JP2016009132A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute color shift correction in accordance with execution conditions of color shift correction according to a change in temperature inside an apparatus.SOLUTION: A control part executes color shift correction at a time S1, acquires information T0 on a temperature inside an apparatus during the execution of the color shift correction, and stored the information (S110). The control part subsequently acquires information Tb on a temperature inside the apparatus at a time S2 and stores the information in the storage part (S120), and then acquires information Tn on a temperature inside the apparatus at a time S3 and stores the information in the storage part (S130). When the acquired temperature information Tn is equal to or higher than the temperature information Tb, the control part determines that the temperature inside the apparatus has increased (S140), and when Tn-T0 equals 3°C, executes color shift correction (S150 and S160). Meanwhile, when the acquired temperature information Tn is lower than the temperature information Tb, the control part determines that the temperature inside the apparatus has decreased (S140), and when T0-Tn equals 1°C, executes color shift correction (S160 and S180).

Description

  The present invention relates to an image forming apparatus that forms an image on a sheet.

  2. Description of the Related Art Conventionally, electrophotographic image forming apparatuses having a plurality of functions such as printers, copiers, and facsimiles have been widely used. In the image forming apparatus, an electrostatic latent image is formed by irradiating each photoconductor with laser light based on an image signal by an exposure unit corresponding to each color, and the toner image on each photoconductor is formed on an intermediate transfer belt. A color image is formed by sequentially transferring and superimposing the images of the respective colors.

  Although high accuracy is required during the transfer operation for superimposing each color image, generally the color of the image is caused by deviations in the scanning position of the exposure part (print head) of each color or uneven driving due to mechanical accuracy. Deviation may occur. Therefore, in order to obtain stable image quality, a plurality of registration marks (color misregistration correction marks) are formed on the intermediate transfer body before and after the printing operation and during the printing operation, and based on the detection results of these registration marks. Color misregistration correction (color registration correction) control for correcting the printing start position and the like is performed.

  For example, in Patent Document 1, a color misregistration correction table composed of data of in-machine temperature and color misregistration amount is created, and the in-machine temperature is supported by referring to the color misregistration correction table from the in-machine temperature acquired during the printing operation. An image forming apparatus that calculates a color misregistration amount to be performed and performs color misregistration correction based on the calculated color misregistration amount is described.

JP 2012-58382 A

  Here, a general relationship between the temperature and the color misregistration amount will be described. FIG. 5 is a graph showing the relationship between the temperature difference between the periphery of the apparatus and in the apparatus, and the color misregistration amount of the image that changes according to the temperature difference. The vertical axis represents the color misregistration amount, and the horizontal axis represents the temperature difference between the periphery of the apparatus and the apparatus.

  Generally, when a printing operation is continuously performed, the temperature in the apparatus increases. During the printing operation, the temperature in the device is controlled by operating the fan provided in the device, so there is a correlation (linear) between the temperature difference between the device periphery and in the device, and the amount of color misregistration. Sex). Specifically, as shown by the solid line in FIG. 5, the color shift amount increases as the temperature difference increases, and it can be seen that the value changes to a value close to the theoretical value indicated by the one-dot chain line in FIG.

  On the other hand, when the printing operation is stopped due to the end of the job, the internal temperature decreases. When the temperature in the apparatus is decreasing, unlike in the printing operation, the temperature in the apparatus is not controlled by the fan, so the temperature change in the apparatus may not be constant (regular). In addition, after the printing operation is stopped, changes in the environment around the device, the operation mode immediately before stopping the printing operation, the use state of the device such as whether jam processing is performed, etc., also affect the temperature change in the device. May give. Specifically, as shown by a broken line in FIG. 5, when the temperature difference between the periphery of the apparatus and the interior of the apparatus becomes equal to or higher than a predetermined temperature, the variation of the color misregistration amount becomes large and changes different from the theoretical value. .

