JP6562784B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer that forms an image on a recording material using an electrophotographic system, and more particularly to a print preparation operation of the image forming apparatus.

  In an electrophotographic color image forming apparatus, a process of transferring a toner image formed on a photosensitive drum onto an intermediate transfer belt by a primary transfer roller disposed opposite to the photosensitive drum is repeated for a plurality of toner colors. As a result, a full-color toner image is formed on the intermediate transfer belt. A so-called tandem-type color, in which four photosensitive drums that create toner images of yellow, magenta, cyan, and black are arranged in the rotation direction of the intermediate transfer belt, and the toner images on the photosensitive drum are sequentially transferred to the intermediate transfer belt. Image forming apparatuses have become mainstream. In color image forming apparatuses, it is desired to shorten the first print output time (hereinafter also referred to as FPOT) and the first copy output time (hereinafter also referred to as FCOT). Here, FPOT is the time from when the print instruction is input until the first recording material is output, and FCOT is the output of the recording material on which the document is copied after the copy key is pressed. Refers to the time until. As one of the time shortening methods, a technique for performing a print preparation operation before inputting a print start or copy start instruction is widely known.

  For example, in Patent Document 1, when an operation in which a print instruction is predicted, such as an operation on the operation unit of the image forming apparatus or an original placement on the original reading apparatus, is detected, the scanner motor is preceded by the print instruction. There has been proposed a print preparation method for starting the rotation. In general, the scanner motor that drives the rotary polygon mirror of the optical scanning device has a stable rotational speed after the start of rotation compared to other motors required for image formation, such as a drive motor that drives the photosensitive drum. It takes a long time to complete. Therefore, by starting the rotation of the scanner motor before receiving the print instruction, it is possible to eliminate the waiting time until the rotation of the scanner motor is stabilized after the print instruction is input, and to start printing. There are advantages you can do.

  As described above, when an operation in which a print instruction is predicted is detected, the scanner motor is stably rotated in advance. Therefore, when an image formation request (print instruction) is actually received, the image formation is promptly performed. Can start. In a color image forming apparatus, a full color mode for forming an image with a full color image and a monochrome mode for forming an image with a black and white image can be selected. For example, in order to perform image formation in the full color mode, not only the scanner motor but also other devices need to be prepared for the full color mode. For example, with respect to the intermediate transfer belt, in order to perform image formation in the full color mode, it is necessary to shift to a contact state in which the intermediate transfer belt and the photosensitive drums of all colors are in contact. In general, the intermediate transfer belt is in contact with the black photosensitive drum and is in a separated state in which the intermediate transfer belt is separated from the yellow, magenta, and cyan photosensitive drums during standby before image formation is requested. In addition, the intermediate transfer belt is also in the separated state described above during the image forming operation in the monochrome mode. The reason why the intermediate transfer belt is separated from the photosensitive drum is to prevent deterioration of the photosensitive drum and the developer and to extend the life of the apparatus. On the other hand, during the image forming operation in the full-color mode, image formation is performed after shifting to a contact state where the intermediate transfer belt is in contact with all the photosensitive drums. According to Patent Document 1 described above, when a full color mode is selected when an operation in which a print instruction is predicted is detected, a preparatory operation for shifting the intermediate transfer belt to a contact state is performed in advance. Thus, when an image formation request in the full color mode is received thereafter, image formation can be started promptly.

Japanese Patent Laid-Open No. 2-141770

  In the image forming apparatus described above, in order to start image formation immediately when an image formation request in the monochrome mode is received, it is necessary to shift the intermediate transfer belt to the separated state when the monochrome mode is selected. is there. Even when the selection of the monochrome mode and the full color mode is repeated before the image formation request is made, the contact between the intermediate transfer belt and the photosensitive drum is repeated every time the selected mode is switched to quickly start the image formation. It is necessary to repeatedly switch to the contact state or the separation state. In general, the contact state and the separation state of the intermediate transfer belt and the photosensitive drum are switched via a drive mechanism, which can be operated up to a predetermined number of prints of the image forming apparatus. It is designed to meet a long life span. However, for example, if the number of times of switching between the contact state and the separation state between the intermediate transfer belt and the photosensitive drum increases, repairs such as replacement of parts are necessary before the device life of the drive mechanism that was originally assumed. There is a problem that time is generated.

  The present invention has been made under such circumstances, and it is an object of the present invention to ensure both the life of the drive mechanism that is driven to perform the print preparation operation according to the color mode setting and the reduction of downtime. .

  In order to solve the above-described problems, the present invention is configured as follows.

(1) a full color mode having a plurality of image forming units for forming images of different color components and forming a full color image using the plurality of image forming units; Color mode information indicating an image forming unit operable in a monochrome mode for forming a monochrome image using a predetermined one image forming unit, and a color mode to be executed among color modes including the full color mode and the monochrome mode When an operation by a user who is expected to input an instruction to start image formation is detected, an operation unit for inputting image input, an input unit for inputting an instruction to start image formation, and the input from the operation unit are detected. Control means for controlling the operation of the image forming means for an image forming preparation operation according to the color mode information. For example, the control means is configured to change the preparation operation in response to the changed the color mode information every time the color mode information is changed, the number of changes of the preparation operation exceeds a predetermined value, the An image forming apparatus , wherein the preparation operation is not changed according to color mode information .

  According to the present invention, it is possible to achieve both the life of the drive mechanism driven for performing the print preparation operation in accordance with the color mode setting and the reduction of downtime.

Sectional view of the image forming apparatus of the embodiment Control block diagram of image forming apparatus of embodiment Schematic diagram of the operation unit of the embodiment Sectional view of the vicinity of the intermediate transfer belt unit of the embodiment The figure explaining the contact-separation mechanism of the intermediate transfer belt unit of the embodiment The figure explaining operation | movement of the cam mechanism of embodiment The figure explaining the cam mechanism, contact sensor, and separation sensor of an embodiment Sectional view of the fixing device of the embodiment The figure explaining temperature adjustment control operation of the fixing device of an embodiment Schematic diagram of the laser scanner unit of the embodiment Flowchart of print preparation operation of embodiment Flow chart of fixing temperature adjustment operation of embodiment Flowchart of control operation of contact / separation mechanism of embodiment Flowchart of drive control operation of scanner motor of embodiment

  Embodiments of the present invention will be described below in detail with reference to the drawings.

[Embodiment]
<Schematic configuration of image forming system>
FIG. 1 is a cross-sectional view of the image forming apparatus of the present embodiment, and FIG. 2 is a control block diagram of the image forming apparatus of the present embodiment. The basic configuration of the image forming apparatus will be described with reference to FIGS.

[Schematic configuration of image forming apparatus]
A control unit 300 in FIG. 2 performs system control of the image forming apparatus in FIG. 1, and includes a CPU 301, a ROM 302, a RAM 303, and a timer 291. A CPU 301 serving as a control unit is a CPU that performs system control of the image forming apparatus. The CPU 301 is connected to a ROM 302 in which a control program is written and a RAM 303 for storing variables used for control and image data read by the image sensor 233 in FIG. 1 via an address bus and a data bus. A RAM 303 serving as a storage unit is a non-volatile memory that can retain stored values even when power supply to the image forming apparatus is stopped. A timer 291 capable of measuring time is connected to the CPU 301, and the CPU 301 sets a time count value of the timer 291 and acquires a timer measurement value. The CPU 301 detects the presence or absence of a document placed on the document table 152 based on the detection result of the document presence / absence sensor 151 serving as a detection unit, via the document feeding device control unit 480. Do. Further, the CPU 301 detects the opening / closing operation of the document pressure plate, the document image on the document pressure plate glass plate 55, and the document image fed by the document feeder control unit 480 via the image reader control unit 280 as an image sensor. Reading by 233 is performed. The image sensor 233 serving as a reading unit outputs the read document image information to the CPU 301 as an analog image signal. The CPU 301 transfers the analog image signal input from the image sensor 233 to the image signal control unit 281.

  During the copying operation, the image signal control unit 281 converts the analog image signal from the image sensor 233 into a digital image signal, performs various processes, converts the digital image signal subjected to the various processes into a video signal, and controls the printer. To the unit 285. Here, the copy operation is an operation in which a document is read by the image sensor 233 and a print operation is performed based on the read data. The image signal control unit 281 first performs various processes on the digital image signal input from the external computer 283 via the external I / F (interface) 282 during a printing operation according to an instruction from the outside. Then, the image signal control unit 281 converts the digital image signal subjected to various processes into a video signal and outputs the video signal to the printer control unit 285.

