JPH07140834A - Image forming device - Google Patents

Abstract

PURPOSE:To attain printing of high quality by eliminating the fluctuation of a fixation temperature. CONSTITUTION:An air duct 115 is formed between guides 111 and 113. The opening of an air intake 116 for the air duct 115 is formed on the trailing end corner part of a paper ejecting part 55. And also, the air fan 118 is arranged on the midway of the air duct 115. When the fan 118 is driven, air flows in from the air intake 116, and also, the air blows to the nip part of a thermal fixing device 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic printer or a copying machine, and more particularly to an image forming apparatus of a type in which toner is thermally fixed on a sheet.

[0002]

2. Description of the Related Art Conventionally, as a heating roller of a heat fixing device provided for fixing toner to paper in an electrophotographic printer or a copying machine, a hollow cylindrical roller made of aluminum or stainless steel is used. A heating roller is often used in which a halogen heater is arranged to heat the entire roller to a constant temperature. In this halogen heater type heating roller, a temperature sensor for keeping the temperature constant and a temperature fuse for preventing overheating are provided in the vicinity of the heating roller. Further, since the entire heating roller is heated, it is necessary to dispose a cover or the like for protecting an operator from high heat when processing a paper jam, which causes a problem of increasing the size of the apparatus.

For this reason, the applicant of the present application, as shown in FIGS. 6 to 10 of the embodiment described later, has an electrode layer 44 provided on the outer periphery of the base portion 45 of the roller and the electrode layer 44 outwardly. A large number of protruding contact points 48, a thin resistance layer 42 arranged on the outer periphery of the electrode layer 44 in a state of being floated from the contact 48 via an elastic support layer 43, and the thin resistance layer 4
2 has a second electrode layer 41 formed on the surface of the second electrode, and a toner fusion preventing layer 30 formed on the surface of the second electrode layer 41. A heating roller was proposed in which a part of the contact 48 and the resistance layer 42 are brought into contact with each other by elastic deformation of the support layer 43 so that heat can be generated only in the nip portion.

[0004]

In the heat fixing, if the heat applied to the paper is small, the fixing may be insufficient, and if the heat is too large, the paper may be damaged. Therefore, in order to perform high-quality image printing, it is necessary to keep the amount of heat generated at the nip portion constant. On the other hand, as a result of using the heating roller that generates heat only in the nip portion, it is not possible to keep the entire heating roller at a constant temperature as in the conventional case. Even if the amount of heat generated in the nip portion is made constant, there are some that take a lot of heat and some that do not take so much depending on the paper used, and in the end, it is not possible to eliminate the variation in fixing temperature.

Therefore, a first object of the present invention is to enable high-quality printing by eliminating fluctuations in the fixing temperature in an image forming apparatus using a heating roller that generates heat only in the nip portion. . Further, in addition to achieving the first object, the second object is to enable temperature control simply and surely and to improve the peelability of the paper from the heating roller.

Further, in addition to these purposes, a third object is to arrange printed sheets in the sheet discharge section.

[0007]

An image forming apparatus of the present invention, which has been made to achieve the first object, comprises an electrophotographic process for performing development and exposure as described in claim 1.
A paper feed unit for feeding paper to the electrophotographic process,
It is arranged between the electrophotographic process and the paper discharge unit, and a nip is formed between the pressure roller and a paper discharge unit for discharging the paper that has been developed and exposed in the electrophotographic process to the outside of the printer. In this way, in the image forming apparatus provided with a heating roller for fixing the image on the sheet which has been developed and exposed so that heat is generated only in the nip portion, the heating roller is forcibly cooled in a portion other than the nip portion. A cooling means is provided.

Further, the image forming apparatus of the present invention made to achieve the second object is, as described in claim 2,
In the image forming apparatus according to the first aspect of the present invention, as the cooling unit, a blower duct containing a blower fan is disposed on the sheet exit side of the heating roller.

Further, in the image forming apparatus of the present invention made to achieve the third object, as described in claim 3, in the image forming apparatus of claim 2, the air intake of the blower duct is performed. It is characterized in that the mouth is provided in the paper discharge section of the image forming apparatus.

[0010]

According to the image forming apparatus of the first aspect, the heating roller is forcibly cooled by the cooling means in the portion other than the nip portion. Therefore, when the nip is formed, the temperature is always initialized, and the continuous printing does not cause an overheated state. As a result, the amount of heat generated in the nip portion is always constant. Therefore, it is not necessary to adjust the printing speed during continuous printing, and high quality printing can be performed with simple control.

Further, according to the image forming apparatus of the second aspect, the cooling is performed by blowing air on the paper outlet side of the heating roller. As the cooling means, for example, a method of contacting a heating roller with a copper piece having good thermal conductivity may be used, but in that case, the copper piece itself stores heat depending on the amount of continuous printing, The cooling capacity may gradually become insufficient. However, according to the image forming apparatus of the second aspect, there is no such variation in the cooling capacity, and the stable cooling capacity can always be exhibited. In addition, the paper wound around the heating roller can be peeled off by the wind pressure.

Further, according to the image forming apparatus of the third aspect, since the air intake port of the blower duct is provided in the paper discharge section of the image forming apparatus, the paper of the paper discharge section is sucked from the air intake port. Due to the suction action of the sheet, it is brought into close contact with the bottom surface of the sheet discharge section. As a result, it is possible to prevent the sheet discharged later from being pushed out and dropping from the sheet discharge section.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the appearance of an electrophotographic printer having the functions of the present invention, which is a laser printer that performs exposure with a laser. The configuration of a laser printer having the functions of the present invention will be described with reference to FIG.

At the lower part of the laser printer main body 1, a paper feed cassette P for accommodating normal printing paper is arranged so that it can be stored inside the main body 1. Ordinary paper supply can be performed by an operator grasping a handle 50 provided on the front surface of the paper feed cassette P and pulling out the paper feed cassette P from the apparatus main body 1.

A paper feed port 51 for manual paper feed is arranged above the paper feed cassette P. A paper lower guide 52 and paper horizontal guides 53, 53 are arranged in front of the paper feed port 51. Above the paper guides 52 and 53, a control panel 57 for setting various printing modes of the laser printer main body 1 is provided. On the right side of the front surface of the laser printer main body 1, there is provided a control unit 58 including a control board for controlling each unit of the laser printer based on the input of the print mode and the like from the control panel 57. . On the upper surface of the laser printer main body 1, a paper discharge section 55 for stacking printed paper is arranged. The paper discharge unit 55 is configured so as to discharge the paper with the printing surface facing down, by a method generally called face down.

Next, the mechanism of the laser printer of the embodiment will be described with reference to FIG. Paper feed cassette P that stores and stacks paper
A feed roller 66 is provided on the paper discharge side of the paper feed cassette P to feed the paper one by one. Further, the half-moon type paper feed roller 5, the feed roller 67, etc. are provided at the corresponding positions on the main body side. On the other hand, when manually feeding paper, the paper guided by the paper lower guide 52 and the paper lateral guide 53 is the sensor 70 and the feed roller 7.
6,77 is guided to the manual feeding route. A registration upper roller 88 and a registration lower roller 89 are disposed behind the manual feed path and behind the confluence point S with the sheet fed from the sheet feeding cassette P. A sensor 71 is arranged immediately in front of both rollers 88 and 89. The upper registration roller 88, the lower registration roller 89, and the sensor 71 perform skew correction of the sheet, timing control of the printing position, and the like. That is, the sensor 71
Is configured to detect the edge of the paper, rotate and stop both rollers 88 and 89 at a predetermined timing in accordance with the detected state, forcibly skew the paper, and control the timing of the printing position. ing.

