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Title:
ROTOR ASSEMBLY AND STEPPING MOTOR INCLUDING SAME
Document Type and Number:
WIPO Patent Application WO/2017/072228
Kind Code:
A1
Abstract:
The present device relates to a rotor assembly, which comprises: a rotor casing (1); a rotor shaft (2) with an external thread, the rotor shaft (2) being installed inside said rotor casing (1); a magnet (3), the magnet (3) being installed outside said rotor casing (1); and a telescopic shaft (4), the telescopic shaft (4) being mounted on the external thread of said rotor shaft (2) via an internal thread on an inner surface of the telescopic shaft. The rotor assembly according to the present device has the advantages of being long, having few components, the manufacturing cost being low, and the linear accuracy being high.

Inventors:
CHEN, Kun (E8-2-201, Glory city communityChizhushan east roa, Wuhu Anhui 0, 241000, CN)
CHENG, Tao (Xinde feicui Wan 1102/ 6-1-1102, Economic development zone / Wuhu, Anhui 9, 241009, CN)
Application Number:
EP2016/075924
Publication Date:
May 04, 2017
Filing Date:
October 27, 2016
Export Citation:
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Assignee:
CONTINENTAL AUTOMOTIVE GMBH (Vahrenwalder Straße 9, Hannover, 30165, DE)
International Classes:
H02K37/14; F16C3/03; H02K7/06
Domestic Patent References:
WO1999044274A11999-09-02
WO2015067690A22015-05-14
Foreign References:
US20130278098A12013-10-24
CN201674378U2010-12-15
CN202300660U2012-07-04
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Claims:
Patent claims

1. A rotor assembly, characterized by comprising:

a rotor casing (1) ;

a rotor shaft (2) with an external thread, the rotor shaft

(2) being installed inside said rotor casing (1);

a magnet (3), the magnet (3) being installed outside said rotor casing (1); and

a telescopic shaft (4), the telescopic shaft (4) being a hollow tube with an internal thread and being installed on the external thread of said rotor shaft (2) via the internal thread on the inner surface of the telescopic shaft.

2. The rotor assembly according to claim 1, characterized in that said rotor assembly further comprises: a bearing (5) installed at the outer periphery of said rotor casing (1) .

3. The rotor assembly according to claim 1, characterized in that the interior of said rotor casing (1) is of a hollow structure, and the external thread of said rotor shaft (2) is at least partially located in the internal hollow structure of said rotor casing (1) .

4. The rotor assembly according to claim 3, characterized in that, through cooperation with the external thread of said rotor shaft (2), said telescopic shaft (4) can be partially or completely rotated into the internal hollow structure of said rotor casing (1) . 5. The rotor assembly according to claim 1, characterized in that said magnet (3) is an annular magnet, and is fitted round and fixed on a cylindrical outer surface of said rotor casing (1) .

6. The rotor assembly according to claim 1, characterized in that the outer surface of said telescopic shaft (4) is provided with a guiding groove or a guiding protrusion.

7. The rotor assembly according to claim 6, characterized in that said guiding groove or guiding protrusion extends from one end of said telescopic shaft (4) in the axial direction of said telescopic shaft (4) but does not penetrate through to the other end of said telescopic shaft (4) .

8. The rotor assembly according to claim 6, characterized in that two guiding grooves or guiding protrusions are provided, and are symmetrically distributed on the outer surface of said telescopic shaft (4).

9. The rotor assembly according to claim 3, characterized in that said rotor casing (1) and said rotor shaft (2) are fitted together by injection moulding, and a bare end (21) of said rotor shaft (2) after injection moulding is located outside a closed end of said rotor casing (1) .

10. The rotor assembly according to claim 1, characterized in that a zigzag structure 22 is formed at the outer periphery of the joint of said rotor shaft (2) and said rotor casing (1) .

11. A stepping motor, comprising:

a stator (6) with a coil wound outside;

a rotor assembly installed inside said stator (6);

a magnetic guide ring (10) surrounding the outer periphery of said stator (6);

an electrical connector (8) for powering the stepping motor; characterized in that said rotor assembly further com¬ prises :

a rotor casing (1); a rotor shaft (2) with an external thread, the rotor shaft (2) being installed inside said rotor casing (1) ; a magnet (3) , the magnet (3) being installed outside said rotor casing (1) ; and a telescopic shaft (4) , the telescopic shaft (4) being a hollow tube with an internal thread and being installed in a fitted manner on the external thread of said rotor shaft (2) via the internal thread on the inner surface of the telescopic shaft, a bearing (5) installed at the outer periphery of said rotor casing (1) .

