JP2015001659A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus which solves the problem that detection accuracy of a patch subjected to color measurement by a colorimeter is degraded by influence of variation in speed of a recording material subjected to color measurement during transportation, which occurs when the recording material rushes into a nip section of transfer rollers on a downstream side of the colorimeter.SOLUTION: An image forming apparatus includes: forming means which forms a detection patch on a recording material; detection means which detects, at a detection position, the detection patch formed on the recording material being transported; and transport means which transports the recording material disposed on a downstream side of the detection position in a recording material transporting direction. The forming means prohibits the formation of the detection patch at a position on the recording material, which is to be transported to the detection position at a timing of a leading edge of the recording material arriving at the transport means.

Description

  The present invention relates to an image forming apparatus such as a printer and a copying machine, and more particularly to an image forming apparatus equipped with a colorimeter.

  In recent years, image forming apparatuses represented by color printers, color copiers, and the like have been required to improve the output image quality. In particular, the chromaticity stability of the output image greatly affects the image quality. However, in an image forming apparatus, the chromaticity of an output image obtained may change due to environmental changes such as temperature and humidity and long-term use. Therefore, in order to realize the chromaticity stability of the output image, it is effective to perform color correction control by detecting the chromaticity of the output image using a colorimeter.

  In order to detect the chromaticity of the output image, for example, Japanese Patent Application Laid-Open No. 2004-228561 discloses a monochrome gradation patch of cyan (C), magenta (M), yellow (Y), and black (K) on a recording material, or CMY. A method of forming a mixed color patch and measuring the color of the patch on the recording material after fixing is disclosed.

JP 2005-173284 A

  Conventionally, the color formed on the recording material at a predetermined timing while the recording material is conveyed is measured by a colorimeter as a detecting means. At this time, the recording material being colorimetrically enters the nip portion of the conveying roller on the downstream side of the colorimeter, resulting in a speed fluctuation. When this speed fluctuation occurs, the patch measured by the colorimeter has a problem that the detection accuracy is lowered due to the influence of the speed fluctuation.

  The invention according to the present application has been made in view of the above situation, and performs color correction control while suppressing the influence of speed fluctuation of the recording material when detecting the patch on the recording material by the detecting means. For the purpose.

  In order to achieve the above object, a forming unit for forming a detection patch on a recording material, a detection unit for detecting a detection patch formed on a conveyed recording material at a detection position, and the detection position A recording medium disposed on the downstream side in the recording material conveyance direction, wherein the forming unit conveys the recording material to the detection position at a timing when the leading edge of the recording material reaches the conveyance unit. It is prohibited to form the detection patch at a position on the material.

  According to the configuration of the present invention, it is possible to perform the color correction control while suppressing the influence of the speed fluctuation of the recording material when the detection unit detects the patch on the recording material.

Schematic configuration diagram of an image forming apparatus Diagram showing the configuration of the colorimetric patch The figure which showed the speed fluctuation of recording material P Flow chart showing color correction control Block diagram showing the main body controller 55 and the colorimeter 10 Diagram showing the configuration of the colorimetric patch Flow chart showing color correction control Block diagram showing the main body controller 55 and the colorimeter 10 Flow chart showing color correction control

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments do not limit the invention according to the claims, and all combinations of features described in the embodiments are not necessarily essential to the solution means of the invention.

(First embodiment)
[Description of Image Forming Apparatus]
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present embodiment. Note that members with Y, M, C, and K added to the end of the reference numerals in the drawing are members for forming yellow, magenta, cyan, and black toner images on the intermediate transfer belt 37, respectively. . However, in the following description, when it is not necessary to distinguish colors, reference numerals excluding Y, M, C, and K at the end are used.

  The photosensitive drum 31 rotates when a driving force of a driving motor (not shown) is transmitted. The driving motor rotates the photosensitive drum 31 in a clockwise direction in accordance with an image forming operation. When the main body control unit 55 receives the image signal, for example, the paper as the recording material P is fed from the paper feed cassette 44 by the paper feed rollers 45 and 46. When the recording material P is fed, the conveyance speed of the recording material P is accelerated by a registration roller 47 which is a roller-like synchronous rotating body for synchronizing the image forming operation described later and the conveyance of the recording material P. Acceleration / deceleration adjustment to decelerate is performed.

  Further, the main body control unit 55 forms an electrostatic latent image on the surface of the photosensitive drum 31 charged to a constant potential by the charging roller 32 by the exposure scanner unit 33 in accordance with the received image signal. The developing unit 38 develops the electrostatic latent image formed on the photosensitive drum 31 with yellow (Y), magenta (M), cyan (C), and black (K) toner for each station. Each developing device is provided with a sleeve 35 to which a developing bias for developing the electrostatic latent image is applied. In this way, the electrostatic latent image formed on the photosensitive drum 31 is developed as a single color toner image by the developing unit 38.

