JP2002072577A - Image-forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable density control of high precision to be executed stably. SOLUTION: An image-forming device is provided with a first control section 28 for controlling image-forming conditions, based on density information detected by a density-detecting sensor 26 and a second control section 30 for controlling the image-forming conditions, based on density of a second toner image for detecting density on output paper outputted from transferring and fixing. At the same time or immediately after finish of control of image-forming conditions by the second control section 30, the density of a first toner image for detecting density 27, formed by a toner image forming means based on the image forming conditions controlled by the second control section 30 is detected by the density-detecting sensor 26. The first control section 28 corrects and controls the image-forming conditions, based on this detected density- detecting information. Thereby the density control of high precision can be conducted stably.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, etc., which forms an image by an electrophotographic system or an electrostatic recording system.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine that forms an image by an electrophotographic system, the characteristics of an installation environment (temperature, humidity, etc.) in which the image forming apparatus is installed, a photosensitive drum, and a developer used. The image density greatly fluctuates due to variations and the like. In particular, in a color image forming apparatus, the tint also changes.

For this reason, for example, a toner image for density detection (hereinafter, referred to as a patch) is formed on a photosensitive drum, and the density of the patch is detected by using a density detection sensor. The image forming conditions are controlled so that the image density is appropriate.

[0004] In this case, D for controlling the charging bias and the developing bias for controlling the maximum density is controlled.
The max control can be performed as follows. That is, a patch having an image ratio of 100% is formed while changing the contrast potential determined by the difference between the charging potential of the photosensitive drum and the developing bias potential, and the patch is read by the density detecting sensor. The contrast potential serving as the target value of the density control is determined.

[0005] Further, as a more accurate concentration control means,
There is also control using a reader unit of a copying machine as an image forming apparatus. That is, an image is formed with a specific test pattern, the test pattern paper on which the test pattern image is formed is set in a reader section, and the test pattern image is read. Based on the read result, a charging bias, a developing bias, an exposure amount And the like to control image forming conditions.

In this case, D for controlling the charging bias and the developing bias for controlling the maximum density is used.
The max control can be performed as follows. That is, while changing the contrast potential in two stages, the image ratio 1
A 00% image is formed and output. Then, the output paper on which this image is formed is placed at a desired position on the glass table of the reader unit in a desired direction, and read by the reader unit.
Based on the reading result, a contrast potential that is a target value of a preset maximum density control is determined.

Further, as another density control means, an image is formed with a specific test pattern, and the user inputs density information while comparing with a sample pattern or the like to obtain a charging bias,
There is also a method of controlling image forming conditions such as a developing bias and an exposure amount.

[0008]

By the way, in the above-described density control, after the density is adjusted by the user's arbitrarily adjusting the image density using a soda unit or by comparing with a sample pattern, the image forming apparatus When the density control by the density detection sensor is performed, the density may change significantly, and a high-quality image cannot be obtained.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of performing stable and accurate density control.

[0010]

In order to achieve the above object, the present invention provides a toner image forming means for forming a first density detecting toner image on an image carrier, and said first density detecting toner. An image forming apparatus comprising: a density detection unit configured to detect image density; a first control unit configured to control an image forming condition based on the density information detected by the density detection unit; A toner image is formed by the toner image forming means, and the image forming conditions are controlled based on the density of the second density detecting toner image on the transfer material which is transferred and fixed on the transfer material and output. A second control unit, and at the same time or immediately after the completion of the control of the image forming condition by the second control unit, based on the image forming condition controlled by the second control unit. The first density detection formed by Detecting the density of the toner image by the density detection means, said first control means is characterized in that correction control an image forming condition based on the detected the density detection information.

[0011] The present invention is characterized in that the density of the second density detecting toner image used for controlling the image forming conditions of the second control means is detected by exposure scanning by a reader scanner means.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments.

First Embodiment FIG. 1 is a schematic sectional view showing an image forming apparatus (a full-color copying machine of a transfer drum type in this embodiment) according to a first embodiment of the present invention.

