JP2006280105A - Driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving device that is small in the number of parts, makes it possible to control the position of a rotating shaft with accuracy, can achieve stable rotating performance, and is highly efficient because of effective use of magnetic flux. <P>SOLUTION: The axial distance from the thrust receiving portion 7d of a first bearing 7 to a magnet end face is made larger than the axial distance from an end face of a first stator 2 to the magnet end face. The axial distance from the thrust receiving portion 8d of a second bearing 8 to a magnet end face is made large than the axial distance from an end face of a second stator 3 to the magnet end face. An air gap is provided between a thinned portion 6e of the rotating shaft 6 and the inside diameter of the first bearing 7, and an air gap is provided between a thinned portion 6f of the rotating shaft 6 and the inside diameter of the second bearing 8. The wall thickness of the abutted portions of the first and second bearings 7 and 8 respectively abutted against the first and second stators 2 and 3 is made larger than the wall thickness of the portions of the first and second bearings 7 and 8 extending from the respective abutted portions to the respective thrust receiving portions 7d and 8d. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a drive device suitable for realizing stable rotation performance and the like.

  Conventionally, a stepping motor has been proposed in which the diameter around the rotation axis is reduced and the output is increased (see, for example, Patent Document 1). A conventional stepping motor described in Patent Document 1 will be described with reference to FIG.

  FIG. 4 is a cross-sectional view showing an internal structure in the axial direction of a stepping motor according to a conventional example (Patent Document 1).

  4, the stepping motor includes a rotor 201, a first coil 202, a second coil 203, a first stator 204, a second stator 205, a rotation shaft (output shaft) 206, and a connection ring 207. .

  The rotor 201 is composed of permanent magnets (magnets) that are divided into four in the circumferential direction and alternately magnetized to different poles. The first coil 202 and the second coil 203 are arranged adjacent to each other in the axial direction of the rotor 201. The first stator 204 is made of a soft magnetic material and is excited by the first coil 202. The second stator 205 is made of a soft magnetic material and is excited by the second coil 203.

  The first stator 204 includes first outer magnetic poles 204A and 204B that face the outer peripheral surface of the rotor 201 with a gap, and first inner magnetic poles 204C and 204D that face the inner peripheral surface of the rotor 201 with a gap. And. The second stator 205 includes second outer magnetic poles 205A and 205B that face the outer peripheral surface of the rotor 201 with a gap, and second inner magnetic poles 205C and 205D that face the inner peripheral surface of the rotor 201 with a gap. And.

  The rotor 201 is fixed to the outer diameter portion of the rotating shaft 206, and is rotatably held by the bearing portion 204E of the first stator 204 and the bearing portion 205E of the second stator 205. The connection ring 207 is made of a nonmagnetic material, and holds the first stator 204 and the second stator 205 in a predetermined phase relationship at a predetermined interval.

  In the above-described configuration, the first outer magnetic poles 204A and 204B, the first inner magnetic poles 204C and 204D, the second electric current of the first stator 204 are switched by switching the energization direction to the first coil 202 and the second coil 203. The polarity of the second outer magnetic poles 205A and 205B and the second inner magnetic poles 205C and 205D of the stator 205 is switched. Thereby, the rotor 201 is rotated.

  In this stepping motor, the magnetic flux generated by energizing the first coil 202 and the second coil 203 is transferred from the outer magnetic pole to the inner magnetic pole facing it, or from the inner magnetic pole to the outer magnetic pole facing it. The flow effectively acts on the magnet constituting the rotor 201 located between the outer magnetic pole and the inner magnetic pole. In addition, since the distance between the outer magnetic pole and the inner magnetic pole can be about the thickness of the cylindrical magnet, the resistance of the magnetic circuit composed of the outer magnetic pole and the inner magnetic pole can be reduced. The smaller the resistance of the magnetic circuit, the more magnetic flux can be generated with less current and the output is improved.

  Further, a stepping motor has been proposed in which the stepping motor described in Patent Document 1 is further improved to effectively use magnetic flux (see, for example, Patent Document 2).

  In the stepping motor described in Patent Document 2, the inner magnetic pole is formed in a cylindrical shape, the rotating shaft inserted into the inner diameter portion of the inner magnetic pole is formed of a soft magnetic material, and is further attached to the stator to rotate the rotating shaft. The bearing that can be held is made of a non-magnetic material. According to this proposal, since the rotating shaft can also be used as a magnetic circuit, the output of the stepping motor is increased. The magnetic attraction of the stator and the rotating shaft at that time is prevented by configuring the bearing with a nonmagnetic material.

  Furthermore, as a stepping motor according to another conventional example, a motor in which the axial direction of the rotating shaft is regulated by a bobbin made of a nonmagnetic material has been proposed. A stepping motor according to another conventional example will be described with reference to FIG.

  FIG. 5 is a sectional view showing an internal structure in the axial direction of a stepping motor according to another conventional example.

  In FIG. 5, the stepping motor includes a rotor 101, a first stator 102, a second stator 103, a first coil 104, a second coil 105, a rotating shaft 106, a first bearing 107, and a second bearing 108. The first bobbin 109, the second bobbin 110, and the connecting ring 111 are provided.

