Patent Application
20080018208
Referring to
The stator is a single stator vane 21 formed integrally from soft magnetic material. The stator vane 21 is provided at two sides thereof with a first coil 28 and a second coil 29, which both electrically connected with the control circuit. There is a rotor hole in the center of the stator vane 21 for receiving the rotor. The shape of the rotor hole in section is a concentric circle with the shape of the rotor in section. The stator vane 21 comprises three magnetic pole end surfaces spaced from each other with 120 degrees. They are first, second, and third magnetic pole end surfaces 23, 24, and 25, respectively. The first, second and third magnetic pole end surfaces 23, 24 and 25 are arc surfaces of identical sizes, and receive the rotor.
The rotor comprises a magnetic rotor 22 and a rotor shaft. The magnetic rotor 22 is made of permanent magnetic iron and comprises fourth magnetic poles disposed radially. The adjacent magnetic poles have opposite polarity, that is, south pole 26 and north pole 27 disposed alternatively. Further, the side of the magnetic pole, which faces the magnetic pole end surface of the stator vane 21 is an arc surface. The end of the rotor shaft is provided with a gear for transmitting the rotation movement of the rotor shaft.
Further, the arc length of the respective magnetic pole end surfaces 23, 24 and 25 of the stator vane 21 is between that of a magnetic pole and that of the two adjacent magnetic poles.
Referring to
In the first stage, the first coil 28 and the second coil 29 are provided with current in the same direction by the control circuit. Due to the electromagnetic induction of the coil, the first magnetic pole end surface 23 and the second magnetic pole end surface 24 are north poles, and the third magnetic pole end surface 25 is south pole. The four magnetic poles of the magnetic rotor 22 are two south poles 26 and two north poles 27 disposed alternatively. Therefore, the first magnetic pole end surface 23 and the second magnetic pole end surface 24 would absorb the magnetic pole 26 adjacent to them, and the third magnetic pole end surface 25 would absorb the north pole 27 of the rotor adjacent to it. Therefore, magnetic moment is generated to the magnetic rotor 22, for driving the anticlockwise rotation of the rotor 22 with a step angle of 45 degrees.
In the second stage, the direction of current in the first coil 28 is change by the control circuit so that the first magnetic pole end surface 23 becomes south pole, the second magnetic pole end surface 24 remains as north pole, and the third magnetic pole end surface 25 loses its polarity. In this way, the first magnetic pole end surface 23 absorbs the north pole 27 of the rotor most adjacent to it, and the second magnetic pole end surface 24 absorbs nearest south pole 26 so that magnetic moment is generated to make the magnetic rotor 22 rotate anticlockwise with a step angle remaining as 45 degrees and depart the original position by 90 degrees.
In the third stage, the direction of current in the second coil 29 is changed by the control circuit, and the direction of current in the second coil 28 remains unchanged. The polarity of the first magnetic pole end surface 23 remains as south pole; the second magnetic pole end surface 24 becomes south pole under the electromagnetic induction; and the third magnetic pole end surface 25 becomes north pole. In this way, the third magnetic pole end surface 25 absorbs the north pole 26 of the rotor 22 adjacent to it, and the first and second magnetic pole end surfaces 23 and 24 absorb north pole 27 of the rotor 22 adjacent them. Therefore, the magnetic moment is generated to make the magnetic rotor 22 rotate anticlockwise with a step angle of 45 degrees and depart the original position by 135 degrees.
In the fourth stage, the direction of current in the first coil 28 is changed by the control circuit so that the first magnetic pole end surface 23 becomes north pole under electromagnetic induction; the second magnetic pole end surface 24 remains unchanged as south pole; and the third magnetic pole end surface 25 loses its polarity. In this way, the first magnetic pole end surface 23 absorbs the south pole 26 of the rotor 22 adjacent to it, and the second magnetic pole end surfaces 24 absorbs north pole 27 of the rotor 22 adjacent to it. Therefore, the magnetic moment is generated to make the magnetic rotor 22 rotate anticlockwise with an angle of 45 degrees and depart the original position by 180 degrees.
The magnetic rotor 22 returns to its original state after rotating 180 degrees and therefore capable of repeating the first, second, third and fourth stages, so that the magnetic rotor 22 continuously rotate in one direction.
The step angle of the stepping motor, 45 degree, which is generated by changing the direction of the current in the coil at each stage, is a quotient of 180 degrees divided by the number of the magnetic poles of the rotor 22.
Referring to
Referring to
In the first stage, the first coil 38 and the second coil 39 is supplied with current through control circuit, so that the first magnetic pole end surface 33 of the stator vane 31 is as north pole, the second magnetic pole end surface 34 also is north pole, and the third magnetic pole end surface 35 is south pole. The third magnetic pole end surface 35 would absorb the north pole 37 of the magnetic rotor 32 adjacent to it, and the first magnetic pole end surface 33 and the second magnetic pole end surface 34 would absorb the south pole 36 of the magnetic rotor adjacent to them. Therefore, the first, second and third magnetic pole end surfaces 33, 34 and 35 of the stator vane 31 generate magnetic moment to the magnetic rotor 32, for driving the anticlockwise rotation of the rotor 32 with a step angle of 22.5 degrees, that is, the stepping precision is 22.5 degrees.
