JP2006011205A - Electrophotographic image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic image forming apparatus capable of steadily conveying a recording medium whether a test pattern detection mode or a regular mode is used. <P>SOLUTION: The electrophotographic image forming apparatus designed such that an image formed by an electrophotographic process is transferred to a recording medium to be conveyed and the transfer image is fixed by a fixing part includes: a color sensor S1 by which a test pattern formed on a recording sheet is detected after fixing; and a biasing plate 103 disposed opposite the color sensor S1. The color sensor S1 and the biasing plate 103 move in synchronization with each other and are movable to a detecting position where they project into a recording sheet conveyance path and come into contact with a sheet being conveyed, and a non-detecting position where they retract from the recording sheet conveyance path. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine or a printer that transfers an image formed by an electrophotographic process onto a recording medium to be conveyed and fixes the transferred image at a fixing unit.

  In recent years, color printers, color copiers, and the like using an electrophotographic process have become widespread, and even in these apparatuses, higher image quality of output images is required.

  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 slight environmental fluctuations may cause color fluctuations, which may cause the color balance to be lost. Therefore, there is a means for stably reproducing colors and color gradations. is doing.

  For example, for each color toner, based on the absolute humidity measured by the temperature / humidity sensor with several kinds of exposure amount and process conditions such as development bias according to the absolute humidity, and gradation correction means such as a lookup table. The optimum process conditions and gradation correction values 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 variations in each part of the apparatus occur. The density of the unfixed single-color toner patch is detected by a density detection sensor for unfixed toner (hereinafter referred to as “density sensor”), and from the detection result, process conditions such as exposure amount and development bias, and gradation correction means such as a lookup table Thus, a stable color and gradation of color are obtained by controlling the density with feedback.

  However, density control using the density sensor detects patches by forming patches on an intermediate transfer member or a photosensitive drum, and changes in the color balance of the image due to subsequent transfer and fixing to a recording medium. There is no control over. 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 after fixing, on the recording medium. There has been proposed a color image forming apparatus provided with a sensor (hereinafter referred to as “color sensor”) for detecting the density or chromaticity of a patch (Patent Document 1).

  In these color image forming apparatuses, the final output formed on the recording medium is fed back to the calibration result 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 11-316476 A

  Here, the operation when the test mode is performed in the color image forming apparatus having a plurality of photosensitive drums will be described. When the test mode is designated on the operation panel (not shown) on the printer, a test pattern image is formed on the photosensitive drum based on the test pattern (patch) signal data, and this is performed in the same process as the operation in the normal print mode. The image is transferred onto a separately conveyed sheet and further conveyed to a fixing device, and a test pattern toner image is fixed on the recording sheet.

  FIG. 10 shows an installation state of patch patterns 81a, b, c... 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 detected result to an image forming unit (not shown), and the color of the toner image formed on the recording medium Control the degree.

  At this time, a pair of rollers 82 is installed on both sides of the color sensor S1, a counter roller 83 is installed on the opposite portion, and the recording sheet P is nipped and conveyed, so that the recording sheet is conveyed during color patch measurement.

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

  However, in the conventional test pattern inspection configuration such as chromaticity, since the sheet is continuously nipped and conveyed by the roller pairs 82 and 83 in addition to the chromaticity measurement using the color sensor S1, the sheet is immediately after fixing. When the pressing force of the roller pairs 82 and 83 is applied to an image in which the cooling is not sufficient and the toner solidification is incomplete, the marks of the roller pair 82 may adhere to the image.

  Further, when the sheet P is continuously nipped and conveyed by the roller pairs 82 and 83 in addition to the chromaticity measurement using the color sensor S1, a convex portion as an obstacle exists in the recording sheet conveyance path. There is a possibility that the probability of recording sheet jamming (paper jam) in the so-called sheet conveyance path due to the presence of “clogging” during sheet conveyance may increase.

  The present invention has been made in view of the above problems, and an object thereof is to provide an electrophotographic image forming apparatus capable of stably transporting a recording medium in both a test pattern detection mode and a normal mode.

