JP2005080362A - Permanent magnet stepping motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a PM type stepping motor which can obtain a minute step angle without enlarging the entire length in an axial direction. <P>SOLUTION: The PM type stepping motor includes a rotor 120 having a cylindrical permanent magnet 122 alternately magnetized at S-poles and N-poles at the same pitch in a circumferential direction, and a stator 130 having claw pole unit stators 130a, 130b and 130c each having a bifilar wound coil 134 and aligned in an axial direction. A pair of yoke elements 131, 132 of each unit stator are assembled so that polarized teeth 131a, 132a are alternately arranged at an equal pitch. A drive circuit has 12 pieces of switching elements in which first switching elements for connecting or disconnecting a power source potential and second switching elements for connecting or disconnecting a ground potential are disposed at 6 pieces of coupling points of the annularly connected coil, and which are rotated at an electrical angle of 360° by 12 steps. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a permanent magnet type (PM type) stepping motor suitable for use in office automation equipment such as printers, high-speed facsimiles, and PPC copying machines.

  There are a plurality of types of PM stepping motors having different numbers of phases, such as single phase, two phases, three phases or more. Single-phase PM type stepping motors are mainly used for driving hands for analog watches, but it is necessary to shift the magnetic permeance and phase between the magnetic poles of the stator and rotor so that the rotation direction of the motor is determined. It is not suitable for equipment that requires high speed rotation and high torque.

Therefore, stepping motors of two or more phases are used in office automation equipment such as printers, high-speed facsimiles, and PPC copying machines.
FIG. 10 is a vertical side view of a conventional two-phase PM type stepping motor.
A two-phase PM type stepping motor 10 shown in FIG. 10 includes two parallel plates 11 and 12 constituting a fixed portion, and a rotor 13 that is rotatably supported in a space surrounded by the plates 11 and 12. And a stator 14 disposed between the plates 11 and 12 so as to surround the rotor 13.
The rotor 13 is integrally fixed to the rotary shaft 13a, a rotary shaft 13a attached via a bearing 11a fixed to the center of the plate 11, a bearing 12a fixed to the center of the plate 12, and It is composed of a cylindrical permanent magnet 13b in which S and N poles are alternately magnetized at the same pitch in the circumferential direction.

  On the other hand, the stator 14 includes two annular unit stators 14a and 14b juxtaposed in the axial direction. Each of the unit stators 14a and 14b has a pair of yoke elements 15 and 16 having comb-like pole teeth formed at a pitch facing the magnetic poles of the rotor 13, and the pole teeth are alternately arranged at an equal pitch. The coil 18 wound around the bobbin 17 is arranged inside the pair of yoke elements thus combined.

FIG. 11 is a longitudinal side view showing a conventional five-phase PM type stepping motor 20. The basic structure is the same as the two-phase case shown in FIG.
That is, the rotor 23 is attached via bearings 21a and 22a provided on the plates 21 and 22, and the stator 24 is configured by juxtaposing five unit stators 24a to 24e in the axial direction. The structure of each unit stator is the same as that of the two-phase case shown in FIG.
The following Patent Document 1 discloses a three-phase PM type stepping motor.

Japanese Patent Laid-Open No. 11-225467 FIG.

  The two-phase PM type stepping motor 10 shown in FIG. 10 and the three-phase PM type stepping motor disclosed in Patent Document 1 can obtain a higher torque and can rotate at a higher speed than the single-phase case. However, in order to reduce the step angle without increasing the number of phases, it is necessary to increase the number of pole teeth. Therefore, it is difficult to manufacture a product having a small step angle.

  On the other hand, in order to reduce the step angle without increasing the number of pole teeth of the unit stator, the number of phases may be increased. However, if the number of phases is increased by monofilar winding of the coil, the five phases shown in FIG. It is necessary to increase the number of unit stators as in the PM type stepping motor 20, and there is a problem that the total length of the entire motor in the axial direction is increased.

  An object of the present invention is to provide a PM-type stepping motor capable of obtaining a minute step angle without increasing the overall length in the axial direction in order to solve the above-described problems (issues) of the prior art. To do.

