JPH0325473A - Fixing device - Google Patents

Abstract

PURPOSE:To detect the position of film by specifying the light transmissivity of a part of the film wherein a toner image on a recording material is heated via the film and fixed, and detecting the film with the aid of this part. CONSTITUTION:A transfer material sheet P carrying an unfixed toner image Ta on an upper surface is guided by a guide 29, and advances between the fixing film 24 in a press-contact part N between a heater 20 and a pressure roller 28, and the pressure roller 28. The toner image Ta is heated in the press- contact part N to turn into a softened and fused image Tb. A conductive coloring material, etc., are mixed into the film 24 to lower its light transmissivity to 75% or below. At a time when the film 24 is shifted in the axial direction, photosensors G provided on both sides detect the film. Consequently, the position and state of the film 24 can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fixing device that performs fixing by applying heat to a toner image via a film.

[Prior art]

Heat roller type fixing devices have been widely used for a long time, but the applicant has previously published Japanese Patent Application Laid-Open No. 63-313182 as a device that can shorten warm-up time and reduce power consumption.
In the issue, we proposed a fixing device that fixes images through film.

[Problems solved by the invention]

However, in order to improve thermal efficiency, the film is thin, especially 5
Since a film with a diameter of 0 μm or less is used, it is difficult to mechanically detect the position of the film.

[Means to solve problems]

The present invention, which solves the above-mentioned problems, has a fixing device that fixes a toner image on a recording material by applying heat to it via a film, and includes a detection means for optically detecting the film. The light transmittance is 75% or less, and the film is characterized by being detected using the portion where the light transmittance is 75% or less.

[Embodiments of the invention]

Embodiments of the present invention will be described below based on the drawings.

FIG. 2 is a sectional view of an electrophotographic copying apparatus to which a fixing device according to an embodiment of the present invention is applied.

In FIG. 2, reference numeral 100 denotes a device housing, and l denotes a reciprocating type document mounting table made of a transparent plate member such as a glass plate, which is disposed on the upper plate 100a of the machine housing. are driven to reciprocate at predetermined speeds in the right direction a and the left direction a' in the drawing, respectively.

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

ioob is a slit opening, which serves as a document illumination section, which is opened on the surface of the top plate 100a of the machine casing, with its length extending in a direction perpendicular to the reciprocating direction of the document table l (direction perpendicular to the plane of the paper). The downward image surface of the original G placed on the original placing table 1 passes through the position of the slit opening ioob sequentially from the right side to the left side during the reciprocating movement of the original placing table l to the right side a. In the process of passing through, the light L from the lamp 7 is received through the slit opening 100b and the transparent original table 1, and the document is illuminated and scanned.

The illumination scanning light reflected from the document surface is imaged and exposed on the surface of the photosensitive drum 3 by the short focus and small diameter imaging element array 2.

The photosensitive drum 3 is coated with a photosensitive layer such as a zinc oxide photosensitive layer, an organic semiconductor photosensitive layer, etc., and is driven to rotate clockwise in the direction of arrow 1] around a central support shaft 3a at a predetermined circumferential speed. The photosensitive drum 3 is uniformly charged with positive or negative polarity by the charger 4, and the photosensitive drum 3 is subjected to imaging exposure (slit exposure) of the original image on the uniformly charged surface.
Electrostatic latent images corresponding to the image-formed and exposed original image are sequentially formed on the surface.

This electrostatic latent image is sequentially developed using a toner made of a resin or the like that softens and melts when heated by a developing device 5, and the developed toner image is transferred to a transfer portion of a transfer discharger 8 serving as a transfer portion. To go.

S is a cassette loaded with transfer material sheets P as recording materials, and the sheets in the cassette are fed and fed one by one by the rotation of the feeding roller 6, and then the sheets are fed onto the drum 3 by the single nozzle roller 9. The timing is set so that when the leading edge of the toner image forming section reaches the position of the transfer discharger 8, the leading edge of the transfer material sheet P also reaches a position between the transfer discharger 8 and the photosensitive drum 3, and the two coincide. The data is taken and fed synchronously. Then, a transfer discharger 8 is applied to the surface of 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 I'll, which will be described later, to remove the unfixed toner image carried thereon. The image is subjected to heat fixing processing and is ejected onto the paper ejection tray l2 outside the machine as an image-shaped object (copy).

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

Next, the fixing device will be described in detail.