  A typical means in the present invention for solving the above-described problems is to transfer an image formed by an electrophotographic process to a transported recording medium and fix the transferred image in a fixing unit. A pattern detection unit that detects a test pattern formed on the medium after fixing; and a counter member disposed to face the pattern detection unit. The pattern detection unit and the counter member are interlocked, It is possible to move to a detection position that contacts a recording medium that is projected and conveyed into the recording medium conveyance path, and a non-detection position that retreats from the recording medium conveyance path.

  In the present invention, the pattern detecting means and the opposing member that opposes the pattern detecting means are allowed to project into and retract from the recording medium conveyance path. Therefore, in the test pattern detection mode, the recording medium is brought into contact with the pattern detecting means for accurate detection. Pattern detection is possible. On the other hand, in the normal mode, the occurrence of jam or the like can be effectively prevented by retracting the pattern detection means and the opposing member.

[First Embodiment]
Next, an image forming apparatus according to an embodiment of the present invention will be specifically described with reference to the drawings.

{Overall configuration of image forming apparatus}
First, the overall configuration of the electrophotographic image forming apparatus will be described with reference to FIG. The image forming apparatus of the present embodiment is a color printer in which four photosensitive drums are arranged in parallel. As the operation of the printer, a normal print mode in which a normal printer is used, a test pattern is recorded on a recording sheet, and the pattern is calculated from the pattern. And a test mode for detecting color density and the like.

  In the figure, reference numerals 50Y, 50M, 50C, and 50K denote photosensitive drums, which are provided in image forming stations provided with developing materials (toners) of yellow, magenta, cyan, and black, respectively.

  Laser light emitted from the corresponding laser scanner devices 51Y, 51M, 51C, and 51K on the surface of each photosensitive drum 50Y, 50M, 50C, and 50K based on image data from an image data input unit (not shown). To form a latent image, which is further developed with a developer of yellow, magenta, cyan, and black, respectively, to form a toner image. The intermediate transfer belt 52 is an intermediate transfer member, and the toner images of the respective colors formed by the photosensitive drums 50Y, 50M, 50C, and 50K are primarily transferred to the intermediate transfer belt 52. A sheet P as a recording medium is stacked on the feeding cassette 53, fed by a feeding roller 54, conveyed by a separating roller pair 55, and conveying roller pairs 56 and 57, and is stopped. Carried to pair 59. It is also possible to feed from the multi-feed unit 40.

  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 to transfer the toner image on the intermediate transfer belt 52, and then the secondary transfer device 60 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.

  Thereafter, when the discharge with the image forming surface facing down is designated, the flapper 67 operates to be conveyed to the discharge roller pair 62 and conveyed to the sheet conveying path 69. Further, the sheet P transported to the sheet transport path 69 is transported by a pair of discharge rollers 68 and 63 and is discharged and stacked on the discharge tray 64 with the image forming surface down.

  When discharge with the image forming surface facing upward is designated, the flapper 67 operates to be conveyed by the discharge roller pair 65 and discharged and stacked on the discharge tray 66 with the image forming surface facing upward.

{Pattern detection means and opposing member}
The image forming apparatus according to the present exemplary embodiment is provided with a pattern detection unit that detects a test pattern formed on the recording sheet in the sheet conveyance path 69 on the downstream side in the sheet conveyance direction from the fixing device 61.

  FIG. 1 is a perspective explanatory view of a sheet conveyance path including a unit portion of a color sensor that detects a test pattern. The sheet conveyance path 69 provided with the test pattern detection means is a space formed by a plurality of guide ribs for conveying the recording sheet in the upward arrow direction of FIG. 1 and a plurality of opposed guide ribs (not shown). The recording sheet P on which the image is fixed is nipped and conveyed by the discharge roller pairs 62 and 68.

  Here, the unit part of the color sensor S1 as the pattern detecting means will be described. 2 is an enlarged explanatory view of the main part including the color sensor unit, and FIGS. 3 and 4 are explanatory views of the state of the color sensor unit in the normal print mode and the test mode, from the back side of FIG. FIG.

  As shown in the figure, the color sensor S1 is attached to a folder 101 that can swing around a shaft 101a in a part of the recording sheet conveying unit.