  In order to solve the above-described problem, a PM stepping motor according to a first aspect of the present invention has an outer periphery mounted on a rotary shaft attached to a fixed portion via a pair of bearings arranged at both ends in the axial direction of the fixed portion. The rotor is configured by integrally fixing a cylindrical permanent magnet in which S poles and N poles are alternately magnetized at the same pitch in the circumferential direction, and is opposed to the outer periphery of the rotor via a predetermined gap. A pair of yoke elements having comb-shaped pole teeth formed at a pitch facing the magnetic poles of the rotor on the inner peripheral side so that the pole teeth are alternately arranged at an equal pitch. There is a stator that is configured by attaching n unit stators (n is an odd number of 3 or more) in the axial direction and attaching them to the fixing part. When the magnetization pitch angle between the different poles of the rotor is P The n unit stators are arranged so that the pole teeth of each one of the yoke elements are shifted by an angle of 2P / n, the 2n coils are connected in a ring shape, and connected to the power supply potential at each of the 2n coupling points. A drive circuit having 4n switching elements in which a first switching element for disconnecting and a second switching element for connecting / disconnecting to the ground potential are rotated by an electrical angle of 360 ° in 4n steps. It is configured.

  Further, in the PM type stepping motor according to claim 2, on the premise of the configuration of claim 1, the stator is composed of three unit stators, and the pole teeth of each one of the yoke elements are shifted by an angle 2P / 3. The coil is configured to be rotated at an electrical angle of 360 ° in 12 steps by a drive circuit having 12 switching elements coupled to 6 terminals.

According to the configuration of the first aspect of the present invention, the coil is bifilar wound, so that the number of phases can be increased and a minute step angle can be obtained without increasing the total axial length. Further, since the length of the rotor is about half that of the conventional example having the same number of phases, the rotor inertia can be halved to enable high-speed rotation.
Furthermore, by connecting the coils in an annular shape, the rise of the single step response is quick, vibration is suppressed, and vibration during rotation can be suppressed low.

  Further, in the case of n = 3, the configuration of claim 2 is obtained, and the axial length can be halved while maintaining the same step angle as compared with the conventional 6-phase PM type stepping motor. it can.

The best mode for carrying out the PM type stepping motor according to the present invention will be described below with reference to the drawings.
FIG. 1 is a longitudinal side view of a six-phase PM stepping motor 100 of this embodiment, and FIG. 2 is an exploded perspective view of the PM stepping motor 100 shown in FIG.

As shown in FIG. 1, the 6-phase PM type stepping motor 100 according to the present embodiment includes two parallel plates 111 and 112 constituting a fixed portion, and a space surrounded by the plates 111 and 112. The rotor 120 is rotatably supported, and the stator 130 is disposed between the plates 111 and 112 so as to surround the rotor 120.
The rotor 120 includes a rotation shaft 121 attached via bearings 113 and 114 fixed to both ends of the fixed portion in the axial direction, that is, the center of the plate 111 and the center of the plate 112, and the rotation shaft 121. It is composed of a cylindrical permanent magnet 122 that is fixed integrally and is alternately magnetized with S and N poles at the same pitch in the circumferential direction.

On the other hand, the stator 130 includes n pieces of unit stators 130a, 130b, and 130c arranged in parallel in the axial direction, in this example, three annular unit stators 130a, 130b, and 130c.
As shown in FIG. 2, the first unit stator 130 a is a claw pole type unit stator, and comb-shaped pole teeth 131 a and 132 a formed at a pitch facing the magnetic poles of the rotor 120. A pair of yoke elements 131 and 132 having the above structure is combined, and a coil 134 wound around a bobbin 133 is arranged inside the combined pair of yoke elements. The second and third unit stators 130b and 130c are configured similarly to the unit stator 130a.

  The plates 111 and 112, the rotor 120, and the stator 130 assembled in the state of FIG. 1 are accommodated in a cup-shaped casing 115 shown in FIG. To do. In FIG. 1, the casing 115 and the lid body 116 are not illustrated, and in FIG. 2, the plates 111 and 112 are not illustrated.

