JPS6176059A - Step motor - Google Patents

Abstract

PURPOSE:To reduce the size of a step motor by providing the first and second coils, an intermediate plate formed with pole teeth, a pair of yokes, and a rotor, and displacing the set of poles in a rotating direction of the prescribed electric angle, thereby reducing the number of parts. CONSTITUTION:A stator 1 is formed of cup-shaped stator yokes 2, 3 of a case, coils 6, 7 held at a pair of coil frames 4, 5, an intermediate plate 8, and a bearing 9, and a rotor 10 is formed of permanent magnets 11a, 11b, a shaft 12 and a magnet holder 13. The yokes 2, 3 are formed by cutting and erecting a plurality of pole elements at the center of the bottom in cylindrical shape to form pole teeth on the inner peripheral side. The plate 8 is in a disc shape, and formed with an engaging projection on the outer periphery, and pole elements 19, 20 of the same number as the pole elements at the center on the front and back surfaces. In this case, the pole teeth of the pole elements of both are formed in a zigzag shape and displaced at 1/4 pitch (90 deg. of electric angle). Thus, the teeth become a relation of 90 deg. displaced on the opposed surfaces between the coil 7 side and the rotor 10 side at the opposing time to obtain a stepwise operation by sequentially exciting the displacing side.

Description

【発明の詳細な説明】 〔技術分野〕 この発明は、ステップ電動機に関するものである。[Detailed description of the invention] 〔Technical field〕 The present invention relates to a step motor.

〔背景技術〕[Background technology]

従来、一般に１００極ないし２００極のステップ電動…
は第１０図のような構造になっていた。すなわち、その
固定子極が突極５０となっており、この各突極５０にコ
イ１ｖ５１を巻いたものである。Conventionally, step motors generally have 100 to 200 poles...
The structure was as shown in Figure 10. That is, the stator poles are salient poles 50, and each salient pole 50 is wound with a coil 1v51.

しη為し、コイｌし５１をまくスペースが突極５０間の
溝５２であるため非常に巻きにぐ〈加工費が高くなって
いた。仮にコイル５１は別に巻いたものを嵌めるとして
も第１０図の例では８個のコイ〃５１を要するという欠
点があった。However, since the space in which the coil 51 is wound is the groove 52 between the salient poles 50, it is very difficult to wind the coil and the processing cost is high. Even if separately wound coils 51 were to be fitted, the example shown in FIG. 10 had the disadvantage that eight coils 51 were required.

〔発明の目的〕[Purpose of the invention]

この発明の目的は、１００極以上の極数を有するととも
にコイル等の部品点数を削減し構造および組立が簡単で
安価にすることができるステップ電動機を提供すること
である。An object of the present invention is to provide a step motor which has a number of poles of 100 or more, reduces the number of parts such as coils, and is simple in structure and assembly and can be made at low cost.

〔発明の開示〕[Disclosure of the invention]

