JPH0648413B2 - 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 provides a heating roller having a cored bar, a rubber layer provided on the cored bar, and a releasing resin provided on the rubber layer, and the heating roller. In a fixing device having a heater provided inside and a pressure roller in pressure contact with a heating roller, the rubber layer has a higher thermal conductivity than the resin layer, and the sum of the thermal resistances of the rubber layer and the resin layer is the same. 2.0 centimeters / second
At a temperature of not more than ° C / calorie, a heating roller and a pressure roller sandwich and convey a recording material supporting an unfixed image made of toner containing a release agent to fix the recording material.

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 the 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 pressing of a copy start key.
Starts rotation in the direction of the arrow. 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 that is integrally formed with the first scanning mirror 39, and The reflected light is reflected by the first mirror 39, the second mirror 36,
An image is formed on the drum 1 through the third mirror 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 sent to the inside of the main body device by the paper feed rollers 11 or 12, and is sent to the photosensitive drum 1 at accurate timing by the registration roller 15 to transfer the latent image tip and the transfer paper. The tip of is matched. After that, the transfer charger 5 and the drum 1
The toner image on the drum 1 is transferred by the transfer paper passing between the transfer roller and the transfer roller.

After the transfer is completed, the transfer paper is separated from the drum 1 by the separation charger 8 and guided to the fixing device 32 by the conveyor belt 17,
It is fixed by pressing and heating, and then the discharge roller 1
It is discharged out of the machine by 9.

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

The pedestal 200 has a deck 54 that can be separated from the main body 100 and can accommodate 2000 sheets of transfer paper, and an intermediate tray 59 for double-sided copying. Also, 20
The lifter 54L of the deck 54 capable of accommodating 00 sheets rises in accordance with the amount of transfer paper so that the transfer paper always contacts the paper feed roller 50.

At the time of double-sided copy or multiplex copy, first, the paper discharge flapper 33 of the main body 100 is raised to store the copied transfer paper in the intermediate tray 59 via the conveyance path 57 of the pedestal 200. At this time, the multiple flapper 52 is lowered during the double-sided copy, and the multiple flapper 52 is raised during the multiple copy. 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 next back side copy or multiplex copy, the transfer sheets stored in the intermediate tray 59 are transferred 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 is passed through the path 58. You are led to 15.

Reference numeral 300 is a recycle type document feeder (RDF), 301 is a stacking tray for setting documents, 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 is measured by the sensor 302.
Are both 303 and 303 detecting the original? Sensor 303
The determination can be made by checking whether or not only (303 is on the back side of the paper surface) detects the document. A more accurate size can be determined by increasing the number of sensors. Also, the size in the length direction is measured by the sensor 303 (302).
Can be determined by the time when the document is detected.

Further, in this RDF 300, the original sent from the stack tray 301 through the sheet path 304 to the exposure surface is sent through the sheet path 305, so that the stack tray 301 is restored again.
Can be loaded to.

The detailed operation of the RDF is described in detail in Japanese Patent Application No. 59-206619 filed by the applicant of the present invention, and therefore the description thereof is omitted here.

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

When the Z-folding is designated, the paper folding unit 450 receives the flapper 45.
4 is turned on, the copy paper is guided to the lower bus, the front end of the paper is stopped at 451 and the portion that is folded into 1/4 through the roller 453 hits 452 and is folded in half and again from 453 to 4
It leads to 400 through 55. 451 when half-folded
It is folded in half at the part of 452 and it goes to 452 as it is 45
Output from 5 to 400. Flapper 4 when unfolded
54 is turned off and is output straight to 400 as it is.

