JP4076467B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus including a fixing device that heats and melts a toner image formed on a printing paper.
[0002]
[Prior art]
A fixing device provided in a conventional image forming apparatus includes a fixing heat roller heated by a heater and a fixing pressure roller that is paired with the fixing heat roller. By passing printing paper between the fixing heat roller and the fixing pressure roller, The toner image formed on the printing paper is fixed. As a method for controlling the temperature of the fixing heat roller, the heater is turned on at the start of the image forming process, and the temperature of the fixing heat roller is set to a first set temperature appropriate for fixing the toner image on the printing paper (hereinafter referred to as “fixing temperature”). The temperature of the fixing heat roller is controlled to be maintained at the fixing temperature during the image forming process. When the image forming process is completed and the process shifts to the standby mode, the power supply to the heater is turned off, and the temperature of the fixing heat roller is lowered to a second set temperature (hereinafter referred to as “standby temperature”) lower than the fixing temperature ( For example, see Patent Document 1).
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-065352
[Problems to be solved by the invention]
However, in the conventional image forming apparatus, the period from the image forming process to the next image forming process is short, and the next image forming process is started in a state where the temperature of the fixing heat roller is not lowered to the standby temperature. In this case, there is a problem in that an overshoot occurs in which the temperature of the fixing heat roller rapidly rises above the fixing temperature when the heater is turned on.
[0005]
SUMMARY An advantage of some aspects of the invention is to provide an image forming apparatus capable of preventing an overshoot occurring in a fixing device when shifting from a standby mode to an image forming process. Is the purpose.
[0006]
[Means for Solving the Problems]
The image forming apparatus according to the present invention includes a fixing heat roller including a plurality of heaters, a fixing unit having a fixing pressure roller for pressing a printing paper on which a toner image is formed to the fixing heat roller, and the fixing heat roller. Detection means for detecting the surface temperature of the roller, and during the image forming process, the temperature of the fixing heat roller detected by the detecting means is maintained at a fixing temperature appropriate for the fixing process, and the image forming process is completed and the standby mode is set. , The heater control means for performing on / off switching control of the plurality of heaters so as to maintain the temperature of the fixing heat roller detected by the detection means at a standby temperature lower than the fixing temperature, and the standby When shifting to the mode, the heater lighting flag indicating that the temperature of the fixing heat roller is equal to or lower than the standby temperature is cleared, and the detection is performed in the standby mode. When the temperature of the fixing heat roller detected by the stage becomes less than the standby temperature, and a flag set means for setting the heater turning-on flag, the heater control means shifts from the standby mode to the image forming processing When the heater lighting flag is not set at this time, a part of the plurality of heaters is turned on, and the plurality of fixing heat rollers detected by the detecting means until the temperature reaches the fixing temperature. When the heater lighting flag is set when shifting to the image forming process from the standby mode, maintaining some of the heaters in the on state, maintaining other heaters in the off state, All of the plurality of heaters are turned on, and all of the heaters are detected until the temperature of the fixing heat roller detected by the detecting unit reaches the fixing temperature. To maintain in a state of being on the over data.
[0009]
According to this configuration, the period from the end of the image forming process to the start of the next image forming process is short, and the next image forming process is started in a state where the fixing heat roller is not lowered to the standby temperature. In this case, a part of the plurality of heaters is turned on and the other heaters are kept off, so that the temperature of the fixing heat roller can be gradually raised to the fixing temperature, and overshoot Can be prevented.
In the standby mode, when the next image forming process is started after the fixing heat roller has fallen to the standby temperature, the temperature of the fixing heat roller is set to the fixing temperature in a short period of time by turning on all of the plurality of heaters. Can be raised.
[0010]
The plurality of heaters include a main heater for raising the temperature of the central portion of the fixing heat roller and a sub-heater for raising the temperature of both end portions of the fixing heat roller, and the heater control means includes the standby mode. When the heater lighting flag is not set when the process proceeds to the image forming process, only the main heater is turned on as the partial heater, and the surface temperature of the fixing heat roller detected by the detecting means is fixed. It is preferable that the main heater is kept on until the temperature is reached , and the sub-heater is kept off .
[0011]
According to this configuration, the period from the end of the image forming process to the start of the next image forming process is short, and the next image forming process is started in a state where the fixing heat roller is not lowered to the standby temperature. In this case, since the main heater is turned on and the sub heater is kept off, the temperature of the fixing heat roller can be gradually raised to the fixing temperature, and overshoot can be prevented.
