JPH07104540A - Process controller - Google Patents

Abstract

PURPOSE:To improve performance for correcting process conditions and to eliminate the trouble of the adjustment of the gain of a toner concentration detector, etc., by detecting the reflectance of light all around the periphery of an image forming body and setting a region where the reflectance of the light is nearly maximum as a toner image forming region. CONSTITUTION:On the all around periphery of a photoreceptor, the reflectance in the vicinity of a point (a) is highest and a density detecting region A is set around the point (a). The region A (positional information detected by an encoder) is stored and moreover, the gain of a concn. detecting sensor is adjusted based on the reflectance of the light of the point (a). After the adjustment, the process conditions (a grid voltage, a developing bias, etc.) are set to be in an initial state to form a toner patch in the region A and detect the density of the toner image of the patch. This toner density is stored as a reference value. When the timing of the correction of the density has just come, the toner patch is formed and its density is detected to correct the process conditions. Thus, the accuracy of the correction of image quality can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects the light reflectance of a toner image formed on an image forming body such as a photoconductor or an intermediate transfer body, and determines process conditions such as charging potential according to the light reflectance. The present invention relates to a process control device that corrects the temperature.

[0002]

2. Description of the Related Art In an image forming apparatus for forming an image using toner, in order to prevent deterioration of the image quality due to deterioration of an image forming body, a charging device, a developer, etc., the image quality is generally corrected. Corrects the image density. The deterioration state of the image forming body or the like is determined by forming a toner image on the image forming body and comparing the density of the toner image with the density in the initial state. Generally, the toner image density is detected by an optical sensor, but when the toner image density is detected by the optical sensor, there is a problem that the sensor output is affected by the image forming body as a base. Therefore, conventionally, as shown in FIG. 5, the light reflectance of the image forming body is detected to correct the sensor output when the toner image density is detected.

A conventional process control method will be described with reference to FIG.

First, the procedure for detecting the toner density in the initial state of an image forming body or the like will be described.

When the base intermediate transfer member or the photosensitive member (image forming member 101) is replaced or maintained,
As shown in FIG. 3A, the light reflectance of the image forming body 101 is set to the reflection type optical sensor 1 disposed adjacent to the image forming body 101.
Detected by 02. The reflection type optical sensor 102 includes a photocoupler having a light emitting unit and a light receiving unit, and irradiates the detection area 103 on the image forming body 101 with a certain constant output a for a certain period of time to detect the light reflectance thereof. To obtain the average value b ₁₁ . Alternatively, the serviceman may adjust the sensor output so that the average of the light reflectances detected with respect to the constant output a for the constant time becomes a predetermined value b ₁₂ (± α). Hereinafter, the averages b ₁₁ and b ₁₂ of the above detection values will be referred to as base detection values b ₁ .

Next, as shown in FIG. 1B, a toner image is formed on the image forming body 101 under predetermined process conditions.
The light reflectance of this toner image is detected by the reflection type optical sensor 102, and the average value b ₂ is obtained. And b ₂ / b
The value of ₁ = B is obtained and stored as the reference value of the image density. That is, the toner image density b at the initial stage of the image forming body or the like
₂ is corrected by the base detection value b ₁ of the image forming body itself and stored.

Next, the procedure for correcting the process conditions according to the deterioration of the image forming body will be described. In the process condition correction process, the timing for performing the process is usually set by monitoring the number of copies, the warm-up time, and the like.

In the correction process, as shown in FIG. 2C, a toner image is formed in the detection area 103 by setting several process conditions. In this example, the grid potential (charging potential) is set to three types to form a toner image, and the charging potential when the toner image is formed at the initial stage is x.
(V), for example, x-30 (V), x (V),
Charging is performed with three kinds of potentials of x + 30 (V). In this case, the detection area 103 is divided into three parts, and toner images are formed at the respective potentials. The densities (light reflectances) of the three types of toner images formed in this way are respectively c,
Assuming d and e, from this value, c / b ₁ = C, d / b ₁
= D, e / b ₁ = E, and the values C, D, E at these three points
Are connected on a graph as shown in FIG. 6 to obtain a concentration line. The initial image density B is superposed on this density line, and the correction value y (V) of the grid voltage is obtained from the value to perform the correction.