この発明のステップ電動機は、第１の発明として、同軸
上に並列した第１および第２のコイＭと、この第１およ
び第２のコイルの間に介在さ八て前記第１および第２の
コイルの内周側で軸方向の両方向に延出する所定数の磁
極子を有しさらにその表面に所定数の磁極歯を形成した
中間板と、前記第１および第２のコイルの軸方向の外側
にそｎぞｎ設けられて各コイルの内周側で軸方向の中間
板側に延出するとともに前記中間板の磁極子の間に位置
する磁極子を有しさらにその表面に所定数の磁極歯を形
成した一対のヨークと、前記コイＭの中心軸上に配置さ
れて外周に前記磁極歯に対向する磁極を形成した回転子
とを備え、前記第１のコイルにおける前記中間板および
ヨークの磁極歯およびこれらに層間する回転子の磁極の
組と、前記第２のコイＭにおける前記中間板およびβ−
りの磁極歯およびこれらに対向する回転子の磁極の組と
が相互に所定の電気角度回転方向にずｎるよりにしたも
のである。また、第２の発明として、同軸上に並列した
第１および第２のコイルと、この第１および第２のコイ
ｌしの間に介在’Ｊｆｌで前記第１および第２のコイル
の内周側で軸方向の両方向に延出する所定数の磁極子を
有しさらにその表面に所定数の磁極歯を形成した中間板
と、前記第１および第２のコイＩしの軸方向の外側にそ
ｎぞｎ設けらｎて各コイルの内周側で軸方向の中間板側
に延出するとともに前記中間板の磁極子の間に位置する
磁極子を有しさらにその表面に所定数の磁極歯を形成し
た一対のヨークと、前記コイルの中心軸上に配置さ几て
ろ方向に７ｉｉ１ｒｉ１されるとともに外周に前記磁極
歯に対向する磁極歯を形成した永久磁石を有する回転子
とを備え、前記第１のコイルにおける前記中間板および
ヨークの磁極歯およびこれらに対向する回転子の磁極歯
の組と、前記第２のコイルにおける前記中間板およびヨ
ークの磁極歯およびこれらに対向する回転子の磁極歯の
組とが相互に所定の電気角度回転方向に、ずれるように
したものである。すなわち、第１６発明において、中間
板およびヨークの磁極子に磁極歯を形成するため１００
極以上の超多極化が可能になり、しかも従来に比して部
品点数の削減、構造および組立の簡単化が図ｎ、小形化
およびコスト安にすることができる。第２の発明におい
て、永久磁石を径方向に着磁するとともに外表面に磁極
歯を形成したためさらに永久磁石の構造が簡単になる。The step motor of the present invention, as a first invention, includes first and second coils M coaxially arranged in parallel, and a step motor interposed between the first and second coils. an intermediate plate having a predetermined number of magnetic pole pieces extending in both axial directions on the inner peripheral side of the coil and further having a predetermined number of magnetic pole teeth formed on its surface; A magnetic pole piece is provided on the outside and extends toward the intermediate plate in the axial direction on the inner peripheral side of each coil, and is located between the magnetic pole pieces of the intermediate plate. a pair of yokes formed with magnetic pole teeth, and a rotor disposed on the central axis of the coil M and formed with magnetic poles facing the magnetic pole teeth on the outer periphery, the intermediate plate and the yoke in the first coil; magnetic pole teeth and a set of rotor magnetic poles interlayered therewith, the intermediate plate in the second coil M, and β-
The magnetic pole teeth of the rotor and the set of magnetic poles of the rotor opposing these teeth are offset from each other by a predetermined electrical angle in the direction of rotation. Further, as a second invention, the first and second coils are arranged in parallel on the same axis, and the inner periphery of the first and second coils is interposed between the first and second coils. an intermediate plate having a predetermined number of magnetic pole pieces extending in both axial directions on the sides thereof and further having a predetermined number of magnetic pole teeth formed on its surface; A magnetic pole piece is provided on the inner peripheral side of each coil and extends toward the intermediate plate in the axial direction, and is located between the magnetic pole pieces of the intermediate plate, and further has a predetermined number of magnetic poles on the surface thereof. A rotor comprising a pair of yokes formed with teeth, and a rotor having a permanent magnet arranged on the central axis of the coil and oriented in the rotary direction and formed with magnetic pole teeth opposite to the magnetic pole teeth on the outer periphery, A set of magnetic pole teeth of the intermediate plate and yoke in the first coil and magnetic pole teeth of the rotor opposing them; and a set of magnetic pole teeth of the intermediate plate and yoke in the second coil and magnetic poles of the rotor opposing them. The sets of teeth are shifted from each other in a predetermined electrical angle rotational direction. That is, in the sixteenth invention, in order to form magnetic pole teeth on the magnetic pole pieces of the intermediate plate and the yoke,
This makes it possible to have a very large number of poles, and also to reduce the number of parts, simplify the structure and assembly, and reduce the size and cost compared to the conventional method. In the second invention, since the permanent magnet is magnetized in the radial direction and magnetic pole teeth are formed on the outer surface, the structure of the permanent magnet is further simplified.

この発明の一実施例を第１図ないし第９図に基づいて説
明する。図において、固定子１はケースを兼ねるカップ
状の固定子ヨーク２，３、一対のコイＭ枠４，５に保持
さｎたコイＡ／６，７、中間板８、軸受９からなり、回
転子１０は永久磁石１１ａ。An embodiment of the present invention will be described based on FIGS. 1 to 9. In the figure, a stator 1 consists of cup-shaped stator yokes 2 and 3 that also serve as a case, coils A/6 and 7 held in a pair of coil M frames 4 and 5, an intermediate plate 8, and a bearing 9, and rotates. The child 10 is a permanent magnet 11a.

