaphragm, and the body portion covers a boundary portion between second layer and the frame.

Advantageous Effects of Invention

[0020] According to an aspect of the present invention, a can of a canned electric rotating machine comprises a first layer composed of resin and a second layer composed of a thin metal plate, and a bellows or a diaphragm is provided on an end of the second layer composed of the thin metal plate in the can. Therefore, difference in thermal expansion between the second layer composed of the thin metal plate and the frame can be absorbed, and stress produced in the second layer composed of the thin metal plate can be lessened, thus preventing buckling distortion of the second layer.

[0021] Further, according to a preferred aspect of the present invention, a spring mechanism is provided to press the first layer of the can against the cylindrical frame at a location where an end of the first layer faces an end of the cylindrical frame in an axial direction of the cylindrical frame. Therefore, a gap is not formed between the other end of the first layer and the other end of the cylindrical frame.

[0022] Further, according to a preferred aspect of the present invention, end pieces are connected to respective end portions of the cylindrical frame in an axial direction of the cylindrical frame, and both end portions of the second layer are connected to the respective end pieces . Therefore, airtightness between the second layer and the cylindrical, frame can be maintained.

[0023] Further, according to a preferred aspect of the present invention, both end portions of the first layer in an axial direction of the first layer faces the respective end pieces, and a distance between the end pieces is larger than an axial length of the first layer by a predetermined length. Therefore, a gap can be formed between an end of the first layer and the end piece, and an elongation of the first layer in an axial direction of the first layer can be absorbed by the gap.

[ 002 ] Further, according to a preferred aspect of the present invention, an elastic 0 ring is inserted into a gap between the cylindrical frame and the first layer at a location where the spring mechanism is provided. Therefore, a displacement of a body portion of the bellows in a radial direction of the bellows can be restrained.

[0025] Further, according to a preferred aspect of the present invention, because the bellows is a cylindrical bellows, contraction of the second layer composed of the thin metal plate in an axial direction of the second layer can be absorbed smoothly.

[0026] Further, according to a preferred aspect of the present invention, a split-ring type stiffening ring is provided between a root portion at an outer diameter side of the bellows and an inner diameter side of the cylindrical frame facing the root portion. Therefore, the thickness of the bellows can be reduced by a certain thickness corresponding to reinforcement by the stiffening ring, and deformation of the bellows in a radial direction of the bellows can be prevented and elasticity of the bellows in an axial direction of the bellows can be maintained.

[0027] Further, according to a preferred aspect of the present invention, because the diaphragm comprises a bellows which extends in a radial direction thereof, contraction of the second layer composed of the thin metal plate in an axial direction of the second layer can be absorbed smoothly .

[0028] Further, according to a preferred aspect of the present invention, the diaphram faces an end surface of the cylindrical frame in an axial direction of the cylindrical frame, and a stiffening ring is provided between the root portion at the cylindrical frame side of the bellows constituting the diaphram and an end surface of the cylindrical frame in an axial direction of the cylindrical frame facing the root portion. Therefore, the thickness of the bellows can be reduced by a certain thickness corresponding to reinforcement by the stiffening ring, and deformation of the bellows caused by a pressure of a pump working liquid can be prevented and contraction of the second layer composed of the thin metal plate in an axial direction of the second layer can be absorbed smoothly .

[0029] Further, according to a preferred aspect of the present invention, a body portion comprising a thin metal plate which is thicker than the thin metal plate of the second layer is continuously provided on the bellows or the diaphragm, and the body portion of the bellows or the diaphragm covers a boundary portion between the second layer and the frame. Therefore, even if minute irregularities are formed in the boundary portion by difference in thermal expansion or the like, deformation or breakage in the boundary portion caused by a pressure of a pump working liquid can be prevented. Brief Description of Drawings

[0030]

[FIG. 1] FIG. 1 is a schematic vertical cross-sectional view showing a pump motor comprising a seal-less pump (non-seal pump) and a canned induction motor for driving the pump as an example of a canned electric rotating machine according to the present invention.