  As described above, the correlation between the temperature difference between the device periphery and the device and the color misregistration amount differs between the case where the temperature inside the device is rising and the case where the temperature inside the device is falling. As in the conventional image forming apparatus described in the literature 1, etc., it is not preferable to set the color misregistration correction execution conditions to be the same under different temperature changes. When color misregistration correction is performed according to one of the temperature conditions, unnecessary correction operations increase and productivity may decrease, or problems such as color misregistration correction not being executed at the optimal timing may occur. is there.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of performing color misregistration correction according to a temperature change in the apparatus.

  In order to solve the above-described problem, an image forming apparatus according to the present invention executes a temperature detection unit that detects a temperature in the apparatus, and performs image color misregistration correction based on the temperature in the apparatus detected by the temperature detection unit. Whether or not to execute color misregistration correction based on different execution conditions depending on whether the temperature inside the device is rising or when the temperature inside the device is falling Is to judge.

  Further, the control unit of the image forming apparatus according to the present invention, when the temperature in the apparatus is rising, the temperature difference in the apparatus between the previous color misregistration correction and the current time, and the set first execution condition. To determine whether or not to perform color misregistration correction, and if the temperature in the device is falling, the temperature difference in the device between the previous color misregistration correction and the current time is set Whether or not to perform color misregistration correction can be determined by comparing the second execution condition with a value smaller than the first execution condition.

  Further, the control unit of the image forming apparatus according to the present invention increases or decreases the temperature in the apparatus based on the current temperature in the apparatus and the temperature in the apparatus after the previous color misregistration correction. Can be determined.

  According to the present invention, it is determined whether or not to perform color misregistration correction based on different execution conditions depending on whether the temperature in the apparatus is rising or the temperature in the apparatus is decreasing. Color misregistration correction can be executed at an optimal timing in each temperature state.

1 is a diagram illustrating a configuration example of an image forming apparatus according to an embodiment of the present invention. 1 is a diagram illustrating a block configuration example of an image forming apparatus. It is a figure for demonstrating the structural example of a registration mark, and color shift correction. 6 is a flowchart illustrating an operation example of the image forming apparatus during color misregistration correction. It is a graph which shows the relationship between the color difference amount which changes according to the temperature difference between apparatus periphery and an apparatus, and a temperature difference.

  Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In addition, the dimension ratio of drawing is expanded on account of description and may differ from an actual ratio.

[Configuration example of image forming apparatus]
First, an image forming apparatus 100 according to an embodiment of the present invention will be described. FIG. 1 shows an example of the configuration of an image forming apparatus 100 according to the present invention. As shown in FIG. 1, the image forming apparatus 100 is called a tandem type image forming apparatus, and includes an automatic document feeder 80 and an apparatus main body 102. The automatic document conveyance unit 80 is attached to the upper part of the apparatus main body 102 and sends out the paper set on the conveyance table to the image reading unit 90 of the apparatus main body 102 by a conveyance roller or the like.

  The apparatus main body 102 includes an operation display unit 70, an image reading unit 90, an image forming unit 10, an intermediate transfer belt 8, a paper feeding unit 20, a registration roller 32, a fixing unit 44, and an automatic paper reversing and conveying unit. 60 (Auto Duplex Unit: hereinafter referred to as ADU), a temperature detection unit 200, and image detection units 202A and 202B.

  The operation display unit 70 includes a touch panel in which a display unit and an input unit are combined, and a plurality of operation keys including a start key and a determination key provided in a peripheral part of the touch panel. The operation display unit 70 displays a menu screen or the like on the screen, or accepts various information such as an image forming condition and a fixing condition input by a touch operation on the menu screen or an operation key operation.

  The image reading unit 90 scans and exposes a document placed on a document table or a document transported by the automatic document transport unit 80 by an optical system of a scanning exposure device, and an image of the scanned document is CCD (Charge Coupled Device). An image information signal is generated by photoelectric conversion by an image sensor. The image information signal is output to the image forming unit 10 after being subjected to analog processing, analog / digital (hereinafter referred to as A / D) conversion processing, pseudo correction, image compression processing, and the like by an image processing unit (not shown).

