JP2014066960A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of recognizing an overlooked error.SOLUTION: An image forming apparatus includes an image forming unit, a carrier that carries a formed image, a conveyor that conveys the carrier, one end sensor, another end sensor, and a control unit. The one end sensor detects an image conveyed to one end side in a main scanning direction that is a direction orthogonal to a direction of movement of the carrier. The other end sensor detects an image conveyed to the other end side on the opposite side of the one end side in the main scanning direction. The control unit causes the image forming unit to form a mark for positional deviation detection in the main scanning direction on the carrier, causes the conveyor to convey the carrier, and executes calculation processing to calculate a relative deviation amount that is a difference between a light-receiving result of the mark by the one end sensor and a light-receiving result of the mark by the other end sensor, and notification processing to notify a user of an error when the relative deviation amount calculated in the calculation processing exceeds an allowable range.

Description

  The present invention relates to an image forming apparatus that forms an image on a sheet. More specifically, the present invention relates to an image forming apparatus having a correction function for correcting image positional deviation.

  Conventionally, in an image forming apparatus, correction processing is performed so as not to cause a positional shift in an image. For example, in Patent Document 1, pattern images are formed on both ends of a transfer belt in the belt width direction, and optical sensors for reading the pattern images are provided on both ends of the transfer belt in the belt width direction. It is disclosed that color matching control is executed based on a sensor reading result.

JP 2003-98793 A

  However, the conventional technique described above has the following problems. That is, in the image forming apparatus, even if an error such as a change in the distance between sensors or a deviation of each apparatus in the image forming unit occurs, the error is overlooked because it is corrected by the correction process. In other words, according to the conventional technique, color matching control is performed based on the detected deviation amount, and thus no error is notified about the sensor or the device. Therefore, it is difficult for the user to specify the error factor.

  The present invention has been made to solve the above-described problems of the prior art. That is, the problem is to provide an image forming apparatus that can recognize an overlooked error.

  An image forming apparatus designed to solve this problem includes a carrier that carries an image, an image forming unit that forms an image on the carrier, and a moving member that moves the carrier. A conveyance body that conveys the image formed in this manner, a one-end sensor that is a sensor that detects an image conveyed to one end in the main scanning direction, which is a direction orthogonal to the traveling direction of the carrier, A second end sensor which is a sensor for detecting an image conveyed to the other end side opposite to the one end side in the main scanning direction, and a control unit, and the control unit is provided with a main unit in the image forming unit. A mark for detecting displacement in the scanning direction is formed on the carrier, and the carrier is carried by the carrier. The light reception result of the mark of the one end sensor and the light reception result of the mark of the other end sensor Relative difference between A calculation process of calculating the amount, the relative shift amount calculated by the calculation process when an unacceptable, is characterized by performing the a notification process of notifying an error.

  In the image forming apparatus disclosed in this specification, an image forming unit causes a carrier to carry an image, and the carrier carries the carrier. Further, since the sensor is provided on each of the one end side and the other end side in the main scanning direction, the sensor can detect an image at each position. Then, the control unit causes the carrier to carry a position deviation detection mark, causes both the sensors to detect the mark, and executes a calculation process for calculating a relative deviation amount that is a difference between the detection results. The control unit further executes notification processing for notifying an error when the relative deviation calculated by the calculation processing exceeds the allowable range.

  When an error occurs in the sensor or the image forming unit, the relative deviation amount obtained from the light reception result of the mark by both sensors changes. If the degree of change exceeds a range where it can be determined that the color misregistration is a simple one, an error such as a sensor error or an image forming unit error may have occurred. Therefore, in the image forming apparatus disclosed in this specification, when the relative deviation amount exceeds the allowable range, the user is notified of the error by notifying the user of the error. it can.

  Further, there are a plurality of the image forming units, and in the calculation process, the relative shift amount is calculated by at least two image forming units, and in the notification process, the relative shift amount calculated for each image forming unit is calculated. Among them, it is desirable to notify an error when at least one relative deviation amount exceeds the allowable range. For example, in a color image forming apparatus having an image forming unit for each color, the relative deviation amount may be calculated for each image forming unit. If even one color exceeds the allowable range, the error can be notified more accurately by notifying the error.

  Further, in the calculation process, the relative deviation amount is calculated in each of the image forming units, and in the notification process, all the relative deviation amounts among the relative deviation amounts calculated for each image forming unit are the allowable values. If the range is exceeded, a sensor error should be reported. If the relative deviation amount exceeds the allowable range in all the image forming units, there is a high possibility that the error is not an individual error of the image forming unit but a sensor error. Therefore, the user can recognize more detailed error contents by specifying and notifying the sensor of the error location. Sensor errors include dirt on the light-receiving surface of the sensor and sensor displacement.

  Further, in the notification process, when all the relative deviations out of the relative deviations calculated for each image forming unit exceed the allowable range, the light reception result of the mark of the one end sensor and the other end are obtained. When at least one of the light reception result of the mark of the sensor is calculated and the light reception result exceeds the sensor allowable range for identifying the sensor that caused the relative deviation amount to exceed the allowable range, the light reception result is It is recommended to notify a sensor that exceeds the range. If the error is limited to a sensor error, it is further determined which sensor the error has occurred by checking whether the light reception results of the individual sensors at one end and the other end exceed the sensor tolerance range. Can be identified. Therefore, the user can recognize more detailed error contents. It should be noted that an error of one of the sensors can be notified by setting the sensor allowable range to approximately 0.5 times the allowable range.

  In the notification process, when only one relative deviation amount exceeds the allowable range among the relative deviation amounts calculated for each image forming unit, the image forming unit in which the relative deviation amount exceeds the allowable range. It is advisable to report this error. When the relative deviation amount exceeds the allowable range for only one image forming unit, there is a high possibility that the error is not a sensor error but an image forming unit error. Therefore, the user can recognize more detailed error contents by limiting the error contents to the image forming unit.

