JP2006143420A - Color image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve patch reading accuracy on a recording medium by a detecting means, without hindering a carry of the recording medium. <P>SOLUTION: This color image forming device fixes a toner image to the recording medium by imparting desired heat and pressure to the toner image on the recording medium by using a fixing device, after transferring the toner image on the recording medium, by forming the toner image by using one or more of exposure devices and one or more of electrophotographic process units. A recording medium carrying passage after fixing the recording medium, has a means for detecting the concentration or chromaticity of a patch row formed on the recording medium, a contact surface with the recording medium arranged in a part of the detecting means, and an energizing means for energizing the recording medium to the contact surface when carrying the recording medium; and can vary force in a plurality of stages for sandwiching the recording medium between the contact surface and the energizing means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrophotographic color image forming apparatus in which a latent image formed on a photosensitive member is developed with toner, transferred onto a recording medium, and fixed to perform recording. In particular, the present invention relates to an 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 these functions and a workstation.

  A plurality of electrophotographic process units having a charging device and a developing device arranged around the photosensitive member are juxtaposed in the device, and an optical image is formed on the surface of the photosensitive member in each process unit by an exposure device using laser, LED light, or the like. A latent image is formed on the surface of the photoconductor by image formation, and the latent image is visualized using toner by a developing device, and then sequentially transferred onto an intermediate transfer belt, and then fixed on a recording medium in a batch to obtain a color image. In recent years, an image forming apparatus that forms the image has been put into practical use.

  Further, a color image forming apparatus employing an electrophotographic system such as a color printer or a color copying machine is required to have a higher output image quality.

  However, in the color image forming apparatus, the color of the obtained image may fluctuate if there are fluctuations in each part of the apparatus due to environmental changes or long-term use. In particular, in the case of an electrophotographic color image forming apparatus, even a slight environmental change may cause a color change, and there is a risk of losing the color balance. Therefore, means for stably reproducing the color and the gradation of the color is provided. Have. For example, for each color toner, the absolute humidity measured by a temperature / humidity sensor having gradation correction means such as a look-up table (LUT) and several kinds of exposure conditions and development biases depending on the absolute humidity. Based on the above, the process conditions at that time and the optimum value for gradation correction are selected.

  In addition, a density detection toner patch is formed on the intermediate transfer member, the photosensitive member, etc. with a single color toner so that a constant color and gradation of the color can be obtained even if fluctuations in each part of the apparatus occur. The density of an unfixed single color toner patch is detected by a density detection sensor for unfixed toner (hereinafter referred to as a density sensor), and the detection result is fed back to process conditions such as exposure amount and development bias, and to gradation correction means such as LUT. By performing the density control by multiplying, a stable color and color gradation are obtained.

  However, density control using the density sensor detects patches by forming a patch on an intermediate transfer member, a photosensitive drum, or the like. Not controlling. The color balance also changes depending on the transfer efficiency in transferring the toner image to the recording medium, and heating and pressurization by fixing. This change cannot be dealt with by density control using the density sensor.

  Therefore, cyan (C), magenta (M), yellow (Y), and black (K) single-color gradation patches or C, M, and Y mixed-color patches are formed on the recording medium, and are fixed on the recording medium after fixing. A color image forming apparatus in which a sensor (hereinafter referred to as a color sensor) for detecting the density or chromaticity of the patch is installed.

  In the measurement by the conventional color sensor, there is one in which a conveyance guide is provided in order to suppress the flutter of the recording medium in the measurement unit by the color sensor. This conveyance guide suppresses the fluttering of the recording medium, and suppresses sensor reading errors due to variations in the distance between the sensor and the recording medium and fluctuations in the inclination of the recording medium due to the fluttering (see Patent Document 1).

  In these color image forming apparatuses, the final output formed on the recording medium is fed back to the calibration table for correcting the exposure amount of the image forming unit, the process conditions, and the density-gradation characteristics. Image density or chromaticity can be controlled. Although it is possible to detect the output image of the color image forming apparatus with an external image reading device or a densitometer / chromaticity meter and perform the same control, this method completes the control within the color image forming apparatus. Is excellent.

