JPH05150686A - Fixing device and temperature control method for fixing device - Google Patents

Abstract

PURPOSE:To provide a fixing device and a temperature control method for the fixing device which is equipped with a temperature detector which can detect the surface temperature of a rotating heating roll with high heat responsiveness without damaging the rotating heating roll and which can stably supply the high quality of printing for a long time by providing the temperature detector. CONSTITUTION:This fixing device is constituted of the aluminum rotating heating roll 2 inside which a halogen lamp 3 being a heating element is housed and whose surface is coated with fluororesin, a pressure roll not shown in figure which pressure-contacts with the roll 2, and the temperature detector 1 which can detect the surface temperature of the roll 2. The thermistor being the temperature detector 1 abuts on the surface of the roll 2 with pressuring by 10g, and the part of a thermistor lead wire which is 10mm on one side by interposing the thermistor is arranged in space which is 0.5mm apart from the surface of the roll 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used in an electronic copying machine, a laser printer or the like and a temperature control method therefor, which can control the surface temperature of a rotary heating roll with a particularly high thermal response. At the same time, it relates to a device which is devised so as not to damage the rotary heating roll.

[0002]

2. Description of the Related Art As is well known, a fixing device for heating and fixing a toner image on a sheet is provided in an electronic copying machine, a laser printer or the like. In this fixing device, a temperature detector having a heat-sensitive element such as a thermistor is brought into contact with the surface of the rotary heating roll, and the surface temperature of the rotary heating roll is controlled to an optimum fixing temperature by this temperature detector so that the temperature of the paper is kept at a predetermined temperature. The toner image of is fixed.

FIG. 6 shows an example of the above conventional fixing device.
This fixing device includes a rotary heating roll 12 made of aluminum which has been subjected to a surface treatment such as a fluororesin coating, a pressure roll (not shown) in pressure contact with the rotary heating roll 12, and a surface of the rotary heating roll 12. It is composed of a temperature detector 11 generally called a soft touch sensor arranged in contact with each other. A halogen lamp 13 as a heating element is fixedly arranged inside the rotary heating roll 12.

FIG. 7 is a diagram for explaining in detail the structure of the temperature detector used in the conventional fixing device shown in FIG. In the temperature detector 11 shown here, a recessed embedding portion 20 is first formed on the upper surface of a heat-resistant sponge 19 made of silicone rubber or the like mounted on the printed wiring board 16, and this recessed portion is a thermosensitive element. A thermistor 1
4 are accommodated. Lead wire 15 of the thermistor 14,
15 'is guided in a groove 21 formed continuously with the recessed embedding portion 20, and a heat collecting plate 22 such as an aluminum foil is attached to the upper portion thereof. This thermistor lead wire 15,15 '
Are led out to the back surface of the board 16 through holes provided in the front and rear portions of the printed wiring board 16, and the ends are soldered to the lands of the conductor pattern formed on the back surface of the board 16. .

The ends 17 and 17 'of the temperature detector are soldered to the land of the conductor pattern on the back surface of the substrate 16 and electrically connected to the thermistor leads 15 and 15'. The heat-resistant sponge 1 is attached to the assembly of the heat-resistant sponge 19 having the substrate 16 and the thermistor 14 mounted thereon.
A film 24 made of polyimide or the like and having excellent heat resistance and insulation is wound so as to cover the entire surface of the thermistor 9 of FIG. The slip heat-resistant insulating film 24 is used for the thermistor 14, thermistor lead wires 15 and 15 ', and the heat collecting plate 22 attached on the thermistor lead wires 15 and 15'.
It has a function of fixing each component such as the above to the heat-resistant sponge 19.

In the conventional fixing device, the surface temperature of the rotary heating roll is controlled by arranging the temperature detector having the above-mentioned structure so that the thermistor mounting surface is in contact with the surface of the rotary heating roll. ..

[0007]

However, the above-mentioned conventional fixing device has the following problems. First,
In the conventional fixing device, since the slipping heat-resistant insulating film is interposed between the thermistor of the temperature detector and the thermistor lead wire and the rotating heating roll, in order to enhance the thermal response of the temperature detector, It is necessary to bring the detector into contact with the surface of the rotary heating roll with a strong pressure of 100 g or more. Therefore, if the rotating heating roll rotates with toner or paper dust adhered to the film on the surface of the temperature detector, a large friction occurs at the contact part with the temperature detector, which causes scratches on the surface of the rotating heat roll. However, the print quality and the life of the rotary heating roll are reduced. At this time, the toner and paper dust adhered to the film on the surface of the temperature sensor hinders the heat collection from the rotating heating roll of the temperature sensor, so that the thermal response of the temperature sensor drops sharply and temperature control becomes unsuccessful. Be stable.

