JP2006030736A - Color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized and low-cost color image forming apparatus which has less color variance and has a high image quality independently of media by realizing and mounting a color sensor and a media sensor with same sensor configurations. <P>SOLUTION: A detection means which detects a density or chromaticity of a patch array formed on a recording medium, a contact surface to the recording medium, which is disposed in a part of the detection means, an energizing means which energizes the recording medium to the contact surface when carrying the recording medium and is capable of varying an energizing force to at least two stages, and a recording medium carrying means which is placed above the detection means and carries the recording medium in such direction that the recording medium is carried away from the contact surface to the recording medium, which is disposed in a part of the detection means, are provided in a recording medium carrying path after fixing of the recording medium. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a configuration of an electrophotographic color image forming apparatus that develops a latent image formed on a photoreceptor with toner, transfers the toner onto a recording medium, and fixes it to perform recording. More particularly, the present invention relates to a color image recording apparatus having functions such as a copying machine and a printer, a color image forming apparatus used as an output device such as a multifunction machine having such functions and a workstation.

  In recent years, color printers are often connected to a plurality of host computers via a network and commonly used for small lot commercial printing (POD). As a typical color printer, there is an electrophotographic color image forming apparatus with low running cost and few failures.

  Disadvantages of electrophotographic color image forming devices are that the color of the resulting image will fluctuate if there is a change in the environment due to environmental changes or long-term use, and the optimum image forming conditions may vary depending on the media used. May be different.

  In order to overcome the first disadvantage, the color variation of the print sample printed on the media is detected by simple detection means, and the settings such as development and transfer are controlled using the detection result. There has been proposed a method (hereinafter abbreviated as a color sensor) for preventing the above-described problem.

  In order to overcome the second disadvantage, as shown in Patent Document 1, the thickness of the medium is detected by a simple detection means, and settings such as transfer and fixing are changed according to the detected thickness of the medium. Thus, there is disclosed a method (hereinafter, abbreviated as a media sensor) for selecting an optimal image forming condition for a medium to be automatically used without manual setting by a user.

JP 2002-182518 A

  In order to overcome the above two disadvantages at the same time, if the methods proposed so far are realized at the same time, it is necessary to separately provide a necessary configuration for each, which makes it difficult to reduce the size and cost of the color image forming apparatus. It was.

  The present invention has been made in view of the above problems, and the object of the present invention is that the color does not fluctuate regardless of changes in the environment or fluctuations in each part of the apparatus caused by long-term use, and the thickness of the media used changes. However, an object of the present invention is to provide a small-sized and low-cost color image forming apparatus capable of forming an image under optimum conditions.

  In order to achieve the above object, according to the first aspect of the present invention, a toner image is formed by using at least one exposure device and at least one electrophotographic process unit, and after the toner image is transferred onto the recording medium, the toner image is transferred onto the recording medium. Patch array formed on a recording medium in a recording medium conveyance path after fixing the recording medium in a color image forming apparatus for fixing the toner image to the recording medium by applying desired heat and pressure to the toner image using a fixing device Detecting means for detecting the density or chromaticity of the recording medium; a contact surface of the recording medium disposed in a part of the detecting means; and urging the recording medium against the contact surface when the recording medium is conveyed; and The direction in which the recording medium moves away from the contact surface between the urging means whose urging force is variable in at least two stages and the recording medium located upstream of the detecting means and disposed in a part of the detecting means It characterized by having a recording medium conveying means for conveying the recording medium.

  According to a second aspect of the present invention, in the first aspect of the present invention, after the leading end of the recording medium passes through the contact surface of the recording medium arranged at a part of the detection means and the contact position of the biasing means, The biasing force of the biasing means is increased.

  According to a third aspect of the present invention, in the first aspect of the present invention, the biasing means has a light reflectance lower than that of the recording medium.

  According to the first aspect of the present invention, the color does not fluctuate regardless of the environmental changes and the fluctuations of each part of the apparatus caused by long-term use, and image formation can be performed under optimum conditions even if the thickness of the medium to be used changes. A small and low-cost color image forming apparatus can be provided.

  According to the second aspect of the present invention, even when the recording medium is a thin paper with low stiffness and the surface has local irregularities, jamming can be prevented and color detection can be performed accurately. Can be performed.

  Further, according to the third aspect of the present invention, since the leading edge of the recording medium can be detected by the sensor sharing the color sensor and the media sensor, the sensor for detecting the leading edge of the recording medium that has been conventionally required can be eliminated. It becomes possible.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

<Embodiment 1>
First, the entire color image forming apparatus will be described with reference to FIG.

