Patent Description:
As an actuator used in a scanner in a multifunction peripheral, a laser beam printer and other apparatuses, an actuator driven to be rotated in a reciprocating manner (hereinafter referred to as "rotary reciprocating drive actuator") has been known. A rotary reciprocating drive actuator includes, for example, a rotating shaft that is a movable body and a driving part including a coil magnet. Such a rotary reciprocating drive actuator is capable of optical scanning of an object by changing the reflection angle of a laser beam by a mirror attached to a rotating shaft that is driven to rotate in a reciprocating manner by energizing the coil. Examples of such rotary reciprocating drive actuators include moving coil type actuators in which a coil is disposed on a rotating shaft and moving magnet type actuators in which a magnet is disposed on a rotating shaft (see, for example, Patent Literature (hereinafter, referred to as PTL) <NUM>).

Prior art further includes <CIT> which discloses a rotary reciprocating drive actuator.

In a rotary reciprocating drive actuator of the moving coil type, heat generated by the coil during driving (when the coil is energized) may adversely affect, for example, the surface condition of the mirror, the bonding condition of the mirror to the rotating shaft, and the shape of the mirror such as warpage. In addition, it is difficult to increase the current input to the coil in view of the heat generation from the coil during the driving, thereby making it difficult to increase the size and amplitude of the mirror serving as a movable object. Further, it is necessary to pull out the wiring, which extends to the coil disposed on the rotating shaft, to the fixed body side, thereby lowering the assembling property.

On the other hand, a rotary reciprocating drive actuator of the moving magnet type does not suffer the above problems related to the coil heat generation and coil wiring. However, in the structure disclosed in PTL <NUM>, a magnet is disposed in the same area as a mirror is on a rotating shaft, and a yoke around which the coil is wound is disposed so as to surround the magnet; therefore, the mirror, namely a movable object, and the yoke are more likely to interfere with each other when the rotating shaft rotates. This configuration makes the increase of the size and amplitude of the mirror difficult.

An object of the present invention is to provide a rotary reciprocating drive actuator capable of increasing the size and amplitude of a movable object such as a mirror, and of stabilizing the drive performance.

A rotary reciprocating drive actuator according to the present invention includes:.

Further embodiments of the invention are defined in the dependent claims.

The present invention can increase the size and amplitude of a movable object such as a mirror, and also stabilize the drive performance.

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

<FIG> is an external perspective view of rotary reciprocating drive actuator <NUM> of an embodiment. <FIG> is an exploded perspective view of rotary reciprocating drive actuator <NUM>. <FIG> is a cross-sectional view of rotary reciprocating drive actuator <NUM>.

Rotary reciprocating drive actuator <NUM> is used, for example, in a LIDAR (Laser Imaging Detection and Ranging) device. Rotary reciprocating drive actuator <NUM> is also applicable to an optical scanning device in a multifunction peripheral, a laser beam printer and other apparatuses.

Rotary reciprocating drive actuator <NUM> includes, as main parts, movable part <NUM>, fixed part <NUM> for rotatably supporting movable part <NUM>, and driving part <NUM> for driving movable part <NUM> to rotate in a reciprocating manner with respect to fixed part <NUM>. Hereinafter, the direction along the rotation axis of movable part <NUM> is referred to as "axial direction or direction of the axis.

Movable part <NUM> includes rotating shaft <NUM> and mirror part <NUM>.

Mirror part <NUM> serves as a movable object in rotary reciprocating drive actuator <NUM>, and is attached to rotating shaft <NUM>. Mirror part <NUM> is formed by, for example, adhering mirror <NUM> to one surface of mirror holder <NUM>. Rotating shaft <NUM> is inserted through insertion holes 122a of mirror holder <NUM> and fastened to mirror holder <NUM>.

Fixed part <NUM> includes base <NUM>, second bearing <NUM>, and third bearing <NUM>.

Base <NUM> includes left side wall part <NUM> and right side wall part <NUM> disposed so as to face each other. Left side wall part <NUM> and right side wall part <NUM> are individually erected at both ends of flat plate-shaped bottom part <NUM> in the axial direction. In other words, base <NUM> is formed to have a substantially U-shaped cross section.

Insertion holes 211a and 212a through which rotating shaft <NUM> is inserted are formed in left side wall part <NUM> and right side wall part <NUM>, respectively. In left side wall part <NUM> and right side wall part <NUM>, formed are notched parts 211b and 212b that allow insertion holes 211a and 212a to communicate with the outer edges of left side wall part <NUM> and right side wall part <NUM>, respectively.