[FIG. 2A] FIG. 2A is a fragmentary cross -sectional view showing part of the pump motor shown in FIG.l.

[FIG. 2B] FIG. 2B is a fragmentary cross -sectional view showing part of the pump motor shown in FIG.l.

[FIG. 3A] FIG. 3A is a fragmentary cross -sectional view showing part of the pump motor shown in FIG.l.

[FIG. 3B] FIG. 3B is a fragmentary cross-sectional view showing part of the pump motor shown in FIG.l.

[FIG. 4A] FIG. 4A is a fragmentary cross-sectional view showing part of the pump motor shown in FIG.l.

[FIG. 4B] FIG. 4B is a fragmentary cross-sectional view showing part of the pump motor shown in FIG.l.

[FIG. 5A] FIG. 5A is a fragmentary cross-sectional view showing part of the pump motor shown in FIG.l.

[FIG. 5B] FIG. 5B is a fragmentary cross-sectional view showing part of the pump motor shown in FIG.l.

Description of Embodiments

[0031] A canned electric rotating machine according to embodiments of the present invention will be described below with reference to FIGS. 1 through 5B. Like or corresponding parts are denoted by like or corresponding numerals throughout drawings and will not be described below repetitively. In the embodiments of the present invention, an induction motor will be described as an example of an electric rotating machine, but the electric rotating machine is not limited to the induction motor .

FIG. 1 is a schematic vertical cross-sectional view showing a pump motor comprising a vertical seal-less pump (non-seal pump) and a canned induction motor for driving the pump as an example of a canned electric rotating machine according to the present invention. As shown in FIG. 1, the pump motor comprises a pump unit P and a motor unit M. The pump unit P comprising a seal-less pump (non-seal pump) has a pump casing 1 having a suction port 2 and a discharge port 3, and an impeller 5 housed in the pump casing 1 and fixed to an end of a main shaft 6. The pump casing 1 is mounted on an impeller-side bracket 7. The main shaft 6 is rotatably supported by bearings 16, 16 disposed at an upper part and a lower part of the pump motor.

[0032] The motor unit M.comprising an induction motor has a motor frame 10, a motor stator 17 housed in a cylindrical frame body 11 of the motor frame 10 and fixed to the frame body 11, and a motor rotor 20 disposed inside the motor stator 17 and fixed to the central part of the main shaft 6. Both ends of the frame body 11 are mounted on a frame side plate 12 disposed at an impeller-side and a frame side plate 13 disposed at a counter-impeller-side, respectively. The frame side plate 12 is fixed to the impeller-side bracket 7 of the pump unit P. The frame side plate 12 is integrally provided with a reinforcing ring portion (reinforcing ring member) 18, and an end of the reinforcing ring portion 18 extends to the vicinity of an impeller-side end of a stator core 17a of the motor stator 17. The frame side plate 13 is integrally provided with a reinforcing ring portion (reinforcing ring member) 19, and an end of the reinforcing ring portion 19 extends to the vicinity of a counter-impeller-side end of the stator core 17a of the motor stator 17.

[0033] A cylindrical can 21 comprises a first layer composed of fiber-reinforced plastics (FRP) or plastics and a second layer composed of a thin metal plate provided on an inner surface of the first layer (described later in detail) . An outer circumferential surface of the can 21, i.e. a surface of the FRP is held in close contact with inner surfaces of the stator core 17a of the motor stator 17, the reinforcing ring portion 18, the reinforcing ring portion 19, the frame side plate 12 and the frame side plate 13. The reinforcing ring portion 18, the reinforcing ring portion 19, the frame side plate 12 and the frame side plate 13 constitute the motor frame 10. 0 rings 22 are interposed at the impeller-side between the frame side plate 12 and the can 21, and 0 rings 23 are interposed at the counter-impeller-side between the frame side plate 13 and the can 21. Further, axial ends of the frame side plates 12 , 13 are formed by annular end pieces 12a, 13a which are configured as separate members from the frame side plates 12, 13, and the end pieces 12a, 13a are connected to the frame side plates 12, 13, respectively at joint portions D (see FIGS. 2A and 2B) by welding. The end piece 12a constitutes part of the frame side plate 12 and the end piece 13a constitutes part of the frame side plate 13, and the frame side plates 12, 13 constitutes part of the motor frame 10. As shown in FIGS. 2A and 2B, the thin metal plate portions of the second layer 21b of the can 21 are welded to the end pieces 12a, 13a at weld portions C, and thus a stator chamber 14 in which the motor stator 17 is disposed is kept in a sealed state. Further, a space enclosed by the cylindrical can 21 constitutes a rotor chamber 15 in which the motor rotor 20 is disposed.

