JPH04242775A - Fixing device for electrophotographic device - Google Patents

Abstract

PURPOSE:To reduce the cost and facilitate the exchange of a thermistor unit. CONSTITUTION:The thermistor 48 of a thermistor unit 45 is pressed onto a fixing roller 26, and a connector 46 is attached to a mounting hole 4Oa provided on a fixing lower cover 40 in such a manner as to be attachable and removable. To exchange the thermistor unit 45, the connector 46 is removed from the mounting hole 4Oa from the outside of the fixing lower cover 40 to release the press of the thermistor 48 to the fixing roller 26, and, thereafter, it is exchanged with a new thermistor 48. The new thermistor 48 is elastically pressed onto the fixing roller 26, and the connector 46 is attached to the mounting hole 40a.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention is applicable to printers, copiers, facsimile machines, etc., using laser electrophotography (a method of recording by transferring an image formed on a photoreceptor onto paper).
This method can be applied to electrophotographic devices that record on paper. Specifically, in such an electrophotographic device, a sheet of paper after image transfer is passed between a fixing roller and a pressure roller to fix the image on the paper, and a thermistor is pressed against the fixing roller to control the surface temperature of the fixing roller. Regarding the fixing device to be detected.

0002

2. Description of the Related Art Some conventional fixing devices have a configuration in which a pressure roller 1 is pressed against a fixing roller 2, and a thermistor 4 of a thermistor unit 3 is pressed against the fixing roller 2, as shown in FIG. There is something I did. This thermistor unit 3 is formed by providing a thermistor 4 on a rigid holding member 5, and supported by an elastic bracket 7 screwed to a cover 6.

[0003] Then, the paper 8 that is conveyed after the image transfer
was passed between the pressure roller 1 and the fixing roller 2 to fix the image on the paper 8 with heat and pressure, while the thermistor 4 detected the surface temperature of the fixing roller 2.

0004

However, in this conventional fixing device, the thermistor unit 3 is supported by a bracket 7 screwed to it inside the cover 6, so the cost is reduced by the need for the bracket 7. In addition, it was difficult to remove the thermistor unit 3 from the cover 6, making it troublesome to replace it.

[0005] Therefore, an object of the present invention is to reduce the cost and to facilitate the replacement of the thermistor.

[0006]

[Means for Solving the Problems] Therefore, the present invention as set forth in claim 1, as shown in the illustrated embodiments below, supports a thermistor unit 45 with a cover such as a fixing lower cover 40, and the thermistor unit 45
In a fixing device 25 of an electrophotographic apparatus that detects the surface temperature of the fixing roller 26 by pressing a thermistor 48 against the fixing roller 26 inside the cover, the connector 46, an elastic holding member 47 that holds the base end thereof, and its surface are used. and the thermistor 48 provided in the thermistor unit 4.
5, connect the connector 46 of the thermistor unit 45 to the mounting hole 40a of the cover, and connect the thermistor 4 to the mounting hole 40a of the cover.
8 is pressed against the fixing roller 26 and removably attached.

[0007] Furthermore, the present invention as set forth in claim 2 provides, for example, as shown in the illustrated embodiment below, in the fixing device 25 as set forth in claim 1, a supporting member 50 outside the cover is provided with a window in the cover. 40b, the thermistor 48 is pressed against the fixing roller 26 and supported in a removable manner.

[0008]

[Operation] According to the present invention, when replacing the thermistor unit 45, the connector 46 is removed from the mounting hole 40a, the thermistor 48 is released from being pressed against the fixing roller 26, and then a new thermistor unit is replaced. 45, the thermistor 48 is elastically pressed against the fixing roller 26, and the connector 46 is inserted into the mounting hole 4.
Attach to 0a.

[0009] Furthermore, in the present invention as set forth in claim 2, when replacing the thermistor unit 45, the connector 46 is removed from the support member 50, the thermistor 48 is released from being pressed against the fixing roller 26, and then a new thermistor unit is replaced. 45, the thermistor 48 is elastically pressed against the fixing roller 26 through the window 40b and supported by the support member 50.

0010

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 4 is a schematic diagram of the overall internal mechanism of a laser printer equipped with a fixing device according to an embodiment of the present invention. What is indicated by the reference numeral 10 in the figure is the main body of the apparatus. Inside the apparatus body 10, a belt-shaped photoreceptor 11 is provided approximately at the center. Around the photoreceptor 11,
In the driving direction indicated by the arrow in the figure, the charger 12, the developer 1
3. Arrange the transfer device 14 and cleaning device 15. An optical writer 16 is placed below the charger 12 and the cleaner 15. In addition, the optical writer 16
A paper feed cassette 18 in which paper 17 is set is detachably attached to the lower side of the paper. A first discharge stack section 20 is provided on the upper side of the apparatus main body 10. On the left side of the diagram,
A second discharge stack section 21 is provided exclusively for stiff paper such as cardboard and envelopes, and very weak paper such as OHP sheets. A paper discharge tray 22 is detachably attached to the second paper discharge stack section 21.

Then, the paper feed roller 23 is driven to feed out the set paper 17 in the paper feed cassette 18 in the direction of arrow A. Then, the paper 17 is conveyed to the upper side of the photoreceptor 11 by the registration rollers 24 at a proper timing. The photoreceptor 11 is driven counterclockwise as shown by the arrow, and at this time, the surface is uniformly charged by the charger 12, and the laser beam L from the optical writer 16 is irradiated to write a static image on the photoreceptor 11. Forms an electrolatent image. This latent image is visualized by toner when it passes through the developing device 13. And this visible image is
The transfer device 14 transfers the image onto the lower surface of the paper 17 that has been conveyed above the photoreceptor 11 . The transferred paper 17 is conveyed between a fixing roller 26 and a pressure roller 27 of a fixing device 25, and the visible image is fixed thereon. On the other hand, photoreceptor 1 after visible image transfer
1 is cleaned by a cleaning device 15.