  In the LED exposure method, the error of the image forming unit includes distortion of the LED head array, contamination of the LED head array, and the like. For example, when the LED head array is distorted, the distance between the LED head array and the photoconductor is within an appropriate range at the center of the photoconductor, but is beyond the proper range at the end of the photoconductor. Or it can happen. Further, when toner adheres to the LED head array, the exposure is diffused, and the image may be blurred or distorted. Alternatively, in the laser exposure method, for example, the position of a mirror that refracts laser light may be displaced.

  In the notification process, when only one relative deviation amount exceeds the allowable range among the relative deviation amounts calculated for each image forming unit, the mark formed by the image forming unit is detected. The portion of the image forming unit that calculated at least one of the light reception result of the mark of the one end sensor and the light reception result of the mark of the other end sensor, and caused the relative deviation amount to exceed the allowable range. When the light reception result exceeds the image forming unit allowable range for specifying the image forming unit, it may be notified that there is an error portion of the image forming unit in a part on the sensor side where the light reception result exceeds the image forming unit allowable range. When the error is limited to one image forming unit, the error of the image forming unit is further detected by checking whether the light reception result of each sensor exceeds the allowable range of the image forming unit. It is possible to specify which side is in the transport direction. Therefore, the user can recognize more detailed error contents. For example, by setting the allowable range of the image forming unit to about 0.7 times the allowable range, it is possible to notify an error of one of the sensors while reducing the influence of thermal expansion.

  In addition, the image forming apparatus disclosed in the present specification includes a fixing unit that thermally fixes an image formed by the image forming unit to a sheet. In the notification process, the allowable range differs for each image forming unit. The image forming unit closer to the fixing unit should have a wider allowable range. An image forming unit closer to a fixing unit serving as a heat source is more susceptible to heat and tends to have a larger relative deviation. This deviation due to heat from the fixing unit inevitably occurs, and it is preferable not to determine that this is an individual error in the image forming unit. Therefore, by increasing the allowable range of the image forming apparatus closer to the fixing unit, it is possible to suppress unnecessary error notification.

  The image forming unit forms an image by an LED exposure method, and the image forming apparatus stores a reference value of the relative deviation amount and a threshold value that is an allowable maximum deviation amount from the reference value. A storage unit may be provided, and in the notification process, a range from the reference value, which is a fixed value stored in the storage unit, to the threshold value may be set as the allowable range. In the LED exposure method, a shift in the main scanning direction hardly occurs. For this reason, the relative deviation amount at the time of shipment from the factory is stored as a reference value, and the relative deviation amount is obtained based on the reference value, thereby making it possible to more accurately detect minute sensor changes and exposure apparatus changes since shipment. User can recognize.

  Further, the image forming unit forms an image by a laser exposure method, and the image forming apparatus accepts a previous deviation amount, which is a relative deviation amount calculated by the previous calculation process, and an allowance from the previous deviation amount. A storage unit that stores a threshold value that is a maximum deviation amount, and in the notification process, a range up to the threshold value with a previous deviation amount that is a variable value stored in the storage unit as a center is the allowable range. Good. In the laser exposure method, deviation in the main scanning direction is likely to occur. Therefore, by storing the previous deviation amount, which is the previous relative deviation amount, and obtaining the relative deviation amount based on the previous deviation amount, it is possible to detect a sudden change in the sensor or a change in the exposure apparatus due to a sudden environmental change or the like. , The user can recognize more accurately.

  According to the present invention, an image forming apparatus capable of recognizing an overlooked error is realized.

1 is a block diagram showing an electrical configuration of an MFP according to an embodiment. 2 is a schematic configuration diagram of an image forming unit of the MFP. FIG. It is explanatory drawing which shows arrangement | positioning of a mark sensor. It is explanatory drawing which shows the example of a mark. It is explanatory drawing which shows the example of the relative deviation | shift amount when there is no deviation | shift of a mark. It is explanatory drawing which shows the example of the relative deviation | shift amount of the mark which shifted | deviated to the main scanning direction. It is a flowchart which shows the procedure of an error detection process. 6 is a flowchart illustrating a procedure of error determination processing in a single-color image forming unit. 5 is a flowchart illustrating a procedure of error determination processing in a multi-color image forming unit. It is a flowchart which shows the procedure of a sensor part error determination process. It is a flowchart which shows the procedure of a process part error judgment process.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an image forming apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. In the present embodiment, the present invention is applied to a multi function peripheral (MFP) having an image reading function and an image forming function.

[MFP configuration]
As shown in FIG. 1, the MFP 100 according to the embodiment includes a control unit 30 including a CPU 31, a ROM 32, a RAM 33, and an NVRAM (nonvolatile RAM) 34. In addition, the control unit 30 includes an image forming unit 10 that forms an image on a sheet, an image reading unit 20 that reads an image of a document, an operation panel 40 that displays an operation status and receives an input operation by a user, and a network I. / F36 and FAXI / F37 are electrically connected.

  The CPU 31 is a control center in the MFP 100. For example, the CPU 31 executes calculations for realizing various functions such as an image reading function, an image forming function, and a FAX data transmission / reception function. The CPU 31 also executes error determination processing described later.

  The ROM 32 stores various control programs for controlling the MFP 100, various settings, initial values, and the like. The RAM 33 is used as a work area from which various control programs are read or as a storage area for temporarily storing image data. The NVRAM 34 is used as a storage area for storing various settings and various initial values based on inspection results before factory shipment.