The image transfer discharger 7 is arranged at a position facing the drum type electrophotographic photosensitive member 13 of the process cartridge C. A charge eliminating charger 54 is disposed beside the image transfer discharger 7. Further, a sheet conveying section 8 is arranged on the downstream side of the image transfer discharger 7 and the charger 54. Further, a thermal fixing device 9 for fixing an image is arranged on the further downstream side of the sheet conveying section 8. The heat fixing device 9 includes a pressure roller 12 and a heating roller 4.
It consists of 0 and is made into a cartridge.

Behind the heat fixing device 9 (upper right in the figure)
A roller 56 for sending out is arranged in the. In front of the pressure roller 12, a guide 59 that guides the sheet sent from the sheet conveying unit 8 to the nip portion between the pressure roller 12 and the heating roller 40 is arranged.

Discharging guides 111 and 112 for face-down discharging are provided at the tip of the feeding roller 56 toward the upper discharging portion 55. In addition, the discharge ports 61 at the ends of the discharge guides 111 and 112.
Feed rollers 62 and 63 for feeding the paper to the paper output unit 55 are disposed in the paper.

The discharge guide 111 has a thermal fixing device 9 at the front end.
Is disposed above the nip portion of the. Also, the paper ejection guide 1
A third paper ejection guide 113 is arranged on the front side of 11. Like the paper discharge guide 111, the tip of the third guide 113 is arranged above the nip portion. The guides 111 and 113 form a ventilation duct 115 therebetween. Then, the air intake port 11 of the blower duct 115
6 is opened at the rear end corner of the paper discharge unit 55. Also,
A fan 118 for blowing air is arranged in the air duct 15. When the fan 118 is driven, air flows in from the air intake port 116 and the heat fixing device 9
Air is blown to the nip part of. The tip of the air duct 115 is configured to gradually reduce its width.

On the other hand, the laser scanner unit D is
It is arranged on the upper part of the process cartridge C. The laser scanner unit D is for performing scanning exposure on the drum 13. The laser scanner unit D includes a semiconductor laser (not shown) and a rotary polygon mirror 2
4, an f-θ lens 25, a reflection mirror 26, a scanner housing 27 for holding them, and the like.
Further, the pre-exposure lamp 10 is arranged above the process cartridge C.

The sheet conveying path in the printing area is the registration rollers 88, 89, the image transfer charger 7, the discharging charger 54, the sheet conveying path 8 and the drum type electrophotographic photosensitive member of the process cartridge C as described above. A path is formed by 13. The process cartridge C is arranged so as to face the above-described image transfer charger 7, paper transport path 8 and the like.
The process cartridge C is a drum type electrophotographic photosensitive member 1.
3 (hereinafter referred to as a drum), a charging device 81, a developing device 82, a cleaning device 83, and the like are made into a cartridge. These respective processes are appropriately arranged inside the main body cover 18 of the process cartridge C.

Next, the structure of the heat fixing device 9 will be described with reference to FIG. The heat fixing is performed by the heating roller 40 and the pressure roller 12 that is in contact with the heating roller 40. The heat generated by the heating roller 40 melts the toner placed on the sheet, so that the sheet is fixed.

In heat fixing, the heating roller 40 and the pressure roller 12 are rotated by driving force transmitted from a driving device (not shown). As a result, the paper 121 is sequentially conveyed, and the toner 121 is melted and fixed. Therefore, the thermal fixing using the heating roller 40 described in the present embodiment generally has a function of conveying a sheet and a function of melting the toner by heat and fixing the toner on the sheet.
It has various kinds of functions. Feeding rollers 90 and 91 are arranged behind the heating roller 40 in the sheet advancing direction. Immediately before that, the blow-out port 112 of the blower duct 115 is opened. Also, the heating roller 4
0 from the upper cover 123 and the lower cover 124 that covers the pressure roller 12 from below.
The whole is made into a cartridge.

