WO2009104376A1

WO2009104376A1 - Thrust force generator and elecromagnetic machine with use of the generator

Info

Publication number: WO2009104376A1
Application number: PCT/JP2009/000615
Authority: WO
Inventors: 朝間淳一; 千葉明; 仁藤淳
Original assignee: モーターソリューション株式会社
Priority date: 2008-02-18
Filing date: 2009-02-17
Publication date: 2009-08-27
Also published as: JP2009192041A

Abstract

This object aims to provide a thrust force generator which has a high productivity and an excellent reliability, and capable of solving such problems as limitation to the number of rotations, occurrence of cavitation and so on when the thrust force generator is applied to a fluid machine; and an electromagnetic machine using the generator. The electromagnetic machine comprises a first permanent magnet (13) fixed to a main shaft (1) and excited in the axial direction, and one or more air core coils (15) which are wound around the first permanent magnet (13) at a position deviated from the center of gravity of the first permanent magnet (13) by a predetermined distance in the axial direction and don't have an iron core, and further includes a thrust force generator (160) which generates an electromagnetic force in the axial direction by supplying a current to the air core coils (15).

Description

Thrust force generator and electromagnetic machine to which the thrust force generator is applied

The present invention relates to a thrust force generating device and an electromagnetic machine to which the thrust force generating device is applied. Particularly, the assembling operation is simple, and the thrust force generating device and the thrust force are designed to reduce the number of parts and the spindle length. The present invention relates to an electromagnetic machine to which a generator is applied.

The bearingless motor is a motor that can rotate without contact while the main shaft is magnetically levitated (see, for example, Non-Patent Document 1). In general motors, the stator is provided with rotating windings (motor windings). However, in bearingless motors, magnetic levitation windings (shaft supporting windings) are additionally provided. ing. When a current is passed through this shaft support winding, a magnetic force acts in the radial direction of the main shaft. By measuring the radial displacement of the main shaft and adjusting this magnetic force, non-contact magnetic levitation support becomes possible.

Conventionally, using this two bearingless motors and a thrust magnetic bearing, a bearingless rotating machine that controls the magnetic levitation of five degrees of freedom motion (x, y, z, θx, θy) other than the rotation direction (θz) of the main shaft. Has been reported (for example, see Non-Patent Document 2). As shown in the sectional view of FIG. 18, the bearingless rotating machine 100 includes a bearingless motor unit 40 including a mover 4 and a stator 5, and a bearingless motor unit including a mover 6 and a stator 7. 50 and a three-unit structure of a thrust magnetic bearing 60.

FIG. 19 is a perspective configuration diagram around the bearingless motor unit 40 and the bearingless motor unit 50. In FIG. 18, the radial displacement sensor 3 is provided for each of the x-axis and the y-axis, and is fixed to a housing (not shown), and measures the distance between the cylindrical sensor target 2 fixed to the main shaft 1. It is supposed to be. Similarly, the radial displacement sensor 14 is provided for each of the x-axis and the y-axis, and measures the distance between the columnar sensor target 8 fixed to the rotary shaft 1.

On the other hand, the thrust magnetic bearing 60 is composed of a disk-shaped magnetic disk 10 and two

stator electromagnets

9 and 11 sandwiching the disk-shaped magnetic disk 10. The axial movement (z) of the main shaft is controlled by the thrust magnetic bearing 60. The axial displacement sensor 18 measures the displacement in the thrust direction using the magnetic disk 10 as a sensor target.

The mover 4 and the mover 6 of the

bearingless motors

40 and 50, the sensor target 2 and sensor target 8, and the magnetic disk 10 are fixed through by the main shaft 1. Since the magnetic disk 10 having a large diameter is fixed to the lower end portion of the main shaft 1, the main shaft 1 has a convex shape as a whole rotating body. Further, at least one displacement sensor is required to control one degree of freedom.

Next, the operation principle of the conventional magnetic bearing will be described with reference to FIG. A control device (not shown) measures the displacement / angle in the radial direction (x, y) and the conical direction (θx, θy) by the radial displacement sensor 3 and the radial displacement sensor 14 and is suitable for the electromagnets 41 and 51. A 4 degree of freedom movement of the main shaft 1 is actively controlled by flowing a large current.
On the other hand, with respect to the axial direction, when an external force is applied to the main shaft 1 in the upward direction in the drawing, the control device controls the main shaft 1 not to move by causing a current to flow through the electromagnet 11 and attracting the magnetic disk 10. On the other hand, when an external force is applied to the main shaft 1 in the downward direction in the drawing, the control device causes a current to flow through the electromagnet 9. The relationship between current and thrust force at this time is non-linear. For linearization, it is necessary to use a push-pull method in which a bias current is passed and the currents of the

electromagnets

9 and 11 are increased on the one hand and decreased on the other hand.

