STEPPING MOTOR

A stepping motor according to various embodiments includes a rotatable shaft, and two or more engine units that are connected to the shaft, and each of the engine units has a rotor and a stator arranged at a circumference of the rotor.

The present application is related to and claims the benefit under 35 U.S.C. §119(a) of a Korean patent application filed on Sep. 4, 2015 in the Korean Intellectual Property Office and assigned Serial number 10-2015-0125482, the entire disclosure of which is hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to a stepping motor that can increase an output torque while maintaining a compact size.

BACKGROUND

A stepping motor is a motor in which one rotation is divided into a plurality of steps, and may have a very high location precision.

The stepping motor has a rotor and a stator, and N poles and S poles of a plurality of magnets may be alternately arranged on an outer peripheral surface of the rotor to be spaced apart from each other at a specific interval and a driving shaft may be fixed to an axis of the rotor.

The stator has a coil and a yoke, the yoke has an inner yoke and an outer yoke arranged around the rotor, and the inner yoke and the outer yoke may have a plurality of teeth formed in a circumferential direction thereof to have a specific pitch.

The stepping motor may be widely utilized in the fields, such as a lens group driving unit of an interchangeable lens type camera system, which may be easily controlled at a high location precision, and a stepping motor having a large size may be used to a high output torque and a high resolution when the stepping motor is applied to a full frame camera, but a big installation space may be necessary when a stepping motor of a large size is applied.

Further, the number of steps may increase to increase resolution (location precision), an output torque may be lowered as a magnetic flux area becomes narrower if the number of steps increases.

SUMMARY

To address the above-discussed deficiencies, it is a primary object to provide a stepping motor that can increase an output torque while maintaining a compact size.

The present disclosure also provides a stepping motor that may increase a resolution (location precision) while increasing an output torque thereof.

A stepping motor according to various embodiments includes a rotatable shaft, and two or more engine units that are connected to the shaft, and each of the engine units has a rotor and a stator arranged at a circumference of the rotor.

According to various embodiments, the stator may have an upper stator and a lower stator, each of the upper stator and the lower stator may have an outer yoke and an inner yoke, and each of the outer yoke and the inner yoke may have a plurality of teeth that are formed along a circumferential direction thereof.

According to various embodiments, the teeth of the upper stator and the teeth of the lower stator may be arranged to have a phase difference.

According to various embodiments, the two or more engine units may be installed to be coaxial with the shaft, and the teeth of an engine unit on one side and the teeth of an engine unit on an opposite side may be arranged to have the same phase.

According to various embodiments, the two or more engine units may be installed to be coaxial with the shaft, and the teeth of an engine unit on one side and the teeth of an engine unit on an opposite side may be aligned to have a phase difference.

DETAILED DESCRIPTION

In the disclosure disclosed herein, the expressions “have”, “may have”, “include” and “comprise”, or “may include” and “may comprise” used herein indicate existence of corresponding features (for example, elements such as numeric values, functions, operations, or components) but do not exclude presence of additional features.

The terms, such as “first”, “second”, and the like used herein may refer to various elements of various embodiments of the present disclosure, but do not limit the elements. For example, such terms are used only to distinguish an element from another element and do not limit the order and/or priority of the elements. For example, a first user device and a second user device may represent different user devices irrespective of sequence or importance. For example, without departing the scope of the present disclosure, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element.

It will be understood that when an element (for example, a first element) is referred to as being “(operatively or communicatively) coupled with/to” or “connected to” another element (for example, a second element), it can be directly coupled with/to or connected to the other element or an intervening element (for example, a third element) may be present. In contrast, when an element (for example, a first element) is referred to as being “directly coupled with/to” or “directly connected to” another element (for example, a second element), it should be understood that there are no intervening element (for example, a third element).

Referring toFIG. 1, a stepping motor according to various embodiments of the present disclosure includes a shaft10, and two or more engine units100and200that are connected to the shaft10.

According to various embodiments, the shaft10extends along an axis11, and the shaft10has a thread12that is formed on an outer peripheral surface thereof at a specific pitch, and a nut member13that is coupled to the thread12to be movable.

