Image forming apparatus

Abstract

This invention provides an image forming apparatus capable of correcting image misalignment. According to an embodiment, the image forming apparatus includes multiple image forming units, an exposure unit, a transfer unit, and a processor. The multiple image forming units form images developed with a developer, which is supplied to latent images formed on each photoreceptor. The exposure unit outputs light for forming latent images on each photoreceptor in the multiple image forming units. The transfer unit transfers multiple images developed by the multiple image forming units onto a medium in an overlapping manner. When the difference between the ambient temperature and the temperature inside the exposure unit during the period from startup to the start of image forming meets predetermined implementation conditions, the processor sets a alignment execution flag indicating the execution of the next position misalignment correction after a predetermined flag setting time has elapsed since the initial position misalignment correction was performed after startup, provided that the difference between the ambient temperature and the temperature inside the exposure unit meets predetermined implementation conditions.

Description

Technical Field

[0001] Embodiments of the present invention relate to an image forming apparatus. Background Technology

[0002] Electrophotographic image forming apparatuses achieve color printing by overlaying images formed by various colors of toner. In such apparatuses, image shift (color shift) sometimes occurs, where overlapping images of different colors are misaligned. One cause of image shift is displacement of parts within the exposure unit (light scanning unit) due to temperature changes. When the temperature change in the exposure unit reaches a specific condition, the image forming apparatus performs positional offset correction (alignment) to correct the image shift. However, existing image forming apparatuses suffer from the problem that image shift can easily occur even after startup, even if the specific conditions for positional offset correction are not met. Summary of the Invention

[0003] The technical problem that the invention aims to solve

[0004] The purpose of this invention is to provide an image forming apparatus capable of correcting image offset.

[0005] Technical solutions for solving technical problems

[0006] According to an embodiment, the image forming apparatus includes multiple image forming units, an exposure unit, a transfer unit, and a processor. The multiple image forming units form images developed with a developer, which is supplied to latent images formed on each photoreceptor. The exposure unit outputs light for forming latent images on each photoreceptor in the multiple image forming units. The transfer unit transfers multiple images developed by the multiple image forming units onto a medium in an overlapping manner. When the difference between the ambient temperature and the temperature inside the exposure unit during the period from startup to the start of image forming meets predetermined implementation conditions, the processor sets a alignment execution flag indicating the execution of the next position offset correction after a predetermined flag setting time has elapsed since the initial position offset correction was performed after startup, provided that the temperature difference between the ambient temperature and the temperature inside the exposure unit meets predetermined implementation conditions. Attached Figure Description

[0007] Figure 1 This is a diagram illustrating an example of the structure of each part in the image forming apparatus according to an embodiment.

[0008] Figure 2 This is a top view showing an example of the structure of the exposure device in the image forming apparatus of an embodiment.

[0009] Figure 3 This is a bottom view showing a structural example of the exposure device in the image forming apparatus of an embodiment.

[0010] Figure 4This is a cross-sectional perspective view showing a structural example of the exposure device in the image forming apparatus of the embodiment.

[0011] Figure 5 This is a diagram illustrating an example of the arrangement of an environmental sensor and a transfer heater in an image forming apparatus according to an embodiment.

[0012] Figure 6 This is a block diagram illustrating a structural example of the control system in an image forming apparatus according to an embodiment.

[0013] Figure 7 This is a diagram illustrating the first example of the relationship between temperature changes and color shifts in various parts of the image forming apparatus according to the embodiment.

[0014] Figure 8 This is a second example of a diagram illustrating the relationship between temperature changes and color shifts in various parts of the image forming apparatus according to an embodiment.

[0015] Figure 9 This is a flowchart illustrating an example of the alignment control operation performed after the image forming apparatus of an embodiment is started. Detailed Implementation

[0016] Hereinafter, the image forming apparatus of the embodiment will be described with reference to the accompanying drawings.

[0017] It should be noted that the scale of each part in the accompanying drawings used in the following description of the embodiments has been appropriately changed. Furthermore, the structures in the accompanying drawings used in the following description of the embodiments are sometimes omitted for illustrative purposes.

[0018] Figure 1 This is a diagram that schematically illustrates a structural example of the image forming apparatus 100 according to an embodiment.

[0019] The image forming apparatus 100 is disposed in a workstation or the like. The image forming apparatus 100 performs printing by electrophotography. The image forming apparatus 100 is, for example, an MFP (multifunction peripheral), a copier, a printer, or a fax machine.

[0020] like Figure 1 As shown, the image forming apparatus 100 includes a paper feed tray 101, a manual paper feed tray 102, a paper feed roller 103, a toner cartridge 104, an image forming unit 105, an exposure device (exposure unit) 106, a transfer belt 107, a transfer roller 108, a fixing unit 109, a heating unit 110, a pressure roller 111, a paper discharge tray 112, a duplex unit 113, a scanner 114, an original document feed device 115, and a control panel 116.

[0021] The image forming unit 105 prints an image using an electrophotographic method. The image forming unit 105 uses toner to form an image printed on an image forming medium P, etc. The image forming medium P is, for example, sheet-like paper. The scanner 114 reads the image from an original document on which the image is formed. For example, the image forming apparatus 100 prints the image read from the original document by the scanner 114 onto the image forming medium (hereinafter referred to as paper) P via the image forming unit 105, thereby achieving image copying of the original document.

[0022] Paper tray 101 holds paper P, which serves as the image forming medium for printing. Manual paper tray 102 is a platform for manually feeding paper P. Paper feed roller 103 is rotated by a motor, thereby taking out the paper P held in paper tray 101 or manual paper feed tray 102 and feeding it onto the transport path. The image forming apparatus 100 forms a paper transport path using multiple rollers, etc. The paper P taken out by paper feed roller 103 is supplied to the transfer position (secondary transfer position) of the transferred image via the transport path.

[0023] The image forming apparatus 100 includes a plurality of toner cartridges 104. The toner cartridges 104 supply toner to the image forming unit 105. The image forming apparatus 100 in... Figure 1 The illustrated structure includes four toner cartridges 104: toner cartridge 104C, toner cartridge 104M, toner cartridge 104Y, and toner cartridge 104K. Toner cartridges 104C, 104M, 104Y, and 104K respectively store toner corresponding to various CMYK colors (cyan, magenta, yellow, black (key)).

[0024] It should be noted that the color of the toner stored in toner cartridge 104 is not limited to the CMYK colors, but can also be other colors. Furthermore, the toner stored in toner cartridge 104 can be special toner. For example, toner cartridge 104 can also store decolorizable toner that becomes invisible at temperatures higher than a specified temperature.

