JPH01288869A - Process condition setting method - Google Patents

Abstract

PURPOSE:To correct the density deviation of an image more accurately by forming a specific concentration part of toner on a photosensitive body and detecting this toner concentration or the toner concentration on a transfer body to set process conditions. CONSTITUTION:A specific concentration part where the toner concentration is lower than the saturation concentration is formed on a belt-shaped photosensitive body 2. For example, the electrifying potential is switched to three stages during one rotation of the photosensitive body 2 to form three kinds of specific concentration parts. Toner concentrations of these parts are detected by a sensor 24, and these values are operated in a CPU to set process conditions such as the electrifying potential of an electrifying charger 21 and the exposure of a light source 61, and set values are outputted to respective control parts. Thus, this method copes with the fatigue of the photosensitive body and the fine change of environmental temperature and humidity to form an image. It is preferable that said toner concentration is compared with the standard toner concentration of toner stuck to a transfer body 24 to set process conditions.

Description

Detailed Description of the Invention (a) Industrial Application Field This invention relates to process condition setting for setting process conditions for forming an image at an optimal density in an image forming apparatus that forms an image using toner. Regarding the method.

(b) Conventional technology In image forming apparatuses using electrophotography, the amount of toner deposited on the photoreceptor changes due to changes in the amount of toner in the developing device, changes in the surface potential of the photoreceptor due to fatigue of the photoreceptor, etc. The concentration may become unstable. Therefore, in the past, the toner concentration in the developing device was measured to keep the amount of toner in the developing device constant, or the surface potential of the photoreceptor was measured and the voltage of the charger was controlled accordingly. As a result, the amount of toner in the developing device and the surface potential of the photoreceptor are kept constant, and their influence on the density of the formed image is prevented.

(C) Problems to be Solved by the Invention However, as mentioned above, the conventional methods for stabilizing the image density include keeping the toner concentration in the developing device constant and the surface potential of the photoconductor constant. This method merely controls each controlling factor regarding toner density individually, but does not control the toner density as a whole (it is difficult to obtain an image with good toner density as an overall image).

An object of the present invention is to provide a process condition setting method that enables image formation with good toner density by detecting toner density on a photoreceptor or transfer member and setting process conditions according to the toner density. .

(Means for Solving Problem d1) This invention forms a specific density area with a toner density lower than the saturation density on a photoreceptor, and transfers the toner density of the specific density area on the photoreceptor or transfer from the photoreceptor to the transfer member. The method is characterized in that the toner density of the transferred specific density area is detected by a density detector, and process conditions such as the charging potential of the photoreceptor and the amount of n light are set in accordance with the detected toner density.

Another method is to form multiple specific density areas on the photoreceptor under different process conditions in test mode.
The toner density of a plurality of specific density areas on the photoconductor or the toner density of a plurality of specific density areas transferred from the photoconductor to the transfer body is detected by a density detector, and the toner density of these specific density areas is set in advance. The method is characterized in that the process conditions in the test mode are set as the process conditions in the image forming mode to form a specific density portion with a toner density close to the standard toner density.

Furthermore, in the method described above, the toner concentration of a specific density area on the photoreceptor or transfer member is detected at multiple locations in the specific density area, and the average value of those detected values is taken as the toner density of the specific density area. Good too.

(e) Effect In this invention, a specific density area is formed by toner on a photoreceptor, and the specific density area is on the photoreceptor or transferred to a transfer member (paper, dielectric sheet, etc.). , the toner density is detected by a density detector.

If the toner density of the specific density portion formed on the photoreceptor or transfer member is lower than the saturation density (Claim 1)
), even small changes in the toner concentration in the developing device, the surface potential of the photoreceptor, etc. will cause a difference in the toner concentration in a specific density area, and the process conditions are set accordingly, so the density deviation of the formed image can be detected in a small range. In addition, in the test mode, a specific density area is formed under several process conditions, and among them, the process condition that causes the formation of a specific density area with a toner density close to a preset standard toner density is If the process conditions are set as the process conditions in the mode (claim 2), a specific density area is formed under a plurality of process conditions at a time, and a process condition that forms a specific density area with an appropriate toner density is selected from among them. Since image formation is performed under the process conditions in the image forming mode, an image with a toner density close to the target toner density (standard toner density) is formed during image formation.

