JP2013015834A - Actuator, optical scanner and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an actuator capable of attaining low cost and downsizing, and rotating a mass part around each of two axes orthogonal to each other, an optical scanner and an image formation device.SOLUTION: A power supply circuit 5 comprises: a first voltage generation part 51 for generating first voltages Vand Vperiodically varying at a first frequency; a second voltage generation part 52 generating second voltages Vand Vperiodically varying at a second frequency different from the first frequency; and a voltage superposition part 53 for superposing the first voltages Vand Von the second voltages Vand V. A mass part is rotated around a first axis line along a pair of elastic parts for supporting the mass part at the first frequency and rotated around the second axis line orthogonal to the first axis line at the second frequency by applying voltage superposed by the voltage superposition part 53 to each piezoelectric device 41, 42, 43 and 44.

Description

  The present invention relates to an actuator, an optical scanner, and an image forming apparatus.

As an optical scanner used in a laser printer or the like, an optical scanner using a structure having a torsional vibrator manufactured by processing a Si substrate by a micromachining technique is known. An optical scanner using such a structure has an advantage that optical scanning can be performed at a higher speed than a polygon mirror.
For example, the actuator according to Patent Document 1 supports a plate-like reflection mirror by a pair of spring portions, each spring portion branches in the middle, and a piezoelectric body is provided at the branch portion. . Such an actuator rotates the reflection mirror while applying a voltage to each piezoelectric body to bend and deform the branch portion and torsionally deform the entire pair of spring portions.

  However, in such an actuator, the reflection mirror is rotated with only one axis along the pair of spring portions as the rotation center axis. Therefore, when such an actuator is used as an optical scanner, light can be scanned only in one direction of main scanning or sub scanning. Therefore, two actuators are required to perform the main scanning and the sub-scanning, resulting in an increase in cost and size.

JP 2004-191953 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide an actuator, an optical scanner, and an image forming apparatus that can rotate a mass portion around two axes orthogonal to each other while reducing cost and size. is there.

Such an object is achieved by the present invention described below.
An actuator according to the present invention includes a vibrating portion including a mass portion and a pair of elastic portions that support the mass portion;
At least one pair of beam portions supporting the vibrating portion;
A piezoelectric element joined on each beam part;
Voltage applying means for applying a voltage to each of the piezoelectric elements,
The voltage applying means applies a voltage to each piezoelectric element to bend and deform each beam part, and in accordance with this, the actuator is configured to drive the vibration part,
The voltage applying means includes a first voltage generator that generates a first voltage that periodically changes at a first frequency, and a second that periodically changes at a second frequency different from the first frequency. And a voltage superimposing unit that superimposes the first voltage and the second voltage, and the voltage superimposed by the voltage superimposing unit is applied to each piezoelectric element. By applying, the mass portion is rotated around the first axis along the pair of elastic portions at the first frequency while the second portion is orthogonal to the first axis. It is configured to rotate at a frequency of 2.
Thereby, the mass part can be rotated around the two axes orthogonal to each other while reducing the cost and the size.

In the actuator according to the aspect of the invention, the voltage applying unit may generate the two types of the first voltages that are 180 degrees out of phase with each other, and the voltage superimposing unit may generate the first voltage. And the second voltage are preferably superimposed, and the two voltages superimposed by the voltage superimposing unit are preferably applied corresponding to the pair of piezoelectric elements.
Accordingly, the mass portion is rotated at the second frequency around the second axis while being rotated at the first frequency around the first axis along the pair of elastic portions with a relatively simple configuration. be able to.

In the actuator according to the aspect of the invention, the vibration portion is supported by the at least one pair of beam portions, supports the mass portion via the pair of elastic portions, and surrounds an outer periphery of the mass portion. It is preferable to have a frame having a frame shape.
Accordingly, the mass portion is rotated at the second frequency around the second axis while rotating at the first frequency around the first axis along the pair of elastic portions at a lower power and more smoothly. Can be moved.

In the actuator according to the aspect of the invention, it is preferable that a pair of the beam portions is provided on both sides of the beam portion via the vibration portion.
Thereby, it is possible to smoothly rotate the mass portion at the second frequency around the second axis while rotating the mass portion around the first axis along the pair of elastic portions at the first frequency. .
In the actuator of the present invention, the mass portion has a plate shape, and when the mass portion is viewed in plan, the two pairs of beam portions are point-symmetric with respect to the center of the mass portion. It is preferable to be provided.
Thereby, the mass portion is rotated at the first frequency around the first axis along the pair of elastic portions at the second frequency around the second axis with a simpler configuration and more smoothly. It can be rotated.

In the actuator of the present invention, each beam portion has a longitudinal shape, and each piezoelectric element extends along the longitudinal direction of the corresponding beam portion, and expands and contracts in the extending direction. It is preferable to bend and deform the part.
Accordingly, the mass portion is rotated at the first frequency around the first axis along the pair of elastic portions at the first frequency with the lower voltage and the larger rotation angle, and the second axis around the second axis. It can be rotated at a frequency.

In the actuator according to the aspect of the invention, it is preferable that each of the beam portions extends in parallel with the first axis.
Thereby, the rotation angle of the mass portion can be increased while reducing the size of the actuator.
In the actuator according to the aspect of the invention, it is preferable that each of the piezoelectric elements is provided over almost the entire region in the longitudinal direction of the corresponding beam portion.
Thereby, the rotation angle of the mass portion can be increased while reducing the size of the actuator.