At present, application of this five-degree-of-freedom control type bearingless rotating machine to an industrial centrifugal pump as shown in FIG. 20 is being studied. FIG. 20 shows an overall structural diagram of a conventional 5-axis active control type bearingless rotating machine for this pump application. Note that the same components as those in FIG. 18 are denoted by the same reference numerals and description thereof is omitted.

In FIG. 20, an impeller 21 is disposed at the left end of the main shaft 1, and a predetermined fluid is sucked from a pump suction port 22 and discharged from a pump discharge port 25.
When the above-described

bearingless motors

40 and 50 are applied to a pump, the five-degree-of-freedom movement of the main shaft 1 is actively controlled. It is possible to operate.

In addition, since the impeller 21 integrated with the main shaft 1 can be floated and rotated completely without contact, seals (shaft seals), bearings, lubricating oil, etc. are not required, and maintenance-free and clean with no dust generation. A pump capable of liquid feeding can be realized.
However, in such an application, since the liquid flows between the stator and the mover, it is necessary to cover the surface of the stator / mover with a partition wall 23 such as a resin cover.

In addition, when a pump is comprised only with the bearingless rotary machine of radial direction 2 degree-of-freedom control (for example, refer patent documents 1 and nonpatent literature 3), force acts on impeller 21 by thrust direction propulsion power during pump drive. However, the impeller 21 and the housing 26 may collide.

Japanese Patent Application Laid-Open No. 2001-016687 “Electric Rotation Drive Device”

By the way, in the above-described conventional pump, since the rotating body has a convex shape as a whole, the processing of the partition wall 23 is complicated, and the housing needs to be separated to insert the rotating body into the housing. Yes, the number of parts increases. Further, when used in a pump or the like, it is necessary to seal the separated part in order to prevent the liquid from leaking, and the assembly work is complicated. For this reason, productivity was bad and cost was high. In addition, since the partition wall 23 that covers such a mover or stator has many corners, there is a problem that cracks are easily generated and the reliability is uneasy.

Furthermore, the thrust force cannot be obtained unless the outer circumference of the magnetic disk 10 is increased. A bearingless motor is characterized by being able to be operated at a higher speed than a normal motor. However, when it is operated at a high speed, there are problems of mechanical strength due to an increase in peripheral speed and problems such as cavitation occurring when applied to a fluid machine. there were. Furthermore, as shown in the cross-sectional view of FIG. 18, the distance between the radial displacement sensor 14 and the electromagnet 9 having the magnetic core is short. If the distance between the displacement sensor and the electromagnet 9 is short, there is a problem that the measurement sensitivity is lowered when the radial displacement sensor 14 such as an eddy current type or an inductance type is used.

The present invention solves the problems such as the limitation on the rotational speed as described above and cavitation when applied to a fluid machine, and has a high productivity and excellent reliability, and a thrust force generator and the thrust force. An object is to provide an electromagnetic machine to which a generator is applied.

For this reason, the electromagnetic machine provided with the thrust force generator of the present invention (1) includes the first permanent magnet attached to the main shaft, the periphery of the first permanent magnet, and the center of the first permanent magnet. An electromagnetic machine having an air core coil without an iron core wound at a position shifted by a predetermined distance in the axial direction, and generating an electromagnetic force in the axial direction by supplying current to the air core coil It is. *

When a current is passed through the air core coil, Lorentz force acts on the air core coil. Since the air-core coil is fixed, it receives a reaction, and a force acts on the first permanent magnet in a direction opposite to the Lorentz force. Accordingly, the thrust direction motion of the main shaft can be actively controlled by supplying an appropriate current to the air-core coil. Since the air-core coil does not have an iron core, the measurement sensitivity of the sensor does not decrease due to a change in the eddy current or inductance value as in the prior art even if the distance from the radial displacement sensor is close.

Further, in the electromagnetic machine provided with the thrust force generator of the present invention (2), the air-core coil is located at a position shifted in the main shaft negative direction from the first coil disposed at a position shifted in the main shaft positive direction. An electromagnetic machine comprising: a second coil disposed symmetrically with respect to the first coil, wherein the second coil and the first coil are each subjected to current control. .

Since Lorentz force is generated for each of the first coil and the second coil, the thrust force can be increased.

Furthermore, the electromagnetic machine provided with the thrust force generator of the present invention (3) is configured to include a support plate at the end of the first permanent magnet in the main axis direction.