An object15, such as a lens, that is to be moved may be attached to the nut member13.

Accordingly, the nut member13may be linearly moved along the thread12in a direction of the axis11as the shaft10is rotated by the two or more engine units100and200, and thus the object15connected to the nut member13also may be linearly moved in the direction of the axis11.

Further, the shaft10may be rotatably supported by one or more brackets31and32, and the brackets31and32have bearings31aand32athat rotatably support an outer peripheral surface of the shaft10.

Referring toFIGS. 1 and 2, the two brackets31and32may be installed to support the two or more engine units100and200, and although the bracket31located on the upper side will referred to as a first bracket31and the bracket32located on the lower side will be referred to as a second bracket32for convenience of description, various embodiments of the present disclosure are not limited thereto.

The two or more engine units100and200may be installed to be coaxial with the shaft10.

According to various embodiments, as illustrated inFIGS. 1 and 2, the two or more engine units100and200may be installed adjacent to one end of the shaft10.

A driver40may be connected to the engine units100and200, and a controller50for transmitting a driving signal may be connected to the driver40.

According to various embodiments, as illustrated inFIG. 8, when an output current is sufficient, the driver40may be connected in parallel to the plurality of engine units100and200, and thus the controller50may control the engine units100and200in the same manner as in the case of installing a single engine unit.

According to another embodiment, as illustrated inFIG. 9, when an output current is not sufficient, two or more drivers41and42may be individually connected to two or more engine units100and200and driving signals for driving the drivers41and42may be transmitted by the controller50in the same method, and thus, the controller50may control the engine units100and200in the same method as in the case of driving a single engine unit.

Although the engine unit of the engine units100and200ofFIG. 1, which is located on the upper side, will be referred to as a first engine unit100and the engine unit, which is located on the lower side, will be referred to as a second engine unit200for convenience of description, various embodiments of the present disclosure are not limited thereto.

Referring toFIGS. 1 and 2, the first engine unit100may include a first rotor110, and a first stator120arranged at a circumference of the first rotor110.

The first rotor110may be installed on one side of the shaft10, and a plurality of magnets (not illustrated) may be arranged on an outer surface of the first rotor110to be spaced apart from each other by a specific interval such that the N poles and S poles of the magnets are alternately arranged.

The first stator120may have an upper stator130and a lower stator140that is arranged below the upper stator130.

The upper stator130may have an upper coil131and an upper bobbin132on which the upper coil131is wound.

The upper bobbin132is installed between an outer yoke133and an inner yoke134, and each of the outer yoke133and the inner yoke134may have a plurality of teeth133aand134athat are formed in a circumferential direction thereof. The plurality of teeth133aand134amay be arranged to be radially spaced apart from an outer peripheral surface of the first rotor110.

Referring toFIG. 3, the teeth133aof the outer yoke133and the teeth134aof the inner yoke134may have the same size and the same period T, and may be assembled to form a zigzag pattern.

Referring toFIG. 2, the outer yoke133may have a cup shape having a plurality of teeth133aon an inner peripheral surface thereof, and the inner yoke134may have a plate shape having a plurality of teeth134aon an inner peripheral surface thereof.

The lower stator140may have a lower coil141and a lower bobbin142on which the lower coil141is wound.

The lower bobbin142is installed between an outer yoke143and an inner yoke144, and each of the outer yoke143and the inner yoke144may have a plurality of teeth143aand144athat are formed in a circumferential direction thereof. The plurality of teeth143aand144amay be arranged to be radially spaced apart from an outer peripheral surface of the first rotor110.

The teeth143aof the outer yoke143and the teeth144aof the inner yoke144may have the same size and the same period T as illustrated inFIG. 3, and may be assembled to form a zigzag pattern.

Referring toFIG. 2, the outer yoke143may have a cup shape having a plurality of teeth143aon an inner peripheral surface thereof, and the inner yoke144may have a plate shape having a plurality of teeth144aon an inner peripheral surface thereof.

<First Phase Difference Between Upper Stator and Lower Stator of First Engine Unit>

According to various embodiments, the teeth133aand134aof the upper stator130and the teeth143aand144aof the lower stator140have the same size and the same period T.