[0025] The image forming apparatus 100 includes a plurality of image forming units 105. Figure 1 In the example shown, the image forming apparatus 100 includes four image forming units 105: image forming unit 105C, image forming unit 105M, image forming unit 105Y, and image forming unit 105K. Image forming units 105C, 105M, 105Y, and 105K each receive toner corresponding to various CMYK colors and form toner images (images) of various colors.

[0026] Each image forming unit 105 includes a developer and a photosensitive drum (photoreceptor). An electrostatic latent image is formed on the surface of the photosensitive drum. The developer uses toner supplied from the toner cartridge 104 to develop the electrostatic latent image formed on the surface of the photosensitive drum. Thus, a toner image formed from toner of various colors is formed on the surface of the photosensitive drum of each image forming unit 105. Each image forming unit 105 transfers the toner image formed on the surface of the photosensitive drum onto the transfer belt 107 at its respective transfer position (primary transfer position).

[0027] Exposure apparatus 106 is also referred to as LSU (laser scanning unit), etc. Exposure apparatus 106 forms electrostatic latent images on the surface of the photosensitive drums of each image forming unit 105 using lasers controlled according to image data. Exposure apparatus 106 is, for example, as described later. Figures 3 to 5 It is constructed as shown.

[0028] The transfer belt 107 is, for example, an annular belt supported by rollers. The transfer belt 107 is configured to have a predetermined length for one revolution. The transfer belt 107 rotates due to the movement of the rollers. By rotating, the transfer belt 107 transfers (first-time transfers) images from the transfer rollers (first-time transfer rollers) of each image forming unit 105C, 105Y, 105M, and 105K. The transfer belt 107 transports the images (toner images) transferred from each image forming unit 105C, 105Y, 105M, and 105K to the position of the transfer roller 108 (secondary transfer position).

[0029] The transfer roller 108 has two rollers that are opposite each other. The transfer roller 108 transfers (secondary transfer) the image formed on the transfer belt 107 to the image forming medium P passing between the transfer rollers 108.

[0030] Toner sensor 117 detects toner adhering to transfer belt 107. Toner sensor 117 detects the toner image on transfer belt 107 between the transfer position (primary transfer position) of image forming unit 105K and the position (secondary transfer position) where the toner image on transfer belt 107 corresponds to the transfer roller 108. For example, toner sensor 117 is configured to face transfer belt 107 between transfer roller and transfer roller 108 of image forming unit 105K.

[0031] The fixing unit 109 heats and presses the paper P on which the image has been transferred. This fixes the image transferred onto the paper P. The fixing unit 109 includes a heating unit 110 and a pressure roller 111 that are positioned opposite each other.

[0032] The heating section 110 is, for example, a roller equipped with a heat source for heating the heating section 110. This heat source is, for example, a heater. The roller heated by the heat source heats the paper P. The pressure roller 111 applies pressure to the paper P passing between the pressure roller 111 and the heating section 110.

[0033] Alternatively, the heating unit 110 may also include an annular belt suspended on multiple rollers. For example, the heating unit 110 includes a plate-shaped heat source, an annular belt, a belt conveyor roller, a tension roller, and a pressure roller. The annular belt is, for example, a film-like component. The belt conveyor roller drives the annular belt. The tension roller applies tension to the annular belt. An elastic layer is formed on the surface of the pressure roller. The heating part of the plate-shaped heat source contacts the inner side of the annular belt and is pressed towards the pressure roller, thereby forming a fixing and pressing area of ​​a predetermined width between the plate-shaped heat source and the pressure roller. Because the pressing area is formed and heated by the plate-shaped heat source, the responsiveness when energized is higher than that of heating methods using halogen lamps.

[0034] The annular belt, for example, has a 200µm thick silicone rubber layer formed on the outer side of a 50µm thick SUS (steel use stainless) substrate or a 70µm thick heat-resistant resin, i.e., polyimide, and the outermost periphery is covered by a surface protective layer such as PFA (perfluoroalkoxy alkane). The pressure roller, for example, has a 5mm thick silicone sponge layer formed on the surface of a 10mm φ iron rod, and the outermost periphery is covered by a surface protective layer such as PFA. The plate-shaped heat source, for example, has a glaze layer and a heating resistor layer stacked on a ceramic substrate. Furthermore, an aluminum heat sink is bonded to the plate-shaped heat source to release excess heat on the opposite side and to prevent substrate warping. The heating resistor layer, for example, is formed from a known raw material such as TaSiO2 and is divided into a predetermined length and number in the main scanning direction.

[0035] Paper tray 112 is the tray for discharging the finished printing paper P.

[0036] The double-sided unit 113 makes the paper P ready for printing on the reverse side. For example, the double-sided unit 113 flips the paper P by turning it back using a roller or the like.

[0037] Scanner 114 reads images from the original document. Scanner 114 is an image reading device for reading images from the original document. Scanner 114 is, for example, an optically scaled-down image reading device that includes an imaging element such as a CCD (charge-coupled device) image sensor. Alternatively, scanner 114 may be an image reading device using a close-contact sensor (CIS) method that includes an imaging element such as a CMOS (complementary metal-oxide-semiconductor) image sensor.

[0038] The original document feeder 115 is also known as an ADF (auto document feeder). The original document feeder 115 sequentially feeds original documents placed on a document tray. The scanner 114 reads the image of the fed original document. Alternatively, the original document feeder 115 may also be equipped with a scanner for reading images from the back of the original document.

[0039] The control panel 116 is a device for operation by an operator (user) of the image forming apparatus 100. The control panel 116 includes a display unit (display device) 1161 and an operation unit (operation device) 1162. The display unit 1161 is a display device (display apparatus) that displays instructions, operation buttons, etc. The display unit 1161 is, for example, a liquid crystal display (LCD) or an organic EL display (OLED). The operation unit 1162 is an input unit (input device) for user input information. The operation unit 1162 is, for example, composed of a touch panel and buttons. In this embodiment, the control panel 116 includes a display device with a touch panel as the display unit 1161 and the operation unit 1162.

[0040] Next, the structure of the exposure device (exposure unit) 106 in the image forming apparatus 100 of the embodiment will be described.

[0041] Figures 2 to 4 This is a diagram illustrating a structural example of the exposure device 106 in the image forming apparatus 100 of an embodiment.

[0042] Figure 2 This is a top view showing an example of the exposure device 106 in the image forming apparatus 100 of the embodiment. Figure 3 This is a bottom view showing an example of the exposure device 106 in the image forming apparatus 100 of the embodiment. Figure 4 This is a cross-sectional perspective view showing an example of the exposure device 106 in the image forming apparatus 100 of the embodiment.

[0043] like Figures 3 to 5 As shown, the exposure apparatus 106 includes a housing 1061, a laser unit 1062, a multifaceted mirror 1063, a multifaceted mirror motor 1064, a reflector 1065, a lens 1066, a first thermistor (first temperature sensor) 1067, and a second thermistor (second temperature sensor) 1068.