  The printer control unit 285 instructs the image forming unit 271 to form an image based on an instruction from the CPU 301. The image forming unit 271 drives the image forming unit 120 based on the input video signal. In addition, the printer control unit 285 controls paper feeding and conveyance of the recording material to the paper conveyance unit 270 based on an instruction from the CPU 301. Further, the printer control unit 285 drives the fixing device 170 based on an instruction from the CPU 301 to perform fixing control for fixing the toner image on the paper on which the image is formed.

  The operation unit 330 is used to input color mode information (full color mode / monochrome mode) for image formation, etc., to display the status of the image forming apparatus, and to start copying. The selected color mode information is stored in the RAM 303. The image forming apparatus according to the present embodiment can operate in a normal power consumption mode in which image formation is performed and a power saving mode in which power consumption is reduced as compared with that during image formation. When the printing operation is not performed for a predetermined time, the CPU 301 shifts to the power saving mode via the power control unit 481. In the power saving mode, the LED backlight of the display unit 311 (see FIG. 3A) of the operation unit 330 is turned off, and power supply to various driving loads is stopped.

[Basic image forming operation of image forming apparatus]
Next, a basic image forming operation will be described with reference to FIGS. When the CPU 301 detects a print setting instruction such as a color mode or a set number input from the operation unit 330 or the like, or opening / closing of a document pressure plate or document placement via the document feeder control unit 480 or the image reader control unit 280. Then, the print preparation operation is performed. In the print preparation operation, the CPU 301 starts temperature control of the fixing device 170. Further, the CPU 301 starts switching of the contact / separation state of the intermediate transfer belt unit 140 and drive control of the scanner motor in the laser scanner unit 103 in accordance with the set color mode. Note that details of the contact transfer state and the print preparation operation of the intermediate transfer belt unit 140 will be described later.

  Next, when the CPU 301 receives a print operation start instruction from the operation unit 330 or the like, the CPU 301 starts a document image reading operation via the document feeder control unit 480. The CPU 301 drives the document transport roller 112 to transport the document from the document table 152 onto the platen glass, and irradiates the platen glass with light from a lamp (not shown). Reflected light from the document is guided to the image sensor 233 via a mirror, and image data of the document read by the image sensor 233 is output to the image signal control unit 281. The document reading is continued until the document reading on the document pressure plate glass plate 55 is completed or until the reading of the image of the final document detected by the document presence / absence sensor 151 is completed.

  On the other hand, when the switching of the contact state of the intermediate transfer belt unit 140 is completed, the CPU 301 controls the image forming unit 120 via the image forming unit 271 and starts an image forming operation of the image data stored in the RAM 303. . The image forming unit 120 includes, for each toner color, an image forming unit 120y for yellow, an image forming unit 120m for magenta, an image forming unit 120c for cyan, and an image forming unit 120k for black. Hereinafter, the subscripts y, m, c, and k representing the toner color are omitted unless necessary. The image forming unit 120 includes a photosensitive drum 101 that is a photosensitive member, a developing device 104, a charging roller 102, a photosensitive drum cleaner 107, and the like. In the image forming unit 120, the surface of the photosensitive drum 101 rotating in the direction of the arrow (clockwise direction) in the drawing is charged by the charging roller 102, and then the photosensitive drum 101 is irradiated with laser light emitted from the laser scanner unit 103 as an exposure unit. A latent image is formed on top. Then, the latent image formed on the photosensitive drum 101 (on the photosensitive member) is developed with toner in the developing device 104. Thereafter, the toner image developed on the photosensitive drum 101 is sequentially superimposed and transferred onto the intermediate transfer belt 130 rotating in the arrow direction (counterclockwise direction) in the figure by the primary transfer roller 105 to which a primary transfer voltage is applied. As a result, a full-color toner image is formed. The full-color toner image transferred to the intermediate transfer belt 130 moves to the secondary transfer unit 118 as the intermediate transfer belt 130 rotates.

  Further, the CPU 301 drives a transport motor (not shown) via the paper transport unit 270 in accordance with the timing at which the toner image on the intermediate transfer belt 130 arrives at the secondary transfer unit 118. The paper feed pickup roller 113, the paper feed roller 114, the registration roller 116, and the paper discharge roller 139 are driven by a conveyance motor (not shown). As a result, the paper feed pickup roller 113 is driven to rotate, and the paper is fed from the paper feed cassette 111 one by one. Then, a secondary transfer voltage is applied at the secondary transfer unit 118, whereby the toner image on the intermediate transfer belt 130 is transferred to the conveyed sheet.

  The sheet on which the toner image is transferred in the secondary transfer unit 118 is conveyed to the fixing device 170. In the fixing device 170, an unfixed toner image on the paper is fixed on the paper by being heated and pressed. Thereafter, the CPU 301 discharges the paper onto the paper discharge tray 132 by the paper discharge roller 139 controlled by the paper transport unit 270. Note that the above-described image forming operation is an example, and the present invention is not limited to the above-described configuration. In this embodiment, the laser scanner unit 103 is provided for each photosensitive drum 101, that is, one laser scanner unit 103 is provided for one photosensitive drum 101. For example, one laser scanner unit 103 may be configured to expose two photosensitive drums 101 or four photosensitive drums 101.

<Control by color mode of image forming apparatus>
[Color mode setting]
FIG. 3A is a front view of the operation unit 330 according to the present embodiment. The operation unit 330 is provided with a start key 306 for starting a copy operation, a stop key 307 for interrupting the copy operation, a numeric keypad 313 for setting a numerical value, and the like. The operation unit 330 is also provided with a power saving button 340 for shifting the image forming apparatus from the normal mode to the power saving mode. A display unit 311 having a touch panel is arranged on the left side of the operation unit 330, and a soft key can be created on the screen. When the “color / monochrome” key 318 displayed on the display unit 311 is pressed, the screen shown in FIG. 3B pops up on the display unit 311 to set the print color mode of the image forming apparatus. it can. FIG. 3B is a setting pop-up screen for setting the print color mode. In the display screen shown in FIG. 3B, the print color mode is set by performing a key operation. The color mode is designated by a “full color” key 321 for designating the full color mode, a “monochrome” key 322 for designating the monochrome mode, and an “auto” key 323 for judging and setting the full color mode / monochrome mode on the image forming apparatus side. The Then, by selecting any of these keys and pressing the “OK” key 314, the print color mode is set. In addition, the CPU 301 performs print preparation operation control in accordance with an operation on the operation unit 330 and a print color mode setting (hereinafter also simply referred to as color mode setting). In this embodiment, the color mode setting is performed using the color mode setting key from the operation unit 330, but the color mode setting may be input via the external I / F 282. Color mode information (for example, monochrome mode) set upon execution of a print job can be changed to other color mode information (for example, full color mode) until an instruction to start image formation is given.

  In the print preparation operation, the CPU 301 shifts the temperature of the fixing device 170 to a predetermined temperature corresponding to the color mode setting. In addition, the CPU 301 switches between the contact state of the intermediate transfer belt unit 140 with each photosensitive drum 101 and the driving of the laser scanner unit 103 according to the color mode setting. A feature of this embodiment is that, when the color mode is switched over a predetermined number of times during the print preparation operation, the print preparation operation control is not switched any more. As a result, it is possible to ensure both the life of the switching mechanism by the preparation operation and the reduction of downtime. Details will be described later.

[Switching control of contact / separation mechanism by color mode]
Next, a contact / separation mechanism that is a switching unit that switches the contact / separation state between the intermediate transfer belt 130 and the photosensitive drum 101 in the full-color mode and the monochrome mode in the present embodiment will be described.

(Description of photosensitive drum / intermediate transfer belt configuration)
FIG. 4 is a cross-sectional view of the vicinity of the intermediate transfer belt unit 140 to which the exemplary embodiment is applied. As shown in FIG. 4A, the intermediate transfer belt 130 is stretched by five rollers: a driving roller 201, an idler roller 202, a secondary transfer inner roller 203, a tension roller 204, and an auxiliary roller 205. These rollers are driven to rotate by a motor for an intermediate transfer belt (not shown), and the intermediate transfer belt 130 rotates following the rotation of the rollers. The drive roller 201, idler roller 202, and secondary transfer inner roller 203 are rotatably supported by the frame 206 of the intermediate transfer belt unit 140. The tension roller 204 is rotatably supported in the vicinity of both ends thereof by a bearing 207 that can move in the direction of arrow C in FIG. The bearing 207 is biased in a movable direction (in the direction of arrow C in the figure) by a spring 208, and the intermediate transfer belt 130 is stretched with a substantially constant tension. Inside the intermediate transfer belt unit 140, there are disposed primary transfer rollers 105 facing the respective photosensitive drums 101 with the intermediate transfer belt 130 interposed therebetween. Both ends of each primary transfer roller 105 are rotatably supported by bearings 210. Has been. The bearing 210 is guided by a frame 206 so as to be movable in one direction (vertical direction in FIG. 4), and the bearing 210 is urged toward the photosensitive drum 101 by a spring 209. The photosensitive drum 101 is driven by a drum motor (not shown) provided corresponding to each photosensitive drum 101.

