JPH0687183B2 - Fixing device - Google Patents

Description

The present invention relates to a fixing device used in electrophotographic copying apparatuses, printers and various other image forming apparatuses, and more particularly to a sheet-like transfer material or recording material having an unfixed material. The present invention relates to a fixing device that heats and pressurizes a material to fix it.

(Prior Art and Problems) Conventionally, in an image forming apparatus such as an electrophotographic copying apparatus, heat is applied to a recording material having an unfixed image, for example, a transfer paper having an unfixed toner image, and the offset of the molten toner is applied. The fixing roller, which has to convey the transfer paper to a predetermined path while preventing the above, is required to have conveyability, releasability, abrasion resistance, fixability, and durability under extremely severe conditions.

In order to satisfy the above requirements, an elastic layer is provided on the cored bar,
An elastic rotating body for fixing, that is, an elastic roller, having a structure in which a thin resin layer is formed on the upper surface of the elastic layer is known.

The fixing roller having such a structure is superior in durability and wear resistance as compared with a fixing roller made only of silicone rubber, and has a resin layer such as a fluorine resin without having an elastic layer on the core metal. When compared with the coated roller, it is excellent in fixing property and transportability (particularly wrinkles and curls).

However, the conventionally known elastic roller is inferior in the wrapping property of the sheet (that the sheet as a recording material does not wrap around the roller), particularly in the solid image. When the sheet is wound, it causes a problem of increasing a jam rate (rate of causing a paper jam) in the fixing device.

(Means for Solving Problems) The present invention is intended to improve the drawbacks of the above-mentioned conventional elastic roller, and of course not only the transportability, releasability, wear resistance, and durability of sheet-like conveyed products such as papers, etc. In particular, it is an object of the present invention to provide an elastic rotating body having good winding properties, fixing properties and imageability of a sheet when used as a fixing device, and a fixing device using the elastic rotating body.

Another object of the present invention is to provide a fixing device which eliminates low-temperature offset, image crushing, improves fixability and image quality, and significantly reduces the occurrence of curls and wrinkles on transfer materials, recording materials, etc. that are conveyed and fixed. It is to be.

In order to achieve the above object, the present invention has a pair of rotating bodies that are in pressure contact with each other and a heating body that heats at least one rotating body, and an unfixed image is formed between the pair of rotating bodies. In a fixing device for fixing by passing a recording material that is provided, at least one rotating body has an elastic layer on a core metal material and a resin layer as a release layer on the elastic metal layer, The sum of the thermal resistance of the mold layers is 1.1 cm · sec · degree / calorie or less.

Embodiment An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 3 is a sectional view showing the configuration of an entire embodiment of the image forming apparatus to which the present invention is applied.

In the figure, the surface of a drum 1 is composed of a photoconductor and a seamless photoconductor using a conductor, is rotatably supported by a shaft, and is a main motor 3 which operates in response to the pressing of a copy start key.
Starts rotation in the direction of the arrow. Then, when the predetermined rotation of the drum 1 and the potential control processing (preprocessing) are completed, the original placed on the original table glass 34 is illuminated by the illumination lamp 40 integrally formed with the first scanning mirror 39,
The reflected light is the first mirror 39, the second mirror 36, and the third mirror.
An image is formed on the drum 1 through the lens 37, the lens 35, and the fourth mirror 38.

The drum 1 is corona charged by the high voltage unit 2. After that, the image irradiated by the exposure lamp 40 is slit-exposed, and an electrostatic latent image is formed on the drum 1 by a known method.

Next, the electrostatic latent image on the photosensitive drum 1 is developed by the developing roller of the developing device 7 and visualized as a toner image, and the toner image is transferred by the transfer charger 5.

The transfer paper in the upper cassette 13 or the lower cassette 14 is
The sheet is fed into the main body by the sheet feeding roller 11 or 12, and is fed in the direction of the photosensitive drum 1 by the registration roller 15 at accurate timing so that the leading edge of the latent image and the leading edge of the transfer sheet are aligned. After that, the transfer paper passes between the transfer charger 5 and the drum 1, so that the toner image on the drum 1 is transferred.

After the transfer is completed, the transfer paper is separated from the drum 1 by the separation charger 8, guided by the conveyor belt 17 to the fixing device 32, fixed by pressing and heating, and then discharged by the discharge roller 19 to the outside of the apparatus.

