JPH052303A - Image forming device - Google Patents

Abstract

PURPOSE:To 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, to achieve the stability of a high image density, and to reduce cost required for the maintenance. CONSTITUTION:A toner sticking quantity calculating part 47 calculates the forecasting value of the sticking quantity of toner stuck on a photosensitive drum 1 by development, from image data for forming an image. A toner sticking quantity measuring part 8 measures the sticking quantity of the toner stuck 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 by an electrifier 2, a developing bias voltage by a developing unit 4, an exposure by an optical system 13, the toner density of the developing unit 4, etc., which are image forming conditions, based on the result of the 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 that the same copy is copied by the same copy machine but the copy has different darkness. 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. In particular, 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 through maintenance by allowing these materials and the process itself.

[0003]

However, there is a limit to allowance in materials and processes themselves, maintenance requires labor and cost, and moreover, the image density varies as compared with the frequency of maintenance. However, there is a problem that the stable image density cannot be obtained only by maintenance.

Therefore, according to the present invention, fluctuations in the image density due to changes in the environment and with time can be optimized without depending on maintenance, and in a cycle shorter than the maintenance cycle, 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]

SUMMARY OF THE INVENTION An image forming apparatus of the present invention comprises a latent image forming means for forming a latent image on an image carrier based on image data, and the image bearing formed by the latent image forming means. A developing means for developing a latent image on the body with a developer, and a developer adhesion amount calculation for calculating, from the image data, a predicted value of an adhesion amount of the developer adhered on the image carrier by the development of the developing means. Means and 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 developer adhesion amount calculation means by the development of the developing means. The developer adhesion amount measuring means for measuring the adhesion amount of the developer, the comparing means for comparing the measured value of the developer adhesion amount measuring means with the predicted value calculated by the developer adhesion amount calculating means, and this comparison The latent image forming means based on the comparison result of the means. Others are provided with an image forming condition changing means for changing an image forming condition in the developing unit.

[0006]

The image used to calculate the predicted value of the amount of developer adhered to the image carrier by development from the image data for forming an image, and the predicted value of the amount of developer adhered The amount of developer adhered to the latent image on the image carrier formed based on the data is measured by development, and the measured amount of developer adhering to the calculated predicted value is compared,
Based on this comparison result, by changing at least one of the image forming condition, such as the charge amount with respect to the image carrier, the developing bias voltage, the exposure amount, and the density of the developer, the change in the image density due to changes in the environment and the passage of time can be suppressed. In addition, without relying on maintenance, it can be optimized in a cycle shorter than the maintenance cycle, high image density stability can be achieved, and maintenance costs (labor costs, equipment, etc.) can be reduced.

[0007]

DETAILED 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 and a first charging unit as a developing unit.
Developing device 4, second developing device 5, third developing device 6, fourth developing device 7, toner adhesion amount measuring unit 8, transfer drum 9 as a transfer material support, pre-cleaning static eliminator 10, cleaner 11,
The static elimination lamps 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 so that an electrostatic charge corresponding to image data is obtained. 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 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 sheet 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 transferred.
1. After removal of electricity by the external pre-separation static eliminator 22 and separation static eliminator 23, it is peeled off from the transfer drum 9 by the separation claw 24,
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 of the color laser printer according to this embodiment and its control means. 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 is mainly composed of 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 the exposure of the modulated laser beam light 14 from the optical system 13. The gradation data buffer 36 stores gradation data from an external device or controller (not shown), corrects the gradation characteristics of the printer, and converts it into laser exposure time (pulse width) data.

The laser drive circuit 37 uses the laser beam light 1
The gradation data buffer 36 is synchronized with the scanning position of 4
The laser drive current (light emission time) is modulated according to the laser exposure time data from. Then, the semiconductor laser oscillator (not shown) in the optical system 13 is driven by the modulated laser drive current. As a result, 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 a monitor light receiving element (not shown) in 3 is compared with a set value, and control is performed to keep the output light amount of the semiconductor laser oscillator at the set value by the drive current.

On the other hand, the toner adhesion amount calculation section 47 calculates a predicted value of the toner adhesion amount based on gradation data from an external device or controller (not shown). That is, after development, the gradation data (or the converted laser exposure time data) received by the gradation data buffer 36 in the range corresponding to the measurement surface of the toner adhesion amount measuring unit 8 is integrated, and this 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, and thus the toner hopper 4
The toner in 2 is replenished in the developing device 4.

