JP2001255711A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform control to stabilize image density even though any gradation correction and any change of an image forming parameter or the like are performed, to prevent a sticking amount from exceeding the upper limit value of the performance of a fixing period even in the case that temperature and humidity environments are fluctuated and to prevent cold offset. SOLUTION: This image forming device is provided with an inputting part to input an image data obtained by converting an image formed by a user by a computer to the image forming device, a gradation correction part to receive the inputted image data as a digital data and to correct gradation in accordance with the input/output characteristics of a printer, an arithmetic part to calculate the toner sticking amount of the image based on a gradation data obtained by the gradation correction, a comparing part to judge whether or not a calculated result by the arithmetic part exceeds the upper limit value of the toner sticking amount decided by the fixing performance of a fixing unit to fix a toner image formed on a recording medium based on the image data and a notice means to generate warning when the calculated result is equal to or above the upper limit value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to gradation control of an image in an image forming apparatus such as a copying machine, a facsimile, and a printer using an electrophotographic method.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus using an electrophotographic method, a charging device, an image writing and exposing device, a developing device, a transfer device, a cleaning device, a charge removing device, etc. are provided around a photoreceptor. After the photoreceptor is uniformly charged, an electrostatic latent image is formed on the photoreceptor by an image writing and exposing device, and the electrostatic latent image is developed into a toner image by a developing device, and then conveyed from a paper feeding device. After the toner image is transferred to the incoming transfer paper by a transfer device, the transferred image is fixed, while, on the photoreceptor, after the residual toner on the photoreceptor is removed by a cleaning device, the charge of the photoreceptor is removed by a static eliminator. The image formation is performed by a series of processes of removing the image.

In an image writing and exposing apparatus for forming an electrostatic latent image on a photoreceptor, an image is formed by modulating laser emission. When printing out an image in the image forming apparatus, the image formed by the user on the personal computer is transmitted to the image forming apparatus as a digital value (data), and the image forming apparatus processes the data so that the image can be formed. Then, an electrostatic latent image is formed on the photosensitive drum as exposure data, and the electrostatic latent image is developed by a developing device and printed on paper.

In this series of image forming processes, the density of the input image data and the density of the output image are not proportional, and the image density does not change linearly with the gradation. The relationship between the input image data and the density value of the output image is referred to as a gradation characteristic. The causes of the inconsistency of the gradation characteristics include a change in the data itself due to the conversion characteristic of each device in the image forming apparatus and a temperature. Changes in the humidity environment and the like are possible.

In color image formation, it is basically required that the density of an output image linearly changes with respect to the tone value of an input image. However, the gradation characteristics are liable to fluctuate because they are affected by changes in the photoconductor sensitivity, surface potential, development bias voltage, development characteristics, and the like in the image forming process. In addition, when the surrounding environment such as the temperature and humidity changes, the change easily occurs.

In order to stably output an image by compensating for the density fluctuation of the output image in the image forming process, automatic density control for controlling the density of the toner and gradation correction for correcting the emission characteristics of the laser beam are performed. The reproducibility of has been stabilized.

By the way, as a method of performing image density and gradation correction with respect to environmental fluctuation, as described in JP-A-10-39555, when the first density gradation control is started,
A band pattern consisting of halftone densities for four colors of Y, M, C, and Bk and a maximum density patch pattern are formed, the test print is read, converted to an optical density, and a contrast potential is corrected from the density information. Adjust the maximum density to a constant value. Also, by forming a gradation patch of 64 gradations and reading the test print, the LUT (lookup table) for converting the density data for each gradation to a laser output signal is optimized, and gradation correction control is performed. Execute. Further, in the second gradation control, a test pattern is formed on the photosensitive drum, the density is detected by an image density sensor provided opposite to the photosensitive drum, and the density after development is supplied with toner. As a result, a method of keeping it properly has been proposed.

The digital image forming apparatus described in Japanese Patent Application Laid-Open No. 5-328131 has a configuration in which a user can arbitrarily select and set a gradation characteristic and automatically adjust the density.

[0009]

Generally, in an image forming apparatus, a toner image is formed on a sheet through a series of image forming processes as described above, and then the toner on the sheet is fixed on the sheet by a fixing device. It has become. However, there is an upper limit to the fixing performance of the fixing device, and in particular, the fixing device tends to be downsized year by year, particularly in recent years due to demands for downsizing of the apparatus and cost reduction. At the same time, there is a demand for higher speed, and the fixing time tends to be shortened, and the upper limit of the amount of toner fixed on paper is decreasing year by year. In particular, the tendency is remarkable in lower printer models.

In the prior art described in Japanese Patent Application Laid-Open No. 10-39555, in order to maintain a constant gradation characteristic with respect to environmental fluctuations, the first gradation control uses density data for each gradation as a laser output signal. LUT (Look Up Table) for conversion to is optimized and gradation correction control is executed. Also,
Further, in the second gradation control, the image density is stabilized by controlling the toner supply amount.

[0011] Also, in Japanese Patent Application Laid-Open No. 5-328131,
A mechanism is provided for the user to adjust the gradation characteristics and to adjust the density so that the density of the entire output image does not change.

As described above, the method of stabilizing an image by correcting the gradation characteristic changed with respect to environmental fluctuation is a method generally performed in an image forming apparatus, and various methods are devised. Have been.

However, as described above, when the gradation characteristic is freely adjusted in response to environmental fluctuations or according to the user's preference, the change in the gradation characteristic causes an increase in the total amount of adhered toner. In some cases, the upper limit of the performance of the fixing device may be exceeded. When the toner amount exceeds the upper limit of the performance of the fixing device, a phenomenon called a so-called cold offset occurs in which the toner is not fixed on the sheet even when the sheet passes through the fixing device. When this occurs, the toner on the sheet is not fixed on the sheet even after the fixing, so that the toner comes off from the sheet, causing a problem that a defect occurs in an image.

In the above prior art, no consideration was given to such a point. The present invention has been made in view of the above points, and an object of the present invention is to provide an image forming apparatus which does not cause a cold offset even when tone correction is performed.

[0015]

In order to achieve the above object, an image forming apparatus according to the present invention comprises: an input section for inputting image data obtained by converting an image created by a user by a computer into the image forming apparatus; A tone correction unit for receiving the adjusted image data as digital data and correcting the tone in accordance with the input / output characteristics of the printer, and a calculation unit for calculating the toner adhesion amount of the image based on the tone data corrected for the tone It is determined whether or not the calculation result by the arithmetic unit exceeds the upper limit of the amount of toner adhesion determined from the fixing performance of the fixing device that fixes the toner image formed on the recording medium based on the image data. And a notifying means for issuing a warning when the calculation result is equal to or larger than the upper limit value.

In order to achieve the above object, the image forming apparatus of the present invention further includes a gradation pattern generation unit (LUT: lookup table) for storing a gradation pattern to be referred to at the time of gradation correction, and an image forming apparatus. A temperature and humidity sensor arranged,
The calculation unit calculates the toner adhesion amount of the image based on the gradation data subjected to the gradation correction and the measurement data of the temperature and humidity sensor, and the calculation result is calculated based on the toner adhesion amount determined from the fixing performance of the fixing device. When the value is equal to or more than the upper limit, a warning may be issued to the user by the notification means.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an image forming apparatus will be described below.

FIG. 1 is a block diagram for explaining one embodiment of the present invention.

When a user forms an image on the computer 2 and prints the image, the image data is transmitted to the connected image forming apparatus 1 through a cable. The image data is input as digital data from the input unit 3 shown in FIG. 1, and the gradation correction unit 4 receives the gradation pattern from the gradation pattern generation unit 5 (LUT: lookup table) according to the input / output characteristics of the printer. To correct the gradation. The gradation data subjected to the gradation correction is input to the calculation unit 6.

The arithmetic unit 6 calculates the amount of toner adhered to the image from the gradation data and the temperature and humidity data from the temperature and humidity sensor 7. The calculated toner adhesion amount is sent to the comparison unit 8 and compared with the upper limit value of the performance of the fixing unit (not shown). (Not shown), output to an output unit 10 via a recording unit 9 including a photosensitive drum (not shown), and the output unit 10 forms a gradation-corrected output image. The above-described gradation correction unit 4, gradation pattern generation unit 5, calculation unit 6, and comparison unit 8 are collectively referred to as a control unit 11.

