JPH05333740A - Image fixing device - Google Patents

Abstract

PURPOSE:To provide an image fixing device capable of always attaining optimum fixing, regardless of an environmental condition by detecting the temperature of the sheet of the image fixing device for a copying machine, a printer, a facsimile, etc., and automatically varying a fixing condition according to the detected temperature of the sheet. CONSTITUTION:In the image fixing device thermally melt-fixing an unfixed toner image 12 transferred on the sheet 4, thereon, by the nipping part N of a fixing roller 1 incorporating a heater 3 and a pressure roller 2 freely turnably pressed to contact with the fixing roller 1, a sheet temperature detector is provided on a paper feeding tray, and the temperature of the sheet is detected in each specified time, so that a fixing temperature, a nipping width, and fixing speed are varied according to the temperature of the sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device using a heat roller used in an electrophotographic image forming apparatus such as a copying machine, a printer and a facsimile, and more particularly, to an optimum fixing regardless of fluctuation of environmental temperature. The present invention relates to an image fixing device that can obtain conditions.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer or a facsimile which uses an electrophotographic process, an electrostatic latent image formed on a photoconductor is visualized with toner and then formed on a recording paper. Images are formed by transferring and fixing to. An image fixing device using a conventional heat roller is composed of a fixing roller that has a heater inside for heating and a pressure roller. The sheet to be fixed is sandwiched by a nip portion between the two, and heat and pressure are applied to the sheet. Is added to fix the toner and the like on the sheet. In such a conventional fixing device, the fixing temperature, the nip width, the fixing speed, etc. are fixed, and when the environmental conditions such as the environmental temperature change, the fixing property is significantly affected.

That is, in a low temperature environment, the temperature of the pressure roller hardly rises and the temperature of the sheet is low, so that fixing failure and cold offset are likely to occur. On the other hand, in a high temperature environment, the pressure roller is easily warmed and the temperature of the sheet is high, so that excessive fixing is likely to occur, and hot offset or separation claw jam occurs.

As a countermeasure for the above, a method of detecting the environmental temperature and changing the fixing condition has been considered, but it is not sufficient, and the fixing failure and the cold offset as described above still occur.
Alternatively, hot offset or separation claw jam occurs due to excessive fixing.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and detects the sheet temperature of an image fixing device such as a copying machine, a printer, a facsimile, etc., and automatically determines a fixing condition corresponding to the detected temperature of the sheet. It is an object of the present invention to provide an image fixing device that always performs optimum fixing regardless of environmental conditions.

[0006]

In order to achieve the above object, the present invention provides a sheet by a fixing roller having a built-in heater and a nip portion of a pressure roller rotatably pressed against the fixing roller. In an image fixing device that fuses the transferred unfixed toner image to a sheet by heat melting, a sheet temperature detection device is provided in the paper feed tray to detect the sheet temperature at every predetermined time, and the fixing temperature can be changed according to the sheet temperature. It is characterized by

In an image fixing device for fixing an unfixed toner image transferred onto a sheet by heat fusion by a nip portion of a fixing roller having a heater built therein and a pressure roller rotatably pressed against the fixing roller. A sheet temperature detecting device is provided in the sheet feeding tray, the sheet temperature is detected every predetermined time, and the nip width is made variable according to the sheet temperature.

In an image fixing device for fixing an unfixed toner image transferred onto a sheet by heat fusion by a nip portion of a fixing roller having a heater and a pressure roller rotatably pressed against the fixing roller. A sheet temperature detecting device is provided in the sheet feeding tray, the sheet temperature is detected at every predetermined time, and the fixing speed is made variable according to the sheet temperature.

[0009]

The sheet temperature is detected when the power of the image fixing apparatus having the above-described configuration is turned on and after a predetermined time has elapsed, and the optimum fixing temperature, nip width, and
Since the fixing speed is set, a good copy according to the sheet temperature can be obtained at any time.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram of the overall configuration of an example of a fixing device to which the present invention is applied. In FIG. 1, a sheet (recording paper) 4 having an unfixed toner image 12 conveyed from a transfer unit of an image forming apparatus (not shown) is shown. Is guided by the upper and lower entrance guide plates (upper 5 and lower 6) and is nipped in the nip portion N between the pressure roller 2 which is rotatably pressed against the fixing roller 1 having the heater 3 built therein. The image (12) is heat-fixed. The sheet 4 after fixing is peeled off from the fixing roller 1 by a separating claw 7 arranged so that the leading end thereof contacts the fixing roller 1, and is discharged from the fixing device by a paper discharge guide plate (lower 8 and upper 9).

