JP2000060101A - Pm type stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the torque and improve torque efficiency per unit volume of a motor by arranging a small diameter stator and a large diameter stator in the inside part and the outside part of a permanent magnet. SOLUTION: A rotor 4 provided with an annular permanent magnet 1, in which both the inner peripheral surface and the outer peripheral surface are multipole-magnetized, a rotor boss 2 and a shaft 3 are installed. A large diameter outer yoke 8 having a plurality of pole teeth protruding from a diskoidal flange part, a larger diameter inner yoke 9, a small diameter inner yoke 10, a small diameter outer yoke 11, a large diameter coil assembly 12 and a small diameter coil assembly 13 are installed. By arranging small-diameter stator and a large-diameter stator on the inside part and the outside part of the permanent magnet 1, respectively, the rotor 4 is excited with the small diameter stator and the large diameter stator, and not only the outside part of the permanent magnet 1 but also the space of the inside part contributes to magnetic torque. Generated torque is the sum of the torques, due to the large diameter stator and the torque due to the small diameter stator. As a result, torque is increased, and torque efficiency per unit volume of a motor is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PM type stepping motor mainly used for driving OA equipment such as a printer, a copying machine, and a facsimile.

[0002]

2. Description of the Related Art A conventional PM stepping motor has a known structure as shown in FIG. FIG. 10 is a half sectional view of a conventional stepping motor. The outer yoke 101, the inner yoke 103, the coil assembly 105, the bracket 109 having the bearing 107, the bracket 111 having the bearing 107, the flange 111 having the bearing 107, the shaft 113, and the outer periphery are multipolar magnetized. Permanent magnet 115
The outer yoke 101, the coil assembly 105, and the inner yoke 103 are laminated on the same axis in the axial direction to form a stator. The shaft 113 is rotatably held by the bearing 107, and a slight gap is provided between the permanent magnet 115 and the pole teeth of the outer yoke 101 and the inner yoke 103.
17 is disposed inside the stator, and the shaft 113
And the permanent magnet 115 are fixed by a rotor boss 119. In the PM type stepping motor having such a configuration, in order to increase the rotational torque, the diameter φD1 of the permanent magnet is increased to increase the permanent magnet 115 facing the stator.
May be increased to increase the surface magnetic flux of the permanent magnet 115.

As another embodiment of a conventional PM stepping motor, there is known a structure shown in FIG. 11 disclosed in Japanese Patent Publication No. 7-20364. FIG. 11 shows a half sectional view. In FIG. 11, the diameter φD1 of the permanent magnet 115
Is similar to the prior art, except that a permanent magnet 115 is disposed radially outside the stator, and the outer yoke 1
01 is outside the permanent magnet 115 and the inner yoke 103
Are disposed inside the permanent magnet 115. With such a configuration, the diameter φD1 of the permanent magnet 115 is increased to increase the surface of the permanent magnet 115 opposing the pole teeth,
The surface magnetic flux of the permanent magnet 115 can be increased.

[0004]

