JPH11258872A - Electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrophotographic device which can accurately read density and line width and which is inexpensive an electrophotographic device by which a recorded image can be obtained on a paper through a process for forming an electrostatic latent image on a photoreceptor by utilizing a laser beam, and developing, transferring, and fixing the electrostatic latent image. SOLUTION: The correction of the density of a toner image is performed by measuring the density by a density sensor 14 with respect to an image for density detection closely formed on a whole surface with 100% density, and correcting the electrifying voltage of an electrifying device 5. Or the correction of the line width of the toner image is performed by measuring the density by the sensor 14 with respect to a halftone image for line width detection obtained by forming the plural lines for one dot in a stripe-state at the interval of 1 to 6 dots between respective lines, and correcting the laser power of an exposing means 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus used as a means for forming an image in, for example, a copying machine or a laser printer.

[0002]

2. Description of the Related Art Conventionally, as a means for forming an image, an electrostatic latent image is formed on a photoreceptor using a laser beam or the like, and the electrostatic latent image is developed, transferred, and fixed. 2. Description of the Related Art An electrophotographic apparatus for obtaining a recorded image is widely used.

FIG. 18 is a schematic diagram showing a schematic configuration of a conventional electrophotographic apparatus for forming a color image. The electrophotographic apparatus includes a developing unit 31Y, 31C, 31M, and 31B that charges a photoconductor, forms a latent image, and forms a toner image.
A transfer unit 32 that transfers the toner image formed by each of the developing units 31Y, 31C, 31M, and 31B to a transfer material, and a fixing unit 33 that fixes the toner image to the transfer material on which the toner image has been transferred. Have. The developing unit 31
Y, 31C, 31M, and 31B form toner images corresponding to each color of yellow, cyan, magenta, and black.

The developing section 31Y includes a photosensitive drum 34 rotatably supported, and the photosensitive drum 34 is driven to rotate in a direction indicated by an arrow in FIG. 18 by a driving device (not shown). A charging device 35 for uniformly charging the surface of the photosensitive drum 34 is provided around the photosensitive drum 34.
Exposure is performed by irradiating the surface of the photosensitive drum 34 charged by the charging device 35 with light to form a latent image; and by attaching toner to the latent image formed by the exposure unit 36, A developing device 37 for forming a toner image and a toner removing unit 38 for removing toner remaining on the surface of the photosensitive drum 34 after transfer are arranged.

The developing units 31C, 31M, and 31B have the same configuration as that of the developing unit 31Y.

The transfer section 32 includes two transfer drums 39 rotatably supported.
The drive 39 is driven to rotate in the direction of the arrow in FIG. 18 by a drive device (not shown). In addition, such that the transfer drums are wound along the circumferential surfaces of the two transfer drums 39, 39,
A transfer belt 40 is disposed, and the transfer belt 40
Rotates with the rotation of the transfer drums 39. Then, the transfer material is electrostatically held on the transfer belt 40,
The transfer material is conveyed as the transfer belt 40 rotates.

The developing units 31Y, 31C, 31M
In FIG. 18, the developing units 31Y and 31B are arranged side by side on the outer peripheral surface of the upper transfer belt 40 in FIG.
The photoconductor drums 34 of C, 31M, 31B are arranged close to the transfer belt 40.

A transfer charger 41 is disposed on the inner peripheral surface of the upper transfer belt 40 at a position facing each photosensitive drum 34. That is, the toner images formed on the photosensitive drums 34 are transferred to the transfer chargers 41.
Is transferred to the transfer material conveyed by the transfer belt 40. Then, the transfer material onto which the toner images of each color have been transferred is conveyed to the fixing unit 33, and the toner images are fixed.

In FIG. 18, a cleaning member 42 for removing dirt from the transfer belt 40, a charge removing member 43 for removing charges accumulated on the transfer belt 40, and a density A sensor 44 is arranged.

The density sensor 44 has a light emitting element and a light receiving element (not shown). The density sensor 4
Reference numeral 4 denotes a light receiving element which receives light emitted from the light emitting element and reflected on the surface of the object to be measured, and outputs a signal corresponding to the amount of received light to measure the density.

At the time of density detection, a toner image as a monitor pattern is formed on the surface of the transfer belt 40 with toner adhered to one surface without any gap, and the density of the monitor pattern is measured by the density sensor 44.

At the time of detecting the line width, the passage time of the monitor pattern formed of the horizontal lines formed on the surface of the transfer belt 40 is detected based on the output from the density sensor 44, and the line width 1 of the monitor pattern is calculated.

Normally, the sensor value from the density sensor 44 is differentiated with respect to time, and the time t from the time when the sensor value suddenly changes to the time when the sensor value changes next is measured. The line width 1 of the pattern is calculated. l = t × (peripheral speed of transfer belt) FIG. 19 shows a graph obtained by differentiating the sensor value with time.

As another method of detecting a line width, there is a method of converting a halftone density into a line width and reading the line width. In this method, a monitor pattern in which a plurality of horizontal lines are formed at predetermined intervals is formed on a transfer belt 40, and the halftone density of the entire monitor pattern is measured by a density sensor 44. In other words, the halftone density changes when the line width changes. Then, as the adjustment of the line width, the beam diameter of the laser of the exposure unit 36 is corrected so that the halftone density is constant.

As described above, the density and line width of the monitor pattern are detected, and correction is performed by changing the charging, exposure, and development conditions based on these results so that an optimum image can be formed. I was

[0016]

In the conventional method of calculating the line width by detecting the transit time of a monitor pattern composed of horizontal lines, the light is emitted from the light emitting element of the density sensor 44 to such an extent that the edge of the line can be detected. It is necessary to narrow the beam diameter of the light. That is, if the beam diameter of the light emitting element is large, it becomes impossible to detect the edge portion of the line with high accuracy. In order to accurately detect the edge portion of the line, the beam diameter of the light emitting element is usually reduced so as to be about twice the desired reading accuracy.

However, the surface of the transfer belt 40 used for a long period of time, such as a scratch, is damaged. In such a case, if the density is measured by narrowing down the beam diameter of the light emitting element, light from the light emitting element is scattered by the flaw,
The output from the density sensor 44 contains much noise.

When the transfer belt 40 is damaged, a monitor pattern having horizontal lines formed thereon is
FIG. 20 shows the waveforms detected by No. 4. In addition,
The beam diameter of the light emitting element is 10 μm, and the line width is 100 μm.
The measurement is performed under the following conditions.

As shown in FIG. 20, when the transfer belt 40 used for a long time is used, since the sensor value of the density sensor 44 contains a lot of noise due to scratches, it is not possible to accurately detect the horizontal line portion. . Further, the density cannot be detected accurately.

As described above, if the beam diameter of the light emitting element is increased, it becomes impossible to detect the edge of the line with high accuracy.
The influence of noise due to the above scratches increases.