In the actuator according to the aspect of the invention, it is preferable that the first frequency is higher than the second frequency.
Accordingly, the mass portion is rotated at the second frequency around the second axis while being rotated at the first frequency around the first axis along the pair of elastic portions, more reliably and smoothly. be able to.
In the actuator according to the aspect of the invention, it is preferable that the first frequency matches a torsional resonance frequency of a vibration system including the mass portion and the vibration portion.
Thereby, since the mass part can be resonantly driven around the first axis along the pair of elastic parts, the mass part can be largely rotated with low power.
In the actuator according to the aspect of the invention, it is preferable that the mass portion includes a light reflecting portion having light reflectivity.
Thereby, the actuator of this invention is applicable to optical devices, such as an optical scanner, an optical switch, and an optical attenuator.

An optical scanner according to the present invention includes a mass part including a light reflecting part having light reflectivity, and a vibration part including a pair of elastic parts supporting the mass part,
At least one pair of bending-deformable beam portions supporting the vibrating portion;
A piezoelectric element joined on each beam part;
Voltage applying means for applying a voltage to each of the piezoelectric elements,
The voltage application means applies a voltage to each piezoelectric element to bend and deform each beam part, and accordingly, drive the vibration part and scan the light reflected by the light reflection part. A configured optical scanner comprising:
The voltage applying means includes a first voltage generator that generates a first voltage that periodically changes at a first frequency, and a second that periodically changes at a second frequency different from the first frequency. And a voltage superimposing unit that superimposes the first voltage and the second voltage, and the voltage superimposed by the voltage superimposing unit is applied to each piezoelectric element. By applying, the mass portion is rotated around the first axis along the pair of elastic portions at the first frequency while the second portion is orthogonal to the first axis. It is configured to rotate at a frequency of 2.
Thereby, main scanning and sub-scanning can be performed with one optical scanner, and as a result, cost reduction and size reduction can be achieved.

An image forming apparatus of the present invention includes a mass unit including a light reflecting unit having light reflectivity, and a vibration unit including a pair of elastic units that support the mass unit,
At least one pair of bending-deformable beam portions supporting the vibrating portion;
A piezoelectric element joined on each beam part;
Voltage applying means for applying a voltage to each of the piezoelectric elements;
Light irradiating means for irradiating light to the light reflecting portion,
The voltage application means applies a voltage to each piezoelectric element to bend and deform each beam part, and accordingly, drive the vibration part and scan the light reflected by the light reflection part, An image forming apparatus configured to form an image on an object,
The voltage applying means includes a first voltage generator that generates a first voltage that periodically changes at a first frequency, and a second that periodically changes at a second frequency different from the first frequency. And a voltage superimposing unit that superimposes the first voltage and the second voltage, and the voltage superimposed by the voltage superimposing unit is applied to each piezoelectric element. By applying, the mass portion is rotated around the first axis along the pair of elastic portions at the first frequency while the second portion is orthogonal to the first axis. It is configured to rotate at a frequency of 2.
Thereby, main scanning and sub-scanning can be performed with one optical scanner, and as a result, cost reduction and size reduction can be achieved.

It is a top view which shows the actuator concerning embodiment of this invention. (A) is the sectional view on the AA line in FIG. 1, (b) is the sectional view on the BB line in FIG. It is CC sectional view taken on the line in FIG. It is a block diagram which shows the structure of the control system of the actuator shown in FIG. FIG. 5 is a diagram illustrating an example of voltages generated in a first voltage generation unit and a second voltage generation unit illustrated in FIG. 4. It is the schematic which shows an example of the image forming apparatus (imaging display) of this invention. It is a block diagram which shows the structure of the control system of the image forming apparatus shown in FIG.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of an actuator of the invention will be described with reference to the accompanying drawings.
1 is a plan view showing an actuator according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line AA and BB in FIG. 1, and FIG. 3 is a cross-sectional view taken along line CC in FIG. FIG. 4 is a block diagram showing the configuration of the control system of the actuator shown in FIG. 1, and FIG. 5 is an example of the voltage generated in the first voltage generator and the second voltage generator shown in FIG. FIG. 6 is a diagram showing an example of a voltage applied to each piezoelectric element of the actuator shown in FIG. In the following, for convenience of explanation, the front side of the page in FIG. 1 is referred to as “up”, the back side of the page is referred to as “down”, the right side is referred to as “right”, and the left side is referred to as “left”. The upper side is called “upper”, the lower side is called “lower”, the right side is called “right”, and the left side is called “left”.

As shown in FIGS. 1 to 3, the actuator 1 includes a base 2 having a vibration part 21 including a one-degree-of-freedom vibration system, and a support substrate 3 that supports the base 2. It has piezoelectric elements 41, 42, 43, 44 for driving the vibration part 21 of the base 2.
The base body 2 includes a vibration part 21 including a one-degree-of-freedom vibration system, two pairs of beam parts 22, 23, 24, 25 that support the vibration part 21, and these beam parts 22, 23, 24, 25. And a support portion 26 that supports the vibration portion 21.

The vibration part 21 includes a mass part 211, a pair of elastic parts 212 and 213 that support the mass part 211, and a frame body 214 that supports the pair of elastic parts 212 and 213.
The mass portion 211 has a plate shape (disc shape in the present embodiment), and includes a light reflecting portion (mirror portion) 215 having light reflectivity near the upper surface (the surface opposite to the support substrate 3). ing. Thereby, the actuator 1 can be applied to optical devices such as an optical scanner, an optical attenuator, and an optical switch.

Such a mass portion 211 is supported by the frame body 214 via a pair of elastic portions 212 and 213.
The frame body 214 has a frame shape (substantially square ring in this embodiment) so as to surround the outer periphery of the mass portion 211. That is, the frame body 214 has a frame shape, and the mass portion 211 is provided inside the frame body 214 in a state of being separated from the mass portion 211.

