JP2012213273A - Spherical motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spherical motor in which a contact of an outer member and an inner member can effectively be prevented and an interval between them can be kept constant by pre-pressuring a bearing ball in an appropriate state.SOLUTION: A holding member 320 installed in an installation side member (outer member: stator 10) of a bearing 32 is pre-pressurized in a direction of an opposite side member (inner member: rotor 20) by magnetic force of a magnetic member (second permanent magnet 380). Thus, the bearing ball 310 held by the holding member 320 abuts on a surface of the rotor 20, and the stator 10 and the rotor 20 are accordingly supported in a relatively rotational manner. Since the magnetic force of the magnetic member has a characteristic that it non-linearly becomes larger as a size of the gap between the stator 10 and the rotor 20 becomes smaller, the bearing ball 310 is pre-pressurized in the appropriate state.

Description

  The present invention relates to a spherical motor that holds an inner member rotatably inside an outer member and rotates one member serving as a rotor around a plurality of axes.

  A spherical inner member is rotatably held inside a spherical outer member having a hollow shell structure inside, and one member is a stator, the other member is a rotor, and the rotor is, for example, three degrees of freedom, or A spherical motor that rotates with a higher degree of freedom is known (Cited document 1).

JP 2009-77463 A

  2. Description of the Related Art Conventionally, as a bearing structure that supports an outer member and an inner member so as to be relatively rotatable in a spherical motor, for example, there is a structure in which a bearing ball rotatably held on a stator side is brought into contact with the surface of a rotor so as to allow rolling. When such a bearing structure is applied to a spherical motor in which the outer member is a stator and the inner member is a rotor, when the stator receives an external force or impact, the rotor stops suddenly or the traveling direction (rotation direction) is changed. There is a problem in that, for example, when the rotor is changed, the rotor may come into contact with or very close to the stator and control of rotation may be disabled. That is, by preloading the bearing ball to the rotor side in an appropriate state, a structure is required in which the outer member and the inner member are not in direct contact and the distance between them is kept constant.

  The present invention has been made in view of the above circumstances, and by preloading the bearing ball in an appropriate state, the contact between the outer member and the inner member is effectively prevented, and the distance between the two is kept constant. The object is to provide a spherical motor that can sag.

  The spherical motor of the present invention is installed on an outer member, an inner member provided inside the outer member, and an installation side member that is one of the outer member or the inner member, and supports the outer member and the inner member so as to be relatively rotatable. A holding member provided on the installation side member so as to be movable forward and backward with respect to a counterpart member which is the other of the outer member and the inner member; A bearing ball that is rotatably held at the tip of the holding member on the advancing side and is brought into contact with the surface of the counterpart member so as to allow rolling, a first permanent magnet provided on the holding member, and the installation side member A magnetic member that preloads the holding member in the direction of the counterpart member and generates a magnetic force that abuts the bearing ball against the surface of the counterpart member, and generates a magnetic force generated from the magnetic member. Characterized in that the size of the gap between the inner member and the outer member has a larger characteristic nonlinearly as decreases.

  The spherical motor of the present invention includes (1) a configuration in which the outer member is a stator and the inner member is a rotor, and (2) a configuration in which the outer member is a rotor and the inner member is a stator. Further, (A) a configuration in which the stator-side magnetic pole is an electromagnet and a rotor-side magnetic pole is a permanent magnet, and (B) a stator-side magnetic pole and a rotor-side magnetic pole are both electromagnets are included. Further, the outer member and the inner member do not have to be completely spherical, and may have a shape constituting a part of a sphere, such as a shape lacking a part or a hemispherical structure.

  According to the present invention, the holding member installed on the installation side member is preloaded in the direction of the mating member by the magnetic force of the magnetic member, so that the bearing ball held by the holding member contacts the surface of the mating member. By this, the installation side member and the counterpart member, that is, the outer member and the inner member are supported so as to be relatively rotatable. In this function, the magnetic force of the magnetic member increases nonlinearly as the gap between the outer member and the inner member decreases, that is, the magnetic force of the magnetic member increases at an accelerated rate as the gap decreases. When the gap between the outer member and the inner member becomes narrow and the suction force acting between the two members increases at an accelerated rate, the mating member is moved from the installation side member accordingly. The repulsive force that repels increases at an accelerated rate. For this reason, compared with the case where repulsive force changes linearly according to distance, the function which maintains the positional relationship of an inner member and an outer member is high, and as a result, contact with an outer member and an inner member is effective. And the distance between the two is kept constant.