[0009]

When the toner image is formed on the image forming body and the density of the toner image is detected by the reflection type photosensor as described above, the image forming body has a light reflectance equivalent to that of the toner. If it has, it becomes difficult to detect the toner image. In particular, in the case of a color toner as compared with a black toner, the toner itself reflects the light of that color, so if the light reflectance of the image forming body is low, the S
In some cases, the / N ratio deteriorates, making correction difficult.

Further, when the light reflectance of the image forming body is high, it is necessary to adjust the gain of the reflection type optical sensor at the time of maintenance in order to prevent the limit over, which is troublesome. .

An object of the present invention is to provide a process control device capable of improving the correction performance of process conditions and eliminating the trouble of adjusting the gain of a toner concentration detector.

[0012]

According to a first aspect of the invention, the light reflectance of a toner image formed on an image forming body such as a photoconductor or an intermediate transfer body is detected, and the light reflectance is detected according to the light reflectance. A process control device for correcting process conditions such as charging potential, means for detecting a light reflectance of the entire circumference of the image forming body, and setting an area where the light reflectance is substantially maximum as a toner image forming area. It is characterized by having.

The invention described in claim 2 is the same as claim 1
In the process control device described in (1), there is provided means for adjusting the gain of the detector for detecting the light reflectance based on the maximum value of the detected light reflectance.

[0014]

According to the first aspect of the invention, the light reflectance of the entire circumference of the image forming body formed in a belt shape or a cylindrical shape is detected, and the area where the detected value is almost maximum is the toner image. Is set as the formation area of the. As described above, when the area having a high light reflectance is set as the toner image forming area, the contrast between the image forming body and the toner image is improved when the toner image is formed, and the S / N ratio is improved. As a result, the toner density detection accuracy is improved, and as a result, the process condition correction accuracy is improved.

According to the second aspect of the invention, the gain of the detector is adjusted in accordance with the maximum value of the light reflectance of the base material of the image forming body. The detector detects the light reflectance of the toner image formed on the image forming body, does not receive light having a higher intensity than the light reflectance of the base of the image forming body, and can detect the base of the image forming body. The problem of limit over does not occur by adjusting the gain according to the light reflectance of the.

[0016]

FIG. 4 is a diagram showing the schematic construction of a color copying machine according to an embodiment of the present invention.

The copying machine has a transparent document placing table 1 on the upper surface of the machine frame. Further, below the original placing table 1,
An exposure optical system 2 is provided. The exposure optical system 2 includes a light source lamp 2a that irradiates a document 13 placed on the document table 1 with light, and reflected light from the document 13 by, for example, a one-dot chain line. As shown, a plurality of reflecting mirrors 2b ...
And an image forming lens 2c arranged on the optical path, and a color separation filter 2 having color filters of three primary colors of red, green and blue.
and d.

On the optical axis of the exposure optical system 2 is a belt-shaped photosensitive member 7 which is composed of an organic photosensitive member (OPC) on which an optical image subjected to exposure scanning is irradiated and which is rotated by rollers 14 and 15. It is arranged. On the paper input side of the photoconductor 7,
Paper feed cassettes 8 and 9 containing transfer paper 19 are provided. The paper feed rollers 23 and 24 are provided on the upper surfaces of the paper feed cassettes 8 and 9, respectively.
These paper feed rollers 23 and 24 are configured to eject the transfer paper 19 from the paper feed cassettes 8 and 9 and send it out toward the intermediate transfer body 10.

A timing roller 25 is provided on the delivery side of the paper feed rollers 23 and 24 in the direction of the intermediate transfer body 10. The timing roller 25 rotates in synchronization with the intermediate transfer body 10. It is supposed to be done. Further, the intermediate transfer member 10 includes the first to third rollers 18a and 18a.
It is configured to be rotationally driven by b and 18c, and is pressed against a drive roller 15 that rotationally drives the photoconductor 7. A transfer charger 21 is provided on the back surface side of the intermediate transfer body 10 at the portion where the drive roller 15 is pressed, and a transfer charger 21 is provided on the front surface side of the intermediate transfer body 10 at the installation portion of the third roller 18c. A transfer roller 22 is provided. The peeling blade 20, the conveyor belt 11, and the fixing device 12 are arranged in this order on the delivery side of the transfer roller 22.