However, in the first conventional example, by increasing the diameter of the permanent magnet 115, the volume occupied by the rotor boss 119 for fixing the permanent magnet 115 and the shaft 113 is also increased. When the rotational force per motor volume is taken into consideration, the efficiency per motor volume may be reduced due to an increase in the space of the rotor boss 119 that is not involved in a typical rotational force. Further, in the second conventional example, there is a possibility that the magnetic path becomes longer and the magnetic resistance and loss increase as much as the pole teeth of the outer yoke 101 are separated from the coil assembly 105 by the thickness of the magnet.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to improve the rotational torque, to increase the rotational efficiency during low-speed rotation and high-speed rotation to increase the rotational efficiency, and to smoothly rotate. To reduce variations in torque ripple, to stabilize the stationary position accuracy of the rotor, to rotate in fine steps, to be economical with good mass productivity, to reduce vibration, and to reduce noise due to foreign matter entry prevention. The purpose of the present invention is to reduce the adverse magnetic effect between the yokes.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a rotor having a ring-shaped permanent magnet whose inner and outer circumferences are multipolarly magnetized on both sides, a rotor boss and a shaft, a mounting portion and a bearing. A plate, a large-diameter outer yoke having a plurality of pole teeth protruding from the disc-shaped collar, a large-diameter inner yoke having a plurality of pole teeth protruding from the disc-shaped collar, and protruding from the disc-shaped collar A small-diameter outer yoke having a plurality of pole teeth, a small-diameter inner yoke having a plurality of pole teeth protruding from a disc-shaped flange, a large-diameter coil assembly, and a small-diameter coil assembly. The outer yoke and the inner peripheral surface of the permanent magnet are arranged with a small gap therebetween, and the large-diameter inner yoke, the large-diameter outer yoke and the outer peripheral surface of the permanent magnet are arranged with a small gap therebetween.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to a mounting plate having a ring-shaped permanent magnet whose inner and outer circumferences are multipolarly magnetized on both sides, a rotor having a rotor boss and a shaft, a mounting portion and a bearing. A large-diameter outer yoke having a plurality of pole teeth protruding from the disc-shaped flange, a large-diameter inner yoke having a plurality of pole teeth protruding from the disc-shaped collar, and protruding from the disc-shaped collar. A small-diameter inner yoke having a plurality of pole teeth, a small-diameter outer yoke having a plurality of pole teeth protruding from a disc-shaped flange, a large-diameter coil assembly, and a small-diameter coil assembly; The inner peripheral surfaces of the yoke and the permanent magnet are disposed with a small gap therebetween, and the outer peripheral surfaces of the large-diameter inner yoke and the large-diameter outer yoke and the permanent magnet are disposed with a small gap therebetween. With this configuration,
The small-diameter stator including the small-diameter outer yoke, the small-diameter inner yoke, and the small-diameter coil assembly, and the large-diameter outer yoke, the large-diameter inner yoke, and the large-diameter coil assembly are respectively provided on an inner portion and an outer portion of the permanent magnet. By arranging the large-diameter stator, the rotor is excited and driven by the small-diameter stator and the large-diameter stator, so that not only the outer part but also the inner part of the permanent magnet can contribute to the magnetic rotational force. Rotating torque is generated in both the inner part and the outer part, which has the effect of increasing the torque and increasing the torque efficiency per motor volume.

According to a second aspect of the present invention, the winding specification for winding the large-diameter coil assembly is different from the winding specification for winding the small-diameter coil assembly. PM type stepping motor.

As described above, by changing the specifications of the two windings, a winding specification having good rotation efficiency and rotation torque in the high-speed rotation region and a winding specification having good rotation efficiency and rotation torque in the low-speed rotation region are provided. It can be set separately, and if necessary, switch the coil assembly to be energized or work together to improve the rotational efficiency during high-speed rotation, energize and excite the winding on the impedance side for high-speed rotation, and rotate at low speed. In order to improve the rotational efficiency in some cases, the winding on the impedance side for low-speed rotation is energized and excited to have an effect of efficiently rotating.

According to a third aspect of the present invention, the permanent magnet is separated into a small-diameter permanent magnet and a large-diameter permanent magnet, and the pitch P of the pole teeth meshes with the center of the magnetic pole of the small-diameter permanent magnet. The center of the magnetic pole of the large-diameter permanent magnet is
2. The PM stepping motor according to claim 1, wherein the stepping motor is shifted by a factor of one. In this way, when the large-diameter permanent magnet and the small-diameter permanent magnet are shifted by a quarter of P in the rotational direction, in the 1-2-phase excitation drive, when the energization of the small-diameter stator is one phase, the energization of the large-diameter stator is performed. When the small-diameter stator is energized in two phases, the large-diameter stator is energized in one phase, so that the three coil assemblies are always energized to reduce the rotating torque ripple and stabilize the stationary position accuracy. Having. Also, in the two-phase excitation drive, by energizing the small-diameter stator and the large-diameter stator alternately, it has the effect of realizing the disassembly step equivalent to the 1-2-phase excitation.