  In the present invention, the magnetic member is constituted by a second permanent magnet disposed at a position spaced apart from the first permanent magnet at a position on the backward side of the holding member. The first permanent magnet and the second permanent magnet include a form in which the same poles are magnetized so as to face each other.

  Further, the present invention includes a form in which the first permanent magnet is formed in a cylindrical shape, and the second permanent magnet is formed in an annular shape and is arranged coaxially with the first permanent magnet.

  Moreover, this invention includes the form arrange | positioned inside the magnetic pole which has a cylindrical part by which the said 1st permanent magnet has the coil wound by the outer peripheral part.

  According to the present invention, the magnetic member is a magnetic pole having a cylindrical portion in which a coil is wound around an outer peripheral portion, and the cylindrical portion is opposed to the outer peripheral surface of the first permanent magnet at a certain distance. Including a form in which the outer peripheral surface of the first permanent magnet is magnetized.

  Further, the present invention includes a form in which the first permanent magnet is formed in a cylindrical shape and is magnetized in a rotationally symmetrical manner with respect to the circumferential direction.

  Further, the present invention includes a form in which the first permanent magnet partially protrudes from the magnetic pole.

  According to the present invention, the magnetic force of the magnetic member has a characteristic that increases nonlinearly as the size of the gap between the outer member and the inner member becomes smaller. A repulsive force due to the corresponding magnetic force can be generated, and therefore, the function of maintaining the positional relationship between the inner member and the outer member is high compared to the case where the repulsive force changes linearly according to the distance, As a result, it is possible to effectively prevent contact between the outer member and the inner member and to keep the distance between them constant.

It is (a) external appearance perspective view of the stator which comprises the spherical motor which concerns on one Embodiment of this invention, (b) It is sectional drawing. It is a perspective view of the rotor which comprises the spherical motor, Comprising: (a) Exploded view of internal structure, (b) Internal structure, (c) Exploded view of whole, (d) Whole external view. It is sectional drawing which shows the attachment structure of the magnetic pole member to a stator. It is a disassembled perspective view of the magnetic pole member. It is a perspective view of the 1st permanent magnet applied to the modification of one Embodiment. It is sectional drawing which shows the structure of the magnetic pole of one Embodiment roughly. It is a diagram which shows the magnetic field analysis (movement amount and attractive force) of the 1st permanent magnet and magnetic pole in a modification. It is a figure for demonstrating the magnetic field analysis, Comprising: (a) Sectional drawing which represents typically the flow of magnetic flux around the 1st permanent magnet, and magnetic force, (b) It is a principal part enlarged view.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
(1) Configuration of One Embodiment FIGS. 1 and 2 respectively show a stator (outer member, installation side member) 10 and a rotor (inner member, mating member) 20 constituting a spherical motor according to an embodiment. In addition, the rotor 20 is rotatably accommodated and held in the stator 10 to constitute the spherical motor of one embodiment. On the stator 10 side, a bearing 32 is provided together with a magnetic pole (magnetic member) 31 as shown in FIG. 3, and the rotor 20 is rotatably held by the bearing 32 with three or more degrees of freedom.

  A stator 10 shown in FIG. 1 has a hollow shell structure and is formed in a substantially spherical shape from a soft magnetic material. Circular flat portions 10a are formed at a plurality of predetermined locations of the stator 10, and bearings 32 (see FIG. 5) rotatably support the rotor 20 accommodated in the stator 10 inside the flat portions 10a. 3) is attached.

  As shown in FIG. 2, the rotor 20 held inside the stator 10 includes an inner sphere portion 21 made of a soft magnetic material, a plurality of rotor magnets 22 embedded in the surface of the inner sphere portion 21, ceramics, and the like. It is made of a nonmagnetic material such as a spherical outer shell portion 23 that covers the inner sphere portion 21 in which the rotor magnet 22 is embedded. In this case, the rotor magnets 22 are arranged at eight locations corresponding to the vertices of the virtual regular hexahedron inscribed in the stator 10.

