JP2010226922A - Air core stepping motor and lens device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stepping motor having an advantage of obtaining higher output, and a lens device using this motor. <P>SOLUTION: The lens device 1 includes a fixed cylinder 12, a mirror cylinder 10 having a driving cylinder provided so as to be relatively rotatable with the moving cylinder, and a stepping motor 20 for driving the driving cylinder to be rotated. The motor 20 has a cylindrical stator 30 and a cylindrical rotor 40 disposed on the outer circumference of the stator, wherein a plurality of pole teeth of the stator 30 oppose the inner circumferential surface of magnets of the rotor 40. The stator 30 is fixed on the outer circumferential surface of the fixed cylinder 12, and the rotor 40 is rotatably supported on the fixed cylinder 12 by bearings 49, 53 in the outer circumference of the stator 30. Since the rotor 40 is disposed on the outer circumferential side, an output moment can be higher than the same size motor of inner rotor type. An area of pole teeth can be increased. Owing to this, high output can be achieved. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an outer rotor type air core stepping motor and a lens apparatus using the motor.

  As a lens device in a single-lens reflex camera or a video camera, there is a type in which a lens arranged in a lens barrel is moved in an optical axis direction using an air core motor. The lens barrel includes, for example, a moving cylinder that holds the lens and moves linearly in the optical axis direction, and a driving cylinder that is rotatably provided inside the moving cylinder, and one of the moving cylinder and the driving cylinder. Has a structure in which a cam is provided, and the other is provided with a cam groove into which the cam is fitted. By rotating the drive cylinder, the movable cylinder moves in the optical axis direction, and zoom and focus operations are performed. An air core motor is used to rotate the drive cylinder.

  Since the air-core motor is hollow, a lens and a shutter can be disposed in the hollow portion if the motor is arranged so that the rotation axis of the motor coincides with the optical axis of the lens barrel. Furthermore, the rotational motion of the motor can be directly transmitted to the rotation of the drive cylinder. Further, since there is no portion that protrudes outward from the lens barrel as in the case of an external motor, it is compact.

  As such an air core motor, a lens barrel using an ultrasonic motor has been proposed (see, for example, Patent Document 1). However, the ultrasonic motor has a problem that the motor efficiency is relatively low and the cost increases because an expensive material is used.

JP 2006-158054 A

  The present invention has been made in view of the above-described problems, and an object thereof is to provide an air-core stepping motor and a lens device using the motor. It is another object of the present invention to provide an air-core stepping motor having advantages such as higher output and easy processing.

  An air-core stepping motor of the present invention comprises a cylindrical stator including a yoke and a coil having a plurality of pole teeth, and a cylindrical rotor including a cylindrical magnet disposed on the outer periphery of the stator, A plurality of pole teeth of the yoke are arranged to face the inner peripheral surface of the magnet.

  According to the present invention, since the rotor is arranged on the outer peripheral side (outer rotor type), the rotor and the outer peripheral side movable part of the driven device can be connected by a simple mechanism. In that case, a connecting member such as a gear or a belt for transmitting the rotation of the rotor to the movable part can be eliminated. Further, when the rotor is disposed on the inner peripheral side (inner rotor type), the rotor is positioned on the outer side with respect to the center of rotation, so that the output moment can be increased. In addition, the area of the pole teeth facing the magnet can be increased. From these things, high output becomes possible.

Furthermore, since the pole teeth are on the outer peripheral side, the stator can be easily manufactured and the mold cost can be reduced.
This point will be described with reference to FIG.
FIG. 6 is a diagram schematically illustrating an example of a stator manufacturing method.
As shown in FIG. 6A, when the pole teeth C are on the inner peripheral side, as shown in FIG. Overlap. Therefore, as shown in FIG. 6C, it is necessary to first draw a portion to be the pole teeth C of the flat plate. On the other hand, when the pole teeth are on the outer peripheral side, the drawing can be performed in a planar manner as shown in FIG.

  In the present invention, if both ends of the winding constituting the coil are drawn out to the hollow portion of the stator and connected to the power source through the hollow portion, wiring to the stator coil on the inner peripheral side Can be clearly guided without interfering with the rotor.

  In this invention, it is preferable to provide the friction brake mechanism which hold | maintains the said rotor non-rotatably with respect to the said stator at the time of the energization of the said coil.

