JPS60247674A - Fixing device of heat roller type for electrophotographic copying machine or the like - Google Patents

Abstract

PURPOSE:To assure the safety of the device itself and to prevent generation of a secondary fault by disposing a safety device to the proper point on the surface of a heat roller in direct contact therewith except in the paper traveling part for the max. size in the axial direction of the heat roller. CONSTITUTION:The safety device 5 disposed at the proper point of the heat roller 2 in direct contact therewith except the paper traveling part 6 for the max. size follows up the surface temp. of the roller 2 when the surface of said roller is overheated in the stage of warming up the surface of the roller 2 from a room temp. state to the temp. optimum for fixing or in the stage of copying continuously small-sized paper, etc. after the warming up. The light emitting condition of a lamp heater 1 disposed on the inside of the roller 2 is adjusted when the temp. set below the melting temp. of the heat resistant parts around the roller 2 is attained. The surface temp. of the roller 2 is thus corrected to the temp. optimum for fixing and thereafter such condition is sustained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fixing device of the +=-RA type in an electrophotographic copying machine.

(Refer to 9 for prior art) As shown in FIG. 1, a heat roller type fixing device used in a conventional electrophotographic copying machine, etc. has a heat roller 2 with a built-in lamp heater 1 and a pressure ruler 3 mounted on a support frame 4. These P-Ras 2 and 3 are arranged at appropriate positions on the paper conveyance path from the transfer section of the photoreceptor drum (not shown) to the paper output tray outside the machine, and the photoreceptor When the paper that has been transferred with an unfixed toner image transferred in the transfer section of the drum passes between the heat ruler 2 and the pressure ruler 3, a predetermined thermal energy and pressure are applied to the paper. It was designed so that it could be used for a long time. In the fixing device, if the surface temperature of the heat roller 20 becomes excessively high (hereinafter referred to as overheating) and the temperature continues for a long period of time, the roller 2
In order to prevent this from melting or igniting heat-resistant parts placed near the heat roller 2, conventionally a safety device 5 such as a thermostat or fuse is placed around one outer periphery of the heat roller 2. 5, the surface temperature of the heat roller 20 was always controlled at 5 so that it was the optimum temperature for fixing, which was below the melting temperature of the heat-resistant parts.

However, the surface temperature of the heat roll 20 decreases when the paper running section contacts the paper during fixing and is absorbed by the paper, whereas this does not occur in the non-paper running section. Naturally, a temperature difference occurs there, and this temperature difference varies depending on the size of the paper, and in the case of the largest size paper, as shown by line a in FIG. While the temperature tends to rise relatively small, in the case of small-sized paper, the temperature rises inside the maximum size paper running section 6 and outside the small size paper running section 6', as shown by the line. tended to be very high. For this purpose, the safety device 5 is disposed on one outer periphery of the location, and when an attempt is made to adjust the temperature of the heat roller 20 during overheating F to ensure the safety of the fixing device itself, the safety device 5 There is a possibility that a malfunction may occur due to the rise in surface temperature of the heat roller 20 that is applied to the area, and to avoid this, the safety device 5
The safety device 5 has to set the operating temperature of the heat roller 2 higher, and if the operating temperature is set higher, the surface temperature of the roller 2 will become considerably high when the heat roller 2 is heated. During this time, the surface temperature of the μm2 remains in an auto-heated state, and the heat resistant parts around the roller melt due to the heat dissipation. In order to avoid this drawback, conventionally, the safety device 5 is placed at a relatively stable temperature location outside the maximum size paper running section 6 of the heat roller 2, and the safety device 5 is placed at a location where the temperature is relatively stable, and the temperature is calculated based on the surface temperature of the roller 2 at that location. The entire surface temperature of the heat μm 2 is always adjusted to the optimum temperature for fixing, and this state is maintained while copying continues.However, this safety device 5 is
In the conventional method of placing the paper outside the maximum size paper running section 6 of the p-ra 2, the safety device 5 itself used for this was a non-contact type, so the safety device @5 The heat roller 20 cannot follow the movement of the heat roller 20.
Since it will not work until the surface temperature reaches a fairly high level, is it a heat-resistant component? ! ! % and that it is almost impossible to completely prevent ignition. (Objective of the Invention) The present invention has been made to eliminate the drawbacks of the conventional heat roller type fixing device, and includes a safety device disposed on one outer periphery of the heat ruler 2. heat roller 2
0 The ability to follow the rate of increase in the surface temperature is improved, and the safety device 5 operates at a temperature below the melting temperature of the heat-resistant parts in any case when the roller 2 is autoheated, so that the parts are protected. The object of the present invention is to provide a heat ruler type fixing device that avoids troubles such as melting and ignition.