When the support plate is made of a magnetic material, the support plate can concentrate the magnetic flux on the first coil and the second coil. For this reason, the generated force in the axial direction can be increased. Moreover, this support plate has the effect of suppressing rattling when the first permanent magnet is attached to the main shaft. The support plate can be made of non-metal. Even in this case, the effect of suppressing rattling when the first permanent magnet is attached to the main shaft can be similarly obtained. The support plate may be a nonmagnetic material. *

Further, the electromagnetic machine of the present invention (4) includes a radial force generator that generates a radial electromagnetic force on the main shaft, and the diameter of the first permanent magnet is fixed to the radial force generator. It is characterized by being formed below the inner diameter of the child. *

The electromagnetic machine includes, for example, a bearingless motor and a magnetic bearing device. The radial force generation device may perform only radial control on the main shaft, or may involve rotation driving.
By forming the diameter of the first permanent magnet to be equal to or smaller than the diameter inside the stator of the radial force generator, the entire rotating body is cylindrical, and the rotating body can be easily inserted into the housing. For this reason, the assembly work of the pump which applied the electromagnetic machine can be performed easily. Since the diameter of the first permanent magnet is smaller than the size of the conventional magnetic disk, cavitation hardly occurs.

Further, in the electromagnetic machine of the present invention (5), the radial direction between the outer peripheral surface of the first permanent magnet, the plating formed on the outer peripheral surface, or the ring covering the outer peripheral surface. A radial displacement sensor for detecting the position was provided.

By using the outer circumference of the first permanent magnet as the sensor target, it is possible to eliminate the extra sensor target and reduce the axial length.

Furthermore, the electromagnetic machine of the present invention (6) is characterized in that the radial force generator is a bearingless motor that rotates the main shaft in a non-contact manner while magnetically levitating.

Further, in the electromagnetic machine of the present invention (7), a second permanent magnet is separately provided on the stator side so as to face the end in the main axis direction of the first permanent magnet, and the second permanent magnet is A repulsive force or an attractive force is generated in the thrust direction with respect to the first permanent magnet. *

The second permanent magnet generates a repulsive force or attractive force in the thrust direction with respect to the first permanent magnet, so that, for example, the thrust force acting on the impeller during pump driving is balanced or canceled out in part, The current of the air core coil can be saved.

As described above, according to the present invention, the first permanent magnet attached to the main shaft and the air-core coil having no iron core are provided, so that by supplying a current to the air-core coil, the axial direction The electromagnetic force can be generated. By causing an appropriate current to flow through the air-core coil, it is possible to actively control the movement of the main shaft in the thrust direction.

In addition, since the diameter of the first permanent magnet is formed to be equal to or smaller than the diameter inside the stator of the radial force generator, the entire rotating body has a cylindrical shape and can be easily inserted into the housing. For this reason, it is excellent in the assembly workability | operativity of the pump which applied the electromagnetic machine, and productivity is high. Since the diameter of the first permanent magnet is about half the size of the conventional magnetic disk, the probability of occurrence of cavitation when operating at the same rotation is greatly reduced. Therefore, an electromagnetic machine with excellent productivity and high reliability can be realized.

1 is a cross-sectional configuration diagram of a five-degree-of-freedom control type bearingless rotating machine according to a first embodiment of the present invention. It is a figure explaining the thrust direction generated force of this invention and a prior art example. It is a figure explaining the principle of the thrust force generator of this invention. It is an analysis model figure in the case of one air-core coil. It is an analysis result at the time of changing the magnet thickness in the case of one air-core coil. It is an analysis model figure in the case of two air-core coils. It is an analysis result at the time of changing a magnet thickness in the case of two air-core coils. It is the analysis result of the surrounding magnetic flux by the presence or absence of a magnetic disk of a cylindrical permanent magnet. It is the analysis result of the surrounding magnetic field by the presence or absence of a magnetic disk of a cylindrical permanent magnet. It is the analysis result of the thrust force with respect to the thickness of a magnetic disc. It is a figure which shows the main components of the prototype of the thrust force generator of this invention. It is data which shows the difference of the transient response by the presence or absence of control of the thrust force generator of this invention. It is a figure which shows the difference of the analytical value of thrust force, and measurement. It is a figure which shows the difference of the analytical value of magnetic flux of radial direction, and measurement. It is a figure which shows the thrust displacement of a rotor, the output of a radial direction displacement sensor, and the shaft support coil | winding U phase current of a bearing rotating machine in the rotation speed of 510 r / min. It is a cross-sectional block diagram of a 5-degree-of-freedom control type bearingless rotating machine that is the second embodiment of the present invention. It is a cross-sectional block diagram of the 5-degree-of-freedom control type bearingless rotating machine which is 3rd Embodiment of this invention. It is sectional drawing of the conventional bearingless rotary machine. FIG. 3 is a perspective configuration diagram around a bearingless motor unit. This is a structural example in which a conventional bearingless rotating machine is applied to a pump.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main axis |