As illustrated inFIG. 3, the teeth133aand134aof the upper stator130and the teeth143aand144aof the lower stator140are arranged to have a first phase difference a1.

For example, the first phase a1is ¼×T for one period T of the teeth133a,134b,143a, and144a(a1=¼ T), voltages applied to the upper coil131and the lower coil141may have a phase difference of 90° as illustrated inFIG. 10.

<First Welding Guides of Upper Stator and Lower Stator of First Engine Unit>

A top surface of the outer yoke143of the lower stator140and a bottom surface of the inner yoke134of the upper stator130may be coupled to each other through welding or the like.

Referring toFIG. 4, the inner yoke134of the upper stator130and the outer yoke143of the lower stator140may have a plurality of first welding guides135and145, corresponding ones of which face each other in a vertical direction. Through the plurality of first welding guides135and145, a first phase difference a1 between the teeth133aand134aof the upper stator130and the teeth143aand144aof the lower stator140may be precisely established.

According to various embodiments, as illustrated inFIG. 4, the plurality of first welding guides135and145may include a plurality of upper welding bosses135that are formed on the bottom surface of the inner yoke134of the upper stator130, and a plurality of lower welding bosses145that are formed on the top surface of the outer yoke143of the lower stator140.

The plurality of upper welding boss135may protrude downwards, and the plurality of low welding bosses145may protrudes upwards. Accordingly, as the upper welding bosses135and the lower welding bosses145are welded while being aligned with each other, the upper stator130and the lower stator140may be coupled to each other in a vertical direction.

The plurality of first welding guides135and145may be arranged to be spaced apart from each other by a first interval S1, and the first interval S1 of the welding bosses135and145may be an integer times as large as a half (T/2) of the period of the teeth133aand134aas in Equation 1.

Referring toFIG. 4, the teeth133aand134aof the upper stator130and the teeth143aand144aof the lower stator140are arranged to be misaligned by a half of the first phase difference a1in opposite directions with respect to the welding bosses135and145such that the first phase difference a1 between the upper stator130and the lower stator140may be precisely established.

For example, as illustrated inFIG. 4, the first phase a1between the teeth133aand134aof the upper stator130and the teeth143aand144aof the lower stator140is ¼×T, a center line C1of the teeth134aof the inner yoke134of the upper stator130may be spaced apart from the first welding bosses135and145by ⅛×T that is a half of the first phase a1in a first direction (arrow K1) and a center line C2of the teeth143aof the outer yoke143of the lower stator140may be spaced apart from the welding bosses135and145by ⅛×T that is a half of the first phase a1in a second direction (arrow K2) that is opposite to the first direction.

Because a coupling location of the upper stator130and the lower stator140may be set through the welding bosses135and145, the teeth133aand134aof the upper stator130and the teeth143aand144aof the lower stator140may precisely implement the first phase difference a1, and thus a resolution of the first stator120may be secured.

According to another embodiment, as illustrated inFIG. 5, the plurality of first welding guides135and145may include a plurality of welding bosses135that are formed on the bottom surface of the inner yoke134of the upper stator130, and a plurality of lower welding recesses146that are formed on the top surface of the outer yoke143of the lower stator140.

Accordingly, as the plurality of welding bosses135are inserted into the plurality of welding recesses146and are fused to the welding recesses146within the welding recesses146through welding, the upper stator130and the lower stator140may be coupled to each other vertically. Further, the welding bosses135may be formed to be larger than the welding recesses146to be fused firmly.

Further, in various embodiments of the present disclosure, a configuration that is opposite to the structure ofFIG. 5may be possible. For example, a plurality of welding recesses may be formed on the bottom surface of the inner yoke134of the upper stator130, and a plurality of welding bosses may be formed on the top surface of the outer yoke143of the lower stator140.

Referring toFIGS. 1 and 2, the second engine unit200may include a second rotor210, and a second stator220that is arranged at a circumference of the second rotor210.

The second rotor210may be fixed to a driving shaft10, and a plurality of magnets (not illustrated) may be arranged on an outer surface of the second rotor210to be spaced apart from each other by a specific interval such that the N poles and S poles of the magnets are alternately arranged.