12. The stepping motor according to claim 11, charac- terized in that said magnet (3) is an annular magnet and is located inside said stator (6) and an outer ring thereof is in a clearance fit with said stator (6) .

13. The stepping motor according to claim 11, charac- terized in that the outer ring of said bearing (5) is press-fitted into said stator (6) .

14. The stepping motor according to claim 11, characterized in that the interior of said rotor casing (1) is of a hollow structure, and the external thread of said rotor shaft (2) is at least partially located in the internal hollow structure of said rotor casing (1) .

15. The stepping motor according to claim 14, charac- terized in that, through cooperation with the external thread of said rotor shaft (2) , said telescopic shaft (4) can be partially or completely rotated into the internal hollow structure of said rotor casing (1) . 16. The stepping motor according to claim 11, characterized in that the outer surface of said telescopic shaft (4) is provided with a guiding groove, said guiding groove extends from one end of said telescopic shaft (4) in the axial direction of said telescopic shaft (4) but does not penetrate through to the other end of said telescopic shaft (4) .

17. The stepping motor according to claim 16, characterized in that said stepping motor further comprises: a front end cover (9) press-fitted into said magnetic guide ring (10) and provided with a protrusion structure, the protrusion structure being at least partially located inside the guiding groove on said telescopic shaft (4), thereby preventing rotation of said telescopic shaft (4) and guiding said telescopic shaft (4) in the axial direction.

18. The stepping motor according to claim 11, charac- terized in that the outer surface of said telescopic shaft (4) is provided with a guiding protrusion, said guiding protrusion extends from one end of said telescopic shaft (4) in the axial direction of said telescopic shaft (4) but does not penetrate through to the other end of said telescopic shaft (4) .

19. The stepping motor according to claim 18, characterized in that said stepping motor further comprises: a front end cover (9) press-fitted into said magnetic guide ring (10) and provided with a groove structure, the groove structure at least partially enclosing the guiding protrusion on said telescopic shaft (4), thereby preventing rotation of said telescopic shaft (4) and guiding said telescopic shaft (4) in the axial direction.

20. The stepping motor according to claim 11, charac- terized in that said rotor casing (1) and said rotor shaft (2) are fitted together by injection moulding, and a bare end (21) of said rotor shaft (2) after injection moulding is located outside a closed end of said rotor casing (1) . 21. The stepping motor according to claim 20, characterized in that a positioning hole (61) is formed on said stator (6), and the bare end (21) of said rotor shaft (2) is at least partially located in the positioning hole (61) . 22. The stepping motor according to claim 11, characterized in that said stepping motor further comprises : a coupling ball (7) installed at an output end of said telescopic shaft (4) .

23. The stepping motor according to claim 17 or 19, characterized in that said stepping motor further comprises: an O-ring (11), the O-ring (11) being arranged on said front end cover (9) in a surrounding manner.

24. The stepping motor according to claim 11, characterized in that said stepping motor further comprises : a rear end cover (12) , the rear end cover (12) being press-fitted onto said electrical connector (8) .

25. The rotor assembly according to claim 11, charac¬ terized in that a zigzag structure 22 is formed at the outer periphery of the joint of said rotor shaft (2) and said rotor casing ( 1 ) .

Description:
Description

Rotor assembly and stepping motor including same Technical Field

The present device relates to the field of automobile parts, in particular to a rotor assembly applied to an adaptive steering headlight of an automobile and a stepping motor including same. Background Art

In order to improve the safety of driving operation of an automobile, provided in industry is a system for adaptively controlling the illumination direction of a vehicle light; the system follows a steering angle of a steering wheel and a pitch angle of a vehicle suspension system to perform rotation in the left, right, up and down directions, such that the illumination direction of the vehicle light (especially a headlamp) not only faces in the direction of travel in a straight line, but also can face in the direction in which a driver steers, and the system plays a major role in improving the running safety of the automobile .