１１ｂ、軸１２．磁石保持具１３からなる。固定子１の
固定子ヨーク２．３は略同−形状に形成さ１〜いずれも
底板の中央に複数の磁極子１４．１５を円筒状に切起し
、その内周側に磁極歯１４”　＋　１５”を形成し、ま
た開口縁の均等４箇所に所定深さでそｎぞｎ係止切欠１
６を形成し、ヨーク３の中心に軸受固定孔１７を形成し
ている。中間板８は磁性体で円板形に形成さｎ、第３図
および第４図のように外周の均等４箇所に係止突起１８
を形成し、中央部に前記磁極子１４．１５と同数の磁極
子１９゜２０を等間隔で表裏２方同にそｎぞｎ切起し、
かつその内局面に磁極歯１４８　ｅ　１５ａと同じ磁極
歯１９ａ。11b, axis 12. It consists of a magnet holder 13. The stator yoke 2.3 of the stator 1 is formed in approximately the same shape, and a plurality of magnetic pole pieces 14.15 are cut and raised in the center of the bottom plate in a cylindrical shape, and magnetic pole teeth 14'' are provided on the inner circumferential side of the stator yoke 2.3 of the stator 1. + 15", and locking notches 1 are provided at four equal locations on the edge of the opening at a predetermined depth.
6, and a bearing fixing hole 17 is formed in the center of the yoke 3. The intermediate plate 8 is made of a magnetic material and is formed into a disk shape, and has locking protrusions 18 at four equal locations on the outer periphery as shown in FIGS. 3 and 4.
, and in the center part, the same number of magnetic pole elements 19.20 as the magnetic pole elements 14 and 15 are cut and raised at equal intervals on both the front and back sides,
And the same magnetic pole tooth 19a as the magnetic pole tooth 148e 15a is provided on the inner surface thereof.

２０ａを形成している。各コイル枠４．５が各固定子ヨ
ーク２．３に納めら几ると各磁極子１４　、１５はコイ
ル枠４．５の内周に位置する。また軸受固定孔１７に油
を含浸した焼結合金製の軸受９を取付け、一方の固定子
ヨーク３の開口に中間板８を被せ、切欠１６に突起１８
を係合させる。切欠１６の深さは突起１８の厚さの半分
としているので、他の固定子ヨーク２を乗せてその切欠
１６を突起１８の厚さの半分の突出部分に係止して一体
に組合す。このとき固定子ヨーク２．３の磁極子１４゜
１５およびこ几らの磁極子１４．１５と中間板８の磁極
子１９．２０の関係を展開状態で第６図のように行き違
いとなるよりにするとともに、磁極歯１４１　、１９８
と磁極歯１５ａ　＃　２０１は互いにｉビフチ（電気角
９０度）ａだけずらせるようにする。20a. When each coil frame 4.5 is housed in each stator yoke 2.3, each magnetic pole piece 14, 15 is located on the inner periphery of the coil frame 4.5. Further, a bearing 9 made of a sintered metal impregnated with oil is installed in the bearing fixing hole 17, an intermediate plate 8 is placed over the opening of one stator yoke 3, and a protrusion 18 is inserted into the notch 16.
engage. Since the depth of the notch 16 is half the thickness of the protrusion 18, another stator yoke 2 is placed on it, and the notch 16 is engaged with the protruding portion of the protrusion 18, which is half the thickness, so that the stator yoke 2 is assembled integrally. At this time, the relationship between the magnetic pole pieces 14 and 15 of the stator yoke 2.3 and the magnetic pole pieces 14 and 15 of the intermediate plate 8 and the magnetic pole pieces 19 and 20 of the intermediate plate 8 will be changed as shown in FIG. In addition, the magnetic pole teeth 141 and 198
and magnetic pole tooth 15a #201 are made to be shifted from each other by i-bift (90 electrical degrees) a.