The second stator220may have an upper stator230, and a lower stator240that is arranged below the upper stator230.

The upper stator230may have an upper coil231and an upper bobbin231on which the upper coil231is wound.

The upper bobbin232is installed between an outer yoke233and an inner yoke234, and each of the outer yoke233and the inner yoke234may have a plurality of teeth233aand234athat are formed in a circumferential direction thereof. The plurality of teeth233aand234amay be arranged to be spaced apart from an outer peripheral surface of the second rotor210by a specific interval.

Referring toFIG. 3, the teeth233aof the outer yoke233and the teeth234aof the inner yoke234may have the same size and the same period T, and may be assembled to form a zigzag pattern.

Referring toFIG. 2, the outer yoke233may have a cup shape having a plurality of teeth233aon an inner peripheral surface thereof, and the inner yoke234may have a plate shape having a plurality of teeth234aon an inner peripheral surface thereof.

The lower stator240may have a lower coil241and a lower bobbin242on which the lower coil241is wound.

The lower bobbin242is installed between an outer yoke243and an inner yoke244, and each of the outer yoke243and the inner yoke244may have a plurality of teeth243aand244athat are formed in a circumferential direction thereof. The plurality of teeth243aand244amay be arranged to be radially spaced apart from an outer peripheral surface of the second rotor210.

Referring toFIG. 3, the teeth243aof the outer yoke243and the teeth244aof the inner yoke244may have the same size and the same period T, and may be assembled to form a zigzag pattern.

Referring toFIG. 2, the outer yoke243may have a cup shape having a plurality of teeth243aon an inner peripheral surface thereof, and the inner yoke244may have a plate shape having a plurality of teeth244aon an inner peripheral surface thereof.

<Second Phase Difference Between Upper Stator and Lower Stator of Second Engine Unit>

According to various embodiments, the teeth233aand234aof the upper stator230and the teeth243aand244aof the lower stator240have the same size and the same period T as illustrated inFIG. 3.

As illustrated inFIG. 3, the teeth233aand234aof the upper stator230and the teeth243aand244aof the lower stator240are arranged to have a second phase difference a2.

For example, the second phase a2is ¼×T for one period T of the teeth233a,234a,243a, and244a(a2=¼T), voltages applied to the upper coil231and the lower coil241may have a phase difference of 90° as illustrated inFIG. 10.

According to various embodiments, the second phase difference a2 of the second engine unit200may be the same as the first phase difference a1 of the first engine unit100.

According to another embodiment, the second phase difference a2 of the second engine unit200may be different from the first phase difference a1 of the first engine unit100.

<Second Welding Guides of Upper Stator and Lower Stator of Second Engine Unit>

A top surface of the outer yoke243of the lower stator240and a bottom surface of the inner yoke234of the upper stator230may be coupled to each other through welding or the like.

The plurality of second welding guides235and245may be formed on the bottom surface of the inner yoke234of the upper stator230and the top surface of the outer yoke243of the lower stator240at locations that correspond to each other vertically, and the second phase difference a2 between the teeth233aand234aof the upper stator230and the teeth243aand244aof the lower stator240may be precisely established through the plurality of second welding guides235and245.

Referring toFIG. 4, the inner yoke134of the upper stator130and the outer yoke143of the lower stator140may have a plurality of first welding guides135and145, corresponding ones of which face each other in a vertical direction. Through the plurality of first welding guides135and145, a first phase difference a1 between the teeth133aand134aof the upper stator130and the teeth143aand144aof the lower stator140may be precisely established.

According to various embodiments, the plurality of second welding guides235and245may include a plurality of upper welding bosses235that are formed on the bottom surface of the inner yoke234of the upper stator230, and a plurality of lower welding bosses245that are formed on the top surface of the outer yoke243of the lower stator240.

The plurality of upper welding boss235may protrude downwards, and the plurality of low welding bosses245may protrudes upwards. Accordingly, as the upper welding bosses235and the lower welding bosses245are fused to each other while being aligned with each other, the upper stator230and the lower stator240may be coupled to each other in a vertical direction.

