JP2012032714A - Electrophotographic image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus which obtains optimal glossiness without fixing failure and paper jam in a system using a transparent toner by setting an predetermined applying amount of transparent toner.SOLUTION: A gradation patch of a transparent toner image is output on a transparent sheet. The gradation patch is read by transmitted light of a transmissive sensor. A gradation correction is performed to be a predetermined target based on the result of the reading and adjustments for an optimal applying amount of a toner and an optimal glossiness are made.

Description

  The present invention relates to an image forming apparatus that forms an image using an electrophotographic system, and more particularly, to an image forming apparatus such as a copying machine, a printer, a FAX, or a multifunction machine having a plurality of these functions.

  Conventionally, as a technique for improving the stability of image quality, it is known to perform processing in the following flow. First, the image forming apparatus is activated, a specific pattern is formed on the image carrier after the warm-up is completed, and the density of the pattern on the image carrier is read. Thereafter, it is fed back to image forming conditions such as γ correction or a specific pattern is printed on the output product, and the density of the pattern is read by the reader unit and fed back to the image forming conditions such as correction. Then, the image quality is stabilized by performing correction based on the fed back information. Furthermore, when the image forming characteristics change due to environmental fluctuations, etc., a specific pattern is formed again on the image carrier in accordance with the amount of environmental fluctuation, and the density of the pattern on the image carrier or the output product is adjusted. read. The image quality is stabilized by feeding back to image forming conditions such as γ correction.

  For example, in the technique described in Patent Document 1, a single-color gradation patch is output, the density of the patch read by the reader unit is calculated, and a desired target (density linearity, lightness linearity, etc.) is obtained. An automatic gradation correction technique for creating a one-dimensional LUT (gradation correction table) is described. Further, the technique described in Patent Document 2 describes a technique in which a patch with a changed loading amount is applied, the loading amount is detected on the photosensitive member or the transfer member, and gradation correction is performed according to the detection result. Has been.

Japanese Patent Laid-Open No. 11-75067 JP 2002-6684 A

  However, in the technique described in Patent Document 1, the toner application amount is detected by the reflection type sensor that detects the reflected light from the medium, and the toner density is determined. Cannot be detected, and optimal glossiness cannot be obtained. In the technique described in Patent Document 2, the toner application amount is detected by the regular reflection light sensor for the halftone and the irregular reflection light sensor for the high density region, and the density control is performed. In this case, when the amount of applied toner is large, the detection accuracy is deteriorated, the maximum amount of applied toner cannot be stably maintained, and a problem such as a paper jam due to poor fixing of the toner or a separation failure occurs in the worst case. There's a problem.

  The above problem is solved by the following configuration according to the present invention. A toner image forming unit that forms a toner image on the recording material; a detection unit that detects a toner loading amount on the toner image formed on the recording material; and a detection result of the detection unit on the recording material An electrophotographic method capable of forming a toner image using a transparent toner, having a control means for controlling the amount of applied toner and a fixing means for heating and fixing the toner image on the recording material to the recording material In this image forming apparatus, the recording material when performing gradation correction of the toner image is a transparent sheet, the detection unit is a transmission type sensor that detects the amount of applied toner by transmitted light, and the control unit is Based on the detection result of the toner application amount on the transparent sheet by the transmission type sensor, the toner application amount on the recording material is controlled.

  According to the present invention, when performing gradation correction of transparent toner, a transparent sheet is used as a recording material, and the toner application amount is detected by a transmission sensor, thereby stably adjusting the optimum toner application amount and glossiness. Adjustments can be made.

1 is a diagram illustrating an image forming apparatus according to a first embodiment. The figure which shows the path | route of the light from the sensor according to the toner applied amount on the transparent sheet which concerns on this invention. FIG. 4 is a diagram illustrating an example of a relationship between a toner loading amount and a transmitted light amount of the image forming apparatus according to the present invention. FIG. 3 is a flowchart of gradation correction to transparent toner in the image forming apparatus according to the first embodiment. FIG. 4 is a diagram showing an example of output levels of gradation patches of the image forming apparatus according to the present invention. The figure explaining the image forming apparatus which concerns on 2nd embodiment. FIG. 10 is a flowchart of gradation correction in the transparent toner according to the second embodiment. The figure for demonstrating the concentration sensor which concerns on 2nd embodiment. The figure which shows the path | route of the light according to the toner on the transparent sheet which concerns on 3rd embodiment. FIG. 10 is a diagram illustrating a relationship between toner properties and a fixing temperature according to a third embodiment.