shaft

2,8 Sensor target 3 Radial

direction displacement sensor

4, 6

Movable element

5, 7

Stator

12, 15 Air-

core coil

13, 19 Permanent magnet 14 Radial

direction displacement sensor

16, 17 Magnetic disk 18 Axial

direction displacement sensor

40 , 50

Bearingless motor unit

60, 160

Thrust force generator

200, 300, 400 Bearingless rotating machine

Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. This is merely an example, and the technical scope of the present invention is not limited to this.

FIG. 1 is a cross-sectional configuration diagram of a five-degree-of-freedom control type bearingless rotating machine 200 according to a first embodiment of the present invention. Note that the same components as those in FIG. 16 described in the background art are denoted by the same reference numerals and description thereof is omitted. FIG. 1 differs from the configuration of the conventional bearingless rotating machine 100 shown in FIG. 16 in that the conventional thrust magnetic bearing 60 portion uses the magnetic disk 10 having a large diameter, so that the rotating body has a convex shape as a whole. In contrast to the above, the rotating body portion of the thrust force generator 160 is formed in a cylindrical shape as a whole.

1, a cylindrical permanent magnet 13 serving as a mover sandwiched from above and below by

magnetic disks

16 and 17 is attached to the lower end portion of the main shaft 1. The permanent magnet 13 is magnetized with an N pole on the upper surface and an S pole on the lower surface. The radial dimension of the permanent magnet 13 is the same as that of the

movers

4 and 6 and the

sensor targets

2 and 8 of the

bearingless motors

40 and 50.

An air-core coil 12 serving as a stator is disposed on the outer periphery of the permanent magnet 13 and the

magnetic disks

16 and 17 and at a position higher than the center of gravity of the permanent magnet by a predetermined distance. Although the air core coil 12 is wound around the main shaft 1, the air core coil 12 is not provided with an iron core as in the prior art. The air core coil 12 is fixed by a resin forming the housing 26.

On the other hand, an air core coil 15 is similarly arranged at a symmetrical position lower than the center of gravity of the air core coil 12 and the center of gravity of the permanent magnet. A magnetic flux generated by the permanent magnet 13 passes through the air core coils 12 and 15.

Next, the configuration of the bearingless rotating machine 200 according to the first embodiment of the present invention will be described. By making the radial direction dimension of the permanent magnet 13 the same as that of the

movers

4 and 6 and the

sensor targets

2 and 8 of the

bearingless motors

40 and 50, the entire rotating body becomes cylindrical and the rotating body is inserted into the housing 26. It can be done easily. For this reason, the assembly work of a pump can be performed easily. Since the partition wall 23 as a resin cover can also be formed in a cylindrical shape, the mechanical strength is increased. Since the radial dimension of the permanent magnet 13 is smaller than that of the conventional magnetic disk 10, cavitation is less likely to occur. However, the radial dimension of the permanent magnet 13 may be smaller than the radial dimension of the

movers

4 and 6 and the

sensor targets

2 and 8.

The operation principle of the thrust force generator 160 of FIG. 1 will be described. The magnetic flux generated from the N pole on the upper surface of the permanent magnet 13 crosses the air core coil 12 and then passes outside the air core coil 12 and the air core coil 15. And after crossing the air-core coil 15, it returns to the south pole of the lower surface. Accordingly, the air core coil 12 passes a magnetic flux that goes out of the N pole of the permanent magnet 13 and goes outward in the radial direction, and the air core coil 15 passes a magnetic flux that flows inward to the S pole.

When an electric current is applied to the air core coil 12 from the front side of the drawing in the drawing to the back direction, while an electric current is supplied to the air core coil 15 from the back direction of the drawing in the drawing to the front side, Lorentz force is applied to the air core coil 12. 15 acts downward. Since the air-core coils 12 and 15 are fixed, an upward force acts on the permanent magnet 13 due to the reaction.

Further, if a current is applied to the air core coils 12 and 15 in the opposite direction, a downward force can be applied to the permanent magnet 13. Accordingly, the axial displacement of the main shaft 1 is measured by the axial displacement sensor 18 and an appropriate current is supplied to the air core coils 12 and 15, whereby the thrust direction motion of the main shaft 1 can be actively controlled. Since the air-core coil 12 does not have an iron core, the measurement sensitivity of the sensor does not decrease due to a change in eddy current or inductance value as in the conventional case even if the air-displacement coil 14 is disposed close to the radial displacement sensor 14.

