JP2001022222A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of improving the shortening of warm-up time and also always obtaining excellent fixation whatever kind of transfer paper it is. SOLUTION: In this image forming device equipped with a fixing roller incorporating at least one or more heaters and a fixing device thermally melting and fixing an unfixed toner image on the transfer paper at a nip part formed by a pressure roller turnably press-contacting with the fixing roller; energizing amount of respective heaters is varied according to the selection of the paper supply port or the ejection port of the image forming device (flowchart).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used in an image forming apparatus such as a PPC copier, a printer, a facsimile, and the like.

[0002]

2. Description of the Related Art In recent years, PPC copiers, printers,
In an image forming apparatus such as an AX, a measure for shortening a warm-up (rise time) of the image forming apparatus is desired as a part of environmental measures. As a countermeasure for this, in each model, the thickness of the fixing roller is made thinner to shorten the temperature rise time. However, when the thickness of the fixing roller is reduced, the fixing strength is remarkably reduced. Therefore, a pressure roller having extremely low rubber hardness is brought into contact with the fixing roller at a low pressure. Roller temperature drops significantly.
Such a defect (fixing defect) relating to the fixing property becomes remarkable especially in the case of thick transfer paper.

That is, in the case of a thin fixing roller, since its strength is naturally reduced, the rubber hardness of the pressure roller is lowered, and the pressure in the nip portion is also significantly reduced. In addition, since the force (fixing pressure) for crushing the toner is weak, a gap is formed between the toners (particles), thereby lowering the thermal conductivity efficiency, and also weakening the function of pushing the toner into the fiber layer in the transfer paper, thereby fixing the toner. Is reduced. Further, since the heat capacity of the fixing roller is small, when the transfer paper passes through the nip portion, the heat of the fixing roller is taken away by the paper, so that the temperature of the fixing roller itself drops greatly. For this reason, when the transfer paper is a thick paper, the heat capacity of the transfer paper is large, so that the amount of heat taken from the fixing roller also becomes large, and as a result, the temperature of the fixing roller decreases and the fixability deteriorates.

Further, as a prior art, (1) Japanese Patent Laid-Open No. 5-2245
Japanese Patent Application Laid-Open No. 59-5959 discloses an apparatus in which energization control is performed every half cycle of an AC voltage when power is supplied to a fixing heater.
Japanese Patent Publication No. 301313 discloses an apparatus for controlling switching of a fixing temperature.

[0005]

However, the conventional image forming apparatus has the following problems. That is, as described above, the "thick paper mode" is separately set as a countermeasure for the above-described problem in the related art. As the specific contents of the “thick paper mode”, (1) the fixing set temperature is set to a high temperature in advance. (2) Pre-rotation of the fixing device is performed in advance, and the fixing roller and the pressure roller are warmed before passing the sheet.
(3) The sheet interval (nip width) at the time of fixing is increased to prevent the temperature of the fixing roller from lowering. (4) Although the transfer speed of the transfer paper is reduced to increase the amount of heat given to the transfer paper, all measures are reversed from the viewpoint of productivity, and the copy speed (copy speed) is reduced. Is not preferred. Also, in the cases of the prior arts (1) and (2), there is a possibility that the copying speed may similarly decrease, and this is not preferable since it is reversed from the viewpoint of productivity.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the problems of the conventional fixing device as described above, to improve the shortening of the warm-up time, and to fix the fixing to any type of transfer paper. An object of the present invention is to provide an image forming apparatus capable of always obtaining good fixing performance without causing a defect.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is directed to a fixing roller having at least one or more heaters built therein, and a rotating roller for the fixing roller. In an image forming apparatus provided with a fixing device that heat-fuses and fixes an unfixed toner image on a transfer sheet at a nip formed by a pressure roller that is freely pressed, according to the selection of a paper feed port of the image forming apparatus. Thus, the amount of current supplied to each heater is made variable.

According to a second aspect of the present invention, in the first aspect of the invention, the amount of power to each heater is made variable in accordance with the selection of the discharge port of the image forming apparatus.

