JP2009128885A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which a color sensor for detecting the color of a toner image already fixed is mounted, which is compact and inexpensive, and attains improvement in color detection accuracy. <P>SOLUTION: The image forming apparatus includes a secondary transfer roller 60a and a fixing device 61 which form a patch pattern 81 on a sheet P; a color sensor S1a which detects the formed patch pattern; a color sensor S1b which is arranged, at a position line-symmetric with the color sensor S1a with a center line L of the sheet P parallel with a conveying direction as a symmetry axis; and a control part which controls density of the toner image based on the read results by the color sensor S1a and the color sensor S1b. The patch pattern 81 is formed on the sheet P within the read range of the color sensor S1a, the patch pattern is not formed on the sheet P within the read range of the color sensor S1b, and the control part controls the density of the toner image formed on the sheet P, based on the difference between the read results by the color sensor S1a and the color sensor S1b. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more specifically, an electrophotographic image forming apparatus that develops a latent image formed on a photoreceptor with toner, transfers and fixes the toner image on a recording medium, and performs recording. Is related to the configuration of In particular, the present invention relates to an image recording apparatus having functions such as a copying machine and a printer, a multifunction apparatus having these functions, and a color image forming apparatus used as an output device such as 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.

  The disadvantage of the electrophotographic color image forming apparatus is that the color of the obtained image changes if there is a change in each part of the apparatus due to environmental changes or long-term use.

In order to overcome such disadvantages, as shown in Patent Document 1, the color of a print sample printed on a medium (recording medium) is detected by simple detection means, and the detection result is used to develop, Proposes to control settings such as transcription. Thus, a method for preventing color fluctuation (hereinafter abbreviated as a color sensor) is disclosed.
JP 2006-011205 A

  However, in the method disclosed in Patent Document 1, in order to improve the color detection accuracy by the color sensor without reducing the transportability of the recording medium, means for biasing the recording medium to the detection unit of the color sensor Is arranged. And when detecting, it energizes, otherwise the state which cancels | releases an energizing is provided.

  In order to realize these two states, it is necessary to use mechanical parts such as cams, gears, and solenoids, which makes it difficult to realize a color image forming apparatus having a color sensor at a small size and at low cost. It was.

  In addition, since the means for urging the recording medium hinders the conveyance of the recording medium, it is difficult to stably convey the recording medium which is weak in a high temperature and high humidity environment.

  The same problem is assumed even in the case of density / position shift by the density sensor regardless of the color sensor.

  The present invention is to provide an image forming apparatus equipped with a color sensor for detecting the color of a toner image after fixing, and capable of improving the color detection accuracy with a small size and low cost. Let it be 1 issue.

  It is a second object of the present invention to provide an image forming apparatus capable of improving density detection accuracy with a small size and low cost even when an unfixed toner image is detected.

  In order to solve the above problems, an image forming apparatus of the present invention has the following configuration.

  (1) Image forming means for forming a toner image on a recording medium, first reading means for reading the toner image formed on the recording medium, and a center line of the recording medium parallel to the transport direction as an axis of symmetry A second reading unit arranged in a line symmetry with the first reading unit; and a control unit for controlling the density of the toner image based on the reading results of the first reading unit and the second reading unit. The image forming unit forms a toner image on the recording medium in the reading range of the first reading unit, and the reading range of the second reading unit includes The toner image is not formed on the recording medium, and the control unit determines whether the toner image to be formed on the recording medium is based on a difference in reading results between the first reading unit and the second reading unit. To control the concentration An image forming apparatus symptoms.

  (2) Transfer means for transferring a toner image onto the intermediate transfer member, first reading means for reading the toner image transferred onto the intermediate transfer member, and the center line of the intermediate transfer member as a symmetry axis A second reading unit arranged at a position symmetrical with the first reading unit; a control unit for controlling the density of the toner image based on the reading result of the first reading unit and the second reading unit; The transfer unit transfers a toner image onto the intermediate transfer body in the reading range of the first reading unit, and the reading range of the second reading unit includes: The toner image is not transferred onto the intermediate transfer member, and the control unit transfers the toner image to the intermediate transfer member based on a difference in reading results between the first reading unit and the second reading unit. Characterized by controlling the concentration of That the image forming apparatus.