[0044] The housing 1061 is a frame that houses the laser unit 1062, the polygon mirror 1063, the polygon mirror motor 1064, the reflector 1065, the lens 1066, the first thermistor 1067, and the second thermistor 1068. The housing 1061 supports the laser unit 1062, the polygon mirror 1063, the polygon mirror motor 1064, the reflector 1065, the lens 1066, the first thermistor 1067, and the second thermistor 1068. The housing 1061 is, for example, made of resin.

[0045] The exposure apparatus 106, as a laser unit 1062, includes laser units 1062C, 1062M, 1062Y, and 1062K. Laser units 1062C, 1062M, 1062Y, and 1062K correspond to image forming units 105C, 105M, 105Y, and 105K, respectively. Each laser unit 1062 emits a laser beam. Each laser unit 1062 controls the emission of its laser beam according to a control signal corresponding to an image formed by its corresponding image forming unit 105. For example, each laser unit 1062 modulates its laser beam according to a control signal corresponding to image data.

[0046] The polygon mirror 1063 reflects the laser light emitted from each laser unit 1062. The polygon mirror 1063 is rotated by the polygon mirror motor 1064, thereby performing polarization scanning on each laser light. The polygon mirror motor 1064 is a motor that rotates the polygon mirror 1063. The polygon mirror motor 1064 generates heat when rotating the polygon mirror 1063, and therefore can become a heat source within the exposure apparatus 106.

[0047] The reflector 1065 and lens 1066 are optical elements used to scan the laser on the photosensitive drum of each image forming section 105. For example, the reflector 1065 is configured to be adjustable in position or angle relative to the housing 1061.

[0048] The first thermistor 1067 is an example of a temperature sensor (temperature detection unit) that detects the temperature near the center (first part) within the exposure apparatus 106. The first thermistor 1067 outputs a signal representing the measured temperature. (This will be discussed later.) Figures 3 to 5 In the structural example shown, the first thermistor 1067 is disposed near the multifaceted mirror motor 1064 located in the center of the housing 1061.

[0049] The second thermistor 1068 is an example of a temperature sensor (temperature detection unit) that detects the temperature near the end (second part) within the exposure apparatus 106. The second thermistor 1068 outputs a signal representing the measured temperature. The second thermistor 1068 detects the temperature of the second part of the exposure apparatus 106, which is further away from the multifaceted mirror motor 1064 than the first part. Figures 3 to 5In the example shown, the second thermistor 1068 is located near the midpoint between the end of the housing 1061 and the multifaceted mirror motor 1064. In this case, the second thermistor 1068 is located at a position farther from the multifaceted mirror motor 1064 than the first thermistor 1067.

[0050] Next, the environmental sensor 211 and the transfer heaters 221 and 222 installed in the image forming apparatus 100 of the embodiment will be described.

[0051] Figure 5 This is a diagram showing an example of the installation of the environmental sensor 211 and the transfer heaters 221 and 222 within the main frame (frame) BF of the image forming apparatus 100 according to the embodiment.

[0052] The environmental sensor 211 includes a sensor that detects the temperature in the environment in which the image forming apparatus 100 is set. The environmental sensor 211 is positioned to detect the temperature within the housing EF of the image forming apparatus 100. Figure 5 In the illustrated structural example, the environmental sensor 211 is located separately from the transfer heaters 221 and 222. The environmental sensor 211 is configured to be less susceptible to localized temperature rises caused by heat emitted from the transfer heaters 221 and 222.

[0053] The transfer heaters 221 and 222 are heaters used to prevent condensation on the paper inside the frame BF or on the photosensitive drum inside the image forming section 105. The transfer heaters 221 and 222 operate when the main power supply to the image forming apparatus 100 is disconnected (hereinafter referred to as power off) and the temperature is below a set temperature. For example, the transfer heaters 221 and 222 have a structure in which a heater is connected to a thermostat that operates when the temperature is below a set temperature in the power off state. If the temperature is below the set temperature and the thermostat is activated, current flows through the transfer heaters 221 and 222, heating the periphery of the heater.

[0054] To prevent condensation on the paper and photosensitive material, transfer heaters 221 and 222 are positioned near the paper feed tray and the photosensitive drum. For example, in Figure 5 In the illustrated structural example, the transfer heater 221 is positioned near the image forming section 105, which includes a photosensitive drum. In the configuration of the image forming apparatus 100 as an electrophotographic printer, the exposure device 106 is positioned near the photosensitive element. Therefore, the transfer heater 221, used to prevent condensation on the photosensitive drum, is positioned near the exposure device 106.

[0055] In addition, Figure 5 In the illustrated structural example, the transfer heater 222 is positioned near the paper feed tray (paper cassette) 101 that contains the paper. Figure 1 and Figure 5 In the structure shown, an exposure device 106 is disposed on the upper part of the paper feed tray 101 that holds the paper. In this structure of the image forming apparatus 100, a transfer heater 222 for preventing condensation on the paper is also disposed near the exposure device 106.

[0056] Next, the structure of the control system in the image forming apparatus 100 of the embodiment will be described.

[0057] Figure 6 This is a block diagram illustrating a structural example of the control system in the image forming apparatus 100 of an embodiment.

[0058] exist Figure 6 In the illustrated structural example, the image forming apparatus 100 includes a system controller 120, a scanner 114, a control panel 116, and a printer 200. The system controller 120 includes 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, the scanner 114, the control panel 116, and the printer 200.

[0059] The processor 121 is equivalent to the central part of a computer that performs calculations and control processes required for the operation of the image forming apparatus 100. Based on system software, application software, or firmware stored in the ROM 122 or auxiliary storage device 124, the processor 121 controls various parts to realize the various functions of the image forming apparatus 100.

[0060] Processor 121 may be, for example, a CPU (central processing unit), MPU (microprocessor), SoC (system on a chip), DSP (digital signal processor), GPU (graphics processing unit), ASIC (application specific integrated circuit), PLD (programmable logic device), or FPGA (field-programmable gate array). Alternatively, processor 121 may be a combination of several of these.

[0061] ROM 122 is equivalent to the main storage device of the computer with processor 121 as its central processing unit. ROM 122 is a non-volatile memory specifically used for reading data. ROM 122 stores the aforementioned program. In addition, ROM 122 stores data or various settings used by processor 121 during various processing operations.

[0062] RAM 123 is equivalent to the main storage device of a computer with processor 121 as its central hub. RAM 123 is a memory used for reading and writing data. RAM 123 is used as a so-called working area to store data temporarily used by processor 121 during various processing operations.

