JPH02143278A - Picture forming device - Google Patents

Abstract

PURPOSE:To improve the safety of a picture forming device by providing an electric current narrowing section having a cross-sectional area smaller than that of the part of a conductive heat producing body in the effective length area corresponding to the recording material passing width section of the heat producing body in the excessive length section of the heat producing body outside the effective length area adjacently to the area. CONSTITUTION:A electric current narrowing section 22b is formed of the same material as that used for forming a heat producing body 22 in an effective length area L adjacently to the effective length area and the width W1 of the section 22b is made narrower than the width W of the heat producing body in the effective length area so that the the part functioning as a fusing section can have a small cross-sectional area. In case abnormal power supply, such as continuous power supply, etc., caused by abnormality in a power source or abnormal temperature control, occurs, the temperature at the heat producing body 22 and electric current narrowing section 22b abruptly rises. Because of the line width ratio between the body 22 and section 22b, the temperature at the section 22b reaches the fusing temperature and blows before the temperature at the effective length area of the heating body 22 causes a fixing film 24, press roller 27, transfer material P, etc., to produce fire or smoke. When the section 22b blows, the power supply to the heating body 22 is discontinued.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to image forming apparatuses such as copying machines, laser beam printers, facsimile machines, microfilm reader printers, image display devices, and recording machines.

More specifically, recording materials (electrofax sheets, static 7m recording sheets, transfer material sheets, An unfixed toner image corresponding to target image information is formed and carried on the surface of a sheet of paper (such as printing paper) by a direct method or an indirect (transfer) method, and the unfixed toner image is a record carrying the image. The present invention relates to an image forming apparatus that performs heat-fixing processing as a permanent 1^1 image on a material surface.

(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 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 a toner image has been formed is heated while being nipped and conveyed.

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

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

Heat roll fixing method ■It takes a considerable amount of time to reach a predetermined temperature, during which time image formation is prohibited.

That is, there is a so-called wait time.

■Because it requires heat capacity, a large amount of electric power is required.

■A special heat-resistant bearing is required because the roller temperature is high for rotating rollers.

■The rollers are configured to be touched directly by hand, which may be dangerous and require protective materials.

■Due to the roller's constant temperature and curvature, the recording material wraps around the roller and the recording material jams. This makes it easy to see the trouble.

Belt fixing method This method also has problems such as the zero term and zero term of the heat roller fixing method, wait time for studs, and large power consumption.

The present invention solves the problems of the above-mentioned conventional apparatus, and eliminates fixing failure and offset.
The purpose of the present invention is to provide an image forming apparatus that can reduce the heat capacity of the +n heating element, thereby reducing standby time, power consumption, and internal temperature rise, and has other remarkable features. do.

(Means for Solving the Problems) The present invention provides an image forming means that forms an unfixed toner image corresponding to target image information by supporting a 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 Lk fixing film;
A heating body is placed on one side of the fixing film, and a heating body is placed on the other side of the fixing film. The fixing film, which is equipped with a pressure member for bringing the two into close contact with each other, 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 pressurizing film as described above. a toner image heat fixing means for introducing the recording material between the recording material and the recording material and heat fixing the unfixed toner image onto the surface of the recording material;
It is a low heat single linear heating element that has a linear or band-shaped current-carrying heating element that generates heat by being energized in the longitudinal direction, with the length extending in the transverse direction of the fixing film, and the effective length corresponds to the middle part of the current-carrying heating element where the recording material passes. The extra length of the heating element outside the effective length range has an energization bottleneck part continuous with the heating element part within the effective length range and having a cross-sectional area smaller than the cross-sectional area of the heating element part. This is an image forming apparatus.

(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 conveyance direction of the recording material. When the image-bearing side is in close contact with the fixing film and is overlapping with the fixing film, the heating body and the pressure member are subjected to a squeezing force at the mutual pressure contact area (fixing nip area). They overlap as one and pass in close contact with each other without coming close to each other.