  4A shows a cross-sectional view of the vicinity of the intermediate transfer belt unit 140 when the full color mode is set as the color mode, and FIG. 4B shows the intermediate transfer when the monochrome mode is set as the color mode. A sectional view of the vicinity of the belt unit 140 is shown. When the full color mode is set, it is necessary to form an image using all color toners. Therefore, all the primary transfer rollers 105 (y, m, c, k) are in contact with the opposing photosensitive drums 101 (y, m, c, k) via the intermediate transfer belt 130. Hereinafter, such a state shown in FIG. 4A is referred to as “contact mode”.

  On the other hand, when the monochrome mode is set as the color mode, image formation using only black toner is performed. Therefore, the primary transfer roller 105k facing the black photosensitive drum 101k is in contact with the intermediate transfer belt 130. The other primary transfer rollers 105 (y, m, c) are separated from the intermediate transfer belt 130 and the opposing photosensitive drums 101 (y, m, c), and are separated from the photosensitive drums 101 (y, m, c). The drum motor (not shown) that drives c) is stopped. As shown in FIG. 4B, the primary transfer rollers 105 (y, m, c) of yellow, magenta, and cyan and the auxiliary roller 205 are retracted upward in the drawing and contact the intermediate transfer belt 130. It is not separated. Further, the intermediate transfer belt 130 is not in contact with the photosensitive drums 101 (y, m, c) of yellow, magenta, and cyan. Then, only the black primary transfer roller 105k is in contact with the black photosensitive drum 101k via the intermediate transfer belt 130. Hereinafter, such a state shown in FIG. 4B is referred to as a “separation mode”.

(Configuration and control of contact / separation switching mechanism)
Next, the contact mode and separation mode switching mechanism described above will be specifically described with reference to FIGS. FIG. 5 is a cross-sectional view of a contact / separation mechanism 400 provided in the intermediate transfer belt unit 140 that switches between the contact mode and the separation mode when viewed from the front side of the intermediate transfer belt unit 140 shown in FIG. It is. The contact / separation mechanism 400 is configured to switch between the contact mode and the separation mode when the slider 402 slides in the horizontal direction (left-right direction in the figure). FIG. 5A shows a state before the slider 402 slides, that is, a state in the contact mode. On the other hand, FIG. 5B shows a state after the slider 402 slides in the direction of arrow A in FIG. The operation when the slider 402 slides will be described later.

  First, the configuration of the contact / separation mechanism 400 will be described with reference to FIG. As shown in FIG. 5A, a slide lever 401 is fixedly connected to the slider 402. The bearings 210a, 210y, 210m, and 210c are support portions that rotatably support both ends of the auxiliary transfer roller 205, the primary transfer rollers 105y, 105m, and 105c of yellow, magenta, and cyan, respectively. The lift arms 404 (a, y, m, c) support the auxiliary rollers 205 and the bearings 210 (a, y, m, c) of the primary transfer rollers 105y, 105m, 105c from below in the drawing. ing. Also, the lift arms 404 (a, y, m, c) are supported in a rotatable state by bearings 403 (a, y, m, c), which are connecting portions to the slider 402, respectively. Further, a lift arm support 405 (a, y, m, c) is provided as a fulcrum when the lift arm 404 (a, y, m, c) rotates.

  FIG. 6 is a diagram for explaining the configuration of a cam mechanism for sliding the slider 402 of FIG. 5 in the horizontal direction (left and right direction in the figure). 6A, the cam gear 502 and the cam portion 503 are fixed to a shaft (shaft) 501, and when the shaft 501 rotates in the direction of the arrow in the drawing, the cam gear 502 and the cam portion 503 are also shown in the arrow in the drawing. Rotate in the direction. The slide lever 401 fixedly connected to the slider 402 is disposed in contact with the cam portion 503 of the cam gear 502. FIG. 6A shows a state where the cam portion 503 does not interfere with the slide lever 401 at all, that is, a state where the cam portion 503 does not press the slide lever 401 in the right direction in FIG. The state of the contact-separation mechanism 400 of a) is shown. In FIG. 5A, the bearings 210 (a, y, m, c) are located below compared to FIG. 5B, and the primary transfer rollers 105 (y, m, c) of yellow, magenta, and cyan are located below. c) and the auxiliary roller 205 are also positioned below. That is, FIG. 5A shows a contact mode in a contact state where the primary transfer roller 105 (y, m, c) is in contact with the intermediate transfer belt 130.

  7 is a top view when the cam gear 502, the cam portion 503, and the shaft 501 shown in FIG. 6 are viewed from above in FIG. As shown in FIG. 7A, the cam gear 502 and the cam portion 503 are fixed to the shaft 501. Further, a flag 601 for detecting contact / separation is fixed to the shaft 501, and the flag 601 also rotates as the shaft 501 rotates. A contact sensor 325 and a separation sensor 326 are disposed at a position facing the flag 601 with the shaft 501 interposed therebetween. The contact sensor 325 and the separation sensor 326 use a photo interrupter that detects the presence or absence of an object by blocking a light beam. That is, the contact sensor 325 and the separation sensor 326 have the same configuration, and the light beam emitted from the light emitting part provided on one wall part through which the flag 601 passes is provided on the other wall part. The light receiving unit receives light. The contact sensor 325 and the separation sensor 326 change between two types of light receiving states, a state in which the light beam emitted from the light emitting unit is received by the light receiving unit and a light blocking state in which the light is blocked by the flag 601 and not received. It is configured to detect. For example, FIG. 7A shows the state of FIG. In FIG. 7A, it can be determined that the flag 601 shields the contact sensor 325 and the contact / separation mechanism 400 is in the contact state (contact mode). At this time, since the separation sensor 326 is not in a state of being shielded by the flag 601, the light beam emitted from the light emitting portion is in a state of being received by the light receiving portion, and is in a separation state (separation mode). It is not judged.

  Next, an operation when a contact / separation motor (not shown) that drives the contact / separation mechanism 400 is driven will be described. By driving a contact / separation motor (not shown), the shaft 501 shown in FIG. 6A rotates, and the cam gear 502 rotates in the arrow direction (clockwise direction) in accordance with the rotation. In FIG. 6B, the cam portion 503 pushes the slide lever 401 in the direction of arrow A by the rotation of the cam gear 502. FIG. 6C shows a state when the cam portion 503 is rotated by 180 ° from FIG. 6A. At this time, the slide lever 401 is pushed most in the direction of the arrow A. Since the slide lever 401 is fixedly connected to the slider 402, the slider 402 is also in a state of being pushed most in the direction of arrow A.

  FIG. 5B shows a state of the contact / separation mechanism 400 at this time. In FIG. 5B, each part is represented by a solid line and a broken line for comparison. The state of each part represented by a broken line is the state (contact mode) shown in FIG. 5A, and the state of each part represented by a solid line shows the original state of FIG. As shown in FIG. 5B, the lift arm 404 (a, y, m) has the movement in the arrow A direction of the slider 402 as an action point and the lift arm support portion 405 (a, y, m, c) as a fulcrum. , C) rotate in the clockwise direction in the figure from the state shown by the broken line to the state shown by the solid line. As a result, the bearings 210 (a, y, m, c) supported by the ends of the lift arms 404 (a, y, m, c) are pushed up in the direction of arrow B in the drawing. When the bearing 210 (a, y, m, c) is pushed up, the primary transfer roller 105 (y, m, c) supported by the bearing 210 (y, m, c) is also pushed up. As a result, the primary transfer roller 105 (y, m, c) enters a separated state (separation mode) in which the primary transfer roller 105 (y, m, c) is not in contact with the intermediate transfer belt 130. FIG. 7B shows the state of the flag 601 at this time. In FIG. 7B, it can be determined that the flag 601 shields the separation sensor 326 and the contact / separation mechanism 400 is in the separation state (separation mode). At this time, since the contact sensor 325 is not in a state of being shielded by the flag 601, the light beam emitted from the light emitting unit is received by the light receiving unit, and the contact state (contact mode). ) Is not determined. Note that the above-described method and configuration of contact / separation detection are examples, and the present invention is not limited to the above-described configuration. For example, a configuration in which the photosensitive drums are separated from each other by moving with respect to the intermediate transfer belt 130 or a configuration in which the photosensitive drums and the intermediate transfer belt are both moved to be in separated states may be employed.

  When the contact / separation motor is driven from the state of FIG. 6C and the cam gear 502 is rotated in the direction of the arrow (clockwise direction), the slide that has been pushed in by the cam portion 503 as shown in FIG. The lever 401 slides in the direction of arrow D. The slide lever 401 slides in the direction of arrow D, which is the opposite direction to the direction of arrow A. Finally, as shown in FIG. Return to contact state (contact mode). The configuration of the contact / separation mechanism described above is merely an example, and the present invention is not limited to the configuration described above.

