JP2000162947A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent unevenness in density or deterioration in density of an image by controlling the difference quantity between the quantity of sprayed air and the quantity of sucked-in air according to the image forming process. SOLUTION: In this image forming device, spraying and sucking-in of air to prevent heat dispersion of transfer paper passing through a fixing and a through path carrying system are conducted. When the maximum difference is made to be 100 and the difference is (spraying)-(sucking-in) according to the image forming process is reviewed, if the power source is 'ON', both fans are stopped and the difference is '0', and pre-multiple rotation is started and post electrification is carried out having only the sucking-in fan working, the difference is '-50'. When copying is started, a photoreceptor drum is rotated, a turbulence of air flow is generated in the periphery and the air is led outside the device by being caught up by the sucking-in fan. The difference at this time is '-50'. Since the turbulence of air flow is minimized when the copy image forming is finished and the photoreceptor drum has its rotation stopped, the air spraying fan is utilized at full force in order to compensate the lowering of heat exhausting efficiency by causing generation of a turbulence by agitating the air flow inside the post electrifying air and under a developing device. The spraying is increased until the difference is '+50'. Both fans are stopped after carrying out heat exhausting for a set period of time.

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 and a printer.

[0002]

2. Description of the Related Art In recent years, an image forming apparatus has been actively proposed as a digital data information transmission by a data communication network and a hardware output device of the information. As this type of image forming apparatus, there is a digital printer or a digital copying machine.

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

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

[0005] The 8-bit digital image data signal generated as described above is input to a laser drive circuit 24. The laser drive circuit 24 is a well-known PWM circuit, and operates in accordance with the magnitude of the input image density signal. Semiconductor laser 20
The light emission time to be n / off is modulated.

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

FIG. 7 shows a general IL characteristic (driving current-light amount characteristic) of the laser.
The driving current used at the time of off is Ion / Io
ff, the laser drive current for the image signal in FIG. 5 is as shown in FIG. 5C, which is the current for driving the laser by the PWM circuit.

The laser driving method is roughly classified into the PWM circuit described above and a binary laser driving circuit. PW
As described above, the M circuit modulates a pulse width signal corresponding to the emission time of the semiconductor laser according to the magnitude of the input image density signal, while the binarization circuit modulates the pulse width signal according to the pixel size. The signal is converted into a two-stage signal of the specific on light emission signal and the off signal, and 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 based on image data by a method such as an error diffusion method or a dither method. Is constant regardless of The difference is that a low density pixel emits a laser with a low probability, and a high density pixel emits a laser with a high probability.

As described above, the laser light driven and 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 a high speed, and a digital electrostatic latent image is formed as image information. Form.

Conventionally, electrophotography has been disclosed in US Pat. No. 2,297,961 and Japanese Patent Publication No. 42-23910.
Numerous methods are known as described in Japanese Patent Publication No. JP-B-43-24748 and Japanese Patent Publication No. 43-24748. Generally,
An electric latent image is formed by various means on a photosensitive drum, which is a recording medium using a photoelectric material, and then the latent image is developed using a toner (developer). The toner image is transferred onto a transfer material such as paper, and the toner image is fixed to the transfer material by heating or solvent vapor to obtain a copy image.

There are also known various developing methods for visualizing an electric latent image using a developer. For example,
Many methods such as a magnetic brush developing method described in U.S. Pat. No. 2,874,063, a powder cloud method described in 221 and 776, a fur brush developing method, a liquid developing method, and the like. 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. However, this method is relatively stable, and a good image can be obtained. Of the two-component developer, such as 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 toner alone have been proposed. According to this developing method, there is no need to control the mixing ratio of the toner to the carrier, and thus there is an advantage that the apparatus is simplified.

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

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

Conventionally, as a transfer path of the transfer paper,
The transfer paper forms a desired print image and is discharged to the outside of the image forming apparatus main body. However, there is only a transfer path to a discharge tray, a sorting device, a transfer device for multiplex printing, or the like.

[0016]

However, in a configuration in which the post-charging device is located above the transfer device and the transfer paper transport section (upstream in the direction of gravity), the transfer paper is heated at a temperature higher than the peripheral temperature of the transport path. In some cases, the heat of the transfer paper is gradually and gradually transmitted toward the upstream side in the direction of gravity and diffuses to the periphery, and the heat is transmitted to the post-charging device and the developing device. Due to this heat transfer, when the developing device and the developer reach a specific temperature or higher, deterioration of the developer and an appropriate amount of toner charge cannot be secured, and as a result, image density lowering, fogging, scattering, tail tailing, image unevenness, etc. It causes image quality failure.

In particular, in a system having a conveying means for conveying a plurality of fixed transfer papers without stagnation (hereinafter, referred to as a "through-pass double-sided conveying system"), about 200 sheets are required for fixing.
The transfer paper heated to a temperature of ° C. reaches the paper feeding step again within a short time such that heat radiation is not completely completed, and reaches the transfer position (transfer portion) via the transfer conveyance member. That is, the transfer paper is conveyed with high heat of about 50 to 100 ° C., and the heat is diffused to the developing device.

Originally, a developing device containing a resin powder toner is generally used in an environment in which the temperature is suppressed to about 50 ° C. At a temperature higher than that, the degree of aggregation of the toner becomes excessively high. In addition, the frequency and the degree of the obstacle to the image quality are deteriorated due to, for example, the triboelectric charging characteristic being lowered.

As described above, in the case of re-feeding in the through-pass double-sided conveyance, heat is more diffused and the frequency of occurrence of the above-mentioned troubles is higher than in the case of feeding the transfer paper from the transfer paper feeder. Separately, when the image forming apparatus is used in high humidity areas, the transfer paper temperature rises due to the heater heat source for drying inside the feeder to prevent the transfer paper from absorbing moisture in the transfer paper feeder. As a result, there is a problem that the temperature rise increases and the frequency of occurrence of failures increases as in the above-described phenomenon. In particular, when an a-Si photoconductor having a long life, high speed output, and a surface layer SiC curable type and high photosensitivity is used as the photoconductor, the charge retention ability is high and there is almost no scattering of irradiation light by the surface layer. Therefore, the minute electrostatic latent image in the minute spot exposed portion by the laser irradiation is held without charge diffusion, so that the development performance of the minute latent image in the developing system is partially uneven due to the influence of heat and the performance is reduced. If there is, the density of the image is directly reduced or the density is uneven. One-component toner (one-component magnetic developer, one-component non-magnetic developer) as a developer, under the influence of excessive heat, it is extremely difficult to stably control the amount of charge by good friction charging to a predetermined range. difficult. Since the application of electric charge by frictional charging is greatly affected by the external environment, particularly the humidity of the environment, the amount of charge of the toner greatly changes with the fluctuation of the environment. Therefore, problems such as poor density and fog are likely to occur.

