JPH02157881A - Image heat fixing device - Google Patents

Abstract

PURPOSE:To make the temperature of a fixing film high with low energy in a short time and to perform fixing excellent in heat efficiency by specifying the heat capacity of a heating body for the fixing film. CONSTITUTION:The fixing film 25 in a fixing device 11 is heated by the heating body 20 when it passes a fixing nip part N. The heating body 20 is obtained by coating an alumina substrate 21 with an electric resistance material, for example, silver palladium, etc., and the heat capacity of the heating body is set as low one which is <=2.05X10<-3>J/K.mm per unit length(1mm) in the longitudinal direction of the heating body. Therefore, the temperature instantaneously rises by pulse input and the film 25 is heated with the low energy so as to perform the fixing. A waiting time for rising is shortened and power consumption is reduced, then the fixing excellent in heat efficiency is performed by a small-sized heating means.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to an image heating system that is incorporated into image forming apparatuses such as copying machines, laser beam printers, facsimile machines, microfilm reader printers, image display devices, and recording machines. Regarding a fixing device.

More specifically, 7tf,,F-A recording material (electrofax) is produced using a developing material (hereinafter referred to as toner) made of heat-melting resin or the like by an appropriate image forming process means such as photography, electrostatic recording, or magnetic recording. An unfixed visual image (hereinafter referred to as a toner image) corresponding to the desired image information is formed and carried on a sheet, electrostatic recording sheet, transfer material sheet, printing paper, etc., using a direct method or an indirect (transfer) method. The present invention relates to an image forming apparatus that heats and fixes the unfixed toner image as a permanently fixed image on the surface of a recording material carrying the image.

(Prior Art) Conventionally, a heat fixing type image fixing device uses a heating roller maintained at a predetermined temperature and a pressure roller having an elastic layer that presses against the heating roller to fix unfixed toner. A roller fixing method is often used in which a recording material on which an image is formed is heated while being nipped and conveyed.

Belt fusing systems are also known, such as those disclosed in U.S. Pat. No. 3,578,797. This is done by: (1) Bringing the toner image into contact with a heating body web and heating it to its melting point to melt it; (2) After melting, the toner is cooled to a relatively high viscosity; (2) The toner image is heated while reducing its tendency to stick. By peeling it off from the body web, it is fixed without causing any offset.

(Problems to be Solved by the Invention) However, all of the above conventional fixing systems have the following problems.

■It takes a considerable amount of time for the temperature to rise to a predetermined temperature, and during this time the image forming operation is prohibited. That is, there is a so-called wait time.

■A large amount of electric power is required because the heat capacity of the heating roller or belt is required.

To explain in detail, in the case of the heat roller fixing method, the temperature of the heating roller is raised mainly by radiation, so the heating element must be heated to a temperature much higher than the fixing processing temperature, and the heating roller to be heated is Because the heat capacity is large, it takes a long time to reach the fixing processing temperature, and so even if the heat capacity of the heating element is reduced, the time required for startup cannot be reduced much.

Even in the belt fixing method, heat is transferred through the belt, which has a large heat capacity, so the temperature of the heating element is lower than the fixing process temperature.
It is necessary to set the temperature to a sufficiently high temperature.

The present invention solves the above-mentioned problems of the conventional apparatus, and makes it possible to reduce the heat capacity of the heating element without causing fixing failure or offset, thereby reducing standby time, power consumption, and It is an object of the present invention to provide an image heat fixing device that causes a small temperature rise inside the machine and has other remarkable features.

(Means for Solving the Problems) The present invention provides a fixing film, a traveling drive means for the fixing film, a heating body disposed on one side of the fixing film, and a heating body disposed on the other side of the fixing film. A pressure member is disposed opposite to the heating body and brings the image bearing surface of the recording material to which the image is to be fixed into close contact with the heating body through the fixing film, and the fixing film at least performs image fixing. At this time, the traveling fixing film and the introduced recording material are brought into close contact with each other by traveling in the forward direction at the same speed as the recording material to which the image is to be fixed, which is conveyed and introduced between the fixing film and the pressure member. By passing through a fixing nip formed by pressure contact between a heating body and the pressure member, the image-bearing surface of the recording material is heated by the heating body through the fixing film to heat and fix the visible image. The heating body has a unit length (1 mm) in the longitudinal direction.
The image heat fixing device is characterized in that it has a low heat capacity heating element of 2.05xlO-3J/mm or less.

