JP2000293068A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the improvement of image quality and the restriction of image formation cost compatible by controlling the operation of preparing for image formation based on the quiescent-time interval of an image forming operation and an amount of moisture in an installation environment. SOLUTION: When a copy button is turned on or a print signal is inputted and in the case where, with a main power source kept on, an environment contains a specific amount of moisture or more and a time interval between the input of an image forming operation signal into a machine and the completion of the previous operation exceeds a specific time, the device judges that the machine is left for a long time with low power M (in a state of not being first in the morning), and starts the operation of preparing for image formation. A developing-unit drive motor is first operated to rotate the sleeve of a developing unit, the copy button is turned on in advance and, at the same time, a drum drive motor is operated to idly rotate a drum. A pre-exposure is lit on and a cleaner system is driven at the same time, and with the cleaner system also idly rotating, an area SS of the operation of preparing for the image formation is added and the drive of the developing unit consequently starts.

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 using an electrophotographic system, and more particularly to a technique for improving the quality of an image formed after a long period of suspension of the apparatus and suppressing toner consumption.

[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. There are digital printers or digital copiers as various kinds of devices.

FIG. 21 shows a schematic configuration of such a conventional image forming apparatus, for example, a digital printer, which will be described below.

A photosensitive drum 1 as an image carrier (photoreceptor)
Is provided with a photoconductive layer on a cylindrical conductive substrate, and is rotatably supported in the direction of arrow Rl in the figure. Around the photosensitive drum 1, a scoro-to-cone charger 2 for uniformly charging the surface of the photosensitive drum 1 is read in order along the direction of rotation, and the original is read, based on an image signal proportional to the density of the surface image. An exposure device (exposure 3 including image information) for exposing the photosensitive drum 1 to form an electrostatic latent image; a developing device 7 for forming a toner image by attaching toner to the electrostatic latent image; Transfer charger (transfer charger) 8 for transferring the toner image formed on the transfer paper P as a transfer material, and an electrostatic separation charger for separating the transfer paper P on which the toner image has been transferred from the photosensitive drum 1 (Separation charger) 9, 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 on the photosensitive drum 1, and the like.

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 the illumination lamp 16 and reflects the reflected light on the photoelectric conversion element 1 as a one-line CCD.
The image is converted into an electric signal corresponding to the image information by forming an image on the image 9.

Here, the reflected light from the document 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 an 8-bit digital image data signal, and thereafter, a black signal generation circuit 22 converts luminance information into density information. LOG conversion is performed to obtain image density data.

[0008] The 8-bit digital image data signal generated as described above is input to a laser drive circuit 24. The drive circuit 24 is a well-known PWM reverse path, and outputs a signal according to the magnitude of the input image density signal. Turn on / off semiconductor laser
Modulating the emission time.

For example, as shown in FIG. 5, when image data for each pixel is input in the laser scanning direction as shown in FIG. 5A, the drive signal for turning on / off the laser is shown in FIG.
(B). That is, the image data is 00h
ex, the on-duty of the laser drive signal is 5% of one pixel scan time, and the on-duty of the laser drive signal at FFhex is 8% of one pixel scan time.
5%, and so on. In this way, shading is realized by performing area gradation within one pixel.

FIG. 7 shows general IL characteristics (driving current-light amount characteristics) of the laser.
The drive current used at the time of OFF is ION / IO
Since it is an FF, the laser drive current for the image signal in FIG. 5A 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 above-described PWM circuit and a binary laser driving circuit. PW
The M circuit modulates to a pulse width signal corresponding to the emission time of the semiconductor laser in accordance with the magnitude of the input image density signal as described above, while the binarization circuit corresponds to the image density signal. The signal is converted into a two-stage signal area of a specific light emission ON signal area and an OFF signal area, and is input to the laser drive circuit 24 to turn on / off the semiconductor laser element.

As a typical binarization method,
2 based on image data based on error diffusion method or dither method
There is a method of generating a quantified signal, and the time for generating a laser beam is basically constant regardless of the density. The difference is that the laser is emitted at a low probability (the area irradiated with the laser light within the predetermined area) in a low density area, and the laser is emitted with a high probability in a high density area.

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 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, Japanese Patent Publication No. 42-23910.
Many 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 toner (developer). 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 copied image.

Various development methods are known for visualizing an electric latent image using a developer. For example, a magnetic brush developing method described in US Pat. No. 2,874,063, a powder cloud method described in US Pat. No. 221 776, a fur brush developing method, a liquid developing method, and the like. There is a method. In these developing methods, a magnetic brush developing method using a two-component developer mainly composed of a toner and a carrier has been widely put into practical use. Of the two-component developer, such as deterioration of the toner and a change in the mixing ratio of the toner and the carrier.

In order to avoid such a problem, various developing methods using a one-component developer consisting only of toner 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, Japanese Patent Application Laid-Open No. 50-4539 discloses a method of imparting a charge by frictional charging with a toner carrier. Japanese Patent Application Laid-Open No. 54-2100 discloses a method in which a friction member is provided. Describes a method of imparting a charge by frictional charging. 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.

There is also a method in which the toner image on the drum after development is adjusted by a developer charge control charger 62 (hereinafter referred to as a post charger) so that the toner charge is adjusted so as to increase the transfer efficiency.

[0020]

In the conventional example described above, when a corona charging method is used as a method for uniformly charging the photoreceptor, ozone generated by corona discharge and nitrate substances as a discharge product are used. Forms a film on the photoreceptor, and when the film adsorbs moisture in the air and absorbs moisture, the surface resistance of the photoreceptor decreases and retains the charge of the exposed electrostatic latent image including image information data. Unsteadily turbulent in the surface direction, disturbing part or all of the image information,
As a phenomenon state on the image, the image flows as if the aqueous ink had flowed into the water. Similarly, when a corona charger is used for the post charger, the same ozone causes image flow obstruction. The same applies to the transfer charger and the separation charger.

This phenomenon has a characteristic that the longer the period of time during which the apparatus is stopped after the image formation, the more noticeable the moisture absorption of the adhered substance on the same portion of the photoreceptor is.

Conventionally, to solve this problem, a method of sucking and discharging ozone gas by sucking air from the inside of the shield case of each charger by a fan has been implemented. However, it is impossible to completely discharge gas. However, it was not possible to prevent adverse effects on the photoreceptor due to substances attached to the photoreceptor surface, and it was not possible to suppress image deletion.

In an apparatus which has a long service life and enables high-speed image formation, substances deposited from a rubber material of a feed roller and a transfer roller for feeding and transferring the transfer sheet are offset from the paper to the photosensitive member. It may be transported and redeposited on the surface of the photoreceptor, and may be gradually laminated over a long period of use, causing image deletion as in the case of the above-mentioned adhered substance.

Further, as a developing method, an electric field flying developing method using a one-component magnetic developer mainly utilizing an electric field developing phenomenon, and a jumping developing method faithfully removes disturbance of an electrostatic latent image on a photoreceptor as it is. Easy to reproduce in the shape, especially,
When the image forming apparatus is started in a high humidity environment, the developer absorbs moisture while standing, and the surface resistance of the developer particles decreases, so that the amount of charge to be held by the developer cannot be maintained. As a result, there is an obstacle that the density reduction and the image deletion phenomenon are more easily recognized.