[0034] In the pump motor having the above structure, three-phase power having a certain frequency and a certain voltage is supplied from an inverter (not shown) of a power-supply unit to a stator winding 17b of the motor unit M, thereby generating rotating-magnetic field and rotating the motor rotor 20. Thus, the impeller 5 fixed to the main shaft 6 is rotated, and a pump working liquid sucked through the suction port 2 of the pump casing 1 is pressurized and discharged through the discharge port 3. At this time, since the pump unit P comprises a seal-less pump (non-seal pump) , the rotor chamber 15 is filled with the pump working liquid, and the pump working liquid in the rotor chamber 15 is stirred by the motor rotor 20. Thus, the pump working liquid having the same circumferential velocity as the motor rotor 20 flows over the inner circumferential surface of the can 21, and a pressure of the pump working liquid is applied to the inner circumferential surface of the can 21.

[0035] FIGS. 2A and 2B are fragmentary cross-sectional views showing part of the pump motor having the above structure according to a first embodiment of the present invention. FIG. 2A shows an end portion of the pump motor at a counter-impeller side and FIG. 2B shows an end portion of the pump motor at an impeller-side. As shown in FIGS. 2A and 2B, the can 21 comprises a two-layer structured can comprising a first layer 21a and a second layer 21b . As a material of the first layer 21a, polyether ether ketone (PEEK) resin or polyimide (PI) resin having high heat resistance and high mechanical strength is used. Further, FRP which is reinforced with reinforcement fiber having high strength such as long fiber of glass, aramid or carbon and has high mechanical strength is used. As FRP resins, in addition to polyether ether ketone (PEEK) and polyimide (PI), polyester amide imide, polyhydantoin, isocyanurate denatured polyester imide, polyamide-imide, polyester and epoxide may be used. These resins have resistance to high-temperature and radiation resistance in common, and thus are suitable for application requiring resistance to high-temperature and radiation resistance. Among these resins, particularly, PEEK and PI have a high application performance in a nuclear power plant and are particularly suitable for use in the nuclear power plant.

[0036] Further, the second layer 21b of the can 21 comprises a thin metal plate held in close contact with the inner surface of the first layer 21a. In this manner, by providing the second layer 21b composed of the thin metal plate held in close contact with the inner surface of the first layer 21a, higher airtightness of the can can be ensured, and wear (erosion) of the inner surface of the can 21 caused by a flow of a pump working liquid over the inner surface of the can 21 can be prevented because the flow of the pump working liquid in the can 21 is brought into contact with the inner surface of the second layer 21b composed of the thin metal plate having wear resistance.

[0037] As described above, by providing the second layer 21b composed of the thin metal plate held in close contact with the inner surface of the first layer 21a composed of FRP, can loss (eddy-current-loss) is generated in the second layer 21b. However, if the thin metal plate has a thickness of 0.05mm to 0.1mm, then the can loss of the thin metal plate becomes 1/10 to 1/2 of that of a general metal can having a thickness of 0.2mm to 0.5mm. Further, also in the case where conductive carbon fiber is disposed in the resin layer, can loss (eddy-current-loss) is generated. However, because volume resistivity of FRP containing carbon fiber is about 100 times that of stainless steel, it is apparent that if the can 21 has a certain thickness, the can loss of the FRP containing carbon fiber can be greatly reduced to 1/100 of that of stainless steel.