  Next, the positional relationship between the pole teeth formed on the yoke elements of the unit stators 130a, 130b, and 130c and the magnetic poles of the permanent magnet 122 formed on the outer periphery of the rotor 120 is based on the developed view of FIG. explain.

Let τs be the interval between the pole teeth 131a of one yoke element 131 of each unit stator. The interval between the pole teeth 132a of the other yoke element 132 is also τs.
The pair of yoke elements 131 and 132 are combined so that the pole teeth 131a and 132a are alternately arranged at an equal pitch.
That is, in each unit stator, the pole teeth 131a of one yoke element 131 are arranged so as to be shifted from the pole teeth 132a of the other yoke element 132 by τs / 2.

Next, let P be the magnetization pitch angle between the different poles of the rotor 120 (the distance between the N pole and the adjacent S pole). Here, τs = 2P. The n unit stators are arranged such that the pole teeth of each one of the yoke elements are shifted by an angle of 2P / n.
In this example, three unit stators 130a, 130b, and 130c are arranged such that the pole teeth 131a of each one of the yoke elements 131 are sequentially shifted by an angle 2P / 3. Incidentally, since the pole teeth 132a of the other yoke element 132 have the same pitch, the pole teeth of the yoke element 132 are also shifted by an angle of 2P / 3 in order.
According to such an arrangement, as shown in FIG. 3, when the pole teeth 131a of one yoke element 131 of the first unit stator 130a are opposed to the N pole of the permanent magnet 122, the first unit fixing is performed. The pole teeth 132a of the other yoke element 132 of the child 130a are opposite to the S pole, and the pole teeth of the second and third unit stators 130b and 130c are shifted by P / 3 from the nearest magnetic pole, respectively. It is in.

  The coils 134 wound around the unit stators 130a, 130b, and 130c of the stator 130 are bifilar windings, and are equivalent to winding a two-phase coil around one unit stator. is there. FIG. 4 is a circuit diagram showing coil connections, and FIG. 5 is a simplified explanatory diagram of the coil arrangement of each unit stator.

  2n coils, that is, six coils in this example, are connected in a ring shape, and terminals A to F are provided at six coupling points. 4 and 5, the terminals of the coils connected to the terminals A to F are represented by a to f.

  The driving circuit includes a first switching element for connecting / disconnecting to the power supply potential and a second switching element for connecting / disconnecting to the ground potential at each of the 2n coupling points of the annularly connected coils. And 4n switching elements.

  In this example, as shown in FIG. 6, the terminal A connected to the coupling line is connected to and disconnected from the transistor TrA1, which is a first switching element for connecting / disconnecting to the power supply potential + E, and to the ground potential. Therefore, the transistor TrA2, which is a second switching element, is connected. Similarly, two transistors TrB1, TrB2, TrC1, TrC2, TrD1, TrD2, TrE1, TrE2, TrF1, and TrF2 are connected to the terminals B to F connected to the respective coupling points, for a total of 12 transistors. A drive circuit is configured.

The 6-phase PM type stepping motor 100 of the present embodiment is rotated by an electrical angle of 360 ° in 12 steps by a drive circuit having 12 switching elements shown in FIG.
Next, the operation of the above 6-phase PM type stepping motor 100 will be described with reference to FIGS.

FIG. 7 is a table showing an excitation sequence when the six-phase PM type stepping motor 100 of the present embodiment is four-phase excited, and shows terminals in the vertical direction and excitation steps in the horizontal direction.
FIG. 8 is an explanatory diagram showing a current direction and a magnetic field vector in each step when excitation is performed according to this excitation sequence.
FIG. 9 is a developed view showing the positional relationship between the pole teeth of the yoke element and the magnetic poles of the rotor in each step when excitation is performed according to this excitation sequence.

In the circuit configuration of FIG. 6, as shown in FIG. 7, in the excitation step R, the transistors TrA1, TrC2, TrE2 are turned on, the power supply potential + E is applied to the terminal a, and the terminals c, e are set to the ground potential.
Thus, as shown in FIG. 8 (R), current flows from terminals a to b to c, and from terminals a to f to e, and the magnetic field vector is directed from terminals a to d, that is, It faces downward in the figure.