■Heating process During this process of passing through the mutual contact area, the unfixed toner image on the recording material surface is heated and softened and melted by the heating body through the fixing film, and in particular, the surface layer is completely softened and melted, exceeding the toner melting point. do. In this case, the heating body, fixing film, toner image, and recording material are well compressed and adhered to each other by the pressure member at the mutual pressure contact portion of the heating body and the pressure member, and heat is transferred effectively, so that the heat can be 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 waste of thermal energy is minimal. In other words, the recording material itself is not heated substantially, only the toner is effectively heated to soften and melt, and the heating chamber n of the toner image can be satisfactorily performed with low electric power.

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. Even if it is conveniently expressed as melting during fixing, the viscosity may actually decrease to the extent of softening. The present invention also includes such cases. Similarly, even when it is conveniently expressed that the toner has cooled and stabilized by +61, depending on the toner, it may be more appropriate to say that the toner has become viscous rather than assimilated. 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 heated, softened and melted is kept in close contact with the fixing film 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. As a result of this cooling and assimilation, the cohesive force of the toner becomes extremely large, causing it to behave as a group, and while the adhesion and fixing force to the recording material side increases, the cohesive force to the fixing film side extremely decreases. When the toner is softened and melted by heating in the second heating process, it is pressed by a pressure member, so at least a part of the toner image penetrates into the surface layer of the recording material, and the permeated portion Due to the anchor effect caused by cooling and assimilation, the adhesion and adhesion of the cooled and assimilated toner to the recording material D1 increases.

(2) Separation (minute) step After the toner image is cold solidified in the above-mentioned 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 causes toner offset with respect to the constant n film. They are easily separated into layers one after another without having to do anything.

In this way, the recording material to which the image is to be fixed is caused to run closely at the same speed so that the surface carrying the unfixed toner image is on the surface of the moving fixing film, and the toner image is transferred by the heating body through the fixing film. Heat it to melt it,
Since the recording material and the fixing film are spaced apart after the toner image has been cold-fixed, toner offset with respect to the fixing film does not occur. It becomes possible to perform simple heating (f) later on by using a heating element with a temperature sufficiently high relative to the temperature (melting point or softening point) at which the toner should be heated in order to fix it. This makes it possible to heat the toner image efficiently, enabling good fusing with less energy and no fusing defects.As a result, standby time when using the device, power consumption, and This achieves the effect of obtaining an image forming apparatus with a small internal temperature rise.

If the toner melts sufficiently at a high temperature among the three processes mentioned in - - Heating, ■ Cooling, and ■ Idea, the recording material should be placed on the fixing film surface immediately after the toner is melted at a sufficiently high temperature in the heating process. Separate layers from and cool after heating T)
This step may be omitted and falls within the scope of the present invention.

(2) Since the heating element used in the present invention is a low heat capacity linear heating element including the above-mentioned linear or band-shaped current-carrying heating element, the current-carrying temperature increase rate of the heating element part is extremely fast, and therefore the above-mentioned ( Although it has the initial point as described in section 1), on the other hand, if a situation occurs where the heating element overheats due to V running of the control microcomputer, for example, the conventional heating roll In the case of a normal heat fixing device such as a type, it is possible to take measures to cut off the current supply by adding a temperature fuse means or a thermoswitch means, but the low heat capacity linear heating element used in the present invention is capable of increasing the temperature. Because the speed is fast, even if a temperature fuse means or thermoswitch means is added, the operation of these means will cut off the current, and the niI will overheat and reach the ignition temperature, heating the fixing film, material, pressure member, etc. It is assumed that this may cause damage or smoke.

Therefore, as described above, the present invention provides an arrangement in which the extra length of the heating element outside the effective length range corresponding to the area where the recording material passes ri> of the energized heating element is connected to the heating element part within the effective length range. The structure includes an energization bottleneck portion having a cross-sectional area smaller than that of the cross-sectional area.

That is, when the current-carrying heating element enters the pass-through state due to a power supply abnormality or temperature control abnormality, the effective length range of the current-carrying heating element reaches an overheating state.The current-carrying bottleneck provided in the extra length of the reed overheats. When the melting temperature is reached, the current supply bottleneck is melted and the current supply to the heating element is cut off.

Therefore, it is possible to strictly prevent the entire length of the energized heating element from overheating and reaching the ignition temperature, causing the fixing film, recording material, pressure member, etc. to become heated to 1 (11) or smoke.