A receiving portion 109 a, part of which protrudes toward the rotating shaft, is formed on the inner peripheral side of the cylindrical portion around which the first coil 104 is wound in the first bobbin 109. Similarly, on the inner peripheral side of the cylindrical portion around which the second coil 105 is wound in the second bobbin 110, a receiving portion 110a is formed, a part of which protrudes toward the rotating shaft. In addition, t of illustration shows the dimension of the rotating shaft direction of the receiving part 109a and the receiving part 110a. The receiving portions 109a and 110a are protruded from the first and second bobbins 109 and 110 to the rotating shaft side, respectively, so that the axial direction of the rotating shaft 106 is regulated.
JP-A-9-331666 Japanese Patent Laid-Open No. 10-229670

  However, in the stepping motor described in Patent Document 2, the rotation shaft (output shaft) can also be used as a magnetic circuit, but the first and second stator bearings are made of non-magnetic material in order to avoid adsorption with the rotation shaft. It is composed. Therefore, since the first and second stators and the rotating shaft are not directly connected magnetically, the magnetic resistance is large and the magnetic efficiency is not good.

  Further, the magnetic flux generated by energizing the first coil affects the second coil, the second outer magnetic pole, and the second inner magnetic pole via the rotating shaft of the soft magnetic material. Similarly, the magnetic flux generated by energizing the second coil affects the first coil, the first outer magnetic pole, and the first inner magnetic pole via the rotating shaft of the soft magnetic material. As a result, there is a problem that the rotation of the rotation shaft becomes unstable.

  Further, both of the stepping motors described in Patent Document 1 or Patent Document 2 require a predetermined distance between the inner diameter of the magnet constituting the rotor and the inner magnetic pole facing it. However, managing the magnet and the inner magnetic pole so as to have a predetermined distance during manufacture has a problem that it takes time and increases the cost.

  In the stepping motor described in Patent Document 1, since the rotating shaft and the bearing are both formed of a soft magnetic material, a magnetic attracting force is generated between the rotating shaft and the bearing during driving. In the radial direction receiving surface (hereinafter referred to as radial receiving surface) and the thrust direction receiving surface (hereinafter referred to as thrust receiving surface). Normally, the radial receiving surfaces of the shaft and the bearing are finished with high accuracy with a very small gap, so even if an adsorption force is generated by the timing of excitation, the shaft hardly moves in that direction, that is, in the radial direction. Also, since the sliding radius is small, the torque loss is small. As a result, the suction force in the radial direction is not a problem in the rotation of the stepping motor.

  On the other hand, in the thrust direction of the shaft, there is usually a predetermined amount of play because stable rotation cannot be performed unless play is provided between the shaft and the bearing. In other words, unlike the radial direction, in the thrust direction, the shaft can move during the rotation by the amount of play required for rotation, and adsorption occurs after the shaft moves. . This affects the rotation performance, and step-out occurs particularly in a stepping motor. In addition, when the stepping motor rotates at a low speed, the step accuracy of the rotor is adversely affected, and the rotation becomes unstable.

  Further, when another part such as a washer is added as a restricting member in the axial direction of the rotating shaft, the number of parts increases and the number of assembly steps also increases, leading to an increase in cost. In this case, in the case of a washer made of a resin material, the wear resistance of the sliding portion and the dimensional stability such as the axial position may be problematic.

  Moreover, like the stepping motor in the other conventional example (FIG. 5), when the axial direction of the rotating shaft is regulated by a bobbin made of a nonmagnetic material, in addition to the same concerns as the resin washer, As a material selection criterion specific to bobbins, a material considering heat resistance may be required as a countermeasure against coil heat generation. Therefore, there may be a limitation that a material having both heat resistance and wear resistance must be selected, which may cause an increase in cost.

  An object of the present invention is to provide a highly efficient drive device that has a small number of parts, enables highly accurate position regulation with respect to a rotating shaft, enables stable rotation performance, and makes effective use of magnetic flux.

  In order to achieve the above-described object, a driving device according to the present invention includes a rotating shaft that forms a part of a magnetic circuit, a bearing that rotatably holds the rotating shaft and forms a part of a magnetic circuit, A magnet fixed and magnetized to the outer peripheral portion of the rotating shaft, a coil concentrically arranged with the magnet, and a magnetic flux acting on the magnet, and an outer peripheral side of the magnet and an outer peripheral side of the coil A stator excited by the coil, and the axial distance from the axial position regulating surface of the rotating shaft of the bearing to the end surface of the magnet is determined from the axially outer end surface of the stator to the magnet. It is characterized by being set larger than the axial distance to the end face.

  In order to achieve the above-described object, a driving device of the present invention is provided with a rotating shaft that forms a part of a magnetic circuit and axially opposite sides of the rotating shaft, and rotatably holds the rotating shaft. And first and second bearings forming a part of the magnetic circuit, a magnet fixed to the outer peripheral portion of the rotating shaft, divided in the circumferential direction and alternately magnetized to different poles, and concentric with the magnet And first and second coils respectively disposed on both sides of the magnet in the axial direction and applying magnetic flux to the magnet, and on the outer peripheral side of the magnet and on the outer peripheral side of the first and second coils, respectively. A first stator and a second stator which are arranged correspondingly and are excited by the first and second coils, respectively, and the magnet from an axial position regulating surface of the rotary shaft in the first bearing. Said first coil in Is set to be larger than the axial distance from the axially outer end surface of the first stator to the end surface of the magnet on the first coil side, and The axial distance from the position restriction surface in the axial direction of the rotating shaft to the end surface on the second coil side of the magnet is determined from the axially outer end surface of the second stator on the second coil side of the magnet. It is characterized by being set larger than the axial distance to the end face.

