JP2006276514A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of controlling fixing temperature precisely so that influences on the fixation temperature by a sheet on which image is formed can be suppressed. <P>SOLUTION: A recording control unit 40 controls voltage of a heater voltage application circuit 44 on the basis of a detection signal from a temperature detection sensor 50 for detecting temperature of a fixing face of a fixing roller 22 and controls heating of the fixing roller 22. When an image formation command is issued, the recording control unit 40 compares the fixing face temperature detected by the temperature detection sensor 50 with reference temperature and, when the former is lower than the reference temperature, sets the fixing face temperature at the start of sheet feeding higher than normal fixation set temperature. When the fixing face temperature is higher than the reference temperature, the fixing face temperature at the start of the sheet feeding is set lower than the normal fixation set temperature. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile machine.

  As an electrophotographic image forming apparatus, for example, a photosensitive drum is used as an image carrier, an electrostatic latent image is formed on the surface, the electrostatic latent image is developed with toner, and transferred to a sheet. There is known an image forming method in which a developed image is fixed. In such an image forming apparatus, a preparatory operation is performed in advance before performing an image forming operation or a fixing operation on the photosensitive drum, and then a steady operation is performed to perform image formation.

In particular, it is necessary to set the fixing temperature when the toner image is transferred to the paper and then fixed, and if the fixing operation is performed in a state deviating from the set temperature, there is a problem that the toner does not fix well and the image quality deteriorates. Will be invited. However, if the preparatory operation is performed until the fixing temperature rises to the set temperature and becomes a steady state, it consumes power and makes the user wait. Therefore, it has been proposed to efficiently control the heater temperature used for fixing and to perform image forming processing efficiently. For example, in Patent Document 1, the temperature of the heat roller is detected prior to the start of heating of the heat roller, and when the detected temperature is equal to or lower than the reference temperature, the fixing temperature of the heat roller is set higher, and the detected temperature is the reference temperature. If the temperature exceeds the fixing temperature, the fixing temperature is set to a lower value, and the rotation of the heat roller and the press roller is started when the detected temperature exceeds a predetermined temperature.
Japanese Patent Laid-Open No. 9-212035

  As in Patent Document 1, the fixing temperature is set high when the heat roller is low, and is set low when the heat roller is high, so that the fixing temperature of the heat roller is finely controlled. It is possible to prevent the deviation from the set temperature necessary for fixing to some extent. However, as a factor affecting the fixing temperature, it is conceivable that the paper to be fixed other than the press roller pressed against the heat roller takes heat. In particular, when image formation processing is continuously performed on paper, the first first sheet tends to be insufficiently fixed because the fixing surface of the fixing unit is often in a low temperature state. The influence on the fixing temperature of the paper is not considered.

  Accordingly, an object of the present invention is to provide an image forming apparatus capable of finely controlling the fixing temperature so as to suppress the influence of the sheet on which image forming processing is performed on the fixing temperature.

  An image forming apparatus according to the present invention includes an image carrier, an image forming unit that forms a visible image on the image carrier and transfers the image to a sheet, a fixing unit that fixes the visible image transferred to the sheet, A control unit configured to control the image forming unit and the fixing unit to form an image on a sheet; and a fixing surface temperature detecting unit configured to detect a fixing surface temperature of the fixing unit. Comparing means for comparing the temperature data detected by the fixing surface temperature detecting means with reference temperature data at the timing when the forming process command is output, and at the paper feed start timing based on the comparison result of the comparing means And a determining means for determining the fixing surface temperature. Further, the determining means determines a fixing surface temperature at a low temperature when it is determined that the temperature data is lower than the reference temperature data, and a fixing at a high temperature when it is determined that the temperature data is higher than the reference temperature data. It is characterized by being set higher than the surface temperature. Further, the low-temperature fixing surface temperature is set higher than a fixing set temperature of the fixing unit, and the high-temperature fixing surface temperature is set lower than the fixing set temperature. Further, the fixing surface temperature at the time of high temperature is set to a temperature at which the temperature of the fed sheet can be raised to a preset fixing temperature before reaching the fixing unit.

