JPS62187373A - Heat fixing device for electrophotographic device - Google Patents

Abstract

PURPOSE:To obtain high-response performance by providing a noncontact temperature sensor used for a temperature detecting means nearby a heat roller and providing a cover which controls convection heat on the rear side of the noncontact temperature sensor. CONSTITUTION:The cover 9 prevents the air between the heat roller 1 and a thermistor 4 as the noncontact temperature sensor from moving the rear side of this thermistor in the heat-up period of the heat roller 1 to reduce the convection of air, and receives radiant heat from the heat roller 1 and conducts it to the part of the thermistor 4 contacting the cover 9. Further, the cover also controls a flow of air at the periphery of the thermistor so as to prevent the detected temperature of the thermistor 4 owing to the convection of the air at the periphery of the heat roller which is generated when the heat roller 1 makes one turn during fixing operation after the heat-up period. Consequently, the heat-up period of the heat roller is shortened to perform stable fixation temperature even during operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fixing device for an electrophotographic apparatus, and more particularly to a thermal fixing device equipped with a temperature detecting means with good responsiveness.

[Conventional technology]

In the fixing device of a copying machine, which heats and fixes a phenomenon agent onto copy paper using a heating element, a temperature-sensitive element such as a thermistor is attached directly to or near the heat roller, and humidity control is performed by the output of the heat-sensitive element to adjust the temperature of the heat roller. The fixing temperature is maintained at the optimum fixing temperature.

[Problem that the invention seeks to solve]

Generally, in conventional heat fixing devices, the temperature detection means detects the heat roller surface temperature by bringing a sensor such as a thermistor into contact with the heat roller surface, but since the sensor is in pressure contact with the heat roller, the sensor In addition to abrasion of the heat roller, toner adheres to the surface of the sensor, causing scratches on the surface of the heat roller, resulting in problems of print quality and shortened life of the heat roller.

For this reason, non-contact temperature sensors that do not come into contact with the heat roller have recently been put into practical use. However, the non-contact n1 degree sensor detects radiant heat and convection heat.

The detected temperature changes significantly depending on the flow of the surrounding air.

Temperature overshoot occurs due to a delay in the response of temperature detection, and fixing performance decreases due to unstable W control temperature.

The second object of the present invention is to solve the above-mentioned problems and provide a heat fixing device that has a long life and can stably supply four high-quality prints.

[Means for solving problems]

In the present invention, a non-contact temperature sensor used as a temperature detection means is arranged near a heat roller, and a convection heat regulation cover is provided on the rear side of the non-contact temperature sensor with respect to the rotational direction of the heat roller. be.

[Effect]

The cover of the present invention prevents the air between the heat roller and the non-contact temperature sensor from moving behind the non-contact temperature sensor during the peak-up period of the heat roller, thereby reducing air convection. The cover receives the radiant heat from the heat roller and conducts it to the non-contact temperature sensor that is in contact with the cover. In addition, during the fixing operation after heat-up is completed, a non-contact temperature sensor is installed to prevent the temperature detected by the non-contact temperature sensor from changing due to air convection around the heat roller that occurs when the peeler rotates. Regulate air flow around the area. This shortens the heat-up period of the heat roller, allowing stable fixing temperature control even during operation.

〔Example〕

An embodiment of the present invention will be described with reference to the drawings.

The configuration of the fixing device will be explained with reference to FIG. The fixing device includes a heat roller 1 housing a heating means (hereinafter referred to as a heater) 3, an auxiliary roller 2 that comes into pressure contact with the heat roller 1. a non-contact thermistor 4 that detects the temperature from the heat roller 1;
Cover 8 covering the back of the non-contact thermistor 4. It includes a terminal base 5 that holds a non-contact thermistor 4 and a fixing device cover 9, and fixes the toner 7 on the paper 6 passing between the heat roller 1 and the auxiliary roller 2.

Figure 2 shows the configuration of the non-contact f-mister 4.
0 is the outer frame, and 11 is the inner frame. The cover 8 may be made of a thin metal or insulating material with a small heat capacity, but this embodiment uses polyimide resin.

Next, the effects will be explained using FIGS. 3 to 5.

In FIG. 3, Δ in FIG. 1 is the surface temperature of the heat roller 1 without the cover 8, and B is the surface temperature of the heat roller 1 with the cover 8 attached. Also, A' is the temperature detected by the non-contact thermistor 4 when the cover 8 is not installed, and B' is the temperature detected by the non-contact thermistor 4 when the cover 8 is attached. In this embodiment, the effect of the cover 8 appears during the heat-up period and during continuous fixing. .