In the above system for controlling a vehicle light, a stepping motor (such as a linear stepping motor) is used as a driving device at present in industry; however, as shown in the Chinese authorized patents with publication numbers CN 201674378 U and CN 202300660 U, the structure of the rotor and the output shaft included in the stepping motor serving as a driving device has the following defects: the shaft inserted into the rotor comprises a smooth guiding portion located outside the rotor, and a threaded portion located inside the rotor and fitted with the rotor; in this structure, in order to achieve a certain travel, the length of the shaft must be more than double the traversed length, such that the manufacturing cost of the shaft is high, the linear accuracy is hard to ensure, and the overall size of the electric motor is too long.

Summary of the Invention The purpose of the present device is to provide a stepping motor applied to a headlight steering system and a rotor assembly included in same, thereby solving the problem of how to increase the travel of the output shaft in the case where the overall size of the electric motor is constant.

A rotor assembly provided by the present device comprises: a rotor casing 1; a rotor shaft 2 with an external thread, the rotor shaft 2 being installed inside said rotor casing 1; a magnet 3, the magnet 3 being installed outside said rotor casing 1; and a telescopic shaft 4, the telescopic shaft 4 being a hollow tube with an internal thread and being installed on the external thread of said rotor shaft 2 via the internal thread on the inner surface of the telescopic shaft.

Preferably, said rotor assembly further comprises a bearing 5 installed at the outer periphery of said rotor casing 1.

Preferably, the interior of said rotor casing 1 is of a hollow structure, and the external thread of said rotor shaft 2 is at least partially located in the internal hollow structure of said rotor casing 1.

Preferably, through cooperation with the external thread of said rotor shaft 2, said telescopic shaft 4 can be partially or completely rotated into the internal hollow structure of said rotor casing 1.

Preferably, said magnet 3 is an annular magnet , and is fitted round and fixed on a cylindrical outer surface of said rotor casing 1.

Preferably, the outer surface of said telescopic shaft 4 is provided with a guiding groove, said guiding groove extends from one end of said telescopic shaft 4 in the axial direction of said telescopic shaft 4 but does not penetrate through to the other end of said telescopic shaft 4, and there are two said guiding grooves which are symmetrically distributed on the outer surface of said telescopic shaft 4.

Preferably, said rotor casing 1 and said rotor shaft 2 are fitted together by injection moulding, and a bare end 21 of said rotor shaft 2 after in ection moulding is located outside a closed end of said rotor casing 1. Preferably, a zigzag structure 22 is formed at the outer periphery of the joint of said rotor shaft 2 and said rotor casing 1.

The present device further provides a stepping motor, comprising:

a stator 6 with a coil wound outside; a rotor assembly installed inside said stator 6; a magnetic guide ring 10 surrounding the outer periphery of said stator 6; an electrical connector 8 for powering the stepping motor; said rotor assembly further comprises: a rotor casing 1; a rotor shaft 2 with an external thread, the rotor shaft 2 being installed inside said rotor casing 1; a magnet 3, the magnet 3 being installed outside said rotor casing 1; and a telescopic shaft 4, the telescopic shaft 4 being a hollow tube with an internal thread and being installed in a fitted manner on the external thread of said rotor shaft 2 via the internal thread on the inner surface of the telescopic shaft; and a bearing 5 installed at the outer periphery of said rotor casing 1.

Preferably, said magnet 3 is an annular magnet and is located inside said stator 6, and an outer ring thereof is in a clearance fit with said stator 6.

Preferably, an outer ring of said bearing 5 is pressed into said stator 6.

Preferably, the interior of said rotor casing 1 is of a hollow structure, and the external thread of said rotor shaft 2 is at least partially located in the internal hollow structure of said rotor casing 1.

Preferably, through cooperation with the external thread of said rotor shaft 2, said telescopic shaft 4 can be partially or completely rotated into the internal hollow structure of said rotor casing 1.

Preferably, the outer surface of said telescopic shaft 4 is provided with a guiding groove, said guiding groove extends from one end of said telescopic shaft 4 in the axial direction of said telescopic shaft 4 but does not penetrate through to the other end of said telescopic shaft 4. Preferably, said stepping motor further comprises: a front end cover 9 press-fitted into said magnetic guide ring 10 and provided with a protrusion structure, the protrusion structure being at least partially located inside the guiding groove on said telescopic shaft 4, thereby preventing rotation of said tel ¬ escopic shaft 4 and guiding said telescopic shaft 4 in the axial direction .

Preferably, said rotor casing 1 and said rotor shaft 2 are fitted together by injection moulding, and a bare end 21 of said rotor shaft 2 after injection moulding is located outside the closed end of said rotor casing 1.

