JP3045935B2 - Permanent magnet type stepping motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PM (permanent magnet) type stepping motor in which a multi-pole magnetized permanent magnet is used as a rotor in a rotary motor and a movable element in a linear motor. In particular, the present invention relates to a stepping motor suitable for realizing low-speed smooth motion by direct driving.

[0002]

2. Description of the Related Art As a typical configuration of a PM type stepping motor, FIG. 5 shows a stepping motor using a claw pole of a two-phase or four-phase drive winding which is widely used. FIG. 6 shows a stepping motor using salient pole type magnetic poles.

[0005] In FIG. 5, reference numeral 51 denotes a rotor using a permanent magnet having a cylindrical shape and N and S poles alternately and multipolarly magnetized on the outer peripheral surface thereof. The stator 52 is composed of two sets of electromagnets having yokes 54 having claw-pole-type pole teeth 53 and solenoid windings 55 and 56 in a number corresponding to the number of magnetic poles of the rotor. The two sets of electromagnets are arranged such that the magnetic field distribution generated when each of the windings is driven is shifted from each other in the rotation direction of the rotor by a half of the magnetic pole pitch of the rotor. The magnetic flux flowing into the yoke 54 from the permanent magnet magnetic pole of the rotor 51 changes by one cycle at a mechanical rotation angle (this is called a mechanical angle) corresponding to the magnetic pole pitch angle of the rotor.

[0004] The rotation angle of the rotor measured by setting the change of one cycle to 360 ° is called an electrical angle. Using this expression,
The two sets of electromagnets are shifted by 90 degrees in electrical angle. Assuming that the origin, which is measured by the electrical angle of the magnetic flux distribution generated when a current flows through the winding 55, is 0 °, the current flowing in the same direction in the winding 56 generates a magnetic flux distribution of 90 ° in electrical angle. At this time, the winding 55 is a 0 ° winding and the winding 56 is a 90 ° winding.
Called winding. If the direction of the current of the winding 55 is reversed,
A magnetic flux distribution of 80 ° is generated, and a magnetic flux distribution of 270 ° is generated by reversing the direction of the current of the winding 56. Each time these drive windings and the energizing direction are switched, the rotor becomes 90 electrical degrees.
Step by 1/2 of the magnetic pole pitch of the rotor at a mechanical angle of °.

In a claw-pole stepping motor, the 0 ° winding and the 90 ° winding are stacked in the axial direction of the rotor. In the salient pole stepping motor, the windings are arranged in the circumferential direction. FIG. 6 shows a configuration example of the salient pole stepping motor in a state where the axial direction of the rotating shaft 61 is arranged perpendicular to the paper surface. In this example, since the cylindrical permanent magnet rotor 62 is magnetized in two poles, one rotation of the rotor is 360 ° in both the electrical angle and the mechanical angle.
The windings 64, 6 are attached to each salient pole of the yoke 63 having four salient poles.
5, 66, 67 four windings are provided. Winding 64
Is 0 °, the winding 65 is 90 °, the winding 66 is 180 °, and the winding 67 is 270 °. By switching the windings to be driven in this order, the rotor 62 advances by 90 degrees in mechanical angle. The 0 ° winding and the 180 ° winding are connected in series so as to have opposite phases, and the 90 ° winding and the 270 ° winding are connected in series so as to have opposite phases.
If a set of windings is used, it can be operated as a two-phase drive winding similarly to the two sets of windings of FIG.

The above describes the basic operation of a stepping motor. In this operation, the rotor makes a dynamic motion. In order to realize smoother movement, micro-step driving is used. In the micro-step drive, the magnitude of the current flowing through each of the two sets of drive windings is also controlled to realize a smooth movement. FIG. 7 is an example of a current flowing through two sets of drive windings by micro-step drive. In this example, the section of 360 ° in electrical angle is divided into 40 minute sections, that is, the section of 90 ° is divided into 10 minute sections, and the magnitude of current flowing through two sets of drive windings is controlled. The magnitude of the current is changed with a waveform close to a cosine wave with respect to the rotation angle for the drive winding of 0 °, and with a waveform approximating a sine wave for the drive winding of 90 °. As a result,
The stepping motor moves in steps of 90 electrical degrees in normal driving, whereas in this driving method, the electrical angle is 9 degrees.
Stepping by step enables smooth movement with little vibration.