JP-A-11-316476

  However, in the example described in Patent Document 1 (Japanese Patent Application Laid-Open No. 11-316476), the recording medium conveyance guide in the sensor measurement unit is fixed, and the recording medium is conveyed into a gap between the pair of conveyance guides to cause a flutter. Therefore, depending on the recording medium, there is a possibility that the suppression of the flutter may be insufficient, and there is room for the fluttering of the gap of the transport guide, which affects the sensing accuracy.

  Further, in the recording medium conveyance path after the toner is fixed to the recording medium, a contact surface with the recording medium arranged in a part of the detection means, and an urging means for urging the recording medium against the contact surface In the meantime, it has been confirmed that the force required to hold the recording medium and suppress the fluttering is small when the recording medium is thin and large when the recording medium is thick.

  However, it has also been confirmed that if the force for pinching the recording medium is too large, the conveyance of the recording medium is hindered, and the smaller the thickness of the recording medium, the smaller the force that can be nipped without hindering the conveyance. For this reason, if a strong clamping force is applied to suppress the fluttering of the recording medium, conveyance of the thin recording medium is hindered. Therefore, in order to perform sensing with high accuracy without disturbing the conveyance of the recording medium, it is conceivable to take measures according to the type and thickness of the recording medium. For this reason, if a strong clamping force is applied to suppress the fluttering of the recording medium, conveyance of the thin recording medium is hindered. Therefore, in order to perform sensing with high accuracy without hindering the conveyance of the recording medium, it is conceivable to take measures according to the type and thickness of the recording medium (see FIG. 12).

  According to the present invention, when a recording medium is transported in a recording medium transport path after fixing the recording medium, a contact surface with a recording medium disposed in a part of the detection unit and the recording medium are urged against the contact surface. The urging means is provided, and the force for clamping the recording medium between the contact surface and the urging means is variable in a plurality of stages, so that the recording medium is not disturbed by the detection means on the recording medium. The purpose is to improve the patch reading accuracy.

  In order to achieve the above object, according to the first aspect of the present invention, a toner image is formed using one or more exposure apparatuses and one or more electrophotographic process units, the toner image is transferred onto a recording medium, and then recorded. A color image forming apparatus for fixing a toner image to a recording medium by applying a desired heat and pressure to the toner image on the medium by using a fixing device, wherein the toner image is fixed on the recording medium on the recording medium conveyance path after fixing the recording medium. A means for detecting the density or chromaticity of the formed patch array, a contact surface of the recording medium disposed in a part of the detection means, and the recording medium is attached to the contact surface when the recording medium is transported. There is provided an urging means for urging, and a force for sandwiching the recording medium between the contact surface and the urging means is variable in a plurality of steps.

  According to a second aspect of the present invention, in the first aspect of the present invention, the contact surface with the recording medium disposed at a part of the detecting means is a recording medium conveying roller disposed upstream and downstream of the contact surface. It is characterized by being disposed in a curved recording medium conveyance path.

  According to a third aspect of the present invention, in the first aspect of the present invention, the urging means has a flat surface that contacts the recording medium during conveyance, and the flat surface is formed substantially parallel to the recording medium during conveyance. It is characterized by being.

  The invention according to claim 4 is the invention according to claim 1 or 3, wherein, in the biasing means, the contact portion with the recording medium has a rib shape formed substantially parallel to the recording medium conveyance direction. It is characterized by.

  According to a fifth aspect of the present invention, in the first aspect of the present invention, an outer peripheral surface of a roller rotatably supported as the urging unit is used, and a contact surface with a recording medium disposed at a part of the detection unit. And a force for sandwiching the recording medium between the roller and the outer peripheral surface of the roller.

  According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the outer peripheral surface of the roller supported so as to be rotationally driven is used as the urging unit, and contact with a recording medium disposed at a part of the detecting unit is performed. It is configured to apply a force for sandwiching the recording medium between the surface and the outer peripheral surface of the roller.

  According to a seventh aspect of the present invention, in the first aspect of the present invention, the mechanism for varying the force for sandwiching the recording medium between the contact surface and the biasing means is fixed on the contact surface side, and the attachment The recording medium is clamped by making the biasing means side movable.

  According to an eighth aspect of the present invention, in the first aspect of the present invention, the mechanism for varying the force for sandwiching the recording medium between the contact surface and the biasing means is fixed on the biasing means side, The recording medium is sandwiched by making the contact surface side movable.

