JPH0572936A - Fixing device for image forming device - Google Patents

Abstract

PURPOSE:To prevent the end of a heating roller from being cooled by an air current flowing along the shaft direction of the heating roller. CONSTITUTION:A heating roller 80 is provided with a hollow roller main body part 83 and a heater 84 passing through the shaft center part of the roller main body part 83. The heater 84 is provided in a state where plural heating parts 83c are provided at appropriate intervals in an axial direction, and the entire heater 84 is deviated toward an upstream side in an air current flowing direction with respect to a recording paper passing area S on the roller main body part 83.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device provided in an image forming apparatus such as an electrophotographic copying machine and a printer. More specifically, it has a pressure roller and a heating roller which are pressed against each other. The present invention relates to a fixing device for fixing a toner image on a recording paper by passing the recording paper on which the toner image is transferred between both rollers.

[0002]

2. Description of the Related Art In an electrophotographic copying machine, an image of a document is exposed on a photosensitive drum to form an electrostatic latent image, and the electrostatic latent image is developed with toner. The toner image formed on the photoconductor drum is transferred onto the recording paper by the transfer device and then fixed onto the recording paper by the fixing device.

As shown in FIG. 9, a fixing device normally has a heating roller 110 in which a heater 112 is provided in a rotating roller body 111 and a heating roller 110 which is pressed against the heating roller 110. And a pressure roller 120. Roller body 111 in heating roller 110
The heater 112 provided inside has a plurality of heat generating portions 113 arranged side by side in the axial direction of the roller.
The rollers 13 are arranged at equal intervals so that the recording paper passage area S on the surface of the roller body 111, which comes into contact with the recording paper, is uniformly heated in the axial direction. Therefore, the respective distances a from each axial end surface of the heater 112 to the recording paper passage area S of the roller body 111 are equal. When the recording paper passes between the rollers, the toner image on the recording paper is heated by the surface of the roller main body portion 111 of the heating roller 110 and the heating roller 1
The toner image is pressed onto the recording paper by the pressure roller 10 and the pressure roller 120, and the toner image is fixed on the recording paper.

Further, in the electrophotographic copying machine, an exhaust fan is provided in order to suppress the temperature rise inside the machine body due to the heating by the heating roller. When the exhaust fan is located on the side of the heating roller 110, as shown in FIG.
The atmosphere around the heating roller 110 is allowed to flow in the axial direction indicated by the arrow D and is discharged to the outside of the gas without convection inside the machine body.

[0005]

However, in such a case, the air flow generated by the exhaust fan 90 is
The air flows in the axial direction along the surface of the roller body 111 of the heating roller 110, and by the air flow, the gas located on the side of the heating roller 110 is brought into the recording paper passage area so as to contact the surface of the roller body 111. Inflow. Heating roller 11
The gas located on the side of 0 has a low temperature because it is not heated by the heating roller 110, and by contacting the surface of the roller body portion 111,
The surface is cooled. In particular, since the end surface of the roller body 111 on the upstream side in the air flow direction is directly cooled by the low-temperature airflow, it may not be heated to a predetermined temperature by the heater 112 provided in the roller body 111. There is.

Further, since the roller main body 111 is designed to rotate, the heater 112 in the roller main body 111 is in a fixed state, so that the air circulation flow of the roller main body 111 is increased. The airflow may flow into the roller main body 111 through the gap between the end face located on the upstream side in the direction and the heater 112 penetrating the end face. as a result,
The temperature of the end surface of the roller body 111 on the upstream side in the air flow direction is significantly reduced. FIG. 9 also shows the amount of heat generated by the heater 112 along the axial direction of the roller body 111 and the surface temperature along the axial direction of the roller body 111. As is apparent from FIG. 9, the end of the recording paper passage area S in the roller body 111 does not rise to a predetermined temperature. As a result, the heating roller 110 and the pressure roller 1
There is a possibility that the toner on the recording paper passing between the sheet and the sheet 20 will not be sufficiently heated, and the toner may be improperly fixed or the toner may adhere to the surface of the heating roller to cause an offset.

