JP2009086590A - Rocking member apparatus, method of reducing pressure in casing of rocking member apparatus, optical deflector and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rocking member apparatus which assures double to triple of Q-value of that under atmospheric pressure when reducing the jitter of the rocking member by composing a structure which can be sealed under a reduced pressure and keeps controllability, to provide a method of reducing pressure in the casing of the rocking member apparatus, and to provide an optical deflector and image forming apparatus. <P>SOLUTION: The rocking member apparatus drives with a driving means the rocking member having a movable plate rockably supported around a torsion shaft by a supporting part with respect to a supporting substrate, and a casing having a structure which encloses the periphery of the rocking member and can be sealed at a reduced pressure, wherein the rocking member is disposed in the sealed casing of which the pressure is reduced to ensure double to triple of Q-value of that under atmospheric pressure. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to an oscillating device, a pressure reducing method inside a housing of the oscillating device, an optical deflector, and an image forming apparatus.
For example, a technology capable of realizing an optical deflector using an oscillator device that can be suitably used in an image forming apparatus such as a projection display that projects an image by deflecting scanning of light, a laser beam printer having an electrophotographic process, a digital copying machine, etc. It is about.

In recent years, many literatures have reported on a vibration system (oscillator device) composed of a movable plate and a torsion spring manufactured by a micro electro mechanical system (MEMS) technique.
Among such oscillating devices, many papers and patent documents are known regarding oscillating devices having a reflecting surface and applied to a scanning display or an electrophotographic optical scanner.

By the way, a microfabricated MEMS device is extremely sensitive to small dust.
Therefore, in such a device, it is necessary to perform packaging for dust prevention.
In particular, in a dynamic device finely processed by the MEMS technology, the Q value is lowered due to gas resistance.
Here, the Q value (also referred to as mechanical Q value) is one of the parameters representing the resonance characteristics, and has a relationship in which the width of the resonating frequency decreases as the Q value increases.
In the case of a low output actuator due to static electricity or the like, it is often used with a vacuum package in order to obtain a high Q value.

For this reason, for example, Patent Document 1 proposes a capacitive MEMS actuator in which the atmospheric pressure in the hermetic container is set to 50 Pa or more and 0.1 MPa or less in the MEMS device housed in the hermetic container. Yes.
(Patent Document 2) proposes an optical scanning device in which the pressure of the vibration space of the mirror is in the range from 0.1 (Torr) to 2 (Torr) in order to vibrate the mirror with a high Q value.
JP 2006-320963 A JP 2004-109651 A

In the oscillator device finely processed by the MEMS technology described above, one of the important problems is a problem of jitter (oscillation of the oscillator) during oscillation.
When the movable plate is oscillated and oscillated at atmospheric pressure, turbulent flow is generated due to the viscosity of air, and jitter is generated due to fluctuations in the amplitude and phase of the vibrating body due to instability of the surrounding fluid.
In an image forming apparatus using an optical polarizer using an oscillator device that generates such jitter, the scanning becomes unstable and the image quality is deteriorated.
In order to deal with such jitter, in the above-described conventional patent documents 1 and 2, a device is proposed in which a vacuum package is applied to reduce jitter and to obtain a high Q value. .

However, in these conventional examples, no consideration is given to obtaining an oscillator device with good controllability under an appropriate vibration Q value.
That is, a high Q value can be obtained by increasing the degree of vacuum, but in order to achieve a high vacuum, the manufacturing process becomes complicated and the cost increases.
Further, if the degree of vacuum is increased and the Q value is increased too much, when the oscillator device is driven, it becomes difficult to control the oscillator device at a frequency deviating from the resonance frequency.
In addition, when the resonance frequency slightly changes due to a change in the environment, the high-Q vibration member may not be driven out of the resonance frequency.
In these cases, it is possible to cope with this by dynamically changing the drive frequency, but complicated work is required and the cost is increased.

In view of the above-mentioned problems, the present invention has a structure that can be sealed under reduced pressure to reduce the jitter of the oscillator,
An object is to provide a rocking device, a pressure reducing method inside a housing of the rocking device, an optical deflector, and an image forming apparatus that can maintain a controllability by securing a Q value that is two to three times that of atmospheric pressure. It is what.

