JP2833088B2 - Fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention provides a method (film heating) in which a recording material is pressed against a heating member via a film to apply heat energy from the heating member to the recording material via the film. System).

This equipment is used for image forming devices such as copiers, laser beam printers, facsimile machines, micro film reader printers, image display (display) devices, and recorders. Direct or indirect (transfer) method 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 composed of a heat-meltable resin by means An unfixed toner image corresponding to the target image information formed in step (1) can be utilized as an image fixing device for performing a heat fixing process as a permanent fixed image on a recording material surface carrying the image.

Further, the present invention is not limited to the image fixing device, and can be used as a means and a device for heat-treating an image bearing member widely, for example, a device for heating a recording material carrying an image to improve surface properties.

(Prior art) A film heating type fixing device is low in comparison with other known heat fixing type devices such as a heat roller type, a hot plate type, a belt fixing type, a flash fixing type and an oven fixing type. A heat capacity linear heating element can be used, which saves power and shortens the wait time (quick start property). Since the fixing point and the separation point can be set separately, offset is also prevented. It has advantages such as solving various drawbacks of the device and is effective.

For example, a method and apparatus disclosed in Japanese Patent Application Laid-Open No. 63-313182 according to the applicant's earlier proposal belong to this, and include a thin heat-resistant film (sheet), a moving driving means for the film, and a film. A heating member fixedly supported and arranged on one side of the recording medium, and a recording material to be fixed on the other surface and opposed to the heating member and to be image-fixed to the heating member via the film. A pressurizing member for bringing the visible image bearing surface into close contact with the recording material to be image-fixed, which is transported and introduced between the film and the pressurizing member at least at the time of image fixing, at the same speed in the forward direction; The recording material is moved and passed through a fixing nip portion formed by pressing the heating element and the pressing member with the traveling moving film interposed therebetween, so that the visible image bearing surface of the recording material is moved by the heating element through the film. Heat energy to a visible image (unfixed toner image) Grant over and allowed softened and melted, and then separating the film and the recording material, or a heating means or apparatus which is based on the toner to separate the film and the recording material after cooling and solidifying.

In the fixing device of the film heating system as described above,
The temperature control of the heating element is performed by a temperature sensor provided in the heating element, a microcomputer of the image forming apparatus main body, and a heating element drive (electric heating) circuit. Although the temperature of the heating element is high, since the film is moving on the heating element at a constant speed, local image deformation of the film does not occur and stable image fixing is performed.

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

Specifically, the surface temperature of the fixing film before entering the pressure contact member (the temperature of the surface of the recording material in contact with the toner image surface, the expected temperature of the fixing film) and the pressure contact of the fixing film entering the pressure contact portion The relationship with the surface temperature rise with the passage of the part stay time was determined by thermal analysis.

FIG. 9 (a) is for a fixing film having a thickness of 40 μm, and FIG. 9 (b) is for a fixing film having a thickness of 80 μm. In each figure, indicates the film surface temperature that can be fixed (about 200 in this example).
° C), is a graph of surface temperature rise when the initial surface temperature of the fixing film is 130 ° C, and is a graph of surface temperature rise when the initial surface temperature of the fixing film is 20 ° C. As can be seen from the graphs of FIGS. 9 (a) and 9 (b), when the surface temperature of the fixing film before entering the press contact portion is low, the surface temperature of the fixing film in the process of passing through the press contact portion becomes the toner fixing temperature. , And the time required for substantially heating the toner image is shortened. Further, when the fixing film is thick to some extent, the fixing temperature may not be reached by the time the film has passed through the pressure contact portion (the graph of FIG. 9B).

Accordingly, there is a problem that when the surface temperature of the fixing film is low, such as at the start of the fixing processing operation, poor fixing due to insufficient heating is likely to occur, and during continuous operation for a long time, high-temperature offset due to excessive melting of the toner is likely to occur.

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

(Means for Solving the Problems) The present invention has a heating body that is maintained at a controlled temperature and a film that moves while being in contact with a recording material, and performs recording by heat of the heating body via the film. In a fixing device for heating an image on a material, a temperature detecting element for detecting a temperature of the film or a member in contact with the film, and a temperature for setting a temperature control temperature of the heating element according to the detected temperature of the temperature detecting element. A fixing device having a temperature control setting unit.

