JPS63225216A - Image forming device - Google Patents

Abstract

PURPOSE:To eliminate the distortion of a recorded image generated by a fluctuation in an oscillation angle without being affected by ambient air flow by housing a deflector including an optical deflector integrally formed with a reflecting mirror and driving coil into a hermetic case in which an inert gas is filled. CONSTITUTION:The optical deflector integrally formed with the reflecting mirror 312 and the driving coil 311 is used as the optical deflector 310 for deflecting and scanning a light signal. The deflector 300 including the optical deflector 310 is housed in the hermetic case 340 and the inert gas is filled in the hermetic case. A case formed with a transparent window for transmission of the deflected light is used for the hermetic case of transparent case is used. A quartz plate or the like is usable as the optical deflector. There is, therefore, no possibility of the unstable oscillation of the optical deflector by the influence of the air flow near the deflector during use thereof, the contamination of the surface of the reflecting mirror, etc., or a degradation in Q by splashed toners, etc.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to electrophotographic color copying machines or laser printers, and is suitable for image forming apparatuses, particularly gas-filled type image forming apparatuses that can effectively protect optical deflectors. The present invention relates to an image forming apparatus having an optical scanning device using protection means.

[Background of the Invention] Some electrophotographic color copying machines use optical signals such as semiconductor lasers as means for forming electrostatic latent images on photosensitive image forming bodies using image signals corresponding to original documents. be.

When color recording is performed using a laser beam scanning device, electrostatic images can be easily formed while being shifted for each color separation image, and a clear color image can be recorded.

FIG. 22 is a configuration diagram showing an example of a laser beam scanning device 30 used in this type of electrophotographic color copying machine.

In the figure, 11 indicates a drum-shaped image forming body,
A photoconductive photoreceptor surface layer made of selenium or the like is formed on its surface, so that an electrostatic image (electrostatic latent image) corresponding to an optical image can be formed.

The laser beam scanning device 30 includes a semiconductor laser 31, and the laser 31 is optically modulated based on a modulation signal obtained by binarizing image information.

The laser beam emitted from the laser 31 passes through a collimator lens 32 and a cylindrical lens 33 and enters a mirror scanner, ie, a deflector 34, which is made up of a rotating polygon mirror.

The laser beam is focused by the deflector 34 and irradiated onto the surface of the image forming body 11 through an f-θ lens 35 and a cylindrical lens 36 for imaging.

The laser beam is scanned by the deflector 34 over the surface of the image forming body 11 at a constant speed in a predetermined direction a.
Image exposure will be exhausted.

In addition, 39 indicates a photosensor, and by receiving the laser beam reflected by the mirror 38, an index signal indicating the start of laser beam scanning is obtained, and one line of image data is written based on this index signal. It will be done.

When using a rotating polygon mirror with the above-mentioned configuration as a deflector, since the deflector is a deflector in which a polygon mirror is attached to a motor and the laser is deflected by rotationally driving it, the following is required. This causes problems such as:

First, the rotating polygon mirror itself becomes large, which becomes a bottleneck in downsizing the optical scanning device.

Second, the rotational noise generated when the motor is driven and the wind noise of the rotating polygon mirror become louder, making it impossible to reduce noise and vibration.

Third, since the bearings of the drive motors for smaller rotating polygon mirrors are usually ball bearings, the bearings wear out over long periods of use, resulting in poor rotational stability and reliability.

Fourth, ball bearings cannot be used for high-speed scanning because the driving speed of a motor is about 1 kHz when converted into frequency.

When using wear-resistant bearings such as air bearings, the machining accuracy of the shaft and bearings is extremely strict, and the shaft may seize due to dust. There are a number of problems, including the fact that it is expensive.

Generally speaking, a rotating polygon mirror may generate miscellaneous light within the optical system due to light scattering on the reflecting surface. Although the degree of light scattering varies depending on the surface precision coating material of the reflective surface, etc., more or less scattered light is generated, and since this scattered light is irradiated onto the image forming body 11, it has a negative effect on the final image. .

In particular, it causes fogging and reduces the reproducibility of fine lines. High quality and high resolution, e.g. 12-24 dots
This is a big problem for laser recording devices that require resolution on the order of s/mm.

Such a problem can be solved by using a mechanical vibrating mirror as the deflector 34,
For example, this problem can be solved by using a galvanometer mirror used in galvanometers and the like.

FIG. 23 shows an example of such a galvano mirror 50.

As is well known, the galvanomirror 50 includes a reflecting mirror 51.
, a drive coil 52, and a ligament (rotation support rod) 53 for mechanically connecting these. The drive coil 52 is placed in a DC magnetic field of a predetermined size.

If a drive current of a predetermined frequency is supplied to the drive coil 52,
Since a predetermined electromagnetic force acts on this drive coil 52, the reflection mirror 51 vibrates.

Therefore, when the reflecting mirror 51 is irradiated with an optical signal modulated by the image signal described above, this optical signal is deflected and reaches the image forming body 11, so that the same optical scanning as described above is performed. .

An example of scanning a laser beam while correcting its velocity using a mechanical vibrating mirror is disclosed in Japanese Patent Application Laid-open No. 54-6094.
There is a galvano mirror scanner device disclosed in No. 4. However, this known example relates to a lens system, and is a device that uses a mechanical vibrator without solving its drawbacks, as will be described later.

[Problems to be Solved by the Invention] By the way, when using a mechanical vibrating mirror as shown in FIG. 23 as a deflector, the reflecting mirror 51 and the driving coil 52 are manufactured separately, and 53, each part becomes larger, and there are other drawbacks as follows.

First, since the ligament is made of metal, it is difficult to swing the mirror over a wide angle.

Second, since the ligament is also made of metal, metal fatigue occurs during long-term use, making it impossible to obtain stable vibrations.

Furthermore, if the ligament, mirror, and supporting frame are made of different materials, stable mirror support and vibration may be difficult due to differences in (linear) expansion coefficients of the materials caused by large changes in ambient temperature or environmental conditions. It may happen. When high-speed scanning is required, such as in laser beam printers and facsimiles, instability of mirror support and mirror vibration affects the final image quality.

If the mirror blurs during beam scanning, the image forming body 11
This is because the location of the beam spot that hits will be irregular. As a result, straight lines may become partially bent, or evenly spaced lines may become irregular.

