JPH0880025A - Permanent magnet type stepper motor - Google Patents

Abstract

PURPOSE: To obtain a stepper motor capable of ensuring a smooth motion even at a low speed by giving a predetermined number of poles to a permanent magnet rotor. CONSTITUTION: A rotation shaft 24 and a cylindrical permanent magnet rotor (MR) 25 rotates around the central axis normal to the paper surface where the cross section is shown. Salient poles of drive windings 22a to 22h are arranged around the rotor. Drive windings 22a and 22b, 22c and 22d, 22e and 22f and 22g and 22h are connected in series in such a manner that torques generated by drive currents applied will be added together thereby constituting four-phase drive windings 23a to 23d. MR 25 is magnetized to two poles, and a pair of salient poles constituting one drive phase are arranged with an electrical angle of 45 deg. away each other. MR 26 to 28 can be substituted for MR25. MR26 is magnetized for 6 poles; MR27 is magnetized for 10 poles; MR28 is magnetized for 14 poles; and the intervals of respective salient poles become 135 deg., 225 deg. and 315 deg. respectively in electrical angle. Therefore, a stepping motor having four-phase drive windings deviated each other by 90 deg. in electrical angle and having 45 deg., 135 deg., 225 deg., and 315 deg. at the intervals for a pair of salient poles can be realized.

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 permanent magnet magnetized in multiple poles is used as a rotor in a rotary motor and a mover in a linear motor. In particular, the present invention relates to a stepping motor suitable for realizing low-speed and smooth movement by direct drive.

[0002]

2. Description of the Related Art As a typical structure of a PM type stepping motor, a stepping motor using a claw pole of a widely used two-phase or four-phase driving winding is shown in FIG. A stepping motor using salient pole type magnetic poles is shown in FIG.

In FIG. 5, reference numeral 51 designates a rotor having a cylindrical shape and using a permanent magnet having N-poles and S-poles alternately magnetized on its outer peripheral surface. The stator 52 is composed of two sets of electromagnets having a yoke 54 having claw pole-type pole teeth 53 and solenoid windings 55 and 56, the number of which corresponds to the number of magnetic poles of the rotor. The two sets of electromagnets are arranged such that the magnetic field distributions generated when the respective windings are driven are displaced from each other by ½ of the magnetic pole pitch of the rotor in the rotational direction of the rotor. The magnetic flux flowing from the permanent magnet magnetic poles of the rotor 51 into the yoke 54 changes by one cycle at a mechanical rotation angle corresponding to the magnetic pole pitch angle of the rotor (this is called a mechanical angle).

The rotation angle of the rotor measured with the change of one cycle as 360 ° is called an electrical angle. Using this expression,
The two sets of electromagnets are arranged with an electrical angle difference of 90 °. Magnetic flux distribution generated when a current flows through the winding 55. If the origin measured by the electrical angle is 0 °, then a current distribution in the winding 56 causes a magnetic flux distribution of 90 ° in electrical angle. At this time, the winding 55 is 0 °, and the winding 56 is 90 °
Called winding. 1 if the direction of the current in the winding 55 is reversed
A magnetic flux distribution of 80 ° is generated, and if the direction of the current of the winding 56 is reversed, a magnetic flux distribution of 270 ° is generated.
°, step by ½ of magnetic pole pitch of rotor at mechanical angle.

In a claw pole magnetic pole stepping motor, a 0 ° winding and a 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 magnetic stepping motor in a state in which the axial direction of the rotary 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 electrical angle and mechanical angle.
Each salient pole of the yoke 63 having four salient poles has windings 64, 6
Four windings of 5, 66 and 67 are provided. Winding 64
Is a 0 ° winding, the winding 65 is a 90 ° winding, the winding 66 is a 180 ° winding, and the winding 67 is a 270 ° winding. By switching the windings to be driven in this order, the rotor 62 steps by 90 ° 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.
When a set of windings is used, it can be operated as a two-phase drive winding in the same manner as the two sets of windings in FIG.

