JP2002311732A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a temperature distribution uniform in the axial direction of a 1st roller. SOLUTION: The fixing device is provided with the 1st roller, a 2nd roller which is brought into press contact with the 1st roller, one or more ventilation part formed along the 1st roller so as to be adjacent to a nip part formed between the 1st and 2nd rollers, and a ventilation means for making air pass through the ventilation parts. In this case, since the ventilation parts are formed adjacently to the nip part and the air passes through the ventilation parts, the 1st roller is cooled by the air, and the quantity of heat per unit area consumed in the paper passing part area becomes equal to the quantity of heat per unit area taken from a non paper passing area, and the temperature distribution is made uniform in the axial direction of the 1st roller.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device.

[0002]

2. Description of the Related Art Conventionally, in a recording apparatus such as an electrophotographic printer, a facsimile, a copying machine, etc., a photosensitive drum as an image carrier is uniformly and uniformly charged by a charging roller. An electrostatic latent image is written thereon by an exposure device, and the electrostatic latent image is developed by a developing device to form a toner image. Then, the toner image is transferred to a recording medium such as a sheet or a film by a transfer roller, and is fixed by a fixing device.

As a fixing method for fixing a toner image by the fixing device, a heat fixing method in which a toner is melted and adhered to a recording medium is generally used. Of the heat fixing methods, the heat roller method is most often used because of its high thermal efficiency and safety.

In the heat roller method, a fixing roller and a pressure roller are pressed against each other, a recording medium is conveyed across a pressure contact portion (hereinafter referred to as a “nip portion”), and the fixing roller is heated so that the unfixed portion is formed. Heat the toner,
It is fixed by melting.

FIG. 2 is a schematic view of a conventional fixing device.

In FIG. 1, reference numeral 11 denotes a fixing device cover;
Is a fixing roller as a first roller rotated in the direction of the arrow, 13 is a pressing roller 13 as a second roller, the fixing roller 12 and the pressing roller 13 are pressed against each other, and The recording medium 16 is conveyed therebetween. Reference numeral 18 denotes a main frame of the transport unit.
Is transported.

A heat source 14, such as a halogen lamp or a ceramic heater, extends in the fixing roller 12 in the axial direction and is energized to heat the fixing roller 12. As a result, when the recording medium 16 passes through the nip portion, the unfixed toner 17 constituting the toner image on the recording medium 16 is heated, melted, and fixed on the recording medium 16.

A temperature sensor 15 is provided in contact with the outer peripheral surface of the fixing roller 12, and a sensor output of the temperature sensor 15 is sent to a control unit (not shown). The control unit includes:
When the sensor output is received, the amount of electric power supplied to the heat source 14 is controlled so that the temperature of the nip portion can be set to a temperature suitable for fixing, that is, a fixing temperature.

The fixing roller 12 is covered by the fixing device cover 11, and the surrounding portion 1 of the main frame 18 is covered by the fixing roller 12.
The pressure roller 13 is surrounded by 8b.

[0010]

However, in the conventional fixing device, it is difficult to make the temperature distribution in the axial direction of the fixing roller 12 uniform. For example, when printing is performed on a recording medium 16 having a small paper size, in the area of the nip portion where the recording medium 16 passes, that is, in the paper passing area, heat is applied to heat and melt the toner 17. In addition to being consumed, the recording medium 16 is heated when the toner 17 is heated and melted, and the heat is consumed accordingly.

On the other hand, in the area of the nip where the recording medium 16 does not pass, that is, in the non-paper passing area, the fixing roller 12, the recording medium 16 and the toner 17
Does not come into contact with the fixing roller 12
Heat is accumulated.

As a result, the temperature in the non-sheet passing area becomes higher than the temperature in the sheet passing area, and it becomes difficult to make the temperature distribution in the axial direction of the fixing roller 12 uniform.

When the temperature sensor 15 is disposed at the center of the fixing roller 12 in the axial direction, the temperature sensor 15 is connected to a portion where the heat is consumed by the recording medium 16 and the toner 17 (the paper passage area). Since the temperature of the fixing roller 12 is detected based on the detected temperature, the temperature at both ends in the axial direction of the fixing roller 12 becomes abnormally high.

