JPS62173480A - Photosensitive body heater controller - Google Patents

Abstract

PURPOSE:To always form an image having a good quality by forming a test image which becomes a reference, on a photosensitive body, and also, controlling a surface temperature of the photosensitive body so that a density of this image always becomes constant. CONSTITUTION:A test pattern 38 being a test image forming means is formed on the base of an original platen 31 and a light beam of a light source is irradiated, its reflected light is irradiated to an original image forming range outside 1d of a photosensitive drum 1, and an electrostatic latent image of a test image is formed on the surface of the photosensitive body. A photosensor 10 detects a reflected light of a pattern image which has been converted to a developed image. As for a relation of a surface temperature of the photosensitive body and a detecting output of the photosensor 10, as the surface temperature rises, the detecting output of the photosensor 10 increases, as well. To a temperature controlling circuit 14, a detecting output of a temperature sensor 3 is also inputted, compared with a set temperature, and thereafter, a control signal is outputted to a heater controlling circuit 15, and the heater controlling circuit 15 controls turns on and off of a heater 2. Accordingly, the surface temperature of the photosensitive body can be controlled so that a state of an image which has been formed on the surface always becomes constant.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a photoreceptor heater control device that is provided in an image forming apparatus using electrophotography and controls the temperature of a photoreceptor.

<Summary of the Invention> The photoreceptor heater control device according to the present invention includes a test image forming means and a density sensor for detecting the density of the test image, in order to always maintain a good image forming state. The temperature of the photoreceptor is set by referring to the stored contents of the storage means so that the detected value becomes a preset reference value.

<Prior art and its drawbacks> In an apparatus that forms images by electrophotography, the surface of a photoreceptor charged with a single polarity is exposed to light to form an electrostatic latent image, and then a developer is supplied to this. Visualize it. The surface of the photoreceptor is charged by a corona discharger before being exposed to light, but the surface potential at this time increases depending on the developer adsorption state (impairing the image quality), which in turn impairs the quality of the image formed on the transfer material. It also influences whether it is good or bad.

This surface potential is easily affected by deterioration of the photoconductor, changes in temperature, and changes in the external environment.Continuous copying of a large number of sheets or use over a long period of time causes a decrease in the surface potential, causing the image on the photoconductor to deteriorate. The concentration may decrease or become uneven.

For this reason, conventional attempts have been made to stabilize the image forming state by changing the current value supplied to the corona discharger or by changing the bias voltage during development. However, with such conventional devices, the photoreceptor tends to leak,
In addition, the influence of ozone increases and the image becomes distorted, resulting in deterioration of image quality such as smudging of the background and poor contrast.

<Object of the Invention> In view of the above-mentioned conventional drawbacks, the object of the present invention is to form a reference test image on a photoreceptor and control the surface temperature of the photoreceptor so that the density of this image is always constant; No photoreceptor leaks or increased ozone effects,
An object of the present invention is to provide a photoconductor heater control device that can always form high-quality images.

<Structure and Effects of the Invention> The photoconductor heater control device of the present invention has been developed by focusing on the fact that the surface potential, which influences the state of image formation on the photoconductor, is affected by the surface temperature. a heater for increasing the temperature of the photoreceptor, a temperature detection means for detecting the temperature of the photoreceptor, and a heater control means for turning on and off the heater so that the temperature detected by the temperature detection means coincides with a preset temperature during copying work. A photoreceptor heater control device comprising: a test image forming means for forming a test image outside the original image forming area of the photoreceptor; a density detection means for detecting the density of the test image; A storage means that stores the relationship with body temperature, and a temperature setting means that determines from the storage means a temperature at which the detected value of the concentration detection means is a preset reference value and sets this temperature as the set temperature. It is characterized by

According to the present invention, with the above configuration, a test image is formed outside the document image forming range on the surface of the photoreceptor, and the test image is used as a reference for determining the image forming state, and the density of this test image is detected by the density detection means. The temperature at which the detection result falls short of the reference value is read from the storage means, and this temperature is set as the set temperature by the temperature setting means, so the surface of the photoreceptor can be controlled to a temperature at which the density of the test image is always constant. . From this, it is possible to control the surface temperature of the photoreceptor so that the state of the image formed on the surface is always constant, and it is possible to prevent unevenness and instability of the image density on the photoreceptor. It is possible to always form high-quality images.

<Embodiment> FIG. 2 is a front sectional view of a main part of a copying machine in which a photoreceptor heater control device according to an embodiment of the present invention is used.

A photosensitive drum 1 is rotatably provided inside the main body of the copying machine, and together with a charging charger 5, a developing device 6, a transfer charger 7, a cleaner 8, and a neutralization charger 9 on its outer periphery, constitutes a copying process section. The photosensitive drum 1 is formed by covering the surface of a hollow cylindrical base material 1a made of aluminum with a photosensitive layer 1b of amorphous silicon (a-3i). A photoreceptor heater 2 is provided on the inner surface of the photoreceptor drum 1 . The photoreceptor heater 2 is provided so as to face the entire inner surface of the photoreceptor drum 1 . A hole 2a is formed in this photoreceptor heater 2, and a temperature sensor 3 is attached to this hole 2a. The temperature sensor 3 is attached so that its temperature sensing portion is in contact with the inner surface of the photoreceptor drum 1, and detects the temperature of the photoreceptor drum 1. This temperature sensor 3 is the temperature detection means of this invention.