This thrust force generator 160 uses the permanent magnet 13 for the mover and does not use a magnetic material for the surrounding stator. For this reason, even if the main shaft 1 is displaced in the radial direction, the magnetic attractive force by the thrust force generator 160 is not generated. Therefore, the influence of the thrust force generator 160 on the

bearingless motors

40 and 50 can be minimized.

FIG. 2 is a diagram for explaining the thrust generating force of the conventional bearingless rotating machine and the thrust force generating device of the present invention. The horizontal axis is the current flowing through the coil, and the vertical axis is the generated force in the thrust direction. As shown in FIG. 2, in the conventional thrust magnetic bearing 60 having the configuration of FIG. 18, the relationship between current and thrust force is non-linear. In order to linearize, a push-pull method is required in which a bias current is passed and the currents of the

electromagnets

9 and 11 are increased on the one hand and decreased on the other hand.

Therefore, complication of the control system and increase in power consumption due to steady current are problems. In the case of the thrust force generator 160 of the present embodiment using the air-core coils 12 and 15, as shown as “thrust force of the present embodiment” in FIG. It has the characteristic of being linear. Thrust force can be obtained as much as the conventional force.

Furthermore, since the magnetic flux from the permanent magnet 13 acts as a fixed bias magnetic flux on the air core coils 12 and 15, the current flowing through the air core coils 12 and 15 required to obtain the thrust force can be small. Note that it is not always necessary to dispose both of the air-core coils 12 and 15, and it is possible to control the axial direction of the rotating body with only one of them.

In the present embodiment, the

magnetic disks

16 and 17 are described as being disposed. However, the

magnetic disks

16 and 17 can be operated even if they are omitted. By adding the

magnetic discs

16 and 17, the generated force in the axial direction can be increased. The

magnetic disks

16 and 17 are structurally reliable when the permanent magnet 13 is attached through the main shaft 1.

Usually, since the permanent magnet 13 is fragile, it is difficult to press fit, and the inner diameter of the permanent magnet 13 is designed to be larger than the outer diameter of the main shaft 1 and needs to be an intermediate fit or a clearance fit. Since the

magnetic discs

16 and 17 are press-fitted with the permanent magnet 13 interposed therebetween, the permanent magnet 13 can attract and fix the

magnetic discs

16 and 17, so that there is structural reliability. The disk may be a nonmagnetic material. In this case, the permanent magnet 13 is fixed by a compressive force from above and below.

Furthermore, problems caused by the difference in thermal expansion coefficient between the permanent magnet 13 and the main shaft 1 when the mover generates heat during rotation can be avoided. When the thermal expansion coefficient of the main shaft 1 is larger than that of the permanent magnet 13, if the permanent magnet 13 is attached to the main shaft 1 with an intermediate fit, the main shaft 1 may be broken. Moreover, when the thermal expansion coefficient of the main shaft 1 is low, the inner diameter of the permanent magnet 13 becomes larger than the outer diameter of the main shaft 1, which causes a problem of rattling. Both problems can be solved by inserting the

magnetic disks

16 and 17 from above and below the permanent magnet 13. Moreover, the displacement in the thrust direction can also be measured by using the magnetic disk 17 as a sensor target.

Hereinafter, the thrust force generation device of the present invention was subjected to magnetic field analysis by the finite element method, prototyped, and incorporated into a 5-degree-of-freedom control type bearingless rotating machine, and the details will be described (Morning, Chiba, Fukao “Cylinder Magnet Movable Coreless Thrust Actuator” (see IEEJ August 2008 Rotating Machine Study Group RM-08-41).

FIG. 3 shows the principle of thrust force generation by the thrust force generator of the present invention. A cylindrical permanent magnet magnetized in the thrust direction is used for the mover, and a coreless coil (air core coil) wound in the rotational direction is used for the stator. A Lorentz force acts on the coil by the radial component of the magnetic flux generated from the permanent magnet and the current of the coreless coil (air core coil). Since the coil is fixed, the reaction generates a force in the thrust direction of the permanent magnet.

Since the mover is cylindrical, the entire rotation spindle can be designed in a cylindrical shape. Thereby, simplification of processing and assembly and reduction in peripheral speed can be expected. By adopting a coreless coil (air-core coil), even if the permanent magnet, which is the mover, is displaced in the radial direction, no unbalanced attractive force is generated in the mover, and the disturbance to the bearingless rotating machine can be reduced. . Control and driving of the thrust magnetic bearing 60 shown in FIG. 18 generally requires an electromagnet bias current and a three-phase inverter. On the other hand, the thrust force generator of the present invention does not require a bias current and can be driven only by a single-phase inverter.