Therefore, a bearing (not shown) provided for supporting both ends of the fixing roller 12 may be abnormally heated, and the durability of the bearing or the like may be reduced, or the bearing or the like may be damaged. Or

When printing is performed on a recording medium 16 having a large paper size immediately after printing is continuously performed on a recording medium 16 having a small paper size, the fixing roller 1
Since the temperature distribution in the axial direction 2 is not uniform, uneven fixing, wrinkles, etc.
At both ends, the unfixed toner 17 is excessively heated, melted, adheres to the fixing roller 12, and stains the surface of the recording medium 16 (hot offset).

Therefore, it is conceivable to dispose the temperature sensor 15 at the end of the fixing roller 12 (end of the non-sheet passing area corresponding to the maximum sheet size). When printing continuously for
Since the temperature sensor 15 detects the temperature of a portion where heat is not consumed (a portion corresponding to the non-sheet passing portion region), if the power amount is controlled based on the temperature, the temperature of the sheet passing portion region decreases. As a result, the toner image cannot be sufficiently fixed on the recording medium 16.

An object of the present invention is to solve the problems of the conventional fixing device and to provide a fixing device capable of making the temperature distribution in the axial direction of the first roller uniform.

[0018]

For this purpose, in a fixing device according to the present invention, a first roller, a second roller pressed against the first roller, and a first roller are disposed between the first roller and the second roller. And a ventilation portion formed adjacent to the nip portion formed along the first roller along the first roller, and ventilation means for allowing air to pass through the ventilation portion.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings. In this case, an example in which the present invention is applied to a printer among recording devices such as an electrophotographic printer, a facsimile, and a copying machine will be described.

FIG. 1 is a schematic view of a fixing device according to a first embodiment of the present invention, FIG. 3 is a perspective view showing a main part of the fixing device according to the first embodiment of the present invention, and FIG. FIG. 2 is a plan view illustrating a main part of the fixing device according to the first exemplary embodiment.

In the drawing, reference numeral 11 denotes a fixing device cover;
Is a fixing roller as a first roller rotated in the direction of arrow A, 13 is a pressing roller as a second roller, and the pressing roller 13 is fixed to the fixing roller 12 by a spring (not shown) as a biasing means. The recording medium 16 such as a sheet or a film is conveyed in a direction indicated by an arrow B by a nip formed between the fixing roller 12 and the pressure roller 13. Reference numeral 18 denotes a main frame of the transport section, and the recording medium 16 is transported along a guide section 18a of the main frame 18.

The printer includes a photosensitive drum (not shown) as an image carrier, a charging roller (not shown) as charging means, an exposure device (not shown) as exposure means,
The image forming apparatus includes a developing unit (not shown) as a developing unit, a drum unit including a transfer roller (not shown) as a transferring unit, and a fixing device as a fixing unit. And
The photosensitive drum is uniformly and uniformly charged by a charging device, an electrostatic latent image is written on the photosensitive drum by an exposure device, and the electrostatic latent image is developed by a developing device to form a toner image. It is formed. Then, the toner image is transferred to the recording medium 16 by the transfer roller and fixed by the fixing device.

A heat source 14, such as a halogen lamp or a ceramic heater, extends in the fixing roller 12 in the axial direction and is energized to heat the fixing roller 12. As a result, when the recording medium 16 passes through the nip portion, the unfixed toner 17 constituting the toner image on the recording medium 16 is heated, melted and fixed.

A temperature sensor 15 is provided in contact with the outer peripheral surface of the fixing roller 12, and a sensor output of the temperature sensor 15 is sent to a control unit (not shown). The control unit includes:
When the sensor output is received, the amount of power supplied to the heat source 14 is controlled so that the temperature of the nip can be set to the fixing temperature.

The guide portion 18a is formed so as to extend upstream and downstream from the nip portion in the conveying direction of the recording medium 16, and the guide portion 18a on the downstream side is formed.
a, in the vicinity of the nip portion, in the vicinity of the nip portion, one or more, in this embodiment, a plurality of, in this embodiment, a plurality of vents having a rectangular shape. A vent 19 as a part is formed.
Note that, instead of the ventilation port 19 having a rectangular shape, a thin slit as a ventilation section may be formed along the axial direction of the fixing roller 12. The vent 19 may be formed in the guide portion 18a on the upstream side.