The present invention has been made in view of the above-mentioned circumstances, and eliminates heat diffusion and temperature rise during through-pass double-sided conveyance. Particularly, the surface of the image carrier (photosensitive drum) has a long life and high speed output. A-layer with high photosensitivity by curing SiC
When using a Si photoreceptor, an image forming apparatus capable of preventing image density reduction and image density unevenness without partial unevenness or performance deterioration due to heat on the development performance of a minute latent image in a developing system. The purpose is to provide.

[0021]

According to the first aspect of the present invention, there is provided an image bearing member, a primary charger for uniformly charging the surface of the image bearing member, and a charged image bearing member. Exposure means for exposing the surface of the carrier to form an electrostatic latent image, a developing device for attaching toner to the electrostatic latent image and developing it as a toner image, and transferring the toner image on the image carrier to transfer paper An image forming apparatus comprising: a transfer device for transferring; and a transfer paper transport unit for transporting the transfer paper to a transfer unit between the transfer device and the image carrier, wherein the developing device and the transfer paper transport unit An air flow jetting means disposed at one end in a direction along the generatrix of the image carrier,
Between the developing device and the transfer paper transport unit, an air flow suction unit disposed at the other end in a direction along the generatrix of the image carrier, and a blowing amount by the air flow injection blowing unit. Control means for controlling a difference amount from the suction amount by the air flow suction means in accordance with an image forming step.

According to a second aspect of the present invention, in the image forming apparatus of the first aspect, a charge amount of the toner image developed on the image carrier is provided between the developing device and the transfer paper transport unit. Providing a developer charge control charger for controlling, and forming an air flow path inside the shield case of the developer charge control charger, the air flow jetting and blowing means and the air flow suction means, and the air flow path And an airflow transmitting means for connecting the two.

According to a third aspect of the present invention, there is provided the first or second aspect.
Wherein the control means controls the difference between the spray amount and the suction amount to be larger in the positive direction after the end of image formation than during the image formation operation. And

The present invention according to claim 4 is based on claims 1, 2,
In the image forming apparatus according to the third aspect, the control unit stops the air flow blowing unit before the image forming operation, generates a relatively small air flow during the image forming operation, and compares the air flow after the image forming operation. A large air flow is generated.

The present invention according to claim 5 is based on claims 1, 2,
The image forming apparatus of (3) or (4) further includes a fixing unit for melting and fixing the toner image on the transfer paper after the transfer of the toner image, and a transfer paper conveying unit for conveying the fixed transfer paper without stagnation. , Characterized in that.

According to a sixth aspect of the present invention, in the image forming apparatus of the fifth aspect, the control means is configured to re-feed a plurality of transfer sheets after fixing the toner image without stagnating a plurality of transfer sheets to form an image. , When feeding paper from the transfer paper feeder,
The air flow rate and the air flow rate are controlled to be different.

The present invention according to claim 7 is based on claims 1, 2,
The image forming apparatus according to any one of 3, 4, 5, and 6, further comprising a photosensitive drum having a photoconductive member for forming an electrostatic latent image formed as a thin layer on a cylindrical conductive substrate as the image carrier, and a minute point exposure as the control means. Means.

According to an eighth aspect of the present invention, in the image forming apparatus according to the seventh aspect, the minute point exposure means scans and exposes a laser beam capable of digital exposure for each pixel to the electrostatic latent image on the photosensitive drum. Forming an image.

According to a ninth aspect of the present invention, in the image forming apparatus of the seventh aspect, the minute point exposure means drives and exposes a plurality of light emitting elements arranged in the main scanning direction.
An electrostatic latent image is formed on the photosensitive drum.

[0030] The present invention according to claim 10 is based on claim 7,
In the image forming apparatus according to the eighth or ninth aspect, the photosensitive drum uses an a-Si photosensitive member.

The present invention according to claim 11 is based on claim 1,
The image forming apparatus of any one of 2, 3, 4, 5, 6, 7, 8, 9, and 10 further includes a conversion unit that converts the multi-valued image data into binary data.

The present invention according to claim 12 is based on claim 1,
The image forming apparatus according to any one of 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11, further comprising: a density characteristic detecting unit configured to detect a gradation density reproduction characteristic in the image forming unit. Calculates an intermediate density between the black image data level and the white image data level detected by the control unit, and uses the calculated value as a target density to correct the image data.

The present invention according to claim 13 is based on claim 1,
2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 1
In the image forming apparatus of the second aspect, the developing device uses a one-component developer.

[0034]

Embodiments of the present invention will be described below with reference to the drawings.

<Embodiment 1> FIG. 1 shows an example of an image forming apparatus according to the present invention. The image forming apparatus shown in FIG.
This is a laser beam printer (hereinafter referred to as "image forming apparatus"), and FIG. 1 is a longitudinal sectional view showing a schematic configuration thereof.

The image forming apparatus shown in FIG. 1 includes a drum type electrophotographic photosensitive member (hereinafter, referred to as "photosensitive drum") 1 as an image carrier. The photosensitive drum 1 is provided with a photoconductive layer (photoconductor for forming an electrostatic latent image) on a cylindrical conductive base, and is rotatably supported in the direction of arrow R1 in the figure. Around the photosensitive drum 1, a scoro-to-cone charger (primary charger) 2 for uniformly charging the surface of the photosensitive drum 1 is read in order along the rotation direction, an original is read, and an image signal proportional to the density of the image is read. An exposure device (micropoint exposure means) 3 for exposing the photosensitive drum 1 based on the image and forming an electrostatic latent image, a developing device 7 for attaching toner to the electrostatic latent image and developing it as a toner image, A developer charge control charger (hereinafter referred to as “post-charger”) 62 for adjusting the charge of the toner image of the toner image on the drum 1 so as to increase the transfer efficiency is provided. Further, a transport system that feeds the transfer paper (transfer material) P by the paper feed unit 109a and transports the transfer paper to the transfer unit via the paper feed path P1 is provided. Then, a corona transfer charger (transfer charger) 8 as a transfer device for transferring the toner image formed on the photosensitive drum 1 onto the transfer paper P, and separates the transfer paper P on which the toner image has been transferred from the photosensitive drum 1. Electrostatic separation charger (separation charger)
9. A cleaning device 13 (see FIG. 2) for removing the residual toner remaining on the photosensitive drum 1 after transferring the toner image, a pre-exposure lamp 30 for removing the residual charge on the photosensitive drum 1, and the like are arranged. The transfer paper P on which the toner image has been transferred is conveyed to the fixing device 12 after being separated from the photosensitive drum 1, where the toner image on the surface is fixed, and a desired print image is formed. It is discharged out of 101. In FIG. 1, reference numeral 105 denotes an interface unit, and reference numeral 106 denotes a computer.

The reader 18 irradiates the original 15 placed on the original glass table 14 with light from the illumination lamp 16 and reflects the reflected light on a photoelectric conversion element (1-line CCD) 19.
The image is converted into an electric signal corresponding to the image information by forming an image on the top. Here, the reflected light from the original 15 illuminated by the illumination lamp 16 is reflected by mirrors 17a, 17b, 1
The photoelectric conversion element 19 is guided by the lens 17d and guided by the lens 17d.
Imaged on top. 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.
In order to convert the luminance information into density information, the black signal generation circuit 22 performs log conversion to obtain image density data.