This obstacle is exacerbated in accordance with the moisture adsorbed on the developer particles. In other words, the obstruction occurs as the density is reduced or the image flow is deteriorated in accordance with the humidity or the amount of moisture in the air. It is necessary to increase the ratio of toner supplied, and users who use a small number of sheets tend to be disadvantageous in terms of copy cost and developer consumption.

In order to solve the problems described above, a method of increasing the polishing effect on the surface of the photoreceptor by applying a developer onto the photoreceptor and supplying the developer to the cleaning device has been adopted.

However, in order to sufficiently enhance the polishing effect, it is necessary to supply a large amount or frequently of a developer to be supplied for polishing, and the developer is supplied every time a copy or printout image is formed. If this is done, the polishing effect will be improved, but for users who use only a small amount of copies or printouts, the developer will be consumed excessively for the number of sheets used.

That is, there have been problems such as an increase in copy cost per sheet and an unnecessary consumption of toner.

The above problems are remarkable in high-speed network-compatible digital copying machines and high-speed printers that need to wait for input of image data and document data output command signals even at night.

In particular, when an a-Si photosensitive member is used as a photosensitive drum having excellent durability and image quality as a photosensitive drum for a high-speed network-compatible digital copying machine or a high-speed printer in a high-humidity environment, a long time Ozone generation due to discharge increases due to use over a long period of time, and when left for a long period of time, the ozone product and discharge product adhere to the surface of the photoreceptor, absorb moisture, and the image is formed as an initial image after the power of the image forming apparatus is turned on. A flow-like image is likely to occur, and this image-flow-like phenomenon is particularly remarkable when laser or LED spot exposure writing using digital data is performed on the photoreceptor.

The size of the laser spot is 600d.
In the case of a spot diameter of 50 to 70 μm corresponding to pi, fine dots are formed, so even a slight disturbance of electric charge is visually integrated as an aggregate thereof and recognized as a difference from a normal part, so that the difference is more noticeable. And become apparent as an image deletion phenomenon.

Therefore, the amount of toner for polishing the drum surface in a high-humidity environment needs to be set to be larger than the standard amount, so that a user who uses a small number of sheets tends to be disadvantageous as described above. Was supposed to be.

As described above, in the case where the image forming apparatus is in the standby state for a long time in the standby state, there is a problem that the image flows due to the adhesion of the drum or moisture, and the density decreases due to the absorption of the developer, and the photosensitive member is polished. When the toner is used for this purpose, the amount of consumption increases, and it has been difficult to achieve both improvement in image quality and suppression of image formation cost.

An object of the present invention is to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide an image forming apparatus capable of achieving both improvement of image quality and suppression of image forming cost. To provide.

[0035]

According to the present invention, there is provided an image carrier capable of forming an electrostatic latent image, charging means for charging the image carrier, and Electrostatic latent image forming means for forming an electrostatic latent image according to image information on a carrier, developing means for developing the electrostatic latent image on the image carrier with a developer, and forming on the image carrier Transfer means for transferring the transferred developer image onto transfer paper being conveyed, fixing means having a temperature control means for fixing the developer image on the transfer paper, and cleaning means for cleaning the surface of the image carrier, Performs an image formation preparation operation by inputting an image formation operation start signal,
After that, in an image forming apparatus including a control unit that performs a normal image forming operation, and a unit that detects a pause time interval from the end of the previous image forming operation to the input of the next image forming operation start signal, Means for detecting the amount of moisture in the environment where the image forming apparatus is installed, wherein the control means controls the image forming preparation operation based on the pause time interval and the amount of moisture in the environment. I do.

The control of the image forming preparation operation by the control means means that the image forming preparation operation is performed when the water content of the environment is equal to or more than a specific water content and the pause time interval is equal to or longer than a specific time. It is also preferable to perform the treatment for a longer time than when the above condition is not satisfied.

The control means has a standby mode in which, when the state in which the image forming operation is not performed is continued for a predetermined time or more, the driving of some of the constituent means is stopped or the apparatus is in a standby state. It is also preferable that the image forming preparation operation is performed when an image forming operation start signal is input in step (1).

A potential detecting means for detecting a surface potential of the image carrier; wherein the control means controls the surface potential of the image carrier to a specific potential in accordance with a detection value of the potential detecting means in the image forming preparation operation. It is also preferable to have a potential control step of adjusting the potential.

Preferably, the control means has a developer image forming step during an image forming preparation operation for forming a developer image on an image carrier in the image forming preparation operation.

The image forming preparation operation by the control means is to form a developer image on the image carrier by operating the image carrier, the charging means, the electrostatic latent image forming means, the developing means and the cleaning means. A first step, a second step of controlling the temperature of the fixing unit to a fixable temperature while operating the image carrier, the charging unit, and the cleaning unit; and operating at least the image carrier and the charging unit. And performing a preparatory operation for a normal image forming operation, wherein the control means detects that the environmental moisture content is in a first specific moisture content region. When the first, second, and third steps are performed, and it is detected that the environmental moisture content is in the second specific moisture content region, the second and third steps are performed, and the environmental moisture content is determined. Is detected as the third specific moisture content region, the third step is performed. And it is also suitable.

The first specific moisture content region has a moisture content of 9 g / m ^3.
That is, the second specific moisture content region is less than 9 g / m ³ and 5 g / m ³ or more, and the third specific moisture content region is 5 g / m ^3.
It is also preferably less than m ^3.

In the developer image forming step during the image forming preparation operation, the control means sets the charging output value of the charging means to the value used in the previous image formation,
It is also preferable that the charging is performed wider than the corresponding area of the developer image formed on the image carrier.

In the developer image forming step during the image forming preparation operation, the control means sets the latent image forming output value by the electrostatic latent image forming means to the value used in the previous image forming, It is also preferable to form an electrostatic latent image corresponding to the developer image formed on the body.

The developing means carries a developer on a developer carrying member, and a developing unit which faces the image carrier by the developer carrying member while regulating the layer thickness of the developer by the developer regulating means. The developing unit forms a developing electric field between the image carrier and the developer carrier in the developing unit, and develops an electrostatic latent image on the image carrier with the developer.
In the developer image forming step during the image forming preparation operation,
It is preferable that the developing electric field output value of the developing unit be the value used in the previous image formation, and that the developer image be formed in correspondence with the electrostatic latent image formed on the image carrier.

It is also preferable that the image carrier is a photosensitive drum in which a photoconductor for forming an electrostatic latent image is formed in a thin layer on a cylindrical conductive substrate.

Preferably, the photosensitive drum uses an a-Si photoreceptor.

It is also preferable that the electrostatic latent image forming means scans and exposes a laser beam which blinks in accordance with image information to enable fine point exposure for each pixel on the image carrier.

It is also preferable that the electrostatic latent image forming means drives a plurality of light emitting elements arranged in a scanning direction to form an electrostatic latent image on the image carrier.

It is preferable that the apparatus further comprises means for converting multi-valued image data into binary image data based on the image information, and wherein the electrostatic latent image forming means forms an electrostatic latent image based on the binary image data. is there.

A density characteristic detecting means capable of detecting a gradation density reproduction characteristic corresponding to each pixel in the scanning direction of the electrostatic latent image forming means, and a gradation density reproduction characteristic detected by the density characteristic detection means. It is also preferable that the image processing apparatus further includes a correction value creation unit that performs correction on the image data based on the correction value.

The developing means preferably uses a one-component developer as a developer.

