JP2007033526A - Electrophotographic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic device capable of forming a stable image by reducing a calibration error even when reflectivity of an image carrier such as an intermediate transfer body and a photoreceptor changes even under low humidity environment in which toner development capability is deteriorated and an image cannot be formed for calibration wherein an amount of toner adhesion is saturated. <P>SOLUTION: The electrophotpographic device has: a plurality of image formation means for forming toner images on the photoreceptor; the intermediate transfer body to which the toner images with colors different from one another formed on the photoreceptors of the respective image formation means are sequentially transferred; and an image detection means comprised of a light emission means for radiating positions where the toner images formed on the photoreceptor and the intermediate transfer body pass with light and a light receiving means for receiving right reflected light and diffused reflected light by the toner images reflected by the intermediate transfer body and the toner images formed on the intermediate transfer body; and a function of controlling optical image forming conditions by a light receiving amount of the image detection means, wherein an image for diffused reflection calibration by black toner is formed on the photoreceptor and the intermediate transfer body. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus such as a printer, a copying machine, or a facsimile, and relates to an electrophotographic apparatus in which an image formed under a predetermined condition is read by an optical reflection density sensor and an image forming condition is adjusted based on the output value. .

  In recent years, as the demand for colorizing documents and creating them quickly increases, the colorization and speeding up of laser beam printers are rapidly progressing.

  As an example of a color printer, black (K), yellow (Y), magenta (M), and cyan (C) color toners are used, and an image forming unit for each color is provided to form a toner image formed by each image forming unit. There is known a tandem color electrophotographic apparatus that forms a color image by being transferred onto an intermediate transfer member.

  In a tandem type electrophotographic apparatus, generally, a plurality of image forming units independently form different toner images on each photoconductor sequentially, and the toner images on these photoconductors are transferred onto an intermediate transfer member in a multiple transfer manner. It is configured.

  Conventionally, in order to stabilize an image, a test image is formed on a photosensitive member or an intermediate transfer member under predetermined conditions, and the toner adhesion amount of the test image is detected by an optical reflection density sensor, whereby toner to a developing device is detected. Replenishment and image forming conditions have been controlled.

  When the test image is formed and the image forming conditions are controlled as described above, it is important that the sensor output characteristic with respect to the adhesion amount is stable with time against dirt and deterioration of the optical reflection density sensor. However, it is difficult for an optical reflection density sensor to maintain stable sensor output characteristics due to ambient environment such as dirt and temperature, deterioration over time, and the like. In order to stabilize the sensor output characteristics of the optical reflection density sensor, a calibration standard for the sensor is provided, variation in sensor sensitivity is corrected, and the toner adhesion amount of the test image is measured. In Patent Document 1, a sensor calibration image in which a developing bias or the like is increased as a configuration standard to sufficiently saturate the toner adhesion amount is read by a sensor and a test image is measured by the sensor output value. I am calibrating.

  However, when the electrophotographic apparatus is in a low humidity environment where the developing ability of the toner is reduced or when the toner is deteriorated, a calibration image in which the toner adhesion amount is saturated cannot be formed. Therefore, if the sensor is calibrated in a situation where the image is not a calibration image having a sufficiently saturated toner adhesion amount, there is a problem that a calibration error occurs and consequently a stable image cannot be provided.

  Furthermore, when the reflectance of an image carrier such as an intermediate transfer member or a photosensitive member has a characteristic that changes with time, calibration of the regular reflection light of the sensor is not reflected in the calibration of diffused light, resulting in a calibration error. There is a problem that it is impossible to provide a stable image using color toners such as yellow, magenta, and cyan.

JP 2003-5465 A

  An object of the present invention is to provide an electrophotographic apparatus that solves the above-described problems. Specifically, an object of the present invention is to provide an electrophotographic apparatus capable of reducing a calibration error and providing a stable image even if the toner adhesion amount of the calibration image is not saturated.

