JP2006038916A - Image forming apparatus control method and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce energy consumption and productivity by shortening a recovery time while preventing a fixing failure in consideration of a low fixing member temperature in the first print after returning from a standby state in an image forming apparatus. Plan.
A toner image transferred onto a transfer paper P by an electrophotographic image forming apparatus is heated and pressurized to be fixed on the transfer paper P. The fixing roller 30 includes one or more heating elements 33 such as halogen heaters so that the temperature can be kept within a control temperature range. In the first print immediately after returning from the standby state, the maximum toner adhesion amount is made smaller than usual. For example, when the maximum adhesion amount is usually 250%, the maximum adhesion amount is 200% for the three sheets immediately after returning.
[Selection] Figure 2

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile, and the like having a fixing device that fixes toner onto transfer paper with heat and pressure, and a control method thereof.

  In recent years, energy saving is also demanded in devices using electrophotographic methods such as copying machines. In particular, a fixing unit with high power consumption is required to have a so-called “on-demand fixing property” in which a heater is turned off during standby and a function is obtained by heating and energizing only during printing. At this time, it is better that the “return time” at which the machine starts to operate after the user sends a print signal is short. However, if the fixing member cooled during standby is not heated to the fixing possible temperature, fixing failure occurs. .

  Recently, however, copying machines and laser printers are rapidly becoming color. Since the color image in the electrophotographic system is a multi-colored superimposed image, the amount of toner adhesion per unit image area is larger than that of a conventional monochrome image. In general, the larger the amount of toner attached, the higher the amount of heat required for fixing. Immediately after returning from the standby state, even if there is no problem in fixing in monochrome printing, fixing in color printing may occur. FIG. 4 shows the cold offset occurrence temperature (fixing lower limit temperature) in relation to the amount of toner on paper and the fixing belt temperature.

  By the way, color images include images corresponding to two colors such as red, blue, and green (for two toner layers), but a color almost black is equivalent to 3C (for three toner layers). When such colors are formed with C (cyan), M (magenta), and Y (yellow) colors being close to 100% and a total of 300% (monochromatic solid ratio), the toner layer becomes thick and uncomfortable. For this reason, a part of the same amount of C, M, and Y may be substituted with BK (black) toner to make the toner layer thin. For example, in an image of C: 100%, M: 100%, Y 100% (total 300%), Bk: 25%, C: 75%, M: 75%, Y: 75% (total 250%), Bk: 50%, C50%, M: 50%, Y: 50% (total 200%), and the like. However, the color reproduction space becomes narrower when Bk toner is used.

  Therefore, as a conventional technique, as disclosed in Patent Document 1, toner consumption information is detected before an image forming operation, and a fixing operation is performed even if the fixing temperature is lower than a predetermined temperature based on the toner consumption information. If it is determined that the fixing operation is possible even if the fixing temperature is lower than the predetermined temperature, the fixing operation is executed. Even when the fixing temperature does not reach a predetermined temperature, printing or copying can be performed, so that there is a technique that can shorten the waiting time until the start of printing at the time of warm-up. That is, in the image forming apparatus, the waiting time can be minimized during the warm-up according to the toner consumption information detected before the image forming operation, and the fixing speed can be optimally controlled, so that the stable high The image quality image can be formed.

  Further, as disclosed in Patent Document 2, an unfixed toner image is transferred at a nip portion formed by a fixing roller having a built-in heater and a pressure roller rotatably pressed against the fixing roller. There is an image forming apparatus that includes a fixing device for heat-melting and fixing, and according to the sheet passing size and the number of sheets passing through one job, the apparatus waits for a predetermined time and then shifts to the next job. That is, after passing a small size paper continuously through the fixing device, even if a large size paper is passed, the paper does not flutter at the time of passing, and the unfixed image is not disturbed and transfer blur does not occur. According to the present invention, it is possible to provide an image forming apparatus that does not use a plurality of thermistors, control drivers, etc., has a simple structure, is easy to manufacture, and does not increase costs.