  According to a ninth aspect of the present invention, in the first aspect of the present invention, the mechanism for changing the force for sandwiching the recording medium between the contact surface and the biasing means is the contact surface side and the biasing means side. Both of them are movable so that the recording medium is sandwiched.

  According to a tenth aspect of the present invention, in the first aspect of the present invention, the mechanism for changing the force for sandwiching the recording medium between the contact surface and the urging unit is a driving device installed in the image forming apparatus. The force for clamping the recording medium between the contact surface and the urging means is made variable by the power transmitted from.

  According to an eleventh aspect of the present invention, in the invention according to any one of the first to tenth aspects, a plurality of stages of setting of the force for holding the recording medium between the contact surface and the biasing means are prepared. Is configured to be able to indicate the magnitude of the force for holding the recording medium.

  A twelfth aspect of the invention is the invention according to any one of the first to tenth aspects, further comprising a detection unit that detects the type of the recording medium in the recording medium conveyance path, and the gap between the contact surface and the biasing unit. Thus, the change of the force for holding the recording medium is automatically set in the image forming apparatus based on the information by the means for detecting the type of the recording medium.

  A thirteenth aspect of the present invention is the method according to any one of the first to tenth aspects, wherein the recording medium conveyance path includes a detecting unit that detects the type of the recording medium, and the gap between the contact surface and the biasing unit. Thus, the user can select the change in the force for holding the recording medium based on information by the means for detecting the type of the recording medium.

  According to the first aspect of the present invention, the recording medium by the detection unit is not hindered by preventing the conveyance of the recording medium by changing the force for clamping the recording medium between the contact surface and the biasing unit in a plurality of stages. The above patch reading accuracy can be improved.

  According to the second aspect of the present invention, it is possible to arrange the contact surface with the detection unit or the recording medium arranged at a part of the detection unit at a place where the recording medium conveyance path is curved, thereby The forming apparatus can be miniaturized.

  According to the third aspect of the present invention, the recording is performed by the contact surface of the recording medium disposed in a part of the detection unit and the urging unit having a flat surface, which is formed substantially in parallel with the recording medium during conveyance. By pinching the medium, it is possible to improve the accuracy of reading the patch on the recording medium by the detecting means.

  According to the invention of claim 4, by reducing the contact area between the biasing means and the recording medium, it is possible to improve the patch reading accuracy on the recording medium by the detecting means without disturbing the conveyance of the recording medium. It becomes possible.

  According to the invention of claim 5, by reducing the contact area between the biasing means and the recording medium, it is possible to improve the patch reading accuracy on the recording medium by the detecting means without disturbing the conveyance of the recording medium. It becomes possible.

  According to the invention described in claim 6, by reducing the contact area between the biasing means and the recording medium, the patch reading accuracy on the recording medium by the detecting means can be improved without disturbing the conveyance of the recording medium. With the roller supported so as to be able to rotate, it is possible to supplement the conveyance capability of the recording medium.

  According to a seventh aspect of the present invention, in the mechanism for changing the force for sandwiching the recording medium between the urging means, the contact surface side is fixed and the urging means side is movable. By making both the contact surface and the urging means movable, it is possible to reduce the deviation of the portion that holds the recording medium.

  According to an eighth aspect of the present invention, in the mechanism for varying the force for sandwiching the recording medium between the urging means, the urging means side is fixed and the contact surface side is movable. By making both the contact surface and the urging means movable, it is possible to reduce the deviation of the portion that holds the recording medium.

  According to the ninth aspect of the present invention, in the mechanism for varying the force for sandwiching the recording medium between the urging means, both the contact surface side and the urging means side are movable, thereby enabling recording. When it is not necessary to pinch the medium, both mechanisms are retracted to a position where they do not come into contact with the recording medium, and it becomes possible to reduce scraping and dirt on the contact surface and the urging means due to the recording medium. .

  According to the tenth aspect of the present invention, when changing the setting of the force for holding the recording medium between the contact surface and the biasing means, the user performs work such as disassembling the image forming apparatus or replacing parts. It is possible to save time and effort.