  According to the present invention, the axial distance from the position restricting surface of the rotating shaft to the magnet end surface in the first and second bearings is set to be larger than the axial distance from the first and second stator end surfaces to the magnet end surface. is doing. That is, the thrust direction receiving portion of the rotating shaft in the first and second bearings is disposed at a position away from the magnet from the contact portion between the first and second bearings and the rotating shaft. The radial direction receiving portion of the rotary shaft in the bearing is disposed close to the magnet side from the contact portion between the first and second bearings and the rotary shaft.

  By providing the thrust direction receiving portion of the rotating shaft at a portion where the magnetic resistance is relatively large and the magnetic flux is small, the influence of adsorption between the rotating shaft and the first and second bearings is reduced. Further, by providing a radial direction receiving portion of the rotating shaft at a portion having a relatively small magnetic resistance, more magnetic flux is allowed to pass. This eliminates the need for additional parts such as washers as an axial restricting member, so the number of parts is small, position control with high accuracy with respect to the rotating shaft is possible, and stable rotational performance can be obtained. In addition, a highly efficient drive device can be provided by effective use of magnetic flux.

  Further, a radial gap is provided between the shaft portion between the radial direction receiving portion and the thrust direction receiving portion of the rotating shaft and the inner diameters of the first and second bearings. As a result, the cross-sectional area through which the magnetic flux flowing from the first and second stators passes is reduced, the magnetic resistance is increased, the magnetic flux flowing through the thrust direction receiving portion is reduced, and the rotating shaft in the thrust direction receiving portion and the first and second Adsorption of the second bearing can be reduced.

  Further, the thickness of the contact portion of the first and second bearings that contacts the first and second stators is set to the thickness of the portion between the contact portion of the first and second bearings and the thrust direction receiving portion. It is set larger than the wall thickness. As a result, the magnetic resistance of the magnetic circuit reaching the thrust direction receiving portion is relatively increased, the magnetic flux flowing through the thrust direction receiving portion is reduced, and the rotation shaft and the first and second bearings are attracted to the thrust direction receiving portion. Can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an exploded perspective view showing a configuration of a stepping motor as a drive device according to an embodiment of the present invention, and FIG. 2 shows an internal structure in the axial direction of the assembled stepping motor shown in FIG. It is sectional drawing.

  1 and 2, the stepping motor includes a magnet 1, a first stator 2, a second stator 3, a first coil 4, a second coil 5, a rotating shaft 6, a first bearing 7, and a second bearing. The bearing 8, the first bobbin 9, the second bobbin 10, and the connecting ring 11 are provided.

  The magnet 1 is formed in a cylindrical shape, and an outer peripheral surface thereof is divided into N parts in the circumferential direction (N = 4 in the present embodiment), and a magnetized part in which S and N poles are alternately magnetized ( 3).

  The first stator 2 is made of a soft magnetic material, and includes an outer tube portion and a donut-shaped bottom plate portion 2c having a hole 2d formed at the center. On the distal end side of the outer cylindrical portion of the first stator 2, tooth-shaped first outer magnetic pole portions 2a and 2b extending in the axial direction are formed. The first outer magnetic pole portions 2a and 2b are formed with a predetermined tooth width at intervals of 720 / N degrees (180 degrees in the present embodiment) in the circumferential direction.

  The second stator 3 is made of a soft magnetic material, and includes an outer cylinder portion and a donut-shaped bottom plate portion 3c in which a hole portion 3d is formed in the center. On the distal end side of the outer cylindrical portion of the second stator 3, tooth-shaped second outer magnetic pole portions 3a and 3b extending in the axial direction are formed. The second outer magnetic pole portions 3a and 3b are formed with a predetermined tooth width at intervals of 720 / N degrees (180 degrees in the present embodiment) in the circumferential direction.

  The first coil 4 is formed in a cylindrical shape, and is wound around a first bobbin 9 described later. The first coil 4 has an outer diameter that is substantially the same as the outer diameter of the magnet 1.

  The second coil 5 is formed in a cylindrical shape and is wound around a second bobbin 10 described later. The outer diameter of the second coil 5 is configured to be approximately the same as the outer diameter of the magnet 1.

  The rotating shaft 6 is made of a soft magnetic material, is inserted into the inner diameter portions of the first coil 4 and the second coil 5, and is bonded and fixed to the inner diameter portion of the magnet 1. The rotary shaft 6 includes a first inner magnetic pole portion 6a, a second inner magnetic pole portion 6b, a radial receiving portion 6c that fits with the first bearing 7, a radial receiving portion 6d that fits with the second bearing 8, A shaft portion 6e, a thin shaft portion 6f, a thrust receiving portion 6g facing the axial end surface of the first bearing 7, and a thrust receiving portion 6h facing the axial end surface of the second bearing 8 are provided.

  The rotary shaft 6 has an outer diameter D1 at a position sandwiching the magnet 1 in an axial range facing the first outer magnetic pole portions 2a, 2b of the first stator 2 facing the magnet 1. 1 inner magnetic pole portion 6a is formed. The radial receiving portion 6 c of the rotating shaft 6 is inserted into the inner diameter portion of the first coil 4. The first inner magnetic pole portion 6 a of the rotating shaft 6 is excited by the first coil 4 to a pole opposite to the first outer magnetic pole portions 2 a and 2 b of the first stator 2. The cross-sectional shape of the first inner magnetic pole portion 6a of the rotating shaft 6 in the direction orthogonal to the rotating shaft is a circular shape as shown in FIG.