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

(1) Overall schematic configuration of the device (Fig. 1) In Fig. 1, 100 is a device housing, and 1 is a reciprocating motion consisting of a transparent plate member such as a glass plate disposed on the top plate 100a of the machine housing. It is a type original document mounting table, and is driven to move back and forth at a predetermined speed on the top plate 100a of the machine casing in directions t to a and to the left a in the drawing, respectively.

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

100b is a direction perpendicular to the reciprocating direction of the machine casing-F face plate 100a, g4a (direction perpendicular to the plane of the paper)
This is a slit opening as the illumination section with y7.81 as the longitudinal direction. The downward image surface of the document G placed on the document platform 1 passes through the position of the slit opening 100b sequentially from the 1i side to the left side during the forward movement toward direction a of the yl document platform 1. In the process of passing through, the light from the lamp 7 is received through the slit 100b and the transparent document mounting metal, and the document is illuminated and scanned. The light reflected from the document surface of the illumination scanning light is image-formed and exposed onto the photosensitive drum 3 by the short focus and small diameter imaging element array 2.

The photosensitive tram 3 has a photosensitive layer such as a zinc oxide photosensitive layer, an organic semiconductor photosensitive layer, etc. subjected to N treatment, and is rotated around a central support shaft 3a at a predetermined circumferential speed in the clockwise direction shown by the arrow. band? The surface of the photosensitive drum 3 is subjected to image forming exposure (slit exposure) of the original image written in +Jf on the charged surface. Electrostatic replacement images corresponding to both the yll and yll images are sequentially formed.

This electrostatic latent image is sequentially developed using a toner made of a resin or the like that softens and melts when heated by the 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 transferred to the tram 31- by the registration roller 9. The timing is set so that when the leading edge of the toner image forming section reaches the transfer discharger 8, the leading edge of the transfer material sheet P also reaches the open position of the transfer discharger 8 and the photosensitive tram 3, so that they are aligned. are fed synchronously. Then, a transfer discharger 8 is applied to the feeding sheet.
As a result, the toner images on the photosensitive drum 3 side are sequentially transferred.

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 11, which will be described later, to heat the unfixed toner image carried thereon. After undergoing a fixing process, it is discharged onto a paper discharge tray 2 outside the machine as an image-formed product (copy).

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

(2) Fixing device (Figures 1 and 2) 24 is an endless belt-shaped fixing film, which includes a drive roller 25 on the left side, a driven roller 26 on the right side, a separation roller 27 arranged below the drive roller 25, These four members 2 of a low heat capacity linear heating body 20 as a heating body arranged on the side between the driving roller 25 and the driven roller 26 are parallel to each other.
The suspension is installed between 5, 26, 27, and 20.

The driven roller 26 is an endless belt-shaped fixing film 2.
The fixing film 24 is rotated clockwise at a predetermined circumferential speed as the drive roller 25 rotates in the clockwise direction. It is rotationally driven at the same peripheral speed as the transport speed of the transfer material sheet P carrying the image Ta on its upper surface without wrinkling, meandering, or speed delay.

Reference numeral 28 denotes a pressure roller having a rubber elastic layer with good superplasticity such as silicone rubber, which serves as a pressure member, and presses the heating member 20 by sandwiching the film portion on the first row side of the endless belt-shaped fixing film 24 described above. The lower surface of the transfer material sheet P is brought into opposing pressure contact with the lower surface of the transfer material sheet P with a total pressure of, for example, 4 to 7 kg by a biasing means (not shown), and is rotated in a forward counterclockwise direction in the conveyance direction of the transfer material sheet P.

Endless belt-shaped constant n film 24 that is rotationally driven
Since the toner image is turned over and used for heating and fixing, it is excellent in heat resistance, superplasticity, and durability, and has a thin wall of 100 μm or less, preferably 50 μm or less. For example, a single layer film of a heat-resistant resin such as polyesterimide, polyetherimide, or PEA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin), or an N gold layer film, such as a 20 μm thick film, at least in image contact. A superplastic coating layer made of PTFE (tetrafluoroethylene resin) with a conductive material added to the surface side is applied to a thickness of 10 μm.