  A network I / F 36 is connected to a network such as a LAN, and connects the MFP 100 and another information processing apparatus. The FAX I / F 37 is connected to a telephone line, and connects the MFP 100 and a destination FAX apparatus. The MFP 100 can perform data communication with an external device or the like via the network I / F 36 or the FAX I / F 37.

[Configuration of MFP Image Forming Unit]
Next, the configuration of the image forming unit 10 of the MFP 100 will be described with reference to FIG. The image forming unit 10 of the MFP 100 is an electrophotographic system and can form a color image. An image reading unit 20 is disposed above the image forming unit 10.

  The image forming unit 10 forms a toner image and transfers the formed toner image onto a sheet, a conveying belt 7 that conveys the sheet, and a fixing device that fixes an unfixed toner image on the sheet to the sheet. 8. The conveyor belt 7 is an endless belt member made of a resin material such as polycarbonate, and is stretched around belt rollers 73 and 74. The conveyance belt 7 circulates and moves counterclockwise on the paper surface by the rotation of the belt rollers 73 and 74.

  The MFP 100 includes a paper feed tray 91 that stores paper on which image formation is performed, and a paper discharge tray 92 that discharges paper on which image formation has been performed. The sheets are pulled out one by one from the sheet feeding tray 91 located at the lower part of the apparatus, and are guided to the sheet discharge tray 92 through the process unit 5 and the fixing device 8 by the conveying belt 7 and other plural roller members. . A paper transport path 11 that is a paper path has a substantially S-shape as shown by a one-dot chain line in FIG. The paper traveling direction, that is, the traveling direction of the conveyor belt 7 is the sub-scanning direction. Further, the direction perpendicular to the sub-scanning direction, that is, the width direction of the transport belt 7 is the main scanning direction.

  The process unit 5 includes process units corresponding to the respective colors of yellow (Y), magenta (M), cyan (C), and black (K). Specifically, a process unit 50K that forms a K-color image, a process unit 50C that forms a C-color image, a process unit 50M that forms an M-color image, and a process that forms a Y-color image in the order of sheet conveyance The parts 50Y are arranged. The process units 50K, 50C, 50M, and 50Y are arranged along the transport belt 7 at a predetermined interval.

  As shown in FIG. 2, the process unit 50K includes a photoconductor 51, a charging unit 52, an exposure unit 53, a developing unit 54, and a transfer unit 55. In FIG. 2, only the process unit 50 </ b> K is provided with a reference numeral, but the process units 50 </ b> C, 50 </ b> M, and 50 </ b> Y of other colors are basically the same except that the color of the toner stored in the developing unit 54 is different. It is a configuration. In FIG. 2, the letters “K”, “C”, “M”, and “Y” are arranged on each photoconductor 51.

  At the time of image formation, the photoreceptor 51 is uniformly charged by the charging unit 52 and exposed by the exposure unit 53. As a result, an electrostatic latent image is formed on the surface of the photoreceptor 51. Then, the electrostatic latent image on the photoconductor 51 is developed by the developing unit 54, whereby a toner image that is an image of toner is formed on the photoconductor 51. In addition, the sheet is conveyed to a position facing the photoconductor 51 in synchronization with the formation of the electrostatic latent image on the photoconductor 51. The toner image on the photoreceptor 51 is transferred onto the paper by the transfer unit 55.

  The paper carrying the K-color toner image in the process unit 50K is further transported along the paper transport path 11 and faces the next process unit 50C. In the case of forming a color image, the toner images of the respective colors formed by the process units 50K, 50C, 50M, and 50Y of the respective colors are superimposed on the paper. On the other hand, in monochrome printing, a toner image is formed only by the process unit 50K and transferred to a sheet. The sheet on which the toner image is transferred is then conveyed to the fixing device 8. The toner image on the paper is heat-fixed on the paper in the fixing device 8. The sheet after fixing is discharged to a paper discharge tray 92.

  Note that the MFP 100 has an LED exposure type as the exposure unit 53. That is, the exposure unit 53 includes an LED head including an LED array and a lens array in which a plurality of LEDs are arranged and fixed in a row. The LED head is disposed along the main scanning direction so that one LED light source corresponds to one pixel.

  For this reason, the LED exposure type exposure unit 53 is unlikely to be an error factor for image scaling in the main scanning direction. In other words, in MFP 100 that employs the LED exposure method, there is a possibility that a relative positional shift in the main scanning direction of the exposed portion by exposure unit 53 may occur, as compared with a device that employs another exposure method. small. The process units 50K, 50C, 50M, and 50Y for the respective colors have the same exposure unit 53.

  Note that image forming processing such as exposure processing by the exposure unit 53, development processing by the developing unit 54, and transfer processing in the transfer unit 55 is performed for each line in the main scanning direction while rotating the photosensitive member 51. One line is a band-like image in which an image for one pixel is continuous in the main scanning direction. The next line in the main scanning direction is formed at a position where the photosensitive member 51 is shifted by one line in the sub-scanning direction. For example, the MFP 100 transfers a toner image for one line in the main scanning direction onto a sheet, advances the photosensitive member 51, the conveyance belt 7, and the transfer unit 55 by one line in the sub-scanning direction, and transfers the next one line. .

"Mark formation and detection"
The MFP 100 further includes a mark sensor 61 as shown in FIG. The mark sensor 61 is provided on the downstream side of the fixing device 8 and on the upstream side of the process unit 5 in the traveling direction of the transport belt 7. As shown in FIG. 3, the mark sensor 61 includes a left sensor 62L and a right sensor 62R that are fixed to each other.

  The sensors 62L and 62R on both sides are positions where the images at both ends in the main scanning direction can be detected, for example, both ends in the width direction of the transport belt 7, and are provided at both ends of the maximum exposure range. The sensors 62L and 62R are reflection type optical sensors each having a light emitting part and a light receiving part. In FIG. 3, examples of optical paths of the sensors 62L and 62R are indicated by broken lines. The sensor 62L is an example of one end sensor, and the sensor 62R is an example of the other end sensor.