JP-A-11-125987 Japanese Patent Laid-Open No. 11-258943

  The present invention considers the above-mentioned conventional points and considers that the fixing member temperature is low in the first print after returning from the standby state, thereby shortening the return time while preventing fixing failure and saving energy. The goal is to achieve both productivity and productivity.

  The control method of the image forming apparatus according to claim 1 of the present invention is a control method for returning from a standby state in an image forming apparatus including a fixing device that fixes toner onto transfer paper with heat and pressure. In the first print after returning from the standby state, the maximum amount of toner adhering to the transfer paper is controlled to be smaller than usual.

  According to a second aspect of the present invention, there is provided a control method for returning from a standby state in an image forming apparatus including a fixing device that fixes toner onto transfer paper with heat and pressure, and the fixing device includes the fixing device. The temperature of the member is detected, and the maximum amount of toner adhering to the transfer paper is controlled to be smaller than normal according to the temperature of the fixing member when starting the return operation from the standby state. .

  According to a third aspect of the present invention, there is provided a control method for returning from a standby state in an image forming apparatus including a fixing device that fixes toner onto transfer paper with heat and pressure, and the fixing device includes the fixing device. It is characterized in that the temperature at the end of the member is detected, and control is performed so that the maximum amount of toner adhering to the transfer paper is smaller than usual according to the temperature at the end of the fixing member at the start of printing.

  According to the fourth aspect of the present invention, in the control method of the image three-image forming apparatus according to any one of the first to third aspects, the maximum toner adhesion amount on the transfer paper is determined by the left and right edges of the image area in the transfer paper transport direction. It is characterized by controlling so that only a part is less than usual.

  An image forming apparatus according to a fifth aspect of the present invention is an image forming apparatus having a fixing device that fixes toner onto transfer paper with heat and pressure. In the first print after returning from the standby state, the developing device It is characterized in that the maximum amount of toner adhered to the transfer paper is made smaller than usual.

  According to the sixth aspect of the present invention, in the image forming apparatus including the fixing device that fixes the toner onto the transfer paper with heat and pressure, the image forming device includes a unit that detects the temperature of the fixing member included in the fixing device, and is in a standby state. The maximum amount of toner adhered to the transfer paper from the developing device is made smaller than usual in accordance with the temperature of the fixing member when starting the return operation from.

  According to the seventh aspect of the present invention, in the image forming apparatus including a fixing device that fixes the toner onto the transfer paper with heat and pressure, the image forming apparatus includes means for detecting a temperature of an end portion of the fixing member included in the fixing device, The maximum amount of toner adhered to the transfer paper from the developing device is made smaller than usual according to the temperature of the end of the fixing member at the start of printing.

  According to the eighth aspect of the present invention, in the image forming apparatus according to any one of the fifth to seventh aspects, the maximum toner adhesion amount on the transfer paper is set to be higher than normal only at the left and right end portions of the image area in the transfer paper transport direction. Featuring less.

  The present invention makes it possible to shorten the return time while preventing poor fixing after returning from the standby state, and to achieve both energy saving and productivity.

  The best mode for carrying out the present invention will be described below with reference to the embodiments shown in the drawings.

    FIG. 1 is an overall schematic view of a copying machine as an example of an image forming apparatus to be an object of the present invention. In FIG. 1, 1 is an image forming unit, 2 is a scanner unit, 3 is a transfer paper P (in this specification, the transfer paper is not only paper but also OHP paper, etc.). 4 is a pressure plate (or a document feeder), and 5 is a contact glass. The paper feed unit 3 includes a pair of paper feed trays 6 and 6 and a manual feed tray 7. In the figure, 8 is a paper discharge unit.

  Reference numeral 10 denotes a photosensitive unit including a photosensitive drum as a toner image carrier. Around the photosensitive unit, a developing device 11, an optical unit 12, a transfer conveyance belt 13, a resist roller pair 14, a thermal fixing device 15, and a double-sided image forming unit. A reversing conveyance unit 16 and the like are disposed. Since the configuration and operation of these copying machines are well known, description thereof will be omitted.