FIG. 1 is a sectional view showing an outline when the present invention is implemented in a full-color image forming apparatus having four image carriers.
The color image forming apparatus shown in FIG. 1 includes four photosensitive drums 1 (1a, 1b, 1c, 1d), and the photosensitive drum 1 surface is sequentially arranged around each photosensitive drum 1 in accordance with the rotation direction. Charging means 2 (2a, 2b, 2c, 2d) for uniformly charging, and exposure means 3 (3a, 3b, 3c, 3c, 3c, 2c) for forming an electrostatic latent image on the photosensitive drum 1 by irradiating a laser beam based on image information 3d), developing means 4 (4a, 4b, 4c, 4d) for attaching toner to the electrostatic latent image to visualize it, and transfer means for transferring the toner image on the photosensitive drum 1 onto a transfer material (transfer) Roller) 5 (5a, 5b, 5c, 5d), cleaning means 6 (6a, 6b, 6c, 6d) for removing the post-transfer toner remaining on the surface of the photosensitive drum 1 after transfer, and the like are provided. Is configured. Here, the photosensitive drum 1, the charging unit 2, the developing unit 4, and the cleaning unit 6 for removing the toner are integrally formed as a cartridge to form a process cartridge 7 (7 a, 7 b, 7 c, 7 d).

  The recording medium S fed from the feeding unit 8 is conveyed to the image forming unit by a conveying unit 9 constituted by a conveying belt, and each color toner image is sequentially transferred to record a color image, and then fixed. The image is fixed by the means 10 and is discharged to the discharge unit 13 by the discharge roller pair 11, 12. In the case of double-sided printing, before the recording medium S is fixed by the fixing unit 10 and discharged by the paper discharge rollers 11 and 12, the paper discharge rollers 11 and 12 are reversed to enter the double-sided conveyance path 15. It is conveyed (arrow A direction). The recording medium S conveyed to the double-sided conveyance path 15 passes through the oblique feeding roller 16 on the front surface of the apparatus main body, and is conveyed vertically downward to the U-turn roller 17, and the image forming unit is formed by the U-turn roller 17 and the registration roller 8 d. It is conveyed to.

  Next, an embodiment according to claim 1 of the present invention will be described in detail with reference to FIG.

  The resist shutter 14 mounted so as to freely rotate with respect to the axis of the resist roller 8d is counterclockwise by a torsion spring (not shown), that is, a force that gives a resistance force when the front end of the recording medium comes into contact. It is hanging. When the leading edge of the recording medium conveyed by the intermediate conveying roller 8c2 is abutted against the registration shutter 14, the registration shutter 14 rotates clockwise, and a skew is corrected by applying a resistance force to the leading edge of the recording medium. The timing at which the leading edge of the recording medium S arrives is detected by the flag 14a provided on the registration shutter 14 shielding the photo interrupter 19.

  In accordance with the detection timing, scanners 3a, 3b, 3c, and 3d (not shown) irradiate the photosensitive drums 1a, 1b, 1c, and 1d to form an electrostatic latent image. Toner is developed on the electrostatic image to form a toner image.

  The recording medium is conveyed by the registration roller 8d, enters the nip of the adsorption roller 9f, is electrostatically adsorbed to the conveyance belt 9a, and is conveyed. When the leading edge of the recording medium S reaches the nip between the photosensitive drum 1a and the transfer roller Tp1, the toner image formed on the photosensitive drum 1a is transferred to the recording medium S.

  In the present embodiment, a sensor 20 as a detection unit is disposed in the conveyance path of the recording medium. A guide member 21 that applies a biasing force toward the recording medium S toward the recording medium S is disposed on the opposite side of the sensor 20.

  The detailed configuration of the sensor 20 and the principle of detecting the thickness of the recording medium S will be described with reference to FIGS.

  A part of the housing of the sensor 20 constitutes a guide that contacts the recording medium S. Inside the sensor 20, an LED 201 as an issuing element and a photodiode 202 as a light receiving element are arranged, and the amount of light reflected by the LED 201 can be detected by the photodiode 202.

  FIG. 3 shows a state immediately after the leading edge of the recording paper S passes through the focal point P of the LED 201 and the photodiode 202.

  The recording paper S is conveyed in the D direction where the sensor 20 moves away by the registration roller 8d and the counter driven roller 8e, but is forcibly conveyed in the C direction along the guide portion of the sensor 20 by the biasing guide member 21.

  The urging guide member 21 is supported to freely rotate about a fulcrum 21a, and presses the recording medium S by the pressing force F1 by the compression spring 22. The other of the compression springs 22 is supported by a cam follower 23. The cam follower 23 is supported so as to freely rotate about a fulcrum 23 a and rotates according to the operation of the cam 24.

