JP2006304424A - Stepping motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stepping motor which can reduce the static angle error to obtain a higher turn angle precision. <P>SOLUTION: The stepping motor comprises a bottomed cylindrical casing 1 made of a conductive metal, a substantially cylindrical stator 2 assembled in the casing 1, a rotor 3 provided rotatably inside of the stator 2 and a lid body 4 covering the opening portion of the casing, wherein the stator 2 is formed in an annular plate shape and fitted in the casing 1, a pair of metal field plates 7 having a plurality of magnetic poles 7a on the inner peripheral part are axially provided in two sets adjacent to each other, and exciting coils 9, 10 are wound around the outer periphery of bobbin 8 made of a synthetic resin which is integrally formed on the outer peripheral surface of the field plate 7. The ampere returns of the exciting coil 10 which are positioned on the bottom plate 1a side of the casing 1 is made smaller than the ampere turns of the exciting coil 9 which are positioned on the opening 1b side. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a stepping motor that can obtain high rotational angle accuracy.

In general, stepping motors are widely used as control systems for various devices that require high positioning accuracy and as drive sources for home appliances.
FIG. 1 shows the structure of a general stepping motor. This stepping motor is a stator formed into a substantially cylindrical shape as a whole in a casing 1 made of a conductive metal formed in a bottomed cylindrical shape. 2, a rotor 3 having a gap formed in the outer peripheral surface thereof is magnetized in the stator 2, and fixed to the lid 4 that closes the opening of the casing 1 and the bottom plate 1 a of the casing 1. A shaft 6 integrated with the rotor 3 is rotatably supported by the bearing 5.

  Here, the stator 2 includes four metal field plates 7, two sets of synthetic resin bobbins 8 covering the field plates 7, and excitation coils 9 and 10 wound around the bobbins 8. It is roughly structured.

  That is, the field plate 7 is formed in an annular plate shape, and a plurality of magnetic poles 7a bent in the axial direction are formed in the circumferential direction at equal intervals in the circumferential direction. Two pairs of field plates 7 are provided adjacent to each other in the axial direction in which the magnetic poles 7a are alternately arranged in the circumferential direction.

  On the outer periphery of these field plates 7, the bobbin 8 is integrally formed by injection molding, and a terminal block 11 is formed at the same time. Then, the exciting coils 9 and 10 are formed by winding the windings having the same wire diameter around the outer circumference of each bobbin 8 the same number of times. Note that the end portions of the exciting coils 9 and 10 are electrically connected to terminals 12 erected on the terminal block 11, respectively.

  By the way, in this type of stepping motor, a magnetic circuit for rotating the rotor 3 is formed by the cooperation of the field plate 7 and the casing 1 when the exciting coils 9 and 10 are energized. For this reason, it is preferable that the outer peripheral surface of the field plate 7 is in close contact with the inner peripheral surface of the casing 1.

  However, in the conventional stepping motor, since the casing 1 is formed in a bottomed cylindrical shape, when the stator 2 is inserted into the casing 1, the field plate 7 positioned on the bottom plate 1a side is Although swelling of the outer peripheral portion of the casing 1 is restrained by the bottom plate 1a and high adhesion can be obtained, the adhesion of the field plate 7 located on the opening 1b side is lowered due to deformation of the casing 1 itself.

  In addition, on the bottom plate 1a side of the casing 1, there is a tendency that a magnetic circuit without loss is easily formed even by the bottom plate 1a originally formed integrally. On the other hand, on the side of the opening 1b, when the lid 4 that closes the opening 1b is fixed to the opening 1b by caulking or the like, the casing 1 is deformed and the adhesion to the field plate 7 tends to be impaired. is there.

  As a result, the magnetic resistance on the exciting coil 9 side becomes larger than that on the exciting coil 10 side, and the magnetic flux on the exciting coil 9 side becomes smaller than that on the exciting coil 10 side. There has been a problem that a static angle error as a motor becomes large.