The present invention provides an oscillator device configured as follows, a pressure reducing method inside a casing of the oscillator device, an optical deflector, and an image forming apparatus.
An oscillator device according to the present invention is an oscillator device that drives, by a driving means, an oscillator that includes a movable plate that is supported by a support portion so as to be swingable about a torsion axis with respect to a support substrate.
Covering the periphery of the oscillating body, provided with a housing with a structure capable of being sealed under reduced pressure,
The oscillating body is disposed inside the casing that is sealed under reduced pressure so as to ensure a Q value that is 2 to 3 times the atmospheric pressure. The inside of the housing is characterized in that the pressure is reduced to 10000 Pa or more and 50000 Pa or less.
Moreover, the oscillator device according to the present invention is characterized in that the casing includes one or more check valves that allow gas to pass from the inside to the outside of the casing.
The oscillator device according to the present invention is characterized in that the casing is formed of a member through which a part of the casing transmits light.
An optical deflector according to the present invention includes any of the oscillator devices described above and an optical deflection element provided on the movable plate of the oscillator device.
The image forming apparatus of the present invention includes a light source, a photosensitive member, and the above-described optical deflector, deflects light from the light source by the optical deflector, and at least part of the light is It is incident on the photoconductor.
Further, the pressure reducing method inside the housing in the oscillator device of the present invention is:
An oscillating body provided with a movable plate supported so as to be swingable around a torsion axis by a support portion with respect to the support substrate is disposed inside a housing having a structure capable of being sealed under reduced pressure so that the oscillating body can be driven. A pressure reducing method inside the housing of the oscillator device configured,
When the pressure inside the casing is reduced, the pressure inside the casing is reduced to a pressure range that can secure a Q value that is twice to three times that at atmospheric pressure.
Moreover, the pressure reduction method inside the housing | casing in the rocking | fluctuation body apparatus of this invention is characterized by making the said atmospheric | air pressure range pressure-reduced into 10,000 Pa or more and 50000 Pa or less.
Further, the pressure reducing method inside the housing in the rocking body device of the present invention uses the rocking body device provided with the check valve when depressurizing the inside of the housing.
The interior of the housing is decompressed by lowering the housing temperature after the check valve is closed while the housing is in a high temperature state.
Further, the pressure reducing method for the inside of the housing in the rocking body device of the present invention uses a rocking body device equipped with the check valve to suck the gas from the check valve when decompressing the inside of the housing. The inside of the housing is decompressed.
Further, the pressure reducing method inside the housing in the oscillator device according to the present invention is as follows.
A method of lowering the temperature of the housing after closing the check valve with the housing in a high temperature state and a method of reducing the pressure inside the housing by sucking gas from the check valve It is characterized by.

  According to the present invention, when reducing the jitter of a rocking body by forming a structure capable of sealing under reduced pressure, it is possible to maintain a controllability by securing a Q value that is two to three times that at atmospheric pressure. An oscillating device, a pressure reducing method inside the housing of the oscillating device, an optical deflector, and an image forming apparatus can be realized.

An oscillating body device for driving an oscillating body provided with a movable plate supported by a support portion so as to be able to oscillate around a torsion axis with respect to a support substrate in an embodiment of the present invention will be described.
FIG. 1 shows a schematic diagram illustrating the oscillator device of the present embodiment.
In FIG. 1, 100 is an oscillator device, 101 is a vibrating body, 102 is a movable plate, 103 is a torsion spring, and 105 is a housing.
In the oscillator device 100 of the present embodiment, the vibrating body 101 constituting the vibration system includes a movable plate 102, a torsion spring 103, and a support portion.

