JPH02158782A - Image forming device - Google Patents

Abstract

PURPOSE:To reduce the heat capacity of a heating body without causing a defective fixing operation and an offset by manipulating a plane on a side on which the unfixed toner image of a recording material is carried in such a way that it is made to adhere to a specific heating body through a fixing film, pressurized, scanned and driven identically with recording material conveyance in speed and a direction. CONSTITUTION:The fixing film 23 and a pressurizing member 22 are in a scanning and driving condition which is identical with a conveying direction for the recording material P in the speed and the direction. The recording material P which is led between the fixing film 23 and a pressurizing member 22 and performs image fixing is provided with pressure on the mutual press-contacting part N of the heating body 21 and the pressurizing member 22 in an overwrapped condition with the fixing film 23 in such a manner that a plane on a side on which the unfixed toner image Ta is carried adheres to the plane of the fixing film 23. Then the recording material P is pressurized, made to adhere to the heating body and efficiently heat-transferred. Regarding the heating body 21, a temperature self-control type linear heating body 21 in which a linear heating body 48 with specific heating width and a PTC heating body 49 are integrally formed is used. Thus the heat capacity of the heating body 21 can be reduced without causing a defective fixing operation and an offset.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image forming apparatus such as a copying machine, a laser beam printer, a facsimile machine, a microfilm league printer, an image display device, and a recording machine.

More specifically, recording materials (electrofax sheets, electrostatic recording sheets, transfer material sheets, An unfixed toner image corresponding to the target image information is formed and carried on the surface of a recording material (such as printing paper) by a direct method or an indirect (transfer) method, and the unfixed toner image is transferred to the surface of the recording material carrying the image. The present invention relates to an image forming apparatus that performs heat-fixing processing to form a permanently fixed image.

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

However, in this type of device, in order to prevent the so-called offset phenomenon in which toner is transferred to the heating roller,
It is necessary to maintain the heating roller at an optimum temperature, and the heat capacity of the heating roller or heating body must be increased. That is, when the heat capacity of the heating roller is small, the temperature of the heating roller tends to fluctuate greatly toward a lower temperature side or a higher temperature side due to paper passing or other external factors due to the relationship with the amount of heat supplied by the heating element. If the temperature changes to the low temperature side,
Insufficient softening and melting of the toner causes poor fixing and low-temperature offset, and when the temperature changes to the high temperature side, the toner is completely melted and the cohesive force of the toner decreases, resulting in high-temperature offset.

In order to avoid this problem, increasing the heat capacity of the heating roller increases the time it takes to heat the heating roller to a predetermined temperature, causing another problem of increasing standby time when using the device. .

As a measure to solve this problem, US Patent No. 3,578
, No. 797, (1) bringing the toner image into contact with a heating body web and heating it to its melting point to melt it, (2) cooling the toner after melting to give it a relatively high viscosity, and (2) making the toner image relatively high in viscosity. A method is known in which fixation is achieved without causing offset by going through the process of peeling off the heating element web in a state where the tendency to adhere is weakened.

In addition, the above-mentioned known method heats the toner image and recording material without applying pressure to the heating body, so there is no need to heat the recording material, compared to other methods. The company says it can melt toner using much less energy.

However, as is well known, if the toner is brought into contact with a heating body without being pressurized, the heat transfer efficiency decreases and it takes a relatively long time to heat and melt the toner.

Therefore, Japanese Patent Publication No. 51-29825 (Special Patent Application No. 47-2)
No. 5896), it has been proposed to add a known pressure welding technique to this to improve the heat transfer coefficient and heat and melt the toner in a short time and sufficiently.

(Problems to be Solved by the Invention) However, in the apparatus disclosed in this publication, in order to heat the toner sufficiently in a relatively short time, ■ Toner images and records are formed between a pair of heating elements. Since the method uses a method in which the material is held under pressure and heated, and then the heating is stopped and then forcibly cooled, the energy required for fixing increases. In other words, by heating the toner image with a pair of heating elements, the toner image is heated from above and below, which may seem efficient at first glance, but on the other hand, in order to heat the toner image from the recording material side, the recording material must first be sufficiently heated. This requires a large amount of energy. Furthermore, in the cooling process, the recording material heated to a raised temperature when heating the toner image cannot be separated unless it is cooled.
A forced cooling method is required, resulting in a large waste of energy.