(Function) (1) The recording material to which the image is to be fixed is introduced between the fixing film and the pressure member, which are driven to travel in the same direction at the same speed as the conveyed recording material. (Art materials) When the image-bearing side is in close contact with the fixing film and is overlapped with the fixing film, the mutual pressure contact area (fixing nip area) between the heating body and the pressure member is subjected to squeezing pressure, and the surfaces may be misaligned due to the speed difference. , they overlap and pass together in close contact with each other without wrinkles.

During this process of passing through the fixing nip, the unfixed toner image on the surface of the recording material is heated and softened and melted by the heating body via the fixing film, and in particular, the surface layer exceeds the toner melting point and is completely softened and melted (high temperature melting). do. In this case, the heating body, fixing film, toner image, and recording material are pressed tightly together by the pressure member in the fixing nip and heat is transferred effectively, so that the toner is sufficiently softened and melted by heating for a short time. to obtain good fixing properties. On the other hand, the temperature rise of the recording material itself is actually extremely small and there is little waste of thermal energy. In other words, the recording material itself is not heated substantially, only the toner is effectively heated to soften and melt, and the toner image can be successfully heat-fixed with low power.

Separation of the recording material and fixing film, which are in close contact with each other and heated after passing through the fixing nip, is as follows: The recording material and the fixing film are separated from each other while the temperature of the painting material is higher than the glass transition point of the toner. Alternatively, the recording material is conveyed while remaining in close contact with the fixing film for a while after passing through the fixing nip, and the toner image is cooled and solidified during the cooling process (natural cooling/forced cooling). and the fixing film are separated from each other.

In the case of (2), the toner, which is still at a temperature higher than the glass transition point at the time of separation, has appropriate rubber characteristics, so the toner image surface at the time of separation does not follow the surface of the fixing film and has an appropriate unevenness. Since the toner is cooled and solidified while its surface properties are maintained, excessive image gloss does not occur on the fixed toner image surface. Furthermore, while the heat-fixed toner image is still at a temperature higher than the glass transition point, the bonding force (adhesive force) between the toner image surface and the fixing film surface in close contact with the fixing film surface is below the glass transition point. This is smaller than the bonding force between the surface of the solidified toner image and the surface of the fixing film that has been cooled to a solidified state. Therefore, there is almost no toner offset to the fixing film surface during the mutual separation process between the recording material and the fixing film, and the separation of the recording material and the fixing film at the separation position is also good, resulting in recording on the fixing film surface due to poor separation. There is no longer any risk of jamming caused by the wood getting wrapped around itself.

While the heat-fixed toner image is still at a temperature higher than the glass transition point, the heat-fixed toner image on the recording material separated from the fixing film surface undergoes a glass transition while the separated recording material is transported to the discharge section. It is cooled to below a point (natural cooling or forced cooling means using air blowers, heat radiation fins, etc.) may be used to solidify and output to the discharge section.

In the case of (2) above, the cohesive force of the toner becomes extremely large due to the cooling and solidification of the toner image in the cooling process before being separated, and the toner behaves as a group, and the adhesion and adhesion to the recording material side increases. While increasing, the resistance to the fixing film side is extremely decreasing. For the recording material, when the toner is heated and softened and melted in the fixing nip section, which is the heating process section, it is pressed by a pressure member, so at least a part of the toner image penetrates into the surface layer of the recording material. The anchoring effect caused by the cooling and solidification of the permeation valve increases the adhesion and adhesion of the cooled and solidified toner to the recording material side. Therefore, at the time when the recording material and fixing film are separated, the toner image is cooled and solidified, and the adhesion and adhesion force to the recording material is sufficiently large, but the adhesion and adhesion force to the fixing film is extremely small, so the part of the recording material where the image has been fixed is fixed. easily separated sequentially without toner offset to the film;
It is then output to the discharge section.

