JPH0797254B2 - Image forming device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an image forming apparatus such as a copying machine, a laser beam printer, a facsimile, a microfilm reader printer, an image display (display) device, and a recording machine.

More specifically, a recording material (electrofax sheet, electrostatic recording sheet, transfer material sheet, transfer material sheet, etc.) is formed by using a toner made of a heat-meltable resin by an appropriate image forming process means such as electrophotography, electrostatic recording, magnetic recording, etc. An unfixed toner image corresponding to desired image information is formed and carried on a surface of a printing paper or the like by a direct method or an indirect (transfer) method, and the unfixed toner image is carried on a recording material surface carrying the image. The present invention relates to an image forming apparatus of a type in which heat fixing processing is performed as a permanently fixed image.

(Prior Art) Conventionally, a fixing device used in this type of device is unfixed by a heating roller that is maintained at a predetermined temperature and a pressure roller that has an elastic layer and is in pressure contact with the heating roller. A roller fixing method is often used in which a recording material on which an attached toner image is formed is heated while being nipped and conveyed.

A belt fixing system as disclosed in US Pat. No. 3,578,797 is also known. This is because the toner image is brought into contact with the heating element web and is heated to its melting point to be melted, and after the melting, the toner is cooled to have a relatively high viscosity, and the toner adhesion tendency is weakened from the heating element web. It is a method of fixing without causing offset by going through the process of peeling.

(Problems to be Solved by the Invention) However, the above-described conventional thermal roll fixing method and belt fixing method have the following problems.

Heat roll fixing method It takes a long time to rise to a predetermined temperature,
During that 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 a heat capacity is required.

A rotating roller with a high roller temperature requires a heat resistant special bearing.

The roller comes into direct contact with the hands, which is dangerous and requires a protective member.

The recording material wraps around the roller due to the constant temperature and curvature of the roller, making it easy to see jams on the recording material.

Belt fixing method This method also has the same problems as the above heat roller fixing method and the same wait time and large power consumption as those mentioned above.

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

(Means for Solving Problems) The present invention is an image forming means for forming a non-fixed toner image corresponding to target image information by carrying a toner made of a heat-meltable resin or the like on a recording material surface, 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 with the fixing film interposed therebetween. A pressure member for closely contacting the surface of the recording material on which the unfixed toner image is carried, and in the same direction at the same speed as the carrying speed of the recording material carrying the unfixed toner image carried from the image forming means side. A toner image heating and fixing means for introducing the recording material between the running-dried fixing film and the pressure member to heat and fix the unfixed toner image on the surface of the recording material. The heating body of At least a substrate, a heat-insulating layer laminated on the surface of the substrate facing the fixing film, the outer surface of which has a curved shape convex in the central portion in the running direction of the fixing film, and a substantially top surface of the convex outer surface of the heat-insulating layer. An image forming apparatus comprising: a heat generating element provided in the image forming apparatus.

(Operation) (1) The recording material to be image-fixed, which is introduced between the fixing film and the pressure member, which is driven to run in the same direction at the same speed as the conveying direction of the recording material, is the unfixed toner on the fixing film surface. While the image-bearing surface is in close contact with the fixing film and the overlapping state with the fixing film, the pressure difference between the heating member and the pressing member (fixing nip portion) is applied while the surface pressure difference occurs between the heating member and the pressing member, and wrinkles occur. They do not get close to each other, and they pass over each other in close contact with each other.

In the heating step, 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 portion thereof is much higher than the melting point of the toner and completely softened and melted. In this case, the heating element, the fixing film, the toner image, and the recording material are satisfactorily pressed and brought into close contact with each other at the mutual pressure contact portion between the heating element and the pressing member, and the heat is effectively transferred. The toner is sufficiently softened and melted to obtain good fixing property.
On the other hand, the temperature rise of the recording material itself is practically small, and the waste of thermal energy is small. That is, the recording material itself is not substantially heated, and only the toner is effectively heated and softened / melted, and the toner image can be satisfactorily heat-fixed with low power.