  The above problem is that the output of the diffuse reflection sensor for detecting a test image with color toners such as yellow, magenta, and cyan is greatly different from that when the toner adhesion amount is not saturated but the reflectance is the saturation adhesion amount. Solved by proofreading with no black toner.

  According to the electrophotographic apparatus of the present invention, it is possible to reduce a calibration error and form a stable image even in a low humidity environment where a calibration image in which the toner developing ability is reduced and the toner adhesion amount is saturated cannot be formed. Advantageous electrophotographic apparatus can be provided.

  An embodiment of the electrophotographic apparatus according to the present invention will be described below.

  FIG. 1 shows a schematic configuration of an electrophotographic apparatus according to the present invention, wherein 101 is an intermediate transfer member, 102 is a first image forming means, 103 is a second image forming means, 104 is a third image forming means, and 105 is a first image forming means. Four image forming means, 106 to 109 are transfer machines, and 110 is an adhesion amount sensor as image detecting means. As shown in FIG. 2, each of the image forming units 102 to 105 includes a charger 201, a photoconductor 202, an exposure unit 203, a developing device 205, and a photoconductor cleaner 206.

  In the image forming unit 102, the photosensitive member 202 using negatively charged OPC is uniformly charged by the charger 201. Next, the exposure unit 203 irradiates the photoconductor 202 with light 204 for forming a latent image in accordance with the image data.

  Thereafter, the latent image formed on the photoconductor 202 is developed with toner by the developing unit 205 to form a toner image. Next, the toner image formed on the photosensitive member 202 is transferred onto the intermediate transfer member 101 by the transfer device 106. Next, the residual toner remaining on the photosensitive member 202 without being transferred to the intermediate transfer member 101 is collected by the photosensitive member cleaner 206.

  Similarly, in the image forming units 103 to 105 having different color toners, toner images are formed on the respective photoconductors 202, and the toner images of the respective colors are transferred onto the recording medium 101 by the transfer machines 107 to 109. Terminate the process.

  FIG. 3 shows a schematic configuration of toner adhesion amount control. The density patch 301 formed on the intermediate transfer body 101 or the upper photosensitive body 202 is detected by the adhesion amount sensor 110, and based on the detected adhesion amount sensor 110 output, the arithmetic device 302 makes the target patch adhesion amount. In addition, the charging potential, which is an image forming condition, is controlled by the charger 201, the exposure unit 203, and the developing bias potential 303.

  In order to control the amount of adhesion, it is necessary that the sensor output characteristic with respect to the amount of adhesion of the patch is always constant when the density patch 301 is detected by the adhesion amount sensor 110.

  FIG. 4 shows sensor output characteristics with respect to the adhesion amount. The horizontal axis represents the toner adhesion amount of the density patch 301, and the vertical axis represents the sensor output characteristic when the sensor light emission current IF is used. The calibration of the adhesion amount sensor 110 is, for example, the difference between the sensor output Vsg when no toner is present due to the regular reflection output of the adhesion amount sensor 110 and the sensor output Vso when the toner adhesion amount at which the sensor output is saturated is detected. The light emission current IF of the sensor is adjusted so that becomes constant. Since the light emitting part of the sensor after adjustment is common, it is reflected in the diffuse reflection output of YMC.

  Therefore, for example, assuming that the sensor emission current IF is IF0 in the initial state before the adhesion amount sensor 110 becomes dirty, the adhesion amount sensor 110 with respect to the toner adhesion amount of the density patch 301 of color toner such as YMC and the density patch 301 of black toner. The output relationship is as shown in FIG.

  Next, when the adhesion amount sensor 110 is contaminated by floating toner or paper dust drifting in the electrophotographic apparatus, the output of the adhesion amount sensor 110 is output at the same ratio for both Color and Black as shown in FIG. descend. This is because the light transmittance of the light emitting part and the light receiving part of the adhesion amount sensor 110 is lowered.