  Similarly, the rotating shaft 6 has an outer diameter D1 at a position sandwiching the magnet 1 in the axial range facing the second outer magnetic pole portions 3a and 3b of the second stator 3 facing the magnet 1. A second inner magnetic pole portion 6b having the shape is formed. The radial receiving portion 6 d of the rotating shaft 6 is inserted into the inner diameter portion of the second coil 5. The second inner magnetic pole portion 6 b of the rotating shaft 6 is excited by the second coil 5 to a pole opposite to the second outer magnetic pole portions 3 a and 3 b of the second stator 3. The cross-sectional shape of the second inner magnetic pole portion 6b of the rotating shaft 6 in the direction orthogonal to the rotating shaft is a circular shape as shown in FIG.

  Moreover, the rotating shaft 6 has fixed the magnet 1 in the 1st inner side magnetic pole part 6a or the 2nd inner side magnetic pole part 6b. Further, the rotary shaft 6 has a radial receiving portion 6c fitted to a first bearing 7 described later, and a radial receiving portion 6d fitted to a second bearing 8 described later, whereby the first bearing 7 and the first bearing 7 are fitted. Two bearings 8 are rotatably held. Note that the stepping motor of the present embodiment is configured to attach a pinion gear or the like to the rotating shaft 6 and output the rotational driving force of the rotating shaft 6 via the pinion gear or the like.

  Here, the first outer magnetic pole portions 2 a and 2 b of the first stator 2, the first bearing 7, and the rotating shaft 6 form a closed magnetic path that penetrates the magnet 1. Further, the second outer magnetic pole portions 3 a and 3 b of the second stator 3, the second bearing 8, and the rotating shaft 6 form a closed magnetic path that penetrates the magnet 1.

  The first bearing 7 is made of a soft magnetic material, and is fixed to the first stator 2 by fitting the contact portion 7 b into the hole 2 d of the first stator 2. Thereby, the 1st bearing 7 and the 1st stator 2 are magnetically connected. Note that the thickness of the first bearing 7 at the contact portion 7b is t1. Further, the first bearing 7 is provided with a radial receiving portion 7a on the magnet 1 side in the axial direction from the contact portion 7b, and a thrust receiving portion 7d is provided on the opposite side to the radial receiving portion 7a in the axial direction. Has been.

  In addition, the rotary shaft 6 is rotatably held by fitting the radial receiving portion 7 a of the first bearing 7 with the radial receiving portion 6 c of the rotating shaft 6. Further, the first bearing 7 and the rotary shaft 6 are magnetically connected at the fitting portion. Further, the thrust receiving portion 7d of the first bearing 7 has a slight gap with respect to the thrust receiving portion 6g of the rotating shaft 6, and is brought into contact with the rotating shaft 6 while having play in a predetermined axial direction. The position of the rotary shaft 6 in the axial direction is restricted.

  Further, the outer diameter of the thin shaft portion 6e of the rotating shaft 6 between the contact portion between the first bearing 7 and the first stator 2 and the thrust receiving portion 6g is formed to be smaller than the outer diameter of the radial receiving portion 6c. Has been. As a result, a radial gap (gap) C is formed between the inner peripheral surface of the distal end portion 7 c of the first bearing 7 and the outer peripheral surface of the thin shaft portion 6 e of the rotary shaft 6. Further, assuming that the thickness of the first bearing 7 from the contact portion 7b to the thrust receiving portion 7d is t2, t1 and t2 are set to have a relationship of t1> t2.

  With the above structure, the first stator 2 and the rotating shaft 6 are magnetically connected via the first bearing 7. Further, the magnetic flux generated by the first coil 4 is mostly from a route having a low magnetic resistance, that is, from the hole 2d of the first stator 2 to the contact portion 7b of the first bearing 7 → the radial receiving portion 7a. And easily flows to the radial receiving portion 6c of the rotating shaft 6. Further, the route from the hole 2d of the first stator 2 to the contact portion 7b of the first bearing 7 → the tip portion 7c → the thrust receiving portion 7d is thinner than the wall thickness t2 of the first bearing 7, The thin shaft portion 6e of the rotating shaft 6 is also thin. Therefore, the magnetic resistance is large, the resulting magnetic flux is small, and the attractive force between the thrust receiving portion 7d of the first bearing 7 and the thrust receiving portion 6g of the rotating shaft 6 is small.

  The second bearing 8 is made of a soft magnetic material, and is fixed to the second stator 3 by fitting the contact portion 8 b into the hole portion 3 d of the second stator 3. Thereby, the 2nd bearing 8 and the 2nd stator 3 are magnetically connected. Note that the thickness of the second bearing 8 at the contact portion 8b is t1. In addition, the second bearing 8 is provided with a radial receiving portion 8a on the magnet 1 side in the axial direction from the contact portion 8b, and a thrust receiving portion 8d is provided on the opposite side to the radial receiving portion 8a in the axial direction. Has been.

