JP2009171797A - Stepping motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-torque stepping motor without increasing a size. <P>SOLUTION: The stepping motor 1 comprises: A-phase, B-phase and C-phase stators 14A-14C attached to a stator shaft 11; A-phase, B-phase and C-phase coils 13A-13C circumferentially wound around the stators between first and second members; a X-phase coil 13D provided between the A-phase coil and the B-phase coil; a Y-phase coil 13E provided between the B-phase coil and the C-phase coil; a rotor 10 rotating around the stator 20 along its outer circumference; and a plurality of rotor magnets 16 provided in a rotor yoke 15, and corresponding to a plurality of stator teeth. While a current flows in the A-phase and B-phase coils in the same direction, a current flows in the X-phase coil in the opposite direction. While a current flows in the B-phase and C-phase coils in the same direction, a current flows in the Y-phase coil in the opposite direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a stepping motor suitable for an outer rotor type having a rotor outside a stator.

  FIG. 15 is a schematic diagram showing a stepping motor. The stepping motor is composed of a fixed electromagnet 101 (stator 102) and a magnet (rotor 104) attached to a rotating shaft. A current is passed through the coil 103 wound around the electromagnet 101 to generate magnetism, and the rotor 104 is rotated by attracting it. The number of phases of the stator differs depending on the motor, and the motor rotates forward when excited in the order of A → B →... When it is excited in the order of B → A →. In the example of FIG. 15, the case of two phases of A phase and B phase is shown. When the electromagnet 101 is magnetized to the north pole by current, the south pole of the rotor 104 is attracted. When the adjacent electromagnet 101 is magnetized to the N pole at the next timing, the rotor 104 rotates and the rotor 104 rotates by repeating that the S pole of the rotor 104 is attracted.

  Such stepping motors include a VR type (Variable Reluctance Type (gear-like core type)), a PM type (Permanent Magnet Type), and an HB type (Hybrid Type). The VR type is a reluctance. Uses torque and does not use a permanent magnet, but uses a gear-shaped iron core as a rotor.The step angle can be reduced, but the torque is slightly low.The PM type has a rotor composed of permanent magnets. However, it is inexpensive, but the step angle cannot be reduced because there is a limit to reducing the magnetizing interval.The HB type is a combined type of PM and VR. In the PM type, the magnet is magnetized in the circumferential direction, but in the HB type, a magnet magnetized in the axial direction is used, and the magnetic pole side is sandwiched between two gear-shaped iron cores. N pole side and S pole side teeth Concave is configured so as to be reversed.

  For example, Patent Document 1 discloses a stepping motor capable of obtaining a large rotational torque by effectively using a repulsive force. In this stepping motor, coils are wound in the circumferential direction on the inner circumferential surface of a stator fixed on the inner circumference of the housing, and four convex portions projecting in the radial direction are circumferentially provided on both sides thereof. Are provided at equal intervals. The first to fourth rotors are fixed on the outer periphery of the first to third rotating shafts rotatably supported by the housing, and the magnets fixed to the respective rotors along the circumferential direction face the respective convex portions. ing. The housing, the rolling bearing, or the second and third rotating shafts are made of a nonmagnetic material so that the magnetic flux sufficiently passes through the rotor at the repulsion position and the convex portion of the stator.

FIG. 16 is a diagram showing another stepping motor. A stepping motor 110 shown in FIG. 16 has A, B, and C phase stators 114 </ b> A to 114 </ b> C with a magnetic shielding plate 117 interposed in a housing 118. Each stator 114A~114C is, the A-phase first stator 114A ₁ and A-phase second stator 114A _2, B-phase first stator 114B ₁ and B-phase second stator 114B _2, C-phase first stator 114C ₁ and C-phase first 2 stators 114 </ _b > C ₂ , and the electrical angles are shifted by 180 deg (1/2 pitch) within each phase. The A phase, the B phase, and the C phase are shifted from each other by 120 deg (1/3 pitch). In this example, an 8-pole stator is shown, but it may be, for example, 32 poles.