[References] (1) Stepping motor with salient magnetic poles Takashi Mishiro: "Precision small motor for electronic equipment" General Electronic Publishing
pp.108-109 (1977) (2) Regarding micro-step drive Hideji Watanabe: Focus on differences in rotor structure Changes in torque characteristics at frequency, full motor utilization, Nikkei BP pp.98-111 (1990)

[0008]

In an actual stepping motor, torque and force other than the torque and force due to the drive current act on the rotor, thereby preventing generation of vibration and smooth movement. In the stepping motor having the pole teeth and salient poles shown in FIGS. 5 and 6, magnetic attraction acts between the permanent magnet and the magnetic pole of the yoke even when no current flows through the drive winding. The rotational torque component of the sum of the suction forces is the detent torque. The presence of detent torque is one of the main factors that limit the reduction of vibration and the achievement of smooth movement in microstep driving.

As a method of reducing vibration and speed fluctuation due to detent torque, one method is to superimpose a current change that just cancels out the detent torque on the current waveform of the microstep drive. The disadvantage of this method is that it requires precise design or measurement of the detent torque, and the circuit becomes complicated. The drastic response is to reduce the detent torque.

FIG. 8 shows the relationship between the magnetic pole of a multi-pole magnetized permanent magnet and the torque generated between one salient pole of the yoke in the rotational angle direction. In FIG. 8, the armature magnetic pole 81-1 is one of the pole teeth or salient poles of the stepping motor.
Are schematically shown. The armature magnetic pole 81-1 faces the multi-polarized permanent magnet magnetic pole 3 of the rotor. The permanent magnet pole 3 has N poles S at a pitch corresponding to an electrical angle of 360 °.
A pair of magnetic poles is magnetized.

81-1, 81-2, 81-3, 81-4
Shows a state in which the rotor rotates and the armature magnetic poles are at electrical angles of 0 °, 90 °, 180 °, and 270 °, respectively. Numeral 83 indicates how the detent torque changes with respect to the rotation angle measured in electrical angle. In this example, the value of the detent torque changes sharply near 0 ° and 180 °, and is gentle near 90 ° and 270 °. The steepness of the change may be reversed depending on the magnetization pitch of the permanent magnet or the size and shape of the armature magnetic pole. In either case, in principle, the electrical angles are 0 °, 90 °, 180 °
At 270 °, the mutual attraction in the rotational direction is in a balanced state, and the magnitude of the resulting torque is zero. For this reason, the detent torque is based on the symmetry of the generated attractive force. If the component that forms one cycle at an electrical angle of 360 ° is used as the basic component, the second component 84 and the fourth component 85
, Etc., will be included. FIG.
Also, the two-phase or four-phase stepping motor shown in FIG. 6 has armature magnetic poles at 90 ° electrical angle intervals. For this reason, the secondary component 84 that is one cycle at an electrical angle of 180 ° is
It cancels out the secondary component of the detent torque generated by the armature magnetic pole shifted by an electrical angle of 90 °. Therefore, only the torque due to the fourth-order component 85 appears to the outside as the motor detent torque. Electric angle 90 °
Is a useful function as a stop position holding function of the stepping motor, and a motor that strongly outputs this component can hold the stop position with the detent torque even when the drive current is cut off. . However, it is an obstacle to smoothly move the motor with low vibration.

An object of the present invention is to provide a stepping motor having a magnetic pole configuration in which a detent torque does not include a fourth-order component in principle and capable of smooth movement even at a low speed.