As described above, a method has been proposed in which the heated toner is cooled and then separated to fix the toner without causing high-temperature offset, but it has not been put to practical use because of the drawbacks mentioned above.

In the above two proposed examples, the heating body is composed of a heating roller, the web fed by the heating roller, and a heat generation source built into the heating roller, heating is performed via the web, and it functions as a web conveyance roller. are doing. For this reason, the method of feeding power to one heat generating source and the form of abutting support for the temperature sensing element become complicated, and the accuracy of temperature control tends to deteriorate.

Furthermore, in a configuration in which the temperature sensing element slides on the heating roller, there are safety problems such as excessive temperature rise due to wire breakage. Furthermore, since both of the above two examples require a heating element with a relatively large heat capacity, there is also the disadvantage that heat radiation into the machine increases and the temperature inside the machine increases significantly.

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

(Means for solving problems) The present invention is.

An image forming means that forms an unfixed toner image corresponding to target image information by carrying toner made of heat-meltable resin or the like on the surface of a recording material.

A fixing film, a traveling drive means for the fixing film, a heating body disposed on one side of the fixing film with the fixing film therein, and a heating body disposed on the other side of the fixing film, the fixing film being connected to the heating body through the fixing film. a pressure member that brings the unfixed toner image-bearing side of the recording material into close contact; a toner image heat fixing means for introducing the recording material between the running driven fixing film and the pressure member and heat fixing the unfixed toner image on the surface of the recording material, the toner image heat fixing means The image forming apparatus is characterized in that the heating element is a self-temperature-controlled linear heating element in which a linear heating element having a predetermined heating width and a PTC heating element are integrally formed.

(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 running in the same direction at the same speed as the recording material conveyance direction, and the unfixed toner remains on the fixing film surface. When the image-bearing side surfaces are in close contact with each other and overlapped together with the fixing film, the mutual pressure contact between the heating body and the pressure member is subjected to a squeezing force, and the surfaces become misaligned or wrinkled due to the speed difference between them. They overlap and pass through in close contact with each other.

■Heating process During this process of passing through the mutual pressure contact section, the unfixed toner image on the surface of the recording material is heated and softened and melted by the heating body through the fixing film, and in particular, the surface layer exceeds the toner melting point and is completely softened and melted. . In this case, the heating body, fixing film, toner image, and recording material are well pressed together by the pressure member at the mutual pressure contact portion of the heating member and the pressure member, and heat is transferred effectively, so that the heat is heated for a short time. The toner is sufficiently softened and melted to provide 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, and only the toner is effectively heated to soften and melt, thereby heating the toner image with low power. Fixation can be performed well.

Here, a note will be made regarding the softening and melting of the toner described in the present invention. The temperature conveniently expressed as the toner's "melting point" refers to the minimum temperature required for the toner to fix. In some cases, the viscosity decreases to such an extent. Therefore, even when the toner is conveniently expressed as melting during fixing, it may actually indicate a decrease in viscosity to the extent of softening.The present invention also includes such cases; Even when it is conveniently expressed as "fixed," depending on the toner, it may be more appropriate to say "high viscosity" rather than "solidification." The present invention also includes such cases.

■Cooling process The toner image that is in close contact with the fixing film surface and sequentially passes through the mutual pressure contact area of the heating body and the pressure member.The recording material portion that has been softened and melted by heating is kept in close contact with the fixing film surface even after passing through the pressure contact area. The conveyance is continued for a while, and this period is used as a cooling process, in which the heat of the toner softened and melted in the heating process is radiated, and the toner is cooled and fixed. Due to this cooling and solidification, the cohesive force of the toner becomes extremely large, causing it to behave as a group, and while the adhesion and adhesion force to the recording material side increases, the cohesive force to the fixing film side decreases significantly. When the toner is heated and softened and melted in the heating process, it is pressurized by the pressure member, so at least a part of the toner image penetrates into the surface layer of the recording material, and the amount of the toner image that penetrates is solidified by cooling. The anchor effect increases the adhesion and adhesion of the cooled and solidified toner to the recording material side.