<First embodiment>
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram schematically showing an internal configuration of an electrophotographic image forming apparatus according to a first embodiment of the present invention. 1, the image forming apparatus 100 includes an image scanner unit 18, an A / D converter 21, a control unit 22, a laser driver 24, a semiconductor laser 20, a polygon mirror 28, and a mirror 17e. In addition, the image forming apparatus 100 includes a photosensitive member 1, a scorotron primary charger 2, a developing device 4, a surface potential sensor 41, a transfer roller 8, a cleaning device 13, a pre-exposure lamp 30, a fixing device 12, a charging control unit 50, and the like. A patch detection unit 51 is provided.

  The image scanner unit 18 includes a document glass table 14 serving as a reader unit, an illumination lamp 16, mirrors 17a, 17b, and 17c, a lens 17d, and a photoelectric conversion element 19. That is, the transmitted light is detected on the original glass table 14 on which the original 15 is placed. The illumination lamp 16 scans the document 15 placed on the document glass table 14. The mirrors 17a, 17b, and 17c guide the transmitted light from the document 15 scanned by the illumination lamp 16 to the lens 17d. The lens 17 d forms an image of the transmitted light from the document 15 on the photoelectric conversion element 19. The photoelectric conversion element 19 converts the imaged transmitted light from the document 15 into an electric signal and outputs it to the A / D converter 21. Through the processing so far, the image scanner unit 18 constitutes a transmissive sensor capable of detecting the transmitted light with respect to the document. The A / D converter 21 digitizes the electrical signal output by the photoelectric conversion element 19 of the image scanner unit 18. The control unit 22 converts the electrical signal digitized by the A / D converter 21 into an image signal of 256 gradations from 0 (00 hex) to 255 (FF hex) in proportion to the image density, and outputs it to the laser driver 24. To do.

  The photoconductor 1 is provided with a photoconductive layer on a cylindrical conductive substrate, and is rotatably supported in an arrow direction. The scorotron primary charger 2 charges the surface of the photoreceptor 1. The laser driver 24 modulates the light emission of the semiconductor laser 20 in accordance with the image signal output by the control unit 22. The semiconductor laser 20 irradiates the photosensitive member 1 with laser light modulated in accordance with the image signal via the polygon mirror 28 and the mirror 17e, and the electrostatic latent image is formed on the photosensitive member 1 charged by the scorotron primary charger 2. Form. The developing device 4 attaches toner to the electrostatic latent image formed on the photoconductor 1 to form a toner image on the photoconductor 1. The transfer roller 8 transfers the toner image formed on the photoreceptor 1 onto the recording paper P. The cleaning device 13 removes residual toner on the photoreceptor 1 after the toner image is transferred. The pre-exposure lamp 30 removes residual charges on the photoreceptor 1. The recording paper P onto which the toner image has been transferred is separated from the photoreceptor 1 and then conveyed to the fixing device 12. By this series of flows, toner images are formed on the recording material. An image forming apparatus to which the present invention can be applied can form a toner image with a transparent toner in addition to a colored toner.

  The fixing device 12 heats and fixes the toner image on the surface of the conveyed recording paper P, and discharges the recording paper P on which the image is formed to the outside of the image forming apparatus. Some photoreceptors 1 have good charging ability and others have poor charging ability due to manufacturing variations. Furthermore, the charging ability of the photosensitive member 1 also changes due to changes in the discharge characteristics of the scorotron primary charger 2 due to long-term use or changes in the usage environment of the image forming apparatus. The surface potential sensor 41 detects the surface potential of the photoreceptor 1 in the vicinity of the developing position by the developing device 4 and outputs a signal to the charging control unit 50 in order to absorb the variation in charging ability of the photoreceptor 1. Based on the signal output from the surface potential sensor 41, the charging controller 50 changes the voltage applied to the grid of the scorotron primary charger 2 so as to keep the surface potential of the photoreceptor 1 at a desired potential.