Furthermore, if the toner concentration is detected at multiple locations in a specific density area and the average value is taken as the toner density (Claim 3), the toner density in the specific density area can be accurately detected and the process conditions can be set accurately. Become.

(FIG. 2 is a front configuration diagram of a copying machine to which the process condition setting method of the present invention is applied. In this embodiment, the process conditions include the charging potential of the photoreceptor (voltage of the charger), the amount of exposure (The voltage of the light source lamp that exposes the original) is shown as an example, but the bias potential of the developing device or the like may also be used as the process condition.

A belt-shaped photoreceptor 2 is located approximately in the center of the copying machine body 1.
It is stretched across several rollers. Around the photoreceptor 2, there are a charger 21, a blank lamp 22, developing devices 23a to 23C1, a transfer body 24, and a cleaning device 2.
5. The static elimination lamps 26 are arranged in the above order. The charger 21 uniformly charges the surface of the photoreceptor 2 by generating corona discharge, and the charging potential of the photoreceptor 2 is adjusted by changing the voltage applied to the charger line. The blank lamp 22 includes LEDs arranged along the photoreceptor 2, and cancels the partial charge on the surface of the photoreceptor 2 by partially exposing the surface of the photoreceptor 2, which is uniformly charged by the charger 21. conduct. The developing devices 23a to 23c are loaded with yellow, magenta, and cyan toners, respectively, and one of them is used during a test mode for setting process conditions.

The cleaning device 25 is for removing toner remaining on the photoreceptor 2, and the neutralization lamp 26 is for removing the charged potential remaining on the photoreceptor 2.

The transfer body 24 is a dielectric sheet stretched between three rollers, and is rotated at the same speed as the circumferential speed of the photoreceptor 2. Transfer body 2
The photoreceptor 2 is brought into contact with the photoreceptor 2 , and a first transfer charger 24 a is disposed at the contact position, and the toner on the photoreceptor 2 is transferred to the transfer member 24 . A 2nd transfer charger 24C1, a peeling charger 24d, and a cleaning device 24e are arranged around the transfer body 24 in the above order. The first transfer charger 24a transfers the toner on the photoconductor 2 to the transfer body 24.
The second transfer charger 24C transfers the toner on the transfer body 24 onto a sheet of paper, and the peeling charger 24d peels off the sheet. Further, the cleaning device 24e removes toner remaining on the transfer body 24.

A toner sensor (
A density detector) 24b is arranged opposite to the transfer body 24. The toner sensor 24b is a reflective optical sensor, and detects the toner concentration on the transfer body 24 using voltage. Note that FIG. 4 is a characteristic diagram of this toner sensor 24b. The toner sensor 24b detects the toner density in a specific density range formed on the transfer body 24 during a test mode to be described later. FIG. 8 is a diagram showing a method of detecting the density in a specific density range by the toner sensor 24b. The solid lines in the figure are specific concentration areas 7a and 7b.
and represents the density of the transfer body 24, and as shown in the figure, the density in the specific density regions 7a and 7b is not flat but has variations. In particular, due to the edge effect of the electric field, more toner is attached to the leading edge of the image, resulting in a higher density, while at the trailing edge of the image, toner is less likely to adhere and the density is lower. ), the toner density is detected 8 times in the intermediate area excluding the leading edge and trailing edge of the image.The results of these 8 toner density detections are averaged by the CPU, which will be described later, and are used as the toner density. .

