JP3472167B2 - Image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a printer.

[0002]

2. Description of the Related Art Recently, an image forming apparatus as a digital data information transmission by a data communication network and a hard output device of the information has been actively proposed. An image forming apparatus of this type includes a digital printer or a digital copying machine.

FIG. 20 shows a schematic configuration of a digital printer. The photoconductor (photosensitive drum) 1 has a photoconductive layer provided on a cylindrical conductive substrate, and is rotatably supported in the direction of arrow R1 in the figure. Then, around the photosensitive drum 1, a scoro-tocon charger (primary charger) that evenly charges the surface of the photosensitive drum 1 substantially in order along the rotation direction.
2. An original is read, the photosensitive drum 1 is exposed based on an image signal proportional to the density of an image, and an exposure device 3 that forms an electrostatic latent image, toner is attached to the electrostatic latent image and developed as a toner image. The developing device 7, the corona transfer charger (transfer charger) 8 that transfers the toner image formed on the photosensitive drum 1 onto the transfer paper P that is a transfer material, and the transfer paper P on which the toner image is transferred to the photosensitive drum 1 An electrostatic separation charging device (separation charging device) 9, a cleaning device 13 that removes residual toner on the photosensitive drum 1 after transferring a toner image, a pre-exposure lamp 30 that removes residual charge on the photosensitive drum 1, and the like. Are arranged. The transfer paper P on which the toner image is transferred is
After being separated from the photosensitive drum 1, it is conveyed to the fixing device 12, where the toner image on the surface is fixed, and a desired print image is formed and discharged to the outside of the image forming apparatus main body.

The reader section 18 irradiates the original 15 placed on the original glass table 14 with an illumination lamp 16 and reflects the reflected light into a photoelectric conversion element (1-line CCD) 19.
By forming an image on the top, it is converted into an electric signal corresponding to the image information. Here, the reflected light from the document 15 illuminated by the illumination lamp 16 is reflected by the mirrors 17a, 17b, 1
The photoelectric conversion element 19 is guided by the lens 17d after being guided to 7c.
Imaged above. The electric signal output from the photoelectric conversion element 19 is A / D converted by the A / D converter 21 to be 8-bit digital image data, and then the black signal generation circuit 22 uses the luminance information as density information. Is converted into image density data by the binarization circuit 23.

The 8-bit digital image data signal generated as described above is input to the laser drive circuit 24. The laser drive circuit 24 is a well-known PWM circuit, and according to the magnitude of the input image density signal, Semiconductor laser 20
Modulates the light emission time for n / off.

For example, as shown in FIG. 5, when image data for each pixel is input in the laser scanning direction as shown in (a), the drive signal for turning the laser on / off is as shown in (b). ing. That is, the on-duty of the laser drive signal when the image data is 00 hex is 5% of the 1-pixel scan time, the on-duty of the laser drive signal when the image data is FF hex is 85% of the 1-pixel scan time, and so on. In this way, shading is realized by making the area gradation within one pixel.

Further, FIG. 7 shows a general IL characteristic (driving current-light quantity characteristic) of the laser.
The drive currents used when off are Ion / Io, respectively.
Since it is ff, the laser drive current for the image signal of FIG. 5 is as shown in (c), and this is the current that the PWM circuit drives the laser.

This laser drive system is roughly classified into the above-mentioned PWM circuit and binary laser drive circuit. PW
The M circuit modulates the pulse width signal corresponding to the time during which the semiconductor laser emits light according to the magnitude of the input image density signal as described above, while the binarization circuit changes the pulse width signal according to the pixel size. It is converted into a two-stage signal of a specific on-light emission signal and an off signal, which is input to the laser drive circuit 24 to turn on / off the semiconductor laser element. As a typical binarization method, there is a method of generating a binarized signal by a method such as an error diffusion method or a dither method based on image data. It is constant regardless of. The difference is that a pixel having a low density emits a laser with a low probability, and a pixel having a high density emits a laser with a high probability.

As described above, the laser light emitted according to the image signal is raster-scanned and written on the photosensitive drum 1 via the polygon mirror scanner 28 and the mirror 17f which rotate at high speed, and a digital electrostatic latent image is stored as image information. Form.

Conventionally, as an electrophotographic method, US Pat. No. 2,297,961 and JP-B-42-23910 are known.
A large number of methods are known, as described in Japanese Patent Publication No. 43-24748 and Japanese Patent Publication No. 43-24748. In general,
An electric latent image is formed on a photosensitive drum, which is a recording medium using a photoelectric substance, by various means, and then the latent image is developed with a toner (developer), and the obtained toner image is formed as necessary. The toner image is transferred onto a transfer material such as paper, and the toner image is fixed on the transfer material by heating or solvent vapor to obtain a copied image.

Various developing methods are also known for visualizing an electric latent image by using a developer. For example,
The magnetic brush developing method described in U.S. Pat. No. 2,874,063, the powder cloud method described in U.S. Pat. No. 2,21,776, a fur brush developing method, a liquid developing method, etc. There is a way. Among these developing methods, a magnetic brush developing method using a two-component developer mainly composed of a toner and a carrier has been widely put into practical use. Of the two-component developer, that is, deterioration of the toner and fluctuation of the mixing ratio of the toner and the carrier.

In order to avoid such drawbacks, various developing methods using a one-component developer consisting of only toner have been proposed. According to this developing method, it is not necessary to control the mixing ratio of the toner to the carrier, which has the advantage of simplifying the apparatus.

In the above-mentioned one-component developing method, it is difficult to apply a charge to the toner because no carrier is used. Therefore, various methods for charging the toner have been studied.

For example, Japanese Patent Laid-Open Publication No. 50-4539 discloses that
A method of imparting an electrostatic charge by frictional charging with a toner carrier, and JP-A-54-2100 describe a method of providing a friction member and imparting an electrostatic charge by frictional charging with the friction member. ing. Further, a method of applying a voltage to the friction member, a method of charging the toner by a charging member such as corona charging, and the like have been devised.

There is also a method of adjusting the toner charge amount of the toner image on the photosensitive drum after development by a developer charge amount control charging device (hereinafter referred to as "post charging device") so that the transfer efficiency becomes high.

[0016]

In the conventional example described above, when the corona charging method is used as a method for uniformly charging the surface of the photosensitive drum 1, ozone generated by corona discharge and substances such as nitrates as discharge organisms are generated. When a film is formed on the photosensitive drum 1 and the film absorbs moisture in the air and absorbs moisture, the surface resistance of the photosensitive drum 1 decreases, and the charge of the electrostatic latent image after exposure including image information data is reduced. The image cannot be held completely and is turbulent in the surface direction, disturbing a part or the whole of image information, and as a phenomenon on the image, the image flows as if the water-based ink flows into water. Similarly, when a corona charger is also used for the post charger, it causes a similar image flow obstruction due to ozone. Transfer charger 8 and separation charger 9
The same is true for.

To solve this problem, a method of sucking and discharging ozone by sucking air from the inside of the shield case of each charger has been conventionally practiced. Also,
In the primary charger 2 that performs uniform charging, a method is adopted in which the air in the shield case is disturbed by a blowing fan from the side opposite to the suction direction to improve the discharge efficiency of ozone gas. However, the transfer charger 8 and the separation charger 9 are different from each other in that the transfer paper P passes through the discharge area of the charger.
Spraying is not suitable. However, since the specific gravity of ozone gas is larger than that of air, it is usually natural to provide an opening at the bottom of the charger from the transfer charger 8 and the separation charger 9 located below the direction of gravity of the photosensitive drum. Ozone can be prevented from dropping from the opening and adversely affecting the photosensitive drum 1.

On the other hand, since the post charger is located below the developing device 7 and above the transfer charger 8, the side surface of the shield case faces the photosensitive drum, like the primary charger 2. In many cases, the configuration is similar to that of the above, and ozone is likely to stay in the shield case. That is, the discharge of ozone gas due to the disturbance of the air in the shield case due to the spraying is effective, but the toner image after development is formed on the photosensitive drum 1 in the portion corresponding to the opening portion of the post charger, and the primary toner image is formed. When the toner is sprayed like the charger 2, the image on the photosensitive drum 1 is disturbed, or the toner on the photosensitive drum 1 is rolled up even if the image on the photosensitive drum 1 is not disturbed, and a transfer guide or a transfer in the transfer paper transport unit is performed. The area around the charging device is soiled by toner scattering, which causes problems such as smearing and transfer unevenness on the image. Therefore, the spraying method cannot be simply used. In other words, the only method for sucking ozone generated by the post charger is air suction by a suction fan.

However, as described above, the ozone gas discharge efficiency is poor only by suction, and since the post charger is installed at the position sandwiched between the developing device 7 and the transfer charger 8, a gap is formed in the periphery. However, the gas discharge becomes extremely small only by sucking air, the adverse effect on the photosensitive drum 1 cannot be prevented, and the image deletion cannot be suppressed.

In particular, when an a-Si photoconductor is used as the photosensitive drum 1 in a high humidity environment, ozone is often generated due to discharge over a long period of time. Object is photosensitive drum 1
Image sticking occurs on the initial image after the power of the image forming apparatus is turned on by adhering to the surface and absorbing moisture.

Further, when a laser or LED spot exposure writing is performed on the photosensitive drum 1 by digital data, this phenomenon of image flow becomes remarkable. Laser spot size is 600 dpi and spot diameter is 50
In the case of ˜70 μm, it becomes more conspicuous and image deletion occurs.

Further, as the developing method, in the electric field flying developing method using a one-component magnetic developer mainly utilizing the electric field developing phenomenon, and the jumping developing method, the disturbance of the electrostatic latent image on the photosensitive drum 1 is faithfully imaged as it is. It is easy to reproduce in a flow state, and particularly in a high humidity environment, the development efficiency is slightly reduced, so that there is a problem that the image deletion phenomenon becomes more visible.

The present invention has been made in view of the above-mentioned circumstances, and improves the discharge efficiency of ozone gas to prevent the image carrier from being adversely affected, suppresses image deletion, and has a high definition regardless of the environment. It is an object of the present invention to provide an image forming apparatus capable of forming a high-quality image without image quality defects such as image deletion.