(2) Separation (Separation) Step After the toner image is cooled and solidified in the above cooling step, the recording material is sequentially separated from the fixing film surface. At this time of separation, the toner image is cooled and solidified, and the adhesion and adhesion force to the recording material is sufficiently large, but the adhesion and fixation force to the fixing film is extremely small, so the part of the recording material where the image has been fixed generates toner offset with respect to the fixing film. They are easily separated one after another without any problems.

In this way, the recording material on which the image is to be fixed is made to run in close contact with the fixing film at the same speed so that the unfixed toner image bearing surface faces the running fixing film surface, and the toner image is heated and melted by a heating body through the fixing film. In addition, since the recording material and the fixing film are separated after the toner image is cooled and fixed, toner offset with respect to the fixing film does not occur, and a heating element with a small heat capacity is used, and power is supplied to the heating element. This can be done with a simple configuration, and by maintaining the heating element at a sufficiently high temperature compared to the temperature (melting point or softening point) at which the toner should be heated for fixing, the toner image can be heated efficiently. As a result, it is possible to achieve sufficiently good fusing with less energy and no fusing defects, resulting in an image forming device that requires less standby time when in use, consumes less power, and has less internal temperature rise. be effective.

In the above separation process (■), the toner does not necessarily have to be cooled and solidified at the separation part between the fixing film and the recording material. If the toner is sufficiently melted in the heating step, the recording material may be separated from the fixing film surface immediately after the toner is melted at a sufficiently high temperature, and the cooling step after the heating step may be omitted; this is within the scope of the present invention. It belongs to Chu.

(2) Since the heating element is a self-temperature-controlled linear heating element that integrally forms a linear heating element with a predetermined heating width and a PTC heating element, Good heat transfer and small temperature fluctuations in the heating part.

(2) Since the PTC heating element has self-temperature control characteristics, no special temperature control means is required and the configuration is simplified.

(2) Since the heating section is determined by the shape of the heating section, it is easy to obtain uniform heating conditions over the entire length.

(Example) <Example 1> (FIGS. 1 to 5) The apparatus of this example is an electrophotographic copying apparatus of a reciprocating document placement table type and a rotary drum type transfer type.

(1) Overall schematic configuration of the device (Fig. 1) In Fig. 1, ioo is the device housing, and 1 is a reciprocating movement made of a transparent plate member such as a glass plate disposed on the top plate 100a of the machine housing. Type manuscript I! It is a stand.

It 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, and it is placed on the upper surface of the document storage table l at a predetermined position reference point a with the image side to be copied facing downward, and the document pressing plate 1a is placed on top of it and pressed down. Set by.

Reference numeral 100b denotes a slit opening, which serves as a document illumination section, and is opened on the surface of the top plate 100a of the machine casing, with its length extending in a direction perpendicular to the reciprocating direction of the document at table l (direction perpendicular to the plane of the paper). The downward image surface of the original G set on the original placing table l passes through the position of the slit opening 100b sequentially from the right side to the left side during the forward movement of the original placing table 1 to the right side a. In the process of passing through, the light L1 of 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 converted into an m-image using a toner made of a resin or the like that softens and melts when heated by a developing device 5, 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. When the leading edge of the image forming section reaches the transfer discharger 8, the timing is adjusted so that the leading edge of the transfer material sheet P also reaches the open position of the transfer discharger 8 and the photosensitive drum 3 and is aligned with the transfer discharger 8. are fed synchronously. Then, the toner image on the photosensitive drum 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 guided by a conveyance guide 10 to a fixing device 20, which will be described later, to heat the unfixed toner image carried thereon. After the fixing process, the image is discharged onto a paper discharge tray 11 outside the machine as a single image formed product (copy).

On the other hand, the surface of the photosensitive drum 3 after the toner image has been transferred is subjected to removal of adhering contaminants such as residual toner by a cleaning device 5112, and static electricity is removed by full-surface exposure L2 to erase the electrical residual memory and repeat the image formation process. Used in formation.

PH1 is a paper feed detection sensor (for example, a photo sensor) disposed in the sheet path section between the feed roller 6 and the registration roller 9, and PH2 is a paper discharge detection sensor (for example, a photo sensor) disposed next to the fixing device 20. It is.