A note will now be given regarding the softening / melting of the toner described in the present invention. The temperature that is conveniently expressed as the "melting point" of the toner means the minimum temperature required for the toner to be fixed. There is a case where the viscosity is reduced to such an extent. Therefore, even if it is expressed as melting when fixing, it may actually show a decrease in viscosity such as softening. The present invention also includes such a case. Similarly, even when it is expressed for convenience that the toner has been cooled and fixed, it may be more appropriate for some toners not to be solidified but to have higher viscosity. The present invention also includes such a case.

Cooling process Sequentially passes through the mutual pressure contact area between the heating element and the pressure member in close contact with the fixing film surface.The recording material part that has been softened / melted by the toner image remains in close contact with the fixing film surface after passing through the pressure contact area. Is continuously continued for a while, and a cooling step is performed during this period to radiate heat of the toner softened and melted in the heating step to cool and fix the toner. By this cooling and solidification, the cohesive force of the toner becomes very large and the toner behaves as a group, and while the adhesion / fixing force to the recording material side increases, that to the fixing film side becomes extremely low. When the recording material is heated and softened and melted in the heating step, the toner is pressed by the pressure member, so at least a part of the toner image penetrates into the surface layer of the recording material, and the solidified portion is cooled and solidified. Due to the anchor effect, the adhesion and fixing force of the cooled and solidified toner to the recording material side increases.

Separation (Separation) Step After the toner image is cooled and solidified by the cooling step, the recording material is sequentially separated from the fixing film surface. At the time of this separation, the toner image is cooled and solidified to have a sufficiently large adhesion / adhesion force to the recording material and an extremely small amount to the fixing film, so that the recording material portion on which the image is fixed causes toner offset to the fixing film. It can be easily and sequentially separated.

In this way, the recording material to be image-fixed is run in close contact with the fixing film at the same speed so that the unfixed toner image bearing surface faces the surface of the running fixing film, and the toner image is heated and melted by the heating body through the fixing film. At the very least, since the recording material and the fixing film are separated from each other after the toner image is cooled and fixed, the toner offset does not occur on the fixing film and the heating element having a small heat capacity is used, and the power is supplied to the heating element. It becomes possible to carry out with a simple structure, and by maintaining a heating body of a sufficiently high temperature with respect to the temperature (melting point or softening point) at which the toner should be heated for fixing, toner image efficiency can be improved. It is possible to heat the unit effectively, and it is possible to perform good fixing without defective fixing with a small amount of energy, and as a result, during standby while using the device. And, power consumption, and further an effect of obtaining a smaller image forming apparatus temperature rise in the apparatus.

If the toner is sufficiently melted at a high temperature among the three steps of heating, cooling, and separation, the recording material is immediately separated from the fixing film surface and heated immediately after the toner is sufficiently melted at a high temperature in the heating step. The cooling process after the process may be eliminated and is within the scope of the present invention.

(2) As described above, the heating element is at least a substrate, and a heat insulating layer laminated on the surface of the substrate facing the fixing film and having an outer surface in the shape of a curved surface with a convex center in the running direction of the fixing film. The heat-generating layer is provided with a heating element substantially on the top surface of the convex curved outer surface of the heat-insulating layer.

The rubbing surface of the heating element against the fixing film is a convex curved surface corresponding to the convex curved outer surface of the heat insulating layer, and the fixing film runs along the convex curved surface, and both sides of the convex curved rubbing surface in the fixing film rubbing direction. It is possible to reduce or eliminate the sliding resistance between the fixing film and the edge edge portion, particularly, the edge edge portion on the upstream side in the film running direction.

Therefore, the overall sliding resistance between the heating element and the fixing film is reduced to reduce the running drive load of the fixing film, and it is possible to use a compact, inexpensive and low torque drive source.
Further, the durability of the fixing film can be extended by reducing or eliminating damages such as scratches and elongation of the fixing film due to tension and tears.

