JP5741322B2 - Image forming apparatus and image forming method - Google Patents

Description

  The present invention relates to an image forming apparatus that has a low-speed printing mode and a high-speed printing mode, and switches to the high-speed printing mode in as short a time as possible when a change to the high-speed printing mode is designated during execution of the low-speed printing mode.

  Conventionally, there is an electrophotographic image forming apparatus. In this image forming apparatus, generally, a photosensitive drum is uniformly charged and initialized, an electrostatic latent image is formed on the photosensitive drum by optical writing, and the electrostatic latent image is converted into a toner image. Is directly or indirectly transferred onto a transfer material such as paper and fixed by a fixing device.

  By the way, in recent years, normal speed printing may be used when normal printing work is not urgent. However, when a large amount of printing is required during busy periods or when there is urgent printing, for example, a high-speed switch provided in advance in the apparatus There is a strong demand for high-speed printing that enables high-speed printing by pressing.

  In order to cope with such a demand, an image forming apparatus having a plurality of print modes, that is, a normal-speed print mode and a higher-speed print mode has been proposed. (For example, refer to Patent Document 1.)

  In addition, the temperature at the start of printing is predicted in advance for each print, and the print speed is reset for each print in accordance with the temperature, and the high-speed performance at the time of continuous printing and the completion of the first print There have been proposed printers and control methods thereof that achieve both time reduction. (For example, see Patent Document 2.)

  By the way, in an electrophotographic image forming apparatus, when a toner image transferred onto a sheet is fixed on the sheet with heat and pressure by a fixing device, the temperature applied to the sheet has an appropriate temperature range per time.

  When the temperature exceeds the upper limit value of the appropriate temperature range, a troublesome phenomenon called offset occurs in which the excessively melted toner adheres to the heat roller side of the fixing device. This is called hot offset.

  Further, when the temperature falls below the lower limit value of the appropriate temperature range, a trouble phenomenon called offset occurs in which a part of the toner that is not sufficiently fixed on the sheet adheres to the heat roller side. This is called a cold offset.

JP 2002-311749 A JP 2000-137407 A

  However, in any case, in Patent Documents 1 and 2, in the case where there are two printing modes of normal speed low speed printing and special time high speed printing, the user switches the high speed switch to change from low speed printing to high speed printing. Will be pressed.

  On the printing device side, from the stage when the high-speed switch is pressed, it is necessary to raise the fixing temperature in order to stop printing and cope with the high-speed conveyance of the paper, and wait for the execution of printing until the fixing temperature rises to a predetermined temperature. become.

  Conversely, from the stage when the low speed switch is pressed to change from high speed printing to low speed printing, it is necessary for the printing apparatus to stop printing and lower the fixing temperature, and wait until the fixing temperature falls to a predetermined temperature. It will be.

  In either case of changing from low speed to high speed or changing from high speed to low speed, the printing operation is stopped until the fixing temperature reaches a predetermined temperature. For this reason, the user has to wait while annoying during the waiting time.

  Although it is convenient to have two print modes, the printing operation stops when the print mode is switched and the user is kept waiting, especially when the print mode is switched from low speed to high speed. It will not function effectively.

  The present invention solves the above-described conventional problems, and has a low-speed printing mode and a high-speed printing mode. When a change is designated to the high-speed printing mode during the low-speed printing mode, the high-speed printing mode is set in as short a time as possible. An object is to provide an image forming apparatus and an image forming method that are switched.