Next, details of the vibrating body in the oscillator device of the present embodiment will be described.
FIG. 2 is a diagram illustrating a vibrating body in the oscillator device of the present embodiment.
In the vibrating body 101 of the present embodiment, the movable plate 102 and the torsion spring 103 may be a plurality of or a gimbal type.
In the present embodiment, the vibrating body 101 can be manufactured using a silicon etching technique.
The vibrating body 101 includes a casing that covers the periphery of the rocking body and can be sealed under reduced pressure.
In other words, the vibrating body 101 is entirely covered with a casing 105 having a structure capable of being sealed under reduced pressure, thereby preventing inflow of gas from the outside.
The support portion 104 of the vibrating body 101 is fixed to the housing 105 inside.
The oscillator device 100 includes a driving unit 107 (see FIG. 5) that drives the vibrating body 101.
As this drive means 107, the means by electrostatic, piezoelectric, electromagnetic, etc. can be used.
The inside of the housing 105 is decompressed. At the time of this pressure reduction, it is desirable to set the atmospheric pressure inside the housing 105 to 10000 Pa or more and 50000 Pa or less.

Next, the description will be given of setting the atmospheric pressure inside the casing to the above value.
FIG. 3 is a diagram for explaining the relationship between the pressure in the casing provided with the vibrator and the scanning jitter.
As shown in FIG. 3, the scanning jitter decreases as the pressure decreases. However, when the pressure exceeds a certain pressure, the jitter decreases rapidly.
When the pressure decreases, the density decreases and the kinematic viscosity coefficient increases. Since the fluid motion is governed by viscosity, the change in scan jitter as shown in FIG. 3 indicates that the cause of the scan jitter is the flow of air.
Further, the reason why the scanning jitter is not 0 at the portion of 40000 Pa or less is mostly due to noise of the sensor measuring the scanning jitter.

In the data of FIG. 3, the dimension of the movable plate is several mm, and the temperature is about 25 ° C.
In the oscillator device according to the present embodiment, the pressure at which the jitter rapidly decreases depending on the temperature used, particularly when the temperature increases, moves to the high pressure side.
This is because as the temperature increases, the gas expands and the density decreases, so the kinematic viscosity coefficient increases.
For this reason, in the oscillator device of the present embodiment, it is appropriate to set the pressure to 10000 Pa or more and 50000 Pa or less as judged from the region of the ambient temperature that is normally used.
Also, even at 25 ° C., if it is 50000 Pa, the scanning jitter is reduced to about 1/3 at 1 atmosphere, so that the effect can be sufficiently expected.

The lower the atmospheric pressure, the smaller the scanning jitter, but the higher the Q value of the oscillation system.
A high Q value means that when driving at the resonance frequency, the driving force becomes small and efficient driving becomes possible. However, when the resonance frequency of the vibration system changes due to environmental changes, the necessary driving force is reduced. It becomes large and inefficient.
In addition, since a high Q value is equivalent to a small vibration damping effect, the controllability when controlling the vibration system is deteriorated.
A slight amount of movement of the resonance frequency due to environmental changes leads to large amplitude fluctuations and phase fluctuations.
That is, in relation to the control of the vibration system, the lower the atmospheric pressure is, the better, and it is desirable to set the atmospheric pressure in a range that allows jitter.
In the present embodiment, as described above, it is desirable that the pressure in the housing provided with the vibrating body is 10000 Pa or more and 50000 Pa or less.

Next, it will be further described that the pressure in the casing is in the above range.
FIG. 4 shows a diagram based on experimental data for explaining the relationship between pressure and Q value.
The Q value may be considered as a nearly linear function with respect to pressure. However, when the pressure drops below this, the change in pressure of the Q value varies depending on the shape and motion of the vibration system.
This is because the continuum approximation does not hold if the pressure becomes smaller than this, which makes the design of the vibration system more difficult.
As can be seen from FIG. 4, it can be estimated that the Q value is three times that at atmospheric pressure at 10,000 Pa and doubles at 50,000 Pa, and the appropriate pressure range is preferably 10,000 Pa or more and 50,000 Pa or less.
In this way, the pressure inside the housing is reduced to a pressure range in which a Q value that is 2 to 3 times the atmospheric pressure can be secured.
Then, the scanning body of the vibrating body can be reduced by disposing the rocking body inside the casing that is sealed under reduced pressure so as to ensure a Q value that is 2 to 3 times the atmospheric pressure. On the other hand, the controllability of the vibration system can be maintained.

Examples of the present invention will be described below.
[Example 1]
In Example 1, an oscillator device to which the present invention is applied will be described.
FIG. 5 shows a schematic diagram for explaining the oscillator device in the present embodiment.
In FIG. 5, the same reference numerals are given to the same components as those in the embodiment shown in FIG.
In FIG. 5, 107 is a driving means, 108 is a check valve, 109 is a magnetic body, and 110 is a light transmitting member.

In this embodiment, the vibrating body 101 constituting the vibration system is covered with a casing 105 having a structure capable of being sealed under reduced pressure.
The casing 105 is formed of a member that partially transmits light.
That is, the front surface of the housing is made of the light transmitting member 110, so that if the light reflecting element is attached to a part of the movable plate 102 of the vibrating body 101, the vibrating body 101 constitutes an optical scanning system. be able to.
The housing 105 has one or more check valves that allow gas to pass from the inside of the housing to the outside, whereby the gas is moved only from the inside of the housing 105 to the outside.
The housing includes one or more check valves (backflow prevention valves) that allow gas to pass from the inside to the outside of the housing.

As the check valve (backflow prevention valve) 108, a structure as shown in FIG. 6 can be used.
In FIG. 6A, the left side is inside the housing 105, and in FIG. 6B, the lower side is inside the housing 105.
FIG. 6A shows a structure in which the movable portion 201 is closed when attempting to flow backward, and the same applies to FIG. 6B, and the movable portion 201 is lowered to close the entrance.
The shape of the check valve 108 is not limited to such a configuration. For example, the check valve 108 may be applied to a mouth of a compression bag.

As described above, the driving means 107 can use electrostatic, piezoelectric, or electromagnetic means, but when driving at a wider angle, it is preferable to use electromagnetic driving.
In the case of this electromagnetic drive, driving can be performed by applying a magnetic body 109 to a part of the movable plate 102 constituting the vibrating body 101 and applying an alternating magnetic field from the driving means 107.
In FIG. 5, the driving means 107 is outside the housing, but may be inside. In the case of being inside, an electric conducting portion such as a conducting wire may be passed through the housing 105.
Further, when a fixed magnetic body and a coil applied to the movable plate 102 are used, the driving can be similarly performed.

[Example 2]
In the second embodiment of the present invention, a method for depressurizing the inside of the housing in the oscillator device of the first embodiment will be described.
In this embodiment, an oscillator device having the same configuration as that of the first embodiment shown in FIG. 5 is used.
In this embodiment, the oscillating body provided with the movable plate described above is disposed inside a housing having a structure capable of decompression sealing, and the interior of the housing of the oscillating body device configured to drive the oscillating body is decompressed. The following method can be used as a method for this.
As a first method, after the check valve is closed with the casing in a high temperature state, the interior of the casing can be decompressed by lowering the casing temperature.
For example, the oscillator device 100 is brought into a high temperature state, the check valve 108 is closed, and the thermally expanded gas is contained in the housing 105. Then, the air pressure inside the housing 105 is lowered by cooling.
As a second method, the inside of the housing 105 may be decompressed by sucking gas from the check valve 108.
Or you may make it use combining the decompression method inside the housing | casing by the 1st method and the 2nd method.
By the above method, the pressure inside the housing can be reduced to a pressure range in which a Q value of 2 to 3 times the atmospheric pressure can be secured, and the reduced pressure is 10000 Pa or more, The pressure can be reduced to 50000 Pa or less.

[Example 3]
In the third embodiment, a configuration example of an image forming apparatus using an optical deflector configured by applying the oscillator device of the present invention will be described.
FIG. 7 is a schematic perspective view illustrating a configuration example of the image forming apparatus in the present embodiment.
In the image forming apparatus of the present embodiment shown in FIG. 7, reference numeral 530 denotes an optical deflector to which the oscillator device of the present invention is applied and which includes an optical deflection element provided on the movable plate. Is one-dimensionally scanned.
Reference numeral 510 denotes a laser light source, 520 denotes a collimator lens, 540 denotes a coupling lens, and 550 denotes a drum-shaped photoconductor.