(2) Fixing device 20 FIG. 2 is an enlarged view of a portion of the fixing device 20 in an image fixing state.

24 is a fixing film feeding shaft, on which the fixing film 23 of a desired set length is wound into a roll, and the leading end of the fixing film 23 is connected to the fixing film winding shaft 2.
It is locked at 7. The fixing film 23 in this embodiment is a thin plastic long film having a heat-resistant treatment and having a thickness of, for example, PET (polyester) of 6 gm as a base material.

Reference numerals 21 and 22 denote a heating body and a pressure roller, which are disposed facing each other on the upper and lower sides of the fixing film portion between the shafts 24 and 27, respectively.

The heating body 21 is positioned and held by a stationary member (not shown) via a heat insulating support member (not shown).

The pressure roller 22 is applied to the lower surface of the heating body with the fixing film 23 in between, applying a predetermined contact pressure (for example, a total pressure of 4 to
6 kg).

Reference numerals 26 and 33 indicate separation upper rollers having a large curvature (strong curvature, small radius) and disposed next to the heating body 21 and the pressure roller 22 so as to face the upper and lower surfaces of the fixing film, respectively. This is the lower separation roller. Reference numeral 32 denotes a conveyor belt made of, for example, EPDM and stretched between the pressure roller 22 and the lower separation roller 33. The pressure roller 22 has an elastic layer made of silicone rubber or the like on a core material made of metal or the like.The zero-separation upper roller 26 and the separation lower roller 33 are rollers that are free to rotate.

The take-up shaft 27 is driven to rotate in the clockwise direction indicated by the arrow by a drive system (not shown), thereby moving the fixing film 23 from the delivery shaft 24 side to the take-up shaft 27 side to the image forming section (transfer section 8).
The sheet P is wound up and run in the same direction at the same speed as the conveyance speed of the sheet P that is conveyed from the sheet P to the fixing device 20 via the guide 10 . The pressure roller 27 is rotated by a drive system (not shown) in the counterclockwise direction as indicated by the arrow at a circumferential speed that is approximately the same as the conveyance speed of the sheet P, and as a result, a suspension is created between the pressure roller 22 and the lower separation roller 33. The conveyor belt 32, which is rotated, is also rotated in conjunction with the belt.

Reference numeral 30 denotes a fixing film remaining amount sensor arm that is brought into contact with the outer surface of the wound fixing film on the feed-out shaft 24 side, and detects the change in the winding diameter as the fixing film is sequentially transferred to the winding shaft 27 side by executing the fixing process. The remaining amount is detected from the gradual decrease, and when the film is near the end, a warning display or sound is displayed to prompt the user to replace the fixing film.

29φ25 is the same lever as the sheet detection sensor disposed on the lower surface side near the fixing device 2!20 in the transfer material conveyance guide lO from the toner image transfer section 8 to the fixing device 20.

In the free state, the tip of the lever 25 projects from the through hole 10a provided in the guide 10 to the upper surface side of the guide IO. In this state, sensor 29 is off. The transfer material sheet P is conveyed along the upper surface of the guide 10 from the transfer unit 8 side to the fixing device 20 side, and the protruding tip of the lever 25 is cut by the tip of the sheet P, so that it goes into the back side of the sheet P and becomes transparent. It sinks into the hole 10a and rotates. This lever 2
The sensor 29 is turned on by the sinking rotation of the seat P.
arrival at the sensor position is detected by a control circuit (not shown). The lever 25 is kept in a sunken and rotating state until the sheet P passes through the lever position by contacting and being pressed against the back surface of the sheet P, and therefore the sensor 29
remains on. Thereafter, when the rear end of the sheet P passes the position of the lever 25 and is separated from the lever 25, the lever 25 becomes free and rotates again, returning to the position in which the tip protrudes from the through hole 10a. This return rotation turns off the sensor 29, and the control circuit detects that the sheet P has passed the sensor position.