[0012]
The plurality of heaters include a main heater for raising the temperature of the central portion of the fixing heat roller and a sub-heater for raising the temperature of both end portions of the fixing heat roller, and the heater control means includes the standby mode. When the heater lighting flag is not set at the time of shifting from the image forming process to the image forming process, only the sub-heater is turned on as the partial heater, and the surface temperature of the fixing heat roller detected by the detecting means is the fixing temperature. Until that time, the sub heater may be maintained in an on state and the main heater may be maintained in an off state.
[0013]
According to this configuration, the period from the end of the image forming process to the start of the next image forming process is short, and the next image forming process is started in a state where the fixing heat roller is not lowered to the standby temperature. In this case, since the sub heater is turned on and the main heater is turned off, the temperature of the fixing heat roller can be gradually raised to the fixing temperature, and overshoot can be prevented.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic side view mainly showing a mechanical configuration of a digital multi-function peripheral according to an embodiment of the present invention.
[0017]
The digital multi-function peripheral 1 includes a main body 200, a sheet post-processing unit 300 disposed on the left side of the main body 200, an operation unit 400 for a user to input various operation commands and the like, and an upper part of the main body 200. The document reading unit 500 disposed on the document reading unit 500 and the document feeding unit 600 disposed above the document reading unit 500.
[0018]
The operation unit 400 includes a touch panel 401, a start key 402, a numeric keypad 403, and the like. The touch panel 401 displays various operation screens and various operation buttons for the user to input various operation commands. The start key 402 is used for the user to input a print execution command and the like, and the ten key 403 is used for inputting the number of prints and the like.
[0019]
The document feeding unit 600 includes a document storage unit 601, a document discharge unit 602, a paper feed roller 603, a document transport unit 604, and the like, and the document reading unit 500 includes a scanner 501 and the like. The paper feed roller 603 feeds the original set in the original storage unit 601, and the original transport unit 604 transports the fed original one by one on the scanner 501 one by one. The scanner 501 sequentially reads the conveyed document, and the read document is discharged to the document discharge unit 602.
[0020]
The main body 200 includes a plurality of paper feed cassettes 201, a plurality of paper feed rollers 202, a transfer roller 203, a photosensitive drum 204, an exposure device 206, a developing device 207, a fixing roller 208, a discharge port 209, a discharge tray 250, and the like. Prepare.
[0021]
The photosensitive drum 204 is uniformly charged by a charging device (not shown) while rotating in the direction of the arrow. The exposure device 206 converts a modulation signal generated based on the image data of the document read by the document reading unit 500 into a laser beam and outputs the laser beam, thereby forming an electrostatic latent image on the photosensitive drum 204. The developing device 207 supplies a black developer to the photosensitive drum 204 to form a toner image.
[0022]
On the other hand, the paper feed roller 202 draws the print paper from the paper feed cassette 201 in which the print paper is stored, and feeds the print paper to the transfer roller 203. The transfer roller 203 transfers the toner image on the photosensitive drum 204 onto the conveyed printing paper. The fixing device 211 includes a fixing heat roller 210 and a fixing pressure roller 208, and fixes the toner image on the printing paper by heating and pressing the printing paper on which the toner image is transferred. Thereafter, the printing paper is carried into the paper post-processing unit 300 from the discharge port 209 of the main body unit 200. The printing paper is also discharged to the discharge tray 250 as necessary.
[0023]
The paper post-processing unit 300 includes a carry-in port 301, a print paper carrying unit 302, a carry-out port 303, a stack tray 304, and the like. The printing paper conveyance unit 302 sequentially conveys the printing paper carried into the carry-in port 301 from the discharge port 209 and finally discharges the printing paper from the carry-out port 303 to the stack tray 304. The stack tray 304 is configured to be movable up and down in the direction of the arrow in accordance with the number of print sheets stacked from the carry-out port 303.
[0024]
FIG. 2 is a perspective view showing the configuration of the fixing device 211 in the digital multi-function peripheral 1 shown in FIG.
[0025]
The fixing device 211 includes a fixing pressure roller 208 having an elastic body made of silicon rubber or the like on the surface, and a fixing heat roller 210 in which a main heater 220 and a sub heater 221 are built. A halogen lamp or the like is used for the main heater 220 and the sub heater 221. The main heater 220 increases the temperature of the central portion of the fixing heat roller 210, and the sub heater 221 increases the temperature of both end portions of the fixing heat roller 210. For example, when the fixing process is performed on an A4 size printing paper, the main heater 220 is turned on. When the fixing process is performed on an A3 size printing paper, both the main heater 220 and the sub heater 221 are turned on. .
[0026]
FIG. 3 is a block diagram illustrating a configuration of a control unit that performs temperature control of the fixing heat roller 210 illustrated in FIG. 2.