The image density data (8
The digital image data signal (bit) is converted into a two-stage signal of an on-light emission time of a specific on-time according to a pixel size and an off signal via a binarization circuit 23, and is input to a laser drive circuit 24, and converted into a drive current After the dot reproducibility correction is applied, 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 may be of course a dither method or another method. Further, the laser drive circuit 24 may employ a method of modulating the on / off emission time of the semiconductor laser according to the magnitude of the input image density signal after the dot reproducibility correction is applied to the drive current by a well-known PWM circuit.

For example, as shown in FIG. 6, laser lighting of binary image data will be briefly described. When image data for each pixel is input in the laser scanning direction as shown in FIG. The drive current to be turned off is as shown in (b). The drive current is turned on for a fixed 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 to the total number of pixels in a specific plurality of pixel regions, and the number of times the laser drive signal is turned on when the FF hex is set is For example, the lighting pixel ratio is set to 100% of the total number of pixels in a specific plurality of pixel regions. However, even at 0% of the lamp pixel ratio, a constant drive current flows as a bias current, and light emission is slight. In this manner, shading is realized by performing area gradation in a specific plurality of pixel regions.

As shown in FIG. 5, in the PWM system, when image data for each pixel is input as shown in FIG. 5A in the laser scanning direction, the drive signal for turning on / off the laser is shown in FIG. It is like. That is, the on-duty of the laser drive signal when the image data is 00 hex is set to 5% of one pixel scan time, and the on-duty of the laser drive signal when the FF hex is set to 85% of one pixel scan time. In this way, shading is realized by performing area gradation within one pixel.

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

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

As described above, the laser beam driven and 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 rotating at high speed, and a digital electrostatic latent image is formed as image information. Form.

In this embodiment, an amorphous silicon drum is used for the photosensitive drum 1. Amorphous silicon drum has high stability and high durability on the conductive base,
It has the feature of long life.

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

In (a), the photoreceptor 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 part and the potential of the laser on part. In a general non-contact surface voltmeter that measures the integrated potential in a sufficiently large area with respect to the spot diameter of the spot, it is apparently measured as a halftone potential. That is, even in the non-image portion (image data 00hex) of the image region, since the slight exposure is performed as described above, the surface potential is attenuated to +400 V, and the image portion of one image region (image data FFhex). At, the surface potential attenuates to +50 V to form an electrostatic latent image.

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

The method of blowing and sucking air to prevent the thermal diffusion of the transfer paper passing through the fixing and through-pass transport systems, which is a feature of the present invention, will be described in detail below.

In the image forming apparatus shown in FIG. 1, the passage of the transfer paper P will be described first. As described above, the transfer paper P is fed by the paper feed unit 109a, and after the transfer of the toner image onto the transfer paper P is completed, the transfer paper P is heated to about 200 ° C. by the fixing device 12 and melted. The resin toner is entangled with the paper fiber and fixed. Thereafter, the transfer sheet P proceeds to the P2 path when the path in the direction of the through-pass transport system has been designated in advance by the paper-direction branching device 107. The transfer paper P is conveyed to the transfer charger 8 through the through-pass double-sided path S and the re-feed path P1. During this time, the transfer paper P
Does not completely dissipate the heat supplied in the fixing operation, so that the re-feeding portion has heat of about 50 to 100 ° C., and heat diffusion occurs to the post-charger 62 and the developing device 7. FIG. 2 is an enlarged view of the periphery of the photosensitive drum 1, and a transfer sheet P re-fed from P1 passes through a register roller 64, and passes between a transfer upper guide 63a and a transfer lower guide 63b which constitute a transfer conveyance unit. To the transfer charger 8. In particular, the transfer upper guide 63a,
When the sheet metal of the lower transfer guide 63b is completely heated and stored by a plurality of sheets, the temperature rises sharply. Here, the blowing fan 60 is connected to the developing device 7 and the transfer paper transport unit 63.
a and 63b are blown from the front side in the longitudinal direction. The blowing air flow from the blowing fan 60 flows from the front side in the longitudinal direction to the back side via a connecting duct (air flow transmitting means) 61 connected to the shield case of the post-charging device 62, and after blowing once to the photosensitive drum 1. The flow also flows in the direction of the developing sleeve, and the transfer conveying section and the developing device 7
Completely forms a heat-blocking airflow due to the airflow.

A side view (X) of the connecting duct 61 in FIG.
FIG. 22 (a) shows a top view (a view taken along a line Y) and a top view (a view taken along a line Y).
(B). In FIGS. 22A and 22B, the blowing fan 60 on the front side sends out an airflow toward the connection duct 61 via the dustproof electrostatic filter 68. The air flow is guided to a 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 wind fins 61b therein. Then, it goes to the back direction and the opening 61c on the back side of the duct 61a.
Through the opening 70 of the supporting metal plate 70 on the back side of the image forming apparatus.
a, enters a duct (airflow transmitting means) 71 for guiding an airflow to a suction fan (airflow suction means) 67 on the back side,
The ink 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 supply 65 capable of supplying power independently and a control device 66 capable of controlling each fan independently.
The control device 66 is electrically connected to a signal from a circuit that controls the entire image forming apparatus via the image data correction device 50 (see FIGS. 1 and 2).

FIG. 23 shows a sequence of the operation of the image forming apparatus, the operation of the post-charging and the operation of the blowing fan (post fan) 60. When the power of the image forming apparatus is turned on, the heater warm-up of the fixing device 12 is started. When the specific temperature is reached, the pre-multi-rotation starts. In the previous multi-rotation, charging is performed by potential control or the like, so that the post charger 62 also operates. However, the blowing fan 60 does not operate for such a short time that there is no excessive ozone generation or temperature rise. Only the suction fan 67 (not shown) operates. At the start of copying, the blowing fan 60 operates at half speed. The half speed is to reduce the fan airflow by half by controlling the input voltage to the fan to half. The reason for the half-speed operation is to prevent the toner image on the photosensitive drum 1 from being disturbed by the air flow in order to blow the airflow onto the photosensitive drum 1 at the post-charging unit. Here, the wind speed of the half-speed operation is set to 0.1 to 0.5 m / sec. When the image formation is completed, the operation is performed at the full speed, the operation is continued within an arbitrary post-processing time period c, heat and ozone are quickly exhausted, and the operation is stopped when a certain time has elapsed. The wind speed of the full-speed operation here is 0.
It is 2 to 1.0 m / sec.

FIG. 24 shows the relationship between the difference between the above-described air flow injection blowing amount and the air flow suction amount, and is a method of controlling the difference between the blowing and suction according to the image forming process.