According to a fourth aspect of the present invention, the permanent magnet is separated into a small-diameter permanent magnet and a large-diameter permanent magnet. The center of the magnetic pole of the large-diameter permanent magnet is P8 in the rotational direction.
2. The PM stepping motor according to claim 1, wherein the stepping motor is shifted by a factor of one. As described above, the large-diameter permanent magnet and the small-diameter permanent magnet are shifted by 1/8 of P in the rotation direction, so that the small-diameter stator side and the large-diameter stator side are alternately energized in the 1-2-phase excitation drive. , W1-2 phase excitation, that is, an operation capable of realizing a stationary step angle which is half that of the 1-2 phase excitation.

According to a fifth aspect of the present invention, in the PM stepping apparatus according to the first aspect, the outer peripheral portion of the bearing is fitted at least with the inner peripheral portion of the mounting plate, the inner peripheral portion of the small-diameter outer yoke, and the small-diameter inner yoke. It is a motor. As described above, by fitting the outer peripheral portion of the bearing with the small-diameter outer yoke and the small-diameter inner yoke, the small-diameter outer yoke and the small-diameter inner yoke can be easily assembled. In addition, the bearing, the mounting plate, the small-diameter outer yoke, and the small-diameter inner yoke have an effect of improving the assembly coaxiality. Further, since the bearing for rotatably supporting the shaft is increased in the axial direction, the bearing has an effect of stably supporting the shaft.

According to a sixth aspect of the present invention, there is provided the PM stepping motor according to the first aspect, wherein the side opposite to the mounting plate and the side of the motor are sealed by a cup-shaped frame. In this way, by keeping the side opposite to the mounting plate and the side of the motor in a sealed state, it has an effect of reducing the intrusion of foreign matter. In addition, the rotor is hermetically sealed and has an effect of preventing rotation of the rotor from becoming unstable due to contact with external components. In addition, the large-diameter outer yoke and the large-diameter inner yoke are configured to be fitted to the inside of the frame, and have an effect of facilitating assembly. In addition, by providing a bearing on the frame, the shaft is rotatably supported by the two bearings, and has a function of stably rotating.

According to a seventh aspect of the present invention, the rotor boss is arranged such that the small-diameter stator is separated vertically and vertically between the small-diameter stators, and the large-diameter stator is sandwiched between the mounting plate and the frame. 7. The PM stepping motor according to claim 6, wherein an axial height of the large-diameter stator is larger than that of the small-diameter stator. By providing the boss portion of the rotor at the center in this manner, the small-diameter inner yoke can be separated to reduce the volume of the motor to accommodate the rotor, and reduce the adverse magnetic influence exerted between the small-diameter inner yokes. It has the effect of doing. The large-diameter stator can be configured higher in the axial direction than the small-diameter stator.

[0015]

(Embodiment 1) The configuration of a first embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a PM according to a first embodiment of the present invention.
FIG. 2 is an exploded perspective view of the mold stepping motor, and FIG. 3 is a positional relationship diagram of the yoke and the permanent magnet in the rotation direction. 1 to 3, a ring-shaped permanent magnet 1 whose inner and outer circumferences are multipolarly magnetized on both sides, a rotor 4 having a rotor boss 2 and a shaft 3, a mounting plate 7 having a mounting portion 5 and a bearing 6, and a disk-shaped A large-diameter outer yoke 8 having a plurality of pole teeth protruding from the collar, a large-diameter inner yoke 9 having a plurality of pole teeth protruding from the disc-shaped collar, and a plurality of poles protruding from the disc-shaped collar. Small-diameter inner yoke 10 having teeth, small-diameter outer yoke 11 having a plurality of pole teeth protruding from a disk-shaped flange, large-diameter coil assembly 12, and small-diameter coil assembly 1
3, a large-diameter stator 1 comprising the large-diameter outer yoke 8, the large-diameter inner yoke 9, and the large-diameter coil assembly 12.
The magnetically stable position 5 and the magnetically stable position of the small-diameter stator 14 comprising the small-diameter outer yoke 11, the small-diameter inner yoke 10, and the small-diameter coil assembly 13 are the same in the rotational direction as shown in FIG. The small-diameter inner yoke 10 and the small-diameter outer yoke 11 and the inner peripheral surface of the permanent magnet 1 are disposed with a small gap therebetween, so that the large-diameter inner yoke 9 and the large-diameter outer yoke 8 The outer peripheral surface of the permanent magnet 1 is arranged with a small gap.