  In the stepping motor, when the coil is not energized, the rotor retains only the detent torque, and becomes rotatable by the balance between the detent torque and the weight of the lens. Therefore, by providing the friction brake mechanism, the rotor can be held so as not to rotate even when the coil is not energized. At the same time, since the non-energized holding is possible, the energizing holding force becomes unnecessary, and the power consumption can be suppressed low.

  Further, in the present invention, the friction brake mechanism is fixed to the friction disk applied to the end face of the rotor, and the stator or the casing in which the friction disk is brought into contact with the end face of the rotor with friction. Biasing means, and the rotor can be held in a non-rotatable manner with respect to the stator or casing by friction between the end face of the rotor and the presser disk.

  By keeping the friction disk in contact with the end face of the rotor, the rotor can be held from rotating due to static friction. During the rotation of the rotor, the motor begins to escape from static friction by the torque of the motor. In order to reduce and stabilize the static friction, for example, a record-like annular protrusion is provided on the end face of the rotor. Although details will be described later with reference to FIGS. 1 and 3, the frictional force can be adjusted by further providing a presser disk 63 and a wave washer 64.

  The lens device of the present invention includes a moving cylinder that accommodates a lens therein and moves forward and backward in the optical axis direction, and a driving cylinder that is provided to be rotatable relative to the moving cylinder. One side is provided with a cam, and the other side is provided with a lens barrel provided with a cam groove into which the cam is fitted, and means for rotationally driving the drive cylinder, and the drive cylinder is rotationally driven. Thus, the lens device is configured to advance and retract the movable cylinder, wherein the rotation driving means includes a cylindrical stator including a yoke and a coil having a plurality of pole teeth, and a cylindrical shape disposed on the outer periphery of the stator. And a cylindrical rotor including a magnet, wherein the plurality of pole teeth of the yoke are air core stepping motors arranged to face the inner peripheral surface of the magnet.

  According to the present invention, if the rotation axis of the motor is arranged so as to coincide with the optical axis of the lens barrel, a lens and a shutter can be arranged in the hollow portion. Furthermore, the rotational movement of the motor can be transmitted directly to the lens barrel. Moreover, since there is no part which protrudes outside from a lens-barrel like an external motor, it becomes compact. Furthermore, the output moment can be increased because the rotor is positioned on the outer side with respect to the rotation center as compared with a motor having the same outer diameter of the inner rotor type. In addition, the area of the pole teeth facing the magnet can be increased. From these things, the high output of the motor becomes possible.

  A specific aspect of the lens device according to the present invention includes a moving cylinder that accommodates a lens therein and moves forward and backward in the optical axis direction, and a driving cylinder that is provided to be rotatable relative to the moving cylinder. A cam barrel is provided on one of the drive cylinders, and a barrel provided with a cam groove into which the cam is fitted, and means for rotating the drive cylinder, and the drive cylinder A lens device that advances and retracts the movable cylinder by rotating the cylinder, wherein the rotation driving means includes a cylindrical stator, a cylindrical rotor disposed on an outer periphery of the stator, and the rotor that moves the rotor. An air-core stepping motor comprising: a stator yoke having a plurality of pole teeth; a coil; and the rotor having a cylindrical shape. Magnet and the magnet A back yoke disposed on an outer periphery of the magnet, and a bracket having a coupling member that accommodates the magnet and the back yoke and is coupled to the drive cylinder, and a plurality of pole teeth of the yoke include the magnet The stator is fixed to the outer peripheral surface of the movable cylinder, and the rotor is moved on the outer periphery of the stator by the rotation support means. It is characterized in that it is supported rotatably.

  In the present invention, it is further provided with a friction brake mechanism that holds the rotor in a non-rotatable manner with respect to the stator when the coil is not energized.

  As is clear from the above description, according to the present invention, the rotor is disposed on the outer peripheral side, and the pole teeth of the yoke are disposed to face the inner peripheral surface of the rotor. A stepping motor having a higher output than the motor can be provided. Furthermore, it can be manufactured at low cost. If this air-core stepping motor is applied to the lens barrel driven by the ultrasonic motor instead of the ultrasonic motor, a low-cost lens device can be provided as compared with the case where the ultrasonic motor is used.

It is a disassembled perspective view which shows the structure of the lens apparatus which concerns on embodiment of this invention. It is a perspective view of a lens apparatus. It is a sectional side view of a lens apparatus. It is a perspective view which shows the magnetic pole piece which comprises a stator. It is a figure explaining the processing method of the copper wire of a coil. It is a figure which illustrates an example of the manufacturing method of a stator typically.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
As shown in FIGS. 1, 2, and 3, the lens device 1 includes a lens barrel 10 and an air-core stepping motor (rotation driving means) 20 for driving a lens disposed in the lens barrel 10. Have.