  As described above, when the color mode is the monochrome mode, the contact / separation mechanism 400 is set to the separation mode, thereby reducing the wear on the surface of the photosensitive drum 101 (y, m, c) due to friction with the intermediate transfer belt 130. can do. As a result, the life of the photosensitive drum 101 (y, m, c) can be extended as compared with the case where the photosensitive drums 101 are not separated. Along with this, a drum motor (not shown) for driving the photosensitive drum 101 (y, m, c) can also be stopped, so that power saving can be achieved.

  In the present embodiment, the intermediate transfer belt unit 140 is shifted to the contact mode or the separation mode in advance according to the set color mode prior to the printing operation by the print preparation operation control described later. As a result, the time required for switching the contact / separation mode before the start of image formation is reduced, and the FPOT is shortened. However, if the contact mode and the separation mode of the contact / separation mechanism described above are switched every time the color mode setting is changed, the bearing 210 of the primary transfer roller 105 (y, m, c) shown in FIG. Drive mechanisms such as (y, m, c) and the shaft 501 shown in FIG. 6 gradually deteriorate. In general, the life of the drive mechanism is designed to have such durability that the image forming apparatus main body satisfies the number of sheets printed during the product life. However, if the color mode setting is frequently changed for one print job execution, the number of prints cannot be satisfied during the predetermined product life, resulting in a print abnormality or expensive driving. Mechanical parts may be replaced. Therefore, in the present embodiment, when the color mode setting frequently changes, the switching according to the mode of the contact / separation mechanism is suppressed, thereby suppressing the deterioration of the driving mechanism and extending the component life, as described above. Generation of a difficult problem can be avoided.

[Fixer temperature adjustment control in color mode]
Next, the adjustment control of the fixing temperature of the fixing device 170 in the full color mode and the monochrome mode in the present embodiment will be described.

(Fixer configuration)
FIG. 8 is a cross-sectional view of a fixing device 170 that is a fixing unit that fixes the unfixed toner image T transferred to the recording material by the secondary transfer unit 118 to the recording material P. In FIG. 8, a fixing device 170 includes a fixing film 6 that is a fixing member of a cylindrical metal member, a pressure roller 9, a heater 1, and a thermistor 5 that is a temperature detecting means. The pressure roller 9 is rotationally driven by a fixing drive motor (not shown). The pressure roller 9 is disposed at a position facing the heater 1 with the fixing film 6 interposed therebetween, and is pressed against the lower surface of the heater 1 with a pressing force of, for example, 5 to 20 kgf by a biasing spring (not shown). The fixing film 6 is driven in the conveying direction of the recording material P and the forward arrow direction (counterclockwise direction) as the pressure roller 9 rotates in the arrow direction (clockwise direction). A fixing nip portion is formed between the fixing film 6 and the pressure roller 9, and a heater 1 is disposed to heat the recording material P passing through the fixing nip portion. The heater 1 is configured to be supplied with power from both ends in the longitudinal direction (the direction perpendicular to the paper surface in the drawing). The AC voltage applied to the heater 1 is AC100V, and the heater 1 generates heat by the applied voltage. A thermistor 5 that detects the temperature of the heater 1 is disposed in the vicinity of the center of the heater 1 in the longitudinal direction. During image formation, the CPU 301 controls power supply to the heater 1 so that the temperature detected by the thermistor 5 becomes a predetermined target temperature. When the recording material P carrying the unfixed toner image T is introduced into the fixing nip portion between the fixing film 6 and the pressure roller 9, the recording material P is heated by the heater 1 and the pressure roller 9. The unfixed toner image T conveyed while being pressurized by the toner is fixed on the recording material P.

(Fixing temperature adjustment control in print preparation operation)
Next, temperature adjustment control of the fixing device 170 in the above-described print preparation operation will be described with reference to FIGS. FIG. 9A is a timing chart showing the relationship between the temperature detected by the thermistor 5 and the power supplied to the heater 1 at the start of the print preparation operation / print operation of the fixing device 170. FIG. 9B is a table showing the print preparation temperature and the print temperature, which are target temperatures during the print preparation operation and the print operation when the full color mode or the monochrome mode is designated as the color mode. In the present embodiment, the temperature of the fixing device 170 in the print preparation operation / printing operation is set to the optimum target temperature in accordance with the color mode set by the input from the operation unit 330. From FIG. 9B, the print preparation temperature, which is the target temperature in the print preparation operation, is 80 ° C., which is the first temperature when the full color mode is set as the color mode, and when the monochrome mode is set. The second temperature is 120 ° C. On the other hand, the print temperature, which is the target temperature when starting the printing operation, is the third temperature, 150 ° C., regardless of whether the color mode is the full color mode or the monochrome mode.

  Next, with reference to FIG. 9A, temperature adjustment of the fixing device 170 in the print preparation operation / print operation will be described. FIG. 9A is a timing chart showing a temperature change (upper diagram) of the heater 1 of the fixing device 170 and a power supply state (lower diagram) to the heater 1 in the print preparation operation / print operation. The horizontal axis in the upper diagram indicates time, the vertical axis indicates the temperature of the heater 1 (fixing temperature in the figure), the horizontal axis in the lower diagram indicates time, and the vertical axis indicates the power supplied to the heater 1 (fixing power in the figure). ). In the figure, T1, T2, T2m, T3, T4m, and T4 indicate time (timing), time T1 indicates the timing for starting the print preparation operation, and time T3 indicates the timing for starting the printing operation. In addition, a graph indicated by a thick solid line in the drawing indicates a state when the color mode is the full color mode, and a graph indicated by a broken line indicates a state when the color mode is the monochrome mode.

  First, temperature adjustment of the fixing device 170 when the color mode set from the operation unit 330 is the full color mode will be described. At time T1 when the print preparation operation is started, the CPU 301 supplies 1000 W to the heater 1 until the temperature detected by the thermistor 5 reaches 80 ° C., which is the print preparation temperature in the full color mode. At time T2, when the temperature detected by the thermistor 5 becomes equal to or higher than the print preparation temperature of 80 ° C., the CPU 301 supplies power to the heater 1 so that the temperature of the thermistor 5 is kept at the print preparation temperature of 80 ° C. Switch from 1000W to 300W. The time T2 when the temperature detected by the thermistor 5 reaches 80 ° C., which is the print preparation temperature, changes depending on the temperature detected by the thermistor 5 at the time T1.

  Subsequently, at time T3 when the printing operation is started, the CPU 301 supplies 1000 W to the heater 1 until the temperature detected by the thermistor 5 reaches 150 ° C., which is a printing temperature for fixing the unfixed toner image on the recording material P. Power supply. At time T4 when the temperature detected by the thermistor 5 reaches the print temperature of 150 ° C. and the recording material P on which the unfixed toner image is formed reaches the fixing device 170, the CPU 301 supplies power to the heater 1 to 1000 W. To 600W. That is, the CPU 301 switches the power supply to the heater 1 from 1000 W to 600 W to fix the unfixed toner image T on the recording material P so that the temperature of the thermistor 5 is maintained at 150 ° C. which is the printing temperature.

  Next, when the color mode is the monochrome mode, or based on whether the original image read by the image sensor 233 is a monochrome image, the temperature adjustment of the fixing unit 170 in the full-color mode or the automatic determination mode for setting the monochrome mode is performed. Will be described. At time T1 when the print preparation operation is started, the CPU 301 supplies 1000 W to the heater 1 until the temperature detected by the thermistor 5 reaches 120 ° C., which is the print preparation temperature in the monochrome mode. Then, at time T2m, when the temperature detected by the thermistor 5 becomes equal to or higher than the print preparation temperature of 120 ° C., the CPU 301 supplies power to the heater 1 so that the temperature of the thermistor 5 is kept at the print preparation temperature of 120 ° C. Switch from 1000W to 400W. Note that the time T2m at which the temperature detected by the thermistor 5 reaches 120 ° C., which is the print preparation temperature, changes depending on the temperature detected by the thermistor 5 at the time T1.

  Subsequently, at time T3 when the printing operation is started, the CPU 301 supplies 1000 W to the heater 1 until the temperature detected by the thermistor 5 reaches 150 ° C., which is a printing temperature for fixing the unfixed toner image on the recording material P. Power supply. Then, at time T4m when the temperature detected by the thermistor 5 reaches the printing temperature of 150 ° C. and the recording material P on which the unfixed toner image is formed reaches the fixing device 170, the CPU 301 supplies power to the heater 1 to 1000 W. To 600W. That is, the CPU 301 switches the power supply to the heater 1 from 1000 W to 600 W to fix the unfixed toner image T on the recording material P so that the temperature of the thermistor 5 is maintained at 150 ° C. which is the printing temperature.

