Image forming apparatus and image forming method

According to one embodiment, an image forming apparatus has a fixing member, a heating unit, and a control unit. The fixing member fixes a toner image, which is formed on a recording medium, to the recording medium. The heating unit heats the fixing member. The control unit controls a heating operation of the heating unit based on a ready temperature corresponding to job information input by a user.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2014-14360, filed on Jan. 29, 2014, the entire contents of which are incorporated herein by reference.

FIELD

The embodiments described herein relate generally to an image forming apparatus and an image forming method that form an image by fixing a toner image to a recording medium.

BACKGROUND

Image forming apparatuses having a fixing device heating and fixing a toner image to a recording medium, for instance a sheet have been known. A ready temperature of the fixing device is set constantly and by a margin. Thus, even on a printing job to which a maximum load is applied, the fixing device maintains good fixing performance up to the final print. However, a quantity of heat at which the fixing device requires actually differs depending on job conditions such as a type of toner, the number of printing sheets, and a sheet size. For this reason, when the image forming apparatus carries out a job having a low load applied to the fixing device, the ready temperature may be excessive to impede energy saving. Further, when returning from a sleep state (power saving state) to a ready state, the image forming apparatus takes a long time to do a warmup for raising a heating temperature of the fixing device to a higher ready temperature than necessary.

DETAILED DESCRIPTION

According to one embodiment, an image forming apparatus has a fixing member, a heating unit, and a control unit. The fixing member fixes a toner image formed on a recording medium to the recording medium. The heating unit heats the fixing member. The control unit controls a heating operation of the heating unit based on a ready temperature corresponding to job information input by a user.

Hereinafter, additional embodiments will be described with reference to the drawings. In the drawings, the same reference numerals indicate the same or similar portions.

The image forming apparatus of a first embodiment will be described with reference toFIGS. 1 to 8.FIG. 1is a cross-sectional view illustrating a multi-function peripheral (MFP)10which is an example of the image forming apparatus of the first embodiment and by which a color image can be formed. The MFP10is controlled in any of a sleep state, a ready state, and a job fulfillment state by a central processing unit (CPU) to be described below. The sleep state is, for instance, a state of the MFP10controlled to inhibit power from being supplied to each part of the MFP10relative to the other states. In other words, the sleep state is a power saving state of the MFP10. In the sleep state, a temperature of the fixing member to be described below is held at a given temperature lower than a ready temperature to be described below. The ready state is, for instance, a state of the MFP10controlled to hold the temperature of the fixing member at the ready temperature and to be able to immediately respond to input of printing job information from a user. When the input of the job information from the user is not present in the ready state in spite of the lapse of, for instance, predetermined time or more even, the MFP10makes up the transition from the ready state to the sleep state. When the job information is input in the sleep state by the user, the MFP10returns from the sleep state to the ready state. When the MFP10returns from the sleep state to the ready state, the MFP10performs a warmup for raising the temperature of the fixing member to the ready temperature. The job fulfillment state is a state of the MFP10controlled such that jobs are carried out based on job conditions included in the job information input from the user. As illustrated inFIG. 1, the MFP10has a printer device11that is an image forming unit, a scanner device12, and a control panel13. The MFP10has the CPU100that is a control unit for controlling the entirety of the MFP10.

The printer device11has an intermediate transfer belt18, four sets of image forming stations20Y,20M,20C and20K, and replenishment cartridges21Y,21M,21C and21K. The intermediate transfer belt18is provided to be rotatable in a direction of an arrow m. The four sets of image forming stations20Y,20M,20C and20K are, inFIG. 1, provided along a lower side of the intermediate transfer belt18. The image forming stations20Y,20M,20C and20K have a configuration to be described below for forming images of respective colors of Y (yellow), M (magenta), C (cyan), and K (black). The replenishment cartridges21Y,21M,21C and21K are, inFIG. 1, provided above the image forming stations20Y,20M,20C and20K so as to be able to be removed by a user.

The four sets of image forming stations20Y,20M,20C and20K each have a photosensitive drum22, an electrification charger23, an exposure scanning head24, a developing device26, and a photoreceptor cleaner27. The photosensitive drum22is provided to be rotatable in an arrow direction illustrated inFIG. 1. The electrification charger23, the exposure scanning head24, the developing device26, and the photoreceptor cleaner27are disposed around the photosensitive drum22in this order. The electrification charger23uniformly charges the photosensitive drum22. The exposure scanning head24exposes the photosensitive drum22. To be specific, the exposure scanning head24applies light, which is modulated based on image data obtained from the scanner device12, to the charged photosensitive drum22. Further, the exposure scanning head24applies light, which is modulated based on image data obtained from the outside via a network, to the charged photosensitive drum22. The exposure scanning head24forms an electrostatic latent image corresponding to the image data on the photosensitive drum22by exposing the photosensitive drum22. The developing devices26of the image forming stations20Y,20M,20C and20K contain two-component developers containing toners of Y, M, C, and K and carriers, respectively. The developing device26develops the electrostatic latent image by supplying the toner to the photosensitive drum22. The developing device26forms a toner image on the photosensitive drum22by developing the electrostatic latent image. The replenishment cartridges21Y,21M,21C and21K contain the toners of Y, M, C, and K replenished into the developing devices26, respectively, when the toners contained in the developing devices26are reduced. As the toner, for instance, erasable toner may be used, or inerasable toner may be used. The erasable toner is, for instance, color erasable toner.

The color erasable toner is toner which a color can be erased, for instance, by heating to a given color erasable temperature or more. The color erasable toner contains color materials, for instance, a colorable compound, a developer, and a decolorant. If a toner image formed using the color erasable toner is heated to the given color erasable temperature or more, the colorable compound and the developer in the color erasable toner are separated, and the toner image is decolored.

The MFP10has a backup roller18a, a driven roller18b, and tension rollers19. The backup roller18a, the driven roller18band the tension rollers19support the intermediate transfer belt18. The MFP10has multiple primary transfer rollers28and a secondary transfer roller30. The primary transfer rollers28are disposed at positions (primary transfer positions) opposite to the photosensitive drums22of the image forming stations20Y,20M,20C and20K, respectively. The primary transfer rollers28transfer toner images of Y, M, C and K from the photosensitive drums22to the intermediate transfer belt18at the respective primary transfer positions. When the MFP10performs color printing, the primary transfer rollers28sequentially superpose the toner images of Y, M, C and K, transferring them to the intermediate transfer belt18. The intermediate transfer belt18carries and rotates the toner images transferred from the photosensitive drums22, thereby conveying the toner images to the secondary transfer roller30. The secondary transfer roller30is disposed at a position (secondary transfer position) opposite to the backup roller18avia the intermediate transfer belt18. The secondary transfer roller30transfers the toner images carried on the intermediate transfer belt18to a recording medium, for instance a sheet P, conveyed to the secondary transfer position.

The MFP10has, inFIG. 1, a sheet feed unit16below the printer device11. The sheet feed unit16has a sheet feed cassette16aand a pickup roller16b. The sheet feed cassette16acontains the sheet P on which the images are printed. The sheet feed cassette16amay contain, as the sheet P, an unused sheet or a used sheet. The used sheet is, for instance, a sheet in which a previously printed image is decolored by a color erasing process. The pickup roller16btakes the sheets P from the sheet feed cassette16aone by one, and sends it to a conveyance path31to be described below. The printer device11has a manual sheet feed tray17and a pickup roller17a. The manual sheet feed tray17is mounted on a sidewall of a main body of the MFP10in an exposed state. The manual sheet feed tray17supports sheets P placed by a user. The pickup roller17atakes the sheets P supported by the manual sheet feed tray17one by one, and sends it to the conveyance path31to be described below.

The printer device11has a conveying unit for conveying the sheets P. The conveying unit includes the conveyance path31, resist rollers31a, and sheet ejection rollers33. The conveyance path31goes from the sheet feed unit16via the secondary transfer roller30and a fixing device32to be described below, and reaches the sheet ejection rollers33to be described below. The conveyance path31guides the sheet P sent out by the sheet feed unit16to the sheet ejection rollers33via the secondary transfer roller30and the fixing device32to be described below. The resist rollers31ainclude a pair of rollers disposed at an upstream position relative to the secondary transfer position along the conveyance path31and in a direction in which the sheet P is conveyed. The resist rollers31aconveys the sheet P to the secondary transfer position in accordance with conveyance timing of the toner images carried on the intermediate transfer belt18. The sheet ejection rollers33include a pair of rollers disposed at an end of the conveyance path31. The sheet ejection rollers33eject the sheet P on which the image is printed by fixing the toner images out of the MFP10. The conveying unit conveys the sheet P in cooperation with the intermediate transfer belt18, the resist rollers31a, and the fixing device32.