  Two rollers 200 (see FIG. 5) are rotatably attached to the folder 101 with the color sensor S1 interposed therebetween, and a counter roller 102 that can be driven and rotated is provided to face the color sensor S1. In the test mode, the recording sheet P is nipped and conveyed between the opposed roller 102 and the roller 200, and at that time, the test pattern is read by the color sensor S1.

  As shown in FIGS. 3 and 4, the folder 101 is configured to be swingable by two cams 107 and 108 attached to the cam shaft 104.

  Further, as shown in FIG. 2, an urging plate 103, which is a facing member, is disposed at a position facing the reading position of the color sensor S1. The urging plate 103 is attached to a rotation shaft 106, and the urging plate 103 can be swung by the rotation of the rotation shaft 106. A cam lever 110 is fixed to the rotation shaft 106, and the rotation shaft 106 can be rotated by rotating the cam lever 110 by a cam 109 attached to the cam shaft 104. As a result, the cams 107, 108, and 109 are rotated by the rotation of the cam shaft 104, so that the folder 101 and the urging plate 103 operate in conjunction with each other.

  As shown in FIG. 2, the rotating shaft 106 is urged clockwise by the tension spring 201 (arrow a direction), and the urging plate 103 is urged away from the color sensor S1. The folder 101 is also urged toward the camshaft 104 by a spring or the like (not shown), and the color sensor S1 is urged away from the urging plate 103.

  Next, the operation of the color sensor unit in the test mode and the normal print mode will be described.

  FIG. 3 shows a state in the test mode, in which a part of the sensor folder 101 including the color sensor S1 is moved into the sheet conveyance path by rotating the cams 107 and 108 provided on the cam shaft 104. The state pushed out is shown. At this time, the cam lever 110 is pushed downward (detection position) by another cam 109 provided at one end of the cam shaft 104.

  As a result, the urging plate 103 (FIG. 2) provided in the color sensor facing portion at the center of the rotation shaft 106 to which the cam lever 110 is attached is pushed out into the sheet conveyance path. Then, the recording sheet is conveyed while being held between the upper surface portion of the color sensor S1 and the urging plate 103. Therefore, the sheet on which the test pattern is recorded is brought into close contact with the surface of the color sensor S1 by the urging plate 103, and normal density or chromaticity determination is performed.

  On the other hand, FIG. 4 shows a state in the normal print mode, in which a part of the sensor folder 101 including the color sensor S1 is attached to the color sensor S1 by rotating and retracting the cams 107 and 108 provided on the camshaft 104. A state in which the sheet is retracted out of the conveyance path is shown. At this time, the cam 109 provided at one end of the cam shaft 104 is retracted, and the cam lever 110 is pulled upward by the spring biasing force of the tension spring 201. For this reason, the urging plate 103 provided in the color sensor facing portion at the center of the rotation shaft 106 to which the cam lever 110 is attached is retracted out of the sheet conveyance path (non-detection position).

  The state in the test mode and the normal print mode will be described in more detail with reference to cross-sectional views of FIGS. FIG. 5 shows the state of the normal print mode, and FIG. 6 shows the state of the test mode.

  In FIG. 5, when the cams 107 and 108 provided on the cam shaft 104 rotate in the direction of the arrow, the folder 101 including the color sensor S1 is suspended around the fulcrum shaft 101a. The folder 101 including the sensor S1 swings and moves. At this time, the color sensor side with respect to the recording sheet conveyance path can be said to be retracted to the area of the alternate long and short dash line L2.

  Further, the urging plate 103 provided at the central portion of the rotating shaft 106 on the lower side of the opposing roller 102 facing the color sensor S1 is L1 with respect to the recording sheet conveyance path by the cam 109 and the cam lever 110 as described above. Evacuated to the area.

  In the normal print mode, as shown in regions L2 and L1 in FIG. 5, the opposing region of the color sensor S1 and the urging plate 103 is in the detection position when both the members are in the non-detection position. Each member is arranged so as to have a wider interval and to become narrower from the upstream side to the downstream side in the recording sheet conveyance direction and to be substantially parallel at the pattern detection position. For this reason, in normal printing, the recording sheet after image fixing is reliably guided between the color sensor S1 and the urging plate 103 and passes without being caught.

