JPH04219773A - Fixing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for an image forming apparatus such as a copying machine or an LBP.

0002

2. Description of the Related Art A fixing device fixes a toner image carried on a transfer paper as a permanent image on the transfer paper. Conventionally, the toner image on the transfer paper is heated and pressed through a roller to fix it. A heated roller type that melts and fixes onto the transfer paper is often used.

This heat roller type fixing device has a pair of fixing rollers, etc., consisting of a heat roller that has a heat source such as a halogen lamp inside and rotates in a fixed direction, and a pressure roller that rotates in pressure contact with the heat roller. A transfer paper carrying the toner image is passed between the fixing rollers, and the toner image is fixed onto the transfer paper.

The surface temperature of the heating roller is detected by a temperature sensing element, and the heat source is controlled via a control circuit based on a signal from the temperature sensing element, so that the surface temperature of the heating roller is controlled to a predetermined constant value. This is because if the surface temperature of the heating roller is too low, the toner image is insufficiently fixed (
This is because the toner image is not sufficiently fixed on the transfer paper and tends to separate), and if it is too high, offset (a phenomenon in which part of the toner image is fused to the heating roller) occurs. It is extremely important to control it to a predetermined constant value.

Here, the heat source of the heating roller is disposed along the longitudinal direction of the heating roller, but if this heat source generates heat uniformly along the longitudinal direction, the end portion of the heating roller will be released. Since the amount of heat is larger than that at the middle part, the temperature at the middle part of the heating roller is higher than at both ends, making it impossible to obtain a uniform temperature distribution over the entire length of the heating roller. Further, when the temperature of the intermediate portion of the heating roller becomes higher than that of both ends, the intermediate portion of the heating roller swells into a drum shape due to thermal expansion, and the transfer paper is likely to wrinkle during fixing.

For this reason, it has been conventionally attempted to make the surface temperature distribution of the heating roller uniform over its longitudinal direction by making the amount of heat generated at the end of the heating roller of the heat source of the heating roller larger than that at the middle portion. There is.

On the other hand, in recent years, image forming apparatus main bodies have become more compact, and there are many cases in which units that dislike heat, such as a developing device, a cleaning device, and a power source, are disposed near a fixing device that has a heat source. In this case, although the fixing device itself has a heat insulating design with respect to the unit, if the distance is short, it will be difficult to avoid the temperature of the unit from rising. In particular, since toner blocking occurs in developing devices and cleaning devices due to temperature rise, it is necessary to avoid heating these devices as much as possible.

[0008] Therefore, a heat exhaust fan for intake and exhaust is disposed near the fixing device to exhaust the heat generated from the fixing device to the outside of the main body of the device, thereby preventing the temperature of the developing device, cleaning device, etc. from rising. It is being

[0009]

[Problems to be Solved by the Invention] However, if a heat exhaust fan is disposed at one end in the longitudinal direction of the heating roller and an air flow is generated in the longitudinal direction of the heating roller, the upstream side of the air flow of the heating roller can be A problem arises in that the temperature of the downstream portion increases while the temperature of the upstream portion decreases, making it impossible to obtain a uniform temperature distribution over the entire length of the heating roller.

This is because on the upstream side of the heating roller's airflow, the heating roller is cooled by fresh air taken in through the louvers on the exterior of the device body, whereas on the downstream side of the heating roller's airflow, the heating roller is cooled by fresh air. This is because the heated air warms the heating roller.

The present invention has been made in view of the above-mentioned problems, and its purpose is to prevent the fixing roller from moving even if the airflow of the exhaust heat exhaust fan is formed in the longitudinal direction of the fixing roller. An object of the present invention is to provide a fixing device that can maintain a uniform surface temperature distribution in the longitudinal direction.

0012

[Means for Solving the Problems] In order to achieve the above object, the present invention has a heat source disposed in the longitudinal direction inside the fixing roller, and an air flow is formed in the longitudinal direction of the fixing roller by a heat exhaust fan for supplying and exhausting. In the fixing device, the amount of heat generated by the heat source of the fixing roller is made larger at both ends of the fixing roller than the middle section, and the amount of heat generated on the upstream side of the air flow by the internal heat exhaust fan at both ends is made larger than the amount of heat generated on the downstream side. The feature is that the amount of heat generated is greater than the amount of heat generated.

[0013]

[Operation] The outer surface temperature of the fixing roller must be constant over its longitudinal direction. Therefore, it is necessary that the amount of heat generated by the heat source at both ends of the fixing roller, where a large amount of heat is radiated, is greater than that at the middle portion.

On the other hand, when a heat exhaust fan is provided to form an air flow in the longitudinal direction of the fixing roller, the part on the upstream side of the air flow of the fixing roller is cooled by fresh air, and the part on the downstream side is heated by the fixing roller. On the contrary, it will be heated by hot air.

