JP4320420B2 - Magnetic bearing and bearing device having the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic bearing that supports a load of a shaft member in a non-contact manner by a magnetic force and a bearing device including the same, and more particularly to a rotary magnetic bearing and a bearing device including the same.
[0002]
[Prior art]
Conventionally, a 5-degree-of-freedom control type magnetic bearing using an electromagnet is known. As shown in FIG. 13, the five degrees of freedom means one degree of freedom in the thrust direction (X direction), two degrees of freedom in the radial direction (Y direction, Z direction), and an inclination direction centered on the radial direction ( 2 directions of freedom (β direction, γ direction), and the rotational direction (α direction) around the thrust direction is excluded.
[0003]
In a five-degree-of-freedom control type magnetic bearing, two electromagnets are provided for each degree of freedom, and are arranged opposite to each other with a shaft member to be supported interposed therebetween. For this reason, the total number of electromagnets is 10. For each degree of freedom, the excitation current for the two electromagnets is independently controlled to generate a desired magnetic force between the two electromagnets, thereby positioning the shaft member. According to the five-degree-of-freedom control type magnetic bearing, a stable system can be constructed.
[0004]
However, the 5-degree-of-freedom control type magnetic bearing requires 10 electromagnets as described above, and further requires 5 sensors to detect the displacement of the shaft member with 5 degrees of freedom, In addition, a controller that independently controls each set of two electromagnets with five degrees of freedom based on the output of each sensor is also required, which complicates and enlarges the entire system.
[0005]
Therefore, several one-degree-of-freedom control type magnetic bearings have been proposed. The one-degree-of-freedom control type magnetic bearing controls only one degree of freedom in the thrust direction (X direction) out of the five degrees of freedom described above, and the other four directions in the Y direction, Z direction, β direction, and γ direction. The degree is supported by the repulsive force (or attractive force) between the permanent magnets. The one-degree-of-freedom control type magnetic bearing has an advantage that the number of electromagnets and the number of sensors can be reduced as compared with the five-degree-of-freedom control type.
[0006]
For example, “Kuji Shimizu, Osamu Taniguchi; Principles and Applications of Magnetic Bearings, Research on Machines, 22, 12 (1970), 8-14” describes a configuration example using the repulsive force between permanent magnets. ing. In addition, `` O.Horikawa, IDSilva; The Magnetic Bearing for Precision Applications, Proceedings for 1st international conference and general meeting of the european society for precision engineering and nanotechnology, vol. 1 (1999), 163-166 '' A configuration example using the attractive force between magnets is described.
[0007]
[Problems to be solved by the invention]
However, in the one-degree-of-freedom control type magnetic bearing using the repulsive force between the permanent magnets described above, leakage of the magnetic flux from the permanent magnet is large, and the Y direction, Z direction, β direction, other than the thrust direction (X direction), The bearing rigidity in the γ direction was not sufficient.
In addition, the above-described single-degree-of-freedom control type magnetic bearing using the attractive force between the permanent magnets requires a large number (six) of permanent magnets, which complicates the structure and causes magnetic flux leakage from the permanent magnets. The bearing stiffness in the Y direction, Z direction, β direction, and γ direction was not sufficient. Furthermore, there has been a problem that the size of the control electromagnet in the thrust direction has to be increased.
[0008]
An object of the present invention is to provide a one-degree-of-freedom control type magnetic bearing that can be simplified in structure and can secure sufficient rigidity in five degrees of freedom excluding the rotation direction of the shaft member, and a bearing device including the same. It is to provide.
[0009]
[Means for Solving the Problems]
  The magnetic bearing according to claim 1 is provided on a side surface of the shaft member.In the axial directionEach of both end faces of the magnetic material comprising a cylindrical magnetic material attachedRing-shaped protruding edge toward the outsideMolded intoBecomeA rotor member and the rotor memberAnd projecting both end portions of the shaft memberOne end surface of the rotor member made of a cylindrical magnetic materialThe ring-shaped protruding edge ofOpposed toConsists of ring-shaped protruding edges facing inwardThe first magnetic pole surface and the other end surface of the rotor memberThe ring-shaped protruding edge ofOpposed toConsists of ring-shaped protruding edges facing inwardA stator member having a second magnetic pole surface and generating a stationary magnetic field between the first magnetic pole surface and the second magnetic pole surface;In order to straddle the facing portion between the ring-shaped protruding edge portion of one end surface of the rotor member and the first magnetic pole surface of the stator member,On the inner surface of the stator member on the first magnetic pole surface sideLeaveWound along the circumferential direction of the first magnetic pole surfaceArrangedFrom the lead wireThus, a magnetic circuit is formed between the ring-shaped protruding edge portion of one end surface of the rotor member and the first magnetic pole surface.A ring-shaped first coil member;In order to straddle the opposing part of the ring-shaped projecting edge of the other end surface of the rotor member and the second magnetic pole surface of the stator member,On the inner surface of the stator member on the second magnetic pole surface sideLeaveWound along the circumferential direction of the second magnetic pole surfaceArrangedFrom the lead wireA loop of magnetic flux opposite to the direction of the magnetic flux loop of the magnetic circuit by the first coil member is provided between the ring-shaped protruding edge of the other end face of the rotor member and the second magnetic pole face. Form the magnetic circuit to be generatedA ring-shaped second coil member;At least one ring-shaped permanent magnet that is incorporated in the stator member and generates a stationary magnetic field between the first magnetic pole surface and the second magnetic pole surface, and disposed on one end surface side of the shaft member. A displacement sensor for detecting displacement in the thrust direction of the shaft member, an output signal from the displacement sensor, and a target position signal in the thrust direction of the shaft member, and an output signal of the displacement sensor and the thrust direction The excitation current is determined based on the target position signal ofControl means for supplying an exciting current to at least one of the first coil member and the second coil member to control the position of the rotor member in the thrust direction is provided.
