JPH1184802A - Multicolor image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multicolor image forming device constituted so that the soil of the surface of the photodetector part of a sensor for measuring surface reflectivity is automatically discriminated and the control processing of color image density is always executed in an optimum state. SOLUTION: This device is constituted so that a color image consisting of plural color toner is formed by electrifying, exposing and developing a photoreceptor drum(photoreceptor) 1 and a toner image is transferred on an intermediate transfer body(image carrier) 5 extending over plural times according to an image information signal inputted from the outside. Besides, it is provided with the infrared light reflection type density sensor(sensor for measuring surface reflectivity) 2, a patch forming circuit 61 forming a patch for measuring density(toner image for measuring density) having the maximum density and a CPU(discrimination means) 60 automatically discriminating the soil of the surface of the photodetector part of the sensor 2 based on the measured result of the density of the patch for measuring density, Then, when the soil of the surface of the photodetector part of the sensor 2 is automatically discriminated and the surface of the photodetector part is soiled, a user is urged to clean the sensor 2. Thus, the control processing of the color image density is always executed in the optimum state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicolor image forming apparatus such as a color copying machine or a printer using a plurality of color toners (developer) as a developer, and more particularly to a density of a toner image. The present invention relates to a multi-color image forming apparatus provided with a density detecting unit for detecting a color image.

[0002]

2. Description of the Related Art A conventional multicolor image forming apparatus will be described with reference to FIG.

FIG. 4 is a cross-sectional view of a conventional multicolor image forming apparatus. As shown, a photosensitive drum 1 which is driven to rotate in the direction of an arrow (counterclockwise) is housed in the entire apparatus. Around the photosensitive drum 1, a plurality of developing devices 4a, 4 supported by a charger 3, a cleaner 11, and a support 4 are provided.
b, 4c, 4d, an intermediate transfer member 5, and the like. A transfer charger 6 and a cleaner 1 are provided around the intermediate transfer body 5.
0 is arranged.

A laser diode 1 constituting an exposure apparatus is provided above the photosensitive drum 1 in the upper part of the apparatus main body.
2. Polyhedral mirror 1 driven and rotated by high-speed motor 13
4, a lens 15 and a folding mirror 16 are arranged.

On the other hand, a transport device 7 and a tray 8 are arranged below the apparatus main body, and a fixing device 9 is arranged below the developing devices 4a to 4d.

When a signal according to a yellow image pattern is input to the laser diode 12, optical information corresponding to the yellow image pattern is irradiated on the photosensitive drum 1, and a latent image is formed on the photosensitive drum 1. An image is formed. When the photosensitive drum 1 further advances in the direction of the arrow, this latent image is developed by the developing device 4a and visualized as a toner image,
The toner image on the photosensitive drum 1 is transferred onto the intermediate transfer body 5. In the illustrated example, a semiconductor laser is used as the image forming means, but an LED or the like may be used.

By performing the above steps for each of the magenta, cyan, and black image patterns, a full-color image is formed on the intermediate transfer member 5 using a plurality of color toners. After that, when the toner images of a plurality of colors on the intermediate transfer body 5 arrive at the transfer site where the transfer charger 6 is arranged,
At this position, the toner image on the intermediate transfer body 5 is transferred to the transfer material supplied to the transfer portion side by this time. Then, the transfer material to which the toner image has been transferred is conveyed to the fixing device 9, where the toner image is fixed by the fixing device 9, and a color image is formed on the transfer material.

The toner remaining on the photosensitive drum 1 is supplied to the cleaner 11 provided with a fur brush, blade means and the like.
, Thereby cleaning the surface of the photosensitive drum 1. Further, the toner on the intermediate transfer member 5 is also removed by the cleaner 10 having a fur brush, a web, and the like, and the surface of the intermediate transfer member 5 is cleaned.

In the above-described multicolor image forming apparatus, if the image density fluctuates due to various conditions such as the use environment and the number of prints, the original correct color tone cannot be obtained.

Conventionally, a toner image (hereinafter, referred to as a patch) for measuring the maximum density of each color is formed on a photosensitive drum or an image carrier in order to judge the state of the image at the time of image formation. Then, the density is automatically detected, and the detection result is fed back to image forming conditions such as an exposure amount and a developing bias, and density control is performed to form an original color image, thereby obtaining a stable color image.

Here, an example of the density control processing will be described.

As shown in FIG. 5, a plurality of patches 105A and 105B having the same pattern but having a difference in density by changing the developing bias are formed on the intermediate transfer member 5, and these patches 105A are formed. , 105B from the irradiation unit 101 of the infrared light reflection type surface reflectance measurement sensor (hereinafter, referred to as a density detection sensor) 2, and the reflected scattered light is similarly received by the density detection sensor 2. The data is measured by the unit 102 and is taken into a CPU unit (not shown). Then, CPU
The unit converts the sensor output voltage into a density, calculates the developing bias for obtaining a desired density by associating the patch density with each developing bias at the time of executing the control, and uses the calculated value as the optimal developing bias at that time for the next time. Used until the density control process. Thus, the optimum developing bias voltage at that time is set.