One possible solution to these drawbacks is to use an optical deflector as a deflector for optical signals.

The optical deflector has the same function as a galvanometer mirror, which is a mechanical vibrating mirror, and as described later, a reflecting mirror, a driving coil for driving the reflecting mirror, and the like are integrally formed on the same substrate. A crystal plate or the like is used as the substrate.

As an optical deflector, please refer to Special Publication No. 60-57052, Special Publication No. 60-57053, or "Crystal Optical Deflector J (65
7 to 658) can be used.

Incidentally, the optical deflectors described in such known documents are essentially those developed for electromagnetic oscillography, and generally have small deflection angles and small vibration frequencies. .

Therefore, it has been considered difficult to apply such a deflector to small, high-speed image forming apparatuses such as laser printers.

However, by using the optical deflector under specific conditions and controlling it appropriately, contrary to conventional expectations, it is possible to achieve high-speed scanning, high stability, high durability, and high image quality. It was confirmed that this was obtained.

By the way, when deflecting an optical signal using a vibrator that is integrally formed with a reflecting mirror and a drive coil, if the optical scanning device was developed for high-speed scanning, it is necessary to minimize air resistance, In order to reduce the moment of inertia, the drive coil must be designed to be as small as possible. In other words, drive coils with small areas are used. Along with this,
Very thin ligaments are also used.

As described above, as the optical deflector itself becomes smaller, lighter, or flatter, the optical deflector becomes more susceptible to the effects of airflow. As described later, the deflector is placed in the document reading section A, and since the optical system is movably provided in the document reading section Δ, the airflow caused by the movement of the optical system is deflected. There is a strong possibility that it will hit the container.

In particular, devices aimed at miniaturization are increasingly susceptible to the influence of surrounding airflow.

The influence of the air flow causes a change in the deflection angle of the optical deflector, and this causes distortion of the recorded image. This leads to image quality deterioration.

Furthermore, since the deflector is installed near the developing device, there is a risk that the reflective mirror surface of the optical deflector may be contaminated by toner scattering or dust adhesion.

Since the light deflector is small, lightweight, thin, and mechanically very weak, it is very difficult to clean the starlight deflector if it becomes contaminated with toner or the like. In other words, its maintenance is troublesome.

Furthermore, there is a risk that the ligament may be damaged if the ligament is touched during cleaning.

In addition to this, the Q of the optical deflector due to air resistance
decreases, making it impossible to drive efficiently.

Furthermore, since this optical deflector is driven in contact with the outside air, especially when a semiconductor laser is used as a light source, a plating treatment such as gold Au is applied to increase the reflectance of the reflecting mirror 312. .

In addition, depending on the case, there may be scratches on the surface of the reflecting mirror 312,
To prevent oxidation, SiO or 5i is applied to the surface after plating.
It is sometimes coated with a protective film such as 02.

Plating with gold or the like increases costs. Coating treatments for surface protection and oxidation prevention similarly increase the cost of the deflector.

Therefore, the present invention proposes an image forming apparatus that completely eliminates such conventional drawbacks.

[Technical means for solving the problem 1 In order to solve the above-mentioned technical problem, in this invention, the image signal is generated by scanning the recording medium by deflection with an optical signal modulated by the image signal. In an image forming apparatus configured to write on a recording medium, an optical deflector that deflects and scans an optical signal is formed by integrally forming a reflecting mirror and a drive coil, and a deflector including an optical deflector is used. is housed in a sealed container, and the sealed container is filled with an inert gas.

As the sealed container, a container with a transparent window for transmitting polarized light may be used, or a transparent container may be used. A crystal plate or the like can be used as the optical deflector.

[Function] The deflector including the optical deflector is housed and fixed in a sealed container, and the deflector is driven.

Therefore, when the deflector is in use, the vibration of the optical deflector may become unstable due to the influence of nearby air currents, the surface of the reflecting mirror may be contaminated by scattered toner, or the surface of the reflecting mirror may be contaminated.
There is no risk of a decrease in

Since the sealed container is filled with inert gas, there is no need for coatings to prevent oxidation or to protect the surface, making it possible to shorten the manufacturing process and reduce the amount of materials used.

[Example] Next, a case in which the image forming apparatus according to the present invention is applied to a simple color image recording apparatus using a laser as an optical signal will be described in detail with reference to FIG. 1 and subsequent figures.

FIG. 6 is a diagram showing a schematic configuration of a laser recording device and its control system to which the present invention is applied.

Color originals are separated into two colors, red and cyan, and CCD
A color original is inputted to a photoelectric conversion element such as , and photoelectrically converted, and this is converted into a digital signal of a predetermined number of bits, and then separated into colors i.

In this example, the signal is separated into three color signals: red, blue, and black.

Each color signal is separated using a semiconductor laser beam.
An electrostatic image is formed by being written on the image forming body 11 via the writing section B. Thereafter, a color toner image is formed by being developed by a developing device corresponding to this color signal.

By repeating this development process for each color signal, a monochrome toner image or a multicolor toner image in which toner images of each color are superimposed is formed on the image forming body 11.

Such multicolor or monochrome toner images are transferred and fixed onto recording paper.

Then, by operating the copy button on the operation panel 56, the data is taken in to the CPUI used for controlling the main body via the operation section circuit 64, and the resulting document scanning start signal is sent to the CPUI. The signal is sent to an optical drive CPU 2 connected via serial communication, and a document reading section A electrically connected to the CPU 2 is driven.

First, the original 82 on the original table 81 is optically scanned by an optical system.

This optical system is composed of a carriage 84 provided with fluorescent lamps 85, 86 and a reflecting mirror 87, and a movable mirror unit 88 provided with mirrors 89 and 89'.

The carriage 84 and the movable mirror unit 88 are caused to travel on the slide rail 83 at predetermined speeds and directions, respectively, by a stepping motor 90.

Optical information (image information) obtained by irradiating the document 82 with fluorescent lamps 85 and 86 is reflected on the reflecting mirror 87 and the mirror 89 .
89' to an optical information conversion unit 100.

When scanning color originals, commercially available warm white fluorescent lamps are used as the fluorescent lamps 85 and 86 to prevent optical enhancement or attenuation of specific colors, and to prevent flickering. These fluorescent lamps 85 and 86 are approximately 40
It is lit and driven by a kHz high frequency power source. In addition, in order to maintain a constant temperature of the tube wall or promote warm-up, the tube wall is kept warm by a heater using a positive temperature coefficient thermistor.