[0063] Auxiliary storage device 124 is equivalent to an auxiliary storage device in a computer with processor 121 as the central processing unit. Auxiliary storage device 124 may be, for example, EEPROM (electrically erasable programmable read-only memory), HDD (hard disk drive), or SSD (solid-state drive). Auxiliary storage device 124 may also store programs. In addition, auxiliary storage device 124 stores data used by processor 121 during various processes, data generated by processing in processor 121, or various setting information. For example, auxiliary storage device 124 may serve as a memory for various setting information such as the implementation conditions for guiding image offset (a threshold for the difference between the temperature of the exposure device and the ambient temperature), the guidance execution time, and the guidance end time.

[0064] It should be noted that the image forming apparatus 100 may replace the auxiliary storage device 124, or may have an interface that allows the insertion of storage media such as memory cards or USB (universal serial bus) memory, in addition to the auxiliary storage device 124.

[0065] The program stored in ROM 122 or auxiliary storage device 124 contains a program for performing the processes described later. As an example, the image forming apparatus 100 is transferred to the administrator of the image forming apparatus 100, etc., with the program stored in ROM 122 or auxiliary storage device 124. The image forming apparatus 100 can also be transferred to the administrator, etc., with the program not stored in ROM 122 or auxiliary storage device 124.

[0066] Furthermore, the program used to perform the processes described later can also be written to ROM 122 or auxiliary storage device 124 through the operation of an administrator or service personnel. The program can be transferred, for example, by recording it on a removable storage medium such as a disk, optical disk, optical disc, or semiconductor memory, or by downloading it via a network.

[0067] The communication interface 125 is an interface for the image forming apparatus 100 to communicate via a network or the like. The communication interface 125 is connected to a user-operated terminal device.

[0068] RTC126 is a circuit that is a clock or has a built-in clock function. For example, processor 121 uses RTC126 to count the elapsed time since a specific moment.

[0069] It should be noted that the system controller 120 may also have an interface for connecting to a display device and an operating device, which are external devices. In this case, the processor 121 may also display the image offset guidance described later on the display device, which is an external device connected via the interface.

[0070] Printer 200 prints images on an image forming medium (paper) P, etc., based on image data. Printer 200... Figure 2 In the illustrated structural example, the paper feed roller 103, toner cartridge 104, image forming unit 105, exposure device 106, transfer roller 108, fixing unit 109, toner sensor 117, environmental sensor 211, and transfer heaters 221 and 222 are connected to the printer processor 201. However, the environmental sensor 211 and transfer heaters 221 and 222 may also be connected to the processor 121 of the system controller 120 without going through the printer processor 201.

[0071] To perform printing functions, the printer processor 201 performs processing such as calculations and control required for printing operations of the image forming apparatus 100. Based on instructions from the processor 121 and various programs, the printer processor 201 performs calculations and control processing required for printing actions. The printer processor 201 outputs the processing results to the processor 121.

[0072] It should be noted that various programs can be stored in a storage unit such as ROM 122 or auxiliary storage device 124, or they can be assembled within the circuitry of the printer processor 201. Alternatively, the storage unit located in the printer 200 can also store various programs. The printer processor 201 can be, for example, a CPU, MPU, SoC, DSP, GPU, ASIC, PLD, or FPGA.

[0073] Next, the position offset correction (color offset correction) of the image offset correction in the image forming apparatus 100 of the embodiment will be described.

[0074] In the image forming apparatus 100, the exposure device 106 may sometimes shift in exposure position due to minor deformations caused by changes in temperature or other factors. The image forming apparatus 100 has a function to perform position shift correction, which corrects for image shifts caused by shifts in the exposure position of the exposure device 106.

[0075] The image forming apparatus 100 generates a color image by overlaying images (toner images of various colors) formed by multiple image forming units 105 using toners of various colors. Therefore, the image forming apparatus 100 needs to adjust the offset of the toner images of various colors during color printing. Such positional offset correction in color printing is also called color offset correction (color registration). When a color image is being processed, color offset correction is performed under the control of the processor 121 or the printer processor 201.

[0076] For example, as a color offset correction, the processor 121 forms a predetermined pattern on the transfer belt 107 for measuring the offset of various color images formed by various color toners. The processor 121 detects the offset of each color image from its ideal position (reference position) based on the predetermined pattern on the transfer belt 107. The processor 121 adjusts the exposure timing of the exposure device 106 based on the offset, thereby correcting the positional offset of each color image. Specifically, the processor 121 calculates the relative positional offset between the transport direction and the scanning direction in each color image based on the reading result of the predetermined pattern. Therefore, the processor 121 adjusts the exposure timing for forming each color image based on the calculated positional offset, so that the image patterns of each color (four colors) overlap.

[0077] The image forming apparatus 100 performs positional offset correction (color offset correction) when a predetermined execution condition for positional offset correction is detected. The execution condition for positional offset correction is set relative to the temperature within the exposure apparatus 106. For example, the image forming apparatus 100 is configured to perform positional offset correction based on temperature changes within the exposure apparatus 106 detected by a first thermistor 1067 and a second thermistor 1068. Alternatively, the image forming apparatus 100 performs positional offset correction during startup when the main power is turned on. Furthermore, the image forming apparatus 100 may also be configured to perform positional offset correction during the initial color printing operation after startup. In this embodiment, the image forming apparatus 100 performs positional offset correction during startup.

[0078] Next, the effect of the switching on / off of the transfer heaters 221 and 222 during the power outage in the image forming apparatus 100 on the exposure apparatus 106 will be explained.

[0079] In this embodiment, power disconnection refers to the state where the main power supply of the image forming apparatus 100 is disconnected. The image forming apparatus 100 with the power disconnected is connected to an external power supply, but is in a state where it stops printing and scanning and does not accept operation instructions other than operation instructions to turn on the main power (operation stop state).

[0080] The transfer heaters 221 and 222 are connected so that they can be supplied with power from an external power source even when the power is off. Therefore, the image forming apparatus 100 does not accept any actions when the power is off, but the transfer heaters 221 and 222 can operate. The period of power off is also called the operation stop period. The image forming apparatus 100, when the power is off, performs a start-up action according to the instruction (start-up instruction) to turn on the main power. After the start-up action, the image forming apparatus 100 becomes capable of performing tasks such as printing and scanning.

[0081] exist Figure 5 In the illustrated structural example, transfer heaters 221 and 222 are positioned near the photoreceptor and the paper tray. When transfer heaters 221 and 222 are turned on during power-off, not only the photoreceptor and the paper tray are heated, but the exposure apparatus 106 is also heated. The state of the exposure apparatus 106 after startup may differ depending on whether transfer heaters 221 and 222 are turned on during power-off. Sometimes, the exposure position of the exposure apparatus 106 changes due to slight deformation corresponding to the temperature distribution within the housing 1061, resulting in image shift (color shift). That is, in the image forming apparatus 100 according to this embodiment, the image shift state after startup can change depending on whether transfer heaters 221 and 222 are turned on during power-off.