  The pair of elastic portions 212 and 213 are connected so that the mass portion 211 can rotate with respect to the frame body 214. More specifically, the pair of elastic portions 212 and 213 can be elastically deformed, have a longitudinal shape, and are provided coaxially with each other, and support the mass portion 211 on both ends. Such a pair of elastic portions 212 and 213 can rotate the mass portion 211 with respect to the frame body 214 by being twisted and deformed around the first axis X using these as the rotation center axis. That is, the vibration part 21 has a one-degree-of-freedom vibration system including a mass part 211 and a pair of elastic parts 212 and 213.

Such a frame 214 of the vibration part 21 is supported by the support part 26 via two pairs of beam parts 22, 23, 24, 25. That is, the frame body 214 and the two pairs of beam portions 22, 23, 24, 25 constitute a vibration system.
The two pairs of beam portions 22, 23, 24, 25 are provided with a pair of beam portions 22, 23 on one side via the vibrating portion 21, and a pair of beam portions 24, 25 on the other side. Is provided.

These beam portions 22, 23, 24, and 25 are provided so as to be point-symmetric with respect to the center of the mass portion 211 in a plan view of the mass portion 211 of the vibration portion 21.
The support part 26 is formed so as to surround the outer periphery of the vibration part 21 described above.
The pair of beam portions 22 and 23 connect the vibration portion 21 (more specifically, the frame body 214) and the support portion 26, respectively. Similarly, the pair of beam portions 24 and 25 connect the vibration portion 21 (more specifically, the frame body 214) and the support portion 26, respectively.

  Each beam portion 22, 23, 24, 25 is elastically deformable, has a longitudinal shape, and extends parallel to the rotation center axis X of the mass portion 211. In such two pairs of beam portions 22, 23, 24, 25, the frame body 214 is made to be the second by bending and deforming the beam portions 22, 25 and the beam portions 23, 24 in directions opposite to each other. The frame body 214 can be rotated around an axis (rotation center axis) Y, and the beam 214, 23 and the beams 24, 25 are bent and deformed in directions opposite to each other, whereby the frame 214 is moved to the first axis. It can be rotated around X.

The base body 2 having such a vibration part 21 is made of, for example, silicon as a main material, and the vibration part 21, the beam parts 22, 23, 24, 25 and the support part 26 are integrally formed. .
And in order to drive such a vibration part 21, the piezoelectric element 41 on the beam part 22, the piezoelectric element 42 on the beam part 23, the piezoelectric element 43 on the beam part 24, and the beam part 25 on A piezoelectric element 44 is provided.

  Here, the piezoelectric elements 41 and 42 and the piezoelectric elements 42 and 43 are the mass part 211 of the vibration part 21 in the same manner as the relationship between the pair of beam parts 22 and 23 and the pair of beam parts 24 and 25 described above. Are provided so as to be point-symmetric with respect to the center of the mass portion 211 in a plan view. Hereinafter, the piezoelectric elements 41 and 42 will be described in detail, but the piezoelectric elements 43 and 44 are the same as the piezoelectric elements 41 and 42.

  The piezoelectric element 41 is joined to the upper surface of the beam portion 22 and configured to expand and contract in the longitudinal direction of the beam portion 22. Thereby, the piezoelectric element 41 can bend and deform the beam portion 22 in the vertical direction by the expansion and contraction thereof. The piezoelectric element 42 is joined to the upper surface of the beam portion 23 and is configured to expand and contract in the longitudinal direction of the beam portion 23. Thereby, the piezoelectric element 42 bends and deforms the beam portion 23 in the vertical direction by the expansion and contraction.

  In other words, the piezoelectric element 41 extends along the longitudinal direction of the beam portion 22 and expands and contracts in the extending direction to bend and deform the beam portion 22. Accordingly, the beam portion 22 can be bent and deformed by the piezoelectric element 41 with a relatively simple configuration. Similarly, the piezoelectric element 42 extends along the longitudinal direction of the beam portion 23 and expands and contracts in the extending direction to bend and deform the beam portion 23. Accordingly, the beam portion 23 can be bent and deformed by the piezoelectric element 42 with a relatively simple configuration.

Each of such piezoelectric elements 41 and 42 includes, for example, a piezoelectric layer composed mainly of a piezoelectric material, and a pair of electrodes that sandwich the piezoelectric layer, although not shown. Yes.
Examples of the piezoelectric material include zinc oxide, aluminum nitride, lithium tantalate, lithium niobate, potassium niobate, lead zirconate titanate (PZT), barium titanate, and various other materials. One or more of them can be used in combination, but at least one of zinc oxide, aluminum nitride, lithium tantalate, lithium niobate, potassium niobate and lead zirconate titanate is mainly used. Are preferred. By configuring the piezoelectric layer of the piezoelectric element 41 with such a material, the actuator 1 can be driven at a higher frequency.

  The piezoelectric element 41 is provided so as to cover almost the entire upper surface of the beam portion 22. Therefore, the piezoelectric element 41 is provided over almost the entire region in the longitudinal direction of the beam portion 22. Accordingly, the beam portion 22 can be bent and deformed more greatly by the operation of the piezoelectric element 41. Similarly, the piezoelectric element 42 is provided so as to cover almost the entire upper surface of the beam portion 23. Therefore, the piezoelectric element 42 is provided over almost the entire region in the longitudinal direction of the beam portion 23. Accordingly, the beam portion 23 can be bent and deformed more greatly by the operation of the piezoelectric element 42.

Since such piezoelectric elements 41 and 42 are both provided on the upper surface of the base body 2, when they are operated to alternately expand and contract with each other (one is extended and the other is contracted), a pair of beam portions 22 and 23 can be bent and deformed in opposite directions.
Similarly to the piezoelectric elements 41 and 42 described above, the piezoelectric elements 43 and 44 are configured. Since such piezoelectric elements 43 and 44 are both provided on the upper surface of the base 2 like the piezoelectric elements 41 and 42 described above, they are alternately expanded and contracted (one is expanded and the other is contracted). When operated in this manner, the pair of beam portions 24 and 25 can be bent and deformed in directions opposite to each other.

