JPS62175787A - Fixing device - Google Patents

Abstract

PURPOSE:To obtain sufficient heat insulation effect and to reduce thermal influence exerted upon a member provided at the periphery of a heating part by isolating a cooling area from a heat reserving area in a casing, and cooling the cooling area with air. CONSTITUTION:A shield member 532 which partitions the heat reserving area A in the vicinity of a heat roller 501 and the cooling area B in the vicinity of a photointerrupter 531 and shields them for heat insulation in provided in an air layer 510 outside a casing member 509. Consequently, air in the cooling area B and a machine is discharged by a heat discharge fan 521 to perform cooling, no influence upon the atmosphere of the heat roller 501 is eliminated by the shield member 5323. Consequently, sufficient heat insulation effect is obtained and various sensors, etc., are provided in the cooling area to reduce thermal influence.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fixing device used in image forming apparatuses such as electrophotographic copying machines and printers.

(Prior Art) Conventionally, this type of fixing device uses a pair of fixing rollers, at least one of which has a heat source such as a halogen heater, to sandwich and convey a support such as copy paper carrying an unfixed image. There is a roller fixing device that fixes the unfixed image.

The fixing roller is warmed up by being rapidly heated until it reaches a predetermined temperature by energizing the heating source at the same time as the power of one image forming apparatus is turned on.

The surface temperature of this fixing roller is detected by a temperature detection element, and once it reaches a predetermined temperature after warming up, the current to the heating source is controlled to maintain that temperature, ensuring stable fixing at all times. It maintains its sexuality.

By the way, heat is emitted from the heated fixing roller by conduction heat or radiant heat through its supporting and driving member, which causes the internal temperature of the machine to rise significantly and damage the electrical parts and mechanical parts arranged around the fixing roller. This causes thermal deterioration and thermal damage to parts.

There is a problem in that toner blocking occurs in the cleaner and developing device.

Therefore, in order to solve the above-mentioned problems, a heat exhaust fan is provided behind or to the side of the fixing device, and the one-nuclear heat exhaust fan is constantly rotated when the power is turned on to prevent the temperature inside the machine from rising.

However, in this case, the so-called first thing in the morning immediately after the power is turned on is
Because the heat exhaust fan rotates even when the inside of the machine is cold, components such as the fixing roller are cooled, resulting in a thermal efficiency of 30%.
It was very bad, about 45%. Therefore, immediately after the power of the apparatus is turned on, the fixing roller is not sufficiently heated, resulting in a problem that the fixing performance of copies is very poor compared to that in a steady state. Particularly in energy-saving high-speed machines, the guaranteed number of sheets to be fixed for continuous copying immediately after the power is turned on is significantly reduced.

Therefore, as proposed in Japanese Patent Publication No. 60-14282, thermal efficiency is increased by covering the fixing roller with a heat insulating material to keep the fixing device warm.

It is known to cool the area around an image carrier using a heat exhaust fan.

(Problems to be Solved by the Invention) However, in the case of such prior art, there is no introduction port for introducing copy paper into the fixing device, and a paper discharge port for discharging copy paper from the fixing device to the outside of the machine. must be provided on the heat insulating material covering the fixing roller. Therefore, when a heat exhaust fan is used to forcibly create an airflow, the atmosphere inside the fixing device also radiates a large amount of heat through air convection through the inlet and paper outlet provided in the heat insulating material, resulting in a sufficient heat retention effect. There was a problem that I couldn't get it. In addition, various sensors such as a jam detection sensor are installed around the fixing roller, and although these sensors are sensitive to heat, they are placed inside the insulation material, so they are not susceptible to thermal damage. There were problems such as shortened lifespan and malfunction.

Therefore, the present invention has been made in order to solve the above-mentioned problems of the prior art.The purpose of the present invention is to obtain a sufficient heat retention effect and to reduce the heat received by the members provided around the heated part. An object of the present invention is to provide a fixing device that can reduce the influence.

