JPH052306A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device which can optimize fluctuations in an image density caused by a change in environment and the lapse of time in a cycle shorter than that of maintenance, without depending on the maintenance, achieve the stability of a high image density, and reduce cost required for the maintenance. CONSTITUTION:A surface potential measuring part 3 measures the surface potential of an electrified photosensitive drum 1. A toner sticking quantity calculating part 47 calculates the sticking quantity of toner sticking on the photosensitive drum 1 by development, from image data A toner sticking quantity measuring part 8 measures the sticking quantity of the toner sticking to a latent image formed on the photosensitive drum 1 based on the image data used for calculating the forecasting value of the above-mentioned toner sticking quantity, by the development A control circuit 45 compares the measured toner sticking quantity with the above-mentioned calculated forecasting value, and executes processing for changing, at least, one of an electrifying quantity, a developing bias voltage, an exposure a toner density, etc., which are image forming conditions, based on the results of the detection and the above- mentioned surface potential measurement.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art For example, it seems that there are many people who have the experience of making different copies of the same original on the same copying machine. Fluctuations in image density in electrophotography are the effects of environmental changes, changes in image forming conditions over time, and deterioration. In analog copying machines, as well as in multi-tone printers or digital copying machines, this fluctuation in image density is suppressed.
Stabilization is important. Particularly in color, not only the density reproducibility but also the color reproducibility is affected, so it can be said that stabilization of the image density is an essential requirement. Therefore, conventionally, it has been attempted to stabilize the image by maintaining these materials and the process itself by allowing them.

[0003]

However, there is a limit to allowance in materials and processes themselves, labor and cost are required for maintenance, and moreover, image density fluctuations are more frequent than the frequency of maintenance. However, there is a problem that a stable image density cannot be obtained only by maintenance.

Therefore, according to the present invention, fluctuations in image density due to changes in the environment and aging can be optimized without relying on maintenance and in a cycle shorter than the maintenance cycle, and high image density stability can be achieved. An object of the present invention is to provide an image forming apparatus capable of reducing the cost required for maintenance.

[0005]

An image forming apparatus according to the present invention comprises a charging means for charging the surface of an image carrier and a surface potential measuring means for measuring the surface potential of the image carrier charged by the charging means. A latent image forming means for forming a latent image on the surface of the image carrier charged by the charging means based on image data, and a latent image on the image carrier formed by the latent image forming means. Developing means for developing with a developer, developer adhesion amount calculating means for calculating, from the image data, a predicted value of the adhesion amount of the developer attached to the image carrier by the development of the developing means, and the developer The adhesion amount of the developer adhered by the development of the developing means to the latent image on the image carrier formed based on the image data used to calculate the predicted value of the developer adhesion amount in the adhesion amount calculation means. The developer adhesion amount measuring means to measure Comparing means for comparing the measured value of the developer adhesion amount measuring means and the predicted value calculated by the developer adhesion amount calculating means, and the comparison result of the comparing means and the measurement result of the surface potential measuring means An image forming condition changing unit that changes at least one image forming condition of the charging unit, the latent image forming unit, and the developing unit is provided.

[0006]

From the image data for forming an image, the predicted value of the amount of the developer adhering to the image carrier by the development is calculated, and the surface potential of the charged image carrier is measured, and the above-mentioned development is performed. Measure the amount of developer adhered to the latent image formed on the image carrier based on the image data used to calculate the predicted value of the amount of developer adhered by development. The calculated predicted value is compared, and based on the comparison result and the measurement result of the surface potential, at least the charge amount with respect to the image carrier, which is the image forming condition, the developing bias voltage, the exposure amount, the concentration of the developer, and the like. By changing one, changes in the image density due to changes in the environment and time can be optimized without relying on maintenance and in a cycle shorter than the maintenance cycle, and high image density stability can be achieved. The cost required for the Maintenance Manual (labor costs, such as equipment) can be reduced.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows the structure of a color laser printer as an example of the image forming apparatus according to the present invention.
In the figure, reference numeral 1 is a photosensitive drum as an image bearing member, which rotates counterclockwise with respect to the drawing. Around the photosensitive drum 1, a charger 2 as a charging unit, a surface potential measuring unit 3,
A first developing device 4, a second developing device 5, a third developing device 6, a fourth developing device 7, a toner adhesion amount measuring unit 8, a transfer drum 9 as a transfer material support, a pre-cleaning static eliminator 1 which are developing means.
0, a cleaner 11, and a charge eliminating lamp 12 are sequentially arranged.