The suction fan 67 rotates at half speed at the front of multiple rotations.
It becomes full speed rotation at the copy start. Suction fan here 6
The wind speed for the full-speed operation of 7 mm is 0.2 to 1.0 m / sec, and the wind speed for the half speed operation is 0.1 to 0.5 m / sec. Looking at the difference between (blowing) and (sucking) according to the image forming process when the maximum difference is set to 100, when the power is turned on, both the fans are stopped, the difference is 0, and At the beginning, post-charging is performed, and only the suction fan 67 operates, and the difference becomes -50.

Next, when the copying is started, the blowing is performed to diffuse the heat while blowing off the heat so as not to disturb the image or to scatter the toner. Since the photosensitive drum 1 rotates during copying, the airflow swirls around the photosensitive drum and is already in a state of being easily diffused to the outside. And get caught up in the air flow. The difference at this time is -50. Here, it is more effective to increase the suction to a difference of about -70.

Next, when the copy image formation is completed,
The rotation of the photosensitive drum 1 stops, and the swirling state of the airflow due to the rotation of the photosensitive drum is reduced, so that the waste heat efficiency is reduced.
In order to compensate for the reduction in efficiency, the blowing fan 60 is set to full speed to violently disturb the airflow in the post-charging device 62 and the developing device 7 to generate a spiral. In order to make the spiral generation more efficient, the above difference is reversed from that during copying,
Increase spraying to +50. After performing waste heat for a certain period of time in this state, both fans are stopped at the same time.

In particular, the air flow rate is different between a case where a through-pass double-sided conveyance system is used in which a plurality of transfer sheets P after fixing are fed again without stagnation and an image is formed, and a case where sheets are fed from a transfer sheet feeder. It is also effective to control the air flow rate or the balance between blowing and suctioning.

As shown by dotted lines A and B in FIG. 24, when the number of sheets set in the through-pass double-sided conveyance system is considered to be larger than the specified number and the temperature rise is considered to be sufficiently excessive, after the image formation is completed as shown in A. After a certain period of time, the suction fan is also strengthened, and the difference is gradually approached to 0 to increase the waste heat efficiency.

Table 1 below shows the difference between spraying and suctioning and phenomena in each image forming process.

[0062]

[Table 1] Difference (spray-suction) Multi-rotation before copying During copying After copying is completed +100 Toner scattering, HH flow Image disorder, toner scattering good +50 Toner scattering Image disorder, toner scattering good ± 0 Toner small scattering good Toner small quantity good −50 Good Good Toner scatter small amount -100 Good Good Toner scatter small amount In the above-described sequence of FIG. 24, the sheet passing condition where a large amount of transfer paper P passes through the through-pass double-sided conveyance system is detected, and the blowing fan 60 is set to S and the difference t. On the other hand, when the sheet passing condition that there is no transfer sheet P passing through the through-pass double-sided conveyance system is detected, the blowing fan 60 is set to S ₁ and the difference t ₁ , so that the fan 60 can be used under more optimal fan conditions according to the condition. it can.

Table 2 below shows the saturation temperature of the developing device 7 at that time. By setting the blowing fan 60 to S and the difference t, it can be seen that the heat of the transfer paper P is not transmitted to the developing device 7 and has an adiabatic effect.

[0064]

Table 2 When blowing fan / differential through ball developing device 7 or other uneven density below the transfer sheet and without _{S 1 / t 1 45 ℃ 55} ℃ S / t 45 ℃ 47 ℃ through the duplex transport system has occurred The method for correcting unevenness in the main scanning direction will be described in detail.

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

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

FIG. 8 (b) shows the potentials at a place where the potential is normally obtained at the target potential of 50V of the exposed portion and at a place higher than the target potential, although the surface potential formation by charging was performed uniformly. I have. This is the surface potential unevenness generated due to the difference in the photosensitivity characteristics of the photosensitive drums 1 as shown by the three types of characteristic curves in FIG. Even if the photosensitivity characteristics of the photosensitive drum 1 are uniform, if the light irradiation amount is not uniform depending on the position in the main scanning direction, the surface potential unevenness occurs.

FIG. 8 (c) shows that although the surface potential formation by charging and the surface potential formation by the potential decay by exposure were performed uniformly, the development was normally performed at the exposed portion potential of 50 V and the target position. Also shows a small place. This is Figure 1
As shown by the three characteristic curves 1, the surface potential of the photosensitive drum 1 and the application D to the developing sleeve for carrying and transporting the developer.
This is density unevenness caused by a difference in developing ability with respect to a developing contrast, which is a difference between C voltages. This occurs when the charging characteristics of the density unevenness are 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 in the main scanning direction of transfer efficiency at the time of transfer and separation (not shown).

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

FIG. 13 is a flowchart showing an 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 improvement mode in the input interface, and the mode is first started.

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

Step (S3) The key for starting the axial unevenness correction mode is pressed to start.

Step (S4) The image forming apparatus shown in FIG.
A test image sample as shown in FIG. As the conditions for forming this sample, three types of image exposure conditions (8 bits) were obtained under the primary charging conditions for forming the surface potential as described above in order to form an image such as solid black, halftone halftone, and solid white. The signals F0, 80,
00hex), developing, transferring and fixing under the above-mentioned developing conditions, outputting a sample, and detecting the gradation density reproduction characteristic by a density characteristic detecting means (not shown).

Step (S5) The output of the sample is placed on the document table by the mode executor at a specific position on the front side and the front or back side of the sample in the paper passing direction. Is detected.

Step (S6) When it is determined that the loading is completed, the original is read by the reader as described above. It is desirable that the reading by the reader be performed at a resolution of about 400 to 600 dpi.

Step (S7) It is determined whether or not the original is a test image sample based on whether or not the density gradation is the same pattern. If it is determined that the sample is not a test image sample, an error is notified in step S11, and the process ends.
In this case, the process may return to step S5.

Step (S8) If it is determined that the sample is a test image sample, the axial density distribution is calculated as shown in FIG. PWM level F0, 80, 00he
When a test image sample is formed by x, the read density distribution of the halftone portion of 80 hex where unevenness is most easily detected is calculated (the density distribution may be calculated by F0, 80, and 00hex, respectively).

Step (S9) When the target density is set to 0.5 in FIG. 14B, the increase / decrease of the read density distribution of the halftone portion with respect to 0.5 corresponds to each pixel in the main scanning direction. Is calculated. Negative correction is negative,
If the plus correction is represented by a plus sign, the required correction density is as shown in FIG.
FIG. 14C shows the required correction density as shown in FIG.

Step (S10) The correction light amount (correction level) for each pixel of the dot exposure laser is obtained from the drawing of the necessary correction density according to FIG. For example, when the required correction density is +0.8 in FIG. 15, the surface potential is -200 V, the photosensitive drum surface light quantity is +0.25 μJ, and the image data is +80 h.
This indicates that ex needs to be corrected. 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.