Standard white plates 97 are provided on the back side of both ends of the platen glass 81.
．． 98 are provided. This is a standard white board 97.9
This is because the image signal is normalized to a white signal by optically scanning 8.

The optical information conversion unit 100 includes a lens 101, a prism 102, a dichroic mirror 103, a CCD 104 that projects a red color-separated image, and a CCD 105 that projects a cyan color-separated image.

An optical signal obtained from the optical system is focused by a lens 101, and separated into red optical information and cyan optical information by a dichroic mirror 103 provided within a prism 102.

The respective color separated images are formed on the light receiving surfaces of the CCDs 104 and 105, thereby obtaining image signals converted into electrical signals. After the image signal is processed by the signal processing means, each color signal is output to the writing section B.

Although not shown, the signal processing means includes signal processing circuits such as an A/D conversion means, an arithmetic processing means, a color separation means, and a binarization means.

As will be described later, the writing section B has a deflector 300 made of an optical deflector using crystal or the like, and the laser beam modulated by the color signal is deflected and scanned by the deflector 300.

When deflection scanning is started, the beam scanning is detected by a laser beam index sensor (not shown), and beam modulation using a first color signal (for example, a blue signal) is started.The modulated beam is transmitted to a high voltage power supply 69. The charge M121 to which a predetermined high voltage is supplied from the image forming member 11 is scanned over the image forming member 11 to which a -1 charge has been applied.

Here, an electrostatic image corresponding to the first color signal is formed on the image forming body 11 by the main scanning by the laser beam and the sub scanning by the rotation of the image forming body 11.

This electrostatic image is developed by a developer 123 containing blue toner. A predetermined bias voltage from the high voltage power supply 70 is applied to the developing device 123 . A blue toner image is formed by development.

Note that when replenishing toner in the developing device 123, the toner replenishing means 66 is controlled based on a command signal from the CPUI, so that toner is replenished when necessary.

The blue toner image is rotated with the cleaning blade 127 released, and an electrostatic image is formed based on a second color signal (for example, a red signal) in the same manner as in the case of the first color signal, and the red toner image is rotated with the cleaning blade 127 released. This is developed to form a red toner image using a developer 124 containing the toner.

Needless to say, a predetermined bias voltage can be applied to the developing unit 124 from the high voltage power supply 70.

Similarly, an electrostatic image is formed based on the third color signal (black signal), and the developing device 125 filled with black toner generates an electrostatic image.
You can complete the development in the same way as last time. As a result, the image forming body 11
A multicolor toner image is written on the top.

Although the formation of a three-color multicolor toner image has been described here, it goes without saying that a two-color or single-color toner image can also be formed.

As described above, the development process is a so-called non-contact development process in which each toner is caused to fly toward the image forming body 11 while AC and DC bias voltages from the high-voltage power supply 70 are applied. An example was shown.

Toner replenishment to the developing devices 124 and 125 is performed by the toner replenishing means 67 based on the command signal from the CPUI in the same manner as described above.
．． 68 is driven, and each developing unit 12 is driven by this.
4,125, a predetermined amount of toner is replenished.

On the other hand, the recording paper P fed from the paper feeding device 141 via the feed roll 142 and the timing roll 143 is
The image forming member 11 can be conveyed onto the surface of the image forming member 11 in a state in which the timing is synchronized with the rotation of the image forming member 11 . Then, by the transfer pole 130 to which a high voltage is applied from the high voltage power supply 71,
The multicolor toner image is transferred onto the recording paper P, and the separation pole 13
Separated by 1.

The separated recording paper P is conveyed to the fixing device 132 (which is constantly controlled at a predetermined temperature by the fixing heater temperature control circuit 63), whereupon the fixing process is completed and a color image is obtained.

The image forming body 11 after the transfer is cleaned by a cleaning device 126 and is prepared for the next image forming process.

In the cleaning device 126, a predetermined DC voltage is applied to the metal roll 128 from the high voltage power supply 72 in order to facilitate collection of the toner cleaned by the blade 127. This metal roll 128 is placed on the surface of the image forming body 11 in a non-contact manner.

After the cleaning is completed, the blade 127 can release the pressure bonding, but in order to remove unnecessary toner that remains behind when the blade 127 is released, an auxiliary cleaning roller 129 is provided. By doing this, unnecessary toner is sufficiently cleaned and removed.

In addition, in FIG. 6, a lighting control circuit 61 for driving fluorescent lamps 85 and 86 is controlled by a command signal from the CPU 2. Similarly, the driving circuit 62 of the stepping motor 90 can be controlled by a command signal from the CPU 2.

The paper feeding device 141 is provided with a sensor 65a, the detection output of which is supplied to a paper size detection circuit 65, and the detection output can be supplied to the CPUI.

The above is the general structure of the main parts of the laser recording apparatus to which the present invention is applied. Next, the structure of each part will be explained in detail with reference to FIG. 7 and subsequent figures.

FIG. 7 shows a more specific relationship of the optical scanning device used in the above-mentioned laser recording device.

After the beam shape of the laser beam emitted from the semiconductor laser 31 is corrected by the collimator lens 32, the laser beam passes through the cylindrical lens 33 and the reflection mirror 41 and is made to enter the deflector 300.

A laser beam is deflected by a deflector 300 in a predetermined direction at a predetermined speed.

As the deflector 300, a reflecting mirror 31 is used as described later.
2 and a drive coil 311 are integrally formed.

The deflected laser beam passes through the scanning lens 42 and the cylindrical lens 36 and is directed to the image forming body 11.
An electrostatic image is formed by focusing on the object.

The cylindrical lenses 33 and 36 are used to correct vertical tilting of a reflecting mirror (described later) provided in the deflector 300.

Here, one cylindrical lens 36 can be a plastic lens.

When such a plus deck lens is used, it is relatively easy to match the surface shape of the lens to an optimal shape, so there is an advantage that the performance of the entire optical system can be improved.

However, if the tilt of the reflecting mirror is very small, the above-mentioned cylindrical lenses 33 and 36 can be omitted.

The scanning lens 42 is used to properly focus the laser beam on the surface of the image forming body 11 and to enable the laser beam to scan the image forming body 11 at a constant speed.

