JPH03138681A - Fixing device - Google Patents

Abstract

PURPOSE:To prevent a press-contact roller from being heated for a long time and to prevent the soiling of a heat roller by silicone oil by providing a means intermittently rotating and driving the heat roller and the press-contact roller when image formation is awaited. CONSTITUTION:At the standby of image formation, the heat roller 71 and the press-contact roller 74 are intermittently rotated and driven. At prescribed time intervals, or at a time when the heat roller 71 is heated on and its temperature exceeds a prescribed temperature, both rollers 71 and 74 are rotated. Thus, oozing of silicone oil, which is caused by local overheating of the press-contact roller 74, can be prevented. Moreover, the soiling of the surface of the heat roller 71 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Al Industrial Application Field) This invention relates to a fixing device for heating and fixing an image on an image forming sheet in an image forming apparatus such as a copying machine.

(b) Conventional Technology In image forming apparatuses such as copying machines, a heat fixing device is used to fix images on image forming paper. This fixing device generally has a heat roller formed in a cylindrical shape and equipped with a heater such as a halogen lamp inside, and a pressure roller that presses the heat roller directly or indirectly.

A silicone rubber layer is formed on the surface of the pressure roller in order to prevent toner, dye, etc. constituting the image from adhering.

(C1 Problem to be Solved by the Invention) Conventionally, the heat roller and the pressure roller are driven to rotate during image formation, but are stopped when in the ready state (image formation standby state). Normally, in the ready state, the heat roller and the pressure roller are driven to rotate. The heat roller surface temperature is maintained at the same temperature as during image formation or a slightly lower temperature, and the temperature is approximately 100'.
It is about 160 degrees from around C. Therefore, the temperature of the pressure contact portion of the pressure roller that is pressed against the pressure roller becomes partially close to that temperature. The silicone rubber that makes up the surface layer of the pressure roller itself has heat resistance, but if only one part of it is heated intensively for a long time at the high temperatures mentioned above, the silicone rubber contained in the rubber will deteriorate. There was a problem in that molecular weight silicone oil oozed out onto the silicone rubber surface, staining the heat roller and the like.

An object of the present invention is to provide a fixing device that can prevent a pressure roller having a silicone rubber layer from being heated for a long time and prevent the surface of the heat roller from being contaminated by silicone oil as described above. .

(d) Means for Solving the Problems The present invention provides a fixing device that includes a heat roller that includes a heater therein, and a pressure roller that directly or indirectly contacts the heat roller and has a silicone rubber layer on its surface. The apparatus is characterized in that means is provided for intermittently driving the heat roller and the pressure roller to rotate during the image forming standby state.

te1 Effect In this invention, since the heat roller and the pressure roller are intermittently rotated during the image forming standby state (ready state), the surface of the pressure roller is not partially heated, and the silicon Oil leakage is prevented. The means for intermittently rotating both rollers is as follows:
For example, it is a control unit that rotates both rollers at predetermined intervals when the heater of the heat roller is turned on and when the temperature of the heat roller is higher than a predetermined temperature.

(f) Examples FIG. 5 is a schematic front view of a copying machine equipped with a fixing device.

A media cartridge 1 is removably provided on the left side of the center inside the main body of the copying machine, and a rolled media sheet 2 is stored inside. The media sheet 2 is a sheet coated with microcapsules encapsulating a photocurable material and dye. In the media sheet, partial microcapsules are hardened by exposure to light to form a latent image, and by overlaying this latent image with an image-receiving sheet (described later) and applying pressure, the unhardened microcapsules are destroyed and the encapsulated dye is formed. etc. are flowed onto the image-receiving sheet. The media sheet 2 is ejected from the media cartridge 1, passes through an exposure section P1 and a pressure development section P2 on the copying machine main body side, and is returned to the media cartridge 1 again.

A document table 3 is provided on the top surface of the copying machine main body, and a document to be copied is placed thereon. Below the document table 3 is a light source, a mirror,
An optical system 4 including a lens is provided, and guides reflected light from the original on the original platen 3 to the exposure section P1. Therefore, the media sheet 2 is exposed to light reflected from the document on the document table at the exposure portion P1, and a latent image is formed.

On the other hand, a paper cassette 6 containing an image receiving sheet 5 is provided on the right side of the copying machine main body. During image formation, the image receiving sheet 5 is fed from the paper cassette 6 and conveyed to the pressure developing section P2. Here, the latent image is superimposed on the latent image on the media sheet and pressurized. This is a development process, in which the uncured microcapsules on the media sheet are destroyed and the encapsulated dye flows out onto the image-receiving sheet.

The image receiving sheet 5 that has passed through the pressure developing section P2 is sent to the fixing device 7, where it undergoes a fixing process and is then discharged to the paper discharge tray 8 on the right side.

FIG. 2 is a diagram showing the configuration of the fixing device 7. As shown in FIG.

The fixing device 7 includes a heat roller 71 having a heater 71a inside, a tension roller 72 disposed downstream of the heat roller 71, an endless heat-resistant belt 73 stretched between the heat roller 771 and the tension roller 72, and a heat-resistant belt 73. Pressure roller 7 that presses against heat roller 7I via
It has 4.

