JP2008197306A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which is capable of uniformly warming the whole heat roller of a fixing section as soon as possible, during pre-print rotation from the start of printing to before the start of feeding paper. <P>SOLUTION: In the image forming apparatus, when a print job is generated, a CPU 1 turns on a heater on and off signal to a SW 19, to turn on a long heater 16 for a large paper width, until the detected temperature of a fixing unit detected by a thermistor 21 reaches a pickup temperature and when the temperature of the fixing unit rises up to the pickup temperature, the CPU 1 outputs a pickup signal, to start feeding of a recording paper and chooses the long heater 16 for the large paper width or a short heater 17 for a small paper width, according to the width of the recording paper, to execute the temperature control of the fixing unit, in maintaining a fixing temperature, during continuous printing. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus including a plurality of heaters having different lengths as heaters of a fixing unit.

  In an electrophotographic image forming apparatus in which toner adhered to a recording paper corresponding to print image information is fixed on the recording paper by heating at a fixing unit, the photosensitive member is modulated by light modulated based on the print image information. An electrostatic latent image is formed on the photosensitive member, and toner is attached to the photosensitive member on which the electrostatic latent image is formed and developed. After the toner adhering to the photosensitive member is transferred to the recording paper, the recording paper to which the toner is adhering is conveyed to a heat roller heated by a fixing heater, and the toner is fixed on the recording paper by the heat roller. .

  In electrophotographic image forming apparatuses having a heat fixing unit used in such facsimile machines and copiers, in recent years, the demand for energy saving has increased, and in particular, power consumption in a state in which image formation is not performed. Therefore, there is an energy saving mode that saves power when image formation is not performed. In this energy saving mode, power consumption is reduced by stopping power supply to the fixing unit.

In addition, in a conventional electrophotographic image forming apparatus, the temperature of the fixing unit is detected using a thermistor or the like, and the temperature of the fixing unit can be higher than the above temperature so as to be maintained at a standby temperature or a fixing temperature. If the system is controlled, the power supply to the heater is stopped, and if it becomes low, the power supply is restarted.
Note that if the heater of the fixing unit is turned on at the start of recording, it takes time for printing to be performed and the user is kept waiting. Therefore, the temperature of the fixing unit is usually set to the standby temperature immediately after the power is turned on. By raising and setting the standby state, the time from the start of recording until the fixing temperature is reached, that is, the fixing start-up time is shortened.

On the other hand, in an electrophotographic image forming apparatus, when an image is formed on a narrow paper, heat is removed only from a part of the printing paper, that is, near the center of the heat roller of the fixing unit. Since the temperature of the edge of the paper rises, a heater for wide paper width and a heater for narrow paper width are provided in the heat roller, and the heater to be used is switched according to the width of the recording paper, so that printing with a short width such as a postcard is performed. In the case of paper, abnormal temperature rise at the end of the heat roller is prevented, and printing can be performed at high speed (see, for example, Patent Document 1).
JP 2003-76213 A

  As described above, when a heater for wide paper width and a heater for narrow paper width are provided in the heat roller and the heater to be used is switched depending on the width of the recording paper, an image is formed on a narrow recording paper. When rotating before printing from the start of printing to the start of recording paper feeding, there is a problem that it takes time for the heat roller to rise to a predetermined temperature.

  The present invention has been made in view of the above problems, and provides an image forming apparatus capable of uniformly warming the entire heat roller of a fixing unit as soon as possible during a pre-printing rotation from the start of printing to the start of paper feeding. For the purpose.

  In order to achieve the above object, an image forming apparatus according to a first aspect of the present invention includes a fixing unit having a plurality of heaters having different lengths, and a control unit that controls the heater according to the temperature of the fixing unit. In the image forming apparatus, the control unit uses a long heater to heat the fixing unit during the rotation before printing from the start of printing to the start of feeding.

An image forming apparatus according to a second aspect of the present invention is the image forming apparatus according to the first aspect, wherein the plurality of heaters include a heater for a wide paper width and a heater for a narrow paper width, Sometimes, the control means heats the fixing unit using a heater for wide paper width,
According to a third aspect of the present invention, there is provided the image forming apparatus according to the first or second aspect, wherein the control means is configured to maintain the fixing temperature during continuous printing after the start of paper feeding. One of the plurality of heaters is used to control the temperature of the fixing unit according to the width.