  The intermediate transfer belt 37 is in contact with the photosensitive drums 31 of the respective colors, and rotates in synchronization with the rotation of the photosensitive drums 31 of the respective colors in the counterclockwise direction during image formation. The single-color toner images developed on the photosensitive drums 31 for the respective colors are sequentially transferred onto the intermediate transfer belt 37 by the action of the primary transfer bias applied to the primary transfer roller 34 to become a multicolor toner image.

  The multicolor toner image formed on the intermediate transfer belt 37 is conveyed to a secondary transfer nip portion formed by the drive roller 41 and the secondary transfer roller 43. The recording material P that has been waiting while being held between the registration rollers 47 is conveyed to the secondary transfer nip portion in accordance with the conveyance of the multicolor toner image. The multicolor toner image on the intermediate transfer belt 37 is secondarily transferred onto the recording material by the action of the secondary transfer bias applied to the secondary transfer roller 43 in the secondary transfer nip portion.

  The fixing unit 51 fixes the multi-color toner image transferred at the secondary transfer nip portion onto the recording material P, and the fixing roller 51a for heating the recording material P and the recording material P are pressed against the fixing roller 51a. Pressure roller 51b is provided. The fixing roller 51a and the pressure roller 51b are formed in a hollow shape, and a heater 51ah is built in the fixing roller 51a. The recording material P on which the multicolor toner image is secondarily transferred is conveyed to the fixing unit 51 and fixed by applying heat and pressure by the fixing roller 51a and the pressure roller 51b.

  In the case of single-sided image formation, the recording material P on which the toner image has been fixed is discharged to the discharge tray 52a by the discharge roller 53, and the image forming operation is completed. In the case of double-sided image formation, the paper is discharged to a paper discharge tray 52b via a discharge roller 50 by a flapper solenoid (not shown). Then, the actuator is switched back by an actuator (not shown), and the acceleration / deceleration adjustment of the conveyance speed of the recording material P is performed again by the registration roller 47 via the double-side conveyance path D. Thereafter, the series of image forming operations described above is performed, and image formation is performed on the second surface of the recording material P. Note that the above-described photosensitive drum 31, charging roller 32, exposure scanner unit 33, primary transfer roller 34, sleeve 35, intermediate transfer belt 37, developing unit 38, secondary transfer roller 43, fixing unit 51, and the like are integrated into an image forming unit. It can also be said.

  The colorimeter 10 includes cyan (C), magenta (M), yellow (Y), and black (K) monochromatic gradation patches formed on the recording material P, or C, M, and Y mixed color patches. In order to measure the color of the K single color patch, it is arranged at the longitudinal center position in the double-sided conveyance path D. In other words, it can be said that the recording material P is disposed at the center position in the direction orthogonal to the conveying direction of the recording material P. In the present embodiment, the colorimeter 10 is disposed in the double-sided conveyance path D, but is not limited thereto, and may be disposed in the conveyance path downstream of the fixing unit 51. For example, it may be disposed between the fixing unit 51 and the discharge roller 53.

  The colorimeter 10 is configured to be able to abut against or be separated from the opposing member 16. The colorimeter 10 and the facing member 16 are in contact with each other during normal single-sided image formation, not the colorimetric patch. Further, when a normal double-sided image is formed instead of the colorimetric patch, the colorimeter 10 is retracted from the double-sided conveyance path D, and the colorimeter 10 and the facing member 16 are in a separated state. The reason why the colorimeter 10 and the facing member 16 are brought into contact with each other when the single-sided image is formed is that floating paper powder that moves due to the flow of air generated by a fan or the like enters the colorimeter surface of the colorimeter 10 or enters from the outside. This is to prevent floating substances such as dust from adhering. Further, the reason for separating the colorimeter 10 and the facing member 16 at the time of double-sided image formation is to suppress the occurrence of image defects due to contact with the recording material P when the recording material P is conveyed. This is to prevent the colorimeter 10 from being stained or damaged by the recording material P.

  On the other hand, when the color measuring patch is formed on the recording material P and the color of the patch is measured, the color measuring device 10 is protruded into the double-sided conveyance path D and brought into contact with the opposing member 16. While the recording material P is nipped and conveyed by the colorimeter 10 and the opposing member 16, the color of the patch is measured at the detection position. During color measurement, in order to stably measure the patches on the recording material P, the recording material P is held between the opposing member 16 with an appropriate force capable of maintaining a normal conveyance state while suppressing the conveyance flutter. . This is because patch colorimetry is performed in a state where the amount of variation in the direction perpendicular to the conveyance direction of the recording material P is reduced as much as possible, thereby suppressing a decrease in detection accuracy.