The fixing device cover 11 is disposed so as to cover the fixing roller 12. One or more of the fixing device cover 11 is provided immediately above the fixing roller 12 in the fixing device cover 11 along the axial direction of the fixing roller 12. In the present embodiment, a plurality of suction ports 32 having a rectangular shape are formed. Instead of the suction port 32 having a rectangular shape, a narrow slit can be formed by extending along the axial direction of the fixing roller 12.

Below the downstream guide portion 18a, a suction chamber 18c is formed integrally with the guide portion 18a adjacent to the pressure roller 13, and the suction chamber 18c is formed in the suction port 18c. An apparatus cooling fan 20 as a ventilation means for passing air is provided. When the device cooling fan 20 is driven, the air around the fixing device is sucked into the fixing device cover 11 through the suction port 32 in the direction of arrow C, and the heat around the fixing roller 12 in the fixing device cover 11 is removed. After being sucked into the suction chamber 18c in the direction of arrow D through the ventilation port 19, it is discharged out of the fixing device in the direction of arrow E.

By the way, the ventilation port 19 and the suction port 32
The shape, size, and the like, and the air flow rate at the vent 19 when the apparatus cooling fan 20 is driven, that is, the cooling air flow rate, per unit area taken from the fixing roller 12 by driving the apparatus cooling fan 20 The amount of heat is set to be equal to the amount of heat per unit area consumed by the recording medium 16 and the toner 17 and taken from the fixing roller 12 when printing on the recording medium 16 having a small sheet size.

FIG. 5 is a block diagram of a control unit of the printer according to the first embodiment of the present invention.

In the figure, 12 is a fixing roller, 15 is a temperature sensor, 21 is a microprocessor for controlling the entire printer, that is, a CPU.
21 is a data R in which various data are recorded according to a control program recorded in a program ROM 22.
Various processes are performed by accessing the AM 23.

Reference numeral 25 denotes a sensor receiving circuit of the paper entrance sensor 24, which receives a signal from the paper entrance sensor 24 and sends it to the CPU 21. 27 is a writing start sensor 2
6, a writing start sensor 2 as a recording medium detecting means for recognizing the front end of the recording medium 16 (FIG. 1).
6 and sends it to the CPU 21.

Reference numeral 28 denotes an LED head, and 29 denotes the LED head.
LED head drive circuit for driving the ED head, 30 is an engine interface circuit, 31 is an engine interface, 35 is a heat source drive circuit for driving the heat source 14, 37 is a power supply LSI having an A / D converter 36,
38 is a power supply interface. Reference numeral 39 denotes a drum motor drive circuit.
Generates a drive signal based on an instruction from the CPU 21 and sends the drive signal to the drum motor 40 to drive the drum motor 40 to operate the drum unit and the fixing roller 12. A feed motor driving circuit 47 generates a drive signal based on an instruction from the CPU 21, sends the drive signal to the feed motor 46, drives the feed motor 46, and rotates a feed roller (not shown).
Is a registration motor drive circuit that generates a drive signal based on an instruction from the CPU 21 and sends the drive signal to the registration motor 48 to drive the registration motor 48 and rotate a registration roller (not shown).
1 is a fan drive circuit that generates a drive signal based on the instruction of 1 and sends the drive signal to the device cooling fan 20 to drive the device cooling fan 20.

Next, the operation of the fixing device having the above configuration will be described.

First, when the power of the printer is turned on and the printer is in a standby state and printing is not being performed, the air vent 19 is not blocked at all. Therefore, when a cooling processing unit (not shown) of the CPU 21 drives the device cooling fan 20 via the fan driving circuit 45,
Air around the fixing device is sucked into the fixing device cover 11 through the suction port 32, takes heat around the fixing roller 12 in the fixing device cover 11, and enters the suction chamber 18 c through the ventilation hole 19. It is discharged after being sucked. In this case, since the vent 19 is not blocked at all, the air in the fixing device cover 11 is taken into the suction chamber 18c through all the vents 19. Therefore, the fixing roller 1
2 is uniformly cooled in the axial direction and the temperature distribution becomes uniform in the axial direction.