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

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

The illustrated correction table 101 and adder 10
4. The main scanning unevenness correction circuit 50 includes the selector 102, the address generation circuit 103 and the selector 102. CPU 100
Is a control means for controlling the whole of the apparatus, in which a control program as a copying machine, a ROM for storing the program according to the flowchart of FIG. 13 described above, and a work area are provided. It has a RAM to be used.

In the configuration shown in FIG.
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, as described above, the correction data of each pixel generated based on the image data obtained by reading the test image sample is written to a corresponding address position of this correction table (configured by the RAM). Therefore, the CPU 100 outputs to the selector 102 a signal for supplying the address from the CPU 100 to the correction table 101, and outputs an address, data to be written, and a write signal to the correction table 101. When the writing of the correction data to all the pixel positions in the main scanning direction is completed in this manner, 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 generating circuit 103 includes the photosensitive drum 1
Is triggered by a beam detect signal provided in the vicinity of the correction table 1 at a predetermined time, in synchronization with the carrier clock of the image data from the black signal generation circuit 22.
01 are sequentially output as address signals. 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 positive and negative correction data as described above, the adder 104 binarizes the image data obtained by correcting the characteristics of the image data in accordance with the characteristics of the printer engine. This is output to the circuit 23.

Although the description will be made before and after, the test image sample is formed by the CPU 100 every predetermined number of main scanning lines.
hex, 80 hex, and f0 hex are output in place of the black signal generation circuit 22. However, since the test image formation is performed to know the characteristics of the printer engine, no data is output from the correction table 101, or data of 0 is always output. In some cases, when forming a test image sample, 00, 80 hex, 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, 0 data is output from the black signal generation circuit 22, so that the test image sample described above can be formed as a result. An advantage in this case is that a test image sample can be formed only with the configuration of FIG.

Since data such as image unevenness is corrected at the 8-bit multi-level signal stage using the correction table 101 described above, uniform data is formed at the time of binarization. In this example, the density unevenness is completely corrected, so that a high-quality image without the density unevenness in the longitudinal direction (main scanning direction) can always be provided. In particular, according to the present embodiment, it is possible to suppress density unevenness in a relatively low density portion (highlight portion).

When the present invention is applied to an apparatus 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 density 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. Note that the laser drive circuit 24 is driven to generate laser light for a time dependent on the pulse width of the pulse width modulation signal.

As described above, by controlling the difference balance between the blowing fan 60 and the suction fan 67 and correcting the density unevenness at the laser writing level using the correction table, the longitudinal direction (main scanning direction) is always maintained. ) Can provide a high quality image without density unevenness.

<Embodiment 2> FIG. 16 shows an image forming apparatus according to Embodiment 2 of the present invention. FIG. 1 is a longitudinal 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. A primary charger (first scoroton-cone charger) that uniformly charges the surface of the photosensitive drum 1 around the photosensitive drum 1 in the rotation direction.
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 recharger (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 to the exposure based on the second image signal proportional to the density of the other color image that has been separated. Device 6,
A second developing device 7 for attaching a toner to the second electrostatic latent image to form a second image; a pre-transfer charger 62 for charging a color superimposed image formed on the photosensitive drum 1 before transfer; Corona transfer charger (transfer charger) 8 for transferring onto a transfer paper P, which is a material, and transferring the transfer paper P on which the color superimposed image has been transferred to the photosensitive drum 1
, A cleaning device 13 for removing residual toner remaining on the photosensitive drum 1 after transferring a color superimposed image, and a pre-exposure lamp for removing residual charge on the photosensitive drum 1 30 and the like are arranged.
The transfer paper P on which the color superimposed image has been transferred is a photosensitive drum 1
After being separated from the fixing device 12, the toner image is conveyed to the fixing device 12, where the toner image on the surface is fixed, a desired print image is formed, and the print image is discharged to the outside of the image forming apparatus main body.

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

Here, the operation of the fan according to the present invention will be described with reference to the same drawings as in the first embodiment.

FIG. 23 shows the sequence of the operation of the image forming apparatus, the operation of the post-charging and the operation of the blowing fan (post fan) 60. When the power of the image forming apparatus is turned on, the heater warm-up of the fixing device 12 is started. When the specific temperature is reached, the pre-multi-rotation starts. In the previous multi-rotation, charging is performed by potential control or the like, so that the post charger 62 also operates. However, the blowing fan 60 does not operate for such a short time that there is no excessive ozone generation or temperature rise. Only the suction fan 67 (not shown) operates. At the start of copying, the blowing fan 60 operates at half speed. The half speed is to reduce the fan airflow by half by controlling the input voltage to the fan to half. The reason for the half-speed operation is to prevent the toner image on the photosensitive drum 1 from being disturbed by the air flow in order to blow the airflow onto the photosensitive drum 1 at the post-charging unit. Here, the wind speed of the half-speed operation is set to 0.1 to 0.5 m / sec. When the image formation is completed, the operation is performed at the full speed, the operation is continued within an arbitrary post-processing time period c, heat and ozone are quickly exhausted, and the operation is stopped when a certain time has elapsed. The wind speed of the full-speed operation here is 0.
It is 2 to 1.0 m / sec.

Here, a connecting duct 61 is directly connected to the post charger 62, and a blowing fan 60 is further connected thereto.

The blowing fan 60 and the suction fan 67 are wired with a power supply 65 capable of supplying electric power independently and a control means 66 capable of controlling each fan independently. Signals from a circuit for controlling the entire apparatus are electrically wired via an image data correction device 50.

FIG. 24 shows the relationship between the difference between the above-described air flow injection blowing amount and the air flow suction amount, and is a method of controlling the difference amount between blowing and suction according to the image forming process.

The suction fan 67 rotates at half speed at the front of multiple rotations.
It becomes full speed rotation at the copy start. Suction fan here 6
The wind speed for the full-speed operation of 7 mm is 0.2 to 1.0 m / sec, and the wind speed for the half speed operation is 0.1 to 0.5 m / sec. Looking at the difference between (blowing) and (sucking) according to the image forming process when the maximum difference is set to 100, when the power is turned on, both the fans are stopped, the difference is 0, and At the beginning, post-charging is performed, and only the suction fan 67 operates, and the difference becomes -50.

Next, when the copying is started, the blowing is performed while blowing off the heat so as not to disturb the image or to scatter the toner. Since the photosensitive drum 1 rotates during copying, the airflow swirls around the photosensitive drum and is already in a state of being easily diffused to the outside. And get caught up in the air flow. The difference at this time is -50. Here, it is more effective to increase the suction to a difference of about -70.

Next, when the copy image formation is completed,
The rotation of the photosensitive drum 1 stops, and the swirling state of the airflow due to the rotation of the photosensitive drum is reduced, so that the waste heat efficiency is reduced.
In order to compensate for the reduction in efficiency, the blowing fan 60 is set to full speed to violently disturb the airflow in the post-charging device 62 and the developing device 7 to generate a spiral. In order to make the spiral generation more efficient, the above difference is reversed from that during copying,
Increase spraying to +50. After performing waste heat for a certain period of time in this state, both fans are stopped at the same time.