Rotating shaft <NUM> with mirror part <NUM> attached thereto is placed into insertion holes 211a and 212a from the outside through notched parts 211b and 212b. Without notched parts 211b and 212b, a complicated assembly operation would be required, for example, inserting rotating shaft <NUM> through the insertion hole 211a of left side wall part <NUM>, insertion hole 122a of mirror holder <NUM>, and insertion hole 212a of right side wall part <NUM> in this order, and further fastening rotating shaft <NUM> with mirror holder <NUM> while mirror part <NUM> is disposed between left side wall part <NUM> and right side wall part <NUM>. On the other hand, as notched parts 211b and 212b are formed in left side wall part <NUM> and right side wall part <NUM>, rotating shaft <NUM> to which mirror part <NUM> is attached in advance can be easily placed into insertion holes 211a and 212a through notched parts 211b and 212b, in the present embodiment.

Second bearing <NUM> and third bearing <NUM> are each composed of a rolling bearing (for example, a ball bearing). A rolling bearing has a low coefficient of friction and can smoothly rotate rotating shaft <NUM>, thereby improving the drive performance of rotary reciprocating drive actuator <NUM>.

Second bearing <NUM> and third bearing <NUM> are disposed in bearing attaching parts (reference numerals thereof omitted) connected to insertion holes 211a and 212a of left side wall part <NUM> and right side wall part <NUM>, respectively. Specifically, second bearing <NUM> and third bearing <NUM> allows the insertion of rotating shaft <NUM> from both sides in the axial direction of rotating shaft <NUM>, and after rotating shaft <NUM> is placed through insertion holes 211a and 212a, second bearing <NUM> and third bearing <NUM> are attached to the bearing attaching parts. In this way, rotating shaft <NUM> is rotatably attached to base <NUM> via second bearing <NUM> and third bearing <NUM>.

Driving part <NUM> includes core unit <NUM> and magnet <NUM>.

Core unit <NUM> includes, for example, first cores <NUM> and <NUM>, second core (relay core) <NUM>, coils <NUM> and <NUM>, rotation angle position holding part <NUM>, first shield member <NUM>, second shield member <NUM>, and first bearing <NUM>. <FIG> is a perspective view illustrating the configuration of core unit <NUM> (excluding first shield member <NUM>, second shield member <NUM>, and first bearing <NUM>). In the present embodiment, core unit <NUM> is formed in a substantially rectangular parallelepiped shape as illustrated in, for example, <FIG>. Core unit <NUM> is fastened to base <NUM> to form a part of fixed part <NUM>.

First cores <NUM> and <NUM> and second core <NUM> are integrated to form one core body C, and form a magnetic circuit when coils <NUM> and <NUM> are energized. First cores <NUM> and <NUM> and second core <NUM> are, for example, each composed of laminated core formed by laminating electromagnetic steel sheets such as silicon steel sheets.

First cores <NUM> and <NUM> include magnetic pole parts 41a and 42a, and leg parts 41b and 42b extending downward from magnetic pole parts 41a and 42a, respectively. When the magnetic pole part is excited by energizing coil <NUM> or <NUM>, the magnetic pole part generates a polarity according to the energization direction.

The portions of magnetic pole parts 41a and 42a-the portions facing magnet <NUM>-each have a shape curved along the outer peripheral surface of magnet <NUM>. Coil <NUM> and <NUM> are disposed on leg parts 41b and 42b, respectively. First cores <NUM> and <NUM> are fixed to second core <NUM> in a posture such that magnetic pole parts 41a and 42a face each other and leg parts 41b and 42b are parallel to each other.

Second core <NUM> allows leg parts 41b and 42b of first cores <NUM> and <NUM> to communicate to each other, and forms an intermediate portion of a magnetic circuit through which magnetic pole parts 41a and 42a are connected to each other. That is, first cores <NUM> and <NUM> are integrally connected to each other via second core <NUM>. In the present embodiment, second core <NUM> is formed to have a U shape, and the ends of leg parts 41b and 42b of first cores <NUM> and <NUM> are connected to the insides of the open ends of leg parts 43a and 43b, respectively. In other words, first cores <NUM> and <NUM> are surrounded by second core <NUM> from three sides (left side, right side and upper side), namely directions orthogonal to rotating shaft <NUM>. The bent portion of second core <NUM> (the connecting portion between leg part 43a or 43b and bridge part 43c) may have a rounded shape or a linearly bent shape.

In the state where rotary reciprocating drive actuator <NUM> is assembled, rotating shaft <NUM> is inserted through the space surrounded by magnetic pole parts 41a and 42a. In addition, magnet <NUM> attached to rotating shaft <NUM> is located in this space and faces magnetic pole parts 41a and 42a via an air gap.

In core unit <NUM>, spacers <NUM> are disposed between magnetic pole part 41a of first core <NUM> and leg part 43a of second core <NUM> and between magnetic pole part 42a of first core <NUM> and leg part 43b of second core <NUM>. Spacers <NUM> are, for example, fixed to first cores <NUM> and <NUM> and second core <NUM> by adhesion or welding. Spacer <NUM> is formed of, for example, a non-magnetic material such as brass or aluminum.