The low heat capacity linear heating body 20 as a heating body is made of, for example, Ta, along its length, approximately at the center of the lower surface of the alumina substrate 21, which has a thickness of 1.0 mm, a width of 10 mm, and a length of 240 mrn.
A linear or band-shaped heating element 22 is provided by coating an electric resistance material such as 2 N to riJl, 0mrn. In this example, this linear or band-shaped heating element 2
Electricity is applied to both longitudinal ends of the heating element 22 to cause the heating element 22 to generate heat over its entire length. Energization is DClooV cycle 2
It has a pulse-like waveform of 0 m5ec, and has an energization 1IIJ control circuit configuration that gives a pulse according to the desired temperature and energy release controlled by the temperature detection element 23 by changing the pulse width, and the pulse width is approximately 0.5 ~5m5ec
The temperature of the heating element 22 is instantaneously raised to around 200 to 300°C each time a pulse or manual input is applied. In addition, in this example, the flow f in the transfer material sheet conveyance direction is higher than the constant 71 device 11.
A sheet leading and trailing edge detection sensor (not shown) is provided near the fixing device of ill, and the sensor's sheet detection (IS)
According to No. 1, the period during which electricity is applied to the heating element 22 is controlled to be as long as necessary (t1) while the sheet P passes through the fixing device 11.

The 5 film 24 is not limited to the endless belt shape.
53 As shown in the example in Fig. 53, the fixing film 24 with an end wound around the feed shaft 30 is connected to the heating body 20 and the pressure roller 28.
between the winding glaze 3 and the winding roller 270)F.
1 and run at the same speed as the transport speed of the transfer material sheet P (7) from the feed-out shaft 30 side to the take-up shaft 31 side.

(3) Fixing Execution Operation In response to the image forming start signal, the device performs an image forming operation and carries the unfixed toner image Ta, which has been conveyed from the transfer section 8 to the fixing device 11, on the upper surface. y When the leading edge of the transferred transfer material sheet P is detected by a sensor (not shown) disposed near the fixing device, the fixing film 24 rotates (or runs).
is started, the transfer material sheet P is guided by the kite 29 and enters between the fixing sheet 24 and the pressure roller 22 at the IE contact part N between the heating member 20 and the applying LE rJ-ra 28, and the unfixed sheet P is The toner image surface adheres to the lower surface of the constant n film 24, which is moving in the same direction at the same speed as the conveyance speed of the sheet P, and is heated in the same TFL state as the fixing film 24 without causing surface misalignment or wrinkles. It passes between the phase pressure contact portion N between the body 20 and the pressure roller 28 while being subjected to a clamping force.

This process of passing through the mutually crimped parts is referred to as the heating process (action).
The toner image is heated to soften and melt as described in (1)-0. In the heating process in this embodiment, as described in Section 1, the heating body 20 is provided with a linear heating element 22,
The heating element 2 is configured to repeatedly generate heat by supplying electricity in a pulsed manner to the heating element 22 having a low heat capacity and integrally formed with the heating element 22.
It is carried out by 1. The toner image Ta of the sheet P7 conveyed at a predetermined conveyance speed is sequentially heated in a linear manner determined according to the width of the heating element 22 of the heating element 20, together with the fixing film 24 on which the sheet P is conveyed. Part I
It is fed into the effective width W and is heated to soften and melt the image Tb.
becomes.

The sheet portion that has passed through the phase pressure contact N between the heating body 20 and the pressure roller 28 is spread between the heating body 20 and the separating roller 27 and travels forward until it reaches the position of the separation roller 27. The fixing film continues to be conveyed while remaining in close contact with the fixing film portion.

This conveyance process is considered as a cooling process (1
)-0, the heat of the softened and melted toner TbO is radiated and the toner is cooled and solidified Te.

When the fixing film 24 reaches the position of the separating roller pair 27, the traveling direction of the fixing film 24 is turned away from the surface of the sheet P along the blood of the separating roller 27, which has a large curvature, and the fixing film 24 and the sheet P are separated. Separation (minute t11) The sheet P is transferred to the Ju1 paper tray 11 by 111. By the time of this separation, the toner has sufficiently cooled and solidified, and the sheet P
Since the adhesion/fixing force of the toner to the fixing film 24 is as large as 1 min, and it is extremely small to the fixing film 24, separation of the constant n film 24 and the sheet P will substantially cause toner offset to the fixing film 24. It can easily be done sequentially.

