JPH06202507A - Heating device - Google Patents

Abstract

PURPOSE:To prevent the reliability or the life of a device caused by migration from being lowered by stopping a voltage impressed on a temperature detection element when a material to be heated is not introduced to the device. CONSTITUTION:When the tip of a recording material 12 carrying an unfixed powder toner image 11 on the upper surface is detected by a sensor 50 arranged toward the side of a fixing device, the turning of a fixing film 7 is started and the voltage is impressed on a thermistor 4 by a computer. Next, power is supplied to a heater 1 by the computer. Then, when the rear end of the recording material is detected by the sensor 50, the power is stopped being supplied to the heater 1 and the voltage is stopped being impressed on the thermistor 4 after the lapse of previously fixed timer time which is until the trailing edge of the recording material is finished being passed through a fixing nip part N after it is continuously carried from that time by a microcomputer. Next, the turning of the film 7 is stopped and the device is kept to be in a standby state until the leading edge of the next recording material is detected by the sensor 50.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film heating type heating device for applying heat from a heating element to a material to be heated through a film to heat the material to be heated.

[0002]

2. Description of the Related Art A heating device of the film heating type as described above is disclosed in JP-A-63-313182 and JP-A-1-2.
It is known in Japanese Laid-Open Patent Publication No. 63679 / Japanese Patent Laid-Open No. 2-157878 / Japanese Laid-Open Patent Publication No. 4-44075-44083.

This device is an electrophotographic copying machine, printer,
An image heating and fixing device in an image forming apparatus such as a fax, that is, a recording material (electrofax sheet, electrofax sheet, etc.) using a toner made of a heat-meltable resin by an appropriate image forming process means such as electrophotography, electrostatic recording and magnetic recording.
A recording material carrying an unfixed toner image corresponding to the target image information formed on the surface of an electrostatic recording sheet, a transfer material sheet, a printing paper, etc. by a direct method or an indirect (transfer) method. It can be used as a device for heat fixing processing as a permanently fixed image on the surface.

Further, it can be widely used as means / apparatus for heat-treating an image carrier, for example, an apparatus for heating a recording material carrying an image to improve surface properties (gloss, etc.), an apparatus for post-treatment.

Such a film heating type heating device, for example, in the case of an image heating and fixing device, is compared with other known image heating and fixing devices such as a heat roller system, a hot plate system and a heat chamber system. Since it is possible to use a low-heat-capacity heating element or a thin film that quickly heats up, it is possible to save power and shorten the wait time (quick start property). In addition, it has an advantage that various drawbacks of other conventional heating devices can be eliminated, and is effective.

[0006] A heating element (hereinafter referred to as a heater) generally has a basic structure of a good heat conductive substrate (ceramic substrate) and a resistance heating element layer provided on the substrate and generating heat by energization. It has a small heat capacity (thermal heater) and controls the energization to the resistance heating element layer so that the output of the temperature detection element that detects the temperature of the substrate is constant, and the temperature of the heater is raised to a predetermined constant temperature. The temperature is adjusted.

[0007]

The fact that the heater has a small heat capacity and a rapid temperature rise and fall leads to the features of this type of film heating type heating device such as power saving and quick start. On the other hand, if the response time of the temperature detecting element is long with respect to the rate of temperature rise and fall of the heater, the control temperature ripple of the heater becomes large.

If the contact state of the temperature detecting element with the substrate is poor, normal temperature control will not be performed, but the temperature of the heater will rise excessively. Further, a fixing device using such a heater tends to cause uneven fixing and uneven gloss.

Therefore, in order to solve such a problem,
It has been proposed that a resistance heating element layer and an electrode for taking out the output of the temperature detecting element are provided on the substrate of the heater, and the temperature detecting element is bonded to accelerate the response of the temperature detecting element (Japanese Patent Application No. 4-303937). .

However, as a new problem in this proposed structure, in this heater, the electrode for taking out the output of the temperature detecting element is usually made of Ag (silver),
This may cause a phenomenon called migration, which is ionized by moisture in the air in a high humidity environment and moved by an electric field between the electrodes to cause a short circuit between the electrodes.

It is an object of the present invention to prevent the deterioration of the reliability and life of the device due to the migration as described above.