According to this configuration, the small-diameter stator 14 and the large-diameter stator 15 are disposed on the inside and the outside of the permanent magnet 1, respectively, so that the rotor 4 is excited by the small-diameter stator 14 and the large-diameter stator 15, Not only the outer part but also the inner part of the permanent magnet 1 can contribute to the magnetic torque.
The generated rotational torque has a function of becoming the torque obtained by adding the torque of the small-diameter stator 14 to the torque of the large-diameter stator 15, and it is possible to realize an excellent PM type stepping motor in which the torque is increased and the torque efficiency per motor volume is improved. Things.

As a further embodiment, a coil assembly will be described. The difference is that the number of turns or the wire diameter of the winding wound around the large diameter coil assembly 12 and the number of turns or the wire diameter of the winding wound around the small diameter coil assembly 13 are different from each other. When the yoke is not magnetically saturated, the rotational torque generated by energizing the coil is basically proportional to the product of the current value and the number of turns of the coil. In order to efficiently magnetize and rotate the yoke in a limited volume occupied by the coil, an optimum winding specification must be set. That is, if the wire diameter, the number of turns, and the resistance value of the winding are optimally selected, the rotation can be performed efficiently. For example, a large-diameter coil assembly 12 is configured with a winding specification in which a low rotation speed, that is, an input signal efficiently rotates in a low-frequency region, and a small-diameter coil, in which a high rotation speed, that is, a winding specification in which an input signal rotates efficiently in a high-frequency region. When the assembly 13 is configured, when rotating at a low speed, the large-diameter coil assembly 12 is energized and rotated.
In the case of high-speed rotation, the small-diameter coil 13 is energized and rotated, so that the coil assembly to be energized can be selected according to the required number of rotations. An excellent PM type that can efficiently rotate at each required number of rotations A stepping motor can be realized.

(Embodiment 2) Hereinafter, the operation of the second embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a half sectional view of a stator of a PM type stepping motor according to a second embodiment of the present invention, and FIGS. 5 and 6 are positional diagrams of a yoke and a permanent magnet in the rotation direction. 4 to 6, the point that the small-diameter stator 14 and the large-diameter stator 15 are configured is the same as in FIGS. 1 to 3 showing the first embodiment.

The difference from the configurations of FIGS. 1 to 3 is that, as shown in FIG. 5, the permanent magnet 1 is separated into a small-diameter permanent magnet 21 and a large-diameter permanent magnet 22, and the pitch P of the pole teeth meshes with each other.
The center of the magnetic pole of the small-diameter permanent magnet 21 and the center of the magnetic pole of the large-diameter permanent magnet 22 are shifted from each other by a quarter of P in the rotational direction. As described above, the large-diameter permanent magnet 22 and the small-diameter permanent magnet 21 are shifted by a quarter of P in the rotational direction, so that the small-diameter stator 1
When the energization of the stator 4 is one-phase, the energization of the large-diameter stator 14 is set to two phases, and when the energization of the small-diameter stator 14 is two-phase, the energization of the large-diameter stator 15 is set to one phase. Since the coils 15 and 15 are energized at the same time, the three coil assemblies are always energized and are not simultaneously energized alternately in the four-phase and two-phase modes. , And an excellent PM stepping motor that stabilizes the stationary position accuracy can be realized. Also, in the two-phase excitation drive, the small-diameter stator 14 and the large-diameter stator 15 are alternately energized to realize a disassembly step equivalent to the 1-2-phase excitation. It is clear that the stationary position accuracy is more stable in the case of. For example, in a PM type stepping motor having a structure in which two coil assemblies are stacked vertically in the axial direction at a basic step angle of 7.5 degrees, P
= 15 degrees, and the deviation between the large-diameter permanent magnet 22 and the small-diameter permanent magnet 21 is 3.75 degrees. In this case, when the large-diameter stator 15 and the small-diameter stator 14 are simultaneously driven by the 1-2-phase excitation, the magnetically stable position of the large-diameter stator 15 and the magnetically stable position of the small-diameter stator 14 coincide with each other. In this state, the coils are rotated by .75 degrees, and three of the four coil assemblies are always energized. When the large-diameter stator 15 and the small-diameter stator 14 are alternately energized by the two-phase excitation, the magnetically stable positions of the large-diameter stator 15 and the small-diameter stator 14 are shifted by 3.75 degrees, so that they are always 3.75 degrees. Rotation, that is, a decomposition step equivalent to 1-2 phase excitation can be realized.

