Image forming apparatus

Abstract

To provide an image forming apparatus that can notify of image misalignment. [Solution] According to the embodiment, the image forming apparatus includes a plurality of image forming units, an exposure unit, a transfer unit, and a processor. The plurality of image forming units form an image by developing the latent image formed on each photoreceptor with a developer supplied to each unit. The exposure unit outputs light to form a latent image on each photoreceptor in the plurality of image forming units. The transfer unit transfers the plurality of images developed by the plurality of image forming units with the developer onto a medium in a superimposed manner. If the difference between the ambient temperature and the temperature inside the exposure unit between the start of startup and the start of image formation satisfies predetermined conditions, the processor displays a guidance on a display device that notifies the misalignment of each image transferred by the transfer unit to the medium after a predetermined guidance start time has elapsed after the startup operation.

Description

Technical Field

[0004] , , ,

[0005] , , , ,

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

Background Art

[0002] An electrophotographic image forming apparatus realizes color printing by overlapping images formed by toners of respective colors. In such an image forming apparatus, image misregistration (color misregistration) may occur in which the images of respective colors to be overlapped are misaligned. Examples of causes of image misregistration include displacement of each part due to the influence of temperature change in an exposure device (optical scanning device). When the temperature change in the exposure device reaches a specific condition, the image forming apparatus executes position misregistration correction (alignment) for correcting image misregistration. However, a conventional image forming apparatus has a problem that image misregistration may easily occur even if a specific condition for executing position misregistration correction is not reached after the startup operation.

Prior Art Documents

Patent Documents

[0006] [Figure 1] Figure 1 shows an example of the configuration of each part in an image forming apparatus according to an embodiment. [Figure 2] Figure 2 is a top view showing an example of the configuration of an exposure apparatus in an image forming apparatus according to an embodiment. [Figure 3] Figure 3 is a bottom view showing an example of the configuration of an exposure apparatus in an image forming apparatus according to an embodiment. [Figure 4] Figure 4 is a cross-sectional perspective view showing an example of the configuration of an exposure apparatus in an image forming apparatus according to an embodiment. [Figure 5] Figure 5 shows an example of the installation of an environmental sensor and a damp heater in an image forming apparatus according to the embodiment. [Figure 6] Figure 6 is a block diagram showing an example of the configuration of a control system in an image forming apparatus according to an embodiment. [Figure 7] Figure 7 shows a first example illustrating the relationship between temperature changes and color shift in each part of the image forming apparatus according to the embodiment. [Figure 8] Figure 8 shows a second example illustrating the relationship between temperature changes and color shift in each part of the image forming apparatus according to the embodiment. [Figure 9] Figure 9 is a flowchart illustrating an example of the operation of the image misalignment guidance process in the image forming apparatus according to this embodiment. [Figure 10] Figure 10 shows an example of an operation screen display that includes guidance for image misalignment, which is displayed on the display unit of the control panel in an image forming apparatus according to an embodiment. [Figure 11] Figure 11 shows an example of an operation screen display that includes guidance for image misalignment, which is displayed on the display unit of the control panel in an image forming apparatus according to an embodiment. [Modes for carrying out the invention]

[0007] The image forming apparatus according to this embodiment will be described below with reference to the drawings. Note that the scale of the various parts in the drawings used in the following description of the embodiments may have been appropriately changed. Also, for illustrative purposes, some components may be omitted from the drawings used in the following description of the embodiments.

[0008] Figure 1 is a schematic diagram showing 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 using an electrophotographic method. The image forming apparatus 100 is, for example, an MFP (multifunction peripheral), a copier, a printer, or a facsimile.

[0009] As shown in Figure 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, an exposure unit (exposure chamber) 106, 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.

[0010] The image forming unit 105 prints an image using an electrophotographic method. The image forming unit 105 uses toner to form an image to be printed on an image forming medium P or the like. The image forming medium P is, for example, a sheet of paper. The scanner 114 reads an image from the original document on which the image has been formed. For example, the image forming apparatus 100 makes a copy of the image from the original document by printing the image read from the original document by the scanner 114 onto the image forming medium (hereinafter referred to as paper) P using the image forming unit 105.

[0011] The paper feed tray 101 holds the paper P, which is used as the image forming medium for printing. The manual feed tray 102 is a stand for manually feeding the paper P. The paper feed roller 103 rotates due to the action of a motor, picking up the paper P contained in the paper feed tray 101 or the manual feed tray 102 and supplying it to the transport path. The image forming apparatus 100 forms the paper transport path with multiple rollers, etc. The paper P picked up by the paper feed roller 103 is supplied through the transport path to the transfer position (secondary transfer position) where the image is transferred.

[0012] The image forming apparatus 100 includes a plurality of toner cartridges 104. The toner cartridges 104 supply toner to the image forming unit 105. In the configuration example shown in Figure 1, the image forming apparatus 100 includes four toner cartridges 104: toner cartridge 104C, toner cartridge 104M, toner cartridge 104Y, and toner cartridge 104K. Each of the toner cartridges 104C, 104M, 104Y, and 104K stores toner corresponding to each color of CMYK (cyan, magenta, yellow, black (key)).

[0013] Furthermore, the toner stored in toner cartridge 104 is not limited to the CMYK colors; it may also be other colors. Additionally, the toner stored in toner cartridge 104 may be a special type of toner. For example, toner cartridge 104 may store a decolorizable toner that becomes invisible when heated above a predetermined temperature.

[0014] The image forming apparatus 100 includes a plurality of image forming units 105. In the example shown in FIG. 1, the image forming apparatus 100 includes four image forming units 105, namely, an image forming unit 105C, an image forming unit 105M, an image forming unit 105Y, and an image forming unit 105K. The image forming units 105C, 105M, 105Y, and 105K receive the supply of toner corresponding to each color of CMYK and form toner images (images) of each color.