In particular, the air flow rate is different between the case where a through-pass double-sided conveyance system is used in which a plurality of fixed transfer sheets P are fed again without stagnation and an image is formed, and the case where paper is fed from a transfer sheet feeder. It is also effective to control the air flow rate or the balance between blowing and suctioning.

As shown by dotted lines A and B in FIG. 24, when the number of sheets set in the through-pass double-sided conveyance system is considered to be larger than the specific number and the temperature rise is considered to be sufficiently excessive, after the image formation is completed as shown in A. After a certain period of time, the suction fan is also strengthened, and the difference is gradually approached to 0 to increase the waste heat efficiency.

As described above, the developing device 7
Thus, the change in the characteristics of the developer due to the temperature rise is suppressed, and it is possible to prevent an image quality failure such as a decrease in density or a change in image quality. Further, the image scanner unit 18 includes the original glass table 1.
The original 15 placed on the scanner 4 is scanned and read by an illumination lamp 16, and image information is converted into an electric signal by a photoelectric conversion element 19. The reflected light from the original 15 scanned by the illumination lamp 16 is Mirrors 17a, 17
b, 17c, a photoelectric conversion element 19 incorporating red, green, and blue filters by a lens 17d.
Imaged on top. The electric signal from which the red, green, and blue components are output by the photoelectric conversion element 19 is digitized by the A / D converter 21,
The signal is sent to the signal processing unit 22 as a color separation unit, and is converted into an image signal proportional to the image density of each of the red and black components.

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

The red image signal (first image signal) and the black image signal (second image signal) are sent to laser drivers 24b and 24a as signal generators, and are supplied in accordance with the red and black image signals. Laser 20b, 20
The light emission of a is turned on / off. The laser light emitted in response to the red signal is used as first image information by a polygon mirror 2.
8. Write a 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 a second electrostatic latent image on the photosensitive drum 1 via the polygon mirror 28 and the mirrors 17f and 17g as second image information.

In the present embodiment, an amorphous silicon drum is used for the photosensitive drum 1. Amorphous silicon drums have features such as high durability and long life.

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

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

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

After the first development, recharging is performed in (d). A voltage of 600 V, which is higher than the desired second development position potential of 400 V, is applied to the grid of the recharger 5, and the first developed non-image portion is, for example, Control is performed to charge to 600V. At that time, the first developing unit is charged to, for example, 500V.

Next, when performing exposure in accordance with the second image information in (e), a constant exposure amount (for example, the first developed non-image portion is attenuated by 200 V) over the entire surface as compared with the second developed single color. Exposure is large). At this time, in the first developing section, the exposure for the fixed exposure amount does not attenuate the potential attenuating in the first non-developing non-image section, but only attenuates, for example, 100V. This is because the first developer scatters the light without transmitting it, and its transmittance was 50%. The surface potential after exposure for the second exposure constant additional exposure amount of 0.25 μJ becomes the second development position target potential of 400 V. The first development non-image portion recharged target potential is represented by a straight line having a known drum sensitivity of 800 V / μJ. It was assumed that it was 600V. Next, also from the known toner layer transmittance of 50%, the amount of light reaching the drum to the first image developing unit is 0.125 μJ. The first method is similar to the method described above.
The target potential after recharging of the developed image portion may be set to 500V.

In this embodiment, a semiconductor laser is used as the second exposure means. However, complicated processing is not required between the second developing single-color mode and the two-color mode. Since the amount of laser light is determined by the laser drive current, a constant offset current is added to the drive current in the second development monochrome mode in the two-color mode. That is, the second image signal is also weakly exposed to the portion where the second image signal is off, and the portion where the second image signal is turned on is also subjected to the exposure that is increased by the same amount of exposure, the potential of the first developed image portion is 400 V, and the first developed image portion is 400 V. The potential of the non-image area is also 400
V, and when the second image signal is on, the first developed non-image portion is exposed to 50V. Thereafter, in the developing process, the second
By applying a bias of 300 V to the developing sleeve,
A sufficient second image density can be obtained without the second developer being mixed into the first developing portion or being developed in the non-image portions of the first and second images.

A description will be given using the operation flow of creating the correction table 50 shown in FIG. 13 as in the first embodiment.

(1) The image forming apparatus of the present embodiment has an “improving image mode” as an image unevenness improvement mode in the input interface, and the mode is first started.

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

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

(4) The image forming apparatus outputs a test image sample as shown in FIG. As the conditions for forming this sample, in order to form an image such as a completely solid black, a halftone halftone, and a solid white, three types of image exposure conditions obtained by the above-described primary charging conditions for forming the surface potential (see FIG. Twelve PWM levels of F0, 80, and 00 hex), developing, transferring, and fixing under the above-described developing conditions, and outputting a sample.

Here, as a feature of this embodiment, a test image sample is output for each of two colors (for example, red and black). Thereafter, the following operations (5) to (10) are performed for each of red and black colors.

After that, the following operations (5) to (10) are performed after the color (red and black).

(5) The output sample is placed at a specific position on the platen by the mode executor at the leading end and the front or back side of the sample in the paper passing direction. Determine whether it has been detected.

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

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

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

(9) Referring to 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 minus correction is represented by a negative sign and the plus correction is represented by a plus sign, the required correction density becomes a required correction density as shown in FIG.

(10) The corrected light amount (correction level) for each pixel of the dot exposure laser is obtained from FIG. As an example, in FIG. 15, the required correction density is +0.8.
In the case of, the surface potential is -200V and the drum surface light amount is + 200V.
This indicates that a correction of +80 hex is required for image data of 0.25 μJ. 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 difference balance between the blowing fan 60 and the suction fan 67 is controlled, and the density unevenness is corrected for each color (red and black) at the laser writing level using the correction table. Thus, a high-quality image without density unevenness in the longitudinal direction (main scanning direction) can always be provided.

<Embodiment 3> FIG. 19 is a schematic structural view of Embodiment 3 of an image forming apparatus according to the present invention.

The photosensitive drum 11 is provided with a photoconductive layer on a cylindrical conductive substrate, and is rotatably supported in the direction of arrow R1 in the figure. A scorotocon charger (primary charger) is provided around the photosensitive drum 1 to uniformly charge the surface of the photosensitive drum 1 in order along the rotation direction.
2. An exposure device 3 for reading an original, exposing the photosensitive drum 1 based on an image signal proportional to the image density, and forming an electrostatic latent image, attaching toner to the electrostatic latent image and developing the toner image as a toner image Developing device 7, post-charging device (pre-transfer charging device) 62 for charging the toner image before transfer, corona transfer charging for transferring the toner image formed on the photosensitive drum 1 onto transfer paper P as a transfer material (Transfer charger) 8, an electrostatic separation charger (separation charger) 9 for separating transfer paper P on which the toner image has been transferred from photosensitive drum 1, and remained on photosensitive drum 1 after transferring the toner image. 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 provided. The transfer paper P on which the toner image has been transferred is conveyed to the fixing device 12 after being separated from the photosensitive drum 1, where the toner image on the surface is fixed, and a desired print image is formed. Is discharged to the outside.