In order to solve the above-described problem, the image forming apparatus according to the present invention includes a second printing mode that prints at a higher speed than an upper limit allowable temperature of the first fixing temperature corresponding to the first printing mode that prints at a low speed. A fixing device in which a lower limit allowable temperature of the fixing temperature is set high; the first fixing temperature is set as an A mode setting temperature; the second fixing temperature is set as a B mode setting temperature; and the upper limit allowable of the first fixing temperature is set Corresponding to an intermediate printing mode in which the temperature intermediate between the temperature and the lower limit allowable temperature of the second fixing temperature is temporarily printed at a medium speed between the printing speed in the first printing mode and the printing speed in the second printing mode. When the mode change is designated to the second print mode during printing in the first print mode, the mode change is switched from the A mode set temperature to the B mode set temperature. The time from when the mode change is designated until the temperature changing based on the set temperature setting reaches the upper limit allowable temperature of the first fixing temperature and the electrostatic latent image formed on the photoconductor The time from the primary transfer to the fixing device is derived , or the time from when the mode change is designated until the lower limit allowable temperature of the second fixing temperature is reached and the static formed on the photosensitive member. Based on the result obtained by deriving the time from the primary transfer of the electrostatic latent image to the fixing device and comparing the lengths of these times, the intermediate print mode is printed or the second print mode is selected. possess a controller for determining in whether to print, and the control device, the during the second waiting the printing of the print mode, the second printing mode than the time for printing in the above intermediate print mode Print formed image When the time when the temperature reaches the lower limit allowable temperature of the second fixing temperature is earlier when the body reaches the fixing device, printing in the second printing mode is performed, and in the intermediate printing mode The time for printing is earlier than the time when the changing temperature reaches the lower limit allowable temperature of the second fixing temperature when the printing medium on which the image in the second printing mode has reached the fixing device. In this case, the intermediate printing mode is configured to be executed .
Further, the image forming method of the present invention has a lower limit allowable temperature of the second fixing temperature corresponding to the second printing mode for printing at a higher speed than the upper limit allowable temperature of the first fixing temperature corresponding to the first printing mode for printing at low speed. An image forming method of an image forming apparatus having a fixing device set to be high, wherein the first fixing temperature is set as an A mode set temperature, the second fixing temperature is set as a B mode set temperature, and the first fixing temperature is set. Intermediate printing for temporarily printing an intermediate temperature between the upper limit allowable temperature of the first fixing temperature and the lower limit allowable temperature of the second fixing temperature at a medium speed between the printing speed in the first printing mode and the printing speed in the second printing mode. An intermediate mode set temperature corresponding to the mode is set, and when mode change is designated in the second print mode during printing in the first print mode, the mode change from the A mode set temperature to the B mode is performed by the mode change. The time required for the temperature changing based on the temperature setting switched to the constant temperature to reach the upper limit allowable temperature of the first fixing temperature from the time when the mode change is designated and the static formed on the photosensitive member. The time from the primary transfer of the electrostatic latent image to the fixing device is derived , or the time from when the mode change is designated until the lower limit allowable temperature of the second fixing temperature is reached and the photosensitive member. The time until the formed electrostatic latent image is primarily transferred and arrives at the fixing device is derived, and while waiting for printing in the second printing mode, the time is longer than the time for printing in the intermediate printing mode. When the time when the changing temperature reaches the lower limit allowable temperature of the second fixing temperature when the print medium on which the image of the second printing mode is formed reaches the fixing device is earlier, the second printing mode. Printing When the print medium on which the image in the second print mode is formed reaches the fixing device, the time during which the print is performed in the intermediate print mode while waiting for printing in the second print mode is executed. When the temperature being reached is earlier than the time required to reach the lower limit allowable temperature of the second fixing temperature, printing in the intermediate printing mode is performed .

  The present invention can provide an image forming apparatus that has a low-speed printing mode and a high-speed printing mode, and switches to the high-speed printing mode in as short a time as possible when the high-speed printing mode is designated during the low-speed printing mode.

1 is a cross-sectional view illustrating an internal configuration of a full-color image forming apparatus (printer) having a plurality of printing speed modes according to Embodiment 1 of the present invention. 1 is a circuit block diagram including a control device for a printer having a plurality of printing speed modes according to Embodiment 1. FIG. FIG. 5 is a diagram illustrating a relationship between a first fixing temperature in a first printing mode, a second fixing temperature in a second printing mode, and an intermediate fixing temperature in an intermediate printing mode. 10 is a flowchart showing an operation of processing when the print mode is changed from the first print mode to the second print mode to the high-speed print mode.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view illustrating an internal configuration of a full-color image forming apparatus (hereinafter simply referred to as a printer) having a plurality of printing speed modes according to the first embodiment.

  A printer 1 shown in FIG. 1 is an electrophotographic secondary transfer tandem color image forming apparatus, and includes an image forming unit 2, a transfer belt unit 3, a paper feeding unit 4, and a fixing device 5. Yes.

  The image forming unit 2 is arranged near the upper running surface of the transfer belt 6 of the transfer belt unit 3 and arranged side by side in a multistage manner. The four images shown from the right to the left in FIG. It is composed of forming units 7 (7y, 7m, 7c, 7k).

  Of the four image forming units 7, three image forming units 7y, 7m and 7c on the upstream side (the right side in the figure) are yellow (Y), magenta (M), cyan (subtractive three primary colors), respectively. A monocolor image is formed with the color toner of C).

  The image forming unit 7k forms a monochrome image using black (K) toner mainly used for dark portions of characters and images. Each of the image forming units 7 has the same configuration except for the color of the toner for developing the image.

  Accordingly, the configuration of the image forming unit 7k for black (K) toner will be described below as an example. The image forming unit 7 includes a photosensitive drum 8 at the bottom. The photosensitive drum 8 has a peripheral surface made of, for example, an organic photoconductive material.

  Hereinafter, the photosensitive drums 8 of the image forming units 7y, 7m, 7c, and 7k may be referred to as photosensitive drums 8y, 8m, 8c, and 8k as needed.

  A cleaner 9, a charging roller 11, an optical writing head 12, and a developing device 13 are disposed in contact with or around the periphery of the photosensitive drum 8. The primary transfer roller 14 is in pressure contact with the lower peripheral surface of the photosensitive drum 8 via the transfer belt 6.

  The primary transfer roller 14 is integrated with the transfer belt 6 together with the transfer belt unit 3. The transfer belt 6 is an endless belt extending in the shape of a flat loop in the left-right direction in the figure in the approximate center of the main body device, and is stretched around the driving roller 15 and the driven roller 16.

  The drive roller 15 and the driven roller 16 are also integrated members integrated with the transfer belt unit 3, and the drive roller 15 is driven by being engaged with a drive system of the main body device. The transfer belt 6 is driven by the drive roller 15 to circulate in the counterclockwise direction indicated by arrows a and b in the figure.

  A secondary transfer roller 17 is pressed against the driven roller 16 via the transfer belt 6. The driven roller 16, the transfer belt 6 and the secondary transfer roller 17 form a secondary transfer portion here.