(Operation) That is, the temperature of the heating element is basically determined at a predetermined temperature by an automatic temperature control system including a temperature sensor provided on the heating element, a microcomputer, and a heating element driving circuit as described above. Temperature control.

The present invention feeds the temperature controlled by the heating temperature control system to a detected temperature of a fixing member or a vicinity of the device, for example, the detected temperature information of the fixing film to the temperature control system as a control factor, and 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 in the pressure contact portion is made substantially the same at the start of the fixing operation and during the continuous operation.

In other words, when the surface temperature of the fixing film is low, such as at the start of the fixing operation, the heating body temperature control temperature is set to an appropriate high level, and the surface temperature of the fixing film increases with the execution of the fixing operation. Thus, the heating body temperature regulation temperature is changed so as to change the heating body temperature regulation temperature appropriately.

This makes it possible to always form a beautiful fixed image without causing a fixing defect due to the low temperature of the fixing film or causing an offset due to a high temperature of the fixing film during a long-time continuous fixing process. Become.

The temperature of the fixing film is substantially the same as the temperature of the pressure roller, the film transport roller, and the temperature of the heating element when no current is supplied. Therefore, instead of the fixing film, the temperature of another part of the fixing device may be detected to change the heating body temperature regulation temperature.

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

Reference numeral 25 denotes an endless belt-shaped fixing film, which is a left driving roller 26, a right driven roller 27, and a heating element fixedly supported by the heater support 21 below the two rollers 26 and 27. The low-heat-capacity linear heating element 20 and the guide roller 26a disposed below the drive roller 26 are suspended between the four members 26, 27, 20, and 26a which are parallel to each other.

The driven roller 27 is an endless belt-shaped fixing film 25.
Of the fixing film 25
A transfer material sheet as a recording material carrying on its upper surface an unfixed toner image Ta conveyed from the image forming unit (9) side at a predetermined peripheral speed in the clockwise direction accompanying the clockwise rotation of the drive roller 26. With the same peripheral speed as the transport speed of P, the rotary drive is performed without wrinkles, meandering, and speed delay.

Reference numeral 28 denotes a pressure roller having a rubber elastic layer having good releasability, such as silicon rubber, as a pressure member, and sandwiching the descending film portion of the endless belt-shaped fixing film 25 to form the heating element 20. The lower surface is brought into opposing pressure contact by a biasing means with a contact pressure of, for example, a total pressure of 4 to 7 kg,
The transfer material sheet P rotates counterclockwise in the forward direction in the transport direction.

Endless belt-shaped fixing film 25 that is driven to rotate
Is repeatedly used for heating and fixing of toner images, so it has excellent heat resistance, release property and durability, and generally has a total thickness of 100 μm.
Hereafter, preferably a thin material having a thickness of 40 μm or less is used.

For example, polyimide, polyetherimide, PES, PFA
(PTFE (tetrafluoroethylene resin)) on a single-layer film of a heat-resistant resin such as (tetrafluoroethylene-perfluoroalkylvinyl ether copolymer resin) or a composite layer film, for example, a 20 μm-thick film at least on the image contacting surface side. 10μ of release coating layer with conductive material added to fluororesin such as PAF
and m-thick ones.

The low-heat-capacity linear heating element 20 as a heating element according to the present example has a horizontally long rigidity, high heat resistance, and heat insulating property whose longitudinal direction is the transverse direction of the fixing film (the direction perpendicular to the running direction of the fixing film 25). A horizontally long member integrally attached and held along the longitudinal direction on the lower surface side of the heater support 21,
2. It comprises a heating element 23, a temperature detecting element 24 as means for detecting the temperature of the heating element 20, and the like.

The heater support 21 secures the overall strength of the heating body 20 and includes, for example, PPS (polyphenylene sulfide), PAI
(Polyamide imide), PI (polyimide), PEEK (polyetheretherketone), high-heat-resistant resin such as liquid crystal polymer, or a composite material of such a resin and ceramic metal or glass.

The heater substrate 22 has a thickness of 1.0 mm, a width of 10 mm, and a length of 2 as an example.
40mm alumina substrate.