  Here, in order to fix the unfixed toner image T to the recording material P, at the time T4 when the recording material P reaches the fixing device 170, the temperature detected by the thermistor 5 by the thermistor 5 is 150 ° C. or higher. The print preparation temperature is set. The higher the print preparation temperature is, the faster the temperature of the heater 1 can reach the print temperature of 150 ° C. after the start of the printing operation. However, if the print preparation temperature is set high, more power must be supplied in order to maintain the heater 1 at a high temperature, which is not efficient from the viewpoint of power saving. Therefore, in the present embodiment, the print preparation temperature setting for the full color mode and the monochrome mode is divided according to the color mode set from the operation unit 330. As a result, the temperature of the fixing device 170 reaches the print temperature of 150 ° C. at the time T4 (time T4m) and the realization of power saving can be realized.

  Next, the difference in setting of the print preparation temperature when the color mode is the full color mode and when the color mode is the monochrome mode will be described. FIG. 9C is a cross-sectional view of the vicinity of the intermediate transfer belt unit 140 and the secondary transfer unit 118, and the upper drawing is a cross-sectional view when the monochrome mode is set as the color mode, and the lower drawing. These are sectional views when the full color mode is set as the color mode. 9C, the time interval TsMono indicated by the thick solid line indicates that the recording material P to which the black toner image T has been transferred after the black image forming unit 120k has started image formation is the fixing device. The time interval until reaching 170 is shown. On the other hand, the time interval TsFull indicated by a thick solid line in the lower diagram of FIG. 9C is the recording material P onto which the yellow toner image T has been transferred after the yellow image forming unit 120y started image formation. Indicates a time interval until the toner reaches the fixing unit 170. As is clear from FIG. 9C, the relationship between the two time intervals TsMono and TsFull is a relationship of time interval TsFull> time interval TsMono. Therefore, the time during which the heater 1 is supplied with electric power from when the image forming unit 120 starts image formation until the recording material P reaches the fixing device 170 is longer in the full color mode than in the monochrome mode. The printing temperature of the fixing device 170 is the same in the monochrome mode and the full color mode. Therefore, the print preparation temperature, which is the temperature of the fixing device 170 at the start of the printing operation, can be set to a lower temperature in the full color mode than in the monochrome mode. In the present embodiment, when the color mode is the full color mode, the print preparation temperature can be set lower when the color preparation mode is not switched according to the color mode. Therefore, the print preparation temperature is maintained. Therefore, it is possible to reduce the supply power. Therefore, there is an effect in terms of power saving. In this embodiment, the print preparation temperature and the supplied power are set to fixed values, but may be changed according to, for example, the environmental temperature and the power supply voltage.

[Scanner motor drive control in color mode]
Next, drive control of the laser scanner unit 103 in the full color mode and the monochrome mode in the present embodiment will be described.

(Description of the configuration of the laser scanner unit 103)
FIG. 10 is a diagram illustrating the configuration of a laser scanner unit 103k that irradiates a laser beam that forms a latent image on the black photosensitive drum 101k. The laser scanner unit 103k includes a laser driver 2101 that controls the emission of laser light from a light source, a rotating polygon mirror 2102 that deflects the emitted laser light, and a scanner motor 2105 that is a drive unit that rotationally drives the rotating polygon mirror 2102. It has. The laser scanner unit 103k includes an imaging lens 2103 for imaging the laser beam deflected by the rotary polygon mirror 2102 on the photosensitive drum 101k, and a reflection for reflecting the deflected laser beam toward the photosensitive drum 101k. A mirror 2104 is provided. At the time of image formation in the monochrome mode, the CPU 301 controls the drive of the scanner motor 2105 so that the rotational speed of the rotary polygon mirror 2102 of the laser scanner unit 103k becomes a predetermined target speed. When the rotational speed of the rotary polygon mirror 2102 reaches a predetermined rotational speed, the CPU 301 outputs an image signal to the laser driver 2101 of the laser scanner unit 103k via the image signal control unit 281 in FIG. A latent image is formed on the screen. When the color mode is the full color mode, the laser scanner units 103y, 103m, and 103c are driven by the CPU 301 in addition to the laser scanner unit 103k. The configuration of the laser scanner units 103y, 103m, and 103c is the same as that of the laser scanner unit 103k, and a description thereof will be omitted.

  When image formation is performed in the monochrome mode, the laser scanner unit 103k needs to be started up before image formation is started. Here, “start-up completion” indicates a state in which the scanner motor 2105 of the laser scanner unit 103k is rotating at a predetermined target speed. Similarly, in the full color mode, it is necessary that all the laser scanner units 103 (y, m, c, k) have been started up. In this embodiment, when image formation is performed in the monochrome mode, only the laser scanner unit 103k is started up, and when image formation is performed in the full color mode, all the laser scanner units 103 (y, m, c, Start up k).

  Therefore, in print preparation operation control to be described later, the CPU 301 starts up the laser scanner unit 103 according to the set color mode prior to the print operation. That is, the CPU 301 starts up all the laser scanner units 103 in the full color mode, and starts up the laser scanner unit 103k in the monochrome mode. As a result, the time required to start up the laser scanner unit 103 (y, m, c, k) from when the print start instruction is received until the actual image formation is started can be reduced, and the FPOT can be shortened. it can.

  However, each time the color mode setting is switched, the drive mechanism of the scanner motor 2105 is gradually changed when the laser scanner unit 103 (y, m, c, k) is switched on in accordance with the set color mode. It deteriorates to. In general, the life of the drive mechanism is designed to have such durability that the image forming apparatus main body satisfies the number of sheets printed during the product life. However, if the color mode setting is continuously switched for one print job execution, the number of sheets to be printed cannot be satisfied during the predetermined product life, resulting in a print error or an expensive drive mechanism component. There is a risk of replacement. For this reason, in the present embodiment, when the color mode setting is frequently changed, the mode switching of the laser scanner unit 103 (y, m, c, k) is suppressed, thereby extending the life of the drive mechanism. Such a problem can be avoided.

(Control of print preparation operation)
Next, the print preparation operation based on the color mode setting, which is a feature of the present embodiment, will be described in detail. FIG. 11 is a flowchart showing a control sequence of the print preparation operation based on the color mode setting. The processing in FIG. 11 is started when the image forming apparatus is turned on or when the image forming apparatus returns from the power saving mode, and is executed by the CPU 301.

  In step (hereinafter referred to as S) 2200, CPU 301 clears the color mode switching count, which is a feature of the present embodiment, to zero. The color mode switching count is a counter indicating how many times the print preparation operation switching by the color mode setting described above has been performed continuously, and is stored in the RAM 303. As will be described later, when the color mode switching count exceeds a predetermined value (threshold), the print preparation operation is not switched. In this embodiment, when the image forming apparatus is turned on or returned from the power saving mode, the CPU 301 determines that a print job different from the previous print job is to be executed, and performs color printing. Clear the mode switch counter to zero. Thus, when the color mode setting is switched during the print preparation operation, the CPU 301 performs a print preparation operation corresponding to the color mode after the switching, and performs control so as to reduce FPOT. In the process described later, the CPU 301 refers to (reads out) the timer value of the timer 291 as the timer value without a print prediction operation. The timer 291 is reset when the image forming apparatus is powered on, but the timer 291 may be reset in S2200.

  In step S2210, the CPU 301 determines whether a print prediction operation for predicting a subsequent print operation start instruction has been performed. Here, the print prediction operation refers to opening / closing of a document pressure plate, placement of a document, and operation of the operation unit 330 via, for example, the document feeder control unit 480 and the image reader control unit 280. If the CPU 301 detects these operations via the document feeder control unit 480 or the image reader control unit 280, the CPU 301 determines that a print prediction operation has been performed, and advances the process to step S2218.

  On the other hand, if the CPU 301 determines that the print prediction operation has not been performed, the CPU 301 advances the process to step S2213. In step S <b> 2213, the CPU 301 refers to the timer value of the timer 291 and determines whether or not the print prediction operation absence timer value is 10 minutes or more, which is the second time. The timer value of the timer 291 as a timer value without a print prediction operation is updated every 1 ms (milliseconds). The CPU 301 can acquire the elapsed time from the end of the previous print preparation operation by reading the timer 291 and acquiring the timer value without print prediction operation. In this embodiment, if a print job is not submitted during the print preparation operation and the print prediction operation described above has not been performed for a predetermined time of 10 minutes, the next print prediction operation uses the previous print job. Determines that it is trying to execute a different job. Therefore, the CPU 301 advances the process to step S2215 when determining that the print prediction non-operation timer value is 10 minutes or more, and returns the process to step S2210 when determining that the print prediction non-operation timer value is less than 10 minutes. In S2215, the CPU 301 clears the color mode switching counter to 0 and returns the process to S2210.