After the transfer, the drum 1 is continuously rotated and its surface is cleaned by a cleaning device 6 formed of a cleaning roller and an elastic blade.

The pedestal 200 can be separated from the main body 100,
It has a deck 54 capable of storing 2000 sheets of transfer paper and an intermediate tray 59 for double-sided copying. Further, the lifter 54L of the deck 54 capable of accommodating 2000 sheets ascends according to the amount of transfer paper so that the transfer paper always contacts the paper feed roller 50.

When performing double-sided copying or multiplex copying, first raise the paper ejection flapper 33 of the main body 100 to pedestal the copied transfer paper.
It is stored in the intermediate tray 59 via the transport path 57 of 200. At this time, the multiple flapper 52 is lowered during double-sided copying, and the multiple flapper 52 is raised during multiple copying. The intermediate tray 59 can store up to 99 transfer sheets. The stored transfer paper is pressed by the intermediate tray weight 53.

At the time of the back side copy or the multiplex copy to be performed next, the transfer sheets stored in the intermediate tray 59 are operated one by one from the bottom by the action of the sheet feeding roller 51 and the weight 53, and the registration roller of the main body 100 through the path 58. Guided to 15.

Reference numeral 300 is a circulation type document feeder (RDF), 301 is a stacking tray for setting a document, and 302 and 303 are document size detection sensors, which are provided at a predetermined interval in the direction perpendicular to the paper surface. The size of the document in the width direction can be determined by checking whether both the sensors 302 and 303 detect the document or only the sensor 303 (assuming 303 is on the back side of the paper) detects the document. A more accurate size can be determined by increasing the number of sensors. Further, the size in the length direction can be determined by the time when the sensor 303 (302) is detecting the document.

Also, in this RDF300, from the stack tray 301 to the sheet path 304
The original sent to the exposure surface through the sheet path 305 can be stacked on the stack tray 301 again.

The detailed operation of RDF is described in Japanese Patent Application No.
Since it is described in detail in No. 206619, it is omitted here.

400 is a finisher, and the copy ejected from the main body is half-folded or Z-folded at a paper folding unit 450 according to designation, and output to a swinging copy tray 401 or to a staple tray 402, and staples each part. The sheets are bound at 403 and dropped to the stacker tray 404.

In the paper folding unit 450, when the Z-folding is designated, the flapper 454 is turned on.
Then, the copy paper is guided to the lower path, the leading edge of the paper is stopped at 451 and the part that is folded into 1/4 through the roller 453 hits the 452 and is folded in half and is again guided from 453 to 455 to 400. . In the case of half-folding, it is folded in half at 451 and is not output to 452 but output from 455 to 400 as it is. When there is no folding, the flapper 454 is turned off and is output straight to 400.

When the staple mode is selected, the finisher 400 outputs a copy to the staple tray 402, turns on the staple 403 according to an instruction from the main body, and staples the sheets. After that, it is dropped to the stacker tray 404. With this repetition, a plurality of copies that are collated and bound are completed. If the staple is not selected, the copy is output to the swinging copy tray 401, and it is possible to make a copy of a plurality of copies by shifting 30 mm to the left and right at a place with a good nail according to an instruction from the main body.

FIG. 1 is an explanatory view showing an embodiment of a fixing device according to the present invention.

In the figure, a transfer material P such as a copy sheet onto which the toner image T has been transferred is separated from the image carrier 1 by the separation charger 8 and conveyed to the fixing device 32 by the conveyor belt 17.