[Explanation of colorimetric patches]
Next, the configuration of the colorimetric patch (detection patch) in the present embodiment will be described with reference to FIG. Here, the case where the size of the recording material P is A3 will be described as an example. The size of the recording material P is not limited to A3. For example, when patches are formed on the recording material P having a size smaller than A3, such as A4, the patches may be formed separately on a plurality of recording materials P. Is possible.

  The colorimetric patch formed on the recording material P includes a colorimetric patch and a correction patch for monitoring the conveyance speed of the recording material P and correcting the colorimetric timing of the colorimeter 10. Yes. The colorimeter 10 is disposed in the double-sided conveyance path D, and the recording material P is switched back and conveyed in the double-sided conveyance path D. Therefore, the leading reference patch 201 is arranged on the rear end side of the recording material P in the conveyance direction of the recording material P. A color patch group 202 for colorimetry is arranged behind the reference patch 201. The correction patch 203 is a patch for monitoring the conveyance speed of the recording material P, and is used to calculate a time T1 from when the reference patch 201 is detected until the correction patch 203 is detected.

  A color patch group 204 for colorimetry is arranged behind the correction patch 203. The color measurement timing of the color patch group 204 is controlled by the main body control unit 55 based on the calculated time T1. The correction patch 205 is a patch for monitoring the conveyance speed of the recording material P, and is used to calculate a time T2 from when the reference patch 201 is detected until the correction patch 205 is detected. A color patch group 206 for colorimetry is arranged behind the correction patch 205. The color measurement timing of the color patch group 206 is controlled by the main body control unit 55 based on the calculated time T2. Here, as an example, a configuration in which three correction patches are formed has been described, but the present invention is not limited to this. For example, three or more correction patches may be formed, or the colorimetric timing of all colorimetric color patches may be controlled from the reference patch 201.

  Next, the relationship between the conveyance roller disposed on the downstream side of the colorimeter 10 and the colorimetric patch formed on the recording material P will be described. FIG. 2 shows the double-sided conveyance roller 207 and the registration roller 47. In the present embodiment, as shown in FIG. 2, the color patch groups 202, 204, and 206 correspond to a distance L <b> 1 from the colorimetric position of the colorimeter 10 until the leading edge of the recording material P enters the double-sided conveyance roller 207. It is arranged except for the position to be. Similarly, the color patch groups 202, 204, and 206 are arranged excluding a position corresponding to a distance L 2 from the colorimetric position of the colorimeter 10 to the end of the recording material P entering the registration roller 47. That is, the formation of a patch is prohibited at a position on the recording material P that is conveyed to the detection position at the timing when the leading edge of the recording material P enters the double-sided conveyance roller 207 or the registration roller 47. The prohibition of patch formation here means that no patch is formed at a position on the recording material P conveyed to the detection position at least at the above timing. There may or may not be a patch at a position on the recording material P other than the above position, and a patch can be arbitrarily formed.

  Here, it is expressed until the leading edge of the recording material P enters, but in other words, it can be said that the leading edge of the recording material P reaches. As described above, if the patch is not formed at a position corresponding to the distance until the leading edge of the recording material P enters the double-sided conveyance roller 207 and the registration roller 47, the recording material P changes in speed, and the colorimetric accuracy is increased. This is because there is a possibility of lowering. Here, the speed fluctuation of the recording material P will be described with reference to FIG.

  FIG. 3 is a graph showing the conveyance speed of the recording material P. Reference numeral 401 denotes a position where the colorimeter 10 measures a colorimetric patch, 402 denotes a position where the recording material P enters the double-sided conveyance roller 207, and 403 denotes a position where the recording material P enters the registration roller 47. As can be seen from the transition of the graph, the conveyance speed of the recording material P greatly fluctuates due to the impact when entering the double-sided conveyance roller 207 and the registration roller 47. In other words, if the color measurement of a patch is performed at the timing when this speed fluctuation occurs, a color different from the patch to be measured is measured due to the influence of the speed fluctuation, which causes a decrease in color measurement accuracy. There is a possibility that.

  In view of such a situation, in this embodiment, the patch is not formed at a position corresponding to the distance until the leading edge of the recording material P enters the double-sided conveyance roller 207 and the registration roller 47. Further, the correction patch 203 is disposed behind the position corresponding to the distance L1 from the colorimetric position of the colorimeter 10 to the leading edge of the recording material P entering the double-sided conveyance roller 207. This is also for suppressing the influence of the speed fluctuation when the recording material P enters the nip portion of the double-sided conveyance roller 207 as described with reference to FIG.