In the image forming apparatus configured as described above, the control of the image forming preparation operation can be performed more efficiently, and high quality image quality can be maintained without excessive consumption of the developer. can do.

[0053]

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

<First Embodiment> FIG. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment.

The photosensitive photosensitive drum 1 as an image carrier (photosensitive body) is provided with a photoconductive layer on a cylindrical conductive base, and is rotatably supported in the direction of arrow Rl in the figure.
Then, around the photosensitive drum 1, in order along the rotation direction, a scoro-to-con charger 2 serving as a charging unit for uniformly charging the surface of the photosensitive drum 1, and reading the original,
Photosensitive drum 1 based on an image signal proportional to the density of the surface image
Exposure 3 including image information emitted from an exposure device (semiconductor laser 20) as an electrostatic latent image forming means for forming an electrostatic latent image by exposing the toner, and adhering toner to the electrostatic latent image to form a toner image A developing device 7 serving as a developing unit that forms a developer, a developer charge control charger 62 (hereinafter referred to as a post-charger) that adjusts the amount of toner charge of the toner image on the photosensitive drum 1 after development so as to increase transfer efficiency. Call) is located.

A corona transfer charger (transfer means) 8 for transferring the toner image formed on the photosensitive drum 1 onto the transfer paper P, and a static roller for separating the transfer paper P on which the toner image has been transferred from the photosensitive drum 1 An electro-separation charger (separation means) 9; a cleaning device 13 as a cleaning means for removing residual toner on the photosensitive drum 1 after transferring the toner image; a pre-exposure lamp 30 for removing residual charge on the photosensitive drum 1; Are located. A transfer system for transferring the transfer paper P is provided, and the transfer paper P on which the toner image has been transferred is transferred to a fixing device 12 as a fixing unit that is controlled to a predetermined fixing temperature after being separated from the photosensitive drum 1. Here, 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.

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 the photoelectric conversion element 1 as a one-line CCD.
The image is converted into an electric signal corresponding to the image information by forming an image on the image 9.

Here, the reflected light from the original 15 irradiated 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 as shown in FIG. 2, which is a block diagram of an image signal conversion block, to obtain 8-bit digital image data. Thereafter, the black signal generation circuit 22 performs LOG conversion in order to convert the luminance information into density information 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 and an OFF signal according to a pixel size via an unevenness correction circuit 50 in the main scanning direction and a binarization circuit 23, and is converted into a laser drive circuit. 24, the drive current is subjected to dot reproducibility correction, and the semiconductor laser 20 is turned ON / OF at a drive signal timing binarized by an error diffusion method in accordance with the magnitude of the input image density signal.
F.

In this embodiment, the binarization circuit 23 is realized by the error diffusion method. However, it is needless to say that the binarization circuit 23 may be realized by the dither method or another method. In addition, the laser drive circuit 24 uses a well-known PWM circuit to add a dot reproducibility correction to the drive current, and the semiconductor laser 20 (hereinafter, the exposure 3 is referred to as a laser beam) according to the magnitude of the input image density signal. Or a method of modulating the ON / OFF light emission time.

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 scanning direction of laser light as shown in FIG. The drive current for turning ON / OFF the light is shown in FIG.
As shown in (b), the light is illuminated for a fixed time at a constant drive current regardless of the image data. However, the ratio of the illuminated pixels to the total number of pixels in a specific plural pixel area changes according to the image data. The exposure density in the pixel area 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 FFhe
The number of times the laser drive signal is turned on at x is 100% of the lighting pixel ratio to the total number of pixels in a specific plurality of pixel regions.
And so on.

However, even at 0% of the lighting pixel ratio, a constant driving 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, it is of course possible to use a PWM method. When the image data for each pixel is input in the scanning direction of the laser beam as shown in FIG. 5A, the drive signal for turning on / off the laser is as shown in FIG. 5B. That is, when the image data is 00 hex, the on-duty of the laser drive signal is 6% of one pixel scan time, and when the FF hex is, the on-duty of the laser drive signal is 85% of one pixel scan time. In this way, shading is realized by performing area gradation within one pixel.

FIG. 7 shows general IL characteristics (driving current-light amount characteristics) of the laser.
The driving currents used at the time of OFF are Ion / Io, respectively.
ff, the laser drive currents for the image signals of FIGS. 6 and 4 are as shown in FIGS. 6B and 5C, which are the binarization circuit 23 and the PWM circuit (not shown) shown in FIG. And a current for driving the semiconductor laser 20 via the laser drive circuit 24. At this time, it is known that the rise of the amount of light when the laser is turned on is improved by setting Ioff to be slightly smaller than Itrehold, instead of 0 mA. Here, the laser light is 680 nm.
Visible light laser is used.

The laser beam emitted and driven in accordance with the image signal as described above is raster-scanned and written on the photosensitive drum 1 via the polygon mirror scanner 28 and the mirror 17f rotating at a high speed, and a digital electrostatic latent image is formed as image information. Form.

In this embodiment, an amorphous silicon (a-Si) drum is used as the photosensitive drum 1. The amorphous silicon drum has characteristics such as high stability of characteristics, high durability and long life on the conductive substrate. The a-Si photoreceptor, which has a long service life, high-speed output, and has a high photosensitivity to the photosensitive layer of the surface layer SiC curable type, has a high charge holding ability and has little scattering of irradiation light by the surface layer. Since the minute electrostatic latent image in the minute spot exposure portion is held without charge diffusion, 600 dpi or 1200 dpi
A minute latent image such as i is faithfully formed to form a high-definition latent image.

First, FIGS. 4A to 4C show respective steps for explaining the image forming process of the present embodiment. In each of the drawings, the relationship between the surface potential of the photosensitive member and the developing bias is schematically shown. Is shown. In FIG. 4A, the photoreceptor is uniformly charged to +420 V by a corona charger.

In FIG. 4B, image information is exposed, and the surface potential of the image information exposed portion is attenuated to +60 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, the potential of the laser light OFF portion and the potential of the laser light ON.
Although there is only the potential of the 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 laser beam, the potential is apparently a halftone potential. Measured. That is, even in the non-image portion (image data 00hex) of the image area, since the slight exposure is performed as described above, the surface potential is +400.
V, and the image portion of one of the image areas (image data F
Fhex), the surface potential attenuates to +60 V to form an electrostatic latent image.

Next, in FIG. 4C, a developing bias voltage (for example, DC DC superimposed with +280 V on AC AC, etc .; DC DC component is shown by a broken line) is applied to the sleeve of the developing device to reverse develop the exposed group. . Here, the developing unit uses a well-known one-component magnetic toner to perform development without contacting the photoconductor.

A sequence for preventing a decrease in density and preventing image bleeding based on the determination of standing for a long time as a feature of the present embodiment will be described below. The following summarizes each condition of the sequence.

Example: Judgment of leaving for a long time in a non-morning state + idle rotation: Overview: The state where the main power supply is ON, the environment is equal to or more than a specific moisture amount, and the previous operation is performed when an image forming operation signal is input. If the time interval from the end time exceeds a specific time, it is determined that the low power M (in the non-morning one state) has been left for a long time, and the motor is idled with the electronically controlled operation during the previous rotation. In the idle rotation, the drum is idled (the developing unit and the cleaner system are also idled as in the conventional specification).

Conditions: 1) HH judgment: water content W is 9 g / m ³ or more.