On the outer periphery of the photoconductor 7 on the side of the driven roller 14,
A charging charger 16 for charging the photoconductor 7 and a discharge lamp 26 for discharging the photoconductor 7 are provided, and toner remaining on the photoconductor 7 is removed below the photoconductor 7 near the charge charger 16. A cleaning device 17, which is a cleaning unit, is provided. And
The cleaning device 17 is provided with cleaning blades 17a, 17a made of, for example, urethane, and these cleaning blades 17a, 17a are provided.
Is pressed against the photoconductor 7 and remains on the photoconductor 7, for example,
It is designed to scrape off toner, etc.

In the vicinity of the central portion above the photoconductor 7, a black and white developing tank 3 in a non-contact state with the photoconductor 7,
Color developing tanks 4 to 6 are provided, and the color developing tanks 4 to 6 individually store yellow, magenta, and cyan color developers.

Further, a density detection sensor 28 or 29 used for image density correction is arranged opposite to the photosensitive member 7 or the intermediate transfer member 10. The density detection sensor is the photoconductor 7.
28 or 29 arranged opposite to the intermediate transfer member 10, that is, at a position where the density of the formed toner image can be detected.

FIG. 3 is a diagram showing an example of an arrangement state of the density detection sensors 28 (29) arranged to face the photoconductor 7 and the intermediate transfer body 10. As shown in the figure, the density detection sensor 28 is arranged so as to face substantially the center of the photoconductor 7 in the width direction, and detects the reflected light in the area where image formation is performed. Similarly, when the density detection sensor is arranged opposite to the intermediate transfer body 10, the density detection sensor 29 detects the reflected light from the image forming area of the intermediate transfer body 10.

At one end of the belt-shaped photoreceptor 7,
A position detecting hole 7a for detecting the rotational position of the belt is provided. The position detection hole 7a is detected by a hole detection unit (not shown) including a rotary encoder, and the rotational position of the photoconductor 7 is recognized. Similarly, the intermediate transfer member 1
Position 0 is also provided with a position detection hole 10a so that the rotational position of the intermediate transfer member 10 can be recognized. A position detecting device is constituted by the position detecting holes 7a and 10a and a hole detecting portion opposed to the position detecting holes 7a and 10a. To be done.

Next, the operation of the color copying machine having the above structure will be described.

First, the copy mode is executed by pressing a copy start switch (not shown). This copy mode has a copy cycle in which yellow, magenta, and cyan are developed and transferred to the intermediate transfer body 10. When the copy mode is executed, first, the yellow copy cycle is executed. become.

That is, the original 13 placed on the original placing table 1 is irradiated with light from the light source lamp 2a to perform exposure scanning. The reflected light from the original 13 is reflected by the reflecting mirror 2b.
... and the image forming lens 2c to solve the color separation filter 2
It is incident on d and is separated by the color separation filter 2d for each color component.

The light for each color component, which has passed through the color filters of the color separation filter 2d in the above exposure scanning, is irradiated onto the photoconductor 7 that is uniformly charged by the charging charger 16, and the photoconductor 7 is at the portion A. Exposed. As a result, the photoconductor 7
A yellow electrostatic latent image corresponding to the image of the original 13 is formed. After that, each of the electrostatic latent images is developed and visualized with the developer supplied from the developing magnet roller at the facing portion of the developing tank 4 having the yellow developer which is the complementary color of the color separation filter. Become a statue. Then, this toner image is transferred to the intermediate transfer member 10 by the transfer charger 21.

Upon completion of the yellow copy cycle, the photoconductor 7 is cleaned by the cleaning device 17 and discharged by the discharge lamp 26. Then, the magenta and cyan toner images are transferred to the intermediate transfer body 10 in the same copy cycle as described above.

When each of the above copy cycles is executed,
The toner image for each color component is transferred to the same position of the intermediate transfer member 10 by the transfer charger, and the toner for each color component is overlaid to form one completed toner image.

On the other hand, the transfer papers 19 stored in the paper feed cassettes 8 and 9 are fed one by one to the timing roller 25 by the paper feed rollers 23 and 24, and the timing roller 25 is fed.
Conveys the transfer paper 19 between the intermediate transfer body 10 and the transfer roller 22 in synchronization with the intermediate transfer body 10. The transferred transfer paper 19 is separated from the intermediate transfer member 10 by the peeling plate 20 after the toner image on the intermediate transfer member 10 is transferred by the transfer roller 22, and is introduced into the fixing device 12 by the transfer belt 11. Then, after the color toner image is fixed on the transfer paper 23, it is discharged to the outside to
This ends the copy mode.