FIG. 2 is a flowchart showing the operation of the image forming apparatus 1 of the present invention. In the image forming apparatus 1 of the present invention shown in FIG. 1, image data formed by a user on the computer 2 is transmitted to the image forming apparatus 1 and input from the input unit 3. The input image data is input to the gradation correction unit 4
Is entered. In the gradation correction unit 4, the image data is converted into gradation data, and the gradation data is converted by referring to the gradation pattern from the gradation pattern generation unit 5 (LUT: lookup table) according to the input / output characteristics of the printer. Is corrected, and the arithmetic unit 6 calculates the toner adhesion amount of the image based on the gradation data after the gradation correction and the temperature and humidity data from the temperature and humidity sensor 7. The calculated amount of adhered toner is sent to the comparing unit 8, and is compared with the upper limit of the amount of adhered toner determined from the performance of the fixing device, and it is determined whether the upper limit is exceeded or less than the upper limit. If the toner adhesion amount exceeds the upper limit, a signal is sent to the computer 2 to issue a warning that the toner has exceeded the upper limit. On the other hand, if it is equal to or lower than the upper limit of the fixing device performance, an image is formed in the recording unit 9 including a photosensitive drum or the like according to the gradation data, and the output unit 10
Prints out the output image.

When a warning is received from the computer 2, the user or software such as a printer driver on the printer readjusts the image density and re-adjusts the image density.
The image data is transmitted to 1, and the above-described operation is repeated until the toner adhesion amount becomes gradation data not exceeding the upper limit value and no warning is given.

Next, a specific operation will be described with reference to FIG. 3, which is a configuration diagram of the recording unit 9 of the image forming apparatus 1.

In FIG. 3, an organic photoconductor (OPC) or a photoconductor drum 21 formed by applying a photoconductor made of A-Si, CdS, Se or the like is coated on the outer peripheral surface of an aluminum cylinder. , And is uniformly charged to a predetermined potential by the roller charger 22.

An image writing / exposure device 23 comprising a laser diode, a polygon mirror, a lens, a mirror and the like (not shown) is disposed above the apparatus main body.

Here, when the gradation data corrected by the control section 11 shown in FIG. 1 is input to the laser driver 24, the laser driver 24 causes the image writing / exposure device 23 to emit light. Then, this light passes through the optical path 25, and optical information corresponding to the image signal is applied to the photosensitive drum 21 to form an electrostatic latent image. When the photosensitive drum 21 further moves in the direction of the arrow, this electrostatic latent image is developed by the developing device 26, and a toner visible image is formed. The developed toner visible image is transferred to a transfer paper 28 by a transfer device 27 to which a predetermined bias voltage is applied.
Transcribed above. Next, the transfer paper 28 onto which the toner image has been transferred
Is transported by the transporting means, and is fixed by a solvent by the fixing device 29 to form a permanent image.

On the other hand, the toner remaining on the photosensitive drum 21 is removed by a cleaning device such as a fur brush or blade means.
Cleaned by 30. A temperature / humidity sensor 7 for measuring the temperature / humidity of the recording unit 9 is disposed in the recording unit 9 described above, and the measurement data is sequentially input to the control unit 11.

An image is formed by the configuration and operation described above.

Next, a method of correcting a gradation will be described in detail.

Generally, in an image forming apparatus for outputting a gradation image, gradation control as shown in FIG. 4 is performed. That is, the image data input from the input unit 3 is processed by the gradation correction unit 4 in a relationship between the image data and the density of the output image,
That is, the gradation characteristics are adjusted so as to have a linear relationship with reference to the data of the gradation pattern generator 5 (LUT: lookup table). In an initial state in which nothing is set in the gradation pattern generation unit 5 (LUT), the image signal is sent to the recording unit 9 as it is, and the gradation characteristics are as shown in FIG. , The image density is not linear.
In order to change this gradation characteristic linearly, gradation correction called γ correction is performed on the image signal in advance, and the image data is adjusted so that the image density becomes linear with respect to the image signal as shown in FIG. Was corrected.

However, the gradation characteristics in the initial state shown in FIG. 5A are obtained when the image forming apparatus is at room temperature and normal humidity (ex. 20 ° C., 50%) and the environment around the image forming apparatus is different. Depending on the situation, the result may not always be as shown in FIG. 5A, but may be as shown in FIGS. 5B and 5C. For example, FIG. 5B shows the gradation characteristics under a high-temperature and high-humidity environment, and FIG. 5C shows the gradation characteristics under a low-temperature and low-humidity environment. Therefore, if the image forming apparatus is in a high-temperature and high-humidity environment and the initial gradation characteristics are as shown in FIG. The tone characteristic may not be a straight line as shown in FIG. 6 and may vary depending on the temperature and humidity environment.