As can be seen from FIG. 5, inward currents flow from b to c and from f to e through the two coils of the third unit stator 130c. The outward current flows from a to b and from a to f in one coil of the two coils and the second unit stator 130b.
As a result, the pole teeth 131a of one yoke element 131 of the third unit stator 130c are excited to the N pole, and the pole teeth 132a of the other yoke element 132 are excited to the S pole, so that the first and second unit stators 130a are excited. , 130b, the pole teeth 131a of one yoke element 131 are excited to the S pole, and the pole teeth 132a of the other yoke element 132 are excited to the N pole. However, the magnetic force generated in the first and second unit stators 130a and 130b is about half of the magnetic force generated in the third unit stator 130c.

  In the following description, a magnetic field generated when a current flows through one coil is referred to as a “weak” magnetic field, and a magnetic field generated when a current in the same direction flows through two coils is referred to as a “strong” magnetic field. Further, in FIG. 9, the polar teeth having a strong magnetic field are indicated by a circle in the polarities N and S, and the polar teeth having a weak magnetic field are indicated by only the polarities N and S. Show. Further, in order to indicate the relative rotational position of the rotor 120, a specific N pole of the rotor 120 is marked with a black dot.

  In the excitation step R, as shown in FIG. 9R, in the rotor 120, the S pole faces the pole teeth 131a of one yoke element 131 of the third unit stator 130c, and the N pole is the third pole. The unit stator 130c is held at a position facing the pole teeth 132a of the other yoke element 132.

Next, in excitation step 1, the transistors TrA1, TrB1, TrD2, and TrE2 are turned on to apply the power supply potential + E to the terminals a and b, and the terminals d and e are set to the ground potential.
As a result, as shown in FIG. 8 (1), current flows from terminals b to c to d, from terminals a to f to e, and the magnetic field vector rotates 30 ° clockwise.

As can be seen with reference to FIG. 5, outward current flows from two coils of the second unit stator 130 b toward a to f and c to d, and 2 of the third unit stator 130 c. An inward current flows from b to c and from f to e through the coils.
As a result, the pole teeth 131a of one yoke element 131 of the second unit stator 130b are excited to the strong S pole, and the pole teeth 132a of the other yoke element 132 are excited to the strong N pole, so that the third unit stator 130c The pole teeth 131a of one yoke element 131 are excited to a strong N pole, and the pole teeth 132a of the other yoke element 132 are excited to a strong S pole. Further, the magnetic forces generated by the second and third unit stators 130b and 130c are the same.

  For this reason, in the excitation step 1, as shown in FIG. 9 (1), the rotor 120 has the S pole of the pole teeth 132a of the yoke element 132 of the second unit stator 130b and the third unit stator 130c. Opposite the intermediate point of the yoke element 131 with the pole teeth 131a, the N pole is the pole teeth 131a of the yoke element 131 of the second unit stator 130b and the pole teeth 132a of the yoke element 132 of the third unit stator 130c. Rotate to a position facing the midpoint of In other words, the rotor 120 is rotated by an angle P / 6 by shifting from the excitation step R to 1.

  Next, in excitation step 2, the transistors TrB1, TrD2, and TrF2 are turned on to apply the power supply potential + E to the terminal b, and the terminals d and f are set to the ground potential. Thereby, as shown in (2) of FIG. 8, current flows from terminal b to c through terminal d, from terminal b through terminal a through f, and the magnetic field vector rotates 30 ° clockwise.

As can be seen from FIG. 5, outward current flows from two coils of the second unit stator 130b toward a to f and c to d, and 1 of the first unit stator 130a. An inward current flows from b to a and from b to c through the two coils and one coil of the third unit stator 130c.
As a result, the pole tooth 131a of one yoke element 131 of the second unit stator 130b is excited to the strong S pole, and the pole tooth 132a of the other yoke element 132 is excited to the strong N pole, and the first unit stator 130a The pole tooth 131a of one yoke element 131 with the third unit stator 130c is excited to a weak N pole, and the pole tooth 132a of the other yoke element 132 is excited to a weak S pole.