The scanner device12is provided at an upper portion of the main body of the MFP10inFIG. 1. The scanner device12obtains image data by optically scanning an image of a document. The MFP10may also obtain image data from the outside via a network. The printer device11of the MFP10forms the toner images on the sheet P, as described above, according to the image data. The MFP10has a sheet ejection tray10a. The sheet ejection tray10ais provided at a space portion formed between the printer device11and the scanner device12inFIG. 1. The sheet ejection tray10areceives the sheet P ejected by the sheet ejection rollers33, thereby containing the sheet P. The image forming apparatus is not limited to the MFP10by which the color image described above can be formed. For example, the number of image forming stations which the MFP10has is not limited. The image forming apparatus may be the MFP by which a monochromatic image can be formed. Further, the image forming apparatus may not be the MFP. For example, the image forming apparatus may be an apparatus having a printing function only. Further, the image forming apparatus may be configured to directly transfer the toner image from a photoreceptor to the sheet. Furthermore, the image forming apparatus may have multiple printer devices.

Hereinafter, the fixing device32will be described with reference toFIGS. 1 and 2. As illustrated inFIG. 1, the fixing device32is provided at a downstream position relative to the secondary transfer position along the conveyance path31and in the direction in which the sheet P is conveyed.FIG. 2is a cross-sectional view illustrating major parts of the fixing device32. As illustrated inFIG. 2, the fixing device32has a fixing member36and a heating unit46. The heating unit46heats the fixing member36. The fixing member36includes, for instance, a fixing belt37and a pressure roller38. The fixing belt37and the pressure roller38come into contact with each other, forming a nip40therebetween. The fixing member36clamps the sheet P in the nip40, and conveying the sheet P. While conveying the sheet P, the fixing member36heats and pressurizes the toner images of the sheet P, thereby fixing the toner images to the sheet P.

The fixing belt37has, for instance, a rubber layer deposited with nickel (Ni) and a fluorine tube covering a surface of the rubber layer. The fixing member36further includes a fixing roller37aand a heating roller37b. The fixing belt37is bridged between the fixing roller37aand the heating roller37b. The fixing roller37ais opposite to the pressure roller38via the fixing belt37a. The heating roller37band the pressure roller38are rollers having, for instance, a hollow structure. The heating unit46has a first heater lamp46aand a second heater lamp46bthat act as heating sources heating the fixing member36. The first heater lamp46ais provided in a hollow interior of the heating roller46a. The second heater lamp46bis provided in a hollow interior of the pressure roller38. The fixing device32further includes a peeling claw39provided around the pressure roller38.

The fixing device32further includes a first thermistor47and a first thermostat48. The first thermistor47and the first thermostat48are provided around the fixing belt37. The first thermistor47detects a temperature of the fixing belt37. The first thermostat48functions as a safeguard of the fixing belt37. The fixing device32further includes a second thermistor50and a second thermostat51. The second thermistor50and the second thermostat51are provided around the pressure roller38. The second thermistor50detects a temperature of the pressure roller38. The second thermostat51functions as a safeguard of the pressure roller38. The fixing device32rotates, for instance, the pressure roller38in a direction of an arrow q, and causes the fixing belt37to be rotated in a direction of an arrow r. The fixing device32may rotate the fixing belt37and the pressure roller38by respective separate drives.

The fixing device32is not limited to the aforementioned structure. For example, the fixing belt or the pressure roller that is the fixing member may be heated using an induction heating (IH) coil. Further, the fixing member36may be made up of a fixing roller and a pressure belt.

The CPU100controls a temperature of the fixing member36according to various control temperatures that are predetermined fixing temperature conditions. Specifically, the CPU100determines whether or not the fixing member36reaches the control temperature from a first result detected by the first thermistor47and a second result detected by the second thermistor48. The CPU100controls a heating operation of the heating unit46based on the determined result. To be specific, the CPU100has on/off control over the heated first or second heater lamp46aor46bof the heating unit46. When determining that the temperature of the fixing member36reaches the control temperature, the CPU100has on/off control over the heating unit46, thereby holding a surface temperature of the fixing member36at a given temperature.

