JP3808811B2 - Axial magnetic levitation rotary motor and rotary device using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an axial magnetic levitation rotary motor including a rotor that is arranged to be magnetically levitated and rotatable between a pair of upper and lower stators arranged to face each other in the axial direction of a vertical axis. In particular, it can be applied to general rotating equipment such as a turbo pump with a rotating impeller, and is particularly useful as a motor for a continuous flow type artificial heart pump that requires high durability.
[0002]
[Prior art]
In Japan, an organ transplant bill was enacted in October 1997, and although heart transplantation has become legally possible, there is a shortage of appropriate donors for patients who need transplantation. Therefore, the development of an artificial heart is eagerly desired as an alternative to living heart transplantation or as a means for assisting the function of living heart over a long period of time. The conventional artificial heart was connected to the patient from the bedside drive device using an air tube, but in recent years it has begun to shift to an implantable artificial heart to improve the patient's level of medical treatment. Application examples are also increasing.
[0003]
There are two types of artificial heart: a pulsatile flow type and a continuous flow type. The pulsatile flow type is a type that pulsates like a living heart, and the diaphragm is moved up and down by filling and discharging one fluid in a sealed pump chamber partitioned by a diaphragm or the like, and filled in the other pump chamber. This is a method of delivering blood with pulsation. Therefore, a predetermined pump chamber capacity is required to deliver a predetermined flow rate, and there is a limit to downsizing. The continuous flow type is a type in which blood is continuously sent out by rotating an impeller. Since blood is sent in a certain direction, operation can be performed efficiently. Moreover, since the flow rate can be ensured without being limited to the pump volume so much, it is easy to reduce the size, and thus has attracted attention as a next-generation artificial heart.
[0004]
However, in the conventional continuous flow type artificial heart, since the impeller is rotated by a motor through a shaft, a seal and a bearing for a hole through which the shaft passes through the impeller are required. However, the durability of these seal members is limited. It was as short as 2 or 3 days, and it was difficult to use for a long period of time, and its practicality was poor. In addition, problems such as blood denaturation due to frictional heat in the vicinity of the seal portion, blood cell destruction in the bearing gap, and blood coagulation due to stagnation of the flow in the shaft and the bearing portion have occurred. Therefore, as shown in FIG. 4, the impeller is levitated and rotated by a magnetic attractive force from the radial direction, thereby exhibiting high durability performance that does not require a mechanical contact portion such as a shaft support by a bearing. A continuous flow artificial heart using a magnetically levitated rotating motor is being developed. The blood that flows axially is taken in from the upper inlet of the impeller that rotates by magnetic levitation, is radiated by the centrifugal force outward in the radial direction inside the impeller, gathers at the outlet on the circumference, and flows into the body It is going.
[0005]
Conventionally, there are several proposal examples of axial magnetic levitation rotary motors that are roughly divided from the above-described radial magnetic levitation rotary motors. For example, a rotary shaft having a permanent magnet with respect to a frame is arranged in the axial and radial directions. The one disclosed in Japanese Patent Laid-Open No. 7-208470, which is supported by a magnetic bearing and simplified the control device, detects the position of the rotor and compares it with the set value, and the amplitude of the rotating magnetic field of the stator relative to the rotor Disclosed in Japanese Patent Application Laid-Open No. 8-322194, which includes a position controller for controlling the position of the rotor and eliminates the need for a levitation winding, or a thrust (axial) control stator above and below the flange portion of the rotor And a radial control stator on the outside of the edge of the collar, and based on detection signals from the rotation angle detection encoder and gap sensor. Configured to control independently the current value of the control stator of al, it is possible to shorten the axial length, and the like as disclosed in JP 2001-124077 Patent Publication No. prevented the occurrence of negative torque.
[0006]
Further, the present inventor has developed an axial type magnetically levitated rotary motor as shown in FIG. This motor performs tilt control with the upper stator and magnetic levitation rotation control with the lower stator. The inclination of the rotor is controlled by adjusting the bias attractive force of the permanent magnet by the inclination control coils X and Y and the permanent magnet attached to the upper stator, and the three-phase four-pole or Magnetic levitation rotation control is performed by generating an 8-pole rotating magnetic field. In addition, the vibration of the rotor in the radial direction was not controlled and was suppressed by passive stability.