Furthermore, when the temperature detector is kept in contact with the surface of the rotary heating roll with a strong pressure for a long period of time, the heat-resistant sponge of the temperature detector is subjected to permanent compression strain in a concave shape along the curved surface of the rotary heating roll, resulting in heat sensitivity If the thermistor, which is an element, is embedded in the sponge and brought into contact with the sponge without applying pressure, it becomes difficult to perform accurate temperature control.

On the other hand, in terms of structure, there are many problems that the number of parts constituting the temperature detector is large, which not only requires troublesome assembling but also is uneconomical in terms of cost.

For this reason, recently, a non-contact type temperature detector capable of detecting the surface temperature of the rotary heating roll at a predetermined interval without contacting the rotary heating roll with the heat sensitive element and the heat sensitive element lead wire is provided. A fixing device has also been proposed. In this fixing device, there is an advantage that it is possible to prevent the pressure contact between the temperature detector and the rotary heating roll, and the occurrence of scratches on the surface of the rotary heating roll due to adhesion of toner, paper powder, etc. on the surface of the temperature detector. is there.

On the other hand, on the other hand, since a layer of air having high thermal insulation is interposed between the temperature detector and the rotary heating roll, the thermal response is poor, and the air of the rotary heating roll is There is a problem in that the temperature control becomes unstable due to a large change in the detected temperature due to the movement due to the thermal convection generated by the rotation.

The present invention has been made based on such a point, and an object thereof is to detect the surface temperature of the rotary heating roll with high thermal response without damaging the rotary heating roll. It is an object of the present invention to provide a fixing device which is provided with a temperature detector capable of performing the above-mentioned operation, and thereby can stably supply high print quality over a long period of time, and a temperature control method for the fixing device. Another object of the present invention is to provide a fixing device which is excellent in assembling workability and economical efficiency by reducing the number of parts of a temperature detector which constitutes the fixing device.

[0014]

In order to achieve the above object, a fixing device according to the present invention is a fixing device comprising at least a rotating heating roll and a temperature detector for detecting the surface temperature of the rotating heating roll. The heat-sensitive element of the temperature detector is brought into contact with the surface of the rotary heating roll, and the heat-sensitive element lead wire is sandwiched between the heat-sensitive element and at least 5 per side.
It is characterized in that the portion of mm or more is arranged within 3 mm from the surface of the rotary heating roll.

At this time, it is conceivable that the temperature detector has a windshield which covers the heat-sensitive element and the heat-sensitive element lead wire except for the portion facing the rotary heating roll. The windshield referred to in the present invention is a cover provided to prevent the heat collection of the heat sensitive element and the heat sensitive element lead wire from being affected by the change in the flow of the air layer. As the shape, various shapes such as a substantially semicircular shape along the surface of the rotary heating roll are conceivable, and various materials such as a metal having a small heat capacity or a heat resistant film can be used.

As shown in FIG. 3A, the length of the heat-sensitive element lead wire increases as the temperature detection capability increases.
If one side is 5 mm or more, the difference between the actual temperature and the temperature detected by the temperature detector becomes about 2 ° C. to 3 ° C., which enables accurate temperature detection. Therefore, the length of the thermosensitive element lead wire is preferably 5 mm or more on at least one side across the thermosensitive element.

Similarly, as shown in FIG. 3B, the distance between the surface of the rotary heating roll and the lead wire of the heat sensitive element is 3 mm.
If it exceeds, the difference between the actual temperature and the detected temperature will rapidly increase, so it is preferable to dispose the heat sensitive element lead wire within 3 mm.

The temperature control method of the fixing device according to the present invention is as follows.
In a fixing device comprising at least a rotary heating roll and a temperature detector for detecting the surface temperature of the rotary heating roll, a heat-sensitive element of the temperature detector is brought into contact with the surface of the rotary heating roll, and a heat-sensitive element lead wire is heat-sensitive. The surface temperature of the rotary heating roll is detected by arranging at least 5 mm or more on each side of the element within 3 mm from the surface of the rotary heating roll, and the temperature of the rotary heating roll is controlled. To do.