In the case where the beam diameter of the light emitting element is narrowed down, the density sensor 44 becomes expensive. Also, the beam diameter changes greatly due to a change in the distance between the density sensor 44 and the transfer belt 40.
It is necessary to increase the accuracy of the position of the density sensor 44. Therefore, the machining accuracy and the position accuracy of the holding member of the density sensor 44 must be increased, and the electrophotographic apparatus itself becomes expensive.

Further, if the density and the line width are determined by different density sensors, the cost of the apparatus is inevitably increased.

On the other hand, in the conventional method of calculating the line width from the halftone density, the relationship of the arrangement of the horizontal lines in the monitor pattern is not taken into consideration, so that the line width is not accurately read. .

More specifically, in digital electrophotography, adjacent lines are colored so as to overlap each other so that white spots do not occur when coloring is performed without any gap on one surface. Therefore, for example, when a monitor pattern including adjacent lines is used, the amount of change in the line width with respect to the entire area of the monitor pattern is reduced, so that the halftone density is smaller than the influence of the change in the line width. In addition, the density of each line itself is more greatly affected.

In the case where a monitor pattern in which the distance between the lines is relatively wide is used, the influence of the change in the line width on the halftone density is negligible. The line width cannot be calculated accurately.

An object of the present invention is to provide an inexpensive electrophotographic apparatus capable of accurately reading density and line width.

[0027]

According to another aspect of the present invention, there is provided an electrophotographic apparatus, comprising: a charging unit for charging a photosensitive member; and a photosensitive member exposed to a laser beam to form a latent image. Exposing means, an image carrying means for carrying a toner image formed by attaching toner to the latent image, and a density detecting means for detecting the density of the toner image. The correction is performed by measuring the density of the image for density detection formed at 100% density without any gap on one surface by the density detecting means and correcting the charging voltage of the charging means, thereby obtaining a line of the toner image. To correct the width, a plurality of one-dot lines are inserted between each line.
What is performed by measuring the density by the density detecting means and correcting the laser power of the exposing means with respect to the halftone image for line width detection formed in stripes at intervals of ~ 6 dots. Features.

According to the above configuration, in the correction of the line width of the toner image, the density of the halftone image for line width detection is measured by the density detecting means. There is no need to reduce the beam diameter of the density detecting means. Therefore, it is possible to eliminate problems such as the necessity of increasing the precision of machining and the position of the holding member of the density detecting means in order to require expensive density detecting means or to increase the position accuracy of the density detecting means. Can be.

Further, since it is not necessary to reduce the beam diameter of the density detecting means and the density is detected in a relatively wide range, even if a scratch or the like is formed on the base of the density detecting image, the influence of the scratch is reduced. be able to. Therefore, the density of the image can be detected with higher accuracy.

Further, the halftone image for line width detection is formed by forming a plurality of 1-dot lines in a stripe pattern with an interval of 1 to 6 dots between each line. Compared with the case of using lines for two dots, the amount of change in the line width with respect to the entire area of the halftone image is large, and the line width can be detected with higher accuracy.

Further, since the intervals between the plurality of 1-dot lines are set to 1 to 6 dots, the density of the lines can be made relatively high. In other words, according to the above interval, the density of the halftone image can be sufficiently changed by the change in the line width. That is, the line width can be detected more accurately by detecting the density of the halftone image.

The electrophotographic apparatus according to the second aspect is the first aspect of the invention.
In the configuration described above, when the exposure unit forms a latent image of the line width detection halftone image on the photoconductor,
The method is characterized in that the plurality of one-dot lines are formed at the same position on the photoconductor.

According to the above configuration, for example, when the photosensitive member is formed on the outer peripheral surface of the rotating member, even if the exposure position on the photosensitive member varies due to the eccentricity of the rotating member, the plurality of ones are reduced.
Since the line for the dot is formed at the same position on the photoconductor,
The problem that the density changes depending on the timing of forming the halftone image can be solved.

According to the third aspect of the present invention, there is provided the electrophotographic apparatus according to the first aspect.
In the configuration described above, the correction of the line width of the toner image is performed by:
The correction is performed after the correction of the density of the toner image is performed.

According to the above arrangement, the line width of the toner image is corrected after the correction of the density of the toner image is performed. , And is changed only by the line width. Therefore, the line width can always be stably detected, and the line width can be accurately corrected.

According to a fourth aspect of the present invention, there is provided the electrophotographic apparatus according to the first aspect.
In the configuration described above, the density detecting unit includes a light emitting unit, a diffuse reflection light receiving unit, and a regular reflection light receiving unit, and when detecting a toner image of a color other than black, the density is detected by an output from the diffuse reflection light receiving unit. When detecting a black toner image,
It is characterized in that the density is detected based on the output from the regular reflection light receiving unit.

According to the above arrangement, when detecting a toner image of a color other than black, the density is detected based on the output from the irregular reflection light receiving section, and when detecting the black toner image, the regular reflection light is detected. Since the density is detected based on the output from the unit, it is possible to detect the density of both the non-black and black toner images on the surface of the same image carrying means. Therefore,
It is possible to eliminate the need for a configuration such as changing the color of the base between a color other than black and black.

According to a fifth aspect of the present invention, there is provided an electrophotographic apparatus.
In the configuration described above, the regular reflectance of the surface on which the density detection image and the line width detection halftone image are formed in the image bearing unit is 10% or more.

According to the above arrangement, the regular reflectance of the surface on which the density detecting image and the line width detecting halftone image are formed is 10% or more in the image carrying means. When the reflectance is measured, the SN ratio exceeds 2, and the regular reflectance of the black image can be accurately measured.

The electrophotographic apparatus according to the sixth aspect is the fourth aspect of the invention.
In the configuration described above, a calibration plate is provided which is capable of protruding and retracting in an area between the density detection unit and the image bearing unit, and the light amount calibration of the density detection unit for colors other than black is performed on the surface of the calibration plate. The light quantity calibration of the density detecting means for black is performed on the surface of the image bearing means.

According to the above arrangement, the calibration of the light quantity of the density detecting means for the color other than black is performed on the surface of the calibration plate which can appear in the area between the density detecting means and the image bearing means. Therefore, stable light quantity calibration can be performed even for long-term use, and the density and the line width can always be stabilized.

According to a seventh aspect of the present invention, there is provided the electrophotographic apparatus according to the fourth aspect.
In the configuration described above, the light amount calibration of the specular reflection light is performed based on the output of the specular reflection light receiving unit in an initial period in which almost no damage occurs on the image bearing unit, and in the period after the initial period, the light amount calibration is performed. It is characterized in that it is performed based on the output of the irregular reflection light receiving unit.

According to the above configuration, the light amount calibration of the regular reflection light is performed based on the output of the regular reflection light receiving unit in the initial period, and in the period after the initial period,
Since it is performed based on the output of the irregular reflection light receiving unit, in the period after the initial period, even if the image carrier starts to be damaged and the regular reflection light amount decreases, the regular reflection is performed by the proportional calculation based on the irregular reflection light amount. Light amount calibration can be performed. Therefore, the light amount calibration of the specular reflection light can be accurately performed without being affected by the decrease in the specular reflection light amount due to the start of the scratch on the image carrier.