FIG. 3 is a perspective view of the heating body 21, and FIG. 4 is an enlarged cross-sectional view thereof. 48 is a linear heating plate made of a highly rigid material such as a metal plate such as aluminum copper or a ceramic plate such as alumina, and is approximately 220 mm (length) x 20 mm (
It has an external dimension of 2 mm (radius) x 2 mm (thickness). Reference numeral 49 denotes a plurality of PTC heating element chips arranged in series densely in sequence along the length of the heating plate 48 on one side of the heating plate 48. Each chip 49 is a plate-shaped plate made of a material such as barium titanate. The body is approximately 25mm (length) x 15mm (radius)
It has external dimensions of x2mm (thickness). The array of PTC heating element chips 49 has electrode layers 521 and 522 common to each chip on both sides thereof, and is integrally attached to the surface of the heating plate 48 via an insulating adhesive layer 51. It's a dress. A heat conductive cover 53 covers the side of the heating plate 48 on which the PTC heating element is provided, and protects the electrode layer 522 and forms a heat transfer path to the heating plate. heating plate 4
The long side edge of 8 is used as a linear heating section, and 5
0 is a fluororesin whose edges are coated along the first child.
A protective layer made of a material with excellent heat resistance and sliding properties, such as silicone resin, which enables sliding contact with the fixing film surface.

By supplying power between the electrode layers 52+ and 522, each P
Since the TC heating element chip 49 generates heat and has a positive temperature coefficient of resistance, when it reaches a temperature specific to the material of the PTC heating element (cure temperature), the resistance value increases rapidly and heat generation is suppressed. Therefore, the linear heating plate 48 integrated with the PTC heating element is maintained at a predetermined temperature (self-temperature controllability).

The pressure roller 22 presses the fixing film 23/transport belt 32, or the fixing film 32/recording material (transfer paper) P/transport belt 32 against the longitudinal side edge of the linear heating plate 48 on which the protective layer 50 is provided. A pressure contact portion N which is constantly pressed and applied with a predetermined contact pressure through
The pressure contact portion N becomes an effective linear heating width.

(3) Operation After setting the original G on the original platen 1, setting the number of images to be formed, specifying the size of the sheet P to be used, specifying the magnification, etc., when the image forming start switch is pressed, the feed starts. The roller 6 starts feeding paper P in the cassette S, and the sensor PH1 detects the paper feeding. Also, image formation on the three surfaces of the photosensitive drum is started. The fixing device 120 operates when a predetermined timer period elapses from the time when the sensor PH1 detects paper feeding, that is, when the sheet P fed from the cassette S passes through the pair of registration rollers 9, the transfer section 8, and the guide 1O, and the leading edge thereof reaches the heating body 21. When the fixing film 23 and the pressure roller 22 reach a position close to the pressure contact portion N, the drive system of the fixing device starts rotating the take-up shaft 27 and the pressure roller 22, and the fixing film 23 is transferred to the feed-out shaft 24. A winding drive state is reached in which the sheet P travels from the side to the winding shaft 27 at the same speed as the transport speed of the sheet P. In addition, the heating body 21 has electrodes 521 and
The PTC heating element 49 generates heat by energizing the PTC heating element 522, and is maintained at a predetermined constant temperature.

Unfixed toner image Ta transported to fixing device 20
Fixing film 2 with the top surface of the sheet carrying
A clamping force is applied to the mutual pressure contact portion N (linear heating width portion) between the heating body 21 and the pressure roller 27 while the heating body 21 and the pressure roller 27 are overlapped together with the fixing film 22 without causing surface displacement or wrinkles. I will pass while receiving it.

This process of passing through the mutual pressure bonding portion N is a heating process so that the toner image Ta is heated and softened and melted Tb described in item (1)-0 of the above-mentioned (function) is in a sufficient state to be fixed.

The sheet portion that has passed through the mutual pressure contact portion N between the heating body 21 and the pressure roller 22 is spread between the heating body 21 and the upper separation roller 26 and travels forward until it reaches the position of the separation rollers 26 and 33. The conveyor belt 32 continues to be conveyed in close contact with the portion of the fixing film 23 that is attached to the fixing film 23. The conveyor belt 32 supports the back surface of the sheet P and maintains close contact with the fixing film 23.

This conveyance process is used as a cooling process in the above (action) (1)-
As described in item 0, the heat of the softened/melted toner Tb is radiated, and the toner is cooled and solidified Tc.