The fixing device 32 has a heating roller 3201 and a pressure roller 3202, and the pressure roller 3202 is brought into pressure contact with the heating roller 3201 at least during fixing by a well-known pressure means. This heating roller 3201 is provided with a heat-resistant elastic body layer of silicon rubber, fluorine rubber, fluorosilicone rubber or the like in a thickness of 0.11 mm or less on the outer peripheral surface of a metal hollow cylindrical roller core metal made of aluminum, stainless steel, copper or the like. Preferably, a heat-resistant release resin layer of PFA, PTFE or the like is further provided thereon in a thickness of 50 μm or less, more preferably 7 to 25 μm. A heating heater 3203 such as a halogen heater and an auxiliary heater 3203 ′ are provided inside the heating roller 3201. The auxiliary heater 3203 ′ is normally in an OFF state and is activated only when the power supply is turned on. To do. Meanwhile, pressure roller 3202
Is a metal hollow cylindrical roller core made of aluminum, stainless steel, copper or the like, and a heat resistant elastic body layer of silicon rubber, fluorine rubber, fluorosilicone rubber, etc.
It is provided in a thickness of 10 mm, and preferably 3 to 100 in the upper layer.
It is made up of a heat-resistant mold-releasing resin layer such as PFA or PTFE having a thickness of μm. For the heat-resistant release resin layer, Daiel GLS-213 (fluorine rubber latex) manufactured by Daikin Industries, Ltd.
A PFA tube manufactured by Gunze Co., Ltd. is suitable. The thick heat-resistant elastic layer of the pressure roller 3202 is for forming a pressure contact area (nip portion) with the heating roller 3201. Inside the hollow of the pressure roller 3202,
A heater 3203 ″ for low heating such as a halogen heater is provided.

A temperature detecting element 3204 such as a thermistor or a thermocouple is arranged in contact with the outer peripheral surface of the heating roller 3201. The detection signal is guided to a known control means (not shown), and the heater 3203 is applied by the control means. By controlling the voltage and the like, the temperature of the outer peripheral surface of the heating roller 3201 is maintained at the toner image melting temperature.

Further, on the outer periphery of the heating roller 3201, the heating roller 32
01 A cleaning member 3205 is provided for removing foreign matter such as offset toner and paper dust attached to the surface from the roller surface. The cleaning member 3205 is configured such that a cleaning web 32051 made of heat-resistant non-woven fabric such as Nomex, Himeron, or polyester is wound from a supply roller 32054 to a winding roll 32053 and is brought into contact with a heating roller 3201 by a pressing roller 32052. . This cleaning web 32051 is wound by a winding roll 32053 which is rotationally driven by a driving means (not shown), and is pulled out from the supply roll 32054 so as to change its abutting position by a small amount. The surface contacts the heating roller 3201. Also a cleaning web
The cleaning effect can be further enhanced by impregnating 32051 with an offset prevention liquid such as dimethyl silicone oil.

Further, on the periphery of the heating roller 3201, curved reflecting plates 3206 and 3206 ′ having heat reflectivity are closely arranged over the entire longitudinal direction. The reflection plate 3206 is arranged around the heating roller 3201 so as to cover the entire surface of the heating roller between the pressing roller 32052 and the entrance of the transfer material P,
The reflection plate 3206 'includes a pressing roller 32052 and a separating claw 3 to be described later.
It is disposed so as to cover the entire surface of the heating roller between the heating roller 208 and the heating roller 208. Covers 3207 and 3207 'having a large thickness for preventing heat radiation, which are made of a heat insulating material such as glass wool, are attached to the outer peripheral surfaces of the reflectors 3206 and 3206'.
It prevents unnecessary heat dissipation from the. That is, the reflector 32
06, 3206 'and covers 3207, 3207' form a covering member for the heating roller 3201.

Further, a casing member 3209 having a substantially U-shaped cross section is provided on the upper side of the fixing device 32, and the cleaning member 3205, the reflection plates 3206 and 3206 ′, the covers 3207 and 3207 ′, and the temperature detection element 32 are provided.
Surrounding 04. On the outside of the casing member 3209, another casing having an L-shaped cross section is provided via an air layer 3210.
3211 is provided.

On the other hand, also on the heating roller 3202 side, a reflection plate 3212 similar to the reflection plate 3206 and a cover 3213 similar to the cover 3207 are provided so as to cover most of the periphery of the pressure roller 3202. A casing 3214 similar to the casing 3209 is provided outside the cover 3213.

These reflectors 3206, 3206 ′, 3212 and covers 3207, 320
By providing 7 ', 3213, it is possible to reduce the heat wasted from the surfaces of the heating roller 3201 and the pressure roller 3202, and to stabilize the temperature measuring property of the temperature detecting element 3204. Therefore, the temperature control of the heating roller 3202 with respect to the set temperature can be stabilized and the power consumption can be reduced.

A guide plate 3215 for guiding the transfer material P to the heating roller 3201 side is provided in the vicinity of the ends of the reflection plate 3206 and the reflection plate 3212 which are close to each other, and the guide plate 3215 is made of PBT (polybutylene terephthalate) or the like. It is made of heat insulating resin.