The fixing film travels along the convex-curved rubbing surface of the heating body and travels into the pressure contact nip portion between the heating body and the pressure member, and presses the fixing film upstream of the nip portion in the fixing film traveling direction. Since a wedge-shaped space having a large opening is formed between the member and the member, when the recording material to be image-fixed is introduced into the pressure contact nip portion (fixing nip portion) between the fixing film and the pressure member and passes through the nip portion. Even if the recording material flutters on the upstream side in the conveying direction of the recording material, contact between the surface of the recording material on which the unfixed toner image is carried and the surface of the fixing film is prevented from rubbing against each other. It is possible to prevent the occurrence of so-called image rubbing that disturbs the image by rubbing the deposited toner image on the surface of the fixing film.

Since the heating element is provided on the substrate via the heat insulating layer, the heat energy generated from the heating element is suppressed from radiating to the substrate side and is efficiently transferred to the fixing film side, that is, to the recording material side to be image-fixed via the fixing film. To improve the thermal efficiency and reduce the electric power required for fixing.

(Embodiment) The apparatus of this embodiment is a reciprocating type / rotating drum type / transfer type electrophotographic copying apparatus.

(1) Overall schematic configuration of the apparatus (FIG. 1) In FIG. 1, 100 is an apparatus box, 1 is a top plate 1 of the box.
This is a reciprocating type document placing table composed of a transparent plate member such as a glass plate disposed on 00a, and reciprocates at a predetermined speed on the machine top plate 100a to the right a and the left a'in the drawing. Driven.

Reference numeral G denotes a document, which is placed by placing the document surface of the document table 1 on the upper surface of the document table 1 according to a predetermined mounting standard with the image surface side to be copied facing downward, and by pressing the document pressure plate 1a onto the document platen 1a. .

Reference numeral 100b denotes a slit opening serving as a document illuminating section which is opened on the surface of the machine top plate 100a with a direction perpendicular to the reciprocating direction of the document placing table 1 (direction perpendicular to the paper surface) as a longitudinal direction. The downward image surface of the document G placed and set on the document placing table 1 sequentially passes through the position of the slit opening 100b from the right side to the left side in the process of reciprocating to the right a of the document placing table 1. , Slit L opening the light L of the lamp 7 in the course of its passage
100b is received through the transparent document placing table 1 and is illuminated and scanned. The light reflected from the document surface of the illumination scanning light is image-wise exposed on the surface of the photosensitive drum 3 by the short-focus small-diameter image-forming 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 rotated in a clockwise direction indicated by an arrow b at a predetermined peripheral speed around the central support shaft 3a. A uniform charging process of positive or negative polarity is performed by the charger 4, and the uniformly charged surface is subjected to imagewise exposure (slit exposure) of the original image, so that the surface of the photosensitive drum 3 is imagewise exposed. An electrostatic latent image corresponding to the original image is sequentially formed.

The electrostatic latent image is sequentially visualized by the developing device 5 with toner made of resin or the like which is softened and melted by heating, and the toner image as the visualized image is transferred to a portion where the transfer discharger 8 as a transfer portion is provided. I will do it.

Reference numeral S denotes a cassette in which transfer material sheets P as recording materials are stacked and housed, the sheets in the cassette are fed out and fed one by one by the rotation of the feeding roller 6, and then a toner image on the drum 3 is fed by the registration rollers 9. When the tip of the forming section reaches the portion of the transfer discharger 8, the tip of the transfer material sheet P also reaches the position between the transfer discharger 8 and the photosensitive drum 3, and the timing is adjusted so that they coincide with each other. Will be sent. Then, the toner images on the photosensitive drum 3 side are sequentially transferred to the surface of the fed sheet by the transfer discharger 8.

The sheet that has received the toner image transfer at the transfer portion is sequentially separated from the surface of the photosensitive drum 3 by separation means (not shown), and is conveyed as a guide.
The unfixed toner image guided and carried by a fixing device 11 to be described later by 10 undergoes heat fixing processing, and is discharged onto a paper discharge tray 12 outside the machine as an image formed product (copy).

