JPH01252984A - Thermal fixing device - Google Patents

Abstract

PURPOSE:To obtain the thermal fixing device which is small in size and is low in cost and has good thermal efficiency by providing surface heaters which thermally fix a developer or developing soln. to a recording medium. CONSTITUTION:While paper 4 on which a toner 12 is transferred slides in contact with the surface heater 8b below the same, the paper passes between the upper and lower surface heaters 8a and 8b and the paper 4 and the toner 12 are heated by the upper and lower panel heaters 8a, 8b during the passage thereof. The toner 12 is melted and is fixed to the paper 4, by which the thermal fixing is executed. Since the surface heater 8a does not come into contact with the toner 12 on the paper 4, the generation of a trouble such as spreading of the setting width is obviated. The paper 4 on which the toner 12 is thermally fixed by the thermal fixing device 8 is discharged by discharge rollers 10 to the outside of an image forming device. The points where the temp. rises are, therefore, only the parts of the heaters 8a, 8b having small heat capacities. The thermal fixing device which does not require the warm up time, reduced electric power consumption and is small in size and low in cost is thereby obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat fixing device, and particularly to a heat fixing device used in an image forming apparatus using an electrophotographic process.

[Conventional technology]

Image forming apparatuses using an electrophotographic process include an electrophotographic copying machine that copies a reflected image from a document, and an optical printer that forms an image with a light beam using a semiconductor laser, a light emitting diode, or the like as a light source.

Conventionally, fixing devices used in this type of image forming apparatus can be broadly classified into those based on three types of methods: heat fixing, pressure fixing, and solvent fixing. Among these fixing methods, in terms of fixing performance, recording medium deformability and stability, as well as recording medium transportability and miniaturization of the device, thermal fixing devices and even thermal roll type devices are recommended. Heat fixing devices have been widely used.

For example, as shown in FIG. 4, a heat roll type heat fixing device uses a heat roller 41 that contacts and heats a developer or developer (hereinafter referred to as toner) 49 attached to a sheet (recording medium) 48. and a pressure roller 42 which is biased and disposed so as to be in pressure contact with the heat roller 41.

The heat roller 41 includes a cylindrical metal core 43 and a heater 4 such as a halogen lamp that heats the metal core 43 from the inside.
4, and a resin coat layer 45 applied to the surface of the metal core 43 to improve releasability from the toner 49.

Further, the pressure roller 42 has a metal core 46 and a metal core 4.
6 is covered with an elastic material 47 such as rubber.

In such a heat roll type heat fixing device, when the heat roller 41 and the pressure roller 42 rotate, the paper 48 with the toner 49 attached to its surface is heated by the heat roller 41 . Since the toner 49 is conveyed while being pressurized between the pressure rollers 42, the toner 49 is melted and the paper 48 is
Heat fixing is performed by fixing the film to the film.

Note that the temperature control of the heat roller 41 is performed by controlling the temperature of the heat roller 41.
This is performed by controlling the energization of the heater 44 using a temperature sensor (not shown) attached so as to be in contact with the surface of the heater 44 .

[Problem to be solved by the invention]

In the conventional heat roll type heat fixing device described above, the metal core 43 having a large heat capacity is heated from the inside by the heater 44, so there is a problem that it takes a long warm-up time.

In addition, since pressure is applied between the heat roller 41 and the pressure roller 42, the paper quality and thickness of the paper 48, or the
Depending on whether 8 is made up of multiple sheets, such as envelopes, the image quality will vary, leading to image deterioration, and the load on the drive source will fluctuate, making it necessary to increase the size of the drive motor. There is a problem with that.

Furthermore, since the fixing method is a contact type in which the heat roller 4 comes into contact with the toner 49, there is a problem that the toner 49 is pressed by the heat roller 41 during fixing, and the print width may be widened.

Furthermore, since the temperature of the heat roller 41, pressure roller 42, etc. increases, they become a heat source that increases the internal temperature when used in an image forming apparatus. Since some devices have limitations, in such a case, a separate cooling device is required, and an input power source to the image forming apparatus is required to be close to IKW, which poses a problem in terms of power consumption.

