JP2586616B2 - Fixing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device in 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 recorder. .

More specifically, a recording material (electrofax sheet, electrostatic recording sheet, transfer material sheet, A non-fixed toner image corresponding to the target image information is formed and supported 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 recorded on a recording material surface carrying the image. The present invention also relates to a fixing device in an image forming apparatus that performs a heat fixing process as a permanently fixed image.

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

A belt fixing system as disclosed in U.S. Pat. No. 3,578,797 is also known. This is done by bringing the toner image into contact with the heating element web and heating it to its melting point to melt it.After melting, the toner is cooled to a relatively high viscosity, and the toner image is removed from the heating element web in a state where the tendency to adhere to the toner is reduced. 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 conventional hot roll fixing method as described above,
The belt fixing method has the following problems.

Thermal roll fixing method It takes a considerable time to rise to a predetermined temperature, during which time the image forming operation is prohibited. That is, there is a so-called wait time.

Large electric power is required because heat capacity is required.

A high heat-resistant roller bearing requires a heat-resistant special bearing.

The configuration is such that the roller touches the roller directly, which is dangerous and requires a protective member.

The recording material is wrapped around the roller due to the constant temperature and the curvature of the roller, so that a jam problem of the recording material is easily observed.

Belt fixing method This method also has the same problems as those of the above-described heat roller fixing method, such as the wait time and large power consumption.

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 a fixing failure or an offset. As a result, the standby time, the power consumption, and the It is an object of the present invention to provide an image forming apparatus having a small temperature rise in the apparatus and having other remarkable features.

(Means for Solving the Problems) The present invention provides a heating element in which a heating element and a temperature detecting element are provided on a substrate, a film in contact with the heating element, and a nip with the heating element via the film. A fixing member for fixing the unfixed image on the recording material by heat from the heating element through the film while nipping and conveying the recording material carrying the unfixed image in the nip. The fixing device according to claim 1, wherein the temperature detecting element is provided on a surface of the substrate on a nip side, and the heating element is provided on the nip side of the temperature detecting element.

(Operation) (1) The recording material to be fixed between the fixing film and the pressing member, which is driven in the same direction at the same speed as the recording material conveyance direction, is unfixed toner on the fixing film surface. While the surface on the image carrying side is in close contact with the fixing film and receives a pressing force on the mutual press contact portion (fixing nip portion) between the heating element and the pressing member, surface displacement occurs due to a speed difference therebetween, and wrinkles occur. It passes over the body without overlapping.

Heating process In the process of passing through the mutual pressure contact portion, the unfixed toner image on the surface of the recording material is heated and softened and melted by the heating element via the fixing film, and particularly the surface layer portion thereof greatly exceeds the melting point of the toner and is completely softened and melted. In this case, the heating element, fixing film, toner image,
The recording material is satisfactorily pressed and adhered by the pressing member, and heat is effectively transferred, so that the toner is sufficiently softened and melted by heating for a short time, and good fixing properties are obtained. On the other hand, the temperature rise of the recording material itself is extremely small in practice, and the waste of heat energy is small. In other words, the recording material itself is not heated substantially, and only the toner is heated and softened and melted effectively, and the heat fixing of the toner image can be satisfactorily executed with low power.

Here, note the softening and melting of the toner described in the present invention. The temperature, which is conveniently expressed as the "melting point" of the toner, means the minimum temperature required for the toner to be fixed. In some cases. Therefore, even when the term “melting” is used for the sake of convenience for fixing, the viscosity may actually decrease such as softening. The present invention includes such a case. Similarly, when the expression that the toner is cooled and fixed is used for convenience, depending on the toner, it may be more appropriate to increase the viscosity rather than to solidify. The present invention includes such a case.

Cooling process The toner image which has passed through the mutual pressure contact part of the heating element and the pressure member in close contact with the fixing film surface and the heated softened and melted recording material part remains in close contact with the fixing film surface even after passing through the pressure contact part Is continued for a while, and during this time, a cooling step is performed, and the heat of the toner softened and melted in the heating step is radiated 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. In addition, while the adhesive / fixing force on the recording material side increases, that on the fixing film side extremely decreases. When the toner is heated and softened and melted in the heating step, the toner is pressed by the pressing member, so that at least a part of the toner image permeates into the recording material surface layer, and the permeated portion is cooled and solidified. The adhesive effect of the solidified toner on the recording material side increases due to the anchor effect of the toner.