[0027]
The temperature sensor 10 is provided in the vicinity of the fixing heat roller 210 and detects the surface temperature of the fixing heat roller 210. The control unit 11 includes a CPU 12, a memory 13, and a clock generation unit 14. The memory 13 includes fixing temperature information for specifying a fixing temperature (for example, 160 degrees) that is set as an appropriate temperature for fixing the toner image on the printing paper by the fixing heat roller 210 during the image forming process, and image formation. Standby temperature information for specifying a standby temperature (for example, 150 degrees) set as the target temperature of the fixing heat roller 210 in the standby mode in which no processing is performed is recorded.
[0028]
The CPU 12 operates based on the clock generated by the clock generator 14. The CPU 12 refers to the fixing temperature information and the standby temperature information recorded in the memory 13 and turns on the main heater 220 and the sub heater 221 so that the temperature of the fixing heat roller 210 detected by the temperature sensor 10 becomes the fixing temperature or the standby temperature.・ Off switch control is performed. Specifically, when the user performs an image forming process start operation using the operation unit 400, the CPU 12 receives an image formation start command from the operation unit 400, turns on the main heater 220 and the sub heater 221, and fixes the fixing heat roller 210. The surface temperature of is increased to the fixing temperature. When the image forming process is completed, the CPU 12 turns off the main heater 220 and the sub heater 221 in order to lower the surface temperature of the fixing heat roller 210 to the standby temperature. When the temperature of the fixing heat roller 210 becomes equal to or lower than the standby temperature, the CPU 12 turns on the main heater 220 and the sub heater 221, and at the same time, a heater indicating that the main heater 220 and the sub heater 221 are in the on state in the memory 13. Set the lighting flag.
[0029]
4 and 5 are flowcharts for explaining the temperature control processing of the fixing heat roller 210 by the control unit 11 shown in FIG.
[0030]
In step S1, the CPU 12 determines whether or not the image forming process has ended. If it is determined that the image forming process has ended, the CPU 12 shifts to a standby mode. In step S2, the main heater 220 and the sub heater 221 are turned off. In step S3
The heater lighting flag recorded in the memory 13 is cleared.
[0031]
In step S <b> 4, the CPU 12 monitors the surface temperature of the fixing heat roller 210 detected by the temperature sensor 10, and determines the surface temperature of the fixing heat roller 210 and the standby temperature specified by the standby temperature information recorded in the memory 13. In comparison, it is determined whether or not the surface temperature of the fixing heat roller 210 is equal to or lower than the standby temperature. When the CPU 12 determines that the surface temperature of the fixing heat roller 210 is equal to or lower than the standby temperature, the CPU 12 proceeds to step S5, turns on the main heater 220 and the sub heater 221, and maintains the on state of the main heater 220 and the sub heater 221 for a certain period. Then, the temperature of the fixing heat roller 210 is raised to the standby temperature. On the other hand, if the CPU 12 determines that the surface temperature of the fixing heat roller 210 is higher than the standby temperature, the CPU 12 proceeds to step S6, turns off the main heater 220 and the sub heater 221, and sets the main heater 220 and the sub heater 221 to the off state for a certain period. And the temperature of the fixing heat roller 210 is lowered to the standby temperature.
[0032]
In step S7, the CPU 12 determines whether or not the heater lighting flag is set in the memory 13. If the heater lighting flag is set, the process proceeds to step S10, and if the heater lighting flag is not set, the step is step. Proceed to S8. In step S8, the CPU 12 determines whether or not the main heater 220 and the sub heater 221 are in an on state, and when determining whether the main heater 220 and the sub heater 221 are in an on state, the CPU 12 proceeds to step S9 and sets a heater lighting flag. In step S5, since the temperature of the fixing heat roller 210 rises gradually and does not rise rapidly by turning on the main heater 220 and the sub heater 221, the main heater 220 is heated in step S8 while the temperature of the fixing heat roller 210 is rising. And the ON state of the sub-heater 221 is detected, and the heater lighting flag can be set in step S9.
[0033]
In step S <b> 10, the CPU 12 determines whether an image formation start command is input from the operation unit 400 by the user performing an image formation process start operation using the operation unit 400, and the image formation start command is not input. In this case, it is determined that the standby mode has been previously performed, and the on / off control of the main heater 220 and the sub heater 221 in steps S4, S5, and S6 is repeated so that the surface temperature of the fixing heat roller 210 is maintained at the standby temperature. .