By the way, the transfer material P having the unfixed toner image T is nipped and conveyed between the heating and pressing rollers 3201 and 3202, and the toner image T is a permanent image on the paper surface by the heat applied by the heated rollers 3201 and 3202. Is fixed as its discharge roller
It is discharged from the device while being sandwiched by 3217 and 3218.

On the discharge port side of the heating roller 3201, a plurality of separation claws 3208 are provided so as to contact the roller surface along the roller axial direction in order to surely separate the transfer material P from the heating roller. In addition, the separation claw 32 is also attached to the outlet side of the pressure roller 3202.
08 'is provided so as to contact the surface of the roller 3202. The separation claw 3208 is held by a support plate 3219 arranged in a separated state from the casings 3209 and 3211, and the separation claw 3208 ′ is also held by a support plate 3220 separated from the casing member 3214. These separation claws 3208 and 3208 ′ are set to 322
With 0'as a fulcrum, the support plates 3219 and 3220 and the paper discharge roller pairs 3217 and 3218 can be moved integrally with the roller pairs 3201 and 3202 so as to be separated therefrom.

As the reflection plates 3206, 3206 ', 3212, it is desirable to use a metal plate having a glossy surface such as an aluminum or copper plate whose surface is polished, or an iron plate subjected to a surface treatment such as chrome plating. Further, the reflection plates 3206, 3206 ', 3212 preferably have a curvature such that they are concentric with the roller peripheral surface, and the thickness thereof is preferably relatively thin.

The covers 3207, 3207 ', 3213 are preferably composed of glass wool, rock wool, ceramic fiber, or foam such as phenol foam or epoxy foam, either individually or in combination.

By the way, in this embodiment, the opening 321 is formed in the support plate 3219.
9'is formed, and an exhaust heat fan 3221 as air cooling means is connected to the opening 3219 '. A heat exhaust fan 32 for exhausting heat around the drum is provided near the image carrier 1.
30 are arranged.

FIG. 2 shows a cross section taken along the line XX of FIG.

Heat-resistant heat insulating sleeves 3223, 3223 'are fitted on the rotating shafts 3224, 3224' of the heating roller 3201, and the heat insulating sleeves 3223, 3223 'are mounted on the frame bodies 3225, 3225' of the fixing device, respectively. It is supported by bearings 3226, 3226 'that are mounted. The rotating shafts 3224 and 3224 'have heat-resistant heat-insulating gears 3227,
3227 'are fitted to each other, and one heat resistant heat insulating gear 3227'
Are meshed with the driving force transmission gear 3228 connected to the driving source M. Then, the heating roller 3201 is rotationally driven by the driving force of the driving source M being transmitted through the driving force transmission gear 3228 and the heat resistant heat insulating gear 3227 '. Further, the other heat-resistant heat-insulating gear 3227 has a gear 322 fixed to the manual knob 3229.
9'is meshed. In the conventional fixing device, the heat loss through the drive system occupies most, but by adopting this configuration, the heat loss to the drive system can be reduced or eliminated, so the thermal efficiency is highly improved. Power consumption can be reduced. Also, with this configuration, heat resistant gears 3227,322
Since heat resistant sleeves 3224 and 3224 'are used in addition to 7', the frame body from the roller end can also prevent heat loss to 3225 and 3225 'and further improve thermal efficiency.

As the heat resistant heat insulating sleeve, polyimide, polyamide imide, polyamide, PPS (polyphenylene sulfide), PBT (polybutylene terephthalate) resin,
A heat insulating member such as a phenol resin or a tetrafluoroethylene resin, or a heat insulating material composed of a mixed material of this kind is preferable.

The gears 3227, 3227 'are preferably made of a heat-resistant material having a good heat-insulating property such as polyimide, polyamide-imide, PPS, modified phenol, or a material containing a tetrafluoroethylene reinforcing filler.

As mentioned above, the heating roller 3201 has a heat resistant sleeve 3224,3
The machine body and the frame bodies 3225 and 3225 'are thermally isolated from each other by 224' and the heat resistant gears and 3227 and 3227 ', and the heat loss transmitted through them is extremely small. In this way, the method in which the roller is thermally isolated from the driving force transmission path is very effective in improving the thermal efficiency.