  According to the eleventh aspect of the invention, when changing the setting of the force for holding the recording medium between the contact surface and the biasing means, a plurality of steps can be set according to the environment and the recording medium to be used. When the user arbitrarily selects from among the urging forces, it is possible to improve the patch reading accuracy on the recording medium by the detection means.

  According to the twelfth aspect of the invention, when changing the setting of the force for holding the recording medium between the contact surface and the biasing means, the recording medium is inserted between the contact surface and the biasing means. It is possible to save the user from setting the holding force and improve usability.

  According to a thirteenth aspect of the invention, when changing the setting of the force for holding the recording medium between the contact surface and the biasing means, the recording medium is inserted between the contact surface and the biasing means. When it is not desired to set the holding force by automatic setting, it is possible to improve usability by enabling the user to set.

<Embodiment 1>
Hereinafter, an embodiment in which the present invention is applied to an image recording apparatus will be specifically described with reference to FIGS. 1 to 3, 11 and 13.

  First, a cross-sectional view showing a configuration of a conventional color image forming apparatus is shown in FIG. 11, and a specific operation function will be described using the same.

  These printer operations include a normal print mode and a test mode.

  First, the operation in the normal print mode will be described.

  The illustrated image forming apparatus is a four-drum full-color type color image forming apparatus, and 50Y, 50M, 50C, and 50K are photosensitive drums, and each of these has developer (toner) of each color of yellow, magenta, cyan, and black. It is provided in each image forming station provided.

  On the surface of each photosensitive drum 50Y, 50M, 50C, 50K, laser beams emitted from the corresponding laser scanner devices 51Y, 51M, 51C, 51k based on image data from an image data input unit (not shown) are provided. A latent image is formed by exposure, and a toner image is formed by developing with a developer of each color of yellow, magenta, cyan, and black.

  An intermediate transfer belt 52 primarily transfers the toner images of the respective colors formed by the photosensitive drums 50Y, 50M, 50C, and 50K. 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, and transport roller pairs 56, 57, and stopped driving. It is conveyed to the roller pair 59.

  When feeding from the multi-feeding unit 40 is designated, sheets P as recording media are stacked on the multi-feeding tray 41 and fed by the multi-feeding roller 42, and a pair of conveying rollers 57. And is conveyed to the registration roller pair 59 that has stopped driving.

  After the skew is corrected by the registration roller pair 59, the sheet P is conveyed to the secondary transfer unit 60 at a predetermined timing, and the toner image on the intermediate transfer belt 52 is transferred. The toner image is fixed by being conveyed to the fixing device 61 by the secondary transfer roller 60a and the intermediate transfer belt 52.

When FD paper discharge is specified in which the image forming surface is discharged downward, the flapper 67 is moved by control means and drive means (not shown),
The sheet P that has passed through the fixing device 61 passes above the flapper 67, is conveyed to the paper discharge roller pair 62, and is conveyed to the conveyance path 69. The sheet P conveyed to the conveyance path 69 is conveyed by a pair of paper discharge rollers 68 and 63 and is discharged and stacked on the paper discharge tray 64 with the image forming surface facing down.
In addition, when FU paper discharge is specified in which the image forming surface is discharged, the flapper 67 is moved by control means and drive means (not shown),
The sheet P that has passed through the fixing device 61 passes under the flapper 67, is conveyed by the pair of paper discharge rollers 65, and is discharged and stacked on the paper discharge tray 66 with the image forming surface facing up.

  Next, the operation in the test mode will be described.

  When the test mode is specified on the operation panel (not shown) on the printer or a personal computer connected to the printer, or the control unit (not shown) automatically selects the test mode based on the detection results of changes in the environment, changes in each part of the device, etc. , A test pattern (patch) signal is generated from a signal generation circuit (not shown), and the surface of each photosensitive drum is exposed by a laser beam emitted based on the test pattern (patch) signal data to form a latent image. .

  Thereafter, after the test pattern was formed on the intermediate transfer belt 52 by the same process as the operation in the normal print mode, the test pattern toner image was transferred onto the sheet P separately conveyed by the secondary transfer roller 60a. Thereafter, the test pattern toner image is further conveyed to the fixing device and fixed on the recording sheet P.