  The transfer belt 6 conveys the toner image transferred by superimposing four colors from the primary transfer roller 14 to the secondary transfer unit. In the secondary transfer portion, the primary transfer toner image on the transfer belt 6 is secondarily transferred onto the paper 18 that is fed from the paper feed portion 4 and conveyed to the secondary transfer portion.

  On the lower left side of the transfer belt 6, an electrical unit 20 is disposed along with the paper feed unit 4. A circuit board on which a control device composed of a plurality of electronic components is mounted is mounted on the electrical component 20.

  The paper feed unit 4 includes a paper feed cassette 19. In the vicinity of the paper feed opening (right side of the drawing) of the paper feed cassette 19, in addition to the paper take-out roller 21, although not particularly shown, a feed roller, a separating member, a standby transport roller pair, and the like are sequentially provided along the paper transport path. Has been placed.

  The secondary transfer portion described above is formed in the paper conveyance direction (vertical upward direction in the figure) of the standby conveyance roller pair. A fixing device 5 is disposed downstream (upward in the drawing) of the secondary transfer portion. The fixing device 5 includes a heating roller 22 and a pressure roller 23.

  The fixing device 5 applies heat and pressure corresponding to the conveyance speed of the paper 18 to the paper 18 that is transferred with the toner image transferred by the secondary transfer portion, conveyed as indicated by an arrow c, and carried into the fixing device 5. The toner image is fixed on the paper 18.

  The paper 18 on which the toner image is fixed on the paper surface is carried out of the fixing device 5 by a carry-out roller (not shown) as indicated by an arrow d, and is also formed on the upper surface of the main body device by a paper-discharge roller (not shown). The image is discharged on the paper discharge tray with the image side down.

  FIG. 2 is a circuit block diagram including a control device mounted on the electrical unit 20 of the printer 1 having a plurality of printing speed modes according to the first embodiment having the above-described configuration. As shown in FIG. 2, the circuit block has a central processing unit (CPU) 25 in the central circuit.

  An interface controller (I / F_CONT) 26 and a printer controller (PR_CONT) 27 are connected to the CPU 25 via a data bus. A printer printing unit 28 is connected to the PR_CONT 27.

  Also connected to the CPU 25 are a ROM (read only memory) 29, an EEPROM (electrically erasable programmable ROM) 31, an operation panel 32 of the main body operation unit, and a sensor unit 33 to which an output from a sensor arranged in each unit is input. Has been.

  A system program is stored in the ROM 29, and the CPU 25 controls each unit in accordance with the system program. Each unit performs a shared process based on control from the CPU 25.

  That is, the I / F_CONT 26 converts print data supplied from a host device such as a personal computer into bitmap data, and expands the converted bitmap data in the frame memory 34.

  In the frame memory 34, a storage area is set for each color of black (K), magenta (M), cyan (C), and yellow (Y). The image data of each color is developed in the corresponding storage area of the frame memory 34.

  The image data developed in the frame memory 34 is output to the PR_CONT 27 and further output from the PR_CONT 27 to the printer printing unit 28.

  The printer printing unit 28 is an engine unit, and under the control of the PR_CONT 27, drives the driving roller 15 of the intermediate transfer belt unit 3 shown in FIG. The drive output to 35 is controlled.

  Further, the printer printing unit 28 drives a conveyance mechanism including various components such as a sheet take-out roller 21, a feeding roller, a standby conveyance roller pair, a paper discharge roller, a photosensitive drum 8, and a heating roller 22 of the fixing device 5. The drive output to the transport mechanism drive unit 36 is controlled.

  Further, the printer printing unit 28 applies voltage to the process load of the image forming unit system such as the charging roller 11, the optical writing head 12, the primary transfer roller 14, and the secondary transfer roller 17, and generates heat from the heating roller 22 of the fixing device 5. The output of the applied power output unit 37 that applies a voltage to the source is controlled.

  The black (K), magenta (M), cyan (C), and yellow (Y) image data output from the PR_CONT 27 is supplied from the printer printing unit 28 to the corresponding optical writing head shown in FIG. 12 is supplied.

  The optical writing head 12 forms an optical latent image on the peripheral surface of the photosensitive drum 8 that is initialized and charged by the charging roller 11 based on the image data supplied from the printer printing unit 28. The developing device 13 converts the electrostatic latent image on the photosensitive drum 8 into a toner image (development).

  The toner image developed on the photoconductive drum 8 has a yellow (Y) toner image, a magenta (M) toner image, a cyan (C) toner image, and a black (K) toner image in this order from the upstream. The transfer roller 14 sequentially superimposes on the transfer belt 6 and performs primary transfer.

  As described above, the transfer belt 6 onto which the toner image is transferred with four colors superimposed conveys the transferred toner image to the secondary transfer portion. The secondary transfer unit secondarily transfers the toner image onto the paper 18 and sends it to the fixing device 5. The fixing device 5 fixes the toner image on the paper 18 by heat and pressure.

  In this image forming process, in this embodiment, the first printing mode for printing at a low speed at the first fixing temperature, the second printing mode for printing at a high speed at the second fixing temperature, and the first printing mode at an intermediate temperature. Three types of printing modes are used: an intermediate printing mode for printing at an intermediate speed of the printing speed of the second printing mode.