  FIG. 3 shows a state in which the magnetic pole member 30 is attached to the flat portion 10 a of the stator 10, and FIG. 4 shows an exploded view of the magnetic pole member 30. As shown in these drawings, the magnetic pole member 30 has a cylindrical coil core portion (cylindrical portion) 301 made of a soft magnetic material and functioning as an iron core of the coil 341. The coil core portion 301 is attached to the stator 10 so that the axis line coincides with the radial direction of the stator 10. In this embodiment, an insertion portion 302 having a diameter smaller than that of the coil core portion 301 is formed at one end portion of the coil core portion 301 through a step portion 303, and this insertion portion 302 is formed on the flat portion 10a. It is inserted from the inside into the mounting hole 10b formed in the center.

  A salient pole surface 304 that is a concave curved surface along the spherical outer surface of the rotor 20 is formed at the tip of the coil core portion 301 on the inner side (the rotor 20 side). A disc-shaped cap 309 is fitted into the center of the salient pole surface 304, and a circular opening 306 is formed at the center of the cap 309 to communicate the inside of the coil core portion 301 and the inside of the salient pole surface 304. ing. The diameter of the opening 306 is smaller than that of a bearing ball 310 to be described later, and the bearing ball 310 fitted into the opening 306 slightly protrudes from the salient pole surface 304 to the rotor 20 side.

  A cylindrical holding member 320 made of a nonmagnetic material is accommodated in the coil core part 301 coaxially with the coil core part 301. A bearing hole 321 is formed in the shaft center of the holding member 320, and a conical ball whose diameter increases toward the tip is formed at the tip of the bearing hole 321 (inside of the stator 10). The holding part 322 is open. A bearing ball 310 partially protruding from the opening 306 is rotatably accommodated and held in the ball holding portion 322. The bearing ball 310 is made of a non-magnetic material having hardness and strength so as not to affect the magnetic flux generated by the magnetic pole 31 described later. Examples of such a material include nonmagnetic ceramic materials.

  The outer peripheral surface of the holding member 320 has a large diameter at the tip end on the ball holding portion 322 side, and a first permanent magnet 370 is externally mounted on the outer peripheral surface on the small diameter side which is the outside. The first permanent magnet 370 is fixed to the outer peripheral surface of the holding member 320 by, for example, press-fitting the holding member 320 therein. Thus, the holding member 320 to which the first permanent magnet 370 is fixed is as follows. It is inserted into the coil core part 301.

  On the outer peripheral surface of the coil core portion 301, an annular coil bobbin 342 around which a coil 341 is wound is externally provided. In the present embodiment, the magnetic pole 31 made of an electromagnet is configured by the salient pole surface 304, the coil core portion 301 on which the salient pole surface 304 is formed, and the coil bobbin 342 and the coil 341 around the coil core portion 301. A lead terminal 343 to which an end of a coil 341 is connected is attached to the coil bobbin 342 via a terminal plate 344. A wiring from an external drive circuit is connected to the lead terminal 343 so that an exciting current flows through the coil 341. The first permanent magnet 370 is disposed inside the magnetic pole 31 having the coil core portion 301 around which the coil 341 is wound on the outer peripheral surface, and the inner peripheral surface of the coil core portion 301 is the first permanent magnet 370. It faces the outer peripheral surface with a certain distance.

  An annular second permanent magnet (magnetic member) 380 is fixed inside the insertion portion 302 of the magnetic pole member 30 so as to be coaxial with the first permanent magnet 370. At the center of the second permanent magnet 380, a shaft 381 protruding inward (rotor 20 side) is fixed coaxially with the coil core portion 301, and a bearing hole 321 of the holding member 320 is formed on the shaft 381. It is slidably inserted. That is, the holding member 320 is slidably supported with respect to the shaft 381.