[0009]

FIG. 1 shows an embodiment of an image forming apparatus according to the present invention. That is, FIG. 1 shows an overall configuration diagram of the image forming apparatus 1 in a state where peripheral devices are mounted,
An ADF 2, a finisher 3, and a double-sided tray 4 are mounted as the peripheral devices. Hereinafter, the configuration and the transfer path of the transfer sheet will be described in detail. Reference numeral 5 denotes a paper feed tray. The transfer paper fed from the paper feed tray 5 is transported by transport rollers 6, and after a predetermined image is formed by image forming means 7, the image is fixed by a fixing device 8 and relay unit 9. The sheet is discharged via the finisher 3. The finisher 3 has a stapler 10 inside, and the transfer paper stapled by the stapler 10 is discharged onto a discharge tray 13 by a transport belt 12 after a predetermined number of staples (binding operation) in a jogger stack unit 11. .

Here, the transport path for transporting the transfer paper toward the finisher 3 in the "non-staple mode" is indicated by a solid line, and the transport path in the "staple mode" is indicated by a dotted line. In this case, the paper thickness that can be fed from the paper feed tray 5 is a general “55 kg to 90 kg paper”, and the paper can be passed through the respective transport paths of “finisher staple / finisher non-staple” from the discharge port on the relay unit 9. Paper thickness setting. Reference numeral 14 denotes a manual feed tray. The paper thickness that can be fed by the manual feed tray 14 is 45 kg to 135 kg paper that can correspond to various application papers, and each transport of only “finisher non-staple” from the discharge port on the relay unit 9. The paper thickness is set so that the path can be passed. This is because staples are not commonly used when the transfer paper is application paper.

FIG. 2 shows the structure of the fixing device 8. The fixing device 8 is provided on a fixing roller 15, a pressure roller 16 that rotates by pressing against the fixing roller 15, and a pressure roller 16 side. A pressure lever 28 for transmitting a pressing force by the pressing spring 17;
The toner on the transfer paper is fixed using the heating by the fixing heater 18 provided inside the transfer paper 15. Here, the outer diameter of the fixing roller 15 is 40 mm, the core metal is a thin 0.4 mm iron roller,
The amount of heat of the fixing heater 18 is 1000 W, and the outer diameter of the pressure roller 16 is 30.
mm low hardness roller made of silicone foam, 35CP
This is an example of a fixing device that achieves a warm-up time of 15 seconds or less with an M machine. Reference numeral 19 denotes a fixing separation claw, reference numeral 20 denotes a pressure separation claw, and reference numeral 21 denotes a discharge branch claw. When the “copy mode” is selected to the “double-sided mode”, the transfer paper is temporarily stored in the double-sided tray 4 by the switching operation of the discharge branch claw 21.

The fixing roller 15 is heated by a fixing heater 18, and its surface temperature is detected by a thermistor 22 slidably contacting the outer peripheral surface of the fixing roller 15, and the temperature of the fixing roller 15 is controlled so as to maintain a constant fixing temperature. Is performed. 23 is a thermal fuse for preventing excessive temperature rise. In the conveyance in the fixing device 8, the fixing roller 15 and the pressure roller 16 rotate in the direction of the arrow in the drawing by the rotational drive from a drive system (not shown), and the transfer paper fed from the paper feed tray 5 is fixed. After fixing through a nip portion between the rollers 15 and 16 via an entrance guide 25 of the apparatus 8, the sheet is discharged by driving a sheet discharging roller 26. The paper discharge from the fixing device 8 is detected by a paper discharge sensor 27.

When the thin fixing roller 15 is employed as described above, it is important how to prevent the temperature of the fixing roller 15 from dropping during paper passing in order to further improve the fixing property. For that purpose, what is required is how to increase the amount of heat supplied to the fixing. Specifically, it is necessary to increase the heater power as much as possible. However, it is impossible to increase the heater power unnecessarily. Therefore, the present inventor focused on how much power is consumed when which peripheral device operates in what kind of paper passing mode,
The power that can be supplied to the fixing unit is “1000 W” in the case of (1) manual feeding / main body feeding to the discharge on the relay unit 9, and (2) “850 W” in the case of manual feeding / main body feeding to the finisher (non-staple). (3) In the case of the finisher (staple) from the main body feeding, it was found that power of "750 W" can be supplied to the fixing.