As a further embodiment, as shown in FIG.
The permanent magnet 1 is composed of a small-diameter permanent magnet 21 and a large-diameter permanent magnet 22.
And the center of the magnetic pole of the small-diameter permanent magnet 21 and the center of the magnetic pole of the large-diameter permanent magnet 22 are shifted by 1/8 of P in the rotation direction with respect to the pitch P at which the pole teeth mesh. There is. As described above, the large-diameter permanent magnet 22 and the small-diameter permanent magnet 21 are shifted by 分 の of P in the rotation direction,
In the 1-2-phase excitation drive, by energizing the small-diameter stator 14 and the large-diameter stator 15 alternately, W1-2-phase excitation, that is, an operation capable of realizing a stationary step angle that is half that of the 1-2-phase excitation, is achieved. An excellent PM type stepping motor that can reduce rotation unevenness and rotate smoothly by rotation can be realized.

For example, in a PM type stepping motor having a structure in which two coil assemblies are stacked vertically in the axial direction at a basic step angle of 7.5, P = 15 degrees, and the displacement between the large-diameter permanent magnet 22 and the small-diameter permanent magnet 21 is 1. 875 degrees. In this case, the angle of rotation when excited by the large-diameter stator 15 and the small-diameter stator 14 is 3.75 degrees, but the deviation between the large-diameter permanent magnet 22 and the small-diameter permanent magnet 21 is one-half of 3.75 degrees. .875 degrees, large-diameter stator 15
And the small-diameter stator 14 are alternately excited by a 1-2-phase excitation drive method, so that the current is supplied to the large-diameter stator 15 for one phase → the small-diameter stator 14 for one phase → the large-diameter stator 15 for two phases → the small-diameter stator 14 for two phases. Repeated phase → ... 1.875
Can rotate by degrees.

In this embodiment, two permanent magnets 1 are used.
The center of the magnetic poles of the two permanent magnets is shifted in the rotation direction, but the magnetic poles of the permanent magnets are not shifted, but the center of the magnetic poles when the small-diameter stator 14 is energized and the large-diameter stator 15 are energized. Even if the center of the magnetic pole at the time of
Obviously, a similar effect can be obtained, and the permanent magnet need not be separated into two.

(Embodiment 3) Hereinafter, the configuration of a third embodiment of the present invention will be described with reference to the drawings. In FIG. 7, the point that the small-diameter stator 14 and the large-diameter stator 15 are configured is the same as in FIGS. The difference from FIGS. 1 to 3 is that the outer peripheral portion of the bearing 6 is fitted at least with the mounting plate 7, the small-diameter outer yoke 11, and the small-diameter inner yoke 10. As described above, by fitting the outer peripheral portion of the bearing 6 with the mounting plate 7, the small-diameter outer yoke 11, and the small-diameter inner yoke 10, the assembly of the small-diameter outer yoke 11 and the small-diameter inner yoke 10 is facilitated. The assembly coaxiality of the mounting plate 7 and the small-diameter outer yoke 11 and the small-diameter inner yoke 10 is improved, and the bearing 6 that rotatably supports the shaft 3 is long in the axial direction, so that the shaft 3 can be stably supported. It is possible to realize an excellent PM stepping motor which has an action, is economical with good mass productivity, is economical, has improved assembly coaxiality, and has low vibration.

(Embodiment 4) Hereinafter, the configuration of a fourth embodiment of the present invention will be described with reference to the drawings. In FIG. 8, the point that the small-diameter stator 14 and the large-diameter stator 15 are configured is the same as in FIGS. The difference from FIGS. 1 to 3 is that the cup-shaped frame 30 closes the side opposite to the mounting plate and the side of the motor. In this way, by keeping the side opposite to the mounting plate and the side of the motor in a sealed state, it has an effect of reducing the intrusion of foreign matter. In addition, the rotor 4 is sealed, and has an effect of preventing rotation of the rotor from becoming unstable due to contact with external components. In addition, the large-diameter outer yoke 8 and the large-diameter inner yoke 9 are configured to be fitted inside the frame 30, and have an effect of facilitating assembly. By providing the bearings 6 on the frame 30, the shaft 3 is rotatably supported by the two bearings 6, and has an effect of stably supporting and rotating the shaft 3 at two points.