Preferably, a positioning hole 61 is formed on said stator 6, and the bare end 21 of said rotor shaft 2 is at least partially located in the positioning hole 61.

Preferably, said stepping motor further comprises: a coupling ball 7 installed at an output end of said telescopic shaft 4; an O-ring 11, the O-ring 11 being arranged on said front end cover 9 in a surrounding manner; and a rear end cover 12, the rear end cover 12 being press-fitted onto said electrical connector 8.

Preferably, a zigzag structure 22 is formed at the outer periphery of the joint of said rotor shaft 2 and said rotor casing 1.

Compared with the prior art, since the present device uses a novel structural design of a rotor assembly and a stepping motor, in the case where the overall external size of the electric motor is constant, the telescopic shaft (output shaft) can provide a longer travel, and at the same time, the manufacturing cost is reduced, and the linear accuracy is ensured.

Description of the Drawings

The drawings constituting a part of the present invention are used to provide further understanding of the present device; schematic embodiments and illustrations thereof of the present device are used to explain the present device, and do not form an inappropriate definition of the present device. In the drawings : Fig. 1 is an exploded view of various parts of said rotor assembly of the present device;

Fig. 2 is a sectional view of the rotor assembly shown in Fig. 1 after being assembled;

Fig. 3A is a perspective schematic view of a telescopic shaft shown in Fig. 1;

Fig. 3B is a front view of the telescopic shaft shown in Fig.

3A;

Fig. 3C is a left view of Fig. 3B;

Fig. 3D is a sectional view of Fig. 3B;

Fig. 4 is a sectional view of a stepping motor comprising the rotor assembly shown in Fig. 1;

Fig. 5A is a perspective schematic view of a front end cover shown in Fig. 4;

Fig. 5B is a top view of the front end cover shown in Fig.

5A; and

Fig. 6 is a perspective schematic view of the stepping motor shown in Fig. 4 after being assembled. Particular Embodiments

The rotor assembly and the stepping motor including same of the present device will be described below with reference to the accompanying drawings and the embodiments.

Embodiment 1

Fig. 1 is an exploded view of various parts of said rotor assembly of the present device, Fig. 2 is a sectional view of the rotor assembly shown in Fig. 1 after being assembled, and as shown in Fig. 1 and Fig. 2, the rotor assembly specifically consists of the following parts: a rotor casing 1; a rotor shaft 2 with an external thread, the rotor shaft 2 being installed inside said rotor casing 1; a magnet 3, the magnet 3 being installed outside said rotor casing 1; and a telescopic shaft 4, the telescopic shaft 4 being a hollow tube with an internal thread and being installed on the external thread of said rotor shaft 2 via the internal thread on the inner surface of the telescopic shaft.

Preferably, said rotor casing 1 has a structure similar to a hollow cylindrical teacup, the material thereof can be selected randomly according to practical requirements, and in the present embodiment, in order to reduce the weight of the rotor assembly, the material of the rotor casing 1 is preferably plastics; said rotor shaft 2 and said rotor casing 1 are fixedly fitted together by means of injection moulding, the external thread of the rotor shaft 2 can be completely or partially located in an internal hollow structure of said rotor casing 1, a bare end 21 of the rotor shaft 2 after the injection moulding is located outside a closed end of the rotor casing 1 (the rotor shaft 2 is inserted into and penetrates the bottom part of said rotor casing 1 which is similar to the closed end of the teacup) , and furthermore, as shown in Fig. 2, in order to guarantee the connection force between the rotor casing 1 and the rotor shaft 2 after the injection moulding, a zigzag structure 22 is designed and formed at the outer periphery of the joint of said rotor shaft 2 and said rotor casing 1.

Preferably, said magnet 3 is an annular magnet, which is fixedly mounted on a cylindrical outer surface of said rotor casing 1 by means of interference or injection moulding.

Preferably, said telescopic shaft 4 is of a hollow tubular plastic structure with an internal thread and is mounted on the external thread of said rotor shaft 2 via the internal thread on the inner surface thereof so that a rotary motion of the rotor shaft 2 can be converted into a linear motion of the telescopic shaft 4. Furthermore, through cooperation with the external thread of the rotor shaft 2, the telescopic shaft 4 can be partially or completely rotated into the internal hollow structure of said rotor casing 1.