[0015] Each image forming unit 105 includes a developing device and a photosensitive drum (photoconductor), etc. An electrostatic latent image is formed on the surface of the photosensitive drum. The developing device develops the electrostatic latent image formed on the surface of the photosensitive drum using the toner supplied from the toner cartridge 104. As a result, toner images formed with toner of each color are formed on the surface of the photosensitive drum of each image forming unit 105. Each image forming unit 105 transfers (primary transfer) the toner image formed on the surface of the photosensitive drum onto the transfer belt 107 at each transfer position (primary transfer position).

[0016] 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 photosensitive drum of each image forming unit 105 with laser light controlled according to image data. The exposure device 106 is configured, for example, as shown in FIGS. 3 to 5 described later.

[0017] The transfer belt 107 is, for example, an endless belt supported by rollers. The transfer belt 107 is configured such that one round has a predetermined length. The transfer belt 107 rotates by the action of the rollers. By rotating, the transfer belt 107 has images transferred (primary transfer) by the transfer rollers (primary transfer rollers) of the image forming units 105C, 105Y, 105M, and 105K. The transfer belt 107 conveys the images (toner images) transferred from the image forming units 1051 to 1054 to the position of the transfer roller 108 (secondary transfer position).

[0018] The transfer roller 108 comprises two rollers facing each other. The transfer roller 108 transfers (secondary transfer) the image formed on the transfer belt 107 onto the image forming medium P that passes between the transfer rollers 108.

[0019] The toner sensor 117 detects toner adhering to the transfer belt 107. The toner sensor 117 detects the toner image on the transfer belt 107 between the transfer position of the image forming unit 105K (primary transfer position) and the position where the toner image on the transfer belt 107 corresponds to the transfer roller 108 (secondary transfer position). For example, the toner sensor 117 is positioned to face the transfer belt 107 between the transfer roller and the transfer roller 108 of the image forming unit 105K.

[0020] The fixing unit 109 heats and pressurizes the paper P on which the image has been transferred. This fixes the image transferred onto the paper P. The fixing unit 109 comprises a heating unit 110 and a pressure roller 111 that are opposite to each other.

[0021] The heating section 110 is, for example, a roller equipped with a heat source for heating the heating section 110. The heat source is, for example, a heater. The roller heated by the heat source heats the paper P. The pressure roller 111 pressurizes the paper P as it passes between the pressure roller 111 and the heating section 110.

[0022] Furthermore, the heating unit 110 may also include an endless belt suspended from 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-like material. 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 on the heating side and is pressed in the direction of the press roller, forming a fixed nip of a predetermined width between it and the press roller. Because the plate-shaped heat source heats while forming a nip region, the responsiveness when energized is higher than in the case of a halogen lamp heating method.

[0023] The endless belt is constructed, for example, on a 50um thick SUS (steel use stainless) substrate or a 70um thick heat-resistant polyimide resin, with a 200um thick silicone rubber layer formed on the outside, and the outermost layer covered with a surface protection layer such as PFA (perfluoroalkoxy alkane). The press roller is constructed, for example, on a φ10mm iron rod surface with a 5mm thick silicone sponge layer formed on the surface, and the outermost layer covered with a surface protection layer such as PFA. The plate-shaped heat source is constructed, for example, on a ceramic substrate with a glaze layer and a heat-resistant layer laminated on top. In addition, an aluminum heat sink is bonded to the plate-shaped heat source on the opposite side to dissipate excess heat and prevent the substrate from warping. The heat-resistant layer is made of a known material such as TaSiO2 and is divided into predetermined lengths and numbers in the main scanning direction.

[0024] The output tray 112 is a tray from which the printed paper P is ejected. The duplex unit 113 prepares the paper P for printing on the reverse side. For example, the duplex unit 113 reverses the front and back sides of the paper P by using rollers or the like to switch the paper P back.

[0025] The scanner 114 reads an image from the original document. The scanner 114 is an image reading device for reading an image from the original document. The scanner 114 is an optical reduction type image reading device equipped with an image sensor such as a CCD (charge-coupled device) image sensor. Alternatively, the scanner 114 may be a contact image sensor (CIS (contact image sensor)) type image reading device equipped with an image sensor such as a CMOS (complementary metal-oxide-semiconductor) image sensor.

[0026] 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. The transported documents are scanned by the scanner 114. The document feeder 115 may also be equipped with a scanner for scanning the back side of the document.

[0027] The control panel 116 is a device for the operator (user) of the image forming apparatus 100 to operate. The control panel 116 comprises a display unit (display device) 1161 and an operation unit (operation device) 1162. The display unit 1161 is a display device (display device) that displays guidance, operation buttons, etc. The display unit 1161 is, for example, a liquid crystal display or an organic EL display. The operation unit 1162 is an input unit (input device) for the user to input information. The operation unit 1162 is, for example, composed of a touch panel and buttons. In this embodiment, the control panel 116 comprises a display device with a touch panel as the display unit 1161 and the operation unit 1162.

[0028] Next, the configuration of the exposure apparatus (exposure unit) 106 in the image forming apparatus 100 according to this embodiment will be described. Figures 2 to 4 show examples of the configuration of the exposure apparatus 106 in the image forming apparatus 100 according to the embodiment. Figure 2 is a top view showing an example of an exposure apparatus 106 in an image forming apparatus 100 according to an embodiment. Figure 3 is a bottom view showing an example of an exposure apparatus 106 in an image forming apparatus 100 according to an embodiment. Figure 4 is a cross-sectional perspective view showing an example of an exposure apparatus 106 in an image forming apparatus 100 according to an embodiment.

[0029] As shown in Figures 3 to 5, the exposure apparatus 106 comprises a housing 1061, a laser unit 1062, a polygon mirror 1063, a polygon motor 1064, a mirror 1065, a lens 1066, a first thermistor (first temperature sensor) 1067, and a second thermistor (second temperature sensor) 1068.

[0030] The housing 1061 is a casing that houses the laser unit 1062, polygon mirror 1063, polygon motor 1064, mirror 1065, lens 1066, first thermistor 1067, and second thermistor 1068. The housing 1061 supports the laser unit 1062, polygon mirror 1063, polygon motor 1064, mirror 1065, lens 1066, first thermistor 1067, and second thermistor 1068. The housing 1061 is made of, for example, resin.