  If the correction patch 203 is detected at the timing when the recording material P enters the nip portion of the duplex conveying roller 207, the time T1 also varies due to the speed variation. As a result, the colorimetric timing of the color patch group 204 determined based on the time T1 also fluctuates, and the colorimetric measurement cannot be performed at an appropriate timing, which causes a decrease in patch detection accuracy. In order to suppress this, the correction patch 203 is disposed at a position where the change in the conveyance speed of the recording material P is stabilized. That is, when the recording material P enters the double-sided conveyance roller 207 behind the position corresponding to the distance L1 from the colorimetric position of the colorimeter 10 to the front end of the recording material P enters the double-sided conveyance roller 207. Is arranged at a position where the change in the conveyance speed of the recording material P generated in the above is stable.

  Similarly, the correction patch 205 is disposed behind the position corresponding to the distance L <b> 2 from the colorimetric position of the colorimeter 10 until the leading edge of the recording material P enters the registration roller 47. This is also to suppress the influence of the speed fluctuation when the recording material P enters the registration roller 47 as described above with reference to FIG.

  If the correction patch 205 is detected at the timing when the recording material P enters the nip portion of the registration roller 47, the time T2 also varies due to the speed variation. As a result, the colorimetric timing of the color patch group 206 determined based on the time T2 also fluctuates, and colorimetry cannot be performed at an appropriate timing, which causes a decrease in patch detection accuracy. In order to suppress this, the correction patch 205 is disposed at a position where the change in the conveyance speed of the recording material P is stabilized. That is, it occurs when the recording material P enters the registration roller 47 behind the position corresponding to the distance L <b> 2 from the colorimetric position of the colorimeter 10 until the leading edge of the recording material P enters the registration roller 47. The recording material P to be conveyed is disposed at a position where the change in the conveyance speed is stable.

  In this embodiment, as an example, the fluctuation in the conveyance speed when the recording material P is conveyed at about 64.3 mm / s was measured. As a result, it was measured that when the leading edge of the recording material P entered the double-sided conveyance roller 207 or the registration roller 47, speed fluctuation occurred for a period of about 15.5 mse. Therefore, in order to suppress the influence of this speed fluctuation, the patches were formed with a patch interval of about 1 mm. The above numerical values are merely examples in the present embodiment, and the patch interval can be appropriately set according to the conveyance speed of the recording material P, the configuration of the conveyance roller, the detection accuracy of the patch to be obtained, or the like.

  Further, here, as an example, a method of devising the position where the patch position is formed according to the double-sided conveyance roller 207 and the registration roller 47 has been described, but the present invention is not limited to this. That is, the number of conveying rollers may be one or three or more, and the position where the patch is formed can be controlled in the above-described manner according to the number and position of the conveying rollers.

[Flowchart showing color correction control]
Color correction in this embodiment will be described with reference to the flowchart of FIG. In step S <b> 301, the main body control unit 55 causes the colorimeter 10 to protrude into the double-sided conveyance path D. In step S <b> 302, the main body control unit 55 turns on an LED that is a light source in the colorimeter 10. In step S303, the main body control unit 55 adjusts the light amount of the LED. Here, the purpose of adjusting the light quantity of the LED is to ensure colorimetric reproducibility and S / N ratio.

  In S304, the main body control unit 55 determines whether the light amount adjustment of the LED is appropriately performed. If the result of the light amount adjustment is inappropriate due to contamination of the colorimetric surface of the colorimeter 10, the main body control unit 55 turns off the LED in S318 and ends the color correction. On the other hand, if the result of the light amount adjustment is appropriate, the main body control unit 55 causes the colorimeter 10 to perform color measurement of the white reference plate which is the facing member 16 in S305. In the following description, the opposing member 16 will be described as a white reference plate. Although a white reference plate is used here, for example, it is possible to adjust a light amount by conveying a reference white recording material.

  After the color measurement of the white reference plate, the main body control unit 55 starts conveyance of the recording material P in S306. In step S <b> 307, the main body control unit 55 transfers the colorimetric patch formed on the intermediate transfer belt 37 onto the recording material P and fixes it on the fixing unit 51. The recording material P on which the colorimetric patches are fixed by the fixing unit 51 is discharged to a paper discharge tray 52b, switched back by an actuator (not shown), and conveyed into the double-sided conveyance path D. The main body control unit 55 causes the colorimeter 10 to measure the color of the patch formed on the recording material P at the timing when the recording material P conveyed in the double-sided conveyance path D passes over the colorimeter 10.

  In step S <b> 308, the main body control unit 55 performs colorimetry on the reference patch 201 that is the head of the patch formed on the recording material P. The reference patch 201 is formed only with K toner. This is because only the K toner is used because the color of the recording material P is often white and the density contrast with the recording material P is large. In this example, a single-color black toner image is formed as the reference patch 201. However, the present invention is not limited to this, and any color patch may be used as long as the colorimeter 10 can perform colorimetry. . In S308, if the reference patch 201 cannot be measured due to insufficient density or the like, in S318, the main body control unit 55 turns off the LED and ends the color correction. On the other hand, if the reference patch 201 can be measured, in step S309, the main body control unit 55 uses the colorimetric timing of the reference patch 201 as a trigger to set the timing for measuring the color patch group 202 formed after the reference patch 201. Control.