In the tree nut 71h example, the linear heating element 22 of the heating element 20
When energized, the temperature is instantaneously raised to a temperature high enough for the toner's melting point (or constant temperature), so there is no need to heat the heating element, and the transmission to the pressure roller 28 during non-fixing is reduced. There is little fever. Also, during fixing, the fixing film, toner image, or sheet is interposed between the heating member 20 and the pressure roller 28, and the heat generation time is short, resulting in a rapid temperature gradient. Even if image formation is performed at a temperature that is low enough for practical purposes, the temperature is maintained below the melting point of the toner.

In the apparatus of this embodiment having such a configuration, the toner image made of the heat-sensitive toner on the sheet P is first heated and melted by the heating body 20 via the fixing film 24, and in particular, the surface layer 5 is completely melted. The heating element, the fixing film, the toner image, and the sheet are in good contact with each other by the pressure roller 28, and heat is efficiently transferred.Thereby, heating of the sheet P itself is minimized. The toner image can be efficiently heated and melted, especially for one copy.
, π By limiting the heat generation time, energy saving can be achieved.

A small heating element is sufficient, so the heat capacity ii1 is small, and there is no need to heat up the heating element in advance, so power consumption during non-image formation can be reduced, and temperature rise inside the machine can also be prevented. Become.

In this 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 heat dissipation of the toner image in the cooling process following the toner image heating process. . Therefore, the time required for cooling can be shortened, and the device can be downsized.

(4) About the heating element 20 FIG. 4(a) is a bottom view of the heating element 20, that is, a plan view of the heating element 20 and the fixing film 24.

Reference numeral 21 denotes a heat-resistant substrate, which is a horizontally elongated member whose length is in the direction across the fixing film (the direction perpendicular to the running direction of the fixing film). In addition to the above-mentioned ceramics such as alumina, heat-resistant glass, heat-resistant resin such as PI-PPS, etc. can also be used as the material. L is the maximum passage area of the recording material that can be passed through the device, and the length of the board 21 is longer than this middle area, and both ends of the board 21 are made longer than the middle area. It is made to protrude as a long portion 2.l.

Reference numeral 22 denotes a heating element provided approximately in the center of the outer surface of the substrate 21 in the form of a line or band along its length. W is the width dimension of this heating element. As for the material, in addition to Ta, N, etc. as mentioned above, a resistor such as nichrome, Rub2A g/Pd, etc. can also be used.

22a and 22a are the extra lengths R- on both ends of the board 21.
A current-carrying electrode for the heating element 22 is provided on the outer surface of each fi, and is made of metal such as Ag-Au-Cu or RuO2.A.
It is a conductive material such as a resistor such as g/P d. Both ends of the heating element 22 are electrically connected to the 'M' and V522a and 22a, and electricity is supplied in the longitudinal direction. In this example, one end side of the heating element 22 has an energizing bottleneck portion 22 connected to the pole 22a at '1' on that side.
Conductivity is established through b. This current supply bottleneck portion 22b is present in the extra length region f of the substrate 21, and the length portion of the heating element 22 corresponding to the maximum passage [1] portion fl region (2) of the recording material is 9. When the effective length of the heating element is taken as the range, the cross-sectional area (FIG. 4(C)) is smaller than the cross-sectional area M (FIG. 4(b)) of the heating element in this range. In this example, the energization bottleneck 22b and the heating element in the effective length range are formed in series from the same material, the thickness d is the same as that of the heating element in the effective length range, and [1] is set to be effective. Width W of heating element in length range
By setting r1]w to be smaller than , it is possible to create a small cross-sectional area portion that functions as a fusing part.

When the same power is applied to the resistor nQ, the smaller the cross-sectional area, the faster the temperature rise rate when energized, and the cross-sectional area 1(ri J+
It is possible to control the F1 temperature rate by defining 'l.

During fixing, electricity is applied to the heating element 22 through the electrodes 22a and 22a at both ends of the heating element 22 and the current bottleneck 22b, so that the heating element 22 spreads over its entire length. ! Warm it up, and then heat the energization bottleneck 22b. In this case, the temperature of the current supply bottleneck portion 22b increases more than that of the heating element 22 portion. During normal operation, the power to the heating element 22 is turned on and off finely in order to adjust the heating element to a predetermined temperature. Therefore, the heating element 22 and the current supply bottleneck 22b are kept at a certain temperature (lower than the melting temperature of the resistor) or below, and the fixing operation is performed without fail.

