JP4575724B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that forms an image using toners of different colors.

  An image forming apparatus using an electrophotographic system includes a printing process in which colored particles are visualized as an image on the surface of a recording body, and a transfer and fixing process in which the visualized colored particle image is fixed on the recording body. First, the photosensitive member is uniformly charged by a charger. Next, a narrowed laser is irradiated onto the photosensitive member to form an electrostatic latent image. The charged toner is developed on the latent image to make the latent image noticeable. Next, an electric charge having the opposite polarity to the toner is supplied to the back surface of the paper by a transfer device, and the toner adhered on the photoconductor is transferred onto a recording material such as paper, an OHP sheet, or an intermediate transfer material to obtain an image. The photographic process is known.

  In this type of image forming apparatus, as a consideration to enable stable reproduction of high-quality image quality over a long period of time, before the start of printing work, after the end of printing work, or between sheets during printing work, It is known that a patch is formed on the surface of a photoreceptor or an intermediate transfer member serving as an image carrier, and a process for controlling various parameters related to printing based on information obtained from the patch is known.

  Here, the patch used for the control as described above has a configuration in which the control is performed using a “toner patch” formed by attaching toner to the photosensitive member or the intermediate transfer member. Reflected light of the toner patch developed on the photosensitive member is monitored by an optical density sensor. The developed toner adhesion amount is measured according to the magnitude of the reflected output. In many cases, a method of monitoring each sensor output while changing the level of the developing bias applied to the developing machine and selecting a developing bias capable of obtaining an optimum toner adhesion amount is employed. .

  There exists patent document 1 as what uses such a method. However, in the case of Patent Document 1, when a plurality of toner patches are continuously developed on the photosensitive member, the toner density in the developing device is reduced in a short time, and image quality adjustment in an unstable state is unavoidable. Even if the toner is replenished, it is difficult to replenish the toner so as to follow the short-term decrease in the toner density, and there is no best method.

  In order to prevent this, if the interval between the toner patches is widened, there is a problem that the time until the detection is completed becomes long and the life of the consumables is shortened. Further, since the response speed of the developing bias power supply usually takes about 30 msec, a toner patch gap corresponding to 30 msec is required.

  Next, FIG. 3 and FIG. 4 show the relationship between the sensor output and the toner adhesion amount with respect to the black and color LED emission currents. When detecting the black toner, if the LED emission current is increased, the sensor output in the region where the toner adhesion amount is low tends to be saturated. On the other hand, when detecting the color toner, if the LED light emission current is reduced, the sensor output generally decreases, and the necessary gain tends not to be obtained. When black and color are detected by one optical density sensor, specularly reflected light is used as a sensor output to detect the amount of black toner attached, and diffusely reflected light is detected when color toner is detected.

  FIG. 2 shows a schematic diagram of an integrated sensor of regular reflection and diffuse reflection. In the case of such an integrated sensor, since the LED light emission current optimum for detection differs between black and color, it is necessary to switch the LED light emission current. A black and color toner patch array is disclosed in Patent Document 2, but such a toner patch array cannot solve the above-described problems.

Japanese Patent No. 3127425

JP-A-9-258504

  In the present invention, even when a large number of toner patches are developed during the print quality adjustment, the toner density in the developing machine is prevented from decreasing in the short term, and the toner patches can be developed stably and efficiently. It is to extend the life of the image carrier or the like by shortening the time required. It is another object of the present invention to provide an image forming apparatus that can detect a toner patch with high accuracy without arranging a plurality of sensors for each color.

The present invention includes an image forming unit that forms an image using toners of different colors, a controller, a single light emitting unit, a regular reflection light receiving unit, and a diffuse reflection light receiving unit. The controller adjusts the current of the light emitting unit to adjust the amount of light of the light emitting unit with respect to two types of detection toner patches, a specular reflection light receiving unit detecting toner patch and a diffuse reflection light receiving unit detecting toner patch formed above. An image forming apparatus comprising: a density detecting unit that detects the specular reflection light receiving unit detection toner patch by the specular reflection light receiving unit by switching, and detects the diffuse reflection light receiving unit detection toner patch by the diffuse reflection light receiving unit. In the apparatus, after the first detection toner patch, which is one of the two types of detection toner patches, is formed, the two types of detection toner patches are subsequently formed. The first detection toner patch and the second detection toner are only formed when a second detection toner patch that is a different type of detection toner patch from the first detection toner patch is formed. A predetermined gap is provided between the patch and the predetermined gap. The predetermined gap is an interval at which the light amount of the light emitting unit can be switched by adjusting a current of the light emitting unit.

  According to the present invention, a stable toner patch can be developed on the photosensitive member even if a plurality of color toner patches are developed. Furthermore, since the toner patches are arranged efficiently, detection and adjustment can be performed in a short time, and the life of the consumables is not reduced. Further, both black toner and color toner can be detected with high accuracy, and stable image quality can be maintained over a long period of time.

  Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic view showing an embodiment of an image forming apparatus according to the present invention. 1 is a charger, 2 is an exposure device, 3 is a developing device, 4 is a photoreceptor, 5 is a first transfer device, and 6 is an optical type. A density sensor, 7 is a second transfer device, 8 is a fixing device, 9 is a belt cleaning brush, and 10 is an intermediate transfer belt.

  The basic movement of the paper in the printer apparatus will be described with reference to FIG. First, the photosensitive member 4 is uniformly charged by the charger 1, and a potential latent image is formed on the photosensitive member by the exposure device 2. The colored particles charged by the agitating action in the developing machine 3 are attached thereto, and the image on the photoreceptor is visualized. Next, an image is transferred from the photosensitive member to the intermediate transfer belt 10. This series of processes is performed for each unit, and a toner image of each color is created on the intermediate transfer belt. The sheet passes through the registration path and is sent to the second transfer unit 7 by the registration roller. Here, the sheet is transferred again from the intermediate transfer belt onto the sheet, and then passes through the fixing unit 8 to finish printing.