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 onto the stacker tray 404. With this repetition, a plurality of copies that are collated and bound are completed. If no staple is selected, the copy is output to the swing 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 where the nail is good 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 known pressure means. This heating roller 3201 has a heat-resistant elastic body layer of silicon rubber, fluorine rubber, fluorosilicone rubber, etc., 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. Provided, and preferably PFA, PTFE on the upper layer.
The heat-resistant mold-releasing resin layer such as is provided in a thickness of 50 μm or less, more preferably 7 to 25 μm. The heating roller 3
A heating heater 3203 such as a halogen heater and an auxiliary heater 3203 ′ are arranged inside the hollow of 201.
The auxiliary heater 3203 'is normally in the OFF state and operates only at the start-up after the power is turned on. On the other hand, the pressure roller 3
202 is a metal hollow cylindrical roller core made of aluminum, stainless steel, copper or the like, provided with a heat resistant elastic body layer of silicon rubber, fluorine rubber, fluorosilicone rubber or the like in a thickness of 2 to 10 mm on the outer peripheral surface thereof, preferably Further, a heat-resistant mold release resin layer such as PFA or PTFE having a thickness of 3 to 100 μm is further provided thereon. As the heat-resistant release resin layer, Daiel GLS-2 manufactured by Daikin Industries, Ltd.
13 (Fusso rubber latex) and PFA of Gunze Co., Ltd.
A tube or the like is suitable. In this way, the pressure roller 32
The heat-resistant elastic layer of No. 02 is thick in order to form a pressure contact region (nip portion) with the heating roller 3201. A heater 3203 ″ for low heating such as a halogen heater is provided inside the hollow of the pressure roller 3202.

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 voltage applied to the heater 3203 is controlled by the control means to keep the temperature of the outer peripheral surface of the heating roller 3201 at the toner image melting temperature. .

Further, a cleaning member 3205 is provided on the outer periphery of the heating roller 3201 to remove foreign matter such as offset toner and paper dust attached to the surface of the heating roller 3201 from the roller surface. This cleaning member 32
Reference numeral 05 denotes a heating roller 32 by a pressing roller 32052 while winding a cleaning web 32051 made of heat-resistant non-woven fabric such as Nomex, Himeron or polyester from a supply roller 3205% 4 to a winding roll 32053.
01 to contact. This cleaning web 32051 is wound by a winding roll 32053 which is rotationally driven by a driving means (not shown), and is drawn from the supply roll 32054 so as to slightly change its contact position, and a new surface of the cleaning web 32051 is always present. Contact with the heating roller 3201. If the cleaning web 32051 is impregnated with an offset prevention liquid such as dimethyl silicone oil, the cleaning effect can be further enhanced.

Furthermore, around the heating roller 3201, curved reflecting plates 3206 and 3206 'having heat reflectivity are closely arranged over the entire longitudinal direction. The reflector 3206 is
Around the heating roller 3201, the pressing roller 320
The reflecting plate 3206 'is arranged so as to cover the entire heating roller surface between 52 and the entrance of the transfer material P, and the reflection plate 3206' covers the entire heating roller surface between the pressing roller 32052 and a separating claw 3208 described later. It is arranged to cover. The outer peripheral surfaces of the reflection plates 3206 and 3206 'are covered with a thick cover 32 made of a heat insulating material such as glass wool for preventing heat radiation.
07, 3207 'are attached to the reflector 320.
It prevents unnecessary heat radiation from 6,3206 '. That is, the reflectors 3206 and 3206 'and the cover 3207,
3207 'constitutes a cover member for the heating roller 3201.

A casing member 3209 having a substantially U-shaped cross section is provided above the fixing device 32, and the cleaning member 32 is provided.
05, reflectors 3206, 3206 ', cover 3207,
Surrounding 3207 'and the temperature sensing element 3204.
An air layer 321 is provided outside the casing member 3209.
Another casing 3211 having an L-shaped cross section is provided via 0.

On the other hand, on the pressure 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. Further, on the outside of the cover 3213, a casing 321 similar to the casing 3209 is provided.
4 are provided.

By providing the reflection plates 3206, 3206 ', 3212 and the covers 3207, 3207', 3213, it is possible to reduce the heat wasted from the surfaces of the heating roller 3201 and the pressure roller 3202, and to detect the temperature. The temperature measurement property of the element 3204 can be stabilized. Therefore, the temperature 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 near 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 ejected outside the apparatus while being nipped by the paper ejection rollers 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 reliably separate the transfer material P from the heating roller. A separation claw 3208 ′ is also provided on the discharge port side of the pressure roller 3202 so as to contact the surface of the roller 3202. The separation claw 3208 is provided on the support plate 32 that is arranged in a state of being separated from the casings 3209 and 3211.
19, the separation claw 3208 'is also held by the casing member 3
It is held by a support plate 3220 in a state of being separated from 214.
These separation claws 3208, 3208 'have support plates 3219, 32 with 3220' as a pivotal fulcrum at the time of jam clearance.
20 and the discharge roller pair 3217, 3218,
It is movable so as to be separated from the roller pairs 3201 and 3202.