  When the MFP 100 forms a color image, the MFP 100 superimposes the toner images of the respective colors on the paper in the process units 50K, 50C, 50M, and 50Y of the respective colors. Therefore, it is required that the positions of images formed on the paper by the process units 50K, 50C, 50M, and 50Y of the respective colors match each other. A relative positional shift between the images of the respective colors is not preferable because it appears as a color shift.

  Therefore, the MFP 100 performs color misregistration correction processing as appropriate. In the color misregistration correction process, the MFP 100 causes the image forming unit 10 to form a color misregistration correction mark on the conveyance belt 7. When correcting color misregistration, the paper is not transported. Color misregistration correction marks are formed at positions corresponding to the sensors 62L and 62R of the mark sensor 61 at both ends of the transport belt 7 in the main scanning direction. The MFP 100 detects a mark formed on the conveyance belt 7 with the mark sensor 61 and corrects color misregistration based on the detection result.

  An example of a color misregistration correction mark is shown in FIG. In this example, each of the marks 64 is a rod-like single color toner image arranged at an oblique angle with respect to the main scanning direction and the sub-scanning direction. As for the color misregistration correction marks, two marks 64 whose inclination directions are opposite to each other are formed with toner of the same color on both ends of the conveying belt 7 in the main scanning direction. The two on the left are the left mark 65L, and the two on the right are the right mark 65R. That is, the mark 64 is a set of four of the left mark 65L and the right mark 65R for each color.

  For example, as shown in FIG. 4, the color misregistration correction marks are arranged in the sub-scanning direction for each color. Each mark 64 formed on the conveyor belt 7 is conveyed in the sub-scanning direction as the conveyor belt 7 moves. When each mark 64 is conveyed to the detection position of the mark sensor 61, the sensors 62L and 62R detect the mark 64 on each side. In the MFP 100, the conveyance belt 7 is an example of a carrier that carries the mark 64, and the belt rollers 73 and 74 that convey the conveyance belt 7 are examples of the conveyance body.

  The MFP 100 sequentially detects the marks 64 that pass intermittently by the mark sensor 61, and acquires the detection timing interval of the two marks 64 of the same color for each of the left and right sensors 62L and 62R. For example, the interval between the intersections of the left mark 65L on the sensor 62L side and the left line 67L, which is a virtual passage position of the sensor 62L, can be acquired from the detection timing interval by the sensor 62L. Similarly, the interval between the intersections of the right mark 65R on the sensor 62R side and the right line 67R, which is a virtual passage position of the sensor 62R, can be acquired from the detection timing interval by the sensor 62R.

  Since each mark 64 is formed obliquely with respect to the main scanning direction, the positional deviation in the main scanning direction can be determined from the distance between the intersection points of the mark 64 and the passing position of the mark sensor 61. The positional deviation in the main scanning direction is a relative relationship between an interval in the main scanning direction between the left mark 65L and the right mark 65R and an interval in the main scanning direction between the sensor 62L and the sensor 62R. The detection timing of the two marks 64 by the sensors 62L and 62R or the interval between the detection timings for each sensor corresponds to the light reception result of the mark 64 of that color.

  For example, as shown in FIG. 5, when the interval TL by the sensor 62L is equal to the interval TR by the sensor 62R, the marks 64 on both ends may be arranged at the same interval as the sensors 62L and 62R in the main scanning direction. Recognize. On the other hand, when the positions of the sensors 62L and 62R of the mark sensor 61 or the formation positions of the marks 64 on both ends are relatively displaced in the main scanning direction, the interval TL by the sensor 62L and the interval TR by the sensor 62R are: Different values. For example, as shown in FIG. 6, when the right mark 65R is shifted to the right in the main scanning direction with respect to the left mark 65L, the interval TRx by the sensor 62R is larger than the interval TL.

In this way, the relative positional shift in the main scanning direction of the marks 64 on both ends can be grasped based on the difference between the left and right intervals TL and TR. The difference between the left and right interval TL and the interval TR is a relative deviation amount TD.
TD = | TL-TR |
That is, the MFP 100 uses the mark sensor 61 to detect the misregistration detection mark 64 in the main scanning direction formed on the conveyance belt 7. Then, the MFP 100 calculates a relative deviation amount TD that is a difference between the interval TL that is the light reception result by the sensor 62L and the interval TR that is the light reception result by the sensor 62R.

  The relative deviation TD is ideally 0 when new, but it is not always exactly 0 due to component variations during assembly. Therefore, the MFP 100 stores the relative deviation amount TDs before factory shipment as an initial value. For example, the mark 64 is formed and detected by the mark sensor 61 before shipment from the factory, and the light reception result and the relative deviation amount TDs in the initial state are acquired and stored in the NVRAM 34.

  Further, a threshold value Ta as a change amount of the allowable relative deviation amount TD in the MFP 100 after the start of use is determined in advance. This threshold value Ta is an allowable deviation amount of the relative deviation amount TD from the reference value. That is, when the relative deviation amount TD exceeds this value and deviates from the reference value, the MFP 100 determines that there is a possibility of some error. The reference value is an initial relative deviation amount TDs obtained before factory shipment, and is a fixed value. The NVRAM 34 of the MFP 100 stores intervals TLs and TRs that are initial values of the intervals TL and TR, a relative deviation amount TDs that is an initial value of the relative deviation amount TD, and a threshold Ta.