  When adjusting the developing bias, the toner patch image data sent from the controller is formed into a test patch latent image determined in advance by the exposure device, and this test patch latent image is subjected to a similar process on the intermediate transfer belt. Then, the toner patch image of each color is detected by the optical density sensor, and the reflection density of the toner patch image is detected. This series of steps is performed while changing the developing bias to create a plurality of toner patches on the intermediate transfer belt.

  FIG. 5A shows a conventional toner patch arrangement. Conventionally, a system in which toner patches of each color are arranged in order on the intermediate transfer belt and patches of the same color are detected in order has been used. In order to change the development bias in the toner patch gap, it is necessary to take a gap corresponding to the development bias response time in the toner patch gap. Next, the arrangement of the toner patches shown in the embodiment of the present invention is shown in FIG. FIG. 5B shows an arrangement when four types of toner patches of yellow, magenta, cyan, and black are detected. Patches of different colors are arranged for each patch, and further, those detected by specular reflection light (black toner patch) and those detected by diffuse reflection light (yellow, magenta, cyan toner patch) are arranged separately in advance, A gap is provided between the black toner patch and the basic color toner patch, and the current flowing through the light emitting element of the LED can be adjusted using this gap.

  FIG. 5C shows an arrangement of toner patches when a custom color is added in addition to yellow, magenta, cyan, and black toner. Depending on the color used, the custom color may be detected with specular reflection light, or may be detected with diffuse reflection light. For this reason, it is arranged between the black toner patch and the yellow, magenta, and cyan toner patches. By arranging in this way, when the custom color toner patch is detected by regular reflection, the arrangement is as shown in FIG. 5C, and when the custom color toner patch is detected by diffuse reflection, FIG. ). By arranging in this way, the order of black toner, custom color toner, and basic color toner is arranged so that it does not always change, and detection can be performed efficiently in a shorter time.

  In some cases, a gap is provided between the black toner patch and the custom color toner patch, and a gap is also provided between the custom color toner patch and the basic color toner patch. In this embodiment, the method for adjusting the developing bias has been described. However, the same effect can be obtained when the laser power of the exposure apparatus is adjusted.

  When adjusting another printing parameter after adjusting the developing bias, it is necessary to provide a gap equal to or more than the distance from the optical density sensor 6 to the development point of the unit corresponding to the most upstream in the process direction and the optical density sensor. . FIG. 6 shows the distance between the development point of the most upstream unit and the optical density sensor. This is because the optimum development bias is calculated from the output of the toner patch of each unit, set to that development bias, and the adjustment is performed with the development bias updated to the optimum value when the next printing parameter is adjusted. Necessary gap. When such adjustment is repeated a plurality of times, such a gap is provided each time.

1 is a schematic view showing an embodiment of an image forming apparatus of the present invention. It is the schematic of an optical density sensor. FIG. 6 is an explanatory diagram illustrating a relationship between a toner adhesion amount and a sensor output when a black toner patch is detected. FIG. 6 is an explanatory diagram illustrating a relationship between a toner adhesion amount and a sensor output when a color toner patch is detected. FIG. 6 is an explanatory diagram showing an arrangement of toner patches. It is explanatory drawing which shows the positional relationship of the developing point of a most upstream unit, and a density sensor.

Explanation of symbols

1 is a charging device, 2 is an exposure device, 3 is a developing device, 4 is a photoreceptor, 5 is a first transfer device, 6 is an optical density sensor, 7 is a second transfer device, 8 is a fixing device, and 9 is a belt cleaner. Brushes 10 are intermediate transfer belts.

Claims (4)

An image forming unit that forms an image using toners of different colors, a controller, a single light emitting unit, a regular reflection light receiving unit, and a diffuse reflection light receiving unit are formed on the image carrier by the image forming unit. Two types of detection toner patches, a regular reflection light receiving unit detection toner patch and a diffuse reflection light reception unit detection toner patch, are adjusted by the controller by adjusting the current of the light emitting unit and switching the light amount of the light emitting unit. An image forming apparatus comprising: a density detection unit that detects the regular reflection light receiving unit detection toner patch by the regular reflection light reception unit, and detects the diffuse reflection light reception unit detection toner patch by the diffuse reflection light reception unit;
After forming the first detection toner patch, which is one of the two types of detection toner patches, the first detection toner patch of the two types of detection toner patches. A predetermined gap is provided between the first detection toner patch and the second detection toner patch only when the second detection toner patch, which is a different type of detection toner patch from the toner patch, is formed. The predetermined gap is an interval capable of switching the light amount of the light emitting unit by adjusting the current of the light emitting unit.   The regular reflection light receiving portion detection toner patch is a black toner patch using black toner, and the diffuse reflection light reception portion detection toner patch is a color toner patch using yellow toner, magenta toner or cyan toner. The image forming apparatus according to claim 1, wherein:   The regular reflection light receiving portion detection toner patch includes a black toner patch using black toner and a custom color toner patch using a custom color toner which is a color toner other than black toner, yellow toner, magenta toner or cyan toner. The image forming apparatus according to claim 1, wherein the toner patch for detecting the diffuse reflection light receiving unit is a color toner patch using yellow toner, magenta toner, or cyan toner.   The regular reflection light receiving portion detection toner patch is a black toner patch using black toner, and the diffuse reflection light reception portion detection toner patch is a color toner patch using yellow toner, magenta toner or cyan toner, and black toner. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a custom color toner patch using a custom color toner which is a color toner other than yellow toner, magenta toner or cyan toner.

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