JPH04139480A - Fixing device - Google Patents

Abstract

PURPOSE:To obtain excellent fixing performance by respectively arranging temperature detection elements in the paper passing part and the paper non- passing part of a fixing roller. CONSTITUTION:Thermistors 8a and 8b respectively abut on the fixing roller 6 at the positions being the paper passing part and the paper non-passing part in a small size part(S) and measure temperatures Ta and Tb at the respective positions. The temperature Tb at the position being the paper non-passing area is controlled so as not to exceed a specified upper limited temperature and the temperature Ta at the position being the paper passing area is controlled so as not to be under a specified lower limited temperature. Thus, the fixing device in which the damage of the member by excessive temperature rise and the faulty fixing caused by the shortage of he temperature are not caused is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fixing device that fixes developer on a recording material.

[Prior Art] Conventionally, a fixing device measures the surface temperature of the fixing roller by bringing a temperature sensing element into contact with the paper passing portion of the fixing roller, and then sets a heater at a certain temperature to maintain a certain temperature. It is controlled intermittently before and after. Also, the size of the paper used as recording material (
Depending on the copy mode (small size paper) or copy mode (continuous copying), the set temperature may be lowered to prevent the roller surface temperature from rising unnecessarily.

[Problems to be Solved by the Invention] However, as in the conventional example described above, if the temperature is measured at a certain point in the paper passing section, the problem may occur depending on the paper size, especially when copying small-sized transfer paper. The surface temperature of the roller in the paper passing section is either controlled to the set temperature, or the temperature in the non-paper passing section rises above the set temperature because heat is not removed by the transfer paper, causing damage to the roller itself and the members in contact with the roller. may be damaged by heat. On the other hand, if the temperature is measured at the non-traffic paper section, if the set temperature is lowered depending on the paper size or copy mode, the temperature at the paper passing section may drop too much, which may adversely affect image fixability. Furthermore, since the set humidity is changed in anticipation, there is a problem in that it is not possible to apply a sufficient amount of heat in response to various conditions of the paper, such as the moisture absorption state of the paper that is actually passed.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a fixing device that does not cause damage to members due to excessive temperature rise or fixing failure due to insufficient temperature.

[Means for Solving the Problems] According to the present invention, the above object is to transport a recording material while holding it between a fixing roller having a heating element inside and a pressure roller disposed in pressure contact with the fixing roller. In the fixing device that fixes the unfixed developer image by using the fixing roller, there is a position on the surface of the fixing roller that is the paper passing area regardless of the size of the recording material, and a position that is non-fixed when the smallest recording material is used. Temperature sensing elements for detecting the temperature of the surface are disposed at at least two locations in the paper passing region so that the temperature at the paper non-passing region does not exceed a predetermined upper limit temperature.

This is also achieved by including a control means for controlling the temperature at the position of the paper passing area so that it does not fall below a predetermined lower limit temperature.

[Function] According to the present invention, one temperature sensing element for measuring the surface temperature of the fixing roller is installed in the paper passing section, and at least another one is shifted in the axial direction and is placed in a position that becomes the illegal paper section in the case of small-sized paper. One temperature sensing element is arranged to measure the roller surface temperature of the paper passing section and the non-traffic paper section. As a result, if the measured temperature in the non-sheet passing area reaches the upper limit temperature that does not cause damage to the roller itself or the members in contact with the roller, the power to the heater is stopped and the temperature is lowered to below the upper limit temperature. When this happens, power is applied to the heater again. In addition, when performing this control operation, if the surface temperature of the paper passing section falls below the lower limit temperature before the surface temperature of the non-authorized paper section falls below the upper limit temperature, the copying operation is stopped at that point and the heater is turned on. Turn on the power, wait for the temperature to recover, and then enable copying. In another aspect, the copying speed is reduced when the surface temperature in the non-sheet passing portion reaches a quasi-upper limit temperature that is several degrees lower than the upper limit temperature that does not damage the roller abutting member. Since the amount of heat transmitted to the transfer paper per unit time increases, it becomes possible to fix the developer in a short heating time, and the amount of heat given to the non-paper passing area decreases, so temperature rise is suppressed. However, if the temperature continues to rise and reaches the upper limit temperature, the power supply to the heater is stopped, and after waiting for the temperature to drop below the semi-upper limit temperature, the normal copying speed is restored. As mentioned above, the surface temperature is measured and controlled in the paper passing section and the non-paper passing section, and one variety is used to fix the temperature at the normal set temperature within a range that does not damage the roller abutting member. Good fixing properties can be obtained for paper in a certain condition.

[Example] A first example and a second example of the present invention will be described based on the accompanying drawings.

(First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS. 1 to 4.

In FIG. 1, l is a photosensitive tram, and the photosensitive drum l
The latent image is developed by the developing device 2. A transfer separation charger 3 transfers the developed image on the photosensitive drum 1 onto a transfer paper serving as a recording material. Further, the cleaner 4 cleans the developer remaining on the photosensitive drum l. The transfer paper transferred by the transfer separation charger 3 is conveyed to a fixing device by a paper conveying device M5, and is conveyed while being nipped by a fixing roller 6 and a pressure roller to fix the developer. As shown in FIG. 2, the surface of the fixing roller 6 is in contact with a thermistor 8 for detecting the surface temperature, a separation claw 9 for separating the transfer paper from the fixing roller 6, and a heat-resistant Baberweb 10 for supplying silicone oil. ing. The sea urchin rough 10 is brought into contact with the fixing roller 6 by a sea urchin roller 11. Further, a fixing guide 12 guides the transfer paper to a predetermined position of the fixing roller, and a halogen heater 13 supplies heat to the fixing roller 6. In such an image forming apparatus, a photosensitive tram l
The latent image formed thereon is developed by the developing device and transferred onto the transfer paper by the transfer separation charger 3. The developer remaining on the photosensitive drum 1 at this time is cleaned by a cleaner 4. The transfer paper is then conveyed to the fixing device side by the paper conveying device 5, and fed to a predetermined position of the fixing roller 6 by the fixing roller 12. Next, the image on the transfer paper is fixed by being conveyed while being heated by a fixing roller 6 and a pressure roller 7. At this time, the silicone oil supplied by Uni Ruff adheres to the fixing roller and contributes to the developer to prevent offset. The finally fixed transfer paper is separated from the fixing roller 6 by a separation claw 9 and discharged.