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 which has been subjected to a surface treatment such as chrome plating. In addition, the reflector 320
The shapes of 6,3206 'and 3212 preferably have a curvature that is concentric with the roller peripheral surface. The thickness is preferably relatively thin.

The covers 3207, 3207 'and 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, an opening 3219 'is formed in the support plate 3219, and an exhaust heat fan 3221 as air cooling means is connected to the opening 3219'. An exhaust heat fan 3230 that exhausts heat around the drum is arranged near the image carrier 1.

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

Heat-resistant heat insulating sleeves 3223 and 3223 'are fitted on the rotary shafts 3224 and 3224' of the heating roller 3201, respectively, and the heat insulating sleeves 3223 and 3223 'are fitted.
Are supported by bearings 3226 and 3226 'mounted on frame bodies 3225 and 3225' of the fixing device, respectively. Heat-resistant heat-insulating gears 3227 and 3227 'are fitted to the rotating shafts 3224 and 3224', respectively, and one heat-resistant heat-insulating gear 3227 'is meshed with a driving force transmission gear 3228 connected to the driving source M. ing. Therefore, the heating roller 3201 is driven by the driving force of the driving source M by the driving force transmission gear 3
It is transmitted through 228 and the heat-resistant heat insulating gear 3227 'and is rotationally driven. Also, the other heat-resistant heat-insulating gear 32
27 includes 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. Further, in this configuration, the heat resistant gear 322
7,3227 'plus heat resistant sleeves 3224,32
Since 24 'is used, the frame from the roller end is also 32
The heat loss to 25, 3225 'can be prevented and the thermal efficiency can be further improved.

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

The gears 3227 and 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 described above, the heating roller 3201 is made of the heat resistant sleeve 3
224, 3224 'and heat resistant gears, 3227, 322
The machine body 7 and the frame bodies 3225 and 3225 'are thermally erected by 7', and the heat loss transmitted through these becomes extremely small. In this way, it is very effective to improve the thermal efficiency by making the roller thermally stand up from the drive force transmission path.

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

As the heating roller 3201, a roller having an outer diameter of φ59.3 mm, a reverse crown amount of 150 μm, an aluminum (A5056) roller core metal wall thickness of 12 mm, and a surface layer coated with silicon rubber of 0.065 mm thickness and PTFE of 10 μm, As the pressure roller 3202, a roller having a hardness of 40 ° (JISA) obtained by coating a stainless steel roller core having an outer diameter of φ60 mm and φ50 mm with a 5 mm thick heat-vulcanizable silicone rubber layer and a 20 μm thick fluorine rubber latex layer, respectively. Using.

As the silicone rubber of the heating roller 3201, rubber 10
A total of 55 parts of titanium oxide, nickel oxide, cobalt oxide, and silica were mixed as a filler to 0 part, and the thermal conductivity K was K = 2.0 × 10 ⁻³ cal / cm · sec ·
K, rubber hardness (JIS A) of 68 degrees was used.

As the toner, 100 parts of styrene-acryl as a binder resin, 60 parts of a magnetic material, polypropylene (3 parts of PP) as a release agent, and 2 parts of a charge control agent (CA agent) were kneaded to obtain an average particle size of 10 μm. A pulverized product to which 0.4% of dry silica was externally added was used.

Further, the heater 3203 in the heating roller is a 870 W halogen heater, and the heater 3203 ′ is a 350 W halogen heater.
The heater 3203 'was turned on only at the time of rising (during weight). On the other hand, the heater 3203 ″ in the pressure roller is 70 W
The sheathed heater was used and turned on only when the copying operation was not performed.

The nip width is 9.0 mm and the heating roller surface temperature is 19 mm.
It was set to 5 ° 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 = t
When the power is turned on in 1, the heaters 3203 and 3203 '
And the heater 3203 ″ are turned on. When the heating roller surface temperature rises as shown in the drawing and reaches the heating roller surface temperature of 170 ° C. (point A, time t1), both rollers 3 stopped.
201 and 3202 start pressure contact rotation, and the surface temperature of the pressure roller rapidly rises.