<Single coil model>
The thrust force generator of the present invention is designed by magnetic field analysis software using 3D-FEM (JMAG-Studio, Japan Research Institute Solutions). In this study, the target value of rated thrust force is 100N. FIG. 4 shows an analysis model (single coil model). The magnetic gap was designed to be 5 mm so that a stator / rotor partition wall with a thickness of several mm could be attached. Due to the limitation of installation space, the length of the proposed actuator portion was set to 45 mm or less. tp, tc, and wc are the magnet thickness, the coil thickness, and the coil width, respectively.

In order to examine the coil width, the radial component of the magnetic flux density at the top of the coil was analyzed when X = 0 at a position 5 mm away from the bottom end of the permanent magnet in FIG. 4 in the radial direction. FIG. 5 shows the analysis results when the magnet thickness is changed. The current of the coreless coil (air core coil) was set to 0 A, and the permanent magnet was set to a neodymium permanent magnet. In either case, the magnetic flux density is maximum at X = 0 mm, and decreases as the distance from the permanent magnet increases. At x = 30 mm, the magnetic flux density decreases to about 10% of the maximum value. For this reason, it is thought that the magnetic flux after 30 mm has little influence on generated force. Therefore, the coil width was determined to be 30 mm.

FIG. 5 shows an analysis result of the thrust force with respect to the coil thickness when the magnet thickness is changed with a coil width of 30 mm. The analysis was performed with a space factor of 50% and a current density of 8 A / mm ² . As the coil thickness increases, an increase in the generated thrust force can be confirmed. However, the generated force is about 55 N at the maximum, and it has been clarified that only one coreless coil (air core coil) cannot obtain a sufficient thrust force that satisfies the target in the magnetic field analysis.

<Double coil / magnetic steel sheet model>
In order to increase the generated force, as shown in FIG. 6, a coreless coil (air-core coil) was added, and a structure in which a permanent magnet was sandwiched between two coils was newly examined (double-coil model). Since the Lorentz force is also generated in the added coreless coil (air core coil) by effectively using the magnetic flux of the permanent magnet, an increase in the thrust force can be expected. Further, even if a coreless coil (air core coil) is added, both coils can be connected in series and a thrust force can be generated. Therefore, driving by a single-phase inverter is also possible. FIG. 7 shows the analysis result of the thrust force with respect to the magnet thickness in the double coil model. The coil thickness was 18 mm, and the current conditions were the same as above. It can be confirmed that the thrust force increases as the magnet thickness increases. In addition, the thrust force increased approximately twice as compared with the single coil model.

By using two coreless coils (air-core coils), the thrust force has been achieved to the target value of 100N in the analysis, but some margin is required in consideration of the error between the measured value and the analyzed value. is there. Therefore, by attaching an electromagnetic steel plate having the same diameter as the magnet to the top and bottom surfaces of the permanent magnet, the radial component of the magnetic flux in the coil portion is increased, and the thrust force is increased. In order to confirm the effect of the electromagnetic steel sheet, the magnetic field around the cylindrical magnet mover with and without the steel sheet was analyzed by 3D-FEM. FIG. 8 shows the magnetic flux, and FIG. 9 shows the radial component of the magnetic flux density when x = 0 at a position 5 mm away from the end of the magnet bottom in the radial direction. ts is the steel plate thickness. Since the magnetic flux density when the electromagnetic steel plate is attached is increased by about 30% at the maximum, an increase in Lorentz force can be expected. In FIG. 10, the analysis result of the thrust force with respect to steel plate thickness is shown. The coil thickness and magnet thickness were 18 mm and 25 mm, respectively. Thrust force increased by about 25% by using electrical steel sheets. From the above analysis results, it was revealed that the electrical steel sheet is effective.

The thrust force generator of the present invention is prototyped and incorporated into an existing bearingless drive system. FIG. 11 shows a cylindrical magnet mover and a coreless coil (air core coil) attached to the outside of the motor frame. Since neodymium permanent magnets are fragile, they are difficult to fix by press-fitting into the shaft, and rattling occurs. On the other hand, the electromagnetic steel sheet can be press-fitted into the shaft and fixed. Therefore, the structure in which the permanent magnet is sandwiched between the two electromagnetic steel sheets can suppress the rattling of the permanent magnet. A 2 mm thick polycarbonate partition was attached to the rotor / stator, and the movable range of the rotor was limited to ± 1 mm. As the displacement sensor, an eddy current displacement sensor (PU-14, Electronic Application Company) was used. When two coreless coils (air-core coils) were connected in series, the inductance and resistance were 225 mH and 10.5 ohms, respectively.