In the unlikely event that abnormal conduction such as continuous energization is performed due to a power supply abnormality or temperature control abnormality, the temperature of the heating element 22 and the energizing bottleneck 22b will rise all at once. By setting the line rJJ ratio of 22b, the effective length range of the heating element 22 [1) when the temperature of the equipment reaches the ignition and smoke generation temperature of the fixing film 24, pressure roller 27, transfer material P, etc. It is possible to cause the portion 22b to reach a melting temperature of Km and be fused.If the energization bottleneck portion 22b is fused, the current to the heating element 22 is cut off, so there is no risk of smoke or ignition.

In addition, since the energization bottleneck 22b, which serves as a fusing part in the event of an abnormality, is provided outside the paper passing area, the temperature within the paper passing area is kept constant, and a good fixed image without unevenness can be obtained. Since it can be constructed only from flame-retardant and heat-resistant materials near the flow-through area, it has the effect of assisting smoke generation, ignition, etc. even when the temperature rises or melts due to continuous energization.

Specifically, substrate 21: -1: length 270 mm, width 10+nm,
J size Irnm alumina heating element 22: length 220mm, medium 1.5mm, J
20 μm thick/Pd resistor conduction bottleneck 22b: length 5 m+n, 111300 μm
The heating element 20 was manufactured according to the specifications of Ag/Pd with a thickness of 20 μm (the heating element 22 and the current-carrying bottleneck 22b were simultaneously formed by screen printing), and was incorporated as the heating element in the fixing device 11 of the image forming apparatus described above. So, the surface of the heating element is 200
A4 (
When 30,000 sheets of transfer material sheet P (width 210 mm) were passed through, the image fixing process was performed without any problem.

- When the temperature control of the gum heating element 20 is turned off and the heating element 22 is continuously energized, the paper passing area reaches an ignition temperature of 430°C M (
7) When the temperature rises to 320°CPU degree, the energization bottleneck part 22
b was fused and the current was cut off without heating the heating element 22.

In order to prevent wire breakage due to melting of the current conducting bottleneck 22b, the current carrying bottle 22b is made on a substrate made of a heat insulating material such as heat-resistant glass, so that cracks may occur in the board due to thermal strain caused by abnormal temperature rise of the current carrying bottleneck 22b. Is it different depending on the crack? It is also good to ensure that the current flow bottleneck portion 22b, which has been melted by the temperature rise, is brought into a disconnection state.

FIGS. 5(a), (b), and (C) show the energization bottleneck 22b,
They are formed in a series from the same material as the heating element in the effective length range, 171 W is the same as the heating element in the effective length range, and the thickness dl is the thickness d of the heating element in the effective length range. By setting it thinner than the above, it is possible to create a small cross-sectional area that functions as a fusing part.

(5) In addition, as shown in FIG. It can also be replaced with film (exchangeable type).

In the case of such a winding and replacing type, the fixing film can be made thinner or more efficient regardless of its durability, and the power consumption can be reduced. For example, an inexpensive base material such as PET (polyester) film is used as the fixing film, and heat-resistant treatment is performed for hours.
For example, a thin material with a thickness of about 2.5 μm or less can be used.

Alternatively, toner offset to the fixing film surface does not substantially occur as described in 1)v, so if the thermal deformation and deterioration associated with use of the fixing film are small, roll stack-P4611a
The taken used sheets are controlled to be rewound to the delivery shaft (!l) in a timely manner, or to
It is also possible to use it multiple times by reversing and exchanging 1!1 (rewind and repeat use type).

For example, in the rewinding and rewinding type, the fixing film is
A composite layer film can be used in which a 25 μm thick polyimide resin film is used as a base material with excellent heat resistance, mechanical strength, etc., and a laminated layer made of a fluororesin or the like with high mold releasability is provided. When waiting for reverse travel to the right, it is preferable to automatically control the pressure release mechanism to maintain the contact between the heating body and the pressure roller in a released state.