Placing spacers <NUM> between second core <NUM> and magnetic pole parts 41a and 42a, which include free ends, can increase the rigidity of core unit <NUM>. It is thus possible to prevent deformation or damage of first cores <NUM> and <NUM> caused by impact or the magnetic force generated between magnet <NUM> and core unit <NUM>. Further, by forming spacer <NUM> with a non-magnetic material, the magnetic flux path in core unit <NUM> can be regulated.

Coils <NUM> and <NUM> are respectively wound around cylindrical bobbins <NUM> and <NUM>. A coil unit composed of coil <NUM> and bobbin <NUM> is disposed outside leg part 41b of first core <NUM>, and a coil unit composed of coil <NUM> and bobbin <NUM> is disposed outside leg part 42b of first core <NUM>, thereby disposing coils <NUM> and <NUM> so as to wind around leg parts 41b and 42b of first cores <NUM> and <NUM>, respectively. The winding directions of coils <NUM> and <NUM> are set in such a way that magnetic flux is suitably generated from one of magnetic pole parts 41a and 42a of first cores <NUM> and <NUM> toward the other magnetic pole part when energization is performed.

In the state where rotary reciprocating drive actuator <NUM> is assembled, rotation angle position holding part <NUM> is incorporated into core unit <NUM> so as to face magnet <NUM> via an air gap. Rotation angle position holding part <NUM> is, for example, attached to bridge part 43c (the portion above first cores <NUM> and <NUM>) of second core <NUM> in a posture such that the magnetic pole faces magnet <NUM>.

Rotation angle position holding part <NUM> is composed of, for example, a magnet, and generates a magnetic attraction force between magnet <NUM> and the rotation angle position holding part. That is, rotation angle position holding part <NUM>, together with first cores <NUM> and <NUM>, forms a magnetic spring between magnet <NUM> and the parts. This magnetic spring holds the rotation angle position of magnet <NUM>, that is, the rotation angle position of rotating shaft <NUM> at the neutral position in the normal state (current is not applied) in which coils <NUM> and <NUM> are not energized.

The neutral position is a reference position for the operation of the reciprocating rotation of magnet <NUM>, in other words, the neutral position is the center of swaying. When magnet <NUM> is held at the neutral position, magnetic pole switching parts 32c and 32d of magnet <NUM> face (are located at the positions opposite to) magnetic pole parts 41a and 42a of first cores <NUM> and <NUM>, respectively. The mounting posture of mirror part <NUM> is adjusted with reference to the state in which magnet <NUM> is at the neutral position.

First shield member <NUM> and second shield member <NUM> each made of an electric conductive material are disposed on both sides of core unit <NUM> in the axial direction, respectively. First shield member <NUM> and second shield member <NUM> can prevent the incident of noise from the outside on core unit <NUM> and the emission of noise from core unit <NUM> to the outside.

First shield member <NUM> and second shield member <NUM> are preferably formed of an aluminum alloy. An aluminum alloy has a high degree of freedom in design and can easily impart the desired rigidity, and thus is suitably used for first shield member <NUM> which is to function as a support for supporting rotating shaft <NUM>.

Rotating shaft <NUM> is rotatably attached to first shield member <NUM> via first bearing <NUM>. First bearing <NUM> is disposed at bearing attaching part 51a formed on the first shield member <NUM>. First bearing <NUM> includes cylindrical body part 53b through which rotating shaft <NUM> is inserted, and flange part 53a disposed at one end of body part 53b. Body part 53b of first bearing <NUM> is fitted into bearing attaching part 51a of first shield member <NUM>, and flange part 53a is locked to the outer surface of first shield member <NUM>. After rotating shaft <NUM> is inserted through bearing attaching part 51a of first shield member <NUM>, first bearing <NUM> is inserted into bearing attaching part 51a from the side where rotating shaft <NUM> protrudes from first shield member <NUM>, and fitted into bearing attaching part 51a. In this way, the end portion of rotating shaft <NUM> on the side where magnet <NUM> is to be disposed can be easily attached to first shield member <NUM>.

First bearing <NUM> is composed of, for example, a slide bearing. Specifically, first bearing <NUM> is preferably a resin molded product such as a fluororesin. First bearing <NUM> composed of a slide bearing can function as a damping part, thereby preventing the driving sound (resonant sound of movable part <NUM>). Further, first bearing <NUM> as a resin molded product can be produced with high degree of freedom in shape and at low cost. In particular, a fluororesin molded product as first bearing <NUM> can prevent expansion and contraction caused by the environmental temperature, and thus is suitable for using rotary reciprocating drive actuator <NUM> in a high temperature environment. In addition, a fluororesin molded product has high processing accuracy and can obtain appropriate sliding property. Such a fluororesin molded product can stably support rotating shaft <NUM> without interfering with the operation of the reciprocating rotation of rotating shaft <NUM>, and is thus suitable as a bearing.

Second shield member <NUM> includes insertion hole 52a, which is larger than the outer shape of magnet <NUM>. Rotating shaft <NUM> with magnet <NUM> mounted thereon is inserted into core unit <NUM> via insertion hole 52a of second shield member <NUM>.