On the other hand, the recorded paper 17 that has come out of the fixing device 25 is conveyed by a paper discharge roller 29 in a paper discharge device 28, further guided upward by a paper conveyance guide 30 and reversed, and then moved by a paper discharge roller 31 in the direction of an arrow. The sheets are discharged in the direction B and stacked on the first discharge stack section 20. Also, paper 17
When the paper is thick paper, OHP sheet, etc., the paper discharge direction is switched by the switching guide 32, the paper is discharged in the direction of arrow C by the paper discharge roller 29, and the paper is stacked on the second paper discharge stack section 21.

By the way, the above-mentioned fixing device 25 has a structure as shown in FIG.
0, and a fixing upper cover 41 that covers the upper side of the pressure roller 27. The fixing roller 26 has a built-in heater 42, and is pressed against the pressure roller 27 by appropriate urging means. A lower entrance guide plate 43 is attached to the lower fixing cover 40, and an upper entrance guide plate 44 is attached to the upper fixing cover 41.

The lower fixing cover 40 also has a mounting hole 40a on the right side in the figure. A connector 46 of a thermistor unit 45 is removably attached to the attachment hole 40a. As shown in FIG. 2, the thermistor unit 45 includes the connector 46, a plate-shaped elastic holding member 47 whose base end is held by the connector 46, and a thermistor 48 provided on the surface of the elastic holding member 47. Then, as shown in FIG. 1, the thermistor 48 is connected to the fixing roller 2.
It becomes pressed against 6. The thermistor 48 is then electrically connected to a temperature control section (not shown) via a lead wire 49 extending from the connector 46.

Then, as shown in FIG. 1, the fixing roller 2
6 and pressure roller 27, both rollers 26 and 27 are rotated.
In the meantime, the image on the paper 17 is fixed by applying heat and pressure to the paper 17 that is conveyed after the image transfer. At the same time, the thermistor 48 detects the surface temperature of the fixing roller 26. Then, in response to the detection signal, the temperature control section controls the surface temperature of the fixing roller 26 to always keep it constant.

Now, during the above-described image fixing, the thermistor 48 has worn out due to friction with the fixing roller 26, for example, so when replacing it, connect the connector 46 from the outside of the lower fixing cover 40 through the mounting hole 40a. Remove it to release the thermistor 48 from pressing against the fixing roller 26. Then, replace it with a new thermistor unit 45,
As shown in FIG. 1 again, the thermistor 48 is connected to the fixing roller 2.
6, and attach the connector 46 to the attachment hole 40a.

Incidentally, in the illustrated embodiment described above, the thermistor 48 is removably supported by the cover, that is, the lower fixing cover 40, but the thermistor 48 may be removably supported by a support member outside the cover. You can also do it.

In this case, for example, as shown in FIG. 3, a window 40b is opened at the lower right side of the lower fixing cover 40 in the figure. On the other hand, a support member 5 fixedly provided outside the lower fixing cover 40
Connector 46 of the thermistor unit 45 is removably attached to the upper end of 0. Then, the tip side of the thermistor 48 is elastically pressed against the surface of the fixing roller 26 through the window 40b, and the whole thermistor unit 45 is supported by the support member 50.

Now, when replacing the thermistor unit 45, the connector 46 is removed from the support member 50 and the pressing of the thermistor 48 against the fixing roller 26 is released. Then, replace the thermistor unit 45 with a new one, and replace the thermistor 48 with the window 40 as shown in FIG.
The connector 46 is attached to the support member 50 by elastically pressing it against the surface of the fixing roller 26 through the connector 46b.

[0020]

Therefore, according to the present invention, costs can be reduced because a separate bracket is not used as in the conventional case, and the thermistor unit can be removed from the outside of the cover, so the thermistor unit can be removed from the outside of the cover. can be easily replaced.

[Brief explanation of the drawing]

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

FIG. 2 is a perspective view of a thermistor unit included in the fixing device.

FIG. 3 is a sectional view showing a fixing device according to an embodiment of the present invention as set forth in claim 2;

FIG. 4 is an overall schematic configuration diagram showing the internal mechanism of a laser printer equipped with a fixing device according to the present invention.

FIG. 5 is a sectional view showing a conventional fixing device.

[Explanation of symbols]

25 Fuser 26 Fixing roller 40 Lower fixing bar (cover) 40a Mounting hole 40b window 45 Thermistor unit 46 Connector 47 Elastic holding member 48 Thermistor 50 Support member outside the cover

Claims (2)

[Claims] 1. A fixing device for an electrophotographic apparatus in which a thermistor unit is supported by a cover, and the thermistor of the thermistor unit is pressed against a fixing roller in the cover to detect the surface temperature of the fixing roller. The thermistor unit is made up of an elastic holding member that holds an end and the thermistor provided on the surface of the thermistor unit, and is removable by pressing the connector of the thermistor unit into the mounting hole of the cover and pressing the thermistor against the fixing roller. A fixing device for an electrophotographic device that is installed. 2. The fixing device for an electrophotographic apparatus according to claim 1, wherein the thermistor is pressed against the fixing roller through a window of the cover and removably supported by a support member outside the cover.