With the above-described operation, in the present embodiment, foreign matter is prevented from being mixed, and a PM type stepping motor excellent in low vibration and low noise can be realized. In this embodiment, two coil assemblies are stacked vertically in the axial direction. However, in the first to fourth embodiments, a multi-phase stator structure in which three or more coil assemblies are stacked vertically in the axial direction is also used. Similar effects can be obtained.

(Embodiment 5) Hereinafter, a fifth embodiment of the present invention will be described with reference to the drawings. 9 is similar to FIG. 8 showing the fourth embodiment in that the motor is closed by the frame 30. What is different from FIG. 8 is that the rotor boss 2 is arranged at a central portion where the small-diameter stator 14 is separated vertically in the axial direction, and the large-diameter stator 15 is sandwiched between the mounting plate 7 and the frame 30; The axial height of the large-diameter stator 15 is larger than that of the small-diameter stator 14. By providing the rotor boss 2 at the center in this manner, the small-diameter inner yoke 10 can be separated and the rotor can be housed by reducing the volume of the motor. Thus, an excellent PM stepping motor having a stable stationary position accuracy can be realized. In addition, the large-diameter stator 15 has an effect that it can be configured higher in the axial direction than the small-diameter stator 14, and can realize an excellent PM type stepping motor with high torque.

[0028]

As is apparent from the above embodiment, the first aspect of the present invention is as follows.
According to the invention described above, the rotor is excited by the small-diameter stator and the large-diameter stator by arranging the small-diameter stator and the large-diameter stator on the inner side and the outer side of the permanent magnet, respectively. In addition, the inner space can also contribute to the magnetic torque, and the generated rotational torque is the torque obtained by adding the torque from the large-diameter stator to the torque from the small-diameter stator. Thus, it is possible to realize a PM type stepping motor having excellent torque efficiency.

According to the second aspect of the present invention, the winding specifications for winding the large-diameter coil assembly and the winding specifications for winding the small-diameter coil assembly are configured to be different from each other, so that the efficiency at a low rotation speed is improved. The coil specifications to be energized can be selected according to the required number of rotations by separately setting the winding specification that is good and the winding specification that is efficient at high speed. , A PM-type stepping motor can be realized.

According to the third aspect of the present invention, the center of the magnetic pole of the small-diameter permanent magnet and the center of the magnetic pole of the large-diameter permanent magnet are quarter of P in the rotational direction with respect to the pitch P at which the pole teeth mesh. With this configuration, the variation of the rotary torque ripple in the 1-2 phase excitation can be reduced, and an excellent PM stepping motor capable of stabilizing the stationary position accuracy in the two phase excitation can be realized.

According to the fourth aspect of the present invention, the center of the magnetic pole of the small-diameter permanent magnet and the center of the magnetic pole of the large-diameter permanent magnet are eight minutes of P in the rotational direction with respect to the pitch P at which the pole teeth mesh. In the 1-2-phase excitation driving, the small-diameter stator and the large-diameter stator are alternately energized to reduce the stationary step angle of W1-2-phase excitation, that is, half of the 1-2-phase excitation. As a result, it is possible to realize an excellent PM type stepping motor that can be smoothly rotated at a fine step angle.

According to the fifth aspect of the present invention, the outer peripheral portion of the bearing is fitted with at least the mounting plate, the small-diameter outer yoke and the small-diameter inner yoke. Excellent P that can be driven with improved vibration
An M-type stepping motor can be realized.

According to the sixth aspect of the present invention, by providing the cup-shaped frame, it is possible to realize an excellent PM type stepping motor capable of preventing foreign matters from entering and reducing abnormal noise.

According to the seventh aspect of the present invention, the rotor boss is disposed at a central portion of the small-diameter stator separated vertically in the axial direction, and the large-diameter stator is sandwiched between the mounting plate and the frame. By setting the height dimension larger than that of the small-diameter stator, it is possible to realize an excellent PM type stepping motor that can increase the torque while reducing magnetic adverse effects between the yokes.