Next, the structure of the heating roller 40 in this embodiment will be described. FIG. 4 is a sectional view of the heating roller 40. In the heating roller 40 of the present embodiment, the base portion 45 is formed on the outer periphery of the support portion 46 made of a material having a high thermal conductivity such as aluminum. The base portion 45 is formed of an elastic insulating material such as rubber or resin.
In the case of the present embodiment, the base portion 45 is configured to soften the contact pressure of the contact 48, which will be described later, but if the thermal conductivity is further enhanced, the base portion such as rubber may not be provided. Good.

The support portion 46 made of aluminum or the like is rotatably supported at both ends by bearings (not shown) provided in the process cartridge C. On the outer periphery of the base portion 45, an electrode layer 44 formed mainly of a metal conductor such as aluminum is formed. As shown in FIG. 5, a large number of contacts 48 are formed on the surface of the electrode layer 44. The contact 48 is formed in a cylindrical shape in the present embodiment, but various shapes such as a cubic pillar or a hemispherical shape are conceivable. Moreover, the electrode layer 44 and the contact 48 are electrically connected. In this case, the contact 48 is the electrode layer 44.
It may be bonded to the upper side, or may be originally formed integrally with the electrode layer 44. In the case of the present embodiment, the material of the contact 48 is made of a material such as tungsten, which has good heat resistance and wear resistance, because the tip end is exposed to high temperature and high pressure conditions.

On the outer periphery of the electrode layer 44, an elastic layer 43 composed of an insulating elastic body or the like is formed. As shown in FIG. 5, the elastic layer 43 is formed with a hole 49 that vertically penetrates at a portion corresponding to the above-mentioned contact 48. Further, the height of the contact point 48 is configured so as to be lower than the height of the hole 49. The elastic layer 43 is bonded onto the electrode layer 44. Here, the height of the contact point 48 is configured to be smaller than the thickness of the elastic layer 43. Therefore,
When no external force is applied to the elastic layer 43, the contact point 48 is embedded in the elastic layer 43 and can be exposed to the outside only after the elastic layer 43 is compressed and deformed.

A thin resistance layer 42 is further arranged on the surface of the elastic layer 43. In this embodiment, the resistance layer 42 has a thickness of about 20 μm and is made of a polycarbonate film in which carbon is dispersed. Thereby, the resistance layer 42 is adjusted to have a predetermined volume resistance value.

A second electrode layer 41 is arranged on the outer surface of the resistance layer 42. In the case of the present embodiment, the second electrode layer 41 is formed by vacuum-depositing aluminum or the like on the outer surface of the resistance layer 42. The vapor-deposited layer has a thickness of 1000 Å to 0.2 mm.

Further, on the surface of the second electrode layer 41, in order to prevent the toner from being fused to the heating roller 40 at the time of fixing the toner, a fusion bonding made of a material such as tetrafluoroethylene is used. The prevention layer 30 is formed. The above-mentioned contact 48 is arranged over the entire heating area of the heating roller 40.

It is to be noted that the contact surfaces of the supporting portion 46, the base portion 45, the electrode layer 44, the elastic layer 43, the resistance layer 42, the second electrode layer 41 and the fusion preventing layer 30 described above are appropriately arranged. Bonded by adhesive or strong mechanical force. Next, the overall configuration of the heating roller 40 will be described with reference to FIG.

In the vicinity of the left end of the heating roller 40, the surface of the second electrode layer 41 described above is exposed to the surface of the heating roller 40. That is, the fusion preventing layer 30 is not formed in this portion. The terminal 11b for power feeding is in contact with the exposed surface of the second electrode layer 41.

The electrode layer 4 is formed on the right end of the heating roller 40.
The surface of No. 4 is exposed to the roller surface. That is, the elastic layer 43, the resistance layer 42,
The common electrode layer 41 and the fusion preventing layer 30 are not configured. The power supply terminal 11a is also in contact with the exposed surface of the electrode layer 44.