(Experimental Example) With the above configuration, the present applicant actually performed a fixing property test using a fixing device as described below.

As heating roller 3201, outer diameter φ59.3mm, reverse crown amount
150 μm, aluminum (A5056) roller core metal wall thickness 12 mm, surface layer 0.065 mm thick silicone rubber and 10 μm thick PTFE coated roller as heating roller 3202, outer diameter φ60 mm,
A roller having a hardness of 40 ° (JIS A) in which a thermally vulcanized silicone rubber layer having a thickness of 5 mm and a fluorine rubber latex layer having a thickness of 20 μm were coated on a φ50 mm stainless steel roller core metal was used.

As the silicone rubber of the heating roller 3201, 55 parts by total of titanium oxide, nickel oxide, cobalt oxide and silica as a filler were mixed with 100 parts of rubber, and the thermal conductivity K was K = 2.0 × 10 ^−3. cal / cm / sec / K, rubber hardness (JISA)
Used a 68 degree one.

As the toner, 100 parts of styrene-acryl which is a binder resin, 60 parts of a magnetic material, and a charge control agent (CA agent) 2
The part was kneaded and pulverized to an average particle size of 10 μm, and 0.4% of dry silica was externally added to the mixture.

Also, the heater 3203 in the heating roller is 870 W and the heater 3203 '
Used a 350 W halogen heater, and the heater 3203 'was turned on only at the start-up (during weight). On the other hand, as the heater 3203 ″ in the pressure roller, a 70 W sheathed heater was used, and it was turned on only during the copying operation.

The nip width was 9.0 mm and the heating roller surface temperature was 195 ° C.

FIG. 4 is a view for explaining a change diagram of the surface temperature of each roller with respect to time for the experiment of the above specific example. Time t = t1
When the power is turned on, the heaters 3203 and 3203 'and the heater 320
3 ″ lights up. When the heating roller surface temperature rises as shown in the figure and the heating roller surface temperature reaches 170 ° C. (point A, time t1), both rollers 3201 and 3202 that have stopped start pressure contact rotation, The surface temperature of the pressure roller also rises sharply.

When the heating roller surface temperature reaches 195 ° C (point B, time t
2) Fixing is possible and both rollers 3201 and 3202 stop rotating. The heating roller 3201 is held by the control means (not shown) so that the surface temperature becomes around 195 ° C. On the other hand, the surface temperature of the pressure roller 3202 drops because heat is not supplied from the fixing roller. After about 5 minutes (point C) from the fixing possible state, the pressure roller temperature becomes the lowest, and then the temperature of the pressure roller gradually increases due to the heat of the heater 3203 ″ from the inside. Therefore, the fixing ability at the point C is the lowest. Therefore, continuous copying at this point C is extremely preferable as a comparative experiment of fixing property.
The temperature change during continuous copying of 250 sheets at the end of 250 sheets (D
(Dots) are included.

The experimental results shown below were performed under the following conditions between C and D. In other words, under the environment of 15 ℃, copy speed 445mm / sec (A3 size paper, 43 sheets / min), weighing 80g / m ² A3 paper with φ24mm solid black arranged in a grid pattern with three pieces at regular intervals. From the continuous copy of 250 sheets, the sample is extracted every 25 sheets, such as the first sheet, the 25th sheet, the 50th sheet ... Was evaluated as the fixability.

This fixing property was evaluated by using Silbon C (trade name, Kojin Co., Ltd., Silbon paper), rubbing 10 times at a pressure of 40 g / cm2, and measuring the density difference before and after rubbing with a Macbeth reflection densitometer. Digitized.

Ie D: φ24 reflection density before rubbing a solid image (1.0 ≦ D ≦
Adjust the image density so that it becomes 1.1. D ': Reflection density after rubbing a φ24 solid color image ΔD: Density reduction rate Then, the average of the density reduction rates of the solid color portions at 9 locations was used to evaluate the fixability.

Further, FIG. 5 shows an operation sequence of the exhaust heat fans 3221 and 3230 in this embodiment. In Figure 5, t0 is when the power is turned on,
t1 is the start of the previous multi-rotation, t2 is the release of the wait after the previous multi-rotation is completed, t2 to t3 is the standby (when copying is possible but not copying), t4 is the copy start, and t4 to t5 is the copy , T5 is the end of copying, and t5 to is the standby.