Further, for example, there is no need to provide a configuration such as a calibration plate for calibrating the amount of specularly reflected light, so that the apparatus can be simplified and the cost of the apparatus can be reduced.

The electrophotographic apparatus according to the eighth aspect is the fourth aspect of the present invention.
In the configuration described above, the light emission amount of the light emitting unit when using the regular reflection light receiving unit is switched between when detecting on the image carrier and when detecting a density detection image or a line width detection halftone image. It is characterized by.

According to the above arrangement, the amount of light emitted from the light emitting unit when the regular reflection light receiving unit is used is detected when the image is detected on the image bearing means, and the density detection image or the line width detection halftone image is detected. Since the time is switched, the amount of light emitted from the light emitting unit can be adjusted so that the amount of reflected light can be detected with the highest accuracy in each case. Therefore, it is possible to accurately detect the respective reflected light amounts of the surface of the image carrier, the image for density detection, and the halftone image for line width detection.

According to a ninth aspect of the present invention, there is provided the electrophotographic apparatus according to the fourth aspect.
The configuration described above is characterized in that the light emission amount of the light emitting unit when the regular reflection light receiving unit is used is larger than the light emission amount of the light emitting unit when the irregular reflection light receiving unit is used.

According to the above configuration, the light emission amount of the light emitting unit when the regular reflection light receiving unit is used is made larger than the light emission amount of the light emitting unit when the irregular reflection light receiving unit is used. The light emission amount of the light emitting unit can be adjusted so that the reflected light amount can be detected with the highest accuracy. Therefore, it is possible to accurately detect the respective reflected light amounts of the regular reflected light amount and the irregularly reflected light amount.

According to a tenth aspect of the present invention, in the configuration of the fourth aspect, the light amount calibration of the regular reflection light is performed at substantially the same position of the image bearing means.

According to the above configuration, since the light quantity calibration of the specular reflection light is performed at substantially the same position of the image carrying means, the influence of the initial dispersion of the belt surface is eliminated, and the light quantity calibration of the regular reflection light is performed. Can be performed stably. Therefore, the density of black with high accuracy,
The line width can be detected.

According to an eleventh aspect of the present invention, in the electrophotographic apparatus according to the tenth aspect, the specular reflected light amount of the entire area of the image carrying means is measured, and the light reflected light amount calibration is performed at a position where the specular reflected light amount is the largest. It is characterized by performing.

According to the above arrangement, the amount of specular reflection light in the entire area of the image bearing means is measured, and the amount of specular reflection light is calibrated at the position where the amount of specular reflection is largest, so that the density or line width of the black image is measured. When the detection is performed, the reflectance on the image carrier does not greatly exceed the measurable area of the density detector, and the density or the line width can be detected stably by the regular reflection light.

According to a twelfth aspect of the present invention, in the configuration of the fourth aspect, the amount of specularly reflected light and the amount of irregularly reflected light of the image bearing means are measured, and the degree of damage caused to the image bearing means is determined based on the measurement results. Is determined.

According to the above arrangement, the amount of specular reflection and the amount of irregularly reflected light of the image carrier are measured, and the degree of damage caused to the image carrier is determined from the measurement result. If a certain degree of damage has occurred in a part of the area, it is possible to form an image for density detection or line width detection in a place other than that area, thereby making it possible to detect the density or line width. It can be performed more accurately. Further, for example, when fatal damage that affects other members occurs on the image bearing unit, such damage can be immediately detected, so that the life of the apparatus is extended. be able to.

[0055]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] The following will describe one embodiment of the present invention with reference to FIGS.

FIG. 1 is a schematic diagram showing a schematic configuration of an electrophotographic apparatus for forming a color image. The electrophotographic apparatus includes developing units 1Y, 1C, 1M, and 1B for charging a photoreceptor, forming a latent image, and forming a toner image.
The image forming apparatus includes a transfer unit 2 that transfers the toner image formed by 1C, 1M, and 1B to a transfer material, and a fixing unit 3 that fixes the toner image to the transfer material onto which the toner image has been transferred. The developing units 1Y, 1C, 1M, and 1B form toner images corresponding to yellow, cyan, magenta, and black, respectively.

The developing section 1Y includes a photosensitive drum (photosensitive member) 4 rotatably supported.
Is driven to rotate in the direction of the arrow in FIG. 1 by a driving device (not shown). Further, around the photosensitive drum 4,
A charging device (charging device) 5 for uniformly charging the surface of the photoconductor drum 4; and an exposure device for irradiating the surface of the photoconductor drum 4 charged by the charging device 5 with light to form a latent image. 6, a developing device 7 for forming a toner image by attaching toner to the latent image formed by the exposing unit 6, and a toner removing unit 8 for removing toner remaining on the surface of the photosensitive drum 4 after transfer. Are located.

The developing units 1C, 1M, and 1B have the same configuration as that of the developing unit 1Y.

The transfer unit 2 is a rotatably supported 2
And two transfer drums 9.9,
It is rotationally driven in the direction of the arrow in FIG. 1 by a driving device (not shown). Further, a transfer belt (image carrying means) 10 is disposed so as to be stretched along the circumferential surface of the two transfer drums 9, 9, and the transfer belt 10 rotates the transfer drums 9, 9. It rotates with.

The transfer belt 10 is made of a modified polyimide or the like (volume resistance 10 ⁹ to 10 ¹³ ) in order to increase the difference between the reflectance of the toner and the reflectance on the transfer belt 10. The specular reflectance is set to 10% or more by making the mold a mirror surface. FIG. 17 is a graph showing the relationship between the regular reflectance of the transfer belt 10 and the SN ratio when measuring the regular reflectance of a black image. As shown in FIG. 17, by setting the regular reflectance of the transfer belt 10 to 10% or more, the SN ratio when measuring the regular reflectance of the black image is 2%.
, The specular reflectance of the black image can be accurately measured.

The transfer material is electrostatically transferred to the transfer belt 1.
The transfer material is conveyed as the transfer belt 10 rotates.

The developing units 1Y, 1C, 1M, 1B
Are arranged side by side on the outer peripheral surface of the upper transfer belt 10 in FIG. 1, and the developing units 1Y, 1C, 1M, 1B
Are arranged close to the transfer belt 10.

The transfer chargers 11 are arranged on the inner peripheral surface of the upper transfer belt 10 at positions facing the respective photosensitive drums 4. That is, the toner images formed on the photosensitive drums 4 are transferred to the transfer material conveyed by the transfer belt 10 by the transfer chargers 11. Then, the transfer material on which the toner images of each color are transferred is
The toner image is conveyed to the fixing unit 3 and fixed.

Further, in FIG. 1, a cleaning member 12 for removing dirt from the transfer belt 10, a charge removing member 13 for removing electric charges accumulated on the transfer belt 10, a density A sensor (density detecting means) 14 is provided.