These terminals 11a and 11b are
It is connected to a power supply (not shown). A predetermined current is supplied to the heating roller 40 from the terminal 11a by this power source. The terminal 11b is connected to the ground side of the power supply. The support portion 46 of the heating roller 40 extends at both ends so as to be rotatably supported by a bearing (not shown) provided on the main body cover 18 of the process cartridge C. A gear (not shown) for rotating the heating roller 40 is provided at the leftmost end of the heating roller 40 so that a driving force from a driving source (not shown) can be transmitted to the heating roller 40.

Next, image recording will be described. Image recording by automatic paper feeding from the paper feeding cassette P will be described. When the image recording start signal is given, the half-moon type paper feed roller 5 is intermittently rotated by one rotation or a plurality of predetermined rotations in the paper feeding direction at every predetermined paper feeding timing. The sheets in the sheet feeding cassette P are separated one by one at each intermittent rotation and fed in the arrangement direction of the feed rollers 66 and 67. The sheet sent out from the sheet feeding cassette P by the half-moon type sheet feeding roller 5 passes through the guide and the sensor 71.
Then, after the leading end is once received by the nip portion of the registration rollers 88 and 89 which has been stopped until that time,
The sheet is fed toward the transfer portion by the registration rollers 88 and 89 which are rotationally driven at a predetermined timing synchronized with the rotation of the drum 13 and the detection timing of the sensor.

Simultaneously with the feeding of the above-mentioned paper, the drum 13 is rotationally driven in the counterclockwise direction in FIG. 2 at a predetermined peripheral speed by an image recording start signal. The drum 13 is subjected to the entire surface pre-exposure by the pre-exposure lamp 10 during the rotation process thereof, and is then uniformly positively or negatively charged by the charger 81. Then, the exposure unit receives the laser beam scanning exposure by the laser scanner unit D, so that an electrostatic latent image of the target image is formed on the peripheral surface thereof. In the scanning exposure, the semiconductor laser outputs a laser beam modulated corresponding to the time-series electric pixel signal of the target image to the rotary polygon mirror 24, and the scanning speed with respect to the rotation angle of the rotary polygon mirror 24 is increased. The f-θ lens 25 converts the speed to a substantially constant speed, and the output direction is changed via the reflection mirror 26.
A laser beam is scanned in the direction of the drum generatrix on the drum surface and exposed.

The electrostatic latent image formed on the surface of the drum 13 is developed with toner by the developing device 82, and the discharging device 7 for image transfer is used.
To the position of. After the toner development, the drum 13
In synchronism with the rotation of the sheet, the sheets are sequentially transferred onto the surface of the transfer sheet fed from the sheet feeding section 6 between the drum 13 and the image transfer discharger 7.

The sheet to which the toner image has been transferred is sequentially separated from the surface of the drum 13 by the action of the charge-eliminating charger, and is introduced into the nip portion between the heating roller 40 and the pressure roller 12 which are the image fixing unit through the sheet conveying section 8. . In this nip portion, the toner is melted by the heat to fix the image. The surface of the drum 13 from which the paper has been separated is cleaned by a cleaning device 83 and is used for repeated image formation.

Next, the operation of performing heat fixing on the heating roller 40 and the pressure roller 12 will be described with reference to FIGS. 7 and 8. FIG. 7 shows the heating roller 40 of this embodiment.
FIG. 6 is a cross-sectional view for explaining a state in which a nip is formed when heat is generated and fixing is performed. FIG. 8 mainly shows the heating roller 4.
It is a fragmentary sectional view for explaining the situation of heat generation of 0.

At the time of fixing, the heating roller 40 is pressed by the pressure roller 12 having the roller 22 made of a material such as silicon rubber around the shaft 23 such as a metal. The pressure of the pressure roller 12 crushes the outer peripheral portion of the heating roller 40 mainly by elastically deforming the elastic layer 43. As a result, a nip portion having an area and pressure suitable for fixing is formed near the contact portion between the heating roller 40 and the pressure roller 12.