Such piezoelectric elements 41, 42, 43, and 44 are connected to a power supply circuit 5 (described later) via a wiring (not shown) (see FIG. 5), and are supplied with electric power. The power supply circuit 5 will be described in detail later.
The support substrate 3 for supporting the base 2 as described above is made of, for example, glass or silicon as a main material, and is bonded to the base 2. Note that the support substrate 3 and the base 2 may be bonded to each other through a bonding layer composed mainly of glass, silicon, or SiO ₂ , for example.

As shown in FIGS. 2 and 3, the support substrate 3 is formed with an opening 31 at a portion corresponding to the vibration portion 21.
The opening 31 constitutes an escape portion that prevents contact with the support substrate 3 when the vibration portion 21 vibrates. By providing the opening (escape portion) 31, the deflection angle (amplitude) of the vibration portion 21 (the mass portion 211 and the frame body 214) can be set larger while preventing the actuator 1 from being enlarged.

Note that the relief portion as described above does not necessarily have to be opened (opened) on the lower surface (the surface opposite to the vibration portion 21) of the support substrate 3 as long as the above-described effect can be sufficiently exerted. . In other words, the escape portion can also be configured by a recess formed on the upper surface of the support substrate 3.
Here, the power supply circuit 5 which is a voltage applying means for applying a voltage to the piezoelectric elements 41, 42, 43, 44 will be described with reference to FIGS. 4 and 5.

  As shown in FIG. 4, the power supply circuit 5 includes a first voltage generating unit 51 that generates a first voltage for rotating the mass unit 211 around the first axis X, and a second mass unit 211. A second voltage generator 52 for generating a second voltage for rotation about the axis Y of the first electrode, and applying the first voltage and the second voltage to the piezoelectric elements 41, 42, 43, 44 in a superimposed manner The voltage superimposing unit 53 is provided.

First voltage generating unit 51, as shown on the right side in FIG. 5 (a) ~ (d), is intended to generate a voltage (voltage for horizontal scanning) that changes periodically with a period T _1. That is, the first voltage generator 51 generates two types of first voltages V ₁₁ and V ₁₂ that periodically change at a _first frequency (1 / T ₁ ).
More specifically, the first voltage generator 51 is shown on the right side of FIGS. 5A and 5B as horizontal scanning voltages (horizontal scanning drive signals) applied to the piezoelectric elements 41 and 42, respectively. As described above, the first voltage V ₁₁ that periodically changes in the period T ₁ is generated.

The first voltage V ₁₁ has a waveform like a sine wave. Therefore, the actuator 1 can perform main scanning of light effectively. Incidentally, the waveform of the first voltage V _11, but is not limited thereto.
Here, the first frequency (1 / T ₁ ) is not particularly limited as long as it is a frequency suitable for horizontal scanning, but is preferably 10 to 40 kHz. The first frequency is preferably set so as to substantially match the torsional resonance frequency of the vibration system composed of the mass part 211 and the elastic parts 212 and 213. That is, it is preferable that the torsional resonance frequency of the vibration system composed of the mass portion 211 and the elastic portions 212 and 213 is designed to be a frequency suitable for horizontal scanning.
Further, the first voltage generator 51 generates a period T as shown in the right side of FIGS. 5C and 5D as horizontal scanning voltages (horizontal scanning drive signals) applied to the piezoelectric elements 43 and 44, respectively. ₁ generates a first voltage V ₁₂ that periodically changes. The first voltage _{V 12} is a first voltage _{V 11} and the same waveform, are 180 ° out of phase relative to the first voltage _{V 11.}

On the other hand, as shown on the left side of FIGS. 5A to 5D, the second voltage generator 52 generates a voltage (vertical scanning voltage) that periodically changes at a period T ₂ different from the period T _1. It is something to be made. That is, the second voltage generator 52 generates the second voltages V ₂₁ and V that periodically change at two different second frequencies (1 / T ₂ ) different from the _first frequency (1 / T ₁ ). ₂₂ is generated.
More specifically, the second voltage generator 52 is shown on the left side of FIGS. 5A and 5C as vertical scanning voltages (vertical scanning drive signals) to be applied to the piezoelectric elements 41 and 43, respectively. As described above, the second voltage V ₂₁ that periodically changes at a period T ₂ different from the period T ₁ is generated.

The second voltage V ₂₁ is a waveform like a sawtooth wave. Therefore, the actuator 1 can effectively sub-scan light. Note that the waveform of the second voltage V ₂₁ is not limited to this.
Here, the second frequency (1 / T ₂ ) is not particularly limited as long as it is different from the _first frequency (1 / T ₁ ) and is suitable for vertical scanning, but the first frequency ( Preferably it is less than 1 / T ₁ ). That is, the period _{T 2} are longer is preferred than the period _{T 1.}

The second frequency (1 / T ₂ ) is preferably 40 to 80 Hz (about 60 Hz). Thereby, the mass part 211 can be rotated around each of two axes (the first axis X and the second axis Y) orthogonal to each other at a frequency suitable for drawing on the display.
In addition, the second voltage generator 51 generates a period T as shown in the left side of FIGS. 5B and 5D as vertical scanning voltages (vertical scanning drive signals) applied to the piezoelectric elements 42 and 44, respectively. ₂ generates a second voltage V ₂₂ that periodically changes. The second voltage V ₂₂ has the same waveform obtained by inverting the second voltage V ₂₁ with respect to a certain reference voltage.