  Between each of the A-phase stator 114A, the B-phase stator 114B, and the C-phase stator 114C, there are an A-phase coil 113A, a B-phase coil 113B, and a C-phase coil 113C wound around the stator core 112 on the circumference. A rotor magnet 116 is provided at a position facing each stator.

The stepping motor 110 configured in this way has no wasted space such as a coil end portion, can be rotated using not only the attractive force but also the repulsive force, and can simultaneously excite all the magnetic poles. This is the type that can generate the highest torque among stepping motors.
JP 2000-184681 A

  However, in a conventional stepping motor, a stepping motor that uses an attractive force and a repulsive force to rotate the rotor with respect to the stator prevents magnetic flux from entering the stator teeth (stator teeth) at the magnet end of the rotor, resulting in magnetic flux leakage. In some cases, the motor output torque is lower than the theoretical value.

  The present invention has been made to solve such problems, and in a stepping motor that obtains rotational torque using both attractive force and repulsive force, leakage magnetic flux generated at the end of the magnet is removed. It is an object of the present invention to provide a stepping motor that can reduce and generate a high torque.

  The stepping motor according to the present invention includes a stator shaft, first and second members having a plurality of stator teeth, and first to third stators attached to the stator shaft, and the first to third stators. , First to third coils wound in a circumferential direction between the first and second members, respectively, between the first stator and the second stator and between the second stator and the third stator. Each having a fourth coil and a fifth coil, a rotor yoke disposed opposite to the first to third stators, and a rotor portion magnetic shielding plate sandwiched between the rotor yokes. A rotor rotating on the outer periphery, a plurality of rotor magnets provided on the rotor yoke corresponding to the plurality of stator teeth, and the rotor are accommodated A current flows in the same direction in the fourth coil while the current in the same direction flows in the first and second coils, and in the same direction in the second and third coils. When the current flows, the current flows through the fifth coil in the opposite direction.

  In the present invention, the current flows through the fourth coil and the fifth coil in directions opposite to those of the first and second coils and the second and third coils, respectively. Accordingly, it is possible to realize high torque and ripple reduction by reducing magnetic leakage and to suppress an increase in weight and volume.

  The rotor magnet is preferably provided so as to protrude from the rotor yoke to at least a part of the rotor part magnetic shielding plate. Since the rotor magnet is provided so as to protrude from at least a part of the rotor magnetic shielding plate from the rotor yoke, the magnetic flux generated at the end of the magnet can be effectively put into the stator teeth. Therefore, magnetic flux leakage at the magnet end can be reduced.

  Furthermore, it is preferable that the rotor magnet is provided so as to penetrate the rotor part magnetic shielding plate. As a result, the number of parts is reduced and the assembly is facilitated. Further, since the protruding portion from the rotor yoke is sufficiently large, the effect of reducing the leakage magnetic flux is great.

  Furthermore, the rotor magnet may be provided individually for each of the first to third stators.

  Further, the starter teeth of the first member and the second member may be arranged with a ½ pitch deviation from each other. Here, in the Nth (N ≧ 2) stator, the first members of the respective stators may be arranged with a shift of (1/2) (N−1) / N pitch. In other words, in the case of the N phase, they can be shifted by 180 × (N−1) / Ndeg.

  Further, the first member of the first stator and the first member of the second stator may be arranged with a shift of 1/3 pitch. Similarly, the first member of the second stator and the first member of the third stator may be arranged with a shift of 1/3 pitch.

  According to the present invention, a high torque stepping motor can be provided without increasing the size.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. In the present embodiment, the present invention is applied to a stepping motor suitably used for a light vehicle or a robot apparatus. The present embodiment is suitable for solving the problems that occur in the stepping motor (Japanese Patent Application No. 2007-010158) previously filed by the present inventors. Here, a stepping motor described in Japanese Patent Application No. 2007-010158 (hereinafter referred to as a reference example) and problems thereof will be described first, and then a stepping motor according to the present invention will be described.