For this reason, in the excitation step 2, as shown in FIG. 9B, in the rotor 120, the S pole faces the pole teeth 132a of the yoke element 132 of the second unit stator 130b, and the N pole is the second. The unit stator 130b rotates to a position facing the pole teeth 131a of the yoke element 131.
In other words, the rotor 120 rotates by an angle P / 6 in the transition from the excitation step 1 to 2.

Next, in excitation step 3, the transistors TrB1, TrC1, TrE2, and TrF2 are turned on to apply the power supply potential + E to the terminals b and c, and the terminals e and f are set to the ground potential.
Thereby, as shown in (3) of FIG. 8, a current flows from terminal b to a through f and from terminal c through d to e, and the magnetic field vector rotates 30 ° clockwise.

As can be seen with reference to FIG. 5, inward currents flow from b to a and from d to e through the two coils of the first unit stator 130a, and 2 coils of the second unit stator 130b. An outward current flows through the coils from a to f and from c to d.
As a result, the pole tooth 131a of one yoke element 131 of the first unit stator 130a is excited to a strong N pole, and the pole tooth 132a of the other yoke element 132 is excited to a strong S pole, and the second unit stator 130b The pole tooth 131a of one yoke element 131 is excited to the strong south pole, and the pole tooth 132a of the other yoke element 132 is excited to the strong north pole.

  For this reason, in the excitation step 3, as shown in FIG. 9 (3), the rotor 120 has the S pole of the pole teeth 131a of the yoke element 131 of the first unit stator 130a and the second unit stator 130b. Opposite the intermediate point of the yoke element 132 with the pole teeth 132a, the N pole is the pole teeth 132a of the yoke element 132 of the first unit stator 130a and the pole teeth 131a of the yoke element 131 of the second unit stator 130b. Rotate to a position facing the midpoint of In other words, the rotor 120 rotates by an angle P / 6 in the transition from the excitation step 2 to 3.

Next, in excitation step 4, the transistors TrA2, TrC1, and TrE2 are turned on to apply the power supply potential + E to the terminal c, and the terminals a and e are set to the ground potential.
Thereby, as shown in (4) of FIG. 8, current flows from terminals c to b to a and from terminals c to d to e, and the magnetic field vector rotates 30 ° clockwise.

As can be seen with reference to FIG. 5, inward currents flow from b to a and from d to e through the two coils of the first unit stator 130a, and 1 of the second unit stator 130b. An outward current flows from c to d and from c to b through the two coils and one coil of the third unit stator 130c.
As a result, the pole tooth 131a of one yoke element 131 of the first unit stator 130a is excited to a strong N pole, and the pole tooth 132a of the other yoke element 132 is excited to a strong S pole, and the second unit stator 130b The pole teeth 131a of one yoke element 131 with the third unit stator 130c are excited to a weak S pole, and the pole teeth 132a of the other yoke element 132 are excited to a weak N pole.

  Therefore, in the excitation step 4, as shown in FIG. 9 (4), in the rotor 120, the S pole faces the pole teeth 131a of the yoke element 131 of the first unit stator 130a, and the N pole is the first. The unit stator 130a rotates to a position facing the pole teeth 132a of the yoke element 132. That is, the rotor 120 rotates by an angle P / 6 by the transition from the excitation step 3 to 4.

  In the same manner, by proceeding with excitation steps 5 to 11 as shown in FIG. 7, the magnetic field vector is set to an electric angle of 30 ° in one step and electric in 12 steps as shown in FIGS. 8 (5) to (11). Rotate 360 degrees. The rotor 120 rotates by a mechanical angle P / 6 in one step and 2P (= τs) in 12 steps.

As described above, the step angle can be set small without increasing the number of unit stators by exciting the coil by bifilar winding and performing four-phase excitation. Further, in the conventional bifilar winding configuration, the direction of the current flowing to each coil is determined, and the current in the opposite direction is passed to the two coils wound around one unit stator at different timings. It is controlled as follows.
Therefore, since only one coil is used for each unit stator for excitation, the generated torque is half that of the monofilar winding.
In the present embodiment, by providing two switching elements at the coupling point of the coils connected in a ring shape, a current in an arbitrary direction can be supplied to the two coils arranged in each unit stator.
Therefore, in the case of four-phase excitation, currents in the same direction can be passed through two coils arranged in one unit stator, and the generated torque is equivalent to that in the case of monofilar winding.