  The cam 24 is rotatably supported about a fulcrum 24a, and can be set to two rotational phases different from each other by 180 degrees by a driving means (not shown).

  FIG. 4 shows a state in which a predetermined time T1 has elapsed after the leading edge of the recording medium S passes through the focal point P of the LED 201 and the photodiode 202, and the cam 24 is rotated 180 degrees by driving means (not shown).

  Since the effective length of the compression spring 22 is shorter than the state shown in FIG. 3, the recording medium S is regulated via the biasing guide member 21 by a pressing force F2 larger than F1.

  FIG. 5 shows a plot of the time obtained when the operation described with reference to FIGS. 3 and 4 and the amount of reflected light detected by the photodiode 202 are performed when the recording medium S is thin paper.

  Even if the force for pressing the recording medium S through the biasing guide member 21 increases from F1 to F2 around time T1, neither the average value of the reflected light amount nor the size of the variation changes. This is because when the recording medium S is thin thin paper, it is stably conveyed along the guide portion of the sensor 20 with a weak pressing force F1.

  FIG. 6 shows a plot of the time obtained when the operation described with reference to FIGS. 3 and 4 and the amount of reflected light detected by the photodiode 202 are performed when the recording medium S is thick paper.

  When the force pressing the recording medium S via the biasing guide member 21 increases from F1 to F2 around time T1, the average value of the reflected light amount increases and the variation becomes smaller. This is because, when the recording medium S is a thick cardboard, the sheet 20 is not stably conveyed along the guide portion of the sensor 20 with a weak pressing force F1, whereas the sensor 20 is stably conveyed with a strong pressing force F2. It is because it is conveyed along a guide part.

  As described above, since the thickness of the recording medium S can be detected before image formation, it is possible to perform image formation under optimum conditions corresponding to the thickness of the recording medium S.

  For example, in the case of thick paper, it is often performed to secure a good fixing property by setting the fixing temperature higher than that of the thin paper or by lowering the conveying speed.

  A toner image pattern for color detection is also formed under optimum conditions according to the thickness of the recording medium S. When the recording medium S on which the toner image pattern is printed passes through the double-sided conveyance path 15 and reaches the sensor 20, it becomes possible to detect color.

  When color detection is performed, if the recording medium S is pressed against the guide portion of the sensor 20 via the biasing guide means 21 with a pressing force corresponding to the thickness of the recording medium S that has already been detected, the recording medium S is detected. Therefore, it is possible to detect the color with high accuracy with little variation in the amount of reflected light due to the fluttering of the image, and to prevent the recording medium S from being jammed due to an excessively large pressing force.

  FIG. 7 shows how to detect the color of the toner image K printed on a thin recording medium with a low stiffness, and FIG. 8 shows how to detect the color of a toner image K printed on a thick recording medium with a low stiffness. Show.

  Since the principle of color detection is disclosed in Japanese Patent Laid-Open No. 9-171279, the details are omitted here.

  FIG. 9 is a flowchart showing a sequence for detecting the thickness of the recording medium S and the color detection based on the toner image pattern printed on the recording medium S as described above.

  As described above, according to the present embodiment, the color sensor and the media sensor are realized and mounted with the same sensor configuration, so that it can be obtained regardless of changes in each part of the apparatus due to environmental changes or long-term use. The object of the present invention is to provide a small-sized and low-cost color image forming apparatus capable of forming an image under optimum image forming conditions depending on the medium to be used.

<Embodiment 2>
Next, a method for accurately detecting the color using the sensor 20 according to the present invention will be described even when the recording medium S is thin paper with low stiffness but has local irregularities on the surface.

  It is detected by the time and the photodiode 202 obtained when the recording medium S, which is a thin paper with a low back, is passed through the recording medium S having a local unevenness on the surface and the operation described with reference to FIGS. 3 and 4 is performed. A plot of the amount of reflected light is shown in FIG.

  When the force that presses the recording medium S through the biasing guide member 21 increases from F1 to F2 around time T1, the average value of the reflected light amount does not change, but there are no locally uneven portions. This is because unevenness locally present on the surface of the recording medium S cannot be flattened with a weak pressing force F1, but can be flattened with a strong pressing force F2.

  In this case, after the leading end of the recording medium S passes through the contact position between the guide portion of the sensor 20 and the biasing guide member 21, the leading end of the recording medium S becomes the contact position by increasing the biasing force of the biasing means. It is possible to prevent jamming caused by being caught and to detect color with high accuracy.

  FIG. 11 shows a state when the leading edge of the recording medium S reaches the registration shutter 14 when performing color detection. The flag 14a provided on the registration shutter 14 shields the photo interrupter 17, thereby detecting the timing when the leading edge of the recording medium S reaches the nip position between the registration roller 8d and the counter driven roller 8e.