  The patch detection unit 51 includes an LED for forming a reference patch on the photoconductor 1 and a density sensor that reads a reflected light amount of the patch formed on the photoconductor 1. Based on the read reflected light amount of the patch on the photoreceptor 1, the toner adhesion amount on the photoreceptor 1 is calculated, and the image control conditions (γ-LUT, charging potential, laser power, etc.) are controlled based on the result. In this embodiment, the non-contact two-component development method is adopted as the development method in the electrophotographic image forming apparatus 100, but is not limited thereto.

[Transparent toner correction]
Next, a method for correcting the applied amount of transparent toner, which is a characteristic part of the present embodiment, will be described below. First, problems of the conventional method will be described. An output product generated by printing a gradation pattern in which the toner application amount is changed in several stages on the colored recording paper P is read by the image scanner unit 18 which is a conventional reflection type system. As a result, when a gradation pattern is printed with colored toner, an image signal according to the gradation pattern can be detected. However, with regard to the transparent toner, an image signal equivalent to a situation where almost no toner is present in all gradations can be obtained. That is, in the transparent toner, gradation correction cannot be performed in the reflection type system, and even if the output level of the gradation patch is FFhex, it is erroneously recognized as 00hex. In this conventional system, not only an optimal glossy feeling cannot be produced in a printed matter, but also the maximum toner amount cannot be controlled, and a paper jam or the like due to poor fixing or worst case separation occurs.

  Therefore, in the present embodiment, the recording material (recording paper P) is a transparent sheet, and a transmissive type system (transmissive sensor) is used for the image scanner unit 18 to detect the amount of applied toner on the transparent sheet. . Based on the detection result, the applied toner amount for output is controlled and corrected. As a result, even when transparent toner is used, an optimum glossy feeling is obtained, and paper jamming due to poor fixing or worst case separation due to poor separation is prevented.

  Whether the gradation change is recognized when the image scanner unit 18 is a transmissive type will be described with reference to FIGS. FIGS. 2A and 2B are diagrams illustrating paths of light emitted from the illumination lamp 16 when the amount of applied toner on the transparent sheet P is relatively small and large. The toner shown here is a colored toner. As shown in FIG. 2A, when the amount of applied toner is small, the amount of light emitted from the illumination lamp 16 is reflected by the toner on the transparent sheet P, and the amount of transmitted light passing through the transparent sheet P increases. . On the other hand, as shown in FIG. 2B, when the amount of applied toner is large, the amount of light emitted from the illumination lamp 16 is reflected by the toner on the transparent sheet P, and the amount of transmitted light passing through the transparent sheet P is large. Less. FIG. 3 shows an example of the amount of transmitted light that has passed through the transparent sheet P and the amount of toner applied on the transparent sheet P. As can be seen from FIG. 3, it can be seen that the greater the amount of applied toner, the less transmitted light.

[Tone correction processing]
Next, FIG. 4 shows a flowchart of the gradation correction of the transparent toner in the present embodiment. In FIG. 4, after the power of the image forming apparatus 100 is turned on (S11), the user selects a gradation correction mode and gives an instruction to start printing using an operation unit (not shown) provided in the image forming apparatus 100 (see FIG. 4). S12). Then, based on an instruction from the user, the control unit 22 outputs a gradation patch without correction using a LUT (lookup table: gradation correction table) on the transparent sheet P (S13). Then, the user places this transparent sheet P on the reader unit (S14). Thereafter, the control unit 22 causes the gradation patch to be read by the transmitted light from the transmissive sensor (S15). Then, the control unit 22 converts the read value into a density (S16). Finally, the control unit 22 determines how the density based on the detection results in S15 and S16 changes with respect to the input signal, and adjusts the gradation so that the target becomes a predetermined target. Correction is performed (LUT is rewritten) (S17). Then, this processing flow ends.

  Using the LUT obtained as described above, the toner amount for the transparent toner per unit area on the recording paper P is corrected. Note that the output level of the gradation patch used in S3 of this embodiment is 0 hex, 10 hex, 20 hex... F0 hex, FF hex as indicated by the gradation patch 501 in FIG.

  As described above, an image forming apparatus using transparent toner can provide gradation correction, provide an optimal glossiness, and provide an image forming apparatus free from fixing defects and paper jams due to excessive toner loading. I can do it.