Here, a schematic configuration near the density sensor 14 is shown in FIGS. Note that FIG.
2A shows a side view, and FIG. 2B shows a front view.

As shown in FIG. 2A, the density sensor 1
A calibration plate 20 is disposed between the transfer belt 4 and the transfer belt 10. Further, the density sensor 14 and the calibration plate 20 are supported by a support frame 21 for keeping the positional relationship between them constant. The support frame 21 is fixed to the bearing of the transfer drum 9 in order to keep the positional relationship between the density sensor 14 and the calibration plate 20 and the transfer belt 10 constant.

The calibration plate 20 is
It is rotatable up and down around the fulcrum.
2B, a position blocking the gap between the density sensor 14 and the transfer belt 10, and an area between the density sensor 14 and the transfer belt 10, as indicated by a broken line in FIG. It can be moved to a position above.

A solenoid (not shown) is arranged on the support frame 21, and the calibration plate 20 is arranged at one of the above two positions by turning on or off the solenoid. Note that the calibration plate 20 includes the density sensor 14 and the transfer belt 10.
Usually, it is arranged only at the time of performing light quantity calibration (details will be described later).

Next, the configuration of the density sensor 14 will be described below.

The density sensor 14 includes a light emitting unit 15, a diffuse reflection light receiving unit 16, and a regular reflection light receiving unit 17. As shown in FIG. 3, the light emitting unit 15 is arranged at a position where the light beam is emitted from a direction inclined by 30 ° with respect to the normal direction of the surface of the transfer belt 10. The irregular reflection light receiving section 16 is arranged in a direction inclined by 60 ° with respect to the normal direction of the transfer belt 10 from the light beam irradiation position on the transfer belt 10. The regular reflection light receiving unit 17 is arranged in a direction in which the light beam emitted from the light emitting unit 15 is regularly reflected on the surface of the transfer belt 10.

The light emitting section 15 and the irregular reflection light receiving section 16 described above.
FIG. 4 shows a schematic circuit diagram of FIG. In addition, the regular reflection light receiving unit 1
Reference numeral 7 is almost the same as the configuration of the irregular reflection light receiving unit 16, and the description is omitted.

In the light emitting section 15, a power supply is connected to the anode side of the light emitting diode, and a current control device is connected to the cathode side of the light emitting diode via a current limiting resistor and a transistor. Is emitted from the light emitting diode. In addition,
In the present embodiment, the light beam diameter of the light beam on the transfer belt 10 is set to 6 mm.

In the diffuse reflection light receiving section 16, a power supply is connected to the collector of the light receiving transistor, and a resistor is connected to the emitter of the light receiving transistor. The current of the emitter changes according to the amount of light received by the light receiving transistor, and the output of the emitter is amplified and output by the operational amplifier.

As described above, the density sensor 14 receives the light radiated from the light emitting unit 15 and reflected on the surface of the transfer belt 10 by the irregular reflection light receiving unit 16 or the regular reflection light receiving unit 17. The density is measured by outputting a corresponding signal.

Next, with respect to the density correction of the color toner image of each color of yellow, magenta and cyan, detection and correction of the density and the line width will be described below. When detecting the density and line width of a color toner image,
The output from the irregular reflection light receiving unit 16 of the density sensor 14 is used as a density sensor value.

First, a 100% concentration (in this embodiment,
The density is detected using a monitor pattern that is colored on one surface with no gap at an ID value of 1.4). The above ID is an abbreviation of Image Density, and ID = log ₁₀ (−
(Reflected light amount / incident light amount)). As shown below, the monitor pattern is a toner image formed by changing three types of developing bias voltages in the charging device 5 described above.
What is transferred on the surface of the transfer belt 10 is used. A: Low voltage (last set development bias voltage −50 V) B: Reference voltage (last set development bias voltage) C: High voltage (last set development bias voltage +50 V)

The size of the monitor pattern is set to a rectangle having a width of 11 mm and a height of 30 mm. The width 11 mm is set in consideration of a light beam diameter of 6 mm on the transfer belt 10 and a meandering amount of the transfer belt 10 of 5 mm. Thereby, erroneous detection of the density due to meandering of the transfer belt 10 can be prevented.

Next, the above three types of monitor patterns are measured as sensor values by the density sensor 14, and the measurement results are plotted with the developing bias voltage on the horizontal axis and the sensor values on the vertical axis as shown in FIG. Plot on the graph. Then, the three points plotted on the graph are connected by a straight line, and the optimal sensor value as the concentration (in the present embodiment,
Is set as the subsequent developing bias voltage value. Thereby, an image having an appropriate density can be provided.

Next, the line width is detected using a halftone monitor pattern in which lines are formed at regular intervals. As shown below, this monitor pattern is exposed by the exposure means 6 in other words,
The toner image formed by changing three types of laser powers on the transfer belt 10 is used. A: Low power (Laser power set last time -0.07m
W) B: Reference power (last set laser power) C: High power (last set laser power + 0.07 m)
W)

As the developing bias voltage, the developing bias voltage value set when the density is detected using the above-described monitor pattern colored with no gap on one surface is used.
As a result, the density of the line of the monitor pattern becomes the optimum density, so that accurate detection of the line width can be performed without being affected by the density of the line.

Next, the above three types of monitor patterns were measured as sensor values by the density sensor 14, and the measurement results were plotted with the laser power value on the horizontal axis and the sensor value on the vertical axis, as in FIG. Plot on a graph.
Then, the three points plotted on the graph are connected by a straight line, and the laser power value that becomes the optimum sensor value (1.7 V in this embodiment) is set as the subsequent laser power value. Thereby, an image having an appropriate line width can be provided.

Here, the above-described halftone monitor pattern will be described. The halftone monitor pattern is composed of a pattern image called 1by2. This 1 by2 is a halftone image formed by repeatedly forming a toner image for one line, forming a toner image for one line at intervals of two lines, and forming a toner image for one line.

Next, the formation of a line on the photosensitive drum 4 will be described. FIG. 6 shows that the above-described 1
This shows a change in density for one rotation of the photosensitive drum 4 when a halftone image of by2 is formed. As shown in FIG. 6, the density changes by about 0.05 V as a sensor value depending on the angular position of the photosensitive drum 4. This is because the distance between the outer periphery and the center of the photosensitive drum 4 fluctuates by about 100 μm, so that when the toner image is transferred from the photosensitive drum 4 onto the transfer belt 10, the outer periphery of the photosensitive drum 4 and the transfer belt This is because a difference in peripheral speed occurs between the toner image and the toner image 10 and the transferred toner image expands and contracts.

As described above, when the concentration is expressed as a sensor value of 0.1.
When the line width is changed by about 05 V, it is 10 μm
This value changes to a certain extent, and this value is a value at which a change in the image appears remarkably. Therefore, in order to accurately detect the line width, it is necessary to perform control so that lines are formed at the same angular position on the photosensitive drum 4.