The plurality of welding guides235and245may be arranged to be spaced apart from each other by a second interval S2, and the second interval S2 of the welding bosses235and245may be an integer times as large as a half (T/2) of the period of the teeth133aand134aas in Equation 2.

According to various embodiments, the second interval S2of the second engine unit200may be the same as the first interval S1of the first engine unit100.

According to another embodiment, the second interval S2of the second engine unit200may be different from the first interval S1of the first engine unit100.

The teeth233aand234aof the upper stator230and the teeth243aand244aof the lower stator240are arranged to be misaligned by a half of the second phase difference azin opposite directions with respect to the second welding guides235and245such that the second phase difference azbetween the upper stator230and the lower stator240may be precisely established.

For example, the second phase azbetween the teeth233aand234aof the upper stator230and the teeth243aand244aof the lower stator240is ¼×T, a center line C3of the teeth234aof the inner yoke234of the upper stator230may be spaced apart from the second welding guides235and245by a half a2/2 of the second phase a2in a first direction (arrow K1) and a center line C4of the teeth243aof the outer yoke243of the lower stator240may be spaced apart from the welding bosses225and245by a half a2/2 of the second phase azin a second direction (arrow K2) that is opposite to the first direction.

Because a coupling location of the upper stator230and the lower stator240may be accurately set through the welding bosses235and245, the teeth233aand234aof the upper stator230and the teeth243aand244aof the lower stator240may precisely implement the second phase difference az, and thus the number of steps that is a resolution of the second stator220may be secured.

According to another embodiment, as illustrated inFIG. 5, the plurality of second welding guides235and246may include a plurality of welding bosses235that are formed on the bottom surface of the inner yoke134of the upper stator230, and a plurality of lower welding recesses246that are formed on the top surface of the outer yoke243of the lower stator240.

Accordingly, as the plurality of welding bosses235are inserted into the plurality of welding recesses246and are fused to the welding recesses246within the welding recesses246through welding, the upper stator230and the lower stator240may be coupled to each other vertically. Further, the welding bosses235may be formed to be larger than the welding recesses246to be fused firmly.

In various embodiments of the present disclosure, a configuration that is opposite to the structure ofFIG. 5may be possible. For example, a plurality of welding recesses may be formed on the bottom surface of the inner yoke234of the upper stator230, and a plurality of welding bosses may be formed on the top surface of the outer yoke243of the lower stator240.

<Same Phase of First Engine Unit and Second Engine Unit>

Referring toFIGS. 3 to 5, the teeth133a,134a,143a, and144aof the first engine unit100and the teeth233a,234a,243a, and244amay be arranged to have the same phase.

In this way, according to the present disclosure, an output torque of the stepping motor may become two times higher by adding an output torque by the first engine unit100and an output torque by the second engine unit200.

Further, if three engine units100are installed in the shaft10, an output torque of the stepping motor may become three times by adding output torques of the three engine units, and if four engine units are installed in the shaft10, an output torque of the stepping motor may become four times by adding outputs of the four engine units.

<Third Welding Guides of First Engine Unit and Second Engine Unit>

Referring toFIG. 4, the first engine unit100and the second engine unit200may be coupled through welding or the like, and third welding guides331and332may be formed between the first engine unit100and the second engine unit200.

The lower stator140of the first engine unit100and the upper stator230of the second engine unit200may have a plurality of third welding guides331and332, corresponding ones of which face each other vertically, and the first engine unit100and the second engine unit200may be arranged to have the same phase through the plurality of third welding guides331and332.

According to various embodiments, the plurality of third welding guides331and332may include a plurality of upper welding bosses331that are formed in the lower stator140of the first engine unit100, and a plurality of lower welding bosses332that are formed in the upper stator230of the second engine unit200.

The plurality of upper welding boss331may protrude downwards, and the plurality of low welding bosses332may protrudes upwards. Accordingly, as the upper welding bosses331and the lower welding bosses332are fused to each other while being aligned with each other, the first engine unit100and the second engine unit200may be coupled to each other in a vertical direction.

