ELECTRIC AXIAL FLOW PUMP
An electric axial flow pump comprising: a stator 6 having a field coil 10, a rotor 3 including a cylindrical hollow shaft 4 having open ends surrounded by the stator and a plurality of magnets 5 fixed around the hollow shaft, and a flow generation section 2 fixed inside the hollow shaft for rotating integrally with the rotor when the field coil is excited, thereby generating flow of a fluid 15 inside the hollow shaft.
The present application claims priority from Japanese application serial No. 2006-198947, filed on Jul. 21, 2006, the content of which is hereby incorporated by reference into this application.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates to an electric axial flow pump having a stator and a rotor.
2. Prior Art
The electric axial flow pump is widely used such as a vacuum pump for sucking electronic parts used in an electronic part mounting device and a circulating pump for circulating cooling water in a cooling circuit used in an automobile and a portable personal computer.
When using the electric axial flow pump as a vacuum pump, there is a case that the electric axial flow pump and a suction section for directly sucking electronic parts are installed separately from each other and an auxiliary section such as a pipe for connecting the electric axial flow pump and suction section is necessary. The reason that the electric axial flow pump and suction section are installed separately from each other is conceivably that the volume of the electric axial flow pump is large. Therefore, a motor having a built-in pump excluding an auxiliary section such as a pipe which is realized by mounting an electric axial flow pump in a suction section rotated by a motor is proposed (for example, refer to Patent Document 1). To mount the electric axial flow pump on the suction section, further miniaturization of the electric axial flow pump is desired.
Further, also with respect to the circulating pump, since the cooling circuit and furthermore an automobile and a portable personal computer are designed according to the volume of the electric axial flow pump, from the viewpoint of enhancement of the degree of freedom of the design of an automobile and a portable personal computer, further miniaturization of the electric axial flow pump is desired. And, a fluidic pump in which the stator of the motor of the electric axial flow pump is described as a claw pole stator, thus the length of the motor in the direction of the rotary shaft is shortened is proposed (for example, refer to Patent Documents 2 and 3).
Patent Document 1: Japanese Patent Application Laid-open Publication No. 2005-220812 (Paragraphs 0020 to 0023, FIG. 2)
Patent Document 2: Japanese Patent Application International Publication No. 2003-505648 (Paragraph 0020, FIG. 2)
Patent Document 3: Japanese Patent Application International Publication No. 2003-515059 (Paragraph 0032, FIG. 3)
SUMMARY OF THE INVENTIONTherefore, the object of the present invention is to provide an electric axial flow pump able to be miniaturized.
To solve the aforementioned object, the present invention provides an electric axial flow pump including a rotor having a cylindrical hollow shaft having open ends which is arranged so as to be surrounded by a stator and a flow generation section which is fixed inside the hollow shaft, rotates integrally with the rotor when a field coil of the stator is excited, thereby generates flow of a fluid inside the hollow shaft.
According to the present invention, an electric axial flow pump capable of miniaturization can be provided.
BRIEF DESCRIPTION OF THE DRAWINGS:
Hereinafter, by referring to the accompanying drawings, an embodiment of the electric axial flow pump relating to the present invention will be explained.
Embodiment 1As shown in FIGS. 1(a) and 1(b), an electric axial flow pump 1 relating to the first embodiment of the present invention has a stator 6 having field coils 10U, 10V, and 10W. Further, the electric axial flow pump 1 has a rotor 3 including a cylindrical hollow shaft 4 having openings 21A and 21B at both ends surrounded by the stator 6 and magnets 5 fixed around the hollow shaft 4. Furthermore, the electric axial flow pump 1 has a flow generation section 2 which is fixed inside the hollow shaft 4, rotates integrally with the rotor 3 when the field coils 10U, 10V, and 10W are excited, thereby generates flow of a fluid 15 inside the hollow shaft 4. The flow generation section 2 lets the fluid 15 flow by rotation and the fluid 15, for example, flows in from the opening 21B at one end of the hollow shaft 4, flows from the opening 21B up to the opening 21A at the other end of the hollow shaft 4 in the direction a rotary shaft 23 of the rotor 3, and flows out from the opening 21A. The flow of the fluid 15 meets the requirements of the axial flow pump.