  The image forming unit 10 forms an image by electrophotography, and includes an image forming unit 10Y that forms a yellow (Y) image, an image forming unit 10M that forms a magenta (M) image, The image forming unit 10C forms a cyan (C) color image, and the image forming unit 10K forms a black (K) color image. In this example, common function names, for example, Y, M, C, and K indicating colors to be formed are added after the reference numeral 10 for description.

  The image forming unit 10Y includes a photosensitive drum 1Y, a charger 2Y, an exposure unit (optical writing unit) 3Y, a developing unit 4Y, and a cleaning unit 6Y arranged around the photosensitive drum 1Y. The image forming unit 10M includes a photosensitive drum 1M, a charger 2M, an exposure unit 3M, a developing unit 4M, and a cleaning unit 6M disposed around the photosensitive drum 1M. The image forming unit 10C includes a photosensitive drum 1C, and a charger 2C, an exposure unit 3C, a developing unit 4C, and a cleaning unit 6C disposed around the photosensitive drum 1C. The image forming unit 10K includes a photosensitive drum 1K, a charger 2K, an exposure unit 3K, a developing unit 4K, and a cleaning unit 6K disposed around the photosensitive drum 1K.

  Respective photosensitive drums (image carriers) 1Y, 1M, 1C, and 1K in the image forming units 10Y, 10M, 10C, and 10K, chargers 2Y, 2M, 2C, and 2K, exposure units 3Y, 3M, 3C, and 3K, development The devices 4Y, 4M, 4C, and 4K and the cleaning units 6Y, 6M, 6C, and 6K have the same configuration. In the following description, Y, M, C, and K are not used unless particularly distinguished.

  The charger 2 charges the surface of the photosensitive drum 1 almost uniformly. The exposure unit 3 includes, for example, an LPH (LED Print Head) having an LED array and an imaging lens, or a polygon mirror type laser exposure scanning device, and scans the photosensitive drum 1 with laser light based on an image information signal. Thus, an electrostatic latent image is formed. The developing device 4 develops the electrostatic latent image formed on the photosensitive drum 1 with toner. As a result, a toner image which is a visible image is formed on the photosensitive drum 1.

  The intermediate transfer belt 8 is stretched by a plurality of primary transfer rollers 7 or the like and is rotatably supported. Along with the rotation of the intermediate transfer belt 8, the primary transfer roller 7 and the photosensitive drum 1 rotate, and a predetermined voltage is applied between the primary transfer roller 7 and the photosensitive drum 1, whereby the photosensitive drum. 1 is transferred onto the intermediate transfer belt 8 (primary transfer).

  The paper feed unit 20 has a plurality of paper feed trays 20A and 20B in which paper P such as A3 and A4 is accommodated. The paper P transported from the paper feed trays 20A, 20B by the rollers 22, 24, 26, 28, etc. is transported to the registration rollers 32. Note that the number of paper feed trays is not limited to two. Further, a single or a plurality of large-capacity paper feeders that can accommodate a large-capacity paper P may be connected as necessary.

  The leading edge of the paper P conveyed to the registration roller 32 is abutted against the registration roller 32 by the loop roller 30 to form a loop, and the bending (for example, skew) of the paper P in the paper conveyance direction D1 is corrected. The The paper P in which the bending of the paper P is corrected is conveyed to the secondary transfer roller 34 at a predetermined timing. In the secondary transfer roller 34, the Y, M, C, and K toner images transferred on the intermediate transfer belt 8 in a superimposed manner are collectively transferred onto the surface of the sheet P conveyed by the registration roller 32 (secondary transfer). Transcription). The second-transferred sheet P is conveyed to the fixing unit 44 on the downstream side in the sheet conveying direction D1.

  The fixing unit 44 includes a pressure roller and a heating roller. The fixing unit 44 fixes the toner image on the surface of the paper P to the paper P by applying pressure and heat treatment to the paper P on which the toner image has been transferred by the secondary transfer roller 34.

  A transport path switching section 48 for switching the transport path of the paper P to the discharge path side or the ADU 60 side is provided on the downstream side of the fixing section 44 in the paper transport direction D1. The transport path switching unit 48 performs transport path switching control based on the selected print mode (single-sided print mode, double-sided print mode, or the like).