  FIG. 13 shows the installation state of patch patterns 81a, 81b, 81c... Formed on the sheet P, color sensors, and the like. The color sensor S1 sequentially detects the patch 81 formed on the P1 side, which is the surface on the sheet P, from the patch 81a, feeds back the detection result to an image forming unit (not shown), and the color of the toner image formed on the recording medium Perform degree control. At this time, the roller pair R is installed on both sides of the color sensor S1, the opposing roller CR is installed on the opposite portion, and the recording paper P is nipped and conveyed, thereby conveying the recording paper at the time of color patch measurement.

  Thereafter, the recording paper P transported by the pair of paper discharge rollers is transported by the pair of paper discharge rollers, and is discharged and stacked on the paper discharge tray with the patch forming surface facing down.

  FIG. 1 shows a recording paper transport unit 100 including a color sensor S1. This is a recording paper conveyance section in the recording paper conveyance path 69 after fixing in FIG. 11 of the conventional example, and the recording paper is formed by a plurality of guide ribs and a plurality of opposed guide ribs not shown in the upward arrow direction in FIG. The space is nipped and conveyed by a pair of paper discharge rollers 62 and 68.

  FIG. 2 is an enlarged view of a main part including the color sensor S1 unit.

  In FIG. 2, a folder 101 that supports the color sensor S1 and is fixed to the recording paper transport unit, an opposing roller 102 that faces the color sensor S1, a biasing plate 103 that holds the recording paper opposite the color sensor S1, A configuration of a rotating shaft 106 that swings the urging plate 103, a motor 108 that moves the rotating shaft, and a roller 110 that is placed beside the color sensor S1 in line symmetry with respect to the optical center is shown.

  FIG. 3 shows a view of the view shown in FIG.

  At this time, the roller 110 is rotating in contact with the counter roller 102 that is always driven to rotate by the main body drive train. The facing roller 102 covers the shaft member with a so-called urethane viscoelastic member except for the central portion and the end portion.

  Further, the recording paper is conveyed in the direction of the arrow upward from the bottom between the surface of the color sensor S1 and the urging plate 103. Further, the urging plate 103 has a plane that contacts the recording medium during conveyance as an urging means, and the plane is formed substantially parallel to the recording medium during conveyance.

  As shown in FIG. 2, the urging force from the urging plate 103 to the surface of the color sensor S1 when the folder 101 holding the color sensor S1 is fixed and the surface of the color sensor S1 and the urging plate 103 abut is applied by the motor 108. It can be controlled by the amount of rotation of the rotation shaft 106. Therefore, a plurality of urging force settings are prepared in the program, and the user selects the urging force to change the urging force setting according to the recording paper, without disturbing the conveyance of the recording paper. It is possible to improve the patch reading accuracy on the recording paper in S1.

<Embodiment 2>
In the first embodiment, the conveyance path after fixing is described as a vertical path parallel to the so-called gravity direction, but the contact surface with the recording medium arranged in a part of the detection unit is The recording medium conveyance roller may be arranged in a curved recording medium conveyance path between the recording medium conveyance rollers arranged upstream and downstream of the contact surface.

  FIG. 4 shows a recording paper transport unit 100 including the color sensor S1.

  As shown in FIG. 4, this is because the recording paper conveyance section in the recording paper conveyance path 69 after fixing in FIG. 11 of the conventional example is refracted in the section between the upstream roller pair 62 and the downstream roller pair 68 on the contact surface. It shows the case. FIG. 5 shows a diagram of the diagram shown in FIG. 4 viewed from the side.

  The recording paper is configured to be nipped and conveyed by a pair of paper discharge rollers 62 and 68 in a space formed by a plurality of guide ribs and a plurality of opposed guide ribs (not shown) in the upward arrow direction in FIG. Therefore, the space in the image forming apparatus can be effectively used by arranging the contact surface with the detection unit or the recording sheet arranged in a part of the detection unit in a place where the recording sheet conveyance path is not linear. The apparatus can be downsized.

<Embodiment 3>
In the first embodiment, an urging plate having a flat surface that is in contact with a recording medium at the time of conveyance as the urging means, and the flat surface is formed substantially parallel to the recording medium at the time of conveyance. Although used, the biasing plate may be a biasing plate characterized in that the biasing plate has a rib shape formed substantially in parallel with the conveyance direction of the recording medium.