  Note that the developer and the configuration of the image forming apparatus used in the image forming apparatus of the present embodiment are not limited to these, and the present invention can be applied to various developers and image forming apparatuses. The output of the gradation patch is 17 gradations in this embodiment, but is not limited to this. Depending on the characteristics of the image to be printed, a plurality of gradations of 17 gradations or more may be detected or reduced.

<Second embodiment>
Since the basic configuration of the image forming apparatus describing this embodiment is substantially the same as that of the first embodiment, a detailed description of the entire image forming apparatus is omitted. Here, the difference from the first embodiment is an image forming apparatus using an intermediate transfer belt as a transfer body in the present embodiment. Thus, in the present embodiment, a system in which usability is improved by automatically performing the tone correction flow described in the first embodiment within the main body of the image forming apparatus will be described. That is, it is not necessary to intervene as shown in S12 to S14 of FIG. 4 in the first embodiment. Automating the gradation correction can meet the needs of the user.

[Tone correction processing]
The gradation correction method according to the present embodiment will be described with reference to FIGS. 6 having the same reference numerals as those in FIG. 1 have the same or the same role. As shown in FIG. 7, first, after the image forming apparatus 100 is turned on (S21), the user selects a gradation correction mode by an operation unit (not shown) provided in the image forming apparatus 100, and prints. The start is instructed (S22). Then, the control unit 22 forms a gradation patch without correction by the LUT on the transparent sheet P (S23). Thereafter, after the gradation patch is fixed on the transparent sheet P, the transparent sheet P is guided to the reversing path 66 by the first switching guide 80, and is reversed by the reversing rollers 78A and 78B and the density sensor 101 is disposed. 67 (S24). Details of the density sensor 101 will be described later with reference to FIG. When the transparent sheet P sent to the duplex conveyance path 67 passes through the density sensor 101, the gradation patch is read by the transmitted light (S25). Then, the control unit 22 converts the read value into a density (S26). Finally, the control unit 22 determines the density with respect to the input signal, and rewrites the LUT so as to become a predetermined target (S27). Thus, the present process is terminated.

  Here, the density sensor 101 will be described. The density sensor 101 irradiates the patch on the transparent sheet P, which has been conveyed at a predetermined timing, with reference light from a white LED as an irradiating means in the density sensor 101. And it receives light with the light-receiving means provided in the facing, and outputs the signal according to the received light quantity.

  FIG. 8A is a schematic cross-sectional view of the vicinity of the density sensor 101 applied to the image forming apparatus 100 as density detection means and a recording medium. As shown in FIG. 8A, the density sensor 101 here is a transmissive sensor configured to detect light from a light source provided at a corresponding position via a conveyed sheet. The density sensor 101 includes a white LED 91 and a charge storage sensor 92 with an RGB on-chip filter. The white LED 91 is made to emit light to the transparent sheet P on which the gradation patch is formed and fixed, and the transmitted light intensity is detected by the charge storage sensor 92 with an RGB on-chip filter. As shown in FIG. 8B, the light receiving portion 93 of the charge storage sensor 92 with the RGB on-chip filter is an independent pixel for each of RGB.

  The charge accumulation amount is adjusted to obtain a desired dynamic range by arbitrarily changing the LED output or the integration time. Then, the toner density on the recording medium is measured with high accuracy from the amount of reflected light by making the above adjustment using a reference index in advance. The charge storage sensor of the charge storage sensor 92 with the RGB on-chip filter may be a photodiode. Several sets of three RGB pixels may be arranged. Furthermore, you may comprise by LED which emits RGB three colors, and a sensor without a filter.

  As described above, in an image forming apparatus using transparent toner, gradation correction with improved usability is possible, optimal glossiness is obtained, and there is no fixing failure or paper jam due to excessive toner loading. Can be provided.

  The density sensor disposed in the image forming apparatus of the present embodiment is disposed in the double-sided conveyance path, but the configuration and the like are limited to those in any position on the conveyance path through which the recording paper P passes. Instead, the present invention can be applied to various image forming apparatuses.

