FIXING DEVICE, IMAGE FORMING APPARATUS AND FACSIMILE APPARATUS

Abstract

A fixing device according to this invention includes an environmental temperature sensor 26 for detecting an ambient environmental temperature; a fixing temperature sensor 25 for detecting the surface of a heating roller 20; and a control unit for controlling the heating temperature of the heating roller, and is characterized in that the heating roller 20 is provided with a heater 20a having a luminous-intensity distribution characteristic generating identical heat at both ends and a center in a longitudinal direction; and the control unit determines which level of a plurality of temperatures the environmental temperature belongs to and controls the heating temperature to a prescribed temperature capable of obviating shortage in fixing strength and offset at the determined temperature level.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional structural view of an image forming apparatus according to the first embodiment of this invention.

FIG. 2 is an appearance view of the image forming apparatus according to the first embodiment of this invention.

FIG. 3 is a schematic cross-sectional view of the fixing device of the image forming apparatus according to the first embodiment of this invention.

FIG. 4( a) is a conventional luminous-intensity distribution characteristic view in the fixing device for comparison of the luminous-intensity distribution characteristic; and FIG. 4(b) is a luminous-intensity distribution characteristic view of the fixing device in the image forming apparatus according to the first embodiment of this invention.

FIG. 5 is a partial exploded perspective view of the ejecting side of the fixing device in the image forming apparatus according to the first embodiment of this invention.

FIG. 6 is a partial sectional view the ejecting side of the fixing device in the image forming apparatus according to the first embodiment of this invention.

FIG. 7 is a block diagram of the control section of the image forming apparatus according to the first embodiment of this invention.

FIG. 8 is a flowchart of fixing temperature control in the first embodiment of this invention.

FIG. 9( a) is a front view of a conventional fixing device; FIG. 9(b) is a sectional view FIG. 9(a); and FIG. 9(c) is a structural view of a heater of the fixing device in FIG. 9(a).

Claims

1. A fixing device comprising: a heating roller for heating a toner on a recording medium;a pressurizing roller for being located oppositely to said heating roller and bringing said recording medium into pressure-contact with said heating roller;an environmental temperature sensor for detecting an environmental temperature around a predetermined device, the fixing device being provided within the predetermined device;a fixing temperature sensor for detecting the surface temperature of said heating roller; anda control unit for controlling the heating temperature of said heating roller, whereinsaid heating roller has a heater, the heater having a luminous-intensity distribution characteristic generating identical heat at both ends and a center in a longitudinal direction of said heating roller.

2. A fixing device according to claim 1, wherein said control unit determines which level of a plurality of temperatures said environmental temperature belongs to and controls said heating temperature to a prescribed temperature capable of obviating shortage in fixing strength and offset based on the determined temperature level.

3. A fixing device according to claim 1, wherein said heater has a light emitting characteristic with a luminous intensity of 100%.

4. A fixing device according to claim 2, wherein said temperature levels are four levels of a normal temperature range of 25° C. to 30° C. (inclusive), a high temperature range higher than 30° C., a slightly low temperature range of 15° C. to 25° C. (inclusive) and a low temperature range of 15° C. or lower.

5. A fixing device according to claim 4, wherein said prescribed temperature capable of the shortage in fixing strength and offset is 170° C. in said normal temperature range, 165° C. in said high temperature range, 180° C. in said slightly low temperature range and 185° C. in said low temperature range.

6. A fixing device according to claim 5, wherein if the surface temperature of said heating roller is lower than 130° C. in said low temperature range, a fixing stabilizing period is set before fixing is carried out.

7. A fixing device according to claim 6, wherein a plurality of guides are provided on an ejecting side of said heating roller and said pressurizing roller, the plurality of guides guide a fixed recording medium guide, the plurality of guides have notches at both ends in a width direction of a carrying path, so that both ends of the recording medium ejected from said heating roller and said pressurizing roller are fed through the notches without hitting both ends of the plurality of guides.

8. A fixing device according to claim 1, wherein a face layer with coarseness of 0.6 Ra is formed on the surface of said heating roller.

9. An image forming apparatus comprising: a photosensitive element for forming an electrostatic latent image;a developer for developing said electrostatic latent image;a transfer roller for transferring the developed visible image on a carried recording medium; anda fixing device according to claim 1.

10. A facsimile apparatus comprising: the image forming device according to claim 9;a communication controller connected to a communication line for performing a facsimile communication; andan image reader for reading an image on a document,wherein during facsimile transmission, said document is read by said image reader, and said image is transmitted through said communication line.

11. A fixing device according to claim 1, wherein the predetermined device comprises a facsimile apparatus.