[0034]
When an image formation start command is input from the operation unit 400, the CPU 12 determines that the standby mode has ended, proceeds to step S11, determines whether the heater lighting flag is set in the memory 13, and turns on the heater. If it is determined that the flag is set, the process proceeds to step S12, and the main heater 220 and the sub heater 221 are turned on. If it is determined that the heater lighting flag is not set, the process proceeds to step S13, and the main heater 220 is turned on. To do. Here, only the main heater 220 is turned on, but the present invention is not limited to this, and only the sub-heater 221 may be turned on.
[0035]
Next, in step S14, the CPU 12 determines whether or not the surface temperature of the fixing heat roller 210 detected by the temperature sensor 10 has reached the fixing temperature, and the surface temperature of the fixing heat roller 210 reaches the fixing temperature. If it is determined that it has reached, the process proceeds to step S15, and the sub heater 221 is turned on. Here, the CPU 12 turns on the sub-heater 221 when the fixing heat roller 210 reaches the fixing temperature. However, for example, when printing on A4 size printing paper, the main heater 220 is turned on without turning on the sub-heater 221. Thus, the temperature of the fixing heat roller 210 can be controlled.
[0036]
As described above, the CPU 12 determines whether or not the heater lighting flag is set in the memory 13 at the start of the image forming process. If the CPU 12 determines that the heater lighting graph is set, the main heater 220 is conventionally set. If the heater lighting graph is not set, the main heater 220 is turned on and the main heater 220 is turned on until the temperature of the fixing heat roller 210 rises to the fixing temperature. The off state of 221 is maintained. As a result, even when the period from the end of the image forming process to the start of the next image forming process is short, and the temperature of the fixing heat roller 210 is not lowered to the standby temperature, the temperature of the fixing heat roller 210 is reduced. It can be raised gradually and overshoot can be prevented.
[0037]
FIG. 6 is a time chart for explaining an example of temperature control processing of the fixing heat roller 210 by the control unit 11 shown in FIG.
[0038]
During the image forming process, the main heater 220 and the sub heater 221 are turned on, and the temperature of the fixing heat roller 210 is maintained at the fixing temperature T1. When the image forming process is completed at time t1, the main heater 220 and the sub heater 221 are turned off by the CPU 12 in order to lower the temperature of the fixing heat roller 210 to the standby temperature T2.
[0039]
When the surface temperature of the fixing heat roller 210 becomes equal to or lower than the standby temperature T2 at time t2, the CPU 12 turns on the main heater 220 and the sub heater 221 and simultaneously sets the heater lighting flag in the memory 13. When the surface temperature of the fixing heat roller 210 becomes equal to or higher than the standby temperature T2, the CPU 12 turns off the main heater 220 and the sub heater 221. As described above, the CPU 12 performs on / off switching control of the main heater 220 and the sub heater 221 in accordance with the surface temperature of the fixing heat roller 210 during the standby mode, thereby maintaining the temperature of the fixing heat roller 210 at the standby temperature T2. Can do.
[0040]
Next, when the CPU 12 receives an image formation start command from the operation unit 400 by the user performing an image formation process start operation using the operation unit 400 at time t <b> 3, the CPU 12 sets the heater lighting flag in the memory 13. The main heater 220 and the sub heater 221 are turned on.
[0041]
FIG. 7 is a time chart for explaining another example of the temperature control processing of the fixing heat roller 210 by the control unit 11 shown in FIG.
[0042]
When the image forming process is completed at time t11 and the mode is changed to the standby mode, the CPU 12 turns off the main heater 220 and the sub heater 221. Next, at time t12, the CPU 12 receives an image formation start command from the operation unit 400, and checks whether or not the heater lighting flag is set in the memory 13. Here, since the temperature of the fixing heat roller 210 is lowered to the standby temperature T2 and the image forming process is started before the main heater 220 and the sub heater 221 are turned on, the heater lighting flag is not set in the memory 13. The CPU 12 confirms that the heater lighting flag is not set in the memory 13 and turns on the main heater 220. Then, the CPU 12 turns on the sub heater 221 at the time t13 when the surface temperature of the fixing heat roller 210 rises to the fixing temperature T1.
[0043]
After time t13, the CPU 12 performs on / off switching control of the main heater 220 and the sub heater 221 so that the surface temperature of the fixing heat roller 210 is maintained at the fixing temperature. Depending on the size of the printing paper and other conditions, the on / off switching frequency of the main heater 220 and the sub heater 221 and the period during which the main heater 220 and the sub heater 221 are on / off can be variously changed.