  FIG. 6 shows a biasing plate having a rib shape.

  As shown in FIG. 6, the urging plate 105 has a rib shape 109 formed substantially in parallel with the conveyance direction of the recording paper, thereby reducing the contact area between the urging plate and the recording paper. The resistance force that hinders the conveyance of the recording paper by the biasing plate can be reduced, and a stronger biasing force can be set than when the biasing plate does not have a rib shape on the same recording paper. Therefore, in order to prevent the conveyance of the recording paper, it is possible to cope with the recording paper in which it is difficult to set a strong urging force that suppresses the fluttering and satisfies the sensing accuracy.

<Embodiment 4>
In the first embodiment, an urging plate having a flat surface that is in contact with a recording medium at the time of conveyance as the urging means, and the flat surface is formed substantially parallel to the recording medium at the time of conveyance. Although used, a roller that is rotatably supported as an urging unit is disposed, and a force for sandwiching the recording medium between the contact surface with the recording medium disposed in a part of the detecting unit and the outer peripheral surface of the roller It may be configured to provide

  FIG. 7 shows an enlarged view of the main part including the color sensor S1 unit.

  In FIG. 7, the folder 101 that supports the color sensor S1 and suspends and swings on a part of the recording paper transport unit, the opposing roller 102 that holds the recording paper opposite the color sensor S1, and the color sensor S1 operate together with the folder 101. 1 shows a configuration of a cam shaft 104 to be rotated and a motor 108 that rotates the cam shaft 104. FIG. 8 is a side view of FIG.

  FIG. 8 shows a configuration of a cam 107 that pushes the folder 101 toward the opposing roller 102, and a spring 111 that is installed between the cam 107 and the folder 101.

  As shown in FIG. 8, by rotating the cam shaft 104 provided with the cam 107 by the motor 108, the recording paper disposed in a part of the color sensor S1 is pushed out by pushing out the folder 101 including the color sensor S1. It is possible to change the setting of the force for holding the recording sheet between the contact surface and the opposing roller 102 and the phase of the cam 107 to hold the recording sheet. Therefore, since the urging means is rotatable, it is possible to reduce the resistance force that hinders the conveyance of the recording paper than when the urging plate is used. Therefore, the reading accuracy of the patch on the recording paper by the color sensor S1 can be improved without hindering the conveyance of the recording paper than when the biasing plate is used.

<Embodiment 5>
In Embodiment 4, a roller that is rotatably supported as an urging unit is disposed, and the recording medium is disposed between the contact surface with the recording medium disposed in a part of the detecting unit and the outer peripheral surface of the roller. Although the configuration is such that a clamping force is applied, a configuration may be employed in which rollers that are supported so as to be rotationally driven as urging means are disposed.

  FIG. 7 shows an enlarged view of the main part including the color sensor S1 unit.

  FIG. 7 shows a configuration of a facing roller 102 that is driven while sandwiching a recording sheet facing the color sensor S1. FIG. 8 is a side view of FIG.

  As shown in FIG. 8, by rotating the cam shaft 104 provided with the cam 107 by the motor 108, the recording paper disposed in a part of the color sensor S1 is pushed out by pushing out the folder 101 including the color sensor S1. It is possible to change the setting of the force for holding the recording sheet between the contact surface and the opposing roller 102 and the phase of the cam 107 to hold the recording sheet. Therefore, since the urging means can be driven to rotate, it is possible to reduce the resistance force that hinders the conveyance of the recording paper than when the urging plate is used. Therefore, it is possible to improve the accuracy of reading the patch on the recording paper by the color sensor S1 without hindering the conveyance of the recording paper as compared with the case of using the roller supported rotatably.

<Embodiment 6>
In the first embodiment, the mechanism for changing the force for sandwiching the recording medium between the contact surface and the urging means is such that the contact surface side is fixed and the urging means side is movable. However, the recording medium may be clamped by making both the contact surface side and the biasing means side movable.

  FIG. 9 is an enlarged view of a main part including the color sensor S1 unit. FIG. 10 shows a view of the view shown in FIG. 9 viewed from the side.

