JP4398740B2 - Electromagnetic actuator - Google Patents

Description

  The present invention relates to an electromagnetic actuator that can be suitably used for a small camera or the like.

  In recent years, extremely small cameras have been mounted on portable electronic devices such as cellular phones. In such a small camera, since it is necessary to perform zoom driving with high accuracy, a step motor is employed as an electromagnetic actuator. Therefore, the step motor used in this way needs to be further downsized as the camera becomes smaller. Furthermore, recently, there is an increasing demand for a camera having a multi-stage zoom function even if it is small. For this reason, it is necessary to make the rotor of the step motor mounted on the small camera more compact and multipolar. When the rotor is miniaturized and multipolarized, the leakage of magnetic flux becomes large, and drive control becomes difficult. However, there is a demand for a small step motor that can overcome this point and stop at a predetermined position and obtain a desired rotational torque.

  For example, Patent Document 1 and Patent Document 2 propose that the soft magnetic material body is disposed close to the rotor for the purpose of improving the rotational performance of the step motor or the stop stability during the step rotation. Yes. However, these patent documents propose a technique whose main purpose is to increase the stability of the rotor at the step rotation position. That is, these patent documents disclose a technique for reliably stopping the rotor of the stepping motor at a predetermined position, and do not disclose a technique for improving the rotational torque.

JP 2003-32991 A JP 2002-136095 JP

  Therefore, the present applicant has previously proposed an electromagnetic actuator suitable for miniaturization that can increase the rotational torque of the rotor and can stop the rotor at a predetermined position (Japanese Patent Application No. 2003-306240). In this electromagnetic actuator, an auxiliary yoke that has a low magnetic resistance and easily induces a magnetic flux is disposed between the magnetic poles of the stator or between the two stators so as to face the circumferential surface of the rotor. According to this electromagnetic actuator, since the magnetic flux from one magnetic pole of the stator to the other magnetic pole of the stator passes through the auxiliary yoke, the magnetic force can be prevented from lowering. Therefore, this electromagnetic actuator can maintain a high magnetic field strength in the gap (magnetic gap) in front of the magnetic pole of the stator, so that the rotational torque of the rotor can be improved as compared with the conventional motor.

  As described above, the electromagnetic actuator having a novel structure proposed by the present applicant improves the rotational torque by including a structure in which an auxiliary yoke that functions as a magnetic path through which magnetic flux easily passes is disposed opposite to the outer periphery of the rotor. However, since this electromagnetic actuator has a structure in which an auxiliary yoke not included in the prior art is newly disposed between the magnetic poles, the manufacturing process becomes more complicated than in the prior art.

  Accordingly, an object of the present invention relates to an improvement of an electromagnetic actuator of a type in which an auxiliary yoke is disposed on the outer periphery of a rotor, and provides an electromagnetic actuator having a structure capable of improving manufacturing efficiency.

  The object is to provide a rotor having a plurality of magnetic poles and two stators arranged on the outer periphery of the rotor, the two stators having an exciting coil and a magnetic pole opposed to the circumferential surface of the rotor. The stator has an auxiliary yoke disposed between the magnetic poles so as to face a part of the circumferential surface of the rotor, and the auxiliary yokes of the two stators are integrally formed. This can be achieved by being formed.

  According to the present invention, since the auxiliary yokes of the two stators are integrally formed, the number of parts can be reduced, so that the manufacturing cost can be reduced. Moreover, the assembly process can be simplified by integrating the auxiliary yoke in this way. Therefore, according to this invention, the electromagnetic actuator which can improve manufacturing efficiency can be provided.

  Further, the auxiliary yoke of the two stators and a connecting member for connecting the auxiliary yoke, the auxiliary yoke and the connecting member are integrally formed of a magnetic material, and the connecting member has a constricted portion with a reduced cross-sectional area. A monolithic structure having Thus, by integrally processing using a magnetic material, it is possible to reduce the component cost. And by forming the constriction part which made the cross-sectional area small, the leakage of the magnetic flux between the auxiliary yokes produced by connecting the auxiliary yokes through which the magnetic flux easily passes can be suppressed.

  Further, an integrated structure in which the auxiliary yoke of the two stators and a connecting member for connecting the auxiliary yoke are included, the auxiliary yoke is formed of a magnetic material, and the connecting member is formed of a nonmagnetic material may be adopted. Good. In this case, leakage of magnetic flux between the auxiliary yokes can be reliably prevented by the nonmagnetic connecting material. Therefore, the structure provided with the narrowed portion is not required.

  Furthermore, the housing further includes a housing that forms a predetermined space in which the rotor rotates, and the housing includes an engaging portion that engages with the auxiliary yoke, and when the auxiliary yoke engages with the engaging portion, the housing You may employ | adopt the structure which cooperates with a housing and forms the said space. In the configuration employing the housing as described above, the auxiliary yoke can be more reliably positioned at a predetermined position. Therefore, the assembling property is improved, and the manufacturing efficiency can be further structured. The auxiliary yoke may be provided between the magnetic poles of the stator, or may be provided between the magnetic poles of the stator and between adjacent stators.

  The housing is constituted by two housing members that sandwich the rotor and the stator, each housing member has the engaging portion, the connecting member is disposed outside the space, and the auxiliary member The yoke may adopt a structure in which the yoke is positioned by the first engaging portion of the first housing member and the second engaging portion of the second housing member. Since the electromagnetic actuator is small and a predetermined torque can be obtained, the portable electronic device including the electromagnetic actuator can be further downsized.

  Hereinafter, two examples will be described as preferred embodiments of the present invention based on the drawings.

  FIG. 1 is a perspective view illustrating an appearance of a step motor 1 according to the first embodiment. FIG. 2 is an exploded perspective view showing the configuration of each part of the step motor 1. The step motor 1 has two sets of stators 10 and 20, a rotor 30 having a rotor shaft 31, and an auxiliary yoke assembly 40 in which two auxiliary yokes are integrated. The step motor 1 further includes an upper presser plate (first housing member) 60 and a lower presser plate (second housing member) 70 that form an integral housing. As shown in FIG. 2, when the upper and lower presser plates 60 and 70 are set, a predetermined space is formed between them. The rotor 30 is housed in this space in a rotatable state. A pair of magnetic poles 13 and 14 formed at both ends of the first stator 10 and a pair of magnetic poles 23 and 24 formed at both ends of the second stator 20 are also accommodated in the space.

  The auxiliary yoke assembly 40 includes a first auxiliary yoke 41 disposed between the magnetic poles 13 and 14 of the first stator 10 and a second auxiliary yoke disposed between the magnetic poles 23 and 24 of the second stator 20. 42 is an assembly member integrally formed through the connection member 45. Here, what is called the connection member 45 is a plane portion that is in contact with each auxiliary yoke portion that does not function as a magnetic flux guiding path at a right angle at a portion that connects each auxiliary yoke. However, since the auxiliary yoke assembly 40 is integrally formed of a magnetic material, there is no clear boundary between the auxiliary yoke and the connecting member. Therefore, the connection member 45 included in the auxiliary yoke assembly 40 can be regarded as a connection portion of each auxiliary yoke that is specially formed to connect a portion that functions as the auxiliary yoke.

  Each of the auxiliary yokes 41 and 42 is adapted to engage with recesses (first engaging portions) 62 and 63 formed in the upper presser plate 60. Therefore, the auxiliary yoke assembly 40 is positioned at a predetermined position of the upper presser plate 60. When the auxiliary yoke assembly 40 is set on the upper presser plate 60, the auxiliary yokes 41 and 42 become part of the side wall that divides the space for housing the rotor 30. That is, the auxiliary yoke assembly 40 forms a space for housing the rotor 30 in cooperation with the upper and lower presser plates 60 and 70 that function as a housing in the set state. At this time, the inner surfaces of the auxiliary yokes 41 and 42 face the peripheral surface of the rotor 30. In addition, concave portions (second engaging portions) 72 and 73 for receiving the lower end sides of the auxiliary yokes 41 and 42 are formed on the lower pressing plate 70 side. When the upper presser plate 60 and the lower presser plate 70 are set, the upper concave portions 62 and 63 and the concave portions 72 and 73 are vertically aligned with each other. Therefore, the auxiliary yoke assembly 40 is reliably positioned by these recesses. The auxiliary yoke assembly 40 will be described in detail later.

  The rotor 30 is a permanent magnet formed in a cylindrical shape. A rotor shaft 31 that rotates integrally from the center of the rotor 30 rises. FIG. 3 is an enlarged plan view showing a peripheral portion of the rotor 30. FIG. 3 shows the magnetic poles 13 and 14 of the first stator 10, the magnetic poles 23 and 24 of the second stator 20, and the auxiliary yoke assembly 40. The rotor 30 has a structure in which 10 poles are magnetized by alternating N and S poles at substantially equal intervals in the circumferential direction. In FIG. 3, the peripheral surfaces of the regions Nr1 to Nr5 are magnetized so as to be N poles, and the peripheral surfaces of the remaining regions Sr1 to Sr5 are magnetized so as to be S poles. In FIG. 3, five N poles are hatched for easy understanding. Furthermore, the part located in the lower part of the auxiliary yoke laminated material 40 is shown with the dotted line. The number of magnetic poles on the circumferential surface of the rotor 30 is preferably about 10 to 14 poles, but may be increased or decreased as necessary.

  Referring to FIG. 2 again, in the first stator 10, an exciting coil 15 is wound around the outer periphery of a yoke portion 11 in which a soft magnetic material such as permalloy having a high magnetic permeability and a large saturation magnetization is formed in a C shape. ing. Magnetic poles 13 and 14 are formed at both ends of the yoke 11. The magnetic poles 13 and 14 are disposed so as to face the peripheral surface of the rotor 30 through narrow gaps G13 and G14, as shown in FIG. The width (or spread angle) of each magnetic pole 13, 14 in the circumferential direction is preferably set to about 1.5 of the magnetic pole width of the rotor 30. The width (opening angle) between the magnetic poles 13 and 14 is preferably set to about 2.5 of the magnetic pole width of the rotor 30.

  The other second stator 20 is formed in the same manner as the stator 10. That is, an excitation coil 25 is wound around the outer periphery of the yoke 21, and magnetic poles 23 and 24 are formed at both ends of the yoke 21. The relationship between the magnetic poles 23 and 24 and the rotor 30 is the same as that of the magnetic poles 13 and 14.

  Furthermore, the structure of the auxiliary yoke laminated material 40 mentioned above is demonstrated in detail. As described above, the auxiliary yoke assembly 40 includes the first auxiliary yoke 41 and the second auxiliary yoke 42. Since the two auxiliary yokes 41 and 42 have the same configuration, the auxiliary yoke 41 will be described. The auxiliary yoke 41 has a shape along the peripheral surface of the opposing rotor 30, that is, a shape that is a part of a cylinder (partial cylindrical shape). The auxiliary yoke 41 is made of a material that easily induces magnetic flux. Specifically, the auxiliary yoke 41 is desirably made of a magnetic material having a low magnetic resistance and a high magnetic permeability, such as permalloy.

  The auxiliary yoke 41 is disposed between the magnetic poles 13 and 14 of the first stator 10. The auxiliary yoke 41 extends in the circumferential direction with a width larger than the circumferential width of one magnetic pole formed on the rotor 30. The auxiliary yoke 41 is disposed so as to face the peripheral surface of the rotor 30 with a predetermined gap. The circumferential width of the auxiliary yoke 41 is preferably set to about 1.5 with respect to the widths of the magnetic poles Nr and Sr of the rotor 30 as described above.

  As described above, the auxiliary yoke 41 disposed near the peripheral surface of the rotor 30 is formed of a material having a lower magnetic resistance than the atmosphere, so that it is easy to induce a magnetic flux, and thus a structure that functions as a guiding path (magnetic path) and Become. In particular. Magnetic flux enters from one end of the auxiliary yoke 41 from the magnetic pole Nr facing the rotor 30, passes through the auxiliary yoke 41, and returns from the other end of the auxiliary yoke 40 to the magnetic pole Sr of the rotor 30. Accordingly, most of the magnetic flux from the one side magnetic pole (for example, the magnetic pole 13) of the first stator 10 to the other side magnetic pole (for example, the magnetic pole 14) through the rotor 30 passes through the auxiliary yoke 41. Since the auxiliary yoke 41 has a low magnetic resistance and a high magnetic permeability, the magnetic energy is not attenuated. As a result, the magnetic field generated in the gap (for example, G13) in front of the magnetic pole of the stator 10 can be formed stronger than in the conventional type in which the magnetic flux on the rotor side passes through the atmosphere. As a result, the rotational torque of the rotor 30 can be improved. The auxiliary yoke 41 is a soft magnetic material, and provides a guide path between adjacent magnetic poles of the rotor even when the rotor 30 is stopped when no power is supplied. Since the magnet portion of the rotor whose magnetic pole faces the auxiliary yoke is easily magnetically coupled, it contributes to the improvement of the accuracy of the stop position.

  Although the first auxiliary yoke 41 of the first stator 10 has been described above, the same applies to the second auxiliary yoke 42 disposed on the second stator 20 side. Even if the auxiliary yoke is disposed only on one stator side, the above-described torque improvement effect can be expected. A more preferred form is a structure in which an auxiliary yoke is disposed between the magnetic poles of each stator. However, compared with a structure that does not include an auxiliary yoke, a structure that newly includes a plurality of auxiliary yokes complicates the manufacturing process. The step motor 1 realizes a structure that eliminates this problem. A configuration that can improve the efficiency of the manufacturing process will be described below.

  As described above, the auxiliary yoke assembly 40 has a structure in which the first auxiliary yoke 41 and the second auxiliary yoke 42 are connected via the connection member 45. In particular, in this embodiment, the auxiliary yoke assembly 40 is manufactured integrally using a magnetic material. Therefore, compared with the case where the auxiliary yoke 41 and the second auxiliary yoke 42 are arranged independently, the number of parts is reduced, so that the cost can be reduced. Further, the auxiliary yoke assembly 40 has an arch shape that is easy to assemble, and can be reliably positioned by engaging with the recesses (see FIG. 2) provided in the presser plate 60 and the lower presser plate 70 as described above. . Therefore, the step motor 1 can be manufactured efficiently.

  Incidentally, the first auxiliary yoke 41 is arranged for inducing a magnetic flux on the first stator 10 side, and the second auxiliary yoke 42 is arranged for inducing a magnetic flux on the second stator 20 side. . When the members installed for such a purpose are connected to each other, the magnetic flux that has entered one auxiliary yoke (for example, the first auxiliary yoke 41) is transferred to the other auxiliary yoke (for example, the second auxiliary yoke 42) side. A state of escaping (leaking) is assumed. Therefore, in the auxiliary yoke assembly 40 according to the present embodiment, it is desirable to form a portion having a reduced cross-sectional area in the connection portion (connection member) between the first auxiliary yoke 41 and the second auxiliary yoke 42. .

  The connecting member 45 of the auxiliary yoke assembly 40 shown in FIGS. 2 and 3 has a shape that is somewhat narrowed toward the center. However, it is desirable that the portion between the auxiliary yokes 41 and 42 has a structure including a narrowed portion having a smaller cross-sectional area. By providing such a constricted portion, it is possible to suppress a state in which the magnetic flux entering one auxiliary yoke leaks to the other.

  FIG. 4 shows an auxiliary yoke assembly 40PR having a preferred structure. FIG. 4A is a plan view of the auxiliary yoke assembly 40PR, and FIG. 4B is a schematic view showing the constricted portion CN on the auxiliary yoke 41 side as viewed from the arrow X direction in FIG. . When the auxiliary yoke assembly 40PR having the narrowed portion CN that can be narrowed down in this way is employed, leakage of magnetic flux between the auxiliary yokes 41 and 42 can be suppressed, and thus the rotational torque of the rotor 30 can be improved more reliably. Can be made. In FIG. 4, the first auxiliary yoke 41 side has been described as an example, but the same applies to the second auxiliary yoke 42 on the opposite side.

  Further, the step motor 2 according to the second embodiment will be described with reference to FIG. The step motor 2 according to the second embodiment is different from the step motor 1 shown in the first embodiment in that a third auxiliary yoke is disposed between the stators 10 and 20. FIG. 5 is a diagram corresponding to FIG. 2, and is an exploded perspective view showing the configuration of each part of the step motor 2. In addition, the same code | symbol is attached | subjected to the same site | part as the structure of the step motor 1 of Example 1. FIG.

  The auxiliary yoke assembly 50 of the step motor 2 includes a first auxiliary yoke 51 disposed between the magnetic poles 13 and 14 of the first stator 10 and a second auxiliary member disposed between the magnetic poles 23 and 24 of the second stator 20. In addition to the yoke 52, a third auxiliary yoke 53 is provided between the stators. If the auxiliary yoke is arranged between the stators in this way, a structure that can more reliably suppress the leakage magnetic field is obtained. The auxiliary yoke assembly 50 here also has a structure in which three auxiliary yokes 51, 52, 53 are connected via a connecting member 55, and these are integrally formed of a magnetic material. The auxiliary yoke assembly 50 also includes a constricted portion 55CN having a reduced cross-sectional area in the connecting member 55, and realizes a structure in which magnetic flux leakage between the auxiliary yokes is suppressed.

  Therefore, in the case of the step motor 2 according to the second embodiment, the number of parts is reduced, so that the cost can be reduced. Further, the auxiliary yoke assembly 50 is also easy to assemble, and can be reliably positioned on the presser plate 60 and the lower presser plate 70. Therefore, the step motor 2 also realizes a structure in which the manufacturing efficiency is improved as in the case of the step motor 1. In the step motor 2, an opening 65 for fitting the third auxiliary yoke 53 is newly formed in the upper pressing plate 60, and an opening 75 is newly formed in the lower pressing plate 70.

  FIG. 6 is a view showing a modification of the auxiliary yoke assembly 50 according to the second embodiment. In the first embodiment described above, since the auxiliary yoke portion and the connecting portion are formed of an integral magnetic material, the narrow portion is provided to suppress the leakage of magnetic flux between the auxiliary yokes. However, when a nonmagnetic material is interposed in the connection portion, leakage of magnetic flux can be more reliably suppressed. FIG. 6A shows an auxiliary yoke assembly 50PR-1 in which the connection member 56 is formed of a nonmagnetic material. As the nonmagnetic material, for example, a resin material such as plastic can be employed. By inserting a magnetic auxiliary yoke into the peripheral surface of the resin material, the integrated auxiliary yoke assembly 50PR-1 shown in FIG. 6A can be manufactured. In this structure, since the magnetic auxiliary yokes do not directly contact each other, the problem of magnetic flux leakage can be reliably suppressed. In the example shown in FIG. 6A, each of the three auxiliary yokes 51 to 53 has a shape provided with tongue pieces 51R to 53R extending in the radial direction from the upper end of the partial cylindrical shape. That is, the auxiliary yokes 51 to 53 are connected to the nonmagnetic connection member 56 via the tongue pieces 51R to 53R, thereby forming an integral auxiliary yoke assembly 50.

  Incidentally, as shown in FIG. 6A, in the case of a structure in which a nonmagnetic connecting member is interposed between the auxiliary yokes, it is not necessary to form the narrowed portion described above. Therefore, as shown in FIG. 6 (B), the connecting member 57 may have a disk shape. In this case, the auxiliary yokes 51 to 53 formed in a partial cylindrical shape may be connected (inserted) to the peripheral portion of the connection member 57 to form an integral structure.

  The preferred embodiment of the present invention has been described in detail above. However, the present invention is not limited to the specific embodiment, and various modifications can be made within the scope of the gist of the present invention described in the claims. Deformation / change is possible. In the above embodiment, an example in which two stators are arranged has been shown, but the same effect can be obtained even in a structure in which three or more stators are arranged. 6 shows a modification of the auxiliary yoke assembly 50 according to the second embodiment, the same applies to the auxiliary yoke assembly 40 according to the first embodiment.

It is the perspective view which showed the external appearance of the step motor which concerns on Example 1. FIG. It is the disassembled perspective view shown so that each part structure of the step motor shown in FIG. 1 could be confirmed. It is the top view which expanded and showed the rotor peripheral part of the step motor of FIG. (A) is a top view of the auxiliary yoke laminated material of a preferable structure, (B) is the schematic diagram shown so that the constriction part by the side of an auxiliary yoke can be confirmed seeing from the arrow X direction by (A). It is the disassembled perspective view shown so that each part structure of the step motor which concerns on Example 2 can be confirmed. It is the figure which showed the modification of the auxiliary yoke laminated material of Example 2.

Explanation of symbols

1, 2 Step motor 10 First stator 13, 14 Magnetic pole 15 Excitation coil 20 Second stator 23, 24 Magnetic pole 25 Excitation coil 30 Rotor 40 Auxiliary yoke assembly 41 First auxiliary yoke 42 Second auxiliary yoke 60 Upper presser plate 70 Lower presser plate CN Constriction

Claims (6)

A rotor having a plurality of magnetic poles, and two stators arranged on the outer periphery of the rotor,
The two stators are electromagnetic actuators having an exciting coil and two magnetic poles opposed to the circumferential surface of the rotor,
Each stator is arranged so that an auxiliary yoke is opposed to a part of the peripheral surface of the rotor between two magnetic poles of the same stator, and the auxiliary yokes of the two stators are integrally formed. An electromagnetic actuator characterized by that. The auxiliary yoke of the two stators and a connecting member for connecting the auxiliary yoke, the auxiliary yoke and the connecting member are integrally formed of a magnetic material, and the connecting member has a narrowed portion with a reduced cross-sectional area. The electromagnetic actuator according to claim 1, wherein: 2. The auxiliary yoke of the two stators and a connecting member for connecting the auxiliary yoke, wherein the auxiliary yoke is made of a magnetic material, and the connecting member is made of a nonmagnetic material. The electromagnetic actuator described. A housing that forms a predetermined space in which the rotor rotates;
The housing includes an engaging portion that engages with the auxiliary yoke, and forms the space in cooperation with the housing when the auxiliary yoke engages with the engaging portion. The electromagnetic actuator according to any one of 1 to 3. The housing is constituted by two housing members that sandwich the rotor and the stator, and each housing member has the engaging portion,
The connecting member is disposed outside the space;
The electromagnetic actuator according to claim 4, wherein the auxiliary yoke is positioned by a first engaging portion of the first housing member and a second engaging portion of the second housing member. A portable electronic device comprising the electromagnetic actuator according to claim 1.

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