FIG. 1(a) is a sectional view of a fixing device according to an embodiment of the present invention. 24 is an endless belt-shaped fixing film;
A drive roller 25 on the left side, a driven roller 26 on the right side, and a low heat capacity linear heating body 20 as a heating body disposed below between the drive roller 25 and the driven roller 26.
It is suspended between members 25-26 and 27-20. This fixing film 24 will be described in detail later.

The driven roller 26 is an endless belt-shaped fixing film 2.
The fixing film 24 is rotated clockwise by the drive roller 25 at a predetermined circumferential speed, that is, the unfixed toner image Ta is conveyed from the image forming section 8 side. It is rotated at the same circumferential speed as the conveyance speed of the transfer material sheet P carrying the transfer material on its upper surface without wrinkling, meandering, or speed delay. This prevention of meandering will be discussed later.

Reference numeral 28 denotes a pressure roller having a rubber elastic layer such as silicone rubber with good mold releasability as a pressure member. The transfer material sheet 1-P is rotated forward and counterclockwise in the conveying direction of the transfer material sheet 1-P.

The low heat capacity linear heating element 20 as a heating element in this example has rigidity, high heat resistance, and heat insulation properties and is horizontally long with its longitudinal direction extending in the transverse direction of the fixing film (direction perpendicular to the running direction of the fixing film 25). Then, it has a heater support 27 and a heater substrate 21 equipped with a heating element 22, a temperature measuring element 23, etc., which are integrally attached and held on the lower surface of the support along the longitudinal length of the lower surface.

The heater support 27 supports the heating body 20 insulatingly with respect to the fixing device 11 and the entire copying device, and is, for example, pps (
Highly heat-resistant resins such as polyphenylene sulfide), FAI (polyamideimide), PI (polyimide), PEEK (polyetheretherketone), and liquid crystal polymers, and composite materials of these resins with ceramics, metals, glass, etc. It can be configured with

As an example, the heater board 21 has a thickness of 1.0 mm.
, a width of 10 mm, and a length of 240 mm. The heating element 22 is made of an electrically resistive material such as Ag/Pd (silver palladium) approximately 10 μm thick and 1 to 3 mm wide along the length of the lower surface of the substrate 21, for example.
The heat-resistant glass 21a is coated thereon with a thickness of about 10 μm as a surface protective layer.

For example, the temperature detection element 23 is mounted on the upper surface of the substrate 2l (heating element 22
This is a low heat capacity temperature measuring resistor made of PT-free or the like, which is coated approximately at the center of the surface (opposite to the surface on which it is provided) by screen printing or the like. As the temperature measuring element, a thermistor having a low heat capacity or the like may be arranged in contact with the substrate 21.

In the case of this example, for the linear or band-shaped heating element 22,
Electricity is applied from both ends in the longitudinal direction to cause the heating element 22 to generate heat over substantially its entire length. The energization is ACIOOV, and the energizing power is controlled by controlling the phase angle of energization by an energization control circuit (not shown) including a dry attack according to the temperature detected by the temperature measuring element 23.

Next, the operation of the fixing device of this embodiment will be explained.

The transfer material sheet P carrying an unfixed toner image Ta on its upper surface, which is conveyed from the transfer section 8 to the fixing device 11 by the image forming apparatus in response to the image forming start signal, is moved to the guide 29.
The pressure contact portion N between the heating body 20 and the pressure roller 28 is guided by
The toner enters between the fixing film 24 and the pressure roller 22, and the unfixed toner image surface comes into close contact with the lower surface of the fixing film 24, which is moving in the same direction at the same speed as the conveyance speed of the sheet P. Fixing film 2 without surface misalignment or wrinkles.
4, it passes through the mutual pressure contact portion N between the heating body 20 and the pressure roller 28 while being subjected to a clamping force.

Since the heating body 20 is energized and heated at a predetermined timing according to the image forming start signal, the toner image Ta is heated at the pressure contact portion N.
It is heated to become a softened and melted image Tb.

The running direction of the fixing film 24 is turned at an abrupt angle (bending angle θ is approximately 45°) at an edge portion S where the curvature of the support 27 is large (the radius of curvature is approximately 2 mm).

Therefore, the sheet P conveyed through the pressure contact portion N while overlapping the fixing film 24 is separated from the fixing film 24 by the curvature at the edge portion S, and is discharged to the paper discharge tray l2. By the time the toner is ejected, the toner has sufficiently cooled and solidified and is completely fixed on the sheet P (toner image Tc).
).