For example, in Japanese Utility Model Laid-Open No. 63-54161, a heater provided inside a heating roller by using a solenoid or a motor is used when a small-sized recording paper is brought into contact with the heating roller. A configuration is disclosed in which the end portion of the heating roller that is not in contact with the recording paper is moved along the axial direction of the heating roller so as not to be heated. However, in such a configuration, when a large-sized recording paper contacting the entire recording paper passage area is brought into contact with the heating roller, the end portion of the recording paper passage area is cooled by the airflow generated by the exhaust fan. There is a risk.

Further, Japanese Patent Laid-Open No. 1-285973 discloses a structure in which the position of the heater inside the heating roller in the heating roller axial direction is changed according to the number of copies or the copying time. However, even with such a configuration, it is not possible to prevent the recording paper passage area from being cooled by the air flow from the exhaust fan.

The present invention is intended to solve such a problem, and an object thereof is to cool an end portion of a recording paper passage area in the heating roller by an airflow flowing in the surface and inside of the heating roller in the axial direction. It is an object of the present invention to provide a fixing device capable of reliably fixing a toner image on a recording sheet by preventing such a phenomenon.

Another object of the present invention is that the temperature of the recording paper passage area of the heating roller is non-uniform in the axial direction due to the airflow flowing along the surface of the heating roller and the airflow flowing inside the heating roller. It is to provide a fixing device that does not become

[0011]

A fixing device of an image forming apparatus according to the present invention has a heating roller and a pressing means pressed against the heating roller, and a recording sheet on which toner is transferred is a heating roller. A fixing device of an image forming apparatus in which the toner is heated and pressed to be fixed on the recording paper by passing between the heating roller and a pressurizing means, and the heating roller flows in a predetermined direction. A hollow roller main body that is rotatably arranged in a state in which the flow direction of the air flow is aligned with the axial direction of the air flow, and a heater that is inserted through the inside of the roller main body. The heater is arranged so that the upstream side of the recording paper passage area of the roller body in the air circulation direction is cooled by the airflow to a temperature equal to or lower than a predetermined temperature. Roller located upstream It is characterized in that so as to heat the end portion of the body, the object can be achieved.

[0012]

In the fixing device of the present invention, since the heater provided inside the roller body of the heating roller heats the upstream end of the roller body in the air flow direction, the recording paper passage area of the heating roller. It is possible to prevent the recording paper passage area from dropping to a predetermined temperature or lower due to the airflow flowing in.

[0013]

EXAMPLES Examples of the present invention will be described below. FIG. 2 shows an example of a copying machine having the fixing device of the present invention.
In the copying machine, a photosensitive drum 40 is provided substantially in the center of the copying machine main body 10, and the photosensitive drum 40 is charged by a charging device 45 provided above the photosensitive drum 40. The photoconductor drum 40 charged by the charging device 45 is the optical system 2 provided on the upper portion of the copying machine body 10.
0 is exposed by the reflected light of the document placed on the document table 11, and an electrostatic latent image corresponding to the document image is formed. The electrostatic latent image on the photoconductor drum 40 is toner-developed by the developing device 30 arranged on the side of the photoconductor drum 40. The toner image on the photosensitive drum 40 is transferred to the transfer device 5
1 is transferred onto the recording paper fed from the paper feeding unit 15. The recording paper on which the toner image is transferred is the photosensitive drum 40.
It is separated by a separating device 52, and is fed to the fixing device 7 of the present invention by the conveying device 60.

In the fixing device 7 of the present invention, the heating roller 80 and the pressure roller 70 are vertically arranged in a parallel state in which they are pressed against each other along the front-back direction of the copying machine main body 10 which is orthogonal to the conveying direction of the recording paper. The recording sheet is disposed so that the recording sheet passes between the rollers 80 and 70.

An exhaust fan 90 is provided above the fixing device 7. The exhaust fan 90 changes the atmosphere around the heating roller 80 in the fixing device 7 to the heating roller 80.
It is arranged at the rear part of the copying machine main body 10 so as to flow in the axial direction. Then, the atmosphere around the heating roller 80 heated by the heating roller 80 by the exhaust fan 90 is discharged to the outside of the copying machine main body 10.