FIG. 2A is an explanatory diagram of an image fixing device according to another embodiment of the present invention, and FIG. 2B shows the relationship between the sheet temperature and the fixing temperature in the image fixing device according to the embodiment of the present invention. It is a graph shown. In FIG. 2A, when the image forming apparatus (not shown) is turned on, the sheet temperature detecting device (infrared radiation thermometer, etc.) provided in the sheet feeding tray (not shown) detects the sheet temperature, and according to the detection signal. The fixing temperature is determined by the fixing temperature control device and the heater 3. The fixing temperature control device may be configured as the entire image forming apparatus or a part of a microcomputer for controlling the part. In any case, the RO storing information about the correspondence between the detected sheet temperature and the fixing temperature suitable for the detected RO
M, and a CPU for controlling the temperature of the fixing roller based on the information stored in the ROM.

The environmental conditions of the office in which the image forming apparatus is installed are different in the morning, noon, and evening, and accordingly, the environmental conditions in the paper feed tray also change. Therefore, the fixing temperature determined when the power of the image forming apparatus is turned on may not be the optimum fixing condition due to the change in the environmental temperature. As a measure against this, in the present invention, the sheet temperature is detected every predetermined time after the power supply of the image forming apparatus is turned on, and the fixing temperature is reset by the fixing temperature control device and the heater 3 according to the detection signal.

In FIG. 2B, when the power of the image forming apparatus (not shown) is turned on, the fixing roller temperature is set to 190 ° C. because the sheet temperature is 10 ° C. However, the sheet temperature is detected again after 1 hour. Then, since the temperature had risen to 25 ° C., the fixing roller temperature is controlled to be lowered to 175 ° C.

In this way, the sheet temperature is detected when the power of the image forming apparatus is turned on and after a lapse of a predetermined time, and the optimum fixing temperature is set according to the detection signal. A good copy can be obtained according to the sheet temperature without being affected by fluctuations.

FIG. 3A is an explanatory view of an image fixing device according to another embodiment of the present invention, and FIG. 3B is a diagram showing a predetermined time after the power is turned on in the image fixing device according to another embodiment of the present invention. FIG. 3C is a graph showing the relationship between time (sheet temperature) and nip width, and FIG. 3C is a relationship diagram between sheet temperature and nip width in an image fixing device according to another embodiment of the present invention. Figure 3
In (a), when the power of the image forming apparatus (not shown) is turned on, the sheet temperature is detected by a sheet temperature detecting device (infrared radiation thermometer or the like) provided in a sheet feeding tray (not shown), and according to the detection signal, The nip width is determined by a fixing nip width control device and a solenoid (not shown) for adjusting the nip width. The nip width is the circumferential width of the contact portion between the rollers 1 and 2. The nip width is changed by making the relative positional relationship between the rollers 1 and 2 close to each other, separating from each other, or finely adjusting the solenoid. As a result, the optimum fixing state can be obtained regardless of the sheet temperature fluctuation. Further, the information about the sheet temperature and the optimum nip width (solenoid driving condition) is stored in the memory of the fixing nip width control device.

In FIG. 3B, when the power of the image forming apparatus (not shown) is turned on, the sheet temperature is 10 ° C.,
The nip width was set to the optimum value of 4 mm, but it increased to 25 ° C when the sheet temperature was detected again 1 hour later, so the nip width should be narrowed (3 mm) according to the temperature increase (contact The solenoid was activated (to reduce the area). That is, the relative positions of both rollers are separated.

In FIG. 3C, the fixing temperature is 185 ° C. and the sheet conveying speed (fixing speed) of the fixing roller is 120 mm / s.
The nip width is reset according to the sheet temperature when ec is set, and thus the optimum nip width becomes narrower as the sheet temperature rises. In this way, the sheet temperature is detected when the power of the image forming apparatus is turned on and after a lapse of a predetermined time, and the optimum nip width is set according to the detection signal, so that a good copy according to the sheet temperature can be obtained at any time. Is obtained.

FIG. 4A is an explanatory diagram of an image fixing device according to another embodiment of the present invention, and FIG. 4B is a diagram showing another embodiment of the present invention when a predetermined time has elapsed since the power was turned on in the image fixing device. A graph showing the relationship between the sheet temperature and the fixing speed, (c) is a relationship diagram between the sheet temperature and the fixing speed in the image fixing device showing another embodiment of the present invention.

FIG. 4A shows a sheet temperature detection device (infrared radiation thermometer or the like) provided in a sheet feeding tray (not shown) for detecting the sheet temperature when the image forming apparatus (not shown) is powered on, and a detection signal thereof is detected. In this embodiment, the sheet conveying speed (fixing speed) of the fixing roller is determined by a fixing speed control device that controls the sheet conveying speed (fixing speed) of the fixing roller and a motor (not shown) according to the above. In this embodiment, the optimum fixing state is obtained by changing the fixing speed according to the fluctuation of the sheet temperature. Data relating to the relationship between the sheet temperature and the fixing speed is stored in the memory of the fixing speed control device.