  The present invention can provide an image forming apparatus equipped with a color sensor for detecting the color of a toner image after fixing, and capable of improving the color detection accuracy with a small size and low cost.

  Further, even when an unfixed toner image is detected, it is possible to provide an image forming apparatus capable of improving density detection accuracy with a small size and low cost.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

  First, the entire image forming apparatus will be described with reference to FIG.

  FIG. 1 is a cross-sectional view schematically showing the case where the present invention is implemented in a full-color image forming apparatus having photosensitive drums as four image carriers.

  First, the operation in the normal print mode in which color (chromaticity) detection is not performed will be described.

  The illustrated image forming apparatus is a four-drum full color type color image forming apparatus. Here, 50Y, 50M, 50C, and 50K are photosensitive drums (image carriers), which are provided in image forming stations provided with developing materials (toners) of yellow, magenta, cyan, and black, respectively.

  On the surfaces (on the image carrier) of the photosensitive drums 50Y, 50M, 50C, and 50K, latent images are formed as follows from the corresponding laser scanner devices 51Y, 51M, 51C, and 51K (exposure means). The That is, a latent image is formed by exposure with laser light emitted based on image data from an image data input unit (not shown). Further, the toner image is formed by developing with toner, which is a developer of each color of yellow, magenta, cyan, and black.

  52 is an intermediate transfer belt, and the toner images of the respective colors formed by the photosensitive drums 50Y, 50M, 50C, and 50K are primarily transferred by the primary transfer rollers 40Y, 40M, 40C, and 40K. A sheet P as a recording medium is stacked on the paper feed cassette 53, fed by a paper feed roller 54, transported by a feed / retard roller pair 55, transport roller pairs 56, 57, and stopped driving. It is conveyed to the roller pair 59.

  After the skew is corrected by the registration roller pair 59, the sheet P is conveyed to the secondary transfer device 60, which is a secondary transfer unit, at a predetermined timing, and the toner image on the intermediate transfer belt 52 (on the intermediate transfer member). Is transcribed. Next, the toner image is fixed by being conveyed to the fixing device 61 (fixing means) by the secondary transfer roller 60a of the secondary transfer device 60 and the intermediate transfer belt 52 (intermediate transfer member).

  When FD (face-down) discharge is specified in which the image forming surface is discharged, the flapper 67 is moved by a control device (control means) and a drive device (drive means) (not shown). Thus, the sheet P that has passed through the fixing device 61 passes above the flapper 67, is conveyed to the conveyance roller pair 62, and is conveyed to the recording paper conveyance path 77. The sheet P transported to the recording paper transport path 77 is transported by the transport roller pair 68 and the paper discharge roller pair 63 and is discharged and stacked on the paper discharge tray 64 with the image forming surface facing down.

  In addition, when FU (face-up) paper discharge is specified with the image forming surface facing upward, the flapper 67 is moved by a control device and a drive device (not shown). As a result, the sheet P that has passed through the fixing device 61 passes under the flapper 67, is conveyed by the discharge roller pair 65, and is discharged and stacked on the discharge tray 66 with the image forming surface facing up. Reference numeral 70 denotes a conveyance roller pair.

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

  FIG. 2 shows a recording paper transport unit 100 including a color sensor S1 (first reading means, second reading means). This is a recording paper transport section in the recording paper transport path 77 after fixing in FIG. In the space formed by the plurality of guide ribs and the plurality of opposed guide ribs (not shown) in the direction of the upward arrow in FIG. The pair 68 is nipped and conveyed. Here, CR is a facing roller disposed facing the color sensor S1.

  FIG. 3 shows an enlarged view of the main part including the color sensor S1 unit.

  The color sensor S1 unit unit supports the color sensor S1 and is instructed to swing freely with respect to the recording paper transport unit 100. Then, a sensor folder 101 pressed toward the counter roller CR by a biasing member (not shown) is instructed to rotate freely to the sensor folder 101 and is driven to rotate with respect to the counter roller CR via the sheet P. It is comprised by the roller. R is a color sensor roller pair.