[0013]

According to the present invention, m is an arbitrary natural number, and N is arranged at regular intervals in the circumferential direction around a cylindrical axis as a rotation axis.
S has a cylindrical permanent magnet rotor alternately multipolar magnetized, and 8 m salient poles arranged at equal intervals in the circumferential direction surrounding the rotor, and wound around a pair of adjacent salient poles. A four-phase stepping motor in which the driving windings are connected in series so that the torque generated when a driving current flows through the windings is additive, so that the driving winding for one phase is used. The number of poles of the magnet rotor is 2m or 6m or 10m or 14
m. Here, the torque generated when a drive current is applied to each of the one-phase drive winding and the one-phase drive winding opposed to each other with the rotating shaft interposed therebetween is added. By connecting them in series as described above, a two-phase stepping motor is obtained.

[0014] The technical idea of the present invention is that a disk-shaped permanent magnet is a multi-pole magnetized with a rotation axis being perpendicular to the disk of the disk-shaped permanent magnet and NS alternately at an equal angle around the rotation axis. The same applies to a permanent magnet rotor and a two-phase or four-phase stepping motor having 8m salient poles arranged at regular intervals around the rotation axis in opposition to the rotor. Can be.

Further, the technical idea of the present invention can be applied to a four-phase linear stepping motor as follows. That is, an armature having an integral multiple of eight salient poles arranged in a straight line, and an armature arranged opposite to the armature and having the arrangement length of the eight salient poles as one unit. And permanent magnets having 2 or 6 or 10 or 14 magnetic poles alternately magnetized by NS at equal intervals, and a driving current wound on a pair of adjacent salient poles is supplied with a driving current through this winding. The drive winding for one phase is obtained by connecting in series so that the thrust generated when flowing is additive. Here, the drive windings for one phase are connected in series so that the thrust generated when a drive current is applied to each winding is additive so that two phases are connected.
It becomes a phase linear stepping motor.

[0016]

FIG. 1 is a diagram illustrating the principle of the present invention. In the figure, reference numeral 3 denotes a part of the permanent magnet magnetic poles which are multipolar magnetized alternately at regular intervals of NS, and the pitch at which a pair of N poles and S poles is magnetized is an electrical angle of 360 °. . In the present invention, a winding wound around a pair of salient poles is used as one driving winding, and an armature having four-phase driving windings wound around eight salient poles is used as a basic unit. In the figure, 1-1 and 1-2 are a pair of salient poles. When the salient pole 1-1 is at a position of 0 electrical angle, the salient pole 1-2 is at a position of 315 °. Are located. Although not shown, the salient pole 1-1 has an electrical angle of 0 °.
When the salient pole 1-2 is at 45 ° or 135 °
Alternatively, they may be arranged at a position of 225 °. The winding 2-1 and the winding 2-2 are connected in series so that the torque generated by the drive current is additive. In order for the torque to be additive, when the interval between a pair of salient poles measured in electrical angle is 0 ° to 180 °, two drive windings are connected so as to be wound in the same direction, and 180 ° to 360 °
In the case of °, they are connected so that they are wound in opposite directions. When the salient pole 1-1 is located at an electrical angle of 0 °, the salient pole 1-
When 2 is located at 45 °, 135 °, 225 °, or 315 °, the number of permanent magnet magnetic poles arranged at an angle of eight salient poles of the armature is 2, 6, respectively.
10,14.

The detent torque waveform shown in FIG. 1 represents only the fourth high frequency component of the detent torque, which is the subject of the present invention. Since the pair of salient poles is arranged at an electrical angle of 315 ° apart, the detent torque caused by the salient pole 1-1 and the detent torque caused by the salient pole 1-2 have opposite phases as shown in the figure. It is canceled. Further, even if a pair of salient poles is arranged at an electrical angle of 45 °, 135 °, or 225 °, the detent torques generated by each pair of salient poles are in opposite phases to each other and are cancelled. Generally speaking, when a pair of salient poles are arranged at an interval of a natural number multiple of 45 °, the fourth order components of the detent torque generated by each of the pair of salient poles are out of phase with each other and cancel each other. It is. In the symmetric two-phase or four-phase stepping motor of the present invention, the secondary high-frequency component of the detent torque is canceled in principle inside the motor. A stepping motor having no fourth-order high-frequency component can be realized.