  FIG. 2 is a schematic view of a thermal fixing device provided in the copying machine of FIG. The thermal fixing device 15 is configured to form a fixing nip with the fixing roller 30 and the pressure roller 32, and heats and pressurizes the toner image transferred onto the transfer paper P by the electrophotographic image forming apparatus. To fix on the transfer paper P. The fixing roller 30 includes one or more heating elements 33 such as halogen heaters, and is configured to keep the temperature within a control temperature range.

  The transfer paper P on which the toner image has been fixed by the thermal fixing device 15 proceeds to the paper discharge conveyance device at the rear stage in the paper discharge direction, and is configured by pressing the driving roller 35 and the driven rollers 36 and 37 together. The paper is discharged from the image forming apparatus onto the paper discharge unit 8 via a paper discharge conveyance roller pair.

A first embodiment of the present invention will be described. In the above-described image forming apparatus, the maximum toner adhesion amount is made smaller than usual in the first print immediately after returning from the standby state. For example, as shown in Table 1 below, when the maximum adhesion amount is usually 250%, the three sheets immediately after returning have a maximum adhesion amount of 200%. The amount of adhesion is 100% when the solid color is solid, and is 0.5 mg / cm ² .

  By doing so, it was possible to shorten the return time while preventing poor fixing, and to achieve both energy saving and productivity.

  A second embodiment of the present invention will be described. The temperature of the fixing member in the standby mode, that is, the fixing roller 30, varies depending on the elapsed time from the end of printing and the use environment. When the time has not elapsed since the end of printing, it is warm, and when it has been a long time since the end of printing, it is cold. Therefore, in the so-called “return mode” from the standby mode to the start of printing, the temperature of the fixing roller 30 is generally detected, and the printing operation is performed after reaching the fixable temperature.

Therefore, in this embodiment, the temperature of the fixing roller 30 at the start of the return is detected, and as shown in Table 2 and FIG. To reduce

  As a result, the restoration time was shortened while preventing fixing failure, and energy saving, productivity and image quality were compatible.

  A third embodiment of the present invention will be described. In many cases, the temperature detection of the fixing roller 30 as a fixing member is performed at substantially the center in the axial direction, and in this case, the end temperature of the fixing roller 30 cannot be detected. When the temperature rises from a low temperature and the central portion reaches the target temperature, the left and right end portions are often at a lower temperature than the central portion because the heat dissipation effect is great. This is more conspicuous as the temperature rise temperature is larger (lower start temperature) and as the temperature rise rate is faster. On the other hand, when the time has not elapsed since the end of printing, the end temperature is not lowered, so there is no fear of fixing failure even after printing after returning. In this case, it is desirable that the maximum amount of toner on the entire screen be secured as much as possible.

Therefore, in this embodiment, separately from the fixing temperature control, the thermistor is brought into contact with the end portion of the fixing roller 30 to start printing after returning from the standby state, that is, the end when the fixing temperature becomes ready. The maximum adhesion amount is changed as shown in Table 3 below depending on the temperature of the part.

  Note that if the end temperature of the fixing roller 30 is less than 138 ° C. at the start of return, even if it is determined that the fixing ready state is detected by other detection means, it is still determined that the fixing ready state is not reached and the printing operation is performed. Can be avoided.

  That is, in this embodiment, the fixing roller 30 end temperature at the start of return is directly detected, and the maximum toner adhesion amount is reduced below normal according to the end temperature of the fixing roller 30 at the start of return, thereby fixing with high accuracy. While preventing defects, the recovery time was shortened, and energy saving, productivity and image quality were compatible.

  A fourth embodiment of the present invention will be described. As described above, the fixability immediately after the return is disadvantageous at both ends of the image area. There is no problem with the fixing property because a sufficient amount of heat is secured in the central portion. In consideration of actual use, there is very little probability that an image with a high toner adhesion amount exists at both ends of the image. For example, both ends of A4 landscape paper correspond to the upper and lower ends of A4 portrait, and although there are portions called headers and footers in the image, it is unlikely that there is a toner image with a high image area. .