First, the heat-up period will be explained. The heat-up period takes tx (approximately 85 seconds) when the cover 8 is attached or not attached to the non-contact thermistor 4, and the heat roller 1
There is a temperature overshoot of about 55° C. when compared with the temperature set value Ts, which has a maximum temperature of pz (about 230° C.). This occurs because the air around the non-contact thermistor 4 becomes warmer and the difference between the surface temperature of the peeler 1-0-ra 1 and the temperature detected by the non-contact thermistor 4 is large. On the other hand, when the cover 8 is attached to the non-contact thermistor 4, the volume of air between the heat roller 1 and the cover 8 is small, so it is easy to warm up, and furthermore, the temperature detected by the non-contact thermistor 4 is equivalent to the fixing temperature. When the heat roller 1 and the auxiliary roller 2 are rotated when the temperature T L ' is reached, the heated air is collected by the cover 8, and the temperature detected by the non-contact thermistor 4 quickly reaches the detection temperature Ts'.
As shown in Figure 3, the peak 1-up period is tz (7
0 seconds), which is an improvement of about 15 seconds compared to tz. The maximum temperature ρz (190°C) is also improved by 40°C compared to pl.

As described above, under the same temperature setting conditions, the heat-up period is shorter and the temperature overshoes to 1 is less than when the cover 8 is not provided. As a result, the waiting time until initial printing can be shortened, and the lifespan of the heat roller 1 and the auxiliary roller 2 can be extended due to the reduction in temperature overshoot, which is highly effective.

Next, the effect during continuous fixing will be explained. When the cover 8 is not attached to the non-contact thermistor 4, the surface temperature of the bee 1 roller 1 is at the set temperature Ts as shown in A in FIG.
The temperature further decreases, and further decreases below the fixable temperature Tb, resulting in non-fixing. FIG. 4 shows the flow of air inside the fixing device without the cover, and FIG. 5 shows the flow of air with the cover 8 attached. P1 without cover 8
~As shown in Figure 4, the surface temperature of the roller 1 decreases because thermal convection occurs forcibly in the rotational direction when the roller 1 rotates, and only the high temperature hot air near the surface of the heat roller 1 decreases. hits non-contact thermistor 4.

This is because the non-contact thermistor 4 detects a temperature higher than the set temperature T s ' and turns off the heater 3.
Since the heat roller 1 radiates heat to the auxiliary roller 2 and the paper 7, the temperature further decreases and non-fixing occurs. On the other hand, when the cover 8 is attached to the non-contact thermistor 4, as shown in FIG. . This hot air is P1
- Since it contains low-temperature air separated from the roller 1 and the two are mixed, a temperature lower than that detected during natural convection during standby is detected, and the third heater 3 is turned on to turn on the heater 3. As shown at B' and B in the figure, the surface temperature of the heater roller 1 rises slightly and does not drop, making it possible to perform stable fixing.

The heat fixing device preferably uses a control circuit disclosed in Japanese Patent Laid-Open No. 60-50565.

〔Effect of the invention〕

According to the present invention, when heating up, the heating up period can be shortened, the amount of temperature overshoot with respect to the set temperature can be minimized, and high response performance can be obtained. Even during continuous fixing, the non-contact temperature detection means of the present invention can stably detect the surface temperature of the heat roller by effectively detecting changes in surrounding thermal convection. By working effectively, it is possible to provide a thermal fixing device that has a long life and stable fixing performance.

[Brief explanation of drawings]

Fig. 1 is a side view of a heat fixing device of an electrophotographic apparatus showing an embodiment of the present invention, Fig. 2 is a front view of a non-contact thermistor, and Fig. 3 is a heat roller with and without a cover. surface temperature changes and. The detected temperature characteristics of the non-contact thermistor, FIGS. 4 and 5, are side views showing the flow of air inside the fixing device with and without a cover. 1...Heat roller, 2...Auxiliary roller, 3...
heater. 4...Non-contact thermistor, 5...Terminal base. 6... Paper, 7... Toner, 8... Cover, 9...
...Fuser. 1st hard 2nd hard 4th - 5th cause

Claims (1)

[Claims] 1. An electrophotographic apparatus comprising a heat roller, a heating means for heating the heat roller, an auxiliary roller that presses into contact with the heat roller, and a temperature detection means for detecting the surface temperature of the heat roller. In the heat fixing device, a non-contact temperature sensor used as the temperature detection means is installed near the heat roller, and a cover for regulating convective heat is provided behind the non-contact temperature sensor with respect to the rotational direction of the heat roller. A heat fixing device for an electrophotographic device, characterized by being provided with. 2. The heat fixing device for an electrophotographic apparatus according to claim 1, wherein the cover is attached directly over or in the vicinity of the non-contact temperature sensor. 3. A heat fixing device for an electrophotographic apparatus according to claim 1, wherein the cover is made of a heat-resistant insulating material such as polyimide resin. 4. A heat fixing device for an electrophotographic apparatus according to claim 3, wherein the cover is held between an inner frame and an outer frame of the non-contact temperature sensor. 5. The electronic device according to claim 3, wherein the cover is made of a transparent heat-resistant insulator to facilitate adjustment of the gap between the contact temperature sensor and the surface of the heat roller and inspection of the sensor section. Heat fixing device for photographic equipment.