JPH0561374A - Fixing device - Google Patents

Abstract

(57) [Summary] [Objective] It is possible to suppress the occurrence of heat damage and high-temperature offset phenomenon of the covering layer of the fixing roller, peripheral members of the fixing roller, and the like, and to shorten the rise time by thinning the fixing roller. To provide a fixing device capable of performing. [Structure] The fixing roller 1 is cooled by air blown from a fan 8. The fan 8 is a cross flow fan, and a guide plate 9 is attached to the discharge port of the fan 8. The guide plate 9 is disposed above the fixing roller 1, and a passage is formed between the guide plate 9 and the fixing roller 1 to guide the air sent from the fan 8 to the rear of the fixing roller 1.
The blowing direction of the fan 8 is opposite to the rotating direction of the fixing roller 1, and the blowing region of the fan 8 is a region along the longitudinal direction of the fixing roller 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used in an image forming apparatus such as an electrophotographic copying apparatus and an electrostatic information recording apparatus.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus such as an electrophotographic copying apparatus, a heat roll type fixing device is used as a fixing device for fixing an unfixed developer image on a transfer material.

A heat roller type fixing device comprises a fixing roller and a pressure roller which is rotated while being pressed against the fixing roller. The fixing roller and the pressure roller cooperate with each other to form an unfixed developer image. A nip portion for nip-conveying the transfer material on which is formed is formed. The fixing roller has a hollow cored bar made of a metal material such as aluminum or iron,
A coating layer having releasability is formed on the outer peripheral surface of the core metal. A heater for heating the surface of the fixing roller to the fixing temperature is arranged in the core of the fixing roller. The heat capacity of the heater is determined by the fixing temperature set for the surface of the fixing roller and the heat capacity of the fixing roller.
The heat capacity of the core metal is dominant as the heat capacity of the fixing roller.

During fixing, the fixing roller is heated by a heater,
The surface temperature of the fixing roller is maintained within a predetermined temperature range. The transfer material on which the unfixed developer image is formed is inserted into the nip portion between the fixing roller and the pressure roller. The transfer material is subjected to heat and pressure while passing through the nip portion, and the unfixed developer image is fixed as a permanent image on the transfer material by the heat and pressure.

[0005]

In recent years, a simpler OA device has been demanded in the market, and it is desired to shorten the rise time until the surface temperature of the fixing roller reaches the fixing temperature. In order to shorten the rise time, it is conceivable to reduce the heat capacity of the core metal by reducing the thickness of the core metal of the fixing roller.

However, in the conventional fixing device, when the thickness of the core metal of the fixing roller is greatly reduced, the heat capacity of the fixing roller becomes extremely small, so that the surface temperature of the fixing roller is apt to change suddenly. As a result, when a small-sized transfer material is continuously fed, a high temperature rise occurs in the non-sheet passing area portion of the fixing roller, and the thermal melting and heat of the covering layer of the fixing roller, the peripheral members of the fixing roller, etc. It may cause deterioration.

Further, the distribution of the surface temperature of the fixing roller in the standby direction becomes non-uniform, and the surface temperature of the central portion of the fixing roller becomes higher than the surface temperature of other portions. Therefore, the offset phenomenon due to the high temperature is likely to occur in the central portion of the fixing roller.

An object of the present invention is to suppress the occurrence of heat damage and high-temperature offset phenomenon of the covering layer of the fixing roller, peripheral members of the fixing roller, etc., and to shorten the rise time by thinning the fixing roller. The object is to provide a fixing device that can perform.

[0009]

According to the present invention, the above object is to provide a fixing device for heating an unfixed developer image on a transfer material with a fixing roller having a heating element therein. This is achieved by providing an air blowing unit that blows air substantially uniformly over the entire area in the longitudinal direction of the roller.

[0010]

In the fixing device of the present invention, the air blowing means blows air substantially uniformly over the entire lengthwise direction of the fixing roller. The outer peripheral surface of the fixing roller is cooled by the air blown from the air blower, and a partial temperature rise is suppressed.

[0011]

Embodiments of the fixing device of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the fixing device of the present invention, FIG. 2 is a diagram showing the relationship between the heat radiation amount and the heat supply amount of the fixing roller of the fixing device of FIG. 1, and FIG. Of the fixing roller surface temperature distribution during standby of the fixing device of FIG.
FIG. 4 is a diagram showing the temperature distribution of the surface of the fixing roller when A3 of the fixing device of FIG. 1 is continuously fed, and FIG. 5 is B of the fixing device of FIG.
FIG. 6 is a diagram showing the temperature distribution of the fixing roller surface during 5R continuous sheet feeding, and FIG. 6 is a diagram showing the relationship between the heat supply amount to the fixing roller and the heat radiation amount from the fixing roller in each sheet feeding state of the fixing device of FIG. ..

As shown in FIG. 1, the fixing device includes a fixing roller 1. The fixing roller 1 has a hollow cored bar 2 made of an aluminum material and having a coating layer (not shown) formed on the outer peripheral surface thereof. The core 2 has a wall thickness of 2 mm. A heater 3 including a halogen lamp is arranged in the core metal 2. The heater 3 heats the fixing roller 1 from the inside.
The amount of heat supplied to the fixing roller 1 by the heater 3 increases at both ends of the fixing roller 1, as shown in FIG.

