JP3056821B2 - Fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art As a fixing device of an image forming apparatus using an electrophotographic process, such as an electrophotographic copying machine, an electrostatic printer, a facsimile, etc., as shown in FIG. 2. Description of the Related Art A heat roller fixing device including a pressure roller 2 which is driven to rotate in a pressure contact with the fixing roller 1 with a transfer paper path carrying a toner image therebetween is widely used. In order to maintain the surface temperature of the fixing roller 1 at a predetermined fixing temperature, a temperature detecting means 5 such as a thermistor or a thermostat for detecting the surface temperature of the fixing roller is provided.
On / off control of the heater 3 is performed.

It is desirable that the surface temperature of the fixing roller is controlled within a predetermined fixing temperature range, and that the temperature is also uniform in the axial direction. As shown in FIG. 6, the heat generating range 3a of the heater 3 is usually provided over the entire length of the fixing roller 1 so that the surface temperature of the fixing roller becomes uniform, but is smaller than the maximum paper size of the fixing roller. When paper of a certain size is continuously passed, the heat of the surface of the fixing roller is absorbed by the transfer paper and the toner in the paper passing range and decreases, and a surface temperature detecting means such as a thermistor usually provided at the center of the fixing roller. 5, the heater is continuously lit, and the paper passing width range is maintained at a predetermined fixing temperature. However, in the non-paper passing range on both sides of the heater, heat is taken from the fixing roller to the paper and toner. Therefore, the surface temperature of the fixing roller becomes higher than the fixing temperature. Therefore, as shown by the curve a in FIG. 8, the temperature distribution of the fixing roller is maintained at a predetermined fixing temperature, for example, 185 ° C. by the thermistor at the center, but rises to 200 ° C. or more at both ends of the non-sheet passing portion. As a result, problems such as breakage of the release layer on the surface of the fixing roller, in particular, the silicone rubber adhesive portion, and poor transport of paper (wrinkles and splashes) due to expansion of the roller diameter occur.

Therefore, as a means for making the temperature distribution in the axial direction of the fixing roller uniform, it is known to embed the heat pipe 4 in the core metal of the fixing roller 1 over substantially the entire length as shown in FIG. ing. As a result, the heat applied to the non-sheet passing portion of the fixing roller is immediately transmitted to the sheet passing area, and the surface temperature distribution curve of the fixing roller becomes substantially uniform as shown by a chain line b in FIG. To quickly transfer the heat applied to both ends of the fixing roller to the paper passing area, a considerably large number of heat pipes are required, and providing the heating portion of the heater over the entire length of the fixing roller has a disadvantage of increasing cost. is there.

Another problem of the heat roller fixing device is as follows.
There is a problem that the fixing roller is damaged by a fixing roller surface temperature detecting means such as a thermistor or a thermostat. A thermistor, a thermostat, or the like for detecting the surface temperature of the fixing roller is usually provided in contact with the surface near the center of the fixing roller in order to eliminate a response delay and increase the accuracy of temperature detection. For this reason, the fixing roller is damaged, and the life of the roller is shortened. If the fixing roller surface temperature detecting means is provided outside the paper width range, there is no adverse effect on the roller life, but as described above, the temperature outside the paper passing width during continuous paper passing becomes higher than the central portion of the paper passing width. And, when paper is not passed, the temperature decreases due to heat transfer or heat radiation to bearings, side plates, etc.,
It is unstable and has a drawback that stable temperature control cannot be performed.

[0006]

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks of the conventional heat roller fixing device, the present invention can detect the surface temperature in the paper width range through the fixing roller surface temperature detecting means with a small detection delay. It is another object of the present invention to provide a fixing device that can be installed without scratching the paper passing width range.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is to press-contact a fixing roller having a built-in heater and the fixing roller across a paper passage of a transfer sheet carrying an unfixed toner image. A fixing roller having a fixing roller surface temperature detecting means, comprising: a heat pipe that rolls on the outer peripheral surface of the fixing roller and extends in the axial direction of the fixing roller. A fixing roller surface temperature detecting means is provided at a part of the length of the fixing roller at a central portion of the sheet passing width, and is slidably contacted with the heat pipe surface at a fixed position.

Further, in order to solve the above-mentioned problems, the present invention provides a fixing roller having a built-in heater and a pressurizing roller which is pressed and driven by the fixing roller across a paper passage of a transfer sheet carrying an unfixed toner image. And a fixing roller having a fixing roller surface temperature detecting means, wherein the fixing roller is provided in an arc shape in a plane orthogonal to the axis of the fixing roller so as to be wrapped in proximity to the outer peripheral surface of the fixing roller with a small gap therebetween. And a fixing roller surface temperature detecting means provided in contact with the heat pipe.