[0010]
  According to a second aspect of the present invention, in the magnetic bearing according to the first aspect, the stator memberThe first magnetic pole surface of the rotor member and the one end surface of the rotor member have the same shape and surface area of the ring-shaped protrusion, and the second magnetic pole surface of the stator member and the rotor member The shape and surface area of the ring-shaped protrusion are the same as the other end surface.Is a thing.
[0011]
  Claim3The invention described in claim1 or claim 2In the magnetic bearing according to claim 1, the first magnetic pole surface of the stator member and the one end surface of the rotor member are divided into a plurality of regions by the ring-shaped protruding edge portion by a ring-shaped groove portion, The second magnetic pole surface of the member and the other end surface of the rotor member are obtained by dividing the ring-shaped protruding edge portion into a plurality of regions by a ring-shaped groove portion.
[0012]
  Claim4The bearing device according to claim 1 is a magnetic bearing according to any one of claims 1 to 4 and the stator member.On the inner surface between the first coil member and the second coil member, a gap is formed between the magnetic bearing and the inner surface.And an attached air dynamic pressure bearing.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0014]
  An embodiment of the present invention is claimed in claim 1.,This corresponds to claim 3.
  The magnetic bearing 10 of the present embodiment is a bearing that supports the load of the shaft 10a shown in FIGS. 1 (a) and 1 (b) in a non-contact manner by a magnetic force, with the thrust direction (X direction) of the shaft 10a as the center. This is a bearing in which the rigidity in the direction of five degrees of freedom excluding the rotation direction (α direction) is positive.
[0015]
The five degrees of freedom include one degree of freedom in the thrust direction (X direction), two degrees of freedom in the radial direction (Y direction, Z direction), and two degrees of freedom in the tilt direction (β direction, γ direction). Is. The thrust direction corresponds to the axial direction of the shaft 10a, the radial direction corresponds to the direction perpendicular to the axial direction, and the tilt direction corresponds to the direction of minute rotation around the radial direction.
[0016]
Further, the magnetic bearing 10 of the present embodiment is a one-degree-of-freedom control type magnetic bearing, and only one degree of freedom in the thrust direction (X direction) is controlled among the five degrees of freedom described above. That is, only the thrust direction (X direction) is an active type, and the four degrees of freedom in other radial directions (Y direction, Z direction) and tilt directions (β direction, γ direction) are passive types.
[0017]
In addition, a motor (not shown) or the like is attached to the shaft 10a (shaft member) to be supported by the magnetic bearing 10 in order to apply a rotational torque in the α direction to the shaft 10a. Diameter of shaft 10a₁Is, for example, 3 mm. FIG. 1A is a schematic diagram showing the overall configuration of the magnetic bearing 10, and FIG. 1B is a cross-sectional view showing the component configuration around the shaft 10a.
[0018]
Next, the magnetic bearing 10 of this embodiment will be specifically described. As shown in FIGS. 1A and 1B, the magnetic bearing 10 includes a rotor 11, a stator 12, coils 13 and 14, a displacement sensor 15, and a control circuit 16. The sensor 15 is fixed to the base member 10b.
The rotor 11 (rotor member) is a cylindrical magnetic member attached to the side surface of the shaft 10a. Further, as shown in FIG. 2 (a), the rotor 11 has both end faces 11a and 11b formed in a ring shape to form a protruding edge portion that faces outward.
[0019]
Diameter φ of outer periphery of both end faces 11a and 11b₂Is the same as the diameter of the rotor 11 (for example, 8 mm), and the inner diameter φ_ThreeIs the outer diameter φ₂Smaller diameter 10a of shaft 10a₁Larger (eg 6 mm). That is, both end faces 11a and 11b have a width Δ₁Is, for example, a 1 mm ring. Further, the height H of both end faces 11a, 11b₁Is, for example, 1 mm. Distance D between both end faces 11a and 11b₁Is, for example, 24 mm.
[0020]
As shown in FIGS. 1A and 1B, the stator 12 (stator member) is a cylindrical magnetic member that encloses the rotor 11, and is an integrated combination of five components (21 to 25). It is. The five parts (21 to 25) will be described later.