FIG. 7 shows an example of (a) the gradation characteristics after the γ correction at the normal temperature and the normal humidity after the gradation correction, and (b) the gradation characteristics at the time of the high temperature and the high humidity. From FIG. 7, it is apparent that even when performing γ correction similar to that at normal temperature and normal humidity at high temperature and high humidity, the gradation characteristic does not become a straight line, and the total toner adhesion amount is compared with that at normal temperature and normal humidity in (a). And (b) at high temperature and high humidity.

Accordingly, in the conventional gradation correction method shown in FIG. 4, the toner amount exceeds the upper limit of the performance of the fixing device,
There is a risk that a phenomenon called a so-called cold offset in which the toner is not fixed on the sheet even when the sheet passes through the fixing device may occur. When the cold offset occurs, the toner on the sheet is not fixed on the sheet even after the fixing, so that the toner peels off from the sheet, causing a problem that a defect occurs in an image.

The following can be cited as a factor that further increases the amount of toner adhered to the image even when the gradation correction is performed.

Generally, a user checks the density of an image output for the first time and adjusts the density of the entire image to his / her preference.

FIG. 8 shows an adjustment screen on a printer driver for the user to adjust the image density on the computer 2.
As shown in FIG. 8, the user can change the density of the print image according to the user's preference while viewing the image 41 on the monitor 40 and the output print image (not shown). The following is a specific method for changing the density by the user.

The image density adjustment bar 42 shown in FIG. 8 can select a density of ± 10 levels centered on the standard value (0), and the gradation curve corresponding to each image density is shown in FIG. The image density is adjusted by changing the tone characteristic in accordance with the image density, which is determined in the tone pattern generation unit 5 (LUT) shown in FIG. Each gradation curve is stored in the gradation pattern generation unit 5 (LUT), and is input to the gradation correction unit 4 as needed. The user operates the printer driver on the computer 2 to operate the monitor 40.
While looking at the image above, adjust the image density and select the desired image density for the user. The data of the selected image density is transmitted to the image forming apparatus 1 through the cable. Based on the data of the selected image density, a tone curve corresponding to the image density is selected by the tone pattern generation unit 5 (LUT). The selected gradation curve is input to the gradation correction unit 4, and gradation correction is performed according to the printer characteristics.

When the density adjustment is performed by the user as described above, the density adjustment is generally performed within a range not exceeding the upper limit of the toner adhesion amount determined from the performance of the fixing device 29 shown in FIG. Is set from the initial state. However, when the environment changes, the amount of adhered toner changes, so the following control is required. Hereinafter, a specific comparison method in the gradation correction unit 4, the calculation unit 6, and the comparison unit 8 will be described.

In the case of normal temperature and normal humidity, the gradation characteristic after gradation correction when the standard value of the parameter γ in γ correction is γ = γavg becomes a straight line as shown in FIG. 9A. Also, the γ value when the density adjustment value is set to -10 of ± 10 steps is γmi
Assuming that the γ value at the time of n and +10 is γmax, the user correction range of the gradation characteristic is γmin <γ <γmax in FIG.
It is considered to be in the range. However, when the printer environment becomes hot and humid, the γ correction range is determined in advance at normal temperature and normal humidity. Therefore, when the environment changes, the gradation curve changes as shown in FIG. 9B. Therefore, the γ correction range (γmi
The toner adhesion amount at the upper limit γmax of n <γ <γmax) is larger than that at normal temperature and normal humidity.

Further details will be described. In FIG.
The user sets the tone correction value γ on the printer driver to a density that is γmax, considering that the user wants to increase the image density according to his / her preference. Since the gradation correction setting at the time of γmax is a setting at normal temperature and normal humidity, even if γ is set to the maximum value of γmax, the adhesion amount T of the image does not exceed the upper limit value Tmax determined by the fixing device. It is set to be.

However, when the printer environment is high temperature and high humidity,
When the image density is maximized, the gradation correction value also becomes γmax in conjunction therewith, and as shown in FIG. 9 (B), the gradation characteristic changes, the density of the entire image increases, and the toner adhesion amount T increases. I do. Therefore, at room temperature and normal humidity, even if the image density is set to the maximum, the upper limit value Tmax of the performance during the fixing period may not be exceeded, but at high temperature and high humidity, the upper limit value Tmax may be exceeded.