"Error detection process"
Next, an error detection process executed in CPU 31 of MFP 100 will be described. This process is performed in parallel with the execution of the color misregistration correction process, and is executed when the color misregistration correction process starts. The color misregistration correction processing is performed when the main power is turned on, when the user receives an instruction after replacing the process unit, and the like. First, the procedure of color misregistration correction and error detection processing will be described with reference to FIG.

  When the error detection process is started, first, the CPU 31 controls each part of the image forming unit 10 to form the mark 64 (S101). For example, a toner image of the mark 64 is formed on the photosensitive member 51 and transferred onto the conveyance belt 7. Then, the conveyor belt 7 on which the mark 64 is placed is moved so that the mark 64 passes the position facing the mark sensor 61.

  Subsequently, the CPU 31 causes the mark sensor 61 to detect the mark 64 (S103). That is, the mark sensor 61 acquires the interval of timing when the mark 64 of the same color passes by the sensors 62L and 62R on both sides. The mark sensor 61 transmits the detection results for all the formed marks 64 to the CPU 31.

  Next, the CPU 31 uses the detection result of the mark 64 to execute an error determination process (S105). The contents of the error determination process will be described later. Further, the CPU 31 determines the presence / absence of an error from the result of the error determination process (S107).

  If the CPU 31 determines that there is an error (S107: Yes), it displays a message notifying the error on the operation panel 40 (S109). In this case, since it is not preferable to form an image in this state, it is preferable to further display guidance for solving the error. If the CPU 31 determines that there is no error (S107: No), it performs color misregistration correction (S111). When error notification (S109) or color misregistration correction (S111) is performed, the error detection process is terminated.

"Single color error judgment process"
Next, the error determination process executed in S105 of FIG. 7 will be described. The error determination process differs depending on whether the process is performed for the single color process unit 5 or the multi-color process unit 5. First, an error determination process for determining whether or not there is an error in the monochrome process unit 5 will be described with reference to FIG.

  When this process is started, the CPU 31 reads from the NVRAM 34 the initial relative deviation amount TDs and the threshold value Ta used in the subsequent determination for the current error determination target (S201). Subsequently, the current relative deviation amount TD of the target color for error determination is calculated from the detection result of the current mark sensor 61 (S203).

Next, the CPU 31 obtains a difference ΔT between the initial relative deviation amount TDs acquired in S201 and the current relative deviation amount obtained in S203 (S205).
ΔT = | TD−TDs |

  As described above, the relative deviation amount TD is a value indicating a relative relationship between the interval between the marks 64 and the interval between the mark sensors 61 in the main scanning direction. Since the MFP 100 includes the LED exposure type exposure unit 53, the interval in the main scanning direction of the formation position of the mark 64 is hardly shifted. Further, since the left and right sensors 62L and 62R of the mark sensor 61 are fixed to each other, the interval in the main scanning direction is hardly shifted.

  That is, if the MFP 100 is in a good state, it is estimated that the relative deviation amount TD does not change greatly from the initial relative deviation amount TDs even if deterioration due to use or simple aging changes. If the difference ΔT is greater than the threshold value Ta, it can be determined that some error has occurred in the mark sensor 61 or the process unit 5.

  Therefore, the CPU 31 determines whether or not the difference ΔT obtained in S205 is equal to or less than the threshold value Ta read in S201 (S207). If the difference ΔT is less than or equal to the threshold Ta (S207: Yes), it is determined that there is no error (S209). If the difference ΔT exceeds the threshold Ta (S207: No), the CPU 31 determines that there is an error (S211). When determining whether or not there is an error, the CPU 31 ends the error determination process. Then, the presence or absence of an error is stored, and the process returns to S107 in FIG. That is, if there is an error (S211), the CPU 31 notifies the error (S109), and if there is no error (S209), the CPU 31 performs color misregistration correction (S111).

  Note that the threshold value Ta may be the same value for all colors, but it is even better if it differs for each color. That is, the allowable range of the difference may be different for each of the process units 50K, 50C, 50M, and 50Y. For example, the process unit 50Y disposed at a position closest to the fixing device 8 is more susceptible to heat during the fixing process than the other process units 50K, 50C, and 50M. Therefore, the threshold value Ta in the yellow process unit 50Y is set to a value larger than the threshold value Ta for other colors. Further, the threshold value may be set to a larger value as the process unit is farther away from the mark sensor 61.

"Multi-color error judgment process"
Next, with reference to FIG. 9, an error determination process performed in the multi-color process units 50K, 50C, 50M, and 50Y will be described. This process is executed in S105 of FIG. 7 instead of the single color error determination process shown in FIG.

  When this process is started, the CPU 31 reads the initial relative shift amount TDs and threshold Ta of each color from the NVRAM 34 (S301). The initial relative deviation amount TDs is acquired for each color before shipment from the factory and stored in the NVRAM 34. The threshold value Ta may be stored for each color, or only one value common to each color may be stored.

  Subsequently, the CPU 31 calculates the current relative deviation amount TD from the detection result of the current mark sensor 61 (S303). In this process, the MFP 100 performs mark formation and mark detection for each color. Therefore, the relative deviation amount TD calculated in S303 is also obtained for each color.

  Next, the CPU 31 obtains a difference ΔT between the initial relative shift amount TDs acquired in S301 and the current relative shift amount TD acquired in S303 for each color (S305). Further, the CPU 31 determines whether or not the difference ΔT obtained in S305 is less than or equal to the threshold value Ta of the color read in S301 for all colors (S307).

  If the difference ΔT is less than or equal to the threshold value for all colors (S307: Yes), the CPU 31 determines that no error has occurred. That is, it is determined that there is no error in both the mark sensor 61 and the process units 50K, 50C, 50M, and 50Y for each color. Therefore, the CPU 31 determines that there is no error (S309), ends this processing, returns to S107 in FIG. 7, and performs color misregistration correction (S111).