Further, the stator 12 is provided with a magnetic pole surface 12a disposed to face one end surface 11a of the rotor 11 and a magnetic pole surface 12b disposed to face the other end surface 11b of the rotor 11, and each magnetic pole surface 12a, 12b serves as a protruding edge toward the inside. Further, the magnetic pole surfaces 12a and 12b are ring-shaped as shown in FIG.
[0021]
Diameter φ of the outer circumference of the pole faces 12a, 12b_FourIs the diameter φ of the outer periphery of the end faces 11a, 11b.₂Is the same (for example, 8 mm), and the inner diameter φ of the pole faces 12a and 12b_FiveIs the diameter φ of the inner periphery of the end faces 11a, 11b._Three(For example, 6 mm). That is, the pole faces 12a and 12b have the same shape and area as the end faces 11a and 11b, and the width Δ₂Has a ring shape of 1 mm, for example. Height H of the pole faces 12a, 12b₂Is, for example, 1 mm.
[0022]
Further, the distance D between the magnetic pole faces 12a and 12b₂Is, for example, 24.2 mm. Therefore, the distance D between the magnetic pole surfaces 12a and 12b₂And the distance D between the end faces 11a and 11b described above₁Difference from (D₂-D₁) Is 0.2 mm. This difference (D₂-D₁) Is an air gap δ between one magnetic pole surface 12a and the end surface 11a.₁(FIG. 1B) and the air gap δ between the other magnetic pole surface 12b and the end surface 11b.₂Sum of (δ₁+ Δ₂). In other words, the difference (D₂-D₁) Corresponds to the total air gap between the stator 12 and the rotor 11.
[0023]
Moreover, the cylindrical trunk | drum part (components 23-25 mentioned later) which opposes the rotor 11 in the radial direction among the stators 12 is the outer periphery diameter (phi).₆Is, for example, 19.2 mm and the inner diameter φ₇Is, for example, 15 mm. Diameter φ of the inner circumference of the body part (23-25)₇Is the diameter of the rotor 11 (φ₂) Is larger than the width δ between the trunk portion (23 to 25) of the stator 12 and the rotor 11._ThreeThe cylindrical space 17 (FIG. 1B) is secured.
[0024]
Width 17 of space 17_ThreeIs the diameter φ of the inner circumference of the body part (23-25)₇And the diameter of the rotor 11 (φ₂) (For example, 3.5 mm). The length D of the space 17_Three(FIG. 2B) is, for example, 26.2 mm and the length D of the stator 12_FourIs, for example, 30.2 mm.
Next, the component configuration of the stator 12 having the above-described external shape will be described. The stator 12 is composed of five parts (21 to 25) as described above. More specifically, the shaft 10a includes disk-shaped parts 21 and 22 each having a passage hole in the center, ring-shaped permanent magnets 23 and 24, and a cylindrical yoke 25.
[0025]
The outer diameters of these parts (21 to 25) are all the outer diameter φ of the stator 12 described above.₆This corresponds to (FIG. 2 (b)). The inner diameters of the permanent magnets 23 and 24 and the yoke 25 are both the inner diameter φ of the stator 12 described above.₇It corresponds to. The diameter of the inner periphery of the disk-shaped parts 21 and 22 is the diameter φ of the inner periphery of the magnetic pole surfaces 12a and 12b._FiveIt corresponds to. In addition, the length D of the permanent magnets 23 and 24_FiveIs, for example, 2 mm, and the length of the yoke 25 is, for example, 22.2 mm.
[0026]
In these five parts (21 to 25), a permanent magnet 23 is disposed between the disk-shaped part 21 and one end of the yoke 25, and the permanent magnet 24 is disposed between the other end of the yoke 25 and the disk-shaped part 22. To be integrated. Incidentally, the above-described body portions (23 to 25) are portions where the permanent magnets 23 and 24 are disposed at both ends of the yoke 25, respectively. Further, each of the magnetic pole surfaces 12a and 12b is formed on the disk-shaped components 21 and 22, respectively.
[0027]
In the stator 12 configured as described above, the magnetic force reaching the other magnetic pole surface 12b from the one magnetic pole surface 12a through the disk-shaped component 21, the permanent magnet 23, the yoke 25, the permanent magnet 24, and the disk-shaped component 22. A circuit is formed. A stationary magnetic field is generated by the permanent magnets 23 and 24 between the magnetic pole surface 12a and the magnetic pole surface 12b.
Therefore, when the rotor 11 is incorporated in the stator 12, the end surfaces 11 a and 11 b of the rotor 11 face the magnetic pole surfaces 12 a and 12 b of the stator 12 and are generated by the permanent magnets 23 and 24 of the stator 12. A stationary magnetic field passes through the inside of the rotor 11. That is, as shown in FIG. 3, the magnetic flux Φ from the permanent magnets 23 and 24 is generated by the stator 12 and the rotor 11.₁A closed magnetic circuit (closed magnetic circuit) serving as a passage is formed.
[0028]
Further, the magnetic circuit by the stator 12 and the rotor 11 has an air gap δ.₁, δ₂Since it is continuous except for (FIG. 1B), the magnetic flux Φ from the permanent magnets 23 and 24₁It can be said that there is almost no leakage. That is, the magnetic flux Φ from the permanent magnets 23 and 24₁Can be used efficiently.