<Third embodiment>
Since the basic configuration of the image forming apparatus 100 describing this embodiment is the same as that of the first embodiment, a detailed description of the entire image forming apparatus is omitted. As a difference from the first embodiment, this embodiment describes a system in which the toner on the transparent sheet is excessively melted.

  For example, the dispersibility of the colorant in the toner particles changes due to slight differences in the production conditions of the toner, and color reproducibility such as color mixing and transparency changes, or the relationship between toner loading and density ( It is generally known that the covering power changes. At this time, the ease with which the toner melts may change, and the density on the paper may change. FIG. 9A is a diagram when the toner on the transparent sheet P has melted too much. When the toner has melted too much, the toner on the transparent sheet P becomes a thin layer, and there is no irregularly reflected light with respect to the irradiated light, and almost all is transmitted light. In this case, regardless of the amount of applied toner on the transparent sheet P, it is determined that the applied amount is small, and as a result, a fixing defect or a paper jam is likely to occur due to the excessive applied amount.

  Therefore, in this embodiment, in order to prevent a situation where the toner is excessively melted and no irregularly reflected light exists, the fixing condition is changed when the gradation correction of the transparent toner is performed. Here, the fixing temperature for the toner image is lowered. As a result, as shown in FIG. 9B, the toner is prevented from being excessively melted, so that fixing failure and paper jam do not occur. The setting of the fixing temperature is obtained in advance by an experiment or the like as shown in FIG. Then, from the experimental result, the gradation patch is recognized by the transmitted light, and the gradation correction is performed by setting the fixing temperature at which no fixing failure occurs. In this embodiment, according to FIG. 10, the temperature at which the gradation of the most hardly soluble toner and the most easily soluble toner can be recognized by the sensor is adopted as the fixing temperature. Specifically, gradation correction is normally performed by lowering the temperature by 10 ° C. with respect to 160 ° C. which is set as the fixing temperature.

  As described above, in the image forming apparatus using the transparent toner, the toner fixing conditions are changed in consideration of the ease of melting of the toner and the change in the covering power that may occur due to the different toner manufacturing conditions. As a result, it is possible to obtain an optimal gloss feeling and to prevent fixing failure and paper jam due to an excessive amount of applied toner.

  In the image forming apparatus of the present embodiment, the fixing temperature is lowered by 10 ° C. as an example of changing the fixing conditions. However, as long as the gradation patch is recognized by the transmitted light and the fixing failure does not occur, the reduction temperature of the fixing temperature is not limited to this. Further, the heating of the toner may be suppressed by shortening the fixing time in the fixing device. The present invention is not limited to the above configuration, and the present invention can be applied to various image forming apparatuses.

  Although the image forming apparatus of the present invention has been described with the above three embodiments, it is not limited to the above-described configuration, and various configurations can be taken according to the scope of the claims.

<Other embodiments>
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

Claims (5)

Toner image forming means for forming a toner image on a recording material;
Detecting means for detecting the amount of toner applied to the toner image formed on the recording material;
Control means for controlling the amount of applied toner on the recording material based on the detection result of the detection means;
Fixing means for heating and fixing the toner image on the recording material to the recording material;
An electrophotographic image forming apparatus capable of forming a toner image using a transparent toner,
The recording material when performing gradation correction of the toner image is a transparent sheet,
The detection means is a transmission type sensor that detects the amount of applied toner by transmitted light,
The electrophotographic image forming apparatus according to claim 1, wherein the control unit controls the amount of applied toner on the recording material based on a detection result of the amount of applied toner on the transparent sheet by the transmission type sensor.   2. The electrophotographic image forming apparatus according to claim 1, wherein the detection unit detects a toner loading amount of a plurality of toner images having different toner amounts per unit area on the recording material. A reader unit;
3. The electrophotographic system according to claim 1, wherein the detection unit is provided in the reader unit and detects the amount of applied toner with respect to a recording material placed on the reader unit by a user. Image forming apparatus.   The electrophotographic image forming apparatus according to claim 1, wherein the detection unit is provided in a conveyance path of the recording material.   When performing tone correction, the detection unit can detect the amount of applied toner according to the characteristics of the toner forming the toner image, and the fixing conditions for fixing the toner image to the recording material by the fixing unit. 3. The electrophotographic image forming apparatus according to claim 1, further comprising changing means for changing the fixing conditions.

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