According to the electric axial flow pump 1, inside the hollow shaft 4 composing the rotor 3, the flow generation section 2 is installed, so that outside the stator 6 surrounding the rotor 3, there is no need to install an auxiliary section such as a pipe and for the rotor 3 and stator 6, before and behind the rotor 3 in the direction of the rotary shaft 23, there is no need to install an auxiliary section such as a pipe. Therefore, the electric axial flow pump can be miniaturized. Further, the flow generation section 2 is installed inside the hollow shaft 4, so that the outside diameter of the shaft of the so-called rotor 3 is increased, thus it is considered to be contrary to miniaturization, though to increase the torque for rotating the rotor 3, it is necessary to fix the magnets 5 onto the outer periphery of the rotor 3 having a large outside diameter and make the radius of rotation of the magnets 5 larger, and an area not narrow is reserved conventionally inside the magnets 5, so that it is not contrary to miniaturization. Inversely, in the electric axial flow pump 1, by reserving a large radius of rotation of the magnets 5, the volume of the flow generation section 2 can be reserved large, so that the torque for rotating the rotor 3 can be increased and the flow rate of the fluid 15 can be increased.
The stator 6 is composed of a plurality of stators 6U, 6V, and 6W arranged in the direction of the rotary shaft 23 of the rotor 3. Alternating currents different in phase are impressed to the respective field coils 10U, 10V, and 10W of the plurality of stators 6U, 6V, and 6W, thus the rotor 3 rotates. Particularly, as shown in
The respective stators 6U, 6V, and 6W are preferably claw pole stators. The respective stators 6U, 6V, and 6W are composed of stator magnetic cores 7U, 7V, and 7W and the circular field coils 10U, 10V, and 10W wound round the stator magnetic cores 7U, 7V, and 7W. Between the stator magnetic cores 7U, 7V, and 7W and the rotor 3, a gap is formed and the stator magnetic cores 7U, 7V, and 7W are supported by a stator frame 8.
The respective stator magnetic cores 7U, 7V, and 7W are composed of a first claw pole core 11A and a second claw pole core 11B. The first claw pole core 11A is composed of a claw pole 12A opposite to the magnets 5, a circular yoke section 13 extending at right angles from one end of the claw pole 12A to the outside diameter side, and an outer-peripheral side yoke 14 extending in the same direction as that of the claw pole 12A from the circular yoke section 13. Similarly, the second claw pole core 11B is composed of a claw pole 12B opposite to the magnets 5, the circular yoke section 13 extending at right angles from the claw pole 12B to the outside diameter side, and the outer-peripheral side yoke 14 extending in the same direction as that of the claw pole 12B from the circular yoke section 13.
As mentioned above, the stators 6U, 6V, and 6W which are claw pole stators are shaped so as to be bent extending from the circular yoke section 13 to the claw poles 12A and 12B, so that the excessive space extending in the direction of the rotary shaft 23 such as the end portion of a slot type field coil which is not a claw pole stator can be eliminated and the stators 6U, 6V, and 6W can be shortened in the length in the direction of the rotary shaft 23.
On the outer periphery of the stator 6, the stator frame 8 is arranged. The stator frame 8 is in the cylindrical shape along the stator 6 and fixes the stator 6. Before and behind the rotor 3 and stator 6 in the direction of the rotary shaft 23, inside the stator frame 8, a pair of bearings 9A and 9B in the circular ring shape is installed. The bearings 9A and 9B support rotatably the rotor 3 and the inside diameters of the bearings 9A and 9B are larger than the inside diameter of the hollow shaft 4. Therefore, the openings 21A and 21B of the hollow shaft 4 are not covered by the bearings 9A and 9B. And, the openings 22A and 22B at both ends of the stator frame 8 and the openings 21A and 21B at both ends of the hollow shaft 4 can be arranged on one straight line. For example, the flow-in direction in which the fluid 15 flows in from the opening 22B into the opening 21B and the flow-out direction in which it flows out from the opening 21A into the opening 22A can be made the same direction. The directions are the same, so that when the hollow shaft 4 is inserted into the route of the existing pipe such as the cooling circuit used in an automobile or a portable personal computer, the electric axial flow pump can be connected to the route, so that the degree of freedom of design of the cooling circuit can be enhanced.