According to the image forming apparatus of the first and second aspects of the present invention, since a long heater is used regardless of the width of the recording paper when rotating before printing from the start of printing to before starting the feeding of the recording paper, as much as possible The entire heat roller of the fixing unit can be quickly warmed quickly.
According to the image forming apparatus of the third aspect of the present invention, when maintaining the fixing temperature during continuous printing after the start of feeding, one of the plurality of heaters is selected according to the width of the recording paper. Since temperature control of the fixing unit is executed, it is possible to prevent an abnormal temperature rise at the end of the heat roller during image formation on a narrow paper sheet.

Hereinafter, an embodiment in which the image forming apparatus of the present invention is applied to a digital multifunction machine having a copying function, a facsimile function, a printing function, a scanner function, and the like will be described.
FIG. 1 is a schematic block diagram showing the hardware configuration of a digital multi-function peripheral. As shown in the figure, the digital multi-function peripheral has a CPU 1, a ROM (Read Only Memory) 2, an SRAM (Static Random Access Memory) 3, and a memory controller 4. , Image memory 5, codec 6, modem 7, network control unit (NCU) 8, scanner 9, operation panel 10, printer image processing circuit 11, printer mechanism control circuit 12, LAN interface (I / F) 13, etc. Each part is connected via a bus 14.

  The CPU 1 controls each part of the hardware of the digital multi-function peripheral via the bus 14 and executes various programs based on the programs stored in the ROM 2. The ROM 2 stores various programs and operation messages necessary for the operation of the digital multi-function peripheral, and the SRAM 3 stores temporary data generated when the program is executed.

  The memory controller 4 controls writing and reading of image signals to and from the image memory 5, and the image memory 5 is configured using an SDRAM or the like, and stores image data to be transmitted, received image data, or read image data. The codec 6 encodes and decodes in accordance with a predetermined encoding method. In order to transmit the image data of the read original, it is encoded by the MH, MR or MMR method, and the image data received from the outside is decoded. To do.

  The modem 7 is connected to the bus 14 and functions as a fax modem capable of facsimile communication. The modem 7 is also connected to the NCU 8 connected to the bus 14. The NCU 8 is hardware for closing and opening an analog line, and connects the modem 7 to the public switched telephone network (PSTN) as necessary.

  The scanner 9 includes a reading document placing table such as an auto document feeder (ADF) or a flatbed scanner (FBS), reads a document using a CCD or the like, and outputs dot image data. The operation panel 10 includes a display unit that displays an operation state of the digital multifunction peripheral or displays an operation screen for various functions, and a plurality of keys for operating the digital multifunction peripheral.

  Further, the printer image processing circuit 11 processes the print image signal and inputs it to the printer engine 15, and the printer mechanism control circuit 12 controls the printer engine 15 to print out received data, copy original data, and the like. To do. The printer engine 15 includes a long heater 16 for a wide paper width and a short heater 17 for a narrow paper width as fixing device heaters. These heaters include a power switch 18 and a heater on / off control switch (SW). Heated by a commercial AC power supply AC via 19 and 20. The thermistor 21 detects the temperature of the fixing device and inputs a temperature detection output to the printer mechanism control circuit 12.

  The LAN interface 13 is connected to the LAN and receives signals from the Internet, while transmitting signals and data to the LAN, and executes interface processing such as signal conversion and protocol conversion.

  The digital multi-function peripheral has the above-described configuration. When sending a facsimile, the image data of the original is read by the scanner 9, and the read image signal is compressed by the codec 6 and is sent to the image memory 5 via the memory controller 4. Accumulated in. The compressed image data is read from the image memory 5, modulated by the modem 7, and transmitted from the NCU 8 to the communication partner through the PSTN. At the time of facsimile reception, the received image data is demodulated by the modem 7, stored in the image memory 5 via the memory controller 4, then decoded by the codec 6, and the printer image processing circuit 11 is printed on the printer engine 15. Printing is executed by supplying an image signal.

Next, the details of the structure of the printer engine 15 will be described with reference to FIG.
The printer engine 15 includes a photosensitive drum 31 serving as an image carrier that is rotationally driven at a predetermined speed. The transfer roller 32 and the photosensitive drum are sequentially arranged around the photosensitive drum 31 in the rotation direction (the arrow direction in the drawing). A memory removal brush 33 that removes the potential of 31, a charging corona charger 34 that is a charger that uniformly charges the surface of the photosensitive drum 31, and an image that exposes an image on the surface of the photosensitive drum 31 to form an electrostatic latent image An LED print head 35 as an exposure device and a developing device 36 for developing the electrostatic latent image formed on the photosensitive drum 31 with toner are provided, and a fixing device 37 is provided on the paper discharge side of the photosensitive drum 31. It has been.