In FIG. 4B, the sheet temperature is 10 ° C. when the image forming apparatus (not shown) is powered on.
Optimum sheet conveyance speed (fixing speed) of the fixing roller is 90
The sheet conveyance speed (fixing speed) of the fixing roller is 120 mm / se because the sheet temperature was raised to 25 ° C. when the sheet temperature was detected again one hour later.
It was accelerated to c.

FIG. 4C shows the sheet conveying speed (fixing speed) of the fixing roller reset according to the sheet temperature when the fixing temperature is 185 ° C. and the nip width of the fixing roller is 3 mm. .. By thus increasing the conveying speed with the temperature rise, a good fixed image could be obtained. In this manner, the sheet temperature is detected when the image forming apparatus is powered on and after a predetermined time has elapsed, and the optimum sheet conveyance speed (fixing speed) of the fixing roller is set according to the detection signal. Good copies are always obtained depending on the sheet temperature.

[0022]

Since the present invention is constructed as described above, it has the following effects. The sheet temperature is detected when the power of the image forming apparatus is turned on and after a predetermined time elapses, and the optimum fixing temperature is set according to the detection signal, so that a good copy according to the sheet temperature can be obtained at any time. Since the sheet temperature is detected when the power of the image forming apparatus is turned on and after a predetermined time elapses, the optimum nip width is set according to the detection signal.
Good copies are always obtained depending on the sheet temperature.
The sheet temperature is detected when the power of the image forming apparatus is turned on and after a predetermined time elapses, and the optimum sheet conveyance speed (fixing speed) of the fixing roller is set according to the detection signal. A good copy is obtained.

[Brief description of drawings]

FIG. 1 is a side view of an image fixing device showing an embodiment of the present invention.

2A and 2B are explanatory views of an image fixing device according to another embodiment of the present invention and a diagram showing a relationship between a sheet temperature and a fixing temperature in the image fixing device according to the embodiment of the present invention.

3A and 3B are explanatory views of an image fixing device according to another embodiment of the present invention and show a relationship between a nip width and a predetermined time (sheet temperature) after the power is turned on in the image fixing device. FIG. 3C is a diagram showing the relationship between the sheet temperature and the nip width in the image fixing device showing another embodiment of the present invention.

FIGS. 4A and 4B are explanatory views of an image fixing device according to another embodiment of the present invention, showing a relationship between a fixing time and a predetermined time (sheet temperature) after the power is turned on in the image fixing device. FIG. 11C is a relationship diagram between the sheet temperature and the fixing speed in the image fixing device according to another embodiment of the present invention.

[Explanation of symbols]

N ... Nip part, 1 ... Fixing roller, 2 ... Pressure roller, 3 ... Heater, 4 ... Sheet, 5 ... On entrance guide plate, 6 ... Entrance guide plate Lower, 7 ... Separation claws, 8 ... Below paper ejection guide plate, 9 ... Above paper ejection guide plate, 10 ... Above paper ejection roller, 11 ... Below paper ejection roller, 12 ...・ Unfixed toner image

Claims (3)

[Claims] 1. An unfixed toner image transferred onto a sheet is fused and fixed to the sheet by a nip portion between a fixing roller having a heater built therein and a pressure roller rotatably pressed against the fixing roller. In the image fixing apparatus, a sheet temperature detecting device is provided in a sheet feeding tray for storing the sheet, the sheet temperature is detected every predetermined time, and a control unit for variably controlling the fixing temperature according to the detected sheet temperature is provided. An image fixing device characterized by being provided. 2. An image in which an unfixed toner image transferred onto a sheet is melted and fixed on a sheet by a nip portion between a fixing roller having a heater built therein and a pressure roller rotatably pressed against the fixing roller. In the fixing device, a sheet temperature detecting device is provided in the sheet feeding tray, the sheet temperature is detected every predetermined time, and the control part for varying the nip width in accordance with the detected sheet temperature is provided. Image fixing device. 3. An image in which an unfixed toner image transferred onto a sheet is fused and fixed on the sheet by a nip portion between a fixing roller having a heater built therein and a pressure roller rotatably pressed against the fixing roller. In the fixing device, a sheet temperature detecting device is provided in the sheet feeding tray, the sheet temperature is detected at predetermined time intervals, and a control unit for varying the fixing speed according to the detected sheet temperature is provided. Image fixing device.