In view of the above-mentioned points, an object of the present invention is to provide a non-contact fixing type thermal fixing device that is small, inexpensive, and has high thermal efficiency by using a planar heater in an image forming bag π using an electrophotographic process. It's about doing.

[Means to solve the problem]

The heat fixing device of the present invention is an image forming apparatus using an electrophotographic process. The present invention is characterized in that it includes a planar heater that thermally fixes the developer or developer onto a recording medium having the developer or developer transferred from the image carrier on its surface.

[Effect]

In the thermal fixing device of the present invention, the planar heater thermally fixes the developer or developer transferred from the image carrier onto the recording medium present on the surface.

〔Example〕

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing an image forming apparatus equipped with a heat fixing device according to an embodiment of the present invention. This image forming apparatus includes a photosensitive drum 1 as an image carrier on which an image charge pattern (electrostatic latent image) is formed by exposure, a charger 2 made of, for example, a corotron or a scorotron, and a charger 2 formed on the photosensitive drum. The electrostatic latent image is removed using a developer or developer (hereinafter referred to as
12 (referred to as toner) (see FIG. 2); a transfer device 5 that adsorbs the toner 12 adhered on the photosensitive drum 1 onto paper (recording medium) 4; and the photosensitive drum 1.
a cleaning device 6 for removing toner 12 remaining on the
a static elimination lamp 7 for removing residual potential on the photosensitive drum 1;
The thermal fixing device 8 of this embodiment heat-fixes the toner 12 on the paper 4, the paper feed roller 9 that feeds the paper 4, the ejection roller 10 that ejects the paper 4, and the paper feed cassette (Fig. The main part thereof consists of a take-out roller 11 (not shown).

As shown in FIG. 2, the heat fixing device 8 of this embodiment includes a pair of planar heaters 8a and The lower planar heater 8b also serves as a guide member for the paper 4, and the paper 4 with toner 12 attached to its surface moves on this planar heater 8b while sliding in contact with it. There is. The toner 12 on the sheet 4 is melted by the heat transmitted and radiated from these planar heaters 8a and 8b, and is fixed (thermally fixed) to the paper 4.

The planar heaters 8a and 8b are, for example, as shown in FIGS. 3(al and ′b), a heating plate 81 made of metal or ceramic, a plurality of ceramic heaters 82 arranged in parallel on the heating plate 81, and a ceramic heater 81 made of metal or ceramic. A pair of silver electrodes 84 connected to the heater 82, a pair of lead wires 85 drawn out from the silver N pole 84, and a ceramic plate or the like placed on the ceramic heater 82 via an insulating plate 86 such as a mica plate. It is composed of a heat sink plate 87 made of a metal plate.

Each ceramic heater 82 is made of a conductive metal oxide such as tin oxide added with antimony oxide or indium oxide added with tin oxide on a ceramic plate 82a such as an alumina plate having a width IQmm, a length of 20 mm, and a thickness of 1 mm. It is formed by vapor-depositing material IJ82b. Furthermore, as the ceramic heater 82, other ceramic heaters such as barium titanate-based positive characteristic ceramic heaters having the same dimensions can also be used.

The ceramic heaters 82 of the planar heaters 8a and 8b are adjusted to have the same low resistance value in order to make the temperature distribution uniform at all locations on the heater surface of the heat sink 87. Also,
The temperatures of the planar heaters 8a and 8b can be easily changed using a temperature controller (not shown), so they are automatically set to the optimum temperature according to the thickness of the paper 4, the feeding speed, etc. The temperature is controlled.

Note that the upper and lower planar heaters 8a and 8b are arranged so that the heating plates 81 are opposed to each other.

Next, the operation of the heat fixing device 8 of this embodiment configured as described above will be explained together with the operation of the image forming device 5 shown in FIG.

The photosensitive drum 1 is uniformly charged by a charger 2 and sent to an exposure process.