The photosensitive drum 1 rotates in the direction of the arrow in the figure,
The surface is uniformly charged by the charger 2. The laser beam light 14 emitted from the optical system 13 which is an exposing means from between the charging device 2 and the first developing device 4 exposes the surface of the photoconductor drum 1 to an electrostatic charge corresponding to the image data. A latent image is formed.

The first to fourth developing devices 4 to 7 visualize the electrostatic latent image on the photosensitive drum 1 corresponding to each color into a color toner image. For example, the first developing device 4 is Magenta, the second developing device 5 is cyan, the third developing device 6 is yellow,
The fourth developing device 7 is adapted to develop black.

On the other hand, the transfer sheet as the transfer material is sent out from the sheet feeding cassette 15 by the sheet feeding roller 16, is once aligned by the registration roller 17, and is attracted to a predetermined position of the transfer drum 9 by the registration roller 17. And is electrostatically attracted to the transfer drum 9 by the attraction roller 18 and the attraction charger 19. The transfer sheet is attracted to the transfer drum 9 and is conveyed as the transfer drum 9 rotates clockwise.

The developed toner image on the photosensitive drum 1 is transferred to a transfer sheet by the transfer charger 20 at a position where the photosensitive drum 1 and the transfer drum 9 face each other. In the case of printing with a plurality of colors, the step of setting one rotation of the transfer drum 9 as one cycle is performed by switching the developing device to multiple-transfer the toner images of a plurality of colors onto the transfer paper.

The transfer paper on which the toner image has been transferred is further conveyed as the transfer drum 9 rotates, and the internal static eliminator 2 before separation is used.
1. After removing the static electricity by the pre-separation external static eliminator 22 and the separation static eliminator 23, the separation nail 24 separates it from the transfer drum 9,
It is conveyed to the fixing device 27 by the conveyor belts 25 and 26.
The toner on the transfer paper heated by the fixing device 27 is melted and fixed on the transfer paper immediately after being discharged from the fixing device 27, and the transfer paper after this fixing is discharged to the tray 28.

FIG. 1 is a block diagram relating to the charging, exposing and developing means and the control means of the color laser printer according to this embodiment. In the figure, the photosensitive drum 1 rotates counterclockwise (in the direction of the arrow in the figure) with respect to the drawing. The charger 2 mainly includes a charging wire 31, a conductive case 32, and a grid electrode 33. Charging wire 31
Is connected to a high voltage power supply 34 for corona and charges the surface of the photoconductor drum 1 by corona discharge. The grid electrode 33 is connected to a high voltage power supply 35 for grid bias, and controls the amount of charge on the surface of the photosensitive drum 1 by the grid bias voltage.

An electrostatic latent image is formed on the surface of the photosensitive drum 1 uniformly charged by the charger 2 by exposure of the modulated laser beam light 14 from the optical system 13. Also,
The surface potential of the photosensitive drum 1 uniformly charged by the charger 2 is measured by the surface potential measuring unit 3.

The gradation data buffer 36 stores gradation data from an external device or controller (not shown),
The tone characteristics of the printer are corrected and converted into laser exposure time (pulse width) data. The laser drive circuit 37 modulates the laser drive current (light emission time) according to the laser exposure time data from the gradation data buffer 36 so as to be synchronized with the scanning position of the laser beam light 14. Then, the semiconductor laser oscillator (not shown) in the optical system 13 is driven by the modulated laser drive current. Accordingly, the semiconductor laser oscillator emits light according to the exposure time data.

Further, the laser drive circuit 37 includes the optical system 1
The output of the monitor light receiving element (not shown) in 3 is compared with the set value, and the output current of the semiconductor laser oscillator is controlled to be the set value by the drive current.