  As will be described in detail later, the intermediate printing mode is temporarily used when the fixing temperature increases from the first fixing temperature to the second fixing temperature when the printing mode is changed from the first printing mode to the second printing mode. Print mode.

  FIG. 3 is a diagram illustrating a relationship between the first fixing temperature in the first printing mode, the second fixing temperature in the second printing mode, and the intermediate fixing temperature in the intermediate printing mode. In the figure, the horizontal axis represents time, and the vertical axis represents the fixing temperature.

  In general, in order to change the processing speed of an image forming apparatus and have two or more printing speed modes, it is necessary to change processing conditions such as charging, exposure, development, and transfer, and print under conditions that match the processing speed. There is. Among these processing conditions, it takes time to change the fixing temperature.

  A temperature Ao indicated by a one-dot chain line in the lower left of FIG. 3 indicates an average value of the first fixing temperatures that are fixing temperatures corresponding to the first printing mode in which printing is performed at a low speed. A waveform α indicates a periodic temperature change based on a current applied to the heating roller 22 of the fixing device 5 in order to maintain the first fixing temperature.

  This temperature change varies. A temperature Ac indicated by a solid line above the temperature Ao is a variable upper limit allowable temperature. When the fixing temperature exceeds the temperature Ac, a hot offset occurs in which the toner that has been melted excessively adheres to the heat roller side of the fixing device.

  Further, a temperature Af indicated by a solid line below the temperature Ao is a lower limit allowable temperature that varies, and when the fixing temperature is lower than the temperature Af, a part of the toner that is insufficiently fixed on the sheet is heated by the heat roller. Cold offset sticking to the side occurs.

  The temperature range indicated by the double-pointed arrow A from the lower limit allowable temperature Af and the upper limit allowable temperature Ao at the fixing temperature in the first printing mode is defined as A region.

  In addition, a temperature Bo indicated by a one-dot chain line in the upper right of the figure indicates an average value of the second fixing temperature that is a fixing temperature corresponding to the second printing mode in which printing is performed at high speed. A waveform β indicates a periodic temperature change based on a current applied to the heating roller 22 of the fixing device 5 in order to maintain the second fixing temperature.

  This temperature change also varies. The temperature Bc is a variable upper limit allowable temperature, and hot offset occurs when the fixing temperature exceeds the temperature Bc. The temperature Bf is a lower limit allowable temperature with variation, and a cold offset occurs when the fixing temperature falls below the temperature Bf.

  Here, a temperature range indicated by a double-pointed arrow B from the lower limit allowable temperature Bf and the upper limit allowable temperature Bc in the fixing temperature of the second printing mode is defined as a B region. In the fixing device 5 of this example, the lower limit allowable temperature (Bf) in the B region is set to a temperature higher than the upper limit allowable temperature (temperature Ac) in the A region.

  Usually, unless it is in a special state, in the first printing mode, the fixing temperature rises and falls in a cycle indicated by a waveform α. Also in the second printing mode, the fixing temperature rises and falls in a cycle indicated by the waveform β.

  When the printing mode is changed from the first printing mode to the second printing mode, the temperature setting of the fixing device 5 is changed from the temperature Ao to the temperature Bo. Based on this change in temperature setting, the temperature of the fixing device 5 must increase by the temperature T from the lower end of the waveform α to the lower end of the waveform β.

  In the middle of the temperature T increase, there is an offset region between the temperature Ac, which is the upper limit allowable temperature of the first printing mode, and the temperature Bf, which is the lower limit allowable temperature of the second printing mode. .

  When the fixing temperature is changed after the paper being printed is discharged, the time required for the temperature change to increase by the temperature T is time t. The user of the printer 1 needs to wait for time t for the start of printing in the second printing mode in order to avoid printing in the offset area.

  Thus, in the section of the temperature range “B area-A area”, a hot offset occurs in the first printing mode and a cold offset occurs in the second printing mode, so the first printing mode changes to the second printing mode. When shifting, a waiting time is generated until the temperature exceeds the temperature range “B region-A region”.

  Thus, normally, when switching from the first printing mode for normal printing to the second printing mode for high-speed printing, it is necessary to wait until the fixing temperature is switched for high-speed printing. Here, the second print mode is a print mode for the user of the printer 1 to use the printer for urgent printing.

  If a high-speed printing mode called the second printing mode is provided for urgent printing in this way and a waiting time for stopping printing occurs when switching from normal printing to high-speed printing, a high-speed corner is required. The print mode may give the user unpleasant discomfort.

  However, in this example, in order not to generate this waiting time, the intermediate temperature M is set at the center of the section of the temperature range “B area-A area”, and the fixing is executed at a conveyance speed at which no offset occurs at the intermediate temperature M. An intermediate printing mode is provided to make use of the usefulness of having the second printing mode.

  FIG. 4 is a flowchart showing an operation of processing when the printing mode is changed from the first printing mode to the second printing mode in the printer 1 having the above-described configuration. This process is a process performed while controlling each unit by the CPU 25 shown in FIG.

  In FIG. 4, when the printing operation is started, first, the CPU 25 determines whether or not a high-speed printing (hereinafter referred to as second printing mode) switch on an operation panel (not shown) is input and is turned “ON”. Is determined (step S1).