Separation (separation) step After the toner image is cooled and solidified by the above-mentioned cooling step, the recording material is sequentially separated from the fixing film surface.
At the time of separation, the toner image has a sufficiently large adhesive / adhesive force to the recording material due to cooling and solidification, and has a very small state with respect to the fixing film, so that the image-fixed recording material portion causes toner offset with respect to the fixing film. It is easily separated one after another.

The recording material to be image-fixed is brought into close contact with the fixing film at the same speed so that the unfixed toner image carrying surface faces the fixing film surface running in this way, and the toner image is heated and melted by a heating element through the fixing film. Since the recording material and the fixing film are separated from each other after the toner image is cooled and fixed, no toner offset occurs with respect to the fixing film, and a heating element having a small heat capacity is used, and power is supplied to the heating element. This method can be performed with a simple configuration, and by maintaining a heating element at a temperature sufficiently high with respect to the temperature (melting point or softening point) at which the toner is to be heated for fixing, the toner image can be efficiently produced. Heating can be performed, and a sufficiently good fixing without a fixing failure can be achieved with a small amount of energy. As a result,
This has the effect of obtaining an image forming apparatus with a small standby time during use of the apparatus, low power consumption, and a small rise in temperature inside 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 separated from the fixing film surface immediately after the toner is sufficiently melted at a high temperature in the heating step. The cooling process after the process may be abolished, and it belongs to the scope of the present invention.

(2) Since the heating member is fixedly supported, the fixing nip portion, that is, the portion between the running fixing film and the heating member at the pressure contact portion between the heating member and the pressing member which presses each other across the fixing film. It is easy to generate a temperature gradient in the heated body due to the heat energy taken by the recording material to be fixed and the traveling fixing film that is introduced and passed through the fixing film. Therefore, it is impossible to accurately detect the temperature of the fixing nip portion in real time. This is difficult, and the temperature of the fixing nip, that is, an appropriate fixing temperature to be controlled at a predetermined temperature, tends to fluctuate greatly due to a delay in temperature detection.

Further, if the heating element mounting substrate of the heating element is made of a material having good thermal conductivity in order to reduce the temperature gradient in the heating element and to solve the above-described problem, the amount of heat dissipation increases and the thermal efficiency deteriorates.

In the present invention, as described above, the temperature detecting element of the heating element is provided on the surface of the heating substrate on the fixing nip side, and the heating element of the heating element is provided on the fixing nip side of the temperature detecting element. From the above, the temperature of the fixing nip portion of the heating element, that is, the fluctuation of the fixing temperature is directly detected by the temperature detecting element, that is, more accurately, without substantially causing the phenomenon of accuracy reduction and detection delay due to the temperature gradient as described above. It is possible to detect in real time, which makes it easy to control the temperature of the surface of the heating element appropriately and stably maintain the fixing temperature at a predetermined substantially constant value, and to obtain a good fixed image without fixing unevenness. It is possible to always output.

Since the heating element of the heating element is provided on the side of the fixing nip with respect to the temperature detecting element, it is possible to prevent the heat from being taken off at the temperature detecting element and uneven temperature in the fixing nip.

(Embodiment) The present embodiment is an electrophotographic copying apparatus of a reciprocating type, a rotating drum type and a transfer type on a document table.

(1) Overall Schematic Configuration of the Apparatus (FIG. 1) In FIG. 1, reference numeral 100 denotes an apparatus housing, and 1 denotes a reciprocating motion made of a transparent plate member such as a glass plate disposed on an upper plate 100a of the apparatus housing. It is a document mounting table of a mold, and is driven to reciprocate at a predetermined speed to the right side a and the left side a 'on the machine housing upper surface plate 100a in the drawing.

G is an original, which is placed on the upper surface of the original placing table 1 with the image side to be copied facing downward according to a predetermined placing reference;
The original is set by placing the original cover 1a on top of the cover.

Reference numeral 100b denotes a slit opening serving as a document illuminating unit which is opened on a surface of the machine housing upper plate 100a with a direction perpendicular to the reciprocating movement 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 table 1 sequentially passes through the position of the slit opening 100b from the right side to the left side during the forward movement of the document table 1 to the right side a. During the passage, the light L of the lamp 7 is received through the slit opening 100b and the transparent document table 1 for illumination scanning. The reflected light of the illumination scanning light on the document surface is image-formed and exposed on the surface of the photosensitive drum 3 by the short-focus 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 indicated by an arrow b at a predetermined peripheral speed around a center support shaft 3a. The charger 4 was subjected to a uniform charging process of positive or negative polarity, and the uniformly charged surface was subjected to the image forming exposure (slit exposure) of the original image to form an image on the surface of the photosensitive drum 3. An electrostatic latent image corresponding to a document image is sequentially formed.

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

S denotes a cassette in which transfer material sheets P as recording materials are stacked and stored, and the sheets in the cassette are fed one by one by the rotation of the feed roller 6, and then the toner on the drum 3 is moved by the registration roller 9. When the leading end of the image forming section reaches the transfer discharger 8, the leading end of the transfer material sheet P also reaches the position between the transfer discharger 8 and the photosensitive drum 3, and the timing is synchronized so that they coincide with each other. Will be fed. Then, the transfer discharger 8 is applied to the surface of the sheet.
As a result, the toner image on the photosensitive drum 3 side is sequentially transferred.

The sheet to which the toner image has been transferred by the transfer unit is sequentially separated from the surface of the photosensitive drum 3 by a separation unit (not shown), and is guided by a conveyance guide 10 to a fixing device 11 described later to heat the unfixed toner image carried. After being subjected to the fixing process, the sheet is discharged onto a discharge tray 12 outside the apparatus 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 by receiving the removal of adhered contaminants such as untransferred toner by the cleaning device 13.

(2) Fixing device (FIGS. 1 and 2) 24 is an endless belt-shaped fixing film, and includes a left driving roller 25, a right driven roller 26, and a driving roller.
A low-heat-capacity linear heating element 20 as a heating element fixedly arranged and supported by the heater holder 23 below the separation roller 27 disposed below the driving roller 25 and the driven roller 26; It is stretched between 25, 26, 27 and 20.

The driven roller 26 is an endless belt-shaped fixing film 24.
The fixing film is also used as the tension roller.
Reference numeral 24 denotes a transfer material sheet P carrying an unfixed toner image Ta conveyed from the image forming unit 8 on the upper surface at a predetermined peripheral speed in the clockwise direction accompanying the clockwise rotation of the drive roller 25.
Is rotated at wrinkles, meanders, and speed delays at the same peripheral speed as the transport speed of.

Reference numeral 28 denotes a pressure roller having a rubber elastic layer having good release properties such as silicon rubber as a pressure member, and the endless belt-shaped fixing film 24 sandwiching the descending side film portion of the heating member 20 so as to sandwich the same. The transfer material sheet P is rotated counterclockwise in the forward direction in the transport direction of the transfer material sheet P by being pressed against the lower surface by a biasing means (not shown) with a contact pressure of, for example, a total pressure of 4 to 7 kg.

Endless belt-shaped fixing film 24 driven to rotate
Is repeatedly used for heating and fixing the toner image, so that a thin material having excellent heat resistance, releasability and durability and having a thickness of generally 100 μm or less, preferably 50 μm or less is used. For example, a single-layer film of a heat-resistant resin such as polyimide / polyetherimide / PEA (tetrafluoroethylene-perfluoroalkylvinyl ether copolymer resin), or a composite layer film such as a 20 μm-thick film having PTFE at least on the image contacting surface side For example, a releasable coat layer obtained by adding a conductive material to (tetrafluoroethylene resin) and having a thickness of 10 μm is applied.

In the present embodiment, the low-heat-capacity linear heating element 20 as a heating element is a cross-section model (transfer of the fixing film) as an insulating substrate (heater substrate) 21 as shown in the schematic cross-sectional view of FIG. Length perpendicular to the direction)
Using an alumina thin thin plate of 240mm, width 10mm, thickness 1mm,
A temperature detecting element 21a is disposed along a longitudinal direction substantially at the center of the surface of the substrate facing the fixing film (hereinafter referred to as the substrate outer surface).
Pt film (resistance temperature detector) 200 µm wide and 10 µm thick
Formed by screen printing in a linear or band shape with an insulating layer 21b on the outer surface of the recording plate including the temperature detecting element 21a.
A heat-resistant glass film having a thickness of 100 μm is formed by screen printing, and is laminated on the insulating layer 21b along the longitudinal direction at the center of the insulating layer 21b with respect to the temperature detecting element 21a via the insulating layer 21b. An Ag / Pd film as 22 was formed by screen printing in a width of 1.5 mm and a thickness of 20 μm in a linear or band shape, and a heat-resistant glass layer as a protective layer 21c was formed on the insulating layer 21b including the heating element 22 to a thickness of 10 μm.
Screen printing.

As the heating element 22, other than Ag / Pd in the above example, a resistor such as RuO ₂ , nichrome, Ta ₂ N or the like, a surface heating element such as a ceramic heater, or the like can be used.

As the substrate 21, various ceramics, heat-resistant glass, heat-resistant resin such as PPS / PI, etc. can be used in addition to the alumina of the above example.

The heating element 22 is energized from both longitudinal ends to generate heat over the entire length of the heating element 22. The temperature of the heating element (fixing temperature) at the fixing nip is detected by a temperature detecting element 21a, and the detected output turns on / off the pulse-like energization to the heating element 22 by an energization control circuit (not shown) or the pulse width. Under the control, the temperature of the fixing nip, that is, the fixing temperature is controlled to a predetermined value.

In this case, the temperature detecting element 21a is provided on the surface of the heating body substrate 21 on the side of the fixing nip, and the heating element 22 is
a, the temperature detecting element 21a can accurately detect the temperature of the fixing nip in real time, and appropriately controls the temperature of the surface of the heating body to control the fixing temperature. It becomes easy to stably maintain a predetermined substantially constant value. And the heating element 22 is a temperature sensing element
Since it is provided on the fixing nip side with respect to 21a, it is possible to prevent heat from being taken away at the temperature detecting element portion and uneven temperature from occurring in the fixing nip.

In this example, the energization has a pulse-shaped waveform of DC 100 V and a cycle of 20 msec, and has an energization control circuit configuration that provides a pulse corresponding to a desired temperature and energy release amount controlled by the temperature detection element 21a by changing the pulse width. The pulse width is controlled in the range of about 0.5 to 5 msec, and the heating element 22 instantly rises to about 200 to 300 ° every time a pulse is input.
Further, in this example, a leading end / rear end detecting sensor (not shown) of the sheet is provided closer to the fixing device on the upstream side of the fixing device 11 in the transfer material sheet conveying direction, and the heating element 22 is detected by a sheet detection signal from the sensor. During the energization period, the sheet P is
Is controlled only for the necessary period of passing.

The fixing film 24 is not limited to the endless belt shape.
As shown in the figure, the end-fixing film 24 wound around the feed shaft 30 is stopped by the take-up shaft 31 between the heating body 20 and the pressure roller 28, under the separation roller 27, and the like. In this case, the transfer material sheet P may travel from the delivery shaft 30 to the winding shaft 31 at the same speed as the transport speed of the transfer material sheet P.

(3) Fixing operation The leading end of the transfer material sheet P carrying the unfixed toner image Ta on the upper surface, which has been conveyed from the transfer unit 8 to the fixing device 11 by the image forming operation of the apparatus in response to the image forming start signal, is fixed to the fixing device. The rotation (or running) of the fixing film 24 is started when it is detected by the above-mentioned sensor (not shown) disposed closer to it,
The transfer material sheet P is guided by the guide 29 and enters between the fixing sheet 24 and the pressure roller 28 at the pressure contact portion N between the heating body 20 and the pressure roller 28 (fixing nip portion) to form an unfixed toner image. The surface adheres to the lower surface of the fixing film 24 in the same direction as the conveying speed of the sheet P and moves in the same direction in the same direction as the sheet P, so that the surface of the fixing film 24 and the heating element 20 are overlapped with the fixing film 24 without causing surface deviation or wrinkling. It passes between the mutual pressure contact portions N with the pressure roller 28 while receiving a clamping force.

The toner image is heated and softened and melted as described in the item (1)-of the above-mentioned (action) as a heating step in the process of passing through the mutual pressing portion. As described above, in the heating step in the present embodiment, a linear heating element 22 is provided on the substrate 21, and the heating element 22 having a low heat capacity formed integrally with the substrate 21 is energized in a pulse shape to repeat heat generation. This is performed by the configured heating element 20. In other words, the toner image Ta on the sheet P conveyed at the predetermined conveying speed, together with the fixing film 24 on which the sheet P is conveyed, is a linear heating unit which is sequentially determined according to the width of the heating element 22 of the heating element 20. After being fed into the effective width W and receiving heat, it becomes a softened / melted image Tb.

The sheet portion that has passed through the mutual press-contact portion N between the heating member 20 and the pressure roller 28 is extended between the heating member 20 and the separation roller 27 until it reaches the position of the separation roller 27, and the fixing portion is traveling forward. It is conveyed while keeping it in close contact with the film part.