回転子１０は、軸１２に保持具１３が圧入により取付け
らｎ１保持具１３に永久磁石１１ｍ　、　１ｌｆｉが取
付けらｎる。この場合、保持具１３のつげ（非磁性材）
　１３ｍで永久磁石ＩＣ、１ｉｔ）を仕切っている。こ
れらの永久磁石１１ａ　、　ｌｌｂはたとえばプラスチ
ック磁石等を成形することにより、外周に前記磁極歯１
９ｆｉ等と同じ磁極歯２１！　、　２１ｂを１００極分
歯車状に形成しく磁極歯１９８等の幅の設定により１０
０極（各磁石１１ａ　、　ｌｌｂは５０極〕以上たとえ
ば２００極にすることもできる）、永久磁石１１３゜１
１ｂともに径方向に着磁さｎるが、永久磁石１１Ｍは外
表面が念とえばＮ極、永久磁石１１ｂの外表面はＳ極と
なるよりに異ならせている。また永久磁石１１１　、１
１ｂ相互の磁極歯２１１１　、２１１）は第７図（ａ）
。In the rotor 10, a holder 13 is attached to the shaft 12 by press fitting, and permanent magnets 11m and 1lfi are attached to the holder 13. In this case, the boxwood (non-magnetic material) of the holder 13
Permanent magnet IC, 1it) is separated by 13m. These permanent magnets 11a and llb are made of, for example, plastic magnets, so that the magnetic pole teeth 1 are formed on their outer peripheries.
21 magnetic pole teeth, same as 9fi etc.! , 21b is formed into a gear shape with 100 poles, and by setting the width of the magnetic pole teeth 198, etc.
0 poles (each magnet 11a, llb has 50 poles) or more, for example, it can be 200 poles), permanent magnet 113°1
Both magnets 1b are magnetized in the radial direction, but the outer surface of the permanent magnet 11M is a north pole, and the outer surface of the permanent magnet 11b is a south pole. Also, permanent magnets 111, 1
1b mutual magnetic pole teeth 2111, 211) are shown in FIG. 7(a)
.

（ｂ）のよりに互いに半ピツチ（１菌号〕電気角で１８
０度回転方向にずらせている（図で黒い部分が歯、白い
部分が歯溝である）。(b) half pitch each other (1 bacteria number) 18 in electric angle
It is shifted in the direction of rotation by 0 degrees (in the figure, the black part is the tooth, and the white part is the tooth groove).

コイル６．７毎に対向する磁極歯１４８１１９８の組お
よび磁極歯１５１　、２０１の組は、コイル６．７に通
電することによってそｎぞｎ異磁極が対向する。したが
って、このステップ電動機の動作は、磁極歯１４１　＊
　１９，１１１９　＃　２０ａと磁極ｍ　２１ａ、２１
ｔ）の対応関係が従来公知の２相コイＭ方式のものと同
様であるため、従来と同じステップ動作をする。The set of magnetic pole teeth 1481198 and the set of magnetic pole teeth 151 and 201 that face each coil 6.7 have different magnetic poles facing each other by energizing the coil 6.7. Therefore, the operation of this step motor is based on the magnetic pole teeth 141 *
19,1119 # 20a and magnetic pole m 21a, 21
Since the correspondence relationship of t) is the same as that of the conventionally known two-phase coil M system, the step operation is the same as the conventional one.

すなわち要約すると、たとえばコイ／Ｓ／６側の磁極歯
１４ａ　、　１９ａに回転子１０の磁極歯２１！１が第
８図のよりに対面対向するとき、他方のコイル７側の磁
極歯１５ａ。２０ｍは回転子１０の磁極歯２１ｂに対し
て第９図のように９０度ずｎた関係になり、反対のとき
は逆の関係となるため、ずｎた側を逐次励磁することに
よってステップ動作が得らｎるのである。その励磁電流
はコイル相互に９０度位相がずｎたものとなる。That is, to summarize, for example, when the magnetic pole teeth 21!1 of the rotor 10 face the magnetic pole teeth 14a and 19a on the coil/S/6 side as shown in FIG. 8, the magnetic pole teeth 15a on the other coil 7 side. 20 m is offset by 90 degrees with respect to the magnetic pole teeth 21b of the rotor 10 as shown in FIG. is obtained. The excitation currents are out of phase with each other by 90 degrees between the coils.

このように構成したため、従来と比べて２個のコイル６
．７でよく、部品点数の削減になり、構造が簡単になる
。しかもドーナツ状のコイｔＶ６゜７のため、加工コス
トは非常に安価で、組立も順次部品を重ねていく方式と
なるためきわめて簡単になる。ま念１枚の中間板８にコ
イ／ｌ／６　、７相互の磁極歯１９ａ　＃　２０ａの片
方ずつを同時に形成するため、軸方向の長さの短縮にな
るとともにコイル相互の磁極歯の位置関係を表わす作業
が不要になる。また中間板８およびその磁極子１９．２
０は金型でプレス加工できるので精度が良い。Because of this configuration, two coils 6 are required compared to the conventional method.
．． 7 is sufficient, reducing the number of parts and simplifying the structure. Moreover, since it is a donut-shaped carp tV6°7, the processing cost is very low, and the assembly is extremely easy as the parts are stacked one on top of the other. Since one side of the coil/l/6 and 7 mutual magnetic pole teeth 19a and #20a are simultaneously formed on one intermediate plate 8, the length in the axial direction is shortened and the positional relationship of the magnetic pole teeth of the coils is changed. This eliminates the need to express the information. Also the intermediate plate 8 and its pole piece 19.2
0 has good precision because it can be pressed using a mold.