On the other hand, the toner adhesion amount calculation unit 47 calculates a predicted value of the toner adhesion amount based on gradation data from an external device or controller (not shown). That is, the gradation data (or the converted laser exposure time data) received in the gradation data buffer 36 in the range corresponding to the measurement surface of the toner adhesion amount measuring unit 8 after development is integrated, and the integrated value is used as the toner value. The value is converted into a value corresponding to the output of the adhesion amount measuring unit 8.

The photosensitive drum 1 on which the electrostatic latent image is formed is developed by the developing device 4. The developing device 4 is, for example, a two-component developing system and stores a developer consisting of toner and carrier, and the weight ratio of the toner to the developer (hereinafter referred to as toner concentration) is determined by the toner concentration measuring unit 39.
It is measured by. Then, the toner replenishment motor 41 that drives the toner replenishment roller 40 is controlled in accordance with the output of the toner concentration measurement unit 39, so that the toner hopper 4
The toner in 2 is replenished in the developing device 4.

The developing roller 43 of the developing unit 4 is formed of a conductive member, is connected to a high voltage power source 44 for developing bias, and rotates in a state in which a developing bias voltage is applied to the photosensitive drum. Toner is attached to the image corresponding to the electrostatic latent image on 1. The toner image in the image area thus developed is transferred to the transfer sheet supported and conveyed by the transfer drum 9.

After the development, the toner adhesion amount calculation unit 4 is first
7, the toner adhesion amount measuring unit 8 measures the toner adhesion amount in the portion where the latent image of the image data used to calculate the predicted value of the toner adhesion amount is developed.

FIG. 3 shows the toner 48 adhering to the photosensitive drum 1 after development and the measuring position 49 on the photosensitive drum 1 of the toner adhering amount measuring unit 8. With respect to the measurement area of the toner adhesion amount measuring unit 8, it is considered that the position where the gradation pattern or the pattern having a high printing rate has a high probability is substantially in the center with respect to the scanning direction (the axial direction of the photosensitive drum 1).

The fluctuation of the density gradation is particularly noticeable when the density of a pictorial original having a large area is continuous, and the color reproduction becomes more noticeable as the area increases. When the color laser printer to which the present invention is applied is used as a color copying machine, there are many applications for taking a document having a large printing area as described above. Therefore, it is necessary to suppress the variation of the density gradation as the color original has a larger printing area.
There is an increased possibility that these patterns will come to the center of the photosensitive drum 1.

Therefore, the toner adhesion amount measuring section 8 whose measurement position is the center of the photosensitive drum 1 measures the toner adhesion amount when a gradation pattern or a pattern having a high printing rate is developed.

The output of the toner adhesion amount measuring unit 8, the output of the toner concentration measuring unit 39, and the output of the surface potential measuring unit 3 are
Each is digitized by the A / D converter 46 and input to the control circuit 45. The control circuit 45 compares the output (measured value) of the toner adhesion amount measuring unit 8 with the predicted value of the toner adhesion amount previously calculated by the toner adhesion amount calculation unit 47, and compares the comparison result with the surface potential measurement unit 3. Depending on the output (measured value), the grid bias voltage of the charging device 2 which is the image forming condition, the developing bias voltage of the developing device 4, the exposure amount of the optical system 13, the toner concentration of the developer, and the emission time of area gradation. And the like is changed.

Further, the control circuit 45 controls switching of gradation data from an external device or controller (not shown) and gradation data of a test pattern of the printer alone, capture of outputs of the measuring units 3, 8 and 39, high voltage power supply. 34, 35, 4
4, control of each output amount, setting of the target value of the laser drive current, setting of the target value of the toner concentration, toner replenishment control, correction processing of the gradation characteristics of the printer for gradation data, and the like.

FIG. 4 shows the toner adhesion amount Q with respect to the gradation data. The curve of the toner adhesion amount with respect to the gradation data has a deviation due to changes in image forming conditions due to time and environment. Therefore, it is a necessary condition for stabilizing the image density that there is little variation in the curve of the toner adhesion amount with respect to the gradation data due to time and environment.

FIG. 5 shows the surface potential of the photosensitive drum 1 uniformly charged by the charger 2 with respect to the absolute value VG (hereinafter simply referred to as grid bias voltage) of the bias voltage applied to the grid electrode 33 of the charger 2. (Hereinafter, referred to as unexposed portion potential) VO, the surface potential (hereinafter, exposed portion potential) VL of the photosensitive drum 1 which is entirely exposed by the optical system 13 at a constant light amount and attenuated, and the developing bias voltage VD (dashed line )
Is shown.

