JPH03208076A - Fixing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is a method in which a recording material is brought into pressure contact with a heating body through a film, and thermal energy is applied from the heating body to the recording material through the film (film heating). The present invention relates to a fixing device (method).

This device can be used to form images such as electrophotography, electrostatic recording, magnetic recording, etc. in image forming devices such as copying machines, laser beam printers, facsimiles, microfilm reader converters, image display devices, and recording machines. Directly or indirectly applied to the surface of a recording material (electrofax sheet, electrostatic recording sheet, transfer material sheet, printing paper, etc.) as an image carrier using a toner made of heat-melting resin or the like using a process means. It can be utilized as an image fixing device that heat-fixes an unfixed toner image corresponding to target image information formed by a (transfer) method as a permanently fixed image on the surface of a recording material carrying the image.

Further, the present invention is not limited to an image fixing device, and can be widely used as a means/device for heat-treating an image carrier, such as a device that heats a recording material carrying an image to modify its surface properties.

(Prior art) Film heating type fixing devices have the following advantages in comparison with other known heat roller type, hot plate type, belt fixing type, flash fixing type, oven fixing type, etc. Since a linear heating element with a low heat capacity can be used, it saves power and shortens wait time (quick start).■Fixing point and separation point can be set separately,
It is effective because it has advantages such as preventing offset and solving various drawbacks of other types of devices.

For example, Japanese Patent Application Laid-Open No. 63-3131 related to the applicant's previous proposal
The method, device, etc. disclosed in Publication No. 82 belongs to this category, and includes a thin heat-resistant film (sheet), a moving drive means for the film, and a fixed support arrangement on one side of the film with the film inside. a heating body, and a pressure member disposed on the other side facing the heating body to bring the image-bearing surface of the recording material to which the image is to be fixed into close contact with the heating body through the film. At least when performing image fixing, the film is moved at the same speed in the same direction as the recording material on which the image is to be fixed, which is conveyed and introduced between the film and the pressure member, and the heating body is placed on both sides of the moving film. The image bearing surface of the recording material is heated by the heating body through the film by passing through a fixing nip formed by pressure contact between the recording material and the pressure member, and heat is applied to the visible image (unfixed toner image). This is a heating means/device that basically applies energy to soften and melt the film and then separate the film and recording material, or separates the film and recording material after the toner has cooled and solidified.

In the above-mentioned film heating type fixing device, temperature control of the heating element is performed by a temperature sensor provided on the heating element, a microcomputer and a heating element drive (electrification heat generation) circuit in the main body of the image forming apparatus. . Furthermore, although the heating element is at a high temperature, since the film is moving over the heating element at a constant speed, stable image fixing is performed without local thermal deformation of the film.

(Problems to be Solved by the Invention) However, one of the problems with this fixing device is that the temperature of the fixing film is different between before image formation and after continuous image formation. In some cases, the amount of heat applied to the toner image differs.

Specifically, the temperature of the surface of the fixing film before the pressure contact member enters the pressure member (the temperature of the surface of the recording material that contacts the toner image surface, the desired temperature of the surface of the fixation film), and the pressure contact of the fixing film that enters the pressure contact part. The relationship between the increase in surface temperature and the elapse of residence time was determined by thermal analysis.

FIG. 9(a) shows a fixing film with a thickness of 40 μm, and FIG. 9(b) shows a fixing film with a thickness of 80 μm. In each figure, ■ is the film surface temperature that can be fixed (approximately 200℃ in this example)
(°C), (2) is a surface temperature increase graph when the initial surface temperature of the fixing film is 130°C, and (2) is a surface temperature increase graph when the initial surface temperature of the fixing film is 20°C. As can be seen from the graphs in FIGS. 9(a) and 9(b), if the surface temperature of the fixing film before entering the pressure contact part is low, the surface temperature of the fixing film as it passes through the pressure contact part allows the toner to be fixed at a constant temperature. The time required to reach the temperature becomes longer, and the actual toner image heating time becomes shorter.