The image forming apparatus according to the present exemplary embodiment includes a light source, a photosensitive member, and the light deflector. The light deflector deflects light from the light source, and at least part of the light is It is configured to be incident on the photoconductor.
More specifically, a part of the movable plate (not shown) of the oscillating body in the optical deflector 530 includes a light reflecting portion. This light reflecting portion is obtained by depositing a metal thin film on the surface of the movable plate 102.
Light emitted from the light source 510 is shaped by the collimator lens 520.
The light scanned by the optical deflector 530 is imaged on the drum-shaped photoconductor 550 by the lens 540 and exposes the drum-shaped photoconductor 550.
An image is formed on the drum-shaped photoconductor 550 by modulating the light emitted from the light source 510.

The schematic diagram explaining the oscillator device in the embodiment of the present invention. The figure explaining the vibrating body in the oscillator device of the embodiment of the present invention. The figure explaining the relationship between the pressure of the oscillator device in the embodiment of the present invention and scanning jitter. The figure by the experimental data explaining the relationship between the pressure and Q value of the oscillator device in the embodiment of the present invention. The schematic diagram explaining the oscillator device in Example 1 of the present invention. The figure explaining the structure of the non-return valve of the rocking body apparatus in Example 2 of this invention. FIG. 6 is a diagram illustrating a configuration of an image forming apparatus according to a third embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100: Oscillator apparatus 101: Vibrating body 102: Movable plate 103: Torsion spring 104: Support part 105: Housing | casing 107: Drive means 108: Check valve 109: Magnetic body 110: Light transmission member 201: Movable check valve Unit 510: Light source 520: Collimator lens 530: Optical deflecting device (optical deflector) using oscillator device
540: Lens 550: Photosensitive drum

Claims (11)

An oscillating body device for driving an oscillating body having a movable plate supported by a support portion so as to be oscillatable about a torsion axis with respect to a support substrate by a driving means,
Covering the periphery of the oscillating body, provided with a housing with a structure capable of being sealed under reduced pressure,
The oscillating body apparatus is characterized in that the oscillating body is disposed inside the casing that is sealed under reduced pressure so as to ensure a Q value that is 2 to 3 times the atmospheric pressure.   2. The oscillator device according to claim 1, wherein the inside of the housing is depressurized to a pressure of 10,000 Pa or more and 50000 Pa or less.   The oscillator according to claim 1 or 2, wherein the casing includes one or more check valves that allow gas to pass from the inside to the outside of the casing.   4. The oscillator device according to claim 1, wherein a part of the casing is formed of a member that transmits light. 5. The oscillator device according to any one of claims 1 to 4,
An optical deflection element provided on the movable plate in the oscillator device;
An optical deflector comprising: A light source, a photoreceptor, and the optical deflector according to claim 5,
An image forming apparatus, wherein light from the light source is deflected by the optical deflector, and at least a part of the light is incident on the photosensitive member. An oscillating body provided with a movable plate supported so as to be swingable around a torsion axis by a support portion with respect to the support substrate is disposed inside a housing having a structure capable of being sealed under reduced pressure so that the oscillating body can be driven. A pressure reducing method inside the housing of the oscillator device configured,
When depressurizing the inside of the housing, the pressure inside the housing is depressurized to a pressure range in which a Q value that is 2 to 3 times the atmospheric pressure can be secured. The decompression method.   The method for reducing the pressure inside the casing of the oscillator device according to claim 7, wherein the pressure range in which pressure is reduced is 10,000 Pa or more and 50000 Pa or less. When depressurizing the inside of the housing, using the oscillator device according to claim 3 or claim 4,
The oscillator according to claim 7 or 8, wherein after the check valve is closed while the casing is in a high temperature state, the inside of the casing is decompressed by lowering the temperature of the casing. A method for depressurizing the inside of a housing in an apparatus. When depressurizing the inside of the housing, using the oscillator device according to claim 3 or claim 4,
The method for depressurizing the inside of the housing in the oscillator device according to claim 7 or 8, wherein the interior of the housing is decompressed by sucking gas from the check valve.   A method of decompressing an interior of a housing in an oscillating device, wherein the decompression method within the housing of claim 9 and claim 10 is used in combination when decompressing the interior of the housing.

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