[0019]

In the fixing device of the present invention constructed as described above, at least the heat-sensitive element is brought into contact with the surface of the rotary heating roll, and the heat-sensitive element and the lead wire of the heat-sensitive element are collected from the rotary heating roll. Since heat can be sufficiently generated, it has a high thermal response. Therefore, it is not necessary to bring the temperature detector into contact with the surface of the rotary heating roll under pressure as in the conventional case. In addition to these, due to the structure of the temperature detector, the contact state of the temperature detector with the rotating heating roll becomes point contact instead of surface contact with the conventional temperature detector, which causes scratches on the rotating heating roll surface and It is possible to prevent the deterioration of the printing quality and the life of the rotary heating roll. Further, the temperature detector has a structure in which the heat-sensitive element is in direct contact with the surface of the rotary heating roll, so that the number of parts can be reduced as compared with the conventional temperature detector shown in FIG. Therefore, the assembling workability becomes simple and the cost becomes economical.

When a windshield covering the heat sensitive element and the heat sensitive element lead wire is provided except for the portion of the temperature detector facing the rotary heating roll, the heat convection generated by the rotation of the rotary heating roll is prevented. Because it can prevent the impact
The temperature can be detected with higher thermal response.

Further, in the case of the temperature control method of the fixing device according to the present invention, as described above, the heat-sensitive element and the heat-sensitive element lead wire can sufficiently collect heat from the rotary heating roll, resulting in high thermal response. Thus, the surface temperature of the rotary heating roll can be detected, and the optimum fixing temperature can be stably maintained for a long period of time.

[0022]

Embodiments of the present invention will be described below with reference to FIGS. The fixing device according to this embodiment is shown in FIG.
As shown in (a) and (b), a rotary heating roll 2 made of aluminum having a halogen lamp 3 as a heating element housed therein and having a surface coated with a fluororesin, and the rotary heating roll 2 are shown.
And a temperature detector 1 for detecting the surface temperature of the rotary heating roll 2 described above.

Next, the structure of the temperature detector 1 will be described with reference to FIG. This temperature detector 1 has a diameter of 1 as a heat sensitive element.
There is a small thermistor 4 of about mm, and the thermistor lead wires (heat sensitive element lead wires) 5 and 5'are connected in a state of facing each other with the thermistor 4 interposed therebetween. Each of the thermistor lead wires 5 and 5'is bent into a substantially U shape, and its tip is soldered to the connecting portions 7 and 7'provided on the printed wiring board 6 made of a polyimide film base material.
The lead wires 9 and 9'of the temperature detector 1 are soldered to the other connecting portions 8 and 8'of the printed wiring board 6 and electrically connected via the thermistor lead wires 5 and 5'and the printed wiring board 6. Connected to each other.

In the first embodiment, the thermistor 4 of the temperature detector 1 formed as described above is brought into contact with the surface of the rotary heating roll 2 with a pressing force of 10 g, and a space separated by 0.5 mm from the surface of the rotary heating roll 2. The difference between the surface temperature of the rotary heating roll 2 and the temperature detected by the temperature detector 1 was measured when the lengths of the thermistor lead wires 5 and 5'located at were changed. That is, the surface temperature of the rotary heating roll 2 is set to 150 ° C., and the left and right portions of the thermistor lead wires 5 and 5 ′ sandwiching the thermistor 4 are located in a space 0.5 mm away from the surface of the rotary heating roll 2. The length was measured by changing the range from 1 mm to 10 mm. The result is shown in FIG.

According to this figure, it can be seen that if the length of the thermistor lead wire is 5 mm or more on one side, the deviation from the actual temperature will be small and it can be detected accurately.

As a second embodiment, contrary to the first embodiment, the relationship between the distance from the surface of the rotary heating roll and the detection accuracy was measured when the length of the thermistor lead wire was constant. That is, the measurement was performed by changing the distance from the surface of the rotary heating roll 2 to the left and right 10 mm portions of the thermistor lead wire sandwiching the thermistor 4 in the range of 0 mm to 6 mm. The conditions other than the above factors are exactly the same as those in the first embodiment. The results are shown in Fig. 3 (b).

From this figure, it can be seen that accurate detection is possible if the distance from the surface of the rotary heating roll is within 3 mm.

In the third embodiment, the thermistor 4 of the temperature detector 1 formed as described above is brought into contact with the surface of the rotary heating roll 2 with a pressing force of 10 g, and further the thermistor lead wires 5, 5.
10m on each side across the 5'thermistor 4
The portion m was placed in a space 0.5 mm away from the surface of the rotary heating roll 2.