The specific density area is formed by exposing the uniformly charged photoconductor 2 with light from the blank lamp 22 and applying toner to it by one of the developing devices 23a to 23c. voltage) is switched in approximately three steps during one rotation of the photoreceptor 2, thereby forming three types of specific density ranges in one process. Note that in the test mode, exposure is performed using a blank lamp, so the amount of exposure is always constant. Therefore, the toner density in the specific density range is
depends on the charging potential of

FIG. 7 is a diagram showing the relationship between the photoreceptor charging potential and the toner density in a specific density range formed. As can be seen from the figure, when the photoconductor charging potential is in region B, the toner concentration is almost saturated, so even if the photoconductor charging potential changes, there is almost no difference in toner concentration, but the photoconductor charging potential When is in the ApJ region, the toner concentration changes in accordance with the photoreceptor charging potential. Therefore, if the photoreceptor charging potential is selected within the range 0, the toner density can be accurately detected according to the change in the photoreceptor charging potential. The range of this region A is approximately 420 to 580 cm, and in the test mode, approximately three types of photoconductor charging potential (voltage of the charger) are set as process conditions within this range, and a specific concentration region is formed. be done. Even if the charger voltage is set in this way, the toner density deposited in a specific density range changes due to fatigue of the photoreceptor, the amount of toner in the developing device, etc., and the toner density is detected by the toner sensor 24b. . In this embodiment, the charged potential of the photoreceptor is set as the process condition in the test mode, and by detecting the toner density in a specific density range in the test mode, the charged potential of the photoreceptor is set as the process condition in the image forming mode. I can do it.

However, when forming good images with a copy machine,
Merely setting the charging potential of the photoreceptor is not sufficient. Then, the exposure amount of the light source lamp of the optical system is also set in accordance with the set charging potential of the photoreceptor. This makes it possible to better reproduce the halftones of the original. Furthermore, Figure 7 also shows the relationship between the charged potential of the photoconductor and the toner concentration when the environmental temperature and humidity change. It can be seen that the density (toner density of the formed image) changes. Therefore, if the toner density in a specific density range is detected and process conditions such as the charging potential of the photoreceptor are set according to the toner density, a good image can be formed regardless of environmental changes.

Figure 5 (A) is a diagram showing the relationship (gamma characteristics) between original density and copy image density when the charged potential of the photoreceptor is changed, and Figure 5 (B) is a diagram showing the relationship between the original density and the copy image density (gamma characteristics) when the charged potential of the photoreceptor is changed. FIG. 3 is a diagram showing the relationship (gamma characteristics) between original density and copy image density when

In FIG. 2A, when the voltage of the charger is increased, the charging potential of the photoreceptor becomes higher overall.

Therefore, if the exposure dose remains low, the residual potential level (
The potential of the exposed area) is high (as a result, the density of the low density area also becomes high, resulting in a sharp image. In the same figure (B), when the original exposure amount is increased, the amount of charge cancellation in the low density area of the original is Therefore, if the exposure amount is increased, the image density in the low density area becomes lighter, and the image is prevented from becoming high-contrast.

FIG. 6 is a diagram showing the relationship between the amount of correction of the charged potential of the photoconductor and the amount of exposure correction determined from the above, and the amount of charged potential correction and the amount of exposure correction are approximately proportional. At the initial stage of use of the photoreceptor, developer, etc., there is no need to perform charging potential correction and exposure amount correction, so the correction amount is O, which becomes the reference value.

A document table 61 and an optical system 6 including a light source, mirrors, lenses, and color separation filters are provided at the top of the copying machine body 1.
During the copying process in the image forming mode, the original on the original platen 61 is scanned and the reflected light is guided to the exposure point P on the photoreceptor 2 (.

Further, a paper feed section 3 including a paper cassette is provided on the right side of the copying machine main body 1, and feeds paper to the 2nd transfer gear 24c position. This paper has a 2nd transfer charger of 24
The toner is transferred by c, fixed by the fixing device 4, and then discharged to the paper discharge tray 5. The fixing device 4 includes a heat roller, the surface temperature of which is detected by a temperature sensor (not shown), and the heater is controlled in accordance with the detection. The surface temperature of the heat roller is controlled at 100-odd degrees during use, but if it is left unused for a long time, it will drop to about the ambient temperature.