In the copying machine configured as described above,
The density correction using the density detection sensors 28 and / or 29 will be described. Here, a case will be described in which density correction is performed using the density detection sensor 29 that is arranged so as to face the intermediate transfer member 10. FIG. 2 is a flowchart showing the density correction procedure.

First, the image density correction system is initialized when the copying machine is installed, the photosensitive member is replaced, or the maintenance is performed. In the initial setting, the toner image forming area for detecting the toner density is set, and the gain of the density detecting sensor 29 is adjusted. First, the intermediate transfer body 10 rotates, the density detection sensor 29 operates, and the surface reflectance of the entire circumference of the intermediate transfer body 10 is measured (n1 → n2 → n3 → n4). During this time, the rotational position of the intermediate transfer member is detected by the position detection device.

Here, the detected surface reflectance is, for example,
It is assumed that the result is as shown in FIG. In this figure, the reflectance is highest around the point a in the entire circumference of the photoconductor, and the density detection area A is set around this point a. The density detection area is 90 mm, for example.
The length is set, and as the setting method of this area, for example, a method of setting a distance reference such as setting 45 mm on both sides centering on the point a, or the point a
There is a setting method based on the light reflectance, such as setting an area in which the average value of the reflectance is maximized.

The density detection area A (position information detected by the encoder) set as described above is stored,
Further, the gain of the density detection sensor 29 is adjusted based on the light reflectance at the point a (n5 → n6). After adjusting the density detection sensor 29 in this way, the process conditions (grid voltage, developing bias, etc.) are set to the initial state, a toner patch is formed in the density detection area A, and the density of the toner image is set. Is detected (n7 → n8). This toner density is stored as a reference value (n8).

Next, at the density correction timing, as shown in the section of the prior art, a toner patch is formed, the density is detected, and the process condition is corrected (n9 → n1).
0 → n11 → n12 → n13, n14).

Although the above example shows the case where the toner patch is formed on the intermediate transfer member and the density is corrected, the same applies to the case where the toner patch is formed on the photosensitive member and the density is corrected. It is possible to improve the accuracy of the image quality correction by measuring the reflectance on the body in advance and setting the area where the light reflectance becomes the maximum value as the toner image forming area and by performing the gain correction of the density detection sensor 28. .

When density correction is performed on the photosensitive member 7, toner patches are formed for toners of yellow, magenta, cyan, and black, and process conditions for forming toner images of respective colors are set. Particularly, the developing bias is corrected corresponding to each color. Further, when the density correction is performed on the intermediate transfer body 10, a toner patch is created for black toner, and the transfer conditions and the like are corrected.

[0039]

According to the first aspect of the invention, when a toner image is formed, the contrast between the image forming body and the toner image is improved, the S / N ratio is improved, and the toner density detection accuracy is improved. As a result, the correction accuracy of the process conditions is improved.

According to the second aspect of the invention, the gain adjustment of the detector is automatically performed according to the detected light reflectance of the image forming body, so that it is not necessary to perform the troublesome gain adjustment and the operation is performed. In addition, the problem of limit over does not occur when the light reflectance is detected.

[Brief description of drawings]

FIG. 1 is a diagram showing a state of light reflectance of the entire circumference of an image forming body (intermediate transfer body).

FIG. 2 is a flowchart showing a processing procedure of process control.

FIG. 3 is a diagram showing an arrangement state of a reflective photosensor for detecting a light reflectance.

FIG. 4 is a diagram showing a schematic configuration of a copying machine including a process control device.

FIG. 5 is a diagram for explaining a process control procedure.

FIG. 6 is a diagram for explaining a grid voltage correction method.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasutaka Maeda 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka

Claims (2)

[Claims] 1. A process control device for detecting a light reflectance of a toner image formed on an image forming body such as a photoconductor or an intermediate transfer body, and correcting process conditions such as a charging potential according to the light reflectance. A process control device comprising means for detecting a light reflectance of the entire circumference of the image forming body and setting a region where the light reflectance is substantially maximum as a toner image forming region. 2. The process control device according to claim 1, wherein based on the maximum value of the detected light reflectance,
A process control device comprising means for adjusting a gain of a detector for detecting a light reflectance.