Here, a connecting duct 61 is directly connected to the post charger 62, and a blowing fan 60 is further connected thereto.

Here, the operation of the fan of the present invention will be described with reference to the same drawings as those in the first embodiment.

The blowing fan 60 and the suction fan 67 are wired with a power supply 65 capable of supplying power independently and a control means 66 capable of controlling each fan independently. Signals from a circuit for controlling the entire apparatus are electrically wired via an image data correction device 50.

FIG. 23 shows a sequence of the operation of the image forming apparatus and the operation of the post-charging and blowing fan (post fan) 60. When the power of the image forming apparatus is turned on, the heater warm-up of the fixing device 12 is started. When the specific temperature is reached, the pre-multi-rotation starts. In the previous multi-rotation, charging is performed by potential control or the like, so that the post charger 62 also operates. However, the blowing fan 60 does not operate for such a short time that there is no excessive ozone generation or temperature rise. Only the suction fan 67 (not shown) operates. At the start of copying, the blowing fan 60 operates at half speed. The half speed is to reduce the fan airflow by half by controlling the input voltage to the fan to half. The reason for the half-speed operation is to prevent the toner image on the photosensitive drum 1 from being disturbed by the air flow in order to blow the airflow onto the photosensitive drum 1 at the post-charging unit. Here, the wind speed of the half-speed operation is set to 0.1 to 0.5 m / sec. When the image formation is completed, the operation is performed at the full speed, the operation is continued within an arbitrary post-processing time period c, heat and ozone are quickly exhausted, and the operation is stopped when a certain time has elapsed. The wind speed of the full-speed operation here is 0.
It is 2 to 1.0 m / sec.

FIG. 24 shows the relationship between the difference between the above-described air flow injection blowing amount and the air flow suction amount, and is a method for controlling the difference between the blowing and suction in accordance with the image forming process.

The suction fan 67 rotates at half speed at the front of multiple rotations.
It becomes full speed rotation at the copy start. Suction fan here 6
The wind speed for the full-speed operation of 7 mm is 0.2 to 1.0 m / sec, and the wind speed for the half speed operation is 0.1 to 0.5 m / sec. Looking at the difference between (blowing) and (sucking) according to the image forming process when the maximum difference is set to 100, when the power is turned on, both the fans are stopped, the difference is 0, and At the beginning, post-charging is performed, and only the suction fan 67 operates, and the difference becomes -50.

Next, when the copying is started, the blowing is performed while blowing the heat so as not to disturb the image or to scatter the toner. Since the photosensitive drum 1 rotates during copying, the airflow swirls around the photosensitive drum and is already in a state of being easily diffused to the outside. And get caught up in the air flow. The difference at this time is -50. Here, it is more effective to increase the suction to a difference of about -70.

Next, when the copy image formation is completed,
The rotation of the photosensitive drum 1 stops, and the swirling state of the airflow due to the rotation of the photosensitive drum is reduced, so that the waste heat efficiency is reduced.
In order to compensate for the reduction in efficiency, the blowing fan 60 is set to full speed to violently disturb the airflow in the post-charging device 62 and the developing device 7 to generate a spiral. In order to make the spiral generation more efficient, the above difference is reversed from that during copying,
Increase spraying to +50. After performing waste heat for a certain period of time in this state, both fans are stopped at the same time.

In particular, the air flow rate is different between the case where a through-pass double-sided conveyance system is used in which a plurality of fixed transfer papers P are fed again without stagnation and an image is formed, and the case where paper is fed from a transfer paper feeder. It is also effective to control the air flow rate or the balance between blowing and suctioning.

As shown by dotted lines A and B in FIG. 24, when the number of sheets set in the through-pass double-sided conveyance system is considered to be larger than the specified number and the temperature rise is considered to be sufficiently excessive, after the image formation is completed as shown in A. After a certain period of time, the suction fan is also strengthened, and the difference is gradually approached to 0 to increase the waste heat efficiency.

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 on a photoelectric conversion element (1-line CCD) 19.
The image is converted into an electric signal corresponding to the image information by forming an image on the top. Here, the reflected light from the original 15 illuminated by the illumination lamp 16 is reflected by mirrors 17a, 17b, 1
The photoelectric conversion element 19 is guided by the lens 17d and guided by the lens 17d.
Imaged on top. The electric signal output from the photoelectric conversion element 19 is A / D converted by an A / D converter 21 to be converted into 8-bit digital image data, and thereafter, the black signal generation circuit 22 converts luminance information into density information. Log conversion is performed to obtain image density data.

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

The 8-bit digital image data signal generated as described above is converted to an LED driving circuit 2 which is a feature of the present invention.
4c, and the LED drive circuit 24c uses 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.

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

In the present embodiment, an amorphous silicon drum is used for the photosensitive drum 1. Amorphous silicon drums are characterized by high stability of the characteristics of the conductive substrate, high durability and long life.

Each step for explaining the image forming process of the present embodiment is the same as that of the first embodiment.

A description will be given using the flow of operation for creating the correction table 50 in FIG. 13 as in the first embodiment.

(1) The image forming apparatus of the present embodiment has an “improving image mode” as an image unevenness improvement mode in the input interface, and the mode is first started.

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

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

(4) The image forming apparatus outputs a test image sample as shown in FIG. As the conditions for forming this sample, in order to form an image such as a completely solid black, a halftone halftone, and a solid white, three types of image exposure conditions obtained by the above-described primary charging conditions for forming the surface potential (see FIG. Twelve PWM levels of F0, 80, and 00 hex), developing, transferring, and fixing under the above-described developing conditions, and outputting a sample.

(5) The output sample is placed on the platen by the mode executor at a specific position at the front end and the front or back side of the sample in the paper passing direction. Determine whether it has been detected.

(6) When it is determined that the loading is completed, the original is read by the reader as described above. It is desirable that the reading by the reader be 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 or not the density gradation is the same pattern.

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

(9) Referring to 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 minus correction is represented by a negative sign and the plus correction is represented by a plus sign, the required correction density becomes a required correction density as shown in FIG.

(10) The correction light amount (correction level) for each pixel of the dot exposure laser is obtained from FIG. As an example, in FIG. 15, the required correction density is +0.8.
In the case of, the surface potential is -200V and the drum surface light amount is + 200V.
This indicates that a correction of +80 hex is required for image data of 0.25 μJ. 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 difference balance between the blowing fan 60 and the suction fan 67 is controlled, and the density unevenness is corrected at the LED writing level using the correction table, so that the longitudinal direction (main scanning direction) is always maintained. Therefore, it is possible to provide a high-quality image without density unevenness.

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. By doing so, it is possible to always provide a high-quality image without density unevenness in the longitudinal direction (main scanning direction).