FIG. 3 is a block diagram of the control section of the copying machine. Overall control is performed by the CPU 40, and its processing program is stored in the RAM 41 in advance. l1 for CPU40
The temperature of the fixing device 4 is input via 045, and l1
047, the detection result of the toner sensor 24b is input. As described above, the toner sensor 24b performs detection n times in each specific density area 7a (7b), and sends the results to the CP.
Input to U40. The CPU 40 calculates the average of the n times of detection values, uses that value as the toner concentration, and sets the charging potential of the charger 21 (charging potential of the photoconductor) and the exposure amount of the light source 61 based on it. control section 48.4 of
Output the setting value to 9.

The relationship between the charging potential correction amount and the exposure amount correction amount shown in FIG. 6 is stored in the RAM 42, and is stored in the toner sensor 24b.
The charging potential and the exposure amount are corrected according to the detection result. The RAM 42 also stores a standard toner density SO to be applied to the transfer body 24. The standard toner density SO is determined by setting the charging potential (VD) of the photoconductor to 500 as a process condition in image forming mode at the initial use of the photoconductor and developer.
When the toner sensor 2
FIG. 1, which shows the toner density detected by d, is a flowchart showing the processing procedure of the copying machine stored in the ROM.

First, when the main body of the copying machine is powered on, initialization of the memory, preliminary operation processing, etc. are carried out in nl, and warm-up (temperature rise) of the fixing device 4 is started. If the temperature T of the fixing device 4 is 70° C. or less, it is assumed that the fixing device 4 has been left unused for a long time, and the process proceeds to n3 to proceed to a test mode in which the charging potential of the photoreceptor (voltage of the charger), etc. is set.

First, at n3, the charging potentials VDI to VD3 of the photoreceptor are set as process conditions for the test mode. The charging potential of the photoreceptor is, for example, VD1=500V, VD2=520V,
Three types of conditions are set: VD3=480V. In addition,
At this time, the ease of toner adhesion is determined by using VDI as the intermediate value.
VD2. Respective values are set in VD3 so that they are above and below VDI. At n4, the photoreceptor is charged and exposed by the blank lamp 22 under the three process conditions to form a specific density range, and the toner density is 81 to S3 under each process condition VDI to VDa.
Detect. As mentioned above, the toner concentrations 81 to S3 are average values obtained by detecting several points in each specific concentration range, and are affected by variations in toner adhesion and the edge effect of the electric field. Accurate values can be obtained without

The toner concentrations S1 to S3 are compared with the standard toner concentration SO stored in the RAM 42 (n5, n6, n7), and the process conditions are such that a toner concentration (any one of 81 to S3) close to the standard toner concentration SO is obtained. (Charging potential) is set as a process condition in image forming mode (n8 to n1
0). However, if the obtained toner concentrations 81 to S3 deviate greatly from the standard toner concentration SO, more toner is deposited than the process conditions set in n3 (process conditions VD1' to VD3' (n13)), Or process conditions V[1)'' to VD3 where less toner is attached
" (n14) is set. In this case, n3 is also set.
Similarly to the setting in , VDI' or VDbi is set as the intermediate value, VD2' or VD2'' is set as the upper limit value, and VD3' or VD3'' is set as the lower limit value. For example, VD
1'=560V, VD2'=580■, VD3'=54
0, VDI"=440■, VD2"=460
V, VD3"=420V. The toner concentration detection process is performed again according to these three process conditions (n4), and the detected toner concentrations 81 to S3 are determined to be close to the standard toner concentration SO. For example, the process conditions (electrostatic potential of the photoreceptor) are set as the process conditions in the image forming mode.In addition, in the test mode, a specific density range with a density slightly lower than the saturation density is set as shown in the 7th national area. The surface potential of the photoreceptor is set to be a little low in order to form the image, and when actually setting the charging potential in the image forming mode, it is set higher than the charging potential set in the test mode.In n15 Based on this charge value, the sixth
The exposure amount of the light source lamp of the optical system is set based on the relationship shown in the figure. Note that if a toner density close to the standard toner density SO cannot be obtained even after setting the process conditions twice, it is determined that there is some kind of error such as a defective charging value, and error processing is performed.