[0018]

FIG. 2 is a block diagram of one embodiment of the present invention, showing a four-phase stepping motor having eight salient poles. The rotating shaft 24 and the cylindrical permanent magnet rotator 25 rotate around a central axis perpendicular to the paper surface. Drive windings 22a, 22
b, 22c, 22d, 22e, 22f, 22g, 22h
Are equidistant, that is, the mechanical angle is 45 °
And is arranged around the rotor. Drive windings 22a and 2
2b, 22c and 22d, 22e and 22f, 22g and 22
h is connected in series so that the torque generated when a drive current flows through each drive winding is additive, and constitutes four-phase drive windings 23a, 23b, 23c, and 23d. Since the permanent magnet rotor 25 is magnetized to two poles,
A pair of salient poles constituting one driving phase are arranged at an electrical angle of 45 ° from each other. Assuming that each drive winding is wound in the same direction as viewed from the rotor side, in this case,
The end of the first drive winding and the start of the second drive winding are connected in series so that the two drive windings are wound in the same direction.

Reference numerals 26, 27 and 28 denote permanent magnet rotors which can be used in place of the two-pole magnetized permanent magnet rotor 25 in the present invention. 26 is magnetized with 6 poles, 27 is magnetized with 10 poles, and 28 is magnetized with 14 poles. Permanent magnet rotor 2
When using 6, the interval between a pair of salient poles is 135 ° in electrical angle
Becomes Also in this case, the end of winding of the first drive winding and the start of winding of the second drive winding are connected to form a series. When the permanent magnet rotor 27 is used, the interval between a pair of salient poles is 225 degrees in electrical angle. In this case, the winding end of the first drive winding and the winding start of the second drive winding are connected in series.
When the permanent magnet rotor 28 is used, the interval between the pair of salient poles is 315 degrees in electrical angle. In this case, the winding end of the first drive winding and the winding start of the second drive winding are connected in series. The above configuration realizes a PM type stepping motor in which the four-phase drive windings shifted by 90 ° in electrical angle and the interval between a pair of adjacent salient poles are 45 °, 135 °, 225 °, or 315 °. doing. In either case, the condition for canceling the fourth-order high-frequency component of the detent torque shown in FIG. 1 in the motor is satisfied.

FIG. 3 is a block diagram of another embodiment of the present invention, showing a four-phase stepping motor having eight salient poles protruding in the direction of the rotation axis at a gap between a stator and a rotor. . Reference numeral 34 denotes a rotating shaft, which supports a rotor constituted by a disk-shaped permanent magnet 37 and a yoke 39 serving as a magnetic path of magnetic flux. An armature yoke 31 has eight salient poles facing the magnetic poles of the disk-shaped permanent magnet 37. 32a, 32
b, 32c, 32d, 32e, 32f, 32g, 32h
Are drive windings wound around eight salient poles arranged at equal intervals around the rotation axis. Drive windings 32a and 32
b, 32c and 32d, 32e and 32f, 32g and 32h
Are connected in series so that the torque generated when a drive current flows through each drive winding is additive, thereby forming a four-phase drive winding. Since the disk-shaped permanent magnet rotor 37 is magnetized to 10 poles in this example, a pair of salient poles constituting one driving phase are arranged at an electrical angle of 225 ° apart from each other. . Also in this case, similarly to FIG. 2, as the number of magnetized poles of the disk-shaped permanent magnet, 2 poles, 6 poles, or 14 poles can be used in addition to 10 poles. The operation when these numbers of magnetized poles are used is exactly the same as that in FIG. 2, and in any case, the detent and the detent described in FIG.
The condition for canceling the fourth-order high-frequency component of the torque inside the motor is satisfied.