In the state where the printer is performing printing, until the front end (the right end in FIG. 1) of the recording medium 16 reaches the vent 19, as in the case where the printer is not performing printing, The vent 19 is not blocked at all. Therefore, the fixing roller 12 is uniformly cooled in the axial direction, and the temperature distribution in the axial direction becomes uniform.

Subsequently, after the recording medium 16 is conveyed and the front end reaches the nip portion, the rear end (the left end in FIG. 1)
Until the paper passes through the nip, heat is consumed by the recording medium 16 and the toner 17, and heat is taken from the paper passing area in the nip of the fixing roller 12. At this time, from the time when the front end of the recording medium 16 reaches the vent 19 to the time when the rear end of the recording medium 16 passes through the vent 19 (after the front end reaches the nip portion, the rear end reaches the nip portion). Is almost equal to the time until the recording medium 16 passes). Therefore, the amount of heat per unit area taken from the non-sheet passing area in the nip portion of the fixing roller 12 by the air in the fixing device cover 11 is equal to the amount of heat per unit area consumed in the sheet passing area.

FIG. 6 is a time chart showing the operation of the device cooling fan according to the first embodiment of the present invention.

In the figure, f1 is the recording medium 16 (FIG. 1)
, The cooling air volume in the paper passing portion area from when the front end of the recording medium 16 reaches the vent 19 to when the rear end of the recording medium 16 passes through the vent 19, f2 is the front end of the recording medium 16 reaching the vent 19 This is the amount of cooling air in the non-sheet passing portion region from when the rear end of the recording medium 16 passes through the vent 19.

As can be seen from FIG.
While the recording medium 16 is blocking the air vent 19, the paper passing area of the fixing roller 12 is hardly cooled because the amount of cooling air is small, and the non-paper passing area is large in the amount of cooling air. The part area is cooled by an amount that is not cooled.

Therefore, the fixing roller 12 can be efficiently cooled while the recording medium 16 blocks the ventilation port 19.

FIG. 7 is a diagram showing the temperature distribution of the fixing roller in the axial direction. In the drawing, the horizontal axis represents the position of the fixing roller 12 (FIG. 1) in the axial direction, and the vertical axis represents
A surface temperature of 2 is taken. A is the temperature sensor 15
Indicates the position of.

In this case, a temperature sensor 15 is disposed at the end of the fixing roller 12 in the axial direction (the end of the non-sheet passing portion area when the recording medium 16 having the maximum sheet size is used).
The temperature distribution of the fixing roller 12 in the axial direction when printing is continuously performed is shown. When printing is continuously performed on the recording medium 16, in a conventional printer,
Based on the temperature detected by the temperature sensor 15, the non-sheet passing area is maintained at the fixing temperature T1, but the sheet passing area is at a temperature T2 lower than the fixing temperature T1. On the other hand, in the present embodiment, based on the temperature detected by the temperature sensor 15, the paper passing area is maintained at the fixing temperature T1, and the non-paper passing area is at a temperature T3 slightly lower than the fixing temperature T1. .

As described above, in the present embodiment, since the fixing roller 12 is cooled by the air in the fixing device cover 11, the amount of heat per unit area consumed in the paper passing portion area and the amount of non-paper passing portion The amount of heat per unit area taken from the region becomes equal. As a result, the fixing roller 12
Temperature distribution in the axial direction can be made uniform.

Therefore, when the temperature sensor 15 is disposed at the end of the fixing roller 12 as in this embodiment,
Since the temperature of the paper passing area can be prevented from lowering, the toner image can be sufficiently fixed on the recording medium 16. Further, when the temperature sensor 15 is disposed at the center of the fixing roller 12 in the axial direction, it is possible to prevent the temperature at both ends from becoming abnormally high, so that both ends of the fixing roller 12 are supported. The bearings and the like (not shown) disposed in the above are not abnormally heated, so that the durability of the bearings and the like is not lowered and the bearings and the like are not damaged.

Even when printing is performed on the recording medium 16 having a large paper size immediately after printing is continuously performed on the recording medium 16 having a small paper size, the temperature distribution in the axial direction of the fixing roller 12 can be improved. Is uniform, so that unevenness in fixing to the recording medium 16, wrinkles, and the like do not occur. Then, at both ends of the recording medium 16, the unfixed toner 17 is not excessively heated and melted. Therefore, the melted toner 17 does not adhere to the fixing roller 12 and the surface of the recording medium 16 is not stained.

Further, since the components of the existing printer can be used, there is no need to add new parts and it is not necessary to change the control method of the printer, so that the cost of the fixing device can be reduced. .

Further, since it is not necessary to detect the width of the recording medium 16 with a sensor or the like, not only the recording medium 16 having a rectangular shape but also a recording medium having a hole, the width of the recording medium 16 varies irregularly in the longitudinal direction. The present invention can also be applied to a recording medium or the like to be used.

Next, a second embodiment of the present invention will be described. In addition, about what has the same structure as 1st Embodiment, the description is abbreviate | omitted by attaching the same code | symbol.

FIG. 8 is a schematic view of a fixing device according to a second embodiment of the present invention.

In the drawing, reference numeral 51 denotes a photosensitive drum as an image carrier, and 52, a transfer roller as a transfer means for transferring a toner image onto the recording medium 16. The transfer roller 52 is brought into pressure contact with the photosensitive drum 51. The transfer unit is provided between the photosensitive drum 51 and the transfer roller 52. A write start sensor 26 is disposed at a predetermined position upstream of the transfer section in the transport direction of the recording medium 16 and detects a front end (right end in the figure) of the recording medium 16 as a recording medium detecting unit. And the writing start sensor 26
Is normally turned off, turned on when the front end of the recording medium 16 reaches, and turned off when the rear end (the left end in the figure) passes.

Next, the control of the device cooling fan 20 as a ventilation means will be described.

FIG. 9 is a time chart showing the operation of the fixing device according to the second embodiment of the present invention.

First, when the power of the printer is turned on and the printer is in a standby state, and printing is not being performed, the ventilation port 19 (FIG. 8) as a ventilation section is not blocked at all. Further, the device cooling fan 20 is not driven.

In a state where the printer is performing printing, when the front end of the recording medium 16 reaches the writing start sensor 26, the writing start sensor 26 is turned on, and the CP starts.
U21 (FIG. 5) is connected to the recording medium 1 via the sensor receiving circuit 27.
6 is detected. Then, a cooling processing unit (not shown) of the CPU 21 performs a cooling process, and starts timekeeping by using a timer (not shown) built in the CPU 21 as the front end of the recording medium 16 is detected. When the time τ1 elapses after that, the drive of the device cooling fan 20 via the fan drive circuit 45 is started. In addition,
Since the time τ1 is equal to the time from when the front end of the recording medium 16 reaches the writing start sensor 26 to when the front end reaches the vent 19, the front end of the recording medium 16 is
, The drive of the device cooling fan 20 is started.

Subsequently, when the rear end of the recording medium 16 passes through the writing start sensor 26 during printing, the writing start sensor 26 is turned off, and the cooling processing means is turned on by the sensor receiving circuit 27. , The rear end of the recording medium 16 is detected.
Then, the cooling processing means starts time measurement using the timer or the like in accordance with detection of the rear end of the recording medium 16, and when the time τ2 elapses from the start of time measurement, the fan drive circuit 45 The drive of the device cooling fan 20 is stopped via the. Note that the time τ2 is equal to the time from when the rear end of the recording medium 16 passes through the writing start sensor 26 to when the rear end passes through the vent 19, so that the rear end of the recording medium 16 is The drive of the device cooling fan 20 is stopped at the timing of passing through.

As described above, the apparatus cooling fan 20 is driven only while the recording medium 16 blocks the air vent 19, and the fixing roller 12 as the first roller is cooled.