In this embodiment, therefore, separately from the fixing temperature control, a thermistor is brought into contact with the end of the fixing roller 30 and the temperature at the end at the time of printing after returning is within 20 mm and the end 20 mm. The maximum adhesion amount of 40 mm is changed as shown in Table 4 below. Other image areas are not changed.

  Also in this embodiment, when the end temperature of the fixing roller 30 is less than 138 ° C. at the start of return, even if it is determined that the fixing ready state is detected by other detection means, it is not yet in the fixing ready state. It is possible to prevent the printing operation from being performed.

  In other words, in this embodiment, the maximum toner adhesion amount is reduced only at both ends where there is a problem with the fixability immediately after the recovery, and the normal toner maximum adhesion amount is secured in other image areas, thereby preventing fixing failure. The recovery time was shortened, and energy saving, productivity and image quality were compatible.

1 is an overall schematic diagram of a copying machine that is an example of an image forming apparatus that is an object of the present invention. FIG. 2 is a schematic view of a heat fixing device provided in the copying machine of FIG. 1. It is a figure which shows the relationship between return start temperature and return end part temperature. FIG. 6 is a diagram illustrating a cold offset occurrence temperature (fixing lower limit temperature) in relation to a toner adhesion amount on paper and a fixing belt temperature.

Explanation of symbols

1: Image forming unit 2: Scanner unit 3: Paper feeding unit 4: Pressure plate (or document feeding device)
5: contact glass 6: paper feed tray 7: manual feed tray 8: paper discharge unit 10: photoconductor unit 11: developing device 12: optical unit 13: transfer conveyance belt 14: registration roller pair 15: heat fixing device 16: reverse conveyance Unit 30: fixing roller 32: pressure roller 33: heating element 35: driving roller 36, 37: driven roller P: transfer paper

Claims (8)

A control method for returning from a standby state in an image forming apparatus having a fixing device for fixing toner onto transfer paper with heat and pressure. In the first print after returning from the standby state, the transfer paper is transferred to the transfer paper. A control method for an image forming apparatus, wherein the maximum toner adhesion amount is controlled to be smaller than usual. A control method for returning from a standby state in an image forming apparatus having a fixing device that fixes toner onto transfer paper with heat and pressure, detecting the temperature of a fixing member provided in the fixing device, and in a standby state A control method for an image forming apparatus, wherein control is performed so that the maximum toner adhesion amount on a transfer sheet is smaller than usual in accordance with the temperature of the fixing member when starting the return operation from. A control method for returning from a standby state in an image forming apparatus including a fixing device that fixes toner onto transfer paper with heat and pressure, and detecting a temperature of an end of a fixing member included in the fixing device, A control method for an image forming apparatus, characterized in that control is performed so that the maximum toner adhesion amount on a transfer sheet is smaller than usual according to the temperature of the end of the fixing member at the start of printing. 4. A control method for an image three-image forming apparatus according to claim 1, wherein the maximum toner adhesion amount on the transfer paper is made smaller than usual only at the left and right end portions of the image area in the transfer paper transport direction. A control method of an image forming apparatus characterized by controlling. In an image forming apparatus equipped with a fixing device that fixes toner onto transfer paper with heat and pressure, the maximum amount of toner adhering from the developing device to the transfer paper is higher than usual in the first print after returning from the standby state. An image forming apparatus characterized in that the number is reduced. An image forming apparatus having a fixing device for fixing toner on transfer paper with heat and pressure, has means for detecting the temperature of a fixing member provided in the fixing device, and is used for starting a return operation from a standby state. An image forming apparatus, wherein the maximum amount of toner adhered to the transfer paper from the developing device is made smaller than usual according to the temperature of the fixing member. An image forming apparatus including a fixing device that fixes toner onto transfer paper with heat and pressure, the image forming apparatus having means for detecting a temperature of an end of a fixing member provided in the fixing device, and the end of the fixing member at the start of printing An image forming apparatus characterized in that the maximum amount of toner adhering to the transfer paper from the developing device is made smaller than usual according to the temperature of the toner. 8. The image forming apparatus according to claim 5, wherein the maximum toner adhesion amount on the transfer paper is less than normal only at the left and right end portions of the image area in the transfer paper transport direction. apparatus.