  After measuring the color patch group 202 in S309, the main body control unit 55 causes the colorimeter 10 to measure the color of the correction patch 203 formed on the recording material P in S310. The correction patch 203 is also formed only with K toner, as with the previous reference patch 201. If the correction patch 203 cannot be measured in S310, the main body control unit 55 turns off the LED in S318 and ends the color correction. On the other hand, if the correction patch 203 has been measured, in S311, the main body control unit 55 stores a time T1 from when the reference patch 201 is measured until the correction patch 203 is measured. In step S312, the main body control unit 55 controls the timing of color measurement of the color patch group 204 formed after the correction patch 203 based on the time T1 by a control signal output from the color measurement timing control unit 701 described later. .

  In step S312, after the color patch group 204 is color-measured, in step S313, the main body control unit 55 causes the colorimeter 10 to measure the color of the correction patch 205 formed on the recording material P. The correction patch 205 is also formed of only K toner, like the reference patch 201 and the correction patch 203. If the correction patch 205 cannot be measured in S313, the main body control unit 55 turns off the LED in S318 and ends the color correction. On the other hand, if the correction patch 205 has been measured, in step S314, the main body control unit 55 stores a time T2 from when the reference patch 201 is measured until the correction patch 205 is measured. In S <b> 315, the main body control unit 55 controls the timing for measuring the color patch group 206 formed after the correction patch 205 based on the time T <b> 2 by a control signal output from the color measurement timing control unit 701 described later. .

  After measuring the color patch group 206 in S315, the main body control unit 55 turns off the LED in S316. Thereafter, in S317, the main body control unit 55 calculates a color correction amount based on the color measurement result measured by the colorimeter 10, and ends the color correction.

  FIG. 5 is a block diagram showing the main body control unit 55 and the colorimeter 10 in the present embodiment. The color measurement unit 703 of the colorimeter 10 transmits the timing of measuring the color of the reference patch 201, the correction patch 203, and the correction patch 205 to the T1 / T2 calculation unit 702 of the main body control unit 55. The T1 / T2 calculation unit 702 calculates the time T1 from the timing when the reference patch 201 and the correction patch 203 are measured. Also, the time T2 is calculated from the timing when the reference patch 201 and the correction patch 205 are measured. Based on the time T1 and time T2 calculated by the color measurement unit 703, the color measurement timing control unit 701 determines the timing at which the color measurement unit 703 performs color measurement. The color measurement unit 703 performs color measurement of the color patch based on the timing (detection timing) transmitted from the color measurement timing control unit 701. Thereafter, the color measurement result (detection result) measured by the color measurement unit 703 is calculated by the color measurement calculation unit 704, and the color value of each color patch is calculated. That is, a correction value is calculated based on the detection result detected by the color measurement unit 703, and an image formed based on the calculated correction value is corrected.

  Here, as an example, a configuration in which the T1 / T2 calculation unit 702 and the colorimetric timing control unit 701 are provided in the main body control unit 55 and the colorimetric calculation unit 704 is provided in the colorimeter 10 is described. is not. The T1 / T2 calculation unit 702, the color measurement timing control unit 701, and the color measurement calculation unit 704 may be provided in either the main body control unit 55 or the colorimeter 10. For example, all three may be provided in the main body control unit 55, or all three may be provided in the colorimeter 10. That is, as long as the timing of measuring the color patch can be controlled from the result of measuring the color of the reference patch and the correction patch, either control unit may be responsible for this control.

  In this way, the color patch is formed on the recording material P except for the position corresponding to the distance from the colorimetric position of the colorimeter 10 to the leading edge of the recording material P entering the conveying roller. As a result, the color patch can be measured by suppressing the influence of the change in the conveyance speed of the recording material P when the leading end of the recording material P enters, and color correction control can be performed with high accuracy.

(Second Embodiment)
In the first embodiment, the color patch is formed on the recording material P except for the position corresponding to the distance from the colorimetric position of the colorimeter 10 to the leading edge of the recording material P entering the conveying roller. Explained. In the present embodiment, although the color patch is formed at a position corresponding to the distance from the colorimetric position of the colorimeter 10 to the leading edge of the recording material P enters the conveyance roller, the patch formed at the corresponding position is measured. A method of not coloring will be described. In addition, description here is abbreviate | omitted about the structure similar to previous 1st Embodiment.