As an example, the heating element 23 is formed by applying an electric resistance material such as Ag / Pd, RuO ₂ , Ta ₂ N, etc. to a width of 1.0 mm (screen printing or the like) along a longitudinal direction substantially in the center of the lower surface of the substrate 22. It is a linear or belt-like low-heat-capacity heating element provided.

As an example, the temperature detecting element 24 is a Pt film / thermistor provided by coating (screen printing or the like) along the length at a substantially central portion of the upper surface of the substrate 22 (the surface opposite to the side on which the heating element 23 is provided). It is a resistance thermometer with low heat capacity. In this example, the temperature of the substrate 22 is detected by the temperature detecting element 24 as the temperature of the heating element 20.

In the case of this example, the linear or belt-like heating element 23 is energized from both longitudinal ends thereof to generate heat over the entire length. The energization supplies power corresponding to a desired temperature and energy release amount controlled by the temperature detecting element 24 and a fixing film temperature detecting unit 31 described later.

The fixing film 25 is not limited to the endless belt shape.
As shown in the figure, the end-fixing film 25 wound in a roll around the feed shaft 41 is locked to the take-up shaft 42 between the heating body 20 and the pressure roller 28 under the guide roller 26a. Then, the transfer material sheet P is moved from the delivery shaft 41 side to the take-up shaft 42 side.
May be configured to run at the same speed as the transport speed of the vehicle.

It is preferable that the heating element 20 be protected by forming a sliding protection layer such as Ta ₂ O ₅ on a surface that is a sliding surface with the fixing film 25.

(2) Fixing execution operation The image forming apparatus performs an image forming operation in response to an image forming start signal, and the transfer material sheet P conveyed from the transfer section (9) to the fixing device 11 is guided by the guide 29 and temperature-controlled. The sheet enters a fixing portion N (fixing nip portion) between the heating member 20 and the pressing roller 28 between the fixing sheet 25 and the pressing roller 28 so that the unfixed toner image surface is at the same speed as the conveying speed of the sheet P. The fixing nip N between the heating element 20 and the pressure roller 28 in a state of being overlapped with the fixing film 24 without causing surface deviation or wrinkling due to close contact with the lower surface of the fixing film 25 in the surface moving state in the same direction.
Pass through while receiving the pinching pressure.

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 within the mutual pressure contact width region between the lower surface of the heating element 20 and the upper surface of the pressure roller 28, that is, the width of the fixing nip N. Exist in the area.

In the process of passing through the fixing nip N in a state where the toner image carrying surface of the sheet P is pressed and adhered to the fixing film surface, a heating element is formed.
The heat of 23 is received via the fixing film 25, and the toner image is melted at a high temperature and softened and adhered Tb to the sheet P surface.

In the case of this apparatus, a sheet P as a recording material and a fixing film are used.
The separation from the sheet P is performed when the sheet P passes through the fixing nip N and exits.

At the time of this 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.
Since the sheet P is small, the sheet P hardly causes toner offset to the surface of the fixing film 25, and the sheet P is always smoothly separated without being wound and jammed with the sheet P adhered to the surface of the fixing film 25 due to poor separation. Go.

And since the toner Tb in a state of a temperature higher than the glass transition point has an appropriate rubber property, the toner image surface at the time of separation has an appropriate uneven surface property without following the fixing film surface. Since the toner image is maintained and cooled and solidified, excessive image gloss does not occur on the fixed toner image surface, and high quality image is obtained.

While the sheet P separated from the fixing film 25 is guided by the guide 43 and reaches the discharge roller pair (44), the temperature of the toner Tb, which is higher than the glass transition point, naturally lowers (natural cooling) and is lower than the glass transition point. , And solidifies Tc, and the sheet P on which the image has been fixed is output onto the tray.

(3) Heating and Temperature Controlling Example I In FIGS. 1 and 2, reference numeral 31 denotes an arrangement which is in contact with the inner surface of the fixing film 25 on the upstream side in the running direction of the fixing film from the press contact portion N which is a fixing nip portion. FIG. 3 is an enlarged cross-sectional view of the temperature detection unit.