On the other hand, the surface of the photosensitive drum 3 after the transfer of the toner image is repeatedly used for image formation after the adhering contaminants such as the transfer residual toner are removed by the cleaning device 13.

(2) Fixing device (Figs. 1 and 2) 24 is an endless belt-shaped fixing film, and has a left driving roller 25, a right driven roller 26, and a driving roller 25.
Between the separating roller 27 arranged below the driving roller 25 and the driven roller 26, and the low heat capacity linear heating body 20 as a heating body disposed below the driving roller 25 and the driven roller 26 in parallel with each other. It is suspended.

The driven roller 26 also serves as a tension roller for the endless belt-shaped fixing film 24.
Is a predetermined peripheral speed in the clockwise direction with the clockwise rotation of the drive roller 25, that is, the same as the conveying speed of the transfer material sheet P having the unfixed toner image Ta conveyed from the image forming portion 8 side on its upper surface. It is driven to rotate with peripheral speed without wrinkles, meandering, or speed delay.

Reference numeral 28 denotes a pressure roller having a rubber elastic layer having a good releasability such as silicon rubber as a pressure member, and sandwiching the film portion on the descending side of the endless belt-shaped fixing film 24 of the heating body 20. The lower surface is brought into counter-pressure contact with an urging means (not shown) with a total pressure of 4 to 7 kg, and rotates counterclockwise in the forward direction of the transfer material sheet P conveyance direction.

Since the endless belt-shaped fixing film 24 that is rotationally driven is repeatedly used for heat fixing of a toner image, it has excellent heat resistance, releasability and durability, and is generally 100 μm or less, preferably 50 μm or less in thickness. Use one. For example, polyimide / polyetherimide / PEA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin)
At least on the image contact surface side of a single layer film of heat resistant resin such as
For example, a releasable coating layer obtained by adding a conductive material to PTFE (tetrafluoroethylene resin) is applied to a thickness of 10 μm.

The low heat capacity linear heating element 20 as a heating element has a layer structure as shown in the cross-sectional model view of FIG. 4 in this example.

That is, 21a is a support member for maintaining the overall strength,
A high-rigidity / high-heat-resistant member having a longitudinal direction in the transverse direction of the fixing film (direction perpendicular to the running direction of the fixing film 24), for example
Resins such as PPS, Bakelite, and polyimide, and other horizontally long rectangular materials.

Reference numeral 21b is a substrate (heater support substrate) fixedly supported along the longitudinal direction on the lower surface side of the support member 21a. This example is an alumina substrate having a length of 240 mm, a width of 10 mm, and a thickness of 1.5 mm. In addition, various ceramics, heat-resistant glass, heat-resistant resins such as PPS / PI, etc. can be used.

Reference numeral 21c is a heat insulating layer formed by laminating on the surface of the alumina substrate 21b facing the fixing film, the outer surface of which is a curved surface having an arc-shaped cross section with a convex portion at the center in the running direction of the fixing film.
This example is a glass heat insulating layer having a maximum thickness (central portion) of 0.5 mm.

Reference numeral 21d is a linear or strip-shaped heating element formed along the length substantially on the top surface of the convex curved outer surface of the heat insulating layer 21c. This example is Ta
Resistance material such as ₂ N / Ag / Pd / RuO ₂ is 1.0 mm wide and 20 μm thick
It is formed by coating (screen printing) with. Other surface heating elements such as nichrome and ceramic heaters can also be used.

Reference numeral 21e is a glass protective layer in which the convex curved outer surface of the heat insulating layer 21c including the heating element 21d is entirely thinly coated in order to protect the surface of the heating element from rubbing between the heating element 21d and the fixing film 24.

Reference numeral 21f denotes a temperature detecting element provided on the surface of the substrate opposite to the side where the heating element is provided, which corresponds to the heating element. This example is a substrate
A Pt film (resistive temperature sensor) as a temperature measuring element is formed on the surface of 21f by a screen printing in a linear or strip shape with a width of 200 μm and a thickness of 10 μm. A bead thermistor or the like can be used as the temperature measuring element.