Further, if the fixing film is thick to some extent, the fixing temperature may not be reached by the time the film passes through the pressure contact section (graph 2 in FIG. 9(b)).

Therefore, when the surface temperature of the fixing film is low, such as at the start of the fixing operation, there is a problem in that high temperature offset is likely to occur due to excessive melting of the toner.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems with a film heating type fixing device and improve the reliability of the device.

(Means for Solving the Problems) The present invention is a fixing device that presses a recording material against a heating body through a film and applies thermal energy from the heating body to the recording material through the film. The fixing device is characterized in that it has a means for detecting the temperature of a component of the device or the vicinity of the device, and changes the temperature control of a heating temperature control system according to the detected temperature.

(Function) That is, the temperature of the heating element is basically adjusted to a predetermined fA by an automatic temperature control system including a temperature sensor provided on the heating element, a microcomputer, and a heating element drive circuit as described above. The temperature is controlled to a controlled temperature.

In the present invention, the temperature control system of the heating body temperature control system is set by adding the detected temperature of a component of the fixing device or the vicinity of the device, for example, the detected temperature information of the fixing film, to the temperature control system as a control factor, and adjusting the temperature according to the detected temperature. By appropriately converting the heating temperature control temperature of the temperature control system, the amount of heat applied to the toner image within the pressure contact section is made almost the same at the start of the fixing operation and during continuous operation.

In other words, when the surface temperature of the fixing film is low, such as at the start of the fixing process, the heating temperature adjustment temperature is set to an appropriately high level to cope with the increase in the surface temperature of the fixing film as the fixing process is performed. The heating body temperature is changed so as to appropriately lower the heating body temperature.

This makes it possible to always form beautiful fixed images without causing fusing failure due to the low temperature of the fixing film or offset caused by the fixing film becoming hot during long-term continuous fixing processing. becomes.

Note that the temperature of the fixing film is approximately close to that of the pressure roller, the film transport roller, etc., and the temperature of the heating element when no electricity is applied. Therefore, instead of the fixing film, the temperature of other parts of the fixing device may be detected to change the heating temperature adjustment temperature.

(Embodiments) (1) Configuration example of fixing device (FIGS. 1 and 2) FIG. 1 shows a schematic configuration of an example of a film heating type fixing device 11 according to the present invention.

Reference numeral 25 designates an endless belt-shaped fixing film, which includes a driving roller 26 on the left side, a driven roller 27 on the right side, and a low heat capacity linear film as a heating element fixedly supported below between both rollers 26 and 27. Heating body 20 and drive roller 2
The four members 26, 27, 20, and 26a are suspended between the four members 26, 27, 20, and 26a, which are parallel to each other, and a kite roller 26a disposed below the member 6.

The driven roller 27 is an endless belt-shaped fixing film 2.
The fixing film 25 is rotated clockwise at a predetermined circumferential speed as the drive roller 26 rotates in the clockwise direction, that is, the unfixed toner image conveyed from the image forming section (9) side. It is rotationally driven at the same circumferential speed as the conveyance speed of the transfer material sheet P as a recording material carrying 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 releasability, such as silicone rubber, as a pressure member. The lower surface is pressed against the lower surface with a total contact pressure of, for example, 4 to 7 kg, and is rotated in a forward counterclockwise direction in the conveyance direction of the transfer material sheet P.

Rotationally driven entreshold-shaped fixing film 25
Because it is repeatedly used to heat and fix toner images, it has excellent heat resistance, releasability, and durability, and generally has a total thickness of 100 μm.
A thin one with a thickness of less than m, preferably less than 40 μm is used.