[0009]

According to the structure for solving the above-mentioned problems, the surface temperature detecting means is provided at the fixed position in sliding contact with the surface of the heat pipe which is in rolling contact with the outer peripheral surface of the fixing roller.
The surface temperature of the paper passing area of the fixing roller is promptly transmitted to the surface temperature detecting means via the heat pipe. Since the heat pipe is in rolling contact with the fixing roller, it does not damage the surface of the fixing roller. In this case, if the heat pipe is provided at the center of the paper width, the temperature in the paper width range of the fixing roller can be reliably detected even if the length of the heat pipe is provided at a part of the length of the fixing roller.

According to another configuration for solving the above-mentioned problem, the heat pipe is wrapped in an arc shape in a plane perpendicular to the fixing roller and close to the outer peripheral surface of the fixing roller at a minute interval from above. The fixing roller is provided and the surface temperature detecting means is provided in contact with the fixing roller, so that the fixing roller surface temperature can be accurately detected with almost no detection delay without damaging the fixing roller.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing a first embodiment for achieving the above object. The fixing roller 1 has a built-in heater 3 having a heat-generating portion over its entire length. A heat pipe 4 having an axial position fixed by a holding member 6 fixed to a machine frame is mounted on the outer peripheral surface of the fixing roller 1. The temperature detecting means 5 is provided in contact with and in sliding contact with this. Since the heat pipe 4 transmits the heat of the fixing roller 1 to the temperature detecting means 5 instantaneously,
The same detection can be performed as when the temperature detecting means 5 directly touches the fixing roller 1, and the heat pipe 4 is in rolling contact with the fixing roller 1. Is small. If the surface of the heat pipe 4 is coated with a thin silicone rubber or the like, the damage can be further prevented. In addition, in the case of this configuration, the heat pipe 4 may be provided only in a short range at the center of the paper width range, which is advantageous in cost.

FIG. 2 is a sectional view showing another embodiment of the present invention. In this embodiment, an arc-shaped flat heat pipe 4 is fixedly provided so as to be wrapped from above with a small gap from the outer peripheral surface of the fixing roller 1, and is provided in contact with the heat pipe 4. Temperature detecting means 5 is provided. Since the heat pipe 4 and the fixing roller are in contact with each other at a small gap, the heat radiation from the fixing roller 1 can be efficiently received and transmitted to the temperature detecting means 5 without delay.
Since the heat pipe 4 is not in contact with the fixing roller 1, the fixing roller is not damaged, and there is no danger of shortening the service life. Further, the heat pipe can be small, and the cost does not increase.

[0013]

As described above, according to the present invention, it is possible to accurately detect the surface temperature of the fixing roller at the central portion of the roller without damaging the fixing roller.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a fixing device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a fixing device showing another embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a configuration of an example of a conventional fixing device.

FIG. 4 is a longitudinal sectional view of a fixing roller of a conventional fixing device.

FIG. 5 is a longitudinal sectional view illustrating a configuration of an example of a conventional fixing device using a heat pipe.

FIG. 6 is a curve diagram showing a temperature distribution of a fixing roller when continuous small-size paper shown in FIG. 5 is continuously fed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing roller 2 Pressure roller 3 Heater 4 Heat pipe 5 Surface temperature detecting means

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-53-66744 (JP, A) JP-A-53-129052 (JP, A) JP-A-57-24975 (JP, A) 26134 (JP, A) Japanese Utility Model Showa 58-38165 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/20 301

Claims (2)

(57) [Claims] A fixing roller having a built-in heater; and a pressure roller which is pressed and driven by the fixing roller across a paper passage of a transfer sheet carrying an unfixed toner image. A fixing roller having a single heat pipe which is in contact with the outer peripheral surface of the fixing roller and extends in the axial direction of the fixing roller, and the heat pipe is provided at a part of the length of the fixing roller at a central portion of the sheet passing width. And a fixing roller surface temperature detecting means slidably contacting the heat pipe surface at a fixed position. A fixing roller having a built-in heater; and a pressure roller which presses and follows the fixing roller across a paper passage of a transfer sheet carrying an unfixed toner image. A heat pipe provided in an arc shape in a plane orthogonal to the axis of the fixing roller so as to be wrapped from above and close to the outer peripheral surface of the fixing roller with a minute gap therebetween, and contact with the heat pipe. A fixing device provided with a fixing roller surface temperature detecting means in a state.