The heating element 20 of this example is the above-mentioned linear or strip heating element 21d.
On the other hand, the heating element 21d is made to generate heat over its entire length by energizing from both longitudinal ends thereof. Energization is a pulse-shaped waveform with a cycle of 20 msec of DC100V, a desired temperature controlled by the temperature sensing element 21f, and a pulse width according to the amount of energy released is given to the energization control circuit configuration.
The pulse width is controlled within the range of 0.5 to 5 msec, and the heating element 21d
Each time the pulse is input, the temperature rises to around 200-300 ℃. Further, in this example, a sheet front and rear end detection sensor (not shown) is provided on the upstream side of the fixing device 11 in the transfer material sheet conveying direction, and the sheet detection signal of the sensor is used to energize the heating element 22. The period is controlled only to the required period in which the sheet P is passing through the fixing device 11.

The fixing film 24 is not limited to the endless belt shape, but the endless fixing film 24 wound around the delivery shaft 30 as shown in FIG. 3 is wound between the heating body 20 and the pressure roller 28 and the separation roller 27. It may be configured such that it is engaged with the take-up shaft 31 via the lower side and travels from the delivery shaft 30 side to the take-up shaft 31 side at the same speed as the conveyance speed of the transfer material sheet P.

(3) Fixing Execution Operation The image forming start signal of the apparatus causes the apparatus to perform the image forming operation, and the leading end of the transfer material sheet P having the unfixed toner image Ta carried on the upper surface is conveyed to the fixing apparatus 11 from the fixing apparatus. When it is detected by the above-mentioned sensor (not shown) arranged nearer, rotation (or running) of the fixing film 24 is started, and the transfer material sheet P is guided by the guide 29 and the heating body 20 and the pressure roller 28. When the unfixed toner image surface enters between the fixing sheet 24 and the pressure roller 22 at the pressure contact portion N with the sheet P, the lower surface of the fixing film 24 is surface-moved in the same direction at the same speed as the conveyance speed of the sheet P. The heating body 20 and the pressure roller in an overlapping state with the fixing film 24 without causing a surface shift or wrinkling due to close contact.
It passes between the mutual pressure contact portion N with 28 while receiving a clamping pressure.

The above-mentioned (action)
The toner image is heated and softened / melted as described in the item (1)-. As described above, the heating step in the present embodiment provides the heating element 20 with the linear heating element 21d, and the heating element 21d integrally formed with the heating element 20 and having a low heat capacity is energized in a pulsed manner to repeat heat generation. This is performed by the heating body 20 configured as described above. That is, the toner image Ta on the sheet P, which is conveyed at a predetermined conveying speed, of the linear heating portion, which is determined in accordance with the width of the heating element 21d of the heating element 20 in sequence, together with the fixing film 24 on which the sheet P is conveyed. It is fed into the effective width W and is heated to become a softened / melted image Tb.

The sheet portion that has passed through the mutual pressure contact portion N between the heating body 20 and the pressure roller 28 is stretched between the heating body 20 and the separation roller 27 until it reaches the position of the separation roller 27. The film is continuously conveyed while being in close contact with it.

This transportation process is referred to as a cooling process, and (1)-
As described in the section, the heat of the softened / melted toner Tb is radiated to cool and solidify the toner Tc.

When the fixing film 24 reaches the position of the separation roller pair 27, the fixing film 24 is moved along the surface of the separation roller 27 having a large curvature.
Fixing film with the traveling direction turned away from the surface
24 and the sheet P are separated (separated) from each other, and the sheet P is discharged to the discharge tray 11. By the time of this separation, the toner is sufficiently cooled and solidified, and as described in (1)-(1)-(action), the toner has a sufficiently large adhesion / adhesion force to the sheet P and an extremely small amount to the fixing film 24. Since it is in the state, the fixing film 24 and the sheet P
The separation of the toners is easily and sequentially performed without substantially causing toner offset to the fixing film 24.