If the film is to be used multiple times, such as a rewinding type or an endless belt type, a felt pad is provided for cleaning the film, impregnated with a slight release agent such as silicone oil, and the pad is brought into contact with the film. Cleaning of 1 m of film and further improvement of mold releasability may also be carried out. When the fixing film is treated with an insulating fluororesin, static electricity that disturbs the toner image is likely to be generated on the film, so it is a good idea to use a grounded static eliminator brush to remove the static electricity. 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. Furthermore, one measure is to add conductive powder, such as carbon black, to the fluororesin to prevent image blur due to static electricity. Furthermore, the charge removal and conductivity of the pressure roller can be carried out by the same means. Further, it is also possible to apply or add a static protection agent such as 1F.

Regardless of whether the fixing film is an endless belt type, a rewinding type, or a rewinding type that can be used repeatedly, the fixing film can be fixed by having a cartridge structure that can be attached to and removed from a predetermined part of the fixing device 11.
Film replacement etc. can be facilitated.

The configuration of the heating element 20 and the communication control to the heating element 22 are not limited to those in the embodiment. The heating element 20 may be of a heated roller type, or the heating element 22 may be a thick film resistor or a PTC characteristic. It may also be a ceramic chip array having a pulsating flow control, and the flow control may be normally continuous instead of being controlled in a pulsed manner.

The toner heated and melted in the heating process may be cooled and solidified by natural heat radiation, or by forced cooling using a blower means, heat radiation fins, etc.

If the toner melts sufficiently at a high temperature, as shown in the example in Figure 6, if the toner is melted at a sufficiently high temperature in the heating process (fixing nip), it can be immediately transferred to the recording material (transfer) without cooling down after the heating process. The material sheet) P may be separated from the fixing film 24.

The apparatus described in the following embodiments is a transfer type electronic copying apparatus, but the image forming process/means may be a direct type in which a toner image is directly formed and carried on electrofax paper, electrostatic recording paper, etc., or a magnetic recording image formation method. Copying machines, laser beam printers, facsimile machines, microfilm reader printers, display devices, and recording machines that form an image using heat-fusible toner on recording Murakami using a method or other appropriate image forming process or means, and then heat and fix it. The present invention can be effectively applied to various image forming apparatuses such as the above.

(Effects of the Invention) As described in F-F below, the present invention enables to reduce the heat capacity of the heating body, which is a heating means, without causing fixing failure or offset in a toner image heat fixing type image forming apparatus, and to improve standby performance. It is possible to realize an image forming apparatus that can always stably output an image formed product with good fixed image quality with less time, power consumption, and internal temperature rise. Furthermore, the thin fixing film can be used by turning the edges over a long period of time without any problem of wrinkles.

In addition, if the heating element of the heating element overheats due to a power supply abnormality or temperature control abnormality, etc., and an abnormal energization situation occurs that causes ignition or smoke, the heating element will overheat and rise in temperature. ′? By quickly blowing out the ilt bottleneck and immediately cutting off the current, it is strictly possible to prevent the heating element from overheating and causing heat problems such as ignition and smoke.
It has a simple configuration without adding a thermoswitch or temperature fuse, and is much more reliable than those using such devices, and is extremely effective in terms of safety measures.

[Brief explanation of the drawing]

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 the fixing device portion, FIG. 3 is a schematic diagram of another example of the configuration of the fixing device, and FIG. 4(a) is a Bottom view of the heating body, the same figure (b) and the same figure (C) are the bb line and c of the same figure (a), respectively.
-c line sectional view, Figure 5 (a) is a F side view of the heating body with another configuration, Figure 5 (b) and (C) are the bb line and c line of Figure 5 (a), respectively.
6 is a schematic diagram of another example of the structure of the fixing device. 3 is a drum-type rotating photoreceptor, 1 is a fixing device, 24 is a fixing film, 20 is a heating element, 28 is a pressure roller, and P is a transfer material sheet. (C) Teien (b)

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 being longitudinally oriented in the transverse direction of the fixing film. A low heat capacity linear heating element having a linear or band-shaped energized heating element that generates heat by being energized in the longitudinal direction, and the heating element is outside the effective length range corresponding to the recording material passing width of the energized heating element. An image forming apparatus characterized in that the extra length part has an energization bottleneck part that is continuous with the heating element part within the effective length range and has a cross-sectional area smaller than the cross-sectional area of the heating element part.