[0082] Next, the changes in the state of the image forming apparatus 100 after startup will be explained.

[0083] In the image forming apparatus 100, the state of image shift varies depending on whether the transfer heaters 221 and 222 are activated during the power-off period before startup. Here, as an example of the image forming apparatus 100, it is envisioned that the main power is turned on during the day to enable printing operations, and the main power is turned off at night to stop printing operations. In this application, the image forming apparatus 100 changes the state of image shift after startup depending on whether the transfer heaters 221 and 222 are activated during the power-off period at night (during the operation stoppage).

[0084] Figure 7 and Figure 8 This is a graph showing the measured values ​​of temperature and image offset of each part when the image forming apparatus 100, which starts from a power-off state (during operation stop), performs printing processing at a specific printing interval.

[0085] Figure 7 This is a graph showing the measured values ​​of temperature and image offset of each part after startup when the transfer heaters 221 and 222 are activated (turned on) during the operation stop period (assuming the heaters are turned on). Figure 8 This is a graph showing the measured values ​​of temperature and image offset of each part after startup when the transfer heaters 221 and 222 are not activated (turned on) during the operation stop period (assuming the heaters are off).

[0086] It should be noted that, Figure 7 and Figure 8 In the middle, the action stop period is set to 14 hours, the printing interval is set to every 8 minutes, and the printing process is set to color printing on two A3-sized sheets of paper. Figure 7 and Figure 8 This indicates the measurement results under the condition that the start-up process (start-up action) is performed after the operation stop period based on the power-on state when the power is off, and position offset correction is performed just before the first print. However, the transfer heaters 221 and 222 are turned off simultaneously with the power-on.

[0087] exist Figure 7 and Figure 8 In the diagram, the detection temperature a of the first thermistor 1067 and the detection temperature b of the second thermistor 1068 are shown, representing the temperature of the exposure apparatus (exposure device) (the temperature within the housing 1061 of the exposure apparatus 106). Additionally, Figure 7 and Figure 8 The ambient temperature, c, is shown as the detection temperature of the ambient sensor 211. Furthermore, Figure 7 and Figure 8 As a measurement value of image offset, the measured value of image offset appearing on paper that has been color-printed by the image forming apparatus 100 is shown. Figure 7 and Figure 8 In the diagram, quadrilateral points represent the measured value d of the image offset in the main scanning direction, and triangular points represent the measured value e of the image offset in the sub-scanning direction.

[0088] First, the temperature inside the housing 1061 of the exposure device 106 after the power is turned on (the temperature of the exposure device) is compared with the ambient temperature.

[0089] Here, the detection temperature 'a' of the first thermistor 1067 is the temperature of the center of the housing 1061 near the faceted mirror motor 1064 in the exposure apparatus 106. The detection temperature 'b' of the second thermistor 1068 is the temperature of the end of the housing 1061 in the exposure apparatus 106 located away from the faceted mirror motor 1064. The temperature of the exposure apparatus (exposure device) can be the detection temperature of the first thermistor 1067 or the second thermistor 1068, or it can be the average of the detection temperatures of the first thermistor 1067 and the second thermistor 1068.

[0090] exist Figure 8 In the example shown, immediately after power is switched on, the temperature difference between the first thermistor 1067 (a), the second thermistor 1068 (b), and the ambient sensor 211 (c) is within 1 degree Celsius. Considering the measurement accuracy of the first and second thermistors 1067 and 1068, and the ambient sensor 211, then... Figure 8 In the example shown, it can be said that the temperature of the exposure apparatus is approximately equal to the ambient temperature immediately after the power is turned on. Therefore, when the transfer heaters 221 and 222 are not activated during the power-off period (when the heaters are off), it is assumed that the temperature of the exposure apparatus becomes almost equal to the ambient temperature immediately after the power is turned on.

[0091] exist Figure 7 In the example shown, immediately after power is turned on, the detection temperature a of the first thermistor 1067 and the detection temperature b of the second thermistor 1068 are higher than the detection temperature c of the ambient sensor 211. Therefore, when the transfer heaters 221 and 222 operate during power-off (when the heaters are turned on), it is assumed that the temperature of the exposure apparatus is higher than the ambient temperature immediately after power is turned on.

[0092] Next, the temperature changes of each part after the printing process begins will be explained.

[0093] exist Figure 8 In the example shown, after the printing operation begins, the detection temperature 'a' of the first thermistor 1067 and the detection temperature 'b' of the second thermistor 1068 both tend to rise. The areas in the housing 1061 where the temperature rises tend to undergo physical expansion. That is, when the exposure apparatus 106 is powered off and the heater is off, the temperature of the central portion and ends of the housing 1061 rises, therefore it is considered that the housing 1061 expands overall. In the case of overall expansion of the housing 1061, the overall deformation of the housing 1061 is relatively smaller compared to the case where the central portion of the housing 1061 expands while the ends contract. As a result, it is considered that the image shift during printing after the start-up operation of the exposure apparatus 106 (after the initial pre-printing positional offset correction) is smaller.

[0094] exist Figure 7In the example shown, after the printing operation begins, the detection temperature a of the first thermistor 1067 tends to increase, while the detection temperature b of the second thermistor 1068 tends to decrease. The increase in the detection temperature a of the first thermistor 1067 is believed to be due to heat generated by the driving of the multi-faceted mirror motor 1064 located at the center of the housing 1061. The decrease in the detection temperature b of the second thermistor 1068 is believed to be due to the cooling of the ends of the housing 1061 due to the temperature difference with the ambient temperature. The ends of the housing 1061 transfer heat generated by the multi-faceted mirror motor 1064, but due to the large temperature difference with the ambient temperature, a tendency for the temperature to decrease is considered.

[0095] exist Figure 7 In the diagram, points d and e represent the image offset during printing after the start action. For example... Figure 7 As shown, when the heater is on while the power is off, during printing after the initial position offset correction, the image offset increases as the temperature of the central portion of the housing 1061 rises and the temperature of the ends decreases. This image offset is believed to be caused by the expansion of the central portion of the housing 1061 due to the temperature increase and the contraction of the ends due to the temperature decrease. When both expansion of the central portion and contraction of the ends occur simultaneously, the overall deformation of the housing 1061 is relatively larger compared to the case where the housing 1061 expands as a whole. It is believed that when the deformation of the housing 1061 increases, the offset of the exposure position of the exposure device 106 increases, and the offset of the image (images of various colors) formed on the medium increases.