The developing device 36 agitates a developer composed of a developing roller 38, a supply roller 39 for supplying toner to the developing roller 38, and toner and a carrier replenished from a toner replenishing unit (not shown) along the bottom thereof. In addition, a stirring paddle 40 that supplies the surface of the developing roller 38 is provided.
The transfer roller 32, the memory removal brush 33, the charging corona charger 34, and the developing roller 38 are each supplied with a high voltage generator 41 for transfer bias, a high voltage generator 42 for memory removal brush, and a high voltage for charging bias. The generator 43 and the development bias high voltage generator 44 are controlled by the printer mechanism control circuit 12 to generate high voltages.

On the other hand, the fixing device 37 is composed of a heat roller 45 and a nip roller 46 that rotates by being pressed against the heat roller 45, and in the heat roller 45, as shown in FIG. 3, a halogen lamp as a long heater 16 for a wide paper width. 47 and a halogen lamp 48 as a short heater 17 for a narrow paper width are arranged.
The CPU 1 controls the heater on / off control switches 19 and 20 via the printer mechanism control circuit 12 based on the output of the thermistor 21 which is a temperature detection element provided in contact with the heat roller 45. Thus, the temperature of the heat roller 45 is controlled to the standby temperature, the fixing temperature, and the like.

The LED print head 35 collects the light beam emitted from each LED chip of the LED array by each corresponding microlens and forms an image on the outer peripheral surface of the photosensitive drum 31, thereby making the LED print head 35 as a whole. The light beam can be irradiated with a predetermined resolution in the axial direction of the photosensitive drum 31.
The memory removal brush 33 removes residual toner, paper dust, and the like on the surface of the photosensitive drum 31 after each toner image transfer process is completed, and removes the charge to prepare for the next image forming process. The motor 49 is a motor for rotating each rotating part of the printer mechanism, and is controlled by the printer mechanism control circuit 12 via the motor driver 50.

  The printer engine is configured as described above. When an image is formed by the printer engine, the surface of the photosensitive drum 31 is uniformly charged by the charging corona charger 34, and then the charged photosensitive drum 31 is charged. Is exposed to light for image formation emitted from the LED print head 35 in accordance with image data to form an electrostatic latent image. The electrostatic latent image formed on the photosensitive drum 31 in this manner is developed into a visible toner image by the developing device 36 with toner. The visible toner image is sequentially transferred onto the recording paper by the charging action of the transfer roller 32, and then the recording paper on which the toner image has been transferred is heated and pressed by the fixing device 37 to fix the toner image, and then discharged. The paper is guided to be discharged by a paper portion (not shown).

Next, the operation when the CPU 1 executes the temperature control of the fixing device via the printer mechanism control circuit 12 will be described with reference to the flowchart of FIG.
FIG. 4 is a flowchart showing the operation when the heater used for heating is switched in accordance with the temperature control state of the fixing unit during standby, rotation before printing, etc. When the power of the digital multi-function peripheral is turned on, the CPU 1 4, the heater control switching program shown in the flowchart of FIG. 4 is started, and it is determined whether or not the standby temperature control is being executed at that time (step 101), and the temperature control at that time is the standby temperature control. If it is determined, temperature control is executed using the long heater 16, that is, the halogen lamp 47 (step 102).

  If it is determined in step 101 that the current temperature control is not the standby temperature control, the CPU 1 determines whether or not the temperature increase during the pre-printing rotation is executed at that time (step 103). If it is determined that the temperature control at that time is a temperature increase during rotation before printing, the temperature increase control is executed using the long heater 16, that is, the halogen lamp 47 (step 104).

  If it is determined in step 103 that the temperature control at that time is not the temperature increase control during the pre-printing rotation, the CPU 1 determines whether or not the temperature control during fixing is being executed at that time (step 105). When it is determined that the temperature control at the time is the temperature control at the time of fixing, a heater corresponding to the width of the recording paper is selected and the temperature control is executed (step 106). That is, when the width of the recording paper is wide, temperature control is performed using the long heater 16, that is, the halogen lamp 47, and when the width of the recording paper is narrow, the short heater 17, that is, the halogen lamp 48 is set. To perform temperature control.

If it is determined in step 105 that the temperature control at that time is not the temperature control during fixing, the CPU 1 determines whether or not the temperature control during sleep is executed at that time (step 107). When it is determined that the temperature control is the sleep temperature control, all the heaters are turned off (step 108).
As described above, while the power of the digital multi-function peripheral is on, the CPU 1 constantly monitors the temperature control state of the fixing device at that time, and switches the heater used for temperature control.

