JPS62175789A - Fixing device - Google Patents

Abstract

PURPOSE:To obtain excellent fixing performance with small electric power by inhibiting an air cooling means from operating for a specific time after the application of power. CONSTITUTION:A heat discharge fan 521 is connected to a control circuit 532 through a driving circuit 531. Further, a detecting circuit 533 which detects the application of power for an image forming device is connected to the control circuit 532. The control circuit 532 operates its internal timer in case of inputting a power-on detection signal from the detecting circuit 533 to inhibit the heat discharge fan 521 from operating for a specific time and drive the heat discharge fan 521 at the specific time later. Thus, the excellent fixing performance is obtained with small electric power.

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 has been constructed by sandwiching and conveying a support such as copy paper carrying an unfixed image between a pair of fixing rollers, at least one of which has a heat source such as a halogen heater. - There is a roller fixing device for fixing 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 via its support and drive member, so the temperature inside the machine increases significantly, causing thermal deterioration and thermal damage to electrical and mechanical parts. In addition, there is a problem in that blocking of toner in the cleaner or developing device occurs.

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 heat exhaust fan is constantly rotated when the power is turned on to prevent the temperature inside the machine from rising.

(Problem to be solved by the invention) However, in the case of such conventional technology, the heat exhaust fan is rotated even though the inside of the machine is cold immediately after the power is turned on, so-called first thing in the morning. Members such as rollers are cooled,
The thermal efficiency was very poor at about 30 to 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, in order to solve this problem, the set temperature of the fixing roller is set higher than the normal set temperature for a predetermined period of time immediately after the power is turned on to accelerate the temperature rise of the roller.
It has been proposed that heat is also applied to the pressure roller side by rotating the roller pair during weighting, thereby improving fixing performance.

However, in the former case, the wait time becomes longer.

Moreover, not only does it shorten the life of the fixing roller and the parts that come into contact with it, but it also shortens the life of the image forming apparatus itself.
With limited power such as 00V and 15A, there is a limit to increasing the wattage of the heater that heats the fixing roller.
It was still incomplete when performing high-speed processing. Also.

In the latter case, the rewait time will be longer.

Furthermore, there is a drawback that the life of parts in the fixing device is shortened, and problems such as noise are likely to occur.

Therefore, in conventional high-speed machines, the current situation is to detect the temperature of the rollers and stop copying when the temperature drops below a predetermined temperature to prevent fusing failures. The problem of poor fixation remained unresolved.

In addition, the thermal efficiency mentioned here means what is expressed by the following formula.

Thermal efficiency η=(Wrotal −floss(T))
XI Q O/ Wrotal (%) Wloss=
(HON/HON+HOFF) XWrota+(
W) Here, W r o t a l : Total power of the heating source in the fixing device (W) Wloss (T) : Amount of heat released when the roller pair is idle-rotated at the roller temperature T ('C) (W) Has: ONt of the heating source, time HOFF: time the heating source is OFF
This was done to solve the problems of the prior art described above, and what is its purpose?

An object of the present invention is to provide a highly efficient fixing device that can achieve good fixing properties with less electric power.

(Means for Solving the Problems) In order to achieve the above object, 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. A fixing device having an air cooling means disposed on the outside is configured to include a control means for prohibiting operation of the air cooling means for a predetermined time after power is turned on.

(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 document 103, and 105 is an imaging optical system including 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 110 is provided. Also.

A fixing device and the like are arranged around the image carrier 1, but P in FIG. 6, 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 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 then fixed by a conveyor belt 4! ! It is transported up to 5.

The fixing 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.
A layer thickness of 0.05 to 2 layers is provided, and preferably a layer of heat-resistant mold release resin such as PFA or PTFE is provided on top of the layer to a thickness of 3 to 2 layers.
It is provided with a thickness of l 00 ILm. A heating heater 503 such as a halogen heater and an auxiliary heater 503' are provided in the hollow interior of the heating roller 501, and the auxiliary heater 503' is normally in an OFF state and is activated only at startup after power is turned on. do. On the other hand, the pressure roller 502
is a hollow cylindrical metal roller core made of aluminum, stainless steel, copper, etc., and a heat-resistant elastic layer of silicone rubber, fluorosilicone rubber, fluorosilicone rubber, etc.
Provided with Low shoe thickness, preferably further on the upper layer, 3~
It is made of a heat-resistant mold release resin layer made of PFA, PTFE, etc. with a thickness of 1100 IL. In this way, the reason why the heat-resistant elastic layer of the pressure roller 502 is thick is that the heat roller 501 has a thick heat-resistant elastic layer.
This is to form a protrusion in the press-contact area between the two. A low heating heater 503'' such as a halogen heater is provided in the hollow interior of the pressure roller 502.

A temperature detection element 504 such as a thermistor or a thermocouple is arranged 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), and the control means controls the temperature detection element 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, a cleaning member 50 is provided on the outer periphery of the heating roller 501 for removing foreign matter such as offset toner and paper dust attached to the surface of the heating roller 501 from the surface of the heating roller 501.
-5 is provided. This cleaning member 505 is configured to extrude a cleaning web 5051 made of a heat-resistant nonwoven fabric such as Nomex, Himeron, or polyester from a supply roll 5054 to a take-up roll 5053 and bring it into contact with the heating roller 501 by a roller 5052. . This cleaning web 5051 is taken up by a take-up roll 5053 that is rotationally driven by a driving means (not shown), and is pulled out from a supply roll 5054 by a small amount while changing its abutting position, so that a new cleaning web 5051 is constantly drawn out. 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.

Further, around the heating roller 501, curved reflecting plates 506 and 506' having heat reflective properties are disposed close to each other over 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.
2 and a separating claw 50g, which will be described later, so as to cover the entire surface of the heating roller. Above reflector plate 506°50
A thick cover 507゜507' made of a heat insulating material such as glass wool for preventing heat radiation is attached to the outer peripheral surface of the reflector plate 506゜506' to prevent unnecessary heat radiation from the reflecting plate 506゜506'. There is. That is, the reflecting plates 506, 506' and the covers 507 and 507' constitute a covering member for the heating a-ra 50.

Further, a casing member 509 having a U-shaped cross section is provided above the fixing device 2!15, and a cleaning member 50
5, Reflector plate 506.506', Cover 507.507
' and surrounds 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, on the pressure roller 502 side, a reflection plate 512 similar to the reflection plate 506 and a cover 513 similar to the cover 507 are provided 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 ends of the reflective plate 506 and the reflective plate 512 that are close to each other.

The guide plate 515 is made of a heat insulating resin such as PBT. Further, a shutter 516 for opening and closing the entrance of the fixing device is disposed at the lower end of the casing member 509.
The shutter 518 is rotationally driven by a plunger (not shown) using 516' as a pivot point. This shutter 516 is closed as shown in the figure during the copying operation.
During non-copying, it is rotated about the first rotation fulcrum 516' and comes into contact with the guide plate 515, and the entrance side is closed to prevent wasteful heat radiation.

By the way, the transfer material P having the undetermined toner image T is conveyed while being held between the heated and unprocessed rollers 501 and 502, and the toner image T is formed as a permanent image on the paper surface by the heat applied by the heated rollers 501 and 502. The image is fixed and is ejected from the apparatus while being held between the paper ejection rollers 517 and 518.

In order to reliably separate the transfer material P from the heating roller, a plurality of separating claws 508 are provided on the discharge port side of the heating roller 501 so as to contact the roller surface along the roller axis direction. 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 and can be moved away from the roller pair 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.

Further, the covers 507, 507', 513 include:
glass wool, rock wool, ceramic fiber,
Alternatively, a single structure or a composite structure of foams such as phenol foam and epoxy foam is preferable.

By the way, in this embodiment, the support plate 519 has an opening 5.
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. The heat exhaust fan 521 is connected to a control circuit 532 via a drive circuit 531. Further, a detection circuit 533 is connected to the control circuit 532 for detecting power-on of one image forming apparatus. When the power-on detection signal is input from the detection circuit 533, the control circuit 532 operates an internal timer (not shown) to prohibit the operation of the heat exhaust fan 521 for a predetermined time, and after the predetermined time has elapsed, the drive circuit The heat exhaust fan 521 is driven through the fan 531.