[0096] Compare Figure 7 and Figure 8 It can be seen that when the power is off and the heater is on, the change in image offset per unit time increases. Figure 7 In the example shown, during the 8-minute printing interval after the start of the action, the change (increase) in image offset increases significantly between the first and third printings (16 minutes). However, in Figure 7 In the example shown, the temperature of the central part of the housing 1061 hardly changes after rising immediately after the initial printing, and the temperature of the ends of the housing 1061 also changes little over time.

[0097] exist Figure 7 In the temperature changes shown, it is difficult to set the position offset correction to be performed under the temperature difference between the temperature of the center and the temperature of the end (the temperature difference between the detection temperature of the first thermistor 1067 and the detection temperature of the second thermistor 1068). If the position offset correction is performed even if the temperature difference between the center and the end is small, a high-precision thermistor is required, and the position offset correction is performed frequently, which slows down the printing operation.

[0098] Therefore, the image forming apparatus 100 in the embodiment is configured to focus on Figure 7 Position offset correction is performed based on the changes in image offset shown.

[0099] exist Figure 7 In the example shown, the change in image offset is large during the period from the first print (0 minutes) after power-on to the third print (16 minutes) (A), and small thereafter. Furthermore, the change in image offset is larger (above 0.05 mm) in both the first and second prints. Therefore, according to... Figure 7 In the example shown, to ensure the image offset is less than 0.05, positional offset correction (secondary positional offset correction) needs to be performed before the second printing (color printing). If positional offset correction is performed before the second color printing, the image offset can be reduced in subsequent color printings.

[0100] However, the image forming apparatus 100 of this embodiment does not experience image shift in monochrome printing, but does experience image shift in color printing of images with multiple overlapping colors. That is, the image forming apparatus 100 does not need to perform position shift correction when color printing is not being performed. Therefore, the image forming apparatus 100 sets a flag (alignment execution flag) to perform position shift correction before color printing, just before performing color printing that requires a second position shift correction. If the alignment execution flag is set when color printing begins, the image forming apparatus 100 performs position shift correction just before performing that color printing.

[0101] exist Figure 7 In the example shown, to set up position offset correction to be performed just before the second color printing, the alignment execution flag can be set at a time (B) before the second color printing is performed. As a specific example, since the second color printing with a larger image offset is 8 minutes after the first printing (C), consider setting the alignment execution flag 7 (8-1) minutes after the first printing (the first printing with position offset correction) 1 minute before that (B).

[0102] The timing for setting the counter-execution flag (in) Figure 7 In the example, B is set to the period when the image offset change increases (7 minutes after the first print). Figure 7 In the example, this refers to the time within A (0–16 minutes), and the time during which the image shift changes significantly compared to the first printing (in... Figure 7 In the example, it is 0-8 minutes before C (e.g., 1 minute ago).

[0103] The image forming apparatus 100 of the embodiment predefines the period during which the change in image offset increases after startup (alignment control period) A, the timing for setting the second alignment execution flag (flag setting time) B, and the time during which the alignment execution flag can be set (flag settable period) C. Therefore, the image forming apparatus 100 can set the alignment execution flag when the timing changes from the first color printing (first position offset correction) after startup to timing B, and can perform position offset correction before the second color printing when the image offset increases.

[0104] Next, an example of the position offset correction control operation after the start-up operation of the image forming apparatus 100 in the embodiment will be described.

[0105] Figure 9 This is a flowchart illustrating an example of the position offset correction control operation after the start-up operation of the image forming apparatus 100 in an embodiment.

[0106] As described above, when the image forming apparatus 100 is in a power-off state (during operation stop), and the temperature is below a specified temperature, the transfer heaters 221 and 222 operate.

[0107] The processor 121 of the image forming apparatus 100 receives a power-on signal when the power is off. For example, when the main power button provided on the image forming apparatus 100 is pressed, a power-on signal is input to the processor 121. When the power-on instruction is input (ACT11, Yes), the processor 121 performs a start-up operation and sets an alignment execution flag (ACT12) indicating that position offset correction will be performed before the first color printing.

[0108] Furthermore, during the startup action corresponding to power-on, the processor 121 determines whether the execution conditions (ACT13) for alignment control after startup (during a specified period A) are met. The processor 121 determines whether to perform alignment control after startup based on whether the preset execution conditions are met. These execution conditions include conditions for determining whether the transfer heaters 221 and 222 are turned on in the power-off state (during the operation stop period).

[0109] For example, as an implementation condition, the processor 121 determines whether the temperature difference between the exposure apparatus and the ambient temperature during the period from when the power is first turned on until the initial printing begins is above a predetermined threshold. The predetermined threshold is set based on the heater capacity of the transfer heaters 221 and 222, the structure of the machine body, and the accuracy of the first and second thermistors, etc. As a specific example, see [reference needed]. Figure 7 The measurement results shown indicate that the threshold value was set to approximately 2°C.

[0110] When calculating the temperature difference between the exposure apparatus and the ambient temperature, the processor 121 acquires temperature information from each sensor immediately after the power is turned on. That is, the processor 121 acquires information indicating the detected temperature from the first thermistor 1067, the second thermistor 1068, and the ambient sensor 211, respectively.

[0111] The processor 121 uses the temperature detected by the environmental sensor 211 as the ambient temperature and the temperatures detected by the first thermistor 1067 and the second thermistor 1068 as the temperature of the exposure apparatus. However, the processor 121 can use the temperature detected by either the first thermistor 1067 or the second thermistor 1068 as the temperature of the exposure apparatus, or it can use the average of the temperatures detected by the first thermistor 1067 and the second thermistor 1068 as the temperature of the exposure apparatus. If the processor 121 obtains the temperature of the exposure apparatus and the ambient temperature, it calculates the difference by subtracting the ambient temperature from the temperature of the exposure apparatus and determines whether the calculated difference is above a predetermined threshold.

[0112] It should be noted that the determination of whether the conditions for performing alignment control are met is not limited to the difference between the temperature of the exposure device and the ambient temperature. For example, it is also possible to determine whether alignment control should be performed by directly detecting whether the transfer heaters 221 and 222 are turned on during startup in the power-off state. As a specific example, the image forming apparatus 100 may also be equipped with a recording unit that records whether the transfer heaters 221 and 222 are turned on during power-off. In this case, the processor 121 can determine whether the transfer heaters 221 and 222 have operated during power-on based on the recorded content of the recording unit.

[0113] If the processor 121 determines that the implementation conditions are not met, i.e., that the alignment control after startup is not performed (ACT13, No), it transitions to the normal operation state after startup. Thus, if the transfer heaters 221 and 222 are not turned on when the power is off, the processor 121 can transition to the normal operation state without performing the alignment control after startup.