  When the color mode setting is switched during the print preparation operation by the above-described processing, the print preparation operation corresponding to the switched color mode is performed, and control is performed to shorten the FPOT. On the other hand, when the print prediction operation is performed immediately after the print preparation operation is completed, the CPU 301 determines that the print setting or the like has been changed in order to execute the same print job. Therefore, the CPU 301 does not clear the color mode switching counter in order not to switch the print preparation operation during the print preparation operation. As a result, it is possible to ensure the life of the switching mechanism accompanying the switching of the print preparation operation control corresponding to the color mode setting described above.

  In step S <b> 2218, the CPU 301 stores the color mode information input and set from the operation unit 330 in the RAM 303. The color mode information stored in the RAM 303 is color mode information of any of the full color mode, monochrome mode, and full color / monochrome automatic determination mode set from the screen of FIG. In step S2260, the CPU 301 executes fixing temperature adjustment. Although details will be described later, as described with reference to FIG. 9, the CPU 301 supplies power to the fixing device 170 in accordance with the color mode information stored in step S <b> 2218 and raises the temperature of the fixing device 170 to the print preparation temperature. In S2270, the CPU 301 executes scanner unit driving. Although details will be described later, as described in FIG. 10, the CPU 301 starts up (starts driving) the necessary laser scanner unit 103 (y, m, c, k) according to the color mode information stored in S <b> 2218, Stop driving unnecessary laser scanner units. In step S2280, the CPU 301 executes control of the contact / separation mechanism. As will be described in detail later, the CPU 301 switches the state of the contact / separation mechanism according to the color mode information stored in S2218, as described with reference to FIGS.

  In step S2290, the CPU 301 clears the print prediction operation execution timer value indicating the time until the print prediction operation is executed to zero. The timer value of the print prediction operation execution timer value is updated by the timer 291 every 1 ms. Therefore, the CPU 301 resets and starts the timer 291, reads the timer value of the timer 291, and acquires the print prediction operation execution timer value, thereby determining the elapsed time since the timer 291 was reset. .

  In step S <b> 2300, the CPU 301 determines whether a print operation start instruction has been received via the operation unit 330 (in the drawing, there is a print operation start instruction). If the CPU 301 determines that a print operation start instruction has been received, the process advances to step S2310. If the CPU 301 determines that a print operation start instruction has not been received, the process advances to step S2305. In step S <b> 2310, the CPU 301 compares the color mode information stored in the RAM 303 with the latest color mode information input and set from the operation unit 330. In this embodiment, as described above, when the color mode setting is switched over a predetermined number of times, the switching according to the color mode of the contact / separation mechanism is performed in order to suppress the deterioration of the drive mechanism. Do not do. For this reason, the color mode information stored in the RAM 303 may be different from the latest color mode information input and set from the operation unit 330. When the full color / monochrome automatic determination mode is set as the color mode, the color mode is determined at the start of the printing operation. That is, the CPU 301 sets the color mode in the full color mode when the image data of the document read by the image sensor 233 (see FIG. 1) is a color image, and sets the color mode in the monochrome image, and saves it in the RAM 303. Then, print operation is performed. Therefore, when the full color / monochrome automatic determination mode is set, the final color mode is not determined during the processing of S2280 described above. Therefore, the state set in the contact / separation mechanism corresponding to the temporary color mode may be different from the finally determined color mode. Therefore, the CPU 301 uses the color mode information stored in the RAM 303 set in the contact / separation mechanism and the color mode when performing the printing operation which is the finally determined or finally set color mode information. And are the same. If the CPU 301 determines that the color mode information setting (color mode setting) is the same as the contact / separation state of the contact / separation mechanism, the CPU 301 advances the process to S2320 to set the color mode information and contact / separation. If it is determined that the mechanism states do not match, the process advances to step S2315. In step S <b> 2315, the CPU 301 executes control of the contact / separation mechanism in accordance with the finally determined or finally set color mode information.

  In S2320, as in S2310, the CPU 301 determines whether the color mode for performing the printing operation is the same as the color mode of the drive state set in the laser scanner unit 103. If the CPU 301 determines that the color mode setting and the drive state of the laser scanner unit 103 are the same, the CPU 301 advances the process to step S2328, and if the CPU 301 determines that the color mode setting is not the same, advances the process to step S2325. In step S2325, the CPU 301 executes drive control of the scanner motor 2105 of the laser scanner unit 103 in accordance with the color mode used when performing the printing operation.

  In step S2328, the CPU 301 supplies power to the heater 1 of the fixing unit 170 until the print temperature, which is a temperature at which the unfixed toner image on the recording material P can be fixed to the recording material P, as described with reference to FIG. Do. In S2330, the CPU 301 enters the following state and starts the printing operation when determining that the printing operation is ready. That is, the CPU 301 determines that the contact / separation state of the contact / separation mechanism is set to a state corresponding to the color mode when performing the printing operation, and the rotation speed of the scanner motor 2105 of the laser scanner unit 103 has reached the target speed. Judging. When the CPU 301 determines that the temperature of the heater 1 of the fixing device 170 has reached the printing temperature, the CPU 301 starts the printing operation. In S2335, the CPU 301 determines whether the printing operation is completed. If it is determined that the printing operation is completed, the process proceeds to S2340. If it is determined that the printing operation is not completed, the process returns to S2335.

  In S2340, the CPU 301 clears the color mode switching count to zero. In S2360, the CPU 301 clears the timer value without a print prediction operation to zero. In step S2370, the CPU 301 stops driving the scanner motor 2105 of the laser scanner unit 103 (stops driving the scanner unit). In S2380, the CPU 301 stops the power supply to the heater 1 of the fixing device 170, stops the fixing temperature adjustment operation, and returns the process to S2210 in order to detect the print prediction operation again.

  In step S <b> 2305, the CPU 301 refers to the timer value of the timer 291 and determines whether the print prediction operation execution timer value is 30 seconds or more, which is the first time. The timer value of the timer 291 as the print prediction operation execution timer value is updated every 1 ms (milliseconds). The CPU 301 can acquire the elapsed time from the end of the print preparation operation by reading the timer 291 and acquiring the print prediction operation execution timer value. If the CPU 301 determines that the print prediction operation execution timer value is 30 seconds or longer, the CPU 301 advances the process to step S2360. If the CPU 301 determines that the print prediction operation execution timer value is less than 30 seconds, the CPU 301 advances the process to step S2308. In step S <b> 2360, the CPU 301 resets the timer 291 and starts the timer 291 to end the print preparation operation, thereby clearing the print prediction non-operation timer value to zero. If it is determined that the print prediction operation has been performed in the process of S2210 until 10 minutes or more have passed since this time, it is determined that the color mode setting for the same print job is continued, and the color mode is switched thereafter. The print prediction operation is not switched. This extends the life of the switching mechanism. Then, the CPU 301 stops driving the laser scanner unit 103 in S2370, and stops the power supply to the heater 1 and stops the fixing temperature adjustment operation in S2380, as in the case where the printing operation is completed.

  In step S2308, the CPU 301 determines whether a print prediction operation for predicting a print operation start instruction has been performed. If it is determined that the print operation has been performed, the process proceeds to step S2220; Return to S2300. In step S2220, the CPU 301 determines whether the print prediction operation performed is a change in color mode. If the CPU 301 determines that the color mode is changed, the process advances to step S2230 to determine that the change is not a change in color mode. In the case, the process proceeds to S2290. In S2230, the CPU 301 updates the color mode switching count by adding 1. In S2240, the CPU 301 determines whether the value of the color mode switching count is equal to or less than a predetermined threshold value. If it is determined that the color mode switching count is equal to or less than the threshold value, the process proceeds to S2218. Advances the process to S2290.

  As a result, when the color mode switching count is equal to or smaller than the threshold, the CPU 301 stores the color mode setting input from the operation unit 330 in the RAM 303 again (S2218), and switches the print preparation operation (S2260, S2270, S2280). On the other hand, if the color mode setting has not been changed or the color mode switching count is greater than the threshold, the CPU 301 again clears the print prediction operation execution timer value to 0 (S2290), and a print operation start instruction is input. Wait for it. In the present embodiment, the threshold value for the color mode switching count is set to 1, and the print preparation operation is switched only once during the print preparation operation. Note that the threshold value of the color mode switching count is determined based on the configuration of the switching mechanism driven in the print preparation operation and the assumed lifetime, and may not be 1. In this embodiment, the color mode switching count is cleared to 0 when 10 minutes have elapsed from the end of the print preparation operation or when the image forming apparatus is powered on. Since the condition for switching the print preparation operation is determined by the configuration of the switching mechanism and the assumed lifetime, the color mode switching count may or may not be cleared at the timing described above. Good.