This image forming apparatus comprises a reader section A for reading and scanning an original G and an apparatus main body B for forming an image based on image information read by the reader section A. By placing the original on a platen glass 1 and performing exposure scanning with an exposure lamp 2, a reflected light image from the original G is condensed on a full-color sensor 4 by a lens system 3 to obtain a color-separated image signal. The color-separated image signal is processed by a video processing unit (not shown).
Sent to

The exposure device 5 converts the input image signal into an optical signal at a laser output unit (not shown), and reflects the converted optical signal, a laser beam L, at a polygon mirror 5a rotating at high speed. Then, the image is projected on the photosensitive drum 6 rotated in the direction of the arrow (clockwise) through the lens system 5b and the reflection mirror 5c for each separation color. At this time, the photosensitive drum 6
Are uniformly negatively charged by a primary charger (corona charger) 7 and form an electrostatic latent image on the photosensitive drum 6 by projection of the laser beam L.

Each developing device 8 contains a toner of each color of yellow, cyan, magenta, and black.
A predetermined developing device (for example, a yellow developing device 8y) is brought close to the photosensitive drum 6 from among y, 8c, 8m, and 8bk,
The electrostatic latent image on the photosensitive drum 6 is reversely developed with a negatively charged toner to be visualized as a toner image (for example, a yellow toner image). Each developing unit 8y, 8c, 8
m and 8bk are selectively brought closer to the photosensitive drum 6 in accordance with each separation color by driving an eccentric cam (not shown). As described above, in the present embodiment, the exposure device 5, the primary charger 7, and the developing devices 8y, 8c, 8m, and 8bk constitute a toner image forming unit.

Then, in synchronization with the formation of the toner image on the photosensitive drum 6, the transfer material P as a sheet of a predetermined size selected from the cassettes 9a, 9b, 9c and 9d.
Is supplied to a transfer drum 11 as a transfer material carrier through a transport unit 10. The transfer material P is stored in the manual tray 12.
Can also be supplied to the transfer drum 11. Transfer drum 1
1 is in contact with the photosensitive drum 6 and is rotated by the rotation of the photosensitive drum 6.

Around the transfer drum 11, an attraction roller 13 and an attraction brush 14 for electrostatically adsorbing the transfer material P around the transfer drum 11, and a transfer brush 1 as a transfer means.
5, Separation charger 16, Separation claw 17, Separation push-up roller 1
8, an outer static eliminator 19, an inner static eliminator 20, a transfer drum pressing brush 21, a transfer drum cleaner 22, and the like. A transfer sheet (not shown) on which the transfer material P is electrostatically adsorbed is integrally stretched in a cylindrical shape in the peripheral opening area of the transfer drum 11 which is rotatably supported. As the transfer sheet, a polycarbonate resin film is used.

Then, an attraction current is applied to the attraction brush 15 to urge the transfer material P by the attraction roller 13 so as to contact the surface of the transfer drum 11 (transfer sheet).
The transfer material P is electrostatically attracted to the surface of the transfer sheet 1 (transfer sheet). The transfer material P electrostatically attracted to the surface of the transfer drum 11 (transfer sheet) moves to a position (transfer section) facing the photosensitive drum 6 by rotation of the transfer drum 11 in the direction of the arrow (counterclockwise), and the transfer bias is applied. Is applied to the transfer material P by the transfer brush 15 to which the toner image (yellow toner image) on the photosensitive drum 1 is transferred.

After the transfer, the untransferred toner remaining on the photosensitive drum 6 is removed by the photosensitive drum cleaning device 23, and is used for forming a toner image of the next color.

In the same manner, each of the developing units 8c containing cyan, magenta and black toners,
The cyan toner image, the magenta toner image, and the black toner image formed and carried on the photosensitive drum 6 by 8 m and 8 bk, respectively, are sequentially transferred onto the transfer material P which is absorbed and carried on the transfer drum 11 (transfer sheet) surface by the transfer brush 15. Multiple transfer is performed to form a full-color image.

Then, the transfer material P is separated from the transfer sheet surface on the transfer drum 11 by the separation charger 16 to which the separation charging bias is applied, the separation claw 17, and the separation pushing roller 18. The transfer material P separated from the transfer sheet surface on the transfer drum 11 is transferred to a fixing roller 24 a of a fixing device 24.
After a full-color image is fixed on the surface, the sheet is discharged onto the tray 25, and a series of image forming operations is completed.

Further, scattered toner and the like adhering to the transfer sheet on the transfer drum 11 are cleaned by the transfer drum cleaner 22 and used for the next image forming transfer. Further, the transfer sheet is then subjected to transfer to the next image forming transfer after the potential applied by the transfer is removed to approximately 0 V by the outer charge remover 19 and the inner charge remover 20 to which the charge removing bias is applied.