In this embodiment, the pressure roller 22 is not provided with a heat source and the toner image is heated only from the surface layer side of the toner image, so the temperature rise of the transfer material is relatively small. In the cooling process, heat dissipation from the toner image is easy.

When the fixing film 23 reaches the position of the pair of separation rollers 26 and 33, the traveling direction of the fixing film 23 is turned away from the sheet 2 surface along the surface of the upper separation roller 26, which has a large curvature, and the fixing film 23 and the sheet P are separated. separated from each other
The toner is then discharged to the paper discharge tray 11. By the time the toner is separated, the toner has been sufficiently cooled and solidified to perform the above-mentioned (action) (1).
)-0, the adhesion/fixing force of the toner to the sheet P is sufficiently large, and the force to the fixing film 22 is extremely small.
3 and the sheet P can be easily and sequentially separated from each other without substantially causing toner offset with respect to the fixing film 23.

The winding drive of the fixing film 23 of the fixing device 20 is stopped when the sheet P passes through the fixing device 20 and its trailing edge is detected by the discharge detection sensor PI (2).

In the present embodiment, the fixing film 23 is sequentially wound from the delivery shaft 24 side to the take-up shaft 27 side at the same speed as the conveyance speed of the sheet P each time the fixing process of the sheet P is executed as described above. It will be used.

The fixing film winding forward drive control starts driving when a predetermined first timer time elapses from the time when paper feed is detected by the paper feed detection sensor PH1, and stops the drive when a predetermined second timer time elapses. During this time, the fixing process for the sheet P is executed, and the discharge detection sensor PH
It is also possible to have a configuration that does not use 2.

FIG. 5 shows the temperature of the toner and the transfer paper, more specifically, the temperature at the center of each cross-sectional direction, when a transfer paper having a toner layer on one surface is conveyed and fixed in the fixing device of the image forming apparatus according to the wooden embodiment. The zero condition, which is a graph obtained by calculating the time change, is as follows.

Heating conditions: Constant temperature 15 due to the PTC characteristics of the heating element 49
Heating is performed by a linear heating section N with a width of 2 mm maintained at 0.01C.

Toner fixing temperature: 125'''C, toner layer thickness 20
#Lm Fixing film: PET film with heat-resistant and sliding treatment, thickness 6ILm Transfer paper thickness: 11001L Room temperature: 20'C Fixing processing speed: 50 mm/s, heating time 4
゜S As shown in FIG. 5, in this embodiment, the toner layer is 140@
C and is well established. Also, although the temperature of the transfer material has risen to 75°C, it is lower than the fixing temperature of the toner, so there is no problem.

When a fixing test was actually conducted under the above conditions, it was possible to obtain a good image without offset.

<Example 2> (Figures 6 and 7) This example differs from Example 1 in that the heating conditions are different, and by applying a high amount of heat to the toner image for only a short period of time, the transfer material is hardly heated. , aims to efficiently and sufficiently melt and soften the toner image, thereby reducing power consumption during the fusing process.

For the above purpose, a PTC heating element is selected as the heating element in this example so that the temperature can be maintained at a higher temperature than in Example-1, and the heating in the present invention apparatus is maintained at approximately 180C. Since the heating element is a linear heating element formed integrally with the PTC heating element, it has excellent followability compared to conventional heating elements in maintaining the temperature of the heating element, and is also highly safe, so the temperature of the heating element can be set high. It is easy and reliable to
On the other hand, since the heating time is determined by the pressure contact width between the pressure roller and the linear heating section and the fixing processing speed (transfer material conveyance speed), in this embodiment, the heating body 57 having the configuration shown in FIG.
is used.

The heating body 57 in the Pt58 diagram has a convex portion 54a with a predetermined line width N.
As in Example-1, PTC heating elements 49 are arranged and integrally formed with an insulating adhesive 51 on a convex heating plate 54 made of a material with excellent thermal conductivity, and are provided on the left and right sides. The convex heating plate 54 is maintained at a predetermined temperature by applying current through the common electrodes 52+522.