For example, polyimite, polyether imite, PES-PF
PTFE (tetrafluoroethylene resin) on at least the image contact side of a single-layer film of a heat-resistant resin such as A (tetrafluoroethylene-barfluoroalkyl vinyl ether copolymer resin) or a composite layer film, such as a 20 μm thick film. It is made of a 10 μm thick releasable coat layer made of a fluororesin such as PAF with a conductive material added thereto.

The low heat capacity linear heating body 20 as a heating body, which is made of wood, has rigidity, high heat resistance, and heat insulation properties, and is horizontally long with the length extending in the transverse direction of the fixing film (direction perpendicular to the running direction of the fixing film 25). A heater support 21 and a heating element 2 integrally attached and held on the lower surface of the support along the longitudinal direction of the lower surface.
3. It has a heater board 22 equipped with a temperature measuring element 24 and the like as means for detecting the temperature of the heating body 20.

The heater support 21 ensures the overall strength of the heating body 20, and is made of, for example, pps (polyphenylene sulfite), FAI (polyamitimide), PI (polyimide).
, PEEK (polyetheretherketone), liquid crystal polymer, or other highly heat-resistant resins, or composite materials of these resins and ceramics, metals, glass, etc.

The heater substrate 22 has a thickness f. Omm, width 10m
It is an alumina substrate with a length of 240 mm.

For example, the heating element 23 is formed of A g/P d, RuO2, Ta2, etc. along the longitudinal direction approximately at the center of the lower surface of the substrate 22.
It is a linear or strip-shaped low heat capacity current-carrying heating element made by coating (screen printing, etc.) an electrically resistive material such as N to a width of 1.0 mm.

For example, the temperature sensing element 24 is mounted on the upper surface of the substrate 22 (the heating element 23
This is a low heat capacity temperature measuring resistor such as a PT film or a thermistor, which is coated (by screen printing, etc.) along an elongated plane approximately in the center of the surface opposite to the side on which it is provided. In this example, the temperature of the substrate 22 is set as the temperature of the heating element 20, and the temperature measuring element 24 is
It is detected by

In the case of this example, electricity is applied to the linear or band-shaped heating element 23 from both ends thereof to generate heat over the entire length of the heating element 23. Electricity is supplied according to the desired temperature and the amount of energy released, which are controlled by the thermometer 24 and the fixing film temperature detection unit 31, which will be described later.

The fixing film 25 is not limited to an endless heel shape, but also has a second shape.
As shown in the figure, the fixing film 25 with an end wound around the feed shaft 41 is passed between the heating body 20 and the pressure roller 28 and under the guide roller 26a, and then wound up @42.
It may be configured such that the transfer material sheet P is stopped at the feed-out shaft 41 side and travels from the take-up shaft 42 side at the same speed as the conveyance speed of the transfer material sheet P.

It is preferable that the heating body 20 is protected by forming a sliding protective layer such as Ta205 on the surface which is the sliding surface with the fixing film 25.

(2) Fixing Execution Operation The image forming apparatus performs an image forming operation in response to the image formation start signal, and the transfer material sheet P conveyed from the transfer section (9) side to the fixing device 11 is guided by the kite 29 and temperature increases. The unfixed toner enters between the fixing sheet 25 and the pressure roller 28 at the pressure contact part N (fixing nip) between the controlled heating body 20 and the pressure roller 28, and the unfixed toner image surface or the sheet P The heating body 20 and the pressure roller 28 are in close contact with the lower surface of the fixing film 25, which is moving in the same direction as the conveying speed of
It passes through the fixing nip N between the two while being subjected to a clamping force.

W is the width dimension of the heating element 23 provided on the lower surface of the heating element, and the heating element 23 is located within the width area of mutual pressure contact between the lower surface of the heating element 20 and the upper surface of the pressure roller 28, and the width of the heating element 23 is within the width of the width of the heating element 23. The toner image bearing surface of the toner image bearing surface of the toner image bearing surface of the sushi plate P is pressed against the fixing film surface, and in the process of passing through the fixing nib part N, the heat of the heating element 23 is transferred to the fixing film. 25, the toner image is melted at high temperature and softened and adhered Tb to the surface of the sheet P.