  Here, in order to increase the amount of light received by the light receiving means by increasing the amount of light emitted by the light emitting means of the adhesion amount sensor 110, the sensor light emission current IF of the adhesion amount sensor 110 is changed from IF0 to the state where there is no toner by regular reflection output. By increasing IF1 (IF0 <IF1) so that the sensor output Vsg is obtained, calibration of specular reflection is performed simultaneously with calibration of diffused light, and an initial state is obtained as shown in FIG. The same characteristics as in FIG.

  However, the above method can cope with a change in light emission amount due to sensor contamination and sensor deterioration, but cannot cope with a change in reflectance of an image carrier such as the intermediate transfer member 101 or the photosensitive member 202. FIG. 5 shows an example of sensor output when measuring the intermediate transfer member 101 with respect to the number of printed sheets when the sensor light emission current IF is constant. The horizontal axis represents the number of printed sheets, and the vertical axis represents the specular reflection sensor output. The reflectivity varies depending on the material forming the intermediate transfer body 101, and the degree of change in reflectivity with time varies. Further, when the reflectivity is high and when the reflectivity is low, it differs depending on a member for applying a load such as a cleaner for the intermediate transfer member 101 such as a blade cleaner or a brush cleaner. For example, when the reflectance is reduced as shown in FIG. 5, the operation of correcting the regular reflection output by the black toner will be described with reference to FIG.

  FIG. 6 shows sensor output characteristics with respect to the adhesion amount. The horizontal axis represents the toner adhesion amount of the density patch 301, and the vertical axis represents the sensor output characteristic when the sensor light emission current IF is used. The calibration of the adhesion amount sensor 110 is, for example, the difference between the sensor output Vsg when no toner is present due to the regular reflection output of the adhesion amount sensor 110 and the sensor output Vso when the toner adhesion amount at which the sensor output is saturated is detected. The light emission current IF of the sensor is adjusted so that becomes constant. Since the light emitting part of the sensor after adjustment is common, it is reflected in the diffuse reflection output of YMC.

  Therefore, for example, when the intermediate transfer body 101 is in the initial state, if the sensor light emission current IF is IF0, the output of the adhesion amount sensor 110 with respect to the toner adhesion amount of the density patch 301 of color toner such as YMC and the density patch 301 of black toner. The relationship is as shown in FIG.

  Next, when the intermediate transfer body 101 is loaded by the cleaner 206 or the like and the reflectance decreases, as shown in FIG. 6B, the output of the adhesion amount sensor 110 for only Black decreases. This is because Color is not affected by the reflectance of the intermediate transfer member 101.

  Here, in order to increase the amount of light received by the light receiving means by increasing the amount of light emitted by the light emitting means of the adhesion amount sensor 110, the sensor light emission current IF of the adhesion amount sensor 110 is a sensor in a state where there is no toner by regular reflection output from IF0. By increasing IF1 (IF0 <IF1) so that the output Vsg is obtained, regular reflection is calibrated and diffused light is also calibrated. As shown in FIG. However, the color is different, and the result of the toner adhesion amount control by the density patch 301 using the YMC color toner is controlled to be smaller than the target adhesion amount.

Therefore, when calibrating the sensor light emission current IF of the diffused light, a calibration member that does not change the reflectance is required. For example, a method of adjusting the sensor light emission current IF of the diffused light by providing a calibration plate can be considered. In addition, a mechanical mechanism for moving the adhesion amount sensor 110 or the calibration plate becomes a problem. Further, as shown in FIG. 7, when the sensor drive current is taken on the horizontal axis and the sensor diffuse reflection output is taken on the vertical axis, the color toner, for example, cyan is used in order to keep the sensor output characteristics from changing regardless of the toner attached amount. Development is required until the toner adhesion amount is constant regardless of the difference between the development bias potential 303 and the potential difference between the latent image potential formed on the photoreceptor 202. The above method requires an adhesion amount of at least 1.74 mg / cm ² or more, which is problematic in a low humidity environment where a toner image cannot be formed and a calibration image in which the toner adhesion amount is saturated cannot be formed.