  As shown in FIG. 1, the lens barrel 10 includes an outermost front lens barrel 11, a fixed cylinder 12 arranged in the front lens barrel 11, and a drive cylinder (illustrated) arranged in the fixed cylinder 12. Not). A cam is provided on the inner peripheral surface of the fixed cylinder 12. On the other hand, a cam groove into which the cam is fitted is formed on the outer peripheral surface of the drive cylinder. By rotating the drive cylinder with respect to the fixed cylinder 12, the cam is guided along the cam groove, and the fixed cylinder 12 advances straight in the optical axis direction. As a result, the lens moves in both directions along the optical axis, and a zoom or focus operation is performed.

Next, the structure of the air core stepping motor 20 will be described with reference mainly to FIGS.
The air-core stepping motor 20 includes a cylindrical stator 30 and a cylindrical rotor 40 disposed on the outer periphery of the stator 30.

Stator 30 has an A-phase stator 30A and a B-phase stator 30B arranged in the axial direction. As shown in FIG. 3, each phase stator has two claw pole type magnetic pole pieces 31 and a coil 32. As shown in FIG. 4, the pole piece 31 includes a flat ring portion 31a, a plurality of triangular pole teeth 31b extending in the rotation axis direction from the outer peripheral edge of the ring portion 31a, and an inner peripheral edge of the ring portion 31a. It has the edge part 31c extended in the same direction as the tooth | gear 31b. The height of the edge 31c is lower than the height of the pole teeth 31b.
Further, a plurality (four in this example) of notches 31x not formed with the pole teeth 31b are formed on the outer peripheral edge of the ring portion 31a. The notch 31x is a copper wire lead-out port of the coil 32, as will be described later.

  In the magnetic pole piece 31, when the pole teeth 31 b are provided so as to rise from the outer peripheral edge of the ring portion 31 a in this way, the processing steps of the magnetic pole piece are reduced compared to the case where the pole teeth 31 b are provided so as to rise from the inner peripheral edge. Can be reduced. That is, as described above with reference to FIG. 6, depending on the diameter of the pole piece, if the pole teeth are on the inner peripheral side, the tips of the pole teeth may overlap when deployed in a plane. For this reason, it is necessary to first draw a portion (near the center) that becomes the pole teeth of the flat plate. On the other hand, when the pole teeth are on the outer peripheral side, they can be developed in a plane, so that such drawing processing is not necessary.

  In each phase stator, the two magnetic pole pieces 31 are arranged so that the pole teeth 31b face each other alternately and in a non-contact manner. And a coil accommodation recessed part is formed between the ring part of the two magnetic pole pieces 31, a pole tooth, and an edge part. The A-phase stator 30A and the B-phase stator 30B are arranged such that the pole teeth 31b of the magnetic pole piece 31 are shifted in the circumferential direction by ½ pitch, and the ring portions 31a of the magnetic pole pieces 31 in contact with each other are outsert molded or the like. Are integrally fixed by a bobbin. A bobbin is shape | molded so that resin may be filled between pole teeth while covering the outer surface of the coil accommodation recessed part of each phase stator.

  A coil 32 is formed by winding a copper wire in each coil housing recess covered with the bobbin. Each coil 32 is insulated from each pole piece 31 by a bobbin. Processing of both ends of each copper wire will be described later. Alternatively, bobbinless can be achieved by forming an air-core coil using a fusion copper wire and applying an insulation treatment.

  As shown in FIG. 3, the rotor 40 includes a cylindrical magnet 41 disposed opposite to the outer peripheral surfaces of the A-phase stator 30 </ b> A and the B-phase stator 30 </ b> B, and a cylindrical shape to which the outer peripheral surfaces of both the magnets 41 are fixed. And a back yoke 42. These are accommodated in a sleeve-like bracket 45. The bracket 45 is composed of a pair of bracket pieces 46 and 51 that are divided into two in the optical axis direction, and the bracket pieces 46 and 51 are fixed by, for example, uneven bonding or adhesion.