In order to prevent this danger, γ for each environment (normal temperature, normal humidity, low temperature, low humidity, high temperature and high humidity) not exceeding Tmax
Is set for each environment so that γ is equal to or less than γlim at the time of γ adjustment for each environment, it is possible to prevent the cold offset that causes the toner to have a poor fixing.

If the image density set by the user exceeds γlim in the environment at that time, a warning is issued to the user and the image density can be reset.

Next, a second embodiment will be described.

In the second embodiment, the present invention is applied to a color image forming apparatus. FIG. 10 is a diagram showing a configuration of a color image forming apparatus 50 according to the second embodiment. As shown in the figure, a photoreceptor belt 51 and a roller charger 52 are arranged inside the entire apparatus, and a plurality of developing units 54a, 54b, 54c and 54d are disposed on the left side of the photoreceptor belt 51. On the right side of the photoreceptor belt 51, a transfer paper (not shown) is supported, and
A transfer drum 53 having a function of transferring an image on the photoreceptor belt 51 onto transfer paper is provided. With the above configuration, the photosensitive belt 51 is driven in a direction indicated by an arrow by a driving unit (not shown).

Next, an image writing and exposing device 55 composed of a laser diode, a polygon mirror, a lens and the like is arranged above the main body of the device 50. A transfer paper cassette 56 for storing transfer paper is disposed below the transfer paper cassette 56.

The above-mentioned exposure device 55 has a yellow (hereinafter referred to as Y
When the signal according to the image data is input, the light is irradiated on the photoreceptor belt 51 through the optical path 57 to form an electrostatic latent image. Further, when the photosensitive belt 51 advances in the direction of the arrow, the latent image is visualized by the developing device 54.

When transfer paper is supplied from a transfer paper cassette 56 by a pickup roller (not shown) in synchronization with the image on the photoreceptor belt 51, the transfer device 58 and the transfer for supporting and transferring the transfer paper are subsequently performed. The transfer paper is electrostatically attracted to the transfer drum 53 by applying a voltage to the drum 53, and the toner image on the photosensitive belt 51 is transferred to the transfer paper via the transfer drum 53.

By performing the above steps in order of magenta (hereinafter abbreviated as M), cyan (hereinafter abbreviated as C), and black (hereinafter abbreviated as BK), a color image is formed on the transfer paper. This transfer paper is transferred to transfer drum 53
Then, the toner is removed from the transfer paper, and then the toner is fixed to the transfer paper by the fixing device 59.

On the other hand, the toner remaining on the transfer drum 53 is removed by a cleaning device such as a fur brush or blade means.
Cleaned by 60.

Then, similarly to the first embodiment, the temperature / humidity change in the image forming apparatus is measured by the temperature / humidity sensor 61 inside the apparatus, and the density of the pattern formed on the transfer drum 53 is measured by the adhesion amount sensor 62. Is measured.

Next, the gradation control in the second embodiment will be described.
This will be described with reference to the flowchart shown in FIG.

FIG. 11 is a flowchart showing the operation of the second embodiment of the image forming apparatus of the present invention. The image forming apparatus of the present invention transmits image data formed by a user on the computer 2 shown in FIG.
Enter more. The input image data is input to the gradation correction unit 4. In the gradation correction unit 4, the image data is converted into gradation data, and the gradation is corrected with reference to the gradation pattern from the gradation pattern generation unit 5 according to the input / output characteristics of the printer. In the second embodiment, the gradation pattern generator 5 (LUT) is prepared for four colors of Y, M, C, and Bk. In accordance with the gradation data after the gradation correction, gradation patterns indicating respective gradation densities are formed on the photosensitive drum for each of Y, M, C, and Bk. The toner adhesion amount is measured by an adhesion amount sensor 62 composed of an optical sensor or the like, and the toner adhesion amount of each color after gradation correction is measured. The measured value of the toner adhesion amount and the temperature / humidity data detected by the temperature / humidity sensor 61 are input to the calculation unit 6, and the calculation unit 6 calculates a more accurate toner adhesion amount at the standard value (0) before the density correction by the user. Understand. Therefore, when the user adjusts the correction of the image density according to his / her preference, the amount of adhesion at each adjustment value is estimated and calculated from the measurement result of the actual gradation pattern, and thus can be calculated more accurately. .