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,
526'. The rotating shaft 524, 524
Heat-resistant gears 527 and 527' are respectively fitted into the drive gears 527 and 527', and one of the heat-resistant gears 527' is meshed with a driving force transmission gear 528 connected to the drive source M. Thus, the heating roller 501 is rotationally driven by the driving force of the driving source M being transmitted through the driving force transmission gear 528 and the heat-resistant gear 527'. 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 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, 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, 527
By using ', the heat retention of the heating roller 501 is improved.

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 and 526' and the frame 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 can reduce or eliminate heat loss to the drive system, so
At high altitudes, thermal efficiency can be improved and power consumption can also be reduced. or,
In this configuration, heat-resistant sleeves 524 and 524' are used in addition to the heat-resistant gears 527 and 527', so that heat loss from the roller ends to the frames 525 and 525' can be prevented and thermal efficiency can be further improved.

The heat-resistant sleeve is made of polyimide, polyamideimide, polyamide, pps (polyphenylene sulfide), PBT (polybutylene terephthalate)4
It is preferable to use a heat-insulating material such as heat-insulating material, phenol-based resin, or a heat-insulating material made of a mixed material of this kind.

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 had an outer diameter of 59.3 ms, an inverted crown amount of 1 0 JL m, an aluminum roller core with a wall thickness of 8.5 ms, and a surface layer coated with silicone rubber with a thickness of 0.5 mm and PTFE with a thickness of 20 IL m. The roller was used as a pressure roller 502, and a stainless steel roller core metal with an outer diameter of 60 mm and a diameter of 50 m5 was coated with a heat-vulcanized silicone rubber layer of 5 m thick and a fluoro rubber latex layer of 30 #Lm thick. A roller was used for each.

In addition, the heater 503 in the heating roller uses an 870W halogen heater, and the heater 503' uses a 350W halogen heater, and the heater 503' is used at startup (during weight).
Only the light was turned on. 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.

The nip width is 9.0 layers, and the heating roller surface temperature is 1.
The temperature was 95°C.

Figure 3 is a graph explaining the change in the surface temperature of each roller with respect to time for the experiment of the specific example described above. 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 501 and 502 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), fixing becomes possible and both rollers 501 and 502 stop rotating. The heating roller 501 is maintained at a surface temperature of about 195° C. by a control means (not shown).

On the other hand, since the pressure roller 502 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 due to the heat from the heater 503'' from inside.Therefore, the fixing ability at the 0 point is the highest. low,
Therefore, if continuous copying is performed at this zero point, it will be extremely preferable as a comparative experiment of fixing properties. This figure shows the temperature change when 250 sheets are continuously copied at the 0 point.
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 C-0. In other words, the copy speed is 445cm/sec in an environment of 15℃ (A3 size paper, 43cm
sheets/min), scale 180 g/m2 1st, 25th sheet out of 250 consecutive copies of 250 sheets of solid black φ24 ■ thorns arranged in a grid pattern of 3 at equal intervals vertically and horizontally on A3 paper. eye.

50th picture...25050th picture, 25
A sample was extracted from each sheet, and solid black at nine locations on each sheet was evaluated for fixability.

This fixability evaluation was based on Silpon C (product name).

Pressure 40g/cm using Silpon paper purchased from Co., Ltd.
2 for 10 times, and the difference in density before and after rubbing was measured using a Macbeth reflection densitometer and quantified.

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 after rubbing the medium 24-color solid image: rate of decrease in density Then, the fixability was evaluated using the average of the rate of decrease in density of the 9 solid-color areas.

In addition, in this experimental example, 1" exhaust heat 7 for 45 minutes after power on
The operation of the fan 521 is prohibited, and after 45 minutes have elapsed since the power was turned on, the heat exhaust fan 521 is turned on. It was made to operate continuously. Note that after 45 minutes have elapsed, even if the heat exhaust fan 521 is operated intermittently once every predetermined time, or the heat roller 5
A temperature sensing element 522 may be provided around 01, and the temperature sensing element 522 may be activated strongly when the detected temperature is above a predetermined temperature, weakly activated when the detected temperature is lower than the predetermined temperature, or activated only when the detected temperature is below the predetermined temperature.

The results of the fixability test under the above conditions are shown in FIG. 4(a).

According to the above 7-way evaluation method, the range in which a normal line image exhibits good fixing performance is when the e-degree reduction rate is 20 to 25% or less, so even under the worst conditions immediately after the power is turned on,
All 0 sheets showed good fixing properties.

FIG. 5(a) shows the change in the heating roller surface temperature in this case.

In addition, in order to calculate the amount of heat effectively used for copy paper, the time change in the amount of heat dissipated when the copy paper is idly rotated without paper passing is shown in Figure 6 (a). Immediately after turning on the power, the amount of idle power generated was 360 W, and the thermal efficiency η immediately after turning on the power was 59%. Further, for reference, when the standby state was continued for more than one hour, the idle rotation number heat amount was 115 W, and the thermal efficiency η was 87%. The fixing properties at this point were good even when the set temperature was 180''c.

Figure 7 shows the temperature rise inside the machine around the paper ejection section and the drum.1 As a typical example, the cleaner section closest to the fixing device is selected for the drum area, and the paper ejection section is located at the electrical component area A such as the jam detection element. In addition, the temperature rise measurement inside the aircraft was performed at an outside temperature of 23℃.
The test was carried out in an environment with a humidity of 60%.

As a result, as shown by the solid line in Figure 7, there was no problem with the temperature rise inside the machine.

In addition, when the heat exhaust fan 521 is kept in the OFF state all the time, the temperature rises as shown by the broken line in FIG.
Blocking of toner in the cleaner occurred.

(Comparative Example) The same fixing device as in the experimental example was used. However, as the air cooling means, as is conventionally known, a heat exhaust fan (not shown) provided at the rear of the fixing device is always operated strongly, and a heat exhaust fan 521 is used.
and 530 were not used.

Therefore, the results of a fixing test under the same conditions as in the experimental example are shown in Figure 4(b).
When the number of continuous copies was approximately 85, the density decrease rate was less than 20%, and after that, the fixing performance became a problem. Figure 5(b) shows the change in the heating roller surface temperature at this time.
It can be seen that the roller surface temperature drops rapidly.

Also, the idling speed heat amount under the above conditions is.

As shown in FIG. 6(b), the power was 520 W immediately after the power was turned on, and the thermal efficiency η at this time was 40%, which is worse than the experimental example. In addition, even in steady state when left on standby for more than 1 hour, the amount of heat dissipated is 31
5W, and the thermal efficiency η is 64%, which is 87% of the experimental example.
It can be seen that it is significantly worse than .

In the above embodiment, the case where two heat exhaust fans are provided has been described, but there may be one or three or more heat exhaust fans. If there are multiple heat exhaust fans, at least one may be controlled as in this embodiment. Just do it.

The installation location of the heat exhaust fan is also not particularly limited.

(Effects of the Invention) The present invention has the configuration and operation described above, and the operation of the air cooling means is prohibited for a predetermined period of time after the power is turned on. This promotes heat dissipation from the roller pair, which reduces the fixing performance immediately after the power is turned on, and to prevent this, there is no need to increase the power supplied to the heating source for the roller pair immediately after the power is turned on, and less power is required. It is possible to provide a highly efficient fixing device that achieves good fixing performance.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the fixing device according to the present invention, FIG. 2 is a cross-sectional view along the line x-X of FIG. 1, and FIG. 3 is a heating roller and a pressure roller immediately after the device is powered on. FIG. 4 is a graph showing the change in density reduction rate with respect to the number of copies of experimental examples and comparative examples of the present invention, and FIG. A graph showing changes in heat roller surface temperature with respect to the number of sheets, FIG. 6 is a graph showing changes in heat radiation amount with respect to time in experimental examples of the present invention and comparative examples, and FIG.
FIG. 8 is a graph showing changes in internal temperature with respect to time, and is an explanatory diagram showing an embodiment of an image forming apparatus to which a fixing device according to the present invention can be applied. Explanation of symbols 5... Fixing bag at 501... Heating roller 502... Pressure roller 503... Heater 50
9...Casing 521...Exhaust heat fan 532
...control circuit

Claims (1)

[Claims] In a fixing device including 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 an air cooling means disposed outside the casing, after turning on the power, the A fixing device characterized by comprising a control means for prohibiting operation of an air cooling means.