This transporting process is defined as a cooling process (1) of the above (action).
As described in section-, the heat of the softened / molten 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 traveling direction of the fixing film 24 is turned in a direction away from the sheet P along the surface of the separation roller 27 having a large curvature, and the fixing film 24 and the sheet P are separated from each other ( Then, the sheet P is discharged to the discharge tray 11. By the time of the separation, the toner is sufficiently cooled and solidified, and the above (action) (1)-
As described in the section, the adhesion / fixing force of the toner to the sheet P is sufficiently large and the adhesion to the fixing film 24 is extremely small. Therefore, the separation between the fixing film 24 and the sheet P substantially reduces the toner offset with respect to the fixing film 24. It is easily done sequentially without any random occurrence.

In the present embodiment, since the linear heating element 22 of the heating element 20 instantaneously rises to a sufficiently high temperature relative to the toner melting point (or fixable temperature) by energization, preheating of the heating element is unnecessary, Heat transfer to the pressure roller 28 during non-fixing is small. Also, at the time of fixing, a fixing film, a toner image, and a sheet are interposed between the heating body 20 and the pressure roller 28, and a sharp temperature gradient occurs due to a short heat generation time.
The temperature of the pressure roller 28 is maintained at a temperature lower than the melting point of the toner even if the temperature of the pressure roller 28 is low and the continuous image formation required for practical use 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 particularly, the surface portion thereof is completely removed. Softens and melts. At this time, the heating member, the fixing film, the toner image, and the sheet are satisfactorily adhered by the pressure roller 28, and the 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, the energy saving can be achieved by limiting the heating time.

A small heating element is sufficient and the heat capacity is small.Therefore, there is no need to raise the temperature of the heating element in advance.Therefore, power consumption during non-image formation can be reduced, and temperature rise in the apparatus can be prevented. Become.

In the present embodiment, since the temperature of the pressure roller 28 is maintained lower than the melting point of the toner as described above, it is possible to promote the heat radiation of the toner image in the cooling step following the toner image heating step. . Therefore, the time required for cooling can be reduced, and the size of the apparatus can be reduced.

The heating element 20 of FIG. 4 was incorporated into the fixing device 11 of the image forming apparatus of FIG. 1, and a thermocouple was attached to a rubbing portion with the fixing film 24 to conduct electricity and fix.
The detected temperature of the thermocouple and the detected temperature of the temperature detecting element 21a were about 4 to 5 ° C. at the maximum, and extremely accurate temperature detection was possible.

When PWM control was performed so that the temperature of the heating element 22 becomes 200 ° C. based on the detected temperature, a good image without a fixing defect due to a low temperature and no offset due to a high temperature was obtained.

Further, when a material having poor heat conductivity such as heat-resistant glass is used as the substrate 21, heat radiation through the substrate 21 is reduced, heat efficiency is improved, and the temperature of the heating body 20 is increased quickly. 450W is required to fix the first sheet in 5 seconds of preheating, but 380W is required for a glass substrate, which is more preferable because it saves energy.

(4) Others As shown in FIG. 3, when a fixed film is used as the fixing film 24, when the fixing film on the delivery shaft side is almost completely wound on the winding shaft side and used, a new roll-wound film is used. It can be replaced (rewinding replacement type).

In the case of such a take-up exchange type, the thickness can be reduced regardless of the durability of the fixing film, and the power consumption can be reduced. For example, an inexpensive base material such as a PET (polyester) film or the like may be used as the fixing film, and a heat-treated thin film having a thickness of about 12.5 μm or less may be used.

Or, since the toner offset to the fixing film surface does not substantially occur as described above, if the thermal deformation or deterioration accompanying the use of the fixing film is small, the used sheet wound on the take-up shaft side can be removed in a timely manner. And rewinding control to the shaft side,
Alternatively, it can be used a plurality of times by reversing the winding shaft side and the sending shaft side, etc. (rewinding repetitive use type).

In the rewinding repeated use type, as the fixing film, for example, a 25 μm thick polyimide resin film is used as a base material having excellent heat resistance, mechanical strength, etc., and a release layer made of a highly releasable fluororesin or the like on its surface. It is preferable to automatically control the pressure release mechanism during reverse rewinding to keep the contact between the heating element and the pressure roller in the released state.