[0013]

However, toner adheres to the surface of the density sensor due to toner leakage from the developing device or toner scattering from the image before fixing developed on the image carrier, and the like. , A phenomenon occurs that the density control becomes impossible and the density control cannot be performed accurately. If the output simply drops due to toner contamination, an appropriate threshold may be provided, and when the output drops below that value, a warning may be issued to the user to prompt the user to clean the density sensor.

However, actually, the output of the density sensor also changes depending on the place where the density measurement patch is formed (that is, the change in the surface reflectance of the photosensitive member or the intermediate transfer member).
Specifically, the output of the density sensor decreases when the reflectance of the portion serving as the base of the density measurement patch decreases. Therefore, in the past, it was not possible to determine the cause of both, and for this reason, it was not possible to take effective measures.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to automatically determine the dirt on the light receiving portion surface of the sensor for measuring the surface reflectance, and to always determine the color image density in an optimum state. It is an object of the present invention to provide a multicolor image forming apparatus capable of performing the control processing described above.

[0016]

In order to achieve the above object, the present invention is directed to a method of charging a photosensitive member, exposing and developing a photosensitive member in response to an external image information signal, and a method of forming a toner image on an image bearing member. A multi-color image forming apparatus that forms a color image with a plurality of color toners by performing a plurality of image transfer operations, and a means for creating an infrared light reflection type surface reflectance measurement sensor and a maximum density density measurement toner image And a determination means for automatically determining the surface contamination of the light receiving portion of the surface reflectance measurement sensor based on the measurement result of the density of the density measurement toner image.

According to a second aspect of the present invention, in the first aspect, the measurement of the toner image for density measurement is performed on the photosensitive member.

According to a third aspect of the present invention, in the first aspect, the measurement of the toner image for density measurement is performed on the image carrier.

According to a fourth aspect of the present invention, in the first aspect of the present invention, a semiconductor laser is used as an exposure light source of the image forming means.

According to a fifth aspect of the present invention, in the first aspect, an LED is used as an exposure light source of the image forming means.

According to a sixth aspect of the present invention, in the first aspect, the color toner is a yellow, magenta or cyan toner.

Therefore, according to the present invention, the discrimination means automatically discriminates the dirt on the surface of the light-receiving portion of the sensor for measuring the surface reflectivity. By encouraging the cleaning of the sensor, the control processing of the color image density can always be performed in an optimum state.

[0023]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

Since the basic configuration of the multicolor image forming apparatus according to the present embodiment is the same as that of the conventional image forming apparatus shown in FIG. 4, the same reference numerals as those shown in FIG. 4 are used in the following description.

FIG. 1 is a block diagram showing a characteristic configuration of a multicolor image forming apparatus according to the present invention.
Denotes a photosensitive drum which is a photosensitive medium, 4 denotes a developing device, 5 denotes an intermediate transfer member 5 which is an image carrier, 2 denotes a density sensor (sensor for measuring surface reflectance) which is a density measuring means, and 60 denotes each of the above process means. The controlling CPU units 60 and 61 are patch creating circuits, and the multicolor image forming apparatus further includes a controller (not shown). Note that the controller receives communication from a host computer (not shown) of the external device, and transmits 8 bits for four colors of magenta, cyan, yellow, and black.
In addition to transferring input data (video data) having density information of t, communication control such as communication of printer status and the like to a host computer in response to a signal from the CPU unit 60 is performed.

In the image forming apparatus according to the present embodiment, the density sensor 2 is used immediately before performing the density control processing.
Is automatically performed. Here, the processing procedure will be described with reference to the flowchart shown in FIG.

The CPU section 60 makes the density sensor 2 emit light with the maximum light quantity (S101), and measures the reflectance of the surface of the photosensitive drum 1 (S102). Here, the preset threshold α is compared with the reflectance of the surface of the photosensitive drum 1 (S10).
3). In this case, if the reflectivity of the surface of the photosensitive drum 1 is lower than the threshold value α, the reflectivity of the surface of the photosensitive drum 1 is low or the lens surface used for the light receiving unit is dirty. 2 indicates that the output has decreased. Conversely, if the reflectance of the surface of the photosensitive drum 1 exceeds the threshold value α, it is determined that the lens surface is not dirty, and the process is terminated (S104).

Next, the CPU section 60 sends a command to create a density measurement patch having the maximum density to the patch creation circuit 61, creates a density measurement patch, and measures the reflectance of the surface (S105). Here, a threshold value β for performing the next determination is set.