In the exposure process, for example, in the case of an electrophotographic copying machine, the reflected light of the irradiated light on the document on the document table causes the optical printer,
Particularly in the case of a laser beam printer, a light beam being scanned by an optical deflector is turned on and off according to image information, thereby forming an image charge pattern as an electrostatic latent image on the photosensitive drum l.

After the exposure process, the photosensitive drum L1 is sent to a developing process, and the electrostatic latent image is developed by the developing device 3 with toner 12 and made visible. - After this, the photosensitive drum 1 is sent to a transfer process, and the toner 12 on the photosensitive drum l is transferred by the transfer device 5 to the paper 4 conveyed by the take-out roller 11 and the paper feed roller 9, and a reproduced image is obtained. , this reproduced image is thermally fixed onto the paper 4 by a thermal fixing device 8 in a fixing process.

Specifically, the paper 4 on which the toner 12 has been transferred passes between the upper and lower planar heaters 8a and 8b while slidingly contacting the lower planar heater 8b, and during this passage, the paper 4 and the toner 12 move upward and downward. The toner 12 is heated by the planar heaters 8a and 8b, and the toner 12 is melted and fixed to the paper 4, thereby performing thermal fixing. At this time, since the planar heater 8a does not come into contact with the toner 12 on the paper 4, problems such as widening of the printing width do not occur.

The paper 4 to which the toner 12 has been thermally fixed by the thermal fixing device 8 is discharged to the outside of the image forming apparatus by a discharge roller 10 .

On the other hand, after the transfer process, the remaining toner 12 is removed from the photosensitive drum 1 by a cleaning device 6, and the static electricity is removed from the photosensitive drum 1 by a static elimination lamp 7, so that the photosensitive drum 1 can be reused.

In the above embodiment, the planar heaters 8a and 8b are planar heaters, but it goes without saying that heaters of other shapes such as arcuate planar heaters may be used as required.

Also, depending on the fixing conditions, only one of the upper and lower planar heaters 8a and 8b may be used as a heater. In this case, the planar heater that is not used as a heater may be removed. , it may be used simply as a guide member for the paper 4.

Furthermore, if preheating of the paper 4 is required, the length of the lower sheet heater 8b in the transport direction of the paper 4 should be made longer than the length of the upper sheet heater 8a in the transport direction of the paper 4. This can be dealt with by

〔Effect of the invention〕

As explained above, according to the present invention, since the only part that becomes high temperature is the part of the planar heater with a small heat capacity, the heat fixing device does not require warm-up time, consumes little power, and is small and inexpensive. It has the effect of being able to provide

Furthermore, since it is a non-contact type fixing method, there is no risk of widening the print width during fixing, and there is no risk of increasing the load on the drive motor.

Furthermore, the planar heater does not become a heat source that causes an increase in the internal temperature of the image forming apparatus, and a cooling device is also unnecessary or can be made very small.

Furthermore, the quality and thickness of the paper (recording medium).

Since the temperature setting can be easily adjusted according to various fixing conditions such as the type (9i11 paper, envelope), stable fixing is possible.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an image forming apparatus equipped with a heat fixing device according to an embodiment of the present invention, FIG. 2 is a side view showing the heat fixing device according to the present embodiment, and FIG. 3 [a] and (1)] are a longitudinal sectional view and a horizontal sectional view showing an example of the planar heater in FIG. 2, and FIG. 4 is a sectional view showing an example of a conventional heat fixing device. In the figure, 1...Photosensitive drum, 2...Charger, 3...Developer, 4...Paper, 5...Transfer device, 6... ... Cleaning device, 7 ... Static elimination lamp, 11a, 9b - Planar heater, 9 ... Paper feed roller, io ... Ejection roller, 11 ... Take-out roller , 12... toner, old... heating plate, 82... ceramic heater, 82a... ceramic) anti, 82b... conductive metal oxide layer, 84... ...Silver electrode, 85. ... Lead wire, 86. ...
・It is a heat sink. .

Claims (1)

[Scope of Claims] In an image forming apparatus using an electrophotographic process, a surface condition for thermally fixing the developer or developer onto a recording medium having the developer or developer transferred from the image carrier on the surface. A heat fixing device characterized by being equipped with a heater.