  The paper P on which single-sided printing has been completed in the single-sided printing mode or the paper P on which double-sided printing has been completed in the double-sided printing mode is discharged onto the paper discharge tray by the paper discharge roller 46.

  In the double-sided printing mode, when an image is formed on the back side of the paper P, the paper P on which the image is formed on the front side is transported to the ADU 60 via the transport roller 62 and the like. In the switchback path of the ADU 60, the reverse rotation control of the ADU roller 64 causes the rear end of the paper P to be transported to the U-turn path section, and is reversed by the transport rollers 66 and 68 provided in the U-turn path section. In this state, the paper is fed again to the secondary transfer roller 34.

  The temperature detection unit 200 is disposed in the vicinity of the primary transfer roller 7 that is easily affected by a temperature change, for example, and on the back side in the apparatus main body 102. By disposing the temperature detection unit 200 on the back side, it is possible to accurately detect a temperature change in the device due to outside air taken in from the front side of the device and exhausted to the back side of the device. The temperature detection unit 200 has a smaller heat capacity than the photosensitive drum 1 and the like, and it is necessary to prevent erroneous detection of temperature due to hot air from the fixing unit 44. preferable.

  The image detection units 202A and 202B are composed of, for example, a light emitting unit made of an LED or the like and a light receiving unit made of a photodiode or the like, and are arranged on both ends of the intermediate transfer belt 8 in the width direction (main scanning direction), for example. Yes. Hereinafter, for the sake of convenience, the image detection units 202A and 202B may be simply referred to as the image detection unit 202. The image detection unit 202 detects a registration mark (see FIG. 3) formed on the intermediate transfer belt 8 at the time of color misregistration correction. In this example, an example in which two image detection units 202A and 202B are used has been described. However, three or more image detection units 202 may be configured according to the number of registration marks.

[Block Configuration Example of Image Forming Apparatus]
Next, a block configuration example of the image forming apparatus 100 will be described. FIG. 2 shows an example of a block configuration of the image forming apparatus 100. As shown in FIG. 2, the image forming apparatus 100 includes a control unit 50 that controls the operation of the entire apparatus. The control unit 50 includes a CPU (Central Processing Unit) 52, a ROM (Read Only Memory) 54, and a RAM (Random Access Memory) 56. The CPU 52 controls each part of the image forming apparatus 100 by developing and executing software (program) read from the ROM 54 in the RAM 56, and realizes functions relating to color misregistration correction and image forming processing.

  When executing the color misregistration correction, the control unit 50 uses a color misregistration correction threshold (execution condition) that differs depending on whether the temperature in the apparatus is increasing or the temperature in the apparatus is decreasing. It is determined whether or not deviation correction is performed. Specifically, the threshold value (second execution condition) used when the temperature in the apparatus is decreasing is smaller than the threshold value (first execution condition) used when the temperature in the apparatus is increasing. Is set to a value. This is because when the temperature in the apparatus is decreasing, the correlation between the temperature difference in the apparatus and the amount of color misregistration is not constant (see the broken line in FIG. 5), so the conditions for color misregistration correction are severe. This is because it is necessary to set and execute color misregistration correction at an optimal timing. Further, if the threshold value is set large when the temperature in the apparatus is decreasing, color misregistration correction may not be executed even when color misregistration occurs.

  The control unit 50 includes a temperature detection unit 200, image detection units 202A and 202B, an operation display unit 70, an image reading unit 90, an image forming unit 10, a paper feeding unit 20, a fixing unit 44, and a storage. The unit 92 and the communication unit 94 are connected to each other. The temperature detection unit 200 detects the temperature in the image forming apparatus 100 and supplies temperature information to the control unit 50. The image detection units 202A and 202B detect registration marks formed on the intermediate transfer belt 8 and supply detection signals to the control unit 50.