FIG. 3A shows a decrease in the sensor output when the reflectance of the surface of the photosensitive drum 1 decreases with respect to the patch density. As shown in FIG. 3A, the higher the patch density, the smaller the decrease in the sensor output. It turns out that it becomes small. That is, the reflectance of the density measurement patch on the photosensitive drum 1 is
It is determined by the reflectance of the surface and the amount of toner per unit area. When the amount of toner is small (that is, when the patch density is low), the reflectance becomes almost equal to the reflectance of the surface of the photosensitive drum 1, and as the amount of toner increases, the amount of toner increases. (That is, the higher the patch density, the more the surface of the photosensitive drum 1 is covered with the toner, and is less affected by the surface reflectance.

FIG. 3B shows the decrease in sensor output due to contamination of the lens surface of the density sensor 2 with respect to the patch density. From this figure, the sensor output is at a substantially constant rate regardless of the patch density. It turns out that it falls. Such a decrease in the output of the density sensor 2 occurs because some of the irradiation light amount and the reflected light amount are cut off by dirt on the lens surface, and is not affected by the density of the density measurement patch.

As is clear from comparison between FIGS. 3A and 3B, when the reflectance of the surface of the photosensitive drum 1 is reduced and when the lens surface of the density sensor 2 is dirty. The difference occurs in the change characteristic (slope of the output characteristic) of the sensor output with respect to the patch density. Therefore, by measuring the surface reflectance of the surface of the photosensitive drum 1 and the density measurement patch having the maximum density and calculating the inclination, the degree of contamination on the lens surface of the density sensor 2 can be checked, and the boundary inclination γ Is set in advance, and a threshold β is set based on this value and the reflectance of the surface of the photosensitive drum 1 measured previously.

Referring to the density characteristics shown in FIG. 3, the reflectivity of the surface of the photosensitive drum 1 measured previously is equal to the intercept of each characteristic line, and a straight line is set as a boundary because the inclination γ is given. (A straight line that serves as a criterion for determining whether the sensor output is decreased due to a decrease in the reflectance of the surface of the photosensitive drum 1 or the sensor output is decreased due to contamination of the lens surface of the density sensor 2) ) Can be uniquely determined. Then, since the CPU 60 stores the density of the density measurement patch created earlier, it is possible to calculate the threshold value β serving as the boundary (S106).

Therefore, if the reflectance of the surface of the photosensitive drum 1 exceeds the threshold β, it is determined that the lens surface of the density sensor 2 is not dirty (S104), and the reflectance of the surface of the photosensitive drum 1 falls below the threshold β. If so, it can be determined that the lens surface is dirty (S107). When it is determined that the lens surface of the density sensor 2 is dirty, a warning is issued from the controller to the host computer to urge the user to clean the density sensor 2,
When the user cleans the density sensor 2 each time according to this warning, the color image density control processing can always be performed in an optimal state.

In this embodiment, the patch for density measurement is formed on the intermediate transfer member 5, but the patch for density measurement may of course be formed on the photosensitive drum 1.

[0035]

As is apparent from the above description, according to the present invention, the discrimination means automatically discriminates the dirt on the surface of the light-receiving portion of the sensor for measuring the surface reflectivity. In this case, the user is encouraged to clean the surface reflectance measurement sensor, so that the color image density control process can always be performed in an optimal state.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a characteristic configuration of a multicolor image forming apparatus according to the present invention.

FIG. 2 is a flowchart illustrating a procedure of a stain determination process of a density sensor.

FIG. 3 is a diagram showing a characteristic of a sensor output with respect to a patch density.

FIG. 4 is a sectional view of the multicolor image forming apparatus.

FIG. 5 is a perspective view showing a density sensor and a density measurement patch.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photosensitive drum (photosensitive member) 2 Density sensor (sensor for measuring surface reflectance) 3 Charger 4a-4b Developing device 5 Intermediate transfer member (image carrier) 6 Transfer charger 12 Laser diode 60 CPU section (determination means) 61 Patch preparation circuit 105A, 105B Density measurement patch (density measurement toner image)

Claims (6)

[Claims] 1. A multi-color image forming apparatus using a multi-color toner by charging, exposing, developing, and transferring a toner image to an image carrier a plurality of times in response to an external image information signal. In the image forming apparatus, an infrared light reflection type surface reflectance measurement sensor, a unit for creating a maximum density density toner image, and the surface reflection based on the density measurement result of the density measurement toner image. A multicolor image forming apparatus, further comprising: a discriminating means for automatically discriminating a light receiving unit surface stain of a rate measuring sensor. 2. The multicolor image forming apparatus according to claim 1, wherein the measurement of the density measurement toner image is performed on the photoconductor. 3. The multicolor image forming apparatus according to claim 1, wherein the measurement of the density measurement toner image is performed on the image carrier. 4. The multicolor image forming apparatus according to claim 1, wherein a semiconductor laser is used as an exposure light source of said image forming means. 5. An LED as an exposure light source for an image forming means.
The multi-color image forming apparatus according to claim 1, wherein 6. The multicolor image forming apparatus according to claim 1, wherein said color toner is yellow, magenta or cyan toner.