  On the other hand, if the difference ΔT exceeds the threshold Ta even for one color (S307: No), there may be an error. If there is a color for which the difference ΔT exceeds the threshold Ta, it is desirable to make a more detailed determination.

  Therefore, the CPU 31 determines whether or not the difference ΔT exceeds the threshold value Ta for all colors (S311). When the difference ΔT exceeds the threshold Ta for all colors (S311: Yes), it can be estimated that an error has occurred in the mark sensor 61, which is a member used in common for all colors. Therefore, the CPU 31 executes sensor unit error determination processing in order to diagnose the error location of the mark sensor 61 in more detail (S313). The sensor unit error determination process will be described later.

  On the other hand, if the difference ΔT exceeds the threshold Ta for all colors (S311: No), the CPU 31 determines that only one of the four colors has the difference ΔT exceeding the threshold Ta. Whether or not (S315). If there is only one color (S315: Yes), it can be estimated that an error has occurred in the process portion of that color. Therefore, in order to diagnose the process part of that color in more detail, process part error determination processing is executed (S317). The process part error determination process will be described later.

  When the difference ΔT exceeds the threshold for only one color (S315: No), the threshold is exceeded for two or three of the four colors, together with No for S311. become. In this case, there may be a sensor error or a process unit error. Or it could be another factor. That is, since it is difficult to estimate the cause of the error with this alone, it is determined that the cause is an unknown error (S319). If it is determined that the error is unknown, another inspection or the like may be performed for more detailed error determination.

  After executing any one of S313, S317, and S319, the CPU 31 ends the error determination process, returns to S107 in FIG. 7, and performs error notification (S109). That is, the CPU 31 notifies the sensor error when the process proceeds to S313, and notifies the process unit error when the process proceeds to S317. As a result, errors that have been overlooked can be recognized. Furthermore, when a detailed error location is determined in S313 or S317, the detailed location may be notified. In addition, when the process proceeds to S319, it is preferable to notify that the error is an unknown factor at this stage or that a more detailed inspection should be performed. By notifying in detail, the overlooked error can be recognized more accurately.

[Sensor part error judgment processing]
Next, the sensor unit error determination process executed in S313 of FIG. 9 will be described with reference to the flowchart of FIG. This process is executed when the difference ΔT between the current relative deviation amount TD and the initial relative deviation amount TDs exceeds the threshold Ta for all colors.

  When the execution of this process is started, the CPU 31 compares the difference ΔT between the current relative deviation amount TD and the initial relative deviation amount TDs for each color (S401). The difference ΔT is calculated for each color in S305 of FIG. If there is an error in the mark sensor 61, the difference ΔT does not differ greatly for each color, and the difference ΔT should be the same for any color.

  If the difference between the differences ΔT of the respective colors is large (S401: No), the CPU 31 determines that the error is not just the mark sensor 61. In other words, when the difference between the differences ΔT is large, there is a high possibility that there are errors in other locations. In other words, the error location cannot be identified. Therefore, the error location is not specified, and it is determined that the cause is an unknown error (S403). In this case, another inspection may be performed in order to grasp the error part in more detail.

  After S403, the CPU 31 ends this sensor unit error determination process, returns to S107 in FIG. 7, and performs error notification (S109). In this case, instead of reporting a sensor error, an error of unknown factor may be reported.

  On the other hand, when the difference between the differences ΔT between the colors is small (S401: Yes), the CPU 31 is highly likely that an error has occurred in the mark sensor 61. In this case, the CPU 31 subsequently determines which of the left and right sensors 62L and 62R of the mark sensor 61 has an error.

Therefore, the CPU 31 reads the interval TLs that is the initial value of the left interval from the NVRAM 34 (S405). The interval TLs is an interval of timing at which the left mark 65L is detected by the sensor 62L at the time of mark detection performed before factory shipment (see FIG. 5). Further, a difference ΔTL between the interval TLs read in S405 and the left interval TL at the time of mark detection performed for the calculation of the current relative deviation amount is calculated (S407).
ΔTL = | TL−TLs |

  Then, the CPU 31 compares the difference ΔTL between the current and initial left intervals TL calculated in S407 with a predetermined sensor threshold value Tb (S409). As a result, it can be determined whether or not the left interval TL exceeds the sensor allowable range, and therefore it can be determined whether or not the sensor causing the error is the left sensor 62L. This sensor threshold value Tb is, for example, a value that is 0.5 times the threshold value Ta used in S307, S311, and S315 of the error determination process (FIG. 9). When a different threshold value Ta is used for each color, the sensor threshold value Tb may be set to a value 0.5 times the color threshold value Ta for each color.

  Note that the processing after S405 may be performed on the inspection result of any one color. In that case, it is preferable to use the result of the process unit arranged near the mark sensor 61. Or you may judge using the average value of the space | interval TL detected by each color. Further, the sensor threshold Tb is not limited to 0.5 times the threshold Ta. Alternatively, the determination may be made using the right interval TR instead of the left interval TL. Or it can also judge using both right and left.

  If the difference ΔTL in the left interval TL is equal to or greater than the sensor threshold value Tb (S409: Yes), it is determined that an error has occurred in the sensor 62L that is the left sensor (S411). On the other hand, when the difference ΔTL in the left interval TL is smaller than the sensor threshold value Tb (S409: No), it is determined that an error has occurred in the sensor 62R that is the right sensor (S413). As the error, for example, the optical axis shift of the sensor or the contamination of the light receiving surface can be considered. If an error location is specified for any one of the sensors, the sensor unit error determination process is terminated, and the process returns to S107 in FIG. 7 to perform error notification (S109).