As shown in FIG. 1, the pressure roller 70 disposed on the lower side of the fixing device 7 is a roller main body 74 made of an elastic member such as urethane rubber, and is integrated with the roller main body 74. The roller body 7 so that
4 has a rotating shaft 73 inserted therethrough. Each end of each rotary shaft 73 is rotatably supported by a pair of brackets 72 and 72 mounted on the copying machine body 10 by bushes 71 and 71, respectively.

The heating roller 80 arranged above the pressure roller 70 has bushes 82 and 8 at its respective ends with respect to a supporting member 81 attached to the copying machine main body 10.
Hollow roller body 8 rotatably supported by 2
3 and a heater 84 that passes through the axial center of the roller body 83. The roller body portion 83 is pressed against the outer peripheral surface of the roller body portion 74 of the lower pressure roller 70 except for the end portions supported by the bushes 82. Each end of the roller body 83 has a pressure roller 7
The diameter is smaller than that of the portion of the roller body 74 which is pressed against the roller main body 74, and the end faces of the respective end portions are open. The atmosphere around the roller body 83 is passed in the direction of arrow D by the exhaust fan 90 as described above. The exhaust fan 90 allows the atmosphere around the roller main body 83 to flow therethrough, so that air also flows into the roller main body 83 from the end surface of the roller main body 83 on the upstream side in the flow direction.

At the end of the roller body 83, which has a small diameter and is located on the downstream side in the direction of air flow, the input gear 8 is provided.
5 is attached, and a rotational force is input to the input gear 85 from a drive source provided in the copying machine main body 10. Then, the roller main body 83 is rotated by the rotational force input to the input gear 85, and the pressure roller 70 pressed against the roller main body 83 is rotated integrally with the roller main body 83. ing.

A heater 8 inserted through the roller body 83
4 is a support tool 81 that supports each end of the roller body 83.
Has a tube 84a each end of which is supported by a pair of brackets 86 and 86 which are attached to the tube 84a, and a heating element 84b inserted through the tube 84a. The heating element 84b includes a plurality of heating portions 84c arranged at equal intervals in the axial direction and adjacent heating portions 8c.
4c and a plurality of conductive portions 84d that connect the four heating elements 84c to each other.
4c generates heat. Each heat generating portion 84c located at each end of the heat generating element 84b is longer in the axial direction than the other heat generating portions 84c, and each heat generating portion 8 excluding the heat generating portion at each end.
The axial lengths of 4c are equal. Each heating unit 84c
Has a heat generation amount proportional to its axial length. Therefore, the heat generation portion 84c located at each end of the heat generation element 84b has a larger heat generation amount than the other heat generation portions 84c. There is.

The heater 84 having the heat generating portion 84c can uniformly heat the recording paper passage area S except for the respective end portions in a state where it is not axially displaced with respect to the roller body portion 83. In the embodiment, the entire heater 84 of the roller main body 83 is arranged so that a part of the heat generating portion 84c located at the upstream end in the air flow direction is located at the end of the roller main body 83 having a smaller diameter. The recording paper passage area S is displaced in the direction opposite to the air flow direction. Therefore, the distance b from the end surface of the heater 84 on the upstream side in the air flow direction to the recording paper passage area S in the roller body 83.
Is larger than the distance c from the other end surface of the heater 84 to the recording paper passage area S in the roller body 83 (b> c).

When the fixing device having such a structure is operated to fix the toner on the recording paper, the heating roller 8
0 heater 84 is energized and exhaust fan 9
0 is driven. As a result, the heat generating portions 84c of the heater 84 generate heat, and the roller body portion 83 is heated.
At the same time, since the exhaust fan 90 is driven, the atmosphere of the roller body 83 of the heating roller 80 flows in the direction indicated by the arrow D in FIG. When such an air flow is generated, a low-temperature gas that is not heated and is located on the side of the heating roller 80 flows into the periphery of the upstream end of the air flow and the roller body 83. To do. As a result, the end portion of the heating roller 80 is cooled by the inflowing airflow.