Core body C composed of first cores <NUM> and <NUM> and second core <NUM> is held between first shield member <NUM> and second shield member <NUM>, and fixed by fastener <NUM> to be integrated into core unit <NUM>. Further, core unit <NUM> is fixed to left side wall part <NUM> of base <NUM> by fastener <NUM> and integrated with base <NUM>.

Magnet <NUM> is a ring-shaped magnet in which at least one S pole 32a and at least one N pole 32b are alternately disposed in the circumferential direction. In the state where rotary reciprocating drive actuator <NUM> is assembled, magnet <NUM> is attached to the peripheral surface of rotating shaft <NUM> so as to be located in the space surrounded by magnetic pole parts 41a and 42a of core unit <NUM>. When coils <NUM> and <NUM> are energized, first cores <NUM> and <NUM> and second core <NUM> are excited to generate polarities in magnetic pole parts 41a and 42a according to the energization direction, thereby generating magnetic force (attraction force and repulsion force) between magnet <NUM> and magnetic pole parts 41a and 42a.

In the present embodiment, magnet <NUM> is magnetized to have different polarities with a plane along the axial direction of rotating shaft <NUM> as a boundary. That is, magnet <NUM> is a two-pole magnet magnetized so as to be equally divided into S pole 32a and N pole 32b. The number of magnetic poles of magnet <NUM> (two in the present embodiment) is equal to the number of magnetic pole parts 41a and 42a of core unit <NUM>. Magnet <NUM> may be magnetized to have two or more poles depending on the amplitude during movement. In this case, magnetic pole parts of core unit <NUM> are provided according to the magnetic poles of magnet <NUM>.

The polarity of magnet <NUM> is switched at boundary portions (hereinafter, referred to as "magnetic pole switching part") 32c and 32d between S pole 32a and N pole 32b. Magnetic pole switching parts 32c and 32d respectively face magnetic pole parts 41a and 42a when magnet <NUM> is held at the neutral position.

As magnetic pole switching parts 32c and 32d of magnet <NUM> face magnetic pole parts 41a and 42a at the neutral position, driving part <NUM> can generate the maximum torque to stably drive movable part <NUM>. In addition, configuring magnet <NUM> with a two-pole magnet improves the driving of a movable object with a high amplitude in cooperation with core unit <NUM>, and also improves the drive performance. The embodiment describes magnet <NUM> including a pair of magnetic pole switching parts 32c and 32d, but magnet <NUM> may include two or more pairs of magnetic pole switching parts.

Rotating shaft <NUM> with mirror part <NUM> and magnet <NUM> mounted thereto is fixed to base <NUM> via second bearing <NUM> and third bearing <NUM>. Mirror part <NUM> is located in the space between left side wall part <NUM> and right side wall part <NUM> of base <NUM>, and magnet <NUM> is located outside (on the left side of) left side wall part <NUM> of base <NUM>.

The portion of rotating shaft <NUM> which is exposed from left side wall part <NUM> (the portion where magnet <NUM> is disposed) is inserted into core unit <NUM> in the axial direction, and fixed to first shield member <NUM> via first bearing <NUM>. Magnet <NUM> is located inside core unit <NUM>, that is, in the space between first shield member <NUM> and left side wall part <NUM> of base <NUM>.

In the state where rotary reciprocating drive actuator <NUM> is assembled, the portion of rotating shaft <NUM> where mirror part <NUM> is disposed is supported at two points, i.e., by left side wall part <NUM> and right side wall part <NUM>. Therefore, the support strength for rotating shaft <NUM> is higher than that for a rotating shaft supported only by left side wall part <NUM> (i.e., cantilevered), and thus the linearity of rotating shaft <NUM> can be maintained even when the size and weight of mirror part <NUM> increase.

In addition, the portion of rotating shaft <NUM> where magnet <NUM> is disposed is supported at two points, i.e., by first shield member <NUM> and left side wall part <NUM>, and thus the linearity of rotating shaft <NUM> can be maintained even when magnetic attraction force between magnet <NUM> and rotation angle position holding part <NUM> increases. In other words, when the portion of rotating shaft <NUM> where magnet <NUM> is disposed is supported only by left side wall part <NUM> to be cantilevered, rotating shaft <NUM> may bend toward rotation angle position holding part <NUM>, thereby disadvantageously reducing the linearity of the rotating shaft as the magnetic attraction force between magnet <NUM> and rotation angle position holding part <NUM> increases. However, such a problem does not occur in the present invention.

In the following, the operation of rotary reciprocating drive actuator <NUM> will be described with reference to <FIG> are diagrams for explaining the operation of the magnetic circuit of rotary reciprocating drive actuator <NUM>.