2) Judgment of leaving for a long time in the non-morning state: ΔTIME: Defined as the time interval between the input of the machine image forming operation signal and the end of the previous operation. Judgment: ΔTIME ≧ 8 hours then Potential control rotation 3) Idling time: The potential control time. (Approximately 20 seconds) 4) Other conditions are the same as during potential control.

Confirmation result in experiment: HH (JJ) in idle rotation
Morning concentration increased by about 0.1. No image deletion.

[0077]

[Table 1] As shown in Table 1, even in a configuration in which the image forming apparatus is equipped with a power saving mode (standby mode),
When the user selects the setting to immediately receive the data signal and immediately print out, it is always in the standby state. 0, such as the sequence for preventing image deletion and density reduction when the main power is turned on as usual Is not performed.

Here, a sequence for providing the above effect even in such a case will be described with reference to FIG. An overview is that if the main power supply is in the ON state, the environment is equal to or more than the specified moisture content, and the time interval between the input of the machine image forming operation signal and the end of the previous operation exceeds the specified time, the low It is determined that the power M has been left for a long time (in the non-morning state),
During the pre-rotation, an electric control operation constituting the image forming preparation operation is performed, and idle rotation is performed. In the idle rotation, the drum is idled (the developing unit and the cleaner system are also idled as in the conventional specification).

As a configuration for detecting the amount of moisture in the environment, for example, a humidity sensor and a temperature sensor can be provided, and it can be obtained by comparing output values from both sensors with a preset moisture content detection chart. . Of course, there is no problem in adopting other methods.

FIG. 3 will be described below in the order of operation. When the copy button is turned on or when a print signal is input, the main power switch On continuation state is detected, and the environment is detected as a specific water amount region, that is, water content W ≧ 9 g / m ^3. If the time interval between the input of the machine image forming operation signal and the end of the previous operation exceeds the specified time of 8 hours, it is determined that the apparatus is to be left in a high-humidity environment for a long time, and the image forming preparation operation is started. .

In the image forming preparation operation, first, the developing device driving motor is operated to rotate the sleeve of the developing device, and at the same time as the copy button is turned on, the drum driving motor is operated to perform idle rotation of the drum. At the same time, the cleaner system drive system (same drive as the main motor) is operated, and the cleaner system is also in the idling state, an area Ss for image forming preparation operation is added, and the developing device drive is turned on.
It will be in the form.

Further, since the main switch On is continued, the rotation driving of the polygon mirror of the exposure scanning system is also in the operation continued state.

Next, the area Ss will be described. If it is determined that the apparatus is to be left on standby for a long time in a high-humidity environment, an Ss region sequence is set. This sequence is composed of sub-sequences having three functions, and is a drum-adhered material scraping sequence for supplying developer on the drum indicated by Pt.

In this sequence, primary charging is performed at a position on the drum corresponding to the pre-exposure position. As the charge amount, output is performed using the control value of the previous day, that is, the last potential control value when the previous power supply was in the energized state. If there is no previous data, output is performed with the program default value. The output time is equal to or longer than the black band width, and has a slightly (approximately 10 mm extra) charged area before and after the black band (developer supplied in a band on the area on the photosensitive drum 1).

In FIG. 3, Ps is a charging start point, and Pe is a charging end point. Here, the time for the normal black belt width,
In total, charging is performed for a time corresponding to 100 mm or more in the circumferential direction on the drum.

The length in the main scanning direction is A in the image area center distribution.
Charging is performed over a nominal width of three widths.

Next, in the laser light exposure, the laser light exposure is started when the rotation speed of the polygon is a predetermined rotation speed. When the laser is turned on, output is performed using the previous power control value. If there is no previous data, output is performed with the program default value. As the image data level, the image area is FF hex solid. The length in the main scanning direction is a nominal width of A3 width in image area center distribution. That is, registration in the main scanning direction (horizontal registration)
Beam scanning of a laser beam having a width not including the adjustment tolerance is performed. Here, a 297 mm image area FFhex is output.

The output time is the time corresponding to the black band width, and here is the time corresponding to the circumferential black band length on the drum.

As in the case of the primary charging, the start point of black band formation exposure by laser light is indicated by Ls, and the end is indicated by Le.

Before the FFhex is output, a bias current is applied to make the laser light output slightly light in order to speed up the rise of the laser light output.

Next, in development, an AC voltage + DC voltage is output. The AC voltage is output at the standard voltage, and the DC voltage is output at the previous DC control value. In the present embodiment, the black band width has its DC control value of 280 V. However, a DC control value of 300 V for the non-image area is output so as to completely cover the area where the temporary charge is output before and after the black band width. The setting is such that reversal development in the area of only primary charging is minimized. FIG.
Although only the C voltage is shown, the AC voltage (not shown) is ON in a region that further covers the DC voltage (for non-image) region. When there is no previous data, a DC control value is output with a program default value. The output time is equivalent to the black band width, and the development start point of black band formation is indicated by Ls, and the end is indicated by Le, similarly to laser beam irradiation.

Here, it is a time corresponding to 100 mm in the circumferential direction on the drum. The DC value is set so that it can be input on the scanning panel and the black band density can be changed.

After the toner black belt is formed on the drum,
This is an idle rotation process. An object indicating this process is an area indicated by V. This process is variable in time and can be selected according to the user's use environment and use situation, and the type of transfer paper used. At the very beginning of this process, the black toner band is transported to the drum cleaning device and dammed to the edge of the cleaning blade, where the deposited toner scrapes off the laminated material on the drum surface.

Since the scraping effect is proportional to the rubbing time, a long time is required as much as possible. If this rotation includes black band formation, idle rotation starts immediately after HH long-time standby determination,
It continues until the potential control ends.

Next, there is a potential control step, which is indicated by Cp. The charging and the exposure are repeated under each level condition, and the potentials on the high potential side and the low potential side detected by the potential detecting means (not shown) are adjusted to predetermined values while changing the charging conditions and the exposure conditions.

Then, the sequence for judging long-term standby standing at high humidity is completed, and the process returns to the normal pre-rotation process. Normally, the image forming apparatus first starts with pre-rotation pre-charging, and after completion of running-in for one rotation of the drum, image area charging, image exposure, and image area developing bias application are performed, and normal image formation is performed.

When the fixing temperature rise in the energy saving mode such as low power consumption at the time of standby is performed in parallel, the fixing thermistor temperature is continued up to 195 ° C. and continued until normal pre-rotation is started. It can also be configured as a system.

However, the rotation time varies depending on the temperature of the fixing thermistor at the start of idling. For example, when the temperature of the fixing thermistor is about 90 ° C. or the like, the time required for temperature rise is short, and the rotation time is shortened accordingly. At that time, since the temperature of the fixing thermistor is higher than room temperature, it is highly likely that the temperature is not the first in the morning, and idle rotation for a long time is not required. Since there is no particular problem, the idle rotation is performed for the maximum time in that state.

The material on the drum surface is scraped off by the supply of the toner, and at that time, the developing device is also idling, and the amount of charge of the developer, which has become difficult to rise due to moisture absorption, gradually increases. In addition, the density is sufficiently high before the ink reaches the reversal point, and the developability is increased until the reproducibility of isolated dots is sufficiently ensured. Even in the numbered copy image, a high-density, uniform, high-quality image without image deletion can be obtained. As described above, even in a humid environment that is the most severe against image flow (such as an environment with a water content of 9 g / m ³ or more per cubic meter unit volume), regardless of the environment, immediately after startup of the image forming apparatus after standby. A good image can be obtained, and even for a user who uses a small number of sheets, the toner consumption for the polishing is controlled only when the standby time is long. As a result, waste of toner, resources, and copy / print costs can be reduced.