The first voltage generation unit 51 and the second voltage generation unit 52 are connected to a control unit (synchronization signal generation circuit) 6 and driven based on a signal from the control unit 6.
A voltage superimposing unit 53 is connected to the first voltage generating unit 51 and the second voltage generating unit 52 as described above. The voltage superimposing unit 53 includes an adder 531 for applying a voltage to the piezoelectric element 41, an adder 532 for applying a voltage to the piezoelectric element 42, and an adder 533 for applying a voltage to the piezoelectric element 43. And an adder 534 for applying a voltage to the piezoelectric element 44.

The adder 531 receives the first voltage V ₁₁ from the first voltage generation unit 51 and receives the second voltage V ₂₁ from the second voltage generation unit 52, superimposes them, and applies them to the piezoelectric element 41. It is like that.
The adder 532 receives the first voltage V ₁₁ from the first voltage generator 51 and receives the second voltage V ₂₂ from the second voltage generator 52 and superimposes them to the piezoelectric element 42. It is designed to be applied.

The adder 533 receives the first voltage V ₁₂ from the first voltage generator 51 and also receives the second voltage V ₂₁ from the second voltage generator 52 and superimposes them to the piezoelectric element 43. It is designed to be applied.
The adder 534 receives the first voltage V ₁₂ from the first voltage generator 51 and also receives the second voltage V ₂₂ from the second voltage generator 52, and superimposes them to the piezoelectric element 44. It is designed to be applied.

The actuator 1 having the above configuration is driven as follows.
For example, while applied to the piezoelectric element 41 by superimposing the voltage _{V 11} and _{V 21,} as shown in FIG. 5 (a), the piezoelectric element by superimposing the voltage _{V 11} and _{V 22,} as shown in FIG. 5 (b) 42 is applied. In synchronization with this, as well as it applied to the piezoelectric element 43 by superimposing the voltage _{V 12} and _{V 21,} as shown in FIG. 5 (c), superimposes the voltage _{V 12} and _{V 22,} as shown in FIG. 5 (d) And applied to the piezoelectric element 44.

Then, in the first period (1 / T ₁ ), the piezoelectric elements 41 and 42 are expanded and the piezoelectric elements 43 and 44 are contracted, and the piezoelectric elements 41 and 42 are contracted and the piezoelectric elements 43 and 44 are expanded. While alternately repeating this state, the piezoelectric elements 41 and 43 are expanded and the piezoelectric elements 42 and 44 are contracted and the piezoelectric elements 41 and 43 are contracted in the second period (1 / T ₂ ). The state of extending the piezoelectric elements 42 and 44 is repeated alternately.

In other words, in the second period (1 / T ₂ ), the expandable range (displaceable length) of the piezoelectric elements 42 and 44 relative to the expandable range (displaceable length) of the piezoelectric elements 41 and 43. In the first period (1 / T ₁ ), the piezoelectric elements 41 and 42 and the piezoelectric elements 43 and 44 are stretched in opposite directions.
By operating the piezoelectric elements 41 to 44 in this way, the mass portions 211 are moved around the first axis X at the first frequency (1) while the respective beam portions 22, 23, 24, 25 are mainly bent and deformed. / _{T 1)} with (with vibration), a second frequency to the second about the axis Y ((1 / _{T 2)} turning is in rotation (vibration).

As described above, in the actuator 1, by applying the voltage superimposed by the voltage superimposing unit 53 to each piezoelectric element 41, 42, 43, 44, the mass unit 211 is converted into a pair of elastic units 212, The second frequency (1 / T) around the second axis Y orthogonal to the first axis X while rotating around the first axis X along the second axis 213 at the first frequency (1 / T ₁ ). ₂ ) Rotate.
Thereby, the mass part 211 can be rotated around each of the two axes orthogonal to each other while reducing cost and size.

In particular, since the number of piezoelectric elements serving as driving sources can be reduced (four in the present embodiment), a simple and compact configuration can be achieved.
In addition, by appropriately changing the first voltage and the second voltage, desired vibration characteristics can be obtained without changing the design of the base 2 and the piezoelectric elements 41, 42, 43, and 44.
In addition, a frame body 214 having a frame shape so as to surround the outer periphery of the mass portion 211 is supported by the two pairs of beam portions 22, 23, 24 and 25, and the mass portion via the pair of elastic portions 212 and 213. 211 is supported, so that the mass portion 211 is moved around the first axis X along the pair of elastic portions 212 and 213 at the first frequency (1 / T ₁ ) with lower power and more smoothly. It can be rotated around the second axis Y at a second frequency (1 / T ₂ ) while being rotated.

Furthermore, since one pair of beam portions is provided on both sides of the vibrating portion via the vibrating portion, the mass portion is smoothly moved at the first frequency around the first axis along the pair of elastic portions. It can be rotated at the second frequency around the second axis while being rotated.
In addition, when the mass portion 211 is viewed in plan, the two pairs of beam portions 22, 23, 24, and 25 are provided so as to be point-symmetric with respect to the center of the mass portion 211. And more smoothly, the mass portion 211 is rotated around the second axis Y while rotating at the _first frequency (1 / T ₁ ) around the first axis X along the pair of elastic portions 212 and 213. It can be rotated at a frequency of 2 (1 / T ₂ ).

Furthermore, each piezoelectric element 41, 42, 43, 44 extends along the longitudinal direction of the corresponding beam portion 22, 23, 24, 25, and expands and contracts in the extending direction, whereby the beam portions 22, 23, 24, 25 is bent at a lower voltage and with a larger rotation angle, the mass portion 211 is moved around the first axis X along the pair of elastic portions 212 and 213 at the first frequency (1 / T ₁ ) Around the second axis Y at a second frequency (1 / T ₂ ).