  Next, the operation in the test mode for detecting color will be described.

  An operation when the test mode is designated by an operation panel (not shown) on the printer or a personal computer connected to the printer will be described. This operation is also performed when a control unit (control means) (not shown) automatically performs the test mode based on detection results of changes in the environment, changes in each part of the apparatus, and the like. That is, a test pattern (patch) signal is generated from a signal generation circuit (not shown), and the surfaces of the photosensitive drums 50Y, 50M, 50C, and 50K are exposed by the laser light emitted based on the test pattern (patch) signal data, and the latent image is exposed. An image is formed.

  Thereafter, after the test pattern is formed on the intermediate transfer belt 52 by the same process as the operation in the normal print mode, the test pattern toner image is separately transferred onto the sheet P conveyed separately by the secondary transfer roller 60a (image forming means). (Toner image) is transferred. Thereafter, it is further conveyed to a fixing device 61 (image forming means), and the test pattern toner image is fixed on the recording sheet P. In this way, a test pattern toner image is formed on the sheet P.

FIG. 4 shows an installation state of patch patterns 81a, 81b, 81c (hereinafter also simply referred to as patch pattern 81) (toner image) formed on the sheet P, the color sensor S1, and the like. The color sensor S1 sequentially detects the patch pattern 81 formed on the P1 side, which is the surface on the sheet P, from the patch pattern 81a, and obtains the color of each patch pattern. The detected result is fed back to an image forming unit (not shown) to control the color of the toner image formed on the recording medium. Incidentally, the fact that the tint sensed by the color sensor is detecting the lightness L ^* includes the L ^* a ^* b ^*, to detect the shade by the color sensor that detects a concentration Sometimes.

  Thereafter, the sheet P transported by the transport roller pair 68 is transported by the paper discharge roller pair 63 and discharged and stacked on the paper discharge tray 64 with the patch forming surface facing down.

  Two color sensors S1 are arranged symmetrically with respect to the center of the sheet P with respect to the width direction (a direction perpendicular to the transport direction) and are equal to the transport direction of the sheet P. That is, two color sensors S1 are arranged at positions that are line-symmetric with respect to the center line L of the sheet P (a center line parallel to the transport direction) as the axis of symmetry. One side S1a (first reading means) of the color sensor S1 is arranged at a position facing the detection toner image (patch pattern 81) in the width direction of the sheet P. The patch pattern 81 is formed in the reading range of the color sensor S1a. On the other hand, the other S1b (second reading unit) of the color sensor S1 is arranged at a position not facing the detection toner image (patch pattern 81).

  FIG. 5 shows a sectional side view of the main part including the color sensor S1 unit.

  A part of the housing of the color sensor S1 constitutes a guide that contacts the sheet P. Inside the color sensor S 1, an LED 201 as a light emitting 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.

  Here, it demonstrates using the graph of FIG. FIG. 6 shows the time obtained when the sheet P on which the detection toner image (patch pattern 81) is printed is held between the conveyance roller pair 62 and the conveyance roller pair 68 and passes over the color sensor S1. Stay on the axis. The amount of reflected light detected by the photodiode 202 disposed in the color sensor S1a and the photodiode 202 disposed in the color sensor S1b is plotted on the vertical axis.

  The amount of reflected light Va (reading result) detected by the photodiode 202 arranged in the color sensor S1a is as follows. That is, as a result of superimposing the reflected light amount corresponding to the amount of the toner image (patch pattern 81) and the minute variation in the distance between the sheet P and the photodiode 202, that is, the minute variation in the reflected light amount due to the sheet P fluttering. is there.

  The amount of reflected light Vb (read result) detected by the photodiode 202 arranged in the color sensor S1b is a minute variation in the distance between the sheet P and the photodiode 202, that is, a minute amount of reflected light due to the fluttering of the sheet P. This is the result of detecting the fluctuation.

  The reflected light amount detection positions of the color sensor S1a and the color sensor S1b and the arrangement of the conveyance roller pair 62 and the conveyance roller pair 68 are arranged symmetrically with respect to the center line L of the sheet P. For this reason, the flapping of the sheet P is equal at the reflected light amount detection positions of the color sensors S1a and S1b.