Here, when vibrating at the natural frequency of the optical deflector 310, the deflection angle θ of the reflecting mirror is 0=A-sinQJt where, A: maximum deflection angle ω of the reflecting mirror: angular velocity t: in time. As you can clearly see, the operation is a sine wave.

Therefore, the spot position of the laser beam is set as a function of θ×(
0), as the scanning lens 42, X(θ) =
A-f-arc-sin (0/A) However, by giving the characteristic that f is the focal length of the scanning lens 42, the position of the spot of the laser beam on the image forming body 1 can be expressed as a function of time t When expressed as (t), from the above equation, X (t)=A−f·ωt.

Therefore, by using the scanning lens 42 as described above, the laser beam can be converted into uniform motion.

When an electrostatic image is formed by uniform motion, image quality without distortion can be obtained.

FIG. 8 shows an example of the optical deflector 310.

The optical deflector 310 includes a vibrator 305 and a frame 315 for mechanically connecting the vibrator 305.

As shown in the figure, the vibrator 305 is configured by integrally forming a reflecting mirror 312, a drive coil 311, and a ligament 313, and a frame 315 having a substantially inverted U-shape is provided to the vibrator 305. This frame 315 is also integrally molded with the vibrator 305. Therefore, the deflector 310
are integrally formed by etching the same substrate.

The shape of the drive coil 311 is selected to be vertically elongated with respect to the shape of the reflecting mirror 312. This is because by forming the coil into a vertically elongated shape, the length of the coil piece that traverses the magnetic field becomes a predetermined length. This makes it possible to obtain the desired rotational moment.

The optical deflector 310 may have a shape as shown in FIG. 9. The figure shows a structure in which the elastic force is roughly increased as a ligament 313, and the ligament piece 31
Zigzag-shaped spring pieces 313b on the left and right sides of 3a
are integrally formed.

As the optical deflector 310, crystal, glass, quartz, etc., which are easily etched and have a large elastic modulus, can be used.

In this example, a crystal is used.

FIG. 1 shows an example of the overall configuration of a deflector 300 using the above-mentioned optical deflector 31'O, and also shows an example of a sealed container 340 covering the deflector 300.

The sealed container 340 has a shape that almost matches the external shape of the deflector 300, and in this example, has a rectangular parallelepiped shape.

The volume is selected to completely cover the entire deflector 1300.

Therefore, the state in which the deflector 300 is covered, that is, the sealed container 340 is attached to the substrate, is as shown in FIG.

In addition, this mounting is done in a state where it is attached and fixed to the board so that the inside thereof is airtight. The inside is filled with inert gas. As the inert gas, haeumganu or neon gas is used.

Using an inert gas prevents the optical deflector 310 housed in the sealed container 340 from being oxidized.

The internal pressure of the sealed container 340 is set to be lower than the external pressure.

The purpose of creating a negative pressure inside the sealed container 340 in this manner is to lower the air resistance of the optical deflector 310 and improve its resonance characteristics by increasing its Q.

Reference numerals 341 and 342 denote side plates for mounting and fixing, and a window hole 343 of a predetermined size is provided on one surface 340a of the sealed container 340 at a position just opposite to the reflecting mirror 312 of the optical deflector 310. As soon as the drilling is completed, this window hole 3
A transparent plate 344 is provided to cover 43.

The size of the window hole 343 is selected to be sufficiently larger than that of the reflecting mirror 312, and the size of the window hole 343 is widened so as not to impede transmission of the polarized light. As the transparent plate 344, a transparent acrylic plate, a glass plate, or the like is used.

The sealed container 340 itself may be a resin molded product,
It may be made of metal.

The deflector 300 is driven while being covered by the sealed container 340 (see FIG. 3).

Since the sealed container 340 is a means for effectively protecting the optical deflector 310 from air currents, scattered toner, etc., the fourth
It can also be configured as shown in the figure.

The example shown in FIG. 4 is a case where the sealed container 340 is made of a transparent member. When a transparent sealed container is used in this way, the window hole 340 for passing polarized light as explained in FIG.
Since the transparent plate 344 and other members can be omitted, the number of parts and costs can be reduced.

An example of the configuration of the deflector 300 will be described next.

In FIG. 1, the deflector mounting portion 320 has a substantially mouth-shaped shape, and among the upper and lower flanges 321 and 322, the upper flange 322 has a step 322A as shown in the figure.
is formed, and the optical deflector 310 is fixedly attached across between this step 322A and the lower flange 321.

Therefore, a pair of clamping pieces 323° 324 forming an inverted U-shape
are provided, and a frame 315 provided on the deflector 310 is held between these holding pieces 323 and 324. The pair of clamping pieces 323 and 324 that clamp the deflector 310 are mounted on the portion 320 with their height and lateral positions determined by the step 322A of the upper flange 322.
The installation is fixed. Reference numerals 325 and 326 are L-shaped restraining pieces used for this purpose.

Note that the ligament 313 provided in the optical deflector 310 shown in the figure is a slightly modified example of the ligament shown in FIG. The one that was formed is no longer used.

The mounting portion 320 to which the optical deflector 310 is fixed is placed in a predetermined DC magnetic field.

Therefore, as the magnetic field generating means 327, an electromagnet is used in this invention. Therefore, the magnetic field generating means 327 will be described below as an electromagnet.

The electromagnet 327 is composed of a substantially U-shaped core (iron core) 328 and a coil 329 wound around the core.
8, a thin core piece 328A as shown in FIG. 5A is used, and a predetermined number of these pieces are laminated.

This thin core 328 may be used by laminating a pair of L-shaped thin core pieces 328B and 328C with their ends facing each other, as shown in FIG.

Each magnetic pole 327A of the electromagnet 327 configured in this way,
327B, the above-mentioned attachment portion 320 is arranged. This allows the deflector 310, in particular the drive coil 31
1 is placed within the magnetic field formed by this electromagnet 327.

Note that in order to increase the magnetic field acting on the drive coil 311 by bringing the pair of magnetic poles 327A and 327B as close as possible, in the illustrated example, the vicinity of the center of the long side of the pair of clamping pieces 323 and 324 is on the drive coil 311 side. It has a folded structure.

In the deflector 300 configured in this way, if a predetermined excitation current is supplied to the coil 329, the magnetic pole 327
A DC magnetic field is formed between A and 327B, which is approximately determined by the magnitude of this excitation current.