As an example of the calculation method, for example, assuming that a gradation curve whose density changes linearly with respect to a gradation value as shown in FIG. And If the gradation characteristic when the density adjustment value is the highest value (+10) is shown in FIG. 7B, the increase in density at each gradation value is calculated by multiplying the standard value by the gradation characteristic. It is possible. Therefore, by calculating according to the above measurement results, it is possible to more accurately predict the toner adhesion amount at that time.

The calculated amount of adhered toner is sent to the comparing section 8 as in the first embodiment, and is compared with the upper limit of the amount of adhered toner determined from the performance of the fixing device 59. It is determined whether it is above or below the value. If the toner adhesion amount exceeds the upper limit, a signal is sent to the computer 2 to issue a warning that the toner has exceeded the upper limit. on the other hand,
If the performance is equal to or lower than the upper limit of the fixing device performance, an image is formed in the recording unit 9 composed of a photosensitive drum or the like according to the gradation pattern, and the output image is printed out in the output unit 10.

When a warning is received, the user or a printer driver or the like re-adjusts the image density, transmits the image data again to the image forming apparatus, and returns to the image density where the toner adhesion amount does not exceed the upper limit. The above operation is repeated until no warning is received.

FIG. 12 is a flowchart showing the operation of the third embodiment of the image forming apparatus of the present invention. The image forming apparatus of the present invention transmits image data formed by a user on a personal computer to the image forming apparatus, and inputs the image data from the input unit 3. The input image data is input to the gradation correction unit 4. In the gradation correction unit 4, the image data is converted into gradation data, and the gradation pattern is generated according to the input / output characteristics of the printer.
The gradation is corrected by referring to the gradation pattern from 5. number 3
In this embodiment, similarly to the second embodiment, the gradation pattern generator 5 (LUT) is prepared for four colors of Y, M, C and Bk. In the third embodiment, based on the temperature and humidity data from the temperature and humidity sensor 61, the contrast potential, which is the difference between the developing bias potential of the developing device 54 and the photosensitive belt potential of the photosensitive belt 51, is changed. The toner adhesion amount is kept constant based on the data. That is, when the temperature and the humidity are high, the toner adhesion amount tends to increase. Therefore, the contrast potential is lowered to reduce the toner adhesion amount on the photosensitive belt 51. In the case of low temperature and low humidity, the toner adhesion amount tends to decrease. Therefore, the contrast potential is increased to increase the toner adhesion amount on the photosensitive belt 51. However, when the user adjusts the image density, even when the contrast potential is lowered to reduce the amount of adhesion, the toner correction may increase the amount of toner adhesion.

In this embodiment, the amount of toner adhered when such potential control and gradation correction are combined is checked. The amount of adhered toner is determined on the photosensitive belt 51 or the transfer drum.
It is measured from the result of measuring the amount of adhesion of the pattern formed on 53. Alternatively, the toner adhesion amount is checked by performing calculations such as predicting and calculating the adhesion amount from the gradation data after the gradation correction and the data of the contrast potential and the temperature and humidity.

The measured value or the calculated value of the toner adhesion amount is sent to the comparing section 8 and compared with the upper limit value of the toner adhesion amount determined from the performance of the fixing device 59 as in the first embodiment. It is determined whether the value is equal to or greater than the upper limit. If the toner adhesion amount exceeds the upper limit, a signal is sent to the computer 2 to issue a warning that the toner has exceeded the upper limit. On the other hand, if it is equal to or less than the upper limit of the performance of the fixing device 59,
In accordance with the gradation data, an image is formed in a recording unit 9 including a photosensitive drum 51 and the like, and an output image is printed out in an output unit 10.

When a warning is received from the computer 2, the user or a printer driver adjusts the image density again, transmits the image data to the image forming apparatus 1 again, and the toner adhesion amount does not exceed the upper limit. Image density
The above operation is repeated until no warning is received.

[0061]

As is apparent from the above description, according to the present invention, control is performed to stabilize the image density by performing any kind of gradation correction, changing image forming parameters, and so on. Even when the environment fluctuates, it is possible to prevent the amount of adhesion from exceeding the upper limit of the performance during the fixing period, and to prevent cold offset.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment according to the present invention.