  As described above, the color sensor S1 and the urging plate 103 are set in the retracted state from the recording sheet conveyance path by the cams 107, 108, 109, the cam lever 110, and the like.

  On the other hand, as shown in FIG. 6, when the cam 107 installed on the cam shaft 104 rotates in the direction of the arrow, the folder 101 including the color sensor S1 is projected into the recording material conveyance path. Further, in conjunction with these operations, the urging plate 103 provided on the rotating shaft 106 rotated by the cam 109 and the cam lever 110 described above protrudes into the recording material conveyance path. As a result, the color sensor S1 and the urging plate 103 are substantially parallel, opposed, and in contact with each other, and the recording sheet can be stably nipped and conveyed by forming the space between the tangent planes.

  At this time, it can be said that the color sensor S1 projects with respect to the recording sheet conveyance path in the region of the alternate long and short dash line L4. Further, the urging plate 103 protrudes in the region L3. As shown in the regions L3 and L4, when the recording sheet is conveyed in the upward direction in the drawing, the recording sheet is held between the upper surface portion of the color sensor S1 and the urging plate 103 and can be stably conveyed. It becomes possible.

  As described above, the color sensor S1 and the urging plate 103 are interlocked with each other via the cam operation to set the two states of projecting and retracting into the recording sheet conveying path, and the color sensor S1 and the urging plate 103. By realizing the pinching and stable conveyance of the recording sheet by the interlocking projecting operation into the recording sheet conveyance path, it is possible to realize high-precision measurement of the color patch formed on the recording sheet after fixing. Further, by causing the color sensor S1 and the urging plate 103 to retreat in conjunction with each other from within the recording sheet conveyance path, the possibility of a convex portion that becomes an obstacle during the conveyance of the recording sheet is eliminated as much as possible, so that the roller trace and recording It becomes possible to eliminate the influence of sheet jam. Further, the above operation is realized by a simple configuration called a cam mechanism.

[Second Embodiment]
Next, the protruding and retracting configuration of the color sensor and the biasing plate to the recording sheet conveyance path according to the second embodiment will be described with reference to FIGS. Note that the basic configuration of the image forming apparatus of the present embodiment is the same as that of the first embodiment described above, and therefore, a duplicate description is omitted. Here, a configuration that is a feature of the present embodiment will be described. Moreover, the same code | symbol is attached | subjected to the member which has the same function as embodiment mentioned above.

  FIG. 8 shows a normal print mode in which the color sensor S1 is retracted from the recording medium conveyance path (non-detection position). FIG. 9 shows a test mode in which the color sensor protrudes from the recording medium conveyance path (detection position).

  As shown in FIGS. 8 and 9, in this embodiment, the color sensor S1 is attached to a folder 111 that can rotate about a shaft 111a, and a sensor actuator A1 is coupled to one end of the folder 111. The urging plate 113, which is a facing member facing the color sensor S1, can be rotated about a rotation shaft 116, and an urging plate actuator A2 is coupled to one end thereof.

  When the normal print mode in FIG. 8 is changed to the test mode, the actuators A1 and A2 operate. That is, from the state where the color sensor is retracted, which is a normal state, one end of the arm portion of the folder 111 is pulled downward by the sensor actuator A1, the folder 111 is rotated, and the urging plate 113 is retracted. As shown in FIG. 9, the color sensor S1 and the urging plate 113 protrude into the recording sheet conveyance path, and the color patch is held while nipping and conveying the recording sheet. It becomes a measurable state.

  On the other hand, when the test mode shown in FIG. 9 is changed to the normal print mode, the actuators A1 and A2 operate in the reverse manner to the state shown in FIG. 8, and the color sensor S1 and the urging plate 113 are moved to the non-detection position. Moving.

  As described above, in the present embodiment, the actuators A1 and A2 can easily realize protrusion and retraction into the recording medium conveyance path as an interlocking operation by obtaining an operation command signal from an electrical signal.