[0031] The exposure apparatus 106 includes laser units 1062, namely laser unit 1062C, laser unit 1062M, laser unit 1062Y, and laser unit 1062K. Laser units 1062C, 1062M, 1062Y, and 1062K correspond to image forming units 105C, 105M, 105Y, and 105K, respectively. Each laser unit 1062 emits laser light. Each laser unit 1062 controls the emission of laser light according to a control signal corresponding to the image formed by the corresponding image forming unit 105. For example, each laser unit 1062 modulates the laser light according to a control signal corresponding to the image data.

[0032] The polygon mirror 1063 reflects the laser light emitted from each laser unit 1062. The polygon mirror 1063 rotates using the polygon motor 1064 to polarize and scan each laser beam. The polygon motor 1064 is the motor that rotates the polygon mirror 1063. The polygon motor 1064 generates heat when rotating the polygon mirror 1063 and can therefore become a heat source within the exposure apparatus 106.

[0033] The mirror 1065 and lens 1066 are optical elements for scanning the laser beam onto the photosensitive drum of each image forming unit 105. For example, the mirror 1065 is provided so that its position or angle relative to the housing 1061 can be adjusted.

[0034] The first thermistor 1067 is an example of a temperature sensor (temperature detection unit) that detects the temperature near the center (first part) inside the exposure apparatus 106. The first thermistor 1067 outputs a signal indicating the measured temperature. In the configuration examples shown in Figures 3 to 5 described later, the first thermistor 1067 is installed near the polygon motor 1064 located in the center of the housing 1061.

[0035] 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 indicating the measured temperature. The second thermistor 1068 detects the temperature of the second part of the exposure apparatus 106, which is further from the polygon motor 1064 than the first part. In the examples shown in Figures 3 to 5, the second thermistor 1068 is installed near the midpoint between the end of the housing 1061 and the polygon motor 1064. In this case, the second thermistor 1068 is installed at a location further from the polygon motor 1064 than the first thermistor 1067.

[0036] Next, the environmental sensor 211 and the damp heaters 221 and 222 installed in the image forming apparatus 100 according to this embodiment will be described. Figure 5 shows an example of the installation of the environmental sensor 211 and the damp heaters 221 and 222 inside the main frame (housing) BF of the image forming apparatus 100 according to the embodiment. The environmental sensor 211 includes a sensor that detects the temperature in the environment in which the image forming apparatus 100 is installed. The environmental sensor 211 is positioned to detect the temperature inside the housing EF of the image forming apparatus 100. In the configuration example shown in Figure 5, the environmental sensor 211 is installed at a distance from the damp heaters 221 and 222. The environmental sensor 211 is positioned so as to be less affected by localized temperature increases caused by the heat emitted by the damp heaters 221 and 222.

[0037] The damp heaters 221 and 222 are heaters for preventing condensation on the paper inside the housing BF or on the photosensitive drum inside the image forming unit 105. The damp heaters 221 and 222 operate when the main power supply of the image forming apparatus 100 is off (hereinafter referred to as power off) and the temperature falls below a set temperature. For example, the damp heaters 221 and 222 have a configuration in which the heater is connected to a thermostat that operates when the temperature falls below a set temperature while the power is off. When the thermostat operates due to the temperature falling below the set temperature, current flows to the heaters of the damp heaters 221 and 222, warming the area around the heaters.

[0038] The damp heaters 221 and 222 are positioned near the paper feed cassette and the photoreceptor drum to prevent condensation on the paper and the photoreceptor. For example, in the configuration example shown in Figure 5, the damp heater 221 is positioned near the image forming unit 105, which houses the photoreceptor drum. Due to its structure as an electrophotographic printer, the image forming apparatus 100 has the exposure unit 106 positioned near the photoreceptor. Therefore, the damp heater 221, which prevents condensation on the photoreceptor drum, is positioned near the exposure unit 106.

[0039] Furthermore, in the configuration example shown in Figure 5, the damp heater 222 is positioned near the paper feed tray (paper feed cassette) 101 that holds the paper. In the configurations shown in Figures 1 and 5, the exposure unit 106 is positioned above the paper feed tray 101 that holds the paper. In an image forming apparatus 100 with such a configuration, the damp heater 222, which prevents condensation on the paper, is also positioned near the exposure unit 106.

[0040] Next, the configuration of the control system in the image forming apparatus 100 according to the embodiment will be described. Figure 6 is a block diagram showing an example of the configuration of the control system in the image forming apparatus 100 according to the embodiment. In the configuration example shown in Figure 6, 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, a scanner 114, a control panel 116, and a printer 200.

[0041] The processor 121 corresponds to the central part of the computer that performs calculations and control necessary for the operation of the image forming apparatus 100. Based on programs such as system software, application software, or firmware stored in the ROM 122 or auxiliary storage device 124, the processor 121 controls each part to realize various functions of the image forming apparatus 100.

[0042] The processor 121 may be, for example, a CPU (central processing unit), MPU (microprocessing unit), 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, the processor 121 may be a combination of several of these.

[0043] ROM122 corresponds to the main memory of the computer, with processor 121 at its core. ROM122 is a non-volatile memory used exclusively for reading data. ROM122 stores the program described above. Furthermore, ROM122 stores data or various settings used by processor 121 in performing various processes.

[0044] RAM123 corresponds to the main memory of a computer centered around processor 121. RAM123 is memory used for reading and writing data. RAM123 is used as a so-called work area, where data temporarily used by processor 121 during various processes is stored.