Without using the thrust force generator of the present invention, the rotor can be magnetically levitated only by the four-degree-of-freedom control of translation / tilt by a bearingless rotating machine. In this case, the movement in the thrust direction is passively supported by the magnetic coupling of the bearingless rotating machine. The thrust direction spring constant at this time was calculated from the natural frequency of the rotor at the time of impact excitation of 8.5 Hz and the mass of 3.6 kg, and was 1.0 × 104 N / m.

As the positioning control in the thrust direction, digital PID control by a microprocessor (SH7047, Renesas Technology) was applied. Similarly, PI control is applied to the current control system of the coreless coil (air core coil), and the frequency band is designed to be sufficiently wider than the positioning control. FIG. 12 shows the thrust direction displacement z of the rotor at the time of impact excitation and the current iz of the coreless coil (air core coil) depending on the presence / absence of positioning control of the thrust thrust force generator. Positioning control was started at the time of free vibration due to impact excitation, and further impact excitation was applied. At the start of control and at the time of re-vibration, no significant vibration or the like was observed, and thus it became clear that the positioning control system in the thrust direction is stable.

Next, the generated force of the prototype thrust force generator of the present invention is measured. Using a force gauge (DS2-200N, IMADA), the current of the coreless coil (air core coil) was measured when a static load was applied in the thrust direction of the rotor. FIG. 13 shows the measurement results in comparison with the analysis results. The force coefficient of the thrust force generator of the present invention obtained by approximating the measurement result by least squares was 23.0 N / A. Therefore, it was clarified that the thrust force generator of the present invention that was prototyped can generate a thrust force with a rated value of 4.5 A and a target value of 100 N. When a load is applied, a current flows through the coreless coil (air core coil) and magnetic flux is generated. However, no touchdown or significant vibration of the bearingless rotating machine was observed. Therefore, it is considered that the steady current of the thrust force generator of the present invention has no influence on the bearingless rotating machine.

From FIG. 13, the error from the analysis value of the force coefficient was about 10%. This is thought to be due to differences in the residual magnetic flux density of the cylindrical magnet, the saturation magnetic flux density of the magnetic steel sheet, and the like. Therefore, as shown in FIG. 8, the radial magnetic flux density at a position z 2 mm away from the side surface of the mover was measured along the thrust direction using a teslameter (GV-300, Nippon Electromagnetic Instrument Co., Ltd.). FIG. 16 shows the measured values in comparison with the analyzed values. The magnetic flux density was the largest in the vicinity of the side surface of the electrical steel sheet, and the difference between the measured value and the analyzed value was about 10%. This difference is considered to be the cause of the difference between the measured value of the force coefficient and the analysis value.

<Influence on bearingless rotating machine>
The effect of the prototype thrust force generator of the present invention on the bearingless rotating machine is verified. Since the natural frequency in the thrust direction is 8.5 Hz, a large excitation force acts in the thrust direction when the bearingless rotating machine rotates at 510 r / min, and the control current of the coreless coil (air-core coil) increases. . This control current may affect the displacement sensor and current signal of the bearingless rotating machine. Thus, a bearingless rotating machine is driven by a general-purpose inverter (V1000, Yaskawa Electric Co., Ltd.), and a displacement sensor output signal for magnetic levitation control and a current waveform are compared depending on whether or not the thrust force generator of the present invention is positioned. . The sensor output and current are measured from the bearingless rotating machine unit on the side close to the thrust force generator of the present invention.

FIG. 15 shows the thrust displacement and radial displacement sensor output of the rotor and the shaft support winding U-phase current of the bearingless rotating machine at a rotation speed of 510 r / min. When positioning control of the thrust force generator of the present invention is not performed, the rotor vibrates greatly in the thrust direction. On the other hand, when positioning control is performed, vibration is suppressed. No significant difference was observed in the displacement / current waveform of the bearingless rotating machine depending on the presence / absence of positioning control of the thrust force generator of the present invention.

Therefore, it has been clarified that the experimentally produced thrust force generator of the present invention has a small influence on the bearingless rotating machine. As described above, it has been found that the electromagnetic machine provided with the thrust force generator of the present invention can be put to practical use.

The second embodiment relates to a method for shortening the spindle length. FIG. 16 shows a cross-sectional configuration diagram of a five-degree-of-freedom control type bearingless rotating machine 300 according to the second embodiment of the present invention. In addition, since the same code | symbol is attached | subjected about the same element as FIG. 1, description is abbreviate | omitted. In the bearingless rotating machine 300, the radial displacement sensor 14 is inserted between the air core coils 12 and 15 that are arranged two above and below. The periphery of the permanent magnet 13 is plated with metal, and the permanent magnet 13 is a target for the radial displacement sensor 14.