Once the process conditions for the image forming mode have been set in the test mode as described above, the process returns to n16.
The sensors and keys are read, and if any input is made, the following processing will be performed corresponding to that input, but if the temperature of the fixing device is 70 degrees or less when it is unused and no input is made If (n2), the process proceeds to n3 and the above-mentioned process conditions are set. In this way, if you set the process conditions in test mode when the temperature of the fixing device drops to 70 degrees or less, you can set the process conditions in a way that fully responds to changes in environmental humidity, etc. You can always get good images. Note that if the input is a print switch (n18), the copying process is performed under the process conditions set in n19.

(g) Effects of the Invention According to the present invention, as described above, by using the process condition setting method set forth in claim 1, the toner concentration in the developing device, the surface potential of the photoreceptor, etc. can be changed slightly to produce a specific density area. Differences in toner density appear and process conditions are set accordingly, so density deviations in the formed image are corrected within a small range, and image formation can be performed in response to photoreceptor fatigue and small changes in environmental temperature and humidity. There are advantages that can be achieved.

Further, according to the method of claim 2, the specific density area is formed under a plurality of process conditions at a time, and the process conditions for forming the specific density area with an appropriate toner density are set as the process conditions in the image forming mode. This has the advantage that process conditions can be set in a short time, and accurate settings can be made to test actual process conditions.

Furthermore, the method of claim 3 has the advantage that the toner concentration in a specific density portion can be detected accurately, and the process conditions can be set accurately.

[Brief explanation of the drawing]

Fig. 1 is a flowchart showing the process condition setting method of the present invention, Fig. 2 is a front configuration diagram of the copying machine, Fig. 3 is a block diagram of the control section of the copying machine, and Fig. 4 is applied to the copying machine. FIG. 5(A) is a diagram showing the characteristics of the toner sensor (density detector) that has been used. (B) shows changes in gamma characteristics when changing the charging potential of the photoreceptor and changes in gamma characteristics when changing the exposure amount, respectively. Figure 6 shows the correction amount of the charging potential of the photoreceptor and the exposure. Figure 7 is a diagram showing the relationship between the amount of correction and the amount of correction. Figure 7 is a diagram showing the relationship between the change in the charged potential of the photoconductor and the toner density in the specific density range formed. Figure 8 is the diagram showing the relationship between the specific density range formed by the toner sensor. FIG. 2 is a diagram showing a detection method. 2-photoconductor, 7a, 7b-specific density range, 21-electrostatic charger, 22-blank lamp, 24-transfer body, 24b-toner sensor.

Claims (3)

[Claims] (1) A specific density area with a toner density lower than the saturation density is formed on the photoreceptor, and the toner density of the specific density area on the photoreceptor or the toner density of the specific density area transferred from the photoreceptor to the transfer member is 1. A method for setting process conditions, which comprises detecting the toner density with a density detector and setting process conditions such as the charging potential of a photoreceptor and the amount of exposure in accordance with the detected toner density. (2) In test mode, multiple specific density areas are formed on the photoreceptor under different process conditions, and the toner density of the multiple specific density areas on the photoreceptor or the multiple specific density areas transferred from the photoreceptor to the transfer member is A test in which the toner density of the density areas is detected by a density detector, and the toner density of these specific density areas is compared with a preset standard toner density to form a specific density area with a toner density that approximates the standard toner density. A process condition setting method characterized by setting process conditions in an image forming mode as process conditions in an image forming mode. (3) In claim 1 or 2, the toner concentration in a specific density area on the photoreceptor or transfer body is detected at a plurality of locations in the specific density area, and the average value of those detected values is calculated as the toner density in the specific density area. How to set process conditions for concentration.