[0045] The auxiliary storage device 124 corresponds to the auxiliary storage device of a computer centered on the processor 121. The auxiliary storage device 124 is, for example, an EEPROM (electric erasable programmable read-only memory), an HDD (hard disk drive), or an SSD (solid state drive). The auxiliary storage device 124 may also store programs. In addition, the auxiliary storage device 124 stores data used by the processor 121 in performing various processes, data generated by processing by the processor 121, or various setting information. For example, the auxiliary storage device 124 is a memory that stores various setting information such as the conditions for implementing image shift guidance (threshold for the difference between the exposure device temperature and the ambient temperature), guidance execution time, and guidance completion time.

[0046] The image forming apparatus 100 may also be equipped with an interface into which a storage medium such as a memory card or a USB (universal serial bus) memory can be inserted, either in place of the auxiliary storage device 124 or in addition to the auxiliary storage device 124.

[0047] The program stored in ROM 122 or auxiliary storage device 124 includes a program for executing the processing described later. As an example, the image forming apparatus 100 is transferred to an administrator or the like with the program stored in ROM 122 or auxiliary storage device 124. The image forming apparatus 100 may also be transferred to an administrator or the like with the program not stored in ROM 122 or auxiliary storage device 124.

[0048] Furthermore, the program for executing the processes described later may be written to the ROM 122 or auxiliary storage device 124 by an administrator or service technician. The program can be transferred, for example, by recording it on a removable storage medium such as a magnetic disk, magneto-optical disk, optical disk, or semiconductor memory, or by downloading it via a network.

[0049] 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 terminal device operated by the user. The RTC126 is a clock or a circuit that incorporates a clock function. The system controller 120 may also be equipped with an interface for connecting to an external display device and an operating device. In this case, the processor 121 may display the image misalignment guidance described later on the external display device connected via the interface.

[0050] The printer 200 prints an image onto an image forming medium (paper) P based on image data. In the configuration example shown in Figure 2, the printer 200 is connected to a printer processor 201, a paper feed roller 103, a toner cartridge 104, an image forming unit 105, an exposure unit 106, a transfer roller 108, a fuser unit 109, a toner sensor 117, an environmental sensor 211, and damp heaters 221 and 222. However, the environmental sensor 211 and damp heaters 221 and 222 may be connected to the processor 121 of the system controller 120 without going through the printer processor 201.

[0051] The printer processor 201 performs calculations and control processes necessary for the printing operation of the image forming apparatus 100 in order to realize the printing function. The printer processor 201 performs calculations and control processes necessary for the printing operation based on instructions from the processor 121 and various programs. The printer processor 201 also outputs processing results to the processor 121.

[0052] The various programs may be stored in a memory unit such as ROM 122 or auxiliary memory device 124, or they may be incorporated into the circuit of the printer processor 201. Alternatively, a memory unit provided in the printer 200 may store the various programs. The printer processor 201 may be, for example, a CPU, MPU, SoC, DSP, GPU, ASIC, PLD, or FPGA.

[0053] Next, positional misalignment correction (color misalignment correction) for correcting image misalignment in the image forming apparatus 100 according to the embodiment will be described. In the image forming apparatus 100, the exposure apparatus 106 may experience a shift in the exposure position due to minute deformations caused by fluctuations in temperature. The image forming apparatus 100 has a function to perform position shift correction to correct image shifts caused by the exposure position shift of the exposure apparatus 106.

[0054] The image forming apparatus 100 generates a color image by superimposing images (toner images of each color) formed by multiple image forming units 105 using multiple colors of toner. Therefore, in color printing, the image forming apparatus 100 needs to adjust for the misalignment of each color's toner image. This positional misalignment correction in color printing is also called color misalignment correction (color registration). Color misalignment correction is performed by the control of the processor 121 or the printer processor 201 when executing a color image.

[0055] For example, as a color misalignment correction, the processor 121 forms a predetermined pattern on the transfer belt 107 to measure the misalignment of each color image formed by each color toner. The processor 121 detects the amount of misalignment of each color image from the ideal position (reference position) based on the predetermined pattern on the transfer belt 107. The processor 121 corrects the positional misalignment of each color image by changing the exposure timing by the exposure device 106 based on the amount of misalignment. Specifically, the processor 121 calculates the relative positional misalignment between the transport direction and the scanning direction in each color image from the reading results of the predetermined pattern. As a result, the processor 121 adjusts the exposure timing for forming each color image so that the image patterns of each color (4 colors) overlap according to the calculated positional misalignment.

[0056] The image forming apparatus 100 performs misalignment correction (color misalignment correction) when it detects that the predetermined conditions for performing misalignment correction have been met. The conditions for performing misalignment correction are set based on the temperature inside the exposure apparatus 106. For example, the image forming apparatus 100 is set to perform misalignment correction in response to changes in the temperature inside the exposure apparatus 106 detected by the first thermistor 1067 and the second thermistor 1068. The image forming apparatus 100 also performs misalignment correction during the startup operation performed when the main power is turned on. The image forming apparatus 100 may also be set to perform misalignment correction when performing the first color print after the startup operation. In this embodiment, the image forming apparatus 100 performs misalignment correction during the startup operation.

[0057] Next, we will explain the effect of switching the damp heaters 221 and 222 on and off while the image forming apparatus 100 is powered off on the exposure apparatus 106. In this embodiment, "power off" refers to the state in which the main power supply of the image forming apparatus 100 is turned off. When the image forming apparatus 100 is powered off, it is connected to an external power supply, but it stops various operations (jobs) such as printing and scanning, and does not accept any operation instructions other than the instruction to turn on the main power supply (operation stop state). The damp heaters 221 and 222 are connected in such a way that power can be supplied from the external power supply even when the power is off. Therefore, when the image forming apparatus 100 is powered off, it does not accept various operations, but the damp heaters 221 and 222 are operational. The period during which the power is off is also referred to as the operation stop period. While the image forming apparatus 100 is powered off, it performs a startup process in response to an instruction to turn on the main power supply (startup instruction). After the startup process, the image forming apparatus 100 becomes capable of executing jobs such as printing and scanning.