In the image forming apparatus, a density detection sensor 26 for density control is arranged so as to face the surface of the photosensitive drum 6.

As shown in FIG. 2, the density detecting sensor 26 is a pair of a light emitting element 26a and a light receiving element 26 which are optical sensors.
b, the light emitted from the light emitting element 26a is reflected on the surface of a patch (first density detection toner image) 27 formed on the photosensitive drum 6, and the reflected light is reflected by the light receiving element 26.
The light is received at b. The light receiving signal from the light receiving element 26b is input to the first control unit 28. The first control unit 28 includes the light receiving element 26
The density is calculated based on the light receiving signal (reflection density information) input from b, and the image forming conditions are controlled based on the calculated density information. This control is referred to as first control.

Further, in the present image forming apparatus, a specific test pattern toner image (patch; second density detection toner image) is formed on the photosensitive drum 6, and the test pattern toner image is transferred and fixed. The output paper on which the test pattern image is formed is placed on the platen glass 1 of the reader unit A.
A second control for reading a test pattern image set thereon and controlling image forming conditions based on the read image density is also performed.

Next, the density control in the present embodiment will be described. As shown in FIG. 2, the above-described first control is performed by the density detection sensor 26 and the first control unit 28, and the above-described second control is performed by the switch (control execution switch) 29 and the second control unit 30.

The first control is automatically performed as follows when the power is turned on and when the number of image forming sheets is 100, for example.

In the first control, a patch having an image ratio of 100% is formed at -10% of the current contrast potential (Vcont) under the control of the first control unit 28, and the light receiving element 26b of the density detection sensor 26 at that time is formed. The light receiving signal (sensor output), which is the reflection density information from the controller, is stored in the first controller 28.
Next, a patch having an image ratio of 100% is formed at + 10% of the current contrast potential (Vcont), and a light reception signal (sensor output) as reflection density information from the light receiving element 26b of the density detection sensor 26 at that time is output. 1 stored in the control unit 28. At this time, the relationship between the contrast potential (Vcont) and the sensor output is as shown in FIG.

Then, the first controller 28 sets a target potential, that is, a contrast potential (Vcont) for obtaining a target sensor output based on the relationship between the contrast potential (Vcont) and the sensor output.
cont).

On the other hand, the second control is started when a user or an administrator turns on a switch (control execution switch) 29 at any time.

In the second control, first, the second control unit 3
By controlling 0, the current contrast potential is set to -10% and +
By switching to 10%, a patch (test pattern toner image) with an image ratio of 100% is formed and stored in the second control unit 30. At this time, the relationship between the contrast potential (Vcont) and the maximum density (Dmax) is as shown in FIG.

Then, in the same manner as in the normal image formation, the image is transferred and fixed, and a transfer material (output paper) on which the patch is formed is output. The patch (test pattern toner image) is read by setting it at a desired position on 1 and in a desired direction. Then, the second control unit 30 sets a target density, that is, a contrast potential (Vcont) for obtaining a target sensor output based on the output image reading result at the two types of contrast potentials (Vcont).
cont).

In the density control of the present embodiment, the first control is performed after the second control. That is, as shown in the flowchart of FIG. 5, when the switch 29 is turned on, the above-described second control is started (step S1),
The transfer material (output paper) on which the patch (test pattern toner image) is formed is output (step S2), and the reader unit A
Read a patch (test pattern toner image) (step S3), and determine a contrast potential (Vcont) based on the read result (step S4).

When the contrast potential (Vcont), which is an image forming condition, is determined by the second control, at the same time or immediately after that, the target density value of the first control is updated. The determined contrast potential (V
In cont), a patch used in the above-described first control is formed (step S5). Then, the density detection value (sensor output value) detected by the density detection sensor 26 is updated as a new target density value of the first control (step S6). That is, after the control by the second control, the contrast control (Vcont) is corrected and controlled by the first control based on the density detection information detected by the density detection sensor 26.

As described above, in the density control of the present embodiment,
The first control performed on the upstream side of the image formation (not including the transfer and fixing steps) can be supplemented by the second control including the transfer and fixing steps, and the first control after the second control. By performing the control, stable and accurate density control can be performed, and a high-quality image can be obtained.

