JPH05341609A - Electrophotographic process controller - Google Patents

Abstract

PURPOSE:To remove fogging and to realize an optimum process control by detecting the fogging level of the base surface of a photosensitive body and controlling a process condition such as developing bias potential, CONSTITUTION:When a power source is turned on, the rotation of the photosensitive body 1 is started and the density of the base surface of the photosensitive body is detected. Namely, whether or not the ratio A obtained by making an output value from an optical sensor 10b detecting the density of the base surface of the photosensitive body after development a denominator and making an output value from an optical sensor 10a detecting the density of the surface of the photosensitive body after cleaning a numerator is >=0.95 is decided. When the ratio A is <0.95, that is, in the case of judging that the fogging level of the base surface of the photosensitive body is equal to or above a prescribed level, a signal for changing the voltage of a copying lamp is outputted to a lamp driving circuit 19. Furthermore, the density of the base surface of the photosensitive body is successively detected, and when the ratio A is <0.95, a signal for stirring developer is transmitted to a developer stirring device 201 at this time. In the case of satisfying a condition that the sensor output ratio A is >=0.95, operation is shifted to a copying cycle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic process control device for controlling process conditions such as a copy lamp voltage, a developing bias voltage, and a stirring condition of a developing tank to desired conditions.

[0002]

2. Description of the Related Art The surface potential of a photoconductor greatly changes due to changes in environmental conditions. For example, if it is an OPC photoreceptor,
In a low temperature environment, there is a potential drop of about 100 V from the potential at room temperature due to the temperature dependence of the mobility of photocarriers. Further, as the number of copied sheets increases, the photosensitive layer causes film slippage due to mechanical stress (polishing effect of a cleaning blade, etc.), and the film thickness decreases, so that the surface potential thereof tends to gradually decrease. In addition, problems such as reduced sensitivity will occur. Further, the developer also has environmental characteristics and is vulnerable to humidity changes. For this reason, a large image quality change occurs due to the environmental change. Therefore,
Process control is performed in order to maintain a copy image at an optimum image quality even when the environment or the like changes or time passes. Usually, this control is performed by detecting the image density on the photoconductor.

[0003]

However, with such a control method, it becomes impossible to perform optimal control when fogging occurs in the image background portion, that is, in the non-image portion of the photoconductor, to a certain extent or more. Such fog occurs due to various causes, and the causes are mainly an increase in residual potential of the photosensitive member, environmental characteristics of the developer, and deterioration due to usage. Among them, the toner to be replenished has a thermal history (for example, 50 °
When the toner is left for 2 days at C), the toner undergoes thermal stress, and the surface physical properties change due to softening of the resin itself, embedding of an external additive, and the like. As a result, the fluidity of the toner and the charge rising characteristics are deteriorated, causing fog in the background portion. If such fog is left as it is and the process control is performed by the above-mentioned conventional method, the optimum process control becomes impossible, and the image quality of the copied image may be deteriorated. Furthermore, the problem of toner scattering inside the machine also arises.

It is an object of the present invention to provide a process control apparatus which solves the problems of image quality deterioration due to fog in the background portion of a copy image and the problems such as toner scattering caused by fog.

[0005]

SUMMARY OF THE INVENTION The present invention comprises an optical sensor for detecting the fog level of a photoconductor substrate, and a process parameter control means for controlling process parameters such as developing bias voltage based on the detection result of the optical sensor. , Is provided.

The optical sensor is composed of a first optical sensor for detecting the density of the photoconductor substrate after development and a second optical sensor for detecting the density of the photoconductor substrate after cleaning. The fogging level is detected from the output ratio of the sensor.

Further, the optical sensor detects the density of a predetermined toner patch formed on the surface of the photoconductor and the density of the photoconductor base, and detects the fog level from the ratio of these densities. To do.

[0008]

The present invention controls the process conditions such as the developing bias voltage by detecting the fog level of the photoconductor substrate by the optical sensor. That is, instead of detecting the density of the surface of the photoconductor, the fog level of the photoconductor base is detected by detecting the surface of the photoconductor base such as an aluminum tube by an optical sensor that transmits the photoconductor. Since the photoconductor base is covered with the photoconductor, the detection does not show the influence of the axial deviation of the photoconductor drum and the secular change does not occur. In this case, the first optical sensor that detects the density of the photoconductor substrate after development and the second optical sensor that detects the density of the photoconductor substrate after cleaning detect the respective densities, and the fog is detected from the sensor output ratio. Detect the level. Also, create a predetermined toner patch on the surface of the photoconductor, detect this density and the photoconductor base density,
The fog level is detected from these density ratios.