[0024]

To achieve the above object, the present invention according to claim 1 provides an image carrier, a primary charger for uniformly charging the surface of the image carrier, and an image after charging. An exposure unit that exposes the surface of the carrier to form an electrostatic latent image, a developing device that adheres toner to the electrostatic latent image to develop it as a toner image, and a charge amount of the toner image on the image carrier are described. An image forming apparatus comprising: a developer charge amount control charging device for controlling; and a transfer device for transferring a toner image on the image carrier after the charge amount control to the inside of a shield case of the primary charging device. A first air flow path formed on the first air flow path, a first air flow jetting and blowing means arranged at one end of the first air flow path in the longitudinal direction, and a first air flow injection and blowing means arranged at the other end of the first air flow path. A first airflow generating means having a first airflow suction means, and the first airflow generating means.
First air flow generating means and the first air flow path
Transmission means, a second air channel formed inside the shield case of the developer charge amount control charger, and a second air channel disposed at one end of the second air channel in the longitudinal direction. Second airflow generating means having two airflow jetting and blowing means and a second airflow suction means arranged at the other end, and the second airflow generating means.
Second air flow generating means and the second air flow path
Of the air flow jetting and blowing amount and the air flow suction amount of the first air flow generating means and the second air flow generating means are controlled so as to be different according to the image forming process. e Bei control means, and said control means, said
The second air flow jetting and spraying means is provided for the image forming operation.
It stops before and emits a relatively small air flow during image forming operation.
Generated, and a relatively large air flow is generated after the image formation is completed.
It is characterized in that it is controlled as follows.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the water content detecting means for detecting the water content in the air, the first air flow generating means and the second air flow generating means. A control means for controlling the difference amount between the air flow injection and blowing amount and the air flow suction amount so as to be different according to the water amount detected by the water amount detecting means,
It is characterized by

According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the first and non-operating states after image formation are performed.
It is characterized by further comprising control means for controlling the operating time of the second air flow generating means in accordance with the amount of water detected by the water content detecting means.

The present invention according to claim 4 relates to claims 1, 2 and
Alternatively, in the image forming apparatus of No. 3, the difference amount of the air flow suction amount with respect to the air flow injection and blowing amount is during image formation in the first air flow generating means and the second air flow generating means, respectively, and the image formation end. The difference amount between the air flow suction amount and the air flow injection and blowing amount in each of the first air flow generating means and the second air flow generating means in the steps from the image formation to the end of the image formation, which is different later. It is characterized by comprising control means for controlling so that the increasing / decreasing direction of is in the opposite direction.

[0028]

The present invention according to claim 5 relates to claims 1, 2 and
The image forming apparatus of 3 or 4 is characterized by further comprising control means capable of independently controlling the first airflow generating means and the second airflow generating means.

The present invention according to claim 6 relates to claims 1, 2 and
In the image forming apparatus described in 3, 4, or 5 , as the image bearing member, a photosensitive drum in which a photoconductor for forming an electrostatic latent image is formed in a thin layer on a cylindrical conductive substrate is used, and as the exposing unit, It is characterized by having a minute point exposure means.

According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect , the minute point exposure means scans and exposes the laser beam capable of digital exposure for each pixel to electrostatically expose the image carrier. It is characterized by forming a latent image.

According to an eighth aspect of the present invention, in the image forming apparatus according to the sixth aspect , the fine dot exposure means drives and exposes a plurality of light emitting elements arranged in the main scanning direction to expose the image carrier. It is characterized in that an electrostatic latent image is formed on.

The present invention according to claim 9 relates to claims 6, 7 and
Alternatively, in the image forming apparatus of Item 8, the photosensitive drum uses an a-Si photosensitive member as the electrostatic latent image forming photoconductor.

The present invention according to claim 10 relates to claim 1,
The image forming apparatus of 2, 3, 4, 5, 6, 7, 8 or 9 is characterized in that it has means for converting into binary data based on multi-valued image data.

The present invention according to claim 11 relates to claim 1,
The image forming apparatus of 2, 3, 4, 5, 6, 7, 8, 9, or 10 includes density characteristic detecting means for detecting the gradation density reproduction characteristic in the image forming portion, and the density characteristic detecting means detects the density characteristic. It is characterized by further comprising a correction value creating means for calculating an intermediate density between the black image data level and the white image data level, and applying the calculated value as a target density to correct the image data.

The present invention according to claim 12 relates to claim 1,
The image forming apparatus of 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11 is characterized in that the developing device uses a one-component developer.

[Operation] With the above-mentioned structure, the discharge efficiency of ozone gas is remarkably improved, the image carrier is prevented from being adversely affected, and the image deletion can be suppressed. It is possible to form a high-quality image without image quality defects such as flow.

Further, when laser or LED spot exposure writing by digital data is performed on the image carrier,
Image deletion can be prevented even when the laser spot size is 600 dpi and the spot diameter is 50 to 70 μm.

Further, as the developing system, the image flow phenomenon does not occur even in the electric field flight developing method and the jumping developing method which use a one-component magnetic developer mainly utilizing the electric field developing phenomenon, and the image deletion phenomenon does not occur on the final image. A high quality image can be formed.

[0040]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment> FIG. 1 shows an example of an image forming apparatus according to the present invention. The image forming apparatus shown in FIG.
FIG. 1 is a laser beam printer (hereinafter referred to as “image forming apparatus”), and FIG. 1 is a vertical cross-sectional view showing its schematic configuration.

The image forming apparatus shown in the figure includes a drum type electrophotographic photosensitive member (hereinafter referred to as "photosensitive drum") 1 as an image bearing member. The photosensitive drum 1 is provided with a photoconductive layer (electrostatic latent image forming photoconductor) on a cylindrical conductive substrate, and is rotatably supported in the direction of arrow R1 in the figure. Then, around the photosensitive drum 1, a scoro-tocon charger (primary charger) 2 for uniformly charging the surface of the photosensitive drum 1 in order along the rotation direction, a document is read, and an image signal proportional to the image density is obtained. The photosensitive drum 1 is exposed to light to form an electrostatic latent image (micropoint exposure means) 3, a developing device 7 for adhering toner to the electrostatic latent image to develop it as a toner image, and a photosensitive material after development. A developer charge amount control charging device (hereinafter referred to as “post charging device”) 62 for adjusting the charge amount of the toner image of the toner image on the drum 1 so as to increase the transfer efficiency is arranged. In addition, a transfer system is provided that transfers the transfer paper (transfer material) P by the paper supply unit 109a and transfers the transfer paper P through the paper supply path P1 to the transfer unit. Then, a corona transfer charger (transfer charger) 8 as a transfer device that transfers the toner image formed on the photosensitive drum 1 onto the transfer paper P, and the transfer paper P on which the toner image is transferred is separated from the photosensitive drum 1. Electrostatic separation charger (separation charger)
9. A cleaning device 13 for removing the residual toner remaining on the photosensitive drum 1 after the transfer of the toner image, a pre-exposure lamp 30 for removing the residual charge of the photosensitive drum 1, and the like are arranged. The transfer paper P on which the toner image is transferred is
After being separated from the photosensitive drum 1, it is conveyed to a fixing device 12, where the toner image on the surface is fixed, a desired print image is formed, and the toner image is discharged to the outside of the image forming apparatus main body 101. 105 in FIG. 1 is an interface section,
Reference numeral 106 is a computer.

The reader section 18 irradiates the original 15 placed on the original glass table 14 with light from the illumination lamp 16 and reflects the reflected light into a photoelectric conversion element (1-line CCD) 19.
By forming an image on the top, it is converted into an electric signal corresponding to the image information. Here, the reflected light from the document 15 illuminated by the illumination lamp 16 is reflected by the mirrors 17a, 17b, 1
The photoelectric conversion element 19 is guided by the lens 17d after being guided to 7c.
Imaged above. The electric signal output by the photoelectric conversion element 19 is A / D converted by the A / D converter 21 to obtain 8-bit digital image data, and thereafter,
The black signal generation circuit 22 performs log conversion to convert the luminance information into the density information and obtains the image density data.

The image density data (8
(bit digital image data signal) is converted into a two-stage signal of an on emission time of a specific on time according to the pixel size and an off signal via the binarization circuit 23, input to the laser drive circuit 24, and converted into a drive current. After the dot reproducibility correction is added, the semiconductor laser is turned on / off at the drive signal timing binarized by the error diffusion method according to the magnitude of the input image density signal.

In the present embodiment, the binarization circuit 23 is realized by the error diffusion method, but of course, the dither method may be used, or another method may be used. Alternatively, the semiconductor laser on / off light emission time may be modulated according to the magnitude of the image density signal input after the laser drive circuit 24 is subjected to dot reproducibility correction to the drive current by a well-known PWM circuit.

For example, the laser lighting of the binary image data will be briefly described as shown in FIG. 6. When the image data for each pixel is input in the laser scanning direction as shown in (a), the laser is turned on. The drive current for turning off / off is as shown in (b), and the light is turned on for a certain time with a constant drive current regardless of the image data. And the exposure density in the plurality of pixel regions is modulated. That is, the number of times the laser drive signal is turned on when the image data is 00 hex is set to 0% of the lighting pixel ratio in the total number of pixels in a specific plural pixel area, and the number of times the laser drive signal is turned on when FF hex is For example, the lighting pixel ratio to the total number of pixels in a specific plural pixel area is 100%. However, even if the lamp pixel ratio is 0%, a constant drive current flows as a bias current, and slight light emission is performed. In this way, shading is realized by making area gradation within a specific plural pixel region.

Further, as shown in FIG. 5, in the PWM method, when the image data for each pixel is input in the laser scanning direction as shown in (a), the drive signal for turning the laser on / off is (b). It looks like. That is, the on-duty of the laser drive signal when the image data is 00 hex is 5% of the 1-pixel scan time, the on-duty of the laser drive signal when the image data is FF hex is 85% of the 1-pixel scan time, and so on. In this way, shading is realized by making area gradation within one pixel.

Further, FIG. 7 shows a general IL characteristic (driving current-light quantity characteristic) of the laser.
The drive currents used when off are Ion / Io, respectively.
Since it is ff, the laser drive currents for the image signals of FIGS. 6 and 5 are as shown in (b) and (c), respectively, which are the binarization circuit 23, the PWM circuit (not shown), and the laser shown in FIG. It is a current for driving the laser 20 via the drive circuit 24. At this time, Ioff is not 0 mA,
By setting it to be slightly smaller than Threshold,
It is known that the rise of the light amount when the laser is on is improved.

Here, as the laser, a visible light laser of 680 nm is used.

As described above, the laser light emitted according to the image signal is raster-scanned and written on the photosensitive drum 1 through the polygon mirror scanner 28 and the mirror 17f which rotate at high speed, and a digital electrostatic latent image is recorded as image information. Form.

In this embodiment, an amorphous silicon drum is used as the photosensitive drum 1. Amorphous silicon drum has high stability of characteristics and high durability on the conductive substrate.
It has a long life. The a-Si photoconductor, which has a long life, high speed output, and is surface-curing SiC-curing type, and has a high photosensitivity in the photosensitive layer, has a high charge retention ability and there is almost no scattering of irradiation light by the surface layer. Since the minute electrostatic latent image in the minute spot exposed portion is held without electric charge diffusion, a minute latent image such as 600 dpi or 1200 dpi is faithfully formed and a high definition latent image is formed.

FIGS. 3A to 3C show steps for explaining the image forming process of the present embodiment, and schematically show the relationship between the surface potential of the photosensitive member and the developing bias in each figure. There is.

In (a), the photoconductor is charged with a corona charger +
It is uniformly charged to 420V.