<Embodiment 2> This embodiment is also described using the image forming apparatus of Embodiment 1 shown in FIGS.

Depending on the configuration, detection method, type of toner and the like of the density detection sensor 26 shown in FIGS. 1 and 2, density detection may not be possible in a high density area as shown in FIG. The horizontal axis in FIG. 6 indicates the density value, and the right side of the figure indicates the high density, and the vertical axis indicates the output value of the density detection sensor 26. As the density increases, the output value becomes a constant value. Cannot be detected.

In order to control the maximum density when the density cannot be detected in the high-density area as described above, in the first control, a patch having an image ratio of, for example, 60% that can be detected by the density detection sensor 26 is fixed. Control in such a manner that the maximum density is controlled in a pseudo manner. However, when such control is performed, the control accuracy of the maximum density may be reduced depending on long-term use of the image forming apparatus and environmental conditions.

Therefore, in the present embodiment, the following density control is performed.

The above-described first control is automatically performed as follows when the power is turned on and when the number of image forming sheets is, for example, 100.

First, under the control of the first control unit 28, the image ratio 60 is set at -10% of the current contrast potential (Vcont).
% Patches are formed, and a light receiving signal (sensor output) as reflection density information from the light receiving element 26b of the density detecting sensor 26 at that time is stored in the first control unit 28. Next, at an image ratio of 60 at + 10% of the current contrast potential (Vcont).
% Patches are formed, and a light receiving signal (sensor output) as reflection density information from the light receiving element 26b of the density detecting sensor 26 at that time is stored in the first control unit 28.

Then, the first controller 28 sets a target density, that is, a contrast potential (Vcont) for obtaining a target sensor output based on the relationship between the contrast potential (Vcont) and the sensor output.
cont).

On the other hand, the second control is started when the user or the administrator turns on the switch (control execution switch) 29 at any time.

In the second control, first, the second control unit 3
By controlling 0, the current contrast potential is set to -10% and +
By switching to 10%, a patch (test pattern toner image) with an image ratio of 100% is formed and stored in the second control unit 30.

Then, in the same manner as in the normal image formation, the image is transferred and fixed, and a transfer material (output sheet) on which the patch is formed is output. The patch (test pattern toner image) is read by setting it at a desired position on 1 and in a desired direction. Then, the second control unit 30 sets a target density, that is, a contrast potential (Vcont) for obtaining a target sensor output based on the output image reading result at the two types of contrast potentials (Vcont).
cont).

In the density control of the present embodiment, the first control is performed after the second control. That is, FIG.
When the switch 29 is turned on, the above-described second control is started, and a transfer material (output paper) on which a patch (test pattern toner image) is formed is output. A patch (test pattern toner image) is read, and a contrast potential (Vcont) is determined based on the read result.

When the contrast potential (Vcont) is determined by the second control, the contrast potential determined by the second control is updated at the same time or immediately thereafter to update the target density value of the first control. At (Vcont), a patch having an image ratio of 60% used in the above-described first control is formed. Then, the density detection value (sensor output value) detected by the density detection sensor 26 is updated as a new target density value of the first control. That is, after the control by the second control, the contrast control (Vcont) is corrected and controlled by the first control based on the density detection information detected by the density detection sensor 26.

As described above, in the density control of this embodiment,
In addition to the effects obtained in the first embodiment, highly accurate density control can be performed even in a high density region where the control accuracy of the first control is not good.

<Embodiment 3> In Embodiments 1 and 2,
In the case of the image forming apparatus (copier) having a leader section, the present embodiment is an example in which the present invention is applied to an image forming apparatus such as a laser printer without a leader section. That is,
The image forming apparatus according to the present embodiment is basically the same as the image forming apparatus according to the first embodiment shown in FIG. 1 except that the reader unit A is not provided. The following describes only the density control using the image forming apparatus shown in FIG.

In this embodiment, the following density control is performed.

The above-described first control is automatically performed as follows when the power is turned on and when the number of image forming sheets is, for example, 100.

First, under the control of the first controller 28, the image ratio 60 is set at -10% of the current contrast potential (Vcont).
% Patches are formed, and a light receiving signal (sensor output) as reflection density information from the light receiving element 26b of the density detecting sensor 26 at that time is stored in the first control unit 28. Next, at an image ratio of 60 at + 10% of the current contrast potential (Vcont).
% Patches are formed, and a light receiving signal (sensor output) as reflection density information from the light receiving element 26b of the density detecting sensor 26 at that time is stored in the first control unit 28.