[0038] In the case where thermosetting PI resin is used for a resin for forming the first layer 21a of the can 21, and dense structure having few void is formed by vacuum exhaust and heat curing under pressure during a resin forming process, the first layer 21a having high airtightness and liquidtightness can be constructed. The first layer 21 composed of FRP reinforced with fiber comprising aramid resin has tensile strength in a circumferential direction which is one to three times that of metal material such as stainless steel.

[0039] In the can 21 having the plural-layer structure, the difference in linear expansion coefficient presents a problem. For example, the linear expansion coefficient of PI or PEEK is approximately 50 ^χ 10^"6 ( 1/°C ) and the linear expansion coefficient of inconel having high wear resistance suitable for the second layer is approximately 12^χ10^~6 (1/°C ) . If a length of the can is 1000mm and a mean temperature of the can during the operation of the motor is 75°C, the elongation difference of the resin and the metal which have the same length at normal temperature (25°C ) becomes δ =1000^χ (75.25) ^χ (50.12) ^χ10^~6 = 1.9mm. In the present embodiment, because the resin part (the first layer 21a) of the can 21 comprises FRP, the difference in the linear expansion coefficient between the resin part and the thin metal plate part (the second layer 21b) can be smaller than that in the above example by adjusting orientation and density of the long fiber. However, it is difficult to equalize the linear expansion coefficients of the resin part and the thin metal plate part.

[0040] Further, because the thin metal plate part of the second layer 21b of the can 21 produces heat by eddy current, internal fluid is circulated along the can to cool the can and the motor. However, even if cooling is performed, it is inevitable that the temperature of the thin metal plate part becomes higher than that of the motor frame 10. This temperature difference also causes the difference in thermal expansion between the second layer 21b composed of the thin metal plate and the motor frame 10. If stress produced by the difference in thermal expansion is not reduced, the second layer 21b composed of the thin metalplatewhichisfragilein structure and has the smallest displacement absorption capability may cause buckling distortion, thus destroying airtightness of the can 21.

[0041] According to the present embodiment, at least one of portions between the second layer 21b composed of the thin metal plate of the can 21 and the frame side plate 12 and between the second layer 21b and the frame side plate 13 in the longitudinal direction of the motor is connected through a bellows 21c. In this embodiment, the second layer 21b and the frame side plate 13 at the counter-impeller-side are connected through the bellows 21c. The bellows 21c absorbs. the difference in thermal expansion between the thin metal plate of the second layer 21b and the frame body 11 of the motor frame 10 to reduce stress produced in the thin metal plate of the second layer 21b. As shown in FIG. 2A, one end of the thin metal plate of the second layer 21b in the longitudinal direction of the second layer 21b is welded to the bellows 21c at a location of A. As shown in FIG. 2B, the other end of the thin metal plate of the second layer 21b is welded to the end piece 12a at the impeller-side. The end pieces 12a and 13a are welded to the respective frame side plates 12 and 13 at locations of D (see FIGS. 2A and 2B) . In this manner, one end of the thin metal plate of the second layer 21b is connected to the frame side plate 12 at the impeller-side via the end piece 12a, and the other end of the thin metal plate of the second layer 21b is welded to the bellows 21c. The end of the bellows 21c is welded to the end piece 13a. Then, the end pieces 12a and 13a are welded to the frame side plate 12 at the impeller-side and the frame side plate 13 at the counter-impeller-side, respectively at locations of D.