Therefore, in order to form a line at the same angular position on the photosensitive drum 4, as shown in FIG. 7, a reflectance different from the surface of the photosensitive drum 4 is set at a position where no image is formed on the photosensitive drum 4. A patch 18 is provided, and an optical sensor 19 is provided at a position where the patch 18 passes so as to face the photosensitive drum 4. Then, the optical sensor 19 reads the difference in reflectance, thereby recognizing the angular position of the photosensitive drum 4 and forming a line so as to be at the same angular position.

Next, changes in density and line width depending on the type of halftone image will be described below. FIG. 8 shows the results of measuring the halftone density (HT reading value) of various halftone images when the line width is constant (100 μm in the present embodiment) and the line density (ID value) is changed. ing. In addition, as a type of the halftone image, 2b
y1, 1by1, 1by2, and 1by6 were used.

FIG. 9 shows the result of conversion into the corresponding line width based on the halftone density obtained from the measurement as shown in FIG. As shown in FIG. 9, when 1 by1 to 1 by6 are used as the halftone image, if the change in the line ID value is set to 0.05 or less, the line width error becomes about 3 μm, and the line width can be accurately adjusted. It can be seen that the measurement can be performed.

FIG. 10 shows the change in halftone density when the line width is changed in various halftone images. Note that 1by1, 1by2, 1by6, and 1by7 were used as the types of halftone images. As shown in FIG. 10, the halftone image 1b
When y1 to 1by6 are used, it can be seen that the halftone density is sufficiently changed with respect to the change in the line width. That is, 1 by 1 to 1 as a halftone image
If by6 is used, the line width can be accurately detected by detecting the halftone density.

FIG. 11 is a graph showing the change between the number of printed pages and the line width when the 1-by-2 image is used as the halftone image. The change in the line width is suppressed to 5 μm or less. It can be seen that the line width is stable even when the number of pages is overlapped.

Next, with respect to the density correction of the black toner image, the detection and correction of the density and the line width will be described below. When the density and the line width of the black toner image are detected, the output from the regular reflection light receiving unit 17 of the density sensor 14 is used as a density sensor value.

First, an 80% concentration (in this embodiment, I
The density is detected using a monitor pattern that is colored over the entire surface without any gap. The reason why the density is set to 80% is that when the density is set to 100%, the reflected light becomes too weak and the density sensor 14 cannot detect the light.

The monitor pattern is as follows:
A toner image formed by changing three types of developing bias voltages in the charging device 5 and transferred onto the surface of the transfer belt 10 is used. A: Low voltage (last set development bias voltage -50 V) B: Reference voltage (last set development bias voltage) C: High voltage (last set development bias voltage +50 V) The size of the monitor pattern is As in the case of the density detection, it is set to a rectangle having a width of 11 mm and a length of 30 mm.

Next, the above three types of monitor patterns are measured as sensor values by the density sensor 14, and the optical density is calculated from the measurement result by the following equation. Optical density = Reflectance of monitor pattern / Reflectance of transfer belt 10

The optical density obtained by the above equation is shown in FIG.
Similarly, the graph is plotted on a graph in which the horizontal axis represents the developing bias voltage and the vertical axis represents the optical density value. Then, the three points plotted on the graph are connected by a straight line, and a developing bias voltage that provides an optimum optical density value (0.3 in this embodiment) as the density is obtained. Then, a value obtained by dividing the developing bias voltage value by 0.8 is set as a subsequent developing bias voltage value. Thereby, the reflectance of the transfer belt 10 is standardized, so that the density can be stably read.

Next, the line width is detected using a halftone monitor pattern in which lines are formed at regular intervals. The line width is detected by setting the laser power of the exposure unit 6 to 3 as in the above-described line width detection of the color toner image.
A monitor pattern in which the toner image formed by changing the type is transferred onto the surface of the transfer belt 10 is used.

Then, similarly to the above, three types of monitor patterns are measured as sensor values by the density sensor 14, and plotted on a graph in which the horizontal axis indicates the laser power value and the vertical axis indicates the sensor value. Then, the three points plotted on the graph are connected by a straight line, and the laser power value that becomes the optimum sensor value (1.7 V in this embodiment) is set as the subsequent laser power value. Thereby, an image having an appropriate line width can be provided.

Here, detection of damage such as a scratch on the transfer belt 10 will be described below.

When a jam occurs and the transfer belt 10 is removed and inserted, or when the transfer belt 10 is
In some cases, damage such as a scratch may occur on the upper surface. For example, when the reflectance of the transfer belt 10 is detected in a portion where a flaw is generated, and the reflectance of a monitor pattern is detected in a portion where a flaw is not generated, the optical density obtained by the above formula for calculating the optical density is used. Density values will not be accurate.

Then, based on the light amount corrected by the regular reflection calibration (details will be described later), the amount of irregularly reflected light and the amount of regular reflected light for one round of the transfer belt 10 are detected, and the amount of light reflected on the transfer belt 10 satisfying the following equation is satisfied. In the area, the monitor pattern and the reflectance of the transfer belt 10 are read. Diffuse reflection light quantity / specular reflection light quantity 1/20

In the area on the transfer belt 10 where no flaw is generated, the above relationship is satisfied. In the area on the transfer belt 10 where the flaw is generated, the amount of specular reflection decreases and the amount of diffuse reflection increases. Expression relations are no longer satisfied. That is, if the reflectance of the monitor pattern and the transfer belt 10 is measured in a region on the transfer belt 10 that satisfies the above equation, it is possible to accurately detect the optical density of the monitor pattern.

If there is an area on the transfer belt 10 that satisfies the following equation, the degree of flaw is severe.
A gap is generated between the transfer material and the transfer belt 10, and the transfer becomes unstable. In this case, the transfer belt 10 needs to be replaced, and an indication that the belt replacement is necessary is displayed on an operation panel or the like. Diffusely reflected light / Specularly reflected light ≧ 3/20

Next, the light emitting section 1 in the density sensor 14
The adjustment of the light amount of the light beam emitted from 5 will be described below.

The detection of the regular reflection light in the monitor pattern means that the light reflected on the surface of the transfer belt 10 in the portion where the toner is not adhered is detected as shown in FIG. That is, the higher the density of the adhered toner, the more significantly the amount of specular reflection of the monitor pattern becomes smaller.

Therefore, as described above, the reflectance of the monitor pattern having the density of 80%, that is, the monitor pattern in which the area occupied by the toner on the surface of the transfer belt 10 is 80%, is the reflectance when only the transfer belt 10 is used. It is 1/5 of the reflectance. Therefore, the light beam amount when detecting the regular reflection light amount of the transfer belt 10 is set to 1/5 of the light beam amount when detecting the regular reflection light amount of the monitor pattern.

When the amount of specular reflection of a monitor pattern is detected, that is, when the density of a black monitor pattern is detected, when the amount of diffuse reflection of a monitor pattern is detected, that is, when the density of a color monitor pattern is detected. The light amount is set to be five times the light amount of the light beam for detection. Thereby, the specular reflection light amount of the black monitor pattern becomes sufficiently large, so that the measurement of the specular reflection light amount can be accurately performed.