[0058] In the configuration example shown in Figure 5, the damp heaters 221 and 222 are positioned near the photoreceptor and the paper feed cassette. When the damp heaters 221 and 222 are turned on while the power is off, not only the photoreceptor and the paper feed cassette but also the exposure apparatus 106 is heated. The state of the exposure apparatus 106 may differ after the startup operation depending on whether or not the damp heaters 221 and 222 were turned on while the power was off. The exposure apparatus 106 may experience slight deformation due to the temperature distribution within the housing 1061, which can cause changes in the exposure position and result in image misalignment (color misalignment). In other words, in the image forming apparatus 100 according to this embodiment, the state of image misalignment after the startup operation may vary depending on whether or not the damp heaters 221 and 222 were turned on while the power was off.

[0059] Next, we will describe the changes in the state of the image forming apparatus 100 after startup according to this embodiment. In the image forming apparatus 100, the state of image misalignment differs depending on whether the dump heaters 221 and 222 were turned on or not during the power-off period before startup. Here, as an example of operation of the image forming apparatus 100, it is assumed 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 the image forming apparatus 100 operated in this manner, the state of image misalignment after startup changes depending on whether the dump heaters 221 and 222 were operated during the power-off period (operation stop period) at night.

[0060] Figures 7 and 8 show the measured temperatures and image misalignment of various parts when the image forming apparatus 100, which was started from a power-off state (operation stop period), performs printing at a specific printing interval. Figure 7 shows the measured temperatures and image shifts of each part after startup when the dump heaters 221 and 222 are activated (turned on) during the shutdown period (assuming the heaters are on). Figure 8 shows the measured temperatures and image shifts of each part after startup when the dump heaters 221 and 222 are not activated (turned on) during the shutdown period (assuming the heaters are off).

[0061] Figures 7 and 8 assume a 14-hour downtime, an 8-minute print interval, and color printing on two A3-sized sheets of paper. Figures 7 and 8 show the measurement results when the startup process (startup operation) is performed upon power-on after the downtime, and positional misalignment correction is performed immediately before the first print. However, it is assumed that the damp heaters 221 and 222 are turned off simultaneously with power-on.

[0062] Figures 7 and 8 show the temperature of the exposure apparatus (exposure chamber) (temperature inside the housing 1061 of the exposure apparatus 106), indicated by the detected temperature a of the first thermistor 1067 and the detected temperature b of the second thermistor 1068. Figures 7 and 8 also show the ambient temperature, indicated by the detected temperature c of the environmental sensor 211. Furthermore, Figures 7 and 8 show the measured values ​​of image misalignment that appeared on paper color-printed by the image forming apparatus 100. In Figures 7 and 8, the measured values ​​d of image misalignment in the main scanning direction are indicated by rectangular points, and the measured values ​​e of image misalignment in the sub-scanning direction are indicated by triangular points.

[0063] First, the temperature inside the housing 1061 of the exposure device 106 (temperature of the exposure device) immediately after power-on is compared with the ambient temperature. Here, the detected temperature a of the first thermistor 1067 is the temperature of the central part of the housing 1061 near the polygon motor 1064 in the exposure apparatus 106. The detected temperature b of the second thermistor 1068 is the temperature of the end of the housing 1061 located away from the polygon motor 1064 in the exposure apparatus 106. The temperature of the exposure apparatus (exposure unit) may be the detected temperature of either the first thermistor 1067 or the second thermistor 1068, or it may be the average value of the detected temperatures of the first thermistor 1067 and the second thermistor 1068.

[0064] In the example shown in Figure 8, immediately after power-on, the difference between the temperature a detected by the first thermistor 1067, the temperature b detected by the second thermistor 1068, and the temperature c detected by the environmental sensor 211 is within 1 degree. Considering the measurement accuracy of the first and second thermistors 1067 and 1068 and the environmental sensor 211, in the example shown in Figure 8, it can be said that immediately after power-on, the temperature of the exposure device and the ambient temperature are approximately equal. Therefore, if the damp heaters 221 and 222 did not operate while the power was off (heater off), it is considered that immediately after power-on, the temperature of the exposure device and the ambient temperature will be approximately equal.

[0065] In the example shown in Figure 7, immediately after power-on, the detected temperatures a of the first thermistor and b of the second thermistor are higher than the detected temperature c of the environmental sensor 211. This suggests that if the damp heaters 221 and 222 operate while the power is off (i.e., the heaters are on), the temperature of the exposure apparatus will be higher than the ambient temperature immediately after power-on.

[0066] Next, we will explain the temperature changes of each part after the printing operation has started. In the example shown in Figure 8, after the printing operation starts, both the detected temperature a of the first thermistor 1067 and the detected temperature b of the second thermistor 1068 tend to rise. The parts of the housing 1061 where the temperature has risen tend to expand physically. In other words, when the heater is off while the exposure device 106 is powered off, the temperature of the central and edge parts of the housing 1061 rises, so it is thought that the entire housing 1061 expands. When the entire housing 1061 expands, the amount of deformation of the housing 1061 as a whole is relatively smaller compared to when only the central part of the housing 1061 expands and the edges contract. As a result, it is thought that the exposure device 106 will have less image misalignment in printing after the startup operation (after positional misalignment correction before the first print).

[0067] In the example shown in Figure 7, after the printing operation starts, the detected temperature a of the first thermistor tends to rise, while the detected temperature b of the second thermistor tends to fall. The rising trend in the detected temperature a of the first thermistor is thought to be due to the heat generated by the polygon motor 1064 located in the center of the housing 1061. The falling trend in the detected temperature b of the second thermistor is thought to be due to the cooling of the edges of the housing 1061 by the temperature difference with the ambient temperature. Although heat generated by the polygon motor 1064 is transferred to the edges of the housing 1061, the temperature tends to fall because the temperature difference with the ambient temperature is large.