In (b), the image information is exposed and the surface potential of the image information exposed portion is attenuated to +50 V to form an electrostatic latent image. Since the image exposure is a pulse-width-modulated light amount as described above, the actual photosensitive drum potential after exposure is, in principle, only the potential of the laser off portion and the potential of the laser on portion. In a general non-contact surface electrometer, which measures the integrated potential in a sufficiently wide area with respect to the spot diameter of, the potential is apparently measured as a halftone potential. That is, even in the non-image portion (image data 00hex) of the image area, since the slight exposure is performed as described above, the surface potential is attenuated to +400 V, and the image portion of one image area (image data FFhex) At, the surface potential is attenuated to +50 V to form an electrostatic latent image.

Next, in (c), a developing bias voltage (eg AC AC to DC DC +3 is applied to the sleeve of the developing device).
00V superimposed etc. The DC component is shown by a broken line. )
Is applied to reversely develop the exposed portion. Here, the developing device uses a known one-component magnetic toner to perform the development without contacting the photoconductor.

The air flow blowing and suction methods for preventing image deletion by the post charger, which is a feature of the present invention, will be described in detail below.

In the image forming apparatus shown in FIG. 1, the transfer paper P is fed by the paper feed unit 109a and is conveyed to the transfer charger 8 through the paper feed path P1 as a condition particularly effective in the present invention. The relationship between the blowing and suction fans of the primary charger 2 and the post charger 62 of the image forming apparatus will be described.

First, the fan of the post charger 62 will be described with reference to FIG. Here, the connection duct (second transmission means) 61 is directly connected to the post charger 62, and the blowing fan 60 is further connected.

The blowing fan (second air flow jetting and blowing means) 60 is provided with the developing device 7 and the transfer paper conveying section 63a.
The airflow is sprayed from the front side in the longitudinal direction between the surface and 63b. The blowing airflow from the blowing fan 60 flows from the front side to the rear side in the longitudinal direction through the first air flow path in the shield case of the post charger 62 and the connecting duct 61, and the accumulated ozone in the shield case is removed. It is disturbed and rolled up with the air, and is easily discharged by the suction airflow from the back side.

A side view of the connecting duct 61 in FIG. 2 (X
FIG. 22 (a) shows a top view (a view taken along line Y) of FIG.
It shows in (b). In FIGS. 22A and 22B, the blower fan 60 on the front side sends out the airflow toward the connecting duct 61 via the electrostatic filter 68 for dust protection. The airflow is guided to the duct 61a provided on the back side of the post charger 62 with respect to the photosensitive drum 1, and also flows toward the photosensitive drum by the wind direction fins 61b therein. After that, the opening 61c on the back side of the duct 61a is turned toward the back.
Through the opening 70 of the supporting sheet metal 70 on the back side of the image forming apparatus.
a suction fan on the back side through a (second air flow suction means)
A duct (second transmission means) 71 for guiding an airflow to 67
Then, it passes through the suction fan 67 and the ozone filter 69, and is discharged to the outside of the image forming apparatus.

The fans of the post charger 62 are wired with a power source 65 capable of independently supplying power and a controller 66 capable of independently controlling each fan.
The control device 66 is electrically wired with a signal from a circuit for controlling the entire image forming apparatus via the image data correction device 50 (see FIGS. 1 and 2).

On the side of the post charger 62, the blowing fan 60 and the suction fan 67 form a second air flow generating means.

Next, the primary charger 2 has the same structure, and only the arrangement and function around the photosensitive drum are different. In FIG. 2, a connecting duct (first transmitting means) 2a is directly connected to the primary charger 2, and a blowing fan (first airflow jetting and blowing means) 2b is further connected thereto. Although the fan configuration of the primary charger 2 is not shown, the numbers of the components of the parts corresponding to the primary charger 2 are attached to FIGS. 22 (a) and 22 (b). The blowing fan 2b on the front side sends out an air flow in the direction of the connecting duct 2a via the electrostatic filter 2c for dust prevention. Air flow is primary charger 2
Is guided to a duct 2d installed on the rear shield side on the side far from the photosensitive drum 1, and also flows toward the photosensitive drum by a wind direction fin 2h therein. After that, the air flows toward the back side through the back side opening 2i of the duct 2d, passes through the back side support sheet metal 70 opening of the image forming apparatus, and the air flow to the back side suction fan (first air flow suction means) 2e. It enters into a duct (first transmission means) 2g for guiding, passes through the suction fan 2e and the ozone filter 2f, and is discharged to the outside of the image forming apparatus.

The fan of the primary charger 2 is also wired with a power source 65 capable of independently supplying electric power and a control device 66 capable of independently controlling each fan. The control device 66 is the entire image forming apparatus. A signal from a circuit for controlling is electrically wired through the image data correction device 50.

On the primary charger 2 side, the blowing fan 2b and the suction fan 2e constitute a first air flow generating means.

FIG. 23 shows the sequence of the operation of the image forming apparatus and the operations of the primary charging, the post charging and the post spraying fan 60 and the primary spraying fan 2b. When the power of the image forming apparatus is turned on, the heater of the fixing device is warmed up. Once started, the pre-multi-rotation starts when the temperature reaches the specified temperature. In the previous multi-rotation, charging is performed by potential control, so
The primary charger 2 and the post charger 62 also operate. But,
The blowing fans 60, 2b do not operate for a short time such that excessive ozone generation or temperature rise does not occur. However, the charging current in the primary charger 2 is larger than that in the post charger 62,
Here, half speed (fan input voltage is 1/2 of rated input voltage
Is a half speed fan operation, which halves the fan air volume. ) (Which will be described later, but at this time, the post-charging suction fan 67 and the primary-charging suction fan 2e described in FIG. 22 are operated). At the start of copying, the primary charging blowing fan 2b operates at full speed. The post-charging blowing fan 60 is not operating here in order to prevent the toner image on the photosensitive drum 1 from being disturbed by the air flow or from scattering the toner.

When the post-processing c after the image formation is completed, the post-charging blowing fan 60 operates at full speed, disturbs the ozone in the shield case of the post-charging device 62, winds it up, and sends it out to the back side intake / exhaust port all at once, and then outside the machine. To discharge. The operation is continued within an arbitrary post-processing time c, and heat and ozone are rapidly discharged at once, and the operation is stopped when a certain time has elapsed. The primary-charged blowing fan 2b reduces its operation to a half-speed operation within the post-processing time c to reduce the generation of noise due to the operating noise of the fan.

The wind speed of the half-speed operation here is 0.1 to 1 m /
Seconds. Also, the wind speed in full speed operation here is 0.2
~ 2.0 m / sec.

FIG. 24 shows the most characteristic configuration of the present invention. It shows the difference between the post-charging and the primary charging of the difference amount between the air flow injection and blowing amount and the air flow suction amount, and is a difference amount controlling method between blowing and suction according to the image forming process for each charger. .

The suction fans 2e and 67 both rotate at a half speed at the pre-multi revolution for both the primary charging and the post charging, and at the full speed at the copy start. Normally, in the image forming apparatus, the suction fan for exhausting ozone gas around the photosensitive drum is also used, and the primary charging and the post charging are commonly used here.

The difference amount of (spraying)-(suction) depending on the image forming process when the maximum difference is 100 and the minimum difference is 0 will be described below.

In post-charging, when the power is on, the fan is blowing and both suctions are stopped, and the difference is 0. The pre-multi-rotation starts, post-charging is performed, and only the suction fan 67 operates and the difference is -50. Becomes

Next, when copying is started, the blowing fan 60 is in a stopped state (A) so as not to disturb the image or scatter the toner. Since the photosensitive drum 1 rotates during copying, the air flow swirls around the photosensitive drum and is already in a state where it easily diffuses to the outside. Therefore, by sucking more heat, the heat swirls and the suction fan 67 It is caught in the air flow of and is guided to the outside of the aircraft. The difference at this time is set to −100 (A ₁ ). Here, it is more effective to increase the suction to a difference of about -70.

Next, when the copy image formation is completed,
Since the rotation of the photosensitive drum 1 is stopped and the spiral state of the air flow due to the rotation of the photosensitive drum is reduced, the exhaust efficiency is reduced.
However, the suction fan 67 is switched to a half speed operation to reduce fan noise after image formation (D). In order to compensate for the two reductions in efficiency, the blowing fan 60 is set to full speed to violently disturb the air flow in the post charger 62 to generate swirls. In order to make the generation of the swirl more efficient, the above difference is reversed from that during copying, and the blowing is strengthened to +50 (D ₁ ). After exhausting air for a certain time in this state, both fans stop at the same time. For the post-charged fan, a cross flow fan or an axial flow fan, which has a large air volume with respect to the rotation speed of the fan blades, is suitable so that the noise does not increase even after the image formation even at full speed operation.

On the other hand, in the primary charger 2, as shown in FIG. 24 (b), the blowing fan 2b and the suction fan 2e are basically operating at the same rotational speed, so that the difference (spraying / suctioning) is completely reduced. It is ± 0 throughout the process. In particular, the blowing and the suction after the image formation are performed at a half speed in both the fans for the primary charger because the air volume is large and the noise is large (D ₂ and D ₃ ).

In other words, the primary charger fan system and the post charger fan system require independent power supply systems and command types, which the controller (fan control circuit) 66 and the power source (fan drive power source) 65 need. It has a multi-purpose command system and multi-purpose power supply system and is realized.

The difference between spraying and suction of the post charger 62 and the phenomenon in each image forming step will be described below. Difference (Spray-Suction) Before Multi-rotation During copying After copying +100 Toner scattering, HH flow Image disturbance, toner scattering good +50 Toner scattering Image disturbance, toner scattering good ± 0 Toner scattering small amount Toner scattering small amount −50 Good good toner scattering Small amount -100 Good Good Toner scattering Small amount Next, in a high humidity environment that is the most severe against image flow (such as an environment where the water content per cubic meter unit volume is 9 g / m ³ or more), the fan operation that emphasizes ozone gas emission efficiency Make it a sequence.

In FIGS. 24 (a) and 24 (b), when the amount of water calculated by the temperature / humidity detected by a temperature / humidity detection sensor (water amount detection means) (not shown) is 9 g or more, copying is started after the start of copying. In order to increase the ozone discharge capacity of the above, the air volume of the post-charging blowing fan 60 is set to the 1/4 speed as shown in (C) of the figure, and when the amount of water is 16 g or more, the half speed (1 (2nd speed). However, do not raise the air volume that disturbs the image on the photosensitive drum. The difference between the blowing and the suction at this time is −75 of (C ₁ ) or −50 of (B ₁ ).

Further, when the water content is 9 g or more, the priority of noise reduction is lowered and the prevention of image flow is emphasized, and the fan wind speed of the post-charging suction fan 67 after image formation is preferentially set to the full speed (E). The difference between the suction and the blowing suction is increased to 0 to enhance the discharge efficiency on the suction side. Similarly, in the primary charger 2, the blowing fan 2b and the suction fan 2e after image formation are operated at full speed (E
₂ ) and (E ₃ ). However, the difference between spraying and suction remains 0 as in the normal environment.

