Image forming apparatus

Abstract

To provide an image forming apparatus that can reduce the time to execute exposure position correction control.SOLUTION: According to an embodiment, an image forming apparatus has an exposure device, a transfer belt, a memory, and a processor. The transfer belt is formed of an endless belt supported by rollers, and has a toner image transferred which is obtained by developing with toner an electrostatic latent image formed by the exposure device. The memory stores setting information related to positional deviation correction of correcting deviation of the position of exposure performed by the exposure device. When the execution frequency setting of the positional deviation correction in setting information is equal to or more than a reference value, the processor executes the positional deviation correction by using an image pattern for positional deviation measurement to be formed over one revolution or more of the transfer belt, and when the execution frequency setting of the positional deviation correction in the setting information is less than the reference value, executes the positional deviation correction by using an image pattern for positional deviation measurement to be formed over less than one revolution of the transfer belt.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] An embodiment of the present invention relates to an image forming apparatus. [Background technology]

[0002] To achieve color printing, the image forming apparatus overlaps images formed by toners of different colors. In the image forming apparatus, thermal expansion caused by a rise in temperature inside the exposure device can cause changes in the position or angle of the lens or mirror, resulting in a shift in the exposure position and color misalignment. For this reason, the image forming apparatus executes exposure position correction control (color registration). The exposure position correction control forms a patch for measuring the positional misalignment on the transfer belt, and detects the amount of misalignment from the ideal position by reading the patch formed on the transfer belt. The correction control also corrects the exposure position misalignment by changing the exposure timing based on the detected amount of misalignment.

[0003] Conventional image forming apparatuses execute exposure position correction control in response to the amount of change in temperature detected by a temperature detection means such as a thermistor provided in the exposure device. In addition, exposure position correction control may be executed when a specified time has elapsed since the previous correction control. However, conventional image forming apparatuses start correction control when the conditions for executing correction control are met even when a user attempts to print. Once exposure position correction control is started, the image forming apparatus cannot execute printing until correction control is completed, which causes a problem that the user must wait a long time for printing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-20142 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide an image forming apparatus capable of shortening the execution time of exposure position correction control. [Means for solving the problem]

[0006] According to an embodiment, an image forming apparatus includes an exposure device, a transfer belt, a memory, and a processor. The transfer belt is an endless belt supported by rollers, and a toner image formed by developing an electrostatic latent image formed by the exposure device with toner is transferred to the transfer belt. The memory stores setting information related to misalignment correction for correcting a deviation in an exposure position by the exposure device. The processor executes misalignment correction using an image pattern for measuring misalignment formed over one or more revolutions of the transfer belt when a frequency setting for execution of the misalignment correction in the setting information is equal to or greater than a reference value, and executes misalignment correction using an image pattern for measuring misalignment formed over less than one revolution of the transfer belt when a frequency setting for execution of the misalignment correction in the setting information is less than the reference value. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing an example of the arrangement of an image forming apparatus according to an embodiment. [Diagram 2] FIG. 2 is a block diagram showing an example of the configuration of a control system in the image forming apparatus according to the embodiment. [Diagram 3] FIG. 3 is a diagram showing an example of a patch for measuring positional deviation used for correcting and controlling the exposure position in the image forming apparatus according to the embodiment. [Figure 4] FIG. 4 is a diagram showing another example of the patch for measuring positional deviation used for correcting and controlling the exposure position in the image forming apparatus according to the embodiment. [Diagram 5] FIG. 5 is a flowchart for explaining an example of an operation of correcting the exposure position in the image forming apparatus according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an image forming apparatus according to an embodiment will be described with reference to the drawings. In addition, in the drawings used in the following description of the embodiments, the scale of each part may be changed as appropriate. In addition, in the drawings used in the following description of the embodiments, the configuration may be omitted for the sake of explanation.

[0009] FIG. 1 is a diagram illustrating an example of the configuration of an image forming apparatus 100 according to an embodiment. The image forming apparatus 100 is placed in a workplace or the like. The image forming apparatus 100 prints by an electrophotographic method. The image forming apparatus 100 is, for example, an MFP (multifunction peripheral), a copier, a printer, or a facsimile.

[0010] As shown in FIG. 1, the image forming apparatus 100 includes a paper feed tray 101, a manual feed tray 102, a paper feed roller 103, a toner cartridge 104, an image forming unit 105, a transfer belt 107, a transfer roller 108, a fixing unit 109, a heating unit 110, a pressure roller 111, a paper output tray 112, a duplex unit 113, a scanner 114, a document feeder 115, and a control panel 116.