  FIG. 10 shows the configuration of the cam shaft 104 provided with the cam 107 and the cam 107 that pushes the folder 101 toward the urging plate 103.

  As shown in FIG. 10, by rotating the cam shaft 104 provided with the cam 107, the entire folder 101 including the color sensor S1 is pushed out, and the urging plate 103 is also moved by the rotation of the rotating shaft 106 by the motor 108. By urging the S1 surface, the recording paper is sandwiched. At that time, the urging force from the urging plate 103 to the surface of the color sensor S1 can be controlled by the amount of rotation of the rotating shaft 106 by the motor 108.

  Therefore, when the color sensor S1 is used, a plurality of urging force settings are prepared on the program, and the user selects the urging force to change the urging force setting according to the recording paper. Thus, it is possible to improve the accuracy of reading patches on the recording paper by the color sensor S1 without disturbing the conveyance of the image.

  When the color sensor S1 is not used, the surface of the color sensor S1 and the urging plate 103 are retracted to a position where they do not come into contact with the recording paper, and the surface of the color sensor S1 and the urging plate 103 are scraped or soiled by the recording paper. Can be reduced.

<Embodiment 7>
In the first embodiment, a setting of force for sandwiching a plurality of recording media is prepared on a program, and a user makes a contact between a contact surface with a recording medium arranged in a part of the detecting means and the urging means. The setting change is performed by selecting the force for pinching the recording medium in step (3). However, the recording medium conveying path has a detecting means for detecting the type of the recording medium, and the change in the force for pinching the recording medium (It may be a configuration characterized in that it can be automatically set in the image forming apparatus based on information by means for detecting the type of the medium).

  An example of an algorithm for changing the setting of the force for holding the recording medium in the present embodiment will be described with reference to the flowchart shown in FIG.

  First, a detection unit that detects the type of the recording medium determines whether the paper is thick paper or thin paper, and performs image formation according to the type of the recording medium. Next, it is determined whether or not to perform color detection, and if so, a contact surface with a recording medium arranged in a part of the detection means based on information about the type of the recording medium already acquired The force for sandwiching the recording medium between the urging means is set to be strong when the paper is thick, and weak when the paper is thin, and the color detection is performed. Therefore, when setting the force for holding the recording medium between the contact surface and the biasing means, the user has to set the force for holding the recording medium between the contact surface and the biasing means. It is possible to save and improve usability.

<Eighth embodiment>
In the seventh embodiment, the recording medium conveyance path has a detecting unit for detecting the type of the recording medium, and the change in the force for holding the recording medium is changed based on the information by the unit for detecting the type of the recording medium. Although it can be automatically set in the forming apparatus, it may be configured such that the user can select based on information by means for detecting the type of the recording medium.

  An example of an algorithm for changing the setting of the force for holding the recording medium in the present embodiment will be described with reference to FIG.

  In the step of determining whether the paper is thick or thin after color detection in FIG. 14, the image forming apparatus not only automatically determines, but also allows the user to select the force for holding the recording medium by determining the user. It is possible to meet a wide range of requests. Therefore, it is possible to cope with a case where it is desired to finely adjust the force for pinching the recording medium set automatically.

FIG. 2 is a perspective view of a recording paper transport unit according to Embodiment 1 of the present invention. It is a perspective view of the color sensor unit principal part which concerns on Embodiment 1 of this invention. It is a side view of the color sensor unit which concerns on Embodiment 1 of this invention. FIG. 6 is a perspective view of a recording paper transport unit according to Embodiment 2 of the present invention. FIG. 6 is a side view of a recording paper transport unit according to Embodiment 2 of the present invention. It is explanatory drawing of the urging | biasing board with a rib which concerns on Embodiment 3 of this invention. It is a perspective view of the color sensor unit principal part which concerns on Embodiment 4, 5 of this invention. It is a side view of the color sensor unit which concerns on Embodiment 4, 5 of this invention. It is a perspective view of the color sensor unit principal part which concerns on Embodiment 6 of this invention. It is a side view of the color sensor unit which concerns on Embodiment 6 of this invention. It is sectional drawing of the conventional color image forming apparatus. It is a related figure of the thickness and pressure of a conventional recording medium. It is a figure which shows the conventional color sensor periphery principal part and color patch. 10 is a flowchart for selecting and determining a force for holding a recording medium according to Embodiments 7 and 8 of the present invention.