  The operation display unit 70 displays a predetermined operation screen based on the display signal supplied from the control unit 50, or supplies the control unit 50 with an operation signal based on a user operation received through an operation screen, an operation key, or the like. Or

  The image reading unit 90 reads the image of the paper P placed on the document table or the like to generate image data, and supplies the generated image data to the control unit 50 or the like. The image forming unit 10 forms a predetermined image on the paper P based on image data supplied from the control unit 50 or the like, or forms a registration mark on the intermediate transfer belt 8.

  The paper feed unit 20 takes out a predetermined paper P from the paper feed tray 20 </ b> A or the like based on the paper information supplied from the control unit 50 and conveys the paper toward the secondary transfer roller 34. The fixing unit 44 heats a built-in heater based on the drive signal supplied from the control unit 50 to fix the toner image on the surface of the paper P.

  The storage unit 92 includes, for example, a nonvolatile semiconductor memory, an HDD (Hard Disk Drive), or the like. The storage unit 92 stores temperature information (T0, Tb, Tn shown in FIG. 4) detected in the apparatus detected by the temperature detection unit 200, and is used when determining whether to perform color misregistration correction. Threshold values (first threshold value, second threshold value) as conditions are stored. For example, 3 ° C. is stored as the first threshold used when the temperature in the apparatus is rising, and 1 ° C. is stored as the second threshold used when the temperature in the apparatus is decreasing. .

  The communication unit 94 includes a network interface and the like, and transmits and receives data to and from an external device connected via a network such as a LAN.

[About color misregistration correction]
First, registration marks 120K, 120C, 120M, and 120Y (sometimes collectively referred to as registration marks 120) formed during color misregistration correction will be described. FIG. 3 is a diagram for explaining registration marks 120 and color misregistration correction. As shown in FIG. 3, the registration marks 120K, 120C, 120M, and 120Y for each color are formed along the sub-scanning direction D1 (paper transport direction) on the intermediate transfer belt 8, and the image detection units 202A and 202B. Are formed at positions corresponding to. The registration mark 120K is configured by combining a mark 121K extending in the main scanning direction D2 and a mark 122K extending in a direction inclined by a predetermined angle (for example, 45 degrees) with respect to the mark 121K in a planar shape. Since the other registration marks 120C, 120M, and 120Y have the same configuration as that of the registration mark 120K, detailed description thereof is omitted.

  Next, color misregistration correction will be described with reference to FIG. When the color misregistration correction is started, the registration marks 120K, 120C, 120M, and 120Y are detected by the image detection units 202A and 202B. The control unit 50 detects a time T1 from the detection of the mark 121K of the K-color registration mark 120K to the detection of the mark 121C of the next C-color registration mark 120C, and a preset mark 121K of the registration mark 120K. Based on the comparison result with the reference time Ts between the registration mark 120C and the mark 121C, the color shift amount of the image in the sub-scanning direction D1 between the K color image and the C color image is calculated.

  Further, the control unit 50 detects the time T2 from the detection of the mark 122K of the K-color registration mark 120K to the detection of the mark 122C of the next C-color registration mark 120C, and the time T1 obtained by the previous detection. Based on the comparison result with (or the reference time Ts), the color misregistration amount of the image in the main scanning direction D2 between the K color image and the C color image is calculated.

  In the above-described example, the case of calculating the color misregistration amount in the main scanning direction D2 and the sub-scanning direction D1 has been described. However, the present invention is not limited to this, and other color misregistration amounts such as bow correction are calculated. You can also

[Operation example of image forming apparatus]
Next, an operation example of the image forming apparatus 100 when executing color misregistration correction according to an embodiment of the present invention will be described. FIG. 4 is a flowchart illustrating an example of the operation of the image forming apparatus 100 when color misregistration correction is performed.

  As shown in FIG. 4, in step S <b> 100, the control unit 50 determines whether or not the image forming apparatus 100 is powered on. The power source includes a main power source and a sub power source. If the control unit 50 determines that the power of the image forming apparatus 100 is on, the control unit 50 proceeds to step S110. If the control unit 50 determines that the power of the image forming apparatus 100 is not on, the control unit 50 continues the power state of the image forming apparatus 100. To monitor.