[0011] The image forming unit 105 prints an image by electrophotography. The image forming unit 105 forms an image to be printed on an image forming medium P or the like using toner. The image forming medium P is, for example, a sheet of paper. The scanner 114 reads an image from an original document on which an image has been formed. For example, the image forming apparatus 100 realizes a copy of the image of the original document by printing the image read from the original document by the scanner 114 onto the image forming medium P by the image forming unit 105.

[0012] The paper feed tray 101 contains an image formation medium P to be used for printing. The manual feed tray 102 is a platform for manually feeding the image formation medium P. The paper feed roller 103 is rotated by the action of a motor to convey the image formation medium P contained in the paper feed tray 101 or the manual feed tray 102 out of the paper feed tray 101. The toner cartridge 104 stores toner to be supplied to the image forming unit 105.

[0013] 1, the image forming apparatus 100 includes four toner cartridges 104, namely, a toner cartridge 1041, a toner cartridge 1042, a toner cartridge 1043, and a toner cartridge 1044. The toner cartridge 1041, the toner cartridge 1042, the toner cartridge 1043, and the toner cartridge 1044 each store a toner corresponding to each color of CMYK (cyan, magenta, yellow, and key (black)).

[0014] The colors of the toner stored in the toner cartridge 104 are not limited to the colors CMYK, and may be other colors. The toner stored in the toner cartridge 104 may be a special toner. For example, the toner cartridge 104 may store a decolorizable toner that is decolorized and becomes invisible at a temperature higher than a predetermined temperature.

[0015] Image forming unit 105 includes a developing unit, a photoconductor drum, and the like. The developing unit develops the electrostatic latent image on the surface of the photoconductor drum using toner supplied from a toner cartridge 104. As a result, a toner image is formed on the surface of the photoconductor drum. The image formed on the surface of the photoconductor drum is transferred (primary transfer) onto a transfer belt 107.

[0016] 1, the image forming apparatus 100 includes four image forming units 105, namely, an image forming unit 1051, an image forming unit 1052, an image forming unit 1053, and an image forming unit 1054. The image forming unit 1051, the image forming unit 1052, the image forming unit 1053, and the image forming unit 1054 each receive a supply of toner corresponding to each color of CMYK to form an image.

[0017] The exposure device 106 is also called an LSU (laser scanning unit), etc. The exposure device 106 forms an electrostatic latent image on the surface of the photoconductor drum of each image forming unit 105 by using a laser light controlled according to image data. The exposure device 106 is composed of, for example, a housing, a laser unit, a polygon mirror, a polygon motor, a mirror, a lens, etc. The exposure device 106 also includes a temperature sensor 1061. The housing supports the laser unit, the polygon mirror, the polygon motor, the mirror, the lens, the temperature sensor 1061, etc. The housing is made of, for example, resin.

[0018] The exposure device 106 includes, as an example, laser units each corresponding to one of the colors CMYK. The laser units for each color emit laser light. Each laser unit controls the emission of the laser light according to a control signal corresponding to image data. Also, each laser unit modulates the laser light according to a control signal corresponding to image data.

[0019] The polygon mirror reflects the laser light emitted from each laser unit. The polygon mirror polarizes and scans each laser light by being rotated by a polygon motor. The polygon motor is a motor that rotates the polygon mirror. Heat generated by the polygon motor is a main cause of increasing the temperature of the exposure device 106. Therefore, the polygon motor is an example of a heat source. The mirror and the lens are optical elements for manipulating the laser light. The mirror is provided so that the position or angle relative to the housing can be adjusted.

[0020] The temperature sensor 1061 detects the temperature inside the exposure apparatus 106. As one example, the temperature sensor 1061 is installed inside the housing of the exposure apparatus 106 described above. The temperature sensor 1061 outputs the measured temperature. The temperature sensor 1061 is, for example, a thermistor.

[0021] The transfer belt 107 is, for example, an endless belt supported by rollers. The transfer belt 107 is configured so that one revolution has a predetermined length. The transfer belt 107 rotates by the action of the rollers. As the transfer belt 107 rotates, an image is transferred (primary transfer) onto it by the transfer rollers (primary transfer rollers) of the image forming units 1051 to 1054. The transfer belt 107 transports the images (toner images) transferred from the image forming units 1051 to 1054 to the position of the transfer roller 108 (secondary transfer position).

[0022] The transfer roller 108 includes two rollers facing each other. The transfer roller 108 transfers (secondary transfer) an image formed on the transfer belt 107 onto the image forming medium P passing between the transfer rollers 108.

[0023] Toner sensor 117 detects toner attached on transfer belt 107. Toner sensor 117 detects the toner image on transfer belt 107 between a transfer position (primary transfer position) of image forming unit 1054 and a position (secondary transfer position) where the toner image on transfer belt 107 corresponds to transfer roller 108. For example, toner sensor 117 is disposed so as to face transfer belt 107 between the transfer roller of image forming unit 1054 and transfer roller 108.

[0024] The fixing unit 109 applies heat and pressure to the image forming medium P onto which the image has been transferred, thereby fixing the image transferred onto the image forming medium P. The fixing unit 109 includes a heating unit 110 and a pressure roller 111 that face each other. The heating unit 110 is, for example, a roller equipped with a heat source for heating the heating unit 110. The heat source is, for example, a heater. The roller heated by the heat source heats the image forming medium P. The pressure roller 111 presses the image forming medium P passing between the pressure roller 111 and the heating unit 110.

[0025] The heating unit 110 may also include an endless belt suspended between multiple rollers. For example, the heating unit 110 includes a plate-shaped heat source, an endless belt, a belt conveying roller, a tension roller, and a press roller. The endless belt is, for example, a film-shaped member. The belt conveying roller drives the endless belt. The tension roller applies tension to the endless belt. The press roller has an elastic layer formed on its surface. The plate-shaped heat source contacts the inside of the endless belt with the heat generating portion side and is pressed toward the press roller to form a fixing nip of a predetermined width between the plate-shaped heat source and the press roller. Since the plate-shaped heat source heats while forming a nip area, the response during energization is higher than that of a heating method using a halogen lamp.

[0026] The endless belt is, for example, a 50 um thick SUS (steel use stainless) base material or a 70 um thick heat-resistant resin polyimide on which a 200 um thick silicone rubber layer is formed, and the outermost circumference is covered with a surface protection layer such as PFA (perfluoroalkoxy alkane). The press roller is, for example, a φ10 mm iron bar on which a 5 mm thick silicone sponge layer is formed, and the outermost circumference is covered with a surface protection layer such as PFA. The plate-shaped heat source is, for example, a ceramic substrate on which a glaze layer and a heat generating resistor layer are laminated. An aluminum heat sink is attached to the opposite side of the plate-shaped heat source to release excess heat and prevent the substrate from warping. The heat generating resistor layer is made of a known material such as TaSiO2, and is divided into a predetermined length and number in the main scanning direction.

[0027] The paper discharge tray 112 is a platform onto which the image forming medium P is discharged after printing. The double-sided unit 113 makes the image forming medium P in a state where printing can be performed on the back side. For example, the double-sided unit 113 uses a roller or the like to switch back the image forming medium P, thereby inverting the image forming medium P.

[0028] The scanner 114 reads an image from a document. The scanner 114 is an image reading device for reading an image from a document. The scanner 114 is, for example, an optical reduction type image reading device equipped with an imaging element such as a charge-coupled device (CCD) image sensor. The scanner 114 may also be a contact image sensor (CIS) type image reading device equipped with an imaging element such as a complementary metal-oxide-semiconductor (CMOS) image sensor.

[0029] The document feeder 115 is also called, for example, an ADF (auto document feeder). The document feeder 115 transports documents placed on a document tray one after another. Images of the transported documents are read by the scanner 114. The document feeder 115 may also include a scanner for reading images from the back side of the documents.

[0030] The control panel 116 includes buttons and a touch panel for operation by an operator (user) of the image forming apparatus 100. The control panel 116 includes an input device through which the user inputs information and a display device for displaying information. The touch panel is, for example, a stack of a display such as a liquid crystal display or an organic EL display and a pointing device for touch input. The buttons and the touch panel function as input devices that accept operations by the operator of the image forming apparatus 100. In addition, the display included in the touch panel functions as a display device that notifies the operator of the image forming apparatus 100 of various information.

[0031] Next, the configuration of a control system in the image forming apparatus 100 according to the embodiment will be described. FIG. 2 is a block diagram showing an example of the configuration of a control system in the image forming apparatus 100 according to the embodiment. In the configuration example shown in FIG. 2, the image forming apparatus 100 has a processor 121, a ROM (read-only memory) 122, a RAM (random-access memory) 123, an auxiliary storage device 124, a communication interface 125, an RTC (real-time clock) 126, a scanner 114, a printer 127, and a control panel 116.

[0032] The processor 121 corresponds to the central part of a computer that performs processes such as calculations and controls required for the operation of the image forming apparatus 100. The processor 121 controls each part to realize various functions of the image forming apparatus 100 based on programs such as system software, application software, or firmware stored in the ROM 122 or the auxiliary storage device 124.

[0033] The processor 121 may be, for example, a central processing unit (CPU), a micro processing unit (MPU), a system on a chip (SoC), a digital signal processor (DSP), a graphics processing unit (GPU), an application specific integrated circuit (ASIC), a programmable logic device (PLD), a field-programmable gate array (FPGA), etc. Alternatively, the processor 121 may be a combination of a plurality of these.

[0034] The ROM 122 corresponds to a main memory device of a computer with the processor 121 at its core. The ROM 122 is a non-volatile memory used exclusively for reading data. The ROM 122 stores the above-mentioned programs. The ROM 122 also stores data or various setting values ​​used by the processor 121 when performing various processes.

[0035] The RAM 123 corresponds to a main storage device of a computer centered around the processor 121. The RAM 123 is a memory used for reading and writing data. The RAM 123 is used as a so-called work area for storing data that is temporarily used when the processor 121 performs various processes.

[0036] The auxiliary storage device 124 corresponds to an auxiliary storage device of a computer with the processor 121 as its core. The auxiliary storage device 124 is, for example, an EEPROM (registered trademark) (electric erasable programmable read-only memory), a HDD (hard disk drive), or an SSD (solid state drive). The auxiliary storage device 124 may also store a program. The auxiliary storage device 124 also stores data used by the processor 121 when performing various processes, data generated by the processes in the processor 121, or various setting values. For example, the auxiliary storage device 124 is a memory that stores setting information for position deviation correction including a setting for the execution frequency of the position deviation correction.

[0037] Note that, instead of the auxiliary storage device 124, or in addition to the auxiliary storage device 124, the image forming apparatus 100 may be provided with an interface into which a storage medium such as a memory card or a USB (universal serial bus) memory can be inserted.

[0038] The programs stored in ROM 122 or auxiliary storage device 124 include programs for executing processes described below. As an example, image forming apparatus 100 is transferred to an administrator of image forming apparatus 100 with the programs stored in ROM 122 or auxiliary storage device 124. Image forming apparatus 100 may also be transferred to an administrator without the programs stored in ROM 122 or auxiliary storage device 124.

[0039] Furthermore, a program for executing the processes described below may be written into the ROM 122 or the auxiliary storage device 124 by an operation by an administrator or a serviceman, etc. The program can be transferred by recording it on a removable storage medium such as a magnetic disk, a magneto-optical disk, an optical disk, or a semiconductor memory, or by downloading it via a network, etc.

[0040] The communication interface 125 is an interface for the image forming apparatus 100 to communicate via a network, etc. The communication interface 125 is connected to a terminal device operated by a user. The RTC 126 is a clock or a circuit with a built-in clock function.

[0041] The printer 127 prints an image on an image forming medium P or the like based on image data. In the configuration example shown in FIG. 2, the printer 127 includes a printer processor 1271, a toner sensor 117, a toner cartridge 104, an image forming unit 105, an exposure device 106, a transfer belt 107, a transfer roller 108, and a fixing unit 109.

[0042] In order to realize the printing function, the printer processor 1271 performs processes such as calculation and control required for the print operation of the image forming apparatus 100. The printer processor 1271 performs processes such as calculation and control required for the print operation based on instructions from the processor 121 and various programs. The printer processor 1271 also outputs the processing results to the processor 121.

[0043] The various programs may be stored in a storage unit such as ROM 122 or auxiliary storage device 124, or may be incorporated into the circuitry of printer processor 1271. Also, the various programs may be stored in a storage unit provided in printer 127. Printer processor 1271 is, for example, a CPU, MPU, SoC, DSP, GPU, ASIC, PLD, or FPGA.

[0044] The toner sensor 117 detects the toner adhering to the transfer belt 107. For example, the toner sensor 117 supplies the result of reading (detecting) an image pattern for measuring misregistration formed on the transfer belt 107 to the processor 121 or the printer processor 1271. The toner sensor 117 may also detect the amount of toner adhering to the transfer belt 107.

[0045] Next, a description will be given of exposure position correction control (hereinafter also referred to as positional deviation correction) for correcting deviation of the exposure position in image forming apparatus 100 according to the embodiment. In the image forming apparatus 100, the exposure device 106 may experience a shift in the exposure position due to a change in temperature or a change over time. The image forming apparatus 100 has a function of executing exposure position correction control (positional misalignment correction) for correcting the exposure position shift caused by the exposure device 106. In the image forming apparatus 100, the positional misalignment correction is performed under the control of the processor 121 or the printer processor 1271.

[0046] For example, as a positional deviation correction, the processor 121 forms a measurement patch (hereinafter simply referred to as a patch) for measuring the positional deviation on the transfer belt 107. The processor 121 detects the amount of deviation from an ideal position (reference position) in the image-formed measurement patch. The processor 121 corrects the deviation of the exposure position by changing the exposure timing of the exposure device 106, etc., based on the amount of deviation.

[0047] FIG. 3 is a diagram showing an example of an image pattern for measuring the positional deviation, which is formed on the transfer belt 107 in order to measure the positional deviation. The image pattern for measuring positional deviation is a set of patches shown in Fig. 3 arranged in the transport direction indicated by the arrow a in Fig. 3. One set of patches is image patterns Y, M, C, and K of each color formed by the image forming units 1051-1554 of each color arranged in the transport direction. Furthermore, the image patterns Y, M, C, and K of each color are configured by arranging predetermined patterns (wedge-shaped image patterns) at three positions, the front, center, and rear, in the scanning direction perpendicular to the transport direction a.

[0048] An image for measuring misregistration is formed by repeatedly forming one set of patches a set number of times (number of sets of patches) on the transfer belt 107. For example, if the number of sets of patches is X, one set of patches is repeatedly formed X times on the transfer belt 107 to form an image pattern for measuring misregistration.

[0049] Processor 121 reads the image pattern (toner image) for measuring misalignment formed on transfer belt 107 with toner sensor 117. Processor 121 calculates the relative misalignment between the transport direction and the scanning direction for each color from the result of reading the image pattern for measuring misalignment. Processor 121 then adjusts the exposure timing according to the calculated misalignment so that the image patterns for each color (four colors) overlap.

[0050] The patches (one set of patches) for measuring the positional deviation are not limited to the image pattern shown in Fig. 3. For example, one set of patches is not limited to those arranged in a predetermined pattern at the front, center, and rear in the scanning direction, but may be those arranged with image patterns at two locations, the front and the rear. Furthermore, the shape of the predetermined image pattern constituting the image patterns Y, M, C, and K of each color is not limited to the shape (wedge shape) shown in Fig. 3.

[0051] FIG. 4 is a diagram showing another example of patches constituting an image pattern for measuring positional deviation, which is formed on the transfer belt 107 in order to measure the positional deviation. In the example shown in Fig. 4, the patches constituting the image pattern for measuring positional deviation are arranged at two positions, the front and rear, in the main scanning direction. In addition, the image pattern of each color in the patch shown in Fig. 4 is wedge-shaped on the front side in the main scanning direction, and the image pattern on the rear side is bar-shaped. The image pattern for measuring positional deviation may be an image pattern in which a set of patches as shown in Fig. 4 is arranged in a predetermined number of sets in the transport direction.

[0052] Next, the settings of the correction control of the exposure position in the image forming apparatus 100 according to the embodiment will be described. In the image forming apparatus 100, it is considered that the deviation of the exposure position occurs due to a change in temperature or a change over time. For this reason, the image forming apparatus 100 sets a threshold value for the amount of temperature change and an execution frequency (execution interval) as execution conditions for executing the misalignment correction. The processor 121 changes (sets) the execution frequency (execution interval), which is an execution condition for the misalignment correction, in response to an instruction from the user. The processor 121 of the image forming apparatus 100 may also set the number of sets of patches used for the misalignment correction in response to the execution frequency setting instructed by the user.

[0053] For example, the user specifies the execution frequency of the position deviation correction on the control panel 116. The processor 121 displays an operation screen for specifying the execution frequency on the touch panel of the control panel 116 and accepts the execution frequency specified by the user. As a specific example, the user specifies, on the control panel 116, an increase / decrease in the execution frequency of the position deviation correction or a length of the execution interval based on a standard value. The processor 121 sets (updates) the execution frequency setting included in the setting information of the position deviation correction according to the execution frequency of the position deviation correction specified by the user. The processor 121 determines whether to execute the position deviation correction depending on whether an execution condition indicated by the set execution frequency setting or the like is met.

[0054] When the processor 121 executes the misalignment correction, it sets the number of sets of patches to be used for the misalignment correction according to the execution frequency indicated by the execution frequency setting. If the execution frequency (execution interval) indicated by the execution frequency setting is equal to or greater than a predetermined value (reference value), the processor 121 executes the misalignment correction using the standard set number of patches. The image pattern for measuring the misalignment, in which the standard set number of patches are arranged, is set to be formed in an area longer than one revolution of the transfer belt 107.

[0055] If the execution frequency indicated by the execution frequency setting is less than a predetermined value, the processor 121 executes positional deviation correction using an image pattern (image pattern for measuring positional deviation) formed in an area that is less than one revolution of the transfer belt 107. The processor 121 forms an image pattern for measuring positional deviation that is less than one revolution of the transfer belt 107 by arranging a number of patches fewer than the standard number of sets.

[0056] For example, assume that the length of one revolution of the transfer belt 107 is 800 mm, and the length of one set of patches in the transport direction is 100 mm or more. In this case, if the execution frequency indicated by the execution frequency setting is equal to or greater than a predetermined value, the processor 121 sets an image of eight sets of patches arranged in the transport direction as the image pattern for measuring misalignment. As a result, if the execution frequency indicated by the execution frequency setting is equal to or greater than a predetermined value, the image pattern for measuring misalignment is formed in an area longer than one revolution of the transfer belt 107.