The plurality of first welding guides331and332may be arranged to be spaced apart from each other by a third interval S3, and the third interval S3 of the welding bosses335and336may be an integer times as large as a half (T/2) of the period of the teeth133a,134a,143a,144a,233a,234a,243a, and244aas in Equation 3.

According to various embodiments, as illustrated inFIG. 5, the plurality of third welding guides331and337may include a plurality of welding bosses331that are formed in the lower stator140of the first engine unit100, and a plurality of welding recesses337that are formed in the upper stator230of the second engine unit200.

Accordingly, as the plurality of welding bosses331are inserted into the plurality of welding recesses337and are fused to the welding recesses337within the welding recesses337through welding, the first engine unit100and the second engine unit200may be coupled to each other vertically. Further, the welding bosses331may be formed to be larger than the welding recesses337to be fused more firmly.

Further, in various embodiments of the present disclosure, a configuration that is opposite to the structure ofFIG. 5may be possible. For example, a plurality of welding recesses may be formed in the lower stator140of the first engine unit100, and a plurality of welding bosses may be formed in the upper stator230of the second engine unit200.

<Fourth Welding Guides of First Engine Unit and First Bracket>

Referring toFIG. 4, the first engine unit100and the first bracket31may be coupled through welding or the like, and the first bracket31and the first engine unit100may have a plurality of fourth welding guides333and334, corresponding ones of which face each other vertically.

According to various embodiments, the plurality of fourth welding guides333and332may include a plurality of upper welding bosses334that are formed in the upper stator130of the first engine unit100, and a plurality of lower welding bosses334that are formed in the first bracket31.

The plurality of upper welding boss333may protrude downwards, and the plurality of low welding bosses334may protrudes upwards. Accordingly, as the upper welding bosses333and the lower welding bosses334are fused to each other while being aligned with each other, the first engine unit100and the first bracket31may be coupled to each other in a vertical direction.

The plurality of fourth welding guides333and334may be arranged to be spaced apart from the aforementioned third welding guides331and332by the same third interval S3.

According to various embodiments, as illustrated inFIG. 5, the plurality of fourth welding guides333and338may include a plurality of welding bosses333that are formed in the first bracket31, and a plurality of welding recesses338that are formed in the upper stator130of the first engine unit100.

Accordingly, as the plurality of welding bosses333are inserted into the plurality of welding recesses338and are fused to the welding recesses338within the welding recesses337through welding, the first bracket31and the first engine unit100may be coupled to each other vertically. Further, the welding bosses333may be formed to be larger than the welding recesses338to be fused more firmly.

Further, in various embodiments of the present disclosure, a configuration that is opposite to the structure ofFIG. 5may be possible. For example, a plurality of welding recesses may be formed in the first bracket31, and a plurality of welding bosses may be formed in the upper stator130of the first engine unit100.

<Fifth Welding Guides of Second Engine Unit and Second Bracket>

Referring toFIG. 4, the second engine unit200and the second bracket32may be coupled through welding or the like, and the second engine unit200and the second bracket32may have a plurality of fifth welding guides335and336, corresponding ones of which face each other vertically.

According to various embodiments, the plurality of fifth welding guides335and336may include a plurality of upper welding bosses335that are formed in the lower stator240of the second engine unit200, and a plurality of lower welding bosses335that are formed in the second bracket32.

The plurality of upper welding boss335may protrude downwards, and the plurality of low welding bosses336may protrudes upwards. Accordingly, as the upper welding bosses335and the lower welding bosses336are welded while being aligned with each other through welding, the second engine unit200and the second bracket32may be coupled to each other in a vertical direction.

The plurality of fifth welding guides335and336may be arranged to be spaced apart from the aforementioned third welding guides331and332by the same third interval S3.

According to various embodiments, as illustrated inFIG. 5, the plurality of fifth welding guides335and339may include a plurality of welding bosses335that are formed in the lower stator240of the second engine unit200, and a plurality of welding recesses339that are formed in the second bracket32.

Accordingly, as the plurality of welding bosses335are inserted into the plurality of welding recesses339and are fused to the welding recesses338within the welding recesses339through welding, the second engine unit200and the second bracket32may be coupled to each other vertically. Further, the welding bosses335may be formed to be larger than the welding recesses339to be fused more firmly.