In this embodiment, since the linear heating element 21d of the heating element 20 is instantly heated to a sufficiently high temperature with respect to the melting point (or fixing temperature) of the toner by energization, preheating of the heating element is unnecessary. The heat transfer to the pressure roller 28 during non-fixing is small. Also during fixing, the fixing film, toner image,
Since the sheet is interposed between the heating body 20 and the pressure roller 28 and a short heat generation time causes a rapid temperature gradient, the pressure roller 28 is unlikely to rise in temperature and is continuous as much as practically required. The temperature is maintained below the melting point of the toner even when the image formation is performed. In the apparatus of this embodiment having such a configuration, the toner image formed of the heat-fusible toner on the sheet P is first heated and melted by the heating body 20 via the fixing film 24, and in particular, its surface layer portion is completely melted. It softens and melts. At this time, the heating roller, the fixing film, the toner image, and the sheet are in good contact with each other by the pressure roller 28, and the heat is efficiently transferred. As a result, 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, energy saving can be achieved by limiting the heating time for energization.

It is sufficient for the heating element to be small, so the heat capacity is small, and there is no need to raise the temperature of the heating element in advance, so it is possible to reduce the power consumption during non-image formation, and also to prevent the temperature rise inside the machine. Become.

In the present embodiment, the temperature of the pressure roller 28 is kept lower than the melting point of the toner as described above, so that it is possible to promote the heat dissipation of the toner image in the cooling step following the toner image heating step. . Therefore, the time required for cooling is short and the device can be downsized.

(4) Heated body 20 Since the rubbing surface of the heated body 20 with the fixing film 24 is a convex curved surface as in the example of FIG. 4, the rubbing is performed as described in the section (2) of (Operation). Side edge of the fixing film in the rubbing direction, especially on the upstream side in the film running direction
The sliding resistance between 21 g (Fig. 4) and the fixing film 24 can be reduced. Or, it can be eliminated and the running drive load of the fixing film can be reduced, and a small and inexpensive low torque one can be used as a drive source.Also, the fixing film 24 can be prevented from being scratched, stretched, or torn. The film's durability can be extended.

As a comparative example, FIG. 6 shows a heating element 20 in which a heating element 21d is provided on a flat surface of an alumina substrate 21b, and the surface of the alumina substrate including the heating element is covered with a protective layer 21e, that is, the fixing film 2.
4 shows a heating body whose sliding surface with respect to 4 is a flat surface, and in the case of this heating body, sliding of the fixing film 24 with the edge edge portion 21g of the sliding surface, particularly on the upstream side in the fixing film running direction. The resistance increases, the torque of the running drive means of the fixing film must be increased, and the fixing film also becomes damaged.

In this case, the surface of the alumina substrate 21b itself facing the fixing film may be formed into a curved shape with a convex center portion in the running direction of the fixing film, but it is difficult to form a curved surface on the highly rigid alumina surface. Therefore, the cost is increased. Therefore, in the present invention, a heat insulating layer having a curved surface convex in the central portion in the traveling direction of the fixing film is laminated and provided on the surface of the substrate 21b so that the heating film is rubbed against the fixing body of the heating body 20 without processing the curved surface of the substrate itself. The surface can be curved.

In the case of the comparative heating element of FIG. 6, the gap (wedge-shaped inlet space) of the fixing nip inlet 21h formed by the fixing film on the upstream side in the running direction of the fixing film and the pressure roller as the pressure member is heated. It is narrow due to the flat surface of the body and the sliding surface of the fixing film, and when the transfer material sheet P as a recording material carrying the unfixed toner image Ta flutters at this narrow fixing nip entrance 21h, the sheet flickers. The unfixed toner image surface of P easily rubs against the fixing film surface at the entrance 21h of the fixing nip or the angular fixing film portion of the fixing film corresponding to the edge portion 21g, so-called image rubbing easily occurs.

In the case of the present invention, since the sliding surface of the heating element 20 with the fixing film 24 is a convex curved surface, the gap at the fixing nip inlet 21h (FIG. 4) is widened and described in the section (2) of (Operation). As described above, the occurrence of so-called image rubbing can be prevented.