  1 is a view showing a rotor of a stepping motor according to a reference example, FIG. 2 is a view showing a stator, FIG. 3 is a sectional view of the stepping motor, and FIG. 4 is a sectional view taken along line IV-IV in FIG. is there.

  The stepping motor 1 according to the reference example has a rotor 10 and a stator 20 made of a magnetic material such as iron provided inside the rotor. The stepping motor 1 has an outer rotor configuration in which the stator 20 is disposed on the inner side and the rotor 10 is disposed on the outer side, and the rotor 10 rotates around the stator 20.

The stator 20 includes a stator shaft 11 made of a nonmagnetic material, and an A-phase stator 14A, a B-phase stator 14B, and a C-phase stator 14C attached to the stator shaft 11. Each stator 14A-14C has the 1st and 2nd member which has eight stator teeth. The first member and the second member are connected by the stator core 12. In this reference example, the first member and the second member of each stator are respectively the A-phase first stator 14A ₁ , the A-phase second stator 14A ₂ , the B-phase first stator 14B ₁ , and the B-phase second stator 14B. ₂ , C-phase first stator 14C ₁ , and C-second phase stator 14C ₂ . Furthermore, each stator has an A-phase coil 13A, a B-phase coil 13B, and a C-phase coil 13C wound in the circumferential direction between the first and second members. Further, a stator magnetic shielding plate 17 is provided between the A-phase stator 14A and the B-phase stator 14B, and between the B-phase stator 14B and the C-phase stator 14C.

  As shown in FIG. 5, the stator teeth 31 and the status lots 32 are deviated from each other by 180 degrees (1/2 pitch) in the stator teeth 31 and the status lots 32 as shown in FIG. 5. In the A phase, the B phase, and the C phase, the stator teeth 31 and the status lot 32 are shifted by 120 deg (1/3 pitch) between the phases. In this example, an 8-pole stator is shown, but it may be, for example, 32 poles. In this reference example, since it is a three-phase stator, it is arranged with a shift of 1/3 pitch, but in the case of an N (N ≧ 2) phase stator, 180 × (N−1) / Ndeg, ( 1/2) (N-1) / N pitches may be shifted. That is, in the case of 2 phases, 90 deg, 1/2 pitch, in the case of 3 phases, 120 deg, 1/3 pitch, in the case of 4 layers, 135 deg, 3/8 pitch, in the case of 5 phases, 144 deg, 2/5 pitch Etc.

  The rotor 10 includes a rotor yoke 15 disposed to face the A-phase stator 14A, B-phase stator 14B, and C-phase stator 14C, and a rotor magnetic shielding plate 19 made of aluminum or the like provided with the rotor yoke 15 interposed therebetween. The outer periphery of the stator 20 is rotated. In this reference example, since the stator has three phases, three rotor yokes 15 are provided, and four rotor part magnetic shielding plates 19 are provided with the rotor yoke 15 interposed therebetween.

  Further, the rotor 10 is provided with eight rotor magnets 16 corresponding to the eight stator teeth in each stator described above. As will be described later, the rotor magnet 16 according to the present reference example is provided so that both ends of the rotor magnet protrude from the end face of the stator 20 into the rotor magnetic shielding plate 19. In particular, in this reference example, the rotor magnet 16 is provided so as to penetrate the magnetic shielding plate 19, thereby reducing magnetic flux leakage to the stator teeth of the stator 20 as much as possible and realizing high torque.

  Furthermore, it has the housing 18 which accommodates the rotor 10, and the stator shaft 11 is rotatably attached via bearing 20A, 20B.

Next, the rotor magnet 16 of the stepping motor according to this reference example will be described. 6 and 7 are enlarged views showing a rotor magnet portion of the stepping motor according to the conventional example and the reference example, respectively. As shown in FIG. 6, in the conventional stepping motor, the rotor magnet 116 is arranged on the end face of each of the stators 114A to 114C in units of each phase. However, with this configuration, the magnetic flux contributing to torque generation is reduced due to magnetic flux leakage at the end of the rotor magnet 116. On the other hand, as shown in FIG. 7, in this reference example, one elongated rotor magnet 16 common to the three phases is used, and the end portion of the rotor magnet 16 protrudes longer than the stators 14A ₁ and 14A _2. The decrease in the amount of magnetic flux, that is, the decrease in torque can be suppressed by the leakage magnetic flux.