(Structure of the Invention) For this purpose, the present invention, when disposing the safety device 5 on one outer periphery of the heat roller 2, places the safety device [15] in the axial direction of the heat roller 2 (maximum size paper traveling s6
The heat roller 20 of the safety device 5 is placed in direct contact with the appropriate location on the outer surface, thereby increasing the followability of the heat roller 20 surface temperature of the safety device 5 to ensure the safety of the device itself. The contact force between the safety device 2 and the safety device 5 may be worn out or damaged, which may cause paper jams on the copy paper during fusing, or may contaminate the surface of the copy paper and affect the quality of the final copy image. This also makes it possible to prevent the occurrence of secondary failures such as a decrease in performance.

(Embodiments) The present invention will be described in detail below based on embodiments shown in the drawings.

FIG. 3 is a partially cutaway front view showing an embodiment of the main part of the fixing device of the heat μm type according to the present invention.

In the same figure, a heat roller 2 with a lamp heater 1 disposed inside is placed between a support frame 4, 4' and a bearing 7.
．． 7' is used to rotatably attach the rollers 2 and 3 to the pressure ruler 3 in a pair above and below, and these rollers 2 and 3 are rotated using an internal drive device (not shown), as is conventional.

However, when arranging the safety device 5 such as a thermostat on one outer periphery of the heat ruler 2, its position should be at a location outside the maximum size paper running section 6 of the heat roller 2 where the surface temperature of the p-ruler 2 is most stable. The safety device 5 is brought into direct contact with the surface of the heat roller 20 at the point where the operating temperature of the surface temperature of the roller 2 is set to be lower than the melting temperature of the heat-resistant member placed near the p-ra 2 during overheating. Immediately when the surface temperature of the heat roller 2 exceeds the set temperature, the safety device 5 operates to adjust the light emitting state of the lamp heater 10, which is a heat source disposed within the heat ruler 2, so that the surface temperature of the heat roller 20 is always optimal for fixing. so that it can be maintained at a suitable temperature.

The present invention is constructed as described above. And now,
If the surface temperature of the heat roller 20 overheats when warming up the surface temperature of the heat roller 20 from room temperature to the optimum temperature for fixing, or when continuously copying small size paper etc. after warming up, the A safety device 5 placed in direct contact with the outside of the maximum size paper running section 6 of the heat roller 2 immediately follows the temperature of the surface of the heat roller 2. When the temperature reaches the set temperature below the melting temperature, the light emitting state of the lamp heater l disposed inside the heat roller 2 is adjusted, and the surface temperature of the heat roller 2 is corrected to the optimum temperature for fixing, and from then on, the state is maintained. sustain.

(Effect of the invention) The present invention is configured and operates as described above,
Heater) When placing the safety device 5 at an appropriate location on the surface of the p-ra 2, select that location as the location where the surface temperature of the heat roller 20 is the most stable outside the maximum size paper running section 6 of the heat roller 2, and place the safety device 5 directly on the surface of the p-ra 2. By arranging them in contact with each other and operating at a temperature below the melting temperature of the surrounding heat-resistant parts when the heat roller 20 overheats,
The safety device 5 has the effect of increasing the followability of the safety device 5 to the rate of increase in the surface temperature of the heat roller 20, making its operation quick and accurate, and further improving the safety of the fixing device itself. Even if the surface of the heat roller 2 is worn or damaged by placing it in direct contact with the surface of the heat roller 2, the contact point is outside the maximum size paper run section 6, so this will not be the cause. This method also has the effect that stable fixing can always be expected without causing a deterioration in the image quality of copies due to jamming of the copy paper or contamination of the surface of the paper.

[Brief explanation of drawings]

Figure 1 is a partially cutaway front view of the main parts of a conventional Hea)P-Ra type fixing device, Figure 2 is a diagram showing the temperature distribution on the surface of the Hea)P-Ra, and Figure 3 is a diagram showing the 1 is a partially cutaway front view showing an embodiment of a heat roller type fixing device of the invention; FIG. In the figure 1... lamp heater, 2... heat roller,
3...Pressure roller, 4,4'...Support frame, 5...Safety device, 6...Maximum size paper running section, 6'...Small size paper running section, 7.7'. ··bearing.

Claims (1)

[Claims] A heat ruler with a built-in lamp heater and a pressure roller are provided as a pair, and when copy paper with an unfixed toner image transferred passes between these rollers, heat energy and pressure are applied to fix the image. In the fixing device configured as above, a safety device such as a thermostat placed on one outer periphery of the heat ruler is installed at an appropriate location outside the maximum size paper running area of the heat roller in order to control the light emission state of the lamp heater in the heat roller. (5) A heater for an electrophotographic copying machine, etc., which is placed in direct contact with the surface, and whose operation is set to 5 so that when the heat ruler overheats, it operates below the melting temperature of heat-resistant parts placed around it. P-Ra type fixing device.