When the power is turned on at t0, the exhaust heat fans 3221 and 3230 become OF
The F state is maintained and the ON state is not reached until time t3.
In this experimental example, the exhaust heat fan 3221 is turned on in a half speed state during standby and turned on in a full speed state during copying.

Also, the exhaust heat fan 3230 is always in the full-speed state from time t3.
Becomes

The main purpose of the exhaust heat fan 3221 to be turned on in the half speed state during standby is to prevent noise.

In this experimental example, the heat exhaust fan 322 is turned on after the power is turned on.
The time t3 until the 1,3230 is operated is variable according to the temperature of the fixing roller when the power is turned on.

In this experimental example, t3 was set as follows.

Note that after the time t3 minutes has elapsed, even if the exhaust heat fans 3221 and 3230 are intermittently operated at predetermined intervals, or if the heating roller 3201
A temperature detecting element 3222 is provided in the vicinity, and when the detected temperature is higher than or equal to a predetermined temperature, it is strong and when it is lower than the predetermined temperature, it is operated weakly
It may be operated only when the temperature is equal to or higher than a predetermined temperature. Also, the exhaust heat fans 3221 and 3230 are always turned on in synchronization with each other.
You do not have to turn it off.

The result of the fixing property test under the above conditions is shown by the curve (a) in FIG.

In the above-mentioned fixing evaluation method, the range showing good fixability in a normal line image is the case where the density reduction rate is 20 to 25% or less. It exhibited fixability.

Also, the amount of offset toner attached to the cleaning web 32051 at this time is very small, and even if the moving speed of the cleaning web 32051 (cleaning web thickness 55 μm) is set to 30 copies / 1 mm, it can be sufficiently cleaned. It was a slight amount.

Further, when the temperature of the fixing roller was increased from 160 ° C. to 230 ° C. in 10 ° steps and the amount of offset toner at each temperature was confirmed, the amount of offset toner was extremely small in any temperature range.

Next, under a high humidity environment of 32.5 ° C and 85%, A3 (size) paper (paper slip direction is horizontal to the advancing direction), B4 paper (vertical ski), A4 (R) paper (longitudinal feed, Vertical scan), A4 paper (transverse feed,
When double-sided copying is performed using (Skip), all the papers are conveyed well, and there is no stacking failure on various trays such as the intermediate tray 59 and the swinging copy tray 401, and there are no wrinkles. There wasn't. Further, since the curl was small, the transfer / separation failure (separation failure or retransfer) on the second surface did not occur at all. Next, image misalignment was confirmed under a low humidity condition of 15 ° C and 15%, but there was no problem at all.

The image shift described above means the following development. That is, the heating roller has an inverted crown shape in order to prevent paper wrinkles in a high humidity environment, and since there is a difference in outer diameter between the center part and both ends, the transfer speed of copy paper between both parts is high. Difference (that is, the transport speed at the edge is faster than the transport speed at the center), and there is a gap between the copy paper and the heating roller, causing image bleeding at both ends on the trailing edge of the copy paper. Say When this phenomenon becomes remarkable, horizontal wrinkles occur on the copy paper.

Next, 50 solid images were continuously fed in an environment of 20 ° C, but the separability of the copy paper was very good.
, The copy paper was ejected with little reliance. The amount of oil applied from the web at this time was about 1.0 × 10 ⁻⁴ g / sheet. In addition, the copy image quality under each environment was able to maintain the high image quality with a glossy and moist feeling. In order to further clarify the effectiveness of the above-described embodiment of the present invention, the following comparative example was performed, which will be shown.

(Comparative Example 1) As a heating roller 3201, a reverse crown amount of 150 μm and a wall thickness of 12 mm
A roller having an outer diameter of the central portion of 59.3 mm was used by coating the aluminum cored bar with PFA or PTFE having a thickness of 35 μm. (Others are the same as the conditions in the above-described experimental example.) (Comparative example 2) As the heating roller 3201, the reverse crown amount is 150 μm, and the wall thickness is 12 mm.
A roller having an outer diameter of 58.8 mm, coated with 0.3 mm of silicon rubber, and the outer periphery of which was coated with 10 μm thick PTFE was used. As the silicone rubber, one having a rubber hardness (JIS A) of 60 degrees was used. The thermal conductivity K _R of silicon rubber is K _R = 0.5 × 10 ⁻³ [cal / cm · sec · deg] The thermal conductivity K _TF of PTFE is K _TF = 0.6 × 10 ⁻³ [cal / cm · sec · deg].