  That is, the amount of reflected light corresponding to the applied amount of the toner image (patch pattern 81) excluding the influence due to the flapping of the sheet P is Va-Vb.

  As described above, according to the present exemplary embodiment, a color sensor system that can detect the amount of reflected light according to the toner image loading amount without interfering with the conveyance of the sheet P without the influence of the sheet P with a simple configuration. Is possible. Therefore, the present invention provides a small, low-cost and good transport performance color image forming apparatus in which the color of an image obtained is stable regardless of environmental changes and fluctuations in each part of the apparatus. The objective is achieved.

  Since the color is detected by the sheet P after fixing, the color on the finally obtained sheet P used by the user is stabilized.

  If the detection pattern of the toner image is changed to a pattern suitable for detecting the position of the toner image by the sensor system described in this embodiment, the influence of the minute flutter of the recording medium is similarly eliminated with a simple configuration. The position of the toner image on the sheet P can be detected. It is possible to control the toner image position by controlling the latent image position (exposure position) on the photosensitive drums 50Y, 50M, 50C, and 50K using the toner image position information obtained by the detection. As a result, the object of the present invention is achieved, which is to provide a small and low-cost color image forming apparatus in which the color shift of the obtained image is small regardless of changes in each part of the apparatus due to environmental changes or long-term use. . Since the toner image position is detected on the fixed sheet P, color misregistration in the finally obtained recording medium used by the user can be reduced.

  The present invention is also applied to a case where color is detected and a toner image is controlled by a toner image transferred to a sheet other than the sheet P that is a finally obtained recording medium.

  D1 in FIG. 1 described in the first embodiment is a density sensor for detecting the color of the toner image transferred onto the intermediate transfer belt 52 by the primary transfer rollers 40Y, 40M, 40C, and 40K (transfer means). . Note that the full-color image forming apparatus of the present embodiment is the same as the configuration of FIG. 1 described in the first embodiment, and therefore the description thereof is omitted and the same reference numerals are used.

  FIG. 7 shows an enlarged side sectional view in the vicinity of the density sensor D1, the intermediate transfer belt 52, and the secondary transfer roller 60a. The intermediate transfer belt 52 is stretched by three rollers, and a density sensor D1 is disposed in the vicinity of one of them. The density sensor D1 is arranged at a position that is equal to the conveyance direction of the intermediate transfer belt 52 (arrow in the figure) and is different in a direction orthogonal to the conveyance direction. That is, two intermediate transfer belts 52 are arranged at symmetrical positions with the center line as the axis of symmetry. The density sensor D1a (first reading unit) is arranged at a position facing the patch pattern 80 (toner image), and the density sensor D1b (second reading unit) is arranged at a position not facing the patch pattern 80. ing.

  FIG. 8 is an upper conceptual view showing the arrangement of the density sensor D1 and the patch pattern 80 (80a, 80b, 80c...).

  The density sensor D1a detects the amount of reflected light including the detection toner image (patch pattern) 80 and the minute transfer of the intermediate transfer belt 52, and the density sensor D1b detects the amount of reflected light only by the minute fluctuation of the intermediate transfer belt 52. To do. Then, by calculating the difference, the amount of light reflected by the toner image (patch pattern) 80 can be accurately read.

  As described above, according to this embodiment, it is possible to realize a density sensor system that can detect the amount of reflected light according to the toner image loading amount with a simple configuration and excluding the influence of minute fluctuations of the intermediate transfer belt 52. Is possible. As a result, the object of the present invention is achieved, which is to provide a color image forming apparatus that is stable and has a small color at low cost, regardless of changes in the environment due to environmental changes or long-term use of the apparatus. The

  In addition, since the sheet P which is the recording medium finally obtained at the time of color detection is not used, the sheet P finally obtained by the user can be used only for image formation intended by the user.