Explanation of symbols

P Recording medium 50 Photosensitive drum 51 Laser scanner device 52 Intermediate transfer belt 53 Paper feed cassette 54 Paper feed roller 55 Feed retard roller 56, 57, 70 Transport roller pair 59 Registration roller pair 60 Secondary transfer section 60a Secondary transfer roller 61 Fixing device 62, 63, 65, 68 Paper discharge roller pair 64, 66 Paper discharge tray 67 Flapper 69 Transport path 81 Density patch S1 Color sensor R Color sensor roller pair CR Opposing roller 100 Conveying unit 101 Sensor folder 102 Opposing roller 103 Energizing Plate 104 Cam shaft 105 Energizing plate with rib 106 Rotating shaft 107 Cam 108 Motor 109 Rib 110 Roller 111 Spring

Claims (13)

  The toner image is formed using one or more exposure apparatuses and one or more electrophotographic process units, and the toner image is transferred onto the recording medium. An image forming apparatus for fixing a toner image onto a recording medium by applying a toner image, and 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 with a recording medium arranged in a part of the detection means; and a biasing means for biasing the recording medium against the contact surface when the recording medium is transported, and the contact surface A color image forming apparatus characterized in that the force for sandwiching the recording medium between the urging means and the biasing means is variable in a plurality of stages.   The contact surface with the recording medium arranged in a part of the detection means is arranged in a curved recording medium conveyance path between the recording medium conveyance rollers arranged upstream and downstream of the contact surface. The color image forming apparatus according to claim 1.   2. A color image forming apparatus according to claim 1, wherein said urging means has a flat surface in contact with the recording medium during conveyance, and the flat surface is formed substantially parallel to the recording medium during conveyance. apparatus.   4. The color image forming apparatus according to claim 1, wherein, in the urging unit, the contact portion with the recording medium has a rib shape formed substantially in parallel with the conveyance direction of the recording medium.   Using the outer peripheral surface of a roller rotatably supported as the urging means, the force for pinching the recording medium between the contact surface with the recording medium arranged in a part of the detecting means and the outer peripheral surface of the roller The color image forming apparatus according to claim 1, wherein:   As the urging means, an outer peripheral surface of a roller supported so as to be rotationally driven is used, and the recording medium is sandwiched between the contact surface with the recording medium arranged in a part of the detecting means and the outer peripheral surface of the roller. 6. The color image forming apparatus according to claim 5, wherein the color image forming apparatus is configured to apply force.   The mechanism for changing the force for sandwiching the recording medium between the contact surface and the biasing means is such that the contact surface side is fixed and the biasing means side is movable to sandwich the recording medium. The color image forming apparatus according to claim 1.   The mechanism for varying the force for holding the recording medium between the contact surface and the biasing means is characterized in that the biasing means side is fixed and the contact surface side is movable to hold the recording medium. The color image forming apparatus according to claim 1.   The mechanism for varying the force for clamping the recording medium between the contact surface and the biasing means clamps the recording medium by making both the contact surface side and the biasing means side movable. The color image forming apparatus according to claim 1.   A mechanism for changing the force for sandwiching the recording medium between the contact surface and the biasing means is configured so that the contact surface and the biasing means are driven by power transmitted from a driving device installed in the image forming apparatus. The color image forming apparatus according to claim 1, wherein a force for sandwiching the recording medium between them is variable.   A plurality of steps of setting the force for holding the recording medium between the contact surface and the biasing means are prepared, and the user can indicate the magnitude of the force for holding the recording medium. The color image forming apparatus according to claim 1.   Information by means for detecting the type of the recording medium is detected by detecting the type of the recording medium in the recording medium conveying path, and a change in the force for holding the recording medium between the contact surface and the biasing means is detected. The color image forming apparatus according to claim 1, wherein the color image forming apparatus is automatically set in the image forming apparatus based on the image quality.   Information by means for detecting the type of the recording medium is detected by detecting the type of the recording medium in the recording medium conveying path, and a change in the force for holding the recording medium between the contact surface and the biasing means is detected. The color image forming apparatus according to claim 1, wherein a user can select the color image based on the color image forming apparatus.

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