In the case of multiple use such as the rewinding repetition type or the endless belt type, a felt pad is provided for cleaning the film surface, and the pad is applied to the film surface by impregnating with a young release agent, for example, silicone oil. The film surface may be cleaned and the releasability may be further improved by making contact with the film surface. In the case where the fixing film is an insulating fluororesin-treated product, static electricity that disturbs the toner image is likely to be generated on the film. Therefore, in order to cope with this, it is preferable to remove the static electricity with a grounded removing brush. A bias voltage may be applied to the brush without grounding to charge the film within a range that does not disturb the toner image. Further, it is one measure to add conductive powder fibers, for example, carbon black or the like, to the fluororesin to prevent the above-mentioned image disturbance due to static electricity. In addition, the charge roller can be de-charged and made conductive by the same means. Further, an antistatic agent or the like may be applied or added.

Fixing film is endless belt type, rewindable type,
Regardless of the type of rewinding and repetitive use, the replacement of the fixing film and the like can be facilitated by making the cartridge structure detachable at a predetermined portion of the fixing device 11.

The configuration of the heating element 20 and the control of energization to the heating element 22 are not limited to those in the embodiment.The heating element 20 may be a non-rotating heat roller type, and the heating element 22 may be a thick film resistor or PTC. A ceramic chip array or the like having characteristics may be used, and the energization control may not be given on the pulse but may be ordinary energization.

The cooling and solidification of the toner heated and melted in the heating step may be performed by natural heat radiation, or may be performed by forced cooling by arranging a blowing means, a heat radiation fin, or the like.

If the toner melts sufficiently at a high temperature, as shown in FIG. 5, if the toner is sufficiently melted at a high temperature in a heating step (fixing nip portion), a recording material (transfer material) is immediately provided without a cooling step after the heating step. The sheet P may be separated from the fixing film 24 surface.

The above-described apparatus is a transfer-type electronic copying apparatus.
The image forming process and means are electrofax paper,
An image is formed on a recording material with a heat-fusible toner by a direct type in which a toner image is formed and held directly on an electrostatic recording paper or the like, a magnetic recording image forming type, or any other appropriate image forming process or means, and heated. The present invention can be effectively applied to various image forming apparatuses such as copiers, laser beam printers, facsimile machines, microfilm reader printers, display devices, and recording machines of a fixing system.

(Effects of the Invention) As described above, the present invention can reduce the heat capacity of the heating element as the heating means without causing defective fixing or offset in the image forming apparatus of the toner image heat fixing type. It is possible to realize an image forming apparatus capable of constantly and stably outputting an image-formed product having a good fixed image quality with low power consumption and low internal temperature rise. Further, the fixing film can be repeatedly used for a long period of time without any problem without generation of wrinkles without any problem.

Further, the temperature detecting element of the heating element is provided on the fixing nip portion side of the heating element substrate, and the heating element is provided on the fixing nip portion side of the temperature detecting element. It is possible to more accurately detect the fluctuation of the temperature, that is, the fixing temperature in real time, thereby easily controlling the temperature of the surface of the heating element appropriately and stably maintaining the fixing temperature at a predetermined substantially constant value. It is possible to always output a good fixed image without fixing unevenness or the like.

Since the heating element of the heating element is provided closer to the fixing nip portion than the temperature detecting element, it is possible to prevent heat from being taken away at the temperature detecting element portion and uneven temperature at the fixing nip portion.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional front view showing a schematic configuration of an embodiment of the apparatus, FIG. 2 is an enlarged view of a fixing device portion, FIG. 3 is a schematic diagram of another configuration example of the fixing device, and FIG. Cross section schematic diagram, fifth
The figure is a schematic diagram of another configuration example of the fixing device. Reference numeral 3 denotes a drum-type rotating photoreceptor, 11 denotes a fixing device, 24 denotes a fixing film, 20 denotes a heating element, 21 denotes a substrate, 21a denotes a temperature detecting element,
Is a heating element, 28 is a pressure roller, and P is a transfer material sheet.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masahide Kinoshita 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroyuki Adachi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (56) References JP-A-59-68766 (JP, A) JP-A-57-161766 (JP, A) JP-A-56-19889 (JP, A) JP-A-62-222281 (JP, A A)

Claims (1)

(57) [Claims] 1. A heating element having a heating element and a temperature detecting element provided on a substrate, a film in contact with the heating element, and a pressure member forming a nip with the heating element via the film. A fixing device that nips and conveys a recording material carrying an unfixed image in the nip and fixes the unfixed image on the recording material by heat from the heating body through the film; A fixing device provided on a nip side surface, wherein the heating element is provided on the nip side with respect to the temperature detecting element.