[Fixing temperature adjustment]
Next, the adjustment operation of the fixing temperature will be described. FIG. 12 is a flowchart showing a control sequence of the fixing temperature adjustment operation. The process of FIG. 12 is started when executing S2260 of FIG.

  In step S1310, the CPU 301 reads the color mode setting stored in the RAM 303, and determines whether the set color mode is a monochrome mode. If the CPU 301 determines that the set color mode is the monochrome mode, the process advances to step S1320. If the CPU 301 determines that the set color mode is not the monochrome mode, the process advances to step S1330. In step S1320, the CPU 301 supplies power to the heater 1 of the fixing unit 170 so that the target temperature of the heater 1 of the fixing unit 170 becomes 120 ° C., which is the print preparation temperature in the monochrome mode (fixing target temperature = monochrome printing preparation temperature). Supply and return processing. For example, when the color mode setting is changed from the full color mode to the monochrome mode from the operation unit 330, the print preparation operation may already be started at the print preparation temperature in the full color mode. In this case, the CPU 301 performs processing for switching the print preparation temperature from the temperature in the full color mode (80 ° C.) to the temperature in the monochrome mode (120 ° C.).

  In S1330, the CPU 301 determines whether or not the color mode setting is the full color / monochrome automatic determination mode. If it is determined that the color mode setting is the automatic determination mode, the process proceeds to S1340. On the other hand, if the CPU 301 determines that the mode is not the automatic determination mode, that is, the full color mode, the process advances to step S1360. In step S1340, the CPU 301 determines whether or not power is already being supplied to the fixing device 170. If it is determined that power is being supplied, the final color mode setting has not been determined since it is an automatic determination mode, so printing is not performed. Return the process without changing the preparation temperature. On the other hand, if the CPU 301 determines that power is not being supplied, the process advances to step S1350.

  Here, when it is determined that the power is being supplied, the reason for returning the processing without changing the print preparation temperature is as follows. That is, in the full color / monochrome automatic determination mode, the printing operation is started, and the image signal control unit 281 determines whether the document image read by the image sensor 233 is a monochrome image. If the CPU 301 determines that the document image is a monochrome image, the CPU 301 performs a printing operation in the monochrome mode, and otherwise performs a printing operation in the full color mode. For this reason, at the time of the print preparation operation of S2260 in FIG. 11, it is not possible to determine whether it is appropriate to perform the print preparation operation in the full color mode or the monochrome mode, so the print preparation temperature is not changed.

  In S1350, the CPU 301 supplies power to the heater 1 of the fixing device 170 so that the target temperature of the heater 1 of the fixing device 170 becomes 120 ° C., which is the print preparation temperature in the monochrome mode (fixing target temperature = monochrome printing preparation temperature). Supply and return processing. Here, the reason why power is supplied to the heater 1 in the monochrome mode even though the final color mode has not been determined is as follows. That is, if the fixing device 170 is at the print preparation temperature (120 ° C.) in the monochrome mode, the time from when the print start instruction is received until the temperature of the heater 1 reaches the print temperature (150 ° C.) is short. For this reason, it is possible to reduce downtime, which is a waiting time until the temperature of the heater 1 rises. When the print operation is started in the monochrome mode when the print preparation operation is performed in the full color mode, the temperature of the heater 1 of the fixing device 170 reaches 120 ° C. which is the monochrome print preparation temperature. Start print operation.

  In step S <b> 1360, the CPU 301 determines whether power is already being supplied to the fixing device 170. If it is determined that power is being supplied, the process returns without changing the print preparation temperature. On the other hand, if the CPU 301 determines that power is not being supplied, the process proceeds to step S1370. Here, the reason why the process is returned without changing the print preparation temperature when it is determined that power is being supplied to the fixing device 170 will be described. As described with reference to FIG. 9, the print preparation temperature (120 ° C.) in the monochrome mode is higher than the print preparation temperature (80 ° C.) in the full color mode, which is the target temperature in the print start operation ( 150 ° C). If power supply to the fixing device 170 has already been started at the print preparation temperature (120 ° C.) in the monochrome mode, the target temperature of the heater 1 is lowered to the print preparation temperature (80 ° C.) in the full color mode. The electric power input before reaching 120 ° C. is wasted. On the other hand, when power supply to the fixing device 170 has already been started at the print preparation temperature in the full-color mode, it is not necessary to switch the print preparation temperature, so the print preparation temperature is not changed. In S1370, the CPU 301 supplies power to the heater 1 of the fixing device 170 so that the target temperature of the heater 1 of the fixing device 170 becomes 80 ° C. which is the print preparation temperature in the full color mode (fixing target temperature = full color printing preparation temperature). Supply and return processing.

[Control of contact / separation mechanism]
Next, the control operation of the contact / separation mechanism will be described. FIG. 13 is a flowchart showing a control sequence of the control operation of the contact / separation mechanism. The process of FIG. 13 is started when executing S2280 and S2315 of FIG.

  In step S1410, the CPU 301 reads the color mode setting stored in the RAM 303, and determines whether the set color mode is a monochrome mode. If the CPU 301 determines that the set color mode is the monochrome mode, the process proceeds to step S1420. If the CPU 301 determines that the set color mode is not the monochrome mode, the process proceeds to step S1440. In S1420, the CPU 301 determines whether or not the state of the contact / separation mechanism is the separation state (separation mode). If it is determined that the contact / separation mechanism is the separation state, the CPU 301 returns the processing without changing the state of the contact / separation mechanism. . On the other hand, it is determined whether or not the state of the contact / separation mechanism is the separation state (separation mode). If it is determined that the contact / separation mechanism is not the separation state, the CPU 301 advances the process to step S1430. In S1430, the CPU 301 shifts the state of the contact / separation mechanism to the separation state (separation mode) and returns the process.

  In step S1440, the CPU 301 determines whether the set color mode is the full color / monochrome automatic determination mode. When the CPU 301 determines that the set color mode is the automatic determination mode, the contact / separation mechanism cannot be determined in which color mode the print preparation operation is appropriate at the time of the print preparation operation. Returns the process without changing the state. On the other hand, if the CPU 301 determines that the set color mode is not the automatic determination mode, that is, the full color mode, the process advances to step S1450. In S1450, the CPU 301 determines whether or not the state of the contact / separation mechanism is the contact state (contact mode), and if it is determined to be the contact state, the CPU 301 does not change the state of the contact / separation mechanism. Return processing. On the other hand, when determining that the state of the contact / separation mechanism is the separation state (separation mode), the CPU 301 advances the processing to step S1460. In S1460, the CPU 301 shifts the state of the contact / separation mechanism to the contact state (contact mode) and returns the process.

[Scanner motor drive control]
Next, the drive control operation of the scanner motor will be described. FIG. 14 is a flowchart showing a control sequence of the scanner motor drive control operation. The process of FIG. 14 is started when executing S2270 and S2325 of FIG.

  In step S2410, the CPU 301 reads the color mode setting stored in the RAM 303, and determines whether the set color mode is a monochrome mode. If the CPU 301 determines that the set color mode is the monochrome mode, the process proceeds to step S2420. If the CPU 301 determines that the set color mode is not the monochrome mode, the process proceeds to step S2415. In step S2420, the CPU 301 determines whether the laser scanner unit 103 (y, m, c) that scans the photosensitive drums 101 whose toner colors are yellow, magenta, and cyan is being started up. If the CPU 301 determines that the laser scanner unit 103 (y, m, c) is being started up, the process advances to step S2430. If the CPU 301 determines that the laser scanner unit 103 (y, m, c) is not starting up, the process advances to step S2450. In S2430, since the color mode is the monochrome mode, the CPU 301 activates only the laser scanner unit 103k that scans the photosensitive drum 101k whose toner color is black. Therefore, the CPU 301 stops the driving of the laser scanner unit 103 (y, m, c) and returns the process in order to execute the process of lowering the laser scanner unit 103 (y, m, c). In step S2450, the CPU 301 determines whether the laser scanner unit 103k that scans the photosensitive drum 101k whose toner color is black is being started up. If the CPU 301 determines that the laser scanner unit 103k is being started up, it returns the process. If it is determined that the laser scanner unit 103k is not being started up, the CPU 301 advances the process to step S2455. In S2455, the CPU 301 executes startup of the laser scanner unit 103k and returns the process.