Two magnetic pole parts 41a and 42a of core body C are disposed in such a way that magnet <NUM> is located between magnetic pole parts 41a and 42a via air gap G. As illustrated in <FIG>, when the coils <NUM> and <NUM> are not energized, magnet <NUM> is held at a neutral position by a magnetic attraction force between magnet <NUM> and rotation angle position holding part <NUM>.

At this neutral position, one of S pole 32a and N pole 32b of magnet <NUM> (S pole 32a in <FIG>) is attracted to rotation angle position holding part <NUM>. At this time, magnetic pole switching parts 32c and 32d individually face the center positions of magnetic pole parts 41a and 42a of core body C.

When coils <NUM> and <NUM> are energized, core body C is excited, and polarities according to the energization direction are generated in magnetic pole parts 41a and 42a. As illustrated in <FIG>, when coils <NUM> and <NUM> are energized, magnetic fluxes are generated inside core body C, and magnetic pole part 41a becomes the S pole and magnetic pole part 42a becomes the N pole. As a result, magnetic pole part 41a magnetized to the S pole attracts N pole 32b of magnet <NUM>, and magnetic pole part 42a magnetized to the N pole attracts S pole 32a of magnet <NUM>, thereby generating torque in magnet <NUM> about the axis of rotating shaft <NUM> in the F direction to rotate magnet <NUM> in the F direction. Along with this rotation, rotating shaft <NUM> also rotates in the F direction, and mirror part <NUM> fixed to rotating shaft <NUM> also rotates in the F direction.

On the other hand, when coils <NUM> and <NUM> are energized in the direction opposite to that in <FIG>, magnetic fluxes are generated inside core body C, and magnetic pole part 41a becomes the N pole and magnetic pole part 42a becomes the S pole (although not illustrated). As a result, magnetic pole part 41a magnetized to the N pole attracts S pole 32b of magnet <NUM>, and magnetic pole part 42a magnetized to the S pole attracts N pole 32a of magnet <NUM>, thereby generating torque in magnet <NUM> about the axis of rotating shaft <NUM> in the direction opposite to the F direction to rotate magnet <NUM> in the -F direction. Along with this rotation, rotating shaft <NUM> also rotates, and mirror part <NUM> fixed to rotating shaft <NUM> also rotates.

Rotary reciprocating drive actuator <NUM> drives mirror part <NUM> to rotate in a reciprocating manner by repeating the above operations.

In practice, rotary reciprocating drive actuator <NUM> is driven by an alternating current wave input from a power supply unit (for example, corresponding to drive signal supply unit <NUM> in <FIG>) to coils <NUM> and <NUM>. That is, the energization directions of coils <NUM> and <NUM> are periodically switched. When the energization direction is switched, the magnetic attraction force between rotation angle position holding part <NUM> and magnet <NUM>, namely the restoring force of the magnetic spring, urges magnet <NUM> to return to its neutral position. Therefore, the torque in the F direction and the torque in the direction opposite to the F direction (-F direction) alternately act on movable part <NUM> about the axis. Movable part <NUM> is thus driven to rotate in a reciprocating manner.

In the following, the driving principle of rotary reciprocating drive actuator <NUM> will be briefly described. In rotary reciprocating drive actuator <NUM> of the present embodiment, when the moment of inertia of a movable body (movable part <NUM>) is J [kg·m<NUM>] and the spring constant in the torsional direction of a magnetic spring (magnetic pole parts 41a and 42a, rotation angle position holding part <NUM>, and magnet <NUM>) is Ksp, the movable body vibrates (rotates in a reciprocating manner) with respect to a fixed body (fixed part <NUM>) at a resonance frequency Fr [Hz] calculated by the equation <NUM>.

Since the movable body constitutes a mass portion in a vibration model of a spring - mass system, when an alternating current wave having a frequency equal to the resonance frequency Fr of the movable body is input to coils <NUM> and <NUM>, the movable body enters a resonance state. That is, by inputting the alternating current wave having a frequency substantially equal to the resonance frequency Fr of the movable body to coils <NUM> and <NUM> from a power supply unit, the movable body can be efficiently vibrated.

A motion equation and a circuit equation showing the driving principle of rotary reciprocating drive actuator <NUM> are shown below. Rotary reciprocating drive actuator <NUM> is driven based on the motion equation expressed by the equation <NUM> and the circuit equation expressed by the equation <NUM>.

That is, the moment of inertia J [kg·m<NUM>] of the movable body, the rotation angle θ(t) [rad], the torque constant Kt [N·m/A], the current i(t) [A], the spring constant Ksp [N·m/rad], the damping coefficient D [N·m/(rad/s)], the load torque TLoss [N m], and the like in rotary reciprocating drive actuator <NUM> can be appropriately changed within the range satisfying the equation <NUM>. Further, the voltage e(t) [V], the resistance R [Ω], the inductance L [H], and the counter electromotive force constant Ke [V/(rad/s)] can be appropriately changed within the range satisfying the equation <NUM>.