[0068] In Figure 7, points d and e indicate the image misalignment during printing after the startup operation. As shown in Figure 7, if the heater is turned on while the power is off, the image misalignment increases during printing after the startup operation (after the initial positional misalignment correction) due to the temperature rise in the center of the housing 1061 and the temperature drop at the edges. This image misalignment is thought to be caused by the expansion of the center of the housing 1061 due to the temperature rise and the contraction of the edges due to the temperature drop. When the expansion of the center and the contraction of the edges occur simultaneously, the amount of deformation of the housing 1061 as a whole is relatively larger than when the housing 1061 as a whole expands. When the amount of deformation of the housing 1061 increases, the exposure position of the exposure device 106 increases, and it is thought that the misalignment of the image (image of each color) printed on the medium increases.

[0069] Comparing Figures 7 and 8, it is clear that the change in image shift per unit time is greater when the heater is turned on while the power is off. In the example shown in Figure 7, during printing every 8 minutes after startup, the change (increase) in image shift is greatest between the first and third prints (16 minutes). However, in the example shown in Figure 7, the temperature of the central part of the housing 1061 rises immediately after the first print and then hardly changes, and the change in temperature at the edges of the housing 1061 over time is also small.

[0070] In the temperature changes shown in Figure 7, it is difficult to set the system to perform misalignment correction based on the temperature difference between the temperature of the center and the temperature of the edges (the temperature difference between the temperature detected by the first thermistor 1067 and the temperature detected by the second thermistor 1068). If the system were to perform misalignment correction even when the temperature difference between the center and the edges is small, a high-precision thermistor would be required, and the misalignment correction would be performed frequently, slowing down the printing operation. However, it is assumed that some users would find the image misalignment of the magnitude shown in Figure 7 acceptable. In other words, in terms of the operation of the image forming apparatus 100, it is sometimes preferable to allow the user to choose whether or not to perform misalignment correction for image misalignment such as that shown in Figure 7.

[0071] The image forming apparatus 100 according to this embodiment has a function to notify the user of image misalignment (alert) when it detects that an image misalignment is occurring as shown in Figure 7. For example, if the difference between the temperature of the exposure apparatus and the ambient temperature immediately after power-on is greater than or equal to a predetermined value, the image forming apparatus 100 displays an image misalignment alert on the display unit 1161. Alternatively, the image forming apparatus 100 may also display an image misalignment alert on the display unit 1161 if it detects that the damp heaters 221 and 222 have operated during the power-off period before power-on.

[0072] Next, the operation of the image misalignment guidance process after the startup operation of the image forming apparatus 100 according to this embodiment will be described. Figure 9 is a flowchart illustrating an example of the operation of the image misalignment guidance process after the startup operation of the image forming apparatus 100 according to the embodiment. As described above, the image forming apparatus 100 operates the damp heaters 221 and 222 when the temperature falls below a predetermined level while the power is off (operation stop period). The image forming apparatus 100 performs a process to display a notification of image misalignment on the display unit 1161 if there is a possibility of image misalignment occurring after startup due to the operation of the damp heaters 221 and 222 while the power is off.

[0073] 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 on the image forming apparatus 100 is pressed, a power-on signal is input to the processor 121. When the processor 121 receives a power-on instruction (ACT11, YES), it performs a startup operation (ACT12) and performs the initial misalignment correction before the first print (ACT13).

[0074] Furthermore, when the processor 121 performs a startup operation in response to power-on, it determines whether or not to provide guidance regarding image misalignment after the startup operation (ACT 14). For example, the processor 121 determines whether or not to provide guidance regarding image misalignment based on whether or not the pre-set conditions for providing guidance regarding image misalignment are met. The conditions for providing guidance regarding image misalignment are set as conditions for determining whether or not the dump heaters 221 and 222 operated (turned on) while the power was on (operation stop period).

[0075] For example, the processor 121 determines whether the difference between the temperature of the exposure device and the ambient temperature from immediately after power-on until the start of the first print is above a predetermined threshold (the conditions for implementation of the guidance). The predetermined threshold is set according to the heater capacity of the damp heaters 221 and 222, the structure of the machine, the accuracy of the first and second thermistors, etc. As an example, referring to the measurement results shown in Figure 7, the predetermined threshold is set to a value of around 2°C.

[0076] When calculating the difference between the exposure device temperature and the ambient temperature, the processor 121 acquires temperature information from each sensor immediately after power-on. Specifically, the processor 121 acquires temperature information from the first thermistor 1067, the second thermistor 1068, and the ambient sensor 211, respectively.

[0077] 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 may use the temperature detected by either the first thermistor 1067 or the second thermistor 1068 as the temperature of the exposure apparatus, or it may use the average value of the temperatures detected by the first thermistor 1067 and the second thermistor 1068 as the temperature of the exposure apparatus.

[0078] When the processor 121 obtains the temperature of the exposure apparatus and the ambient temperature, it subtracts the ambient temperature from the temperature of the exposure apparatus to calculate a difference value, and determines whether the calculated difference value is equal to or greater than a predetermined threshold.

[0079] Furthermore, the decision of whether or not to provide guidance for image misalignment is not limited to the difference between the temperature of the exposure apparatus and the ambient temperature. For example, the decision of whether or not to provide guidance for image misalignment may be made by detecting whether or not the damp heaters 221 and 222 operated while the power was on. As a specific example, the image forming apparatus 100 may be provided with a recording unit that records whether or not the damp heaters 221 and 222 were turned on while the power was off. In this case, the processor 121 should determine whether or not the damp heaters 221 and 222 operated while the power was on based on the contents recorded by the recording unit.

[0080] If the processor 121 determines that it should provide guidance for image misalignment (ACT 14), it decides whether or not to start providing guidance for image misalignment (ACT 15). For example, the processor 121 is set to start providing guidance for image misalignment after a predetermined guidance start time (e.g., 8 to 16 minutes) has elapsed since the startup operation (initial positional misalignment correction).

[0081] In the example shown in Figure 7, because positional misalignment correction is performed immediately before the first print, the amount of image misalignment variation is large in the third print after the startup operation. Therefore, referring to the measurement results in Figure 7, it is possible to set the system to start displaying the image misalignment guidance before the third print. In this case, the guidance start time, which is the elapsed time from the startup operation until the guidance starts, should be set to 8 to 16 minutes.