In the embodiments shown in FIGS. 2 and 3, an armature yoke having eight salient poles has been described. The number of salient poles is assumed to be 8 m, where m is a natural number, and the number of permanent magnet magnetic poles is increased by m times. It is apparent that the electrical angle between adjacent salient poles can be maintained at a natural number multiple of 45 ° even if the configuration is made as follows. Also,
It is also apparent that the present invention can be applied to a so-called outer-rotor type motor in which the positional relationship between the rotor and the stator is reversed in FIG.

FIG. 4 shows another embodiment of the present invention and shows an example of a linear motor having eight salient poles. In the figure, reference numeral 47 denotes a permanent magnet having ten magnetic poles magnetized at equal intervals in the movable direction. Reference numeral 49 denotes a yoke serving as a magnetic path of a magnetic flux. Reference numeral 41 denotes an armature yoke having eight salient poles arranged at equal intervals in the movable direction. Drive windings 42a, 42b, 42c, 42d, 42e, 42f,
42g and 42h connect two adjacent drive windings in series similarly to FIGS. 2 and 3 to form four-phase drive windings.
The length of 10 times the magnetizing interval of the permanent magnet 47 and the length of 8 times of the interval between the adjacent salient poles are matched. In this case,
The magnetic pole width of one pair of NS of the permanent magnet 47, that is, twice the length of the magnetization interval is an electrical angle of 360 °, and the adjacent salient poles are arranged at an electrical angle of 225 °. As in the case of FIGS. 2 and 3, the number of magnetized magnetic poles of the permanent magnet is 2 poles, 6 poles, or 1 pole at a length of eight times the interval between adjacent salient poles.
If there are four poles, the adjacent salient poles have electrical angles of 45 °, 135 °,
This means that they are arranged at an interval of 315 °, and in any case, the condition for canceling the fourth-order high-frequency component of the detent torque described in FIG. 1 is satisfied inside the motor.

In the case of a linear motor, the length of the armature and the permanent magnet magnetic pole can be arbitrarily integer times as long as eight times the salient pole interval of the armature as a basic unit. .

[0024]

As described above, according to the present invention,
Of the detent torque generated by the attractive force between the salient poles of the armature of the stepping motor and the permanent magnet, the magnetization period of the permanent magnet, which was difficult to cancel in the motor in the conventional configuration, was used as the basic period. And a component generated by a rotation angle or a displacement corresponding to the fourth-order cycle can be effectively canceled. Even in the conventional configuration, the secondary high-frequency component of the detent torque is canceled in principle inside the motor. By applying the present invention, not only the secondary but also the fourth-order high-frequency component of the detent torque can be canceled. . Therefore, the stepping motor to which the present invention is applied has a small detent torque, and can realize a smooth movement by direct driving even at a low speed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a schematic configuration diagram of a four-phase stepping motor according to an embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a four-phase stepping motor according to another embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a linear stepping motor according to another embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of a conventional claw pole type stepping motor.

FIG. 6 is a schematic configuration diagram of a conventional salient pole type stepping motor.

FIG. 7 is a current waveform diagram illustrating an example of micro-step driving.

FIG. 8 is an explanatory diagram showing a relationship among a magnetic pole of a permanent magnet, a yoke salient pole, and torque.