  Here, in this reference example, one configuration common to all phases is used, but each phase may be provided individually. In this case, in each phase, the rotor magnet protrudes from both ends or at least one end of the stator.

  Conventionally, the end face of the stator and the end face of the rotor magnet coincide with each other. Therefore, since the magnetic flux does not enter the stator teeth (stator teeth) and cannot be used effectively, the motor output is lower than the calculation. This drawback is particularly noticeable when an embedded structure is used. On the other hand, in this reference example, since a single magnetic flux can be applied to each phase by using a single rotor magnet extending beyond both ends of the stator, the leakage magnetic flux is reduced and torque is increased. Can be improved.

  Next, the effect of the stepping motor according to the reference example will be described. 18 and 19 are graphs showing torque increase verification results by a magnetic field analysis simulation in the stepping motor according to the conventional example shown in FIG. 6 and the reference example shown in FIG. 7, respectively. The horizontal axis represents the rotation angle, and the vertical axis represents the torque. The conventional stepping motor in which the end portion of the rotor magnet is equal to the end surface of the stator has a maximum torque of 66.5 Nm, a minimum torque of 57.9, an average torque of 62.0 Nm, and a torque cripple of 13.7%. The stepping motor according to the reference example had a maximum torque of 72.5 Nm, a minimum torque of 62.4, an average torque of 67.4 Nm, and a torque cripple of 14.9%.

  Thus, in the reference example, by providing the rotor magnet so as to penetrate the shielding plate, the leakage magnetic flux was reduced, and as a result, the maximum torque could be improved by about 10%. In the reference example, the rotor magnet is provided not only on the rotor yoke but also on the shielding plate. Preferably, by providing one rotor magnet common to each phase so as to penetrate the shielding plate, the leakage magnetic flux with respect to the stator teeth that has been conventionally generated at the end of the magnet is reduced. That is, by effectively putting magnetic flux into the stator teeth, it is possible to provide a stepping motor with extremely high torque while maintaining a state where there is little wasted space. For example, a direct drive is preferable for a device such as a robot that is accelerating and decelerating, but with this configuration, a high torque can be obtained, so that a direct drive is possible. Further, by using one rotor magnet, the number of parts is reduced, and assembly is facilitated.

  Next, problems of the stepping motor according to the reference example will be described. In the stepping motor shown in FIG. 3, magnetic leakage between the phases becomes a problem. In order to prevent this magnetic leakage, it is conceivable that the distances between the phases are sufficiently separated, or a magnetic material is installed between the phases, and magnetic flux obstruction due to eddy current is used (hereinafter also referred to as passive shielding). . However, these methods inevitably increase the volume and weight of the stepping motor. Therefore, as a result of earnest experiment research by the inventor of the present application, by installing a coil between the phases and passing a current in a direction that interferes with the magnetic flux (hereinafter also referred to as active shielding), higher torque and reduced ripple are achieved by reducing magnetic leakage. It has been found that an increase in weight and volume can be suppressed.

  10A and 10B are diagrams for explaining the problems of the stepping motor according to the reference example. FIG. 10A is a cross-sectional view of the stepping motor, and FIG. 10B is a magnetic flux contour diagram (high contour line) of the motor cross-section. Fig. 10 (contour figure) and Fig. 10 (c) are enlarged views showing the phase of (b). As shown in FIG. 10 (a), the direction of the current of the drive torque generating coil is A phase, B ′ phase, C ′ phase facing forward in the plane of the paper, and A ′ phase, B phase, C phase, the depth direction of the plane of the page. To do. In this case, since the current directions are the same in the B phase and the C phase, and in the B ′ phase and the C ′ phase, as shown in FIGS. appear. This biased magnetic leakage becomes a loss when converting from magnetic force to torque, and torque unevenness occurs.