The above describes the basic operation of a stepping motor. In this operation, the rotor moves in a stepwise manner. In order to realize smoother movement, microstep drive 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 smooth movement. FIG. 7 is an example of currents flowing through two sets of drive windings by microstep driving. In this example, the section of the electrical angle of 360 ° is divided into 40 minute sections, that is, the section of 90 ° is divided into 10 minute sections, and the magnitude of the current flowing through the two sets of drive windings is controlled. The magnitude of the current is changed in the drive winding of 0 ° with a waveform close to a cosine wave with respect to the rotation angle, and in the drive winding of 90 ° with a waveform approximate to a sine wave. As a result,
The stepping motor moves in steps of 90 ° in electrical angle in normal driving, whereas it is 9 ° in electrical angle in this driving method.
Each step is taken, enabling smooth movement with little vibration.

[Reference] (1) Stepping motor with salient poles Takashi Mijo: "Precision small motor for electronic devices" General Electronic Publishing
pp.108-109 (1977) (2) Micro-step drive Shuji Watanabe: Torque characteristics change depending on the frequency due to the difference in rotor structure, 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 driving current act on the rotor to prevent vibration and smooth movement. In the stepping motor having the pole teeth and salient poles shown in FIG. 5 and FIG. 6, a magnetic attractive force acts between the permanent magnet and the magnetic pole of the yoke even when no current is passed through the drive winding. The rotational torque component of the total of this suction force is the detent torque. The existence of detent torque is one of the main factors that limit the reduction of vibration and the realization of smooth movement in microstep drive.

As a method of reducing the vibration and speed fluctuation due to the detent torque, one method is to superimpose a current change that exactly cancels the detent torque on the current waveform of the microstep drive. The disadvantage of this method is that it requires accurate design or measurement of detent torque, and it is also complicated in terms of circuitry. The drastic measure is to suppress the detent torque.

FIG. 8 shows the relationship between the magnetic poles of a permanent magnet magnetized in multiple poles 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.
Is schematically shown. The armature magnetic pole 81-1 faces the multi-pole magnetized permanent magnet magnetic pole 3 of the rotor. The permanent magnet magnetic poles 3 have 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 is rotated and the armature magnetic poles are at the electrical angles of 0 °, 90 °, 180 °, and 270 °, respectively. Reference numeral 83 shows the state of changes in the detent torque with respect to the rotation angle measured by the electrical angle. In this example, the detent torque value changes sharply in the vicinity of 0 ° and 180 °, and is gentle in the vicinity of 90 ° and 270 °. The steepness of the change may be reversed depending on the magnetization pitch of the permanent magnets and the size and shape of the armature magnetic poles. In either case, in principle, electrical angles 0 °, 90 °, 180
Since the mutual attractive forces in the rotational directions are balanced at 0 ° and 270 °, the magnitude of the resulting torque is 0. For this reason, the detent torque has a quadratic component 84 and a quadratic component 85 when the component having one cycle at an electrical angle of 360 ° is the basic component due to the symmetry of the generated attractive force.
It will contain a lot of high frequency components of even order. Figure 5
The two-phase or four-phase stepping motor shown in FIG. 6 has armature magnetic poles at an electrical angle of 90 °. Therefore, the secondary component 84 that has one cycle at an electrical angle of 180 ° is
They cancel each other out with the secondary component of the detent torque generated by the armature magnetic poles which are deviated by an electrical angle of 90 °. Therefore, as the detent torque of the motor, only the torque due to the quaternary component 85 appears outside. Electric angle 90 °
Is a useful function as a stop position holding function of the stepping motor, and a motor that strongly produces this component can hold the stop position with the detent torque even if the drive current is cut off. . However, it hinders smooth movement of the motor with low vibration.

It is an object of the present invention to provide a stepping motor which has a magnetic pole structure which does not theoretically include a fourth-order component in detent torque and which is capable of smooth movement even at low speeds.

[0013]

According to the present invention, m is an arbitrary natural number, N is a circumferential axis with a cylindrical axis as a rotation axis, and N is equally spaced.
S Alternately magnetized cylindrical permanent magnet rotors and 8m 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 a drive winding for one phase is formed by connecting the drive windings in series so that the torque generated when a drive current is applied to this winding is additive, The number of poles of the magnet rotor is 2m or 6m or 10m or 14
It is characterized by being m. Here, the torque generated when a drive current is applied to each of the drive windings for one phase and the drive windings for one phase facing each other across the rotation axis is additive. A two-phase stepping motor becomes a two-phase stepping motor by connecting in series.