  If the switch is not “ON” (No in S1), the CPU 25 waits for printing in the first printing mode (printing at a normal transport speed lower than the speed in the second printing mode) or prints. , It is monitored whether the switch of the second print mode is “ON”.

  Then, when the switch of the second printing mode is turned “ON” (Yes in S1), the CPU 25 sets the first fixing temperature that is the fixing temperature of the first printing mode up to that time to the fixing of the second printing mode. The temperature is switched to the second fixing temperature, which is a temperature (step S3).

  Based on the temperature switching instruction from the CPU 25, the applied power output unit 37 increases the temperature of the fixing device 5 from the first fixing temperature at the average temperature Ao to the second fixing temperature at the average temperature Bo. Switch the current applied to the heat source built in to a strong current.

  As a result, the current output from the applied power output unit 37 is changed from the low power of the waveform α for maintaining the first fixing temperature so far to the high power of the waveform β for maintaining the subsequent second fixing temperature. The temperature of the fixing device 5 corresponding to the temperature T shown in FIG.

  Here, the CPU 25 determines the time t1 until the temperature starting from the first fixing temperature of the waveform α reaches the upper limit allowable temperature temperature Ac in the A region as the thermistor temperature during the measurement of the immediately preceding fixing temperature. Calculation is made from a predetermined temperature rise characteristic of the fixing device 5 (step S4).

  Further, the CPU 25 calculates a time t2 until an image whose image formation has started before the switch “ON” of the second print mode reaches the fixing device 5 (step S5).

  Here, there are various cases where the image includes an image on the photosensitive drum 8, an image on the transfer belt 6, and an image on a sheet. Depending on the certain position, the time t2 at which the sheet on which the image is primarily transferred finally reaches the fixing device 5 varies.

  The time t2 is the longest when the electrostatic latent image exposed in the image forming unit 7y is on the photosensitive drum 8. These times t2 are calculated based on the encoders or the number of drive pulses of the drive source motors of the belt drive unit 35 and the transport mechanism drive unit 36.

  Then, the CPU 25 determines whether or not “time t1> time t2” (step S6). If “time t1> time t2” is determined in this determination (Yes in S6), it is earlier that the sheet on which the image is formed reaches the fixing device 5 before the temperature reaches the temperature Ac.

  Therefore, the CPU 25 stops the subsequent latent image formation on the photosensitive drum 8, and the fixing device 5 before the temperature reaches the temperature Ac, that is, the sheet on which the image up to where the latent image has been formed is primarily transferred. Then, the image-formed paper that has reached is fixed and discharged to the paper discharge tray (step S7). This completes preparations for executing the second print mode.

  Next, the CPU 25 calculates a time t3 until the temperature reaches Bf which is the lower limit allowable temperature in the B region (step S8). Further, the CPU 25 calculates a time t4 from when the uppermost photosensitive drum 8y is developed with the latent images sequentially superimposed to reach the fixing device 5 (step S9).

  Further, when “time t1> time t2” is not satisfied in the determination in step S6 (determination in S6 is No), the temperature reaches the temperature Ac rather than the sheet on which the image is formed reaches the fixing device 5. fast.

  In this case, the CPU 25 switches the setting of the fixing temperature to the first fixing temperature (step S10). In this process, the upper limit value of the first fixing temperature, that is, the upper limit allowable temperature is set. As a result, the temperature of the fixing device 5 that has risen toward the temperature Ac remains at the temperature in the region A.

  Subsequently, the CPU 25 stops the subsequent latent image formation on the photosensitive drum 8, fixes the image-formed paper that has reached the fixing device 5 at the temperature in the area A, and discharges it to the paper discharge tray ( Step S11).

  Next, the CPU 25 switches the setting of the fixing temperature to the second fixing temperature (step S12). And the process of step S8, S9 mentioned above is performed. Thereby, in this case, preparations for executing the second printing mode are completed.

  Subsequent to the process of step S9, the CPU 25 determines whether or not “time t4> time t3” (step S13). If “time t4> time t3” (Yes in S13), the temperature reaches the temperature Bf faster than the sheet on which the image in the second printing mode is formed reaches the fixing device 5.

  Therefore, there is no possibility that a cold offset will occur even if the sheet is passed through the fixing device 5. Therefore, the CPU 25 starts printing in the second print mode (step S14).

  If “time t4> time t3” is not satisfied in the determination in step S13 (No in S13), the sheet on which the image in the second print mode is formed is fixed to the fixing device 5 rather than the temperature reaches the temperature Bf. Is reached at the same time or earlier (time t4 ≦ time t3).

  Therefore, when the sheet is passed through the fixing device 5, a cold offset occurs. Therefore, in this case, the CPU 25 calculates time t5 when printing is performed in the intermediate printing mode at the printing speed provided between the first printing mode and the second printing mode (step S15).

  Further, the CPU 25 calculates a time t6 until printing can be performed in the second print mode after “t3-t4” time (step S16). Then, the CPU 25 determines whether or not “time t5> time t6” (step S17).

  If “time t5> time t6” is determined in this determination (Yes in S17), the time until printing is enabled in the second printing mode is earlier than the time for printing in the intermediate printing mode.

