JPH08262889A - Electrophotographic device - Google Patents

Abstract

PURPOSE: To provide an electrophotographic device simple in structure, small in size and capable of preventing an overheat on the end part of a fixing roller even in the case of fixing a recording paper of the narrower width than the fixation width. CONSTITUTION: A heat radiation roller 11 is pressed to and away from the fixing roller 7 through heat radiation roller control means by system control means not shown in Figure. When a recording paper width detection means detects the recording paper of the narrower width than the fixation width, the heat radiation roller 11 is pressed onto the fixing roller 7, the heat of the overheat part on the end part is radiated to the recording paper passing part where the temp. is dropped to uniformly keep thermal distribution of the fixing roller 7. Timing when the heat radiation roller control means drives the heat radiation roller 11 is decided based on the timing when the passing of the recording paper is detected by a recording paper passing detection means provided on the front of the fixing roller.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus such as a facsimile machine or a copying machine having a fixing roller heated by an internal heat source, and more particularly to an end portion of a fixing roller at the time of fixing a recording sheet having a width smaller than the fixable width. The present invention relates to an electrophotographic device which is designed to protect against overheating.

[0002]

2. Description of the Related Art Facsimile devices and copiers capable of recording on recording papers of plural kinds of width have been generalized, and an electrophotographic device used for the same needs to fix evenly wide recording papers and narrow recording papers. . Generally, the fixing unit includes a fixing roller and one temperature detector arranged in the center thereof.
When the recording paper is carried into the fixing roller portion at the time of fixing, the heat of the fixing roller is absorbed by the recording paper, and the temperature of the surface of the fixing roller is temporarily lowered. The temperature of the fixing roller is detected by a detector, and on / off of the heater is controlled based on the detected temperature to keep the surface temperature of the fixing roller substantially constant. Therefore, when a heater having a uniform heat distribution is used, when fixing a wide recording paper, the heat of the fixing roller is evenly taken by the wide recording paper, so that the surface temperature of the fixing roller also becomes uniform. The temperature detector and the heater are properly controlled, but when fixing a narrow recording paper, the end of the fixing roller, which does not pass through the recording paper when the center is set to a predetermined fixing temperature, is caused by the recording paper. Since it does not absorb heat, it has the drawback of becoming overheated. It is also possible to use a heater with a low heat distribution at the end so that the end of the fixing roller does not become abnormally overheated even if the width of the recording paper is narrow. When the recording paper width is the same as the fixing width, the heat distribution becomes non-uniform, and the surface temperature of the fixing roller becomes non-uniform, resulting in uneven fixing.

Conventionally, as a technique for preventing this overheated state, for example, there is one described in Japanese Patent Laid-Open No. 5-210325. In this publication, an endless belt having a small heat capacity is provided by pressing against the outer peripheral surface of a fixing roller, and this endless belt is driven in conjunction with the fixing roller during fixing. The endless belt is heated and controlled by a ceramic heater that can be turned on and off as appropriate to efficiently prevent temperature unevenness on the surface of the fixing roller pressed against the endless belt.

[0004]

The device disclosed in the above-mentioned publication has a small power consumption by providing an endless belt having a small heat capacity provided in contact with the fixing roller and a heater for heating and controlling the endless belt. Can efficiently eliminate the unevenness of the surface temperature of the fixing roller, but requires an endless belt, a driving roller and a driven roller for driving the endless belt, a ceramic heater, and the like, which makes the apparatus complicated and large. There's a problem. An object of the present invention is to solve the above problems and provide an electrophotographic apparatus having a simple and small structure capable of preventing overheating of the end portion of the fixing roller even when fixing a recording sheet having a width smaller than the fixing width. To do. Another object of the present invention is to provide an electrophotographic apparatus having a simple and compact structure in which the recording paper width is automatically detected and the heat diffusion on the surface of the fixing roller is controlled according to the detected recording paper width. To do.

[0005]

In order to achieve the above object, the present invention is capable of rotating while contacting the fixing roller 6 in an electrophotographic apparatus having the fixing roller 6 heated by an internal heat source. It is characterized in that it comprises a heat diffusion roller 10. Further, before the recording paper 22 passes through the fixing roller 6, the recording paper width detection means 9 for detecting the width of the recording paper 22 and the recording paper width detection means 9 detect that the recording paper having a width smaller than a predetermined width has passed. The heat diffusion roller control means 11 for operating the heat diffusion roller 10 is sometimes provided.

[0006]

In the present invention, the heat diffusing roller 10 is rotated while being in contact with the fixing roller 6 to absorb the heat of the surface of the fixing roller and prevent the surface from being overheated. Further, when it is detected by the recording paper width detecting means that a recording paper having a width equal to or smaller than a predetermined width is detected, the heat diffusion roller 1
0 is operated, that is, the heat diffusion roller is separated from the fixing roller when the recording paper width is less than or equal to a predetermined width, and is contacted with the fixing roller when the recording paper width is greater than or equal to the predetermined width, so that optimum heat diffusion can be performed according to the recording paper width. .