Hereinafter, a control system60of the MFP10based on ready temperature control of the fixing device32will be described with reference toFIG. 3.FIG. 3is a block diagram illustrating the control system60based on the control of the fixing device32. As illustrated inFIG. 3, the control system60has the CPU100that is a control unit, and a read only memory (ROM)101and a random access memory (RAM)102that are storage units. The CPU100controls the entirety of the MFP10. The CPU100is connected to the first thermistor47, the second thermistor50, the control panel13, the first heater lamp46a, and the second heater lamp46b. The control panel13has a display unit and control buttons. The control panel13is an input unit by which job information of a user is input to the MFP10by receiving an operation of the user. The CPU100controls the control panel13, the first heater lamp46a, and the second heater lamp46b. The CPU100is further connected to an external device104such as a personal computer (PC) via an external interface103. The external interface103is an input unit by which the job information of the user is input from the external device104to the MFP10.

The ROM101stores a control program managing a basic operation for an image forming process, and control data. The ROM101stores, as the control data, the control temperature of the fixing member36. The control temperature includes a fixing reference temperature, a fixing lower limit temperature, and a ready temperature. The fixing reference temperature and the fixing lower limit temperature are temperatures of the fixing member36when the toner images are fixed to the sheet. The ready temperature is a temperature of the fixing member36when the MFP10is in a ready state. In other words, the ready temperature is a target temperature of the fixing member36when the MFP10returns from the sleep state to the ready state. The ROM101has a table101ato store the ready temperature. The RAM102stores control parameters, the number of printing sheets, a printing time, and the like.

Hereinafter, the conditions for the ready temperature of the fixing member36which is previously stored in the table101aof the ROM101will be described with reference toFIGS. 4 and 5.FIG. 4is a view illustrating storage contents of the fixing reference temperature and the fixing lower limit temperature of the fixing device32(fixing member36) which the ROM101stores. The ROM101stores the fixing reference temperature and the fixing lower limit temperature, which correspond to job conditions included in the job information of the user.FIG. 5is a view illustrating storage contents of the ready temperature which the table101aof the ROM101stores when the fixing reference temperature and the fixing lower limit temperature are the temperatures as illustrated inFIG. 4. The table101astores the ready temperature corresponding to the job conditions included in the job information of the user.

To be specific, as illustrated inFIG. 4, the ROM101uses parameters of the job conditions as a toner mode, and stores the fixing reference temperature and the fixing lower limit temperature that correspond to the parameters. The toner mode is a type of toner to be used. The toner mode includes a color mode and a monochrome mode. When the type of toner to be used is color toner, the toner mode is the color mode. When the type of toner to be used is monochromatic toner, the toner mode is the monochrome mode. The fixing reference temperature is a temperature having a margin such that poor fixing does not occur even when the MFP10continuously prints the maximum number of sheets. The fixing lower limit temperature is a temperature that does not cause poor fixing if the number of printing sheets is one. As illustrated inFIG. 4, the ROM101stores a temperature value of 160° C. as the fixing reference temperature when the toner mode is the color mode. Further, the ROM101stores a temperature value of 150° C. as the fixing lower limit temperature when the toner mode is the color mode. Thus, when the MFP10fixes the toner images made of, for instance, the color toner, the CPU100controls the temperature of the fixing member36using the fixing reference temperature as 160° C. and using the fixing lower limit temperature as 150° C. Further, the ROM101stores a temperature value of 140° C. as the fixing reference temperature when the toner mode is the monochrome mode. Further, the ROM101stores a temperature value of 130° C. as the fixing lower limit temperature when the toner mode is the monochrome mode. Thus, when the MFP10fixes the toner images made of, for instance, the monochromatic toner, the CPU100controls the temperature of the fixing member36using the fixing reference temperature as 140° C. and using the fixing lower limit temperature as 130° C.

The table101aof the ROM101uses the parameters of the job conditions as the number of printing sheets and the toner mode, and stores the ready temperature conditions corresponding to these parameters. The ready temperature conditions include multiple ready temperatures. Specifically, as illustrated inFIG. 5, the table101astores, for instance, a temperature value of 150° C. as the ready temperature when the toner mode is the color mode and when the number of printing sheets is one. The table101astores, for instance, a temperature value of 152° C. as the ready temperature when the toner mode is the color mode and when the number of printing sheets is not less than two and not more than five. The table101astores, for instance, a temperature value of 155° C. as the ready temperature when the toner mode is the color mode and when the number of printing sheets is not less than six and not more than ten. The table101astores, for instance, a temperature value of 160° C. as the ready temperature when the toner mode is the color mode and when the number of printing sheets is not less than eleven.