The unit 31 has a temperature detecting element 33 embedded in a silicone sponge 32, and the surface is covered with a slidable PTFE tape 34.The unit 31 is disposed in contact with the fixing film at the above-described position. The temperature of the fixing film immediately before entering the pressure contact portion N is detected.

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

According to experiments conducted by the present inventors, when Canon-made toner is used, sufficient fixing cannot be performed on the fixing film 25 at 20 ° C. before entering the pressure contact portion unless the heating body 20 is maintained at 190 ° C. or higher (fixing). If the temperature was higher than 210 ° C., the toner was over-melted and offset occurred. Further, as shown in FIG. 4, each temperature changed depending on the temperature of the fixing film before entering the pressure contact portion.

In this embodiment, as shown in Table 1 set based on the results of FIG. 4, the microcomputer controls the temperature control temperature of the heating body temperature control system according to the fixing film temperature detected by the temperature detection unit 31. It was done.

That is, the temperature of the heating element 20 is adjusted to 200 ° C. at the start of the fixing process, and the adjusted temperature of the heating element 20 drops to 195 ° C. and 190 ° C. as the fixing film temperature increases.

This makes it possible to always form beautiful fixed images without causing fixing defects due to the low temperature of the fixing film and without causing offset due to the high temperature of the fixing film during long-term continuous fixing processing. Become.

Table 1 Fixing film temperature Heating temperature control temperature 0 to 30 ° C 200 ° C 31 to 60 ° C 195 ° C 61 to 100 ° C 190 ° C 101 ° C or more 185 ° C (4) Heating temperature control temperature control example II In the above control example I, fixing film Although the temperature is detected, when a very thin fixing film having a thickness of, for example, 20 μm or less is used, a portion that slides with the temperature detection unit 31 may be damaged. Also, when temperature is detected in a non-contact manner, since the fixing film is wavy, a constant space (for example,
(0.3mm) is difficult to maintain and may not be detected.

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

FIG. 5 shows the temperature change of the fixing film 25 and the temperature change of the driven roller 27 when the fixing device is operated for 10 minutes and then stopped. In the apparatus of the present embodiment, a temperature detecting element 41 is provided on the driven roller 27 as shown in FIG. 6 so that the heating element 20 is set to 193 ° C. when the detected temperature is 60 ° C. or lower. If the detected temperature is 60 ° C. or higher, the heating element 20 is controlled to 188 ° C.

As described above, the method of estimating the fixing film temperature by detecting the temperature of the portion other than the fixing film 25 does not require the temperature detecting device to contact the fixing film 25, and is effective for increasing the durability of the fixing film 25. It is a method.

In this embodiment, the temperature of the driven roller 27 is detected.
The temperature of a portion near the fixing film 25 such as the driving roller 26 and the pressure roller 28 may be detected.

If the gap between the temperature detecting element 31 and the fixing film 25 can be kept constant with a device capable of stably transporting the fixing film 25, it is effective to detect the temperature in a non-contact manner.

(5) 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 the present embodiment is an electrophotographic copying apparatus of a reciprocating platen type, a rotating drum type, and a transfer type.

Reference numeral 100 denotes an apparatus housing, and reference numeral 1 denotes a reciprocating type document placing table made of a transparent plate member such as a glass plate disposed on an upper plate 100a of the apparatus housing. Reciprocatingly driven at a predetermined speed in the direction a and the left side a ′.

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

Reference numeral 100b denotes a slit opening serving as a document illuminating unit which is opened on a surface of the machine housing upper plate 100a with a direction perpendicular to the reciprocating movement direction of the document placing table 1 (direction perpendicular to the paper surface) as a longitudinal direction.

The downward image surface of the document G placed and set on the document table 1 sequentially passes through the position of the slit opening 100b from the right side to the left side during the forward movement of the document table 1 to the right side a. During the passage, the light L of the lamp 3 is received through the slit opening 100b and the transparent document table 1 for illumination scanning. The reflected light of the illumination scanning light on the document surface is image-formed and exposed on the surface of the photosensitive drum 4 by the short-focus small-diameter imaging element array 2.