Hereinafter, a method of correcting unevenness in the main scanning direction when density unevenness occurs in the developing device and other portions will be described in detail.

FIG. 8 is a schematic diagram showing a cause 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.

FIG. 8A shows that the charging potential is a target potential of 400 V.
2 shows potentials at a place where a potential is normally obtained and a place smaller than a target potential. This is because the charging ability characteristic of the photosensitive drum differs from the surface potential characteristic obtained on the drum with respect to the current applied to the corona wire of the primary charger, as shown by the three characteristic curves in FIG. It is uneven.

Even when the charging ability of the photosensitive drum is uniform, if the charging ability of the primary charger is not uniform depending on the position in the main scanning direction, surface potential unevenness occurs.

FIG. 8 (b) shows the potential at a place where the potential is normally obtained at the target potential of 50 V of the exposure part and at a place larger than the target potential, although the surface potential formation by charging is performed uniformly. I have. This is the surface potential unevenness caused by the difference in the photosensitivity characteristics of the photosensitive drums as shown by the three types of characteristic curves in FIG. Even if the photosensitivity characteristics of the photosensitive drum are uniform, if the light irradiation amount is not uniform depending on the position in the main scanning direction, uneven surface potential 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 position where the development was normally performed at the potential of 60V of the exposed portion and the target were compared. Also shows a small place. This is Figure 1
As shown by the characteristic curve of the three types of glue, the density unevenness occurs due to the difference in the developing ability with respect to the developing contrast, which is the difference between the surface potential of the photosensitive drum and the DC voltage applied to the developing sleeve that carries and transports the developing toner. . This uneven density occurs when the charging characteristics of the toner are not uniform in the main scanning direction, or when the gap between the drum and the developing sleeve is not 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 or separation (not shown).

Here, all the causes of unevenness described above are comprehensively detected from the output printout image and corrected. FIG. 13 shows an outline of the flow of the correction operation.

(Step Sl) The image forming apparatus of the present embodiment has an “improving image mode” as an image unevenness improvement mode in the input interface.
First, start the mode.

(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. The conditions for forming this sample are as follows: in order to form an image such as a completely solid black, a halftone halftone, and a solid white, the primary charging conditions for forming the surface potential as described above and the image exposure conditions are three kinds With the 8-bit signal, F0, 80,
00hex), developing, transferring and fixing under the above-mentioned developing conditions, and outputting a sample.

(Step S5) The output sample is placed on the document table 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, and the loading is completed by the document recognition means (not shown). 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 this 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 the step S5.

(Step S8) If it is determined that the sample is a test image sample, the distribution of the axial density is calculated as shown in FIG. 14 (b). F0,80,00h of PWM level
When the test image sample is formed by ex, the read density distribution of the halftone portion of 80 hex where the 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 (b) of FIG. 14, the increase / decrease of the read density distribution of the halftone portion from 0.5 corresponds to each pixel in the main scanning direction. Is calculated as follows. 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.

(Step S10) The correction light amount (correction level) for each pixel of the dot exposure laser is determined from FIG. As an example, FIG. 15 shows that when the required correction density is +0.8, the surface potential needs to be corrected to 200 V, the drum surface light amount needs to be +0.25 μJ, and the image data needs to be corrected to +80 hex.

A correction amount level corresponding to each pixel in the main scanning direction is assigned by this capacity, and a correction table is created. Here, this mode ends, and the operation panel, which is the input interface unit of the image forming apparatus, returns to the normal copy or print mode.

When the correction amount corresponding to each pixel position in the main scanning direction is determined in this way, it is stored in the correction table in the main scanning unevenness correction circuit 50 (see FIG. 1).

FIG. 16 shows a specific circuit configuration of the unevenness correction circuit 50 in the main scanning direction in the embodiment.

The illustrated correction table 101 and adder 10
4, the selector 102 and the address generation circuit 103 constitute the unevenness correction circuit 50. A CPU 100 controls the overall operation of the apparatus, and includes therein a control program as a copier and the control program shown in FIG.
RO that stores the program according to the flowchart of FIG.
M and a RAM used as a work area.

In the configuration shown, the correction table 101
Has a capacity of at least the number of pixels in the main scanning direction (9 bits per pixel, one 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 a signal to the selector 102 to supply the address from the CPU 100 to the correction table,
An address, data to be written, and a write signal are output for 1. When the writing of the correction data to all the pixel positions in the main scanning direction is completed in this way, a signal for selecting an address from the address generation circuit 103 is output to the selector 102, and a read signal is output.

The address 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.

As will be described 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, and f0 hex may be written into the correction table at an appropriate timing and output. 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.

Using the correction table described above, 8
In order to perform data correction such as image unevenness at the bit multi-level signal stage, data without unevenness is formed at the time of binarization, and density unevenness is completely corrected at the time of laser beam writing. It is possible to provide a high quality image without density unevenness in the direction (main scanning direction). In particular, according to the first 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, in the state where the main power supply is kept ON, the environment is equal to or more than the specific water content, and the time interval between the input of the machine image forming operation signal and the end of the previous operation is the specific time. If it exceeds, it is determined that the low power M has been left for a long time (in a non-morning state), the electronic control operation is performed during the pre-rotation, and the idling is performed, so that the image forming apparatus enters the environment immediately after startup after standby. A good image can be obtained regardless of this, and even if the user uses a small number of sheets, the toner consumption for the polishing is controlled only when the standby time is long. Waste of resources and resources,
Copy / print costs can be reduced.

In addition, it is possible to reduce the copy cost per sheet, and at the same time, the laser scanning exposure system a-
Even when an image forming apparatus having a Si photoreceptor is used in a high-humidity environment, ozone generated by corona discharge, discharge organisms, and deposits from rubber materials of a feed roller and a transport roller adhere to the surface of the photoreceptor. Even in this case, occurrence of image deletion can be prevented.

Further, the developer is deposited on the photoreceptor and supplied to the cleaning device, sufficient polishing time is taken, and the polishing effect on the photoreceptor surface can be improved. In addition, it is possible to prevent the occurrence of image-flowing images even in the initial image after turning on the power of the image forming apparatus that forms digital data with minute dots, and to further derive functions and effects that can prevent a decrease in density and a deterioration in image flow. Will come.

That is, the developability has been increased until the density is sufficiently high and the reproducibility of isolated dots is sufficiently ensured. Even in the first copy image in the morning in a high humidity environment, there is no image deletion. High density and always longitudinal direction (main scanning direction)
A good quality image without density unevenness can be obtained.

<Embodiment 2> FIG. 17 is a schematic configuration diagram showing an image forming apparatus according to a second embodiment of the present invention.