Therefore, the amount of heat generated by the heat source of the fixing roller is made larger at both ends of the fixing roller than at the middle section, and
The amount of heat generated on the upstream side of the air flow by the internal exhaust heat fans at both ends is made larger than the amount of heat generated on the downstream side, so that the outer surface temperature of the fixing roller is kept constant over its longitudinal direction.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the accompanying drawings.

First, a first embodiment of the present invention will be explained with reference to FIGS. 1 to 6.
This is explained by:

FIG. 2 shows a side view of the main part of the fixing device 1, and in the figure, reference numeral 10 indicates a halogen lamp 11 as a heat source.
This is a heating roller that is rotated in a fixed direction via a drive gear 12, and a pressure roller 13 that rotates in pressure contact with the heating roller 10 is disposed below the heating roller 10. Further, the driving gear 1 in the longitudinal direction of the heating roller 10
A heat exhaust fan 14 is provided on the second side, and the heat exhaust fan 14
This forms an air flow in the longitudinal direction of the heating roller 10 and the like, so that the heat emitted by the heating roller 10 around the heating roller 10 is discharged to the outside of the fixing device 1 .

That is, when a transfer paper carrying an unfixed toner image is conveyed between a pair of fixing rollers consisting of heating and pressure rollers 10 and 13, this toner image is transferred to the heating and pressure roller 1.
0.0,13 is heated and pressurized to melt and fix the image, and it is fixed as a permanent image on the transfer paper.

A temperature sensing element (not shown) is brought into contact with the heating roller 10, and the halogen lamp 11 is turned on so that the surface temperature of the heating roller becomes a constant value via the temperature sensing element.
N, OFF It is assumed that it is controlled.

Now, the halogen lamp 11 is connected to the heating roller 1.
The amount of heat generated in the longitudinal direction is determined so that the surface temperature of the heating roller 10 remains constant along the longitudinal direction. Hereinafter, the amount of heat generated in the longitudinal direction of the halogen lamp 11, which is a characteristic configuration of the present invention, will be explained.

First, the left and right ends A and B of the heating roller 10
It is necessary to heat the middle part C more than the middle part C. Therefore, as shown in FIG. 1, the amount of heat generated per unit length of the halogen lamp 11 needs to be high at the left and right ends A and B of the heating roller 10, and low at a constant value at the middle part C of the heating roller 10. There is. However, the right end B side of the heating roller 10 where the drive gear 12 is disposed protrudes a little longer than the left end A and releases a large amount of heat, and also heat is radiated via the drive gear 12. The amount of heat generated on the right end B side of the heating roller 10 needs to be slightly larger than that on the left end A side.

On the other hand, a heat exhaust fan 14 is provided on one side of the drive gear 12 of the heating roller 10, and the heat exhaust fan 14 causes air to flow from the left end A side to the right end B side in the longitudinal direction of the heating roller 10. , the left end A side of the heating roller 10 is cooled by fresh air sucked through a louver etc. provided on the side wall of the image forming apparatus main body, and the right end B side of the heating roller 10 is cooled. A phenomenon occurs in which the air is heated by hot air that is sequentially heated by the heating roller 10.

Therefore, if only the influence of the heat exhaust fan 14 is considered, the amount of heat generated on the left end A side of the heating roller 10 of the halogen lamp 11 needs to be larger than that on the right end B side.

Considering the above, the halogen lamp 11
FIG. 1 shows the amount of heat generated per unit length of the heating roller 10 in the longitudinal direction. That is, the amount of heat generated at the intermediate portion C of the heating roller 10 is the smallest compared to that at the left and right ends A and B, but is constant over the longitudinal direction of the heating roller 10. ，
The amount of heat generated on the B side increases in a mountain shape, and the value is the same as that of heating roller 1.
The left end A side of 0 is larger than the right end B side.

FIG. 3 shows the surface temperature distribution in the longitudinal direction of the heating roller 10 when a fixing operation is actually performed using the fixing device 1 equipped with the heating roller 10 having the halogen lamp 11 as described above.

In this case, the heating roller 10 has a wall thickness of 1.5 m.
The temperature sensing element for controlling the surface temperature of the heating roller 10 is provided in the middle of the heating roller 10. Further, if the amount of heat generated per unit length in the longitudinal direction of the heating roller 10 of the halogen lamp 11 is 100 at the intermediate portion C of the heating roller 10, the maximum value at the left end A side of the heating roller 10 is 160. , the maximum value on the right side B side is 1
It is 50. In addition, T1 in the figure indicates the surface setting temperature of the heating roller 10.

A broken line P in the figure shows the surface temperature distribution of the heating roller 10 when the heat exhaust fan 14 is not used. In this case, the surface temperature of the heating roller 10 is slowly decreasing from the left end A side to the right end B side across the set temperature T1.
The influence of the heat exhaust fan 14 on 0 can be understood.