  The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a stepping motor capable of reducing a static angle error and thus obtaining high rotational angle accuracy.

  In order to solve the above-mentioned problems, a first aspect of the present invention provides a bottomed cylindrical casing made of a conductive metal, a substantially cylindrical stator incorporated in the casing, and an inner side of the stator. And a rotor having an outer peripheral surface magnetized, and the stator is formed in an annular plate shape and is fitted in the casing and has an inner periphery. Two pairs of metal field plates having a plurality of magnetic poles bent in the axial direction are provided adjacent to each other in the axial direction, and a synthetic resin bobbin is integrally formed on the outer peripheral surface of the field plate. In the stepping motor in which the exciting coil is wound around the outer periphery of each bobbin, the amperage of one of the exciting coils located on the bottom plate side of the casing is used. Turn, it is characterized in that it has less than the other ampere-turns of the exciting coil positioned on the opening side.

  According to a second aspect of the present invention, in the first aspect of the present invention, the wire diameter of the one exciting coil is made smaller than the wire diameter of the other exciting coil, and The number of turns is smaller than the number of turns of the other exciting coil.

  Furthermore, the invention according to claim 3 is the invention according to claim 1 or 2, wherein the one exciting coil and the other exciting coil have the same resistance value. .

  As described above, in the stepping motor assumed by the invention according to any one of claims 1 to 3, when the stator is fitted into the bottomed cylindrical casing made of conductive metal, In the field plate that is positioned, the swelling of the outer peripheral portion of the casing is restricted by the bottom plate, and high adhesion can be obtained. On the other hand, the field plate located on the opening side has low adhesion due to deformation of the casing itself. Therefore, the magnetic resistance for the excitation coil on the bottom plate side is smaller than the magnetic resistance for the excitation coil on the opening side.

  As a result, the magnetic flux generated by the excitation coil on the bottom plate side is larger than the magnetic flux generated by the excitation coil on the opening side. Here, the magnetic flux is proportional to the ampere-turn of the exciting coil (the product of the number of turns (number of turns) of the exciting coil and the number of amperes per turn).

  On the other hand, in the invention according to any one of claims 1 to 3, the ampere turn of one exciting coil located on the bottom plate side of the casing is connected to the other exciting coil located on the opening side (lid side). Therefore, the magnetic fluxes generated by the two exciting coils can be made substantially equal. As a result, the static angle error can be reduced as compared with the conventional one, and thus high rotation angle accuracy can be obtained.

  By the way, in the invention described in claim 1, in order to make the ampere turn of the exciting coil on the bottom plate side smaller than that of the exciting coil on the opening side, the configuration in which only the number of turns of the exciting coil is reduced, or its line It is possible to adopt a configuration in which only the diameter is reduced, but depending on the outer diameter, thickness, material, etc. of the casing, the difference in the magnetic resistance with respect to the excitation coil between the bottom plate side and the opening side when the stator is fitted becomes large In such a stepping motor, the difference in the number of turns and the difference in the wire diameters between the two exciting coils may become extremely large, resulting in inconvenience.

  In this respect, according to the invention described in claim 2, since the ampere turn of the exciting coil on the bottom plate side is made smaller than that on the opening side by reducing both the wire diameter and the number of turns, the above-mentioned adverse effects are avoided. It can be avoided.

  In particular, according to the third aspect of the invention, since the resistance values of both exciting coils are equal, there is no possibility of causing electrical restrictions or specification changes on the power supply side.

Hereinafter, an embodiment of a stepping motor of the present invention will be described based on the drawings. Note that the basic configuration of the stepping motor of the present embodiment is the same as that shown in FIG.
In the present embodiment, in the stepping motor shown in FIG. 1, the excitation coil (the other excitation coil) located on the lid 4 side is used as the wire diameter of the excitation coil (one excitation coil) 10 located on the bottom plate 1a side of the casing 1. A coil smaller than the wire diameter of the coil 9 is selected.