Further, the magnetic flux Φ from the permanent magnets 23 and 24₁, The air gap δ between the magnetic pole surface 12 a of the stator 12 and the end surface 11 a of the rotor 11.₁And an air gap δ between the magnetic pole surface 12b of the stator 12 and the end surface 11b of the rotor 11₂This magnetic flux Φ₁By this loop, the stator 12 and the rotor 11 are considered to be connected by a virtual spring.
[0029]
Here, the sign of the virtual spring stiffness is “positive” with respect to the four degrees of freedom of the radial direction (Y direction, Z direction) and the tilt direction (β direction, γ direction). That is, when the rotor 11 is displaced from an ideal position in two degrees of freedom in the radial direction (the state shown in FIG. 4A), the rotor 11 has a magnetic flux Φ.₁Restoring force F by loop₁Work. Further, when the rotor 11 is tilted from an ideal position in two degrees of freedom in the tilt direction (the state shown in FIG. 4B), the rotor 11 has a magnetic flux Φ.₁Restoring torque F due to the loop of₂Work.
[0030]
In any case, the rotor 11 has a restoring force F₁(Or restoring torque F₂), One end face 11a faces the magnetic pole face 12a of the stator 12 and the other end face 11b faces the magnetic pole face 12b of the stator 12, that is, moves toward an ideal position. It will be.
As a result, the rotor 11 is stably held in an aligned state in which the end surfaces 11a and 11b are opposed to the magnetic pole surfaces 12a and 12b. That is, the magnetic flux Φ from the permanent magnets 23 and 24 is related to the four degrees of freedom in the radial direction (Y direction, Z direction) and the tilt direction (β direction, γ direction).₁With this loop, the rigidity of the rotor 11 can be sufficiently ensured.
[0031]
On the other hand, with respect to one degree of freedom in the thrust direction (X direction), the magnetic flux Φ from the permanent magnets 23 and 24 is₁The stiffness of the virtual spring due to the loop becomes negative. For this reason, in the magnetic bearing 10 of the present embodiment, the cylindrical space 17 (see FIG. 1) between the stator 12 and the rotor 11 is used to correct the rigidity of the virtual spring in the thrust direction and make it “positive”. Ring-shaped coils 13 and 14 are arranged in (b)), and a displacement sensor 15 and a control circuit 16 are further provided.
[0032]
One ring-shaped coil 13 (first coil member) is attached to the inner surface of the stator 12 on the magnetic pole surface 12a side via a support component (not shown). The coil 13 is made of a conductive wire wound along the circumferential direction of the magnetic pole surface 12a. Similarly, the other ring-shaped coil 14 (second coil member) is attached to the inner surface of the stator 12 on the magnetic pole surface 12b side via a support component (not shown). The coil 14 is made of a conductive wire wound along the circumferential direction of the magnetic pole surface 12b.
[0033]
The ring-shaped coils 13 and 14 have an outer diameter of, for example, 14 mm, an inner diameter of, for example, 9 mm, and a length of, for example, 5 mm. The distance between the coil 13 and the component 21 of the stator 12 and the distance between the coil 14 and the component 22 of the stator 12 are, for example, 0.5 mm.
In this way, the ring-shaped coil 13 is arranged on the inner surface of the stator 12 on the magnetic pole surface 12a side. Therefore, by supplying an exciting current to the coil 13, the magnetic flux Φ₂A magnetic circuit serving as a passage (see FIG. 5) can be formed. This magnetic flux Φ₂, The air gap δ between the magnetic pole surface 12 a of the stator 12 and the end surface 11 a of the rotor 11.₁Across. That is, the coil 13, the rotor 11, and the stator 12 function as an electromagnet.
[0034]
In addition, since the ring-shaped coil 14 is disposed on the inner surface of the stator 12 on the magnetic pole surface 12b side, by supplying an excitation current to the coil 14, the magnetic flux φ_ThreeThe magnetic circuit that becomes the passage of the can be formed. This magnetic flux Φ_Three, The air gap δ between the magnetic pole surface 12 b of the stator 12 and the end surface 11 b of the rotor 11.₂Across. That is, the coil 14, the rotor 11, and the stator 12 also function as electromagnets.
[0035]
Furthermore, the magnetic flux Φ by the coil 13₂The direction and strength of the loop is determined according to the direction and strength of the excitation current flowing through the coil 13. Similarly, the magnetic flux Φ by the coil 14₂The direction and strength of the loop is determined according to the direction and strength of the excitation current flowing through the coil 14. The excitation current for the coils 13 and 14 is independently controlled by the control circuit 16 based on the output signal from the displacement sensor 15.
[0036]
The displacement sensor 15 is disposed on one end face side of the shaft 10a, and detects displacement (displacement from the initial gap) in the thrust direction (X direction) of the shaft 10a. A sensor target is attached to the end surface of the shaft 10a. The output signal of the displacement sensor 15 becomes zero when the gap with the sensor target is equal to the initial gap.