[0042] The thin metal plate part of the second layer 21b of the can 21 has a thickness of, for example, 0.05mm to 0.1mm, and the bellows 21c has a thickness of, for example, about 1mm. The weld portions C, i.e. a weld portion between the thin metal plate of the second layer 21b and the end piece 12a and a weld portion between the bellows 21c and the end piece 13a constitute thin plate joint, and thus non-filler welding is used. In order to perform reliable connection without using a filler metal (filler) while minimizing deformation of base material, the weld portion C is formed by stretching the end piece 13a in an axial direction of the end piece 13a so as to taper the inner surface of the end piece 13a. Further, the first layer 21a composed of FRP of the can 21 is provided in such a state that the first layer 21a is put between the end pieces 12a and 13a. The distance between the end surfaces of the end pieces 12a and 13a in an axial direction thereof is slightly longer than a length of the first layer 21a in an axial direction thereof, and thus an axial gap E is formed at one of locations where the end surfaces of the end pieces 12a and 13a face the end surface of the first layer 21a. This gap E can absorb an axial elongation of the first layer 21a composed of resin.

[0043] Because the second layer 21b composed of the thin metal plate at the inner diameter side of the first layer 21a composed of resin is very thin, if there is an axial gap between the first layer 21a and the end piece 13a, then the second layer 21b composed of the thin metal plate may enter into the axial gap E by pressure load and may be deformed. In order to prevent such state, the inner diameter side of the gap E between the end piece 13a and the first layer 21a composed of resin should be covered by the body portion of the bellows 21c which is thicker than the second layer 21b and is hardly deformed by pressure. Further, an elastic 0 ring 24 should be inserted into the gap E so that the axial deformation of the bellows 21c is possible and the radial deformation of the body portion of the bellows 21c is suppressible .

[0044] Further, a spring mechanism 25 is interposed between the end piece 13a at the side of the gap E and the first layer 21a composed of resin to press the first layer 21a in an axial direction of the first layer 21a so that an axial gap is not formed between the first layer 21a and the end piece 12a. Thus, the first layer 21a composed of resin is pressed against the end surface of the end piece 12a at all times in the axially opposite side of the gap E, thereby forming no gap between the first layer 21a and the end piece 12a. The spring mechanism 25 may comprise a plurality of springs which are disposed at equal intervals in a circumference direction of the first layer 21a, or may comprise a single spring having substantially the same diameter as the first layer 21a. Further, a groove (or grooves) is provided in the end piece 13a to house the spring mechanism 25. However, the groove (or grooves) may be provided in the first layer 21a composed of resin (FRP) .

[0045] The bellows 21c is fabricated from a metal into a corrugated cylindrical configuration having continuous concavo-convex portions. It is necessary for the bellows 21c to have a low spring constant by making the bellows 21c thin properly in order to facilitate axial deformation of the second layer 21b composed of the thin metal plate. Therefore, stiffening rings 26 are mounted on the outer circumferential side of the bellows 21c to prevent the bellows 21c from being deformed by pressure in the rotor chamber 15. In general, in the case of using the bellows having a relatively small thickness, in some cases, the stiffening rings are mounted on the outer circumferential side of the bellows to prevent the bellows from being deformed by pressure inside the bellows (in this embodiment, pressure in the motor rotor chamber 15) . A normal stiffening ring comprises an integral ring continuously formed in a circumferential direction of the ring and is configured to support pressure load by hoop stress. Because the stiffening ring having an integral-ring structure cannot be mounted after profile forming of the bellows 21c, the stiffening ring 26 is mounted in advance on a parallel cylinder as a bellows material, and then the parallel cylinder is integrally shaped in a corrugated die into a bellows. However, in the present invention, the stiffening ring 26 is sufficient if the stiffening ring 26 has a function for preventing buckling distortion of corrugated shape of the can 21 because the hoop stress is held by the end piece 13a which is held into close contact with the outer circumferential side of the bellows 21c . Therefore, the stiffening ring 26 may comprise a split-ring type stiffening ring, and may be mounted on the bellows 21c after profile forming of the bellows 21c.