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 Rl in the figure. Around the photosensitive drum 1, a first scoro-to-cone charger 2 for uniformly charging the surface of the photosensitive drum 1 in order along the direction of rotation thereof, a document is read, and one of the colors separated into two colors is read. A first exposure device that exposes the photosensitive drum 1 based on a first image signal proportional to the density of the surface image to form a first electrostatic latent image; A first developing device 7 for forming one toner image, a second scorotron charger 5 (hereinafter referred to as a recharger) for charging the photosensitive drum 1 after carrying the first toner image, and the other disassembled device A second exposure device (exposure 6) for performing exposure of an amount obtained by adding a certain exposure amount to an exposure amount based on a second image signal proportional to the density of the color image to form a second electrostatic latent image; A second developing device for forming a second toner image by attaching toner to the second electrostatic latent image 7
A, a pre-transfer charger 62 for charging a color superimposed image formed on the photosensitive drum 1 before transfer, a corona transfer charger (transfer charger) 8 for transferring onto a transfer paper P as a transfer material, An electrostatic separation charger (separation charger) 9 for separating the transfer paper P on which the image has been transferred from the photosensitive drum 1; a cleaning device 13 for removing the residual toner on the photosensitive drum 1 after transferring the color superimposed image; A pre-exposure lamp 30 for removing the residual charge of the drum 1 and the like are arranged.

The transfer paper P on which the color superimposed 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 is provided with 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 signals from which the red, green, and blue components are output by the photoelectric conversion element 19 are A / A
After being digitized by the D converter 21, it is sent to a 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, the image data is corrected for each pixel by the axial direction (main scanning direction) unevenness correction circuit 50 (see 50 in FIG. 19 showing the image conversion block configuration).

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.
Laser 20b, 2 according to the red and black image signals
The light emission of 0a is turned on / off.

The laser beam emitted according to the red signal writes a first electrostatic latent image on the photosensitive drum 1 via the polygon mirror 28 and the mirror 17e as first image information. 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 this embodiment, an amorphous silicon (a-Si) drum is used for the photosensitive drum 1. Amorphous silicon drums have features such as high durability and long life.

FIG. 18 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 photoconductor is schematically shown.

In FIG. 18A, the photosensitive member is charged to, for example, +400 V by a corona charger, and then, FIG.
Performs a first exposure of the image information, attenuates the surface potential of the exposed portion to, for example, +50 V, and forms a first electrostatic latent image.

Next, in FIG. 18C, a developing bias voltage (for example, +300 V: indicated by a broken line) is applied to the sleeve of the first developing device, and the exposed portion is reversely developed.

After the first development, recharging is performed in FIG. 18D, and the desired second development position potential of 400 V is applied to the grid.
A larger voltage of 600 V is applied to control the first developed non-image portion to be charged to, for example, 600 V. 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 FIG. 18E, a fixed exposure amount (for example, the first developed non-image portion Exposure that is large (by the exposure amount attenuated by 200 V) is performed. At this time, in the first developing section, the exposure for the fixed exposure amount does not attenuate as much as the potential decay in the first developing non-image section, and for example, attenuates by only 100 V. This is because the first developer scatters the light without transmitting it, and its transmittance was 50%. The surface potential after the exposure of 0.25 μJ is added to the second exposure.
The target potential after recharging of the first developed non-image portion, which becomes the target potential of 400 V at the developing position, is a known drum sensitivity of 800 V / μ.
It was 600 V assuming the straight line of J.

Next, also from the known toner layer transmittance of 50%, the amount of light reaching the drum to the first image developing section is 0.125 μJ.
Becomes The target potential after recharging of the first developed image portion may be set to 500 V in the same manner as described above.

In this embodiment, a semiconductor laser is used as the second exposure means. However, no complicated processing is 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 developing single-color mode in the two-color mode. That is, the second image signal is also weakly exposed to the 0ff portion, and the On portion is also exposed to the same amount of exposure as that of the 0ff portion. 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 portion is also 400 V,
Further, when the second image signal is on, the first developed non-image portion is exposed to 50V.

Thereafter, 3 is applied to the second developing sleeve in the developing process.
By applying a bias of 00V, the second developer becomes the first developer.
A sufficient second image density can be obtained without being mixed in the developing section or being developed in the non-image areas of the first and second images.

A sequence for preventing a decrease in density and preventing image bleeding based on the determination of standing for a long time as a feature of the present invention will be described below. The following summarizes each condition of the sequence.

Example: Judgment of leaving for a long time in a non-morning state + idle rotation: Outline: The state where the main power supply is kept ON, the environment is equal to or more than a specific water content, and the time when the machine image forming operation signal is input and the previous time If the time interval from the end of the operation exceeds a specific time, it is determined that the low power M (in the non-morning one state) is left for a long time, and the motor is idled during the pre-rotation by turning on the electric control operation. In the idle rotation, the drum is idled (the developing unit and the cleaner system are also idled as in the conventional specification).

Conditions: 1) HH judgment: water content W is 12 g or more.

2) Judgment of leaving for a long time in the non-morning state: ΔTIME: Defined as the time interval between the input of the machine image forming operation signal and the end of the previous operation. Judgment: ΔTIME ≧ 8 hours then Potential control rotation 3) Idling time: The potential control time. (Approximately 20 seconds) 4) Other conditions are the same as during potential control.

Confirmation result in experiment: HH morning concentration increased by about 0.1 due to idle rotation. No image deletion.

As shown in Table 1 of the first embodiment, even in a configuration in which the image forming apparatus is equipped with a power saving mode, the user always selects a setting for receiving a data signal and immediately printing out. In such a case, the standby state is always maintained, and a sequence in which the image is prevented from flowing when the main power is turned on and a sequence in which the density is prevented from decreasing are not performed.

Here, even in this case, the sequence for providing the above-mentioned effect is exactly the same as that of the first embodiment described with reference to FIG. However, when it is detected that the water content W ≧ 12 g as the specific water content area, if the time interval between the input of the machine image forming operation signal and the end of the previous operation exceeds the specified time of 8 hours, the long time in a high humidity environment Judgment is made to stand by for a while.

Hereinafter, a method of correcting unevenness in the main scanning direction when density unevenness occurs in the developing device and other portions will be described in detail.

A description will be given using the operation flow of creating the correction table 60 in FIG. 13 as in the first embodiment.

(Step Sl) The image forming apparatus of the present embodiment has an “improving image mode” as a mode for improving image unevenness in the input interface.
First, start the mode.

(Step S2) Next, an axial unevenness (unevenness in the main scanning direction) 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. The conditions for forming this sample are as follows: in order to form an image such as a completely solid black, a halftone halftone, and a solid white, the primary charging conditions for forming the surface potential as described above and the image exposure conditions are three kinds The PWM levels F0, 80,
00hex), developing, transferring and fixing under the above-mentioned developing conditions, and outputting a sample.

Here, as a feature of the second embodiment,
A test image sample is output for each of two colors (for example, red and black). Thereafter, the following steps S5 to S10
Work for each color (red and black).

(Step S5) 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, and the placement is completed by the document recognition means (not shown). 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 this original is a test image sample based on whether or not the density gradation is an equivalent 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 the step S5.

(Step S8) If it is determined that the sample is a test image sample, the distribution of the axial density is calculated as shown in FIG. F0,80,00h of PWM level
When the test image sample is formed by ex, the read density distribution of the halftone portion of 80 hex where the 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 (b) of FIG. 14, the increase / decrease of the read density distribution of the halftone portion from 0.5 corresponds to each pixel in the main scanning direction. Is calculated as follows. 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.

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

A correction amount level corresponding to each pixel in the main scanning direction is assigned by this capacity, and a correction table is created. Here, this mode ends, and the operation panel, which is the input interface unit of the image forming apparatus, returns to the normal copy or print mode.