[0007]
[Problems to be solved by the invention]
However, in the axial type magnetically levitated rotary motor proposed by the present inventor, the vibration of the rotor in the radial direction depends only on the passive stability. Absorption was difficult. In addition, among the conventional examples described in the above publications, a simplified control system does not rely on static stability for any one of radial and axial position control and rotational control freedom. It is a structure that does not get For this reason, the rigidity of the degree of freedom that is statically stable is low, and it is difficult to maintain the static stability when it rotates at high speed. In addition, the 5-axis control bearing that does not simplify the control system has a drawback that the entire apparatus becomes large.
[0008]
Therefore, in the present invention, stable rotation with no fear of shaft runout or the like even during high-speed rotation is achieved by organically linking radial and axial position control in magnetic levitation control, rotation control, and tilt control. It is an object of the present invention to provide a high-precision axial type magnetically levitated rotary motor that maintains the above and a rotating device using the same.
[0009]
[Means for Solving the Problems]
For this reason, the technical solution means adopted by the present invention is:
In an axial magnetic levitation rotary motor including a rotor that is disposed so as to be magnetically levitated and rotatable between a pair of upper and lower stators provided with electromagnets arranged opposite to each other in the axial direction of the vertical axis , two sets of opposition to the upper stator A radial control electromagnet and a permanent magnet for generating a bias attracting force that attracts the rotor upward, current is passed through the radial control electromagnet to strengthen the magnetic flux of one set of salient poles, and the other In order to control the position of the rotor in the radial direction by weakening the magnetic flux of the set, the rotor's magnetic levitation rotation control coil and the rotor's tilt control coil are installed in the lower stator so that they can be controlled individually. This is an axial magnetic levitation rotary motor characterized in that it is configured .
A rotary device using the axial magnetic levitation rotary motor described above, wherein a turbo pump impeller is installed on a rotor of the axial magnetic levitation rotary motor to constitute a turbo pump.
The rotating device may be a continuous flow type artificial heart pump.
[0010]
Embodiment
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an axial magnetic levitation rotating motor and a rotating device using the same according to the present invention will be described below in detail with reference to the drawings. 1 to 3 are diagrams showing one embodiment of the present invention, FIG. 1 is a basic conceptual diagram of an axial magnetic levitation rotary motor of the present invention, FIG. 2 is a conceptual diagram of a radial control unit, and FIG. 3 is a magnetic levitation It is a conceptual diagram of a rotation control part. As shown in FIG. 1, the basic configuration of the axial magnetic levitation rotary motor of the present invention is a magnetic levitation rotation between a pair of upper and lower stators 1 and 7 each having an electromagnet arranged opposite to the vertical axis. In an axial magnetic levitation rotary motor having a freely disposed rotor 4, the upper stator 1 performs radial control of the rotor 4, and the lower stator 7 performs magnetic levitation rotation control and tilt control of the rotor 4. It is characterized by comprising.
[0011]
In the following, the principle that led to the invention of the axial magnetic levitation rotary motor of the present invention and the rotating equipment using the same, the theoretical analysis thereof, and the consideration of the test results will be described in detail. The principle of an axial magnetic levitation rotary motor used as a rotary device, preferably applied to an artificial heart pump, of the present invention will be described. As shown in FIG. 1, the basic configuration of the axial magnetic levitation rotary motor of the present invention is composed of an upper stator 1, a rotor 4, and a lower stator 7. In the upper stator 1, the bias attractive force is generated by using the permanent magnet 2. Further, two sets of opposing radial control electromagnets 3 are installed in the upper stator 1, and a current is passed through these electromagnets to strengthen the magnetic flux of one set of salient poles and weaken the magnetic flux of the other set. Then, radial control that is position control of the rotor 4 in the radial direction (radial direction orthogonal to the rotation axis) is performed.