Further, when the water content is 9 g or more, FIG.
4 fan operation after image formation is extended (F, F ₁ , F ₂ ,
F ₃ and F ₄ ) to more reliably discharge the ozone gas from the shield case of the post charger 62 and the shield case of the primary charger 2.

Needless to say, the sequences described above can be combined and selected according to the specifications of the image forming apparatus.

As described above, the high humidity environment (the water content per cubic meter unit volume is 9
In an environment of g / m ³ or more), a fan operation sequence that emphasizes ozone gas discharge efficiency makes it possible to obtain a good image regardless of the environment.

The method of correcting unevenness in the main scanning direction when density unevenness occurs in the developing device 7 and other parts will be described in detail below.

FIG. 8 is a schematic diagram of a factor analysis of the cause of density unevenness in the main scanning direction. The vertical axis represents the surface potential on the photosensitive drum, and the horizontal axis represents an arbitrary position in the main scanning direction.

(A) shows potentials at a place where the charging potential is normally obtained at the target potential 400V and at a place smaller than the target potential. This is because the charging ability characteristic of the photosensitive drum 1 is different from the characteristic of the surface potential obtained on the photosensitive drum 1 with respect to the current applied to the corona wire of the primary charger 2 as shown by the three types of characteristic curves in FIG. It is the surface potential unevenness that occurs. Even if the charging ability characteristics of the photosensitive drum 1 are uniform, if the charging ability of the primary charger 2 is not uniform depending on the position in the main scanning direction, uneven surface potential occurs.

FIG. 8B shows the potentials at the place where the target potential 50V of the exposed portion is normally obtained and the place where the surface potential is higher than the target potential, although the surface potential formation by charging is performed uniformly. There is. This is the surface potential unevenness that occurs due to the different photosensitivity characteristics of the photosensitive drum 1 as shown by the three types of characteristic curves in FIG. Even if the photosensitivity characteristic of the photosensitive drum 1 is uniform, if the light irradiation amount is not uniform depending on the position in the main scanning direction, uneven surface potential occurs.

In FIG. 8C, although the surface potential formation by charging and the surface potential formation by the potential attenuation by exposure were performed uniformly, the potential and the potential at the exposed portion were normally 50 V. Also shows a small place. This is Figure 1
As shown in the three types of characteristic curves of No. 1, the surface potential of the photosensitive drum 1 and the application D to the developing sleeve carrying and carrying the developer D
This is density unevenness that occurs because the developing ability with respect to the developing contrast, which is the difference in C voltage, is different. This density unevenness occurs when the charging characteristic is non-uniform in the main scanning direction, or when the gap between the photosensitive drum 1 and the developing sleeve is non-uniform depending on the position in the main scanning direction.

Further, there is density unevenness due to non-uniformity of transfer efficiency at the time of transfer or separation (not shown) in the main scanning direction.

Here, all the above-mentioned factors causing unevenness are comprehensively detected from the output printout image and corrected.

FIG. 13 is a flow chart showing the outline of the flow of the correction operation.

Step (S1) The image forming apparatus of this embodiment has an "improving image mode" as an image unevenness improving mode in the input interface, and first starts that mode.

Step (S2) Next, an axial direction unevenness (main scanning direction unevenness) correction mode is selected.

Step (S3) Start the axial unevenness correction mode. Press the key to start.

Step (S4) The image forming apparatus outputs a test image sample as shown in FIG. The conditions for forming this sample are:
In order to form an image of completely solid black, halftone halftone, solid white, or the like, three types of image exposure conditions are obtained by the primary charging conditions for forming the surface potential as described above (F0, 80 in FIG. 12 with an 8-bit signal). , 00 hex), develop, transfer, and fix under the above-mentioned developing conditions, output a sample, and detect the tone density reproduction characteristic by the density characteristic detecting means (not shown).

Step (S5) The output sample is placed on the document table by the mode executor at a specific position such that the leading end and the front or rear side of the sample in the sheet passing direction are completed by the document recognition means (not shown). Judge whether or not is detected.

Step (S6) When it is determined that the placement is completed, the document is read by the reader as described above. 400-60 reading by this reader
It is desirable to read at a resolution of about 0 dpi.

Step (S7) Whether the original is a test image sample or not is determined based on whether the density gradations are the same pattern. If it is determined that it is not the test image sample, an error is notified in step S11, and this processing ends. In this case, step S
You may return to 5 processing.

Step (S8) When it is determined that the image is a test image sample, the axial density distribution is calculated as shown in FIG. 14 (b). When the test image sample is formed at the PWM level of F0, 80, 00 hex, the read density distribution of the halftone part of 80 hex where the unevenness is most easily detected is calculated (F0, 8
The density distribution may be calculated at 0:00 hex. ).

Step (S9) When the target density is set to 0.5 in FIG. 14 (b), the increase / decrease in the read density distribution of the halftone portion with respect to 0.5 is made to correspond to each pixel in the main scanning direction. Calculate to. If the negative correction is represented by a negative sign and the positive correction is represented by a positive sign, the required correction density is as shown in FIG.
It is a diagram of the required correction density as if the polarity was reversed.

Step (S10) The correction light amount (correction level) for each pixel of the dot exposure laser is obtained from the diagram of the required correction density with reference to FIG. As an example, in FIG. 15, when the required correction density is +0.8, the surface potential is −200 V, the photosensitive drum surface light amount is +0.25 μJ,
This indicates that the image data needs to be corrected by +80 hex. A correction amount level corresponding to each pixel in the main scanning direction is assigned by this capacity, and a correction table is created. Here, this mode ends, and the operation panel, which is the input interface unit of the image forming apparatus, returns to the normal copy or print mode.

In this way, when the correction amount corresponding to each pixel position in the main scanning direction is determined, it is stored in the correction table in the main scanning unevenness correction circuit 50 (see FIGS. 1 and 2) as the correction value creating means. It will be.

FIG. 21 shows a concrete circuit configuration of the main scanning unevenness correction circuit 50 in the present embodiment.

The illustrated correction table 101 and adder 10
4, the selector 102, and the address generation circuit 103 form a main scanning unevenness correction circuit 50. CPU100
Is a control unit that controls the entire apparatus, and has a control program as a copying machine, a ROM storing the program according to the flowchart of FIG. 13 described above, and a work area as a work area. It has a RAM to use.

In the configuration shown, the correction table 101
Has a capacity of at least the number of pixels in the main scanning direction (9 bits per pixel, 1 bit of which is plus or minus sign bit). Then, the correction data of each pixel generated based on the image data obtained by reading the test image sample as described above is written in the corresponding address position of this correction table (which is configured by the RAM). Therefore, the CPU 100 outputs a signal for supplying the address from the CPU 100 to the correction table 101 to the selector 102, and outputs the address, the data to be written, and the write signal to the correction table 101. When the writing of the correction data for all the pixel positions in the main scanning direction is completed in this way, a signal for selecting an address from the address generation circuit 103 is output to the selector 102, and a read signal is output.

The address generation circuit 103 includes the photosensitive drum 1
A beam detect signal provided in the vicinity of is used as a trigger, and when a predetermined time comes, the correction table 1 is synchronized with the carrier clock of the image data from the black signal generation circuit 22.
Address signals are sequentially output to 01. As a result, the correction table 101 outputs the correction signal in synchronization with the image data (pixel data) from the black signal generation circuit 22. The adder 104 adds the data from the correction table 101 to the image data from the black signal generation circuit 22, and outputs the result to the binarization circuit 23. Since the correction table stores the positive and negative correction data as described above, the adder 104 binarizes the image data obtained by correcting the characteristics of the image data according to the characteristics of the printer engine. It will be output to the circuit 23.

Before and after explanation, the test image sample is formed by the CPU 100 by setting 00 for each predetermined number of main scanning lines.
The data of hex, 80 hex, and f0 hex are output instead of the black signal generation circuit 22. However, since it is a test image formation for knowing the characteristics of the printer engine, no data is output from the correction table 101, or 0 data is always output. In some cases, when forming a test image sample, the correction table 101 may include 00, 80 hex, and f0he
It is also possible to write x at an appropriate timing and output it. At this time, if the image reading is not performed, the data of 0 is output from the black signal generation circuit 22, so that the test image sample shown above can be formed as a result. The advantage in this case is that a test image sample can be formed only with the configuration of FIG.

Since the correction table 101 described above is used to correct data such as image unevenness at the 8-bit multi-valued signal stage, uniform data is formed at the time of binarization, and at the time of laser writing. In this case, the density unevenness is completely corrected, and it is possible to always provide a high-quality image having no density unevenness in the longitudinal direction (main scanning direction). In particular, according to the present embodiment, it becomes possible to suppress uneven density in a relatively low density portion (highlight portion).

When applied to a device for forming an image by the PWM method, the output of the adder 104 is D / A converted and compared with the triangular wave from the triangular wave generating circuit, as shown in FIG. , A signal having a pulse width depending on the concentration may be generated and supplied to the laser drive circuit 24. The reason why the pulse width signal is generated even when the density is 0 is as described above. The laser drive circuit 24 is driven so as to generate laser light for a time period depending on the pulse width of the pulse width modulation signal.

As described above, the primary charging blowing fan 2b and the suction fan 2e, the post-charging blowing fan 60, and the suction fan 67 are independently controlled to control the difference balance between the blowing fan and the suction fan. By correcting the density unevenness at the laser writing level using the correction table, it is possible to always provide a high-quality image having no density unevenness in the longitudinal direction (main scanning direction).

<Second Embodiment> FIG. 16 shows a second embodiment of the image forming apparatus according to the present invention. The figure is a vertical cross-sectional view showing a schematic configuration of the image forming apparatus.

The photosensitive drum 1 has a photoconductive layer provided on a cylindrical conductive substrate, and is rotatably supported in the direction of arrow R1 in the figure. Then, around the photosensitive drum 1, a primary charging device (first scorotocon charging device) that charges the surface of the photosensitive drum 1 uniformly along the rotation direction thereof.
2. A first exposure device 3, which reads a document, exposes the photosensitive drum 1 based on a first image signal proportional to the density of one color image separated into two colors, and forms a first electrostatic latent image, A first developing device 4 for forming a first image by attaching toner to the first electrostatic latent image, and a recharging device (second scorotron charger) for charging the photosensitive drum 1 after carrying the first image. )
5. Second exposure for forming a second electrostatic latent image by performing exposure of an amount obtained by adding a certain exposure amount to the exposure amount based on the second image signal proportional to the density of the separated other color image Device 6,
A second developing device 7 for forming a second image by attaching toner to the second electrostatic latent image, a pre-transfer charger 62 for charging the color superposed image formed on the photosensitive drum 1 before transfer, a transfer Corona transfer charger (transfer charger) 8 for transferring onto the transfer paper P, which is a material, and the transfer paper P on which the color superposed image is transferred, on the photosensitive drum 1.
From the electrostatic separation charger (separation charger) 9, a cleaning device 13 for removing the residual toner remaining on the photosensitive drum 1 after transferring the color superposed image, a pre-exposure lamp for removing the residual charge on the photosensitive drum 1. 30 and the like are arranged.
Further, the transfer paper P on which the color superposed image is transferred is the photosensitive drum 1
After being separated from the sheet, it is conveyed to the fixing device 12, where the toner image on the surface is fixed, a desired print image is formed, and the sheet is discharged to the outside of the image forming apparatus main body.