  As described above, the color sensor S1 and the urging plate 113 are used in conjunction with a plurality of actuators to set the two states of protruding and retracting into the recording sheet conveyance path, and the color sensor S1 and the urging force. Realizing high-precision measurement of the color patches formed on the recording sheet after fixing by realizing the nipping and stable conveyance of the recording sheet by the interlocking movement operation of the plate 113 into the recording sheet conveyance path. .

  Further, by causing the color sensor S1 and the urging plate 113 to retreat from the recording sheet conveyance path, the possibility of a convex portion that becomes an obstacle during conveyance of the recording sheet is eliminated as much as possible. It becomes possible to eliminate the influence of the recording sheet jam.

[Other Embodiments]
The image forming apparatus of the above-described embodiment has shown an apparatus that performs primary transfer onto an intermediate transfer belt and secondary transfer of the primary transfer image onto a recording sheet. However, the present invention is similar to a system using a so-called transfer conveyance belt. Of course, an apparatus that directly transfers an image from a photosensitive drum to a recording sheet may be used.

  In the above-described embodiment, the conveyance path after fixing is described as a vertical path that is parallel to the so-called gravitational direction. May be orthogonal or oblique.

It is a perspective explanatory view of a sheet conveyance path including a unit portion of a color sensor that detects a test pattern. It is principal part explanatory drawing of the unit part of the color sensor which detects a test pattern. It is a perspective explanatory view in a state where the color sensor and the urging plate are in the detection position. It is a perspective explanatory view in a state where the color sensor and the urging plate are in the non-detection position. It is sectional explanatory drawing in the state which has a color sensor and a biasing plate in a non-detection position. It is sectional explanatory drawing in the state which has a color sensor and a biasing plate in a detection position. 1 is an overall schematic explanatory diagram of an image forming apparatus. It is sectional explanatory drawing of the state which has the color sensor and urging | biasing board which concern on 2nd Embodiment in a non-detection position. It is sectional explanatory drawing of the state which has the color sensor and urging | biasing board which concern on 2nd Embodiment in a detection position. It is explanatory drawing of a prior art.

Explanation of symbols

A1 ... Sensor actuator A2 ... Energizing plate actuator P ... Sheet S1 ... Color sensor
40 ... Multi feed section
50Y, 50M, 50C, 50K ... Photosensitive drum
51Y, 51M, 51C, 51K ... Laser scanner device
52… Intermediate transfer belt
53… Feeding cassette
54… Feeding roller
55… Separation roller pair
56, 57… Conveying roller pair
59… Registration roller pair
60… Secondary transfer section
60a ... secondary transfer roller
61… Fixer
62… discharge roller pair
64… discharge tray
65… discharge roller pair
66… discharge tray
67… Flapper
68, 63… discharge roller pair
69… Sheet conveyance path
101 ... Folder
101a ... axis
102… Opposite roller
103… Biasing plate
104… Camshaft
106… Rotating shaft
107,108 ... cam
109… Cam
110… Cam lever
111… Folder
111a ... axis
113… Biasing plate
116… Rotation axis
200…
201… Tension spring

Claims (4)

In an electrophotographic image forming apparatus that transfers an image formed by an electrophotographic process to a recording medium to be conveyed, and fixes the transferred image in a fixing unit.
Pattern detecting means for detecting a test pattern formed on a recording medium after fixing;
A facing member disposed to face the pattern detecting means;
Have
The pattern detection means and the opposing member are linked to each other, and can be moved to a detection position that contacts the recording medium that protrudes into the recording medium conveyance path and a non-detection position that retreats from the recording medium conveyance path, respectively. An electrophotographic image forming apparatus characterized by the above. The electrophotographic image forming apparatus according to claim 1, wherein the pattern detection unit and the counter member are moved to the detection position or the non-detection position by a rotation operation of a cam. The electrophotographic image forming apparatus according to claim 1, wherein the pattern detection unit and the opposing member are moved to the detection position or the non-detection position by an operation of an actuator. The facing area of the pattern detecting means and the facing member has a wider interval when in the non-detecting position than in the detecting position, and becomes narrower from the upstream side to the downstream side in the recording medium conveyance direction. 4. The electrophotographic image forming apparatus according to claim 1, wherein the electrophotographic image forming apparatus is arranged so as to be substantially parallel at the pattern detection position.

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