[0012]
The lower stator 7 generates torque in the rotational direction by generating a rotating magnetic field of three phases and eight poles (the number and number of poles can be changed as appropriate, and may be three phases and four poles) by the levitation and rotation control coil 6. To control rotation. At the same time, the magnetic field is applied to the rotor 4 by applying a reverse attractive force equal to the bias attractive force of the permanent magnet of the upper stator 1 to the rotor 4. Moreover, these two vector controls are performed by using DQ control which calculates | requires the force actually produced | generated by adding two vectors of rotational torque and levitation. In the lower stator 7, the inclination of the rotor 4 is controlled by generating a two-phase six-pole magnetic field by the inclination control coil 5 independent of the three-phase eight-pole.
[0013]
<Radial control>
FIG. 2 is an explanatory diagram of radial control performed by the rotor 4 and the upper stator 1. In the radial control, as shown in FIG. 2B, the magnetic flux in the gap between the rotor 4 and the magnetic poles of the electromagnet 3 is generated by the magnetic flux generated by the electromagnet 3 (white arrow) and the bias magnetic flux (black arrow) generated by the permanent magnet 2. This is done by adding strength to strength. First, the radial distance of the rotor 4 is obtained by a sensor. The displacement of the rotor 4 with respect to the upper stator 1 is represented by d = d1-d2. Position control of the rotor to d = 0 is performed by radial control. By detecting the deviation of the rotor 4, a control current for returning the rotor 4 to the center is passed through the electromagnet 3. As shown in FIG. 2A, when the rotor 4 is shifted to the right in the drawing with respect to the upper stator 1 (that is, the magnetic pole of the electromagnet 3), it is generated from the electromagnet 3 as shown in FIG. By flowing the magnetic flux as shown in the figure, the magnetic flux strengthens on the left side and weakens on the right side. As a result, a leftward force is applied to the rotor 4. In this way, radial control of the rotor 4 is performed.
[0014]
Now, assuming that the magnetic flux generated by the electromagnet 3 is φ _c , the number of turns of the coil is N, the current is I, and the magnetoresistance R is equal on both the left and right, φ _c is
φ _c = NI / R
Since the sum and difference of the magnetic flux generated by the electromagnet 3 and the magnetic flux φ _m generated by the permanent magnet 2 become the magnetic flux passing through the cross-sectional area S of the gap, the respective magnetic flux densities are
B ₁ = (φ _m + φ _c ) / S
B ₂ = (φ _m −φ _c ) / S
Therefore, the attractive forces F ₁ and F ₂ generated by the left and right salient poles are
F ₁ = (φ _c ² + 2φ _c φ _m + φ _m ² ) / 2Sμ _{0
^{F 2 = (φ c 2 -2φ}} c φ m + φ m 2) / 2Sμ 0
From these two suction forces, the suction force actually applied to the rotor 4 is
F = F ₁ −F ₂ = 2φ _c φ _m / Sμ ₀
Thus, an attractive force in the radial direction proportional to the coil current of the radial control electromagnet 3 can be generated.
[0015]
<Floating rotation control>
FIG. 3 is an explanatory diagram of magnetic levitation and rotation control performed by the rotor 4 and the lower stator 7. The rotation control is performed by generating torque as illustrated in the lower stator 7 by a rotating magnetic field of three phases and eight poles (the number of phases and the number of poles can be changed as appropriate) by an electromagnet. As shown in the figure, the magnetic levitation control is performed by generating a downward attractive force equal in magnitude to the upward bias attractive force by the upper stator 1. DQ control is performed to obtain the actual force generated by adding two vectors of the torque for rotation control and the attractive force that opposes the bias attractive force for magnetic levitation.
[0016]
Now, the direction of the rotor magnetic flux is defined as the straight axis (d-axis), and the direction perpendicular to it is defined as the horizontal axis (q-axis). Considering that the permanent magnet installed in the rotor is replaced with an electromagnet, the current flowing through the electromagnet is I _f . If the currents in the d-axis and q-axis directions flowing through the magnetic levitation / rotation control stator are I _d and I _q , respectively, the attractive force F in the axial direction is determined by the following equation.
F = K ₁ {(I _d + I _f ) ² + I _q ² } (1)
Here, K ₁ is a coefficient determined from the magnetic circuit shape.
The rotational torque T is
T = K _{2 If} I _q (2)
It becomes. K ₂ is a coefficient determined from the magnetic circuit shape.