Further, as illustrated inFIG. 5, the table101astores, for instance, a temperature value of 130° C. as the ready temperature when the toner mode is the monochrome mode and when the number of printing sheets is one. The table101astores, for instance, a temperature value of 132° C. as the ready temperature when the toner mode is the monochrome mode and when the number of printing sheets is not less than two and not more than five. The table101astores, for instance, a temperature value of 135° C. as the ready temperature when the toner mode is the monochrome mode and when the number of printing sheets is not less than six and not more than ten. The table101astores, for instance, a temperature value of 140° C. as the ready temperature when the toner mode is the monochrome mode and when the number of printing sheets is not less than eleven.

The MFP10returns from the sleep state to the ready state based on the ready temperature corresponding to printing job information input by a user among the ready temperatures stored in the table101a. Accordingly, when the MFP10returns to the ready state and conducts print, even the final sheet P can be printed without occurrence of the poor fixing.

When the control panel13receives the job information that is input by a user and is associated with the printing during a period of the sleep state, the MFP10returns from the sleep state to the ready state. Further, when the external device104connected to the MFP10receives the job information that is input by a user and is associated with the printing during a period of the sleep state, the MFP10returns from the sleep state to the ready state. Hereinafter, the process of the MFP10returning from the sleep state to the ready state when the MFP10initiates the printing in response to the user's input of the job information associated with the printing from the control panel13or the external device during a period for which the MFP10is in the sleep state will be described with reference toFIG. 6.FIG. 6is a flow chart illustrating the process of returning from the sleep state to the ready state in the MFP10. As illustrated inFIG. 6, for example, when the control panel13receives input of the job information from a user, the CPU100determines from the job information whether a toner mode is a color mode or a monochrome mode in ACT120. When the CPU100determines that the print mode is the color mode, the controlling process of the CPU100proceeds to ACT121. When the CPU100determines that the print mode is the monochrome mode, the controlling process of the CPU100proceeds to ACT122.

In ACT121, the CPU100determines from the job information whether or not the number of printing sheets is equal to or more than two in the color mode. When the CPU100determines that the number of printing sheets is not equal to or more than two (when the number of printing sheets is one), the controlling process of the CPU100proceeds to ACT123. In ACT123, the CPU100refers to the storage contents of the table101aillustrated inFIG. 5, thereby setting the ready temperature to 150° C. in a ready state when causing the MFP10to return from a sleep state to the ready state. In ACT121, when the CPU100determines that the number of printing sheets is equal to or more than two (when the number of printing sheets is multiple), the controlling process of the CPU100proceeds to ACT124. In ACT124, the CPU100refers to the storage contents of the table101aillustrated inFIG. 5, and selects a temperature corresponding to the number of printing sheets when the toner mode is the color mode. In ACT126, depending on the selected result, the CPU100sets the ready temperature in the ready state when causing the MFP10to return from the sleep state to the ready state to the temperature corresponding to the number of printing sheets when the toner mode is the color mode.

On the other hand, in ACT122, the CPU100determines from the job information whether or not the number of printing sheets is equal to or more than two in a monochrome mode. In ACT122, when the CPU100determines that the number of printing sheets is not equal to or more than two (when the number of printing sheets is one), the controlling process of the CPU100proceeds to ACT127. In ACT127, the CPU100refers to the storage contents of the table101aillustrated inFIG. 5, thereby setting the ready temperature when causing the MFP10to return from the sleep state to the ready state to 130° C. In ACT122, when the CPU100determines that the number of printing sheets is equal to or more than two (when the number of printing sheets is multiple), the controlling process of the CPU100proceeds to ACT128. In ACT128, the CPU100refers to the storage contents of the table101aillustrated inFIG. 5, and selects a temperature corresponding to the number of printing sheets when the toner mode is the monochrome mode. In ACT130, depending on the selected result, the CPU100sets the ready temperature when causing the MFP10to return from the sleep state to the ready state to the temperature corresponding to the number of printing sheets when the toner mode is the monochrome mode.

In ACT123, ACT126, ACT127or ACT130, if the CPU100sets the ready temperature when causing the MFP10to return from the sleep state to the ready state, the controlling process of the CPU100proceeds to ACT131. In ACT131, the CPU100determines from the results of the detection of the first and second thermistors47and48whether or not the temperature of the fixing member36is equal to or less than the ready temperature. In ACT131, when the CPU100determines that the temperature of the fixing member36is equal to or less than the ready temperature, the controlling process of the CPU100proceeds to ACT132. In ACT132, the CPU100warms up the MFP10. Specifically, the CPU100controls the first and second heater lamps46aand46bsuch that the temperature of the fixing member36is higher than the ready temperature. The CPU100repeats the processes of ACT131and ACT132until the temperature of the fixing member36is higher than the ready temperature.