[Explanation of colorimetric patches]
The configuration of the colorimetric patch (detection patch) in this embodiment will be described with reference to FIG. In addition, description here is abbreviate | omitted about the structure similar to what was demonstrated in previous FIG. The difference from the patch of FIG. 2 is that a color patch 202a is arranged at a position corresponding to a distance L1 from the colorimetric position of the colorimeter 10 to the leading edge of the recording material P entering the double-sided conveyance roller 207. A color patch 204 a is arranged at a position corresponding to a distance L 2 from the colorimetric position of the colorimeter 10 to the point where the leading edge of the recording material P enters the registration roller 47. Although a patch is formed at a position corresponding to the distance until the leading edge of the recording material P enters the double-sided conveyance roller 207 and the registration roller 47, speed fluctuation occurs in the recording material P, and the colorimetric accuracy is lowered. There is a possibility that. Therefore, color measurement of the color patches 202a and 204a is not performed.

  Note that “do not measure color” in the present embodiment means that an output value based on the detection operation by the colorimeter 10 is not obtained. For example, the colorimetric values (output values) of the color patches 202a and 204a are obtained from the amount of light received by the light receiving unit that does not irradiate light from the light emitting unit of the colorimeter 10, does not receive light by the light receiving unit of the colorimeter 10. “No color measurement” can be performed by a method such as “No”.

[Flowchart showing color correction control]
The color correction in the present embodiment will be described using the flowchart of FIG. Note that description of steps similar to those in the flowchart of FIG. 4 is omitted.

  Steps S301 to S309 are the same as those in FIG. In step S <b> 601, the main body control unit 55 determines whether or not the color measurement of all the color patches arranged from the reference patch 201 to the correction patch 203 has been completed. If the color measurement of all the color patches has been completed, the process proceeds to S310. If the color measurement of all the color patches has not been completed, the process proceeds to S602. In step S <b> 602, the main body control unit 55 determines whether or not the color measurement patch is disposed on the recording material P at a position corresponding to the distance L <b> 1 from the color measurement position of the colorimeter 10 to the duplex conveyance roller 207. . If it is arranged at a corresponding position, in S603, the main body control unit 55 controls the colorimeter 10 so that the color measurement of the patch is not performed. If it is not arranged at the corresponding position, the process proceeds to S309 and the colorimetry is continued.

  Steps S310 to S312 are the same as those in FIG. In step S <b> 604, the main body control unit 55 determines whether the color measurement of all the color patches arranged from the correction patch 203 to the correction patch 205 has been completed. If all color patches have been measured, the process proceeds to S313. If all color patches have not been measured, the process proceeds to S605. In step S <b> 605, the main body control unit 55 determines whether or not the color measurement patch is disposed on the recording material P at a position corresponding to the distance L <b> 2 from the color measurement position of the colorimeter 10 to the registration roller 47. If it is arranged at a corresponding position, in S606, the main body control unit 55 controls the colorimeter 10 so that the color measurement of the patch is not performed. If it is not located at the corresponding position, the process proceeds to S312 and the colorimetry is continued. Steps S313 to S318 are the same as those in FIG.

  FIG. 8 is a block diagram showing the main body control unit 55 and the colorimeter 10 in the present embodiment. Since 701 to 704 in FIG. 8 have the same configuration as in FIG. 5, description thereof is omitted here. The difference from FIG. 5 is that the distance L1 and the distance L2 are calculated by the L1 / L2 calculation unit 705. The L1 / L2 calculation unit 705 stores the distance from the leading edge of the recording material P to the reference patch 201 in advance. The L1 / L2 calculation unit 705 calculates positions corresponding to L1 and L2 based on the timing at which the reference patch 201 is detected by the colorimeter 10 and the conveyance speed of the recording material P. The L1 / L2 calculation unit 705 transmits information on the positions corresponding to the calculated L1 and L2 to the colorimetric timing control unit 701. Based on the position information corresponding to L1, the colorimetric timing control unit 701 does not measure the color of the patch arranged at the position corresponding to the duplex conveying roller 207 from the colorimetric position of the colorimeter 10 on the recording material P. In addition, the timing for measuring the color patch is controlled. Further, the colorimetric timing control unit 701 does not perform colorimetry on the patch arranged at the position corresponding to the registration roller 47 from the colorimetric position of the colorimeter 10 on the recording material P based on the position information corresponding to L2. As described above, the timing for measuring the color of the color patch is controlled.

  Here, as an example, a configuration in which the T1 / T2 calculation unit 702, the colorimetric timing control unit 701, and the L1 / L2 calculation unit 705 are included in the main body control unit 55, and the colorimetric calculation unit 704 is described in the colorimeter 10 is described. However, it is not limited to this. The T1 / T2 calculation unit 702, the color measurement timing control unit 701, the L1 / L2 calculation unit 705, and the color measurement calculation unit 704 may be provided in either the main body control unit 55 or the colorimeter 10. For example, all four may be provided in the main body control unit 55, or all four may be provided in the colorimeter 10. That is, as long as the timing of measuring the color patch can be controlled from the result of measuring the color of the reference patch and the correction patch, either control unit may be responsible for this control.