  FIG. 11 is a diagram illustrating a method for solving the problem according to the reference example. As shown in FIG. 11A, biased magnetic leakage can be reduced by sufficiently separating the distances between the phases. Alternatively, as shown in FIG. 11B, a non-magnetic material having high electrical conductivity is used for the plates sandwiched between the phases. As a result, an eddy current is generated in a direction that disturbs the magnetic flux. This passive shielding can suppress biased magnetic leakage. However, in the method shown in FIG. 11A and / or FIG. 11B, an increase in weight and an increase in volume cannot be avoided.

  12A and 12B are diagrams showing the stepping motor according to the present embodiment. FIG. 12A is a sectional view of the stepping motor, FIG. 12B is a sectional magnetic flux contour diagram of the stepping motor, and FIG. c) shows an enlarged view between the phases. When the current of the driving torque generating coil flows in the same direction as in FIG. 10 described above, an active shielding coil (Y phase coil 13E) is provided between the B phase and the C phase. Then, a current is passed through the active shielding coil in a direction opposite to the direction of the B-phase and C-phase currents. The same applies between the B ′ phase and the C ′ phase. Further, an active shielding coil (X-phase coil 13D) is also provided between the A-phase and the B-phase, and a current can flow in the direction opposite to the direction of the A-phase and B-phase currents. As shown in FIGS. 12B and 12C, the magnetic field generated by the active shielding coil generates a magnetic field in the direction of blocking magnetic leakage. This can reduce magnetic leakage in a small space. Therefore, a reduction in torque unevenness can be realized, and an increase in weight and volume can be suppressed.

FIG. 13 is a diagram illustrating the excitation timing of active shielding. FIG. 14 is a diagram illustrating the direction of current and the direction of magnetic flux at timings T = t _{1 to} t ₆ . When the coils are set to the A phase, the B phase, and the C phase (A ′ phase, B ′ phase, and C ′ phase) from the top of the stepping motor, the X phase (A ′ phase and B ′ phase) is between the A phase and the B phase. The phase between the phases is the X ′ phase), and the phase between the B phase and the C phase is the Y phase (the phase between the B ′ phase and the C ′ phase is the Y ′ phase).

At time _{t 1,} since the driving current according to the A-phase and B-phase are both identical in High, flow Low current to the X phase. In addition time t _2, the order drive current according to the B-phase and C phase are both Low, flow High current in the opposite direction from that in the Y-phase. At time t ₃ , the A phase and the C phase are currents in the same direction, and the B phase is the current in the opposite direction. Therefore, it is not necessary to flow current in the X phase and the Y phase for active shielding. At time t _4, since the driving current according to the A-phase and B-phase are the same both at Low, flow High current in the opposite direction from that in the X phase. In addition the time t _5, since the driving current according to the B-phase and C phase are both High, flow Low current in the opposite direction from that in the Y-phase. At time t _6, A phase and the C phase become the same direction of the current, since the B phase has a current in the opposite direction, X-phase, it is not necessary to flow a current to the active shield is the Y-phase.

  In the present embodiment, in a three-phase stepping motor, while currents in the same direction flow in the A phase and the B phase and currents in the same direction flow in the B phase and the C phase, A current is passed through the phase and the Y phase. That is, by flowing current in the X phase and the Y phase at the timing of canceling the leakage magnetic flux, the leakage magnetic flux can be canceled and the magnetic flux bias can be reduced. Accordingly, it is possible to realize high torque and ripple reduction by reducing magnetic leakage and to suppress an increase in weight and volume.

  It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention. For example, in the present embodiment, the outer rotor type stepping motor has been described. However, the present invention can also be applied to an inner rotor type stepping motor. Moreover, although this Embodiment demonstrated the example applied to the stepping motor concerning a reference example, it cannot be overemphasized that the magnetic leakage in a normal three phase (or more) stepping motor can be reduced.