[0057] Furthermore, if the execution frequency indicated by the execution frequency setting is less than a predetermined value, the processor 121 forms an image pattern for measuring misalignment with four sets of patches, which is half the number of standard sets. In this case, the image pattern for measuring misalignment, which is made up of four sets of patches arranged in the transport direction, is formed in an area that is less than one revolution of the transfer belt 107. As a result, if the execution frequency indicated by the execution frequency setting is less than a predetermined value, the image pattern for measuring misalignment is formed in an area that is shorter than one revolution of the transfer belt 107.

[0058] For example, if it takes 4 seconds to read an image with 8 sets of patches arranged in the transport direction, it will take 2 seconds to read an image with 4 sets of patches arranged in the transport direction. Therefore, the fewer the number of sets of patches arranged in the transport direction, the shorter the time required to read the image pattern for measuring positional deviation.

[0059] On the other hand, when the patches for measuring misalignment are formed over one revolution or more of the transfer belt 107, the misalignment can be detected over the entire transfer belt 107, and therefore highly accurate misalignment correction can be achieved. When the patches for measuring misalignment are formed over less than one revolution of the transfer belt 107, the misalignment is detected over only a part of the transfer belt 107, and therefore it is expected that the accuracy of the misalignment correction will decrease. However, in reality, when the standard number of sets of patches is eight, even if the number of sets of patches is reduced to four, there is no decrease in the accuracy of the misalignment correction that is noticeable to the naked eye.

[0060] That is, even if misalignment correction is performed using a patch formed when the transfer belt 107 has made less than one revolution, the accuracy of misalignment correction required for practical use may be ensured. When a user specifies a frequency of execution of misalignment correction less than a predetermined value (reference value), the image forming apparatus 100 sets the number of sets of patches to a number of sets that results in less than one revolution of the transfer belt 107. This allows the image forming apparatus 100 according to the embodiment to shorten the execution time of misalignment correction when the execution frequency indicated by the execution frequency setting is less than the predetermined value.

[0061] The number of sets of patches may be reduced within a range that ensures the accuracy of positional deviation correction acceptable for practical use. For example, the image forming apparatus 100 may be set to gradually reduce the number of sets of patches within an acceptable range. In this case, if the execution frequency indicated by the execution frequency setting is less than a predetermined value, the processor 121 gradually reduces the number of sets of patches as the execution frequency decreases.

[0062] This allows the image forming apparatus to reduce the number of patch sets in the image for identifying misalignment as the user performs misalignment correction less frequently (longer execution intervals).As a result, the image forming apparatus can shorten the execution time of misalignment correction as the user performs misalignment correction less frequently (longer execution intervals).

[0063] The user may specify the accuracy of the misalignment correction instead of the frequency or interval of the misalignment correction. When the user specifies a correction accuracy lower than the standard, the image forming apparatus may reduce the number of sets of patches constituting the image pattern for measuring misalignment within an allowable range. In this way, the image forming apparatus can reduce the time required for the misalignment correction if the user specifies a lower accuracy of the misalignment correction.

[0064] Next, the operation of exposure position correction control (positional deviation correction) in image forming apparatus 100 according to the embodiment will be described. FIG. 5 is a flowchart for explaining an example of an operation of exposure position correction control (positional deviation correction) in image forming apparatus 100 according to the embodiment. In the image forming apparatus 100, the processor 121 receives an instruction to change settings related to the positional deviation correction (ACT11). The settings related to the positional deviation correction include an execution frequency or an execution interval, which are execution conditions for the positional deviation correction. The processor 121 receives an instruction to change the execution conditions as a change in the settings related to the positional deviation correction by the user.

[0065] For example, the user specifies the frequency of execution of the positional deviation correction as an execution condition of the positional deviation correction on the control panel 116. As a specific example, the user specifies an increase or decrease in the execution frequency of the positional deviation correction based on a standard value or specifies the length of the execution interval on the control panel 116. Furthermore, the user may specify the correction accuracy of the positional deviation correction instead of the execution frequency or execution interval of the positional deviation correction. In this case, too, the correction accuracy may be specified based on a standard value.

[0066] Furthermore, the processor 121 may receive an instruction to set the execution conditions of the positional deviation correction from an external terminal device connected via the communication interface 125. In this case, the user specifies the execution frequency of the positional deviation correction as the execution condition of the positional deviation correction in the terminal device connected via the communication interface 125. As a specific example, the user may specify in the terminal device how to increase or decrease the execution frequency of the positional deviation correction or how long the execution interval is based on a standard value.