The adhesive assembly of the heating plate 54 and the PTC heating element 49 is bonded to a highly rigid S, U via a heat insulator 55 such as Bakelite to prevent deformation due to pressure with the pressure roller 22.
It is supported and fixed to a support body 56 made of a material such as S.

It is preferable to cover the convex portion 54a with a protective layer 50 in the same manner as in Example-1.A fixing test was conducted in the image forming apparatus shown in FIG. 1 described above by replacing the heating element 21 with the heating element 57 shown in FIG. However, a good fixed image was obtained.

FIG. 7 shows the temperature of the toner and the transfer paper, more specifically, the temperature at the center of each cross-sectional direction, when the fixing device of the image forming apparatus of this embodiment performs the fixing process while conveying the transfer paper having a toner layer on the surface. The zero condition, which is a graph obtained by calculating the time change, is as follows.

Heating condition: linear heating element 5 maintained at a constant temperature of 180″C
7 (FIG. 6) for 8 ms.

Toner fixing temperature: 125°C - Toner layer thickness 20 m Fixing film: PET, thickness 6 lm Transfer paper thickness, 100 m Room room temperature = 20"C In this example, toner fixing temperature 125 Since the heat treatment is carried out by the heating element 57 maintained at 180'C, which is much higher than °C, the toner is sufficiently heated to exceed the fixing temperature by short-term heating, and good fixing properties can be obtained.

On the other hand, the temperature rise of the transfer paper is extremely small (less energy is wasted than in Example-1).

Furthermore, in this embodiment, since the pairs of electrodes 521 and 522 are each integrally constructed over the longitudinal direction of the heating body 54, power can be supplied from one end in the longitudinal direction. Considering that the heating element is fixed, it can be said that supplying power to the heating element is extremely easy.

Furthermore, in this embodiment, in contrast to conventional roller fixing in which the heating element is a halogen lamp and the heating element is a fixing roller, and the heating element and the heating element are arranged separately with a long spatial distance between them, (1) The heating element and the heating element are integrated, and the heating element is thinner: J membrane 50 and heat-resistant sheet 2.
3 to directly heat the toner image. Moreover, since it is sufficient to use a compact heating element, its heat capacity is small. The delay in heating up is extremely small, and the rate of temperature rise is extremely high.

Therefore, during image formation, the transfer material P is placed on the upstream side of the heating body 54 by the transfer material detection arm 25 (FIGS. 1 and 2).
If you start energizing the PTC heating element 49 when the transfer material P reaches the position N, the heating element surface temperature will rise to the fixing temperature by the time the transfer material P reaches the pressure contact part N. The wait time of the fixing device is substantially zero even if the fuser is not energized. Therefore, ■ power consumption during non-image formation can be reduced, and ■ temperature rise inside the machine can also be prevented.

(5) In other examples 1 and 2, the heating element 49 is Nagai's PTC
A heating element may be used, or a plurality of PTC heating element chips 4
9 may be arranged roughly.

As in the embodiment, the fixing film 23 is sequentially wound and run from the delivery shaft 24 side to the take-up shaft 27 side every time the fixing process is completed, and when the entire length has been wound and used, it is replaced with a new fixing film. In addition to using a replaceable winding system, there is virtually no toner offset to the fixing film surface, so
If the thermal deformation or deterioration of the film is small, the wound used fixing film is sent to the winding shaft 27 side in a timely manner.
It can be used multiple times by controlling the rewind to the side or by reversing and exchanging the winding side and the sending side (repeated rewinding type), or it can be made into an endless belt type and rotated. It is also possible to provide a configuration in which the image is subjected to the fixing process.

In the roll-up and replaceable type, the fixing film 23 can be made of, for example, a thin and inexpensive polyester base material that has been subjected to heat-resistant treatment, and it can be made thin regardless of durability, and power consumption can be reduced. can.

In the rewinding and reuse type, the fixing film is, for example, a 25 pm thick polyimide resin film 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. It is preferable that the provided composite layer film be used, and that the contact pressure between the heating body 21 and the pressure roller 22 is released during rewinding and reverse running.