[0037]
The control circuit 16 (control means) is a device that independently controls feedback of the excitation current for the coils 13 and 14. The control circuit 16 receives an output signal from the displacement sensor 15 and a target position signal (Xr) in the thrust direction of the shaft 10a. The control circuit 16 controls the excitation current to the coils 13 and 14 so that the output signal of the displacement sensor 15 becomes zero. That is, an exciting current is supplied to at least one of the coils 13 and 14.
[0038]
When an excitation current is supplied only to the coil 13, the magnetic flux Φ by the coil 14 described above_ThreeLoop is not formed, and the magnetic flux Φ by the coil 13 is₂Loops are formed. Conversely, when an excitation current is supplied only to the coil 14, the magnetic flux Φ by the coil 13₂Loop is not formed, and the magnetic flux Φ by the coil 14 is_ThreeLoops are formed.
Further, when an exciting current is supplied to both the coils 13 and 14, the magnetic flux Φ₂, Φ_ThreeBoth loops are formed. At this time, magnetic flux Φ₂Loop and magnetic flux Φ_ThreeIt is formed so as to be in the opposite direction to the loop (state in FIG. 5). The magnetic force F (attraction force) for moving the shaft 10a in the thrust direction will be described by taking as an example a case where an excitation current is supplied to both the coils 13 and 14.
[0039]
This magnetic force F is expressed by the following equation (1), and the air gap δ between the end surface 11a of the rotor 11 and the magnetic pole surface 12a of the stator 12 is expressed as follows.₁And an air gap δ between the end surface 11 b of the rotor 11 and the magnetic pole surface 12 b of the stator 12.₂It corresponds to the combined force with the magnetic force Fb (attraction force) generated in the above.
[0040]
F = Fa + Fb (1)
Furthermore, the air gap δ₁The magnetic force Fa generated in the air gap δ is expressed by the following equation (2).₁, That is, the magnetic flux Φ by the permanent magnets 23 and 24₁And magnetic flux Φ by the coil 13₂Difference with (Φ₁−Φ₂) Is proportional to the square of the magnetic flux. K is a constant. Magnetic flux Φ₁, Φ₂In FIG. 5, the arrow direction in FIG. 5 is positive.
[0041]
Fa = −K (Φ₁−Φ₂)²  ... (2)
Similarly, the air gap δ₂The magnetic force Fb generated in the air gap δ is expressed by the following equation (3).₂, That is, the magnetic flux Φ by the permanent magnets 23 and 24₁And the magnetic flux Φ by the coil 14_ThreeAnd sum (Φ₁+ Φ_Three) Is proportional to the square of the magnetic flux. Magnetic flux Φ₁, Φ_ThreeAlso, the direction of the arrow in FIG. 5 is positive.
[0042]
Fb = K (Φ₁+ Φ_Three)²  ... (3)
As can be seen from these equations (2) and (3), the air gap δ₁Magnetic force Fa and air gap δ₂The magnetic force Fb is generated in the opposite direction. Therefore, the combined force of the magnetic forces Fa and Fb (magnetic force F of the equation (1)) can be expressed by the following equation (4) by substituting the equations (2) and (3) into the equation (1). it can. The magnetic force F corresponds to the difference in magnitude between the two magnetic forces Fa and Fb.
[0043]
F = K {2 (Φ₁Φ₂+ Φ₁Φ_Three) + Φ_Three ²−Φ₂ ² } (4)
That is, the magnetic flux Φ by the coils 13 and 14 is controlled by controlling the excitation current to the coils 13 and 14.₂, Φ_ThreeBy changing the magnitude and direction of the magnetic force F, the magnetic force F according to the equation (4) can be applied as a thrust force in the shaft 10a.
In particular, when the magnitudes of the excitation currents to the coils 13 and 14 are equal, the magnetic flux Φ₂, Φ_ThreeAre also equal in size (Φ₂= Φ_Three), And the above equation (4) becomes the following equation (5). As can be seen from equation (5), the direction of the excitation current to the coils 13 and 14 is reversed, and the magnetic flux Φ₂, Φ_ThreeThe direction of the magnetic force F can be reversed only by reversing the direction of.
[0044]
F = 4KΦ₁Φ₂ ... (5)
Further, when an excitation current is supplied to one of the coils 13 and 14, for example, when an excitation current is supplied only to the coil 13, the magnetic flux Φ generated by the coil 14 as described above._ThreeLoop is not formed (Φ_Three= 0), magnetic flux Φ by the coil 13₂Loop is formed (Φ₂Therefore, the above equation (4) becomes the following equation (6).
[0045]
F = K {2 (Φ₁Φ₂) −Φ₂ ² } ... (6)
Further, normally, the magnetic flux Φ by the permanent magnets 23 and 24₁Compared to the magnetic flux Φ of the coil 13₂Is very small (Φ₁≫Φ₂) Is taken into consideration, the above equation (6) becomes the following equation (7). As can be seen from the equation (7), the direction of the excitation current to the coil 13 is reversed, and the magnetic flux Φ₂The direction of the magnetic force F can be reversed only by reversing the direction of.