[0046] Two 0 rings 22a and two back-up rings 22b are provided in combination between the first layer 21a and the frame side plate 12 (or reinforcing ring portion 18) at the outer circumferential side of the first layer 21a composed of FRP of the can 21 and in the vicinity of the axial end of the first layer 21a. Two 0 rings 23a and two back-up rings 23b are provided in combination between the first layer 21a and the frame side plate 13 (or reinforcing ring portion 19) at the outer circumferential side of the first layer 21a composed of FRP of the can 21 and in the vicinity of the axial end of the first layer 21a. Even if the second layer 21b composed of the thin metal plate is broken and high-pressure fluid in the rotor chamber 15 enters between the first layer 21a composed of FRP and the end piece 13a (or 12a) , the high-pressure fluid is prevented from reaching the stator core. Detection holes 27 and 28 for detecting leak pressure are provided in the inner circumferential surfaces of the frame side plates 12 and 13 in the vicinity of the both axial ends of the frame side plates 12 and 13 and at locations nearer to respective axial end surfaces of the frame side plates 12 and 13 than the 0 rings 22a and 23a to detect the high-pressure fluid which has entered therein, thereby detecting breakage of the second layer 21b composed of the thin metal plate and the bellows 21c. Pressure detectors (not shown) may be connected to the respective detection holes 27 and 28 to monitor pressures of the detection holes 27 and 28 at all times and to issue an alarm when the pressure increases abnormally.

[0047] FIGS. 3A and 3B are fragmentary cross-sectional views showing part of the pump motor according to a second embodiment of the present invention. FIG. 3A shows an end portion of the pump motor at a counter-impeller-side and FIG. 3B shows an end portion of the pump motor at an impeller-side. The second embodiment of the present invention is different from the first embodiment of the present invention in that a bellows 21d connected to the second layer 21b composed of the thin metal plate in the axial direction of the can 21 is constructed not as a cylindrical bellows but as a bellows 21d extending in a radial direction of the end piece 13a along the axial end surface of the end piece 13a. In order to form the weld portion C for the bellows 21d, a projecting portion 13b having a small thickness and extending from the axial end surface of the end piece 13a to the end portion of the bellows 21d is provided. Further, a plurality of stiffening rings 29 having different diameters are provided between the bellows 21d and the axial end surface of the end piece 13a. The stiffening rings 29 can be inserted into the route portion of the bellows without using a split-ring type stiffening ring.

[0048] According to the second embodiment of the present invention, since the bellows 21d extends in a radial direction of the end piece 13a, the elongation of the second layer 21b composed of the thin metal plate is absorbed not by expansion and contraction of concavo-convex of the bellows 21d but by functioning of the bellows 21d as a diaphragm. Therefore, although the bellows is formed in the present embodiment, different configuration may be employed as long as such configuration functions as a diaphragm.

[0049] FIG.4A and 4B are schematic cross-sectional views showing a modified example of the first and second embodiments. FIG. 4A shows an end portion of the pump motor at a counter-impeller-side and FIG. 4B shows an end portion of the pump motor at an impeller-side. In this embodiment, a thick plate portion 21e which is thicker than the thin metal plate of the second layer 21b is connected to the second layer 21b at a side where the bellows 21c is not connected to the second layer 21b composed of the thin metal plate of the can 21, and the thick plate portion 21e is configured to cover the contact portion E of the. first layer 21a composed of FRP and the end piece 12a. The thin metal plate of the second layer 21b is very thin. If the inner circumferential surfaces of the first layer 21a and the end piece 12a which the outer circumferential surface of the thin metal plate of the second layer 21b contacts have even a little unevenness, there is a possibility that the thin metal plate is broken due to the pressing load to the thin metal plate of the second layer 21b by the pressure in the rotor chamber 15. As shown in FIG. 4, because the thick member (having a thickness of about 1mm) which is thicker than the thin metal plate of the second layer 21b covers the boundary portion (contact portion E) between the first layer 21a composed of FRP and the end piece 12a, even if minute irregularities are formed on the boundary portion due to the difference in thermal expansion or the like, breakage of the thin metal plate (thick plate portion 21e) can be restrained.