  As shown in FIG. 1, the front bracket piece 46 has a cylindrical shape, and a recess 47 extending in the circumferential direction is formed on the inner peripheral surface. Both magnets 41 and the back yoke 42 are accommodated in the recess 47. As shown in FIG. 1, a plurality of record-like annular protrusions are formed on the end surface 46 a on the front side of the bracket piece 46. In addition, a plurality of (three in this example) recesses are formed on the end surface 46a. The recesses are arranged at equal central angles (120 ° in this example). Each recess accommodates a bearing (rotation support means) 49 that supports rotation in the radial direction.

  The bracket piece 51 on the near side (lens barrel side) has a ring portion 51a and a semi-cylindrical portion 51b extending in the barrel direction in the axial direction from the outer peripheral edge of the ring portion 51a. An end surface on the near side of the front bracket piece 46 is applied to the ring portion 51a and fixed. Further, as shown in FIG. 1, a plurality (three in this example) of concave portions are formed on the outer peripheral surface of the ring portion 51a. The recesses are arranged at equal central angles (120 ° in this example). Each recess accommodates a bearing (rotation support means) 53 that supports rotation in the thrust direction (axial direction). Further, a bar 55 extending in the axial direction in the lens barrel direction is formed in a portion of the ring portion 51a where the semi-cylindrical portion 51b is not provided. The bar 55 is connected to the drive cylinder of the lens barrel 10 described above.

Next, a state where the air-core stepping motor 20 is mounted on the lens barrel 10 will be described with reference mainly to FIG.
In the stepping motor 20, the stator 30 is fixed to the outer peripheral surface of the fixed cylinder 12 of the lens barrel 10. The rotor 40 is disposed outside the stator 30 and is rotatably supported by the front and front bearings 49 and 53 (see FIG. 1) with respect to the fixed cylinder 12. The front bearing 49 slides on the outer peripheral surface of the sliding ring 52 fixed to the outer peripheral surface of the fixed cylinder 12 and supports the rotor 40 in the radial direction. Further, as shown in FIG. 1, the front bearing 53 slides on the annular step portion 11a of the front barrel 11 and supports the rotor 40 in the thrust direction. The lens specification is displayed on the semi-cylindrical portion 51b of the front bracket 51, and covers the outer peripheral surface of the front barrel 11 (see also FIG. 2).

  As shown in FIG. 5, the copper wires 33 of the coils 32 of the stator 30 are once drawn out of the magnetic pole pieces 31 of the respective phase stators, and then gathered together to form notches 31x of the magnetic pole pieces 31. As shown in FIG. 3, it is guided into the fixed cylinder 12 through the hole 12a penetrating the fixed cylinder 12, and soldered to a flexible substrate (not shown). In this way, wiring to the coil 32 of the stator 30 disposed on the inner peripheral side can be processed without interfering with the rotor 40.

Further, as shown in FIGS. 1, 2, and 3, a friction brake mechanism 60 that supports the rotor 40 so as not to rotate with respect to the stator 30 when the coil 32 is not energized is provided at the tip of the barrel 10. Is provided.
The friction brake mechanism 60 includes a friction disk 61 applied to the front end surface 46a of the front bracket piece 46 of the rotor 40, and a biasing means 62 that brings the friction disk 61 into contact with the front end surface 46a with friction. The urging means 62 is disposed between the presser disk 63 fixed by screwing to the distal end of the fixed cylinder 12 of the lens barrel 10, and between the presser disk 63 and the friction disk 61, and the friction disk 61 is attached to the bracket front end surface 46a. And a wave washer 64 for energizing.

  When the friction disk 61 is in contact with the bracket front end surface 46a by the biasing means 63, the coil 45 is not energized and the bracket 45 is stationary with the friction disk 61 even when the rotor 40 is rotatable. It is held so as not to rotate due to friction. Since the bracket front end surface 46a is provided with a record-like annular projection, the frictional force can be reduced and stabilized. At the time of rotation, the motor torque starts to escape from static friction and start rotating. In order to adjust the frictional force, the pressing disk 63 is rotated to change the distance between the disk 63 and the bracket front end surface 46a, and the urging force of the wave washer 64 is adjusted.