[0114] If the processor 121 determines that the conditions for implementing the alignment execution control are met (ACT13, Yes), it performs the normal printing process and begins the alignment execution control during the specified period A after startup. When the processor 121 begins the alignment execution control, it determines whether color printing has been accepted (ACT14). If the processor 121 does not have an indication for color printing (ACT14, No), it proceeds to ACT18.

[0115] Upon receiving the first color print (ACT14, yes), processor 121 performs position offset correction and cancels the alignment execution flag (ACT15). Here, the alignment execution flag, which is set during startup, is established during the first color print. Therefore, processor 121 performs position offset correction based on the alignment execution flag set at startup, just before the first color print. After performing position offset correction, processor 121 performs the first color print and proceeds to ACT16.

[0116] When the processor 121 performs the first position offset correction (first color printing), it determines whether a predetermined flag setting time B (ACT16) has elapsed. Here, flag setting time B indicates the time at which the alignment execution flag for performing position offset correction is set during (before) the second color printing. For example, the processor 121 sets the alignment execution flag when time B has elapsed since the first color printing accompanying the position offset correction (when the first alignment execution flag is canceled).

[0117] Processor 121 remains in standby mode from the time of performing the first position offset correction until the time of setting the flag B (ACT16, No). It should be noted that processor 121 also accepts printing requests, including color printing, during the period from performing the first position offset correction until the time of setting the flag B. When processor 121 is requested to perform color printing during the period from performing the first position offset correction until the time of setting the flag B, it performs color printing without position offset correction.

[0118] If time B has elapsed since the first position offset correction was performed (ACT16, yes), processor 121 sets an alignment execution flag (ACT17) in order to perform position offset correction in the next color printing. For example, as Figure 7 As shown, when the flag setting time B is set to 7 minutes, the processor 121 sets the alignment execution flag 7 minutes after the first color printing accompanied by position offset correction.

[0119] Additionally, if no color printing occurs after startup (ACT14, No), the processor 121 monitors whether a predetermined C time (the period during which the flag for setting the second alignment execution flag can be set) has elapsed (ACT18). If the predetermined C time has not elapsed (ACT18, No), the processor 121 returns to ACT14. Alternatively, if the predetermined C time has elapsed after startup without color printing (ACT18, Yes), the processor 121 proceeds to ACT19 while maintaining the alignment execution flag.

[0120] That is, if the processor 121 performs the first position offset correction (with color printing accompanying the position offset correction) during the flag setting period C, it sets the second alignment execution flag at the timing indicated by the flag setting time B. Alternatively, if the processor 121 does not perform the position offset correction (with color printing accompanying the position offset correction) during the flag setting period C, it maintains the alignment execution flag set at the start operation.

[0121] If the processor 121 sets the alignment execution flag after the flag setting time B has elapsed, or if a predetermined time C has elapsed without color printing (ACT18, yes), it determines whether color printing was accepted before the predetermined time A has elapsed (ACT19). In this case, when the processor 121 accepts the color printing execution request (ACT19, yes), it checks whether the alignment execution flag has been set (ACT20).

[0122] If the processor 121 does not set the alignment execution flag when accepting color printing (ACT20, No), it further checks whether the state meets the normal alignment conditions (the conditions for performing position offset correction under normal operating conditions) (ACT21). If the processor 121 determines that the alignment execution flag is not set and the state does not meet the normal alignment conditions (ACT21, No), it performs color printing and proceeds to ACT23.

[0123] Additionally, if the alignment execution flag is set (ACT20, yes), the processor 121 performs position offset correction and cancels the alignment execution flag (ACT22). After performing position offset correction, the processor 121 performs the accepted color printing and proceeds to ACT23.

[0124] Additionally, when the processor 121 reaches a state that satisfies the normal alignment conditions (ACT21, yes), it performs position offset correction (ACT22). In this case, the processor 121 performs the accepted color printing and proceeds to ACT23.

[0125] While repeating the processing of ACT19-22, the processor 121 monitors whether the specified A time (the implementation period of bit execution control after startup) (ACT23) has elapsed.

[0126] If the specified time A has not elapsed (ACT23, No), processor 121 returns to ACT19 and repeats the above process. Alternatively, if the specified time A has elapsed (ACT23, Yes), processor 121 terminates the bit alignment control after startup (period A after startup).

[0127] As described above, the image forming apparatus of this embodiment determines whether the difference between the temperature of the exposure apparatus and the ambient temperature during the period from when the power is turned on until printing begins is greater than or equal to a predetermined threshold. If the calculated difference is greater than or equal to the predetermined threshold, the image forming apparatus performs post-start alignment execution control. As post-start alignment execution control, the image forming apparatus sets an alignment execution flag indicating the next position offset correction when a predetermined flag setting time has elapsed since the first position offset correction after startup.

[0128] Furthermore, the image forming apparatus of the embodiment determines whether the transfer heater operated during the power-off period (operation stop period) before power was turned on. If the image forming apparatus determines that the transfer heater operated during the power-off period (operation stop period) before power was turned on, it performs alignment execution control after startup.

[0129] According to the embodiment of the image forming apparatus, even in the second or subsequent color printing after startup due to the operation of the transfer heater during power disconnection, positional offset correction can be performed before the image offset becomes large. As a result, the image forming apparatus according to the embodiment can provide users who desire high-quality color printing without color offset with printing results that suppress minor image offsets after startup.

[0130] Several embodiments of the present invention have been described, but these embodiments are given by way of example and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, and are included in the scope of the invention as set forth in the claims and its equivalents.

[0131] As described above, the following image forming apparatus can be implemented according to the detailed embodiments.

[0132] [1] An image forming apparatus comprising: a plurality of image forming units that form developer images obtained by developing latent images formed on each photoreceptor using a developer; an exposure unit that outputs light for forming latent images on each photoreceptor in the plurality of image forming units; a transfer unit that transfers an image superimposed with the plurality of developer images formed by the plurality of image forming units onto a medium; and a processor that, when the difference between the ambient temperature and the temperature inside the exposure unit during the period from startup to the start of image forming meets a predetermined implementation condition, sets an alignment execution flag indicating the execution of the next position offset correction after a predetermined flag setting time has elapsed since the initial position offset correction was performed after startup.

[0133] [2] The image forming apparatus according to [1] further comprises: an environmental sensor that measures the ambient temperature; and a temperature sensor that measures the temperature inside the exposure unit, wherein the specified implementation condition is a difference obtained by subtracting the detected temperature of the environmental sensor from the detected temperature of the temperature sensor, and the difference is above a specified temperature.

[0134] [3] According to the image forming apparatus of [1], wherein the plurality of image forming units form developer images of various colors for forming a color image, and the position offset correction is a process for correcting the offset of the developer images of various colors in color printing for forming a color image with overlapping developer images of various colors.