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a facsimile machine or a copying machine having the electrophotographic apparatus of the present invention. In the figure, the operating means 1 comprises a key switch and a display device,
It is used to send a facsimile or start copying. The reading unit 2 is for reading a transmission document, and if the temperature becomes too high, a photoelectric element such as a CCD for reading causes an abnormality, so that the reading unit 2 has a structure protected against overheating. The recording means 3 is for charging, transferring, and developing to form a hard copy of received data and copy data. The conveying means 4 is for performing the sub-scanning for the reading / recording. The recording paper passage detecting means 5 detects passage of the recording paper immediately before the fixing means,
The heat diffusion roller 11 is controlled by the heat diffusion roller control means 12 to be described later.
It is for determining the timing of the operation of. The fixing unit 6 is for thermally fixing the toner developed by the recording unit 3. A fixing roller 7, a heater 8 and a heater temperature detector 9 are attached to the fixing means 6.

The recording paper width detecting means 10 is for detecting the recording paper width conveyed to the fixing means 6. The heat diffusion roller 11 is for diffusing heat on the surface of the fixing roller 7. The thermal diffusion roller control means 12 is for pressing the thermal diffusion roller 11 to or from the fixing roller 7 according to the recording paper width information from the recording paper width detection means 10. The system control means 13 is for controlling the entire apparatus, for example, it monitors the key input from the operation means 1 and controls the processing such as facsimile reception and copying according to the type of the key input. Based on the temperature information from the heater temperature detector 9, ON / OFF is controlled so as to maintain the heater 8 at the fixing temperature, and when the recording paper width detecting means 10 detects a narrow recording paper, the heat diffusion roller control is performed. The means 12 is activated to control the heat diffusion roller 11 to press it against the fixing roller 7. The encoding / decoding means 14 is for compressing and reproducing image information. The MODEM 15 is a modulation / demodulation device. N
The CU 16 is a network control means.

FIG. 2 shows an embodiment of the configuration of the present invention. In the figure, the same components as those in FIG. 1 are designated by the same reference numerals. Reference numeral 21 is a heating roller, and 22 is a recording paper. The heater 8 is incorporated in the fixing unit 6 and heats the fixing roller 7. A pressure roller 21 is arranged so as to face the fixing roller 7, and the toner of the developed recording paper is fixed by the recording means 3 not shown in FIG. A heater temperature detector 9 is attached to the fixing roller 7,
The system control means 13 is notified of the temperature. The heat diffusion roller 11 is pressed or released from the fixing roller 7 by the system control means 13 via the heat diffusion roller control means 12 not shown in FIG. When the recording paper width detection means 10 detects a recording paper narrower than the fixing width, the heat diffusion roller 11 is pressed against the fixing roller 7 to diffuse the heat of the overheated portion at the end to the recording paper passage portion where the temperature has dropped. The heat distribution of the fixing roller 7 is kept uniform. The timing at which the thermal diffusion roller control means 12 drives the thermal diffusion roller 11 is determined based on the timing at which the passage of the recording paper 22 is detected by the recording paper passage detection means 5 provided in front of the fixing roller 7.

FIG. 3 shows a thermal diffusion roller 1 according to this embodiment.
It is an example of No. 1. In the heat diffusion roller 11, a heat diffusion film 32 having a high heat conductivity is provided around a cylindrical heat insulator 31 forming a roller body. As described above, since the main body of the heat diffusion roller 11 is a heat insulator, the heat of the high temperature portion of the fixing roller 7 is not stored in the main body of the heat diffusion roller 11 but moves to the low temperature portion through the heat diffusion film 32.

FIG. 4 shows an example of the structure of the heat diffusion roller control means 12 in this embodiment. In the figure, the heat diffusion roller 11 is arranged so as to be pressed against the fixing roller by the spring 41. When the solenoid 42 is driven, the heat diffusion roller 11 is pulled in the direction opposite to the direction in which the spring 41 is pulled, and a gap is formed between the heat diffusion roller 11 and the fixing roller 7, so that the heat diffusion effect by the heat diffusion roller 11 disappears. With this configuration, when the recording paper width detection unit 10 detects a recording paper width narrower than the fixing width, the solenoid 42 is not driven and the fixing roller 7 and the heat diffusion roller 11 are brought into contact with each other to prevent overheating at the end portion of the fixing roller 7. When the recording paper width of the fixing width is detected, the solenoid 42 is driven to separate the fixing roller 7 from the heat diffusion roller 11 to eliminate the heat diffusion effect. As described above, the heat diffusion roller control unit 12 controls the position of the heat diffusion roller 11 according to the width of the recording paper to be fixed, so that the heat nonuniform distribution of the fixing roller 7 can be eliminated regardless of the recording paper width. .