The photoreceptor drum 1 is connected to the photoreceptor shaft 4 by a flange portion (not shown).
The rotational force in the direction of arrow A is transmitted by a transmission means (not shown). The photoreceptor heater 2 is directly fixed to the photoreceptor shaft 4, and the photoreceptor heater 2 is stopped even when the photoreceptor drum 1 is rotating.

A document table 31 is provided on the top surface of the copying machine main body. The document table 31 is made of transparent hard glass, and the document 41 is placed on the upper surface thereof. A scanner having a light a 32 and mirrors 33 to 36 is provided below the document table 31 so as to be movable back and forth in the direction of arrow A or B. 37 is a lens.

During the copying process, reflected light from the light source 11I%41 of the light source 32 is reflected by the photoreceptor drum 1 as shown by the dashed line in the figure.
irradiated onto the surface of A developer is supplied from the developing device 6 to the electrostatic latent image thus formed, and the image is visualized. A photosensor 10 is provided below the developing device 6 as a density detecting means of the present invention.

FIGS. 3(A) and 3(B) are a bottom view of the original platen and a bottom view of the photoreceptor, respectively, of the stem copying machine described above.

The width of the photosensitive drum 1 in the rotation axis direction is the original image forming range 1
It is slightly wider than C. This original image forming range 1
c corresponds to the width of the document placement range 31a of the document table 31. A test pattern 38, which is a test image forming means of the present invention, is formed on the bottom surface of the document table 31 facing the outside of the document image forming area 1d of the photosensitive drum 1. During the copying process, this test pattern 38 is also irradiated with light from the light source, and the reflected light is irradiated onto the outside of the original image forming area 1d of the photosensitive drum 1. As a result, an electrostatic latent image of the test image is formed on the surface of the photoreceptor.

The photosensor 10 includes a light emitting element 10a and a light receiving element 10.
It is composed of b. The light emitting element 1o emits light to a region 1d outside the document image forming range, and the reflected light is received by the light receiving element 10b. Since this photosensor 10 is provided below the developing device 6, it detects the reflected light of the developed pattern image. Therefore, when the density of the pattern image is high, the detection value of the photosensor 10 is low, and when the density is low, the detection value is low.

FIGS. 5A to 5C are diagrams showing the characteristics of the photosensitive drum. Further, FIG. 6 is a diagram showing the relationship between the surface temperature of the photosensitive drum and the detection output of the sensor.

The surface potential VB of the photosensitive drum 1 having the amorphous silicon photosensitive layer 1b is approximately inversely proportional to the surface temperature T, as shown in FIG. 5(A). In other words, it has negative characteristics with respect to temperature.

Further, as shown in FIG. 12B, the image density ID on the photoreceptor surface decreases as the surface potential VE increases and the ID becomes higher, so that the two have the relationship shown in FIG.

These factors include the surface temperature T of the photoconductor and the photosensor 1.
The relationship with the detection output IL of 0 is as shown in FIG.
As the surface temperature T increases, the detection output IL of the photosensor 10 also increases.

FIG. 4 is a block diagram of the control section of the copying machine.

An operation signal from the operation panel 16 is input to CP[Jll via the I10 interface 17.

Further, the CPU II outputs a signal for controlling the operation of each device in the copying process section to the copying process section control circuit 21 via the ■/○ interface 20. CPU 1
A program including control of the copying process section is stored in the ROM 18 connected to the ROM 18, and control signals are output from the I10 interface 20 in accordance with this program. Further, the detection output of the photosensor 10 is transmitted to the C
Input to PUII.

Further, the set temperature of the photosensitive drum 1 is output as a digital signal to the D/A converter 13 via the I10 interface 12. The D/A converter 13 converts this into an analog signal and outputs it to the temperature control circuit 14. The detection output of the temperature sensor 3 is also input manually to the temperature control circuit 14, and after comparing it with a set temperature, a control signal is output to the heater control circuit 15. The heater control circuit 15 controls on/off of the heater 2 based on the control signal from the temperature control circuit 14 .

The RAM 19 connected to cpuz stores the data output by the user, and the memory area M1 stores the set temperature t1. In addition to the above programs, the ROM 18 also contains the surface temperature T and the detection output I of the photosensor 10 shown in FIG.
The relationship with L is memorized. This ROM 18 is the storage means of this invention.

FIG. 1 is a flowchart showing the operation of the copying machine.