[Brief description of the drawings]

FIG. 1 is a half sectional view of a PM type stepping motor according to a first embodiment of the present invention.

FIG. 2 is an exploded perspective view of a PM type stepping motor according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a positional relationship between a yoke and a permanent magnet of a PM type stepping motor in a rotation direction according to the first embodiment of the present invention.

FIG. 4 is a half sectional view of a stator of a PM type stepping motor according to a second embodiment of the present invention.

FIG. 5 is a view showing a positional relationship between a yoke of a PM type stepping motor and a permanent magnet in a rotation direction according to a second embodiment of the present invention.

FIG. 6 is a diagram showing a positional relationship between a yoke of a PM type stepping motor and a permanent magnet in a rotation direction according to a second embodiment of the present invention.

FIG. 7 is a half sectional view of a PM stepping motor according to a third embodiment of the present invention.

FIG. 8 is a half sectional view of a PM stepping motor according to a fourth embodiment of the present invention.

FIG. 9 is a half sectional view of a PM type stepping motor according to a fifth embodiment of the present invention.

FIG. 10 is a half sectional view of a conventional stepping motor.

FIG. 11 is a half sectional view of a conventional stepping motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1,115 Permanent magnet 2,119 Rotor boss 3,113 Shaft 4 Rotor 5 Mounting part 6 Bearing 7,111 Mounting plate 8 Large diameter outer yoke 9 Large diameter inner yoke 10 Small diameter inner yoke 11 Small diameter outer yoke 12 Large diameter coil assembly 13 Small diameter Coil assembly 14 Small diameter stator 15 Large diameter stator 21 Small diameter permanent magnet 22 Large diameter permanent magnet 30 Frame 101 Outer yoke 103 Inner yoke 105 Coil assembly 107 Bearing 109 Bracket

Claims (7)

[Claims] 1. A rotor having a ring-shaped permanent magnet whose inner and outer circumferences are multipolarly magnetized on both sides, a rotor boss and a shaft, a mounting plate having a mounting portion and a bearing, and a plurality of disc-shaped flanges. A large-diameter outer yoke having pole teeth, and a large-diameter inner yoke having a plurality of pole teeth protruding from a disc-shaped flange;
A small-diameter outer yoke having a plurality of pole teeth protruding from a disc-shaped flange, a small-diameter inner yoke having a plurality of pole teeth protruding from a disc-shaped collar, a large-diameter coil assembly, and a small-diameter coil assembly PM type stepping motor. 2. A winding specification for winding a large-diameter coil assembly,
2. The PM stepping motor according to claim 1, wherein winding specifications for winding the small-diameter coil assembly are different from each other. 3. The permanent magnet is separated into a small-diameter permanent magnet and a large-diameter permanent magnet, and the center of the magnetic pole of the small-diameter permanent magnet and the center of the magnetic pole of the large-diameter permanent magnet are aligned with respect to the pitch P at which the pole teeth mesh. 2. The P according to claim 1, wherein the P is shifted by a quarter of P.
M type stepping motor. 4. A permanent magnet is separated into a small-diameter permanent magnet and a large-diameter permanent magnet, and the center of the magnetic pole of the small-diameter permanent magnet and the center of the magnetic pole of the large-diameter permanent magnet are rotated with respect to the pitch P at which the pole teeth engage. 2. The apparatus according to claim 1, wherein the shift is made 1/8 of P in the direction.
The described PM stepping motor. 5. The PM stepping motor according to claim 1, wherein an outer peripheral portion of the bearing is fitted with at least an inner peripheral portion of the mounting plate, the small-diameter outer yoke, and the small-diameter inner yoke. 6. The PM stepping motor according to claim 1, wherein the side opposite to the mounting plate and the side of the motor are sealed by a cup-shaped frame. 7. The rotor boss includes a small-diameter stator vertically and vertically separated and disposed therebetween, and a large-diameter stator sandwiched between a mounting plate and a frame, wherein the large-diameter stator has an axial height dimension of the small-diameter stator. 7. The PM type stepping motor according to claim 6, wherein the motor is larger.