  By having the above configuration, the fixing surface temperature is determined at the timing when the image forming processing command is output, and the fixing surface temperature is determined at the paper feeding start timing. Depending on the height of the sheet, it is possible to prevent the fixing temperature from being affected by heat deprived of the sheet during fixing. As described above, when image forming processing is continuously performed on a sheet, the first first sheet is fixed at the fixing operation temperature depending on the temperature state of the fixing surface at the start of the rotational driving of the image carrier. It is easy to be affected. For example, if the temperature of the fixing surface is low, the heat required to increase the temperature of the fixing surface increases. Therefore, if the heat is removed from the paper during the fixing operation of the paper, the fixing surface temperature fluctuates and the fixing is insufficient. It will fall into. Therefore, by determining the fixing surface temperature at the sheet feeding start timing based on the fixing surface temperature detected at the timing when the image forming processing command is output, insufficient fixing during the sheet fixing operation can be suppressed. it can.

  The temperature data of the fixing surface temperature detected at the timing when the image forming processing command is output is determined to be lower than the reference temperature data, and the temperature data is the reference temperature data. If the fixing surface temperature detected at the start timing of rotation of the image carrier is low, the fixing surface temperature at low temperature is set high. Therefore, even when the temperature state of the fixing surface is low, even if the sheet is deprived of heat during the fixing operation, the fixing is prevented from being insufficiently fixed.

  Also, by setting the fixing surface temperature at low temperature higher than the fixing setting temperature of the fixing unit and setting the fixing surface temperature at high temperature lower than the fixing setting temperature, fixing is performed when the fixing surface temperature is lower than the reference temperature. Even if the paper is deprived of heat during operation, it is prevented that the fixing temperature drops below the fixing temperature, and if the fixing surface temperature is higher than the reference temperature, the temperature is raised to the fixing temperature. Image processing can be performed by starting paper feeding before the image forming operation is performed, and it is possible to shorten the image forming processing time, and the fixing operation is performed before the fixing temperature becomes higher than the fixing temperature. This prevents the fixing surface temperature from becoming excessively high. If the fixing surface temperature at high temperature is set to a temperature at which the temperature of the fed paper reaches the fixing means before reaching the fixing means, the fixing surface temperature is reached when the fed paper reaches the fixing means. The temperature is raised to the fixing set temperature, and the paper transport operation is performed in parallel with the preparation operation for raising the temperature to the fixing set temperature, so that the image forming processing time is shortened and the fixing unit is prepared. It is possible to minimize power consumption during operation.

  Hereinafter, embodiments according to the present invention will be described in detail. The embodiments described below are preferable specific examples for carrying out the present invention, and thus various technical limitations are made. However, the present invention is particularly limited in the following description. Unless otherwise specified, the present invention is not limited to these forms.

  FIG. 1 is a schematic cross-sectional view of the entire image forming apparatus according to the present invention. A paper discharge tray 10 is provided in the upper part of the image forming apparatus 1, and a recording unit 2 and a paper feeding unit 3 are arranged in the lower part thereof.

  In the paper feed unit 3, a paper feed cassette 11 is arranged, and a plurality of sheets of a predetermined size are stacked on the flapper 12. A pickup roller 13 is disposed at the right end of the paper feed cassette 11. The flapper 12 is urged upward by a spring member (not shown) so that the upper surface of the stacked paper comes into pressure contact with the pickup roller 13. When the pickup roller 13 is rotationally driven in this state, the sheets are fed one by one to the sheet conveyance path by the frictional force.

  The fed paper is first conveyed to the recording unit 2 by the feed roller 14 and the press roller 15. The recording unit 2 includes a developing device 16, a cleaning unit 17, a corona charger 18, a photosensitive drum 19, a transfer roller 20, an exposure head 21, and a fixing roller 22 for recording on the conveyed paper. The cleaning unit 17 cleans the surface of the photosensitive drum 19 by capturing foreign matters such as residual toner and paper dust attached to the surface of the photosensitive drum 19 after transfer. The corona charger 18 uniformly charges the surface of the photosensitive drum 19 by the discharge from the corotron. An electrostatic latent image is formed on the uniformly charged photosensitive drum 19 by exposing the photosensitive drum 19 with an exposure head (LED head) 21 in accordance with an image recording signal. Then, the toner in the developing device 16 is transferred to the electrostatic latent image formed on the photosensitive drum 19 to visualize the electrostatic latent image. The transfer roller 20 is installed at a position facing the photosensitive drum 19 with the paper interposed therebetween, and a toner image formed on the surface of the photosensitive drum 19 is transferred to the paper when a predetermined voltage is applied. The transferred toner image is sandwiched between the fixing roller 22 and the press roller 23 and heated and pressed to be fixed on the paper. The fixed sheet is sandwiched between the sheet discharge roller 24 and the press roller 25 and is carried out to the sheet discharge tray 10.