In this embodiment, the polarity of the potential or voltage is negative due to the reversal development. Grid bias voltage V
As G increases, the unexposed portion potential VO and the exposed portion potential V
L decreases respectively. Linearly approximating the exposed portion potential VL and the unexposed portion potential VO with respect to the grid bias voltage VG can be expressed by the following equation. VO (VG) = K1 · VG + K2 …… (1) VL (VG) = K3 · VG + K4 …… (2) where K1 to K4 are constants

Here, the developing density changes depending on the relationship between the developing bias voltage VD, the exposed portion potential VL, and the unexposed portion potential VO. Now, the contrast potential VC and the background potential VBG are defined as follows. VC = VD (VG) -VL (VG) ... (3) VBG = VO (VG) -VG (VG) ... (4)

The contrast potential VC is particularly related to the density of solid areas (see FIG. 6). The background potential VBG is mainly involved in the density of the low density portion in the multi-gradation method using pulse width modulation (see FIG. 7).

FIG. 8 shows the toner adhesion amount Q with respect to the gradation data when the background potential VBG is increased. The low-concentration region changes in the direction of the arrow C in the figure. Therefore, the developing density can be changed by the contrast potential VC and the background potential VBG. Here, formula (1)-
The following equation is obtained from (4). VG (VC, VBG) = (VC + VBG-K2-K4) /
(K1 + K3) (5) V D (VBG, VG) = K1 · VG + K2 -VBG (6)

From the above equations (5) and (6), the exposed portion potential VL and the unexposed portion potential V with respect to the grid bias voltage VG.
When the relationship (K1, K2) of O is known, the grid bias voltage VG and the developing bias voltage VD can be uniquely determined by determining the contrast potential VC and the background potential VBG.

After obtaining the relationship (K1, K2) between the exposed portion potential VL and the unexposed portion potential VO with respect to the grid bias voltage VG obtained by the surface potential measuring portion 3, the contrast potential VC and the background potential VBG are set. Equation (5),
From (6), the grid bias voltage VG and the developing bias voltage VD are uniquely determined, a plurality of density patterns are imaged under these conditions, and the toner adhesion amount Q after these development is measured and set in advance. Compared with the reference value, based on the deviation ΔQ, the contrast potential VC to obtain an appropriate development density
And the correction values ΔVC and ΔVBG of the background potential VBG are inferred. Based on this inference result, the grid bias voltage VG and the developing bias voltage VD are set again, the toner adhesion amount of the density pattern is measured, and the measurement is repeated until it is within the acceptable range.

FIG. 9 shows the solid image density D with respect to the exposure amount P of the laser beam light. In this embodiment, the area where the image density D starts to saturate with respect to the exposure amount P is used, and when the light amount changes, the change mainly affects the low density portion (see FIG. 10). Therefore, the fluctuation of the low density portion can be corrected by changing the exposure amount.

FIG. 11 shows the relationship between the toner density T / D and the toner adhesion amount Q. Toner density T / D
The toner adhesion amount Q monotonically increases. Toner density lower limit value d
Is a value that is empirically determined by a carrier adhesion to the photosensitive drum 1 and the toner concentration upper limit value e due to a problem such as an increase in uncharged toner. In the range sandwiched between the two (between two broken lines), Change the concentration. FIG. 12 shows a change in the toner adhesion amount Q with respect to the gradation data when the toner density is increased.

FIG. 13 shows image data, laser exposure time (pulse width) PD, toner adhesion amount Q, and printer output image density D. When the color laser printer to which the present invention is applied is a part of a digital copying machine, a laser exposure time PD for a certain gradation data, a toner adhesion amount Q,
The printer output image densities D correspond to each other. When the toner adhesion amount Q fluctuates due to time and the environment (one-dot chain line g), the conversion between the gradation data and the laser exposure time PD is changed (two-dot chain line h) to change the toner adhesion amount Q to the image data. The relationship can be made constant. In the present embodiment, the number of steps of the laser exposure time PD is larger than the number of steps of the gradation data, and a selection means for selectively selecting the laser exposure time PD for each gradation data is provided. Next, the toner adhesion amount measuring unit 8 will be described in detail.