The above-described technical idea of the present invention has a disc-shaped permanent magnet, in which the axis perpendicular to the disc is the axis of rotation, and the disc is magnetized in multiple NS poles alternately at equal angles around the axis of rotation. The same applies to the permanent magnet rotor of 2 and the 2-phase or 4-phase stepping motor having 8m salient poles arranged at equal intervals around the rotation axis so as to face the rotor. You can

Furthermore, 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 integer multiple of 8 salient poles arranged in a straight line, and an armature that is disposed so as to face the armature, and the disposition length for the 8 salient poles is taken as one unit And a permanent magnet having 2 or 6 or 10 or 14 magnetic poles, which are alternately magnetized in NS at equal intervals, and drive current is applied to this winding by winding a drive winding wound on a pair of adjacent salient poles. The drive windings for one phase are formed by connecting in series so that the thrust generated when they flow is additive. Here, by connecting the drive windings for one phase described above in series so that the thrust generated when a drive current is applied to each winding is additive
It becomes a phase linear stepping motor.

[0016]

FIG. 1 is a diagram for explaining the principle of the present invention. In the figure, 3 represents a part of the permanent magnet magnetic poles which are alternately magnetized in multiple poles at equal intervals, and the pitch at which a pair of magnetic poles of N pole and S pole is magnetized is an electrical angle of 360 °. . In the present invention, an armature having four-phase drive windings wound on eight salient poles is configured as a basic unit, with a winding wound on a pair of salient poles as one drive winding. In the figure, 1-1 and 1-2 are this pair of salient poles, so that when salient pole 1-1 is at an electrical angle of 0 °, salient pole 1-2 is at a position of 315 °. It is arranged. Although not shown, the salient pole 1-1 has an electrical angle of 0 °.
Salient pole 1-2 is 45 ° or 135 ° when
Alternatively, it 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 to make the torque additive, when the distance between the pair of salient poles measured by the electrical angle is 0 ° to 180 °, the two drive windings are connected so as to be wound in the same direction, and 180 ° to 360 °.
In the case of °, connect so that they are wound in opposite directions. When salient pole 1-1 is at the position of electrical angle 0 ° salient pole 1-
When 2 is at a position of 45 °, 135 °, 225 °, or 315 °, the numbers of permanent magnet magnetic poles arranged at an angle of eight salient poles of the armature are 2, 6, respectively.
10 and 14.

The detent torque waveform of FIG. 1 represents only the fourth-order high frequency component of the detent torque which is the subject of the present invention. Since the pair of salient poles are arranged at an electrical angle of 315 °, 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. And is canceled. Even if the pair of salient poles are arranged at the electrical angle of 45 °, 135 °, or 225 °, the detent torques generated by the pair of salient poles have opposite phases to each other and are canceled. Generally speaking, when a pair of salient poles are arranged at intervals of a natural multiple of 45 °, the fourth-order components of the detent torque generated by each pair of salient poles have opposite phases to each other and cancel each other out. Be done. In the symmetrical two-phase or four-phase stepping motor of the present invention, the secondary high frequency component of the detent torque is canceled out in principle inside the motor. Therefore, when the present invention is applied, the secondary detent torque and It is possible to realize a stepping motor which does not have a fourth-order high-frequency component.

[0018]