  Further, a manual paper feed mechanism and a reverse conveyance mechanism are provided on the side surface of the apparatus main body, and when performing manual paper feed, the side cover 26 is opened and the paper is inserted into the paper feed roller 27. . The inserted paper is conveyed to the feed roller 14 and the press roller 15 by the paper feed roller 27 and recording operation is performed. Also, when performing reverse conveyance, the paper recorded on one side is once sandwiched between the paper discharge roller 24 and the press roller 25 and then conveyed, and then the paper discharge roller 24 is rotated in reverse to be conveyed to the reverse conveyance path. Then, the feed roller 28 and the press roller 29, and the feed roller 30 and the press roller 31 are transported downward by two pairs of transport rollers. Then, the sheet is conveyed again to the feed roller 14 and the press roller 15 and a recording operation is performed on the other side, and recording is performed on both sides of the sheet.

  FIG. 2 is a schematic diagram illustrating a circuit configuration in the recording unit 2. A recording control unit 40 that controls the entire recording operation includes a charging voltage application circuit 41 that applies a predetermined voltage to the corona charger 18, a developing voltage application circuit 42 that applies a predetermined voltage to the developing roller 32 and the supply roller 33, A voltage control signal is transmitted to a cleaning voltage application circuit 43 that applies a predetermined voltage to the cleaning roller 34, the recovery roller 35, and the sponge body 36, and a heater voltage application circuit that applies a voltage to the heater provided in the fixing roller 22, respectively. Voltage control of each member is performed. The recording control unit 40 receives a detection signal from a temperature detection sensor 50 that detects the fixing surface temperature of the fixing roller 22 and controls the heater voltage application circuit to adjust the fixing surface temperature of the fixing roller 22. The recording control unit 40 also performs voltage control of the transfer roller 20, but is omitted in this embodiment. In addition, the recording control unit 40 performs exposure control of the LED head 21 based on the image signal.

  FIG. 3 shows an image forming process flow in the present embodiment. When receiving the signal for instructing the image forming process on the paper, the recording control unit 40 detects the temperature in the apparatus and determines the fixing surface temperature Temp1 which is the driving start timing of the main motor (S100a). Tempm1 may be determined by storing Temp1 data corresponding to the internal temperature in advance, detecting the internal temperature at the timing when the processing command is issued, and reading Temp1 data corresponding to the detected temperature. Next, a fixing surface temperature Temp2 as a paper feed start timing is determined (S100b).

FIG. 4 is a processing flow showing the Temp2 determination task. In this task, first, it is checked whether or not the sheet on which image formation processing is performed is the first sheet (S200). If it is the first sheet, the current fixing surface temperature Temp is detected by a detection signal from the temperature detection sensor 50 (S201), and it is checked whether or not the detected fixing surface temperature Temp is equal to or higher than the reference temperature Ts. (S202). If the reference temperature Ts or sets the Temp2 to a high temperature during the fixing surface temperature _{T L} (S203), when lower than the reference temperature Ts is set to Temp2 low temperature during the fixing surface temperature _{T H} (S204). If it is determined in step S200 that the sheet is not the first sheet, Temp2 is set to the high-temperature fixing surface temperature _TL .

Here, the high temperature fuser surface temperature T _L, is set lower than the low temperature fixing surface temperature T _H, when compared with conventional fixing temperature T _F,
T _L <T _F <T _H
It is set to become. _TL is set to a temperature at which the fixing surface temperature can be raised to _TF in the time from when the paper is fed by the pickup roller 13 until it reaches the fixing roller 22.

  When Temp2 is determined as described above, the voltage control of the heater voltage application circuit 44 is started, and the heater of the fixing roller 22 starts heating (S100c). Then, it is checked whether or not the fixing surface temperature Temp has been raised to Temp1 (S101), and when the temperature is raised to Temp1, a pre-rotation process of the photosensitive drum is performed (S102). In the pre-rotation process, the main motor starts to rotate, and the photosensitive drum 19, the supply roller 33, the developing roller 32, the transfer roller 20, and the cleaning roller 34 start to rotate. Then, voltage control of the charging voltage application circuit 41, the development voltage application circuit 42, and the cleaning voltage application circuit 43 is started.