A pressure roller 4 is rotatably pressed against the fixing roller 1. The pressure roller 4 is a rubber roller.
The pressure roller 4 cooperates with the fixing roller 1 to form a nip portion, and the transfer material on which the unfixed toner image is formed is nipped and conveyed.

A guide plate 5 for guiding the transfer material to the nip portion is provided on the upstream side of the fixing roller 1.

On the downstream side of the fixing roller 1, separation claws 6 and 7 are provided.
Is provided. The separation claw 6 prevents the transfer material from wrapping around the fixing roller 1, and the separation claw 7 prevents the transfer material from wrapping around the pressure roller 4.

The fixing roller 1 is cooled by the air blown from the fan 8. The fan 8 is a cross flow fan, and a guide plate 9 is attached to the discharge port of the fan 8. The guide plate 9 is disposed above the fixing roller 1, and a passage is formed between the guide plate 9 and the fixing roller 1 to guide the air sent from the fan 8 to the rear of the fixing roller 1.
The blowing direction of the fan 8 is opposite to the rotating direction of the fixing roller 1, and the blowing region of the fan 8 is a region along the longitudinal direction of the fixing roller 1.

The surface temperature of the fixing roller 1 is the thermistor 10.
The temperature detected by the thermistor 10 is used for controlling the surface temperature of the fixing roller 1. In controlling the surface temperature of the fixing roller 1, the heater 3 is operated according to the temperature detected by the thermistor 10.
The heating operation and the stopping thereof are performed, and the surface temperature of the fixing roller 1 is maintained at 180 ° C.

When forming an image on a transfer material, a main power source is turned on to the image forming apparatus. Next, the heating operation of the heater 3 is performed until the temperature detected by the thermistor 10 reaches 180 ° C. Since the core metal 2 of the fixing roller 1 is thin, the heat capacity of the fixing roller 1 is small, so that the rising time until the temperature detected by the thermistor 10 reaches 180 ° C. by heating the heater 3 is shortened.

When the temperature detected by the thermistor 10 reaches 180 ° C., the heating operation of the heater 3 is stopped and the fan 8 is driven. After that, the standby state is entered, and the heating operation and stopping of the heater 3 are repeated.

During standby, as shown in FIG. 3, the fixing roller 1
Has a small heat capacity, the surface temperature at the central portion of the fixing roller 1 becomes higher than the surface temperature at other portions due to the heating operation and stop of the heater 3, but the surface of the fixing roller 1 is cooled by the air blown from the fan 8. An increase in the surface temperature of the central portion of the fixing roller 1 is suppressed. The heat capacity from the fixing roller 1 due to the blowing of the fan 8 is shown in FIG.
As shown in (3), it becomes large in the central portion of the fixing roller 1.

When shifting from the standby state to the image forming operation, the start button is pressed. The transfer material on which the unfixed developer image is formed is inserted into the nip portion between the fixing roller 1 and the pressure roller 4. While passing through the nip portion of the transfer material, the unfixed developer image is heated and pressed, and the unfixed developer image is fixed on the transfer material as a permanent image.

In the nip portion, as shown in FIG. 2, in the transfer material passage area of the fixing roller 1, heat is transferred from the fixing roller 1 to the transfer material. For example, when an A3 size transfer material is passed, the amount of heat radiated from the fixing roller 1 to the transfer material is a heat amount Q ₃ , and when a B5R size transfer material is passed, the fixing roller 1 transfers to the transfer material. The heat radiation amount of is the heat amount Q ₄ .

Immediately after the transfer material passes through the nip portion, the temperature detected by the thermistor 10 falls below 180 ° C., and the heating operation of the heater 3 is started. However, since the surface temperature of the fixing roller 1 in the transfer material passing region is lower than the surface temperature of the non-paper passing region, a temperature rise occurs in the non-paper passing region of the fixing roller 1 with the heating operation of the heater 3. However, the surface of the fixing roller 1 is cooled by the air blown by the fan 8, and the temperature rise in the paper non-passage area of the fixing roller 1 can be suppressed.

When the B5R size transfer material is continuously fed, as shown in FIG. 5, the surface temperature is suppressed to about 230 ° C. by driving the fan 8 in the non-sheet feeding area of the fixing roller 1. Therefore, as is clear from FIG. 7, it is possible to prevent the coating layer of the fixing roller 1 from melting. The balance of the amount of heat when the fan 8 is stopped and the balance of the amount of heat when the fan 8 is operating in each state are shown in FIG.

Next, another fixing device will be described. FIG. 8 is a diagram showing a state in which a fixing roller used in another embodiment of the fixing device of the present invention is cooled, and FIG. 9 is a state in which the fixing roller used in the fixing device in FIG. 8 is not cooled. FIG.