In this way, toner images can be heated and fixed without causing toner offset with respect to the fixing film, poor separation or wrapping of the recording material, using a heating element with a small heat capacity, and using a simple configuration for power supply to the heating element. By maintaining a heating element at a temperature sufficiently high compared to the temperature (melting point or softening point) at which the toner should be heated in order to fix it, it is possible to efficiently heat the toner image. Therefore, sufficiently good fixing without defective fixing is possible with less energy, and as a result, it is possible to obtain an image forming apparatus with less standby time during use, less power consumption, and less internal temperature rise.

(2) Also, in the fixing device of the method according to the present invention (SURF fixing method), the total thickness is 100 μm (preferably 4 μm).
When heat-fixing an image through a fixing film (with a diameter of 9μ or less), the fact that the temperature of the heating element provided in the heating element can be within 20°C above the fixing process temperature is actively utilized. By setting the heat capacity per length in the longitudinal direction of the body to 2.0 sx 10'' J/K·mm or less, fixing processing can be performed with low energy and in a short time.

In other words, it is effective to raise the temperature of the heating element by making the heat capacity of the heating element very small, making it possible to achieve a quick start and reduce power consumption.

(Embodiment) FIG. 7 shows a schematic configuration of an example of an image forming apparatus incorporating an image heat fixing device 11 according to the present invention. The image forming apparatus of this example is an electrophotographic copying apparatus of a reciprocating document table type, a rotating drum type, and a transfer type.

(1) Overall schematic structure of the copying machine In FIG. 7, 100 is a device housing, and l is a reciprocating original document holder made of a transparent plate member such as a glass plate disposed on the top plate 100a of the machine housing. It is a mounting stand, and is driven to reciprocate at a predetermined speed on the top plate 100a of the machine casing in the right direction a and the left direction a in the drawing, respectively.

G is a document, which is placed by placing the image side to be copied facing down on the top surface of the document table l according to a predetermined placement standard, and placing the document pressure bonding plate 1a on top of it and pressing it down. .

Reference numeral 100b denotes a slit opening, which serves as a document illumination section, and is opened on the surface of the top plate 1008 of the machine casing, with its length extending in a direction perpendicular to the direction of reciprocating movement of the document table 1 (direction perpendicular to the plane of the paper). The downward image surface of the document G set on the document platform 1 passes through the position of the slit opening 100b sequentially from the right side to the left side during the forward movement of the document platform 1 to the right side a. During the passage, the light from the lamp 7 is received through the slit opening 100b and the transparent original table 1, and the document is illuminated and scanned. The illumination scanning light reflected from the document surface is imaged and exposed on the surface of the photosensitive drum 3 by the short focus and small diameter imaging element array 2.

The photosensitive drum 3 is coated with a photosensitive layer such as a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer, and is driven to rotate clockwise as shown by an arrow around a central support shaft 3a at a predetermined circumferential speed, and is charged during the rotation process. The image-forming exposed original image is formed on the surface of the photosensitive drum 3 by being subjected to a positive or negative charging process by the charger 4, and the image-forming exposure (slit exposure) of the original image on the charged surface thereof. Electrostatic latent images corresponding to the images are sequentially formed.

This electrostatic latent image is sequentially visualized by a developing device 5 using toner made of a resin or the like that softens and melts when heated, and the developed toner image is transferred to a location where a transfer discharger 8 is provided as a transfer section. I will do it.

S is a cassette loaded with transfer material sheets P as recording materials, and the sheets in the cassette are fed one by one by the rotation of the feeding roller 6, and then the toner on the drum 3 is transferred by the registration roller 9. The timing is set so that when the leading edge of the image forming section reaches the position of the transfer discharger 8, the leading edge of the transfer material sheet P also reaches the open position of the transfer discharger 8 and the photosensitive tram 3, so that they are aligned. Feeds synchronously. Then, the toner image on the photosensitive tram 3 side is sequentially transferred onto the surface of the fed sheet by the transfer discharger 8.