Further, 75 is a thermistor that detects the surface temperature of the heat roller 71, 76 is a cleaner that cleans paper powder, dust, etc. adhering to the heat roller surface, and 77 is a fan that blows cooling air around the tension roller 72.

The image receiving sheet sent from the pressure developing section P2 passes between a heat resistant belt 73 (heat roller??) and a pressure txo and a rough 4. At this time, the coloring reaction of the dye (color-forming dye) on the image-receiving sheet is promoted, and the thermoplastic resin previously coated on the image-receiving sheet is softened and covers the image surface, giving the image gloss. This image-receiving sheet is further sent downstream along the heat-resistant belt 73, cooled by a cooling fan, and then separated at the tension roller 72 by the force of the heat-resistant belt 73 being wound upward. At this time, since the image receiving sheet is sufficiently cooled, no offset occurs.

FIG. 3 is a block diagram of the main parts of the copying machine.

A heater drive signal based on detection by the thermistor 75 is input to the one-chip microcomputer 1). The heater drive signal is a comparison value of the voltage divided by the resistors R1 and R2 and the voltage divided by the resistor R3 and thermistor 75 by the comparator 78. The comparator 78 outputs '1)' if the surface temperature of the heat roller rough 1 is lower than a preset value, and inputs '1)' if it is higher, to the microcomputer 1). In the microcomputer 1), the heater 71 of the heat roller is adjusted according to this value.
Performs on/off control of a. Note that in a copying machine in which the temperature of the heat roller is lowered when ready, the resistor R1 is made a variable resistor.

Further, the microcomputer 1) is manually input with operation signals for the print switch 12 from the operation section of the main body F of the copying machine. In response to this signal, the microcomputer 1) operates a clutch 13 that transmits high-speed rotational force to the heat roller 71.
Turn on the heat roller, heat-resistant heald, pressure roller, etc.
Hereinafter, it will be referred to as the fixing roller. ) is rotated at a high speed suitable for image formation.

On the other hand, in the ready state, the microcomputer 1
), the clutch 14 that transmits low-speed rotational force is intermittently turned on, and the fixing roller is intermittently rotated at low speed.

An example of actual driving of the fixing roller will be explained.

Is the rotation system of the fixing device in Figure 1? 1) A flowchart showing one example. In this example, the fixing device is rotated when the heater of the heat roller is turned on.

If the print switch is operated, the process proceeds to the copying process as described above (nl), but when the print switch is in the ready state, the output of the comparator 78 can be seen (n2). When the surface temperature of the heat roller 71 is too low (when the comparator output is "H"), the low speed clutch 14 is turned on and the fixing roller is rotated at a low speed, and the heater 7
1a is turned on and the heat roller is heated (n3.n
4). However, when the temperature of the heat roller has not dropped much or has risen to a specified temperature, both the heater and rotation are turned off (n5, n6).

If the fixing device is turned on every time the heater is turned on (when the comparator output becomes "H"), the fixing roller will be rotated every certain period of time, so the pressure roller will partially rotate. This can prevent concentrated heating.

Further, FIG. 4 is a flowchart showing another example of rotational drive. In this example, when the heater is turned on during ready, the fixing roller is rotated at predetermined time intervals.

When the print switch is operated, the copy processing routine advances to one of the ready routines (n12), and if the comparator output is "'H", the heater 71a is turned on, and "L"
”, turn off the heater 71a (n13→n14
．． n15), and the rotation of the fixing roller is when the heater is on (
n14), the timer is set to 1 and is switched every time the time elapses (nll-+n16→n17).

As described above, in this invention, since the fixing roller is intermittently rotated during the ready state, it is possible to prevent the silicone oil from seeping out due to the pressure roller being partially heated too much. In addition, by rotating intermittently and at low speed, it is possible to suppress frictional deterioration of the heat-resistant heald.

Note that the fixing roller may be rotated at predetermined time intervals when ready, regardless of whether the heater is on or off.

(G1 Effects of the Invention As described above, according to the present invention, by intermittently rotating the heat roller pressure roller (fixing roller), the pressure roller is prevented from being heated locally, and silicone oil) It is possible to prevent protrusion from occurring and prevent the heat roller and the like from getting dirty.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing the processing procedure when the copying machine is ready to operate the fixing device according to the embodiment of the present invention, and FIG.
13 is a block diagram of the main parts of the copying machine, FIG. 13 is a configuration diagram of the fixing device, FIG. 4 is a flowchart showing other processing procedures at ready time, and FIG. 5 is a schematic front view of the copying machine. 71-heat roller, 71a-heater, 72-tension roller, 73-heat-resistant belt, 74-pressing roller.

Claims (1)

[Claims] (1) In a fixing device comprising a heat roller having a heater therein, and a pressure roller that directly or indirectly contacts the heat roller and has a silicone rubber layer on its surface, when the image formation standby state is set, the heat roller is heated. A fixing device comprising means for intermittently rotationally driving a roller and a pressure roller.