The drive coil 311 is rotatably arranged in this DC magnetic field, so if a predetermined drive current is supplied to the drive coil 311, a rotational moment is generated in the drive coil 311, causing the drive coil 311 to vibrate. do.

This causes the reflection mirror 312 to vibrate with the frequency of the drive current as a period. The deflection angle of the reflecting mirror 312 is controlled by the amplitude value of the drive current.

Here, as the thickness of the crystal plate used as the optical deflector 310 increases, the natural frequency fO of the deflector 3 becomes smaller, but on the other hand, it becomes difficult to process. In addition, since the deflection angle becomes small, the thickness is preferably about 0.1 mm to 0.5 mm.

When forming the optical deflector 310 by processing a quartz plate, photolithography and etching techniques are usually applied as the processing means, which enables microfabrication. The etched surface of the optical deflector 310 is usually plated with silver after being chromium plated to reduce electrical resistance.

The reflecting mirror 312 used has the following shape.

That is, while the shape of the laser beam that has passed through the collimator lens 32 is truncated as shown in FIG. It can be transformed into an elliptical shape. Therefore, the shape of the reflecting mirror 312 is as follows:
A rectangular shape that becomes longer in the main scanning direction may be used.

From this point of view, as the reflecting mirror 312, the first
It can take various shapes as shown in FIG.

Figure A has a rectangular shape, Figure B has a rhombic shadow shape, Figure C shows a rectangle with the corners of each of the four sides cut off, and the figure has a horizontally long ellipse shape.

When the reflecting mirror 312 is vibrated at high speed,
Air resistance is a particular problem, so in such cases,
It is convenient to use an elliptical reflecting mirror as shown in the figure.

The length of the reflecting mirror 312 in the stacking direction varies depending on the focal length of the scanning lens 42, the diameter of the beam spot that can be focused on the image forming body 11, the scanning width on the image forming body 11, etc. For example, a desirable value is about 4 to 10 mm.

Now, the optical deflector 310 is driven by an external signal.

An example of a separately excited drive circuit using an optical deflector 310 is shown in FIG.

In FIG. 12, 330 indicates a sine wave oscillator, which can be an oscillator using an RC circuit or a crystal resonator.

When using a crystal resonator, it is sufficient to use one whose natural oscillation frequency is divided into a predetermined value and then shaped into a sinusoidal waveform using a low-pass filter.

Here, the oscillation frequency, that is, the drive frequency for the drive coil 311 will be explained.

As described above, the optical deflector 310 has a natural frequency fo, and the resonance characteristic of the deflection angle θ with respect to the natural frequency fo is as shown in FIG.

As is clear from the resonance characteristics in Fig. 13, when driving at a frequency that deviates from the natural frequency fo, the efficiency with respect to the deflection angle with respect to the input current decreases, and the natural frequency f
To obtain the deflection angle θ such as opening to the left when vibrating at o,
Requires very large input current.

However, if too large an input current is applied to the drive coil 311, there is a risk that this coil will be burnt out, causing a failure. Therefore, a very large current cannot be used as a drive current.

Further, it is possible that variations occur in the natural frequency fo of the deflector 310, and in such a case, the natural frequency f is changed in order to unify the driving frequency f.

Even when driving the drive coil 311 at a frequency other than the above, it is desirable that the relationship between the drive frequency f and the natural frequency fo be within the following range: If-fol≦fo/Q. Here, Q indicates the sharpness of the resonance characteristic.

In other words, considering manufacturing variations, the natural frequency f
Since it is difficult to process O so that it is equal to the driving frequency f, its natural frequency fo is within the range of approximately ±fo/Q from the driving frequency f, and the optical deflection The child 310 is to be used.

This is because within the range of deviation of about ±fo/Q, the drive current for obtaining the necessary deflection angle θ does not become that large. However, the drive frequency f is always constant.

As Q, an optical deflector 310 having a resonance sharpness of about 10 to 1000 can be used.

For this reason, the frequency of the sine wave oscillator 330 is set within a range that satisfies the above equation.

The output of the sine wave oscillator 330, that is, the drive signal, is supplied to the next stage offset adjuster 331, and its DC offset is adjusted.

When installing the deflector 300 in an optical scanning system, if the installation position is not as designed, adjust the DC level of drive No. 48 (1 point mg shown) as shown in FIG. This makes it possible to adjust the horizontal shake position.

For this reason, in the offset adjustment M unit 331, by adjusting the DC level, the image forming body
The scanning position in No. 1 is set to be a prescribed scanning position.

The scanning width of the offset-adjusted drive signal is adjusted by an amplitude adjuster 332.

As an example of this adjustment method, the method described in Japanese Patent Application No. 61-81296 already disclosed by the present applicant can be used.

This method is for adjusting the deflection angle of the optical deflector 310. In this case, by detecting the scanning width on the image forming body 11 and adjusting the amplitude of the amplitude adjuster 332 using the detection output, it is possible to always control the scanning width to a constant value.

The drive signal whose DC offset and amplitude have been adjusted is sent to the above-mentioned drive coil 311 via the output amplifier 333.
through resistor R.

The reason for using the resistor gR is as follows.

That is, in order to avoid heat generation while driving the drive coil 311, it is necessary to lower the total resistance r of the drive coil 311 and suppress the value of the drive current i flowing through it.

If such a relationship is selected, the drive coil 311
The voltage drop V across is v=ir.

Here, the DC offset and amplitude value are adjusted by adjusting the drive voltage value supplied to the drive coil 311, so in order to finely adjust the DC offset and amplitude value, this drive voltage V is adjusted. Must be fine-tuned. However, it is very difficult to adjust the drive voltage vt by a very small amount and set it to the required C offset and amplitude value. Furthermore, if it is necessary to set the C offset or amplitude value, a lot of time will be spent on the adjustment work.

Therefore, a dummy resistor R is connected in series with the drive coil 311 as shown in the figure. By doing this,
It is possible to increase only the drive voltage V (v=(r+R)·i) applied to the drive coil 311 while keeping the resistance value of the drive coil 311 as r and the drive current flowing through it as i.

Incidentally, when r==about 10Ω, R is selected to be about 990Ω.

In this way, a reasonably large drive voltage can be applied across the series circuit of the resistor R and the drive coil 311, so that the adjustment value of the drive voltage V for the necessary DC offset and amplitude value can be adjusted using the resistor. 100 more than without R
The degree becomes larger. Therefore, the DC offset and amplitude ′a
Easy to adjust.