  After a predetermined time from the detection timing, if the cam 24 is rotated 180 degrees after the leading end of the recording medium S passes through the contact position Q between the guide portion of the sensor 20 and the biasing guide member 21, the biasing guide member 21 is interposed. And a strong pressing force F2 can be applied to the recording medium, and unevenness that exists locally can be flattened.

  As described above, according to the present embodiment, even when the recording medium S is a thin paper with low stiffness but has local unevenness on the surface, the sensor 20 according to the present invention is used to accurately color. Detection can be performed.

<Embodiment 3>
Next, a method for detecting the leading end position of the recording medium S using the sensor 20 according to the present invention will be described.

  When the biasing guide member 21 has a configuration in which the light reflectance of the recording medium S is low, and the thin paper with the low waist and the thick paper with the low waist are passed, the operation described with reference to FIGS. 3 and 4 is performed. 13 and FIG. 14 show plots of the time obtained and the amount of reflected light detected by the photodiode 202, respectively.

  13 and 14, that is, the timing at which the amount of reflected light detected by the photodiode 202 reaches a certain threshold value VS may be regarded as the timing at which the leading edge of the recording medium S passes through the focal positions of the LED 201 and the photodiode 202. Is possible.

  Therefore, a dedicated sensor for detecting the front end of the recording medium S, for example, the photo interrupter 19 is not required.

1 is a side sectional view showing a schematic configuration of a color image forming apparatus according to the present invention. 2 is a side sectional view showing a detailed configuration in the vicinity of a sensor of the color image forming apparatus according to Embodiment 1 of the present invention. FIG. It is a sectional side view which shows a mode that media detection is performed with the sensor which concerns on Embodiment 1 of this invention. It is a sectional side view which shows a mode that media detection is performed with the sensor which concerns on Embodiment 1 of this invention. It is a plot of time and reflected light amount when media detection is performed by the sensor according to the first embodiment of the present invention. It is a plot of time and reflected light amount when media detection is performed by the sensor according to the first embodiment of the present invention. It is a sectional side view which shows a mode that color detection is performed with the sensor which concerns on Embodiment 1 of this invention. It is a sectional side view which shows a mode that color detection is performed with the sensor which concerns on Embodiment 1 of this invention. It is a flowchart which shows the sequence which performs a media detection and a color detection with the sensor which concerns on Embodiment 1 of this invention. It is a plot of time and reflected light amount when media detection is performed by the sensor according to Embodiment 2 of the present invention. It is a sectional side view which shows a mode that color detection is performed with the sensor which concerns on Embodiment 2 of this invention. It is a sectional side view which shows a mode that color detection is performed with the sensor which concerns on Embodiment 2 of this invention. It is a plot of time and amount of reflected light when media detection is performed by the sensor according to Embodiment 3 of the present invention. It is a plot of time and amount of reflected light when media detection is performed by the sensor according to Embodiment 3 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a-1d Photosensitive drum 2a-2d Charging device 3a-3d Scanner unit 4a-4d Developing device 5 Transfer device 6a-6d Cleaning means 7a-7d Process cartridge 8d Registration roller 9 Electrostatic conveyance belt unit 10 Fixing device 12a-12d Transfer Roller 13 Drive roller 14 Registration shutter 15 Double-sided conveyance path 17 U-turn roller 19 Photo interrupter 20 Sensor 21 Energizing means 22 Compression spring 23 Cam follower 24 Cam 201 LED
202 photodiode

Claims (3)

A toner image is formed using at least one exposure device and at least one electrophotographic process unit, and after transferring the toner image onto the recording medium, a desired heat and pressure are applied to the toner image on the recording medium using a fixing device. In a color image forming apparatus for fixing a toner image to a recording medium by
Detection means for detecting the density or chromaticity of a patch array formed on the recording medium in the recording medium conveyance path after fixing the recording medium, a contact surface between the recording medium arranged in a part of the detection means, and recording An urging means for urging the recording medium with respect to the contact surface when the medium is conveyed, and an urging force that is variable in at least two stages; an upstream side of the detecting means; and the detecting means A color image forming apparatus comprising: a recording medium conveying unit that conveys a recording medium in a direction away from a contact surface with a recording medium arranged in part.   The urging force of the urging unit is increased after the leading end of the recording medium passes through a contact surface of the urging unit with a contact surface with a recording medium arranged in a part of the detecting unit. Item 2. A color image forming apparatus according to Item 1.   2. A color image forming apparatus according to claim 1, wherein said urging means has a light reflectance lower than that of the recording medium.

Images