In ACT131, when the CPU100determines that the temperature of the fixing member36is not equal to or less than the ready temperature (when the temperature of the fixing member36is higher than the ready temperature), the controlling process of the CPU100proceeds to ACT133. In ACT133, the CPU100causes the MFP10to return from the sleep state to the ready state. In ACT134, the CPU100causes the MFP10of the ready state to initiate the printing according to the job information.

As described above, when returning from the sleep state to the ready state, the MFP10changes the ready temperature according to the job information input by the user. Thus, when a load on the fixing device32is small such as when the number of printing sheets is small, the MFP10can reduce the time required for a warmup (W/U). Hereinafter, the warmup time when the MFP10returns from the sleep state to the ready state will be described with reference toFIGS. 7 and 8.

FIG. 7Ais a graph illustrating a warmup time when the MFP10returns from a sleep state to a ready state in order to print one sheet in color when a temperature of the fixing member36of the fixing device32during the sleep state is 117° C. The vertical axis of the graph ofFIG. 7Aindicates the temperature of the fixing member36, and the horizontal axis indicates the operation state of the MFP10. For example, a ready temperature when the toner mode is the color mode and when the MFP10receives job information about one printing sheet is 150° C. as illustrated inFIG. 5. Thus, the CPU100sets the ready temperature to 150° C. according to the job information. When the temperature of the fixing member36rises from 117° C. to 150° C. by performing a warmup, the MFP10returns from the sleep state to the ready state. As illustrated inFIG. 7A, when the temperature of the fixing member36during the sleep state is 117° C., if the MFP10receives input of the job information from a user (job reception), the MFP10becomes the ready state after a warmup time α1. In contrast, when 160° C. (seeFIG. 4) that is a fixing reference temperature, for instance, in the case of the color mode is set as the ready temperature, the warmup time requires β1(>α1) as illustrated inFIG. 7A. Thus, the MFP10sets the ready temperature to 150° C. according to the job information, and can thereby reduce the warmup time.

FIG. 7Bis a graph illustrating a warmup time when the MFP10returns from a sleep state to a ready state in order to print one sheet in color when a temperature of the fixing member36of the fixing device32during the sleep state is 136° C. The vertical axis of the graph ofFIG. 7Bindicates the temperature of the fixing member36, and the horizontal axis indicates the operation state of the MFP10. For example, a ready temperature when the toner mode is the color mode and when the MFP10receives job information about one printing sheet is 150° C. (seeFIG. 5). Thus, the CPU100sets the ready temperature to 150° C. according to the job information. When the temperature of the fixing member36rises from 136° C. to 150° C. by performing a warmup, the MFP10returns from the sleep state to the ready state. As illustrated inFIG. 7B, when the temperature of the fixing member36during the sleep state is 136° C., if the MFP10receives input of the job information from a user, the MFP10becomes the ready state after a warmup time α2. In contrast, when 160° C. (seeFIG. 4) that is a fixing reference temperature, for instance, in the case of the color mode is set as the ready temperature, the warmup time requires β2(>α2) as illustrated inFIG. 7B. Thus, the MFP10sets the ready temperature to 150° C. according to the job information, and can thereby reduce the warmup time.

FIG. 8Ais a graph illustrating a warmup time when the MFP10returns from a sleep state to a ready state in order to print one sheet in monochrome when a temperature of the fixing member36of the fixing device32during the sleep state is 117° C. The vertical axis of the graph ofFIG. 8Aindicates the temperature of the fixing member36, and the horizontal axis indicates the operation state of the MFP10. For example, a ready temperature when the toner mode is the monochrome mode and when the MFP10receives job information about one printing sheet is 130° C. as illustrated inFIG. 5. Thus, the CPU100sets the ready temperature to 130° C. according to the job information. When the temperature of the fixing member36rises from 117° C. to 130° C. by performing a warmup, the MFP10returns from the sleep state to the ready state. As illustrated inFIG. 8A, when the temperature of the fixing member36during the sleep state is 117° C., if the MFP10receives input of the job information from a user, the MFP10becomes the ready state after a warmup time α3. In contrast, when 160° C. (seeFIG. 4) that is a fixing reference temperature, for instance, in the case of the color mode is set as the ready temperature, the warmup time requires β3(>α3) as illustrated inFIG. 8A. Thus, the MFP10sets the ready temperature to 130° C. according to the job information, and can thereby reduce the warmup time.