After the power is turned on, step nl (hereinafter “step ni”)
'' is simply referred to as "ni"), the warming amplifier is started. Also, at n2, the heater 2 is controlled so that the surface temperature T becomes the set temperature t1 stored in the memory area M1. This temperature control is This is always done during the execution of the work.At n3, the contents of the counter (2), which counts the number of copying processes, is cleared.

When warming up is completed at n4, the process advances to n5, where data is set. The data set here includes the number of copies, copy magnification, paper size, document size, etc., and is set by human power from the operation panel 16, detection by a sensor, or calculation.

Next, when the print switch is operated at n6, the process advances to nl, where the copying process is performed. Each time the copying process is completed, the contents of the counter I are incremented by 1 at n9 and the process proceeds to nlO. Whenever a replication process is performed on nl, nl
8, the detection output 12 of the photosensor 10 is detected. n
At lo, it is determined whether the absolute value of the difference between the reference value 11 of the photosensor 10 and the current detection output 12 is greater than or equal to a set value. If the difference between the two is greater than or equal to the set value, ni
1, the temperature t2 that satisfies the reference value 11 is read out from the ROM 18 based on the detection output 12. Next, the temperature t2 read out at n12 is stored in the memory area M1 as the set temperature t1, and the process proceeds to n13. These nil and nl2 are the temperature setting means of this invention.

If the difference between the reference value z1 and the current detection output 12 is smaller than the set value at n10, the process directly proceeds to n13. n1
In step 3, it is determined whether the contents of the counter (2) match the set number N of sheets. If the two do not match in n13, the process returns to nl and the copying process is repeated. The copying process for the set number of sheets N is repeated, and n1
If the contents of the counter I match the set number N in step 3, the process advances to n14, a wait cycle is executed, and the process returns to nl.

As described above, according to this embodiment, a test image can be formed outside the original image forming area 1d of the photosensitive drum 1 during execution of the copying process.

The density of this test image is detected as the amount of light received by the photosensor, and the difference between the detected output and a reference value is determined. When this difference exceeds the set value k, the set temperature can be changed by the temperature setting means.

For example, as shown in FIG. 7, in the initial state of the photosensitive drum 1, the surface temperature T and the detection output IL of the photosensor 10 are
When the relationship between photoreceptor drum 1 and
The detection output of the photosensor 10 when the image density formed on the surface of the image is in an ideal state is defined as a reference value β1. The temperature that satisfies this reference value i1 is tl, and in the initial state, the copying process is executed with this temperature t1 as the set temperature. After the copying process continues, when the detection output of the photosensor 10 exceeds the set value k and reaches 12, the line 81 is changed to
Parallel movement is made along the horizontal axis to a position where the detection output is 12 at the set temperature t1, and a line 82 is obtained. If a temperature t2 that satisfies the reference value 11 is found on this diagram 82 and the heater is controlled using this temperature t2 as the set temperature, the photosensor 10
The detection output IL should be the reference value 11.

In this way, by changing the surface temperature T so that the detection output IL of the photosensor 10 maintains the reference value 11, a good image forming state can always be maintained.

Note that a preliminary scan may be performed before the copying process is started, and the density of the test image may be detected only during this preliminary scan to control the surface temperature. At this time, in order to prevent the image forming state from changing due to the continuation of the copying process for a long time, a timer may be used to detect the continuous time of the copying process, and a preliminary scan may be performed after a certain period of time has elapsed.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing the operation of a copying machine having a photoconductor heater control device according to an embodiment of the present invention, FIG. 2 is a front cross-sectional view showing the configuration of the main parts of the copying machine, and FIG. 3(A)
and (B) are respectively a bottom view of the document table and a bottom view of the photosensitive drum of the copying machine, FIG. 4 is a block diagram of the control section of the copying machine, and FIGS. The figure shows the characteristics of the photoreceptor included in the copying machine, and Figure 5 (
A) represents the relationship between surface potential and surface temperature, and (B)
represents the relationship between the image density and the surface potential, and (C) represents the relationship between the image density and the detection output of the density detection means.
The figure shows the relationship between surface temperature and detection output. FIG. 7 is a diagram showing the relationship between the surface temperature of the photoreceptor of the copying machine and the detection output of the density detection means, and is a diagram illustrating the operation of reading out the temperature to be set from the detection output. 1-Photoconductor drum, 2-Photoconductor heater, 3-Temperature sensor, 10-Photo sensor (density detection means), 38-Test image.

Claims (1)

[Claims] (1) A heater that increases the temperature of the photoconductor, a temperature detection device that detects the temperature of the photoconductor, and a heater that turns on and off so that the temperature detected by the temperature detection device matches a preset temperature during copying operations. A photoreceptor heater control device comprising: a heater control means for turning off the heater; a test image forming means for forming a test image outside the original image forming area of the photoreceptor; a density detection means for detecting the density of the test image; A storage means that stores the relationship between the density of the image and the temperature of the photoreceptor, and a temperature setting that determines from the storage means a temperature at which the detected value of the density detection means becomes a preset reference value, and sets this temperature as the set temperature. A photoreceptor heater control device comprising means.