In the case of a wood sample device, the recording material sheet P and the fixing film 2
Separation from the sheet P is performed when the sheet P passes through the fixing nip portion N and exits.

At this time of separation, the temperature of the toner Tb is still higher than the glass transition point of the toner, and therefore, the bonding force (adhesive force) between the sheet P and the fixing film 25 at this time of separation is small. The sheets P are always separated smoothly without causing almost any toner offset to the surface of the fixing film 25, and without causing a jam due to the sheet P being stuck to the surface of the fixing film 25 due to poor separation.

Since the toner Tb, which is at a temperature higher than the glass transition point, has appropriate rubber properties, the toner image upon separation does not resemble the back surface of the Otoshi Uta film, and has an appropriate uneven surface. Since this surface property is maintained and the toner is cooled and solidified, excessive image gloss does not occur on the fixed toner image surface, resulting in a high quality image.

The sheet P separated from the fixing film 25 is guided by the kite 43 and while reaching the paper ejection roller pair (44), the temperature of the toner Tb, which is higher than the glass transition point, naturally cools down (natural cooling).
The temperature reaches a temperature below the glass transition point and solidifies Tc, and the sheet P on which the image has been fixed is output onto the tray.

(3) Example of heating temperature control temperature control In Figs. 1 and 2, 31 is arranged in contact with the inner surface of the fixing film 25 on the upstream side in the fixing film traveling direction of the pressure contact part N, which is the fixing nip part. FIG. 3 is an enlarged sectional view of the temperature detection unit.

The unit 31 has a temperature sensing element 33 embedded in a silicone sponge 32, the surface of which is covered with a PTFE tape 34 with good sliding properties, and is placed in contact with the fixing film at the above-mentioned position. The temperature of the fixing film just before it enters the pressure contact section N is detected.

The detected temperature information is sent as a control factor to a microcomputer of a heating temperature control system (not shown).

According to experiments conducted by the inventors, when using Canon toner, sufficient fixing cannot be achieved with the fixing film 25 at 20°C before the pressure contact area unless the heating element 20 is maintained at 190°C or higher. (Lowest temperature that can be fixed). At temperatures above 210°C, the toner overmelted and caused offset. Further, as shown in FIG. 5, each temperature varied depending on the temperature of the fixing film before entering the pressure contact portion.

In this embodiment, as shown in Table 1, which is set based on the results shown in FIG. This is what I did.

In other words, the heating element 20 is heated at 200° at the start of the fixing operation.
As the temperature of the fixing film increases, the temperature of the heating body temperature decreases to 195°C and 190°C.

This makes it possible to always form beautiful fixed images without causing fusing failure due to the low temperature of the fixing film, or offset due to the high temperature of the fixing film during long continuous fixing processing. becomes.

Table 1 Fixing film Heating body 0 to 3 1 to 6 1 to 1 101 ° 3 00 C 6 0 ° C oo'c C or more 2 0 00 1 9 50 1 9 00 1 8 50 (4) Example of heating temperature control temperature control (2) In the above control example (2), the temperature of the fixing film was detected, but when a very thin fixing film, for example, 20 μm or less, is used, the portion that slides with the temperature detection unit 31 may be damaged. Furthermore, when detecting temperature without contact, it is difficult to maintain a constant space (for example, 0.3 mm) at all times because the fixing film is wavy, and detection may not be possible.

In this embodiment, in order to solve these problems, the temperature of parts of the fixing device other than the fixing film 25, such as the temperature of the driven roller 27 and the temperature of the pressure roller 28, changes in a manner similar to the temperature of the fixing film. Focusing on this, the temperature of the parts other than the fixing film 25 is detected and the heating temperature adjustment temperature is switched.