  Further, by fitting the radial receiving portion 8 a of the second bearing 8 with the radial receiving portion 6 d of the rotating shaft 6, the rotating shaft 6 is rotatably held. Further, the second bearing 8 and the rotating shaft 6 are magnetically connected at the fitting portion. Further, the thrust receiving portion 8d of the second bearing 8 has a slight gap with respect to the thrust receiving portion 6h of the rotating shaft 6, and comes into contact with the rotating shaft 6 while having play in a predetermined axial direction. The position of the rotary shaft 6 in the axial direction is restricted.

  Further, the outer diameter of the thin shaft portion 6f of the rotating shaft 6 between the contact portion between the second bearing 8 and the second stator 3 and the thrust receiving portion 6h is formed to be narrower than the outer diameter of the radial receiving portion 6d. Has been. As a result, a radial gap (gap) C is formed between the inner peripheral surface of the tip end portion 8 c of the second bearing 8 and the outer peripheral surface of the thin shaft portion 6 f of the rotary shaft 6. Further, assuming that the thickness of the second bearing 8 from the contact portion 8b to the thrust receiving portion 8d is t2, t1 and t2 are set to have a relationship of t1> t2.

  With the above structure, the second stator 3 and the rotating shaft 6 are magnetically connected via the second bearing 8. Further, the magnetic flux generated by the second coil 5 is mostly from a route having a low magnetic resistance, that is, from the hole 3d of the second stator 3, and the contact portion 8b of the second bearing 8 → the radial receiving portion 8a. And easily flows to the radial receiving portion 6d of the rotating shaft 6. Further, the route from the hole 3d of the second stator 3 to the contact portion 8b → the tip portion 8c → the thrust receiving portion 8d of the second bearing 8 is thinner than the wall thickness t2 of the second bearing 8. The thin shaft portion 6f of the rotating shaft 6 is also thin. Therefore, the magnetic resistance is large, the resulting magnetic flux is small, and the attractive force between the thrust receiving portion 8d of the second bearing 8 and the thrust receiving portion 6h of the rotating shaft 6 is small.

  The first bobbin 9 is made of a nonmagnetic material, and the first coil 4 is wound around it. The first coil 4 is wound around the outer periphery of the cylindrical portion 9a of the first bobbin 9, and the coil terminal is wound on the bobbin terminal 9c.

  The second bobbin 10 is made of a nonmagnetic material, and the second coil 5 is wound around it. The second coil 5 is wound around the outer periphery of the cylindrical portion 10a of the second bobbin 10, and the coil terminal is wound on the bobbin terminal 10c.

  The connection ring 11 is formed in a cylindrical shape, and fixes the first stator 2 and the second stator 3. Thereby, the 1st stator 2 and the 2nd stator 3 can be arranged in a desired position and a desired phase.

  The first stator 2 and the second stator 3 are formed in the same shape, and the first outer magnetic pole portions 2 a and 2 b of the first stator 2 and the second stator 3 are connected via the connection ring 11. The second outer magnetic pole portions 3a and 3b are arranged so as to face each other. At that time, as shown in FIG. 3, the relationship between the magnetization phase of the magnet 1 and the first outer magnetic pole portions 2 a and 2 b of the first stator 2 is related to the magnetization phase of the magnet 1 and the second stator 3. The second outer magnetic pole portions 3a and 3b are arranged so as to be shifted by approximately 180 / n (45 in this embodiment) with respect to the relationship with the second outer magnetic pole portions 3a and 3b.

  The connection ring 11 is made of a nonmagnetic material, and the first outer magnetic pole of the first stator 2 is separated by dividing the magnetic circuit between the first stator 2 and the second stator 3. The configuration is such that the influence is less likely to occur between the portions 2 a and 2 b and the second outer magnetic pole portions 3 a and 3 b of the second stator 3.

  The first outer magnetic pole portions 2a and 2b of the first stator 2 are opposed to the outer peripheral surface of the magnet 1 with a predetermined gap, and the second outer magnetic pole portions 3a and 3b of the second stator 3 are magnets. It faces the outer peripheral surface of 1 with a predetermined gap. Further, as described above, the first inner magnetic pole portion 6a and the second inner magnetic pole portion 6b are formed on the rotary shaft 6 fixed to the inner diameter portion of the magnet 1.

  The magnetic flux generated by the first coil 4 is generated by the first outer magnetic pole portions 2 a and 2 b of the first stator 2 facing the outer peripheral surface of the magnet 1 and the rotating shaft 6 fixed on the inner peripheral surface of the magnet 1. Since it passes between the first inner magnetic pole part 6a, it acts on the magnet 1 effectively. At this time, there is no need to provide a gap between the first inner magnetic pole portion 6 a of the rotating shaft 6 and the inner peripheral surface of the magnet 1.

  Similarly, the magnetic flux generated by the second coil 5 is generated by rotating the second outer magnetic pole portions 3 a and 3 b of the second stator 3 facing the outer peripheral surface of the magnet 1 and the inner peripheral surface of the magnet 1. Since it passes between the second inner magnetic pole part 6b of the shaft 6, it acts on the magnet 1 effectively. At this time, there is no need to provide a gap between the second inner magnetic pole portion 6 b of the rotating shaft 6 and the inner peripheral surface of the magnet 1.

  Therefore, the stepping motor according to the present embodiment can be configured to have a smaller distance between the outer magnetic pole part and the inner magnetic pole part as compared with those proposed in Patent Document 1 and Patent Document 2. Thereby, a magnetic resistance can be made small and the output of a stepping motor can be raised.