FIG. 2 is a block diagram of an embodiment of the present invention, showing a four-phase stepping motor having eight salient poles. The rotary shaft 24 and the cylindrical permanent magnet rotor 25 rotate about a central axis perpendicular to the paper surface. Drive windings 22a, 22
b, 22c, 22d, 22e, 22f, 22g, 22h
Eight salient poles with are equally spaced, that is, with a mechanical angle of 45 °
It 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 is passed through the respective drive windings is added, and constitutes four-phase drive windings 23a, 23b, 23c, and 23d. Since the permanent magnet rotor 25 is magnetized to have two poles,
The pair of salient poles forming one drive phase are arranged at an electrical angle of 45 ° from each other. If each drive winding is wound in the same direction when 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 that can be used in place of the permanent magnet rotor 25 magnetized 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 6 is used, the distance between a pair of salient poles is 135 ° in electrical angle
Becomes Also 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 27 is used, the distance between the pair of salient poles is 225 ° 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 distance between the pair of salient poles is 315 ° 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. With the above configuration, a PM type stepping motor in which the four-phase drive windings which are deviated by an electrical angle of 90 ° and the distance between a pair of adjacent salient poles is 45 °, 135 °, 225 ° or 315 ° is realized. are doing. In any case, the condition for canceling the fourth-order high-frequency component of the detent torque shown in FIG. 1 inside 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 projecting in the direction of the rotation axis in the gap portion between the stator and the rotor. . Reference numeral 34 denotes a rotating shaft, which supports a rotor composed of a disk-shaped permanent magnet 37 and a yoke 39 serving as a magnetic path of magnetic flux. Reference numeral 31 is an armature yoke having 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 on 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 torques generated when a drive current is passed through the respective drive windings are connected in series to form a four-phase drive winding. Since the disk-shaped permanent magnet rotor 37 is magnetized to have 10 poles in this example, the pair of salient poles forming one drive phase are arranged at an electrical angle of 225 ° from each other. . Also in this case, as in the case of FIG. 2, as the number of the magnetic poles of the disk-shaped permanent magnet, two poles, six poles or 14 poles can be used in addition to 10 poles. The operation when these numbers of magnetic poles are used is exactly the same as that of FIG. 2, and in any case, the detent and
The condition for canceling the fourth high-frequency component of torque inside the motor is satisfied.

Although the armature yoke having eight salient poles has been described in the embodiments of FIGS. 2 and 3, the gas of salient poles is 8 m, where m is a natural number, and the number of permanent magnet magnetic poles is multiplied by m. Even with this configuration, it is obvious that the electrical angle between adjacent salient poles can maintain a relationship of a natural multiple of 45 °. 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, showing an example of a linear motor having eight salient poles. In the drawing, 47 is a permanent magnet having 10 magnetic poles magnetized at equal intervals in the movable direction. Reference numeral 49 is a yoke that serves as a magnetic path for magnetic flux. Reference numeral 41 is an armature yoke having eight salient poles arranged at equal intervals in the movable direction. Drive windings 42a, 42b, 42c, 42d, 42e, 42f wound around each salient pole,
42g and 42h are two-phase drive windings in which two adjacent drive windings are connected in series as in FIGS. 2 and 3.
The length of 10 times the magnetizing interval of the permanent magnet 47 and the length of 8 times the interval between adjacent salient poles are matched. In this case,
The magnetic pole width of the NSI pair of the permanent magnets 47, that is, the length twice the magnetizing interval has an electrical angle of 360 °, and the adjacent salient poles are arranged at an electrical angle of 225 °. As in the case of FIG. 2 and FIG. 3, the number of magnetized magnetic poles of the permanent magnet is 2 poles, 6 poles or 1 pole at a length 8 times the interval between the adjacent salient poles.
If there are four poles, the adjacent salient poles have an electrical angle of 45 °, 135 °,
This means that they are arranged at an interval of 315 °, and in any case, the condition for canceling the fourth high-frequency component of the detent torque in the motor described in FIG. 1 is satisfied.

In the case of a linear motor, the length of 8 times the salient pole spacing of the armature is used as a basic unit, and the armature and the permanent magnet magnetic poles can be used as arbitrary integral lengths. .

[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 magnetizing cycle of the permanent magnet, which was difficult to cancel in the motor in the conventional configuration, was used as the basic cycle. It is possible to effectively cancel the components generated by the rotation angle and the displacement corresponding to the fourth-order cycle. Even with the conventional configuration, the secondary high-frequency component of the detent torque is canceled out in principle inside the motor, and by applying the present invention, not only the secondary high-frequency component of the detent torque but also the fourth-order high-frequency component can be canceled out. . Therefore, the stepping motor to which the present invention is applied has a small detent torque, and a smooth motion can be realized by direct driving even at a low speed.

[Brief description of drawings]

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

FIG. 2 is a schematic configuration diagram of a 4-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 showing an example of microstep driving.