  As shown in FIG. 4, the first permanent magnet 370 and the second permanent magnet 380 are both magnetized by being partitioned in their axial directions (in the radial direction as a spherical motor) and parallel to each other. The entire opposing surface is the same pole (for example, N pole). Therefore, the first permanent magnet 370 and the second permanent magnet 380 repel each other, but the second permanent magnet 380 is fixed inside the insertion portion 302 while the first permanent magnet 370 is fixed. Since the holding member 320 is slidably supported on the shaft 321, the first permanent magnet 370 moves inward due to repulsion.

  For this reason, the holding member 320 to which the first permanent magnet 370 is fixed is preloaded on the inner side (the rotor 20 side), so that the bearing ball 310 fitted in the opening 306 always moves from the salient pole surface 304 to the rotor 20 side. Project slightly. In this state, the outer end of the first permanent magnet 370 protrudes from the outer end surface of the coil core portion 301 to the outside, and the first permanent magnet 370 and the second permanent magnet 380 are mutually connected. A slight gap is formed between the opposing surfaces.

  In the magnetic pole member 30 with the coil bobbin 342 externally mounted on the coil core part 301, the insertion part 302 is inserted from the inside into the mounting hole 10b of the flat part 10a of the stator 10, and the step part 303 and the coil bobbin 342 are formed on the inner surface of the flat part 10a. In the combined state, it is fixed to the flat portion 10a by a disk-shaped fixing member 360 disposed on the outer surface side of the flat portion 10a. A concave portion 361 into which the insertion portion 302 is fitted is formed on the inner surface of the fixing member 360, and the fixing member 360 is fixed to the coil core portion 301 with a fastening member such as a screw. That is, the magnetic pole member 30 is fixed to the flat portion 10a by the fixing member 360, the step portion 303 of the coil core portion 301, and the coil bobbin 342 sandwiching the flat portion 10a. For example, 18 magnetic pole members 30 including the magnetic poles 31 are provided in the stator 10. In this case, the spherical motor has 18 rotors for the rotor 20 and 18 poles for the stator 10.

  As shown in FIG. 3, the rotor 20 is held inside the stator 10 by the surface of the outer shell portion 23 coming into contact with the bearing ball 310 protruding from the salient pole surface 304 of each magnetic pole member 30. The bearing ball 310 urged toward the rotor 20 by the second permanent magnet 380 contacts the surface of the outer shell portion 23 of the rotor 20. In this state, the rotor 20 is secured with a certain clearance from the salient pole surface 304 and is rotatably held when the bearing ball 310 rolls. The bearing 32 includes a bearing ball 310, a holding member 320, a first permanent magnet 370, a second permanent magnet 380, and a shaft 351.

(2) Action of One Embodiment According to the spherical motor of the one embodiment, an excitation current is passed from the external drive circuit to the coil 341, and the direction of the excitation current is switched appropriately according to the rotational position of the rotor 20. Thus, the direction of the magnetic force generated between the rotor magnet 22 on the rotor 20 side and the magnetic pole 31 on the stator 10 side is switched, and the rotor 20 rotates. That is, the present embodiment is a brushless motor, and the rotor 20 has at least one degree of freedom, or the first axis, the second axis, and the third axis, with the direction perpendicular to the cutting plane passing through the rotation center as an axis. It can be rotated in the center with 3 degrees of freedom.

  In this embodiment, the rotor 20 is rotatably supported by the stator 10 via the bearing 32, but in this bearing 32, the first permanent magnet 370 receives the repulsive force of the second permanent magnet 380. The repulsive force is transmitted to the bearing ball 310 via the holding member 320, and the bearing ball 310 is in contact with the rotor 20 in a preloaded state. Thus, the rotor 20 is supported by the bearing ball 310 preloaded by the repulsive action of the magnet, so that, for example, when the stator 10 receives an impact from the outside, the rotor 20 stops suddenly, or the traveling direction (rotational direction) ), The rotor 20 and the stator 10 are not in contact with each other, and the distance between the rotor 20 and the stator 10 is kept constant.

Now, the two permanent magnets 370 and 380 constituting the bearing 32 are arranged opposite to each other with the same polarity with a gap between the opposing surfaces. In such a configuration, when the strengths of the magnetic poles of the permanent magnets 370 and 380 are m1 and m2, and the gap between the two is G, the repulsive force F is
F = K (m1 · m2) / G ²
And is known to be inversely proportional to the square of the gap G between the two (K is a coefficient).