なお、磁極子１４．１５，１９．２０は別体のものをヨ
ーク２．３および中間板８に植付けるようにしてもよい
。また実施例では回転を得るため回転子１０の磁極歯２
９　、２１ｂ　ｔ−回転方向にずらせているが、中間板
８の磁極歯１９．２０またはその磁極歯１９．２０とと
もにずらせるようにしてもよい。全体として相対的にず
ルてい１ば動作は同じだからである。また実施例は２相
コイルを用いたが２相以上の複数コイＭを用いたもので
第１および＠２のコイＭの関係にこの発明の溝底を適用
することによっても同効果が得らｎる。Incidentally, the magnetic pole pieces 14.15 and 19.20 may be separately attached to the yoke 2.3 and the intermediate plate 8. In addition, in the embodiment, in order to obtain rotation, the magnetic pole teeth 2 of the rotor 10 are
9, 21b t-Although they are shifted in the rotational direction, they may also be shifted together with the magnetic pole tooth 19.20 of the intermediate plate 8 or with its magnetic pole tooth 19.20. This is because the overall operation is the same if there is a relative shift. Further, although the embodiment uses a two-phase coil, a plurality of coils M having two or more phases are used, and the same effect can be obtained by applying the groove bottom of the present invention to the relationship between the first and @2 coils M. nru.

〔発明の効果〕〔Effect of the invention〕

この発明によｎば、従来に比して部品点数を削減できる
とともに構造および組立が著しぐ簡単になり、小形化を
図ｎるとともにコスト安になるという効果がある。According to the present invention, the number of parts can be reduced compared to the prior art, and the structure and assembly can be significantly simplified, resulting in miniaturization and cost reduction.

【図面の簡単な説明】[Brief explanation of drawings]

第１図はこの発明の一実施例の分解斜視図、第２図はそ
の断面図、第３図は中間板の断面図、第４図はその平面
図、第５図は磁極子の拡大斜第６図は＆ｆ磁極子Ｓ開園
、第７図は回転子の磁極歯の展開図、第８図はコイル側
の固定子および回転子の磁極歯の関係を示す説明図、第
９図はコイル側の固定子および回転子の磁極歯の関係を
示す説明図、第１０図は従来例の側面図である。 １・・・固定子、２．３・・・ヨーク、６．７・・・コ
イ１１８・・・中間板、１０−・・回転子、ｌｌａ　、
　ｌｌｂ　・・・永久磁石、１４，１５，１９．２０・
・・磁極子、１４！＠１５ａｔ１９ａ　、　２０１　・
ａ極歯、２Ｃ、２１ｂ−・・回転子磁極歯第１図 第２図 ０ａ 第３図 第４図 第６図 １１ａ　　２１ａ １１ｂ　　２１ｂ 第７図 第８図 に 第９図 第１０図Fig. 1 is an exploded perspective view of an embodiment of the present invention, Fig. 2 is a sectional view thereof, Fig. 3 is a sectional view of the intermediate plate, Fig. 4 is a plan view thereof, and Fig. 5 is an enlarged perspective view of the magnetic pole piece. Figure 6 shows &f magnetic pole S opening, Figure 7 shows a developed view of the rotor's magnetic pole teeth, Figure 8 is an explanatory diagram showing the relationship between the stator on the coil side and the rotor's magnetic pole teeth, and Figure 9 shows the coil. FIG. 10 is an explanatory diagram showing the relationship between the magnetic pole teeth of the stator and rotor on the side, and FIG. 10 is a side view of a conventional example. 1... Stator, 2.3... Yoke, 6.7... Coil 118... Intermediate plate, 10-... Rotor, lla,
llb...Permanent magnet, 14, 15, 19.20.
...Magnetic pole piece, 14! @15at19a, 201 ・
a Pole teeth, 2C, 21b - Rotor magnetic pole teeth Fig. 1 Fig. 2 Fig. 0a Fig. 3 Fig. 4 Fig. 6 Fig. 6 11a 21a 11b 21b Fig. 7 Fig. 8 Fig. 9 Fig. 10