Accordingly, it is understood that the attractive force in the axial direction is the sum of the force generated by the d-axis current, the rotor current, and the force generated by the q-axis current, and the rotational torque is proportional to the q-axis current. Since _If is known, if the required torque is known, the q-axis current I _q can be obtained from the above equation (2), and the rotation of the rotor can be controlled. Further, if the required attraction force F is obtained and the q-axis current I _q is obtained from the rotation control, the d-axis current I _d is obtained from the above equation (1), and the attraction control (magnetic levitation control) of the rotor is possible. Become. Actually, this is realized by a rotating magnetic field of three phases and eight poles (the number of phases and the number of poles can be changed as appropriate).
[0017]
Although not shown, the configuration example of the artificial heart centrifugal pump as a rotating device using the axial magnetic levitation rotating motor of the present invention described above is described through the central portion of the upper stator in the axial magnetic levitation rotating motor. A blood inflow pipe (stationary side) is disposed, and the inflow pipe is connected to a centrifugal pressurization chamber (rotation side) of the impeller fixed to the rotor via a sealing sliding contact means or the like, and the impeller centrifugal pressurization chamber In order to flow out blood collected at the outer peripheral portion, a configuration is adopted in which the outer peripheral portion of the centrifugal pressurizing chamber of the impeller is connected to a stationary-side outflow pipe through a sealing sliding contact means or the like. When an axial flow pump or a diagonal flow pump is used as an artificial heart, a blood outflow pipe is arranged through the center of the lower stator, and the outer periphery of the pump is configured around the inflow pipe and the magnetic levitation impeller similar to the centrifugal pump. The structure which connects a part and an outflow pipe is employ | adopted. With the above configuration, durability is high due to light rotation that does not require a mechanical support portion such as a bearing, and problems such as blood degeneration, blood cell destruction, and blood clotting due to stagnation are also solved.
[0018]
As described above, in the axial magnetic levitation rotating motor of the present invention, the permanent magnet 2 is disposed on the upper stator 1 to generate a bias attracting force to attract the rotor 4 upward, and the upper stator 1 has two sets. The opposing electromagnet 3 was disposed to control the position in the radial direction. The lower stator 7 having 12 salient poles (the number of poles can be changed as appropriate, which may be 6 salient poles or 24 salient poles) is configured with a tilt control coil 5 and a levitation and rotation control coil 6 separately. Thereby, tilt control and levitation and rotation control can be performed independently. Using this motor, the magnetic levitation performance in water and the pump performance were measured.
[0019]
As a result, with a motor having an outer diameter of 79 mm and a height of 80 mm, the vibration of the rotor in the radial direction is 0.5 mm at the rotation speed and vibration amplitude (mm) in the X direction and Y direction (both radial directions orthogonal to the rotation axis). Was controllable within. Further, in the relationship between the rotational speed and the vibration amplitude in the Z direction (axial direction), the vibration of the rotor in the axial direction could be controlled within 0.65 mm. As a centrifugal pump, magnetic levitation rotation was possible up to a maximum rotational speed of 1100 rpm, and the HQ (flow rate / lift) characteristics as a pump were a maximum flow rate of 4.3 l / min and a maximum lift of 48.6 mmHg. From the above results, the predetermined performance could be confirmed for the application of the axial magnetic levitation rotary motor of the present invention to a rotary device such as a centrifugal pump using the same.
[0020]
As described above, the embodiments of the axial magnetic levitation rotary motor of the present invention and the rotating device using the same have been described, but within the scope of the present invention, the positional relationship between the rotor, the upper stator and the lower stator, and the radial Upper stator shape, type, rotor shape, type and material, including the number of control coils and permanent magnets, number of poles and location, number of poles and location of magnetic levitation rotation control coils and tilt control coils The shape and type of the lower stator including the pump, the arrangement of the pump section on the rotor when configuring rotating equipment such as a pump (in addition to attaching a pump to the rotor, the rotor itself can be an impeller), pump, etc. The shape and type of the rotating device (for example, a rotating pump such as a centrifugal pump, a mixed flow pump, or an axial flow pump that rotates an impeller) Applies to all pump-flop or the like are possible), the the control mode of each control coil can be appropriately selected.