[Process part error judgment processing]
Next, the process unit error determination process executed in S317 of FIG. 9 will be described with reference to the flowchart of FIG. This process is executed when the difference ΔT between the current relative deviation amount TD and the initial relative deviation amount TDs is large for one color and exceeding the threshold value Ta. That is, the following processing is executed only for the process unit of the color for which it is determined that the difference ΔT exceeds the threshold Ta in S315 of FIG.

  When the execution of this process is started, the CPU 31 reads from the NVRAM 34 the interval TLs that is the initial value of the left interval and the interval TRs that is the initial value of the right interval (S501). Subsequently, a difference ΔTL between the interval TLs read in S501 and the left interval TL at the time of the current mark detection is calculated. Similarly, a difference ΔTR between the interval TRs read in S501 and the right interval TR at the time of the current mark detection is calculated (S502).

  Further, the difference ΔTL on the left is compared with the process threshold value Tc (S503). Thus, it can be determined whether or not the left interval TL exceeds the allowable range of the image forming unit, so that it is possible to determine whether or not the error location is in the left part of the process unit. The process threshold value Tc is preferably 0.5 to 0.8 times the threshold value Ta used in S307, S311, and S315 of the error determination process (FIG. 9), for example, 0.7 times. Further, when it is determined that the left difference ΔTL is greater than or equal to the process threshold value Tc (S503: Yes), it is determined that there is an error part on the left side of the process part (S507).

  On the other hand, when it is determined that the left difference ΔTL is smaller than the process threshold Tc (S503: No), the right difference ΔTR is compared with the process threshold Tc (S505). If it is determined that the right difference ΔTR is greater than or equal to the process threshold value Tc (S505: Yes), it is determined that there is an error location on the right side of the process portion (S509). If an error location is specified in S507 or S509, the process unit error determination process is terminated, and the process returns to S107 in FIG. 7 to perform error notification (S109).

  If it is determined that both the left difference ΔTL and the right difference ΔTR are smaller than the process threshold Tc (S505: No), it is determined that this is an overall error of the process unit (S511). In this case, another inspection may be performed in order to grasp the error part in more detail. When determining the error location, the CPU 31 ends the process section error determination processing, returns to S107 in FIG. 7, and performs error notification (S109).

  The partial error in the process unit includes, for example, inclination and distortion of the LED head, partial breakage, and the like. This process can narrow down the error part of the process part to some extent, so that the time required for maintenance can be shortened.

[Laser exposure method]
The MFP 100 of this embodiment can employ a laser exposure method instead of the LED exposure method. However, since the laser exposure method has a light polarization portion, the enlargement / reduction of the image in the main scanning direction is more likely to occur than the LED exposure method. In addition, since the optical path length is long, it is easily affected by heat. Therefore, in the image forming apparatus of the laser exposure method, in each of the above-described determinations, it is preferable to compare the current relative deviation amount with the relative deviation amount at the previous detection instead of comparing with the initial relative deviation amount before factory shipment. . Since the deviation in the main scanning direction in the laser exposure method often proceeds little by little, it is possible to prevent the error from being judged unnecessarily by comparing with the previous value.

  Therefore, every time the error detection process is executed, the CPU 31 stores the relative deviation amount TD at that time in the NVRAM 34 as the previous deviation amount. Therefore, the previous shift amount is a variable value. Then, the maximum allowable deviation from the previous deviation is stored as the threshold Td. The threshold value Td may be a fixed value equal to the threshold value Ta of the LED exposure method. Alternatively, the threshold value Td may be a variable value that takes into account environmental changes, secular changes, and the like. The NVRAM 34 also stores the left and right intervals TL and TR at the previous detection, in addition to the previous deviation amount and the threshold value Td.

  In the error determination process, the CPU 31 determines an allowable range based on the previous deviation amount stored in the NVRAM 34 and the threshold value Td. In this way, even in a laser exposure type image forming apparatus, it is possible to appropriately determine an error location.

  As described above in detail, according to the MFP 100, the process units 50K, 50C, 50M, and 50Y cause the conveyance belt 7 to form the misregistration detection marks 64. Since the mark sensor 61 includes the left sensor 62L and the right sensor 62R, the mark 64 can be detected at each position. The CPU 31 calculates a relative deviation amount TD that is a difference between the detection results, and a notification process for notifying an error when the relative deviation amount TD calculated by the calculation process exceeds an allowable range. Execute.

  When an error occurs in the MFP 100, a change occurs in the relative deviation amount ΔT obtained from the light reception result of the mark 64 by both the sensors 62L and 62R. If the degree of change is beyond the range where it can be determined that the color misregistration is merely, it is considered that an error such as an error of the sensors 62L and 62R, an error of the process units 50K, 50C, 50M, and 50Y has occurred. . Therefore, when the difference ΔT from the reference value of the relative deviation amount TD exceeds the threshold value Ta, the user can recognize that an overlooked error has occurred by notifying the user of the error.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, the present invention is not limited to the MFP, and can be applied to any apparatus having an image forming function such as a copying machine, a scanner, and a FAX.

  In the above embodiment, the initial relative deviation amount TDs and the threshold value Ta are stored, the current relative deviation amount TD is compared with the initial relative deviation amount TDs, which is a reference value, and the difference ΔT is equal to or less than the threshold value Ta. Based on whether or not, it is determined whether or not it is within the allowable range. Instead, an allowable upper limit value and an allowable lower limit value as an allowable range of the current relative deviation amount TD are stored, and determination is made based on whether or not the relative deviation amount TD is between them. You can also. In this case, the initial relative deviation TDs + threshold Ta is the allowable upper limit, and the initial relative deviation TDs−threshold Ta is the allowable lower limit. Then, the CPU 31 may determine whether or not the calculated relative deviation amount TD is included in an allowable range between the allowable upper limit value and the allowable lower limit value.