Moreover, it has the advantage of being able to be adjusted accurately in a short time.

FIG. 15 shows the data on the characteristics of the laser recording device mentioned above. In this table, Type T refers to the maximum paper size of the recording paper up to A4 size, and Type 2 and is up to A3 size.

Since the recording paper size differs in this way, the recording speed and furthermore the resolution differs, so the driving frequency is also appropriately selected according to the difference in conditions.

Roughly speaking, when the recording paper sizes differ in this way, the deflection angle of the reflecting mirror also differs, so the deflection angle of the recording beam also differs accordingly.

Note that the shape of the reflecting mirror 312 is preferably elliptical.

By the way, an example of the developing devices 123 to 125 that can be used in the laser recording apparatus shown in FIG.
As shown in the figure. Since all of these basic configurations are almost the same, the configuration of one of them, for example, the developing device 123, will be explained.

In the figure, 421 indicates a housing, and a cylindrical sleeve 422 is rotatably housed within this housing 421. A magnetic roll 423 having 8 N and S poles is provided within the sleeve 422 . A layer regulating piece 424 is pressed against the outer peripheral surface of the sleeve 422 to regulate the layer thickness of the developer attached to the sleeve 422 to a predetermined thickness. The predetermined thickness refers to a predetermined value from 10 to 500 μm.

Inside the housing 421, first and second stirring members 425, 426 are provided. The developer reservoir in the developer reservoir 429 is moved by the first agitation member 42 that rotates counterclockwise.
5 and a second stirring member 426 that rotates in a direction opposite to that of the first stirring member 425 so as to overlap each other, and the stirred and mixed developer mixture rotates in opposite directions to each other. sleeve 422 and magnetic roll 42
The developer adheres to the surface of the sleeve 422 and is conveyed by the feeding force of the rotating part 3.

The electrostatic latent image formed on the image forming body 11 is developed in a non-contact manner by the developer deposited on the image forming body 11.

Note that during development, the development bias signal supplied from the power source 430 is completely applied to the sleeve 422. The developing bias signal can be supplied from the power supply 430, and this developing bias signal consists of a DC component selected to have approximately the same potential as the potential of the non-exposed portion of the image forming body 11, and an AC component superimposed thereon.

As a result, only the toner T in the developer on the sleeve 422 selectively migrates to the surface of the image forming member 11, which has been made into a latent image, and is deposited on the surface of the image forming member 11, thereby performing the development process. .

Note that 427 is a replenishment toner container, and 428 is a toner replenishment roller. 431 indicates a development area.

A two-component developer is used as the developer, and when no developing bias is applied, the image forming body 11 and the developer do not come into contact with each other. The T is caused to fly and is selectively attached to the electrostatic image on the image forming body 11 for development.

When using such a non-contact developing method, multicolor toner images consisting of a blue toner image, a red toner image, a black toner image, etc. are sequentially developed on the image forming body 11, and the previous toner image is It has the advantage that it will not be damaged during subsequent development and can realize thin layer development.

When using the above-mentioned two-component development as a developer, the thickness of the developer is 2000 μm.
m or less, preferably 100011 m or less, especially 10 to 5
This results in an unprecedentedly thin developer layer of 00 um, more preferably 10 to 400 um. In this case, development is performed with the gap between the image forming body 11 and the sleeve 422 made small.

Note that even if the bonding force between the developer carrier and the toner or the bonding force between the carrier and the sleeve 422 is weak, since the developer layer is extremely thin, the sleeve 422
It is attached strongly enough to the top. Therefore, toner scattering and the like do not occur.

By making the developer layer thinner and reducing the gap between the image forming body 11 and the sleeve 422, the oscillating electric field required to blow the toner can be reduced. As a result, the developing bias voltage can be lowered.

Therefore, in addition to reducing toner scattering from this point of view, there are also advantages such as controlling leakage discharge due to the developing bias from the sleeve surface.

Furthermore, when the gap between the image forming body 11 and the sleeve 422 is made small, the electric field strength formed in the developing area 431 (the spatial area where the image forming body 11 and the sleeve 422 face each other) due to the latent image increases, As a result, subtle changes in gradation and fine patterns can be developed better.

A thinner developer layer generally reduces the amount of toner transported to the development area and reduces the amount of development. An effective way to increase the conveyance amount is to rotate the sleeve at high speed.

However, when the linear velocity ratio between the image forming body 11 and the sleeve 422 becomes 1:10, the velocity component of the developed toner that is parallel to the latent image surface becomes large, and directionality appears in the development, resulting in poor image quality. to degrade.

For this reason, as the lower limit of the thin layer, it is necessary that the toner adheres to the sleeve surface at a density of at least 0.04 mg/cm2. In general, when the linear velocity of the sleeve 422 is Vs 1°, the linear velocity of the image forming member 110 is Vd, and the amount of toner in the thin layer on the sleeve 422 is Mt, l Vs l/Vd I ・Mt≧0.4 (
m87cm2) It is necessary to satisfy the condition of IVsl/Vdl≦10.

Considering the development efficiency, l Vs 1/Vd I ・ M ≧0
．． 5 (mg/crr+ 2)lVsl/Vdl≦
8 is preferable, and furthermore, from the experimental results, I Vs
l/Vd l ・Mt≧0.5 (m87cm2) lVs
It has been found that it is more preferable that L/Vdl≦5.

The ratio of toner to carrier in the developer at this time is preferably such that the ratio of the total surface area of toner to carrier in a unit volume is 0.5 to 2, as described above.

By setting the above conditions, the toner in the thin layer can be efficiently developed, the developability is stable, and good image quality can be obtained.

As a means for forming a thin developer layer, the sleeve 42 is used.
A layer regulating piece 424 made of a pressing plate that is lightly elastically pressed against the layer 2 is preferably used.

This layer regulating piece 424 is composed of an elastic plate that is pressed against the sleeve 422 so that its tip faces upstream of rotation of the sleeve. By allowing the developer to pass between the sleeve 422 and the layer regulating piece 424, a thin layer can be formed.

The gap between the tip of the layer regulating piece 424 and the sleeve 422 is set to 0.0.
When the length is 8 mm or more, a certain amount of toner can be stably conveyed despite variations in mounting precision and mechanical precision. Further, it is preferable to set the gap between the tips to 0.1 mm or more because stability will be increased.

Of course, it is not desirable to make the gap at the tip unnecessarily large, and it has been observed that when the rIR gap is increased to 5 mm or more, the uniformity of all the developer deteriorates.

Next, the thinned developer layer develops the electrostatic image on the image forming body 11 conveyed to the development area in a non-contact manner.
It has been found that the following conditional expressions (1) and (2) need to be satisfied in order to achieve preferable development.

l (vs 1-nωmh' /3)/Vd l≦1
0...(1) l (vs 1-nct+mh' /3) /
Vd I ・mt≧0.4 [mg/cm2]
(2) Here, Vsl is the linear velocity of the sleeve [mm/sec] n is the number of magnetic poles of the magnetic roll [poles] ωm is the rotational angular velocity of the magnetic roll [radfan/sec]
h' is the height of the magnetic brush [mm], Vd is the linear velocity of the image forming member [n+m/sec], and mm is the amount of toner deposited per unit area of the sleeve [mg/cm2].

V s l +0m is positive when it is in the same direction as the movement of the image forming body 11. Also, the height of the magnetic brush is
This refers to the average height of the magnetic brush on the sleeve that stands on top of the magnetic field inside the sleeve. Specifically, the linear velocity Vsl of the sleeve is: 100 to 1000 mn+/see The number of magnetic poles n is 4 to 16 The rotational angular velocity ωm of the magnetic roll is 30 to 150 radian/sec The high h' of the magnetic brush is 50 to 400 μm Image forming body 1
Linear velocity Vd of 1 is 30 to 500 mm/see Toner adhesion amount mt per unit area of sleeve is 30 to 500 mm/see
It is assumed to be 1011g/cm2.

These relationships serve as a guideline for achieving preferable development, but they vary depending on the distance d between the image forming body 11 and the sleeve 422, the magnitude of the bias voltage, and the like.

Preferred development conditions taking such factors into consideration are shown by the following formula.

5≦Vp-p/(d-h')≦50(KV/mm)・
...(3) Here, Vp-p is the peak-to-peak voltage of the AC bias (KV), d is the distance between the image forming body and the sleeve (μm), and h'' is the maximum height of the magnetic brush ( μm).

The maximum height of the magnetic brush refers to the maximum height of the magnetic brush that stands on the magnetic pole in the sleeve 422.

Incidentally, FIG. 17 illustrates the conditions of each part during development by non-contact jumping. FIG. 18 shows a specific example of the developer. FIG. 19 shows the developing bias conditions at that time.

In addition to the above-mentioned developing method, the developing device disclosed in Japanese Patent Application Laid-open No. 176069/1988, which was previously proposed by the applicant of the present invention, can also be applied to the image recording apparatus according to the present invention.

In the device disclosed in the above publication, the magnetic roll does not rotate and a fixed magnet is used, so the mechanism is simple.

By the way, when an optical deflector 310 as shown in FIG. 8 or 9 is used as the optical deflector of the deflector 300, reciprocating scanning is possible, unlike scanning using a rotating polygon mirror. When such reciprocating scanning is employed, the optical scanning system may have a configuration as shown in FIG. 20.

That is, by arranging the index sensors 39 and 45 in the front and rear directions of the scanning direction, it is possible to detect the start and end of laser beam scanning (since this is the return of the beam).
Since the start of scanning can be detected, corresponding image information can be recorded on the image forming body 11.

In addition, in FIG. 20, 44 indicates a reflecting mirror.

Although the image forming apparatus according to the present invention shown in FIG. 6 is applied to a tubular type color image recording apparatus, it can also be applied to a monochrome image recording apparatus.

FIG. 21 shows an example of this monochrome image recording apparatus.

The laser beam modulated by the black and white image signal enters the deflector 300 provided in the optical scanning system 510, is reflected by the mirror surface of the reflecting mirror 312, and then passes through the scanning lens 42, the cylindrical lens 36, and the mirror 4.
6, the periphery of the image forming body 11 is irradiated.

The image forming body 11 is an endless belt-shaped photoreceptor 520, and is rotated and conveyed counterclockwise on the upper surface of a conveyance table 524 by three photoreceptor support rollers 521, 522, and 523. During this rotational drive, since a predetermined charge is applied to the surface of the cutting tool by the charged transfer pole 525, an electrostatic latent image corresponding to the image information can be formed by the laser beam irradiation described above.

Toner is supplied to the electrostatic image by a developing roller 526 which also functions as a developing device, and the electrostatic image is turned into a toner image.

Thereafter, the recording paper is conveyed below the conveyor table 524, but on the other hand, one sheet of recording paper is carried into the destination apparatus by the operation of the paper feed roller 531 from the automatic paper feeder 530 attached to the apparatus in parallel. , its tip is detected by the sensor 541,
The second paper feed roller 540 starts rotating in response to the detection output, and roughly feeds the recording paper. Then, by the action of the sensor 542 that detects the leading edge again, the second paper feed slot-ra 5
40 is stopped, and after the timing with the toner image described above is adjusted, rotation is resumed to continue conveying the recording paper.

After the toner image of the photoreceptor 520 integrated with the recording paper is transferred to the recording paper at the charged transfer pole 525, the recording paper is separated and the entire surface is exposed to a laser beam to eliminate the charge. Thereafter, the adhesion force of the residual toner is weakened by the cleaning means 527, and then it is removed by the cleaning action of the developing roller 526.

The auxiliary cleaning means 527 is a brush device using insulating fibers, and is of a type that does not interfere with the charging of the electrostatic latent image formed in the preceding cycle.

In this way, the photoreceptor 520 is charged again at the charged transfer pole 525 and moves on to the next cycle of rotation and conveyance to form a new electrostatic latent image, but at the same time it receives a toner image transfer. The recording paper is placed on the photoreceptor support roller 52
1Iili! be done. Thereafter, after the toner is melted and fixed by the fixing roller 550, it is separated by the separation claw 551 and guided to the paper ejection roller 552, and the residual potential is removed by the static elimination brush 553, and the recording paper is formed on the upper surface of the optical scanning system 510. The paper is ejected onto the paper ejection surface that has been

Even in such a black and white laser recording device, the deflector 3
00 is used covered in a sealed container 340.