The developing roller 43 of the developing device 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 adhered on the photosensitive drum 1 after development and the measurement position 49 on the photosensitive drum 1 of the toner adhesion 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 photoconductor drum 1).

The fluctuation of the density gradation is particularly noticeable when the density gradation 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 variations in density gradation for color originals with a large print 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 unit 8 having the central portion of the photosensitive drum 1 as a measurement position 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 and the output of the toner concentration measuring unit 39 are 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 according to the comparison result, the image forming condition is determined. At least one of the grid bias voltage of the charging device 2, the developing bias voltage of the developing device 4, the exposure amount of the optical system 13, the toner concentration of the developer, the light emission time of area gradation, and the like is changed.

Further, the control circuit 45 controls switching of grayscale data from an external device or controller (not shown) and grayscale data of a test pattern of the printer alone, taking in each output of the measuring units 8 and 39, and the high voltage power source 34. , 35, 44
Output amount control, laser drive current target value setting, toner density target value setting, toner replenishment control, and gradation data printer gradation characteristic correction processing.

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 the change of the image forming condition 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 the 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 with 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. A linear approximation of the exposed portion potential VL and the unexposed portion potential VO with respect to the grid bias voltage VG can be expressed as the following equation. VO (VG) = K1 · VG + K2 …… (1) VL (VG) = K3 · VG + K4 …… (2) where K1 to K4 are constants

Here, the development 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) -V D (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 relation (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.

The surface potential of the photosensitive drum 1 is measured in advance, and the exposed portion potential V with respect to the grid bias voltage VG is measured.
After obtaining the relation (K1, K2) between L and the unexposed portion potential VO,
The contrast potential VC and the background potential VBG are set. The grid bias voltage VG and the developing bias voltage VD are uniquely determined by the above equations (5) and (6), a plurality of density patterns are imaged under these conditions, and the toner adhesion amount Q after development is measured. Then, the correction values ΔVC and ΔVBG of the contrast potential VC and the background potential VBG, which are suitable for the development density, are inferred from the deviation ΔQ by comparing with a preset reference value. 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, a region 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, and the toner is within a 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 the 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 in the photoelectric conversion unit 52. Converted into a current and further converted into a current / voltage, 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. The specular reflectance that is relatively shallow with respect to the normal of the reflecting surface is shown by a solid line o, and the specular reflectance that is deep by a broken line is shown by a broken line p. 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 again exposed to light. 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 level of sensitivity 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 photosensitive drum 1. That is, the toner adhesion amount measuring unit 8 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. One end of the shielding member 61 is connected to the flapper 63 of the solenoid 62 by a pin, so that the shielding member 61 moves in the direction of the arrow in the figure according to the opening / closing operation of the flapper 63 by the on / off operation of the solenoid 62. Has become.

The shielding member 61 is closed when the toner adhesion amount measuring unit 8 is not measured to shield the measurement surface from the outside, and is opened only during the measurement, so that the contamination of the measurement surface due to scattering of toner can be reduced. Therefore, it is possible to lengthen 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 adhered on the photosensitive drum due to development is calculated from the image data for forming an image, and the predicted amount of toner adhered is calculated. The amount of toner adhering to the latent image formed on the photosensitive drum formed on the basis of the image data used to calculate the value is measured by development, and the measured amount of toner adhering and the predicted value calculated above. By changing at least one of the image forming condition such as the charge amount with respect to the photoconductor drum, the developing bias voltage, the exposure amount, and the toner concentration based on the comparison result. The fluctuation can be optimized without relying on maintenance and in a cycle shorter than the maintenance cycle, high image density stability can be achieved, and maintenance costs (human Costs, such as equipment) can be reduced.

FIG. 21 shows another example of the structure of the toner adhesion amount measuring unit 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, 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 of the light source 51 reflected by the surface of the photosensitive drum 1, and the second photoelectric conversion section 55 is provided in the second photoelectric conversion section 55. Is provided at a position for receiving the light that does not include the principal ray of the principal ray of the reflected light on the surface of the photosensitive drum 1.
As a result, the first photoelectric conversion section 52 receives the specularly reflected light on the surface of the photosensitive drum 1, and the second photoelectric conversion section 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 of 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 diffusely reflected light is smaller than that of specularly reflected light.