Further, since the heat generating element 21d is provided on the substrate 21b via the heat insulating layer 21e, the heat energy generated from the heat generating element is diffused to the substrate 21b side as described in (2) of the above (Operation). It can be efficiently and effectively transferred to the toner image surface of the transfer material P which is the recording material to be image-fixed by being pressed by the heat insulating layer 21e, that is, through the fixing film.
The thermal efficiency is increased, and the electric power required for fixing can be reduced.

That is, there is a limit to the heat insulating property of the ceramic substrate 21b itself, and according to the experiment, a heating body having a structure in which the substrate 21b is provided with the heating element 21d via the heat insulating layer 21c as shown in FIG. As shown in FIG. 6, the heating element 21d is directly attached to the surface of the substrate 21b.
The fixing power was about 10% lower than that of the one equipped with.

The temperature measuring element 21f may be arranged on the side opposite to the heat generating body 2d with the heat insulating layer 21c in the middle as in the example of FIG.
The temperature gradient between the heating element and the heating element 21d can be directly and accurately detected without substantially causing the phenomenon of deterioration of detection and detection delay, and the temperature of the heating element surface can be accurately adjusted to the required fixing temperature. The key can be controlled.

(5) Others When the end film is used as the fixing film 24 as shown in FIG. 3, if the fixing film on the delivery shaft side is almost entirely wound on the winding shaft side and used, a new roll film is used. It is also possible to use a method of exchanging (winding exchange type).

In the case of such a winding exchange type, the thickness can be reduced regardless of the durability of the fixing film, and the power consumption can be reduced. For example, PET (polyester) as a fixing film
It is possible to use an inexpensive base material such as a film, which is heat-treated and has a thin wall thickness of, for example, about 12.5 μm or less.

Alternatively, since toner offset to the surface of the fixing film does not substantially occur as described above, if the thermal deformation or deterioration associated with the use of the fixing film is small, the used sheet wound on the winding shaft side can be timely It is also possible to use it repeatedly for a plurality of times by controlling the rewinding to the feeding shaft side or reversing the winding shaft side and the feeding shaft side (rewinding repetitive use type).

As the fixing film in the rewinding and reusing type, for example,
It is possible to use a composite layer film in which a polyimide resin film having a thickness of 25 μm is used as a base material having excellent heat resistance and mechanical strength, and a release layer made of fluororesin or the like having high release properties is provided on the surface of the polyimide resin film. At the time of rewinding and reverse traveling, it is preferable to automatically control the pressure release mechanism to keep the pressure contact between the heating body and the pressure roller in the released state.

When it is used multiple times such as rewinding repetitive use type or endless belt type, a felt pad is provided for cleaning the film surface, and a slight release agent such as silicone oil is impregnated to bring the pad into contact with the film surface. For example, the film surface may be cleaned and the releasability may be further improved. In the case where the fixing film is an insulating fluororesin-treated product, static electricity that disturbs the toner image is easily generated in the film. Therefore, in order to deal with the static electricity, it is also possible to perform static elimination processing with a grounding static elimination brush. A bias voltage may be applied to the brush without being grounded to charge the film within a range that does not disturb the toner image. Further, it is also a measure to prevent the image distortion due to the static electricity described above by adding a conductive powder fiber such as carbon black to the fluororesin. In addition, depressurization and conductivity of the pressure roller can be performed by the same means. Further, an antistatic agent or the like may be applied or added.

Regardless of whether the fixing film is an endless belt type, a rewinding exchange type, or a rewinding repetitive use type, the fixing film can be detachably attached to a predetermined portion of the fixing device 11 to facilitate the exchange of the fixing film. it can.

The configuration of the heating element 20 and the control of energization to the heating element 21d are not limited to those of the embodiment, the heating element 20 may be a non-rotating heat roller type, and the heating element 21d may be a thick film resistor or PTC. It may be a ceramic chip array or the like having characteristics, and the energization control may not be pulsed but may be normal energization.