FIG. 2 is a flowchart showing the operation of the first embodiment according to the present invention.

FIG. 3 is a configuration diagram illustrating a recording unit according to the first embodiment of the present invention.

FIG. 4 is a block diagram illustrating an operation of a conventional image forming apparatus.

FIG. 5 is an explanatory diagram for explaining an environmental change of gradation characteristics.

FIG. 6 is an explanatory diagram illustrating an example of gradation characteristics after gradation correction.

FIG. 7 is an explanatory diagram illustrating a change in tone characteristics due to an environment after tone correction.

FIG. 8 is a diagram illustrating an adjustment screen for adjusting image density by a user.

FIG. 9 is a view for explaining a difference in gradation characteristics of a density adjustment range by a user between normal temperature and normal humidity and high temperature and high humidity.

FIG. 10 is a configuration diagram illustrating an image forming apparatus according to a second embodiment of the invention.

FIG. 11 is a flowchart showing the operation of the second embodiment according to the present invention.

FIG. 12 is a flowchart showing the operation of the third embodiment according to the present invention.

[Explanation of symbols]

1 ... image forming apparatus, 2 ... computer, 3 ...
Input unit, 4: gradation correction unit, 5: gradation pattern generation unit, 6: calculation unit, 7: temperature and humidity sensor, 8: comparison unit, 9: recording unit , 10 ... output unit, 11 ... control unit, 21 ... photosensitive drum, 22 ... charger, 23 ...
Image writing / exposure device, 24 ・ ・ ・ Laser driver, 25 ・
..Optical paths, 26 ... developers, 27 ... transfer devices, 28 ...
・ Transfer paper, 29 ・ ・ ・ Fixer, 30 ・ ・ ・ Cleaner, 40 ・
..Monitor, 41 ... Image, 42 ... Image density adjusting bar, 50 ... Color image forming apparatus, 51 ... Photoconductor belt, 52 ... Charging device, 53 ... Transfer drum , 54a-54d
... Developing device, 55 ... Image writing exposure device, 56 ...
Transfer paper cassette, 57: Optical path, 58: Transfer device, 59
... fixing unit, 60 ... cleaner, 61 ... temperature and humidity sensor, 62 ... adhesion amount sensor.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H027 DA09 DA11 DA14 DE07 EA01 EA05 EB01 EC06 EC10 EJ15 FA07 GA30 ZA07 5C074 AA05 DD03 DD08 DD16 EE03 EE11 EE20 GG13 GG16 9A001 HH28 HH34

Claims (7)

[Claims] An input unit for inputting image data obtained by converting an image created by a user by a computer to an image forming apparatus; receiving the input image data as digital data; In an image forming apparatus including a gradation correction unit that corrects
A calculation unit that calculates the amount of toner adhered to the image based on the gradation data corrected for gradation, and a fixing unit that fixes the toner image formed on the recording medium based on the image data based on the calculation result by the calculation unit A comparison unit that determines whether or not the upper limit value of the toner adhesion amount determined from the performance is exceeded; and a notifying unit that issues a warning when the calculation result is equal to or more than the upper limit value. Image forming apparatus. 2. An image forming apparatus according to claim 1, wherein said notifying means is directly notified to a user via a computer or the like. 3. An image forming apparatus according to claim 1, wherein said notifying means feeds back to printer-related software on said computer, and adjustment is performed inside said software. 4. In the image forming apparatus, a temperature and humidity sensor is provided inside the apparatus, and a toner adhesion amount of the image is calculated based on the gradation data subjected to gradation correction and measurement data of the temperature and humidity sensor. The image forming apparatus according to claim 1, wherein: 5. The image forming apparatus according to claim 1, further comprising an adhesion amount sensor for measuring an amount of toner adhered to the image, inputting the adhesion amount measurement result to the arithmetic unit, and comparing the result in the comparison unit based on the result. The image forming apparatus according to claim 1, wherein: 6. The image forming apparatus according to claim 1, further comprising a gradation pattern generating section (LUT: lookup table) for storing a gradation pattern to be referred to at the time of gradation correction. 2. The image forming apparatus according to claim 1, wherein a gradation pattern when the user performs density correction is stored in the image forming apparatus. 7. The image forming apparatus according to claim 1, further comprising a mechanism for adjusting a developing bias potential of a developing device and a drum potential of a photosensitive drum.