  In step S2415, the CPU 301 determines whether the color mode stored in the RAM 303 is a full color mode. If the CPU 301 determines that the set color mode is the full color mode, the process proceeds to S2440. If the CPU 301 determines that the set color mode is not the monochrome mode (the full color / monochrome automatic determination mode), the process proceeds to S2418. . In step S <b> 2440, the CPU 301 determines whether the laser scanner unit 103 (y, m, c) that scans the photosensitive drums 101 whose toner colors are yellow, magenta, and cyan is being started up. If the CPU 301 determines that the laser scanner unit 103 (y, m, c) is being started up, the process advances to step S2450. If the CPU 301 determines that the laser scanner unit 103 (y, m, c) is not starting up, the process advances to step S2445. In S2445, the CPU 301 executes the startup process of the laser scanner unit 103 (y, m, c), and further advances the process to S2450 in order to start up the laser scanner unit 103k.

  In step S2418, the CPU 301 determines whether the laser scanner unit 103k that scans the photosensitive drum 101k whose toner color is black is being started up. When the CPU 301 determines that the laser scanner unit 103k is being started up, the CPU 301 returns the processing, and when it is determined that the laser scanner unit 103k is not being started up, all the laser scanner units 103 (y, m, c, k) are returned. The process proceeds to S2440. That is, if the color mode setting determined in S2415 is the full color / monochrome automatic determination mode, the laser scanner unit 103 (y, m, c, k) for all colors is selected unless the laser scanner unit 103k is in the process of starting. Launch. As a result, regardless of whether the color mode is set to the full color mode or the monochrome mode, it is possible to make the scanner unit startup process unnecessary at the start of the printing operation. On the other hand, if the laser scanner unit 103k is being started up, it can be determined that the start-up process of any one of the laser scanner units 103 is executed in accordance with either color mode setting. The change of the falling operation is not performed.

  As described above, according to the present embodiment, when the print preparation operation control switching by the color mode setting set by the operation unit of the image forming apparatus is continuously performed a predetermined number of times or more, it is more than that. The print preparation operation control is not switched. Therefore, it is possible to ensure the life of the switching mechanism accompanying the switching of the preparation operation control corresponding to the color mode setting. On the other hand, if the switching of the color mode setting is less than the predetermined number, the time required for the preparation operation can be reduced. Therefore, it is possible to realize both the ensuring of the life of the switching mechanism by the preparation operation and the reduction of downtime, and the optimum print preparation operation can be performed.

  As described above, according to the present embodiment, it is possible to achieve both of ensuring the life of the drive mechanism that is driven to perform the print preparation operation according to the color mode setting and reducing the downtime.

140 Intermediate transfer belt unit 301 CPU
330 Operation unit

Claims (17)

A plurality of image forming units for forming images of different color components, a full color mode for forming a full color image using the plurality of image forming units, and a predetermined one of the plurality of image forming units Image forming means operable in a monochrome mode for forming a monochrome image using two image forming units;
An operation unit for inputting color mode information indicating a color mode to be executed among color modes including the full color mode and the monochrome mode ;
An input means for inputting an instruction to start image formation;
When an operation by a user who is predicted to input an instruction to start image formation is detected, the operation of the image forming unit is controlled for an image formation preparation operation according to the color mode information input from the operation unit. Control means;
With
The control means changes the preparation operation according to the changed color mode information every time the color mode information is changed, and when the number of changes of the preparation operation exceeds a predetermined value, the color mode An image forming apparatus , wherein the preparation operation is not changed according to information . Said color mode information, the image forming apparatus according to claim 1, wherein the indication of the start can be changed until the input. Characterized in that said control means during a period from the start the preparation operation until the first time elapses, when an instruction of the start from the input means is not input, the Ru terminates the preparation operation The image forming apparatus according to claim 1 or 2. Storage means for storing the number of times of the preparation operation,
If the control means does not detect an operation that is predicted to be input of an instruction to start image formation after the preparatory operation is finished and until a second time elapses, the control means The image forming apparatus according to claim 3, wherein the stored number of the preparation operations is cleared. Storage means for storing the number of times of the preparation operation,
3. The image formation according to claim 1, wherein when the image forming operation for forming an image on a recording material is executed, the control unit clears the number of the preparation operations stored in the storage unit. apparatus. Storage means for storing the number of times of the preparation operation,
3. The image according to claim 1, wherein the control unit clears the number of times of the preparatory operation stored in the storage unit when the power of the image forming apparatus is turned on. Forming equipment. Storage means for storing the number of times of the preparation operation;
A power control unit capable of shifting to a power saving mode for stopping power supply to the image forming unit;
With
The control unit clears the number of the preparatory operations stored in the storage unit when the power supply control unit is returned from the power saving mode in order to supply power to the image forming unit. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. Comprising reading means for reading a document;
It said reading means includes a document table document to read is performed is placed, and detecting means for detecting the presence of a document on the document table,
An operation in which an input of an instruction to start image formation is predicted is that a document to be read is placed on the document table,
Said control means based on a detection result of said detecting means, an image forming apparatus according to any one of claims 1 to 7, characterized in that to detect the placement of the document. Operation input of an instruction of start of the image formation is predicted, claims, characterized in that said from said input means and the input of the instruction to start image forming is an operation for inputting et al or different the operating unit 8. The image forming apparatus according to any one of 1 to 7 . Each of the plurality of image forming units includes a photosensitive member having the toner image Ru is formed, and a exposing means for exposing said photosensitive member,
It said exposure means comprises a rotary polygonal mirror for deflecting the laser light from the light source to expose a pre-Symbol photoreceptor, and a driving unit for rotating the rotary polygon mirror,
Wherein, as the preparation operation, when the color mode information of the full-color mode, rotates the rotary polygon mirror of the plurality of image forming units, when the color mode information of the monochrome mode 10. The image forming unit according to claim 1 , wherein the rotating polygon mirror of the predetermined image forming unit is rotated and the image forming unit is controlled so as not to rotate the rotating polygon mirror of another image forming unit . the image forming apparatus according to any one. Each of the plurality of image forming units includes a photosensitive member having the toner image Ru is formed,
The image forming means includes: an intermediate transfer belt to which a toner image formed on the photoconductor of each of the plurality of image forming units is transferred; and the photoconductor and the intermediate transfer belt of each of the plurality of image forming units. Switching means for switching between the contact state and the separation state ,
Wherein, as the preparation operation, wherein when the color mode information of the full-color mode, the so said photosensitive member of said plurality of image forming units and said intermediate transfer belt is the abutment state switching And when the color mode information is the monochrome mode, the photosensitive member of the predetermined image forming unit and the intermediate transfer belt are in contact with each other , and the photosensitive member of the other image forming unit and the intermediate transfer belt and an image forming apparatus according to any one of claims 1 to 9, wherein the controller controls the switching means such that the separated state. The image forming means includes a fixing means for fixing the toner image transferred to the recording material to the recording material,
The fixing unit includes a heater that heats the toner image transferred to the recording material, and a temperature detection unit that detects a temperature of the heater.
As the preparatory operation , when the color mode information is the full color mode, the control unit controls the fixing unit so that the heater temperature becomes a first temperature, and the color mode information is the monochrome mode. 10. The fixing device according to claim 1, wherein in the mode, the fixing unit is controlled so that a temperature of the heater becomes a second temperature higher than the first temperature. 11 . Image forming apparatus. The control means switches the color mode information from the monochrome mode to the full color mode while the fixing means is controlled so that the temperature of the heater becomes the second temperature by the preparation operation . If, the image forming apparatus according to claim 12 where the temperature of pre-Symbol heater is characterized in that it does not change the control to be the first temperature. Comprising reading means for reading a document;
The color mode information further includes an automatic determination mode for determining the monochrome mode or the full color mode based on an image of a document read by the reading unit,
The control means is configured to rotate the rotary polygon mirrors of the plurality of image forming units when the color mode information is the automatic determination mode and the preparation operation relating to the rotary polygon mirror is not executed. The image forming apparatus according to claim 10, wherein an image forming unit is controlled to continue the preparatory operation being performed when the preparatory operation relating to the rotary polygon mirror is being performed . Comprising reading means for reading a document;
The color mode information further includes an automatic determination mode for determining the monochrome mode or the full color mode based on an image of a document read by the reading unit,
The image forming apparatus according to claim 11, wherein the control unit does not perform the preparatory operation related to the switching unit when the color mode information is the automatic determination mode . Comprising reading means for reading a document;
The color mode information further includes an automatic determination mode for determining the monochrome mode or the full color mode based on an image of a document read by the reading unit,
When the color mode information is in the automatic determination mode and the preparatory operation relating to the fixing unit is not executed, the control unit controls the fixing unit so that the temperature of the heater becomes the second temperature. 14. The image forming apparatus according to claim 12, wherein when the preparatory operation is executed, the preparatory operation relating to the fixing unit is not changed . The control unit controls the fixing unit so that a temperature of the heater becomes a third temperature higher than the second temperature when an instruction to start image formation is input. Item 17. The image forming apparatus according to any one of Items 12, 13, and 16 .

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