Thus, rotary reciprocating drive actuator <NUM> can obtain an efficient and large vibration output when the coil is energized by the alternating current wave corresponding to the resonance frequency Fr determined by the moment of inertia J of the movable body and the spring constant Ksp of the magnetic spring.

Rotary reciprocating drive actuator <NUM> may include angle sensor <NUM> (see <FIG>) for detecting the rotation angle of rotating shaft <NUM>. Angle sensor <NUM> is fixed to, for example, right side wall part <NUM> of base <NUM>.

Angle sensor <NUM> includes, for example, an optical sensor and an encoder disk. The encoder disk is attached to rotating shaft <NUM> and rotates integrally with magnet <NUM> and mirror part <NUM>. In other words, the rotation position of the encoder disk is the same as the rotation position of rotating shaft <NUM>. The optical sensor emits light to the encoder disk and detects the rotation position (angle) of the encoder disk based on the reflected light, thereby detecting the rotation positions of magnet <NUM> and mirror part <NUM>.

Providing angle sensor <NUM> enables detection of the rotation angle of movable part <NUM> including magnet <NUM> and rotating shaft <NUM>. It is thus possible to control a rotation angle position and a speed of a movable body, specifically mirror part <NUM> serving as the movable object, during driving.

<FIG> is a block diagram illustrating the configuration of main parts of an optical scanning device including rotary reciprocating drive actuator <NUM>.

Optical scanning device A includes laser emitting unit <NUM>, laser control unit <NUM>, drive signal supply unit <NUM>, and position control signal calculation unit <NUM>, in addition to rotary reciprocating drive actuator <NUM>.

Laser emitting unit <NUM> includes, for example, a laser diode (LD) serving as a light source and a lens system for converging a laser beam output from the light source. Laser control unit <NUM> controls laser emitting unit <NUM>. The laser beam emitted from laser emitting unit <NUM> is incident on mirror <NUM> of rotary reciprocating drive actuator <NUM>.

Position control signal calculation unit <NUM> generates and outputs a drive signal for controlling rotating shaft <NUM> (mirror <NUM>) to be at a target angle position by referring to the angle position of rotating shaft <NUM> (mirror <NUM>) acquired by angle sensor <NUM> and the target angle position. For example, position control signal calculation unit <NUM> generates a position control signal based on the obtained angle position of rotating shaft <NUM> (mirror <NUM>) and a signal indicating the target angular position converted by using sawtooth waveform data, and the like stored in a waveform memory (not illustrated), and outputs the position control signal to drive signal supply unit <NUM>.

Drive signal supply unit <NUM> supplies a drive signal to coils <NUM> and <NUM> of rotary reciprocating drive actuator <NUM> based on the position control signal in such a way that rotating shaft <NUM> (mirror <NUM>) is rotated to be at a desired angle position. As a result, optical scanning device A can emit scanning light from rotary reciprocating drive actuator <NUM> to a predetermined scanning region.

Rotary reciprocating drive actuator <NUM> according to the present embodiment has the following features.

Rotary reciprocating drive actuator <NUM> includes movable part <NUM> including rotating shaft <NUM> on which mirror part <NUM> (movable object) is to be disposed; fixed part <NUM> configured to support rotating shaft <NUM>; and driving part <NUM> configured to rotate rotating shaft <NUM> about an axis of rotating shaft <NUM> with respect to fixed part <NUM> by utilizing electromagnetic interaction, driving part <NUM> including coils <NUM> and <NUM> and cores <NUM> to <NUM> to be disposed at fixed part <NUM>, and magnet <NUM> to be disposed on rotating shaft <NUM>.

Magnet <NUM> is a ring-shaped magnet such that at least one S pole 32a and at least one N pole 32b are alternately disposed on the outer peripheral surface of the magnet in the circumferential direction of the magnet; cores <NUM> to <NUM> include magnetic pole parts 41a and 42a that are excited to generate polarities by energizing coils <NUM> and <NUM>, and cores <NUM> and <NUM> are disposed in such a way that magnetic pole parts 41a and 42a face the outer peripheral surface of magnet <NUM> via air gap G when rotating shaft <NUM> is attached to fixed part <NUM>; the number of magnetic poles of magnet <NUM> is equal to the number of magnetic pole parts 41a and 42a; and rotary reciprocating drive actuator <NUM> further includes rotation angle position holding part <NUM> configured to hold the rotation angle position of rotation shaft <NUM> at a neutral position by a magnetic attraction force generated between magnet <NUM> and rotation angle position holding part <NUM>, and rotation angle position holding part <NUM> is disposed on fixed part <NUM> so as to face magnet <NUM> via air gap G.

As a result, each time the energization direction of coils <NUM> and <NUM> is switched, magnet <NUM> is magnetically attracted to rotation angle position holding part <NUM> and urged to return to its neutral position (reference position for the operation). Rotary reciprocating drive with improved energy efficiency and responsiveness and high amplitude thus can be achieved. In addition, the heat generated by the coil is less likely to be transmitted to a movable object as compared to a rotary reciprocating drive actuator of the moving coil type; therefore, when the movable object is a mirror, it is possible to avoid adverse effects caused by heat (for example, bond deterioration and warpage) on the mirror.