[0067] When the processor 121 receives an instruction from the user to change the execution conditions, the processor 121 updates the settings related to the position error correction, such as the execution frequency, according to the settings instructed by the user (ACT12). Here, it is assumed that the setting information related to the position error correction is stored in the auxiliary storage device (memory) 124. The setting information related to the position error correction includes information indicating the execution conditions of the position error correction. As the execution conditions, a threshold value for the amount of temperature change for executing the position error correction and an execution frequency (execution interval) are set.

[0068] For example, when a user instructs to change the execution frequency setting of the misalignment correction, the processor 121 updates the execution frequency setting of the misalignment correction in response to the user's instruction. The execution frequency setting is information indicating the elapsed time until the misalignment correction is executed (the execution interval of the misalignment correction). The processor 121 may also store information indicating the number of sets of patches in the image pattern for measuring the misalignment according to the execution frequency setting in the memory as setting information.

[0069] The processor 121 determines whether or not an execution condition indicated by the setting information regarding the positional deviation correction is reached. Here, it is assumed that the image forming apparatus 100 has a temperature change threshold and an elapsed time (execution interval) set as the execution condition. That is, the processor 121 identifies the amount of temperature change based on the temperature detected by the temperature sensor 1061, and determines whether the amount of temperature change has reached a threshold value that is an execution condition (ACT13). If the amount of temperature change has not reached the threshold value (ACT13, NO), the processor 121 further determines whether a predetermined time (execution interval) for executing the position deviation correction has elapsed (ACT14).

[0070] If the amount of temperature change is less than the threshold value and the predetermined time for performing the position deviation correction has not elapsed (ACT14, NO), the processor 121 returns to ACT11 and executes the above-mentioned process.

[0071] The processor 121 determines to perform misalignment correction when the temperature change amount is equal to or greater than the threshold value (ACT13, YES) or when a predetermined time has elapsed (ACT14, YES). When performing misalignment correction, the processor 121 sets the number of sets of patches according to the misalignment correction settings (ACT15). As described above, the processor 121 specifies the number of sets of patches to be used for misalignment correction according to the execution frequency setting included in the misalignment correction settings. The processor 121 sets the number of sets of patches, which is the number of times one set of patches is repeatedly formed on the transfer belt 107.

[0072] When the processor 121 sets the number of sets of patches, it forms patch images of the set number of sets on the transfer belt 107 (ACT16). The processor 121 repeatedly executes the process of forming one set of patch images on the transfer belt 107 using each image forming unit 1051-1054 for the number of sets of patches. As a result, an image pattern for position measurement is formed on the transfer belt 107 in which the patches for the set number are lined up in the conveyance direction.

[0073] The processor 121 calculates the relative positional shift between the transport direction and the scanning direction for each color from the reading result of the image pattern for measuring positional shift formed on the transfer belt 107 (ACT17). For example, the processor 121 reads the image pattern for measuring positional shift on the transfer belt 107 with the toner sensor 117 and acquires the reading result. The processor 121 detects the amount of shift for each color based on the acquired reading result of the image pattern for measuring positional shift.

[0074] When the processor 121 detects the misalignment, the processor 121 adjusts a control value related to the exposure control for the exposure device 106 so that the image patterns of each color (four colors) overlap in accordance with the detected misalignment (ACT18). For example, the processor 121 adjusts the exposure timing in accordance with the amount of misalignment of each color so that the images of each color overlap. This allows the processor 121 to realize the correction of the misalignment using the image pattern for measuring the misalignment in accordance with the execution frequency setting.

[0075] As described above, the image forming apparatus according to the embodiment sets an image pattern for measuring misalignment according to the execution frequency setting for exposure misalignment correction control (misalignment correction). If the execution frequency setting for misalignment correction is equal to or greater than a predetermined value, the image forming apparatus executes misalignment correction using an image pattern for measuring misalignment formed over one or more revolutions of the transfer belt. If the execution frequency setting for misalignment correction is less than a predetermined value, the image forming apparatus executes misalignment correction using an image pattern for measuring misalignment formed over less than one revolution of the transfer belt.

[0076] As a result, if the execution frequency specified by the user is less than the reference value, the image forming apparatus forms an image for measuring the positional deviation less than one revolution of the transfer belt, thereby shortening the time required for correction. As a result, a user who specifies an execution frequency setting less than the reference value can reduce the waiting time due to the exposure position correction control.

[0077] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims.