[0135] [4] According to the image forming apparatus of [3], if the alignment execution flag is set when the processor accepts color printing, the position offset correction is performed before the color printing is about to be performed.

[0136] [5] According to the image forming apparatus of [1], if the processor performs an initial position offset correction within a predetermined flag settable period after the start-up, the alignment execution flag is set when a predetermined flag setting time has elapsed since the initial position offset correction.

[0137] [6] According to the image forming apparatus of [5], wherein the processor sets an alignment execution flag during the start-up operation, cancels the alignment execution flag when performing the first position offset correction within the flag settable period after the start-up, and sets the alignment execution flag when a predetermined flag setting time has elapsed since the first position offset correction.

[0138] [7] According to the image forming apparatus of [6], if the processor does not perform the initial position offset correction during the flag setting period, it does not perform the setting of the alignment execution flag based on the flag setting time, but maintains the alignment execution flag set during the start-up operation.

[0139] [8] According to the image forming apparatus of [5], the mark can be set for a period of time longer than the mark setting time.

[0140] [9] According to the image forming apparatus of [5], the mark setting time is shorter than the interval for position offset correction in the normal operating state.

[0141]

[10] The image forming apparatus according to [5] includes a memory having a rewritable storage area, the storage area being able to store a set value representing the time of the flag setting.

[0142]

[11] An image forming apparatus comprising: a plurality of image forming units that form developer images obtained by developing latent images formed on each photoreceptor using a developer; an exposure unit that outputs light for forming latent images on each photoreceptor in the plurality of image forming units; a transfer unit that transfers an image of the plurality of developer images superimposed on the plurality of image forming units onto a medium; a heater disposed within a frame of the image forming apparatus and heating at a predetermined temperature; and a processor that, when the heater is turned on during a pre-start operation stop period, sets an alignment execution flag indicating the execution of the next position offset correction after a predetermined flag setting time has elapsed since the initial position offset correction was performed after startup.

[0143]

[12] The image forming apparatus according to

[11] further comprises: an environmental sensor that measures the ambient temperature; and a temperature sensor that measures the temperature inside the exposure unit, wherein the specified implementation condition is a difference obtained by subtracting the detected temperature of the environmental sensor from the detected temperature of the temperature sensor, and the difference is above a specified temperature.

[0144]

[13] According to the image forming apparatus of

[11] , wherein the plurality of image forming units form developer images of various colors for forming a color image, and the position offset correction is a process for correcting the offset of the developer images of various colors in color printing for forming a color image with overlapping developer images of various colors.

[0145]

[14] According to the image forming apparatus of

[13] , if the alignment execution flag is set when the processor accepts a color printing, the position offset correction is performed before the color printing is about to be performed.

[0146]

[15] According to the image forming apparatus of

[11] , if the processor performs an initial position offset correction within a predetermined flag settable period after startup, the alignment execution flag is set when a predetermined flag setting time has elapsed since the initial position offset correction.

[0147]

[16] According to the image forming apparatus of

[15] , wherein the processor sets an alignment execution flag when starting the operation, cancels the alignment execution flag when performing the first position offset correction within the flag settable period after the start, and sets the alignment execution flag when a predetermined flag setting time has elapsed since the first position offset correction.

[0148]

[17] According to the image forming apparatus of

[16] , if the processor does not perform the initial position offset correction during the flag setting period, it does not perform the setting of the alignment execution flag based on the flag setting time, but maintains the alignment execution flag set during the start-up operation.

[0149]

[18] According to the image forming apparatus of

[15] , the mark can be set for a period of time longer than the mark setting time.

[0150]

[19] According to the image forming apparatus of

[15] , the mark setting time is shorter than the interval for position offset correction in the normal operating state.

[0151]

[20] The image forming apparatus according to

[15] includes a memory having a rewritable storage area, the storage area being able to store a set value representing the time of the flag setting.

Claims

1. An image forming apparatus, characterized in that, have: Multiple image forming units form developer images, which are obtained by developing latent images formed on each photoreceptor using developer; An exposure unit that outputs light for forming latent images in each of the plurality of photoreceptors in the plurality of image forming units; The transfer unit transfers an image onto a medium, which overlaps the multiple developer images formed by the multiple image forming units. The processor, when the difference between the ambient temperature and the temperature inside the exposure unit during the period from startup to the start of image formation meets the specified implementation conditions, sets a positioning execution flag indicating the execution of the next position offset correction after a specified flag setting time has elapsed since the initial position offset correction was performed after startup.

2. The image forming apparatus according to claim 1, characterized in that, It also has: An environmental sensor that measures ambient temperature; A temperature sensor measures the temperature inside the exposure unit. The specified implementation condition is that the difference between the temperature detected by the temperature sensor and the temperature detected by the environmental sensor is above a specified temperature.

3. The image forming apparatus according to claim 1, characterized in that, The plurality of image forming units form developer images of various colors for forming color images. The position offset correction is a process that corrects the offset of the developer images of various colors in color printing, which is used to form a color image with overlapping developer images of various colors.

4. The image forming apparatus according to claim 3, characterized in that, If the processor has set the alignment execution flag when accepting a color printing application, it will perform the position offset correction before the color printing is about to begin.

5. The image forming apparatus according to claim 1, characterized in that, If the processor performs an initial position offset correction within a specified flag-settable period after startup, the alignment execution flag is set when a specified flag-setting time has elapsed since the initial position offset correction.

6. The image forming apparatus according to claim 5, characterized in that, The processor sets a positioning execution flag during startup. When performing the initial position offset correction within the flag settable period after startup, the positioning execution flag is canceled. When a predetermined flag setting time has elapsed since the initial position offset correction, the positioning execution flag is set.

7. The image forming apparatus according to claim 6, characterized in that, If the processor does not perform the initial position offset correction within the flag settable period, it will not implement the setting of the alignment execution flag based on the flag setting time, but will maintain the alignment execution flag set during the startup action.

8. The image forming apparatus according to claim 5, characterized in that, The period during which the mark can be set is longer than the time the mark was set.

9. The image forming apparatus according to claim 5, characterized in that, The setting time of the marker is shorter than the interval for position offset correction under normal operating conditions.

10. An image forming apparatus, characterized in that, have: Multiple image forming units form developer images, which are obtained by developing latent images formed on each photoreceptor using developer; An exposure unit that outputs light for forming latent images in each of the plurality of photoreceptors in the plurality of image forming units; The transfer unit transfers an image onto a medium, which overlaps the multiple developer images formed by the multiple image forming units. A heater, which is disposed within the frame of the image forming apparatus, heats up at a specified temperature; The processor, when the heater is turned on during the pre-start operation stop period, sets an alignment execution flag indicating the execution of the next position offset correction after a predetermined flag setting time has elapsed since the initial position offset correction was performed after startup.

Images