When the same experiment as in (Experimental example) was conducted, in (Comparative example 1), as shown by the line (b) in FIG. 6, the fixing property was deteriorated from the middle of continuous paper feeding. This is a problematic level in actual use.

In addition, a large amount of offset toner adheres to the web, and toner that cannot be completely cleaned by the web adheres to the next copy paper, which significantly deteriorates the copy image quality.

Further, under high humidity, wrinkles occurred on A3 paper, B4 paper, and A4 (R) paper. There was no wrinkle on the A4 paper, but the curl of the paper was large, and stacking failure occurred on various trays.

Therefore, when the reverse crown amount was set to 200 μm, the occurrence of paper wrinkles under high humidity disappeared, but a noticeable image shift occurred in a low humidity environment, and copy image quality deteriorated remarkably. Also.
In each environment, the copy image quality was glossy and flat.

Next, in (Comparative Example 2), fixability, toner offset,
As for wrinkles, curls, image shifts, and image quality, relatively good results were obtained, but in the passage of a solid image, the wrapping force on the heating roller was strong and the separation nail 3208 forcedly peeled it off. , Marks of separated nails (hereinafter referred to as nail marks) were prominent. In the case of extreme development, the copy paper may have wrinkles on the entire surface, and if the separation claw is soiled with toner, it may cause jamming.

To prevent the above phenomenon, a low viscosity (for example, 25 ℃
Good results were obtained when a large amount of silicone oil having a viscosity of 100 Cs or 300 Cs in (1) was applied, but copy stains and other oil stains tended to occur, and copy quality deteriorated.

In addition, it is difficult to always apply an appropriate amount of low-viscosity oil, and if the size of the device is increased, the cost is increased, or if an appropriate amount of oil adheres to the drum surface during double-sided copying, abnormal images such as fog may occur, and The paper feed roller 51 slips, causing a paper feed failure, which is not preferable.

The above results are summarized in the table below.

As described above, in Comparative Example 2, good results were obtained except for the nail marks.

Therefore, regarding nail marks, silicone rubber and resin (PTF
Detailed experiments were performed under various thermal resistances by changing the thickness of E) as shown in the following table.

In the above table, K _TF is for all test rollers
Using 0.6 × 10 ⁻³ [cal / cm · sec · deg], the sum R _H of the thermal resistances of the rubber layer and the resin layer is R _H = (2πK _R ) ⁻¹ .ln (r ₂ / r ₁ ) + (2πK _TF ) ^-1 .ln (r ₃ / r ₂ ) [cm ・ sec ・ deg / cal], where r ₁ , r ₂ and r ₃ are core metal, rubber layer and resin The radius at the outer surface of the layer. Also, the outer diameter of the aluminum cored bar is 58.8 mm, and the hardness of the silicon rubber is 60 ° (JIS A)
Is.

In this way, from the viewpoint of thermal resistance, the sum of the thermal resistance of the elastic layer (rubber layer) and the release layer (resin layer) is 1.1 [cm ・ sec ・
[deg / cal] or less, it is understood that the result is good for nail marks and is good when integrated with the results for other items in the previous table.

The reasons for the above results will be described below.

(Experimental example) and (Comparative example 2) have similar results except that the nail marks are removed. What is common to both is that the roller has elasticity.

On the other hand, (Comparative Example 1) is almost a rigid roller.

FIGS. 7A and 7B schematically show how toner is fixed in the nip portion of both rollers. In FIG. 7, 3201 is a fixing roller, T is toner, and P is copy paper. FIG. 7 (a) is an elastic type, and FIG. 7 (b) is a rigid type. As shown in FIG. 7 (a), the elastic type roller deforms itself due to the unevenness of the toner, so that the contact area with the toner is large and the heat transfer efficiency is high (the arrow indicates the heat flow). Moreover, since the contact pressure per unit contact area is relatively weak, the toner image is less likely to be crushed.