[0044]
As described above, according to the present embodiment, when the CPU 12 receives an image formation start command from the operation unit 400 during the standby mode, the heater lighting flag indicating that the main heater 220 and the sub heater 221 are turned on during the standby mode. It is determined whether or not the heater 13 is set in the memory 13. If it is determined that the heater lighting flag is set, the main heater 220 is turned on, and the main temperature until the surface temperature of the fixing heat roller 210 rises to the fixing temperature T1. Since the state in which the heater 220 is turned on and the state in which the sub-heater 221 is turned off is maintained, it is possible to prevent overshoot that occurs when shifting from the standby mode to the image forming process. On the other hand, when the CPU 12 determines that the heater lighting flag is not set, the main heater 220 and the sub heater 221 are simultaneously turned on, so that the surface temperature of the fixing heat roller 210 can be raised to the fixing temperature T1 in a short period of time. it can.
[0045]
【The invention's effect】
According to the present invention, the waiting period from the end of the image forming process to the start of the next image forming process is short, and the next image forming process is started with the fixing heat roller not lowered to the waiting temperature. In such a case, the temperature of the fixing heat roller can be gradually raised by turning on some of the plurality of heaters provided on the fixing heat roller, and overshoot can be prevented.
[Brief description of the drawings]
FIG. 1 is a schematic side view mainly showing a mechanical configuration of a digital multi-function peripheral according to an embodiment of the present invention.
FIG. 2 is a perspective view illustrating a configuration of a fixing device in the digital multifunction peripheral 1 illustrated in FIG.
FIG. 3 is a block diagram illustrating a configuration of a control unit that performs temperature control of the fixing heat roller illustrated in FIG. 2;
4 is a flowchart for explaining temperature control processing of a fixing heat roller by a control unit shown in FIG. 3;
FIG. 5 is a flowchart for explaining temperature control processing of the fixing heat roller by the control unit shown in FIG. 3;
6 is a time chart for explaining an example of temperature control processing of the fixing heat roller by the control unit shown in FIG. 3; FIG.
7 is a time chart for explaining an example of temperature control processing of the fixing heat roller by the control unit shown in FIG. 3; FIG.
[Explanation of symbols]
10 Temperature Sensor 11 Control Unit 12 CPU
13 Memory 14 Clock generator 208 Fixing pressure roller 210 Fixing heat roller 220 Main heater 221 Sub heater

Claims (3)

A fixing heat roller including a plurality of heaters and a fixing unit having a fixing pressure roller for pressing the printing paper on which the toner image is formed to the fixing heat roller;
Detecting means for detecting a surface temperature of the fixing heat roller;
During the image forming process, the temperature of the fixing heat roller detected by the detecting unit is maintained at a fixing temperature appropriate for the fixing process, and when the image forming process is completed and the standby mode is entered, the detecting unit detects the temperature. Heater control means for performing on / off switching control of the plurality of heaters so as to maintain the temperature of the fixing heat roller at a standby temperature lower than the fixing temperature ;
When shifting to the standby mode, the heater lighting flag indicating that the temperature of the fixing heat roller has become equal to or lower than the standby temperature is cleared, and in the standby mode, the temperature of the fixing heat roller detected by the detection means is Flag setting means for setting the heater lighting flag when the temperature is equal to or lower than the standby temperature,
The heater control means includes
If the heater lighting flag is not set when shifting from the standby mode to the image forming process, a part of the heaters in the plurality of heaters is turned on, and the temperature of the fixing heat roller detected by the detection unit Until a fixing temperature is reached, keep some heaters in the plurality of heaters on, and keep other heaters off,
When the heater lighting flag is set when the image forming process is shifted from the standby mode, all of the plurality of heaters are turned on, and the temperature of the fixing heat roller detected by the detecting unit becomes the fixing temperature. Until all the heaters are on until
An image forming apparatus. The image forming apparatus according to claim 1,
The plurality of heaters includes a main heater for raising the temperature of the central portion of the fixing heat roller and a sub-heater for raising the temperature of both end portions of the fixing heat roller.
The heater control means includes
When the heater lighting flag is not set when the standby mode is shifted to the image forming process, only the main heater is turned on as the partial heater, and the surface of the fixing heat roller detected by the detection unit The image forming apparatus, wherein the main heater is kept on and the sub-heater is kept off until the temperature reaches a fixing temperature. The image forming apparatus according to claim 1 ,
The plurality of heaters includes a main heater for raising the temperature of the central portion of the fixing heat roller and a sub-heater for raising the temperature of both end portions of the fixing heat roller.
The heater control means includes
When the heater lighting flag is not set when the image forming process is shifted from the standby mode, only the sub heater is turned on as the partial heater, and the surface temperature of the fixing heat roller detected by the detection unit until but becomes the fixing temperature is maintained while turning on the sub-heater, an image forming apparatus characterized by maintaining in the oFF state of the main heater.

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