In such a configuration, by using the outer periphery of the permanent magnet 13 as a sensor target, it is possible to eliminate an extra sensor target and reduce the axial length. In order to improve the sensitivity of the sensor, the plating is preferably made of nickel, which is a magnetic material. On the other hand, a thin ring may be provided on the outer periphery of the permanent magnet 13 instead of plating. Generally, the roundness of the outer periphery of the permanent magnet 13 is low. By providing the ring, the roundness can be improved.

When the ring material is metal, the ring is the target for the radial displacement sensor. On the other hand, when the material of the ring is non-metallic, the plated surface of the permanent magnet 13 is the target.

In the third embodiment, a second permanent magnet is separately provided on the stator side so as to face the end in the main axis direction of the first permanent magnet, and the second permanent magnet is opposed to the first permanent magnet. The present invention relates to an electromagnetic machine including a thrust force generator that generates a repulsive force or a suction force in a thrust direction. FIG. 17 shows a sectional configuration diagram of a five-degree-of-freedom control type bearingless rotating machine 400 according to the third embodiment of the present invention. Note that the same elements as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.

In FIG. 17, a hollow ring-shaped permanent magnet 19 is fixed to the housing 26 so as to face the permanent magnet 13 below the permanent magnet 13.
In such a configuration, when the permanent magnet 19 has an N pole on the upper side in FIG. 3 and an S pole on the lower side, a magnetic attractive force is constantly generated between the permanent magnet 19 and the permanent magnet 13. By applying this magnetic attractive force, the thrust force acting on the impeller 21 during the pump operation is balanced or canceled, and the current of the air-core coils 12 and 15 is saved.

On the other hand, if the magnetic pole of the permanent magnet 19 is reversed, the thrust force in the opposite direction with respect to the main shaft 1, that is, the repulsive force can be generated. Effective when repulsive force is required. Further, if the permanent magnet 19 is movable in the thrust direction and the distance from the permanent magnet 13 is adjusted, the generated thrust force can be adjusted. In the present embodiment, the permanent magnet 13 and the permanent magnet 19 are described as generating a magnetic attractive force. However, the permanent magnet 19 is not necessarily provided, and instead of the permanent magnet 19, an iron plate, an iron ring, or the like is used. A ferromagnetic material may be provided. In this case, there is an advantage that the cost can be reduced. *

As mentioned above, although this invention was demonstrated using specific embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. For example, the bearingless rotating machine has been described as a representative example, but the present invention can be similarly applied to other electromagnetic machines. Various modifications or improvements can be added to the above embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

Claims

A first permanent magnet attached to the main shaft and excited in the axial direction;
One or more air-core coils that do not have an iron core wound around the first permanent magnet and at a position shifted in the axial direction by a predetermined distance from the center of the first permanent magnet;
An electromagnetic machine including a thrust force generator that generates an axial electromagnetic force by supplying a current to the air-core coil.
A first coil disposed at a position where the air-core coil is displaced in the main axis positive direction;
A second coil disposed symmetrically with the first permanent magnet with respect to the first coil at a position shifted in the negative direction of the main axis;
The electromagnetic machine according to claim 1, further comprising a thrust force generator in which the second coil and the first coil are current-controlled.
The electromagnetic machine according to claim 1, further comprising a support plate at an end of the first permanent magnet in the main axis direction.
A radial force generator for generating a radial electromagnetic force on the main shaft;
4. The electromagnetic machine according to claim 1, wherein a diameter of the first permanent magnet is equal to or less than a diameter inside a stator of the radial force generator. 5.
A radial displacement sensor for detecting a radial position between the outer peripheral surface of the first permanent magnet, the plating formed on the surface of the outer peripheral surface, or the ring covering the outer peripheral surface is provided. The electromagnetic machine according to claim 4.
The electromagnetic machine according to claim 4 or 5, wherein the radial force generator is a bearingless motor that rotates the main shaft in a non-contact manner while magnetically levitating.
A first permanent magnet attached to the main shaft and excited in the axial direction;
One or more air-core coils that do not have an iron core wound around the first permanent magnet and at a position shifted in the axial direction by a predetermined distance from the center of the first permanent magnet;
A thrust force generator for generating an axial electromagnetic force by supplying current to the air-core coil is provided, and a second permanent magnet is separately provided on the stator side so as to face the end in the main axis direction of the first permanent magnet. Is provided, and the second permanent magnet generates a repulsive force or an attractive force in the thrust direction with respect to the first permanent magnet.