(Means for Solving the Problems) In order to solve the above objects, the present invention includes a pair of rollers, at least one of which has a heating source, a casing that covers the periphery of the pair of rollers, and a casing that covers the periphery of the pair of rollers; The cooling area is configured to include a shielding member that insulates and shields the cooling area from the heat retention area, and an air cooling means connected to the cooling area.

(Example) The present invention will be explained below based on illustrated embodiments.

FIG. 8 is an explanatory diagram showing an image forming apparatus to which the fixing device according to the present invention can be applied.

In the figure, 103 is a document, 104 is a document lamp for illuminating the M document 103, and 105 is an imaging optical system consisting of a plurality of mirrors, lenses, etc. assembled together. Reference numeral l denotes an image carrier consisting of a cylindrical photosensitive drum, which is pivotally supported so as to be rotatable in the direction of arrow a in FIG.
Around the negative charger 107. Developing device 108, transfer charger 2. A cleaner IO is provided. Further, a fixing device and the like are arranged around the image carrier l, but P in FIG. 0, which is omitted for convenience of explanation, is a transfer material.

In this image forming apparatus, an original 10 is placed on the surface of an image carrier l uniformly charged by a negative charger through an imaging optical system.
Image 3 is formed to form an electrostatic latent image. Then, this electrostatic latent image is made visible by the developing device 108, and the visible image on the image carrier 1 is transferred to the transfer material P by the transfer charger 2.
The image is fixed in a fixing device.

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

In the figure, a transfer material P such as a copy paper onto which a toner image T has been transferred is separated from an image carrier 1 by a one-separation charger 3, and is transported to a fixing device 5 by a transport belt 4.

The fixed stone device 5 includes a heating roller 501 and a pressure roller 50.
2, and the pressure roller 502 has a heating roller 50
1 by a known pressure means at least during fixing. This heating roller 501 has a heat-resistant elastic material layer such as silicone rubber or fluorine rubber on the outer peripheral surface of a hollow cylindrical roller core made of metal such as aluminum, stainless steel, or copper.
Provided with a thickness of 0.05 to 2 cm, preferably a layer of heat-resistant mold release resin such as PFA or PTFE is further provided as an upper layer.
It is provided with a thickness of 100IL. The heating roller 50
A heating heater 5 such as a halogen heater is installed in the hollow interior of 1.
03 and an auxiliary heater 503' are provided, and the auxiliary heater 503' is normally in an OFF state and operates only at startup after the power is turned on. On the other hand, the pressure roller 502 is mounted on the outer peripheral surface of a hollow cylindrical roller core metal made of aluminum, stainless steel, copper, or the like.

A heat-resistant elastic layer made of silicone rubber, fluorosilicone rubber, etc. is provided to a thickness of 2 to 10s+m, preferably,
Furthermore, on the upper layer, PFA, PTF with a thickness of 3 to 11001L
It is made of a heat-resistant mold-releasing resin layer such as E.

The reason why the heat-resistant elastic layer of the pressure roller 502 is thick in this way is to form a protrusion in the pressure contact area between the pressure roller 502 and the heating roller 501 . In the hollow interior of the pressure roller 502, there is a heater 503 for low heating such as a halogen heater.
” is provided.

A temperature detection element 504 such as a thermistor or thermocouple is placed in contact with the outer peripheral surface of the heating roller 501, and the detection signal is guided to a known control means (not shown), which controls the heater 503. By controlling the applied voltage, etc., the temperature of the outer peripheral surface of the heating roller 501 is maintained at the toner image melting temperature.

Further, on the outer periphery of the heating roller 501, there is added %o-
Cleaning member 5 for removing foreign matter such as offset toner and paper dust attached to the surface of the roller 501
05 is provided. This cleaning member 505 is configured to bring a cleaning web 5051 made of a heat-resistant nonwoven fabric such as Nomex, Himeron, or polyester into contact with the heating roller 501 using a pressing roller 5052 while winding it up from a supply roll 5054 onto a take-up roll 5053. . This cleaning web 5051 is taken up by a take-up roll 5o53 that is rotationally driven by a driving means (not shown), and is pulled out from the supply roll 5o54 little by little while changing its abutting position, so that a new cleaning web 5051 is always created. The surface contacts the heating roller 501. Further, if the cleaning web 5051 is impregnated with an anti-offset liquid such as dimethyl silicone oil, the cleaning effect can be further enhanced.

Furthermore, around the heating roller 501, curved reflecting plates 506 and 506' having heat reflecting properties are disposed close to each other along the entire longitudinal direction. The reflecting plate 506' is disposed so as to cover the entire surface of the heating roller between the roller 5052 and the entrance opening for the transfer material P.
The heating roller is disposed so as to cover the entire surface of the heating roller between the heating roller and a separating claw 508, which will be described later. Above reflector plate 506°506
A thick cover 507゜507' made of a heat insulating material such as r lath wool is attached to the outer peripheral surface of the reflective plate 507゜507' to prevent unnecessary heat radiation from the reflector plate 506゜506'. There is. That is, the first reflecting plate 506, 506' and the covers 507 and 507' constitute a covering member for the heating roller 501.

Further, a casing member 509 having a U-shaped cross section is provided above the fixing device 5, and a cleaning member 5051
It surrounds the reflectors 508 and 506', the covers 507 and 507', and the temperature sensing element 504. Another casing 511 having an L-shaped cross section is provided outside this casing member 509 with an air layer 510 in between.

On the other hand, a reflecting plate 512 similar to the reflecting plate 506 and a cover 513 similar to the cover 507 are provided on the pressure roller 502 so as to cover most of the periphery of the pressure roller 502, respectively. Further, a casing 514 similar to the casing 509 is provided on the outside of the cover 513.

These reflectors 506, 506', 512 and cover 5
By providing 07, 507', and 513, it is possible to reduce the heat wastefully lost from the surfaces of the heating roller 501 and the pressure roller 502, and to stabilize the temperature measurement performance of the temperature sensing element 504. can. Therefore, temperature control for the set temperature of the heating roller 502 can be stabilized, and power consumption can be reduced.

A guide plate 515 that guides the transfer material P toward the heating roller 501 is provided near the mutually close ends of the reflector plate 506 and the reflector plate 512, and the guide plate 515 is made of a heat insulating resin such as PBT. has been done. Further, a shutter 516 for opening and closing the entrance of the fixing device is provided at the lower end of the casing member 509, and the shutter 516 is rotationally driven by a plunger (not shown) about 516' as a rotational fulcrum. This shutter 516 is in an open state as shown in the figure during a copying operation, and when not in a copying state, it is rotated about a single rotation fulcrum 516' and comes into contact with the guide plate 515, closing the entrance side and eliminating waste. Prevents heat radiation.

By the way, the transfer material P having the unfixed toner image T is conveyed while being held between rollers 501 and 502 before being heated and pressed, and the toner image T is formed into a permanent image on the paper surface by the heat applied by the heated rollers 501 and 502. The image is fixed as a sheet, and is ejected from the apparatus while being held between the ejecting rollers 517 and 51B.

In order to reliably separate the transfer material P from the heating roller, a plurality of separating claws 50B are provided on the discharge port side of the heating roller 501 along the roller axis direction so as to contact the roller surface. Further, the separation claw 508, which is provided on the discharge port side of the pressure roller 502 so that the separation claw 508' comes into contact with the surface of the roller 502, is attached to the casing 509°51.
The one-separation claw 508' is also held by a support plate 520 that is spaced apart from the casing member 514. These separation claws 508.50
8' is a supporting plate 519, 520 and a pair of paper ejection rollers 517°51, with 520' as a rotational fulcrum during jam clearance, etc.
8, the label can be moved away from the pair of rollers 501 and 502.

As the reflective plates 506, 506', and 512, it is desirable to use a metal plate with a glossy surface, such as an aluminum plate with one surface polished, a copper plate, or an iron plate with a surface treatment such as chrome plating. Board 506, 506
', 512 preferably has a curvature concentric with the circumferential surface of the roller, and preferably has a relatively thin thickness.

The covers 507, 507', and 513 are preferably made of glass wool, rock wool, ceramic fiber, or foam such as phenol foam or epoxy foam, either singly or in combination.

By the way, in this embodiment, the opening 5 is provided in the support plate 519.
19' is formed, and a heat exhaust fan 521 as an air cooling means is connected to the opening 519'. Also,
A heat exhaust fan 530 is arranged near the image carrier 1 to exhaust heat around the drum. A photo interrupter 531 for jam detection is attached to the inner surface of the support plate 519, as clearly shown in FIG. 1(b). In the air layer 510 outside the casing member 509, there is a heat retention area A near the heating roller 501 and a photo interrupter 53.
A shielding member 532 is provided that partitions and insulates and shields the cooling region B in the vicinity of one region. This shielding member 532 almost completely covers the heat retention area A and the cooling area B, except for a notch portion for preventing interference with a part of the jam detection actuator (not shown) located across the heat retention area and the cooling area. It is shielded by Materials for forming this shielding member 532 include glass wool, Danmax, PBT,
It is preferable to use a heat-resistant heat insulating material such as polycarbonate. However, even if the cooling area B and the air inside the machine are exhausted and cooled by the heat exhaust fan 521, the shielding member 5
32 to the atmosphere around the heating roller 501! In addition, a temperature detection element 522 is provided in the cooling area B, and the heat exhaust fan 521 is operated only when the temperature detected by the temperature detection element 522 exceeds a predetermined temperature. In this case, the heat exhaust fan 521 operates only when necessary, so problems such as noise caused by the operation of the heat exhaust fan 521 can be reduced.

FIG. 2 shows a cross section taken along the line XX of FIG. 1.

Heat-resistant heat insulating sleeves 523 and 523' are fitted onto the rotating shafts 524 and 524' of the heating roller 501, respectively. Bearing 526,5
26'. The rotation shaft 524, 524'
Heat-resistant gears 527 and 527' are fitted into the drive gears 527 and 527', respectively, and one heat-resistant gear 527' is meshed with a driving force transmission gear 528 connected to a driving source M. Therefore, the heating roller 501 is connected to the driving force transmission gear 52 by the driving force of the driving source M.
8 and a heat-resistant gear 527', and is driven one rotation. A gear 529' fixed to a manual knob 529 is meshed with the other heat-resistant gear 527, and the manual knob 529 is rotatably supported by the frame 525. By manually rotating the first manual knob 529, the heating roller 501 is rotated via the gear 529' and the heat-resistant gear 527, and the jammed transfer material P can be removed.

Since the heat-resistant gears 527 and 527' are made of a heat insulating material, the heating roller 501
7' to drive transmission members such as other gears. Therefore, this heat-resistant gear 527.52
7' improves the heat retention of the heating roller 501.

Further, the heat-resistant sleeves 523 and 523' are also made of a heat insulating material to prevent heat dissipation due to heat transfer from the ends of the heating roller 501 to the bearings 526, 526' and the frames 525 and 525'. Therefore, heat loss from the ends of the heating roller 501 is greatly reduced.

Generally, the heat-resistant gears 527, 527' are often provided with a large number of other drive transmission members in conjunction with each other, and therefore, conventional heat loss occupies most of the heat loss in such drive systems. On the other hand, something like this configuration works by reducing or eliminating heat loss to the drive system.
It can greatly improve thermal efficiency and reduce power consumption. In addition, in this configuration, heat-resistant sleeves 524, 524' are used in addition to heat-resistant gears 527, 527', so that the frame 52 from the end of the roller, E2! It is possible to significantly improve thermal efficiency by preventing heat loss to '.

The above-mentioned heat-resistant sleeve may be a heat-insulating material such as polyimide, polyamide-imide, polyamide, PPS (polyphenylene sulfide), PBT (polybutylene terephthalate) resin, phenol resin, or a heat-insulating material made of a mixed material of this type. Preferably, the material is made of a barrier material.

The gears 527, 527' may be made of a heat-resistant material with good heat insulation properties, such as polyimide, polyamide-imide, PPS, modified phenol, or tetrafluoroethylene with a reinforcing optical fiber added. preferable.

As mentioned above, the heating roller 501 is connected to the heat-resistant sleeve 52.
4,524' and the heat-resistant gears 527, 527' provide a thermally isolated state from the machine body and the frame body 525, 525', and the heat loss transmitted through these is extremely small. In this way, thermally isolating the roller from the driving force transmission path is very effective in improving thermal efficiency.

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

The heating roller 501 has an outer diameter of 58.3 mm, an inverted crown amount of 150 mm, an aluminum roller core with a wall thickness of 13.51111 mm, a surface layer of 0.5 mm thick silicone rubber, and a 20 JLm thickness. A roller coated with PTFE,
As the pressure roller 502, the outer diameter is φ60, and the outer diameter is φ5011.
Rollers were used in which a heat-vulcanized silicone rubber layer with a thickness of 51 mm and a fluoro rubber latex layer with a thickness of 30 IL meters were coated on a stainless steel roller core metal.

Moreover, the heater 503 in the heating roller is 870W1. A 350 W halogen heater was used as the heater 503', and the heater 503' was turned on only during startup (during wait). On the other hand, the heater 503 inside the pressure roller
” used a 70W sheathed heater and was turned on only when copying was not being performed.

In addition, the nip width is 9.01mm, and the heating roller surface temperature is 1mm.
The temperature was 95°C.

FIG. 3 is a diagram illustrating changes in the surface temperature of each roller with respect to time for the experiment of the above specific example. 0 time 1 = 0
When the power is turned on, the heaters 503, 503' and 503'' light up.The heating roller surface temperature rises as shown in the figure, and when the heating roller surface temperature reaches 170°C (point A), it stops. Both rollers 1 and 2 begin to rotate under pressure, and the surface temperature of the pressure rollers also rises rapidly.

When the surface temperature of the heating roller reaches 195° C. (point B), it becomes ready for fixing and both rollers 1 and 2 stop rotating. Then, the heating roller 1 is heated to 195° C. by a control means (not shown).
The surface temperature is maintained at the same temperature as before and after. On the other hand, since the pressure roller 2 is no longer supplied with heat from the fixing roller, its surface temperature decreases. Approximately 5 minutes after the fixing ready state (0 point), the pressure roller temperature reaches its lowest temperature, and then gradually rises as it receives heat from the heater 503'' from inside.Therefore, the fixing plow blade at the 0 point is the highest. low.

Therefore, if continuous copying is performed at this 0 point, it is extremely preferable as a comparison experiment of fixing properties.
The table includes the time when the sheet is finished (point D).

The experimental results shown below were conducted under the following common conditions between CD and CD. In other words, the copy speed is 445 mm/see in an environment of 15 degrees Celsius (A3 size paper, 43
sheets/min), scale 180 g/m2 250 sheets of 250 sheets were continuously copied by forming solid black sheets of φ24 tungsten layer arranged in a grid pattern of 3 pieces at equal intervals vertically and horizontally on A3 paper, 1st sheet, 25 sheets 25th sheet, 50th sheet, ...250th sheet, and so on.
The solid black in the area was evaluated for fixability.

To evaluate this fixation, use Silpon C (trade name, purchased from Shirupon Paper Co., Ltd.) and rub it 10 times at a pressure of 40 g/c Oboro 2, and measure the density difference before and after rubbing with a Macbeth reflection densitometer. and digitized it.

D: Reflection density before rubbing the φ24 solid black image (1,0
The image density is adjusted so that ≦D≦1.1. ) D': Reflection density ΔD=Ws degree reduction rate after rubbing the φ24 solid chromatic image.Fixability was evaluated based on the average of the density reduction rates of the 9 solid chromatic parts.

In addition, in this experimental example, the first condition is that the heat exhaust fan 52
1 is always operated, and the second condition is that the heat exhaust fan 52
1.530, the detected temperature of the temperature detection element 522 is 80℃
If the temperature exceeds the temperature, the temperature detection element 522 is strongly activated.
When the detected temperature became lower than 80°C, it was operated at the strength of 171O when the temperature was 80°C or higher.

The fixing test results under the above first condition are shown in Figure 4 (a
), and the results of the fixing test under the second condition are shown in Figure 4 (a).
’).

According to the above fixation evaluation method, the range in which a normal line image exhibits good fixability is when the density reduction rate is 20 to 25% or less, so even under the worst conditions immediately after the power is turned on, the first
．． All 250 sheets exhibited good fixing properties under the second condition.

FIGS. 5(a) and 5(a') show changes in the heating roller surface temperature in this case.

In addition, in order to calculate the amount of heat effectively used in copy paper, the time changes in the amount of heat released when the copy paper is rotated idly are shown in Figures 6(a) and 6(a'). In this experimental example, the idling speed heat value immediately after the power is turned on is 360W.
, it was 385W. The thermal efficiency η immediately after the power was turned on was 60%. Further, for reference, when the standby state was continued for more than one hour, the idle rotation heat dissipation power was 115 W in both cases, and the thermal efficiency η was 87%. At this point, the fixing performance was good even when the set temperature was kept at 180°C. Figure 7 shows the temperature rise inside the machine at the paper ejection section.2 As a typical example, the paper ejection section is The temperature rise measurement inside the aircraft was conducted at an outside temperature of 23℃ and a humidity of 60%.
It was conducted under the following conditions.

Various sensors such as a jam detection sensor 531 are installed in the paper ejection section, and in this example, the heat resistance limit temperature of these sensors is 85°C, so under the second condition, the temperature detection element 522 is The detection temperature was set at 80°C.

As a result, there was no problem with the temperature rise inside the aircraft under the first condition shown by the solid line (a) in Figure 7, and under the second condition shown by the broken line (b) in Figure 7. Ta.

Further, even when the heat exhaust fan 521 is operated, since the shielding member 532 is provided, the heating roller 501
Convection does not occur in the surrounding air layer and there is no significant heat dissipation.
However, since the air layer 51O in the cooling area B is exhausted,
Although heat radiation from surrounding members increases slightly, the amount of increase in heat radiation is small, about 5 to 25 W. On the other hand, when the heat exhaust fan 521 is always PFF, the temperature rise rate in the cooling area B is moderated due to the presence of the shielding member 532 compared to the case without the shielding member 532 (two-dot chain line) (Fig. Although (dashed line), a malfunction occurred in the photo interrupter 531 and the like installed in the paper discharge section in a high-temperature environment.

(Effect of the invention) The present invention consists of the above configuration and operation.

By providing a shielding member that insulates and shields the cooling area from the heat-retaining area in the casing, and allowing the air cooling means to cool the cooling area, a sufficient heat-retaining effect can be obtained, and by providing various sensors etc. in the cooling area, Thermal effects can be reduced.

[Brief explanation of drawings]

FIG. 1(a) is an explanatory diagram showing one embodiment of the fixing device according to the present invention, FIG. 1(b) is an enlarged explanatory diagram of the main part of FIG. 1(a), and FIG. Figure 3 shows the change in the surface temperature of the heating roller and pressure roller immediately after the device is powered on. 5 is a graph showing the change in heating roller surface temperature with respect to the number of copies in the experimental example of the present invention. FIG. 6 is a graph showing the change in heat radiation amount with respect to time in the experimental example of the present invention. , FIG. 7 is a graph showing changes in internal temperature with respect to time in an experimental example of the present invention, and FIG. 8 is an explanatory diagram showing an example of an image forming apparatus to which the fixing device according to the present invention can be applied. Description 5... Fixing device 501... Heating roller 5
02... Pressure roller 503... Heater 509.
...Casing 521...Exhaust heat fan 532...
・Shielding member A... Heat retention area B... Cooling area

Claims (1)

[Claims] a pair of rollers, at least one of which has a heating source; a casing that surrounds the pair of rollers; a shielding member that insulates and shields a cooling area from a heat-retaining area in the casing;
A fixing device comprising: an air cooling means connected to the cooling area.