The flow generation section 2 includes a fin 16, a pillar 17, and a metal fitting 18. It may be considered that the fin 16 and pillar 17 compose a propeller. The fin 16 is spirally arranged and fixed around the pillar 17. The pillar 17 is fixed to the hollow shaft 4 by the fitting 18 so as to make the rotary shaft 23 coincide with the central axis of the pillar 17. The fin 16 and pillar 17 rotate integrally with the rotor 3 and move the fluid 15 in the direction of the rotary shaft 23. The pillar 17 is installed on the rotary shaft 23, and the fin 16 is arranged around it, and the diameter thereof slowly increases in the direction of the rotary shaft 23. The direction in which the thickness increases coincides with the flow direction of the fluid 15. As the fluid 15 flows, the thickness of the pillar 17 at the position of the flow destination increases, thus the flow space of the fluid 15 between the hollow shaft 4 and the pillar 17 is narrowed, so that the fluid 15 is compressed as it flows. The compression of the fluid 15 may be also caused by the centrifugal force acting on the fluid 15 rotating in correspondence with the rotation of the rotor 3. Further, the pitch of the fin 16 spirally wound round the pillar 17 is slowly narrowed in the flow direction of the fluid 15, thus the fluid 15 can be compressed. As mentioned above, by compressing the fluid 15, the compressed fluid 15 can be finally discharged from the opening 21A into the opening 22A where the non-compressed fluid 15 exist. A pumping function for causing a pressure difference to the fluid 15 in the direction of the rotary shaft 23 like this in correspondence with the rotation of the rotor 3 is developed. Such a pumping function appears remarkably when the fluid 15 is a compressive fluid like air.
As shown in
In the stator 6, the stators 6U, 6V, and 6W have the same structure, so that the stator 6W will be then explained in detail.
As shown in
As shown in
The first claw pole core 11A and second claw pole core 11B have the same structure, so that the first claw pole core 11A will be explained in detail. FIGS. 5, 6, and 7 respectively show a bottom view, a top view, and a cross sectional view of the first claw pole core 11A. For the second claw pole core 11B, the claw pole 12A in the explanation on the claw pole 12A may be replaced with the claw pole 12B.
The first claw pole core 11A, including the claw pole 12A, is preferably formed by compacting magnetic powder. Furthermore, magnetic powder is preferably insulating-coated magnetic powder (iron powder). Magnetic powder with an average maximum width of 20 to 150 μm can be used. Further, as insulating coating, an oxide film with magnetic powder coated which is an inorganic oxide is acceptable and the film thickness is preferably several tens nm or less. By use of insulating-coated magnetic powder, in the first claw pole core 11A of the claw pole 12A, an eddy current loss is caused hardly and the output density of the electric axial flow pump 1 can be improved. Further, magnetic powder is compacted by a punch of the die assembly, so that compared with a one structured by laminating a silicon steel plate, a complicated magnetic pole structure can be obtained. And, since the first claw pole core 11A and second claw pole core 11B are in the same shape, by compacting magnetic powder by the same die, the first claw pole core 11A and second claw pole core 11B in the same shape can be formed easily.
When compacting magnetic powder, thereby forming the first claw pole core 11A, the magnetic powder is compacted by the die, though the compacting direction thereof is the direction of the rotary shaft 23 in which the claw pole 12A extends. At this time, the punch for compacting the first claw pole core 11A, to prevent the punch from buckling, the sectional area of the punch in proportion to the length of the first claw pole core 11A, which is a compacted piece, in the direction of the rotary shaft 23 is necessary.