In addition, fixed part <NUM> includes first shield member <NUM> (first support) and left side wall part <NUM> (second support) of base <NUM> which are disposed so as to face each other with magnet <NUM> therebetween in the axial direction; rotating shaft <NUM> is rotatably attached to first shield member <NUM> via first bearing <NUM> and to left side wall part <NUM> via second bearing <NUM>; and one of first bearing <NUM> and second bearing <NUM> is a rolling bearing, and the other of first bearing <NUM> and second bearing <NUM> is a slide bearing.

In the present embodiment, first bearing <NUM> is a slide bearing, and second bearing <NUM> is a rolling bearing.

As the portion of rotating shaft <NUM> where magnet <NUM> is disposed is supported by first shield member <NUM> and left side wall part <NUM>, the linearity of rotating shaft <NUM> can be maintained even when the magnetic attraction force between magnet <NUM> and rotation angle position holding part <NUM> increases. In other words, when the portion of rotating shaft <NUM> where magnet <NUM> is disposed is supported only by left side wall part <NUM> to be cantilevered, rotating shaft <NUM> may bend toward rotation angle position holding part <NUM> to reduce the linearity of the rotating shaft as the magnetic attraction force between magnet <NUM> and rotation angle position holding part <NUM> increases; however, such a problem does not occur in the present invention.

It is thus possible to increase the size of magnet <NUM> to increase the drive torque, thereby successfully increasing the size of a movable object, as well as increasing the amplitude of the movable object by increasing the diameter of magnet <NUM>. In addition, the linearity of rotating shaft <NUM> can be maintained and thus the drive performance can be stabilized.

A slide bearing serving as first bearing <NUM> can function as a damping part, thereby preventing the driving sound (resonant sound of movable part <NUM>). Alternatively, first bearing <NUM> may be composed of a rolling bearing, second bearing <NUM> may be composed of a slide bearing, and second bearing <NUM> may function as a damping part.

First bearing <NUM> includes cylindrical body part 53b through which rotating shaft <NUM> is inserted, and flange part 53a disposed at one end of body part 53b. Body part 53b is fitted into bearing attaching part 51a formed in first shield member <NUM> (first support), and flange part 53a is locked to the outer surface of first shield member <NUM>. As a result, the end portion of rotating shaft <NUM> on the side where magnet <NUM> is disposed can be easily attached to first shield member <NUM>.

In addition, first bearing <NUM> is a resin molded product. A resin molded product serving as first bearing <NUM> can be produced with high degree of freedom in shape and at low cost.

Further, first bearing <NUM> is formed of a fluororesin. This configuration can prevent expansion and contraction of first bearing <NUM> caused by the environmental temperature, and thus high processing accuracy and appropriate sliding property can be obtained. Therefore, rotary reciprocating drive actuator <NUM> can be used in a high temperature environment, and can stably support rotating shaft <NUM> without interfering with the operation of the reciprocating rotation, thereby improving reliability.

In addition, magnet <NUM> is a two-pole magnet, and two magnetic pole switching parts 32c and 32d of magnet <NUM> face magnetic pole parts 41a and 42a when magnet <NUM> is held at the neutral position. This configuration allows magnet <NUM>, that is, a movable body including rotating shaft <NUM>, to move in a reciprocating manner from the neutral position within the same angle range in one direction and the opposite direction about the axis.

First shield member <NUM> and second shield member <NUM> each made of an electric conductive material are disposed on both sides of core unit <NUM>-which includes cores <NUM> to <NUM> and coils <NUM> and <NUM>-in the axial direction. This configuration can prevent the incident of noise from the outside on core unit <NUM> and the emission of noise from core unit <NUM> to the outside, thereby improving the reliability of rotary reciprocating drive actuator <NUM>.

Only one of first shield member <NUM> and second shield member <NUM> may be provided, and for example, second shield member <NUM> may not be disposed.

First support is composed of first shield member <NUM>. In other words, first shield member <NUM> functions as a shield that prevents noise into and out of core unit <NUM> and also functions as a support that supports rotating shaft <NUM>. As a result, the number of parts can be reduced and space can be saved. Alternatively, a support for supporting rotating shaft <NUM> may be provided separately from first shield member <NUM>.

First shield member <NUM> is formed of an aluminum alloy. As a result, the degree of freedom in design increases and sufficient rigidity can be imparted, so that first shield member <NUM> can function as a support for movable part <NUM>.

The movable object is mirror <NUM> that reflects scanning light. This configuration allows the use of rotary reciprocating drive actuator <NUM> as a scanner for optical scanning.

Rotary reciprocating drive actuator <NUM> according to the present embodiment also has the following features.