Claims (2)

【特許請求の範囲】[Claims] （１）同軸上に並列した第１および第２のコイルと、こ
の第１および第２のコイルの間に介在されて前記第１お
よび第２のコイルの内周側で軸方向の両方向に延出する
所定数の磁極子を有しさらにその表面に所定数の磁極歯
を形成した中間板と、前記第１および第２のコイルの軸
方向の外側にそれぞれ設けられて各コイルの内周側で軸
方向の中間板側に延出するとともに前記中間板の磁極子
の間に位置する磁極子を有しさらにその表面に所定数の
磁極歯を形成した一対のヨークと、前記コイルの中心軸
上に配置されて外周に前記磁極歯に対向する磁極を形成
した回転子とを備え、前記第１のコイルにおける前記中
間板およびヨークの磁極歯およびこれらに対向する回転
子の磁極の組と、前記第２のコイルにおける前記中間板
およびヨークの磁極歯およびこれらに対向する回転子の
磁極の組とが相互に所定の電気角度回転方向にずれるよ
うにしたステップ電動機。(1) first and second coils that are coaxially arranged in parallel; and a coil that is interposed between the first and second coils and extends in both axial directions on the inner peripheral side of the first and second coils. an intermediate plate having a predetermined number of magnetic pole pieces extending therefrom and further having a predetermined number of magnetic pole teeth formed on its surface; a pair of yokes that extend toward the intermediate plate in the axial direction and have magnetic pole pieces located between the magnetic pole pieces of the intermediate plate, and further have a predetermined number of magnetic pole teeth formed on their surfaces; and a central axis of the coil. a rotor disposed above and having magnetic poles facing the magnetic pole teeth formed on the outer periphery, a set of magnetic pole teeth of the intermediate plate and yoke in the first coil and magnetic poles of the rotor facing these; A step motor in which the magnetic pole teeth of the intermediate plate and yoke in the second coil and a pair of magnetic poles of the rotor opposing these are mutually shifted by a predetermined electrical angle in a rotating direction. （２）同軸上に並列した第１および第２のコイルと、こ
の第１および第２のコイルの間に介在されて前記第１お
よび第２のコイルの内周側で軸方向の両方向に延出する
所定数の磁極子を有しさらにその表面に所定数の磁極歯
を形成した中間板と、前記第１および第２のコイルの軸
方向の外側にそれぞれ設けられて各コイルの内周側で軸
方向の中間板側に延出するとともに前記中間板の磁極子
の間に位置する磁極子を有しさらにその表面に所定数の
磁極歯を形成した一対のヨークと、前記コイルの中心軸
上に配置されて径方向に着磁されるとともに外周に前記
磁極歯に対向する磁極歯を形成した永久磁石を有する回
転子とを備え、前記第１のコイルにおける前記中間板お
よびヨークの磁極歯およびこれらに対向する回転子の磁
極歯の組と、前記第２のコイルにおける前記中間板およ
びヨークの磁極歯およびこれらに対向する回転子の磁極
歯の組とが相互に所定の電気角度回転方向にずれるよう
にしたステップ電動機。(2) first and second coils that are coaxially arranged in parallel; and a coil that is interposed between the first and second coils and extends in both axial directions on the inner peripheral side of the first and second coils. an intermediate plate having a predetermined number of magnetic pole pieces extending therefrom and further having a predetermined number of magnetic pole teeth formed on its surface; a pair of yokes that extend toward the intermediate plate in the axial direction and have magnetic pole pieces located between the magnetic pole pieces of the intermediate plate, and further have a predetermined number of magnetic pole teeth formed on their surfaces; and a central axis of the coil. a rotor having a permanent magnet disposed above and magnetized in the radial direction and having magnetic pole teeth opposing the magnetic pole teeth formed on the outer periphery, the magnetic pole teeth of the intermediate plate and the yoke in the first coil; and a set of magnetic pole teeth of the rotor opposing these, a set of magnetic pole teeth of the intermediate plate and yoke of the second coil, and a set of magnetic pole teeth of the rotor opposing these, mutually in a predetermined electrical angle rotation direction. A step motor that is made to shift.