The sheet to which the toner image has been transferred in the transfer section is sequentially separated from the three surfaces of the photosensitive drum by a separating means (not shown) and transferred to the conveying device 1.
0, the unfixed toner image carried thereon is guided to a fixing device 11 (described later) to be heated and fixed, and then passed through a guide 35 and an ejection roller 36 as an image-formed product (copy) onto a paper ejection tray 12 outside the machine. is discharged.

On the other hand, after the toner image has been transferred, the photosensitive tram 3 is subjected to removal of adhered contaminants such as residual toner by a cleaning device 13, and is used repeatedly for image formation.

(2) Fixing device 11 FIG. 1 is an enlarged view of the fixing device 11 portion.

Reference numeral 25 designates an endless belt-shaped fixing film, which includes a driving roller 26 on the left side, a driven roller 27 on the right side, and a low heat capacity linear film as a heating element fixedly supported and disposed below between both rollers 26 and 27. Heating body 20, drive roller 26
The four members 26, 27, 20, and 26a are suspended between the four members 26, 27, 20, and 26a, which are parallel to each other, with a guide roller 26a disposed below.

The driven roller 27 is an endless belt-shaped fixing film 2.
The fixing film 25 also serves as a tension roller No. 5, and the fixing film 25 is rotated clockwise at a predetermined circumferential speed as the drive roller 26 rotates clockwise, that is, the unfixed toner image conveyed from the image forming unit 8 side. Wrinkles, meandering,
Rotation is driven without speed delay.

Reference numeral 28 denotes a pressure roller having a rubber elastic layer with good release properties such as silicone rubber, which serves as a pressure member, and holds the downward side film portion of the endless belt-shaped fixing film 25 between them. The lower surface of the transfer material sheet P is brought into opposing pressure contact with the lower surface of the transfer material sheet P with a total pressure of, for example, 4 to 7 kg by a biasing means (not shown), and is rotated in a forward counterclockwise direction in the conveyance direction of the transfer material sheet P.

Endless belt-shaped fixing film 25 that is rotatably driven
Since it is used repeatedly to heat and fix toner images, it should have excellent heat resistance, releasability, and durability, and be thinner, with a thickness of 100 μm or less, preferably 50 μm or less. For example, polyimide, polyetherimide, PES-PF
A A (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin) or other heat-resistant resin single-layer film or composite layer film, such as a 20 μm thick film, with PTFE (tetrafluoroethylene resin) on at least the image contact side. - A releasable coating layer made of a fluororesin such as PAF with a conductive material added to a thickness of 10 μm.

The low heat capacity linear heating body 20 as a heating body in this example has rigidity, high heat resistance, and heat insulation properties and is horizontally long with the length extending in the transverse direction of the fixing film (direction perpendicular to the running direction of the fixing film 25). It comprises a support body 24 and a substrate 21 equipped with a heating element 22, a temperature measuring element 23, etc., which are integrally attached and held on the lower surface side of the support body along the longitudinal length of the lower surface.

The support body 24 ensures the overall strength of the heating body 20, and is made of, for example, pps (polyphenylene sulfide), P
AI (polyamideimide), PI (polyimide), PE
Highly heat-resistant resins such as EK (polyetheretherketone) and liquid crystal polymers, and the combination of these resins with ceramics, metals, and
It can be constructed from a composite material such as glass.

The substrate 21 is an alumina substrate, for example, and the heating element 22
As an example, an electrically resistive material such as silver palladium is placed along the longitudinal direction approximately in the center of the lower surface of the substrate 21 with a width of 1.0 mm.
It is a linear or strip-shaped current-carrying heating element with a low heat capacity that is coated (screen printing, etc.) on the substrate 21. It is a low heat capacity temperature measuring resistor such as a PT film, which is coated (by screen printing, etc.) along the longitudinal direction of the substantially central part of the surface.

In this example, the linear or strip-shaped heating element 22 is energized from both longitudinal ends thereof. The back surface temperature of the substrate 21 is detected by the thermometer 23, and the energy necessary to maintain the heating element at the fixing temperature is applied by changing the energization pulse width.