At this time, the roller main body portion 83 is heated by the heat generation portions 84c of the heater 84 provided therein, and the heater 84 is heated by the roller main body portion 8.
Since the recording sheet passing region S of No. 3 can be heated almost uniformly except for each end portion, the state is shifted in the upstream direction of the air circulation flow direction with respect to the recording sheet passing region. An end of the main body 83 on the upstream side in the air flow direction is sufficiently heated by the heating element 84c located in the end and extending in the axial direction. As a result, the end portion of the recording paper passage area S on the upstream side in the air flow direction does not have a possibility of lowering to the predetermined temperature or lower even if it is cooled by the unheated airflow flowing from the side.

The airflow flowing in from the side of the roller main body 83 is heated by the end of the roller main body 83 on the upstream side in the air flow direction, and flows in the axial direction of the roller main body 83. Since the airflow is sequentially heated by the heated roller body portion 83 during the flowing and during the flowing, the surface of the roller body portion 83 may be cooled below a predetermined temperature by the airflow. There is no. Then, the heated air flow should not convection in the main body 10 of the copying machine.
The exhaust fan 90 discharges the image to the outside of the copying machine body 10.

In this way, when the surface of the roller body portion 83 of the heating roller 80 is heated and the roller body portion 83 and the pressure roller 70 are rotated, both rollers 70 and 8 are heated.
During 0, the recording paper on which the toner image is transferred is passed. The toner on the recording paper is transferred to the roller body portion 83 of the heating roller 80.
The toner image is fixed on the recording paper by being pressed on the recording paper while being heated on the surface.

A roller body portion 83 of the heating roller 80
FIG. 3 shows the amount of heat generated by the heater 84 and the surface temperature of the roller body 83 along the axial direction of FIG. As apparent from FIG. 3, the surface temperature of the roller main body 83 is higher than the predetermined temperature in the recording paper passage area S. Further, the surface temperature in the axial direction of the surface of the roller body 111 of the heating roller 110 shown in FIG. 9 is shown by the broken line in FIG. In this embodiment, the decrease in the surface temperature at the end of the roller main body 83 on the upstream side in the air flow direction is reliably suppressed.

A second embodiment of the present invention is shown in FIG. In this embodiment, each heating portion 8 of the heater 84 of the heating roller 80 is
All 4c have the same length in the direction of air flow, and are arranged at equal intervals. Further, in this embodiment, the entire heater 84 is in a state of being displaced to the upstream side in the air flow direction. Therefore, the heat generating portion 84c located at the upstream end in the air flow direction heats the upstream end of the roller body 83 in the air flow direction, and the heat generating portion 84c causes the roller body 83 to move to the upstream side. It is ensured that the ends are cooled below a certain temperature.

FIG. 4 also shows the temperature along the axial direction of the surface of the roller main body 83 and the amount of heat generated along the axial direction of the heater 84 in this case. Also in this embodiment, the recording paper passage area S
There is no possibility that the end portion of the upstream side in the direction of air flow in the above will fall below a predetermined temperature.

FIG. 5 shows still another embodiment of the present invention.
In the present embodiment, the heater 84 of the heating roller 80 is displaced to the upstream side in the air circulation flow direction with respect to the recording paper passage area S, as in the previous embodiment, and the heating element 8 is used.
4b is such that the axial length of each heat generating portion 84c excluding the heat generating portion 84c positioned at each end is sequentially shortened from the axial length in the air flow direction. With this configuration, the airflow flowing into the roller main body portion 83 and flowing through the roller main body portion 83 is sequentially reduced in heating by each heat generating portion 84c, so that the inside of the roller main body portion 83 is reduced. It is suppressed that the air flow becomes extremely hot during the passage.

A fourth embodiment of the present invention is shown in FIG. In the present embodiment, the heat generating portion 8 located at the downstream end in the air flow direction.
4c has a smaller amount of heat generation than the heat generating portion 84c located upstream of the heat generating portion 84c in the air flow direction. Other configurations are similar to those of the embodiment shown in FIG. In the present embodiment, the temperature of the surface of the roller main body 83 becomes even more uniform due to the air flow passing through the surface of the roller main body 83 and the inside thereof.

Furthermore, a fifth embodiment of the present invention is shown in FIG. In the present embodiment, in the heater 83, the heat generating portions 84c except the heat generating portions 84c located at each end have the same length, and the recording paper passage area S of the roller main body 83 is also used.
So that it is heated evenly except at each axial end,
The recording paper passage area S is not displaced in the axial direction. The heat generating portion 84c of the heater 84 located at the upstream end of the heat generating element 84b in the air flow direction.
Is longer than the heat generating portion 84c arranged at the other end so as to extend to the upstream side in the air flow direction. In this case, the temperature along the axial direction of the surface of the roller main body 83 and the heat generation amount along the axial direction of the heater 84 are also shown in FIG. Heat generating portion 84c located at the upstream end in the air flow direction
Is sufficiently larger than the other heat generating parts, and the heat generating part 84c sufficiently heats the upstream end of the recording paper passage area S of the roller body 83 in the air flow direction. Thus, there is no possibility that the end portion of the recording paper passage area S on the upstream side in the air flow direction will be lowered to a predetermined temperature or lower.

Further, FIG. 8 shows a sixth embodiment of the present invention. In this embodiment, the heat generating portion 84c located at the downstream end of the heater 83 in the air flow passage direction has the same length as the heat generating portion 84c and the heat generating portion 84c adjacent to the upstream side in the air flow direction. .. Other configurations are similar to those of the embodiment shown in FIG. In this embodiment, the surface of the roller body 83 is heated so as to become more uniform.

In the above embodiment, the pressure roller 70 pressed against the heating roller 80 is used to press the toner on the recording paper against the recording paper. However, instead of the pressure roller, heating is performed. A pressure belt that is pressed against the rollers may be used.

[0033]

According to the fixing device of the image forming apparatus of the present invention, the heater provided on the heating roller as described above allows the recording paper to pass through the heating roller by the air current flowing from the side of the heating roller into the roller main body. Due to the fact that the cooling of the area is compensated,
The toner on the recording paper is surely heated over the entire area, and the occurrence of improper fixing and offset is prevented.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a fixing device of the present invention.

FIG. 2 is a cross-sectional view showing the overall configuration of a copying machine provided with the fixing device of the present invention.

FIG. 3 is a schematic diagram for explaining the operation of the fixing device of the present invention.

FIG. 4 is a schematic view showing a fixing device according to a second embodiment of the invention.

FIG. 5 is a schematic view showing a fixing roller in a fixing device according to a third exemplary embodiment of the present invention.

FIG. 6 is a schematic view showing a fixing roller in a fixing device according to a fourth exemplary embodiment of the present invention.

FIG. 7 is a schematic view showing a fixing roller of a fixing device according to a fifth exemplary embodiment of the present invention.

FIG. 8 is a schematic view showing a fixing roller of a fixing device according to a sixth exemplary embodiment of the present invention.

FIG. 9 is a schematic diagram for explaining the operation of a conventional fixing device.

[Explanation of symbols]

 10 Copy Machine Main Body 70 Pressure Roller 80 Heating Roller 83 Roller Main Body 84 Heater 84b Heater 84c Heater 90 Exhaust Fan

Claims (1)

[Claims] 1. A toner comprising a heating roller and a pressing means pressed against the heating roller, wherein the recording paper on which the toner is transferred passes between the heating roller and the pressing means. Is a fixing device of an image forming apparatus in which a sheet of paper is heated and pressed to be fixed on the recording sheet, wherein the heating roller has a flow direction and an axial direction of the air flow in an air flow flowing in a predetermined direction. It is provided with a hollow roller main body that is rotatably arranged in a matched state, and a heater that is inserted through the inside of the roller main body. The end portion of the roller body located upstream of the recording paper passage area in the air flow direction is heated so as to ensure that the upstream portion in the flow direction is cooled to a predetermined temperature or lower by the air flow. Specially The fixing device of an image forming apparatus according to.