As described above, the density sensor is used for detecting the amount of specular reflection of the black monitor pattern, for detecting the amount of irregular reflection of the color monitor pattern, and for detecting the amount of reflection of the transfer belt 10. Since the light amount of the light beam emitted from the light emitting unit 15 in 14 is the optimum light amount in each case, the measurement of the reflected light amount in each case can be performed with high accuracy.

Next, the calibration of the light amount in the density sensor 14 will be described below. The calibration of the light amount as described below is performed each time a predetermined operation of the electrophotographic apparatus is performed, and thereafter, the above-described detection of the density and the line width of the monitor pattern is performed.

First, calibration of the amount of irregularly reflected light used in detecting the density of a color toner image will be described.

When calibrating the amount of diffuse reflection,
A calibration plate 20 having an ID value of 0.42 is inserted between the transfer belt 10 and the density sensor 14. Then, a light beam is emitted from the light emitting unit 15, reflected by the calibration plate 20, and the irregularly reflected light receiving unit 16 measures the irregularly reflected light of the light beam. At this time, the light amount of the light beam emitted from the light emitting unit 15 is set so that the output of the density sensor 14 becomes a predetermined sensor value (2.9 V in the present embodiment).

Next, calibration of the amount of regular reflection light used when detecting the density of a black toner image will be described.

Calibration of the amount of specular reflection is performed in an initial period in which scarcely occurs on the transfer belt 10 (a period until printing of about 10,000 pages in this embodiment) and a period thereafter. Perform different calibration.

In the initial period, a light beam is emitted from the light emitting section 15 of the density sensor 14 onto the transfer belt 10, the light reflected from the transfer belt 10 is received by the regular reflection light receiving section 17, and a sensor as the amount of the regular reflection light is received. The light amount of the light beam emitted from the light emitting unit 15 is set so that the value becomes a predetermined value (2.9 V in the present embodiment). At this time, the sensor value as the amount of diffusely reflected light output from the diffusely reflected light receiving unit 16 is also stored at the same time.

Then, after the initial period, the regular reflection light receiving section 1
7, the specular reflection light amount is determined based on the irregular reflection light amount by the irregular reflection light receiving unit 16 by the following expression. Regular reflection light quantity = Initial regular reflection light quantity x Diffuse reflection light quantity / Initial diffuse reflection light quantity

FIG. 13 shows the transition of density between the case where the calibration of the specular reflection light amount is switched between the initial period and the period after the initial period, and the case where the calibration of the initial period is continued after the initial period. It is a graph shown. If the calibration in the initial period is continued after the initial period, the density increases after printing about 10,000 pages. This is because damage such as a scratch starts to occur on the transfer belt 10, thereby reducing the amount of regular reflection light and increasing the amount of light beam to maintain the amount of regular reflection light at a constant value.

As described above, by switching the calibration of the regular reflection light amount between the initial period and the period after the initial period, the light amount of the light beam can be accurately controlled, and the density and the line width can be detected. Can be performed with high accuracy.

Here, the identification of the position on the transfer belt 10 where the light quantity calibration is performed will be described below.

First, detection of a position on the transfer belt 10 will be described. The detection of the position on the transfer belt 10 is as follows.
This is performed by forming a hole in the non-image area of the transfer belt 10 and detecting the position of the hole with an optical sensor. This utilizes the fact that reflected light returns on the transfer belt 10, but does not return where holes are formed.

The width of the hole is determined by dividing the width of the hole in the horizontal direction by the width of the transfer belt 10 plus the light from the optical sensor so that the optical sensor can accurately detect the hole even if the transfer belt 10 meanders. The beam diameter is used.

In the above description, holes were formed in the non-image area of the transfer belt 10. However, patches such as white were formed in the non-image area of the transfer belt 10, and the reflectance between the patch portion and the transfer belt 10 was changed. Depending on the difference, the position on the transfer belt 10 may be detected. Also in this case, the width of the patch portion in the horizontal direction is equal to the meandering width of the transfer belt 10 plus the diameter of the light beam from the optical sensor, similarly to the horizontal width of the hole.

With the above configuration, the transfer belt 10
The upper position can be specified.

Next, the setting of the position on the transfer belt 10 for performing the light quantity calibration will be described. This is performed in order to determine the optimal position on the transfer belt 10 for performing the light amount calibration because the reflectance on the transfer belt 10 varies depending on the position.

First, at any one point on the transfer belt, the light emitting section 15 emits light so that the sensor value of the density sensor 14 becomes lower than usual (in this embodiment, about 50% of normal). Set the light amount of the light beam. Then, the sensor value for one round of the transfer belt 10 is measured based on the light amount of the low light beam, and the position on the transfer belt 10 where the sensor value becomes the highest is specified. Then, normal light quantity calibration is performed at the position on the transfer belt 10 where the sensor value is highest. The reason why the normal light amount calibration is performed at such a position is that the higher the light amount, the higher the value obtained when measuring the density of the monitor pattern, thereby increasing the SN ratio.

The reason for setting the position on the transfer belt 10 for performing the light quantity calibration as described above is as follows.

As described above, the optical density at regular reflection is
Since the reflectance of the monitor pattern is defined as a value obtained by dividing the reflectance by the reflectance on the transfer belt, the reflectance on the transfer belt 10 is measured near the position where the monitor pattern is formed. At this time, since the monitor pattern is formed at an arbitrary position on the transfer belt 10, the position at which the reflectance is measured on the transfer belt 10 is also an arbitrary position.

Therefore, when the reflectance on the transfer belt 10 is measured at a position on the transfer belt 10 having a high reflectance, and the light amount calibration is performed at a position on the transfer belt 10 having a low reflectance, Therefore, the upper limit of the measurable range of the density sensor 14 is exceeded. For example, in the density sensor 14 used in the present embodiment, the upper limit of the voltage of the light receiving sensor is 3 V, and the sensor value does not change even if light of an amount larger than that is received.

However, if the position on the transfer belt 10 for performing the light quantity calibration as described above is set, such a problem does not occur.

Next, the mounting position of the density sensor 14 will be described below.

The density sensor 14 needs to accurately adjust the distance and angle to the transfer belt 10. FIG.
(A) and (b) are schematic diagrams illustrating a distance L and an angle α between the density sensor 14 and the transfer belt 10,
FIG. 3A shows the distance L, and FIG. 3B shows the angle α. Note that the distance L indicates a distance when a vertical line is dropped on the transfer belt 10 from the center of the lens that emits light in the light emitting unit 15, and the angle α is that light is emitted from the light emitting unit 15. An angle formed by a straight line connecting the center of the lens and a light arrival point on the transfer belt 10 and a perpendicular to the surface of the transfer belt 10 at the light arrival point on the transfer belt 10 is shown.

FIG. 15 is a graph showing a change in the distance L and a change in the sensor value when the light amount of the light beam is constant. FIG. 16 is a graph showing a change in the angle α and a change in the sensor value when the light amount of the light beam is constant.