In rotary reciprocating drive actuator <NUM>, fixed part <NUM> includes first shield member <NUM> (first support) and left side wall part <NUM> (second support) of base <NUM> which are disposed so as to face each other with magnet <NUM> therebetween in the axial direction, and includes right side wall part <NUM> (third support) disposed so as to face left side wall part <NUM> with mirror part <NUM> (movable object) therebetween; and rotating shaft <NUM> is rotatably supported at three locations, i.e., by first shield member <NUM>, left side wall part <NUM>, and right side wall part <NUM>.

As the portion of rotating shaft <NUM> where magnet <NUM> is disposed is supported at two points, i.e., by first shield member <NUM> and left side wall part <NUM>, the linearity of rotating shaft <NUM> can be maintained even when the magnetic attraction force between magnet <NUM> and rotation angle position holding part <NUM> increases. In addition, the portion of rotating shaft <NUM> where mirror part <NUM> is disposed is supported at two points, i.e., by left side wall part <NUM> and right side wall part <NUM>, thereby maintaining the linearity of rotating shaft <NUM> even when the size and weight of mirror part <NUM> increase.

Further, rotating shaft <NUM> is rotatably attached to first shield member <NUM> (first support) via first bearing <NUM>, to left side wall part <NUM> (second support) via second bearing <NUM> of base <NUM>, and to right side wall part <NUM> (third support) of base <NUM> via third bearing <NUM>; and first bearing <NUM> is a slide bearing, and second bearing <NUM> and third bearing <NUM> each are a rolling bearing. As second bearing <NUM> and third bearing <NUM> each are rolling bearings, rotating shaft <NUM> on which the movable object is mounted can be stably held by two rolling bearings, thereby improving the reliability of the durability of rotary reciprocating drive actuator <NUM>. In addition, a slide bearing serving as first bearing <NUM> can function as a damping part, thereby preventing the driving sound (resonant sound of movable part <NUM>).

While the invention made by the present inventors has been specifically described based on the preferred embodiments, it is not intended to limit the present invention to the above-mentioned preferred embodiments but the present invention may be further modified within the scope by the appended claims.

For example, mirror part <NUM> serves as a movable object in the embodiment; however, the movable object is not limited thereto. The movable object may be, for example, an image capturing device such as a camera.

Further, for example, rotary reciprocating drive actuator <NUM> is driven by resonance in the embodiment, but the present invention can also be applied to the drive by non-resonance.

Claim 1:
A rotary reciprocating drive actuator (<NUM>), comprising:
a movable part (<NUM>) including a rotating shaft (<NUM>) on which a movable object (<NUM>) is disposed;
a fixed part (<NUM>) configured to support the rotating shaft (<NUM>); and
a driving part (<NUM>) configured to rotate the rotating shaft (<NUM>) about an axis of the rotating shaft (<NUM>) with respect to the fixed part (<NUM>) by utilizing electromagnetic interaction, the driving part (<NUM>) including a coil (<NUM>, <NUM>) and a core (<NUM>, <NUM>, <NUM>) each disposed on the fixed part (<NUM>), and a magnet (<NUM>) disposed on the rotating shaft (<NUM>), wherein
the magnet (<NUM>) is a ring-shaped magnet such that an S pole (32a) and an N pole (32b) are alternately disposed on an outer peripheral surface of the magnet (<NUM>) in a circumferential direction of the magnet (<NUM>),
the core (<NUM>, <NUM>, <NUM>) includes magnetic pole parts (41a, 42a) that are excited to generate a polarity by energizing the coil (<NUM>, <NUM>), and the core (<NUM>, <NUM>, <NUM>) is disposed in such a way that the magnetic pole parts (41a, 42a) face the outer peripheral surface of the magnet (<NUM>) via an air gap (G) when the rotating shaft (<NUM>) is attached to the fixed part (<NUM>), and
the number of magnetic poles of the magnet (<NUM>) is equal to the number of the magnetic pole parts (41a, 42a), and wherein
the rotary reciprocating drive actuator (<NUM>) further includes a rotation angle position holding part (<NUM>) configured to hold a rotation angle position of the rotation shaft (<NUM>) at a neutral position by a magnetic attraction force generated between the magnet (<NUM>) and the rotation angle position holding part (<NUM>), the rotation angle position holding part (<NUM>) being disposed on the fixed part (<NUM>) so as to face the magnet (<NUM>) via the air gap (G), and characterized in that
the fixed part (<NUM>) includes a first support (<NUM>) and a second support (<NUM>) disposed so as to face each other with the magnet (<NUM>) therebetween in a direction of the axis,
the rotating shaft (<NUM>) is rotatably attached to the first support (<NUM>) via the first bearing (<NUM>) and to the second support (<NUM>) via the second bearing (<NUM>), and
one of the first bearing (<NUM>) or the second bearing (<NUM>) is a rolling bearing, and the other of the first bearing (<NUM>) or the second bearing (<NUM>) is a slide bearing.