In other words, on the basis of a length L1 (refer to
In a compacted piece produced by compacting magnetic powder, to obtain a high magnetic characteristic, a compacting pressure of about 10 ton/cm2 is necessary and the sectional area of the punch corresponding to it is necessary at the extending end 12T of the claw pole 12A in the axial direction. And, to preserve the sectional area of the punch, the results of trial manufacture show that it is necessary to control a thickness H2 (refer to
Furthermore, when ejecting the first claw pole core 11A compacted at the compacting pressure of 10 ton/cm2 from the die, a tapered surface 12K inclined at a draft taper angle θ from the direction of the rotary shaft 23 is necessary and it is necessary in the claw pole 12A to form the draft taper angle θ tapering from the base thereof to the extending end 12T in the axial direction. The results of trial manufacture show that to compact magnetic powder and draw the first claw pole core 11A from the die, a draft taper angle θ of 8° or more is necessary. When the draft taper angle θ is as large as possible, the drawing operation can be performed easily. However, when the draft taper angle θ is increased, the area of the magnetic pole surface 12F of the claw pole 12A is reduced and the magnetic characteristic is lowered, so that the inventors confirm that the draft taper angle θ is preferably 10° or less hardly affecting the magnetic characteristic. Therefore, it is found that the draft taper angle θ is preferably set between 8° and 10°.
Further, a ratio of L1/L2 of the maximum length L1 of the first claw pole core 11A in the direction of the rotary shaft 23 to the minimum length L2, in relation to the sectional area of the punch, the number of poles of the motor which is the sum of the numbers of the first claw poles 12A and second claw poles 12B, and the draft taper angle θ, has an upper limit and when the number of poles of the motor is 50 or less, is desirably 5 or less. Meanwhile, the maximum length L1 of the first claw pole core 11A in the direction of the rotary shaft 23 is measured in the claw pole 12A and the minimum length L2 is measured in the circular yoke section 13.
The first claw pole core 11A is formed by compacting of magnetic powder as mentioned above, thus the magnetic powder can be compacted at a high compacting pressure from the base of the claw pole 12A to the extending end 12T in the axial direction, so that the density of the first claw pole core 11A including the claw pole 12A can be increased to 7.5 g/cm3 or more.
The stator 6W is formed using the first claw pole core 11A and second claw pole core 11B prepared by various materials as shown in
The powder core 1, compared with the SPCC, 35A300, 50A1300, and SS400 (Japanese Industrial Standard), may be considered that a magnetic flux density B (T) is low as a whole and the magnetizing characteristic is deteriorated. On the other hand, the powder core 2 may be considered that a magnetic flux density B (T) equivalent to that of the SPCC or SS400 is obtained as a whole and the magnetizing characteristic is equivalent to that of the SPCC or SS400.
Therefore, when the stator 6W using the first claw pole core 11A and second claw pole core 11B for compacting magnetic powder so as to control the density of the powder core 1 to 7.3 g/cm3 is used for the electric axial flow pump 1, the magnetic flux density B is low and the magnetic characteristic is deteriorated, so that when the magnets 5 (refer to
On the other hand, the SPCC, 35A300, 50A1300, and SS400 are formed by bending a cold rolled steel sheet and a silicon steel sheet, so that an eddy current loss is caused to the claw pole 12A, circular yoke section 13, and outer peripheral side yoke 14, so that it may be considered that if the input power is fixed, to ensure the magnetic characteristic, high-speed rotation may not be performed. According to the first claw pole core 11A and second claw pole core 11B for compacting magnetic powder so as to control the density of the powder core 2 to 7.5 g/cm3, the magnetic powder is mutually insulated from each other by insulating coating, so that an eddy current loss is caused hardly and there is no effect of the magnetostriction due to bending forming.
Furthermore, as the electric axial flow pump 1, it is desired to ensure high magnetomotive force by using the magnets 5 having a high residual magnetic flux density for the rotor 3 and to install the first claw pole core 11A and second claw pole core 11B for effectively using the magnetomotive force, so that firstly rare-earth magnets of permanent magnets are used for the magnets 5, and the magnetic flux density is controlled between 1.2 T and 1.4 T, thus high magnetomotive force is ensured. Next, to install the first claw pole core 11A and second claw pole core 11B capable of effectively using the high magnetic flux density (magnetomotive force), the dimensional relationship between the first claw pole core 11A and the second claw pole core 11B is found by the examination indicated below.