  Next, it is checked whether or not the fixing surface temperature Temp has been raised to Temp2 (S103), and when the temperature has been raised to Temp2, the pickup roller 13 is driven and rotated to start feeding and control the conveyance of the sheet (S104a). At the same time, voltage control for image formation is started, and a series of image forming processes such as charging, exposure, development, and transfer are performed as described above (S104b).

  When the image forming process is completed, a post-rotation process is performed (S105). In the post-rotation process, the voltage of the transfer roller 20 is controlled, the residual toner adhering to the transfer roller 20 is collected, and the rotation of the main motor is stopped at a predetermined timing after the post-rotation process (S106). Move on.

5, the fixing surface temperature Temp when the Temp2 is set to the low temperature during the fixing surface temperature _{T H} (FIG. 5 (a)) and when it is set to a high temperature during the fixing surface temperature _{T L} (FIG. 5 (b)) It is a graph which shows transition of. In the graph, the timing when an image formation command is issued is a time t _s, the timing of the sheet feed start is the time t _k.

If Temp2 is set to the low temperature during the fixing surface temperature T _H is lower temperature than the reference temperature Ts at which the image forming command is issued, fixing temperature T _F higher low temperature fixing surface temperature T than _The fixing surface temperature is raised to _H and sheet feeding is started. For this reason, even if the sheet is sandwiched between the fixing roller 22 and the press roller 23 and the sheet is deprived of heat, the fixing temperature does not fall below the set fixing temperature _TF so that insufficient fixing does not occur. For the second and subsequent sheets after the image forming process for the first sheet is completed, the fixing surface temperature becomes excessively high by performing the heating control of the heater based on the normal fixing setting temperature _TF. To prevent.

Temp2 is when it is set to a high temperature during the fixing surface temperature T _L is the paper feed start timing at low elevated temperature during fixing surface temperature T _L of the fixing setting temperature T _F is set. For this reason, paper feeding is started before the fixing surface temperature rises to the fixing set temperature _TF. However, the temperature setting of the fixing surface temperature _TL at the high temperature is performed as described above. Since it is set so that the temperature can be raised to the fixing set temperature _TF in the time until it reaches the fixing roller, when the fixing operation is performed, the temperature is raised to the fixing set temperature _TF so that the fixing is not insufficient. . For this reason, the fixing surface temperature does not become excessively high, and the sheet processing is performed in parallel with the operation of raising the fixing surface temperature, so that the image processing time can be shortened.

1 is a schematic sectional view of an entire image forming apparatus according to an embodiment of the present invention. It is the schematic regarding the circuit structure of a recording part. 3 is an image forming process flow according to the embodiment of the present invention. It is a determination task flow of Temp2 which is a paper feed start temperature. It is a graph which shows transition of fixing surface temperature Temp.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Recording part 3 Paper feeding part
17 Cleaning means
18 Corona charger
19 Photosensitive drum
20 Transfer roller
21 Exposure head
22 Fixing roller
32 Developing roller
34 Cleaning roller
50 Temperature sensor

Claims (4)

An image carrier, an image forming unit that forms a visible image on the image carrier and transfers the image to a sheet, a fixing unit that fixes the visible image transferred to the sheet, the image forming unit, and the fixing unit Control means for performing image formation on the paper by controlling, and fixing surface temperature detecting means for detecting the fixing surface temperature in the fixing means,
The control means compares the temperature data detected by the fixing surface temperature detection means with reference temperature data at the timing when the image forming processing command is output, and paper based on the comparison result of the comparison means An image forming apparatus comprising: a fixing unit that determines a fixing surface temperature at a sheet feeding start timing.   The determining means determines the low-temperature fixing surface temperature when it is determined that the temperature data is lower than the reference temperature data, and the high-temperature fixing surface temperature when the temperature data is determined to be higher than the reference temperature data. The image forming apparatus according to claim 1, wherein the image forming apparatus is set higher than the image forming apparatus.   3. The fixing surface temperature at the low temperature is set higher than a fixing set temperature of the fixing unit, and the fixing surface temperature at the high temperature is set lower than the fixing set temperature. The image forming apparatus described in 1.   4. The image according to claim 2, wherein the fixing surface temperature at the time of high temperature is set to a temperature at which the temperature of the fed sheet can be raised to a fixing setting temperature before reaching the fixing unit. Forming equipment.

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