Here, the connection duct 61 is directly connected to the pre-transfer charger 62, and the blowing fan 60 is further connected.

Further, the image scanner section 18 illuminates the original 15 placed on the original glass table 14 with the illumination lamp 1.
6 scans and reads, and the photoelectric conversion element 19 converts image information into an electric signal.
The reflected light from the document 15 scanned by the
The light is guided to a, 17b, and 17c, and is imaged by the lens 17d on the photoelectric conversion element 19 including the red, green, and blue filters. The electric signals from which the red, green, and blue components have been output by the photoelectric conversion element 19 are digitized by the A / D converter 21, and then sent to the signal processing unit 22 as a color separation unit to red and black. Is converted into an image signal proportional to the image density of each component.

Here, the axial direction (main scanning direction) unevenness correction table 50 corrects the image data for each pixel (see 50 in FIG. 18).

The red image signal (first image signal) and the black image signal (second image signal) are sent to the laser drivers 24b and 24a as a signal generator, and the red and black image signals are sent. Lasers 20b, 20
The light emission of a is turned on / off. The laser light emitted in response to the red signal is the polygon mirror 2 as the first image information.
8. Write the first electrostatic latent image on the photosensitive drum 1 via the mirror 17e. The laser light emitted in an amount corresponding to the black signal writes the second electrostatic latent image on the photosensitive drum 1 as the second image information via the polygon mirror 28 and the mirrors 17f and 17g.

In this embodiment, an amorphous silicon drum is used as the photosensitive drum 1. Amorphous silicon drums have the characteristics of high durability and long life.

FIG. 17 illustrates the image forming process in the two-color image forming mode of the present embodiment.
(F) shows each process, and the surface potential of the photosensitive drum 1 is schematically shown in each figure.

In (a), the photosensitive drum 1 is charged by the corona charger 2 to, for example, + 400V, and then in (b) the first exposure of the image information is performed, and the surface potential of the exposed portion is set to + 50V, for example. Attenuate to form a first electrostatic latent image.

Next, in (c), a developing bias voltage (for example, +300 V: shown by a broken line) is applied to the developing sleeve of the first developing device 4 to reverse-develo the exposed portion.

After the first development, recharging is carried out in (d), but 600 V, which is larger than the desired second development potential 400 V, is applied to the grid of the recharger 5, and the first development non-image area is, for example, It is controlled to be charged to 600V. At that time, the first developing section is charged to, for example, 500V.

Next, when the exposure according to the second image information is performed in (e), a constant exposure amount is applied to the entire surface (for example, the first development non-image area is attenuated by 200 V compared to the second development single color). Large exposure is performed. At this time, in the first developing section, the exposure by the constant exposure amount does not attenuate as much as the potential in the first developing non-image area, but only 100 V, for example. This is because the first developer does not transmit light but scatters it, and the transmittance was 50%. The target potential after recharging at the first developing non-image area is such that the surface potential after exposure with the second exposure constant addition exposure amount of 0.25 μJ becomes the second developing position target potential 400 V by the known straight line of drum sensitivity 800 V / μJ. Assuming it was 600V. Next, the amount of light reaching the first image developing unit on the drum is 0.125 μJ from the known toner layer transmittance of 50%. First as in the method described above
After recharging the developed image portion, the target potential may be set to 500V.

In the present embodiment, the semiconductor laser is used as the second exposure means, but complicated processing or the like is not required in the second developing monochromatic mode and the two-color mode. Since the light amount of the laser is determined by the laser drive current, a constant offset current is added to the drive current in the second developing monochromatic mode in the two-color mode. That is, weak exposure is also applied to the part where the second image signal is off, and exposure is also applied to the on part with an exposure amount almost equal to that, and the potential of the first developed image part is 400 V and the first developed image part is The potential of the non-image area is also 400
V, and when the second image signal is on, the first developing non-image portion is exposed to 50V. After this, in the developing process, the second
By applying a bias of 300V to the developing sleeve,
It is possible to obtain a sufficient second image density without the second developer being mixed in the first developing portion or being developed in the first and second image non-image portions.

Now, the fan operation of the present invention will be described with reference to the drawings used in the first embodiment.

The air flow blowing and suction methods for preventing image deletion by the post charger, which is a feature of the present invention, will be described in detail below.

In the image forming apparatus shown in FIG. 1, the transfer paper P is fed by the paper feed unit 109a and conveyed to the transfer charger (transfer device) 8 through the paper feed path P1 as a condition particularly effective in the present invention. The relationship between the blowing and suction fans of the primary charger 2 and the post charger 62 in the image forming apparatus in such a state will be described.

First, the post charger fan will be described with reference to FIG. Here, the connecting duct 61 is directly connected to the post charger 62, and the blowing fan 6 is further connected.
0s are connected.

The blowing fan 60 blows air from the front side in the longitudinal direction between the developing device 7 and the transfer sheet conveying portions 63a and 63b. The blowing air flow from the blowing fan 60 flows from the front side to the back side in the longitudinal direction through the shield case of the post charger 62 and the connecting duct 61, disturbs the retained ozone in the shield case and winds it up with the air. The suction airflow from the side makes it easier to discharge.

22A and 22B are a side view and a top view of the connecting duct 61 in FIG. 22 (a),
In (b), the blowing fan 60 on the front side sends out an air flow toward the connecting duct 61 via the dust-proof electrostatic filter 68. The air flow is the photosensitive drum 1 of the post charger 62.
To the duct 61a installed on the back side of the
Moreover, the wind direction fins 61b in the air flow also flow toward the photosensitive drum. After that, head toward the back and use the duct 61
a through the opening 61c on the back side of the a, and through the opening 70a of the support sheet metal 70 on the back side of the image forming apparatus, the suction fan 67 on the back side.
Into the duct 71 for guiding the air flow to the suction fan 67
And passes through the ozone filter 69 and is discharged to the outside of the image forming apparatus.

A power supply 65 capable of independently supplying power and a control device 66 capable of independently controlling each fan are wired to the fans. The control device 66 is connected to a circuit for controlling the entire image forming apparatus. Signal is electrically wired through the image data correction device 50 (see FIGS. 1 and 2).

Next, the primary charger 2 has the same structure, and only the arrangement and function around the photosensitive drum are different. In FIG. 2, a connection duct 2a is directly connected to the primary charger 2, and a blowing fan 2b is further connected. Although the fan configuration of the primary charger 2 is not shown, the numbers of the components of the parts corresponding to the primary charger 2 are attached to FIGS. 22 (a) and 22 (b). The blowing fan 2b on the front side sends out an air flow in the direction of the connecting duct 2a via the electrostatic filter 2c for dust prevention. Air flow is primary charger 2
Is guided to a duct 2d installed on the rear shield side on the side far from the photosensitive drum 1, and also flows toward the photosensitive drum by a wind direction fin 2h therein. After that, it goes through the opening 2i on the back side of the duct 2d toward the back side, passes through the opening of the support sheet metal 70 on the back side of the image forming apparatus, and enters the duct 2g for guiding the air flow to the suction fan 2e on the back side. 2e and the ozone filter 2f, and is discharged to the outside of the image forming apparatus.

The fan for the primary charger 2 is also wired with a power source 65 capable of independently supplying power and a control device 66 capable of independently controlling each fan. The control device 66 is an image forming apparatus. A signal from a circuit for controlling the whole is electrically wired through the image data correction device 50.

FIG. 23 shows the sequence of the operation of the image forming apparatus and the operations of the primary charging, the post charging, the post spraying fan 60 and the primary spraying fan 2b. When the power of the image forming apparatus is turned on, the heater of the fixing device is warmed up. Once started, the pre-multi-rotation starts when the temperature reaches the specified temperature. In the previous multi-rotation, charging is performed by potential control, so
The primary charger 2 and the post charger 62 also operate. But,
The blowing fans 60, 2b do not operate for a short time such that excessive ozone generation or temperature rise does not occur. However, the charging current in the primary charger 2 is larger than that in the post charger 62,
Here, half speed (fan input voltage is 1/2 of rated input voltage
Is a half speed fan operation, which halves the fan air volume. ) (Which will be described later, but at this time, the post-charging suction fan 67 and the primary-charging suction fan 2e described in FIG. 22 are operated). At the start of copying, the primary charging blowing fan 2b operates at full speed. The post-charging blowing fan 60 is not operating here in order to prevent the toner image on the photosensitive drum 1 from being disturbed by the air flow or from scattering the toner.

When the post-processing c after the image formation is completed, the post-charging blowing fan 60 operates at full speed, disturbs the ozone in the shield case of the post-charger 62, winds it up, and immediately sends it out to the back side intake / exhaust port, and then outside the machine. To discharge. The operation is continued within an arbitrary post-processing time c, and heat and ozone are rapidly discharged at once, and the operation is stopped when a certain time has elapsed. The primary-charged blowing fan 2b reduces its operation to a half-speed operation within the post-processing time c to reduce the generation of noise due to the operating noise of the fan.

The wind speed of the half-speed operation here is 0.1 to 1 m /
Seconds. Also, the wind speed in full speed operation here is 0.2
~ 2.0 m / sec.

FIG. 24 shows the most characteristic configuration of the present invention. It shows the difference between the post-charging and the primary charging of the difference amount between the air flow injection and blowing amount and the air flow suction amount, and is a difference amount controlling method between blowing and suction according to the image forming process for each charger. .

The suction fans 2e and 67 both rotate at a half speed in the pre-multi revolution for both the primary charging and the post charging, and become a full speed rotation at the copy start. Normally, in the image forming apparatus, the suction fan for exhausting ozone gas around the photosensitive drum is also used, and the primary charging and the post charging are commonly used here.

The difference amount of (spraying)-(suction) depending on the image forming process when the maximum difference is 100 and the minimum difference is 0 will be described below.

In the post-charging, when the power is on, the fan is blowing and both suctions are stopped, and the difference is 0. The pre-multi-rotation starts and post-charging is performed, and only the suction fan 67 operates and the difference is -50. Becomes

Next, when copying is started, the blowing fan 60 is in a stopped state (A) so as not to disturb an image or scatter toner. Since the photosensitive drum 1 rotates during copying, the air flow swirls around the photosensitive drum and is already in a state where it easily diffuses to the outside. Therefore, by sucking more heat, the heat swirls and the suction fan 67 It is caught in the air flow of and is guided to the outside of the aircraft. The difference at this time is set to −100 (A ₁ ). Here, it is more effective to increase the suction to a difference of about -70.

Next, when the copy image formation is completed,
Since the rotation of the photosensitive drum 1 is stopped and the spiral state of the air flow due to the rotation of the photosensitive drum is reduced, the exhaust efficiency is reduced.
However, the suction fan 67 is switched to a half speed operation to reduce fan noise after image formation (D). In order to compensate for the two reductions in efficiency, the blowing fan 60 is set to full speed to violently disturb the air flow in the post charger 62 to generate swirls. In order to make the generation of the swirl more efficient, the above difference is reversed from that during copying, and the blowing is strengthened to +50 (D ₁ ). After exhausting air for a certain time in this state, both fans stop at the same time. For the post-charged fan, a cross flow fan or an axial flow fan, which has a large air volume with respect to the rotation speed of the fan blades, is suitable so that the noise does not increase even after the image formation even at full speed operation.

On the other hand, in the primary charger 2, as shown in (b) of FIG. 24, the blowing fan 2b and the suction fan 2e are basically operating at the same rotational speed, so that the difference (spraying / suctioning) is completely reduced. It is ± 0 throughout the process. In particular, the blowing and the suction after the image formation are performed at a half speed in both the fans for the primary charger because the air volume is large and the noise is large (D ₂ and D ₃ ).

That is, the primary charger fan system and the post charger fan system require independent power supply systems and command types, which the controller (fan control circuit) 66 and the power source (fan drive power source) 65 need. It has a multi-purpose command system and multi-purpose power supply system and is realized.

The difference between spraying and suction of the post charger 62 and the phenomenon in each image forming process will be described below. Difference (Spray-Suction) Before Multi-rotation During copying After copying +100 Toner scattering, HH flow Image disturbance, toner scattering good +50 Toner scattering Image disturbance, toner scattering good ± 0 Toner scattering small amount Toner scattering small amount −50 Good good toner scattering Small amount -100 Good Good Toner scattering Small amount Next, in a high humidity environment that is the most severe against image flow (such as an environment where the water content per cubic meter unit volume is 9 g / m ³ or more), the fan operation that emphasizes ozone gas emission efficiency Make it a sequence.

In FIGS. 24 (a) and 24 (b), when the amount of water calculated by the temperature / humidity detected by the temperature / humidity detection sensor (not shown) is 9 g or more, the ozone discharge capacity during copying after the start of copying is increased. Therefore, the air volume of the post-charging blowing fan 60 is set to 1/4 speed as shown in (C) of the figure, and to half speed (1/2 speed) as shown in (B) when the amount of water is 16 g or more. . However, do not raise the air volume that disturbs the image on the photosensitive drum. The difference between the blowing and the suction at this time is -75 of (C ₁ ) or (B
It becomes -50 of ₁ ).

Further, when the water content is 9 g or more, the priority of noise reduction is lowered and the prevention of image flow is emphasized, and the fan wind speed of the post-charging suction fan 67 after image formation is preferentially set to the full speed (E). The difference between the suction and the blowing suction is increased to 0 to enhance the discharge efficiency on the suction side. Similarly, in the primary charger 2, the blowing fan 2b and the suction fan 2e after image formation are operated at full speed (E
₂ ) and (E ₃ ). However, the difference between spraying and suction remains 0 as in the normal environment.

As described above, the high humidity environment (the water content per cubic meter is 9
In an environment of g / m ³ or more), a fan operation sequence that emphasizes ozone gas discharge efficiency makes it possible to obtain a good image regardless of the environment.

A method of correcting unevenness in the main scanning direction when density unevenness occurs in the developing device or other devices will be described in detail below.

Similar to the first embodiment, description will be made using the operation flow for creating the correction table 50 in FIG.

(1) The image forming apparatus of the present embodiment has an "improving image mode" as an image unevenness improving mode in the input interface, and first starts that mode.

(2) Next, an axial nonuniformity (main scanning nonuniformity) correction mode is selected.

(3) Start the axial unevenness correction mode. Press the key to start.

(4) The image forming apparatus outputs a test image sample as shown in FIG. As the forming conditions of this sample, in order to form an image of completely solid black, halftone halftone, solid white, etc., three kinds of image exposure conditions were obtained by the primary charging condition for forming the surface potential as described above (Fig. 12 PWM levels F0, 80, 00 hex), and the sample is output after developing, transferring and fixing under the above-mentioned developing conditions.

A feature of this embodiment is that a test image sample is output for each of the two colors (for example, red and black). After this, perform the following steps (5) to (10) for each red and black color.

(5) The output sample is placed on the document table by the mode executor at the specific position such that the leading end and the front or rear side of the sample in the sheet passing direction are completed by the document recognizing means (not shown). Judge whether it is detected.

(6) When it is determined that the placement is completed, the document is read by the reader as described above. It is desirable that reading by this reader is performed at a resolution of about 400 to 600 dpi.

(7) Whether this original is a test image sample or not is determined based on whether the density gradations are the same pattern.

(8) When it is determined that the image is a test image sample, the distribution of the axial density is calculated as shown in FIG. 14 (b). When the test image sample is formed at the PWM level of F0, 80, and 00hex, the read density distribution of the halftone portion of 80hex where the unevenness is most easily detected is calculated (the density distribution is calculated at F0, 80, and 00hex, respectively). May be.).

(9) As shown in FIG.
In the case of 5, the increase / decrease of the read density distribution of the halftone portion with respect to 0.5 is calculated so as to correspond to each pixel in the main scanning direction. If the negative correction is represented by a negative sign and the positive correction is represented by a positive sign, the necessary correction density is a diagram of the necessary correction density as shown in FIG.

(10) The correction light amount (correction level) for each pixel of the dot exposure laser is obtained from the diagram of the required correction density with reference to FIG. As an example, the required correction density is +0.8 in FIG.
In the case of, the surface potential is -200 V, and the drum surface light quantity is +
This indicates that it is necessary to correct 0.25 μJ and +80 hex for image data. A correction amount level corresponding to each pixel in the main scanning direction is assigned by this capacity, and a correction table is created. Here, this mode ends, and the operation panel, which is the input interface unit of the image forming apparatus, returns to the normal copy or print mode.

As described above, the primary charging fan and the post-charging fan are independently controlled to control the difference balance between the blowing fan and the suction fan, and the density unevenness at the laser writing level is corrected using the correction table. By correcting for each color (red and black), it is possible to always provide a high-quality two-color image without density unevenness in the longitudinal direction (main scanning direction).

<Third Embodiment> FIG. 19 is a schematic block diagram of an image forming apparatus according to a third embodiment of the present invention.

The photosensitive drum 11 has a photoconductive layer provided on a cylindrical conductive substrate, and is rotatably supported in the direction of arrow R1 in the figure. Then, around the photosensitive drum 1, a scoro-tocon charger (primary charger) for uniformly charging the surface of the photosensitive drum 1 in order along the rotation direction thereof.
2. An original reading device, an exposure device 3 that exposes the photosensitive drum 1 based on an image signal proportional to the image density to form an electrostatic latent image, and toner is attached to the electrostatic latent image to develop it as a toner image. Developing device 7, post-charger (pre-transfer charger) 62 for charging the toner image before transfer, corona transfer charging for transferring the toner image formed on the photosensitive drum 1 onto a transfer paper P which is a transfer material. Device (transfer charger) 8, electrostatic separation charger (separation charger) 9 that separates the transfer paper P on which the toner image has been transferred from the photosensitive drum 1, and after the toner image has been transferred, remains on the photosensitive drum 1. A cleaning device 13 for removing residual toner, a pre-exposure lamp 30 for removing residual charges on the photosensitive drum 1, and the like are arranged. The transfer paper P on which the toner image is transferred is separated from the photosensitive drum 1 and then conveyed to the fixing device 12, where the toner image on the surface is fixed, and a desired print image is formed, and the image forming apparatus main body is formed. Is discharged to the outside.

Here, the transfer duct 61 is directly connected to the pre-transfer charger 62, and the blowing fan 60 is further connected thereto. The reader unit 18 irradiates the original 15 placed on the original glass table 14 with the illumination lamp 16 and reflects the reflected light into a photoelectric conversion element (1-line CCD) 19.
By forming an image on the top, it is converted into an electric signal corresponding to the image information. Here, the reflected light from the document 15 illuminated by the illumination lamp 16 is reflected by the mirrors 17a, 17b, 1
The photoelectric conversion element 19 is guided by the lens 17d after being guided to 7c.
Imaged above. The electric signal output from the photoelectric conversion element 19 is A / D converted by the A / D converter 21 to obtain 8-bit digital image data, and then the black signal generation circuit 22 converts the luminance information into the density information. The image is subjected to log conversion to obtain image density data.

Here, as shown in FIG. 1 or 4, the main-scanning unevenness correction circuit 50 of the present invention corrects the image density data for each pixel in the main-scanning direction. A correction method in the main scanning unevenness correction circuit will be described in detail later.

The 8-bit digital image data signal generated as described above is applied to the LED drive circuit 2 which is a feature of the present invention.
4c, the LED drive circuit 24c is a well-known PWM
The circuit modulates the light emission time for turning on / off the semiconductor laser according to the magnitude of the input image density signal.

As described above, the LED light which is driven and emitted according to the image signal is written on the photosensitive drum 1 to form a digital electrostatic latent image as image information.

In this embodiment, an amorphous silicon drum is used as the photosensitive drum 1. Amorphous silicon drums have the characteristics of a conductive substrate with high stability and high durability and long life.

The respective steps for explaining the image forming process of this embodiment are the same as those in the first embodiment.

Now, the fan operation of the present invention will be described with reference to the drawings used in the first embodiment.

The air flow blowing and suction methods for preventing image deletion by the post charger, which is a feature of the present invention, will be described in detail below.

In the image forming apparatus shown in FIG. 1, the transfer paper P is fed by the paper feed section 109a and conveyed to the transfer charger (transfer device) 8 through the paper feed path P1 as a condition particularly effective in the present invention. The relationship between the blowing and suction fans of the primary charger 2 and the post charger 62 in the image forming apparatus in such a state will be described.

First, referring to FIG. 2, the post charger fan will be described. Here, the connecting duct 61 is directly connected to the post charger 62, and the blowing fan 6 is further connected.
0s are connected.

The blowing fan 60 blows air from the front side in the longitudinal direction between the developing device 7 and the transfer sheet conveying portions 63a and 63b. The blowing air flow from the blowing fan 60 flows from the front side to the back side in the longitudinal direction through the shield case of the post charger 62 and the connecting duct 61, disturbs the retained ozone in the shield case and winds it up with the air. The suction airflow from the side makes it easier to discharge.