Further, in this example, a sheet leading edge/trailing edge detection sensor (
(not shown), and depending on the sheet detection signal of the sensor, the current supply period to the heating element 22 is determined by the sheet P.
1 is controlled only during the necessary period.

The fixing film 25 is limited to the shape of an endless belt.
As shown in the figure, the fixing film 25 with an end wound around the feed-out shaft 30 is passed between the heating body 20 and the pressure roller 28 and under the guide roller 26a to the wind-up shaft 30.
from the feed-out shaft 30 side to the winding shaft 311.
7P7 may be configured to run at the same speed as the conveyance speed of the transfer material sheet P.

(3) Fixing execution operation The image forming start signal causes the device to perform an image forming operation, and the leading edge of the transfer material sheet P carrying the unfixed toner image Ta on its upper surface is conveyed from the transfer section 8 to the fixing device 11. When detected by the above-mentioned sensor (not shown) disposed near the fixing film 25, rotation or running of the fixing film 25 is started, and the transfer material sheet P is guided by the guide 29 and heated by the heating body 2.
The fixing sheet 25 and the pressure roller 28 easily enter the pressure contact part N (fixing nip part) between the fixing sheet 25 and the pressure roller 28, and the unfixed toner image surface is conveyed at the same speed and in the same direction as the conveyance speed of the sheet P. The fixing film 25 is brought into close contact with the lower surface of the fixing film 25 in a surface-shifting state, and a squeezing force is applied to the fixing nip N between the heating body 20 and the pressure roller 2B while the fixing film 24 overlaps with the fixing film 24 without causing surface displacement or wrinkles. I will pass while receiving it.

W is the width dimension of the heating element 22 provided on the lower surface of the heating element, and the heating element 22 is in the area where the lower surface of the heating element 20 and the upper surface of the pressure roller 28 are in mutual pressure contact, that is, in the fixing nip N. Exists within the area.

The toner image bearing surface of the sheet P passes through the fixing nip N while being in close contact with the fixing film surface.
2 through the fixing film 24, the toner image is melted at a high temperature and is softened and adhered to the sheet 2 surface Tb.

In the case of this example device, the sheet P which is the recording material and the fixing film 2
Separation from the sheet 4 is performed when the sheet P passes through the fixing nip N and comes out.

At this time of separation, the temperature of the toner Tb is still higher than the glass transition point of the toner, and therefore, the bonding force (adhesive force) between the sheet P and the fixing film 25 at this time of separation is small, so that the sheet P is attached to the fixing film 25. Toner offset to the 25th surface hardly occurs, and the sheet P is always smoothly separated without being stuck to the 25th surface of the fixing film and jammed due to poor separation.

Since the toner Tb at a temperature higher than the glass transition point has appropriate rubber characteristics, the toner image surface upon separation does not follow the fixing film surface but has an appropriate uneven surface. Since the toner is maintained and cooled to solidify, the fixed toner image surface does not have appropriate image gloss, resulting in high quality images.

While the sheet P separated from the fixing film 25 is guided by a guide 35 and reaches a pair of paper ejection rollers 36, the temperature of the toner Tb, which is higher than the glass transition point, naturally falls 1 (natural cooling) to a temperature lower than the glass transition point. The temperature reaches solidification Tc,
The sheet P on which the image has been fixed is output onto the tray 12.

In this embodiment, the linear heating element 22 of the heating element 20 is heated instantaneously to a high enough temperature relative to the melting point (or fixing temperature) of the toner when energized, so there is no need to preheat the heating element. , heat transfer to the pressure roller 28 during non-fixing is small. Furthermore, even during fixing, the fixing film, toner image, and sheet are interposed in the fixing nip N between the heating body 20 and the pressure roller 28, and a rapid temperature gradient occurs due to the short heat generation time. The temperature of the pressure roller 28 does not easily rise, and its temperature is maintained below the melting point of the toner even when continuous image formation is performed to the extent required for practical use. In the apparatus of this embodiment having such a configuration, the toner image made of heated hostile toner on the sheet P is first transferred to the fixing film 2.
5 and is heated and melted by the heating body 20, and in particular, the surface layer portion thereof is completely softened and melted. At this time, pressure roller 2
8, the heating body, fixing film, toner image, and sheet are brought into close contact with each other, and heat is efficiently transferred. Thereby, the heating of the sheet P itself can be suppressed as much as possible, and the toner image can be efficiently heated and melted. In particular, by limiting the time for energization and heat generation, it is possible to save energy.