  When the coil 32 of the stepping motor 20 is energized, the rotor 40 rotates around the stator 30 by the generated magnetic field. At this time, the front and front bearings 49 and 53 are in rolling contact with the outer peripheral surface of the sliding ring 52 and the annular step portion 11a of the front lens barrel 11, respectively. Further, the semi-cylindrical portion 51 b of the front bracket 51 rotates while sliding on the outer peripheral surface of the front barrel 11. The front end face 46a of the bracket piece 46 on the front side is in contact with the friction disk 61, but as described above, since the record-like annular protrusion is formed on the end face 46a, the contact area is reduced and the stationary face 46a is stationary. The difference between friction and dynamic friction can be reduced, and friction can be stabilized. Then, the rotation of the rotor 40 rotates the drive cylinder of the lens barrel 10 to which the connecting member 55 of the bracket 45 is connected, and thereby the fixed cylinder 12 moves straight in the optical axis direction.

  When the coil 32 is de-energized, the rotor 40 stops rotating. The rotor 40 is held so as not to rotate due to friction between the front end surface 46 a of the bracket 45 and the friction disk 61.

DESCRIPTION OF SYMBOLS 1 Lens apparatus 10 Lens tube 11 Front lens tube 12 Fixed tube 20 Air core stepping motor (rotation drive means)
30 Stator 31 Magnetic pole piece 32 Coil 33 Copper wire 40 Rotor 41 Magnet 42 Back yoke 45 Bracket 46, 51 Bracket piece 47 Recess 49 Bearing 52 Sliding ring 53 Bearing 55 Bar 60 Friction brake mechanism 61 Friction disk 62 Biasing means 63 Pressing disk 64 wave washer

Claims (7)

A cylindrical stator including a yoke and a coil having a plurality of pole teeth;
A cylindrical rotor including a cylindrical magnet disposed on the outer periphery of the stator;
With
An air core stepping motor, wherein a plurality of pole teeth of the yoke are arranged to face the inner peripheral surface of the magnet.   2. The air-core stepping motor according to claim 1, wherein both ends of a winding constituting the coil are drawn out to a hollow portion of the stator and connected to a power source through the hollow portion.   The air core stepping motor according to claim 1, further comprising a friction brake mechanism that holds the rotor in a non-rotatable manner with respect to the stator when the coil is not energized. The friction brake mechanism is
A friction disk applied to the end face of the rotor;
Urging means fixed to the stator or a casing accommodated in the stator, the friction disk contacting the end face of the rotor with friction,
The air-core stepping motor according to claim 3, wherein the rotor is held non-rotatable with respect to the stator or casing by friction between an end surface of the rotor and the presser disk. There is a moving cylinder that houses a lens and moves forward and backward in the optical axis direction, and a driving cylinder that is provided to be rotatable relative to the moving cylinder, and a cam is provided on one of the moving cylinder and the driving cylinder. And a lens barrel provided with a cam groove into which the cam is fitted,
Means for rotationally driving the drive cylinder;
A lens device that advances and retracts the movable cylinder by rotationally driving the drive cylinder,
The rotation driving means;
A cylindrical stator including a yoke and a coil having a plurality of pole teeth;
A cylindrical rotor including a cylindrical magnet disposed on the outer periphery of the stator;
With
2. A lens apparatus according to claim 1, wherein the plurality of pole teeth of the yoke is an air-core stepping motor disposed to face the inner peripheral surface of the magnet. There is a moving cylinder that houses a lens and moves forward and backward in the optical axis direction, and a driving cylinder that is provided to be rotatable relative to the moving cylinder, and a cam is provided on one of the moving cylinder and the driving cylinder. And a lens barrel provided with a cam groove into which the cam is fitted,
Means for rotationally driving the drive cylinder;
A lens device that advances and retracts the movable cylinder by rotationally driving the drive cylinder,
The rotation driving means;
An air-core stepping motor comprising a cylindrical stator, a cylindrical rotor disposed on the outer periphery of the stator, and a means for rotatably supporting the rotor with respect to the movable cylinder,
The stator is
A stator yoke having a plurality of pole teeth;
Coils,
Have
The rotor is
A cylindrical magnet,
A back yoke disposed on the outer periphery of the magnet;
A bracket provided with a connecting member that houses the magnet and the back yoke and connects to the drive cylinder;
Have
Furthermore, the plurality of pole teeth of the yoke is an air-core stepping motor arranged to face the inner peripheral surface of the magnet,
The lens device, wherein the stator is fixed to an outer peripheral surface of the movable cylinder, and the rotor is rotatably supported by the movable cylinder on the outer periphery of the stator by the rotation support means.   The lens apparatus according to claim 6, further comprising a friction brake mechanism that holds the rotor in a non-rotatable manner with respect to the stator when the coil is not energized.

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