  In step S110, the control unit 50 executes color misregistration correction. The color misregistration correction is executed, for example, when the power is turned on (in the morning) or when there is a predetermined temperature change in the apparatus as will be described later. In this example, the execution time of color misregistration correction in step S110 is time S1. Further, the control unit 50 acquires the temperature information T0 in the apparatus at the time S1 when the color misregistration correction is performed from the temperature detection unit 200, and stores the acquired temperature information T0 in the apparatus in the storage unit 92.

  In step S120, the control unit 50 acquires the temperature information Tb in the apparatus at time S2 after a predetermined time has elapsed from time S1, from the temperature detection unit 200, and stores the acquired temperature information Tb in the apparatus in the storage unit 92. The time S2 is, for example, a time one minute before the time S3 described later. As a result, it is possible to determine with high accuracy and accuracy whether the temperature in the apparatus has recently increased or decreased immediately after determining whether or not to perform color misregistration correction.

  In step S <b> 130, the control unit 50 acquires the temperature information Tn in the apparatus at the time S <b> 3 after a predetermined time has elapsed from the time S <b> 2 from the temperature detection unit 200, and stores the acquired temperature information Tn in the apparatus in the storage unit 92. In this example, the time S3 is the current time.

  In step S140, the control unit 50 compares the acquired temperature information Tn at time S3 in the apparatus with the temperature information Tb at time S2, and determines whether the temperature information Tn is equal to or higher than the temperature information Tb. When the control unit 50 determines that the acquired temperature information Tn is equal to or higher than the temperature information Tb, the temperature in the device has increased, or the temperature in the device has fluctuated between time S2 and time S3. It judges that there is no, and it progresses to step S150. On the other hand, if the control unit 50 determines that the acquired temperature information Tn is less than the temperature information Tb, the control unit 50 determines that the temperature in the apparatus is decreasing and proceeds to step S180.

  When the temperature information Tn is equal to or higher than the temperature information Tb, in step S150, the control unit 50 subtracts the temperature information T0 at time S1 from the temperature information Tn at time S3 (Tn−T0), and the calculation result (temperature difference) is obtained. It is determined whether or not the predetermined threshold value is 3 ° C. When determining that the calculation result is 3 ° C., the control unit 50 determines that the color misregistration of the image (registration mark 120) exceeds the allowable value (set value), and proceeds to step S160.

  In step S160, if the temperature in the apparatus has risen and the temperature difference in the apparatus between the current time (time S3) and the previous color shift correction time (time S1) is 3 ° C., the controller 50 performs color shift correction. Since the execution condition is satisfied, color misregistration correction is executed. For example, the control unit 50 performs color misregistration correction in the main scanning direction and the sub-scanning direction as color misregistration correction. In this example, the execution time of color misregistration correction in step S160 is time S4.

  Subsequently, in step S170, the control unit 50 acquires the temperature information T0 in the apparatus at the time S4 at the time of the current color misregistration correction from the temperature detection unit 200, and the temperature information stored in the storage unit 92 at the previous color misregistration correction. Is updated to the latest temperature information T0. As the update information of the temperature information T0, the temperature information Tn at the time S3 can be used when the time difference between the time S3 and the time S4 is short.

  On the other hand, if the control unit 50 determines in step S150 that the calculation result does not reach 3 ° C. (below 3 ° C.), the color shift of the image does not exceed the allowable value or the color shift has not occurred. It judges and returns to step S120 and monitors the temperature state in an apparatus continuously.

  On the other hand, when the temperature information Tn is less than the temperature information Tb, in step S180, the control unit 50 subtracts the temperature information Tn at time S3 from the temperature information T0 at time S1 (T0-Tn), and the calculation result ( It is determined whether or not (temperature difference) is 1 ° C. preset as a threshold value. When determining that the calculation result is 1 ° C., the control unit 50 determines that the color misregistration of the image exceeds the allowable value, and proceeds to step S160.