A small heating element is sufficient, so the heat capacity is small, and there is no need to heat up the heating element in advance, so power consumption during non-image formation can be reduced, and temperature rise inside the machine can also be prevented. Become.

FIGS. 3(a) and 3(b) show a plan view and an enlarged sectional view of the heating body 20 of this embodiment on the sliding surface side of the fixing film.

The heating element has a thickness of 0.64 mm, a width of 5.0 mm, and a length of 25 mm.
A heating resistor made of silver palladium is formed as a heating element 22 on a 0 mm thick alumina substrate 21 with a width of 3 mm and a thickness of 20 μm by screen printing, and a protective layer 21a made of heat-resistant glass with a thickness of 10 μm is further formed on the substrate 21. There is a temperature sensing element (temperature sensing element) such as a thermistor on the spinal side of the
In this way, the heating element 22, the protective layer 21a, and the inspection
The substrate 2 on which the fA element 23 is provided is fixedly supported on a rigid support 24 via a heat insulating plate 24a made of PI or the like. Reference numerals 22a and 22a are power feeding electrode portions at both ends of the heating element 22.

Alumina, which is the heating element substrate 21, has a thermal conductivity of 25 J/1s.
-5. Since it has excellent thermal conductivity, the temperature of the heating element can be detected with good response by the thermistor 23, and the energizing energy can be controlled accordingly.
2 can be maintained at a fixable temperature. When, for example, a heat fixing toner manufactured by Canon Co., Ltd. was used as the developing material, the temperature of the heating element was maintained at an average of around 180° C. by applying an average current of 150 W during the fixing process, and the toner image could be successfully heat fixed.

Here, the heating element 22 of this embodiment has a unit length in the longitudinal direction (1 m
Heat capacity per m) is 0.18x 1O-3J/1mm
(3mm x 0.02m1x 1ma+ x 3.O
x, 1O-3J/mm3.
The time from the start of image formation to the start of preheating until the transfer material sheet P enters the fixing device 11 is 5 seconds, and sufficient fixation can be achieved. That is, this embodiment allows a fixing device that uses low power and does not require standby time.

In the conventional heat roller type fixing device, the standby time becomes long even if the heating element has a low heat capacity for the following reasons. That is, (1) there is an air layer between the heating element and the heating roller, and in order to raise the temperature of the heating roller mainly by radiant heat, the temperature of the heating element must be raised to a temperature much higher than the toner melting point.

■It takes time to heat up the heating roller because it has a large heat capacity.

On the other hand, in this embodiment, there is no air between the heating element and the toner.
Since the structure is such that heat is transmitted only through the protective layer 21a of 0 μm and the fixing film 25 of 40 μm, a) the heating element temperature may be close to the toner melting point.

b) The only portion that needs to be heated is the pressure contact portion between the protective layer 21a and the fixing film 25, which has a very small heat capacity.

Because of the characteristics a) and b), it is effective to raise the temperature of the heating element by making the heat capacity of the heating element very small as in this example, and it is possible to quickly start and reduce power consumption. It will become.

(4) Other embodiments In the embodiments described above, the heating element 2 is provided on the surface of the substrate 21.
In order to accurately detect the temperature of the substrate 2 with the thermometer 23 provided on the back side of the substrate 21, the substrate 21 is an alumina substrate with excellent thermal conductivity.
A part of the heat generated by the heating element 22 escapes through the
Therefore, it is conceivable that the effect of the low heat capacity heating element 22 is reduced to some extent.

FIGS. 4(a) and 4(b) show that a substrate (alumina substrate) is used to prevent part of the heat generated by the heating element 22 from escaping through the substrate 21 and to increase the rate of temperature rise of the heating element 22. ) A plan view of the fixing film moving surface side of the heating element 20 having a configuration in which the heating element (current heating resistance layer) 22 is provided on the 21 side via a 500 μm thick heat insulating layer 21b made of glass, and an enlarged cross section. The figure shows. Reference numerals 22d and 22d designate gold electrodes for power supply that are provided on the surface of the heating element 22 in parallel along its length with an interval W between them.