Further, as described above, since the application paper is passed only by "manual feeding", the heater power is 850 W / 1000 W, and the heater power is 750 W when feeding the main body corresponding to 55 kg to 90 kg paper. In the case of / 850W / 1000W and 90 kg paper, a satisfactory fixing property can be secured by energizing the 750W heater by the configuration of the fixing device 8. Therefore, in the present invention, by changing the power supplied to the fixing in accordance with the paper feed port / discharge port, good fixing performance can be obtained even when a thin fixing roller is used. In this case, the method of reducing the power of the 1000 W heater to about 850/750 W can be achieved by changing the amount of current supplied to the heater to 85% and 75%, respectively.

The operation of the present invention will be described in detail with reference to the flowchart of FIG. In the present invention, as shown in the flowchart of FIG. 3, after inputting the image forming operation signal, it is determined whether or not the sheet feeding port is the main body sheet feeding. First, here, in the case of main body feeding, it is determined whether or not the setting of the paper discharge port is a finisher. Next, if the setting of the paper discharge port is a finisher (YES), it is determined whether the setting mode is the staple mode. Then, in the case of the staple mode (YE
In step S), the amount of current supplied to the fixing heater is set to 75%. In the case of the non-staple mode, the energizing amount of the fixing heater is 85%.
Set to. Next, in a case where the sheet is not the main body feeding / finisher discharging (discharging on the relay unit 9), the fixing heater power supply amount is set to 100%. On the other hand, if the paper feed port is manual paper feed, it is determined whether the setting of the paper discharge port is a finisher. Then, when the setting of the paper discharge port is a finisher, the energization amount of the fixing heater is set to 85%. Further, when the setting of the discharge port is not the finisher discharge (the relay unit 9
For discharging paper upward, the amount of power supplied to the fixing heater is set to 100%. Then, after setting the amount of power supply to each fixing heater, a predetermined image forming operation is started.

[0016]

The present invention is as described above. According to the first aspect of the present invention, there is provided a fixing roller including at least one or more heaters, and a pressing roller rotatably pressed against the fixing roller. In an image forming apparatus provided with a fixing device for thermally fusing and fixing an unfixed toner image on transfer paper at a nip formed by a pressure roller, the amount of power to each heater is made variable according to a paper feed port. By making the power supplied to the fixing device variable according to the paper feed port, the warm-up time can be significantly reduced by the thin fixing roller, and good fixing is always achieved on any type of transfer paper. There is an effect that the property can be obtained.

According to a second aspect of the present invention, in the first aspect of the invention, the power to be supplied to the fixing device is made variable according to the sheet discharge port, so that the thin-walled fixing roller can greatly reduce the warm-up time. In addition to the shortening, it is possible to obtain good fixability on any type of transfer paper.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an image forming apparatus to which the present invention is applied.

FIG. 2 is an enlarged view of a main part showing the identification attachment device.

FIG. 3 is a flowchart illustrating a control procedure.

[Explanation of symbols]

 Reference Signs List 1 image forming apparatus 2 ADF 3 finisher 4 double-sided tray 5 paper feed tray 7 image forming means 8 fixing device 9 relay unit 10 stapler 11 jogger stack unit 15 fixing roller 16 pressure roller 18 fixing heater

Claims (2)

[Claims] An unfixed toner image is heat-fused and fixed on a transfer paper at a nip formed by a fixing roller having at least one or more heaters therein and a pressure roller rotatably pressed against the fixing roller. An image forming apparatus comprising a fixing device for causing the heater to vary the amount of power to each heater in accordance with the selection of a paper feed port of the image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the amount of power to each heater is made variable in accordance with the selection of a discharge port of the image forming apparatus.