FIG. 8Bis a graph illustrating a warmup time when the MFP10returns from a sleep state to a ready state in order to print one sheet in monochrome when a temperature of the fixing member36of the fixing device32during the sleep state is 136° C. The vertical axis of the graph ofFIG. 8Bindicates the temperature of the fixing member36, and the horizontal axis indicates the operation state of the MFP10. For example, a ready temperature when the toner mode is the monochrome mode and when the MFP10receives job information about one printing sheet is 130° C. as illustrated inFIG. 5. Thus, the CPU100sets the ready temperature to 130° C. according to the job information. Since the temperature of the fixing member36is 136° C., the MFP10need not perform a warmup, and immediately returns from the sleep state to the ready state. In contrast, when 160° C. that is a fixing reference temperature, for instance, in the case of the color mode is set as the ready temperature, the warmup time requires β4. Thus, the MFP10sets the ready temperature to 130° C. according to the job information, and can thereby reduce the warmup time.

Even when the MFP10receives the job information in which the number of printing sheets is equal to or less than ten, the ready temperature when the MFP10returns from the sleep state to the ready state is set to be lower than the fixing reference temperature like the foregoing. Thus, the MFP10can reduce the warmup time.

According to the first embodiment, the MFP10stores the multiple ready temperatures, which correspond to the job conditions using the number of printing sheets and the toner mode as the parameters, in the table101a. The CPU100selects and sets the ready temperature when MFP10returns from the sleep state to the ready state from the table101aaccording to the job conditions included in the printing job information input by the user. The MFP10returns from the sleep state to the ready state at the ready temperature corresponding to the job information of the user. Thus, a time required for the warmup in returning from the sleep state to the ready state can be reduced. Further, according to the first embodiment, due to the reduction of the warmup time, it is possible to improve operability of the MFP10and to save consumption energy.

Hereinafter, an MFP10according to a second embodiment will be described with reference toFIGS. 9 and 10. The second embodiment and the first embodiment differ in the parameters of the job conditions. The parameters of the job conditions in the MFP10according to the second embodiment are, for instance, a sheet type and a toner mode. The MFP10stores multiple ready temperatures corresponding to the parameters in a table101a. In the MFP10according to the second embodiment, the same components as described in the first embodiment above are given the same reference numerals, and detailed description thereof will be omitted.

FIG. 9is a view illustrating storage contents of ready temperatures which the table101aof a ROM101stores. The table101astores the ready temperatures corresponding to job conditions included in job information of a user. The table101auses the parameters of the job conditions included in the job information of the user as the sheet type and the toner mode, and stores ready temperature conditions corresponding to these parameters. The ready temperature conditions include multiple ready temperatures. To be specific, as illustrated inFIG. 9, the table101astores, for instance, a temperature value of 150° C. as the ready temperature condition when the toner mode is a color mode and the type of the sheet P is a plain sheet having a size of A4. The table101astores, for instance, a temperature value of 152° C. as the ready temperature condition when the toner mode is a color mode and the type of the sheet P is a plain sheet having a size of A3. The table101astores, for instance, a temperature value of 155° C. as the ready temperature condition when the toner mode is a color mode and the type of the sheet P is a thick sheet having the A4 size. The table101astores, for instance, a temperature value of 160° C. as the ready temperature condition when the toner mode is a color mode and the type of the sheet P is a thick sheet having the A3 size.

Further, as illustrated inFIG. 9, the table101astores, for instance, a temperature value of 130° C. as the ready temperature condition when the toner mode is a monochrome mode and the type of the sheet P is a plain sheet having the A4 size. The table101astores, for instance, a temperature value of 132° C. as the ready temperature condition when the toner mode is a monochrome mode and the type of the sheet P is a plain sheet having the A3 size. The table101astores, for instance, a temperature value of 135° C. as the ready temperature condition when the toner mode is a monochrome mode and the type of the sheet P is a thick sheet having the A4 size. The table101astores, for instance, a temperature value of 140° C. as the ready temperature condition when the toner mode is a monochrome mode and the type of the sheet P is a thick sheet having the A3 size.