  Further, since the inner diameter portion of the magnet 1 is filled with the first inner magnetic pole portion 6a and the second inner magnetic pole portion 6b of the rotating shaft 6, those proposed in Patent Document 1 and Patent Document 2 above. As compared with the above, the mechanical strength of the magnet 1 can be increased. Further, since the first inner magnetic pole portion 6a and the second inner magnetic pole portion 6b of the rotating shaft 6 act as a back metal, the magnetic deterioration of the magnet 1 can be reduced.

  The features of the stepping motor of the present embodiment are as follows.

  The axial distance from the thrust receiving portion 7d, which is the position restriction surface in the axial direction of the rotating shaft 6 in the first bearing 7, to the end surface on the first coil 4 side in the magnet 1 is the axial direction in the first stator 2. It is set to be larger than the axial distance from the outer end surface to the end surface of the magnet 1 on the first coil 4 side. In addition, the axial distance from the thrust receiving portion 8 d that is the position restricting surface in the axial direction of the rotating shaft 6 in the second bearing 8 to the end surface on the second coil 5 side in the magnet 1 is determined in the second stator 3. It is set to be larger than the axial distance from the end surface on the outer side in the axial direction to the end surface on the second coil 5 side in the magnet 1.

  Further, a thrust receiving portion 7d is disposed outside the end face of the first coil 4 and opposite to the magnet 1 in the first bearing 7, and the end face of the second coil 5 in the second bearing 8 is disposed. A thrust receiving portion 8d is disposed outside and on the opposite side of the magnet 1.

  Further, a radial gap is provided between the narrow shaft portion 6e between the radial receiving portion 6c and the thrust receiving portion 6g in the rotating shaft 6 and the inner diameter of the first bearing 7, so that the radial receiving portion 6d in the rotating shaft 6 is provided. A gap in the radial direction is provided between the thin shaft portion 6f between the thrust receiving portion 6h and the inner diameter of the second bearing 8.

  Further, the thickness of the contact portion of the first bearing 7 that contacts the first stator 2 is larger than the thickness of the portion of the first bearing 7 between the contact portion and the thrust receiving portion 7d. It is set. Further, the thickness of the contact portion of the second bearing 8 that contacts the second stator 3 is larger than the thickness of the portion of the second bearing 8 that extends from the contact portion to the thrust receiving portion 8d. It is set.

  Next, a driving mechanism in the stepping motor of the present embodiment will be described in detail.

  FIG. 3 is a view for explaining the rotation operation of the stepping motor shown in FIG. 2, (a) to (d) are cross-sectional views taken along the line AA in FIG. h) is a cross-sectional view taken along line BB in FIG.

  In FIG. 3, (a) and (e) are the same timing point, (b) and (f) are the same timing point, (c) and (g) are the same timing point, d) and (h) are the same timing.

  From the state of (a) and (e), the first coil 4 and the second coil 5 are energized to excite the first outer magnetic poles 2a, 2b of the first stator 2 to the N pole, and the second The second outer magnetic poles 3a and 3b of the stator 3 are excited to the S pole. Along with this, the magnet 1 rotates 45 degrees counterclockwise and enters the states shown in (b) and (f).

  Next, the energization to the first coil 4 is reversed, the first outer magnetic poles 2a and 2b of the first stator 2 are excited to the S pole, and the second outer magnetic poles 3a and 3b of the second stator 3 are excited. Is excited to the south pole. Along with this, the magnet 1 further rotates 45 degrees counterclockwise, and enters the states shown in (c) and (g).

  Next, the energization to the second coil 5 is reversed, the first outer magnetic poles 2a, 2b of the first stator 2 are excited to the S pole, and the second outer magnetic poles 3a, 3b of the second stator 3 are excited. Is excited to the N pole. Along with this, the magnet 1 further rotates 45 degrees counterclockwise and enters the state shown in (d) and (h).

  Thereafter, by sequentially switching the energization directions to the first coil 4 and the second coil 5 as described above, the magnet 1 rotates sequentially to a position corresponding to the energization phase.

  Two magnetized layers obtained by dividing the outer peripheral surface of the magnet 1 in the circumferential direction are provided in the axial direction, one magnetized layer facing the first stator 2 and the other facing the second stator 3. The phases of the first and second stators 2 and 3 may be the same by shifting the phases of the magnetized layers of the first and second stators by 180 / N degrees.

  In the present embodiment, the magnetic flux generated by energization of the first coil 4 and the second coil 5 is directly applied to the magnet 1 so that the stepping motor has a high output and can be very miniaturized. . In other words, in addition to the diameter of the magnet 1, the diameter of the stepping motor is such that the first outer magnetic poles 2 a and 2 b of the first stator 2 and the second outer magnetic pole 3 a of the second stator 3 are arranged on the outer peripheral surface of the magnet 1. It is sufficient if the size is sufficient to make 3b face each other. Further, the length of the stepping motor (the dimension in the axial direction) only needs to be a length obtained by adding the lengths of the first coil 4 and the second coil 5 to the length of the magnet 1.

  That is, the size of the stepping motor is determined by the diameters and lengths of the magnet 1, the first coil 4, and the second coil 5. Therefore, if the diameters and lengths of the magnet 1, the first coil 4, and the second coil 5 are made very small, it is possible to realize an ultra-small stepping motor.