In the drawing, f3 is the amount of cooling air in the paper passage area, and f4 is the length of time from when the front end of the recording medium 16 reaches the vent 19 to when the rear end of the recording medium 16 passes through the vent 19. This is the amount of cooling air in the non-sheet passing area between the two.

As can be seen from the figure, the paper passage area of the fixing roller 12 is hardly cooled, and the non-paper passage area is not cooled while the recording medium 16 blocks the air vent 19. It is cooled by a minute.

Therefore, the fixing roller 12 can be efficiently cooled only while the recording medium 16 blocks the ventilation port 19.

FIG. 10 is a diagram showing the temperature distribution of the fixing roller in the circumferential direction. In the drawing, the horizontal axis represents the position in the circumferential direction of the fixing roller 12 (FIG. 8), and the vertical axis represents the surface temperature of the fixing roller 12. A is a temperature sensor 1
5 indicates the position, and b indicates the position of the suction port 32.

In the first embodiment, since the apparatus cooling fan 20 is driven even when the printer is in a standby state and printing is not performed, the line L
As indicated by 1, there is a case where cooling is locally performed from the vicinity of the position of the suction port 32 to the nip portion.

On the other hand, in the present embodiment,
Since the fixing roller 12 is cooled only while the recording medium 16 is blocking the ventilation port 19, the position of the temperature sensor 15 and the suction port 32 are located from the nip as shown by the line L <b> 2.
The surface temperature can be made uniform up to the nip portion via the position, i.e., over the entire circumferential direction of the fixing roller 12.

As described above, in the present embodiment, the fixing roller 12 is cooled only while the recording medium 16 is blocking the ventilation port 19, so that the fixing roller 12 can be cooled not only in the axial direction but also in the circumferential direction. The temperature distribution can be made uniform.

Therefore, when the temperature sensor 15 is disposed at the end of the fixing roller 12, it is possible to prevent the temperature of the paper passing area from lowering, so that the toner image is sufficiently fixed on the recording medium 16. can do. Further, when the temperature sensor 15 is disposed at the center of the fixing roller 12 in the axial direction, it is possible to prevent the temperature at both ends from becoming abnormally high, so that both ends of the fixing roller 12 are supported. The bearings and the like (not shown) disposed in the above are not abnormally heated, so that the durability of the bearings and the like is not lowered and the bearings and the like are not damaged.

In addition, immediately after printing is continuously performed on the recording medium 16 having a small paper size, the printing is performed on the recording medium 16 having a large paper size. Since the temperature distribution is uniform, no uneven fixing, wrinkles, etc. are generated on the recording medium 16 in the width direction and the longitudinal direction. Then, at both ends of the recording medium 16, the unfixed toner 17 is not excessively heated and melted. Therefore, the melted toner 17 does not adhere to the fixing roller 12 and the surface of the recording medium 16 is not stained.

Further, since the temperature distribution of the fixing roller 12 can be made uniform in the axial direction and the circumferential direction, it is possible to sufficiently prevent the entire fixing device from being distorted. Therefore, the durability of the fixing device can be improved, and the cost can be reduced.

Further, since the fixing roller 12 is not cooled more than necessary except when the recording medium 16 is blocking the air vent 19, the time from when the power is turned on to when printing is completed is shortened. Power consumption can be suppressed.

In each of the above embodiments, the vent 19
Although the fixing roller 12 is cooled by sucking air through the air inlet, the fixing roller 12 can be cooled by blowing air through the vent 19.

The present invention is not limited to the above embodiment, but can be variously modified based on the gist of the present invention, and these are not excluded from the scope of the present invention.

[0070]

As described above in detail, according to the present invention, in the fixing device, the first roller, the second roller pressed against the first roller, and the first and second rollers are provided. Adjacent to a nip formed between the two rollers, one or more ventilation portions are formed along the first roller, and ventilation means for allowing air to pass through the ventilation portion.

In this case, one or more ventilation portions are formed adjacent to the nip portion formed between the first and second rollers, and air is passed through the ventilation portion. Is cooled, and the amount of heat per unit area consumed in the paper passing area is equal to the amount of heat per unit area taken from the non-paper passing area. Therefore, the temperature distribution in the axial direction of the first roller can be made uniform.