Another fixing device is, as shown in FIGS. 8 and 9, a fixing roller 1 having a heater 3 therein.
The pressure roller 4, the guide 5, the separation claws 6 and 7, and the thermistor 10.

The fixing roller 1 is cooled by the fan 11.
One end of a suction duct 12 is attached to the suction port of the fan 11. The other end of the suction duct 12 is directed to the photosensitive drum in the image forming apparatus. An opening 13 for exposing a part of the outer peripheral surface of the fixing roller 1 to the inside of the suction duct is provided below the suction duct 12. A partition plate 14 is provided in the suction duct 12, and the partition plate 14 forms an A channel and a B channel that are switchable with each other. Switching between the A channel and the B channel is performed by the channel switching plate 15. The flow path switching plate 15 is a shaft 16 provided in the suction duct 12.
Is rotatably supported by the solenoid, and the rotary motion of the flow path switching plate 15 about the shaft 16 is turned on / off by a solenoid (not shown)
This is performed by the F operation.

The solenoid is turned on when the temperature detected by the thermistor 10 is lower than 160 ° C., and the thermistor 1
When the detected temperature of 0 is 160 ° C. or higher, the OFF operation is performed. When the solenoid is turned on, as shown in FIG. 9, the flow path switching plate 15 is angularly rotated to a position substantially parallel to the partition plate 14, the A flow path is opened, and the B flow path is closed. On the other hand, when the solenoid is turned off, as shown in FIG. 8, the flow path switching plate 15 is angularly rotated to the position where the A flow path is closed, and the B flow path is opened.

When the main power source of the image forming apparatus is turned on, the heating operation of the heater 3 is started and the solenoid is turned on as shown in FIG. 10 (step 10).
1). The passage switching plate 15 is angularly rotated by the ON operation of the solenoid, so that the A passage is opened and the B passage is closed.

Next, the fan 11 is driven, and the air around the photosensitive drum is sucked into the fan 11 through the A passage in the suction duct 12. The air sucked into the fan 11 is exhausted from the discharge port to the outside of the image forming apparatus, and heat is dissipated in the image forming apparatus.

When it is determined that the temperature detected by the thermistor 10 is 160 ° C. or higher (step 102), the solenoid is turned off (step 103). The A flow path is closed and the B flow path is opened by the OFF operation of the solenoid. The air around the photosensitive drum is sucked by the fan 11 through the B passage in the suction duct 12, and the air sucked by the fan 11 is exhausted to the outside of the image forming apparatus. Since the outer peripheral surface of the fixing roller 1 is exposed on the B flow path through the opening 13, the air flowing along the B flow path contacts the outer peripheral surface of the rotating fixing roller 1, so that the fixing roller 1 of the fixing roller 1 is exposed. The outer peripheral surface is cooled, and the temperature rise in the central portion of the fixing roller 1 can be suppressed.

Further, it is possible to suppress the occurrence of a high temperature offset phenomenon that occurs during image formation. Furthermore, B5R
When continuously transferring a transfer material of a size, the fixing roller 1
It is possible to suppress the high temperature in the non-sheet passing area, and it is possible to prevent the melting of the coating layer of the fixing roller 1 due to the temperature increase.

[0034]

As described above, according to the fixing device of the present invention, by blowing air to the fixing roller, the coating layer of the fixing roller, the peripheral member of the fixing roller and the like are thermally damaged and the high temperature offset phenomenon occurs. Can be suppressed, and the rise time can be shortened due to the thinning of the fixing roller.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a fixing device of the present invention.

FIG. 2 is a diagram showing the relationship between the amount of heat radiation and the amount of heat supplied to the fixing roller of the fixing device of FIG.

FIG. 3 is a diagram showing a temperature distribution of the surface of a fixing roller when the fixing device of FIG. 1 is on standby.

FIG. 4 is a diagram showing a temperature distribution on the surface of a fixing roller when the fixing device of FIG.

FIG. 5 is a diagram showing a temperature distribution of a fixing roller surface when the fixing device of FIG.

6 is a diagram showing the relationship between the amount of heat supplied to the fixing roller and the amount of heat radiated from the fixing roller in each sheet passing state of the fixing device of FIG.

FIG. 7 is a diagram showing a relationship between a surface temperature of a fixing roller and a defect occurring in the fixing roller.

FIG. 8 is a diagram showing a state in which a fixing roller used in another embodiment of the fixing device of the present invention is cooled.

9 is a diagram showing a state in which a fixing roller used in the fixing device in FIG. 8 is not cooled.

FIG. 10 is a flowchart showing a switching operation of a flow path in the suction duct of the fixing device of FIG.

[Explanation of symbols]

 1 Fixing Roller 3 Heater 4 Pressure Roller 8,11 Fan 9,12 Guide Plate 15 Flow Path Switching Plate

Claims (2)

[Claims] 1. In a fixing device for heating an unfixed developer image on a transfer material with a fixing roller having a heating element inside, substantially uniform air is blown to the fixing roller over substantially the entire area in the longitudinal direction of the fixing roller. A fixing device comprising a blowing unit. 2. The fixing device according to claim 1, further comprising blower control means for controlling blower operation of the blower means.