  Therefore, between the first permanent magnet 370 and the second permanent magnet 380, a repulsive force (non-linear repulsive force) that is inversely proportional to the square of the gap between them acts along the radial direction of the spherical motor. That is, this means that the magnetic force generated from the second permanent magnet 380 has a characteristic that increases nonlinearly as the size of the gap between the stator 10 and the rotor 20 decreases. For this reason, this non-linear repulsive force is transmitted to the bearing ball 310 via the holding member 320, and the bearing ball 310 is preloaded against the rotor 20 with a force having the same magnitude as the repulsive force, and in this state, the rotor 20 is always in contact. Is supported rotatably.

(3) Modified example of one embodiment In the above-mentioned one embodiment, the second permanent magnet 380 is eliminated, and a modified example in which a nonmagnetic member to which the shaft 381 is fixed is arranged at the same location may be adopted. it can. That is, in this modification, the permanent magnet is only the first permanent magnet 370 around the holding member 320. Further, as shown in FIG. 5, the first permanent magnet 370 is equally magnetized with a plurality of poles (in this case, four poles and two pole pairs) along the circumferential direction.

  In the case of the magnetic pole in which the coil core portion 301 and the coil 341 are arranged around the first permanent magnet 370, the relative movement amount of the first permanent magnet 370 with respect to the coil core portion 301 is represented by X as shown in FIG. Then, as shown in FIG. 7, in a range where the movement amount X is relatively small, an attractive force (nonlinear attractive force) proportional to the square of the movement amount X is a moving direction (spherical surface) of the first permanent magnet 370. Works in the radial direction of the motor). Here, the movement amount X is the length of a portion of the first permanent magnet 370 that does not oppose the inner peripheral surface of the coil core portion 301 (a portion protruding outward from the coil core portion 301). Increases as the gap between the rotor 20 and the salient pole surface 304 decreases. That is, the magnetic force generated from the magnetic pole has a characteristic that increases nonlinearly as the size of the gap between the stator 10 and the rotor 20 decreases. This non-linear suction force is transmitted to the bearing ball 310 via the holding member 320, and the bearing ball 310 is preloaded against the rotor 20 with a force having the same magnitude as the suction force, and the rotor 20 is always rotatable in this state. Supported by

  Such an action occurs equally regardless of whether the coil 341 of the magnetic pole 31 is energized or not energized when the magnetic force of the first permanent magnet 370 is stronger than the electromagnet of the magnetic pole 31. . The reason is explained by the following magnetic field analysis.

  First, when the coil 341 is not energized, the magnet is not considered for each pole (N pole, S pole), but is considered as an aggregate of minute magnets (nodes). FIG. 8 schematically shows the flow of magnetic flux and the magnetic force around the first permanent magnet 370, and the area where the first permanent magnet 370 and the inner peripheral surface of the coil core portion 301 of the magnetic pole 31 are opposed to each other. At this node, the magnetic force acts substantially horizontally (in the radial direction of the first permanent magnet 370) in FIG. On the other hand, at a node in an area where the first permanent magnet 370 and the coil core part 301 are not opposed to each other, a magnetic force acts toward the coil core part 301 in the vicinity (downwardly diagonally downward in the drawing).

  For this reason, when the 1st permanent magnet 370 is arrange | positioned in the state shifted | deviated from the coil core part 301 which opposes like this embodiment, the part (each node) which mainly shifted | deviated to the direction of the coil core part 301. The power to move is working. This magnetic field analysis example is a case where the outer circumference of the first permanent magnet 370 is magnetized to four poles, but the direction in which the magnetic force is generated is slightly different even at other magnetization numbers. It is the same.

  On the other hand, when the magnetic pole 31 becomes the N pole in the state where the coil 341 is energized, a force in the attraction direction works from the magnetic pole 31 to the S pole (in this case, two locations) of the first permanent magnet 370, and the N pole ( In this case, a force in the direction of repulsion acts on the two places. Each direction is the horizontal direction in FIG. 8 (the radial direction of the first permanent magnet 370), and since the axis of the first permanent magnet 370 is the shaft 381, the radial direction of the first permanent magnet 370 Movement is restricted. Further, in the first permanent magnet 370, since the same pole exists at a position symmetrical with respect to the central axis, the radial attractive force to the magnetic pole 31 is canceled out. Also, since there are two N poles and two S poles in the axial direction of the first permanent magnet 370, the magnetic force in the axial direction (the radial direction of the spherical motor) is canceled out and is not generated.