Then, the first control section 28 sets the target potential, that is, the contrast potential (Vcont) for obtaining the target sensor output based on the relationship between the contrast potential (Vcont) and the sensor output.
cont).

On the other hand, the second control in the present embodiment is started when the user or the administrator turns on the switch (control execution switch) 29 at any time.

In the second control of this embodiment, first, a patch (test pattern toner image) having an image ratio of 100% at the current contrast potential is formed under the control of the second control unit 30. Then, transfer and fixing are performed in the same manner as in normal image formation, and a transfer material (output paper) on which this patch is formed is output.

The user or the administrator compares the patch density on the output paper with a predetermined density sample prepared in advance to determine whether the patch density on the output paper is high or low.

When it is determined that the patch density is high based on the result of this determination, the input operation section (not shown) is operated to input the high patch density to the second control section 30 to thereby increase the contrast. The potential is lowered, and a patch image is output again at this contrast potential. If it is determined that the patch density is low based on the determination result, the input control unit (not shown) is operated to operate the second control unit 30.
Then, by inputting that the patch density is low, the contrast potential is increased, and a patch image is output again with this contrast potential. By repeating such an operation several times, the density is set to a level comparable to the density sample, and the target density, that is, the contrast potential (V
cont).

When the contrast potential (Vcont) is determined by the second control, the contrast potential determined by the second control is updated at the same time or immediately after that in order to update the target density value of the first control. At (Vcont), a patch used in the above-described first control is formed. Then, the density detection value (sensor output value) detected by the density detection sensor 26
Is updated as a new target density value of the first control. That is, after the control by the second control, the contrast control (Vcont) is corrected and controlled by the first control based on the density detection information detected by the density detection sensor 26.

As described above, the same effect as in the first embodiment can be obtained also in the density control of the image forming apparatus having no reader unit, so that the density control can be performed stably and with high accuracy. A high-quality image can be obtained.

In the image forming apparatus of each of the embodiments described above, the patch (density detecting toner image) formed on the photosensitive drum is detected by the density detecting sensor.
Patch on intermediate transfer member or transfer member (toner image for density detection)
The present invention can be similarly applied to an image forming apparatus configured to perform density detection by forming an image.

[0062]

As described above, according to the present invention, high-density control can be stably performed with high accuracy, and a high-quality image can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a density control system of the image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a relationship between a contrast potential (Vcont) and a sensor output in density control according to the first embodiment.

FIG. 4 is a diagram showing a relationship between contrast potential (Vcont) and maximum density (Dmax) in density control according to the first embodiment.

FIG. 5 is a flowchart of density control in the first embodiment.

FIG. 6 is a diagram showing a relationship between a density and a sensor output.

[Explanation of symbols]

 Reference Signs List 5 Exposure device 6 Photosensitive drum (image carrier) 7 Charger 8y, 8c, 8m, 8bk Developing device 11 Transfer drum 24 Fixing device 26 Density detecting sensor (density detecting means) 26a Light emitting element 26b Light receiving element 28 First control unit ( 1st control means) 29 switch 30 2nd control part (2nd control means) A leader part (leader scanner means) B main body

Claims (2)

[Claims] 1. An image forming apparatus comprising: a toner image forming unit that forms a first density detecting toner image on an image carrier; and a density detecting unit that detects the density of the first density detecting toner image. A first control unit for controlling image forming conditions based on the density information detected by the density detection unit; a second density detection toner image formed by the toner image formation unit; Second control means for controlling image forming conditions based on the density of the second density detection toner image on the transfer material transferred and fixed on the transfer material, and the second control Simultaneously with or immediately after the completion of the control of the image forming conditions by the means, the density of the first density detection toner image formed by the toner image forming means based on the image forming conditions controlled by the second control means is adjusted. Detected by density detection means, An image forming apparatus, wherein the first control means corrects and controls image forming conditions based on the detected density detection information. 2. The apparatus according to claim 1, wherein the density of the second density detection toner image used for controlling the image forming condition of the second control means is detected by exposure scanning by a reader scanner means. The image forming apparatus as described in the above.