Next, from the above results, the inside diameter D and number of poles M are set so as to maximize the output torque and particularly using the electric axial flow pump in which the number of poles is set to 24 and 32, the average width angle T (refer to
In
The first claw pole core 11A and second claw pole core 11B are structured as described above, thus the pumping efficiency of the electric axial flow pump 1 can be improved.
As shown in
As shown in
The magnets 5 are produced mainly from a binder and magnet powder. The powder core 19 is produced mainly from a binder and soft magnetic powder.
Further, at least one surface of the magnetic pole of each of the magnets 5 is joined mechanically to the powder core 19. The mechanical joint is caused during the process of compacting of a powder material. Hereinafter, the compacting process will be explained. Firstly, the magnets 5 are compacted temporarily by compacting for each segment. During the temporary compacting, they are magnetized by the magnetization field and are given anisotropy. Next, using the hollow shaft 4 as a part of the die, for the powder core 19 and temporarily compacted magnets 5, real compacting for simultaneously applying pressure in the compact direction in the direction of the rotary shaft 23 is performed. By this real compacting, the hollow shaft 4, powder core 19, and magnets 5 are compacted integrally and the magnets 5 and powder core 19 are joined mechanically. The rotor 3 is formed by a powder material, thus the same effect as that shown in
The electric axial flow pump 1 of the third embodiment additionally has a phase splitting section 25 for generating a second single-phase alternating current obtained by shifting the phase of a first single-phase alternating current of a single-phase AC source 26 by a predetermined angle of about 90°. The phase splitting section 25 can be composed of a capacitor and may include a coil. The phase splitting section 25 connects the first single-phase alternating current and second single-phase alternating current respectively to the field coils 10A and 10M. By this connection, the stators 6A and 6M are arranged by shifting by a predetermined phase at an electrical angle in the peripheral direction, for example, when the phase splitting section 25 is composed of a capacitor, by shifting by about 90° and to the field coils 10A and 10M, a single-phase power source having a phase difference angle of 90° at an electrical angle is connected. By use of such a constitution, the electric axial flow pump 1 driven by the single-phase AC source 26 can be provided.
Embodiment 4
FIGS. 17(a) and 17(b) are a side view of the electric axial flow pump 1 relating to the sixth embodiment of the present invention and a cross sectional view thereof in the direction of the rotary shaft 23. The difference of the electric axial flow pump 1 of the sixth embodiment shown in
FIGS. 18(a) and 18(b) are a side view of the electric axial flow pump 1 relating to the seventh embodiment of the present invention and a cross sectional view thereof in the direction of the rotary shaft 23. The difference of the electric axial flow pump 1 of the seventh embodiment shown in
FIGS. 19(a) and 19(b) are a side view of the electric axial flow pump 1 relating to the eighth embodiment of the present invention and a cross sectional view thereof in the direction of the rotary shaft. The difference of the electric axial flow pump 1 of the eighth embodiment shown in
FIGS. 20(a) and 20(b) are a side view of the electric axial flow pump 1 relating to the ninth embodiment of the present invention and a cross sectional view thereof in the direction of the rotary shaft. The difference of the electric axial flow pump 1 of the ninth embodiment shown in
Claims
1. An electric axial flow pump comprising:
- a stator having a field coil,
- a rotor including a cylindrical hollow shaft having open ends surrounded by the stator and a plurality of magnets fixed around the hollow shaft, and
- a flow generation section fixed inside the hollow shaft for rotating integrally with the rotor when the field coil is excited, thereby generating flow of a fluid inside the hollow shaft.
2. The electric axial flow pump according to claim 1, wherein the stator is a claw pole type stator.
3. The electric axial flow pump according to claim 2, wherein the stator has a plurality of claw poles formed by compacting insulating-coated magnetic powder on the inner peripheral surface and a circular ring-shaped stator magnetic core for covering the field coil, and the field coil is a circular coil mounted inside the stator magnetic core.
4. The electric axial flow pump according to claim 1, wherein the flow generation section has a fin for rotating integrally with the rotor and moving the fluid in a direction of a rotary shaft of the rotor.