Preferably, as shown in Figs. 3A to 3D, an outer surface of said telescopic shaft 4 is provided with a guiding groove or guiding protrusion (the drawings do not provide an example of the guiding protrusion) , and said guiding groove or guiding protrusion extends from one end of said telescopic shaft 4 in the axial direction of said telescopic shaft 4 but does not penetrate through to the other end of said telescopic shaft 4. The number of said guiding groove (s) or guiding protrusion ( s ) is not defined, and in the present embodiment, there are two said guiding grooves or guiding protrusions (structures 41 and 42 shown in the drawings are guiding grooves), and the two guiding grooves or guiding protrusions are distributed symmetrically on the outer surface of said telescopic shaft 4.

Preferably, as shown in Fig. 1 and Fig. 2, in order to enable the above-mentioned rotor assembly to be fixedly mounted in the motor better, said rotor assembly also comprises a bearing 5 mounted at the outer periphery of said rotor casing 1, and the bearing 5 can be fixedly mounted at the outer periphery of the rotor casing 1 by means of injection moulding, cold pressing or interference .

The above-mentioned rotor assembly structure is mainly applied to the stepping motor, and cooperates with other components such as a stator and a coil to control a system such as an automobile steering headlight system or an air intake/exhaust system.

Embodiment 2

The present embodiment will describe a stepping motor which has a compact structure and a long travel, and the stepping motor comprises the rotor assembly as described in embodiment 1.

Fig. 4 is a sectional view of the stepping motor comprising the rotor assembly as shown in Fig. 1 and Fig. 2; as shown in Fig. 4, the stepping motor described in the present embodiment comprises the following structures: a stator 6 with a coil wound outside; a rotor assembly installed inside said stator 6; a magnetic guide ring 10 surrounding the outer periphery of said stator 6; an electrical connector 8 for powering the stepping motor; wherein said rotor assembly further comprises: a rotor casing 1; a rotor shaft 2 with an external thread, the rotor shaft 2 being installed inside said rotor casing 1; a magnet 3, the magnet 3 being installed outside said rotor casing 1; and a telescopic shaft 4, the telescopic shaft 4 being a hollow tube with an internal thread and being installed in a fitted manner on the external thread of said rotor shaft 2 via the internal thread on the inner surface of the telescopic shaft; and a bearing 5 mounted at the outer periphery of said rotor casing 1, the bearing 5 can be fixedly mounted at the outer periphery of the rotor casing 1 by means of injection moulding, cold pressing or interference .

Preferably, said magnet 3 is an annular magnet, which is located in said stator 6, an outer ring thereof being in clearance fit with said stator 6.

Preferably, an outer ring of said bearing 5 is press-fitted (for example, press-fitted with interference) into said stator 6 so as to support the above-mentioned rotor assembly.

Preferably, said rotor casing 1 has a structure similar to a hollow cylindrical teacup, the material thereof can be selected randomly according to practical reguirements, and in the present embodiment, in order to reduce the weight of the rotor assembly, the material of the rotor casing 1 is preferably plastics; and said rotor shaft 2 and said rotor casing 1 are fixedly fitted together by means of injection moulding, and the external thread of the rotor shaft 2 can be completely or partially located in an internal hollow structure of said rotor casing 1.

Preferably, said telescopic shaft 4 is a hollow tubular plastic structure with an internal thread and is mounted on the external thread of said rotor shaft 2 via the internal thread on the inner surface of the telescopic shaft so that a rotary motion of the rotor shaft 2 can be converted into a linear motion of the telescopic shaft 4. Furthermore, by means of cooperation with the external thread of the rotor shaft 2, the telescopic shaft 4 can be partially or completely rotated into the internal hollow structure of said rotor casing 1.

Preferably, as shown in Figs. 3A to 3D, an outer surface of said telescopic shaft 4 is provided with a guiding groove, and said guiding groove extends from one end of said telescopic shaft 4 in the axial direction of said telescopic shaft 4 but does not penetrate through to the other end of said telescopic shaft 4. The number of the guiding groove (s) is not defined, and in the present embodiment, there are preferably two said guiding grooves (structures 41 and 42 shown in the drawings) , and the two guiding grooves are distributed symmetrically on the outer surface of said telescopic shaft 4. Alternatively, if no guiding groove is formed on the outer surface of said telescopic shaft 4, the guiding protrusion (the drawings do not provide an example) can realize the guiding function, and said guiding protrusion also extends from one end of said telescopic shaft 4 in the axial direction of said telescopic shaft 4 but does not penetrate through to the other end of said telescopic shaft 4. The number of the guiding protrusion ( s ) is not defined, but preferably is two, and the two guiding protrusions are distributed symmet ¬ rically on the outer surface of said telescopic shaft 4.