Further, in various embodiments of the present disclosure, a configuration that is opposite to the structure ofFIG. 5may be possible. For example, a plurality of welding recesses may be formed in the second engine unit200, and a plurality of welding bosses may be formed in the second bracket32.

<Third Phase Difference Between First Engine Unit and Second Engine Unit>

According to another embodiment, as illustrated inFIG. 6, the teeth133a,134a,143a, and144aof the first engine units100and the teeth233a,234a,243a, and244aof the second engine200may be arranged to have a third phase difference a3.

The third phase difference a3 may be ¼(x) T for one period T of the teeth as in Equation 4.

Here, x represents the number of engine units, and when the number of engine units is 2, the third phase difference a3is ⅛×T, when the number of engine units is 3, the third phase difference a3is 1/12×T, and the number of engine units is 4, the third phase difference a3is 1/16×T.

Further, when the number of engine units is 2, the third phase difference a3between the first engine unit100and the second engine unit200is ⅛×T, voltages applied to the upper coil131of the first engine unit100and the upper coil231of the second engine unit200may have a phase difference of 90° as illustrated inFIG. 10.

The adjacent teeth144aand233aof the first engine unit100and the second engine unit200may be arranged to be misaligned by a half a3/2 of the third phase difference a3in opposite directions with respect to the third welding guides335and336, and through this, a third phase difference a3between the first engine unit100and the second engine unit200may be established.

For example, referring toFIG. 7, when the third phase difference a3is ⅛×T, an imaginary line C5 that extends perpendicularly to an end of any one tooth144aof the first engine unit100may be spaced apart from the third welding guides335and336by ⅛×T that is a half of the third phase difference a3in the first direction (arrow K1), and an imaginary line C6 that extends perpendicularly to an end of a tooth233aof the second engine unit200may be spaced apart from the third welding guides335and336by ⅛×T that is a half of the third phase difference a3in the second direction (arrow K2).

In this way, as the first engine unit100and the second engine unit200have the third phase difference a3, an output of the stepping motor becomes two times as compared with the case of installing a single engine unit and a resolution of the stepping motor becomes two times by adding the number of steps (resolution) of the first engine unit100and the number of steps (resolution) of the second engine unit200. In addition, if three engine units are coupled to the shaft10and the three engine units are arranged to have a third phase difference a3 of 1/12 T, the resolution of the stepping motor may become three times.

Further, because the configurations of the third welding guides331and332, the fourth welding guides333and334, and the fifth welding guides335and336are the same as or similar to those of the preceding embodiments, a detailed description thereof will be omitted.

According to various embodiments, because two or more engine units100and200are installed on an outer peripheral surface of the shaft10in a row, two or more rotors110and120may be provided in the shaft10in a row as inFIG. 2. Because the two rotors110and120may be magnetized at the same time while being installed integrally with the shaft10, the magnetic poles of the two or more rotors110and120may be precisely established.

Referring toFIG. 11, in another embodiment of the present disclosure, the first engine unit100and the second engine unit200may be installed at opposite ends of the shaft10, respectively.

The first bracket31may be arranged at one end of the shaft10, and the first engine unit100may be coupled to the first bracket31. The first bracket31and the first engine unit100may be coupled to each other through the aforementioned fourth engine guides333and334or333and338.

The second bracket32may be arranged at an opposite end of the shaft10, and the second engine unit200may be coupled to the second bracket32. The second bracket32and the second engine unit200may be coupled to each other through the aforementioned fifth engine guides335and336or335and339.

Because the remaining configurations thereof are the same as or similar to those of the preceding embodiments, a detailed description thereof will be omitted.

According to various embodiments of the present disclosure, an output torque of a stepping motor can be increased while the stepping motor has a compact size, by connecting two or more engine units to a shaft.

According to various embodiments of the present disclosure, an output torque of a stepping motor can be increased and a resolution (location precision) of the stepping motor can be increased as well by providing a phase difference between the teeth of two or more engine units.

According to various embodiments, a stepping of various layouts may be implemented at low costs because two or more engine units are installed in a shaft.