The MFP10returns from the sleep state to the ready state when a control panel13receives the job information that is input by a user and is associated with the printing during a period of the sleep state. Further, the MFP10returns from the sleep state to the ready state when an external device104connected to the MFP10receives the job information that is input by a user and is associated with the printing during a period of the sleep state. Hereinafter, the process of the MFP10returning from the sleep state to the ready state when the MFP10initiates the printing in response to the user's input of the job information associated with the printing from the control panel13or the external device during a period during which the MFP10is in the sleep state will be described with reference toFIG. 10.FIG. 10is a flow chart illustrating the process of returning from the sleep state in the MFP10. As illustrated inFIG. 10, for example, when the control panel13receives input of the job information from a user during a period during which the MFP10is in the sleep state, the CPU100determines from the job information whether a toner mode is a color mode or a monochrome mode in ACT120. When the CPU100determines that the toner mode is the color mode, the controlling process of the CPU100proceeds to ACT141. When the CPU100determines that the print mode is the monochrome mode, the controlling process of the CPU100proceeds to ACT146.

In ACT141, the CPU100determines from the job information whether or not a type of a sheet P is a plain sheet having a size of A4 in a color mode. When the CPU100determines that the type of the sheet P is the plain sheet having the A4 size, the controlling process of the CPU100proceeds to ACT142. In ACT142, the CPU100refers to the storage contents of the table101aillustrated inFIG. 9, thereby setting a ready temperature in the ready state when causing the MFP10to return from the sleep state to the ready state to 150° C. In ACT141, when the CPU100determines that the type of the sheet P is not the plain sheet having the A4 size, the controlling process of the CPU100proceeds to ACT143. In ACT143, the CPU100refers to the storage contents of the table101aillustrated inFIG. 9, and selects a temperature corresponding to the type of the sheet P when the toner mode is the color mode. In ACT144, depending on the selected result, the CPU100sets the ready temperature in the ready state when causing the MFP10to return from the sleep state to the ready state to the temperature corresponding to the type of the sheet P when the toner mode is the color mode.

On the other hand, in ACT146, the CPU100determines from the job information whether or not the type of the sheet P is a plain sheet having a size of A4 in a monochrome mode. In ACT146, when the CPU100determines that the type of the sheet P is the plain sheet having the A4 size, the controlling process of the CPU100proceeds to ACT147. In ACT147, the CPU100refers to the storage contents of the table101aillustrated inFIG. 9, and sets the ready temperature in the ready state when causing the MFP10to return from the sleep state to the ready state to 130° C. In ACT146, when the CPU100determines that the type of the sheet P is not the plain sheet having the A4 size, the controlling process of the CPU100proceeds to ACT148. In ACT148, the CPU100refers to the storage contents of the table101aillustrated inFIG. 9, and selects a temperature corresponding to the type of the sheet P when the toner mode is the monochrome mode. In ACT149, depending on the selected result, the CPU100sets the ready temperature in the ready state when causing the MFP10to return from the sleep state to the ready state to the temperature corresponding to the type of the sheet P when the toner mode is the monochrome mode.

In ACT142, ACT144, ACT147or ACT149, the CPU100sets the ready temperature when causing the MFP10to return from the sleep state to the ready state, and then performs processes of ACT131to ACT134as in the first embodiment. The CPU100performs ACT131to ACT134, thereby initiating the printing according to the job information input by the user (ACT134).

According to the second embodiment, the MFP10stores the ready temperature conditions, which correspond to the job conditions using the toner mode and the sheet type as the parameters, in the table101a. The CPU100selects and sets the ready temperature when the MFP10returns from the sleep state to the ready state from the table101aaccording to the printing job information input by the user. Like the first embodiment, the MFP10returns from the sleep state to the ready state at the ready temperature corresponding to the job information of the user. Accordingly, it is possible to reduce the time required for the warmup in returning from the sleep state to the ready state. Further, according to the second embodiment, as in the first embodiment, due to the reduction of the warmup time, it is possible to improve the operability of the MFP10and to save the consumption energy.

According to at least one of the embodiments described above, it is possible to reduce the time required for the warmup when the image forming apparatus is caused to return from the sleep state to the ready state. Further, according to the embodiments, it is possible to improve the operability of the image forming apparatus and to save the consumption energy.

The aforementioned embodiments are not limited to the aforementioned configurations, and may be variously modified. For example, the parameters of the job conditions may be things other than the toner mode, the number of printing sheets, and the sheet type. Further, the fixing reference temperature or the fixing lower limit temperature of the fixing member is optional depending on a type of the image forming apparatus.