The figure which shows the rotor of the stepping motor concerning embodiment of this invention, The figure which shows the stator of the stepping motor concerning embodiment of this invention, Sectional drawing of the stepping motor concerning embodiment of this invention, It is sectional drawing in the IV-IV line of FIG. 3 of the stepping motor concerning embodiment of this invention. It is a figure explaining the shift | offset | difference of the stator teeth, status lot, and electrical angle within and between phases. It is a figure which expands and shows the rotor magnet part of the stepping motor concerning the former. It is a figure which expands and shows the rotor magnet part of the stepping motor concerning embodiment of this invention. It is a graph which shows the torque increase verification result by the magnetic field analysis simulation in the conventional stepping motor shown in FIG. It is a graph which shows the torque increase verification result by the magnetic field analysis simulation in the stepping motor concerning the embodiment of the invention shown in FIG. It is a figure explaining the problem of the stepping motor concerning a reference example, (a) is a sectional view showing a stepping motor, (b) is a magnetic flux contour figure in a motor section, (c) is a figure of (b). It is a figure which expands and shows between phases. It is a figure which shows the method of eliminating the problem concerning a reference example. It is a figure which shows the stepping motor concerning embodiment of this invention, Comprising: (a) is sectional drawing which shows a stepping motor, (b) is a magnetic flux contour figure in the cross section of a stepping motor, (c) is between phases It is an enlarged view. It is a figure which shows the excitation timing of the active shielding in the stepping motor concerning embodiment of this invention. It is a diagram showing the direction and the magnetic flux direction of the current at the timing T = t ₁ ~t ₆ in a stepping motor according to the embodiment of the present invention. It is a schematic diagram which shows a general stepping motor. It is a figure which shows the other conventional stepping motor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stepping motor, 10 Rotor, 11 Stator shaft 12 Stator core, 13A A phase coil, 13B B phase coil 13C C phase coil, 13D X phase coil, 13E Y phase coil 14A A phase stator, 14A ₁ A phase 1st stator 14A ₂ A-phase second stator, 14B B-phase stator 14B ₁ B-phase first stator, 14B ₂ B-phase second stator 14C C-phase stator, 14C ₁ C-phase first stator 14C ₂ C-phase second stator, 15, 41 Rotor yoke 16 , 42 Rotor magnet, 17 Stator magnetic shielding plate 18 Housing, 19 Rotor magnetic shielding plate 20 Stator, 20A, 20B Bearing 31 Stator teeth, 32 Status lot

Claims (7)

A stator shaft;
First to third stators having first and second members having a plurality of stator teeth and attached to the stator shaft;
In the first to third stators, first to third coils wound in a circumferential direction between the first and second members, respectively.
A fourth coil and a fifth coil respectively provided between the first stator and the second stator and between the second stator and the third stator;
A rotor yoke disposed opposite to the first to third stators, and a rotor magnetic shielding plate provided across the rotor yoke, the rotor rotating around the stator around the stator;
A plurality of rotor magnets provided on the rotor yoke corresponding to the plurality of stator teeth;
A housing for housing the rotor,
While current in the same direction flows in the first and second coils, current flows in the fourth coil in the opposite direction, and current in the same direction flows in the second and third coils. A stepping motor in which current flows through the five coils in the opposite direction. The stepping motor according to claim 1, wherein the rotor magnet is provided so as to protrude from the rotor yoke to at least a part of the rotor magnetic shielding plate. The stepping motor according to claim 2, wherein the rotor magnet is provided so as to penetrate the rotor part magnetic shielding plate. The stepping motor according to any one of claims 1 to 3, wherein the rotor magnet is individually provided for each of the first to third stators. The stepping motor according to any one of claims 1 to 4, wherein the starter teeth of the first member and the second member are arranged with a ½ pitch shift from each other. 6. The stepping motor according to claim 1, wherein the first member of the first stator and the first member of the second stator are arranged with a shift of 1/3 pitch. . 6. The Nth (N ≧ 3) stator is characterized in that the first member of each stator is arranged with a shift of (1/2) (N-1) / N pitch. A stepping motor according to claim 1.

Images