Due to the adhesion of toner to the surface of the photosensitive drum 1 due to development, the reflected light distribution becomes as indicated by the broken line n. 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 in the light amount of the specular reflection light 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,
A wide range of measurement with higher accuracy becomes possible.

[0055]

As described in detail above, according to the present invention, fluctuations in 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, 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 toner adhering to the photosensitive drum and a measurement position on the photosensitive drum of a toner adhering amount measuring unit.

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 the relationship between the potential of an unexposed portion on the surface of the photosensitive drum, the potential of a low density pattern, and the 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 the toner adhesion amount with respect to the gradation data when the exposure amount is changed.

FIG. 11 is a diagram showing a relationship between toner density 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 an image output from a printer.

FIG. 16 is a diagram showing the specular reflectance of a photosensitive 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 photosensitive drum.

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

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

[Explanation of symbols]

1 ... Photosensitive drum (image bearing member), 2 ... Charging device (charging means), 4-7 ... Developing device (developing means), 8 ... Toner adhesion amount measuring unit, 9 ... Transfer drum, 13 ...... Optical system (exposure means), 13 ・ ・ ・ Laser beam light, 20 ・ ・ ・ Transfer charger, 27 ・ ・ ・ Fixer, 34 ・ ・ ・ Corona high voltage power supply, 35
...... High voltage power supply for grid bias, 36 ・ ・ ・ Gradation data buffer, 37 ・ ・ ・ Laser drive circuit, 39 ・ ・ ・ Toner density measuring unit, 40 ・ ・ ・ Toner replenishing roller, 43 ・ ・ ・ Developing roller, 44 ・ ・ ・ For developing bias High-voltage power supply, 45 ... Control circuit, 46 ... A / D converter, 47 ... Toner adhesion amount calculation unit, 51 ... Light source, 52, 55 ... Photoelectric conversion unit, 61
...... Shielding member.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location G03G 15/08 115 7635-2H

Claims (4)

[Claims] 1. A latent image forming means for forming a latent image on an image carrier based on image data, and a developing process for developing the latent image formed by the latent image forming means on the image carrier with a developer. Means, a developer adhesion amount calculation means for calculating, from the image data, a predicted value of the adhesion amount of the developer adhered on the image bearing member by the development of the developing means, and the developer adhesion amount calculation means A developer adhesion amount for measuring the adhesion amount of the developer adhered by the development of the developing means to the latent image formed on the image carrier based on the image data used to calculate the predicted value of the agent adhesion amount. Measuring means, comparing means for comparing the measured value of the developer adhesion amount measuring means with the predicted value calculated by the developer adhesion amount calculating means, and the latent image forming means or the latent image forming means based on the comparison result of the comparing means. Change the image forming conditions in the developing means And an image forming condition changing unit. 2. A light source for irradiating the image carrier with a light having a wavelength that is reflected by the image carrier and is absorbed or scattered by the developer on the image carrier. The image forming apparatus according to claim 1, further comprising: a photoelectric conversion unit having sensitivity to a wavelength of light output from the light source and receiving reflected light from the image carrier. 3. The light source and photoelectric conversion means of the developer adhesion amount measuring means are provided at positions not on the surface of the image carrier in the direction of the normal line, and one light source for irradiating the image carrier with light, A first photoelectric conversion unit that receives light from the light source that is specularly reflected by the image carrier, and a second photoelectric conversion unit that receives light from the light source that is diffusely reflected by the image carrier.
The image forming apparatus according to claim 2, further comprising a photoelectric conversion unit. 4. A latent image forming means for forming a latent image on an image carrier based on image data, and a developing process for developing the latent image formed by the latent image forming means on the image carrier with a developer. Means, a developer adhesion amount calculation means for calculating a predicted value of an adhesion amount of the developer adhered on the image carrier by the development of the developing means from the image data, and a surface of the image carrier facing each other. And 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 developer adhesion amount calculation unit is developed by the development unit. The developer adhesion amount measuring means for measuring the adhesion amount of the adhered developer and the developer adhesion amount measuring means and the image carrier are provided so as to be openable and closable at the time of measurement of the developer adhesion amount measuring means. Other than the above, the developer adhesion amount measuring means and the image carrier are A shielding member for shielding the space, a 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 latent value based on the comparison result of the comparing means. An image forming apparatus comprising: an image forming condition changing unit that changes an image forming condition in an image forming unit or a developing unit.