Moreover, since each beam part 22,23,24,25 is extended in parallel with the 1st axis line X, the rotation angle of the mass part 211 can be enlarged, making the actuator 1 smaller. it can.
Furthermore, since each piezoelectric element 41, 42, 43, 44 is provided over almost the entire region in the longitudinal direction of the corresponding beam portion 22, 23, 24, 25, the actuator 1 is further miniaturized. The rotation angle of the mass part 211 can be increased.

The actuator 1 as described above can be suitably applied to an optical scanner provided in an image forming apparatus such as a laser printer, a barcode reader, a scanning confocal laser microscope, or an imaging display.
Here, based on FIG. 6 and FIG. 7, a case where the actuator 1 is used as an optical scanner of an imaging display will be described as an example of an image forming apparatus.

FIG. 6 is a schematic diagram illustrating an example of an image forming apparatus (imaging display) according to the present invention, and FIG. 7 is a block diagram illustrating a configuration of a control system of the image forming apparatus illustrated in FIG.
As shown in FIG. 6, the image forming apparatus 10 includes an actuator 1 that is an optical scanner and a light irradiation device 7 that irradiates the actuator 1 with light, and the actuator 1 performs main scanning with light from the light irradiation device 7. Further, an image is formed (drawn) on the screen 9 by performing sub-scanning.

The screen 9 may be provided in the main body of the image forming apparatus 10 or may be a separate body. Further, the surface of the screen 9 (viewing side surface) may be irradiated with light from the light irradiation device 7 and displayed, or the back side of the screen 9 (surface opposite to the viewing side surface) may be displayed. The light from 7 may be irradiated and transmitted through the surface for display.
As shown in FIG. 7, the light irradiation device 7 includes light sources 71, 72, 73 of three colors of R (red), G (green), and B (blue), a cross dichroic prism (X prism) 74, a mirror 75 and a lens 76.

The light source 71 emits red light and is connected to a light source driver 81 for driving the light source 71. The light source 72 emits green light and is connected to a light source driver 82 for driving the light source 72. The light source 73 emits blue light and is connected to a light source driver 83 for driving the light source 73.
Each drive driver 81, 82, 83 is connected to the control unit 6A and operates based on a signal from the control unit 6A. Here, the control unit 6A receives image information (image signal) from a host computer (not shown), and operates each of the drive drivers 81, 82, and 83 in accordance with the image information. The control unit 6A controls driving of the power supply circuit 5 based on behavior information of the actuator 1 (mass unit 211) detected by a detection unit (not shown).

  In such an image forming apparatus 10, light of each color is irradiated from the light sources 71, 72, and 73 to the actuator 1 (light reflection unit 215) via the cross dichroic prism 74, the mirror 75, and the lens 76. At this time, the red light from the light source 71, the green light from the light source 72, and the blue light from the light source 73 are combined by the cross dichroic prism 74. In addition, the intensity of light output from the light sources 71, 72, and 73 of each color changes according to image information received from a host computer (not shown).

The light reflected by the light reflecting portion 215 (three colors of combined light) is irradiated on the screen 197.
At this time, the light reflected by the light reflecting portion 215 is scanned in the horizontal direction of the screen 9 (main scanning) by the rotation of the mass portion 211 of the actuator 1 around the first axis X. On the other hand, the light reflected by the light reflecting portion 215 is scanned (sub-scanned) in the vertical direction of the screen 9 by the rotation of the mass portion 211 of the actuator 1 around the second axis Y.

In this way, the image forming apparatus 10 forms an image (draws) on the screen 9. In such an image forming apparatus 10, it is possible to perform two-dimensional scanning, that is, main scanning (horizontal scanning) and sub-scanning (vertical scanning) by providing only one actuator 1, thereby reducing cost and size. Can be achieved.
The actuator of the present invention has been described based on the illustrated embodiment, but the present invention is not limited to this. For example, in the actuator of the present invention, the configuration of each part can be replaced with an arbitrary configuration that exhibits the same function, and an arbitrary configuration can be added.

For example, in the embodiment described above, the actuator 1 has been described as including two pairs of beam portions. However, if the mass portion can be rotated around each of two axes orthogonal to each other, the beam portion is a pair. Or three or more pairs.
Further, the shape, size, arrangement, and the like of the beam are not limited to those of the above-described embodiment as long as the mass part can be rotated around the two axes orthogonal to each other.

  In the above-described embodiment, the piezoelectric element is bonded only to the upper surface of the beam portion. However, the piezoelectric element may be bonded to the lower surface of the beam portion. What is joined to the upper surface and what is joined to the lower surface may be mixed. In such a case, it is preferable that the plurality of piezoelectric elements be provided symmetrically with respect to the first axis and / or the second axis. This eliminates the need to generate a plurality of types of voltages having phase differences in the first power generation unit and the second power generation unit, and simplifies the configuration of the first power generation unit and the second power generation unit. Can be.

In the above-described embodiment, the structure in which the shape is substantially symmetric (left-right symmetric) with respect to the first axis and the second axis in plan view has been described. However, the structure may be asymmetric.
In the above-described embodiment, the configuration in which the light reflecting portion is provided on the upper surface of the mass portion (the surface opposite to the support substrate) has been described. For example, in the configuration provided on the opposite surface. There may be a configuration provided on both sides.

  DESCRIPTION OF SYMBOLS 1 ... Actuator 2 ... Base | substrate 21 ... Vibrating part 211 ... Mass part 212, 213 ... Elastic part 214 ... Frame body 215 ... Light reflection part 22, 23, 24, 25 ... Beam part 26 ...... Support section 3... Support substrate 31... Opening 41, 42, 43, 44... Piezoelectric element 5... Power supply circuit 51... First voltage generation section 52. Superimposing units 531, 532, 533, 534... Adder 6, 6 A... Control unit 7 .. Light irradiation device 71, 72, 73. 82, 83 ... Drive driver 9 ... Screen 10 ... Image forming apparatus X ... First axis Y ... Second axis

Such an object is achieved by the present invention described below.
The actuator of the present invention includes a mass part,
Two elastic parts that support one and the other of the mass parts in a rotatable manner ;
A frame that supports the two elastic portions and surrounds the outer periphery of the mass portion;
Two frame support parts that support the frame so as to be rotatable around an axis orthogonal to the rotation axis of the mass part;
A piezoelectric element that is a drive source for rotating the mass unit ;
Anda voltage applying means for applying a voltage to the piezoelectric element,
Each of the two frame support parts has a beam part,
Each of the beam parts has a longitudinal shape, and has a first side located on the mass part side and a second side located farther than the first side with respect to the mass part, The first side extends parallel to the rotation axis of the mass unit;
The piezoelectric element is provided in each of the beam portions,
Said voltage applying means, first generates a first voltage generator for generating a first voltage to have a first frequency, the second voltage to have a second frequency different from the first frequency 2 voltage generators, and a voltage superimposing unit that superimposes the first voltage and the second voltage,
By applying a voltage that is superimposed by the voltage superimposing unit to each piezoelectric element, while the parts by weight is rotated at the first frequency, said frame so as to rotate in the second frequency It is configured.
Thereby, the mass part can be rotated around the two axes orthogonal to each other while reducing the cost and the size.

  In the actuator according to the aspect of the invention, it is preferable that the first frequency is higher than the second frequency.
  Thereby, the mass portion is rotated at the second frequency around the second axis while being rotated at the first frequency around the first axis along the two elastic portions more reliably and smoothly. Can do.
  In the actuator according to the aspect of the invention, it is preferable that the first frequency matches a torsional resonance frequency of a vibration system including the mass portion and the two elastic portions.
  Thereby, since the mass part can be resonantly driven around the first axis along the two elastic parts, the mass part can be largely rotated with low power.

In the actuator of the present invention, the mass portion has a plate shape, and when the mass portion is viewed in plan, the two frame body support portions are point-symmetric with respect to the center of the mass portion. Is preferably provided.
Accordingly, the mass portion is rotated at the first frequency around the first axis along the two elastic portions at a second frequency around the second axis with a simpler configuration and more smoothly. It can be rotated.

The actuator of the present invention, each of the piezoelectric element, by stretching the rotation axis parallel to the direction of the parts by weight, it is preferable that the bending deformation of the respective beam portions.
Accordingly, the mass portion is rotated at the first frequency around the first axis along the two elastic portions at a lower voltage and at a larger rotation angle, while the second axis is rotated around the second axis. It can be rotated at a frequency.

In the actuator according to the aspect of the invention, it is preferable that each of the piezoelectric elements is provided over almost the entire region in a direction parallel to the rotation axis of the mass portion of the corresponding beam portion.
Thereby, the rotation angle of the mass portion can be increased while reducing the size of the actuator.

In the actuator according to the aspect of the invention, it is preferable that the mass portion includes a light reflecting portion having light reflectivity.
Thereby, the actuator of this invention is applicable to optical devices, such as an optical scanner, an optical switch, and an optical attenuator.

The optical scanner of the present invention includes a mass part including a light reflecting part having light reflectivity,
Two elastic parts that support one and the other of the mass parts in a rotatable manner ;
A frame that supports the two elastic portions and surrounds the outer periphery of the mass portion;
Two frame support parts that support the frame so as to be rotatable around an axis orthogonal to the rotation axis of the mass part;
A piezoelectric element that is a drive source for rotating the mass unit ;
Anda voltage applying means for applying a voltage to the piezoelectric element,
Each of the two frame support parts has a beam part,
Each of the beam parts has a longitudinal shape, and has a first side located on the mass part side and a second side located farther than the first side with respect to the mass part, The first side extends parallel to the rotation axis of the mass unit;
The piezoelectric element is provided in each of the beam portions,
Said voltage applying means, first generates a first voltage generator for generating a first voltage to have a first frequency, the second voltage to have a second frequency different from the first frequency 2 voltage generators, and a voltage superimposing unit that superimposes the first voltage and the second voltage,
By applying a voltage that is superimposed by the voltage superimposing unit to each piezoelectric element, while the parts by weight is rotated at the first frequency, said frame so as to rotate in the second frequency It is configured.
Thereby, main scanning and sub-scanning can be performed with one optical scanner, and as a result, cost reduction and size reduction can be achieved.

An image forming apparatus according to the present invention includes a mass part including a light reflecting part having light reflectivity,
Two elastic parts that support one and the other of the mass parts in a rotatable manner ;
A frame that supports the two elastic portions and surrounds the outer periphery of the mass portion;
Two frame support parts that support the frame so as to be rotatable around an axis orthogonal to the rotation axis of the mass part;
A piezoelectric element that is a drive source for rotating the mass unit ;
Anda voltage applying means for applying a voltage to the piezoelectric element,
Each of the two frame support parts has a beam part,
Each of the beam parts has a longitudinal shape, and has a first side located on the mass part side and a second side located farther than the first side with respect to the mass part, The first side extends parallel to the rotation axis of the mass unit;
The piezoelectric element is provided in each of the beam portions,
Said voltage applying means, first generates a first voltage generator for generating a first voltage to have a first frequency, the second voltage to have a second frequency different from the first frequency 2 voltage generators, and a voltage superimposing unit that superimposes the first voltage and the second voltage,
By applying a voltage that is superimposed by the voltage superimposing unit to each piezoelectric element, while the parts by weight is rotated at the first frequency, said frame so as to rotate in the second frequency It is configured.
Thereby, main scanning and sub-scanning can be performed with one optical scanner, and as a result, cost reduction and size reduction can be achieved.

These beam portions 22, 23, 24, and 25 are provided so as to be point-symmetric with respect to the center of the mass portion 211 in a plan view of the mass portion 211 of the vibration portion 21.
Here, as shown in FIG. 1, the beam portion 22 has a longitudinal shape, a first side located on the mass portion 211 side, and a first side located farther than the first side with respect to the mass portion 211. There are two sides, and each side extends in parallel to the first axis X that is the rotation axis of the mass portion 211. Similarly, the beam portions 23, 24, and 25 also have a first side and a second side that are parallel to the first axis X, respectively.
The support part 26 is formed so as to surround the outer periphery of the vibration part 21 described above.
The pair of beam portions 22 and 23 connect the vibration portion 21 (more specifically, the frame body 214) and the support portion 26, respectively. Similarly, the pair of beam portions 24 and 25 connect the vibration portion 21 (more specifically, the frame body 214) and the support portion 26, respectively.

Claims (13)

A vibration part comprising a mass part and a pair of elastic parts supporting the mass part;
At least one pair of beam portions supporting the vibrating portion;
A piezoelectric element joined on each beam part;
Voltage applying means for applying a voltage to each of the piezoelectric elements,
The voltage applying means applies a voltage to each piezoelectric element to bend and deform each beam part, and in accordance with this, the actuator is configured to drive the vibration part,
The voltage applying means includes a first voltage generator that generates a first voltage that periodically changes at a first frequency, and a second that periodically changes at a second frequency different from the first frequency. And a voltage superimposing unit that superimposes the first voltage and the second voltage, and the voltage superimposed by the voltage superimposing unit is applied to each piezoelectric element. By applying, the mass portion is rotated around the first axis along the pair of elastic portions at the first frequency while the second portion is orthogonal to the first axis. 2. An actuator configured to rotate at a frequency of 2.   The voltage applying means generates the two kinds of the first voltages whose phases are shifted from each other by 180 °, and the voltage superimposing unit is configured to generate the first voltage and the second voltage. The actuator according to claim 1, wherein the two voltages superposed by the voltage superimposing unit are applied corresponding to the pair of piezoelectric elements.   The vibrating portion is supported by the at least one pair of beam portions, supports the mass portion via the pair of elastic portions, and forms a frame shape so as to surround an outer periphery of the mass portion. The actuator according to claim 1, comprising:   4. The actuator according to claim 1, wherein one pair of the beam portions is provided on both sides of the vibrating portion via the vibrating portion. 5.   The mass part has a plate shape, and when the mass part is viewed in plan, the two pairs of beam parts are provided so as to be point-symmetric with respect to the center of the mass part. 4. The actuator according to 4.   Each of the beam portions has a longitudinal shape, and each of the piezoelectric elements extends along the longitudinal direction of the corresponding beam portion and expands and contracts in the extending direction to bend and deform the beam portion. Item 6. The actuator according to any one of Items 1 to 5.   The actuator according to claim 6, wherein each beam portion extends in parallel to the first axis.   The actuator according to claim 6 or 7, wherein each of the piezoelectric elements is provided over substantially the entire region in the longitudinal direction of the corresponding beam portion.   The actuator according to any one of claims 1 to 8, wherein the first frequency is higher than the second frequency.   The actuator according to any one of claims 1 to 9, wherein the first frequency coincides with a torsional resonance frequency of a vibration system including the mass portion and the vibration portion.   The actuator according to claim 1, wherein the mass part includes a light reflecting part having light reflectivity. A vibration part including a mass part provided with a light reflection part having light reflectivity, and a pair of elastic parts supporting the mass part;
At least one pair of bending-deformable beam portions supporting the vibrating portion;
A piezoelectric element joined on each beam part;
Voltage applying means for applying a voltage to each of the piezoelectric elements,
The voltage application means applies a voltage to each piezoelectric element to bend and deform each beam part, and accordingly, drive the vibration part and scan the light reflected by the light reflection part. A configured optical scanner comprising:
The voltage applying means includes a first voltage generator that generates a first voltage that periodically changes at a first frequency, and a second that periodically changes at a second frequency different from the first frequency. And a voltage superimposing unit that superimposes the first voltage and the second voltage, and the voltage superimposed by the voltage superimposing unit is applied to each piezoelectric element. By applying, the mass portion is rotated around the first axis along the pair of elastic portions at the first frequency while the second portion is orthogonal to the first axis. An optical scanner configured to rotate at a frequency of 2. A vibration part including a mass part provided with a light reflection part having light reflectivity, and a pair of elastic parts supporting the mass part;
At least one pair of bending-deformable beam portions supporting the vibrating portion;
A piezoelectric element joined on each beam part;
Voltage applying means for applying a voltage to each of the piezoelectric elements;
Light irradiating means for irradiating light to the light reflecting portion,
The voltage application means applies a voltage to each piezoelectric element to bend and deform each beam part, and accordingly, drive the vibration part and scan the light reflected by the light reflection part, An image forming apparatus configured to form an image on an object,
The voltage applying means includes a first voltage generator that generates a first voltage that periodically changes at a first frequency, and a second that periodically changes at a second frequency different from the first frequency. And a voltage superimposing unit that superimposes the first voltage and the second voltage, and the voltage superimposed by the voltage superimposing unit is applied to each piezoelectric element. By applying, the mass portion is rotated around the first axis along the pair of elastic portions at the first frequency while the second portion is orthogonal to the first axis. An image forming apparatus configured to rotate at a frequency of 2.

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