  Accordingly, in this case, the CPU 25 starts printing in the second print mode after “t3-t4” time (step S18). Further, when “time t5> time t6” is not satisfied in the determination in step S17 (No in determination in S17), the CPU 25 starts printing in the intermediate print mode (step S19).

  In this case, the CPU 25 determines whether or not there is a print to be printed in the subsequent second print mode every time printing in the intermediate print mode is completed (step S20).

  If printing is present (Yes in S20), the process returns to step S8, and the processes in and after step S8 are repeated. If there is no printing (No in S20), the printing process is terminated.

  As described above, in the printing process control of this example, when printing in the high-speed second printing mode during the printing operation, the waiting time for mode switching is reduced, and the user of the image forming apparatus feels frustrated by the waiting time. Can be switched to the high-speed second print mode without giving

  Therefore, when an image forming apparatus equipped with a convenient high-speed printing mode in addition to the normal-speed printing mode is switched to the high-speed printing mode, the user is not frustrated, causing less discomfort and high-speed printing. You can make use of the usefulness of the mode.

Although several embodiments of the present invention have been described, the present invention is included in the invention described in the claims and the equivalents thereof. Hereinafter, the invention described in the scope of claims of the present application will be appended.
[Appendix 1]

There is a fixing device in which the lower limit allowable temperature of the second fixing temperature corresponding to the second printing mode for printing at a high speed is set higher than the upper limit allowable temperature of the first fixing temperature corresponding to the first printing mode for printing at low speed. And
The first fixing temperature is set as an A mode set temperature,
The second fixing temperature is set as a B mode set temperature,
A temperature intermediate between the upper limit allowable temperature of the first fixing temperature and the lower limit allowable temperature of the second fixing temperature is temporarily set at a medium speed between the printing speed in the first printing mode and the printing speed in the second printing mode. The intermediate mode setting temperature corresponding to the intermediate printing mode for printing
When a mode change is designated in the second print mode during printing in the first print mode, the mode change is changing based on the temperature setting switched from the A mode set temperature to the B mode set temperature. The time from when the mode change is designated until the upper limit allowable temperature of the first fixing temperature is reached and until the electrostatic latent image formed on the photoconductor is primarily transferred and reaches the fixing device. And the time from when the mode change is designated until the lower limit allowable temperature of the second fixing temperature is reached and the electrostatic latent image formed on the photosensitive member are primarily transferred to the fixing device. And a control device that determines whether to perform printing in the intermediate printing mode or to perform printing in the second printing mode based on a result of comparing the lengths of these times and
An image forming apparatus comprising:
[Appendix 2]

When the second printing mode is designated, the control device switches the temperature setting so that the fixing temperature becomes the second fixing temperature and waits for the temperature to rise, while the printing medium being printed in the first printing mode If it is determined that the fixing temperature reaches the upper limit allowable temperature of the first fixing temperature before reaching the fixing device, the temperature setting is returned to the temperature setting of the first fixing temperature and the subsequent printing medium is set. After the image formation is stopped and the fixing to the printing medium is executed, the temperature setting is switched again so that the fixing temperature becomes the second fixing temperature, and printing in the second printing mode is waited. The image forming apparatus according to appendix 1.
[Appendix 3]

When the second printing mode is designated, the control device switches the temperature setting so that the fixing temperature becomes the second fixing temperature and waits for the temperature to rise, while the printing medium being printed in the first printing mode When it is determined that the fixing temperature reaches the fixing device earlier than the upper limit allowable temperature of the first fixing temperature, image formation on the subsequent printing medium is stopped and fixing on the printing medium is performed. 2. The image forming apparatus according to claim 1, wherein after the execution, the printer waits for printing in the second print mode.
[Appendix 4]

While the control device waits for printing in the second printing mode, the fixing temperature is lower than the lower limit of the second fixing temperature than the printing medium on which the image is formed in the second printing mode reaches the fixing device. The image forming apparatus according to appendix 1 or 2, wherein printing in the second printing mode is executed when it is determined that the temperature is reached earlier.
[Appendix 5]

The control device waits for printing in the second printing mode, and when the printing medium on which the image in the second printing mode has been formed reaches the fixing device than the time for performing printing in the intermediate printing mode. When it is determined that the time for the fixing temperature to reach the lower limit allowable temperature of the second fixing temperature is earlier, the time for performing the printing in the second printing mode and performing the printing in the intermediate printing mode is the first time. When it is determined that the fixing temperature is earlier than the time required to reach the lower limit allowable temperature of the second fixing temperature when the printing medium on which the image of the two printing mode is formed reaches the fixing device, the printing in the intermediate printing mode is performed. The image forming apparatus according to appendix 1 or 2, wherein:
[Appendix 6]