[0050] FIG.5A and 5B are schematic cross-sectional views showing a modified example of the first and second embodiments. FIG. 5A shows an end portion of the pump motor at a counter-impeller-side and FIG. 5B shows an end portion of the pump motor at an impeller-side. As shown in FIGS. 5A and 5B, an end piece is integrated with the frame side plate 12 or 13. In the case where the end piece at the side where the spring mechanism 25 is provided is integrated with the frame side plate 13, differently from the embodiments shown in FIG. 2A and FIG. 3A, it is necessary to provide a pressure detection hole for detecting leak pressure not at the location where the pressure detection hole faces the end piece but at the location where the pressure detection hole faces the first layer 21a composed of FRP as shown in FIG.5A.

[0051] Although certain preferred embodiments of the present invention have been shown and described in detail, it should be understood that various changes and modifications may be made therein without departing from the scope of the appended claims.

For example, the resin layer constituting the first layer 21a of the can 21 comprises FRP in the above embodiments, but only simple resin may be used as long as there is no problem in strength.

Industrial Applicability

[0052] According to the present invention, because the can of the canned electric rotating machine comprises a first layer 21a of fiber-reinforced plastics or plastics and a second layer 21b of thin metal plate provided on an inner surface of the first layer, and a bellows 21c is provided at an end of the thin metal plate of the second layer 21b, the canned electric rotating machine can ensure reduction of fluid friction loss, excellent pressure resistance, and excellent heat resistance, and can solve a problem of difference in thermal expansion of components.

Claims

[Claim 1]

A canned electric rotating machine comprising:

a cylindrical frame;

a stator housed in said cylindrical frame, said stator comprising a stator core and a stator winding provided on said stator core; a can configured to enclose said stator; and

a rotor rotatably provided in a space surrounded by said can; wherein said can comprises a first layer composed of resin and a second layer composed of a thin metal plate, and a bellows or a diaphragm is provided at an end portion of said second layer.

[Claim 2]

A canned electric rotating machine according to claim 1, wherein a spring mechanism is provided to press said first layer against said cylindrical frame at a location where said first layer faces said cylindrical frame in an axial direction of said cylindrical frame.

[Claim 3]

A canned electric rotating machine according to claim 1 or 2 , wherein end pieces are connected to respective end portions of said cylindrical frame in an axial direction of said cylindrical frame, and both end portions of said second layer are connected to the respective end pieces .

[Claim 4]

A canned electric rotating machine according to claim 3, wherein both end portions of said first layer in an axial direction of said first layer faces the respective end pieces.

[Claim 5]

A canned electric rotating machine according to claim 2, wherein an elastic 0 ring is inserted into a gap between said cylindrical frame and saidfirstlayerata location where said spring mechanism is provided.

[Claim 6]

A canned electric rotating machine according to any one of claims 1 to 5, wherein said bellows is a cylindrical bellows.

[Claim 7]

A canned electric rotating machine according to claim 6, wherein a split-ring type stiffening ring is provided between a root portion at an outer diameter side of said bellows and an inner diameter side of said cylindrical frame facing said root portion.

[Claim 8]

A canned electric rotating machine according to any one of claims 1 to 5, wherein said diaphragm comprises a bellows which extends in a radial direction thereof.

[Claim 9]

A canned electric rotating machine according to claim 8, wherein said diaphram faces an end surface of said cylindrical frame in an axial direction of said cylindrical frame, and a stiffening ring is provided between said root portion at the cylindrical frame side of said bellows constituting said diaphram and an end surface of said cylindrical frame in an axial direction of said cylindrical frame facing said root portion.

[Claim 10]

A canned electric rotating machine according to any one of claims

1 to 5, wherein said bellows or said diaphragm comprises a thin metal plate which is thicker than the thin metal plate of said second layer.

[Claim 11]

A canned electric rotating machine according to claim 10, wherein a body portion comprising a thin metal plate which is thicker than the thin metal plate of said second layer is continuously provided on said bellows or said diaphragm, and said body portion covers a boundary portion between said second layer and said frame.