In this embodiment, the case where n = 3 has been described, but the present invention can also be applied to a case where n is an odd number of 5 or more.
For example, when n = 5, each unit stator is arranged by shifting the pole teeth of one yoke element by 2P / 5, and 2 for each of 10 terminals of 10 coils connected in an annular shape. Each unit is configured to rotate at an electrical angle of 360 ° in 20 steps by a drive circuit having a total of 20 switching elements.

  The PM type stepping motor of the present invention is applicable to applications that require a very small step angle in the fields of office equipment, medical equipment, home appliances, and the like.

It is a vertical side view of the 6-phase PM type stepping motor concerning an embodiment of the invention. It is a disassembled perspective view of the PM type stepping motor shown in FIG. FIG. 2 is a development view showing a positional relationship between pole teeth formed on a yoke element of the PM stepping motor shown in FIG. 1 and magnetic poles of a permanent magnet formed on the outer periphery of a rotor. It is a circuit diagram which shows the connection of the coil of the PM type stepping motor shown in FIG. It is explanatory drawing which simplified the coil arrangement | positioning of each unit stator of PM type stepping motor shown in FIG. It is a circuit diagram which shows the structure of the drive circuit of PM type | mold stepping motor shown in FIG. It is a table | surface which shows the excitation sequence in the case of carrying out 4 phase excitation of the PM type stepping motor shown in FIG. FIG. 8 is an explanatory diagram showing a current direction and a magnetic field vector in each step when the PM stepping motor shown in FIG. 1 is excited according to the excitation sequence of FIG. 7. FIG. 8 is a development view showing a positional relationship between pole teeth of a yoke element and magnetic poles of a rotor in each step when the PM type stepping motor shown in FIG. 1 is excited according to the excitation sequence of FIG. 7. It is a vertical side view which shows the structure of the conventional 2 phase PM type | mold stepping motor. It is a vertical side view which shows the structure of the conventional 5-phase PM type | mold stepping motor.

Explanation of symbols

100: 6-phase PM type stepping motor 111, 112: plate 120: rotor 121: rotating shaft 122: permanent magnet 130: stator 130a, 130b, 130c: unit stator 131, 132: yoke elements 131a, 132a: pole teeth 133: Bobbin 134: Coil

Claims (2)

A cylinder in which S and N poles are alternately magnetized at the same pitch in the circumferential direction on the outer peripheral portion on a rotating shaft attached to the fixed portion via a pair of bearings arranged at both ends in the axial direction of the fixed portion. A rotor configured by integrally fixing a permanent magnet,
A pair of yoke elements having comb-shaped pole teeth formed at a pitch facing the outer circumference of the rotor with a predetermined gap and facing the magnetic poles of the rotor on the inner circumference side, the pole teeth, etc. The number of annular unit stators configured by arranging bifilar-wound coils inside the pair of yoke elements combined so as to be alternately arranged at a pitch in the axial direction (n is an odd number of 3 or more) And a stator configured to be juxtaposed and attached to the fixed part,
When the magnetization pitch angle between the different poles of the rotor is P, the n unit stators are arranged such that the pole teeth of each one of the yoke elements are shifted by an angle of 2P / n, and 2n coils Are connected in a ring, and each of 2n coupling points is provided with a first switching element for connecting / disconnecting to the power supply potential and a second switching element for connecting / disconnecting to / from the ground potential. A permanent magnet type stepping motor characterized in that it is configured to rotate at an electrical angle of 360 ° in 4n steps by a drive circuit having individual switching elements. The stator is composed of three unit stators, each of which is arranged so that the pole teeth of one yoke element are shifted by an angle 2P / 3, and the coil is connected to 6 terminals and has 12 switching elements. 2. The permanent magnet type stepping motor according to claim 1, wherein the permanent magnet type stepping motor is configured to rotate by 360 degrees in an electrical angle of 360 degrees by a circuit.

Images