However, as shown in FIG. 8, by forming the density patch 301 with black toner, if the toner adhesion amount of the density patch 301 is at least 0.4 mg / cm ² or more, the sensor is used regardless of the toner adhesion amount. The sensor diffusion output with respect to the light emission current IF becomes equal. As shown in FIG. 9, when the toner layer thickness of the density patch is plotted on the horizontal axis and the reflectance is plotted on the vertical axis, FIG. 9A shows the reflectance with respect to the layer thickness of the black toner, and FIG. As shown in the reflectivity with respect to the layer thickness, the layer thickness at which the reflectivity of the black toner does not change is smaller than that of the color toner. Therefore, by forming the calibration density patch 301 with the black toner, the toner developing ability can be improved. Even in a low-humidity environment where a calibration image in which the toner adhesion amount is lowered and cannot be formed, the calibration error can be reduced even when the reflectance of the image carrier such as the intermediate transfer member 101 or the photosensitive member 202 changes. .

  According to the present embodiment described above, the reflectance of an image carrier such as an intermediate transfer member or a photosensitive member can be formed even in a low humidity environment where a calibration image in which the toner developing ability is reduced and the toner adhesion amount is saturated cannot be formed. Thus, an electrophotographic apparatus capable of reducing a calibration error and forming a stable image even in the case where a change occurs can be provided.

The block diagram which shows the schematic mechanism of an electrophotographic apparatus. Example 1 FIG. 2 is a configuration diagram illustrating a schematic configuration of an image forming unit. Example 1 FIG. 3 is a diagram illustrating a schematic configuration of toner adhesion amount control. Example 1 The figure which shows the sensor output characteristic with respect to adhesion amount. Example 1 FIG. 6 is a diagram illustrating an example of sensor output when measuring an intermediate transfer body with respect to the number of printed sheets. Example 1 The figure which shows the sensor output characteristic with respect to adhesion amount. Example 1 The figure which shows the sensor output characteristic with respect to the sensor light emission current by the toner adhesion amount. Example 1 The figure which shows the sensor output characteristic with respect to the sensor light emission current by the amount of toner adhesion. Example 1 The figure which shows the reflectance with respect to toner layer thickness. Example 1

Explanation of symbols

DESCRIPTION OF SYMBOLS 101: Recording medium 102-105: Image formation means 106-109: Transfer device 110: Image detection means 201: Charger 202: Photoconductor 203: Exposure means 204: Latent image formation light 205: Developer 206: Photoconductor cleaner 301 : Adhesion amount patch 302: Arithmetic unit 303: Development bias potential

Claims (3)

  A plurality of image forming means for forming a toner image on the photoreceptor, an intermediate transfer body to which toner images of different colors formed on the photoreceptor of each of the image forming means are sequentially transferred, the photoreceptor and Light emitting means for irradiating light to a position through which the toner image formed on the intermediate transfer member passes, and regular reflection light and diffusion reflected by the intermediate transfer member and the toner image formed on the intermediate transfer member In an electrophotographic apparatus having an image detecting means comprising a light receiving means for receiving reflected light and having a function of controlling a light image forming condition by an amount of light received by the image detecting means, a light emitting means at the time of diffuse reflection measurement of the image detecting means In order to determine the quantity of light, an electrophotographic apparatus is characterized in that an image for diffuse reflection calibration with black toner is formed on the photosensitive member or the intermediate transfer member.   2. The electrophotographic apparatus according to claim 1, wherein the image detecting means differs in light quantity by the light emitting means during specular reflection measurement and diffuse reflection measurement. The toner image is at least 0.4 mg / cm ² or more adhesion amount electrophotographic apparatus according to claim 1, further comprising a for diffused reflection calibration.

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