When the heating roller surface temperature reaches 195 ° C. (point B, time t2), fixing is possible and both rollers 3201, 3202
Stops 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 decreases 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.In this figure, the temperature change at the time of continuous copying of 250 sheets at point C is the end of 250 sheets (point D). Is included.

The experimental results shown below were performed under the following conditions between C and D above. That is, under the environment of 15 ° C, the copy speed is 445 mm / sec (A3 size paper, 43 sheets / minute), and the weighing amount is 80 g / m ² A3 paper is a flat black of φ24 mm, which is arranged in a grid pattern at intervals of 3 in a matrix. To form 2
1st, 25th, 5th from 50 copies
Samples were extracted every 25 sheets, such as the 0th sheet, ..., 250th sheet, and the solid black at 9 locations on each sheet were evaluated for fixing property.

This fixing property was evaluated by using a symbol C (trade name, Kojin Co., Ltd., symbol paper), rubbing 10 reciprocations at a pressure of 40 g / m ² , and measuring the temperature difference before and after rubbing with a Macbeth reflection densitometer. Digitized.

Ie D: reflection density before rubbing a φ24 solid black image (1.
The image temperature is adjusted so that 0 ≦ D ≦ 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.

In addition, the exhaust heat fans 3221 and 323 in the present experimental example
The operation sequence of 0 is shown in FIG. In FIG. 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, t2 to t3 are the standby (when copying is possible but not copying), t4. Is at the start of copying, t4 to t5 is at copying, t5 is at the end of copying, t
5 is at the time of standby.

When the power is turned on at t0, the exhaust heat fans 3221 and 3
230 keeps the OFF state, and becomes the ON state only at time t3. In this experimental example, the exhaust heat fan 3221 is turned on in the half speed state during standby and turned on in the full speed state during copying.

Further, the exhaust heat fan 3230 is always turned on in the full speed state from time t3.

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

In this experimental example, the heat exhaust fan 32 is turned on after the power is turned on.
The time t3 until the 21, 3230 is operated is variable according to the fixing roller temperature when the power is turned on.

In this experimental example, t3 was set as follows.

After the time t3 minutes has elapsed, the exhaust heat fans 3221 and 323 are
0 is intermittently operated every predetermined time, or a temperature detecting element 3222 is provided around the heating roller 3201 to operate strongly when the detected temperature is equal to or higher than a predetermined temperature and weakly operate when the detected temperature is lower than the predetermined temperature. You may make it operate only at the time. Further, the exhaust heat fans 3221 and 3230
Need not necessarily be synchronized and turned on and off.

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

In the above fixing evaluation method, the range in which a normal line image exhibits good fixability is the case where the density decrease rate is 20 to 25% or less.
It showed good fixability for all 0 sheets.

Further, the offset toner adhered to the cleaning web 32051 at this time is very small, and the cleaning web 32051 (the thickness of the cleaning web is 55 μm).
Even when the moving speed of m) was set to 30 copies / mm, the amount was small enough to be sufficiently cleaned.

In addition, the temperature of the fixing roller should be 1
When the amount of offset toner was checked at each temperature by increasing the amount by 0 °, the amount of offset toner was extremely small in any temperature range.

Next, in a high humidity environment of 32.5 ° C. and 85%, A3 (size) paper (the paper slip direction is a horizontal slip relative to the traveling direction),
B4 paper (vertical ski), A4 (R) paper (longitudinal feed, vertical ski),
When double-sided copying was performed using A4 paper (horizontal feed, horizontal skip), all the papers were conveyed well, and there was a poor stacking on various trays such as the intermediate tray 59 and the swinging copy tray 401. , No wrinkles occurred. 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 low humidity of 15 ° C. and 15%, but there was no problem at all.