5. The electric axial flow pump according to claim 4, wherein the fin is fixed directly to the rotor.
6. The electric axial flow pump according to claim 4, wherein the flow generation section has a pillar installed on the rotary shaft for slowly increasing thickness in the direction of the rotary shaft, and the fin is arranged around the pillar.
7. The electric axial flow pump according to claim 1, wherein the flow generation section has a propeller for rotating integrally with the rotor and moving the fluid in a direction of a rotary shaft of the rotor.
8. The electric axial flow pump according to claim 1, wherein the flow generation section has slits formed inside the hollow shaft in a twisted direction to the direction of the rotary shaft of the rotor.
9. The electric axial flow pump according to claim 1, further comprising:
- a cylindrical stator frame arranged on an outer periphery of the stator for fixing the stator and
- a pair of bearings in a circular ring shape installed inside the stator frame before and behind the rotor for supporting rotatably the rotor, wherein inside diameters of the bearings are larger than an inside diameter of the hollow shaft.
10. The electric axial flow pump according to claim 9, wherein openings at both ends of the stator frame and the openings at the both ends of the hollow shaft are arranged on one straight line and a flow-in direction of the fluid and a flow-out direction thereof are the same direction.
11. The electric axial flow pump according to claim 1, wherein a plurality of the stators are installed in a direction of a rotary shaft of the rotor and to the respective field coils of a plurality of the stators, polyphase AC voltages different in phase are impressed.
12. The electric axial flow pump according to claim 1, wherein so as to permit respective different phases of a three-phase AC power source to be connected one by one to the field coils of the respective stators, the stators are shifted 120° by 120° at an electrical angle and three the stators are arranged in a direction of a rotary shaft of the rotor.
13. The electric axial flow pump according to claim 12, wherein two or more groups of the three stators are installed in the direction of the rotary shaft.
14. The electric axial flow pump according to claim 1, further comprising:
- a phase splitting section for generating a second single-phase alternating current obtained by shifting a phase of a first single-phase alternating current of a single-phase AC source by 90°, wherein:
- so as to permit the first single-phase alternating current and the second single-phase alternating current to be connected one by one to the field coils of the respective stators, the stators are shifted by 90° at an electrical angle and two the stators are arranged in a direction of a rotary shaft.
15. The electric axial flow pump according to claim 14, wherein two or more groups of the two stators are installed in the direction of the rotary shaft.
16. The electric axial flow pump according to claim 1, wherein the rotor has a powder core installed between the hollow shaft and the magnets.
17. The electric axial flow pump according to claim 3, wherein:
- a thickness of the claw poles in a radial direction is 2 mm or more,
- the claw poles have a flat surface perpendicular to a direction of a rotary shaft at an extending end of the rotor in the direction of the rotary shaft and a draft taper inclined at an angle within a range from 8° to 10° to the direction of the rotary shaft tapering from a base of the claw poles to the extending end, and
- a ratio of a length of the claw poles in the direction of the rotary shaft to a minimum thickness of the stator magnetic core in the direction of the rotary shaft is less than 5.
18. The electric axial flow pump according to claim 17, wherein assuming the relationship between a number M of the claw poles and an inside diameter D of the stator as M=a·D, a coefficient a is between 0.35 and 0.5.
19. The electric axial flow pump according to claim 17 or 18, wherein a ratio of T/P of an average width angle T of a maximum width angle and a minimum width angle occupied by the claw poles in a peripheral direction of the stator magnetic core to a pitch angle P occupied by a pitch of the claw pole cores in the peripheral direction is between 0.4 and 0.45.
20. The electric axial flow pump according to claim 3, wherein density of the stator magnetic core is 7.5 g/cm3 or more.
Type: Application
Filed: Jul 20, 2007
Publication Date: Feb 14, 2008
Inventors: SATOSHI KIKUCHI (Hitachi), Motoya Ito (Hitachinaka), Ryoso Masaki (Narashino), Chio Ishihara (Tokyo), Shoji Ohiwa (Saitama), Kazuhide Ebine (Narashino)
Application Number: 11/780,720
International Classification: F04D 3/00 (20060101);