At the time of actual fixing, the sheet (not shown) on which the toner is transferred is fed into the nip portion, and the heating roller 40 and the pressure roller 12 rotate in the sheet feeding direction so that the sheet is sequentially fed. Is sent and fixing is performed. The action of heat generation due to the formation of the nip portion will be described with reference to FIG.

FIG. 8A shows the state of the heating roller 40 when the nip portion is not formed. Since the contact 48 is not in contact with the resistance layer 42, the contact 48 and the resistance layer 42 are not shown.
No current can flow between and. Therefore, in this state, the resistance layer 42 does not generate heat. On the other hand, when the elastic layer 43 is compressed due to the formation of the nip portion of the heating roller 40, the contact 48 becomes the resistance layer 42 as shown in FIG. 8B.
To be electrically connected.

Therefore, the current passes through the contact 48 and the resistive layer 42.
Is supplied to. The resistance layer 42 is heated by the current supplied from the contact 48. The current supplied to the resistance layer 42 reaches the second electrode layer 41 and is made to flow to the ground side. The heat generated by the heat generation of the resistance layer 42 is transferred to the second layer from the resistance layer 42.
It is transmitted to the sheet sandwiched in the nip portion through the electrode layer 41 and the fusion preventing layer 30. Therefore, this heat is used for melting the toner.

As described above, the heat used for melting the toner is transmitted through the second electrode layer 41 and the fusion preventing layer 30 and is transmitted through the resistance layer 42. The second electrode layer 41 and the fusion preventing layer 30 are formed of extremely thin layers, and the thinner these layers, the better the electrothermal efficiency. In the present embodiment, since the heating roller 40 is housed in the cartridge, there is no risk of the operator touching it or hitting it against something, and the thermal resistance of the second electrode layer 41 and the fusion preventing layer 30 is reduced. Can be extremely small.
Therefore, the heat generated in the resistance layer 42 can be transferred to the surface of the heating roller 40 very efficiently, and extremely efficient fixing can be achieved.

Further, the heating roller 40 generates heat only near the nip portion pressed by the pressure roller 12. Therefore, the thermal influence on other members around the fixing unit can be made extremely small. Next, returning to FIG. 3, the characteristic part of the present embodiment will be described.

The blower fan 118 is in a driving state during printing. Therefore, during printing, air is blown to the surface of the heating roller 40 immediately after the nip portion between the heating roller 40 and the pressure roller 12 through the blowout port 122 of the blower duct 115. By this air, the heating roller 4
0 is well cooled and returns to its initial state with respect to temperature.
That is, the heating roller 40 generates heat at a constant temperature determined by the relationship between the resistance value of the resistance layer 42 and the applied current in the nip portion, but the temperature is initialized in the non-nip portion. Therefore, even if continuous printing is performed, heat is not stored in the heating roller 40, and the heat generation temperature of the nip portion is always constant. As a result, in continuous printing, complicated control such as gradually increasing the paper feeding speed is not required, and nevertheless, it is possible to always perform printing with constant quality.

Further, as a result of the air being blown through the blower duct 115, the leading end of the sheet 120 that has undergone heat fixing receives a downward force due to this air. Therefore, the paper 120 is easily separated from the heating roller 40. As a result, the paper is not wound around the heating roller 40, and a good paper discharge operation can be performed. Further, there is also an effect that the peeling claw which was necessary in the previous proposal dated October 29, 1993 is unnecessary.

Next, a method of discharging the sheet after fixing will be described. As described above, the sheet 120 separated from the heating roller 40 by the air blown from the air duct 115 is sandwiched between the delivery rollers 90 and 91, and the sheet ejection guide 11
It is sent out to the paper discharge passage formed by 1 and 112.
Then, after passing through the paper discharge passage, the delivery roller 6
The sheet is discharged to the sheet discharge section 55 by the numerals 2, 63. Here, the air intake port 116 of the blower duct 115 is opened at the rear end corner of the paper discharge unit 55. Therefore, when the sheets are continuously discharged by the continuous printing, even if the first sheet is discharged to the sheet discharge section 55, the blower fan 118 is still driven. Is the air intake 1
The air sucked into the blower duct 115 from 16 is adsorbed to the air intake 116. After that, even if the second sheet is discharged to the sheet discharge section 55, the first sheet is fixed by this suction, so it is pushed out by the frictional force of the second sheet discharged above. Never be As a result, the problems such as the drop of the discharged paper during continuous printing, which are often experienced in the conventional laser printer, do not occur.