  As described above, according to the present embodiment, the first stator 2, the second stator 3, the rotating shaft 6, the first bearing 7, and the second bearing 8 are formed of a soft magnetic material, One bearing 7 is provided with a radial receiving portion 7 a on the magnet 1 side from the contact portion 7 b, and a thrust receiving portion 7 d is provided at a position away from the magnet 1. Further, the second bearing 8 is provided with a radial receiving portion 8a on the magnet 1 side from the contact portion 8b, and a thrust receiving portion 8d is provided at a position away from the magnet 1.

  With the above configuration, regions having different magnetic resistances are provided in the magnetic circuit including the rotating shaft 6, the first and second bearings 7 and 8, and the first and second stators 2 and 3. Here, in the same kind of material (soft magnetic material), the magnetic circuit has a large magnetic resistance if the path is long and small if the path is short, but the magnetic flux flows in a portion having a smaller magnetic resistance. Therefore, by providing the thrust direction receiving portion of the rotating shaft 6 at a portion where the magnetic resistance is relatively large and the magnetic flux is small, the influence of the adsorption between the rotating shaft 6 and the first and second bearings 7 and 8 is reduced. .

  Further, by providing a radial direction receiving portion of the rotating shaft 6 at a portion having a relatively small magnetic resistance, more magnetic flux is allowed to pass. This eliminates the need for additional parts such as washers as an axial restricting member, so that the number of parts is small, position control with high accuracy with respect to the rotating shaft 6 is possible, and stable rotational performance can be obtained. In addition, a highly efficient stepping motor can be provided by effective use of magnetic flux.

  Further, a radial gap is provided between the narrow shaft portion 6e between the radial receiving portion 6c and the thrust receiving portion 6g of the rotating shaft 6 and the inner diameter of the first bearing 7, and the second shaft of the rotating shaft 6 A radial gap is provided between the thin shaft portion 6 f between the radial receiving portion 6 d and the thrust receiving portion 6 h and the inner diameter of the second bearing 8.

  With the above configuration, in order to provide a region having a lower magnetic resistance and a region having a higher magnetic resistance in the magnetic circuit, the mutual relationship in the radial direction between the rotary shaft 6 and the first and second bearings 7 and 8 is obtained. By changing (a portion where the air gap is provided, a portion where the air gap is not provided), the effect of providing the large and small regions of the magnetic resistance in the magnetic circuit can be increased. That is, in the rotary shaft 6 and the first and second bearings 7 and 8, the rotary shaft 6 and the first and second bearings 7 and 8 are completely in contact with each other on the radial receiving surface, and the magnetic resistance is minimized. Thus, it is possible to pass a large amount of magnetic flux.

  On the other hand, in the region from the rotating shaft 6 to the thrust receiving surfaces of the first and second bearings 7 and 8, there is a gap (gap) between the rotating shaft 6 and the inner diameters of the first and second bearings 7 and 8. Provided. Accordingly, in the axial cross section of the first and second bearings 7 and 8, the area of the first and second bearings 7 and 8 is small, and the first and second coils 4 and 5 are away from each other. The magnetic flux passing through the bearings 7 and 8 decreases. Thereby, the influence of adsorption of the rotating shaft 6 and the first and second bearings 7 and 8 on the thrust receiving surface is reduced, and a stepping motor with stable rotational performance can be provided.

  In addition, the thickness of the contact portion 7b in contact with the first stator 2 in the first bearing 7 is larger than the thickness of the portion of the first bearing 7 between the contact portion 7b and the thrust receiving portion 7d. The thickness of the abutting portion 8b in contact with the second stator 3 in the second bearing 8 is set to be large, and the thickness of the portion between the abutting portion 8b and the thrust receiving portion 8d in the second bearing 8 is set. Set larger than.

  With the above-described configuration, in order to provide a region having a lower magnetic resistance and a region having a higher magnetic resistance in the magnetic circuit, the thickness of the first and second bearings 7 and 8 is partially changed so that the magnetic circuit The effect of providing a large and small region of magnetoresistance in the circuit can be increased. That is, in order to flow the magnetic flux flowing from the first and second stators 2 and 3 to the first and second bearings 7 and 8 without loss, the first and second stators 2 and 3 and the first and second stators are used. It is desirable that the thickness of the contact portion of the bearings 7 and 8 is sufficient.

  On the other hand, in order to prevent the rotation shaft 6 and the first and second bearings 7 and 8 from adsorbing, the first and second regions in the region from the abutting portion to the thrust receiving surfaces of the first and second bearings 7 and 8 are used. If the thickness of the second bearings 7 and 8 is thin, the magnetic resistance of the contact portion becomes relatively large. Therefore, the magnetic flux reaching the thrust receiving surfaces of the first and second bearings 7 and 8 is reduced, and as a result, the force that the rotating shaft 6 and the first and second bearings 7 and 8 adsorb can be reduced. Thereby, the influence of the adsorption | suction on a thrust receiving surface becomes smaller, and the stepping motor of the stable rotational performance can be provided.

[Other embodiments]
In the said embodiment, although it has set as the structure which attaches a pinion gear etc. to the rotating shaft 6, and outputs the rotational driving force of the rotating shaft 6, this invention is not limited to this. It goes without saying that the same effect can be obtained even when a structure in which the lead screw is coaxially attached to the rotating shaft 6 or a structure in which the rotating shaft 6 and the lead screw are integrated is used.