FIG. 14 shows the structure of the toner adhesion amount measuring unit 8. In the figure, the light from the light source 51 is applied to the surface of the photoconductor drum 1, and the reflected light reflected by the photoconductor drum 1 or the toner that has been developed and attached depends on the amount of the reflected light at the photoelectric conversion unit 52. Converted into a current and further converted into a current / voltage, and then the transmission circuit 53
Is transmitted to the A / D converter 46, converted into a digital signal here, and taken into the control circuit 45.

The light source 51 is current-driven by the light source drive circuit 54. The light source drive circuit 54 includes a control circuit 45.
Is controlled by ON / OFF control or a signal for adjusting the amount of drive current to the light source 51.

FIG. 15 shows the spectral reflectance of the output image. Yellow Y, Magenta M, Cyan C, Black BK
Spectral reflectances are shown for images in which each toner is output in a single color by a color printer.

FIG. 16 shows the specular reflectances of the photosensitive drums at different incident angles. A solid line o represents a specular reflectance having a relatively shallow angle with respect to the normal line of the reflecting surface, and a broken line p represents a specular reflectance having a deep angle. It indicates that the deeper the angle, the less the wavelength dependence of reflection.

This can be understood from the fact that the reflection on the surface has a characteristic with respect to the angle as shown in FIG. In FIG. 17, RT represents the reflectance in the direction parallel to the incident angle, and Rs represents the reflectance in the direction perpendicular to the incident angle. Therefore, when the incident angle is shallow, compared with the reflection on the surface of the photoconductor drum, the light is transmitted through the photoconductor layer of the photoconductor drum, reflected by the conductive support member having a metallic luster that supports the photoconductor layer, and exposed again. The light transmitted through the body layer is large.

Therefore, in the case of the photosensitive drum 1 of this embodiment, the incident angles of the color toners (Y, M, C) are made shallow and the wavelength of the light of the light source 51 is set to a wavelength range of 800 nm or more. , Wide dynamic range.
Further, with respect to black toner, the limited range of the wavelength is 300 to 1 by being incident at a relatively deep angle.
It is not in the range of 000 nm.

However, as shown in FIG. 18, since the photosensitivity of the photosensitive drum is as high as 500 to 800 nm, stray light to the image area due to specular reflection and scattering of the toner image to be measured are avoided. Therefore, avoid wavelengths in this region. In this embodiment, the highest sensitivity level of 1
A wavelength other than / 10 was selected, and a wavelength of 860 nm or more, preferably in the range of 860 to 1000 nm was selected. As the photoelectric conversion unit 52 at this time, a photodiode having the sensitivity (converted current amount with respect to received light amount) as shown in FIG. 19 was used.

FIG. 20 shows the installation state of the shielding member provided between the toner adhesion amount measuring unit 8 (and the surface potential measuring unit 3) and the photosensitive drum 1. That is, the toner adhesion amount measuring unit 8 (and the surface potential measuring unit 3) is arranged such that its measurement surface faces the surface of the photosensitive drum 1. A plate-shaped shield member 61 is provided so as to be openable and closable close to the measurement surface side of the toner adhesion amount measuring unit 8 (and the surface potential measuring unit 3). One end of the shielding member 61 is connected to the flapper 63 of the solenoid 62 by a pin, and the flapper 6 is controlled by turning the solenoid 62 on and off.
According to the opening / closing operation of 3, the shielding member 61 moves in the direction of the arrow in the figure.

The shielding member 61 is closed when the toner adhesion amount measuring unit 8 (and the surface potential measuring unit 3) is not measured to shield the measurement surface from the outside, and is opened only at the time of measurement to scatter toner. It is possible to reduce the contamination of the measurement surface due to, and it is possible to extend the period in which highly accurate measurement is possible.