22A and 22B are a side view and a top view of the connecting duct 61 in FIG. 22 (a),
In (b), the blowing fan 60 on the front side sends out an air flow toward the connecting duct 61 via the dust-proof electrostatic filter 68. The air flow is the photosensitive drum 1 of the post charger 62.
To the duct 61a installed on the back side of the
Moreover, the wind direction fins 61b in the air flow also flow toward the photosensitive drum. After that, head toward the back and use the duct 61
a through the opening 61c on the back side of the a, and through the opening 70a of the support sheet metal 70 on the back side of the image forming apparatus, the suction fan 67 on the back side.
Into the duct 71 for guiding the air flow to the suction fan 67
And passes through the ozone filter 69 and is discharged to the outside of the image forming apparatus.

A power supply 65 capable of independently supplying power and a control device 66 capable of independently controlling each fan are wired to the fan, and the control device 66 is connected to a circuit for controlling the entire image forming apparatus. Signal is electrically wired through the image data correction device 50 (see FIGS. 1 and 2).

Next, the primary charger 2 has the same structure, and only the arrangement and function around the photosensitive drum are different. In FIG. 2, a connection duct 2a is directly connected to the primary charger 2, and a blowing fan 2b is further connected. Although the fan configuration of the primary charger 2 is not shown, the numbers of the components of the parts corresponding to the primary charger 2 are attached to FIGS. 22 (a) and 22 (b). The blowing fan 2b on the front side sends out an air flow in the direction of the connecting duct 2a via the electrostatic filter 2c for dust prevention. Air flow is primary charger 2
Is guided to a duct 2d installed on the rear shield side on the side far from the photosensitive drum 1, and also flows toward the photosensitive drum by a wind direction fin 2h therein. After that, it goes through the opening 2i on the back side of the duct 2d toward the back side, passes through the opening of the support sheet metal 70 on the back side of the image forming apparatus, and enters the duct 2g for guiding the air flow to the suction fan 2e on the back side. 2e and the ozone filter 2f, and is discharged to the outside of the image forming apparatus.

The fan for the primary charger 2 is also wired with a power source 65 capable of independently supplying power and a controller 66 capable of independently controlling each fan. The controller 66 is an image forming apparatus. A signal from a circuit for controlling the whole is electrically wired through the image data correction device 50.

FIG. 23 shows the sequence of the operation of the image forming apparatus and the operations of the primary charging, the post charging and the post spraying fan 60 and the primary spraying fan 2b. When the power of the image forming apparatus is turned on, the heater of the fixing device is warmed up. Once started, the pre-multi-rotation starts when the temperature reaches the specified temperature. In the previous multi-rotation, charging is performed by potential control, so
The primary charger 2 and the post charger 62 also operate. But,
The blowing fans 60, 2b do not operate for a short time such that excessive ozone generation or temperature rise does not occur. However, the charging current in the primary charger 2 is larger than that in the post charger 62,
Here, half speed (fan input voltage is 1/2 of rated input voltage
Is a half speed fan operation, which halves the fan air volume. ) (Which will be described later, but at this time, the post-charging suction fan 67 and the primary-charging suction fan 2e described in FIG. 22 are operated). At the start of copying, the primary charging blowing fan 2b operates at full speed. The post-charging blowing fan 60 is not operating here in order to prevent the toner image on the photosensitive drum 1 from being disturbed by the air flow or from scattering the toner.

When the post-processing c after the image formation is completed, the post-charging blowing fan 60 operates at full speed, disturbs the ozone in the shield case of the post-charger 62, winds it up, and sends it out to the back side intake / exhaust port all at once, and then outside the machine. To discharge. The operation is continued within an arbitrary post-processing time c, and heat and ozone are rapidly discharged at once, and the operation is stopped when a certain time has elapsed. The primary-charged blowing fan 2b reduces its operation to a half-speed operation within the post-processing time c to reduce the generation of noise due to the operating noise of the fan.

The wind speed of the half-speed operation here is 0.1 to 1 m /
Seconds. Also, the wind speed in full speed operation here is 0.2
~ 2.0 m / sec.

FIG. 24 shows the most characteristic structure of the present invention. It shows the difference between the post-charging and the primary charging of the difference amount between the air flow injection and blowing amount and the air flow suction amount, and is a difference amount controlling method between blowing and suction according to the image forming process for each charger. .

The suction fans 2e and 67 both rotate at a half speed at the pre-multi revolution for both the primary charging and the post charging, and become full speed at the copy start. Normally, in the image forming apparatus, the suction fan for exhausting ozone gas around the photosensitive drum is also used, and the primary charging and the post charging are commonly used here.

The difference amount of (spraying)-(suction) depending on the image forming process when the maximum difference is 100 and the minimum difference is 0 will be described below.

In post-charging, when the power is on, the fan is blowing and both suctions are stopped, and the difference is 0. The pre-multi-rotation starts and post-charging is performed, and only the suction fan 67 operates and the difference is -50. Becomes

Next, when copying is started, the blowing fan 60 is in a stopped state (A) so as not to disturb an image or scatter toner. Since the photosensitive drum 1 rotates during copying, the air flow swirls around the photosensitive drum and is already in a state where it easily diffuses to the outside. Therefore, by sucking more heat, the heat swirls and the suction fan 67 It is caught in the air flow of and is guided to the outside of the aircraft. The difference at this time is set to −100 (A ₁ ). Here, it is more effective to increase the suction to a difference of about -70.

Next, when the copy image formation is completed,
Since the rotation of the photosensitive drum 1 is stopped and the spiral state of the air flow due to the rotation of the photosensitive drum is reduced, the exhaust efficiency is reduced.
However, the suction fan 67 is switched to a half speed operation to reduce fan noise after image formation (D). In order to compensate for the two reductions in efficiency, the blowing fan 60 is set to full speed to violently disturb the air flow in the post charger 62 to generate swirls. In order to make the generation of the swirl more efficient, the above difference is reversed from that during copying, and the blowing is strengthened to +50 (D ₁ ). After exhausting air for a certain time in this state, both fans stop at the same time. For the post-charged fan, a cross flow fan or an axial flow fan, which has a large air volume with respect to the rotation speed of the fan blades, is suitable so that the noise does not increase even after the image formation even at full speed operation.

On the other hand, in the primary charger 2, as shown in (b) of FIG. 24, the blowing fan 2b and the suction fan 2e are basically operating at the same rotational speed, so that the difference (spraying / suctioning) is completely reduced. It is ± 0 throughout the process. In particular, the blowing and the suction after the image formation are performed at a half speed in both the fans for the primary charger because the air volume is large and the noise is large (D ₂ and D ₃ ).

That is, the primary charger fan system and the post-charger fan system require independent power supply systems and command types, which the controller (fan control circuit) 66 and the power source (fan drive power source) 65 need. It has a multi-purpose command system and multi-purpose power supply system and is realized.

The difference between spraying and suction of the post charger 62 and the phenomenon in each image forming step will be described below. Difference (Spray-Suction) Before Multi-rotation During copying After copying +100 Toner scattering, HH flow Image disturbance, toner scattering good +50 Toner scattering Image disturbance, toner scattering good ± 0 Toner scattering small amount Toner scattering small amount −50 Good good toner scattering Small amount -100 Good Good Toner scattering Small amount Next, in a high humidity environment that is the most severe against image flow (such as an environment where the water content per cubic meter unit volume is 9 g / m ³ or more), the fan operation that emphasizes ozone gas emission efficiency Make it a sequence.

In FIGS. 24 (a) and 24 (b), when the amount of water calculated by the temperature and humidity detected by a temperature / humidity detection sensor (not shown) is 9 g or more, the ozone discharge capacity during copying after the start of copying is increased. Therefore, the air volume of the post-charging blowing fan 60 is set to 1/4 speed as shown in (C) of the figure, and to half speed (1/2 speed) as shown in (B) when the amount of water is 16 g or more. . However, do not raise the air volume that disturbs the image on the photosensitive drum. The difference between the blowing and the suction at this time is -75 of (C ₁ ) or (B
It becomes -50 of ₁ ).

Further, when the water content is 9 g or more, the priority of noise reduction is lowered and the prevention of image flow is emphasized, and the fan wind speed of the post-charging suction fan 67 after image formation is preferentially set to the full speed (E). The difference between the suction and the blowing suction is increased to 0 to enhance the discharge efficiency on the suction side. Similarly, in the primary charger 2, the blowing fan 2b and the suction fan 2e after image formation are operated at full speed (E
₂ ) and (E ₃ ). However, the difference between spraying and suction remains 0 as in the normal environment.

As described above, the most humid environment (the water content per cubic meter unit volume is 9
In an environment of g / m ³ or more), a fan operation sequence that emphasizes ozone gas discharge efficiency makes it possible to obtain a good image regardless of the environment.

The method of correcting unevenness in the main scanning direction when density unevenness occurs in the developing device and other parts will be described in detail below.

Similar to the first embodiment, description will be made using the operation flow of creating the correction table 50 in FIG.

(1) The image forming apparatus according to the present embodiment has an "improving image mode" as an image unevenness improving mode in the input interface, and the mode is started first.

(2) Next, an axial direction unevenness (main scanning direction unevenness) correction mode is selected.

(3) Start the axial unevenness correction mode. Press the key to start.

(4) The image forming apparatus outputs a test image sample as shown in FIG. As the forming conditions of this sample, in order to form an image of completely solid black, halftone halftone, solid white, etc., three kinds of image exposure conditions were obtained by the primary charging condition for forming the surface potential as described above (Fig. 12 PWM levels F0, 80, 00 hex), and the sample is output after developing, transferring and fixing under the above-mentioned developing conditions.

A feature of this embodiment is that a test image sample is output for each of the two colors (for example, red and black). After this, perform the following steps (5) to (10) for each red and black color.

(5) The output sample is placed on the document table by the mode executor at the specified position with the leading end and the front or back side of the sample in the sheet passing direction, and the document recognizing means (not shown) is used to complete the placement. Judge whether it is detected.

(6) When it is determined that the placement is completed, the document is read by the reader as described above. It is desirable that reading by this reader is performed at a resolution of about 400 to 600 dpi.

(7) Whether or not this original is a test image sample is determined by whether or not the patterns have the same density gradation.

(8) When it is determined that the image is a test image sample, the distribution of the axial density is calculated as shown in FIG. 14 (b). When the test image sample is formed at the PWM level of F0, 80, and 00hex, the read density distribution of the halftone portion of 80hex where the unevenness is most easily detected is calculated (the density distribution is calculated at F0, 80, and 00hex, respectively). May be.).

(9) As shown in FIG.
In the case of 5, the increase / decrease of the read density distribution of the halftone portion with respect to 0.5 is calculated so as to correspond to each pixel in the main scanning direction. If the negative correction is represented by a negative sign and the positive correction is represented by a positive sign, the necessary correction density is a diagram of the necessary correction density as shown in FIG.