The toner solidified by heating and melting in the heating step may be cooled and solidified by natural heat dissipation, or may be forcedly cooled by arranging an air blowing means, heat dissipation fins or the like.

If the toner is sufficiently melted at a high temperature, if the toner is sufficiently melted at a high temperature in the heating step (fixing nip portion) as shown in FIG. 7, the recording material (transfer material) is immediately transferred without a cooling step after the heating step. The sheet P may be separated from the surface of the fixing film 24.

The apparatus of the above embodiment is a transfer type electronic copying apparatus, but the image forming process / means is a direct type in which a toner image is directly formed and carried on an electrofax paper, an electrostatic recording sheet, or a magnetic recording image forming type. Other copiers, laser beam printers, facsimiles, microfilm reader printers, display devices, recorders, etc. that form an image with heat-fusible toner on a recording material by an appropriate image forming process / means and heat-fix the image. The present invention can be effectively applied to the various image forming apparatuses.

(Effects of the Invention) As described above, according to the present invention, in the toner image heat fixing type image forming apparatus, it is possible to reduce the heat capacity of the heating member which is the heating means without causing the fixing failure or the offset, and the waiting time or It is possible to realize an image forming apparatus capable of always stably outputting an image-formed product having a good fixed image quality with low power consumption and further temperature rise inside the apparatus. Further, the fixing film can be repeatedly used for a long period of time without any problem of wrinkling and without any problem.

In addition, the sliding resistance between the heating element and the fixing film can be reduced to reduce the required torque of the running drive source of the fixing film, and damage such as scratches on the fixing film can be reduced to extend the durability. It is possible to prevent the occurrence of image rubbing due to the contact and sliding contact of the surface of the unfixed toner carrying recording material with the surface of the fixed film in some part, and the fixing power can be reduced by improving the heat insulating property.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view showing a schematic configuration of an apparatus of one embodiment, FIG. 2 is an enlarged view of a fixing device portion, FIG. 3 is a schematic view of another configuration example of the fixing device, and FIG. FIG. 5 is a cross-sectional model view showing the layer structure, FIG. 5 is a cross-sectional model view showing another layer structure, FIG. 6 is a cross-sectional model view showing the layer structure of a heating body of a comparative example, and FIG. 7 is another structure of the fixing device. FIG. 6 is a schematic diagram of an example. 3 is a drum type rotary photosensitive member, 11 is a fixing device, 24 is a fixing film, 20 is a heating member, 21a is a supporting member, 21b is a substrate, 21c is a heat insulating layer, 21d is a heating element, 21e is a protective layer, and 21f is a thermometer. Element, 28
Is a pressure roller, and P is a transfer material sheet.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shigeo Kimura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroyuki Adachi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (56) Reference JP 59-68766 (JP, A) JP 55-39303 (JP, A) JP 57-124878 (JP, A) JP 64-49071 (JP, A) JP-A-64-19376 (JP, A) JP-A-64-263679 (JP, A)

Claims (1)

[Claims] 1. An image forming means for forming an unfixed toner image corresponding to desired image information by carrying a toner made of a heat-meltable resin or the like on a recording material surface, a fixing film, and running of the fixing film. A driving unit, a heating body fixedly supported on one side of the fixing film, and a heating body disposed on the other side of the fixing film, and the recording material is unfixed with respect to the heating body via the fixing film. A fixing member provided with a pressure member for closely contacting the surface on which the deposited toner image is carried, and fixed by running in the same direction at the same speed as the carrying speed of the recording material carrying the unfixed toner image carried from the image forming means side. A toner image heat fixing means for introducing the recording material between the film and the pressure member to heat and fix the unfixed toner image on the surface of the recording material, and the heating body of the toner image heat fixing means is At least And a heat insulating layer laminated on the surface of the substrate facing the fixing film and having an outer surface in the shape of a curved surface convex in the central portion in the running direction of the fixing film, and provided on a substantially top surface of the convex outer surface of the heat insulating layer. An image forming apparatus having a heating element.