[Explanation of symbols]

 1-1, 1-2 salient poles 2-1 and 2-2 drive windings 3 permanent magnet magnetic poles 22a to 22h salient poles 23a to 23d drive windings 24 rotating shafts 25, 26, 27, 28 cylindrical permanent magnet rotor Reference Signs List 31 armature yokes 32a to 31h drive winding 34 rotating shaft 37 disk-shaped permanent magnet 39 yoke 41 armature yokes 42a to 42h drive winding 47 permanent magnet 49 yoke

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H02K 37/00-37/24 H02K 41/03

Claims (6)

(57) [Claims] 1. A cylindrical permanent magnet rotor which is alternately multipolar magnetized by NS alternately at equal intervals in a circumferential direction with a cylindrical axis as a rotation axis, where m is an arbitrary natural number, and a circumferential direction surrounding the rotor. It has 8m salient poles arranged at equal intervals, and a driving winding wound on a pair of adjacent salient poles is formed so that a torque generated when a driving current is applied to this winding is additive. A four-phase stepping motor having a drive winding for one phase connected in series, wherein the number of poles of the permanent magnet rotor is 2 m or 6
m or 10 m or 14 m. 2. When m is an arbitrary natural number, a cylindrical permanent magnet rotor, which is multipole-magnetized by alternating NS at equal intervals in the circumferential direction with the cylindrical axis as a rotation axis, and a circumferential direction surrounding the rotor. It has 8m salient poles arranged at equal intervals, and a driving winding wound on a pair of adjacent salient poles is formed so that a torque generated when a driving current is applied to this winding is additive. By connecting in series, a drive winding for one phase is formed, and a drive winding for one phase and a drive winding for one phase opposed to each other with a rotating shaft interposed therebetween are provided with drive currents for the respective windings. A two-phase stepping motor connected in series such that the torque generated when the current flows is additive, wherein the number of poles of the permanent magnet rotor is 2 m, 6 m, 10 m, or 14 m. Magnet type stepping motor. 3. A disk-shaped magnet, wherein m is an arbitrary natural number, and an axis perpendicular to the disk of the disk-shaped permanent magnet is set as a rotation axis, and NS is alternately multipolar magnetized at an equal angle around the rotation axis. And a driving winding wound around a pair of adjacent salient poles having 8m salient poles arranged at equal intervals around the rotation axis in opposition to the rotor. A four-phase stepping motor which is connected in series so that a torque generated when a drive current is applied to the winding is additive so as to be a drive winding for one phase, wherein a pole of the permanent magnet rotor is provided. Number 2m or 6
m or 10 m or 14 m. 4. A disk-shaped magnet, wherein m is an arbitrary natural number, and an axis perpendicular to the disk of the disk-shaped permanent magnet is a rotation axis, and NS is multipolar magnetized alternately at an equal angle around the rotation axis. And a driving winding wound around a pair of adjacent salient poles having 8m salient poles arranged at equal intervals around the rotation axis in opposition to the rotor. By connecting in series so that the torque generated when a drive current flows through this winding is additive, a drive winding for one phase is formed, and the drive winding for this phase and the rotating shaft are sandwiched. A two-phase stepping motor in which drive coils for one phase facing each other are connected in series so that a torque generated when a drive current flows through each of the windings is additive. Permanent magnet, wherein the number of poles of the rotor is 2 m, 6 m, 10 m, or 14 m Type stepping motor. 5. An armature having an integral multiple of eight salient poles linearly arranged, and an armature disposed opposite to the armature, wherein the arrangement length of the eight salient poles is defined as one unit. And a permanent magnet having 2 or 6 or 10 or 14 magnetic poles alternately and NS-magnetized at equal intervals within one unit, and a driving winding wound on a pair of adjacent salient poles is provided on this winding. A four-phase linear permanent magnet type stepping motor that is connected in series so that the thrust generated when a driving current flows is additive so that the driving winding for one phase is used. 6. An armature having an integral multiple of eight salient poles arranged in a straight line, and an armature disposed opposite to the armature and having an arrangement length of eight salient poles as one unit. And a permanent magnet having 2 or 6 or 10 or 14 magnetic poles alternately and NS-magnetized at equal intervals within one unit, and a driving winding wound on a pair of adjacent salient poles is provided on this winding. By connecting in series so that the thrust generated when the drive current flows is additive, a drive winding for one phase is formed, and the drive current for one phase is applied to each winding. A two-phase linear permanent magnet type stepping motor connected in series so that the thrust generated when flowing is added.