The exciting coil 10 is formed with a smaller number of turns than the exciting coil 9.
As a result, the excitation coil 10 located on the bottom plate 1a side of the casing 1 is set to have an ampere turn smaller than that of the excitation coil 9 located on the lid 4 side.
Further, the exciting coil 9 and the exciting coil 10 are formed so that their resistance values are equal.

  It should be noted that to what extent the wire diameter and the number of turns in the exciting coil 10 are smaller or smaller than that of the exciting coil 9, the outer diameter, thickness, material, manufacturing error of the casing 1, the thickness, shape of the field plate 7, It differs depending on the outer diameter and manufacturing error.

Generally, when the magnetic resistance of the exciting coil 9 is _RφA and the magnetic resistance of the exciting coil 10 is _RφB , after the stator 2 is fitted in the casing 1, as described above,
R _φA > R _φB
become. As a result, if the magnetic flux of the exciting coil 9 is φ _A and the magnetic flux of the exciting coil 10 is φ _B ,
φ _A <φ _B
become.

Then, the magnetic flux phi _A is proportional to the ampere-turns AT _A of the exciting coil 9, the magnetic flux phi _B is proportional to the ampere-turns AT _B of the excitation coil 10. Therefore,
AT _A / R _φA = AT _B / R _φB
If the ampere turn AT _B of the exciting coil 10 is determined so that the magnetic fluxes φ _A and φ _B of the exciting coils 9 and 10 can be made equal to each other, the static angle error is reduced and a high rotation angle is obtained. Accuracy can be obtained.

(Experimental example)
In order to demonstrate the effect of the present invention, for a stepping motor having an outer diameter of 10 mmφ, as a stepping motor according to the present invention, an exciting coil 9 is wound by winding a winding having a wire diameter of 0.063 ^{φ around} the bobbin 8 630 times. In addition to the formation, the exciting coil 10 was prepared by winding a winding having a wire diameter of 0.050 ^{φ around} the bobbin 8 420 times.
In addition, as a conventional stepping motor for comparison, both the exciting coils 9 and 10 were prepared by winding a winding having a wire diameter of 0.063 ^φ for 630 times.

The static angle error was measured for each of the two stepping motors thus obtained. Here, the stationary angle error δ is the maximum value (Δθ) of the positive error (+ Δθ) of the actual stationary angle with respect to the set value when the stepping motor is stopped at the set angle value a plurality of times. _max ) and the minimum negative error (-Δθ) (-Δθ _min )
δ = (Δθ _max + | Δθ _min | / 2)
Is obtained.

  As a result of the experiment, in the stepping motor for comparison, the static angle error δ was 2 °, whereas in the stepping motor according to the present invention, the static angle error was 1 °, 1/2.

It is a longitudinal cross-sectional view which shows the structure of the stepping motor used as the premise of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Casing 1a Bottom plate 1b Opening 2 Stator 3 Rotor 7 Field plate 8 Bobbin 9, 10 Excitation coil

Claims (3)

A cylindrical casing with a bottom made of a conductive metal, a substantially cylindrical stator incorporated in the casing, a space inside the stator and a space around the axis so as to be rotatable about the axis, and an outer peripheral surface. With a magnetized rotor,
In addition, the stator is formed in an annular plate shape and fitted in the casing, and a pair of metal field plates having a plurality of magnetic poles bent in the axial direction on the inner peripheral portion is formed in the axial direction. A stepping motor in which a synthetic resin bobbin is integrally formed on the outer peripheral surface of the field plate and an excitation coil is wound around the outer periphery of each bobbin.
A stepping motor characterized in that an ampere turn of one exciting coil located on the bottom plate side of the casing is made smaller than an ampere turn of the other exciting coil located on the opening side.   The wire diameter of the one exciting coil is made smaller than the wire diameter of the other exciting coil, and the number of turns of the one exciting coil is made smaller than the number of turns of the other exciting coil. Item 5. A stepping motor according to item 1.   3. The stepping motor according to claim 1, wherein the one exciting coil and the other exciting coil have the same resistance value.

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