Then, the required amount of the above-mentioned inert gas can be filled with the inside of the sealed volume W340 being brought to a negative pressure.

[Effects of the Invention] As explained above, according to the present invention, the reflecting mirror 3
12 and a drive coil 311 are integrally molded.
10 is used to deflect an optical signal, this optical deflector 3
10 is covered with a sealed container 340, and the inside thereof is filled with an inert gas.

According to this configuration, the optical deflector 310 can be driven without being affected by surrounding airflow.
The deflection angle of the optical deflector 310 is stabilized, and recorded image distortion caused by fluctuations in the deflection angle can be eliminated.

Further, the optical deflector 310, especially the reflective surface of the reflective mirror 312, is not contaminated by toner etc. scattered from the drum, and the life of the optical deflector 310 can be extended.

If toner etc. scatters, the sealed container 3 will be contaminated.
40 itself, there is no particular problem since dirt on the sealed container 340 itself can be easily cleaned.

Since the optical deflector 310 is prevented from being oxidized by being filled with an inert gas, there is no need to apply gold plating to prevent oxidation or coat it with a protective film as in the conventional case.

As a result, these manufacturing steps can be completely eliminated, and the optical deflector 310 can be provided at a low cost by reducing the manufacturing steps and materials used.

Since the inside of the sealed chamber 1340 is under negative pressure, the moment of inertia of the optical deflector 310 is reduced, and its Q can be increased in appearance. Therefore, it is possible to efficiently drive the optical deflector 310 with a read clock.

Note that by using the optical deflector, it is possible to realize an image forming apparatus with much higher reliability and higher image quality than in the past. A comparison with the conventional device is as follows.

First, since the optical deflector itself is very small, it can be made smaller compared to the case where a rotating polygon mirror is used, and since a motor is not used as a rotational drive source, There is no noise, and even when scanning at high speed, stable deflection vibration can be achieved at all times.

Second, compared to a device using a mechanical vibrating mirror, not only high-speed scanning is possible, but also a compact deflector with a large deflection angle can be realized.

Thirdly, since the optical deflector is formed by etching or the like, it has high precision and there is no variation in the product.

Moreover, since the ligament part is also made of a material with a large elastic modulus, there is less metal fatigue like that of metal rods used in mechanical vibrating mirrors, and stable operation can be expected over a long period of time.

Fourth, since the optical deflector is integrally molded, a large deflection angle and a high natural frequency can be obtained, making it extremely suitable for use in devices that use a large recording paper size and perform higher speed recording.

Fifth, since the reflecting mirror surface of the optical deflector is not so large compared to the beam spot, the influence of light scattering on the reflecting surface is small. Furthermore, since the optical deflector is integrally molded, stable vibration of the mirror can be obtained even if the ambient temperature or environmental conditions change. Therefore, regular beam scanning can be performed.

Therefore, even during high-speed recording, a good final image can always be obtained.

For this reason, the image forming apparatus according to the present invention has the following features:
Its reliability is very high, and accordingly, a highly reliable recording device can be provided.

Therefore, as mentioned above, it is extremely suitable for application to a simple color copying machine or a laser recording device such as a laser printer.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing the relationship between the deflector and the sealed container, which are the main parts of this invention, Fig. 2 is a perspective view of the sealed container attached, Fig. 3 is its sectional view, and Fig. 4 is FIG. 5 is a perspective view showing another example of a sealed container, FIG. 5 is a configuration diagram of a core, and FIG. 6 is a main part showing an example in which the image forming apparatus according to the present invention is applied to a color image recording apparatus. The configuration diagram, Figure 7 shows the main parts of the optical system when using an optical deflector, Figures 8 and 9 show an example of the optical deflector, and Figure 10 shows the dot shape of the laser beam. FIG. 11 is an explanatory diagram of the shape of the reflecting mirror, FIG. 12 is a system diagram showing an example of a driving circuit for the reflecting mirror, and FIG. 13 is a diagram showing the resonance characteristics of the deflector.
Fig. 14 is an explanatory diagram of DC offset, Fig. 15 is a diagram showing a characteristic table such as development conditions of the laser recording device, Fig. 16 is a sectional view showing an example of a developing device, and Fig. 17 is a non-contact development condition. FIG. 18 is a diagram showing the composition of the developer, FIG. 19 is a diagram showing the developing bias conditions, FIG. 20 is an optical system diagram showing another example of FIG. 7, and FIG. 21 is a diagram showing the present invention. 22 is a configuration diagram showing an example of an optical system using a rotating polygon mirror, and FIG. 23 is an example of an optical system using a mechanical vibrating mirror. FIG. A... Original reading section B... Writing section 11... Drum 3o as an image forming body... Laser beam scanning device 31... Semiconductor lasers 123 to 125... Developing unit 300... Deflector 310... Optical deflector 311... Drive coil 312... Reflection mirror 313... Ligament 315... Frame 320... Optical deflector mounting portions 327A, 327B... Magnetic pole 327...・Magnetic field generating means 329...Coil 340...Hermetically sealed container 343...Window hole 344...Transparent plate Patent applicant Konishiroku Photo Industry Co., Ltd. Figure 3 Figure 7 Figure 9 Rabbit: Ranbijun 10 Fig. 10 A mouth Fig. 11 A OCD Fig. 12 Fig. 13 Fig. 14 Fig. 15 Fig. 16 Fig. 10: Fig. 17 Fig. 18 Fig. 19 Fig. 20 Fig. 22 Fig. Dan Q; Fixed ray 1' J to eel f

Claims (5)

[Claims] (1) In an image forming apparatus that writes the image signal onto a recording medium by deflecting and scanning the recording medium with an optical signal modulated by an image signal, as an optical deflector that deflects and scans the optical signal. , a reflecting mirror and a driving coil are integrally formed, the deflector including the optical deflector is housed in a sealed container, and the sealed container is filled with an inert gas. Features of the image forming device. (2) The image forming apparatus according to claim 1, wherein helium gas or neon gas is used as the inert gas. (3) The image forming apparatus according to Claims 1 and 2, wherein the sealed container is a sealed container in which a transparent window for transmitting polarized light is formed. (4) The image forming apparatus according to claim 1, wherein a transparent container is used as the sealed container. (5) The image forming apparatus according to any one of claims 1 to 3, wherein the optical deflector is made of a quartz substrate.