As described above, the CPU 1 switches the heater used for the temperature control of the fixing device. Details of the temperature control of the fixing device will be described below with reference to the flowchart of FIG. 5 and the waveform diagram of FIG.
When the power of the digital multi-function peripheral is turned on, the CPU 1 starts the temperature control program shown in the flowchart of FIG. 5, sets the temperature control to the standby temperature control (step 201), and then shifts the fixing device to the energy saving mode. The timer Ta for measuring the time for starting is started (step 202).

  Next, the CPU 1 determines whether or not the temperature of the fixing device is higher than the standby temperature based on the temperature detected by the thermistor 21 (step 203). If the temperature has not reached the standby temperature, the heater on / off signal to the SW 19 is determined. By turning on, the long heater 16, that is, the halogen lamp 47 for wide paper width is turned on (step 204).

If it is determined in step 203 that the temperature of the fixing device has become higher than the standby temperature, the CPU 1 turns off the long heater 16 by turning off the heater on / off signal to the SW 19 (step 205), and then the print job is executed. It is determined whether or not it has occurred (step 206).
If it is determined that a print job has not occurred, the CPU 1 determines whether or not the timer Ta has expired (step 207). If it is determined that the timer Ta has not expired, the process returns to step 203. It is determined again whether the temperature of the fixing device is higher than the standby temperature.

  On the other hand, if it is determined in step 206 that a print job has occurred, the CPU 1 switches the temperature control to the temperature increase control during rotation before printing (step 208), and then whether or not the detected temperature of the thermistor 21 has reached the pickup temperature. (Step 209), if the pickup temperature has not been reached, the heater on / off signal to the SW 19 is turned on to turn on the long heater 16 as shown in FIG. 6B (step 210). ). As a result, as shown in FIG. 6A, the temperature detected by the thermistor 21, that is, the temperature of the fixing device increases.

The standby temperature and fixing temperature of the fixing device are 100 to 140 ° C. and 180 to 200 ° C., respectively. For example, when the fixing temperature is 200 ° C., the pickup temperature is set to 195 ° C.
Further, after the printing is started, as shown in FIG. 6 (d), the rotation of each rotating portion of the printer engine is started by the motor 49.

  When the temperature detected by the thermistor 21 rises to the pickup temperature and it is determined in step 209 that the temperature of the fixing device has reached the pickup temperature, the CPU 1 turns on / off the heater to the SW 19 as shown in FIG. After the long heater 16 is turned off by turning off the off signal (step 211), as shown in FIG. 6E, the pickup signal is output to start feeding the recording paper and to start printing ( Step 212).

  When the printing is started, the CPU 1 switches the temperature control to the temperature control at the time of fixing (step 213), determines whether or not the printing is completed (step 214), and determines that the printing is not completed. Based on the temperature detected by the thermistor 21, it is determined whether or not the temperature of the fixing device is higher than the fixing temperature (step 215).

  When the temperature of the fixing device has not reached the fixing temperature, the CPU 1 determines whether or not the width of the recording paper is wide (step 216), for example, determines that the recording paper is A3 and the width of the recording paper is wide. In this case, by turning on the heater on / off signal to SW19 and turning off the heater on / off signal to SW20, the long heater 16 is turned on, and when the short heater 17 is on, the short heater 17 is turned on. Is turned off (step 217), the process returns to step 214, and it is determined whether or not printing is completed.

  Further, when the recording paper is determined to be, for example, A4 and the width of the recording paper is narrow, the CPU 1 turns on the heater on / off signal to SW20 and the heater on / off to SW19 as shown in FIG. 6C. By turning off the signal, the short heater 17 is turned on. If the long heater 16 is on, the long heater 16 is turned off (step 218), and then the process returns to step 214 to complete printing. Determine whether or not.

  If it is determined in step 215 that the temperature of the fixing device has reached the fixing temperature based on the temperature detected by the thermistor 21, the CPU 1 turns off the heater by turning off the heater on / off signal to the SWs 19 and 20. After that (step 219), the process returns to step 214 to determine whether or not the printing is completed.

  When this fixing temperature control is executed, as shown in FIGS. 6F and 6G, the LED print head 35 emits light for image formation according to the image data, whereby the photosensitive drum 31 is used. The electrostatic latent image formed on the photosensitive drum 31 is developed into a visible toner image by the toner by the developing unit 36 and sequentially transferred onto the paper by the transfer roller 32, and then the toner image is transferred. As the sheet passes through the fixing device 37, the toner image is fixed by being heated and pressurized.