The image shift described above refers to the following phenomenon. 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 (i.e., the transport speed at the edge is higher than the transport speed at the center), there is a gap between the copy paper and the heating roller, and image bleeding appears at both edges 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 a 20 ° C. environment, but the separability of the copy paper was very good, and the copy paper was ejected to the separating claw 3208 with little dependence.
The amount of oil applied from the web at this time is about 1.0 x 10
It was ^-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 the heating roller 3201, a reverse crown amount of 150 μm,
35 μm thick PFA or 12 mm thick aluminum cored bar
A roller coated with PTFE and having an outer diameter of the central portion of 59.3 mm was used. (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 150 μm,
0.3 mm on an aluminum core bar with a wall thickness of 12 mm and an outer diameter of 58.8 mm
mm silicon rubber is coated, and further 10 μm on the outer circumference.
A thick PTFE coated roller was used. As the silicone rubber, one having a rubber hardness (JISA) of 60 degrees was used. Note that here, the thermal conductivity K of silicon rubber
_R is K _R = 0.5 × 10 ⁻³ [cal / cm · sec · deg] PTFE thermal conductivity K _TF is K _TF = 0.6 × 10 ⁻³ [cal / cm · sec · deg] Is.

When the same experiment as in (Example) was carried out, in (Comparative Example 1), as shown by the line (b) in FIG. 6, the fixing property was deteriorated from the middle of continuous sheet 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. No wrinkles were generated on the A4 size paper, but the curling of the paper was large, and defective stacking occurred in 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 the copy image quality deteriorated remarkably. 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 when a solid image is passed, the wrapping force around the heating roller is strong and it is forcibly peeled off by the separation claw 3208. , The trace of the separated nail (hereinafter referred to as the nail trace)
Appeared remarkably. In the extreme case of this phenomenon, the copy paper may have wrinkles on the entire surface, and if the separation claw is soiled with toner, it may cause a jam.

In order to prevent the above-mentioned phenomenon, a low viscosity (for example, 25
Good results were obtained when a large amount of silicone oil with a viscosity of 100 Cs or 300 Cs) was applied.
Oil stains such as oil streaks tended to occur on copy paper, which deteriorated copy quality.

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 (PT
Detailed experiments were conducted under various thermal resistances by changing the thickness of FE) as shown in the following table.

In the above table, K _TF is 0.
At 6 × 10 ⁻³ [cal / cm · sec · deg], the sum _RH of the thermal resistances of the rubber layer and the resin layer is _RH = (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 outside the core metal, rubber layer and resin layer The radius on the side. The outer diameter of the aluminum core metal is 58.8 mm, and the hardness of the silicone rubber is 60 ° (JISA).

Thus, from the viewpoint of thermal resistance, the sum of the thermal resistances of the elastic layer (rubber layer) and the separation layer (resin layer) is 2.0 [cm · sec.
・ If it is less than or equal to deg / cal], it is found that the result is good for the nail mark, and is good when integrated with the results for the 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.

That is, for the elastic type, FIG. 7 (b)
In this case, since the elastic layer contacts the paper as if it envelops the toner, the contact area is larger than that of the rigid type, and the amount of heat that flows to the toner is large even with the same roller surface temperature for the same thermal resistance. Since the amount of heat applied to the entire toner is made uniform, the amount of heat required for fixing can be reduced, and the synergistic effect further improves the fixing performance. Comparing this with that of the rigid type, the relationship between the film thickness (elastic layer thickness + release layer thickness) and heat flow is shown in FIG. 8, and it can be seen that the difference is large. Here, the heat flow means the amount of heat that flows to the toner in one second when a solid image is passed.

In the case of the rigid type, the heat transfer efficiency is low, the contact pressure per unit contact area is larger than that of the elastic type, the toner image is greatly crushed, and so-called spots such as toner scattering in the non-image area occur. Cheap. The reason why the elastic type roller has better fixing property, toner offset, and image quality is largely due to the above-mentioned characteristics.

In the present experimental example and comparative example, the toner uses polypropylene (hereinafter referred to as PP) as a release agent, but PP
Has a melting point of 140 to 150 ° C., and the toner has a melting point of 140 to 150 ° C.
When PP is melted by being heated to 150 ° C or higher, it has poor compatibility with styrene-acrylic which is a binder resin.
Further, since the reaction proceeds in a direction to stabilize the surface state of the toner (that is, the surface is in a low energy state), the PP is biased toward the toner surface, the releasing effect is increased, and The adhesion of the heating roller is reduced and the separation of the copy paper is promoted.

Thus, it is considered that when a large amount of heat is applied to the toner, the viscoelasticity of the toner and the release agent act together to reduce the winding property.

The following was confirmed as data demonstrating that the winding property at the time of solid color is related to the release agent in the toner and the viscoelasticity of the toner. 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. It can be presumed that this endotherm is used because the release agent PP is melted and the viscoelasticity of the toner is changed, and in fact, when the toner is heated to the melting point of PP, the above endotherm appears. confirmed. Then, when the heating is further continued, the temperature of the toner rises again. Although the detailed principle has not been clarified yet, the reason why the wrapping property is extremely good at the temperature of the above endothermic period and no wrapping occurs is that PP melts and is biased to the toner surface and It seems certain that it is due to changes in viscoelasticity. Therefore, when the heating amount is determined, the roller having elasticity and a large amount of transferred heat can easily reach the temperature of the heat absorption time or higher.

The reason why the PFA roller has good claw marks in (Comparative Example 1) is that the contact area is small and therefore not only easy to peel off, but also the release layer (which can also be called a heat insulating layer) of the roller has a small thickness of 35 μm. It can be said that a large amount of heat flows per unit contact area when the roller comes into contact with the toner, and as a result, the degree of melting of PP in the vicinity of the contact surface and the degree of protrusion to the surface are high, and the winding 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 when the roller comes into contact with the toner, the unit contact is made. Since the amount of heat flowing per area is relatively small, the viscoelasticity of the toner cannot be sufficiently obtained, and PP is difficult to melt. As a result, the releasing effect is insufficient and nail marks are remarkably generated. In the case of the roller of the present experimental example, since the thickness of the release layer was reduced as much as possible within the range where elasticity can be secured, 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 wrinkles, curls, and image shift are good with the elastic roller seems to be largely due to the soft pressing, but the clear mechanism is not known.

The fixing roller according to the present exemplary embodiment has a characteristic that the thermal resistance is as small as possible and has elasticity, and the thickness of the elastic body is preferably 10 μm or more.

The fixing device having the fixing roller of the present invention is particularly effective for toner containing a release agent. As a release agent in the toner, polypropylene, polyethylene and other low molecular weight waxes were added, and effective results were obtained.

(Effect of the Invention) In the present invention, the toner is made to contain a release agent as described above, and a rotating roller for heating and pressure fixing, a rubber layer on the core metal, and a releasing resin layer on the rubber layer are provided. Formed, the sum of the thermal resistance of the elastic layer and the resin layer is 2.0 cm ・ sec ・ deg / cal.
As described below, in combination with the action of the release agent, the heat transfer property is improved while ensuring elasticity, and as a result, the performance of the entire apparatus such as the finish of the copy and the reduction of the apparatus trouble can be improved. Get the effect.

[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 an entire image forming apparatus to which the device of FIG. 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. Fig. 1 Diagram showing the test results of the apparatus, Figs. 7 (a) and 7 (b) are schematic diagrams showing the contact state between the roller and toner, and Fig. 8 is a comparison of the thermal conductivity of the elastic roller and the rigid roller. FIG. 3201 ... Rotating body (heating roller)

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-57-89785 (JP, A) JP-A-56-48664 (JP, A) JP-A-57-26883 (JP, A) JP-A-54- 99640 (JP, A) JP 58-189647 (JP, A) JP 60-123856 (JP, A) JP 62-191871 (JP, A) JP 63-131164 (JP, A) JP 60-195573 (JP, A) JP 58-23626 (JP, B2) JP 61-34146 (JP, B2) JP 61-4855 (JP, B2) JP 1-36627 (JP, B2)

Claims (1)

[Claims] 1. A heating roller having a core, a rubber layer provided on the core, and a releasable resin layer provided on the rubber layer, and a heater provided inside the heating roller. And a heat roller and a pressure roller in pressure contact with each other, the rubber layer has a higher thermal conductivity than the resin layer, and the sum of the thermal resistances of the rubber layer and the resin layer is 2.0 cm. Seconds
A fixing device characterized in that a recording material supporting an unfixed image composed of toner containing a release agent is sandwiched and conveyed by a heating roller and a pressure roller at a temperature of not more than a degree / calorie to perform fixing.