  Similarly, when the magnetic pole 31 becomes the S pole while the coil 341 is energized, a force in the attraction direction acts from the magnetic pole 31 to the N pole (in this case, two locations) of the first permanent magnet 370, and N A repulsive force acts on the pole (in this case, two locations). As a result, as in the case where the magnetic pole 31 is the N pole as described above, the attractive forces in the radial direction and the axial direction of the first permanent magnet 370 are canceled and do not occur.

  As described above, the first permanent magnet 370 behaves even when the coil 341 is energized in the same manner as when the coil 341 is not energized, and the bearing ball 310 rotates with the same amount of force as the non-linear attractive force described above. 20 is preloaded and abuts.

  When the coil 341 is energized, the amount of magnetic flux generated by the current flowing through the coil 341 increases toward the outer periphery of the magnetic pole 31, and the magnetic pole 31 causes a magnetic interaction with the first permanent magnet 370. It does not increase on the inner circumference side. For this reason, the effective magnetic force of the inner peripheral portion of the magnetic pole 31 is weaker than the magnetic force of the first permanent magnet 370, and this also acts when the coil is energized in the same manner as when no current is energized.

  In the above embodiment, the first permanent magnet 370 is not necessarily cylindrical, and may be divided into a plurality of pieces in the circumferential direction, for example. The same applies to the second permanent magnet 380 in the previous embodiment.

10: Stator (outer member, installation side member)
20 ... Rotor (inner member, counterpart member)
31 ... Magnetic pole (magnetic member)
32 ... Bearing 301 ... Coil core part (cylindrical part)
310 ... Bearing ball 320 ... Holding member 341 ... Coil 370 ... First permanent magnet 380 ... Second permanent magnet (magnetic member)

Claims (7)

An outer member;
An inner member provided inside the outer member;
A plurality of bearings installed on the installation side member that is one of the outer member and the inner member, and supporting the outer member and the inner member in a relatively rotatable manner;
A spherical motor with
The bearing is
A holding member provided on the installation side member so as to be movable forward and backward with respect to the other side member which is the other of the outer member or the inner member;
A bearing ball that is rotatably held at the leading end of the holding member and is brought into contact with the surface of the counterpart member so as to be able to roll;
A first permanent magnet provided on the holding member;
A magnetic member that is provided on the installation side member and generates a magnetic force that preloads the holding member in the direction of the counterpart member and causes the bearing ball to abut against the surface of the counterpart member;
With
The spherical motor according to claim 1, wherein the magnetic force generated from the magnetic member has a characteristic that increases nonlinearly as the size of the gap between the outer member and the inner member decreases.   The magnetic member is composed of a second permanent magnet disposed at a position spaced apart from the first permanent magnet at a position on the retracting side of the holding member. The spherical motor according to claim 1, wherein the permanent magnet and the second permanent magnet are magnetized so that the same poles face each other. The first permanent magnet is formed in a cylindrical shape,
The spherical motor according to claim 2, wherein the second permanent magnet is formed in an annular shape and is disposed coaxially with the first permanent magnet.   The spherical motor according to any one of claims 1 to 3, wherein the first permanent magnet is disposed inside a magnetic pole having a cylindrical portion in which a coil is wound around an outer peripheral portion. The magnetic member is a magnetic pole having a cylindrical portion around which a coil is wound on an outer peripheral portion, and the cylindrical portion has an inner peripheral surface facing the outer peripheral surface of the first permanent magnet at a certain distance. And
The spherical motor according to claim 1, wherein the outer peripheral surface of the first permanent magnet is magnetized.   6. The spherical motor according to claim 5, wherein the first permanent magnet is formed in a cylindrical shape and is magnetized in a rotationally symmetrical manner with respect to the circumferential direction.   The spherical motor according to claim 5, wherein a part of the first permanent magnet protrudes from the magnetic pole.

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