  On the other hand, if it is determined in step 214 that printing has ended, the CPU 1 turns off the heater on / off signal to the SWs 19 and 20 to turn off the heater (step 220), and then restarts the timer Ta. A timer Tb for measuring the time for shifting to the standby mode is started (step 221). Thereafter, the CPU 1 determines whether or not a print job has occurred (step 222). If it is determined that no print job has occurred, the CPU 1 determines whether or not the timer Tb has expired (step 223). . If it is determined that the timer Tb has not expired, the CPU 1 returns to step 222 and determines again whether a print job has occurred.

  On the other hand, if it is determined in step 223 that the timer Tb has timed up, that is, the transition time to the standby mode has elapsed, the CPU 1 switches the temperature control to the standby temperature control (step 224). Based on the detected temperature, it is determined whether the temperature of the fixing device is higher than the standby temperature (step 225).

  If it is determined that the temperature of the fixing device is lower than the standby temperature, the CPU 1 turns on the heater 16 to turn on the long heater 16 by turning on the heater on / off signal to the SW 19 (step 226). If it is determined that it is higher, the heater ON / OFF signal to the SW 19 is turned off to turn off the long heater (step 227), and then it is determined whether a print job has occurred (step 228).

  If it is determined in step 228 that a print job has not occurred, the CPU 1 determines whether or not the timer Ta has timed up (step 229), and if it is determined that the timer Ta has not timed up, Returning to step 225, it is determined again whether the temperature of the fixing device is higher than the standby temperature.

  On the other hand, if it is determined in step 229 or step 207 that the timer Ta has timed up, that is, the transition time to the energy saving mode has elapsed, the CPU 1 switches the temperature control to the sleep temperature control (step 230), SW19, By turning off the heater on / off signal to the SW 20, the long heater 16 and the short heater 17 are turned off (step 231), and it is determined whether or not a print job has always occurred.

  If it is determined in step 232, step 222, or step 228 that a print job has occurred, the CPU 1 returns to step 208 and switches the temperature control to the temperature increase control during pre-printing rotation, and prints in the same manner as described above. Perform processing for execution.

  As described above, during the pre-print rotation from the start of printing to the start of recording paper feeding, the long heater for wide paper width is used regardless of the width of the recording paper, so the entire heat roller of the fixing unit is as fast as possible When maintaining the fixing temperature during continuous printing after the start of paper feeding, a long heater for a wide paper width and a short heater for a narrow paper width are used according to the width of the recording paper. Since either one is selected and the temperature control of the fixing device is executed, it is possible to prevent an abnormal temperature rise at the end of the heat roller when forming an image on a narrow sheet.

  In the above-described embodiment, the heater has been described as being provided with two long and short heaters. However, the present invention is also applicable to an image forming apparatus provided with three long, medium, and short heaters. In this case, a long heater is used to increase the temperature during rotation before printing, and either a long, medium, or short heater is used according to the width of the recording paper during fixing.

  In the above embodiments, the case where the image forming apparatus of the present invention is applied to a digital multifunction peripheral has been described. However, the image forming apparatus of the present invention is also applied to other image forming apparatuses such as a facsimile machine and a copier. be able to.

It is a schematic block diagram which shows the hardware constitutions of a digital multi-function peripheral. It is a figure which shows the detail of the structure of a printer engine. It is a figure which shows the arrangement | positioning state of the halogen lamp in a heat roller. It is a flowchart which shows an effect | action when performing temperature control of a fixing device. It is a flowchart which shows the detailed effect | action of the temperature control of the heater of a fixing device. It is a figure which shows the operation waveform at the time of printing execution.

Explanation of symbols

1 CPU
2 ROM
3 SRAM
4 Memory controller 5 Image memory 6 Codec 7 Modem 8 NCU
9 Scanner 10 Operation Panel 11 Image Processing Circuit for Printer 12 Printer Mechanism Control Circuit 13 LAN I / F
14 Bus 15 Printer Engine 16 Long Heater 17 Short Heater 18 Power Switch 19, 20 Switch (SW)

Claims (3)

An image forming apparatus comprising: a fixing unit having a plurality of heaters having different lengths; and a control unit that controls the heater according to the temperature of the fixing unit.
An image forming apparatus characterized in that the control means heats the fixing unit using a long heater at the time of pre-printing rotation before starting feeding after starting printing. The image forming apparatus according to claim 1,
The plurality of heaters comprises a heater for wide paper width and a heater for narrow paper width, and the control means heats the fixing unit using the heater for wide paper width during rotation before printing. Image forming apparatus. The image forming apparatus according to claim 1, wherein:
The control unit executes temperature control of the fixing unit using any of the plurality of heaters according to the width of the recording paper when maintaining the fixing temperature during continuous printing after the start of feeding. Image forming apparatus.

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