When the temperature sensor is disposed at the end of the first roller, it is possible to prevent the temperature in the paper passing area from lowering, so that the toner image is sufficiently fixed on the recording medium. be able to. In addition, when the temperature sensor is disposed at the center of the first roller in the axial direction, it is possible to prevent the temperature at both ends from becoming abnormally high, so that both ends of the first roller are supported. Therefore, the disposed bearings and the like are not abnormally heated, and the durability of the bearings and the like is not reduced, and the bearings and the like are not damaged.

Also, immediately after printing is continuously performed on a recording medium having a small paper size, even when printing is performed on a recording medium having a large paper size, the temperature distribution in the axial direction of the first roller is not affected. Since the recording medium is uniform, unevenness in fixing to the recording medium, wrinkles, and the like do not occur. Then, at both ends of the recording medium, the unfixed toner is not excessively heated and melted. Therefore, the melted toner does not adhere to the first roller, and the surface of the recording medium is not stained.

Further, since the components of the existing printer can be used, there is no need to add new parts and it is not necessary to change the control method of the printer, so that the cost of the fixing device can be reduced. .

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a fixing device according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of a conventional fixing device.

FIG. 3 is a perspective view illustrating a main part of the fixing device according to the first embodiment of the invention.

FIG. 4 is a plan view illustrating a main part of the fixing device according to the first embodiment of the invention.

FIG. 5 is a block diagram of a control unit of the printer according to the first embodiment of the present invention.

FIG. 6 is a time chart showing an operation of the device cooling fan according to the first embodiment of the present invention.

FIG. 7 is a diagram illustrating a temperature distribution of a fixing roller in an axial direction.

FIG. 8 is a schematic diagram of a fixing device according to a second embodiment of the present invention.

FIG. 9 is a time chart showing an operation of the fixing device according to the second embodiment of the present invention.

FIG. 10 is a diagram illustrating a temperature distribution of a fixing roller in a circumferential direction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Fixing device cover 12 Fixing roller 13 Pressure roller 16 Recording medium 19 Vent 20 Device cooling fan

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[Procedure amendment]

[Submission date] July 10, 2002 (2002.7.1)
0)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction contents]

[0018]

For this purpose, a fixing device according to the present invention includes a first roller heated by a heat source and a second roller disposed opposite to the first roller. An image on the recording medium is fixed by sandwiching the recording medium between the first roller and the second roller. And, near the first roller, there is provided a ventilation portion formed along the first roller, and ventilation means for passing air near the first roller in the ventilation portion. Further, as the recording medium passes between the first roller and the second roller,
Part is blocked by the recording medium.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0070

[Correction method] Change

[Correction contents]

[0070]

As described above in detail, according to the present invention, in the fixing device, the first roller heated by the heat source and the second roller disposed opposite to the first roller are provided. And fixing the image on the recording medium by sandwiching the recording medium between the first roller and the second roller. And, near the first roller, there is a ventilation portion formed along the first roller, and ventilation means for passing air near the first roller in the ventilation portion. In addition, a part of the ventilation section is blocked by the recording medium as the recording medium passes between the first roller and the second roller.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0071

[Correction method] Change

[Correction contents]

In this case, a ventilation portion is formed near the first roller along the first roller, and air is passed through the ventilation portion, so that the first roller is cooled by the air, and The amount of heat per unit area consumed in the paper area is equal to the amount of heat per unit area taken from the non-paper passing area. Therefore, the temperature distribution in the axial direction of the first roller can be made uniform.

Claims (5)

[Claims] 1. A first roller; (b) a second roller pressed against the first roller; and (c) a nip formed between the first and second rollers. And a ventilation unit formed adjacent to the first roller along the first roller, and (d) ventilation means for allowing air to pass through the ventilation unit. 2. The fixing device according to claim 1, wherein the ventilation portion is formed downstream of the nip portion in a recording medium conveyance direction. 3. The fixing device according to claim 1, wherein the ventilation unit sucks air through the ventilation unit. 4. The fixing device according to claim 1, wherein the ventilation unit is driven only when paper is passed. 5. The fixing device according to claim 1, wherein the first roller is covered by a fixing device cover.