In the second stage, the direction of current in the second coil 39 is changed through the control circuit, but the direction of the current in the first coil 38 remains unchanged. Due to electromagnetic induction, the first magnetic pole end surface 33 of the stator vane 31 acts as north pole; the second magnetic pole end surface 34 is south pole; and the third magnetic pole end surface 35 loses its polarity. In this way, the first magnetic pole end surface 33 absorbs the south pole 36 of the rotor adjacent to it, and the second magnetic pole end surface 34 absorbs north pole 37 of the rotor adjacent to it, so that magnetic moment is generated to make the magnetic rotor 32 rotate anticlockwise with a angle 22.5 degrees and depart the original position by 45 degrees.
In the third stage, the direction of current in the first coil 38 through the control circuit, and the direction of current in the second coil 39 remains unchanged. Due to electromagnetic induction, the first magnetic pole end surface 33 of the stator vane 31 becomes south pole; the second magnetic pole end surface 34 remains as south pole; and the third magnetic pole end surface 35 becomes north pole. The third magnetic pole end surface 35 absorbs the south pole 36 of the rotor adjacent to it, and the first and second magnetic pole end surfaces 33 and 34 absorb north pole 37 of the rotor adjacent to it, so that magnetic moment is generated to the rotor 32 for making the magnetic rotor 32 rotate anticlockwise with another angle 22.5 degrees, and thus depart the original position by 67.5 degrees.
In the fourth stage, the direction of current in the second coil 39 through the control circuit, and the direction of current in the first coil 38 remains unchanged. Due to electromagnetic induction, the first magnetic pole end surface 33 of the stator vane 31 becomes south pole; the second magnetic pole end surface 34 remains as north pole; and the third magnetic pole end surface 35 loses its polarity. Therefore, the first magnetic pole end surface 33 absorbs the north pole 37 of the rotor adjacent to it, and the second magnetic pole end surfaces 34 absorbs south pole 36 of the rotor adjacent to it, so that magnetic moment is generated to make the rotor 32 rotate anticlockwise with angle 22.5 degrees, and thus depart the original position by 90 degrees.
However, in the present embodiment, the rotor 32 has eight magnetic poles, with four south poles 36 and four north poles 37 disposed radially and alternatively. Therefore, the rotor 32 returns to its original state after rotating 90 degrees and repeat the first, second, third and fourth stages so as to make the rotor 32 continuously rotate in one direction.
Further, the step angle of the stepping motor, 22.5 degrees, which is generated by changing the direction of the current in the coil at each stage, is a quotient of 180 degrees divided by the number of the magnetic poles of the rotor.
The stepping motor of the present utility model increases the stepping precision by increasing the number of magnetic poles of the magnetic rotor, and the minimum step angle thereof is a quotient of 180 degrees divided by the number of the magnetic poles of the magnetic rotors. Therefore, the stepping precision of the stepping motor can be continuously increased by increasing the number of the magnetic poles of the rotor. However, since the stator vane of the present utility model is provided with three magnetic pole end surfaces, it generates magnetic moment to the rotor by changing its magnetic pole so as to drive the rotation of the rotor. However, to prevent the condition of equilibrium of magnetic moments, the number of magnetic poles of the rotor is an even number greater than 2 and can not be divided exactly by 3. Therefore, the number of the magnetic poles can be 4, 8, 10, 14, 16, 20, 22, 26, 28, 32, 34 and 38, etc. When the number of the magnetic poles of the rotor increases, the stepping behaviors of the stepping motor are similar, that is, they all realize the stepping by driving the rotation of the magnetic rotor by the magnetic pole end surfaces through changing the direction of the current in coils in turn. In addition, the stator of the present utility model is a single stator vane formed integrally and can be manufactured simply with low cost.
The following is a further improvement of the stepping motor of the present Utility Model. The three magnetic pole end surfaces of the stator vane can be separated by three narrow grooves spaced by 120 degrees with each other. The three narrow grooves are disposed along the radial direction of the rotor. The two ends of each narrow groove are connected with the stator vane, and the connecting portion is thin, where the magnetic field is saturated and thus generates magnetic moment to the rotor. The distances between the ends of the narrow grooves to the axis of the rotor are identical. In addition, the stator can also be a stator vane consisting of three vanes in the same plane, which correspond to the three magnetic pole end surfaces respectively. Therefore, it can be manufactured simply and low costly.
In summary, the stator of the stepping motor of the present Utility Model is a single stator vane integrally formed, or a stator vane consisting of three vanes, and therefore it can be manufactured simply with low cost. The number of the magnetic poles of he magnetic rotor of the stepping motor is an even number, which is greater than 2 but can not be divided exactly by 3. The minimum step angle thereof is the quotient of 180 degrees divided by the number of magnetic poles. Therefore, the stepping precision can be continuously increased by increasing the number of the magnetic poles. Therefore, the stepping motor of the present Utility Model can be manufactured simply and low costly, and it has high stepping precision. Also, according to the practical requirement, the stepping precision can be continuously increased by increasing the number of the magnetic poles of the rotors.
| Number | Date | Country | Kind |
|---|---|---|---|
| 200620130640.5 | Jul 2006 | CN | national |