Next, temperature control of the fixing roller will be explained.

As shown in FIG.
8. In the small size section (S), place 8 at the position where the paper does not pass through.
The thermistors b are in contact with each other, and let the respective measured temperatures be 'r, ,'r. FIG. 4 shows a flowchart of temperature control, where T□ is the fixing set temperature, T is the lower limit temperature for fixing, and T2 is the fixing roller itself and the contact members (web 10, Uniraflow 911, separation claw 9 etc)
This is the upper limit temperature that does not cause damage to the T2.
>Tl>TIL.

When the transfer paper size is L, Ta and Tb are both paper passing sections and there is no temperature difference, so temperature control is TIL < Ta <
There are almost no cases where the heater is intermittently controlled so that Ts becomes Tb>72. However, when the transfer paper size is S, heat is not removed from the 8b section by the transfer paper, so as the copying operation progresses, Tb>T
In the case of T, < T, the heater continues to be energized, so it may become Tゎ〉T2. At that time, the power to the heater is stopped, and after Tb<T2, the heater is powered again. Also, if Tb〉〉Ta and the temperature difference is large, if the power supply to the heater is stopped, Ta〉〉Ta〉
There is a possibility that it will be TIL. In the worst case, the copying operation is stopped, and after Tb<72, the heater is energized and the copying operation is performed.

As described above, this embodiment provides a fixing device that is free from damage to members due to excessive temperature rise and fixing failure due to insufficient temperature.

<Second Embodiment> Next, a second embodiment of the present invention will be described based on FIG. 5. Note that explanations of parts common to the first embodiment will be omitted.

In this embodiment, control is performed to reduce the copying speed when the temperature reaches 1"2L, which is slightly lower than T2.
The flowchart is shown in FIG. At this time, the magnitude relationship of temperature is T2>T2L>T□, and the magnitude relationship of copying speed is α>
It is β.

In the case of transfer paper size L, both Ta and Tb are paper passing parts and there is no temperature difference, so temperature control is performed by controlling the heater intermittently based on the magnitude relationship between Ta and T, and Tb>T2L. There is no such case, and the copying speed can be kept at αCpl.

However, when the transfer paper size is S, heat is not removed by the transfer paper in the 8b section, so as the copying operation progresses, Tb>T, and if T<T, the heater continues to be energized, so In some cases, Tb>T2L. In that case, the copy speed is reduced from αcps to βcp. When the copying speed is reduced, the amount of heat applied to the transfer paper per unit time increases, so for the same amount of heat supplied, Ta tends to reach T, and when T,>T, the power to the heater is stopped. After waiting until Tb<T2L, the copying speed is returned to αcp11. βcps
If T, > T does not occur even if the speed is reduced to
>72, the power supply to the heater is stopped and Tb<
After waiting for T2L, copy speed αCp11
Return to

This embodiment also provides the same effects as the first embodiment.

[Effects of the Invention] As explained above, temperature detection elements are arranged in the paper passing portion and non-paper passing portion of the fixing roller, and the heater is intermittently controlled by the signal from the temperature detection element in the paper passing portion. , by controlling the heater intermittently or reducing the copying speed based on the signal from the temperature detection element in the non-paper passing area.
Good fusing performance can be obtained by performing fusing at the normal temperature range that does not damage the fusing roller itself or the members in contact with it, and it is suitable for transfer paper in various conditions. A sufficient amount of heat can also be applied to fix the film.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a schematic configuration of the apparatus according to the first embodiment of the present invention, FIG. 2 is a sectional view showing a schematic configuration of a fixing device used in the apparatus shown in FIG. 1, and FIG. FIG. 4 is a flowchart showing the temperature control method of the device shown in FIG. 2; FIG. 5 is a flowchart showing the temperature control method of the second embodiment of the present invention. . 6...Fuser roller 7...
......Pressure rollers 8a, 8b...Temperature sensing element patent applicant Canon Co., Ltd. agent

Claims (3)

[Claims] (1) In a fixing device that fixes an unfixed developer image by sandwiching and conveying a recording material between a fixing roller having a heating element inside and a pressure roller disposed in pressure contact with the fixing roller, the above-mentioned fixing device The temperature of the surface of the roller is set at at least two points: the position where the paper passes regardless of the size of the recording material, and the position where the paper does not pass when the smallest recording material is used. A temperature detection element is provided to detect the temperature so that the temperature at the position where the paper does not pass through is set to not exceed a predetermined upper limit temperature, and the temperature at the position where the paper pass area is set does not fall below a predetermined lower limit temperature. A fixing device characterized in that it has a control means for controlling the fixing device. (2) The fixing device according to claim 1, wherein the control means controls the temperature by intermittently energizing the heating element. (3) The fixing device according to claim 1, wherein the control means controls the temperature by changing the conveyance speed of the recording material.