  In this way, the colorimeter 10 measures the color patch except for a position corresponding to the distance from the colorimetric position of the colorimeter 10 until the leading edge of the recording material P enters the conveyance roller. As a result, the color patch can be measured by suppressing the influence of the change in the conveyance speed of the recording material P when the leading end of the recording material P enters, and color correction control can be performed with high accuracy.

(Third embodiment)
In the previous second embodiment, although the color patch is formed at a position corresponding to the distance from the colorimetric position of the colorimeter 10 until the leading edge of the recording material P enters the conveyance roller, it is formed at the corresponding position. Explained how to avoid color measurement of patches. In the present embodiment, although the color patch formed at a position corresponding to the distance from the colorimetric position of the colorimeter 10 to the leading edge of the recording material P enters the conveying roller is measured, the color correction amount is calculated. A method that is not used as information will be described. In addition, about the structure similar to previous 1st Embodiment and 2nd Embodiment, description here is abbreviate | omitted.

[Explanation of colorimetric patches]
The colorimetric patch (detection patch) in this embodiment has the same configuration as the colorimetric patch described in FIG. 6 of the second embodiment, and a description thereof is omitted here. A difference from the second embodiment is that color measurement is performed on a patch arranged at a position corresponding to a distance until the leading edge of the recording material P enters the double-sided conveyance roller 207 and the registration roller 47. However, since the speed fluctuation may occur in the recording material P and the color measurement accuracy may be lowered, the color measurement results of the color patches 202a and 204a are not used for the calculation of the color correction amount. Note that “color measurement” in the present embodiment with respect to the second embodiment is to obtain a colorimetric value (detection value) based on the detection operation of the colorimeter 10. However, the present embodiment is characterized in that the output obtained from the color patches 202a and 204a is not used for calculation of color correction.

[Flowchart showing color correction control]
Color correction in the present embodiment will be described using the flowchart of FIG. Note that description of steps similar to those in the flowchart of FIG. 4 is omitted.

  Steps S301 to S316 are the same as those in FIG. In step S901, a color correction amount is calculated. At this time, the main body control unit 55 does not use the color measurement result of the patch arranged at the position corresponding to the distance L1 from the color measurement position of the color measuring device 10 on the recording material P to the duplex conveying roller 207. Further, the color measurement result of the patch arranged at the position corresponding to the distance L2 from the color measurement position of the color measuring device 10 on the recording material P to the registration roller 47 is not used. A color correction amount is calculated based on the result excluding the color measurement result. Since S318 is the same as FIG. 4, description thereof is omitted. Here, excluding the color measurement result means that the detection result from the position on the recording material P conveyed to the detection position at least at the above timing is excluded. For example, it is possible to further improve the accuracy of color correction by excluding detection results that may include noise from detection results other than the upper one.

  The block diagram showing the main body control unit 55 and the colorimeter 10 in the present embodiment is the same as FIG. 8 of the second embodiment, and will be described with reference to FIG. Since the configuration of each block is the same as in the second embodiment, detailed description thereof is omitted. Here, transmission of information different from that of the second embodiment will be described. The L1 / L2 calculation unit 705 calculates positions corresponding to L1 and L2 based on the timing at which the reference patch 201 is detected by the colorimeter 10 and the conveyance speed of the recording material P. The L1 / L2 calculation unit 705 transmits information on the positions corresponding to the calculated L1 and L2 to the colorimetric calculation unit 704. The colorimetric calculation unit 704 uses the colorimetric results of the patches arranged from the colorimetric position of the colorimeter 10 on the recording material P to the position corresponding to the double-sided conveyance roller 207 based on the position information corresponding to L1. Not in. Further, based on the position information corresponding to L2, the color measurement result of the patch arranged at the position corresponding to the registration roller 47 from the color measurement position of the color measuring device 10 on the recording material P is not used. Calculation is performed based on the result excluding the above colorimetric result.

  Here, as an example, a configuration in which the T1 / T2 calculation unit 702, the colorimetric timing control unit 701, and the L1 / L2 calculation unit 705 are included in the main body control unit 55, and the colorimetric calculation unit 704 is described in the colorimeter 10 is described. However, it is not limited to this. The T1 / T2 calculation unit 702, the color measurement timing control unit 701, the L1 / L2 calculation unit 705, and the color measurement calculation unit 704 may be provided in either the main body control unit 55 or the colorimeter 10. For example, all four may be provided in the main body control unit 55, or all four may be provided in the colorimeter 10. That is, as long as the timing of measuring the color patch can be controlled from the result of measuring the color of the reference patch and the correction patch, either control unit may be responsible for this control.