[0009]

1 is a block diagram of an electrophotographic copying machine according to an embodiment of the present invention. Photoreceptor 1 has a wall thickness of 2 mm and a diameter of 10
The charge generation layer is uniformly applied to a 0 mm, 340 mm long aluminum tube at a film thickness of 1 μm, and the film thickness is 35 μm.
Of an organic semiconductor coated with a charge transfer layer. Reference numeral 2 is a charger, and 3 is an optical system for irradiating a document on a document table and coupling reflected light onto the photoconductor. Reference numeral 4 is a developing device for developing the electrostatic latent image with toner, and 5 is a transfer device for transferring the toner image on the photoconductor onto the transfer paper 6. The toner image transferred to the transfer paper 6 is heated and fixed by the fixing device 7 and discharged to the outside of the machine. A cleaner unit 8 removes residual toner on the surface of the photoconductor by an internal blade. Reference numeral 9 is a static elimination lamp arranged on the downstream side of the cleaner unit 8. In this embodiment, the first optical sensor 1 arranged downstream of the developing tank 4 is used as an optical sensor for detecting the density of the non-image portion of the photoconductor.
0b and a second optical sensor 10a for detecting the density of the non-image portion of the photoconductor after passing through the cleaner unit 8. These sensor outputs are respectively fed to amplifiers 11c and 1c.
The signal is amplified by 1b and is input to the CPU 13 after passing through the A / D converters 12c and 12b. CPU1
Reference numeral 3 detects the fog level of the non-image portion of the photoconductor from the output ratio of these sensors. The optical sensors 10a and 10b
Is configured to use an infrared light emitting diode having a wavelength of 890 nm that passes through the photoconductor in the light emitting portion, irradiate the photoconductor with the infrared light emitting diode, and receive the reflected light by the phototransistor. In addition, in the present embodiment, in addition to this, a temperature sensor 17 for detecting the temperature near the surface of the photoconductor is provided, and this output is supplied to the amplifier 11a,
It is input to the CPU 13 through the A / D converter 12a. This sensor output is also used for process control. The CPU 13 drives the high-voltage power supply circuit 14 of the charger 2, the bias power supply circuit 15 of the developing tank 4, the lamp drive circuit 19, the toner replenishment drive device 18, and the developer agitation drive device 20 based on these sensor output results. Reference numeral 21 is a blank lamp for forming a toner patch on the photoconductor.

FIG. 2 shows the actual fog level on the horizontal axis and the optical sensor 1 arranged on the downstream side of the developing tank 4 on the vertical axis.
The ratio of the output value of 0b and the output value of the optical sensor 10a arranged on the downstream side of the cleaner unit 8 is shown. In the embodiment, the output value ratio is 0.95 or more and the fog is small, and when the output value ratio is less than 0.95, process conditions such as a copy lamp voltage described later are controlled. FIG. 3 is a flowchart showing the control operation of this embodiment.

When the power source is turned on, the photoconductor 1 starts to rotate, and the optical sensor 10b and the optical sensor 10a detect the density of the photoconductor substrate. An optical sensor 10a for detecting the density of the surface after cleaning, using the output value of the optical sensor 10b for detecting the density of the photoconductor substrate after development as a denominator.
It is determined whether or not the ratio A whose output value is the numerator is 0.95 or more (n2), and when it is determined to be less than 0.95, that is, the fog level of the photoconductor base is a certain level or more,
In step n3, a signal for changing the copy lamp voltage is output to the lamp drive circuit 19. After that, the base density of the photoconductor is again detected by the two sensors 10b and 10a sequentially (n
4). Then, at n5, as in the case of n2, the sensor output ratio A
And 0.95, and if A is less than 0.95, it is considered that the degree of fog level has not been improved,
Proceeding to n6, this time the signal for changing the developing bias voltage is sent to the developing bias power source 15. Further, in n7, the two sensors 10b, 10 are used to detect the density of the photoconductor substrate.
If the ratio A is less than 0.95,
This time, a signal for stirring the developer is sent to the developer stirring drive device 20. Then, concentration detection is further performed by the two sensors (n10), and if the output ratio A of them is less than 0.95, it is considered that process control cannot be performed for some reason, and the machine is stopped. (N12). In the steps up to n11, when the condition that the sensor output ratio A is 0.95 or more is satisfied, the process proceeds to n13, the process described below is optimized, and the process proceeds to the copy cycle (n13, n14). . The effect of this embodiment is shown in FIG. The horizontal axis represents the number of copies, and the vertical axis represents the sensor output ratio. When the toner that has undergone thermal history is replenished, the output ratio A becomes less than 0.95.
It can be seen that when the number of copies reaches 40, the developing tank is agitated in step n9 in FIG. 3 and the optical sensor output ratio A is recovered to around 1.0. On the other hand, FIG.
Shows the characteristics when the process control of this embodiment is not adopted. When the toner that has undergone thermal history is replenished, the output ratio of the optical sensor sharply decreases when the number of copies reaches about 40.