[0046]
F = 2K (Φ₁Φ₂... (7)
The same applies to the case where the exciting current is supplied only to the coil 14 (Φ_Three≠ 0, Φ₂= 0), the direction of the excitation current is reversed, and the magnetic flux Φ by the coil 14_ThreeThe direction of the magnetic force F can be reversed only by reversing the direction.
Thus, with respect to one degree of freedom in the thrust direction (X direction), the position of the shaft 10a is controlled by controlling the excitation current to the coils 13 and 14 so that the output signal of the displacement sensor 15 becomes zero. Thus, the gap between the displacement sensor 15 and the sensor target (not shown) of the shaft 10a is stably held in a state equal to the initial gap. In other words, the rigidity of the virtual spring in the thrust direction is also “positive”.
[0047]
In the magnetic bearing 10 of the present embodiment described above, the permanent magnets 23 and 24 provided on the stator 12 have four degrees of freedom in the radial direction (Y direction, Z direction) and the tilt direction (β direction, γ direction). Magnetic flux from₁With this loop, the rigidity of the rotor 11 can be sufficiently ensured. Further, the magnetic flux Φ by the stator 12 and the rotor 11₁The magnetic circuit of the air gap δ₁, δ₂Because it is continuous except for the magnetic flux Φ₁There is almost no leakage of the magnetic flux Φ from the permanent magnets 23 and 24₁Can be used efficiently.
[0048]
Furthermore, regarding one degree of freedom in the thrust direction (X direction), the magnetic flux Φ from the coils 13 and 14 provided between the stator 12 and the rotor 11 (cylindrical space 17).₂, Φ_ThreeWith this loop, the rigidity of the rotor 11 can be sufficiently ensured.
Therefore, in the one-degree-of-freedom control type magnetic bearing 10 of the present embodiment, a load of five degrees of freedom of the shaft 10a is sufficient in a state in which the rotational movement (α direction) of the shaft 10a by a motor (not shown) is made free. Rigid and stable support.
[0049]
Further, the one-degree-of-freedom control type magnetic bearing 10 of the present embodiment has a very small number of parts and a simple structure (two ring-shaped permanent magnets, two ring-shaped coils, and one displacement sensor). Realization of downsizing and cost reduction. Further, since it can be easily assembled, it is promising as a small-sized magnetic bearing for mass production.
Here, the result measured about the rigidity of the magnetic bearing 10 of this embodiment is demonstrated. As shown in FIG. 6A, this measurement was performed by detecting the displacement of the shaft 10a from the ideal position using the two measurement sensors 31 and 32 installed on the base member 10b. The two measuring sensors 31 and 32 are both equidistant from the center of gravity of the magnetic bearing 10 X₀It is installed at a point (for example, 23.5 mm).
[0050]
Then, the output of the measurement sensor 31 (displacement y₁) And the output (displacement y) of the sensor 32 for measurement₂) And the average value y shown in FIG._SUM(= (Y₁+ Y₂) / 2) and the difference value y_diff(= (Y₂-Y₁) / 2). Of these, the average value y_SUMRepresents the translational deviation of the center of gravity of the shaft 10a in the radial direction, and the difference value y_diffRepresents the inclination of the shaft 10a. Note that the measurement by the displacement sensor 15 is also performed at the same time.
[0051]
When control in the thrust direction (feedback control of excitation current from the control circuit 16 to the coils 13 and 14) is started in a state in which the rotational torque in the α direction is not applied to the shaft 10a, the displacement X and translational displacement of the shaft 10a in the thrust direction are started. (Average value y_SUM) And slope (difference value y_diff) Are as shown in FIGS. 7A to 7C, respectively. The horizontal axis is time t, and the reference (t = 0) corresponds to the time when control in the thrust direction is started.
[0052]
As shown in FIGS. 7A to 7C, the shaft 10a has a displacement X in the thrust direction and a translational deviation (average value y)._SUM) And slope (difference value y_diff) Converges to a constant value as time t passes. In the steady state, as shown in FIGS. 8A to 8C, the displacement X and the translational deviation (average value y)_SUM) And slope (difference value y_diff) Are stabilized within a range of ± 0.1 μm.
[0053]
Further, the translational deviation (average value y) when a disturbance is applied to the shaft 10a._SUM) And slope (difference value y_diff) Changes as shown in FIGS. 9 (a) and 9 (b). That is, it attenuates while vibrating. As can be seen from FIG. 9C in which the range of 0.30 ≦ t ≦ 0.35 is expanded, the translational deviation of the shaft 10a (average value y_SUM) Has a natural frequency of 205 Hz and a slope (difference value y_diff) Has a natural frequency of 114 Hz.
[0054]
Therefore, the translational deviation of the shaft 10a (average value y_SUM) Natural frequency of 205 Hz and the mass of the shaft 10a of 11.5 × 10^-3Based on Kg, the radial translational rigidity of the shaft 10a is calculated to be 1.91 × 10^FourN / m.
Further, the inclination of the shaft 10a (difference value y_diff) Natural frequency of 114 Hz and a moment of inertia of the shaft 10a of 1.96 × 10^-6Kgm²Based on the above, the rotational rigidity in the tilt direction of the shaft 10a is calculated to be 1.00 Nm / rad.