In the above-described first to third embodiments, an example has been described in which an image is formed by a binarization process using an error diffusion method or the like (or a dither method or the like). However, the image is formed according to the PWM method. Of course, it can be applied to the case. Further, when an image is formed by the PWM method, basically, pixels having different shades (actually, pixels having different sizes due to area modulation and having different shades when viewed from human eyes) are formed. Perceived.)
If the density distribution is simply read by the reader unit of the embodiment, the density unevenness of each pixel can be corrected. However,
In order to read without shifting even one pixel, it is necessary to read at a very high precision. As a practical problem, it is difficult to determine the characteristics of each pixel formed on the printer engine side from the read image. Printer resolution is 600d
In the case of 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, PW
Even in the case of forming by the M method, it is desirable to detect the density unevenness in the main scanning direction based on the average value of a plurality of pixels consecutively read in the main scanning direction, and to correct it.

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

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

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

Examples of the storage medium for supplying the program code include a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM,
CD-R, magnetic tape, nonvolatile memory card, RO
M or the like can be used.

When the computer executes the readout program code, not only the functions of the above-described embodiment are realized, but also the OS (Operating System) running on the computer based on the instruction of the program code. It is needless to say that the present invention includes a case where the system performs some or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

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

[0166]

As described above, according to the present invention,
Eliminates heat diffusion and temperature rise during through-pass double-sided conveyance, especially when using an a-Si photosensitive member with a high photosensitivity and a surface layer SiC curing type as an image carrier (photosensitive drum) that has a long life and high speed output. In addition, it is possible to prevent the image density from lowering and the density unevenness without causing partial unevenness or performance deterioration due to heat on the developing performance of the minute latent image in the developing system.

Further, a one-component toner (one-component magnetic developer, one-component non-magnetic developer) as a developer is not exposed to the influence of excessive heat, the toner charge amount is not largely changed, and the density is not changed. There is an effect that a high quality image can be provided on the final image without causing problems such as defects and capri.

[Brief description of the drawings]

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

FIG. 2 is an enlarged view of FIG.

FIGS. 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 illustrating image processing according to the first embodiment.

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

FIGS. 6A and 6B are diagrams illustrating laser lighting of binary image data.

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

FIGS. 8A to 8C are schematic diagrams in which the cause of the occurrence of density unevenness in the main scanning direction is analyzed.

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

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

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

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

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

FIGS. 14A to 14C are diagrams showing test image samples, reading densities, and densities required for correction.

FIG. 15 is a diagram illustrating a correction amount.

FIG. 16 is a longitudinal sectional view illustrating 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 illustrating image processing according to the second embodiment.

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

FIG. 20 is a longitudinal 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.

FIG. 22 (a) is a view taken in the direction of the arrow X in FIG. 2; (B) is a view on arrow Y in FIG. 2.

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Image carrier (photosensitive drum) 2 Primary charger (scorotron charger) 3 Exposure means (exposure apparatus) 7 Developing apparatus 8 Transfer apparatus (transfer charger) 20 Micropoint exposure means (laser) 20c Micropoint exposure means (light emission) Element, LED) 50 Correction value creation unit (main scanning unevenness correction circuit) 60 Air flow injection blowing unit (Blowing fan) 61 Air flow transmission unit (Connecting duct) 62 Developer charge control charger (Post charger) 66 Control unit (Fan control circuit) 67 Air flow suction means (suction fan) 71 Air flow transmission means (duct)

Claims (13)

[Claims] An image bearing member, a primary charger for uniformly charging the surface of the image bearing member, an exposing means for exposing the charged surface of the image bearing member to form an electrostatic latent image; A developing device that attaches toner to the latent image to develop it as a toner image; a transfer device that transfers the toner image on the image carrier onto transfer paper; and a transfer unit between the transfer device and the image carrier. A transfer paper transport unit that transports the transfer paper, wherein the developing device and the transfer paper transport unit, between one end of the image carrier along the generatrix. Air flow spraying means provided; air flow suction means provided at the other end in the direction along the generatrix of the image carrier between the developing device and the transfer paper transport unit; The amount of air blown by the airflow spraying means and the airflow suction means Control means for controlling a difference amount from the suction amount according to an image forming process. 2. A developer charge control charger for controlling a charge amount of a toner image developed on the image carrier is provided between the developing device and the transfer paper transport unit, An air flow path is formed inside a shield case of the charger, and air flow transmitting means is provided for connecting the air flow jetting / blowing means and the air flow suction means to the air flow path. 2. The image forming apparatus according to 1. 3. The control unit controls the difference amount between the spray amount and the suction amount to be larger in the positive direction after the completion of image formation than during the image formation operation. The image forming apparatus according to claim 1. 4. The image forming apparatus according to claim 1, wherein the control unit stops the air flow blowing unit before the image forming operation, generates a relatively small air flow during the image forming operation, and generates a relatively large air flow after the image forming operation. The image forming apparatus according to claim 1, wherein a flow is generated. 5. A fixing device for fixing a toner image on a transfer sheet after transfer of a toner image, and a transfer sheet transfer unit for transferring a plurality of fixed transfer sheets without stagnation. The image forming apparatus according to claim 1, 2, 3, or 4, wherein: 6. The method according to claim 1, wherein the control unit controls an air flow rate and an air flow rate based on a case where a plurality of transfer sheets after fixing the toner image are fed again without stagnating the image and a case where a sheet is fed from a transfer sheet feeder. The image forming apparatus according to claim 5, wherein the flow rate is controlled to be different. 7. A photosensitive drum having a photoconductive member for forming an electrostatic latent image formed in a thin layer on a cylindrical conductive substrate as the image carrier, and a micropoint exposure device as the control device. The image forming apparatus according to claim 1, 2, 3, 4, 5, or 6. 8. The apparatus according to claim 7, wherein the minute point exposure means forms an electrostatic latent image on the photosensitive drum by scanning and exposing a laser beam capable of digital exposure for each pixel. Image forming device. 9. The image processing apparatus according to claim 1, wherein the minute point exposure unit forms an electrostatic latent image on the photosensitive drum by driving and exposing a plurality of light emitting elements arranged in a main scanning direction. 8. The image forming apparatus according to 7. 10. The image forming apparatus according to claim 7, wherein the photosensitive drum uses an a-Si photosensitive member. 11. The image processing apparatus according to claim 1, further comprising a conversion unit configured to convert the multi-valued image data into binary data based on the multi-valued image data.
The image forming apparatus according to 8, 9, or 10. 12. An image forming section comprising density characteristic detecting means for detecting a gradation density reproduction characteristic, calculating an intermediate density between a black image data level and a white image data level detected by the density characteristic detecting means. Using the calculated value as the target concentration,
And a correction value generating means for performing correction on the image data.
12. The image forming apparatus according to 8, 9, 10, or 11. 13. The method according to claim 1, wherein the developing device uses a one-component developer.
13. The image forming apparatus according to 8, 9, 10, 11, or 12.