FIG. 5 shows an example of the structure of the recording paper passage detecting means 5. The recording paper passage detecting means 5 is composed of an actuator 52 and a photo interrupter 51 arranged between the conveying roller 53 and the fixing roller 7 / pressure roller 21, and the recording paper 22 sent by the conveying roller 53. It is for detecting the passage of. Regarding the recording paper 22 sent by the conveyance roller 53, the photo interrupter 51 detects the ON state when the actuator 52 is pressed, and the OFF state is detected when the recording paper 22 passes by. To be detected.

FIG. 6 is a diagram showing a configuration example of the recording paper width detecting means 10. To apply this embodiment, a recording paper cassette provided with a recording paper width designation lever is used. The user sets the recording paper width designation lever of the recording paper cassette in advance according to the size of the stored recording paper. When the recording paper cassette is set in the main body, the recording paper width detection means 10 changes the state of the switch group 61 arranged corresponding to the set recording paper width designation lever according to the set state of the designated lever, and changes to that state. The corresponding voltage information appears at the port, and the information is used as recording paper width information by the system control means 1.
3 is output.

FIG. 7 shows the effect of uniformizing the surface temperature distribution of the fixing roller 7 according to the present invention. Consider the temperature distribution on the fixing roller when a heater having a uniform heat distribution is used. The horizontal axis represents the axial distance of the fixing roller, and the vertical axis represents the temperature of the roller surface at that position. In the figure, (a)
Is the temperature in the fixing standby state, (b) is the fixing temperature,
(C) shows the temperature when there is no diffusion roller. FIG. 7A shows the temperature distribution when the recording paper width is the same as the fixing width, and FIG. 7B shows the temperature distribution when the recording paper width is narrow. As can be seen from the figure, since the temperature distribution when the recording paper is equal to the fixing width is uniform, the entire temperature may be set to the fixing temperature during fixing. On the other hand, when the recording paper is narrower than the fixing width and there is no heat diffusion roller, the temperature of the central portion of the fixing roller with the recording paper is absorbed by the recording paper, so the temperature becomes low, but the fixing It can be seen that there is no such absorption at the end of the roller, so the temperature becomes high, and when the fixing temperature is set at the center, the end becomes overheated. However, when the heat diffusion roller and the heat diffusion roller control means as in the present invention are provided, the temperature on the fixing roller becomes uniform, so that the end portion does not become overheated.

[0015]

According to the present invention, it is possible to obtain an electrophotographic apparatus having a simple and compact structure capable of preventing the end portion of the fixing roller from being overheated even when fixing a recording sheet having a width smaller than the fixing width. Also, since the width of the recording paper is automatically detected and the heat diffusion on the surface of the fixing roller is controlled according to the detected width of the recording paper, a simple and compact electronic device capable of optimal heat diffusion according to the width of the recording paper. A photographic device is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of a facsimile machine or a copying machine having an electrophotographic apparatus of the present invention.

FIG. 2 is a diagram for explaining an example of the configuration of the present invention.

FIG. 3 is a diagram showing an example of a heat diffusion roller in the present embodiment.

FIG. 4 is a diagram showing a configuration example of a heat diffusion roller control means in the present embodiment.

FIG. 5 is a diagram showing a configuration example of recording paper passage detection means in the present embodiment.

FIG. 6 is a diagram showing a configuration example of recording paper width detection means in the present embodiment.

FIG. 7 is a diagram showing an effect of uniformizing the surface temperature distribution of the fixing roller according to the present invention.

[Explanation of symbols]

1: Operating means, 2: Reading means, 3: Recording means, 4:
Transporting means, 5: recording paper passage detecting means, 6: fixing means,
7: fixing roller, 8: heater, 9: heater temperature detector,
10: recording paper width detecting means, 11: heat diffusion roller, 12:
Heat diffusion roller control means, 13: system control means, 1
4: Encoding / decoding means, 15: MODEM (modulator / demodulator), 16: NCU (mesh control means), 21: pressure roller, 22: recording paper, 31: heat insulator, 32: heat diffusion film,
41: spring, 42: solenoid, 51: photo interrupter, 52: actuator, 53: transport roller, 61: switch group, 62: port

Claims (2)

[Claims] 1. An electrophotographic apparatus having a fixing roller heated by an internal heat source, the electrophotographic apparatus comprising a heat diffusion roller capable of rotating in contact with the fixing roller. 2. The electrophotographic apparatus according to claim 1, further comprising: recording paper width detecting means for detecting a width of the recording paper before the recording paper passes through the fixing roller; An electrophotographic apparatus comprising: a heat diffusion roller control unit that operates the heat diffusion roller when it is detected that a recording sheet having a width equal to or less than a width is detected.