In order to compare the heating / heating control characteristics of the fixing device according to the third embodiment and the conventional fixing device as shown in FIG. 6, a halogen lamp as a heating element,
Each of the temperature detectors was connected to a temperature controller having a semiconductor switch at the output stage and operated at a set temperature of 150 ° C. The test results are shown in FIG. According to FIG. 4, the thermal responsiveness of the fixing device according to the present embodiment is much faster than that of the conventional fixing device, and the temperature control after the surface temperature of the rotary heating roll exceeds the set temperature of 150 ° C. It can be seen that the fixing device of this embodiment has a small ripple.

In this embodiment, furthermore, the above-mentioned two types of fixing devices were mounted inside an electronic copying machine to actually perform the fixing operation, and the print quality was observed. The fixing operation was continuously performed until the print quality was defective, and after the operation was stopped when the defect was generated, the surface states of the rotary heating roll and the temperature detector were observed. In the conventional fixing device, when printing about 20,000 sheets of A4 size printing paper, characters on the paper were faint or black streaks were generated on the paper, whereas in the fixing device of this embodiment, 50, The print quality was good even after printing 000 sheets. Further, at this time, many small scratches were observed on the surface of the rotary heating roll of the conventional fixing device, and toner and paper dust were attached to the surface of the temperature detector.

Next, a fourth embodiment of the present invention will be described with reference to FIG. In the case of this embodiment, the windshield 10 formed of a polyimide film and formed in a substantially semicircular shape is attached to the printed wiring board 6 of the temperature detector 1 in the third embodiment, along the surface of the rotary heating roll. And all other configurations are the same. Due to the presence of the windshield 10, the temperature detector 1 can detect the surface temperature of the rotary heating roll with higher thermal responsiveness without being affected by the heat convection generated with the rotation of the rotary heating roll. it can.

[0032]

As described above in detail, according to the fixing device and the temperature control method of the fixing device according to the present invention, the surface temperature of the rotary heating roll can be controlled with high thermal response and the rotary heating roll can be controlled. Since surface damage is eliminated, high print quality can be stably supplied over a long period of time. Also, since the surface of the rotary heating roll is not damaged, the life of the rotary heating roll is extended, and the temperature detector to be used has a simpler structure and a smaller number of parts compared to the conventional one, so that the cost can be reduced. You can

[Brief description of drawings]

1A and 1B are diagrams showing an embodiment of the present invention, in which FIG. 1A is a perspective view of a fixing device, and FIG. 1B is a side view of the fixing device.

FIG. 2 is a perspective view of a temperature detector showing an embodiment of the present invention.

FIG. 3A is a graph showing a comparison of detected temperatures according to the length of the heat sensitive element lead wire according to the first embodiment, and FIG. 3B is a rotary heating roll and the heat sensitive element lead according to the second embodiment. It is the graph which showed the comparison of the detection temperature when changing the distance with the line.

FIG. 4 is a graph showing heating / heating control characteristics of a fixing device according to a third embodiment of the present invention and a conventional fixing device.

FIG. 5 is a perspective view showing a state in which a windshield is attached to a temperature detector in a view showing a fourth embodiment of the present invention.

FIG. 6 is a perspective view of a fixing device showing a conventional example.

FIG. 7 is a perspective view of a temperature detector showing a conventional example.

[Explanation of symbols] 1 temperature detector 2 rotating heating roll 3 halogen lamp (heating element) 4 thermistor (heat sensitive element) 5 thermistor lead wire (heat sensitive element lead wire) 5'thermistor lead wire (heat sensitive element lead wire) 6 printed wiring Board 7 Connecting part 7'Connecting part 8 Connecting part 8'Connecting part 9 Lead wire of temperature sensor 9'Lead wire of temperature sensor 10 Windshield

Claims (3)

[Claims] 1. A fixing device comprising at least a rotary heating roll and a temperature detector for detecting a surface temperature of the rotary heating roll, wherein a thermosensitive element of the temperature detector is in contact with the surface of the rotary heating roll, and The fixing device is characterized in that the heat-sensitive element lead wire has at least a portion of 5 mm or more on one side sandwiching the heat-sensitive element and arranged within 3 mm from the surface of the rotary heating roll. 2. The fixing device according to claim 1, wherein the temperature detector has a windshield that covers the heat-sensitive element and the heat-sensitive element lead wire except for a portion facing the rotary heating roll. apparatus. 3. A fixing device comprising at least a rotary heating roll and a temperature detector for detecting the surface temperature of the rotary heating roll, wherein a thermosensitive element of the temperature detector is in contact with the surface of the rotary heating roll, The surface temperature of the rotary heating roll is detected by arranging at least 5 mm or more on each side of the element lead wire within 3 mm from the surface of the rotary heating roll so as to control the temperature of the rotary heating roll. A method for controlling the temperature of a fixing device, which is characterized in that