A fixing device in which the lower limit allowable temperature of the second fixing temperature corresponding to the second printing mode for printing at a high speed is set higher than the upper limit allowable temperature of the first fixing temperature corresponding to the first printing mode for printing at a low speed; An image forming method of an image forming apparatus,
The first fixing temperature is set as an A mode set temperature,
The second fixing temperature is set as a B mode set temperature,
A temperature intermediate between the upper limit allowable temperature of the first fixing temperature and the lower limit allowable temperature of the second fixing temperature is temporarily set at a medium speed between the printing speed in the first printing mode and the printing speed in the second printing mode. The intermediate mode setting temperature corresponding to the intermediate printing mode for printing
When a mode change is designated in the second print mode during printing in the first print mode, the mode change is changing based on the temperature setting switched from the A mode set temperature to the B mode set temperature. The time from when the mode change is designated until the upper limit allowable temperature of the first fixing temperature is reached and until the electrostatic latent image formed on the photoconductor is primarily transferred and reaches the fixing device. And the time from when the mode change is designated until the lower limit allowable temperature of the second fixing temperature is reached and the electrostatic latent image formed on the photosensitive member are primarily transferred to the fixing device. To determine whether to perform printing in the intermediate printing mode or printing in the second printing mode, based on the result of comparing the length of the time to reach
An image forming method.
[Appendix 7]

When the second printing mode is designated, while the temperature setting is switched so that the fixing temperature becomes the second fixing temperature and the temperature rise is waited for, the printing medium being printed in the first printing mode is transferred to the fixing device. If it is determined that the fixing temperature reaches the upper limit allowable temperature of the first fixing temperature before reaching, the temperature setting is returned to the temperature setting of the first fixing temperature, and image formation on the subsequent printing medium is stopped. And after the fixing to the printing medium is executed, the temperature setting is switched again so that the fixing temperature becomes the second fixing temperature, and the printing in the second printing mode is waited for. Image forming method.
[Appendix 8]

When the second printing mode is designated, while the temperature setting is switched so that the fixing temperature becomes the second fixing temperature and the temperature rise is waited for, the printing medium being printed in the first printing mode is transferred to the fixing device. When it is determined that the fixing temperature is earlier than the upper limit allowable temperature of the first fixing temperature, the image formation on the subsequent printing medium is stopped and the fixing on the printing medium is executed, The image forming method according to appendix 6, wherein the image forming apparatus waits for printing in the second print mode.
[Appendix 9]

While waiting for printing in the second printing mode, the fixing temperature reaches the lower limit allowable temperature of the second fixing temperature, rather than the printing medium on which the image is formed in the second printing mode reaches the fixing device. The image forming method according to appendix 6 or 7, wherein printing in the second printing mode is executed when it is determined that the printing is early.
[Appendix 10]

  While waiting for printing in the second printing mode, when the printing medium on which the image in the second printing mode is formed reaches the fixing device, the fixing temperature is higher than the time for printing in the intermediate printing mode. 2 When it is determined that the time to reach the lower limit allowable temperature of the fixing temperature is earlier, the printing in the second printing mode is executed, and the time in which the printing in the intermediate printing mode is performed is the image in the second printing mode. When it is determined that the fixing temperature is earlier than the time required to reach the lower limit allowable temperature of the second fixing temperature when the printing medium on which is formed reaches the fixing device, printing in the intermediate printing mode is performed. The image forming method according to appendix 6 or 7, characterized by:

  The present invention can be used in an image forming apparatus that has a low-speed printing mode and a high-speed printing mode, and switches to the high-speed printing mode in as short a time as possible when a change to the high-speed printing mode is designated during the low-speed printing mode.

1 Image forming device (printer)
2 Image forming unit 3 Transfer belt unit 4 Paper feeding unit 5 Fixing device 6 Transfer belt 7 (7y, 7m, 7c, 7k) Image forming unit 8 (8y, 8m, 8c, 8k) Photosensitive drum 9 Cleaner 11 Charging roller 12 Optical writing head 13 Developing device 14 Primary transfer roller 15 Drive roller 16 Driven roller 17 Secondary transfer roller 18 Paper 19 Paper feed cassette 20 Electrical section 21 Paper take-out roller 22 Heating roller 23 Pressure roller 25 CPU (central processing unit)
26 Interface controller (I / F_CONT)
27 Printer Controller (PR_CONT)
28 Printer printing section 29 ROM (read only memory)
31 EEPROM (electrically erasable programmable ROM)
32 Operation panel 33 Sensor section 34 Frame memory

Claims (8)