  That is, in the structure using the lead screw, the rotating shaft 6 may be offset in the thrust direction, and the lead screw may be pressed against the motor side by a leaf spring, for example. In this case, the tip of the rotating shaft 6 may be formed in a spherical shape (sphere R), and the bearing may be formed in a planar shape that receives only the thrust surface. If the tip of the rotary shaft 6 has a spherical R shape, it is close to point contact, so there is little concern about the suction of the rotary shaft 6 and the bearing. Therefore, with respect to the magnetic resistance, if only the radial receiving portion of the rotating shaft 6 is made sufficiently small, the magnetic flux will not be reduced and the efficiency can be prevented from being lowered.

It is a disassembled perspective view which shows the structure of the stepping motor as a drive device which concerns on embodiment of this invention. It is sectional drawing which shows the internal structure of the axial direction of the assembly completion state of the stepping motor shown in FIG. It is a figure for demonstrating rotation operation of the stepping motor shown in FIG. 2, (a)-(d) is sectional drawing in alignment with the arrow AA of FIG. 2, (e)-(h) It is sectional drawing which follows the arrow BB line of FIG. It is sectional drawing which shows the internal structure of the axial direction of the stepping motor which concerns on a prior art example. It is sectional drawing which shows the internal structure of the axial direction of the stepping motor which concerns on another prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnet 2 1st stator 2a, 2b 1st outer side magnetic pole part 3 2nd stator 3a, 3b 2nd outer side magnetic pole part 4 1st coil 5 2nd coil 6 Rotating shaft 6a, 6b Inner magnetic pole part 6c , 6d Radial receiving part 6e, 6f Thin shaft part 6g, 6h Thrust receiving part
7 first bearing 7a radial receiving portion 7b abutting portion 7d thrust receiving portion 8 second bearing 8a radial receiving portion 8b abutting portion 8d thrust receiving portion 9 first bobbin 10 second bobbin 11 connecting ring

Claims (5)

A rotating shaft that forms part of the magnetic circuit;
A bearing that rotatably holds the rotating shaft and forms part of a magnetic circuit;
A magnet fixed on the outer periphery of the rotating shaft and magnetized;
A coil that is arranged concentrically with the magnet and causes a magnetic flux to act on the magnet;
A stator disposed on the outer peripheral side of the magnet and on the outer peripheral side of the coil, and excited by the coil;
The axial distance from the axial position regulating surface of the rotating shaft of the bearing to the end surface of the magnet is set to be larger than the axial distance from the axially outer end surface of the stator to the end surface of the magnet. The drive device characterized. A rotating shaft that forms part of the magnetic circuit;
First and second bearings respectively disposed on both axial sides of the rotary shaft, holding the rotary shaft rotatably and forming part of a magnetic circuit;
A magnet fixed to the outer periphery of the rotary shaft, and magnetized alternately in different poles by dividing in the circumferential direction;
A first coil and a second coil which are concentric with the magnet and are respectively disposed on both sides in the axial direction of the magnet, and cause a magnetic flux to act on the magnet;
A first stator and a second stator disposed on the outer peripheral side of the magnet and corresponding to the outer peripheral sides of the first and second coils, respectively, and excited by the first and second coils, respectively; ,
An axial distance from an axial position restriction surface of the rotating shaft of the first bearing to an end surface of the magnet on the first coil side is defined as an axially outer end surface of the first stator. Set larger than the axial distance to the end face on the first coil side,
An axial distance from an axial position restricting surface of the rotating shaft of the second bearing to an end surface of the magnet on the second coil side is determined from an axially outer end surface of the second stator in the magnet. The drive device characterized in that it is set larger than the axial distance to the end face on the second coil side. The first stator includes a first outer magnetic pole portion facing the outer peripheral surface from one end surface of the magnet, and the second stator has a second outer surface facing the outer peripheral surface from the other end surface of the magnet. With an outer magnetic pole,
The rotating shaft includes first and second inner magnetic pole portions facing the first and second outer magnetic pole portions, respectively.
The first outer magnetic pole part, the first bearing, and the rotating shaft form a closed magnetic path that penetrates the magnet, and the second outer magnetic pole part, the second bearing, and the rotating shaft, Forming a closed magnetic path through the magnet;
In the first bearing, a thrust direction receiving portion is formed outside the end face of the first coil and opposite to the magnet, and outside the end face of the second coil in the second bearing; The driving device according to claim 2, wherein a thrust direction receiving portion is formed on a side opposite to the magnet. The rotating shaft includes a first radial direction receiving portion that fits into the first bearing, a first thrust direction receiving portion that faces the position regulating surface of the first bearing, and the second bearing. And a second radial direction receiving portion that fits with the second direction thrust receiving portion facing the position regulating surface of the second bearing,
A radial gap is provided between a shaft portion between the first radial direction receiving portion and the first thrust direction receiving portion of the rotating shaft and an inner diameter of the first bearing, and the rotating shaft A radial gap is provided between a shaft portion between the second radial direction receiving portion and the second thrust direction receiving portion and an inner diameter of the second bearing. 2. The drive device according to 2 or 3.   The thickness of the contact portion of the first bearing that contacts the first stator is set to be larger than the thickness of the portion of the first bearing from the contact portion to the thrust direction receiving portion. And the thickness of the contact portion of the second bearing that contacts the second stator is greater than the thickness of the portion of the second bearing that extends from the contact portion to the thrust direction receiving portion. The driving device according to claim 2, wherein the driving device is set to be larger.

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