As is apparent from FIG. 2, the air intake port 1
Since 16 also opens upward along the rear end wall of the paper discharge portion, it does not hinder the intake of air even after the paper discharge is adsorbed. Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and it goes without saying that the present invention can be implemented in various modes without departing from the scope of the invention.

For example, the heating roller used in the heat fixing device 9 is not limited to the mode as in the embodiment, and the heating elements may be arranged linearly. Further, the cooling means may also be such that a copper piece having good thermal conductivity is brought into contact with the heating roller instead of blowing air.

[0051]

As is apparent from the above description, according to the image forming apparatus of the present invention, the fixing is performed without troublesome control although the heating roller of the type that generates heat only at the nip portion is used. Temperature fluctuations can be eliminated,
It can always enable high quality printing.

Further, according to the image forming apparatus of the second aspect, in addition to the above effect, the temperature can be controlled easily and surely, and moreover, the peelability of the paper from the heating roller is also improved. It is also possible to eliminate the peeling claw.
Furthermore, according to the image forming apparatus of the third aspect, in addition to these effects, it is possible to arrange the printed sheets in the sheet discharge section.

[Brief description of drawings]

FIG. 1 is a perspective view of a laser printer as an example.

FIG. 2 is a central cross-sectional view of a laser printer as an example.

FIG. 3 is a central cross-sectional view of a main part of the laser printer according to the embodiment.

FIG. 4 is a central cross-sectional view of a heating roller of an example.

FIG. 5 is an exploded perspective view of a main part of the heating roller of the embodiment.

FIG. 6 is a perspective view of the entire heating roller of the embodiment.

FIG. 7 is a cross-sectional view for explaining formation of a nip portion by a heating roller and a pressure roller in an example.

FIG. 8 is a partial cross-sectional view for explaining the mechanism of heat generation at the nip portion in the example.

[Explanation of symbols]

1 ... Laser printer device main body, 4 ... Engaging member,
9 ... Thermal fixing device, 11a, 11b ... Terminal, 12 ... Pressure roller, 13 ... Drum type electrophotographic photoreceptor, 18 ... Main body cover, 30 ... Fusion prevention layer, 33 ... Shutter, 40 ... Heating roller, 41 ... Second electrode layer, 42 ... Resistive layer, 43
... Elastic layer, 44 ... Electrode layer, 45 ... Base part,
46 ... Support, 48 ... Contact, 49 ... Hole, 1
11, 112 ... Paper ejection guide, 113 ... Third guide, 115 ... Air duct, 116 ... Air intake, 118 ... Fan, 122 ... Blow-out,
C ... Process cartridge, D ... Laser scanner unit.

Claims (3)

[Claims] 1. An electrophotographic process for developing and exposing, a paper feeding unit for supplying a sheet to the electrophotographic process, and a sheet developed and exposed in the electrophotographic process is discharged to the outside of the printer. And a sheet that has been developed and exposed so that heat is generated only in the nip portion by forming a nip between the discharge portion and the electrophotographic process and the paper discharging portion. An image forming apparatus having a heating roller for fixing an image to the image forming apparatus, further comprising: a cooling unit for forcibly cooling the heating roller in a portion other than the nip portion. 2. The image forming apparatus according to claim 1,
As the cooling means, on the paper exit side of the heating roller,
An image forming apparatus having a blower duct that accommodates a blower fan. 3. The image forming apparatus according to claim 2,
An image forming apparatus, wherein the air intake port of the blower duct is provided in a paper discharge section of the image forming apparatus.