A solid line Q in the figure shows the case where the heat exhaust fan 14 is used, and most of the parts of the heating roller 10 that contribute to fixing are controlled to a set temperature T1. In this case, a portion of the left and right ends A and B of the heating roller 10 has fallen below the set temperature T1, but the heating and pressure rollers 10 and 1
Considering that the nip width formed by No. 3 is larger at the ends than at the middle, such temperature drop has no effect on the fixing operation.

Here, even if the temperature at the end of the heating roller 10 is slightly lowered, there is a possibility that wrinkles will occur in the transfer paper during the fixing operation. As shown in FIG.
For example, the taper amount may be set to 50 μm for the heating roller 10 having an outer diameter of 32 mm at both ends.

Furthermore, as shown in FIG. 6, the heating roller 1
Although a heat source 15 similar to the halogen lamp 11 of the heating roller 10 may be provided not only on the pressure roller 13 side but also on the pressure roller 13 side, the present invention can of course be applied to the heat source 15 of the pressure roller 10 as well. It is.

Next, a second embodiment of the present invention will be described with reference to FIGS. 7 and 8.
This is explained by: Components having the same functions as those in the first embodiment are designated by the same reference numerals, and their explanations will be omitted.

In this embodiment, the drive gear 12 of the heating roller 10
is attached to the left end A side, which is opposite to that of the first embodiment.

In this case, on the left end A side of the heating roller 10, the amount of heat radiated increases by the length of the left end A due to the installation of the drive gear 12 and the influence of the drive gear 12, and vice versa. On the right end B side, the amount of heat dissipated is correspondingly smaller.

Therefore, compared to that of the first embodiment, the amount of heat generated in the longitudinal direction of the halogen lamp can be determined as shown in FIG. 7, taking into account the above effects. In this case, since the influence of the drive gear 12 etc. is smaller than the influence of other heat exhaust fans 14 etc., the basic heat generation distribution per unit length in the longitudinal direction of the heating roller 10 of the halogen lamp 11 is the first. Although it is the same as that of the embodiment, the amount of heat generated at the left end A of the heating roller 10 is slightly larger than that of the first embodiment, and the amount of heat generated at the right end B of the heating roller 10 is the same as that of the first embodiment. It's a little smaller than that. Therefore, the difference in the maximum amount of heat generated at the left and right ends A and B of the heating roller 10 is larger than that in the first embodiment.

In the first and second embodiments described above, the halogen lamp 11 was used as the heat source for the heating roller 10, etc., but it is not limited to this, and other sources such as an infrared lamp or a ceramic heater can be used. Of course. In this case, the amount of heat generated in the longitudinal direction of the heat source such as the heating roller 10 may be changed by using a coil-type heating element, or by changing the area or length of a plate-shaped or rod-shaped heating element. You can go there. Note that the heat source does not need to be provided inside the heating roller 10;
Of course, it may be arranged near the outside of the heating roller 10, or may be arranged both inside and outside the heating roller 10.

Further, the type of exhaust heat fan 14 may be either an exhaust fan or an intake fan, and the temperature detection element of the heating roller 10 may be located at either the middle or the end of the heating roller 10. Of course, it may be provided.

[0038]

Effects of the Invention As is clear from the above description, according to the present invention, the amount of heat generated by the heat source of the fixing roller is made larger at both ends of the fixing roller than at the middle part, and the amount of heat generated by the heat source of the fixing roller is increased by internal heat exhaust fans at both ends. The amount of heat generated on the upstream side of the airflow is greater than the amount of heat generated on the downstream side, so that the outer surface temperature of the fixing roller is kept constant over its longitudinal direction.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the ratio of the amount of heat generated by a heat source to the longitudinal direction of a heating roller of a fixing device according to a first embodiment.

FIG. 2 is a side view of the main parts of the fixing device according to the first embodiment.

FIG. 3 is a diagram showing the surface temperature distribution of the heating roller of the fixing device according to the first embodiment.

FIG. 4 is a diagram showing the external shape of a heating roller.

FIG. 5 is a diagram showing the external shape of a heating roller.

FIG. 6 is a side view of the main parts of the fixing device according to a modified example of the first embodiment.

FIG. 7 is a diagram showing the ratio of the amount of heat generated by the heat source to the longitudinal direction of the heating roller of the fixing device according to the second embodiment.

FIG. 8 is a side view of the main parts of a fixing device according to a second embodiment.

[Explanation of symbols]

10 Heating roller (fixing roller) 11
Halogen lamp (heat source) 14 Heat exhaust fans A, B Both ends of heating roller

Claims (1)

[Claims] Claim 1: In a fixing device in which a heat source is arranged in the longitudinal direction inside the fixing roller, and an air flow is formed in the longitudinal direction of the fixing roller by an exhaust heat fan for supplying and exhausting, the amount of heat generated by the heat source of the fixing roller is reduced. A fixing device characterized in that the fixing roller has a larger amount of heat at both end portions than at an intermediate portion thereof, and the amount of heat generated on the upstream side of the air flow by internal heat exhaust fans at both ends is made larger than the amount of heat generated on the downstream side.