There is a fixing device in which the lower limit allowable temperature of the second fixing temperature corresponding to the second printing mode for printing at a high speed is set higher than the upper limit allowable temperature of the first fixing temperature corresponding to the first printing mode for printing at low speed. And
The first fixing temperature is set as an A mode set temperature,
The second fixing temperature is set as a B mode set temperature,
A temperature intermediate between the upper limit allowable temperature of the first fixing temperature and the lower limit allowable temperature of the second fixing temperature is temporarily set at a medium speed between the printing speed in the first printing mode and the printing speed in the second printing mode. The intermediate mode setting temperature corresponding to the intermediate printing mode for printing
When a mode change is designated in the second print mode during printing in the first print mode, the mode change is changing based on the temperature setting switched from the A mode set temperature to the B mode set temperature. The time from when the mode change is designated until the upper limit allowable temperature of the first fixing temperature is reached and until the electrostatic latent image formed on the photoconductor is primarily transferred and reaches the fixing device. the fixing device time and derivation, or the time the electrostatic latent image formed on the photosensitive member from the time the mode change is designated until it reaches the lower allowable temperature of the second fixing temperature is primarily transferred the deriving a time to reach, based on a result of comparing the length of their time, and a control unit that determines whether to perform printing in the second print mode or printing in intermediate print mode
I have a,
The control device waits for printing in the second printing mode, and when the printing medium on which the image in the second printing mode has been formed reaches the fixing device than the time for performing printing in the intermediate printing mode. When the time during which the changing temperature reaches the lower limit allowable temperature of the second fixing temperature is earlier, the time during which the printing in the second printing mode is executed and the printing in the intermediate printing mode is performed is the second time. When the print medium on which the print mode image is formed reaches the fixing device, if the changing temperature is earlier than the time for reaching the lower limit allowable temperature of the second fixing temperature, printing in the intermediate print mode is executed. To
An image forming apparatus.   When the second printing mode is designated, the control device switches the temperature setting so that the fixing temperature becomes the second fixing temperature and waits for the temperature to rise, while the printing medium being printed in the first printing mode If it is determined that the fixing temperature reaches the upper limit allowable temperature of the first fixing temperature before reaching the fixing device, the temperature setting is returned to the temperature setting of the first fixing temperature and the subsequent printing medium is set. After the image formation is stopped and the fixing to the printing medium is executed, the temperature setting is switched again so that the fixing temperature becomes the second fixing temperature, and printing in the second printing mode is waited. The image forming apparatus according to claim 1.   When the second printing mode is designated, the control device switches the temperature setting so that the fixing temperature becomes the second fixing temperature and waits for the temperature to rise, while the printing medium being printed in the first printing mode When it is determined that the fixing temperature reaches the fixing device earlier than the upper limit allowable temperature of the first fixing temperature, image formation on the subsequent printing medium is stopped and fixing on the printing medium is performed. The image forming apparatus according to claim 1, wherein the image forming apparatus waits for printing in the second print mode after execution.   While the control device waits for printing in the second printing mode, the fixing temperature is lower than the lower limit of the second fixing temperature than the printing medium on which the image is formed in the second printing mode reaches the fixing device. 3. The image forming apparatus according to claim 1, wherein printing in the second printing mode is executed when it is determined that the temperature is reached earlier. 4. A fixing device in which the lower limit allowable temperature of the second fixing temperature corresponding to the second printing mode for printing at a high speed is set higher than the upper limit allowable temperature of the first fixing temperature corresponding to the first printing mode for printing at a low speed; An image forming method of an image forming apparatus,
The first fixing temperature is set as an A mode set temperature,
The second fixing temperature is set as a B mode set temperature,
A temperature intermediate between the upper limit allowable temperature of the first fixing temperature and the lower limit allowable temperature of the second fixing temperature is temporarily set at a medium speed between the printing speed in the first printing mode and the printing speed in the second printing mode. The intermediate mode setting temperature corresponding to the intermediate printing mode for printing
When a mode change is designated in the second print mode during printing in the first print mode, the mode change is changing based on the temperature setting switched from the A mode set temperature to the B mode set temperature. The time from when the mode change is designated until the upper limit allowable temperature of the first fixing temperature is reached and until the electrostatic latent image formed on the photoconductor is primarily transferred and reaches the fixing device. the fixing device time and derivation, or the time the electrostatic latent image formed on the photosensitive member from the time the mode change is designated until it reaches the lower allowable temperature of the second fixing temperature is primarily transferred the to derive the time and to reach to,
While waiting for printing in the second print mode, the temperature that is changing when the print medium on which the image in the second print mode is formed reaches the fixing device than the time for printing in the intermediate print mode When the time to reach the lower limit allowable temperature of the second fixing temperature is earlier, the printing in the second printing mode is executed,
While waiting for printing in the second printing mode, the time for printing in the intermediate printing mode is changing when the printing medium on which the image in the second printing mode is formed reaches the fixing device. If the temperature is earlier than the time required to reach the lower limit allowable temperature of the second fixing temperature, printing in the intermediate printing mode is performed.
An image forming method. When the second printing mode is designated, while the temperature setting is switched so that the fixing temperature becomes the second fixing temperature and the temperature rise is waited for, the printing medium being printed in the first printing mode is transferred to the fixing device. If it is determined that the fixing temperature reaches the upper limit allowable temperature of the first fixing temperature before reaching, the temperature setting is returned to the temperature setting of the first fixing temperature, and image formation on the subsequent printing medium is stopped. The printing apparatus according to claim 5 , wherein after the fixing to the printing medium is executed, the temperature setting is switched again so that the fixing temperature becomes the second fixing temperature, and printing in the second printing mode is waited. Image forming method. When the second printing mode is designated, while the temperature setting is switched so that the fixing temperature becomes the second fixing temperature and the temperature rise is waited for, the printing medium being printed in the first printing mode is transferred to the fixing device. When it is determined that the fixing temperature is earlier than the upper limit allowable temperature of the first fixing temperature, the image formation on the subsequent printing medium is stopped and the fixing on the printing medium is executed, 6. The image forming method according to claim 5 , wherein printing in the second print mode is waited. While waiting for printing in the second printing mode, the fixing temperature reaches the lower limit allowable temperature of the second fixing temperature, rather than the printing medium on which the image is formed in the second printing mode reaches the fixing device. early as when it is determined, the second to execute printing of a print mode, image forming method according to claim 5 or 6, wherein the.

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