The thicker the heat insulating layer 21b is, and the more a material with poor thermal conductivity is used, the lower the power consumption and the faster the heating rate, but the accuracy with which the temperature detection element 23 detects the temperature of the heating element deteriorates. Therefore, the thickness, material, etc. should be determined depending on the characteristics of the toner used (for example, the temperature that causes high-temperature offset and the temperature range that causes low-temperature offset).

For example, the thermostatic toner manufactured by Canon Co., Ltd. has a wide temperature range, so it is
Even when the substrate 21 made only of glass with a thickness of mm was used, the fixing process could be performed without any problem, and in this case, the fixing state was achieved within about 3 seconds with an applied power of 200 W or less.

Further, as in the heating body 20 shown in FIGS. 6(a) and 6(b), a heat insulating body made of PI resin (polyimide) is used as the substrate 21, and a heating element 22 with a diameter of 0.1 mm is placed on the surface of the heat insulating body substrate 21. The heat capacity per unit length in the longitudinal direction of the heating element is also 8.
2 x 10-'J/ + nm (0,1 mm x O,
1mm x 2 x 4.1 x 1O-3J/Kn)
With 't', low electrode and quick start possible.

The temperature measuring element 23 is embedded within the thickness of the substrate 21. 22
Reference character e denotes a spring-shaped conductor, which is configured to absorb expansion and contraction of the nichrome wire 22 due to temperature changes. Further, the end portion of the nichrome wire 22 that does not act on fixing is thick and has low resistance, so that the amount of heat generated is small.

According to experiments, the heat capacity per unit longitudinal length of a resistance wire with a diameter of 0.5 mm is approximately 2. OX 10-'J/Km
m (0.5mX O,5mX 2 pieces x 4.l
Even with a heating element of X 10-3 J/+am'), fixing was possible in about 7 seconds when 300 W was applied, and a quick-start fixing device was possible.

(5) Others (a) About the heating element 20 In addition to alumina, the substrate 21 can be made of heat-resistant glass or heat-resistant resin such as PI-PPS.The heating element 22 can be made of nichrome/RuO2 in addition to Ta2N. - A resistor such as Ag/Pd can be used. As the temperature measuring element 23, in addition to a temperature measuring resistor such as a PT film, a bead thermistor with a low heat capacity or the like can be used.

It is preferable to provide a sliding protective film layer such as a thin heat-resistant glass layer on the lower surface of the heating element on which the fixing film 25 slides. The heating element 22 was arranged on the upper surface side of the substrate 21 (on the side opposite to the side of the substrate 21 facing the fixing film), and the temperature measuring element 23 was arranged on the lower surface side of the substrate 21 (on the side of the substrate 21 facing the fixing film). Alternatively, both the heating element 22 and the temperature measuring element 23 may be arranged on the lower surface side of the substrate 21. heating element 2
2 may also be controlled by normal energization control instead of pulse energization.

(b) When using a fixing film 25 with an end as in the device shown in FIG. It is also possible to use a method of exchanging it with the winder (winding exchange type).

In the case of such a rewinding type, it is possible to reduce the thickness of the fixing film regardless of its durability, and it is possible to reduce the power consumption. For example, the fixing film may be made of an inexpensive base material such as a PET (polyester) film, and may be heat-resistant treated and thin, for example, about 12.5 μm or less.

Alternatively, as mentioned above, toner offset to the fixing film surface does not substantially occur, so if the thermal deformation and deterioration caused by use of the fixing film are small, the used sheet that has been wound up on the winding shaft side can be moved in a timely manner. It is also possible to use it multiple times by controlling the rewind to the delivery shaft side, or by reversing and exchanging the take-up shaft side and the delivery shaft side (@return and rewind usage type).

For example, in the rewinding and reusable type, the fixing film is
A composite layer film can be used in which a 25 μm thick polyimide resin film is used as a base material with excellent heat resistance and mechanical strength, and a release layer made of a fluororesin or the like with high mold release properties is provided on the surface. During rewinding and reverse running, it is preferable to automatically control the pressure release mechanism to maintain the release state after the heating body and the pressure roller come into contact with each other.

If the film is to be used multiple times, such as a rewinding type or an endless belt type, a felt pad is provided for cleaning the film surface, and the pad is impregnated with a slight release agent such as silicone or oil, and the pad is applied to the film surface. The film surface may be cleaned and the releasability may be further improved by bringing the film into contact with the film surface. When the fixing film is treated with an insulating fluororesin, static electricity that disturbs the toner image is likely to be generated on the film, so it is a good idea to eliminate the static electricity using a grounded static elimination brush. The film may be charged within a range that does not disturb the toner image by applying a bias voltage to the brush without being grounded. Furthermore, one measure is to add conductive powder fibers, such as carbon black, to the fluororesin to prevent the above-mentioned image disturbance caused by static electricity. Furthermore, the charge removal and conductivity of the pressure roller can be carried out by the same means. Furthermore, an antistatic agent or the like may be applied or added.

Regardless of whether the fixing film is of an endless belt type, a winding and replacing type, or a rewinding and reusing type, it is possible to facilitate the replacement of the fixing film by configuring a cartridge that can be attached to and removed from a predetermined part of the fixing device 11. can.

As described above, the fixing device of the present invention is not limited to the transfer type electrophotographic device illustrated in FIG. Copying machines, laser beam printers, facsimile machines, microfilm reader printers, etc. that form an image using heat-fusible toner on a recording material using a magnetic recording image forming method or other appropriate image forming process or means, and then heat and fix the image. It can be effectively applied as an image heat fixing device in various image forming apparatuses such as display devices and recording machines.

(Effects of the Invention) As described above, the image heat fixing device of the present invention heats images thermally efficiently using a small and simple heating means with a small heat capacity, and can solve problems such as defective fixing, offset, and recording material jamming with less energy. It has features such as low standby time and power consumption when using the device, and low temperature rise inside the machine, which enables sufficiently good image fixation without causing problems such as those of conventional devices. It is practical as an image heat fixing device that does not have a conventional image heating system, and the intended purpose can be achieved well.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the fixing device of the first embodiment, FIG. 782 is a schematic diagram of other component devices, and FIGS. 3(a) (b)
4 is a plan view and an enlarged cross-sectional view of the fixing sliding surface side of the heating body.
Figures (a) and (b) and Figures 5 (a) and 5 (b) are the same views of heating bodies with other configurations, respectively, and Figures 6 (a) and (b) are side views of heating bodies with still other configurations. FIG. 5, an enlarged cross-sectional view, and FIG. 7 are schematic configuration diagrams of an example of an image forming apparatus incorporating a fixing device according to the present invention. 11 is the overall code of the fixing device, 20 is the heating body, 25 is the fixing film, 28 is the pressure roller, P is the sheet, Ta is the unfixed toner, Tb is the heat-softened/melted toner, Tc is the solidified toner, N is the fixing nip part .

Claims (1)

[Claims] (1) A fixing film, a traveling drive means for the fixing film, a heating body fixedly supported on one side of the fixing film with the fixing film inside, and a heating body disposed on the other side facing the heating body. The pressure member is disposed and brings the visible image bearing surface of the recording material on which the image is to be fixed into close contact with the heating body through the fixing film, and the fixing film is pressed against the fixing film at least when image fixing is performed. The heating body and the pressure member are caused to travel at the same speed in the forward direction of the recording material to be image-fixed, which is conveyed and introduced between the pressure member and the traveling fixing film and the introduced recording material are brought into close contact with each other. The image bearing surface of the recording material is heated by the heating body through the fixing film by passing through a fixing nip formed by pressure contact of the recording material, and the heating body heats and fixes the visible image. Unit length in direction (
An image heat fixing device characterized in that it has a low heat capacity heating element of 2.05×10^-^3 J/K·mm or less per 1 mm).