The toner used in this example has a sufficiently high viscosity when melted by heating, so even if the toner temperature when separated from the fixing film 24 is higher than the melting point of the toner, the adhesion force of the toners to each other is sufficient to maintain the adhesion of the toner to the fixing film. Extremely greater than force. Therefore, when the fixing film 24 and the sheet P are separated, toner offset with respect to the fixing film 24 does not substantially occur.

In addition, in this embodiment, the heating element 22 of the heating element 20
and the substrate 21 have a small heat capacity, and these are the support body 2.
7, the surface temperature of the heating body 20 at the pressure contact portion N rises to a high enough temperature relative to the melting point of the toner (or the temperature at which it can be fixed to the sheet P) in a short period of time. There is no need to raise the temperature of the heating element in advance (so-called standby temperature control), saving energy.
Moreover, it also prevents the temperature inside the aircraft from rising.

Next, the fixing film 24 used in this embodiment will be explained.

The fixing film 24 has heat resistance, releasability, durability, etc.
In general, single or composite layer films of 100 .mu.m or less, preferably 40 .mu.m or less, can be used.

FIG. 3 is a schematic cross-sectional view of the layer structure of an example of a composite layer film, in which 24a is a heat-resistant layer as a base film of the fixing film, and 24b is the outer surface of the heat-resistant layer 24a (the side facing the toner image). It is a release layer laminated on the surface).

The heat-resistant layer 24a is made of, for example, polyimide, polyetheretherkent (PEEK), polyethersulfone (PES).
), polyetherimide (PEN), polyvalabanic acid (
PPA), highly heat-resistant resin films such as PFA, and Nj
, SUS, KL, and other metals with excellent strength and heat resistance can be used.

The release layer 24b is preferably made of, for example, fluororesin such as PTFE (polytetrafluoroethylene)-PFA-FEP, silicone resin, or the like. Release layer 2 for heat-resistant layer 24a
The laminated form of 4b is made by adhesive lamination of the release layer film, lamination by electrostatic coating, vapor deposition, CVD, etc. of the release layer material, and co-extrusion of the heat-resistant layer material and the release layer material. This can be done by forming a layered film.

In this embodiment, a conductive colorant such as carbon black graphite whisker is mixed into the release layer to lower the light transmittance of the film 24 to 75% or less. As a result, when the film 24 shifts in the axial direction, it is detected by the photosensors G provided at both ends, and the driven roller 26 is activated by the solenoid H in response to this detection signal.
can be tilted back to its original position.

More specifically, as shown in an enlarged view in FIG. G2 light on film 24
This is detected by the interruption of the flow, and the driven roller 26 is adjusted by the solenoid H so as to return it in the direction of the arrow a.

According to the authors' experiments, a film made of 10 μPI and 5 μ PTFE had a spectral transmittance of 75% or more at 900 nm, and sensor G2 was sometimes unable to detect the film position, as shown in Figure 1 (C). .

There are methods to detect 75% or more film, such as increasing the sensitivity of the sensor, but in this case, the drawback is that if the film gets dirty during use or the sensor light receiving part gets dirty, detection will not be possible. be.

This embodiment uses P as a means to solve these problems.
900 nm by dispersing 5% carbon black in TFE
The spectral transmittance of the film is set to 55%, so that the film position can be detected reliably. If the light transmittance is 75% or less, it can be detected reliably, but it is preferably 50% or less in a device that will be used for a long period of time.

Further, although there are the above-mentioned means for lowering the light transmittance, it is better to disperse a conductive material because it can prevent the film from being charged. This allows not only light detection but also electrostatic offset prevention. Also, not necessarily
It is not necessary to mix the pigment into the release layer, and the pigment may be mixed into the base material.

FIG. 4(a) is a diagram showing a second embodiment of the fixing device of the present invention.

Reference numeral 32 denotes a heating roller as a heating body, which has a built-in heater 33, and by causing the heater 33 to generate heat appropriately according to the heating roller surface temperature detected by the temperature measuring element 41, the surface of the heating roller 32 is brought to a predetermined temperature. Can be maintained.

Reference numeral 34 designates a small-diameter separation upper roller disposed downstream of the heating roller 32 in the conveying direction of the sheet 1-P. 25 is a drive roller that rotates and runs the fixing film, and 26 is a driven roller that always applies an appropriate tension to the fixing film. Note that both the drive roller 25 and the heating roller 2 are rotated clockwise at the same speed as the conveyance speed of the sheet P.

The fixing film 34 has four members 32, 34 parallel to each other.
, 25 and 26.

36 is a pressure roller arranged opposite to the lower side of the heating roller 32, 35 is a lower separation roller arranged opposite to the T side of the upper separation roller 34, and 37 is the pressure roller 36 and the lower separation roller. This is an endless belt-like conveyor belt 1 (backup belt) suspended between 35 and 35. Pressure roller 3
6 is a roller whose surface layer is made of an elastic material such as silicone rubber. The downward film portion of the endless belt-shaped fixing film 24 is sandwiched between the pressure roller 36 and the heating roller 32, and a total contact pressure of, for example, 4 to 7 kg is obtained by a biasing means (not shown). ing. The pressure roller 36 rotates as a result of the rotation of the heating roller 32, and the conveyor belt 37 also presses the sheet P against the fixing film 34.
It rotates counterclockwise at the same speed as the conveyance speed of the sheet P.

The image forming apparatus performs an image forming operation in response to an image forming start signal, and the transfer material sheet P carrying the unfixed toner image Ta on its upper surface is transported from the transfer section 8 to the fixing device 11 by rotating the heating roller 32. Therefore, when the fixing film 24 and the conveyor belt 37 are rotating, the guide 29
The unfixed toner image surface enters between the fixing film 24 and the conveyor belt 37 at the pressure contact portion N between the heating roller 32 and the pressure roller 36, and the unfixed toner image surface is moved at the same speed as the conveyance speed of the sheet P. The heating roller 32 and the pressure roller 36 are in close contact with the lower surface of the fixing film 24 rotating in the same direction, and the heating roller 32 and the pressure roller 36 are in contact with each other in an overlapping state with the fixing film 24 without causing wrinkles or surface misalignment. It passes through while being subjected to a pinching force.

In the process of passing through the mutual pressure contact portion N, the toner image Ta on the sheet P is heated and becomes a softened and melted image Tb.

The sheet portion that has passed through the mutual pressure contact portion N between the heating roller 32 and the pressure roller 36 is spread and travels between the heating roller 32 and the upper separating roller 34 until it reaches the position of the upper separating roller 34. The fixing film continues to be conveyed in close contact with the fixed fixing film part. The conveyor belt 37 is seat P
supports the back surface of the sheet P and maintains close contact between the sheet P and the fixing film 24.

During this conveyance process, the heat of the softened/melted toner image Tb is radiated and becomes a cooled/solidified toner image Tc.

Although the toner heat radiation in this heat radiation/cooling process is natural radiation cooling in the case of this example, it is also possible to forcibly radiation cool the toner by providing a heat radiation fin with an air blowing means or the like.

When the fixing film 24 is conveyed to the position of the upper separation roller 34, the traveling direction of the fixing film 24 is turned in a direction away from the surface of the sheet P along the surface of the upper separation roller 34 having a large curvature.
The fixing film 24 and the sheet P are separated from each other, and the sheet P is conveyed to the paper discharge tray 12. By the time of this separation, the toner has sufficiently cooled and solidified, and the adhesion and adhesion of the toner to the sheet P is sufficiently large, and the strength to the fixing film 24 is extremely small. Separation of one toner P is easily accomplished sequentially without substantially causing toner offset to the fixing film 24.

In this example, the temperature of the heating roller, which is the heating body, is
It becomes possible to set the temperature higher than that which causes high-temperature offset in the conventional heated roller fixing method, and fixing performance is improved. Furthermore, the allowable temperature range of the heating element is wide on the high temperature side, making it possible to simplify temperature control.

Further, when fixing a multi-color toner image, especially a toner image of three or more colors, it is easy to mix colors because it can be sufficiently melted at a high temperature. Further, since the toner is once melted, cooled and solidified while in close contact with the fixing film, and then peeled off from the fixing film, it is possible to make the surface properties of the toner image similar to the surface properties of the fixing film. Therefore, for example, by making the surface of the fixing film flat, it is possible to provide the surface of the toner image Tc with a gloss similar to that of a silver halide photograph.

Further, by making the fixing film 24 thin as described above, heat accumulation in the fixing film is prevented and the cooling process of the toner image is made more efficient. Furthermore, when a thin resin film was used as the fixing film, the adhesion to the toner image was improved and the heat transfer efficiency was improved.

Note that the heating body 32 is not limited to the heating roller;
As shown in FIG. 2, the fixed heating body 20 shown in the first embodiment may be used. In that case, in addition to the above effects, the heating element 22
Since the heat capacity of the substrate 2l is small and it is insulated, the temperature rise rate is fast and there is no need for standby temperature control. Further, by arranging a separation stay 38 having an end face with a larger curvature in place of the upper separation roller 34, it becomes possible to separate the sheet P from the fixing film 24 more reliably.

To explain the fixing film 24 of this embodiment, the circumferential length of the fixing film 24 is 350 mm, which is longer than the maximum sheet P length that can be used in this image forming apparatus, 300 mm.
It is made into an endless shape by pasting sheet-like films together at the D portion. Although the film has a light transmittance of 75% or more, the bonded portion is as shown in Figure 4 (b).
) by coloring with pigments as shown in the enlarged view.
The spectral transmittance in nm is set to 30% or less. (The sensor G has a detection sensitivity peak at 800 nm) By doing this, the position of the bonded portion D can be detected by the photosensor G, and the bonded portion D
The endless film 24 is rotated at a timing such that it does not come into contact with the sheet P being conveyed. Generally, there is a level difference in the bonded area, so if that area comes into contact with the image, uneven gloss will occur, but this example avoids this.

FIG. 5(a) shows the third fixing device used in the apparatus of the present invention.
It is a figure showing an example of.

In place of the heating body 20 of the first embodiment shown in FIG. 1, a transparent member such as heat-resistant glass is arranged, and a radiation source such as a halogen lamp is placed inside the endless fixing film 24 via the member. 40, the toner image is heated.

In this embodiment, since heating is performed by radiation, it is possible to instantaneously raise the temperature of l-ner and melt it. Therefore, since it is only necessary to heat the sheet P when it is in the pressure contact part N, it is possible to save power and to reduce the rise in temperature inside the machine.

In this example, as shown in the developed view of FIG. 5(b), the surface of the release layer was plasma-treated only at the edge of the film (the part outside Sea 1-P), and furthermore, pigment was applied on the surface of the release layer. Use a colored one, with the part that touches the sheet transparent. By doing this, the meandering of the film can be prevented as in Example 1, and the toner image can be efficiently melted by radiation.

As shown in FIG. 6(a), the fixing film is not limited to an endless film 24, but is a film 24 with an end wound around a feed shaft 30, and can be wound into a sheet by winding it around a winding shaft 3l. It may be configured to run at the same speed as P.

Here, as shown in Figure 6 (bLllm developed diagram), the part 200 mm from the end of the edged film on the feeding shaft side is colored with pigment to reduce the light transmittance to 50% or less. The detection element G detects this position and displays to the user that the film has finished.This prevents the device from malfunctioning due to the device being moved even though the film has finished. You can avoid this.

〔Effect of the invention〕

As explained above, by setting the light transmittance of at least a part of the film to 75% or less and optically detecting the film in this part, the film can be processed without damaging the film.
This makes it possible to detect the position, condition, etc. of the film and improves the durability of the film.

[Brief explanation of drawings]

FIG. 1(a) is a sectional view of a fixing device according to an embodiment of the present invention, and FIG. 1(b). (c) is a diagram showing the detection of deviation of the fixing film; FIG. 2 is a sectional view of a copying machine using the fixing device of the embodiment of FIG. 1 (a); FIG. 3 is a diagram used in an embodiment of the present invention. 4(a) is a sectional view of a fixing device according to another embodiment of the present invention; FIG. 4(b) shows a bonding part of the film used in FIG. 4(.11k). 5(a) is a sectional view of a fixing device according to yet another embodiment of the present invention; FIG. 5(b) is a developed view of the film; FIG. 6(a) is a further embodiment of the present invention. FIG. 6(b) is a sectional view of the fixing device of the embodiment. FIG. 6(b) is a developed view of the film. In the figure, 20...Heating body 24...Fixing film 28...Pressure roller

Claims (2)

[Claims] (1) A fixing device that fixes a toner image on a recording material by applying heat through a film, which has a detection means for optically detecting the film, and has a light transmittance of at least a portion of the film of 75% or less. A fixing device characterized in that the film is detected using a portion having a light transmittance of 75% or less. (2) The fixing device according to claim 1, wherein the film is endless, and the detection means detects deviation of the film.