[0082] If the processor 121 determines to start providing guidance for image misalignment (ACT 15, YES), it displays the image misalignment guidance on the display unit 1161 (ACT 16). For example, the processor 121 displays the image misalignment guidance in addition to the operation screen displayed on the display unit 1161. Alternatively, the processor 121 may display a button on the display unit 1161 to instruct the system to perform positional misalignment correction.

[0083] As an example of an image misalignment notification (alert) displayed on the display unit 1161, the processor 121 may display a message indicating that the color misalignment (image misalignment) may be larger than usual. Alternatively, the processor 121 may display a message recommending positional misalignment correction as an example of a notification displayed on the display unit 1161. Alternatively, the processor 121 may display a guide on the display unit 1161 leading to an instruction button for instructing positional misalignment correction.

[0084] Figures 10 and 11 show examples of displays where the display unit 1161 shows guidance regarding image misalignment. Figure 10 shows an example of a display that shows a notification of image misalignment on a part of the main operation screen (home screen) 300 displayed on the display unit 1161 when the image forming apparatus 100 is in standby (waiting for operation). The home screen 300 in the example display shown in Figure 10 displays mode selection buttons 301-310 for selecting various operating modes, as well as an alignment (position shift correction) button 321 and an image shift guidance (message) 331. The image shift guidance 331 displays a guidance message as described above. The alignment button 321 is a button that instructs the system to perform position shift correction. In the example display shown in Figure 10, the alignment button 321 is displayed together with the image shift guidance 321.

[0085] Figure 11 shows an example of a display that shows a guide indicating image misalignment on a portion of the copy operation screen 400 displayed on the display unit 1161 when copy is selected as the operation mode. The copy operation screen 400 in the example display shown in Figure 11 displays mode selection buttons 402-405 for selecting various copy modes, a status display unit 401, a color mode display unit 406, and a density display unit 407, as well as an alignment (position shift correction) button 421 and an image shift guidance (message) 431. The image shift guidance 431 displays a guidance message as described above. The alignment button 421 is a button that instructs the user to perform position shift correction. In the example display shown in Figure 11, the alignment button 421 is displayed together with the image shift guidance 421.

[0086] When the processor 121 displays a message indicating image misalignment, it receives an instruction to perform positional misalignment correction (ACT17). For example, when the processor 121 detects instruction input to the alignment buttons 321 and 421 in the display example shown in Figure 10 or Figure 11, it determines to perform positional misalignment correction. If the processor 121 determines to perform positional misalignment correction (ACT17, YES), it performs positional misalignment correction (ACT19). After performing positional misalignment correction, the processor 121 terminates the image misalignment guidance (ACT20).

[0087] Furthermore, if the processor 121 displays the image misalignment guidance and there is no instruction to perform positional misalignment correction (ACT17, NO), it decides whether or not to terminate the image misalignment guidance (ACT18). For example, the processor 121 decides to terminate the image misalignment guidance if the guidance termination time is longer than the guidance start time since the startup operation (initial positional misalignment correction). For example, the guidance termination time can be set to 30 to 40 minutes. In this case, if the guidance start time is 8 minutes and the guidance termination time is 40 minutes, the display unit 1161 will display the image misalignment guidance for 32 minutes from the start of the guidance.

[0088] If the processor 121 determines that it has not yet reached the time to terminate the image misalignment guidance (ACT18, NO), it returns to ACT16 and continues the image misalignment guidance on the display unit 1161. Also, if the processor 121 determines that it has terminated the image misalignment guidance (ACT18, YES), it terminates the image misalignment guidance displayed on the display unit 1161 (ACT20).

[0089] As described above, the image forming apparatus according to the embodiment determines whether the difference value obtained by subtracting the ambient temperature from the temperature of the exposure apparatus from the time immediately after power-on until printing starts is greater than or equal to a predetermined threshold. If the calculated difference value is greater than or equal to the predetermined threshold, the image forming apparatus displays a notification of image misalignment on the display unit along with the operation screen after a predetermined time has elapsed since startup.

[0090] Furthermore, the image forming apparatus according to the embodiment determines whether the damp heater operated during the power-off period (operation stop period) before power-on. If the image forming apparatus determines that the damp heater operated during the power-off period (operation stop period) before power-on, it displays an image misalignment notification on the display unit along with the operation screen after a predetermined time has elapsed since startup.

[0091] According to the image forming apparatus of this embodiment, the user can be notified that image misalignment may occur during printing after startup due to the operation of the damp heater while the power is off. Furthermore, according to the image forming apparatus of this embodiment, the user can be recommended to perform positional misalignment correction as guidance for image misalignment. As a result, for users who desire high-quality color printing without color misalignment, printing with reduced image misalignment can be provided by allowing them to select to perform positional misalignment correction for image misalignment after startup. At the same time, for users who can tolerate slight color misalignment, high-speed printing can be provided by omitting positional misalignment correction for image misalignment after startup, thereby reducing the time required for positional misalignment correction.

[0092] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, 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, as well as in the claims of the invention and its equivalents.