When the sensor value changes by 0.2 V, the density ID value changes by about 0.04, and the line width changes by about 3 μm. In a color image, the ID value of the density that can be distinguished by humans is about 0.05, and the line width is about 5 μm.
The error of the sensor value needs to be 0.2 V or less.

As described above, the error of the sensor value is 0.2 V
15 and 16, it is necessary to set the distance error to ± 0.2 mm or less and the angle error to ± 2 ° or less from FIGS.

[0132]

As described above, in the electrophotographic apparatus according to the first aspect of the present invention, the charging means for charging the photoreceptor, the exposing means for exposing the photoreceptor with a laser to form a latent image, and The image forming apparatus includes an image holding unit that holds a toner image formed by attaching toner to the latent image, and a density detecting unit that detects the density of the toner image. The density of the toner image is corrected by 100%. The density detection is performed by measuring the density of the density detection image formed on one surface with no gap on the entire surface and correcting the charging voltage of the charging unit. The density of the halftone image for line width detection, in which a line corresponding to one dot was formed in a striped manner with an interval of 1 to 6 dots between each line, was measured by the density detecting means. Exposure laser It is configured to be performed by correcting over.

This eliminates the necessity of narrowing the beam diameter of the density detecting means unlike the prior art, so that an expensive density detecting means is required, and in order to increase the accuracy of the position of the density detecting means, the machining accuracy and the like are reduced. It is possible to solve the problem that it is necessary to increase the positional accuracy of the holding member of the density detecting means.

In addition, even if a scratch or the like is formed on the background of the density detection image, the effect of the scratch can be reduced, so that the density of the image can be detected more accurately.

Further, the amount of change in the line width with respect to the entire area of the halftone image is increased, so that the line width can be more accurately detected.

According to the above-mentioned interval, the density of the halftone image can be sufficiently changed by the change of the line width. Therefore, the line width can be detected more accurately by detecting the density of the halftone image. It has the effect of being able to do so.

According to a second aspect of the present invention, in the electrophotographic apparatus, when the exposure unit forms the latent image of the line width detection halftone image on the photoconductor, the plurality of one-dot lines are formed. This is a configuration in which it is formed at the same position on the photoconductor.

Thus, in addition to the effect of the first aspect, since the plurality of one-dot lines are formed at the same position on the photosensitive member, a change in density depends on the timing of forming a halftone image. This has the effect that the problem of occurrence can be solved.

An electrophotographic apparatus according to a third aspect of the invention is configured such that the correction of the line width of the toner image is performed after the correction of the density of the toner image.

Thus, in addition to the effect of the first aspect, the density of the halftone image is not affected by the density of each line, but changes only by the influence of the line width. Line width can be detected stably,
There is an effect that the line width can be corrected accurately.

According to a fourth aspect of the present invention, in the electrophotographic apparatus, the density detecting means includes a light emitting section, a diffuse reflection light receiving section, and a regular reflection light receiving section, and when detecting a toner image of a color other than black, The configuration is such that the density is detected based on the output from the irregular reflection light receiving unit, and when the black toner image is detected, the density is detected based on the output from the regular reflection light receiving unit.

Thus, in addition to the effect of the configuration of the first aspect, it is possible to detect the density of both the color other than black and the black toner image on the surface of the same image carrying means. Therefore, there is an effect that it is not necessary to change the color of the base between the color other than black and the black.

According to a fifth aspect of the present invention, in the electrophotographic apparatus, the regular reflectance of the surface on which the density detecting image and the line width detecting halftone image are formed is 10% or more. It is.

Accordingly, in addition to the effect of the configuration of claim 4, the SN ratio when measuring the regular reflectance of the black image is 2
And the specular reflectance of the black image can be accurately measured.

According to a sixth aspect of the present invention, there is provided an electrophotographic apparatus, comprising: a calibration plate which is capable of protruding and retracting in an area between the density detecting means and the image bearing means; The calibration is performed on the surface of the calibration plate, and the light amount calibration of the density detecting unit for black is performed on the surface of the image bearing unit.

Thus, in addition to the effect of the configuration of claim 4, stable light quantity calibration can be performed even for long-term use, and the density and line width can be always stabilized. It works.

In the electrophotographic apparatus according to the present invention, the calibration of the light amount of the specular reflection light is performed based on the output of the specular reflection light receiving portion in an initial period in which scars are scarcely generated on the image bearing means. In the period after the initial period,
This is a configuration performed based on the output of the irregular reflection light receiving unit.

Thus, in addition to the effect of the configuration of claim 4, even if the image carrying means starts to be damaged in the period after the initial period and the regular reflection light amount decreases, the proportional calculation is performed based on the irregular reflection light amount. Thereby, the light quantity calibration of the specular reflection light can be performed. Therefore, there is an effect that the light amount calibration of the specular reflection light can be accurately performed without being affected by the decrease in the specular reflection light amount due to the start of the scratch on the image carrying means.

Further, for example, there is no need to provide a configuration such as a calibration plate for calibrating the amount of specularly reflected light, so that the apparatus can be simplified and the cost of the apparatus can be reduced. To play.

According to an eighth aspect of the present invention, in the electrophotographic apparatus, the amount of light emitted from the light emitting unit when the regular reflection light receiving unit is used can be determined by comparing the amount of light emitted from the image bearing unit with the density detection image or the line width detection half. This is a configuration that switches between when a tone image is detected.

Thus, in addition to the effect of the configuration of claim 4, in each case, the amount of light emitted from the light emitting section can be adjusted so that the amount of reflected light can be detected with the highest accuracy. There is an effect that the amount of reflected light of each of the surface of the image carrier, the density detection image, and the line width detection halftone image can be detected with high accuracy.

An electrophotographic apparatus according to a ninth aspect of the present invention is configured so that the light emission amount of the light emitting unit when the regular reflection light receiving unit is used is larger than the light emission amount of the light emitting unit when the irregular reflection light receiving unit is used.

Thus, in addition to the effect of the configuration of claim 4, in each case, the amount of light emitted from the light emitting section can be adjusted so that the amount of reflected light can be detected with the highest accuracy. There is an effect that each reflected light amount of the regular reflected light amount and the irregular reflected light amount can be detected with high accuracy.

The electrophotographic apparatus according to the tenth aspect of the present invention
This is a configuration in which the light amount calibration of the regular reflection light is performed at substantially the same position of the image carrying means.

Thus, in addition to the effect of the configuration of the fourth aspect, it is possible to stably calibrate the amount of regular reflection light, and to accurately detect the density and line width of black. To play.

The electrophotographic apparatus according to the eleventh aspect of the present invention
In this configuration, the amount of specular reflection light in the entire area of the image bearing unit is measured, and the light amount calibration of the specular reflection light is performed at a position where the amount of specular reflection is largest.

Thus, in addition to the effect of the configuration of claim 10, when the density or the line width of the black image is detected, the reflectance on the image carrying means greatly exceeds the measurable area of the density detecting means. This makes it possible to stably detect the density or the line width by the regular reflection light.