In such a configuration, similarly to the first embodiment, a good image can be obtained regardless of the environment immediately after the image forming apparatus is started up after the standby state. Waste, resources and copy / print costs can be reduced.

<Embodiment 3> FIG. 20 is a schematic configuration diagram showing a third embodiment of the image forming apparatus according to the present invention. In the figure, the same components as those of the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

The characteristic configuration of this embodiment is as follows.
An exposure apparatus, which is an electrostatic latent image forming means for performing exposure 3 on the photosensitive drum 1, does not use a polygon mirror scanner. Instead, a plurality of exposure light emitting elements 20c (LEDs) are arranged in the axial direction of the photosensitive drum 1. It is in the point of arrangement.

8b generated in the same manner as in the first embodiment
it digital image data signal to the LED drive circuit 24c
The drive circuit 24c is a well-known PWM circuit and controls the light emission of the LED 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 this embodiment, an amorphous silicon drum is used as the photosensitive drum 1. Amorphous silicon drums are characterized by high stability of characteristics, high durability and long life on the conductive substrate.

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

A sequence for preventing a decrease in density and preventing image bleeding based on the determination of standing for a long time as a feature of the present invention will be described below. The following summarizes each condition of the sequence.

Example: Judgment of leaving for a long time in a non-morning state + idle rotation and its variation: Outline: A signal of machine image forming operation when the main power supply is ON, the environment is in a specific moisture content area, and If the time interval between the input and the end of the previous operation exceeds a specific time, it is determined that the low power M (in the non-morning one state) is left for a long time, and the motor is idled with the electric control operation during the previous rotation.

In the idle rotation, the drum is idled (the developing unit and the cleaner system are also idled as in the conventional specification). Conditions: 1) HH area judgment: (a) Toner black band + idle rotation (Pt + V + Cp): moisture content W ≧ 9 g (b) Idle rotation (V + Cp): moisture content 9 g> W ≧ 5 g (c) Normal pre-rotation only (Cp): less than 5 g of water content 2) Long-term non-morning determination: ΔTIME: Defined as the time interval between the input of the machine image forming operation signal and the end of the previous operation, determination: ΔTIME ≧ 8 hours then determination Potential control rotation at the previous rotation of the job 3) Idle rotation time: The potential control time. (Approximately 20 seconds) 4) Other conditions are the same as during potential control.

Confirmation result in experiment: HH morning concentration increased by about 0.2 by idling. No image deletion.

[0180] With the idling, the JJ morning concentration increased by about 0.15. No image deletion.

In the image forming apparatus of this embodiment, similarly to the first embodiment, when the main power supply is in the ON state, the environment is equal to or more than the specific water content, and the machine image forming operation signal is output. If the time interval between the input and the end of the previous operation exceeds a specific time, it is determined that the low power M (in a non-morning state) has been left for a long time, and the power control operation is performed during the pre-rotation. However, the water content of the environment is classified into three stages, and the necessary image forming preparation operation is selected and performed according to the water content.

As described above, by changing the sequence of the image forming preparation operation in accordance with the amount of water, unnecessary control is omitted when the amount of water is low. The consumption of the developer can be suppressed.

Further, regarding the method of correcting unevenness in the main scanning direction when density unevenness occurs in the developing device and other areas, the first method is also described.
Image unevenness is eliminated by the correction operation of the flow shown in FIG. 13 similar to the embodiment.

Therefore, similarly to the first embodiment, it is possible to obtain a good image regardless of the environment immediately after the image forming apparatus is started up after the standby state, and to leave the standby state even for a user who uses a small number of sheets. Since the supply of the polishing toner is controlled only when the time is long, it is possible to use the toner while appropriately suppressing the toner consumption, so that the waste of the toner, the resources, and the cost of the copy print can be reduced.

When the image forming apparatus is used in a high-humidity environment, ozone generated by corona discharge, discharge organisms, and deposits from the rubber material of the feed roller and the transport roller adhere to the surface of the photoreceptor. However, occurrence of image deletion can be prevented. In addition, the developer is deposited on the photoreceptor and supplied to the cleaning device, sufficient polishing time is taken, and the polishing effect on the photoreceptor surface can be improved. It is possible to prevent the occurrence of an image-flowing image even in the initial image after power-on of the image forming apparatus that forms fine dots with fine dots, and also has the effect of preventing a decrease in density and a deterioration in image flow.

In other words, the developability has been increased until the density is sufficiently high and the reproducibility of isolated dots is sufficiently ensured. Even in the first copy image in the morning in a high humidity environment, there is no image deletion. High density and always longitudinal direction (main scanning direction)
And an image forming apparatus capable of obtaining a high-quality image having no density unevenness.

In the 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).
Needless to say, the present invention can be applied to a case where an image is formed according to a method.

When forming an image by the PWM method,
Basically, pixels having different shades (actually, area modulation) can be formed for each pixel so that pixels of different sizes are perceived as shades when viewed from the human eye. 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.
If the resolution of the printer is 600 dpi, 1/600
This is because it is necessary to read an image with a displacement of less than inch, which is very difficult as a practical problem.

Therefore, as described above, the PWM
Even in the case of forming by the 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 correct it.

Although the present invention has been described using a copying machine as an example, the present invention may be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, and a printer).

In this case, since the above processing can be performed by a portion corresponding to the host computer, the present invention uses a storage medium storing the program code of the software for realizing the functions of the above-described embodiment in a system or an apparatus. And the computer (or CPU or MPU) of the system or apparatus reads out and executes the program code stored in the storage medium.

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

As a storage medium for supplying the program code, for example, a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD
-R, a magnetic tape, a nonvolatile memory card, a ROM, 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. ) May perform some or all of the actual processing, and the processing may realize 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, It goes without saying that the present invention also includes a case where a CPU or the like provided in the function expansion board or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

[0197]

According to the present invention described above, it is possible to control the image forming preparation operation more efficiently, and to maintain high quality image quality without excessive consumption of the developer. be able to.

That is, when the image forming apparatus is stopped in an environment having a specific water content or more, an image forming preparation operation for recovering image quality is performed. It is possible to obtain a good image, and even for users who use a small number of sticks, the developer is controlled to supply the developer only when the standby time is long, so the toner consumption is appropriately and automatically suppressed. It is possible to reduce the consumption of the developer and to reduce the image forming cost.

In a high-humidity environment, even if ozone generated by corona discharge, discharge organisms, or substances deposited from the rubber material of the paper feed roller or the transport roller adhere to the surface of the image bearing member or the photosensitive drum, the adhered matter is not removed. This can be removed in the image forming preparation operation, and the occurrence of image deletion or the like can be prevented, and a good image can be obtained.

Even when the developer absorbs moisture, the developing device is driven and mixed with an unhygroscopic developer almost sealed in the developing container, or an image forming process different from the image forming process. By consuming the developer absorbed by forming the developer image in the preparation operation,
A good developer state can be created as a developing characteristic, and high-quality image quality can be provided even after a long period of suspension.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment.

FIG. 2 is a block diagram of an image signal conversion block.

FIG. 3 is a diagram illustrating a sequence of an image forming preparation operation.

FIG. 4 is a potential diagram for forming an electrostatic latent image on an image carrier.

FIG. 5 is a diagram illustrating laser lighting in a PWM method.

FIG. 6 is a view for explaining laser lighting in binary image data.