[0093] As described above, the following image forming apparatus can be implemented according to the detailed embodiments. [1] An image forming apparatus, Multiple image forming units that form images by developing the latent images formed on each photoreceptor with the developer supplied to each, An exposure unit that outputs light to form a latent image on each of the multiple image forming units, The transfer unit transfers multiple images developed by the multiple image forming units with a developer onto a medium, A processor that, when the difference between the ambient temperature and the temperature inside the exposure chamber between the start of startup and the start of image formation satisfies predetermined conditions, displays a message on a display device indicating the misalignment of each image transferred by the transfer unit to the medium after a predetermined guidance start time has elapsed after the startup operation, It has. [2] The image forming apparatus described in [1] above, Furthermore, an environmental sensor that measures ambient temperature, It has a temperature detection unit that measures the temperature inside the exposure chamber, The predetermined condition is that the difference between the temperature detected by the temperature sensor and the temperature detected by the environmental sensor is equal to or greater than a predetermined temperature. [3] The image forming apparatus described in [1] above, The image forming apparatus has a heater located inside its housing that generates heat at a predetermined temperature or below. [4] The image forming apparatus described in [3] above, The heater is provided near the plurality of image forming units. [5] The image forming apparatus described in [3] above, Furthermore, it has a paper feed cassette for storing paper on which the images formed by the plurality of image forming units are transferred, The heater is provided near the paper feed cassette. [6] The image forming apparatus described in [1] above, The processor displays a message on the display device recommending the execution of positional misalignment correction as guidance. [7] The image forming apparatus described in [1] above, The processor displays a message on the display device that guides the user to perform an operation to correct the misalignment. [8] The image forming apparatus described in [1] above, The processor displays a message on the display device indicating that there may be a significant image misalignment as a form of guidance. [9] The image forming apparatus described in [1] above, The processor displays a button on the display device that instructs the execution of the positional misalignment correction.

[10] The image forming apparatus described in [9] above, The processor terminates the guidance when it performs positional misalignment correction in response to an input instruction to the button.

[11] The image forming apparatus described in [1] above, The processor terminates the guidance when a guidance end time longer than the guidance start time has elapsed since the startup operation.

[12] In an image forming apparatus, Multiple image forming units that form a developer image by developing the latent image formed on each photoreceptor with a developer, An exposure unit that outputs light to form a latent image on each of the multiple image forming units, A transfer unit that transfers an image formed by superimposing multiple developer images created by the multiple image forming units onto a medium, A heater is provided inside the housing of the image forming apparatus and generates heat at a predetermined temperature or below. If the heater was turned on during the shutdown period before startup, the processor displays a message on the display device indicating the misalignment of the image transferred by the transfer unit to the medium after a predetermined guidance start time has elapsed since the startup operation. It has.

[13] The image forming apparatus described in

[12] above, The heater is provided near the plurality of image forming units.

[14] The image forming apparatus described in

[12] above, Furthermore, it has a paper feed cassette for storing paper on which the images formed by the plurality of image forming units are transferred, The heater is provided near the paper feed cassette.

[15] The image forming apparatus described in

[12] above, The processor displays a message on the display device recommending the execution of positional misalignment correction as guidance.

[16] The image forming apparatus described in

[12] above, The processor displays a message on the display device that guides the user to perform an operation to correct the misalignment.

[17] The image forming apparatus described in

[12] above, The processor displays a message on the display device indicating that there may be a significant image misalignment as a form of guidance.

[18] The image forming apparatus described in

[12] above, The processor displays a button on the display device that instructs the execution of the positional misalignment correction.

[19] The image forming apparatus described in

[18] above, The processor terminates the guidance when it performs positional misalignment correction in response to an input instruction to the button.

[20] The image forming apparatus described in

[12] above, The processor terminates the guidance when a guidance end time longer than the guidance start time has elapsed since the startup operation. [Explanation of Symbols]

[0094] 100…Image forming apparatus 101... Paper feed tray 102...Tray 103... Paper feed roller 104... Toner cartridge 104C... Toner cartridge 104K... Toner cartridge 104M... Toner cartridge 104Y... Toner cartridge 105…Image forming unit 105C...Image forming section 105K...Image forming section 105M...Image forming section 105Y...Image forming unit 106… Exposure device (exposure unit) 1061... Housing 1062... Laser Unit 1062C…Laser Unit 1062K… Laser Unit 1062M… Laser Unit 1062Y…Laser Unit 1063...Polygon Mirror 1064...Polygon motor 1065...Mirror 1066... ​​Lens 1067...First thermistor (first temperature sensor) 1068...Second thermistor (second temperature sensor) 107…Transfer belt 108…Transfer roller 109... Fixing section 110...Heating section 111... Pressure roller 112... Paper output tray 113... Double-sided unit 114... Scanner 116... Control Panel 1161...Display unit (display device) 1162...Operation unit 117... Toner sensor 120... System Controller 121… Processor 124... Auxiliary storage devices 125...Communication Interface 200... Printer 201…Printer Processor 211…Environmental Sensors 221, 222... Dump heater (heater).

Claims

1. In an image forming apparatus, Multiple image forming units that form images by developing the latent images formed on each photoreceptor with the developer supplied to each, An exposure unit that outputs light to form a latent image on each of the multiple image forming units, The transfer unit transfers multiple images developed by the multiple image forming units with a developer onto a medium, A processor that, when the difference between the ambient temperature and the temperature inside the exposure chamber between the start of startup and the start of image formation satisfies predetermined conditions, displays a message on a display device indicating the misalignment of each image transferred by the transfer unit to the medium after a predetermined guidance start time has elapsed after the startup operation, An image forming apparatus having

2. Furthermore, an environmental sensor that measures ambient temperature, It includes a temperature sensor for measuring the temperature inside the exposure chamber, The predetermined condition is that the difference obtained by subtracting the temperature detected by the environmental sensor from the temperature detected by the temperature sensor is equal to or greater than a predetermined temperature. The image forming apparatus according to claim 1.

3. The processor displays a message on the display device recommending the execution of positional misalignment correction as guidance. The image forming apparatus according to claim 1.

4. The processor displays a button on the display device that instructs the execution of the positional misalignment correction. The image forming apparatus according to claim 1.

5. In an image forming apparatus, Multiple image forming units that form a developer image by developing the latent image formed on each photoreceptor with a developer, An exposure unit that outputs light to form a latent image on each of the multiple image forming units, A transfer unit that transfers an image formed by superimposing multiple developer images created by the multiple image forming units onto a medium, A heater is provided inside the housing of the image forming apparatus and generates heat at a predetermined temperature or below. If the heater was turned on during the shutdown period before startup, the processor displays a message on the display device indicating the misalignment of the image transferred by the transfer unit to the medium after a predetermined guidance start time has elapsed since the startup operation. An image forming apparatus having

Images