Figure 5 shows the temperature change of the fixing film 25 and the driven roller 2 when the fixing device is stopped after operating for 10 minutes.
7 shows the temperature change. Since both of them undergo similar temperature changes, the device of this embodiment is equipped with four temperature detection elements on the driven roller 27 as shown in FIG. 6, and the detected temperature is 600C.
In the following cases, the temperature of the heating element 20 is adjusted to 193'C, and when the detected temperature is 60°C or higher, the temperature of the heating element 20 is adjusted to 188°C.

This method of estimating the temperature of the fixing film by detecting the temperature of parts other than the fixing film 25 does not require a temperature detection device to come into contact with the fixing film 25, and is effective for increasing the durability of the fixing film 25. It is a method.

Note that in this embodiment, the temperature of the driven roller 27 was detected, but
Fixing film 25 such as drive roller 26 and pressure roller 28
It is also possible to detect the temperature of a portion close to .

Furthermore, if the gap between the temperature sensing element 31 and the fixing film 25 can be kept constant with a device that can transport the fixing film 25 stably, non-contact temperature detection is also effective.

(5) Heating body temperature adjustment salinity control example m When the fixing device is stopped (the heating body 20 is not energized and the fixing film 25 is stopped), the heating body 20 has approximately the same temperature as the fixing film 25. becomes.

Therefore, the temperature of the fixing film while it is stopped can be detected by the temperature detection element 24 of the heating body 20. Furthermore, the rise in temperature of the fixing film during operation is correlated with the energization time from the start of operation.
Predictable.

Focusing on this point, this embodiment detects the temperature of the fixing film using the temperature detection element 24 of the heating element 20 without providing a special temperature detection device dedicated to detecting the temperature of the fixing film, and also starts the operation using a microcomputer during operation. The temperature of the fixing film is predicted by counting the continuous energization time, and the heating temperature control temperature is changed according to these temperatures.

For example, when using Canon's heat-fixing toner A, the relationship between fixing film temperature and heating element temperature is shown in Figure 7.
When the temperature of the fixing film is 600°C or less, the optimum temperature control temperature of the heating element is 190°C, or the fixing film is too hot! 40°
When the temperature is C or higher, the heating element is on! High plow at 90°C, 185
It's passing through °C. Furthermore, it is known that in this fixing device, the temperature of the fixing film increases by about 600 C when electricity is applied for one minute (for fixing five sheets).

Therefore, in this embodiment, the fixing film temperature detected by the temperature detection element 24 of the heating body 20 before the start of the fixing operation is 60°C.
In the following cases, the heating element 20 is energized to 1900C. Also, the temperature of the fixing film is already 6 before the fixing operation.
If the temperature is 0'C or higher, heat the heating element 20 to 185°C from the first sheet.
By controlling the temperature, it is possible to always obtain sufficient fixing performance and to form an image without offset without using a special fixing film temperature detection operation.

(6) Example of Image Forming Apparatus (FIG. 8) FIG. 8 shows a schematic configuration of an example of an image forming apparatus incorporating the fixing device 11 of FIG. 1 described above. The image forming apparatus of this example is an electrophotographic copying apparatus of a reciprocating document table type, a rotating drum type, and a transfer type.

100 is a device cabinet; 1 is a top plate 100a of the device cabinet;
This is a reciprocating type document mounting table made of a transparent plate member such as a glass plate disposed above, and it reciprocates at a predetermined speed on the top plate 100a of the machine casing in the right direction a and the left direction a' in the drawing. Driven.

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. .

Reference numeral 100b denotes a slit opening, which serves as a document illumination section, and is opened on the surface of the top plate 100a of the machine casing, with its length extending in a direction perpendicular to the direction of reciprocating movement of the document table 1 (direction perpendicular to the plane of the paper).