  As described above, the color measurement calculation unit 704 does not use the color measurement result of the patch arranged at the position corresponding to the distance from the color measurement position of the colorimeter 10 to the leading edge of the recording material P enters the conveyance roller. The color correction amount is calculated. As a result, the influence of fluctuations in the conveyance speed of the recording material P when the leading edge of the recording material P enters can be suppressed, and color correction control can be performed with high accuracy.

(Modification)
The arrangement location of the colorimeter 10 is not limited to the direction orthogonal to the conveyance direction of the recording material P, that is, the central position in the longitudinal direction, and may be arranged at any position in the longitudinal direction. Further, the number of colorimeters 10 is not limited to one, and a plurality of colorimeters may be installed. Further, the configuration in which the facing member 16 is disposed at a position opposite to the color measuring device 10 has been described. However, it is possible to perform color measurement even in a configuration without the facing member 16. The colorimeter 10 can be of a type that receives light separated by a diffraction grating, a type that receives light that has passed through an RGB color filter, or the like.

  Further, the reference patch 201 and the correction patches 203 and 205 are not limited to K toner, and may be any color that can provide contrast with the recording material P. Further, although the electrophotographic image forming apparatus using the intermediate transfer belt has been described as an example of the image forming apparatus, an electrophotographic image forming apparatus using the transfer conveyance belt system may be used. Further, the colorimeter can be mounted on an existing image forming apparatus such as an ink jet image forming apparatus or a thermal transfer image forming apparatus.

P Recording material 10 Colorimeter 47 Registration roller 307 Double-sided conveyance roller 202, 204, 206 Color patch

Claims (14)

Forming means for forming detection patches on the recording material;
Detection means for detecting a detection patch formed on the recording material being conveyed at a detection position;
A transport unit configured to transport a recording material disposed downstream of the detection position in the transport direction of the recording material,
The forming unit prohibits the detection patch from being formed at a position on the recording material that is transported to the detection position at a timing when the leading edge of the recording material reaches the transporting unit. apparatus.   The image forming apparatus according to claim 1, further comprising a correcting unit that corrects an image formed by the forming unit based on a detection result detected by the detecting unit.   The forming means has a correction patch for correcting the detection timing by the detection means on the downstream side of the position on the recording material conveyed to the detection position at the timing when the leading edge of the recording material reaches the conveyance means. The image forming apparatus according to claim 1, wherein the image forming apparatus is formed. Fixing means for fixing the detection patch formed on the recording material,
4. The image according to claim 1, wherein the detection unit is disposed between the time when the recording material is fixed on the fixing unit and before the recording material is discharged from the image forming apparatus. 5. Forming equipment.   The image forming apparatus according to claim 1, wherein the forming unit forms a single color toner image or a mixed color toner image as the detection patch. Forming means for forming detection patches on the recording material;
Detection means for detecting a detection patch formed on the recording material being conveyed at a detection position;
A transport unit configured to transport a recording material disposed downstream of the detection position in the transport direction of the recording material,
When the detection means detects the detection patch, the detection means detects the detection patch formed at a position on the recording material that is conveyed to the detection position at a timing when the leading edge of the recording material reaches the conveyance means. An image forming apparatus characterized by prohibiting   The image forming apparatus according to claim 6, further comprising a correcting unit that corrects an image formed by the forming unit based on a detection result detected by the detecting unit.   The forming means corrects the detection timing by the detection means downstream of the position on the recording material being transported to the detection position at the timing when the leading edge of the recording material reaches the transport means. The image forming apparatus according to claim 6, wherein a patch is formed. Fixing means for fixing the detection patch formed on the recording material,
9. The image according to claim 6, wherein the detection unit is disposed between the time when the recording material is fixed on the fixing unit and before the recording material is discharged from the image forming apparatus. Forming equipment.   The image forming apparatus according to claim 6, wherein the forming unit forms a single color toner image or a mixed color toner image as the detection patch. Forming means for forming detection patches on the recording material;
Detection means for detecting a detection patch formed on the recording material being conveyed at a detection position;
Transport means for transporting the recording material disposed downstream of the detection position in the transport direction of the recording material;
Correcting means for correcting the image formed by the forming means based on the detection result detected by the detecting means;
The correction unit performs correction based on a detection result excluding at least a detection result detected at a position on the recording material conveyed to the detection position at a timing when the leading edge of the recording material reaches the conveyance unit. An image forming apparatus.   The forming means corrects the detection timing by the detection means downstream of the position on the recording material being transported to the detection position at the timing when the leading edge of the recording material reaches the transport means. The image forming apparatus according to claim 11, wherein a patch is formed. Fixing means for fixing the detection patch formed on the recording material,
The image forming apparatus according to claim 11, wherein the detection unit is disposed after the recording material is fixed to the fixing unit and before being discharged from the image forming apparatus.   The image forming apparatus according to claim 11, wherein the forming unit forms a single color toner image or a mixed color toner image as the detection patch.

Images