FIG. 7 is a diagram showing IL characteristics of a laser.

FIG. 8 is a view for explaining the cause of the occurrence of density unevenness in the main scanning direction.

FIG. 9 is a diagram showing characteristics of a drum surface potential by a charging wire.

FIG. 10 is a diagram illustrating characteristics of a drum surface potential depending on an image exposure amount.

FIG. 11 is a diagram illustrating characteristics of a drum surface potential depending on a development contrast.

FIG. 12 illustrates a lighting pixel ratio.

FIG. 13 is a flowchart for improving image unevenness.

FIG. 14 is a diagram showing a test image and a target density.

FIG. 15 is a graph for obtaining a correction light amount.

FIG. 16 is a block diagram of an unevenness correction circuit.

FIG. 17 is a schematic configuration diagram of an image forming apparatus according to a second embodiment.

FIG. 18 is a diagram illustrating an image forming process.

FIG. 19 is a diagram showing a configuration of an image signal conversion block.

FIG. 20 is a schematic configuration diagram of an image forming apparatus according to a third embodiment.

FIG. 21 is a schematic configuration diagram of an image forming apparatus according to the related art.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum (image carrier) 2 scorotron charger 3 exposure 7 developing device 8 corona transfer charger 9 electrostatic separation charger 12 fixing device 13 cleaning device 14 document glass table 15 document 16 illumination lamp 17a, 17b, 17c, 17f Mirror 17d lens 18 reader unit 19 photoelectric conversion element 21 A / D converter 22 black signal generation circuit 23 binarization circuit 24 laser drive circuit 28 polygon mirror scanner 50 unevenness correction circuit 100 CPU 101 correction table 102 selector 103 address generation circuit 104 addition vessel

Claims (17)

[Claims] An image carrier that forms an electrostatic latent image; a charging unit that charges the image carrier; and an electrostatic latent image that forms an electrostatic latent image on the image carrier in accordance with image information. Image forming means, developing means for developing an electrostatic latent image on the image carrier with a developer, transfer means for transferring a developer image formed on the image carrier to transfer paper to be conveyed, A fixing unit having a temperature control unit for fixing the developer image on the transfer paper; a cleaning unit for cleaning the surface of the image carrier; and performing an image forming preparation operation by inputting an image forming operation start signal. Control means for performing the image forming operation of the image forming apparatus, wherein a means for detecting a pause time interval from the end of the previous image forming operation to the input of the next image forming operation start signal; and the image forming apparatus To detect the amount of water in the environment where it is installed It includes a stage, the said control unit, an image forming apparatus and performs control of the image forming preparation operation on the basis of the water content of the pause time interval and the environment. 2. The control of the image forming preparation operation by the control unit means that the water content of the environment is equal to or more than a specific water content,
2. The image forming apparatus according to claim 1, wherein when the pause time interval is equal to or longer than a specific time, the image forming preparation operation is performed for a longer time than when the condition is not satisfied. 3. The control unit includes a standby mode in which, when a state in which an image forming operation is not performed is continued for a predetermined time or more, driving of some of the constituent units is stopped or in a standby state. 3. The image forming apparatus according to claim 1, wherein the image forming preparation operation is performed when an image forming operation start signal is input in a certain state. 4. An image forming apparatus comprising: a potential detecting unit configured to detect a surface potential of the image carrier; wherein the control unit controls the surface potential of the image carrier according to a detection value of the potential detecting unit in the image forming preparation operation. The image forming apparatus according to claim 1, further comprising a potential control step of adjusting the potential to a specific potential. 5. The image forming preparatory operation according to claim 1, wherein the control unit includes a developer image forming step during an image forming preparatory operation for forming a developer image on an image carrier. 5. The image forming apparatus according to claim 4. 6. The image forming preparation operation by the control unit includes: operating the image carrier, the charging unit, the electrostatic latent image forming unit, the developing unit, and the cleaning unit to form a developer image on the image carrier. A first step of forming, while operating the image carrier, charging means and cleaning means,
A second step of controlling the temperature of the fixing unit to a fixable temperature, and a third step of operating at least the image carrier and the charging unit to perform a preparation operation for a normal image forming operation; The control means performs the first, second, and third steps when detecting that the moisture content of the environment is in the first specific moisture content region, and determines that the moisture content of the environment is in the second specific moisture content range. When it is detected that the moisture content is in the moisture content region, the second and third steps are performed. When the moisture content of the environment is detected in the third specific moisture content region, the third process is performed. The image forming apparatus according to claim 1, wherein the image forming apparatus performs a step. 7. The first specific moisture content region has a moisture content of 9 g / m.
Is ³ or more, the second specific water content region is at 5 g / m ³ or more than 9 g / m ^3, claim third specific water content region and less than 5 g / m ³ 6 An image forming apparatus according to claim 1. 8. In the developer image forming step during the image forming preparation operation, the control unit sets the charging output value of the charging unit to a value used at the time of the previous image forming and forms the image on the image carrier. The image forming apparatus according to claim 5, wherein charging is performed wider than a corresponding area of the developer image to be formed. 9. The developer image forming step during the image forming preparation operation, wherein the control unit sets a latent image forming output value by the electrostatic latent image forming unit to a value used at the time of previous image forming. 9. The image forming apparatus according to claim 5, wherein an electrostatic latent image is formed corresponding to a developer image formed on the image carrier. 10. The developing unit supports a developer on a developer carrier, and faces the image carrier by the developer carrier while regulating a layer thickness of the developer by a developer regulating unit. Transporting the developer to the developing unit, forming a developing electric field between the image carrier and the developer carrier in the developing unit, and developing the electrostatic latent image on the image carrier with the developer; In the developer image forming step during the image forming preparation operation, the developing electric field output value in the developing unit is set to the value used at the time of the previous image forming, and the electrostatic latent image formed on the image carrier is The image forming apparatus according to claim 5, wherein a developer image is formed correspondingly. 11. The image bearing member according to claim 1, wherein the image carrier is a photosensitive drum in which a photoconductor for forming an electrostatic latent image is formed in a thin layer on a cylindrical conductive substrate. The image forming apparatus as described in the above. 12. The image forming apparatus according to claim 11, wherein the photosensitive drum uses an a-Si photoreceptor. 13. The image forming apparatus according to claim 1, wherein the electrostatic latent image forming means scans and exposes a laser beam which blinks in accordance with image information, thereby enabling the image carrier to perform minute point exposure for each pixel. An image forming apparatus according to any one of claims 1 to 12. 14. The image forming apparatus according to claim 1, wherein the electrostatic latent image forming unit drives a plurality of light emitting elements arranged in a scanning direction to form an electrostatic latent image on the image carrier. The image forming apparatus according to claim 1. 15. An image forming apparatus, comprising: means for converting multi-valued image data into binary image data based on image information, wherein the electrostatic latent image forming means forms an electrostatic latent image based on the binary image data. 13. A method according to claim 13 or claim 1.
5. The image forming apparatus according to 4. 16. A density characteristic detecting means capable of detecting a gradation density reproduction characteristic corresponding to each pixel in the scanning direction of the electrostatic latent image forming means, and a gradation density reproduction detected by the density characteristic detecting means. 16. A correction value generating means for correcting image data based on characteristics.
An image forming apparatus according to claim 1. 17. The image forming apparatus according to claim 1, wherein the developing unit uses a one-component developer as a developer.