[0012]

According to the present invention, there is provided a good heat conductive substrate and a resistance heating element layer provided on the board, wherein the resistance heating element has a constant detection output. In a heating device that heats a material to be heated through a film by heat from a heating body whose temperature is controlled by energizing a layer, applying a voltage to the temperature detecting element does not introduce the material to be heated into the device. It is a heating device, which is characterized by stopping at times.

[0013]

[Function] By stopping the voltage application to the temperature detecting element when the material to be heated is not introduced into the device, migration does not occur during that time, so the migration is delayed and the reliability and device life of the device are reduced. Can be prevented.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic configuration diagram of an example of an image heating and fixing device A as a film heating type heating device according to the present invention. The fixing device A is disposed in an image forming apparatus such as an electrophotographic copying machine, which is not shown in the drawing, and includes a transfer material having an unfixed toner image 11 formed and carried by an image forming section of an appropriate image forming process mechanism. The recording material 12 is heated to fix the image.

Reference numeral 7 denotes an endless belt-shaped fixing film, which has a driving roller 8 on the left side and a driven roller 9 on the right side.
And a low-heat-capacity linear heater 1, which is a heating body fixedly supported and disposed below the rollers 8 and 9, and is stretched between the three members 8 and 9 parallel to each other. There is.

The driven roller 9 also serves as a tension roller for the endless belt-shaped fixing film 7.
The fixing film 7 is rotationally driven in the clockwise direction at a predetermined peripheral speed without wrinkling, meandering, or speed delay as the driving roller 8 is rotationally driven in the clockwise direction.

Reference numeral 10 denotes a pressure roller as a pressure member having a rubber elastic layer having a good releasability such as silicon rubber, and the lower film portion of the endless belt-shaped fixing film 7 is connected to the heating body 1. It is sandwiched between and is pressed against the lower surface of the heater 1 by a biasing means with a contact pressure of, for example, a total pressure of 4 to 7 kg, and rotates in the forward counterclockwise direction in the transport direction of the recording material 12.

Since the endless belt-shaped fixing film 7 which is rotationally driven is repeatedly subjected to heat fixing of the toner image, it is excellent in heat resistance, releasability and durability, and is generally 1
A thin film having a thickness of 00 μm or less, preferably 40 μm or less is used. For example, a single layer film of a heat-resistant resin such as polyimide, (PI), polyetherimide (PEI), PES, PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin), or a composite layer film, for example, a 20 μm thick film. Of at least the image contacting surface side, a release coating layer having a thickness of 10 μm formed by adding a conductive material to a fluororesin such as PTFE (tetrafluoroethylene resin) / PAF.

The heater 1 as a heating element is a cross-sectional view of FIG. 1, a plan view with a partly omitted / partially cutaway view of FIG. 2, a perspective view of a temperature sensing element portion of FIGS. 3 and 4, and an enlarged cross-sectional model. As shown in the figure, it is a low-heat-capacity linear heater having a longitudinal direction in a direction intersecting the film moving direction, a substrate 2 having good thermal conductivity, a resistance heating element layer 3, a thermistor 4 which is a temperature detecting element, and a surface protective layer. It consists of 5 mag.

The substrate 2 is a ceramic material having heat resistance, electrical insulation, low heat capacity, and high heat conductivity, such as alumina or AlN. As an example, the thickness is 1.0 mm, the width is 10 mm, and the length is 2.
It is a 40 mm alumina substrate.

The resistance heating element layer 3 has one surface (front surface side) of the substrate 2 as a film sliding side surface and Ta ₂ N, silver palladium, ruthenium oxide, etc. along the longitudinal direction at substantially the center of the surface. Is a linear or band-shaped layer having a low heat capacity, which is provided by coating (screen printing or the like) the electric resistance material of 1. to a width of 1.0 mm.

Since the substrate surface of the heater 1 on the side provided with the resistance heating layer 3 is a sliding surface with the film 7,
The surface of the substrate including the resistance heating element layer 3 is preferably surface-protected by forming a sliding protection layer 5 of Ta ₂ O ₅ or the like.

The thermistor 4 as a temperature detecting element,
It is arranged as follows on the surface (rear surface) opposite to the surface of the substrate on which the resistance heating layer 3 is provided.

That is, as shown in FIG. 3, a pair of electrodes 4a, 4a made of Ag are provided on the back side of the substrate, and the electrodes 4a, 4
The thermistor 4 is adhered between a by a conductive adhesive 4b. The conductive adhesive is a resin such as epoxy, silicon, or polyimide in which Ag particles are dispersed.

Then, the heater 1 is provided on one side surface of the horizontally long heat insulating heater holder 6 along the longitudinal direction of the heater accommodating groove 6a, and the surface on the side where the energization resistance heating layer 3 is provided. Is fitted outside and fixedly held by a holder 6 with an adhesive 18, and the holder 6 is fixedly supported by an adhesive 19 on the lower surface of a support 20 as a stationary member of the fixing device with the heater 1 facing downward. .

The heater holder 6 is made of, for example, PPS (polyphenylene sulfide), PAI (polyamide imide), PI (polyimide), PEEK (polyether ether ketone), high heat resistant resin such as liquid crystal polymer, these resins and ceramics, metal, It can be composed of a composite material such as glass.

FIG. 5 is a block circuit diagram of an energization control system for the energization resistance heating element layer 3 of the heater 1. When the voltage of the AC power supply 53 is applied between the electrodes 3a, 3a at both ends of the energization resistance heating element layer 3, heat is generated and the entire heater 1 including the substrate 2 is rapidly heated. This heater 1
The substrate temperature is detected as the heater temperature by the thermistor 4, and the microcomputer (CPU) 51 uses the detected information so that the detection output of the thermistor 4 becomes constant, that is, the heater 1 has a predetermined temperature ( (Fixing temperature)
Thus, the relay 52 is controlled to control the energization of the resistance heating element layer 3. 54.55.56 is the thermistor 4
A DC5V power source, a relay, and a circuit adjustment resistor for the energizing system. The relay 55 is controlled by the computer 51.

In this embodiment, a sheet leading edge / rear edge detection sensor 50 is provided on the upstream side of the fixing device A in the recording material conveying direction, and the energization resistance of the heater 1 is detected by the recording material detection signal of the sensor 50. The energization period for the heating element layer 3 is controlled only during the required period in which the recording material 12 as the material to be heated is passing through the fixing device A. That is, the heater 1 is not energized when the paper is not passed.

FIG. 6 is a control flow. An image forming mechanism (not shown) performs an image forming operation in response to an image forming start signal, and the leading end of the recording material 12 carrying the unfixed powder toner image 11 on the upper surface is conveyed toward the fixing device A toward the fixing device. When detected by the arranged sensor 50 (step 1), the computer 51 starts the rotation of the fixing film 7 and turns on the voltage application to the thermistor 4 (step 2).

Next, the computer 51 turns on the power to the heater 1 (step 3). By this energization, the heater 1 rapidly rises in temperature and reaches a predetermined fixing temperature, and the temperature is controlled by the thermistor 4 to detect the temperature. That is, the temperature of the heater 1 is adjusted by turning off the power to the heater when the temperature of the heater is higher than the target temperature and turning it on when the temperature of the heater is lower than the target temperature.

On the other hand, the recording material 12 is guided by the guide 16 (FIG. 1) to press the contact portion N between the heater 1 and the pressure roller 10.
(Fixing nip portion) fixing film 7 and pressure roller 10
Between the heater 1 and the unfixed toner image surface in close contact with the lower surface of the fixing film 7 in the surface moving state without causing surface deviation or wrinkling, and the heater 1 in the overlapping state with the moving fixing film 7. The fixing nip portion N between the pressure roller 10 and the pressure roller 10 is passed while receiving a clamping pressure.

The toner image bearing surface of the recording material 12 receives the heat of the heater 1 through the fixing film 7 as it passes through the fixing nip portion N in a state of pressing contact with the fixing film surface.
The toner image 11 is melted at a high temperature and softened and adhered to the surface of the sheet 12.

In the case of the apparatus of this embodiment, the recording material 12 and the fixing film 7 are separated from each other when the recording material 2 passes through the fixing nip portion N and comes out. The temperature of the toner at this separation point is higher than the glass transition point (ring and ball type).

The sheet 12 separated from the fixing film 7 is guided by the guide 17 and the temperature of the toner, which is higher than the glass transition point, is naturally lowered (natural cooling) while reaching the discharge roller.
Then, the temperature becomes lower than the glass transition point and the solidification is reached.

When the rear end of the recording material 12 is detected by the sensor 50, the microcomputer 51 continues to convey the recording material from that point in consideration of the conveying speed of the recording material and the rear end of the recording material is fixed. After passing a predetermined timer time until the passage through the nip portion N (step 4), energization of the heater 1 is stopped (step 5), and then voltage application to the thermistor 4 is turned off (step 6). ). Then, the rotation of the fixing film 7 is stopped, and the apparatus is kept in a standby state until the sensor 50 detects the leading edge of the next recording material.

The recording material 12 that has passed through the fixing device A is discharged outside the device as an image-formed product (copy, print) on which the image has been fixed.

With this device, a voltage (DC
If the voltage of 5 V) is continuously applied, the electrodes 4a and 4a are short-circuited due to migration in an environment of about 25 ° C. and 60% RH in about 50,000 hours. If the user does not turn off the power of the apparatus after fixing 10 pages of A4 size per day, the apparatus will fail due to migration at about 20,000 pages.

By the way, the time required for fixing 10 pages in A4 size is about 10 minutes even if 1 page is 1 minute. That is, in a time other than 10 minutes for fixing,
If a voltage is not applied to the thermistor 4, migration does not occur during that time, so that the life of the device can be extended. In other words, if the thermistor 4 is energized for 10 minutes a day, migration will not occur until 300,000 hours, and about 3 million pages can be fixed.

7 and 8 show a film heating type fixing device of a type different from the device shown in FIG.
Of course, the present invention can be effectively applied to such a type of device.

That is, in the case of the apparatus of FIG. 1 described above, a strong tension acts on the endless belt-shaped fixing film 7 around the entire circumference during driving, but in the case of the apparatus of FIG. 7 (Japanese Patent Laid-Open No. 4-4).
No. 4075-44083), tension acts only on the fixing nip portion N and the film portion in the contact portion area between the outer surface of the film inner surface guide member 13 and the film upstream of the fixing nip portion N in the film rotation direction. , Tension does not act on most of the remaining film (tension-free type device).

In such a tension-free type device, the force for moving the film 7 in the longitudinal direction of the heater 1 when the film is driven (film shift force) is smaller than that in the device shown in FIG. The means or the film deviation control means can be simplified. For example, the film shift control means can be a simple member such as a flange member that receives the film end portion, and the film shift control means can be omitted to reduce the cost and size of the apparatus.

The film 7 is not limited to the endless belt shape, and the endless fixing film 7 wound around the delivery shaft 14 as shown in FIG.
Alternatively, the winding shaft 15 may be engaged with the winding shaft 15 and the winding shaft 15 may be engaged with the winding shaft 15 so that the recording material 12 travels at the same speed as the conveying speed of the recording material 12.

[0043]

As described above, in the film heating type heating apparatus of the present invention, the voltage application to the temperature detecting element is stopped when the material to be heated is not introduced into the apparatus, so that migration occurs during that period. Since it does not exist, it is possible to delay the occurrence of migration and prevent the reliability of the device and the life of the device from decreasing.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a film heating type heating device (image heating and fixing device) according to an embodiment.

[Figure 2] Plan view of the heating element (heater) with the middle part omitted and partially cut away

FIG. 3 is a perspective view of a temperature detecting element portion.

FIG. 4 is an enlarged cross-sectional model view of the temperature sensing element portion.

FIG. 5 is a block circuit diagram of an energization control system for the heater.

[Fig. 6] Control flow diagram

FIG. 7 is a schematic configuration diagram of another type of device.

FIG. 8 is a schematic configuration diagram of still another type of device.

[Explanation of symbols]

 1 General Reference Code of Heater (Heater) 2 Heater Substrate 3 Electric Resistance Heater Layer 4 Temperature Detection Element (Thermistor) 5 Surface Protection Layer 6 Heater Holder 7 Fixing Film 8 Drive Roller 9 Driven Roller (Tension Roller) 10 Pressure Roller N Fixing nip portion 12 Recording material as heated material 11 Unfixed toner image 50 Leading and trailing edge detection sensor of recording material

Claims (1)

[Claims] 1. A good heat conductive substrate and a resistance heating element layer provided on the substrate, wherein energization to the resistance heating element layer is controlled so that the detection output of the temperature detecting element becomes constant. In a heating device for heating a material to be heated through a film by heat from a heating body to be temperature-controlled, heating characterized by stopping voltage application to the temperature detection element when the material to be heated is not introduced into the device. apparatus.