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

[Explanation of symbols]

 1-1, 1-2 salient pole 2-1, 2 drive winding 3 permanent magnet magnetic pole 22a-22h salient pole 23a-23d drive winding 24 rotary shaft 25, 26, 27, 28 cylindrical permanent magnet rotor 31 Armature Yoke 32a-31h Drive Winding 34 Rotation Shaft 37 Disc Permanent Magnet 39 Yoke 41 Armature Yoke 42a-42h Drive Winding 47 Permanent Magnet 49 Yoke

Claims (6)

[Claims] 1. A cylindrical permanent magnet rotor, in which m is an arbitrary natural number, is magnetized in multiple poles alternately in the circumferential direction with the cylindrical axis as a rotation axis and is NS-alternated at equal intervals, and in the circumferential direction surrounding the rotor. Have 8m salient poles arranged at equal intervals and make the torque generated when a drive current is passed through a drive winding wound on a pair of adjacent salient poles. A four-phase stepping motor having a drive winding for one phase by connecting in series, wherein the number of poles of the permanent magnet rotor is 2 m or 6
A permanent magnet type stepping motor having a length of m, 10 m, or 14 m. 2. A cylindrical permanent magnet rotor, in which m is an arbitrary natural number, and which is multipolarly magnetized with NS alternating alternately in the circumferential direction with the cylinder axis as the rotation axis, and in the circumferential direction surrounding the rotor. Have 8m salient poles arranged at equal intervals and make the torque generated when a drive current is passed through a drive winding wound on a pair of adjacent salient poles. By connecting them in series, a drive winding for one phase is formed, and the drive winding for this one phase and the drive winding for one phase facing each other across the rotation axis are driven by respective drive currents. A two-phase stepping motor connected in series so that the torque generated when the current flows is additive, wherein the number of poles of the permanent magnet rotor is 2 m or 6 m or 10 m or 14 m. Magnet type stepping motor. 3. A disk shape in which m is an arbitrary natural number, an axis perpendicular to the disk of the disk-shaped permanent magnet is a rotation axis, and NS is alternately magnetized into multiple poles at equal angles around the rotation axis. Permanent magnet rotor and 8m salient poles arranged at equal intervals around the axis of rotation to face the rotor and drive windings wound around a pair of adjacent salient poles. A four-phase stepping motor in which a drive winding for one phase is formed by connecting in series so that the torque generated when a drive current is applied to this winding is additive, and the pole of the permanent magnet rotor. The number is 2m or 6
A permanent magnet type stepping motor having a length of m, 10 m, or 14 m. 4. A disc-shaped permanent magnet having a multi-pole magnetized in an NS alternating manner at an equal angle around the rotation axis with an axis perpendicular to the disk of the disc-shaped permanent magnet as a rotation axis, where m is an arbitrary natural number. Permanent magnet rotor and 8m salient poles arranged at equal intervals around the axis of rotation to face the rotor and drive windings wound around a pair of adjacent salient poles. A drive winding for one phase is formed by connecting in series so that the torque generated when a drive current is applied to this winding is additive, and the drive winding for this one phase and the rotary shaft are sandwiched. A two-phase stepping motor in which a drive winding for one phase facing each other is connected in series so that the torque generated when a drive current is applied to each winding is additive, A permanent magnet characterized in that the number of poles of the rotor is 2 m or 6 m or 10 m or 14 m Type stepping motor. 5. An armature having salient poles that are an integral multiple of 8 arranged in a straight line, and an armature that is disposed so as to face the armature, and the disposition length corresponding to the eight salient poles is one unit A permanent magnet having 2 or 6 or 10 or 14 magnetic poles which are alternately magnetized in NS at equal intervals, and a drive winding wound around a pair of adjacent salient poles is provided in this winding. A four-phase linear permanent magnet type stepping motor in which a drive winding for one phase is formed by connecting in series so that the thrust generated when a drive current is applied is additive. 6. An armature having linearly arranged salient poles of an integral multiple of 8, and the armature is arranged so as to face the armature, and an arrangement length corresponding to the eight salient poles is defined as one unit. A permanent magnet having 2 or 6 or 10 or 14 magnetic poles which are alternately magnetized in NS at equal intervals, and a drive winding wound around a pair of adjacent salient poles is provided in this winding. A drive winding for one phase is made by connecting in series so that the thrust generated when a drive current is applied is additive, and the drive winding for this 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 it flows is additive.