  Further, in the embodiment adopting the laser exposure method, instead of storing the previous deviation amount and the threshold value Td, the allowable upper limit value and the allowable lower limit value may be stored and judged. In this case, the previous deviation amount TD + threshold value Td is the allowable upper limit value, and the previous deviation amount TD−threshold value Td is the allowable lower limit value. Then, the CPU 31 may determine whether or not the calculated relative deviation amount TD is included in an allowable range between the allowable upper limit value and the allowable lower limit value.

  When a fixed value is used as the threshold value Ta, the influence of heat may be added to the light reception result by the sensor. That is, the relative deviation amount TD may be corrected according to the environmental temperature, the distance between the process unit and the fixing device, and the like.

  Even in the LED exposure method, an error may be determined by using the relative displacement amount of the previous value as a reference value and comparing the current relative displacement amount with the reference value. Further, in the case of the laser exposure method, a fixed relative displacement amount can be adopted as a reference value. Even in the error determination process in the monochrome image forming unit, the left and right intervals TL and TR may be compared with their reference values to determine which side has the error.

  In addition to the LED exposure method and the laser exposure method, a line type ink head can be applied to the image forming unit. In addition to the conveying belt, a transfer belt or a sheet can be applied to the carrier. When the transfer belt is a carrier, a roller member that conveys the transfer belt can be applied to the carrier. When a sheet is applied as the carrier, the conveyance member that conveys the sheet is the conveyance body.

  The processing disclosed in the embodiments may be executed by a single CPU, a plurality of CPUs, hardware such as an ASIC, or a combination thereof. Further, the processing disclosed in the embodiment can be realized in various modes such as a recording medium or a method recording a program for executing the processing.

DESCRIPTION OF SYMBOLS 10 Image formation part 7 Conveyance belt 8 Fixing apparatus 31 CPU
34 NVRAM
50K, 50C, 50M, 50Y Process part 53 Exposure part 61 Mark sensor 62L, 62R Sensor 64 Mark 73, 74 Belt roller

Claims (9)

A carrier carrying an image;
An image forming unit for forming an image on the carrier;
A carrier that conveys an image formed by the image forming unit by moving the carrier;
One end sensor which is a sensor for detecting an image conveyed to one end side in the main scanning direction which is a direction orthogonal to the traveling direction of the carrier;
The other end sensor which is a sensor for detecting an image conveyed to the other end side opposite to the one end side in the main scanning direction;
A control unit;
With
The controller is
A mark for detecting displacement in the main scanning direction is formed on the carrier in the image forming unit, the carrier is transported to the carrier, and the light reception result of the mark of the one end sensor and the other end sensor A calculation process for calculating a relative deviation amount which is a difference between the light reception result of the mark and
A notification process for notifying an error when the amount of relative deviation calculated by the calculation process exceeds an allowable range;
An image forming apparatus characterized in that The image forming apparatus according to claim 1,
There are a plurality of the image forming units,
In the calculation process, the relative shift amount is calculated by at least two image forming units,
In the notification process, an error is notified when at least one of the relative shift amounts calculated for each image forming unit exceeds the allowable range. The image forming apparatus according to claim 2,
In the calculation process, the relative deviation amounts are calculated in all the image forming units,
In the notification process, an error of a sensor is notified when all of the relative shift amounts calculated for each image forming unit exceed the allowable range. The image forming apparatus according to claim 3,
In the notification process, when all of the relative deviation amounts calculated for each image forming unit exceed the allowable range, the light reception result of the mark of the one end sensor and the other end sensor When at least one of the light reception result of the mark is calculated and the light reception result exceeds the sensor allowable range for identifying the sensor that caused the relative deviation amount to exceed the allowable range, the light reception result satisfies the sensor allowable range. An image forming apparatus that notifies a sensor exceeding the number. In the image forming apparatus according to any one of claims 2 to 4,
In the notification process, when only one relative deviation amount exceeds the allowable range among the relative deviation amounts calculated for each image forming unit, the error of the image forming unit in which the relative deviation amount exceeds the allowable range. An image forming apparatus characterized in that The image forming apparatus according to claim 5,
In the notification process, when only one relative deviation amount exceeds the allowable range among the relative deviation amounts calculated for each image forming unit, the mark formed by the image forming unit is detected. Calculate at least one of the light reception result of the mark of the one end sensor and the light reception result of the mark of the other end sensor, and identify the part of the image forming unit that caused the relative deviation amount to exceed the allowable range When the light reception result exceeds the allowable range of the image forming unit for performing image formation, an image forming unit is notified that an error portion of the image forming unit exists in a part on the sensor side where the light reception result exceeds the allowable range of the image forming unit apparatus. The image forming apparatus according to any one of claims 2 to 6,
A fixing unit for thermally fixing an image formed by the image forming unit to a sheet;
In the notification process, the permissible range is different for each image forming unit, and the permissible range is wider as the image forming unit is closer to the fixing unit. In the image forming apparatus according to any one of claims 1 to 7,
The image forming unit forms an image by an LED exposure method,
The image forming apparatus includes a storage unit that stores a reference value of the relative deviation amount and a threshold value that is an allowable maximum deviation amount from the reference value;
In the notification process, the range from the reference value, which is a fixed value stored in the storage unit, to the threshold is set as the allowable range. In the image forming apparatus according to any one of claims 1 to 7,
The image forming unit forms an image by a laser exposure method,
The image forming apparatus includes a storage unit that stores a previous deviation amount, which is a relative deviation amount calculated by the previous calculation process, and a threshold value, which is an allowable maximum deviation amount from the previous deviation amount,
In the notification processing, an image forming apparatus characterized in that a range up to the threshold value with a previous deviation amount as a variable value stored in the storage unit as the center is set as the allowable range.

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