  In step S160, if the temperature in the apparatus has decreased and the temperature difference between the previous color misregistration correction (time S1) and the current (time S3) is 1 ° C., the control unit 50 sets the color misregistration correction execution condition. Since this is satisfied, color misregistration correction is executed. For example, the control unit 50 performs color misregistration correction in the main scanning direction and the sub-scanning direction as color misregistration correction.

  Subsequently, in step S170, the control unit 50 acquires the temperature information T0 in the apparatus at the time of the current color misregistration correction (time S4) from the temperature detection unit 200, and the temperature stored in the storage unit 92 at the previous color misregistration correction. The information is updated to the latest temperature information T0. The update information may be temperature information Tn at time S3.

  On the other hand, if the control unit 50 determines in step S180 that the calculation result does not become 1 ° C. (below 1 ° C.), the color shift of the image does not exceed the allowable value or the color shift has not occurred. It judges and returns to step S120 and monitors the temperature state in an apparatus continuously. At the time of color misregistration correction, the above-described operation is repeatedly executed.

  In the above-described embodiment, the threshold used to determine whether or not to perform color misregistration correction is set to 3 ° C. when the temperature in the apparatus is rising. However, the present invention is limited to this. No, it may be set to 2 ° C, or may be set to 3 ° C or higher. Similarly, the threshold value used for determining whether to perform color misregistration correction when the temperature in the apparatus is decreasing is set to 1 ° C., but is not limited to this. Any value other than 1 ° C. may be used as long as it is smaller than the threshold used.

  As described above, in the present exemplary embodiment, the color misregistration correction execution condition is set depending on whether the temperature in the image forming apparatus 100 is rising or the temperature in the image forming apparatus 100 is decreasing. A different condition is set. As a result, as shown in FIG. 5, the correlation between the amount of color misregistration and the temperature difference in the device at the previous time and the current temperature difference between the case where the temperature inside the device rises and the case where the temperature falls. Even if they are different from each other, the color misregistration correction can be executed at an optimal timing, and a high-quality image without color misregistration can be obtained.

  Further, according to the present embodiment, the color misregistration correction threshold when the temperature in the apparatus is rising is set to a value larger than the color misregistration correction threshold when the temperature in the apparatus is decreasing. Therefore, it is possible to prevent unnecessary color misregistration correction from being performed when the temperature in the apparatus is rising. Thereby, the fall of productivity can be avoided. On the other hand, when the temperature in the apparatus is decreasing, the threshold value for color misregistration correction is set to a value smaller than the threshold value in the case where the temperature in the apparatus is increasing. Even when the color misregistration amount changes sharply (see FIG. 5), the color misregistration correction can be executed at an accurate timing. As a result, it is possible to obtain a high-quality image without color misregistration.

  It should be noted that the technical scope of the present invention is not limited to the above-described embodiments, and includes those in which various modifications are made to the above-described embodiments without departing from the spirit of the present invention.

50 control unit 100 image forming apparatus 120, 120K, 120C, 120M, 120Y registration mark 200 temperature detection unit P paper T0, Tn, Tb temperature information

Claims (3)

A temperature detector for detecting the temperature in the device;
A controller that performs color misregistration correction of an image based on the temperature in the apparatus detected by the temperature detector;
The control unit determines whether or not to perform color misregistration correction based on different execution conditions when the temperature in the apparatus is increasing and when the temperature in the apparatus is decreasing. Image forming apparatus. The controller is
Whether or not the color misregistration correction is executed by comparing the temperature difference in the device between the previous color misregistration correction and the current time with the set first execution condition when the temperature in the apparatus is rising. Determine whether
When the temperature in the apparatus is decreasing, the temperature difference in the apparatus between the previous color misalignment correction and the current time is compared with the second execution condition having a value smaller than the set first execution condition. The image forming apparatus according to claim 1, wherein it is determined whether or not to perform color misregistration correction. The controller is
3. The apparatus according to claim 1, wherein whether the temperature in the apparatus is rising or falling is determined based on a current temperature in the apparatus and a temperature in the apparatus after the previous color misregistration correction. The image forming apparatus described in 1.

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