Preferably, as shown in Figs . 5A and 5B, said stepping motor also comprises the front end cover 9 which is press-fitted into said magnetically conductive ring 10 and is provided with a protruding structure, and the protruding structure is at least partially located in the guiding groove on said telescopic shaft 4 so as to prevent said telescopic shaft 4 from rotating and guide said telescopic shaft 4 in the axial direction. In the present embodiment, two protruding structures (91 and 92) which are distributed symmetrically are comprised in said front end cover 9, and are located in said guiding grooves 41 and 42, to axially guide and restrict the positioning of said telescopic shaft 4. Alternatively, when the guiding structure on said telescopic shaft 4 is a guiding protrusion, in order to cooperate with the guiding protrusion to guide, a groove structure is formed on said front end cover 9 (the drawings do not provide an example) ; the groove structure at least partially encloses the guiding protrusion on said telescopic shaft 4 so as to prevent said telescopic shaft 4 from rotating and guide said telescopic shaft 4 in the axial direction. In the same way, the number of the protrusion ( s ) on said front end cover 9 can be two, and the protrusions are distributed symmetrically in said front end cover 9.

Furthermore, said front end cover 9 is in clearance fit with said magnetically conductive ring 10, in order to effectively fix and lock the whole motor; said magnetically conductive ring 10 is provided with a plurality of jaw piece structures, and these jaw piece structures are bent and then pressed onto said front end cover 9. Preferably, as shown in Fig. 4, said rotor casing 1 and said rotor shaft 2 are fitted together by means of in ection moulding, the bare end 21 of the rotor shaft 2 after the injection moulding is located outside the closed end of the rotor casing 1 (the rotor shaft 2 is inserted into and penetrates through a bottom part of said rotor casing 1 which is similar to a closed end of a teacup) , and furthermore, in order to guarantee the connection force between the rotor casing 1 and the rotor shaft 2 after the injection moulding, the zigzag structure 22 is designed and formed at the outer periphery of the joint of said rotor shaft 2 and the rotor casing 1.

Preferably, as shown in Fig. 4, a positioning hole 61 is formed on said stator 6, the bare end 21 of said rotator shaft 2 is at least partially located in the positioning hole 61, such that the positioning hole 61 can replace a traditional rear bearing to support said rotor shaft 2, and cooperate with said bearing 5 to support said rotor shaft 2 at both ends. In addition, in order to reduce friction between said bare end 21 and said positioning hole 61, grease can be smeared on the bare end 21 or the positioning hole 61.

Preferably, as shown in Fig. 4 and Fig. 6, said stepping motor also comprises a coupling ball 7 mounted on an output end of said telescopic shaft 4, wherein the coupling ball 7 can be fixedly mounted on said telescopic shaft 4 by hot riveting, adhesive dispensing or inserting a pin laterally.

Preferably, as shown in Fig. 6, said stepping motor also comprises an O-ring 11, wherein the O-ring 11 is provided on said front end cover 9 in a surrounding manner, and when the stepping motor is mounted in a customer interface, said O-ring 11 is pressed and deforms so as to provide a pre-tensioning force for the mounting.

Preferably, as shown in Fig. 6, said stepping motor also comprises a rear end cover 12, wherein the rear end cover 12 is press-fitted onto said electrical connector 8.

The working manner and principle of the above-mentioned stepping motor are as follows : when the stator 6 wound with the coil supplies power via a pin connector 8, magnetic field loops are formed between said stator 6, said magnetically conductive ring 10 and said annular magnet 3 to generate a torgue which drives said rotor casing 1 to rotate so as to drive the rotor shaft 2 to rotate, and due to the cooperation of the threads, the telescopic shaft 4 converts the rotational motion into linear motion, driving the coupling ball 7 to move back and forth along the axial direction of said telescopic shaft 4.

Although the present device has been disclosed above in terms of the preferred embodiments, the present device is not limited to this . Any modification or amendment made by any person skilled in the art without departing from the spirit and scope of the present device should be included in the protection scope of the present device, and therefore the protection scope of the present device shall be the scope defined in the claims.