The photosensitive drum 4 is coated with a photosensitive layer such as a zinc oxide photosensitive layer and an organic semiconductor photosensitive layer, and is driven to rotate clockwise as indicated by an arrow b at a predetermined peripheral speed around a center support shaft 4a. The charging device 5 receives a uniform charging process of positive or negative polarity, and the uniformly charged surface receives image forming exposure (slit exposure) of the original image, thereby forming an image on the surface of the photosensitive drum 4. An electrostatic latent image corresponding to a document image is sequentially formed.

The electrostatic latent image is successively visualized by a toner made of a resin or the like which is softened and melted by heating by the developing device 6, and the developed toner image is transferred to a portion where a transfer discharger 9 as a transfer portion is provided. I will do it.

S denotes a cassette in which transfer material sheets P as recording materials are stacked and stored, and the sheets in the cassette are fed out one by one by the rotation of the feed roller 7, and then the toner on the drum 4 is transferred by the registration roller 8. When the leading end of the image forming section reaches the transfer discharger 9, the leading end of the transfer material sheet P also reaches the position between the transfer discharger 9 and the photosensitive drum 4, and the timing is synchronized so that they coincide with each other. Will be fed. Then, the transfer discharger 9 is applied to the surface of the sheet.
Accordingly, the toner images on the photosensitive drum 4 side are sequentially transferred.

The sheet to which the toner image has been transferred in the transfer unit is sequentially separated from the surface of the photosensitive drum 4 by a separation unit (not shown),
The unfixed toner image Ta guided and carried by the fixing device 11 described above is subjected to the heat fixing process by the reference numeral 10, and passes through a guide 43 and a discharge roller 44 as an image formed product (copy), and is supplied to a discharge tray 12 outside the machine. Is discharged on top.

The cleaning device 13 cleans the surface of the photosensitive drum 4 after the image transfer.
Is used for image formation repeatedly after removing contaminants such as transfer residual toner.

(Effects of the Invention) As described above, in the film heating type fixing device, the present invention detects the temperature of a component member of the device, more specifically, the temperature of the fixing film temperature or a temperature near the fixing film temperature. By changing the heating temperature control temperature according to the temperature, the optimum temperature control temperature can be set regardless of the film temperature, and the calorific value for the toner image based on the level of the temperature of the fixing film before the recording material enters the fixing unit. The occurrence of high-temperature offset due to excessive application and the occurrence of fixing failure due to insufficient heat quantity are prevented, and a beautiful fixed image can be obtained from the start of the fixing process to the continuous process.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a fixing device according to one embodiment. FIG. 2 is the same view of the fixing device of another embodiment. FIG. 3 is an enlarged sectional view of a fixing film temperature detecting unit. FIG. 4 is a graph showing the relationship between the fixing film temperature immediately before the pressure contact portion, the heating element temperature, the high-temperature offset temperature, and the lower limit temperature at which fixing is possible. FIG. 5 is a graph showing changes in the fixing film temperature and the driven roller temperature during the fixing operation and during the stop. FIG. 6 is a partial view of an example in which a temperature detecting element is provided on a driven roller. FIG. 7 is a graph showing a relationship among a fixing film temperature, a heating element temperature, a high-temperature offset temperature, and a lower limit temperature at which fixing is possible. FIG. 8 is a schematic configuration diagram of an example of an image forming apparatus. FIG. 9 shows (a) and (b) that the fixing film thickness is 40
FIG. 8 is a graph showing the relationship between the fixing film staying time of the fixing film and the film surface temperature change in the case of μm and 80 μm. Numeral 11 denotes a fixing device, 25 denotes a fixing film, 20 denotes a heating element, 22 denotes a substrate, 23 denotes an electric heating resistor, 24 denotes a heating element temperature detecting element, and 31 denotes a fixing film temperature detecting unit.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Akira Yamamoto 3-30-3 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-63-313182 (JP, A) JP-A-1 −161344 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 13/20 G03G 15/20

Claims (1)

(57) [Claims] A fixing device for heating an image on the recording material by the heat of the heating member through the film; In the above, it is characterized by having a temperature detection element for detecting the temperature of the film or a member that comes into contact with the film, and a temperature adjustment temperature setting means for setting the temperature adjustment temperature of the heating element according to the detection temperature of the temperature detection element. Fixing device.