[0078] Image forming apparatuses according to the embodiments will be listed below. [1] The image forming apparatus An exposure device; a transfer belt, which is an endless belt supported by rollers, onto which a toner image formed by developing the electrostatic latent image formed by the exposure device with toner is transferred; a memory for storing setting information regarding positional deviation correction for correcting a deviation in an exposure position by the exposure device; a processor that executes the positional deviation correction using an image pattern for measuring positional deviation that is imaged over one revolution or more of the transfer belt when a frequency setting of execution of the positional deviation correction in the setting information is equal to or greater than a predetermined value, and executes the positional deviation correction using an image pattern for measuring positional deviation that is imaged over less than one revolution of the transfer belt when a frequency setting of execution of the positional deviation correction in the setting information is less than the predetermined value; has. [2] In the image forming apparatus according to [1], The image pattern for measuring the positional deviation is an image pattern formed by repeating one set of patches. [3] [2] In the image forming apparatus according to the present invention, The processor, forming an image pattern for measuring positional deviation, in which a standard set number of the patches are arranged, on the transfer belt when the execution frequency setting is equal to or greater than the predetermined value; When the execution frequency setting is equal to or greater than the predetermined value, an image pattern for measuring positional deviation in which the patches are arranged in a number of sets less than the standard number of sets is formed on the transfer belt. [4] [3] In the image forming apparatus according to the present invention, When the execution frequency setting is less than the predetermined value, the processor creates, on the transfer belt, an image pattern for measuring positional deviation in which the patches are arranged in sets equal to or less than half the number of the standard sets. [5] [3] In the image forming apparatus according to the present invention, When the execution frequency setting is less than the predetermined value, the processor creates an image pattern for measuring positional deviation on the transfer belt in which the number of sets of patches is reduced each time the execution frequency indicated by the execution frequency setting becomes lower. [6] In the image forming apparatus according to [1], an input device through which a user inputs information; The processor updates the setting information related to the position deviation correction stored in the memory in response to information input using the input device. [7] [6] In the image forming apparatus according to the present invention, When an instruction to reduce the frequency of execution of the positional deviation correction from a standard frequency is input using the input device, the processor updates the setting of the frequency of execution of the positional deviation correction so that it becomes less than the predetermined value. [8] [6] In the image forming apparatus, When an instruction to set the accuracy of the positional deviation correction lower than standard is input using the input device, the processor updates the setting of the execution frequency of the positional deviation correction to less than the predetermined value. [9] In the image forming apparatus according to [1], A communication interface for connecting to a terminal device, The processor updates the setting information related to the position deviation correction stored in the memory in response to information input using the terminal device.

[10] [9] In the image forming apparatus according to the present invention, When an instruction to reduce the frequency of execution of the positional deviation correction from a standard frequency is input using the terminal device, the processor updates the setting of the frequency of execution of the positional deviation correction so that it becomes less than the predetermined value. [Explanation of symbols]

[0079] 100...image forming apparatus, 105 (1051, 1052, 1053, 1054)...image forming unit, 106... exposure device, 1061...Temperature sensor, 107...Transfer belt, 108...transfer roller, 109…fixing part, 116…Control panel (input device), 117...Toner sensor, 121...processor, 124...Auxiliary storage device (memory), 125...Communication interface, 127...Printer, 1271...Printer processor.

Claims

1. An exposure device; a transfer belt, which is an endless belt supported by rollers, onto which a toner image formed by developing the electrostatic latent image formed by the exposure device with toner is transferred; a memory for storing setting information regarding positional deviation correction for correcting a deviation in an exposure position by the exposure device; a processor that executes the positional deviation correction using an image pattern for measuring positional deviation that is imaged over one revolution or more of the transfer belt when a frequency setting of execution of the positional deviation correction in the setting information is equal to or greater than a predetermined value, and executes the positional deviation correction using an image pattern for measuring positional deviation that is imaged over less than one revolution of the transfer belt when a frequency setting of execution of the positional deviation correction in the setting information is less than the predetermined value; An image forming apparatus comprising:

2. The image pattern for measuring the positional deviation is an image pattern formed by repeating one set of patches. The image forming apparatus according to claim 1 .

3. The processor, forming an image pattern for measuring positional deviation, in which a standard set number of the patches are arranged, on the transfer belt when the execution frequency setting is equal to or greater than the predetermined value; forming an image pattern for measuring positional deviation on the transfer belt, the image pattern including a number of sets of the patches arranged that is smaller than the standard number of sets, when the execution frequency setting is equal to or greater than the predetermined value; The image forming apparatus according to claim 2 .

4. when the execution frequency setting is less than the predetermined value, the processor creates, on the transfer belt, an image pattern for measuring positional deviation in which the number of sets of the patches is equal to or less than half the number of the standard sets; The image forming apparatus according to claim 3 .

5. when the execution frequency setting is less than the predetermined value, the processor creates an image pattern for measuring positional deviation on the transfer belt, the image pattern having a reduced number of sets of the patches each time the execution frequency indicated by the execution frequency setting becomes lower; The image forming apparatus according to claim 3 .

Images