FIG. 6 shows a block diagram of another embodiment of the present invention. The configuration is different from the first embodiment shown in FIG. 1 in that one optical sensor 10 is arranged downstream of the stripping static eliminator instead of the optical sensors 10a and 10b.
In this embodiment, the toner patch 22 is formed on the photoconductor 1 when the power is turned on as shown in FIG. The toner patch 22 is created by exposing a standard white plate on the document table and controlling the blank lamp 21 to be turned on and off. The fog level of the photoconductor substrate is obtained from the ratio between the density of the toner patch 22 detected by the optical sensor 10 and the density of the photoconductor substrate between the patches. FIG. 8 shows a process control flow. After power on, n1, n4, n7, n1
The density detected at 0 is the density of the toner patch 22 and the photoconductor substrate between the patches. The result A of the ratio in which the detected density of the toner patch is the denominator and the detected density of the photoconductor substrate is the numerator is compared with 0.95 at n2, n5, n8, and n11. In the example, three toner patches 22 were created. The grid bias voltage at this time is -70
0 V, copy lamp voltage is 70 V, developing bias voltage is -400 V when creating patches, and -200 between patches.
It was set to V.

When A satisfies the condition of 0.95 or more, the process is optimized in n13. This optimization process is performed by detecting the optical density of the toner patch, comparing the result with the optimum image quality adjustment value obtained when the copier was shipped, and correcting the copy lamp voltage so that they are the same. Be seen.

The control of n3 may be omitted and the control of n6 may be performed. Regarding the developing bias voltage, the characteristics shown in FIG. 9 have been obtained through experiments. In the figure, the horizontal axis represents the ratio between the toner patch density and the photoconductor substrate density, and the vertical axis represents the increase in the developing bias voltage. Therefore, at n6, the developing bias voltage is controlled by utilizing the characteristic shown in FIG.

[0015]

EFFECT OF THE INVENTION By detecting the fog level of the photoconductor base and controlling the process conditions such as the developing bias voltage, the fog which could not be removed by the conventional control is removed and the optimum process control is performed. Will be able to. In particular, the fog detection is performed by detecting the ratio of the density of the photoconductor base material after development and the density of the photoconductor base material after cleaning, or by detecting the ratio of the toner patch and the photoconductor base material density to detect the level of detection accuracy. Will increase.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an electrophotographic copying machine according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a fog level and an optical sensor output ratio in the example.

FIG. 3 is a flowchart showing an operation of process control in the same embodiment.

FIG. 4 is a diagram showing a relationship of an optical sensor output ratio with respect to the number of copies in this embodiment.

FIG. 5 is a diagram showing a relationship of an optical sensor output ratio with respect to the number of copies in a conventional device.

FIG. 6 is a configuration diagram of an electrophotographic copying machine according to a second embodiment of the present invention.

FIG. 7 is a diagram showing a toner patch according to the second embodiment.

FIG. 8 is a flowchart showing the operation of process control according to the second embodiment.

FIG. 9 is a graph showing an increase in developing bias with respect to a sensor output ratio in the second embodiment.

[Explanation of symbols]

 1-Photoreceptor 10b-First Optical Sensor 10a-Second Optical Sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number for FI Technical indication G03G 15/08 115 115922-2H (72) Inventor Kunio Ohashi 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka No. Sharp Co., Ltd.

Claims (3)

[Claims] 1. An electrophotographic process comprising: an optical sensor for detecting a fog level on a photoconductor base; and process parameter control means for controlling process parameters such as a developing bias voltage based on the detection result of the optical sensor. Control device. 2. The optical sensor comprises a first optical sensor for detecting the density of a photoconductor substrate after development and a second optical sensor for detecting the density of a photoconductor substrate after cleaning. The electrophotographic process control apparatus according to claim 1, wherein the fog level is detected from an output ratio of a sensor. 3. The optical sensor detects the density of a predetermined toner patch formed on the surface of the photoconductor and the density of the photoconductor base, and detects the fog level from the ratio of these densities. The electrophotographic process control device according to claim 1.