If the film is to be used multiple times, such as a rewinding type or an endless belt type, a felt pad for cleaning the film should be provided and it should also be impregnated with a slight release agent, such as silicone oil. It may be possible to clean the film surface and further improve the releasability by bringing it into contact with the fixing film.If the fixing film is treated with an insulating fluororesin, static electricity may be generated on the film that disturbs the toner image. To deal with this problem, it is possible to eliminate the static electricity with a grounded static elimination brush, or to charge the film within a range that does not disturb the toner image by applying a bias voltage to the brush without grounding it. One measure is to add conductive powder fibers, such as carbon black, to the image forming apparatus 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. Also,
An antistatic agent or the like may be applied or added.

In either method, the fixing film 23 is the fixing device 2! I2
By configuring the cartridge to be detachably attached to a predetermined location of the fixing film, it is possible to facilitate the work of replacing the fixing film.

As long as the viscosity of the toner when heated and melted is sufficiently high, the toner temperature when separating the fixing film and the toner may be equal to or higher than the toner melting point. In this case, the fixing film and the toner image may be separated when the transfer paper P passes through the pressure contact portion between the heating body 21 and the pressure roller 22.

There is no need for the temperature of the pressure roller 22 to be kept below the toner melting point.

The above-mentioned embodiments are transfer type electronic copying devices, but the image forming process/means is a direct type in which a toner image is directly formed and carried on electrofax paper, electrostatic recording paper, etc. Laser beam printer, facsimile, microfilm league printer, display, which forms an image using heat-fusible toner on a recording material using a recording image forming method or other appropriate image forming process or means, and heats and fixes it. The present invention can be effectively applied to various image forming apparatuses such as apparatuses and recording machines.

(Effects of the Invention) As described above, the present invention makes it possible to reduce the heat capacity of the heating body, which is the heating means, without causing fixing failure or offset in a toner image heat fixing type image forming apparatus. , it is possible to realize an image forming apparatus with low standby time, low power consumption, and low internal temperature rise. Furthermore, the thin fixing film can be used repeatedly over a long period of time without any problem of wrinkles.

By integrally forming the heating element with the linear heating part and the PTC heating element, (1) heat transfer between the heating part and the heat generating part is good, and temperature fluctuations in the heating part are small;

(2) Since the PTC heating element has self-temperature control characteristics, no special temperature control means is required, and the configuration is simplified.

(2) Since the heating section is determined by the shape of the heating section, it is easy to obtain uniform heating conditions throughout the length.

[Brief explanation of the drawing]

The drawings show an embodiment of the apparatus; FIG. 1 is an overall schematic diagram of the image forming apparatus, FIG. 2 is an enlarged view of the fixing device in a fixing state, and FIG. 3 is a perspective view of the heating body. FIG. 4 is an enlarged cross-sectional view thereof, FIG. 5 is a temperature change diagram, FIG. 6 is an enlarged cross-sectional view of the heating element in the second embodiment, FIG. 7 is a temperature change diagram, and FIG. 8 is a temperature change diagram. FIG. 6 is a state diagram of the apparatus when the fixing film is replaced. 3 is a photosensitive drum, 8 is a transfer discharger, P is a transfer material sheet (
20 is the overall code of the fixing device, 21 and 57 are heating bodies, and 48-54 are linear heating plates. 49 is a PTC heating element, 521 and 522 are electrodes, 23 is a fixing film, 22 is a pressure roller, 27 is a winding shaft, 24
is the delivery axis. Patent applicant: Canon Co., Ltd. Representative: Yukio Takanashi
) Time (-3) Time M (ms)

Claims (1)

[Claims] (1) An image forming means for forming an unfixed toner image corresponding to target image information by carrying toner made of a heat-melting resin or the like on the surface of a recording material, a fixing film, and a driving means for driving 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; The fixing film is provided with a pressure member for bringing the surfaces into close contact with each other, and is driven to run in the same direction at the same speed as the conveyance speed of the recording material carrying the unfixed toner image conveyed from the image forming means side, and the pressure member. and a toner image heat fixing means for heating and fixing the unfixed toner image on the surface of the recording material by introducing the recording material between the recording material and the toner image heat fixing means, the heating body of the toner image heat fixing means having a predetermined heating width. An image forming apparatus characterized in that the image forming apparatus is a self-temperature-controlled linear heating element in which a linear heating element and a PTC heating element are integrally formed.