  If the detection pattern of the toner image is changed to a pattern suitable for detecting the transfer position of the toner image by the sensor system described in this embodiment, the influence of the minute flutter of the intermediate transfer belt 52 can be similarly reduced. The transfer position of the toner image can be detected. It is possible to control the toner image position by controlling the latent image position (exposure position) on the photosensitive drums 50Y, 50M, 50C, and 50K using the toner image position information obtained by the detection. As a result, the object of the present invention is achieved, which is to provide a small and low-cost color image forming apparatus in which the color shift of the obtained image is small regardless of changes in each part of the apparatus due to environmental changes or long-term use. .

  Since the sheet P finally obtained at the time of toner image position detection is not used, the sheet P finally obtained by the user can be used only for image formation intended by the user.

Side sectional conceptual diagram showing the entire color image forming apparatus Perspective view showing the configuration of the recording paper transport unit 1 is a perspective view illustrating a configuration of a color sensor unit according to Embodiment 1. FIG. An upper conceptual diagram showing a color sensor and a patch pattern arrangement according to the first embodiment. Side sectional conceptual diagram showing color sensor and patch pattern arrangement according to embodiment 1 Plot diagram of time and reflected light amount when color detection is performed by the color sensor according to the first embodiment An upper conceptual diagram showing a density sensor and a patch pattern arrangement according to the second embodiment. An upper conceptual diagram showing a density sensor and a patch pattern arrangement according to the second embodiment.

Explanation of symbols

40Y, 40M, 40C, 40K Primary transfer roller (transfer means)
50Y, 50M, 50C, 50K Photosensitive drum (image carrier)
51Y, 51M, 51C, 51K Laser scanner device (exposure means)
52 Intermediate transfer belt (intermediate transfer member)
53 Feeding cassette 54 Feeding roller 55 Feed / retard rollers 56, 57, 70 Conveying roller pair 59 Registration roller pair 60 Secondary transfer unit (secondary transfer device)
60a Secondary transfer roller (transfer means) (image forming means)
61 Fixing device (image forming means)
62, 68 Transport roller pair 63, 65 Paper discharge roller pair 64, 66 Paper discharge tray 67 Flapper 77 Recording paper transport path 81 Density patch 100 Transport unit 101 Sensor folder 201 LED (light emitting element)
202 Photodiode (light receiving element)
CR opposing roller D1 density sensor D1a density sensor (first reading means)
D1b Density sensor (second reading means)
P sheet (recording medium)
R color sensor roller pair S1 color sensor S1a color sensor (first reading means)
S1b color sensor (second reading means)

Claims (3)

An image forming means for forming a toner image on a recording medium; a first reading means for reading the toner image formed on the recording medium; and a first axis with a center line of the recording medium parallel to the transport direction as an axis of symmetry. Second reading means arranged in a line symmetry with the reading means, and a control means for controlling the density of the toner image based on the reading result of the first reading means and the second reading means. An image forming apparatus,
The image forming unit forms a toner image on the recording medium in a reading range of the first reading unit, and forms a toner image on the recording medium in a reading range of the second reading unit. Do not do,
The image forming apparatus according to claim 1, wherein the control unit controls a density of a toner image formed on a recording medium based on a difference between reading results obtained by the first reading unit and the second reading unit. A transfer unit that transfers a toner image onto the intermediate transfer member; a first reading unit that reads the toner image transferred onto the intermediate transfer member; and the first line with the center line of the intermediate transfer member as a symmetry axis. An image comprising: a second reading unit arranged in a line symmetry with the reading unit; and a control unit for controlling the density of the toner image based on the reading result of the first reading unit and the second reading unit. A forming device,
The transfer unit transfers a toner image onto the intermediate transfer member within a reading range of the first reading unit, and a toner image onto the intermediate transfer member within a reading range of the second reading unit. Do not transcribe,
The image forming apparatus according to claim 1, wherein the control unit controls a density of a toner image transferred to the intermediate transfer body based on a difference between reading results obtained by the first reading unit and the second reading unit. The image forming apparatus according to claim 1, wherein
Exposure means for forming a latent image on the image carrier,
The image forming apparatus according to claim 1, wherein the control unit controls an exposure position of the exposure unit based on a difference between reading results of the first reading unit and the second reading unit.

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