(10) The correction light amount (correction level) for each pixel of the dot exposure laser is obtained from the diagram of the required correction density with reference to FIG. As an example, the required correction density is +0.8 in FIG.
In the case of, the surface potential is -200 V, and the drum surface light quantity is +
This indicates that it is necessary to correct 0.25 μJ and +80 hex for image data. A correction amount level corresponding to each pixel in the main scanning direction is assigned by this capacity, and a correction table is created. Here, this mode ends, and the operation panel, which is the input interface unit of the image forming apparatus, returns to the normal copy or print mode.

As described above, the primary charging fan and the post charging fan are independently controlled to control the difference balance between the blowing fan and the suction fan, and the density unevenness is corrected at the LED writing level using the correction table. By doing so, it is possible to always provide a high-quality image without density unevenness in the longitudinal direction (main scanning direction).

In each of the above-described first to third embodiments, an example in which an image is formed by the binarization processing by the error diffusion method or the like (or the dither method or the like) has been described, but the image is formed by the PWM method. Of course, it can be applied to cases. In addition, when an image is formed by the PWM method, basically, a pixel having a difference in lightness and darkness for each pixel (actually, it is a pixel of a different size due to area modulation. Can be perceived as
The density distribution can be corrected by simply reading the density distribution with the reader unit according to the embodiment. However,
In order to read even one pixel without deviation, it is necessary to read with a very high accuracy, and as a practical matter, it is difficult to determine the characteristics of each pixel formed on the printer engine side from the read image. Printer resolution is 600d
This is because if it is pi, it is necessary to read an image with a deviation of less than 1/600 inch, which is very difficult as a practical problem. Therefore, as described above, the PW
Even in the case of forming by the M method, it is desirable to detect the density unevenness in the main scanning direction by the average value of the read plural pixels in the main scanning direction and correct it.

Although the present invention has been described by taking the printer as an example, the present invention can be applied to a system including a plurality of devices (for example, host computer, interface device, reader, printer, etc.).

In this case, since the above processing can be performed by the portion corresponding to the host computer, the present invention uses a storage medium recording a program code of software for realizing the functions of the above-described embodiment as a system or a storage medium. It can also be achieved by supplying the program to the device and causing the computer (or the CPU or MPU) of the system or the device to read and execute the program code stored in the storage medium.

In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.

As a storage medium for supplying the program code, for example, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM,
CD-R, magnetic tape, non-volatile memory card, RO
M or the like can be used.

Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also the OS (operating system) running on the computer is executed based on the instruction of the program code. It goes without saying that it also includes the case where the system) performs a part or all of the actual processing and the processing realizes the functions of the above-described embodiments.

Furthermore, after the program code read from the storage medium is written in the memory provided in the function expansion board inserted into the computer or the function expansion unit connected to the computer, based on the instruction of the program code, A CPU provided in the function expansion board or function expansion unit performs a part or all of the actual processing,
It goes without saying that the processing includes the case where the functions of the above-described embodiments are realized.

[0214]

As described above, according to the present invention,
Efficient discharge of ozone gas can be remarkably improved, the image carrier can be prevented from being adversely affected by ozone gas, and image deletion can be suppressed. In addition, high-definition images with high image quality without image deterioration such as image deletion regardless of environment. Can be formed.

When laser or LED spot exposure writing with digital data is performed on the image carrier,
Image deletion can be prevented even when the laser spot size is 600 dpi and the spot diameter is 50 to 70 μm.

Further, as the developing system, the image flow phenomenon does not occur even in the electric field flight developing method and the jumping developing method which use the one-component magnetic developer mainly utilizing the electric field developing phenomenon, and the final image on the image is not generated. A high quality image can be provided.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a schematic configuration of an image forming apparatus according to a first embodiment.

FIG. 2 is an enlarged view of FIG.

3A to 3C are diagrams schematically showing a relationship between a surface potential of a photosensitive drum and a developing bias.

FIG. 4 is a block diagram showing image processing according to the first embodiment.

5A to 5C are diagrams showing a relationship between image data of each pixel, a laser drive signal, and a drive current.

6 (a) and 6 (b) are views for explaining the laser lighting of binary image data.

FIG. 7 is a diagram showing general IL characteristics (driving current-light quantity characteristics) of a laser.

FIGS. 8A to 8C are schematic diagrams in which factors that cause density unevenness in the main scanning direction are analyzed.

FIG. 9 is a diagram showing a relationship between a charging wire current and a drum surface potential.

FIG. 10 is a diagram showing a relationship between an image exposure amount and a drum surface potential.

FIG. 11 is a diagram showing a relationship between development contrast potential and development density.

FIG. 12 is a diagram showing a relationship between image data and a wide area integrated image exposure amount.

FIG. 13 is a flowchart showing an outline of the flow of a correction operation.

14A to 14C are diagrams showing a test image sample, a read density, and a correction required density.

FIG. 15 is a diagram illustrating a correction amount.

FIG. 16 is a vertical sectional view showing a schematic configuration of an image forming apparatus according to a second embodiment.

17A to 17F are schematic diagrams for explaining an image forming process in a two-color image forming mode according to the second embodiment.

FIG. 18 is a block diagram showing image processing according to the second embodiment.

FIG. 19 is a vertical sectional view showing a schematic configuration of an image forming apparatus according to a third embodiment.

FIG. 20 is a vertical cross-sectional view showing a schematic configuration of a conventional image forming apparatus.

FIG. 21 is a diagram showing a specific circuit configuration of a main scanning unevenness correction circuit.

22 (a) is an X-ray arrow view of FIG. 2; (B) is a view on the Y line arrow in FIG.

FIG. 23 is a diagram showing an operation sequence of the image forming apparatus, a primary charger and a post charger, a post-charging blowing fan, and a primary-charging blowing fan.

FIG. 24A is a timing chart showing a blowing amount of a blowing fan of a post charger, a suction amount of a suction fan, and a difference between the two. (B) is a timing chart showing the blowing amount of the blowing fan of the primary charger, the suction amount of the suction fan, and the difference between the two.

[Explanation of symbols]

1 Image Carrier (Photosensitive Drum) 2 Primary Charger (Scorotron Charger) 2a First Transmission Means (Connecting Duct) 2b First Air Flow Jetting Means (Blowing Fan) 2e First Air Flow Means (Suction) Fan) 2g First transmission means (duct) 3 Exposure means (exposure device) 7 Developing device 8 Transfer device (transfer charger) 20 Small point exposure means (laser) 20c Small point exposure means (light emitting element, LED) 50 Correction Value creating means (main scanning unevenness correction circuit) 60 Second airflow jetting and blowing means (blowing fan) 61 Second transmitting means (connecting duct) 62 Developer charge amount control charger (post charger) 66 Control means ( Fan control circuit) 67 Second air flow suction means (suction fan) 71 Second transmission means (duct)

─────────────────────────────────────────────────── ─── Continued Front Page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G03G 15/02 G03G 21/00 540

Claims (12)

(57) [Claims] 1. An image carrier, a primary charger for uniformly charging the surface of the image carrier, an exposing unit for exposing the surface of the image carrier after charging to form an electrostatic latent image, and the electrostatic charger. A developing device for adhering toner to the latent image to develop it as a toner image, a developer charge amount control charger for controlling the charge amount of the toner image on the image carrier, and the image carrier after the charge amount control. An image forming apparatus including: a transfer device that transfers the toner image of step 1 to a transfer material, the first image forming device being formed inside the shield case of the primary charger.
Air flow passage, a first air flow jetting / blowing means arranged at one end of the first air flow passage in the longitudinal direction, and a first air flow suction arranged at the other end. First air flow generating means having a means, first transmitting means connecting the first air flow generating means and the first air flow path, and inside the shield case of the developer charge amount control charger. A second air flow path formed on the second air flow path, a second air flow jetting and blowing means arranged at one end of the second air flow path in the longitudinal direction, and a second air flow injection and blowing means arranged at the other end of the second air flow path. Second air flow generating means having a second air flow suction means, second transmitting means connecting the second air flow generating means and the second air flow path, and the first air flow generating The amount of difference between the air flow jetting and blowing amount and the air flow suction amount of each of the image forming means and the second air flow generating means depends on the image forming process. E Bei and control means for controlling differently, the control means, said second air flow ejection blow generated hand
The step is stopped before the image forming operation, and
Generates a relatively small air flow, and is relatively large after image formation is completed.
An image forming apparatus , which is controlled to generate a threshold airflow . 2. A water content detection means for detecting the water content in the air, and a difference between the air flow injection and spray quantity and the air flow suction quantity of each of the first air flow generation means and the second air flow generation means. The image forming apparatus according to claim 1, further comprising: a control unit that controls the amount to be different according to the amount of water detected by the water amount detection unit. 3. The first and second non-operating devices after image formation
The image forming apparatus according to claim 2, further comprising a control unit that controls an operation time of the air flow generating unit according to the moisture amount detected by the moisture amount detecting unit. 4. The difference amount of the air flow suction amount with respect to the air flow jetting and blowing amount differs between the first air flow generating means and the second air flow generating means after image formation and after image formation ends, respectively. In the steps from the image formation to the end of the image formation, the increasing / decreasing direction of the difference amount of the air flow suction amount with respect to the air flow jetting and blowing amount in each of the first air flow generating means and the second air flow generating means. The image forming apparatus according to claim 1, 2 or 3, further comprising: a control unit that controls so as to be in a reverse direction. 5. The image according to claim 1, 2, 3, or 4 comprising the individually controllable control means and said first air flow generating means and the second air flow generating means, it is characterized by Forming equipment. 6. The image bearing member includes a photosensitive drum having a thin layer of a photoconductor for forming an electrostatic latent image formed on a cylindrical conductive substrate, and the exposing unit includes a micro dot exposing unit. The image forming apparatus according to claim 1, 2, 3, 4, or 5 . 7. A micro-point exposure means, according to claim 6 in which the digital exposure of each pixel with a laser beam capable of scanning exposure to form an electrostatic latent image on the image carrying body, it is characterized by Image forming device. 8. The minute point exposure means forms an electrostatic latent image on the image bearing member by driving and exposing a plurality of light emitting elements arranged in the main scanning direction. The image forming apparatus according to item 6 . 9. The image forming apparatus according to claim 6, wherein the photosensitive drum uses an a-Si photosensitive member as the electrostatic latent image forming photoconductor. 10. A means for converting into binary data based on multi-valued image data is provided, wherein: 1, 2, 3, 4, 5, 6, 7,
The image forming apparatus according to item 8 or 9 . 11. A density characteristic detecting means for detecting a gradation density reproducing characteristic in an image forming section is provided, and an intermediate density between a black image data level and a white image data level detected by the density characteristic detecting means is calculated, Using the calculated value as the target concentration,
A correction value creating means for adding a correction to the image data is provided, and the correction value creating means is provided.
The image forming apparatus according to item 8, 9, or 10 . 12. The developing device uses a one-component developer, wherein the developing device is one, two, three, four, five, six, seven ,.
The image forming apparatus according to 8, 9, 10, or 11 .