[0021]
【The invention's effect】
As described above in detail, according to the present invention, the rotor including the electromagnet disposed opposite to the axial direction of the vertical axis is provided between the pair of upper and lower stators so as to be magnetically levitated and rotatable. In the axial magnetic levitation rotary motor, the upper stator performs the rotor radial control and the lower stator performs the magnetic levitation rotation control and tilt control of the rotor. Since magnetic levitation control is performed with the lower stator while performing radial position control and tilt control, smooth rotation is possible with little vibration such as shaft runout, regardless of mechanical support. In addition, a part of the magnetic levitation force in the lower stator can be caused to function as the rotation control force, thereby enabling efficient control.
[0022]
In addition, when a magnetic levitation rotation control coil and a rotor tilt control coil are installed in the lower stator and can be controlled separately, radial control and magnetic control are performed on both sides of the rotor in the axial direction. The floating control and the rotation control are organically linked to enable stable rotation of the rotor while eliminating mechanical support, and further, the rotor tilt control can be performed individually and finely controlled.
Further, when a permanent magnet is attached to the upper stator to generate a bias attractive force for attracting the rotor upward, the rotor shaft is caused by the interaction with the attractive force of the electromagnet disposed on the lower stator. Magnetic levitation control is performed while a centering function is provided by biasing forces attracting each other on both sides in the direction, and stable rotation is possible with little shaft runout.
[0023]
Furthermore, when an impeller of a turbo pump is installed in the rotor of the axial magnetic levitation rotary motor described in any one of the above, and the turbo pump is configured, the characteristics of the axial magnetic levitation rotary motor are utilized as they are, and the mechanical Rotating equipment such as a pump capable of eliminating all the adverse effects of rotation due to support and having high durability and stable rotation without shaft runout is realized.
In addition, when the rotating device is a continuous flow type artificial heart pump, there are no problems such as light rotation and durability due to the lack of a mechanical support, and blood degeneration, blood cell destruction, blood coagulation due to itchiness, etc. In addition to elimination, stable rotation without shaft run-out can realize a continuous-flow artificial heart pump that is free of failure, and ensures stable blood circulation.
Thus, according to the present invention, the position control in the radial direction and the axial direction in the magnetic levitation control, the rotation control, and the tilt control is organically coordinated, so that there is no risk of shaft runout or the like even during high-speed rotation. A highly accurate axial type magnetically levitated rotary motor that can maintain the rotation and a rotating device using the same are provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing one embodiment of the present invention, and is a basic conceptual diagram of an axial magnetic levitation rotary motor.
FIG. 2 is a conceptual diagram of the radial control unit.
FIG. 3 is a conceptual diagram of the magnetic levitation and rotation control unit.
FIG. 4 is a cross-sectional view of a main part showing a conventional example of a radial support type magnetically levitated rotary motor.
FIG. 5 is an exploded perspective view of an axial support system (axial) magnetic levitation rotary motor which is a prerequisite technology of the present invention.
[Explanation of symbols]
1 Upper stator 2 Permanent magnet 3 Radial control coil (electromagnet)
4 Rotor 5 Tilt control coil (electromagnet)
6 Magnetic levitation rotation control coil (electromagnet)
7 Lower stator

Claims (3)

In an axial magnetic levitation rotary motor including a rotor that is disposed so as to be magnetically levitated and rotatable between a pair of upper and lower stators provided with electromagnets arranged opposite to each other in the axial direction of the vertical axis , two sets of opposition to the upper stator A radial control electromagnet and a permanent magnet for generating a bias attracting force that attracts the rotor upward, current is passed through the radial control electromagnet to strengthen the magnetic flux of one set of salient poles, and the other In order to control the position of the rotor in the radial direction by weakening the magnetic flux of the set, the rotor's magnetic levitation rotation control coil and the rotor's tilt control coil are installed in the lower stator so that they can be controlled individually. An axial magnetic levitation rotary motor characterized by comprising. A rotary device using the axial magnetic levitation rotary motor according to claim 1 , wherein a turbo pump impeller is installed on a rotor of the axial magnetic levitation rotary motor to constitute a turbo pump. . The rotating device according to claim 2 , wherein the rotating device is a continuous flow type artificial heart pump.

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