An electrophotographic apparatus according to a twelfth aspect of the present invention
In this configuration, the amount of specular reflection and the amount of irregularly reflected light from the image carrier are measured, and the degree of damage caused to the image carrier is determined based on the measurement results.

Thus, in addition to the effect of the fourth aspect, for example, when a certain degree of damage has occurred in a part of the area on the image carrying step, the density detection or the line may be performed in a place other than the area. This makes it possible to form a width detection image, thereby providing an effect that density or line width can be detected more accurately. Further, for example, when fatal damage that affects other members occurs on the image bearing unit, such damage can be immediately detected, so that the life of the apparatus is extended. It has the effect of being able to do so.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a schematic configuration of an electrophotographic apparatus according to an embodiment of the present invention.

FIG. 2 shows a schematic configuration near a concentration sensor;
FIG. 1A shows a side view, and FIG. 1B shows a front view.

FIG. 3 is a schematic diagram showing a schematic configuration of a density sensor.

FIG. 4 is a circuit diagram schematically showing a circuit of a density sensor.

FIG. 5 is a graph in which the results obtained by measuring three types of monitor patterns as sensor values using a density sensor are plotted. The horizontal axis represents the developing bias voltage, and the vertical axis represents the sensor values.

FIG. 6 is a graph showing a change in density for one rotation of the photosensitive drum when the 1-by-2 halftone image is formed on the transfer belt.

FIG. 7 is a schematic diagram illustrating a schematic configuration of a photosensitive drum provided with patches.

FIG. 8 is a graph showing the results of measuring the halftone density of various halftone images when the line width is fixed and the line density is changed.

FIG. 9 is a graph showing a result of conversion into a corresponding line width based on a halftone density obtained from the measurement as shown in FIG.

FIG. 10 is a graph showing a change in halftone density when a line width is changed in various halftone images.

FIG. 11 is a graph showing a change in the number of printed pages and a line width when a 1-by-2 image is used as a halftone image.

FIG. 12 is a schematic diagram showing how light is reflected on a transfer belt to which toner has adhered.

FIG. 13 is a graph showing the transition of the density when the calibration of the regular reflection light amount is switched between the initial period and the period after the initial period, and when the calibration of the initial period is continued after the initial period. It is.

FIGS. 14A and 14B are schematic diagrams illustrating a distance and an angle between a density sensor and a transfer belt, wherein FIG. 14A illustrates a distance, and FIG. Explain.

FIG. 15 is a graph showing a change in distance and a change in sensor value when the light amount of the light beam is constant.

FIG. 16 is a graph showing a change in the angle and a change in the sensor value when the light amount of the light beam is fixed.

FIG. 17 is a graph showing the relationship between the regular reflectance of the transfer belt and the SN ratio when measuring the regular reflectance of a black image.

FIG. 18 is a schematic diagram illustrating a schematic configuration of a conventional electrophotographic apparatus.

FIG. 19 is a graph showing a result of time-differentiating a sensor value of a density sensor.

FIG. 20 is a graph showing a change in a sensor value of a density sensor when a transfer belt used for a long time is used.

[Explanation of symbols]

 Reference Signs List 4 photosensitive drum (photoreceptor) 5 charging device (charging means) 6 exposing means 9 transfer drum 10 transfer belt (image carrying means) 14 density sensor (density detecting means) 15 light emitting section 16 diffuse reflection light receiving section 17 regular reflection light receiving section 20 calibration Plate

Continued on the front page (72) Inventor Takashi Kitagawa 22-22, Nagaikecho, Abeno-ku, Osaka City, Osaka Inside (72) Inventor Tomoe Matsuoka 22-22, Nagaikecho, Abeno-ku, Osaka City, Osaka

Claims (12)

[Claims] A charging unit for charging the photosensitive member; an exposure unit for exposing the photosensitive member with a laser to form a latent image; and a toner image formed by attaching toner to the latent image. An image carrying means for carrying the image; and a density detecting means for detecting the density of the toner image. The density of the toner image is corrected with respect to the density detecting image formed at 100% density without any gap on one surface. This is performed by measuring the density by the density detecting means and correcting the charging voltage of the charging means. The line width of the toner image is corrected by dividing a plurality of one-dot lines by 1 to 6 dots between each line. The density detection is performed on the halftone image for line width detection formed in stripes at intervals of minutes by measuring the density by the density detection means and correcting the laser power of the exposure means. Electrophotographic apparatus. 2. The method according to claim 1, wherein when the exposing means forms the latent image of the line width detecting halftone image on the photosensitive member, the plurality of one-dot lines are formed at the same position on the photosensitive member. The electrophotographic apparatus according to claim 1, wherein: 3. The electrophotographic apparatus according to claim 1, wherein the correction of the line width of the toner image is performed after the correction of the density of the toner image is performed. 4. The density detecting means includes a light emitting section, a diffuse reflection light receiving section, and a regular reflection light receiving section. When a toner image of a color other than black is detected, the density is detected by an output from the diffuse reflection light receiving section. 2. The electrophotographic apparatus according to claim 1, wherein when detecting a black toner image, the density is detected based on an output from a regular reflection light receiving unit. 5. The electronic device according to claim 4, wherein the regular reflectance of the surface on which the density detecting image and the line width detecting halftone image are formed is 10% or more. Photo equipment. 6. A calibration plate which can protrude and disappear in an area between said density detecting means and said image bearing means, wherein the light quantity calibration of the density detecting means for colors other than black is performed on the surface of said calibration plate. 5. The electrophotographic apparatus according to claim 4, wherein the light quantity calibration of the density detecting means for black is performed on the surface of the image bearing means. 7. The light amount calibration of the specular reflected light is performed in an initial period in which scars are scarcely generated on the image bearing means.
5. The electrophotographic apparatus according to claim 4, wherein the detection is performed based on the output of the regular reflection light receiving unit, and is performed based on the output of the irregular reflection light receiving unit in a period after the initial period. 8. The light emission amount of the light emitting unit when the regular reflection light receiving unit is used is switched between when detecting on the image bearing means and when detecting a density detection image or a line width detection halftone image. The electrophotographic apparatus according to claim 4, wherein: 9. The electrophotographic apparatus according to claim 4, wherein the light emission amount of the light emitting unit when using the regular reflection light receiving unit is larger than the light emission amount of the light emitting unit when using the irregular reflection light receiving unit. 10. The electrophotographic apparatus according to claim 4, wherein the light amount calibration of the regular reflection light is performed at substantially the same position of the image bearing means. 11. The electrophotographic apparatus according to claim 10, wherein the amount of specular reflection light in the entire area of the image bearing means is measured, and the light amount calibration of the specular reflection light is performed at a position where the amount of specular reflection is largest. 12. The electrophotographic apparatus according to claim 4, wherein the specular reflection light amount and the irregular reflection light amount of the image carrying means are measured, and the degree of damage caused to the image carrying means is determined from the measurement result. .