As described above, according to the above-described embodiment, the predicted value of the amount of toner adhering to the photosensitive drum due to development is calculated from the image data for forming an image, and the toner is charged by the charger. The surface potential of the photosensitive drum is measured, and the amount of toner adhered by the development to the latent image on the photosensitive drum formed based on the image data used to calculate the predicted value of the amount of adhered toner is calculated. Measure,
The measured toner adhesion amount and the calculated predicted value are compared, and based on the comparison result and the measurement result of the surface potential, the charge amount with respect to the photosensitive drum which is the image forming condition, the developing bias voltage, the exposure amount, By changing at least one of the toner density, changes in the image density due to changes in the environment and time can be optimized without relying on maintenance and in a cycle shorter than the maintenance cycle, and high image density stability The cost required for maintenance (labor cost, equipment, etc.) can be reduced.

FIG. 21 shows another example of the structure of the toner adhesion amount measuring section 8. The same parts as those in FIG. 13 are designated by the same reference numerals, and the description thereof will be omitted. Only different parts will be described.
In the figure, the light from the light source 51 is applied to the surface of the photoconductor drum 1, and the reflected light reflected by the photoconductor drum 1 or the developed and attached toner is the first photoelectric conversion unit 5.
In the second and second photoelectric conversion units 55, the current is converted into a current according to the light amount of the reflected light, and further current / voltage converted, and then transmitted to the A / D converter 46 by the transmission circuits 53 and 56, respectively. It is adapted to be converted into a digital signal and taken into the control circuit 45.

The first photoelectric conversion section 52 is provided at a position for receiving the light including the principal ray of the principal ray reflected by the surface of the photosensitive drum 1 by the light source 51, and the second photoelectric conversion section 55 is provided by the second photoelectric conversion section 55. Is provided at a position for receiving the light of the principal ray of the reflected light of the surface of the photosensitive drum 1 that does not include the principal ray.
As a result, the first photoelectric conversion unit 52 receives the specularly reflected light on the surface of the photosensitive drum 1, and the second photoelectric conversion unit 55 receives the diffusely reflected light on the surface of the photosensitive drum 1.

FIG. 22 shows the first photoelectric converter 52 and the second photoelectric converter 52.
The distribution of reflected light from the photoelectric conversion unit 55 and the photosensitive drum 1 is shown. The principal ray from the light source 51 and the principal ray of the reflected ray of the principal ray on the photosensitive drum 1 are shown by a chain line l.

The solid line m shows the distribution of reflected light on the photosensitive drum 1 on which nothing is attached. At the angle of the principal ray 1 of the reflected light, the amount of light due to specular reflection of the surface of the photoconductor drum 1 and the conductive support member that supports the photoconductor layer is large.
If it deviates from that angle, it becomes diffused light scattered by the surface of the photoconductor layer, the photoconductor layer, and the conductive support member, and the amount of diffused reflection light is smaller than that of specular reflection light.

The distribution of the reflected light becomes as shown by the broken line n due to the adhesion of the toner to the surface of the photosensitive drum 1 by the development. The specularly reflected light is scattered and reduced by the granular toner, and the diffusely reflected light is increased. Therefore, the first photoelectric conversion unit 52 measures the decrease of the specular reflection light, and the second photoelectric conversion unit 55 measures the increase of the diffuse reflection light.

Here, in the measurement of the toner adhesion amount by the specular reflection light, when the toner adhesion exceeds a certain amount, the change of the specular reflection light amount becomes extremely small. Further, in the case of diffuse reflected light, when the amount of adhered toner is less than a certain amount, the amount of light may be smaller than that of the diffuse reflected light of the photosensitive drum 1 on which toner is not adhered, depending on the toner and the photoconductor. ..

Therefore, by measuring the specular reflection light and the diffuse reflection light, respectively, and converting the toner adhesion amount from the respective light amounts at that time, as compared with the measurement of only one,
It is possible to measure a wide range with higher accuracy.

[0055]

As described in detail above, according to the present invention, fluctuations in image density due to changes in the environment and aging can be optimized without relying on maintenance, and in a cycle shorter than the maintenance cycle, resulting in high image quality. It is possible to provide an image forming apparatus that can achieve density stability and reduce maintenance costs.

[Brief description of drawings]

FIG. 1 is a block diagram relating to a charging, exposing, developing means and its control means of a color laser printer according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a color laser printer.