[0055]
From these measurement results, the magnetic bearing 10 of the present embodiment has sufficient rigidity in the four degrees of freedom in the radial direction and the tilt direction of the shaft 10a when the rotational torque in the α direction is not applied to the shaft 10a. It can be seen that it can be secured. Therefore, sufficient rigidity can be ensured in the four degrees of freedom in the radial direction and the tilt direction even in a use state where the rotational torque in the α direction is applied to the shaft 10a.
[0056]
Furthermore, the rotational torque in the α direction was applied to the shaft 10a and rotated at 6000 rpm, and after the supply of the rotational torque was stopped, the time until the rotation of the shaft 10a naturally stopped was measured. As can be seen from FIG. 10, the rotational speed of the shaft 10a gradually decreases with time, and stops after a lapse of 300 seconds or more. From this result, it can be seen that the magnetic bearing 10 of the present embodiment is a magnetic bearing with very low loss.
[0057]
In the above-described embodiment, the width Δ of the end faces 11a and 11b of the rotor 11₁And the width Δ of the magnetic pole faces 12a and 12b of the stator 12₂However, the present invention is not limited to this.
In the above-described embodiment, the example in which both the end surfaces 11a and 11b of the rotor 11 and the magnetic pole surfaces 12a and 12b of the stator 12 are formed in a single ring shape has been described, but the present invention is not limited to this configuration. For example, as shown in FIG. 11, a ring-shaped groove 35 may be provided in each of the end surface 11a and the magnetic pole surface 12a, and the groove 35 may be divided into two regions (claim 4). In the case of FIG. 11, both the end surface 11a and the magnetic pole surface 12a are formed in a double ring shape. The same applies to the end face 11b and the magnetic pole face 12b.
[0058]
The number of the groove portions 35 is not limited to one and may be two or more. One or more grooves 35 are provided in the end faces 11a, 11b and the magnetic pole faces 12a, 12b, and the end faces 11a, 11b and the magnetic pole faces 12a, 12b are divided into a plurality of regions (ring shapes), thereby freeing the magnetic bearing 10 from five degrees The degree of rigidity can be further increased.
Further, in the above-described embodiment, two ring-shaped permanent magnets are provided on the stator 12, but one ring-shaped permanent magnet may be provided. In this case, it is preferable that one permanent magnet is provided near the center of the stator 12 in the thrust direction.
[0059]
Further, in the above-described embodiment, a stationary magnetic field is generated between the magnetic pole faces 12a and 12b by the permanent magnet (one or more) of the stator 12, but an electromagnet is provided instead of the permanent magnet, and the permanent magnet is steadily generated by the electromagnet. You may comprise so that a magnetic field may be generated. In this case, the system is not complicated because only a constant excitation current is supplied to the electromagnet.
[0060]
  In the above-described embodiment, the displacement sensor 15 is provided for controlling the thrust direction. However, the displacement sensor 15 can be omitted. In this case, the same control can be performed by estimating the displacement of the shaft 10a based on the back electromotive voltage generated in the coils 13 and 14.
  Furthermore, in the above-described embodiment, the example in which the magnetic bearing 10 is used alone has been described. However, as shown in FIG. 12, the magnetic bearing 10 and the air dynamic pressure bearing 36 may be combined (claims).4Bearing device). In this case, the air dynamic pressure bearing 36 is preferably attached between the coils 13 and 14 on the inner surface of the stator 12 of the magnetic bearing 10.
[0061]
According to the bearing device in which the magnetic bearing 10 and the air dynamic pressure bearing 36 are combined, the load of the shaft 10a is supported by the magnetic bearing 10 when the rotational torque in the α direction is not applied to the shaft 10a. When 10a starts to rotate, the load can be supported by the air dynamic pressure bearing 36.
The air dynamic pressure bearing 36 is a bearing that supports the load of the shaft 10a by the rigidity of the air flow generated by the rotation of the shaft 10a. The gap between the air dynamic pressure bearing 36 and the rotor 11 is about several μm to 10 μm.
[0062]
Therefore, according to the bearing device in which the magnetic bearing 10 and the air dynamic pressure bearing 36 are combined, the contact of the shaft 10a at the start and stop of rotation can be prevented (magnetic bearing 10), and the rotational accuracy of the shaft 10a can be increased with high accuracy. It can also be maintained (air dynamic pressure bearing 36). Further, since contact can be prevented, the surface state can be maintained with high accuracy. Such a bearing device (magnetic bearing 10 + air dynamic pressure bearing 36) is preferably used for a bearing for rotating a mirror of a laser printer or a bearing for a hard disk drive (HDD), for example.
[0063]
In addition, not only the air dynamic pressure bearing 36 but also a motor for giving a rotational torque to the shaft 10 a can be incorporated between the coils 13 and 14 in the inner surface of the stator 12 of the magnetic bearing 10.
[0064]
【The invention's effect】
As described above, according to the present invention, the structure can be simplified, and sufficient rigidity can be secured in five degrees of freedom excluding the rotation direction of the shaft member.
[Brief description of the drawings]
1 is an overall configuration diagram of a magnetic bearing 10. FIG.
FIG. 2 is a diagram showing a configuration of a rotor 11 and a stator 12. FIG.
FIG. 3 shows magnetic flux Φ by permanent magnets 23 and 24.₁It is a figure explaining the loop of.
[Fig.4] Magnetic flux Φ₁Restoring force F by loop₁And restoring torque F₂FIG.
FIG. 5 shows magnetic flux Φ by coils 13 and 14₂, Φ_ThreeIt is a figure explaining the loop of.
6 is a diagram showing a configuration when measuring the rigidity of the magnetic bearing 10. FIG.
FIG. 7 shows displacement X and translational deviation (average value y) of shaft 10a._SUM) And slope (difference value y_diff) Is a measurement result showing a time change.
FIG. 8 shows displacement X and translational deviation (average value y) of shaft 10a in a steady state._SUM) And slope (difference value y_diff).
FIG. 9 shows a translational deviation (average value y) when a disturbance is applied to the shaft 10a._SUM) And slope (difference value y_diff).
FIG. 10 is a measurement result showing a change over time in the rotational speed of the shaft 10a.
FIG. 11 is a view showing a configuration in which a groove portion is provided in an end surface 11a of a rotor and a magnetic pole surface 12a of a stator.
12 is a configuration diagram of a bearing device in which the magnetic bearing 10 and the air dynamic pressure bearing 36 are combined. FIG.
FIG. 13 is a diagram illustrating the degree of freedom of the shaft member (shaft).
[Explanation of symbols]
10 Magnetic bearing
10a shaft
11 Rotor
12 Stator
13, 14 coil
15 Displacement sensor
16 Control circuit
23, 24 Permanent magnet

Claims (4)

A rotor member formed of a cylindrical magnetic material attached to the side surface of the shaft member in the axial direction, and formed by forming each of both end faces of the magnetic material into ring-shaped projecting edges toward the outside ;
It is made of a cylindrical magnetic material that encloses the rotor member and projects both end portions of the shaft member, and is an inwardly ring-shaped member that is disposed opposite to the ring-shaped projecting edge portion of one end surface of the rotor member . A first magnetic pole surface comprising a projecting edge portion, and a second magnetic pole surface comprising an inward ring-shaped projecting edge portion opposed to the ring-shaped projecting edge portion of the other end surface of the rotor member. A stator member that generates a stationary magnetic field between the first magnetic pole surface and the second magnetic pole surface;
So as to straddle the portion facing the first pole face of the ring-shaped projecting edge portion and the stator member of one end face of said rotor member, Oite the inner surface of the first magnetic pole surface of the stator member, Ri Do from conductors which are arranged wound along the circumferential direction of the first magnetic pole surface, the magnetic circuit between the ring-shaped projecting edge portion and the first magnetic pole surface of the one end face of said rotor member A ring-shaped first coil member to be formed;
So as to straddle the portion facing the second magnetic pole surface of the stator member and the ring-shaped projecting edge portion of the other end face of said rotor member, Oite the inner surface of the second magnetic pole surface of the stator member, Ri Do from conductors which are arranged wound along the circumferential direction of the second magnetic pole surface, between the ring-shaped projecting edge portion and the second magnetic pole surface of the other end surface of said rotor member, said first A ring-shaped second coil member that forms a magnetic circuit that generates a magnetic flux loop in a direction opposite to the direction of the magnetic flux loop of the magnetic circuit by one coil member;
At least one ring-shaped permanent magnet incorporated in the stator member and generating a stationary magnetic field between the first magnetic pole surface and the second magnetic pole surface;
A displacement sensor that is disposed on one end face side of the shaft member and detects a displacement of the shaft member in a thrust direction;
An output signal from the displacement sensor and a target position signal in the thrust direction of the shaft member are input, an excitation current is determined based on the output signal of the displacement sensor and the target position signal in the thrust direction, and the first A magnetic bearing comprising: control means for supplying an exciting current to at least one of the one coil member and the second coil member to control the position of the rotor member in the thrust direction. The magnetic bearing according to claim 1,
The first magnetic pole surface of the stator member and the one end surface of the rotor member have the same shape and surface area of the ring-shaped protruding edge, and
The magnetic bearing according to claim 1, wherein the second magnetic pole surface of the stator member and the other end surface of the rotor member have the same shape and surface area of the ring-shaped protrusion . The magnetic bearing according to claim 1 or 2,
The first magnetic pole surface of the stator member and the one end surface of the rotor member are divided into a plurality of regions by the ring-shaped protruding edge portion by a ring-shaped groove portion,
The magnetic bearing , wherein the second magnetic pole surface of the stator member and the other end surface of the rotor member are divided into a plurality of regions by a ring-shaped protruding edge portion by a ring-shaped groove portion . The magnetic bearing according to any one of claims 1 to 4 ,
A bearing comprising: an air dynamic pressure bearing attached to an inner surface of the stator member between the first coil member and the second coil member with a gap between the stator and the magnetic bearing. Equipment .

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