The downward image surface of the document G set on the document platform 1 passes through the position of the slit opening 100b sequentially from the right side to the left side during the forward movement of the document platform 1 to the right side a. In the process of passing, the light L from the lamp 3 is received through the slit opening 100b and the transparent original table 1, and the document is illuminated and scanned. The light reflected from the document surface of the illumination scanning light is imaged and exposed on the surface of the photosensitive drum 4 by the short focus and small diameter imaging element array 2.

The photosensitive tram 4 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 around a central support shaft 4a at a predetermined circumferential speed. The photosensitive drum 4 is uniformly charged with positive or negative polarity by the charger 5, and the image-forming exposure (slit exposure) of the original image is applied to the uniformly-charged surface of the photosensitive drum 4. Electrostatic latent images corresponding to the original image 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 a developing device 6, and the developed toner image is transferred to a location where a transfer discharger 9 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 and fed one by one by the rotation of the feeding roller 7, and then the sheets are fed onto the drum 4 by the registration roller 8. When the leading edge of the toner image forming section reaches the position of the transfer discharger 9 (effect of the invention), the leading edge of the transfer material sheet P also reaches the position between the transfer discharger 9 and the photosensitive drum 4, and the both are separated. The timing is set to match and the data is fed synchronously. Then, the toner image on the photosensitive tram 4 side is sequentially transferred onto the surface of the feeding sheet by the transfer discharger 9.

The sheet to which the toner image has been transferred in the transfer section is sequentially separated from the four surfaces of the photosensitive drum by a separating means (not shown) and transferred to the conveying device 1.
0, the unfixed toner image Ta carried thereon is guided to the fixing device 11 by the heat fixing process, and then passes through a guide 43 and a discharge roller 44 as an image-formed product (cod) to be discharged outside the machine. The paper is discharged onto the paper discharge tray 12.

The surface of the photosensitive tram 4 after image transfer is cleaned by a cleaning device 13.
After removing the adhered contaminants such as residual toner after transfer, it is repeatedly used for image formation.

FIG. 5 shows fixing during fixing operation and during stoppage As explained above, in a film heating type fixing device, the present invention focuses on the constituent members of the device, more specifically, the parts that reach the fixing film temperature or a temperature close to it. By detecting the temperature and changing the heating temperature adjustment temperature according to the detected temperature, it is possible to prevent the occurrence of high temperature offset due to the application of too much heat to the toner image, which is based on the temperature state of the fixing film before the pressure contact part. On the contrary, it is possible to prevent the occurrence of fixing failure due to insufficient heat, and to obtain beautiful fixed images from the start of the fixing process to the continuous process.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a fixing device according to an embodiment. FIG. 2 is the same diagram as above of another embodiment of the fixing device. FIG. 3 is an enlarged sectional view of the fixing film temperature detection unit. FIG. 4 is a graph showing the relationship between the temperature of the fixing film immediately before the pressure contact part, the temperature of the heating element, the high temperature offset temperature, and the lower limit temperature for fixing. Graph of changes in film temperature and driven roller temperature. FIG. 6 is a partial view of an example in which a temperature sensing element is provided on a driven roller. FIG. 7 is a graph showing the relationship between fixing film temperature, heating element temperature, high temperature offset temperature, and lower limit fixable temperature. FIG. 8 is a schematic configuration diagram of an example of an image forming apparatus. In Figure 9 (a) and (b), the thickness of the fixing film is 4.
A graph showing the relationship between the time the fixing film stays in the pressure contact area and the film surface temperature change in the cases of 0 pm and 80 μm. 11 is the general code of the fixing device, 25 is the fixing film, 20
22 is a substrate, 23 is a current-carrying heating resistor, 24 is a heating element temperature detection element, and 3l is a fixing film temperature detection unit.

Claims (1)

[Claims] (1) A fixing device that presses the recording material against a heating body through a film and applies thermal energy from the heating body to the recording material through the film, and detects the temperature of the constituent members of the fixing device or the vicinity of the device. What is claimed is: 1. A fixing device having means for changing the temperature control of a heating temperature control system according to the detected temperature.