JPH0713004Y2 - Fuser - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention relates to a fixing device used in a copying machine, a printer or the like of an electrophotographic apparatus.

2. Description of the Related Art Typical examples of conventional fixing devices are shown in FIGS. A heat roller 11 that is in contact with the transfer surface of the transfer paper and has a halogen lamp 13 that serves as a heat source in the hollow part, is formed by applying Teflon to the surface of the base material such as alum, and an elastic layer such as silicon rubber on the outer peripheral surface. The pressure roller 12 having the same is pressure-contacted,
The surface temperature of the heat roller 11 is controlled by turning on and off the halogen lamp 13 via the thermistor 14.

As shown in FIG. 4, the heat roller 11 has a uniform body thickness in the sheet width direction. Bearings 6 are attached to both ends of the heat roller 11 and a driving gear 5 is attached to one end thereof. , In such a fixing device, the halogen lamp of the heat source
When 13 is turned on, loss of heat quantity due to the bearing 6 and the gear 5 is expected at both ends of the heat roller 11 in the initial stage. Therefore, the luminous rate distribution of the halogen lamp 13 is as shown in FIG.
The light emission rate at both ends is increased by about 20% with respect to the center of the sheet passing width, and the surface temperature distribution of the heat roller 11 in the sheet passing direction becomes constant by turning the halogen lamp 13 on and off in the overall temperature fluctuation. I am trying. At this time, the overall temperature fluctuation due to the turning on and off of the halogen lamp 13 is performed within a range that does not cause a problem in the fixing process.

The problem to be solved by the invention is that when the actual paper is passed, the amount of heat absorbed by the paper is larger in the central part than in the paper width direction,
This tendency becomes particularly noticeable when a small size paper is passed through the center. Therefore, the heat roller during paper passing
As shown in FIG. 6, the temperature distribution in the paper passing width direction of 11 shows a high value at both end portions with respect to the central portion.

Here, when the installation position of the thermistor 14 is in the central part, the temperature at both ends becomes higher than the target fixing set temperature,
At that portion, there is a problem that so-called hot offset occurs in which unfixed toner on the transfer paper is transferred to the surface of the heat roller 11.

Further, when the installation position of the thermistor 14 is provided at the end of the heat roller 11, the temperature of the central part becomes lower than the target fixing set temperature, so that there is a problem that defective fixing occurs at that part. Therefore, the heat roller 11 in the paper width direction
It is required that the table temperature distribution of is always constant.

An object of the present invention is to solve the problems of the conventional fixing device as described above, and to provide a fixing device capable of performing a stable fixing process because the temperature distribution of the entire surface of the heat roller in the sheet width direction becomes constant. .

Means for Solving the Problems In order to achieve the above-mentioned object, the present invention is such that the thickness of the body of the heat roller is made thicker in the central portion in the width direction of the paper and gradually becomes thinner toward both ends. The light emission rate of the halogen lamp for heat source installed in the hollow part of this heat roller is the maximum emission rate part in the central part in the paper width direction, and the emission rate is gradually decreased toward both ends to the minimum emission rate. The light emission rate is increased from the minimum light emission rate section toward both ends, and the intermediate light emission rate section is formed at both ends.

Action The heat roller of the present invention has a thicker body portion in the width direction of the paper passage, and the thickness gradually decreases as the center portion becomes thicker and closer to both ends. Therefore, the heat capacity of the center portion becomes large. Since the light emission distribution ratio by the halogen lamp is maximum in the center, both ends are in the middle, and the middle thereof is the minimum, the heat distribution can maintain a constant temperature in the sheet width direction.

Example In FIG. 1, the thickness of the body of the heat roller 1 is made thicker in the central portion 1a in the width direction of the paper and gradually becomes thinner toward both end portions 1b, and installed in the hollow portion of the heat roller 1. The luminous efficiency of the heat source halogen lamp 3 is set so that the central portion I is the maximum luminous portion in the sheet width direction, the luminous efficiency is gradually reduced toward both ends, and the intermediate portion II is the minimum luminous rate. On the contrary, the light emission rate is increased toward the portion III, the light emission rate at both end portions III is made smaller than that at the central portion I, and the intermediate light emission rate is made larger than that at the intermediate portion II.

Both ends 1b of the heat roller 1 are supported by bearings 6 like the conventional one, and a gear 5 is attached to one end to rotate the heat roller 1. A pressure roller 12 and a thermistor 14 are also provided as in the above.

The thickness of the body of the heat roller is maximum in the central part 1a,
Since the thickness gradually decreases toward 1b, the heat capacity in the paper passing width direction is maximum at the central portion 1a and minimum at both end portions 1b.

Therefore, the light emission rate of the halogen lamp 3 is distributed in accordance with such a heat capacity distribution. Therefore, the distribution is maximum at the central portion 1a and becomes gradually smaller toward both end portions 1b as shown in FIG. However, since heat loss due to the bearing 6 and the gear 5 cannot be ignored at both ends 1b of the heat roller 1, the light emission rate at both ends 1b is increased next to that at the central portion 1a, and the central portion 1a and the both ends 1b are increased. The light emission rate was set to the minimum in the intermediate portion 1c between and. As a result, the distribution of the amount of heat supplied by the halogen lamp 3 matches the heat capacity distribution of the heat roller 1 in the paper passing width direction, which makes the temperature of the heat roller 1 substantially uniform in the paper passing width direction.

By the way, the amount of heat absorbed by the paper at the time of paper passing is larger in the central portion 1a than in the both end portions 1b, but since the central portion 1a has a larger heat capacity than the both end portions 1b, in the paper passing width direction. The surface temperature drop gradient of the heat roller 1 is also constant. That is, the surface temperature distribution of the heat roller 1 in the paper passing width direction can be set to a constant value in the overall temperature fluctuation due to the turning on and off of the halogen lamp 3.

Advantageous Effects of Invention The invention is as described above, and the thickness of the heat roller body is maximized in the central part in the width direction of the paper and gradually reduced toward both ends, so that the luminous efficiency of the halogen lamp is in the central part. The maximum surface temperature is gradually decreased toward both ends, the minimum value is set before both ends, and the intermediate value is set at both ends. Therefore, there is an effect that a stable fixing process can be performed.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view of an embodiment of the present invention, FIG. 2 is a luminous rate distribution diagram according to the above, FIG. 3 is a side view of a fixing device of the same type as the present invention, and FIG. Front view,
FIG. 5 and FIG. 6 are distribution charts of the luminous rate and the temperature of the same as above. 1 ... Heat roller, 1a ... Center part 1b ... Middle part, 1c ... Both ends 3 ... Halogen lamp, 5 ... Gear 6 ... Bearing

Claims (1)

[Scope of utility model registration request] 1. A heat source installed in a hollow portion of a heat roller, wherein a body portion of the heat roller is formed so that a central portion thereof is thickened and a thickness thereof is gradually reduced toward both ends thereof in a paper width direction. In the direction of paper width, the luminous intensity distribution of the halogen lamp is the maximum luminous efficiency part in the center, and the luminous efficiency is gradually decreased toward both ends to form the minimum luminous efficiency part. The fixing device is characterized in that the light emission rate is increased in order toward the opposite portion, and the intermediate light emission portion is formed at both ends.