On the other hand, as shown in FIG. 7 (b), since the rigid type roller hardly deforms itself, the contact area with the toner is smaller than that of the elastic type roller. Therefore, the heat transfer efficiency is low, the contact pressure per unit contact area is larger than that of the elastic type, the crushing of the toner image is large, and so-called fly dust, etc., in which the toner is scattered to the non-image portion, is likely to occur. The reason why the elastic type roller has better fixing property, toner offset, and image quality is largely due to the above-mentioned characteristics.

Further, it is considered that the winding property at the time of solid black depends largely on the viscoelasticity of the toner. That is, when the toner is heated, its temperature naturally rises, but when it reaches a certain temperature, there is an endothermic period at which the temperature does not rise temporarily even though the toner continues to be heated. Therefore, it is considered that the heat energy at that time is absorbed by the toner and used for the change of viscoelasticity. Then, when the heating is further continued, the temperature of the toner rises again. Although the detailed principle has not been clarified yet by the inventor, it has been confirmed that the wrapping property is extremely good at the temperature of the endothermic period or higher and the wrapping does not occur. Therefore, in the case where the heating amount is set, according to the roller having elasticity and large amount of transferred heat,
The temperature above the endothermic time is easily reached.

The reason why the PFA roller claw marks are good in (Comparative Example 1) is that the contact area is small and therefore not only easy to peel off, but also the release layer of the roller (which can be said to be a heat insulating layer) is as thin as 35 μm. In addition, when the roller and toner come into contact with each other, a large amount of heat flows per unit contact area, and as a result,
The melting degree of PP near the contact surface and the degree of protrusion to the surface are high,
It can be said that the wrapping property is small.

On the other hand, in the case of (Comparative Example 2), since the thickness of the release layer (that is, the thickness of the heat insulating layer) is as thick as 0.310 mm, the thermal resistance of the roller is high, and the unit contact area when the roller and the toner contact each other. Since the amount of heat flowing to the contact is relatively small, the viscoelasticity of the toner cannot be obtained sufficiently and the PP is difficult to melt, resulting in an insufficient releasing effect and significant nail scratching.
In the case of the roller of the present embodiment, the thickness of the release layer is reduced as much as possible within the range where elasticity can be secured, so that the heat conduction of the release layer can be increased and the unit contact area per unit area can be increased. The amount of heat supplied to the toner was sufficient and good results were obtained. Also, due to the elastic effect, good results were obtained in all of fixing property, offset property, wrinkle, curl, and image shift. The reason why the elastic roller has good wrinkles, curls, and image shifts depends largely on the place where the soft pressing is performed.

(Effects of the Invention) The present invention provides the above-mentioned elastic layer and resin when the rotating roller for performing heating and pressure fixing as described above is formed by forming the elastic layer on the core metal and the resin layer thereon. Since the sum of the thermal resistance of the layers is set to 1.1 cm / sec / deg / cal or less, the heat transfer is improved while ensuring elasticity, and as a result, the performance of the entire device, such as the finish of the copy and the reduction of device troubles, is improved. The effect is to improve.

[Brief description of drawings]

FIG. 1 is a sectional view of a fixing device as an embodiment of the present invention, FIG. 2 is a sectional view taken along the line XX of the device of FIG. 1, and FIG. 3 shows the entire image forming apparatus to which the device of FIG. 1 is applied. FIG. 4 is a sectional view showing the structure, FIG. 4 is a diagram showing temperature changes with time on the surface of each roller of the apparatus of FIG. 1, FIG. 5 is an operation sequence diagram of an exhaust heat fan of the apparatus of FIG. 1, and FIG. 1 is a diagram showing the test results of the apparatus, FIG. 7 is a schematic diagram showing the contact state of the roller and the toner. 3201 …… Rotating body (heating roller)

Continuation of the front page (56) Reference JP-A-57-89785 (JP, A) JP-A-60-205560 (JP, A) JP-A-61-138272 (JP, A) JP-A-60-19178 (JP , A) JP 60-263979 (JP, A) JP 61-41163 (JP, A) JP 61-84671 (JP, A)

Claims (1)

[Claims] 1. A pair of rotating bodies that are in pressure contact with each other and a heating body that heats at least one rotating body, and a recording material having an unfixed image is passed between the pair of rotating bodies. In at least one of the rotating members, an elastic layer is provided on the cored bar material, and a resin layer as a release layer is provided on the core layer. Is less than 1.1 cm / sec / degree / calorie.