FIG. 3 is a diagram showing the toner adhering to the photosensitive drum and a measurement position of the toner adhering amount measuring unit on the photosensitive drum.

FIG. 4 is a diagram showing a toner adhesion amount with respect to gradation data.

FIG. 5 is a diagram showing an unexposed portion potential, an exposed portion potential, and a developing bias voltage of a photosensitive drum with respect to a grid bias voltage of a charger.

FIG. 6 is a diagram showing an image density of a solid portion with respect to a contrast potential.

FIG. 7 is a diagram showing a relationship between a potential of an unexposed portion on a surface of a photosensitive drum, a potential of a low density pattern and a developing bias voltage.

FIG. 8 is a diagram showing a toner adhesion amount with respect to gradation data when the background potential is increased.

FIG. 9 is a diagram showing a solid image density with respect to an exposure amount.

FIG. 10 is a diagram showing a toner adhesion amount with respect to gradation data when an exposure amount is changed.

FIG. 11 is a diagram showing the relationship between toner concentration and toner adhesion amount.

FIG. 12 is a diagram showing a change in toner adhesion amount with respect to gradation data when the toner density is increased.

FIG. 13 is a diagram showing a relationship among image data, laser exposure time, toner adhesion amount, and printer output image density.

FIG. 14 is a block diagram showing a configuration of a toner adhesion amount measuring unit.

FIG. 15 is a diagram showing the spectral reflectance of a printer output image.

FIG. 16 is a diagram showing the specular reflectance of a photoconductor drum at different light incident angles.

FIG. 17 is a diagram showing the reflection characteristics of the surface of the photosensitive drum with respect to the light incident angle.

FIG. 18 is a diagram showing a photosensitivity characteristic of a photosensitive drum.

FIG. 19 is a diagram showing sensitivity characteristics of a photoelectric conversion unit.

FIG. 20 is a diagram showing an installation state of a shielding member provided between the toner adhesion amount measuring unit and the surface potential measuring unit and the photosensitive drum.

FIG. 21 is a block diagram showing another configuration example of the toner adhesion amount measuring unit.

22 is a diagram showing a distribution of reflected light from the first photoelectric conversion unit and the second photoelectric conversion unit in FIG. 21, and the photosensitive drum.

[Explanation of symbols]

1 ... Photosensitive drum (image bearing member), 2 ... Charging device (charging means), 3 ... Surface potential measuring section, 4 to 7 ... Developing device (developing means), 8 ... Toner adhesion amount measuring section , 9 ... Transfer drum, 13 ... Optical system (exposure means), 13 ... Laser beam light, 20 ... Transfer charger, 27 ... Fixer, 34 ... Corona high voltage power supply, 35 ... Grid bias High-voltage power supply, 36 ... Gradation data buffer, 37 ... Laser drive circuit, 39 ... Toner density measuring unit, 40 ... Toner supply roller, 43 ... Developing roller, 44 ... High voltage power supply for developing bias, 45 ... ... control circuit, 46 ... A / D converter,
47 ... Toner adhesion amount calculation unit, 51 ... Light source, 52, 5
5 ... Photoelectric conversion part, 61 ... Shielding member.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location G03G 15/08 115 115635-2H

Claims (1)

Claim: What is claimed is: 1. A charging means for charging the surface of an image carrier,
Surface potential measuring means for measuring the surface potential of the image carrier charged by the charging means, and latent image formation for forming a latent image on the surface of the image carrier charged by the charging means based on image data. Means, developing means for developing the latent image formed on the image carrier by the latent image forming means with a developer, and developing from the image data by the developing means to adhere to the image carrier. A developer adhesion amount calculation means for calculating a prediction value of the developer adhesion amount, and the image formed based on the image data used for calculating the prediction value of the developer adhesion amount in the developer adhesion amount calculation means. The developer adhesion amount measuring means for measuring the adhesion amount of the developer adhered to the latent image on the carrier by the developing means, the measured value of the developer adhesion amount measuring means and the developer adhesion amount calculating means. Ratio to compare with the calculated predicted value And an image forming condition changing unit that changes at least one image forming condition of the charging unit, the latent image forming unit, and the developing unit based on the comparison result of the comparing unit and the measurement result of the surface potential measuring unit. An image forming apparatus comprising: