JPS62175788A - Fixing device - Google Patents

Abstract

PURPOSE:To obtain excellent fixing performance with small electric power without causing a noise to be generated by operating a cooling means when the detected temperature of a temperature detecting element rises above specific temperature. CONSTITUTION:The temperature detecting element 522 such as a thermistor is provided in the vicinity of a paper discharge part at the periphery of a couple of rollers 501 and 502, and this temperature detecting element 522 is connected directly to a control circuit while heat discharge fans 521 and 530 are connected through a driving circuit 531. This control circuit 532 operates the heat discharge fans 521 and 530 when the detected temperature of the temperature detecting element 522 rises above specific temperature, and also operates them at faster speed in copying operation than when the copying operation is off. Consequently, a rise in the temperature in a machine is suppressed during the copying operation and heat efficiency is improved greatly to obtain excellent fixing performance.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a fixing device used in an image forming apparatus such as an electrophotographic copying machine or a printer.

(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 the 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 always strongly 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 to speak. 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.

In addition, since the heat exhaust fan is constantly rotating strongly, there are problems in quiet environments where the noise of the heat exhaust fan becomes audible when copying is not in progress, and power is wasted. .

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

Thermal efficiency η=(WIoLal Wloss(↑))×t
oo/W Ding. L, 1 (%) WIO8S= (HON/HON+HOFF) XW
+ota+(W) where WIoLal: Total power of the heating source in the fixing device (W) Wloss(T): Heat radiation amount (W) when the roller pair is idly rotated at roller temperature T ("O) HON: Heating HOFF: The amount of time the heating source is on is 0FFL, and the amount of time the heating source is on is 1.
The present invention has been made in order to solve the above-mentioned problems of the prior art, and its purpose is to provide a highly efficient fixing system that does not cause noise etc. and can achieve good fixing performance with less electric power. An object of the present invention is to provide a fixing device.

(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. In a fixing device having an air cooling means disposed on the outside and a temperature detection element for detecting a temperature around the pair of rollers, the air cooling means is activated when a temperature detected by the temperature detection element exceeds a predetermined temperature. Furthermore, the apparatus is configured to include a control means that operates more strongly during the copy operation than when the copy is not operated.

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

FIG. 7 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 for rotation in the direction of arrow a in FIG.
Around the negative charger 107. A developing device 108, a transfer charger 2, and a cleaner 110 are provided. Also.

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.

This image forming apparatus forms an image of a document 103 via an imaging optical system 105 on the surface of an image carrier l that is uniformly charged by a charger 107 to form an electrostatic latent image. . Then, this electrostatic latent image is visualized by a developer tOa,
A visible image on the image carrier 1 is transferred to a transfer material P by a transfer charger 2.
Transcribe it to.

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 I by a separation charger 3 and is transported to a fixing device 5 by a transport belt 4.

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.
It is provided to a thickness of 0.05 to 2 cm, and preferably, a layer of heat-resistant mold release resin such as PFA or PTFE is further provided on top of the layer to a thickness of 3 to 11 cm.
00B thickness. A heating heater 503 such as a halogen heater is provided in the hollow interior of the heating roller 501.
An auxiliary heater 503' is 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 layer of heat-resistant elastic material such as silicone rubber, fluorosilicone rubber, or fluorosilicone rubber is provided to a thickness of 2 to Losm, and preferably, a layer of PFA or PTFE with a thickness of 3 to 100Lm is provided on top of the layer.
It is made of a material with a heat-resistant and releasable resin layer. 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 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 heater 503. By controlling the voltage and the like, 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 to remove 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
A cleaning web 5051 made of a heat-resistant nonwoven fabric such as Nomex, Himeron, or polyester is transferred to the supply roll 5.
054 onto a take-up roll 5053 and is brought into contact with the heating roller 501 by a pressing roller 5052. This cleaning web 5051 is
When the take-up roll 5053 is rotated and driven by a driving means (not shown), the cleaning web 5051 is pulled out from the supply roll 5o54 little by little while changing its contact position, so that a new surface of the cleaning web 5051 is always brought into contact with the heating roller 501. Contact. Furthermore, 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, 506' having heat reflecting 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.
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 glass wool for preventing heat radiation is attached to the outer peripheral surface of the reflecting plate 506゜506' to prevent unnecessary heat radiation from the reflecting plate 506゜506'. . That is, the first reflecting plates 506, 506' and the covers 507 and 507' constitute a covering member for the heating roller 501.

Further, a casing member 509 having a substantially U-shaped cross section is provided above the fixing bag w15, and a cleaning member 505
2 reflector 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 50B 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.

By providing these reflective plates 506, 506', 512 and covers 507, 507', 513, it is possible to reduce heat wasted from the surfaces of the heating roller 501 and pressure roller 502, and also to detect temperature. The temperature measurement performance of the element 504 can be stabilized. 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 sandwiched between the 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 fixed image, 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 surface of the roller along the direction of the roller. 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.
1, and the separating claw 508' is also held by a support plate 520, which 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 reflecting plates 506, 506', and 512, it is desirable to use a metal plate having a glossy surface, such as an aluminum or copper plate with one surface polished, or an iron plate with surface treatment such as chrome plating. In addition, reflective plates 506, 50
The shape of 6', 512 preferably has a curvature of 1 so as to be 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 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. On the other hand, roller pair 501.
502 and near the paper discharge section, between the support plate 519 and the casing member 509.

A temperature sensing element 522 such as a thermistor is provided,
The temperature sensing element 522 is directly connected to a control circuit 532, and the heat exhaust fans 521 and 530 are connected to a control circuit 532 via a drive circuit 531. This control circuit 532 controls the temperature sensing element 5
When the detected temperature of 22 becomes a predetermined temperature or higher, the heat exhaust fans 521 and 530 are operated, and moreover, they are operated more strongly during the copy operation than when the copy is not operated. Further, if the predetermined temperature is not reached, the heat exhaust fans 521 and 530 are not operated.

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

The rotating shafts 524, 524' of the heating roller 501 have fI
J thermal insulation sleeves 523 and 523' are respectively fitted, and the insulation sleeves 523 and 523' are supported by bearings 526 and 526' mounted on frames 525 and 525' of the fixing device, respectively. The rotating shaft 524
, 524' are fitted with heat-resistant gears 527, 527', respectively, and one of the heat-resistant gears 527' is meshed with a driving force transmission gear 528 connected to the driving 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 is rotated.
It is now possible to remove etc.

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
By using 7', the heat retention of the heating roller 501 is improved.

Further, the heat-resistant sleeves 523, 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, 525'. Therefore, the heat loss from the end of the heating roller 501 is reduced by a factor of 10.

Generally, the heat-resistant gear 527, 527' is often provided with a number of other drive transmission members in conjunction with each other.
Therefore, conventional heat losses are predominant in such drive systems. On the other hand, with the present configuration, heat loss to the drive system can be reduced or eliminated, so thermal efficiency can be highly improved and power consumption can be reduced. or,
In this configuration, heat-resistant sleeves 524, 524' are used in addition to heat-resistant gears 527, 527', so heat loss from the roller ends to the frames 525, 52.5' can be prevented and thermal efficiency can be improved. You can improve.

The heat-resistant sleeve may be a heat-insulating material such as polyimide, polyamide-imide, polyamide, pps c polyphenylene sulfide), PBT (polybutylene terephthalate) resin, phenol resin, or a heat-insulating material made of a mixed material of this type. It is preferable that the material be made of a plastic material.

The gears 527, 527' are preferably made of a heat-resistant material with good heat insulation properties, such as polyimide, polyamide-imide, pps, modified phenol, or tetrafluoroethylene with a reinforcing filler added. .

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 φ59.3, a reverse crown of 1150 gm, and an aluminum roller core with a wall thickness of 6.5 mm.
Layer 1 Silicone rubber with a thickness of 0.5 mm and 20 JL on the surface layer
The pressure roller 502 is a roller coated with m-thick PTFE.
A roller having an outer diameter of 60 mm and a 50 mm thick stainless steel roller core bar coated with a 5-layer heat-vulcanized silicone rubber layer and a 30 gm thick fluoro rubber latex layer was used.

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'' in the pressure roller
A 70W sheathed heater was used, and it was turned on only when copying was not being performed.

Note that the nip opening was 9.0 layers, and the heating roller surface temperature was 195°C.

FIG. 3 is a graph explaining the change in surface temperature of each roller with respect to time for the experiment of the above specific example. 6 hours 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 l 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 (at 6 points), the pressure roller temperature reaches its lowest temperature, and then gradually rises as it receives heat from the heater 503'' from inside.
The fixing ability at 6 points is the lowest.

Therefore, if continuous copying is performed at these 6 points, it will be extremely preferable as a comparison experiment of fixing properties.1 This figure shows the temperature change when 250 sheets were continuously copied at 6 points.
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 445 mm/sec in an environment of 15°C (A3 size paper, 43
The 1st and 25th sheets of 250 consecutive copies were made by forming solid black sheets of 24 m in diameter on 180 g/m2 A3 paper, arranged in a lattice pattern of 3 pieces at equal intervals vertically and horizontally. , 50th sheet, ...250th sheet, etc., samples are extracted every 25 sheets, and 9 samples are taken for each sheet.
The solid black in the area was evaluated for fixability.

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

The sample was rubbed back and forth with lO at a pressure of 40 g/c (Silpon Paper, purchased from Co., Ltd.), and the difference in density before and after the rubbing was measured using a Macbeth reflection densitometer and quantified.

D2 φ24 Reflection density before rubbing solid black image (1,0
The image density is adjusted so that ≦D≦1.1. ) D': Reflection density after rubbing the φ24 solid chromatic image ΔD: Density reduction rate Then, the fixability was evaluated using the average of the density reduction rates of the 9 solid chromatic parts.

In addition, in this experimental example, the heat exhaust fans 521 and 530 are activated strongly when the temperature detected by the temperature detection element 522 becomes 80°C or higher during copying operation, and when copying is not activated, that is, during wait and standby. Temperature sensing element 522
When the detected temperature exceeds 80 degrees Celsius, it will operate at the same lunar strength as when copying is in progress.

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

According to the fixation evaluation method described above, the range in which normal line images exhibit good fixability is when the density reduction rate is 20 to 25% or less.
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 by copy paper, the time change in the amount of heat released when the copy paper is idly rotated is shown in Figure 6 (a). Immediately after, the idling speed heat value was 360W. The thermal efficiency η immediately after the power is turned on is 59%, and for reference, the idle rotation speed when the standby state is continued for more than 1 hour.
% amount was 115W, and #l efficiency η was 87%.

The fixing properties at this point were good even when the set temperature was 180°C.

Various sensors such as a jam detection sensor (not shown) are installed in the paper ejection section, and in this experimental example, the heat resistance limit temperature of these sensors is 85 degrees Celsius, so the temperature detection element 52
The detection temperature of No. 2 was set at 80°C. As a result, there was no problem with the temperature rising inside the aircraft.

Additionally, if the temperature detected by the temperature detection element 522 becomes 80 degrees Celsius or higher during copying and the heat exhaust fans 521 and 530 are strongly operated, the air in the fixing device is not directly sucked, but the fixing device The amount of heat dissipated from the device increases by about 50W.

However, since it takes about 45 minutes to reach the set temperature of 80° C. after the power is turned on, the fan will not operate under adverse conditions immediately after the power is turned on, and good fixing performance can always be obtained.

Further, when the heat exhaust fan 521 operates during the copy operation approximately one hour after the power is turned on.

The maximum amount of heat radiation was 225 W, the thermal efficiency η was 74%, and good fixing performance was obtained even when the set temperature was 185°C.

Furthermore, if the heat exhaust fans 521 and 530 are kept OFF all the time, various sensors installed in the paper ejection section may malfunction, and toner in the cleaner may be blocked in a high-temperature environment due to the rise in temperature inside the machine. .

(Comparative Example) As the fixing device, the same one 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 bag 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.

In addition, the amount of heat of idling formation under the above conditions is shown in Figure 6 (
As shown in 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. Further, even in a steady state when the device is left on standby for more than one hour, the amount of heat dissipated is as high as 315 W, and the thermal efficiency η is 64%, which is significantly worse than 87% in the experimental example.

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

The air cooling means is activated when the detected temperature of the temperature sensing element provided around the pair of rollers exceeds a predetermined temperature, and moreover, the air cooling means is activated more strongly during copying operation than when copying is not activated. It is possible to suppress the rise in temperature inside the machine during copying, and the temperature around the roller pair does not reach the specified temperature immediately after the power is turned on, so the air cooling means does not operate and thermal efficiency is greatly improved. It is possible to obtain good fixing properties. In addition, even when the air cooling means is operated, it is operated weakly when copying is not in operation, so there is a noise problem in which the operating sound of the air cooling means is disturbing, as when the air cooling means is operated strongly when copying is not in operation. This also reduces power consumption compared to when the system is operated strongly all the time.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the fixing device according to the present invention, and FIG. 2 is an x-X cross-sectional view of FIG. A graph showing changes in surface temperature; FIG. 4 is a graph showing changes in density reduction rate with respect to the number of copies of experimental examples of the present invention and comparative examples;
FIG. 5 is a graph showing changes in heating roller surface temperature with respect to the number of copies in experimental examples of the present invention and comparative examples, and 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. FIG. 7 is an explanatory diagram showing an embodiment of an image forming apparatus to which the fixing device according to the present invention can be applied. Explanation of symbols 5... Fixing bag gi 501... Heating roller 502... Pressure roller 503... Heater 521
...Exhaust heat fan 522...Temperature detection element 532
... Control circuit patent applicant: Canon Co., Ltd., Partner: Patent attorney Yoshikazu Kano ゝ、ζmi、
,. Agent Patent Attorney Oku 1) Noriyuki ,,'
・Figure 2, Figure 3, Figure 7! n3

Claims (1)

[Claims] a pair of rollers, at least one of which has a heating source; a casing that surrounds the pair of rollers; an air cooling means disposed outside the casing; and a temperature sensing element that detects the temperature around the pair of rollers. The fixing device has a control means that operates the air cooling means when the temperature detected by the temperature detection element exceeds a predetermined temperature, and operates the air cooling means more strongly during copying operation than when copying is not performed. A fixing device characterized by: