JPH0419688A - Fixing device - Google Patents

Abstract

PURPOSE:To make the ability of scraping offset toner and the ability of applying a releasing agent excellent by driving a releasing agent applying roller so that its circumferential speed may be relatively different from a fixing roller or a pressure roller. CONSTITUTION:The rotation of a driving shaft 14 which is driven by a motor is transmitted to an oil applying roller 13 through belt pulleys 15 and 16 and a timing belt 17, and the roller 13 is driven independently of the fixing roller 1 and the circumferential speed thereof is increased in a forward direction with respect to the roller 1. Since the roller 13 and the roller 1 rotate while rubbing each other, the ability of scraping the offset toner from the surface of the roller 1 is enhanced and the ability of supplying the silicone oil to the surface of the roller 1 is also improved. Thus, the ability of removing the offset toner and the ability of applying the releasing agent are always kept optimum.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fixing device for an image forming apparatus such as a copying machine, a printer, or a facsimile machine.

[Prior Art] Conventionally, in an image forming apparatus such as a copying machine, a fixing device or a fixing device for fixing a developer image formed on a recording material to the recording material by a developing process such as electrostatic photography has been used. FIG. 4 shows an example of such a fixing device.

In the example shown in FIG. 4, the recording material is introduced from the direction A in the figure into the nip formed by the pair of fixing rollers l and the pressure roller 2, and as it passes through the nip, the pressure and the built-in fixing roller Heat is applied by the heater 3, and the developer is melted and fixed to the recording material.

In a fixing device having such a configuration and operation, the fixing roller 1 is usually formed as a roller with a hard surface such as metal, while the pressure roller 2 is formed as a roller with a soft surface such as silicone rubber. A roller formed as a roller is used.

In the above-mentioned fixing operation, it is known that some of the developer that has been carried onto the recording material and transported to the nip section is offset and adheres to the fixing roller, and if this is left unattended, it may cause problems in the future. During the fixing operation, the offset developer adheres to the recording material, resulting in smearing of the image.

Therefore, in a conventional general fixing device, a cleaning mechanism for the fixing roller is provided in association with the fixing roller (for example, above the fixing roller in FIG. 4). The cleaning mechanism in this example winds up a thin sheet material called a web, which is made of nonwoven paper impregnated with a release promoter such as silicone oil, from an unwinding shaft 4 in conjunction with the passage of the recording material. Since the shaft 5 is not used to drive the winding, a web roller 6 made of an elastic material such as rubber is pressed against the fixing roller by a spring (not shown) to provide a certain amount of nip. In addition to wiping off the dirt caused by the offset, the silicone oil impregnated with the web is uniformly applied onto the surface of the fixing roller 1.

The web method is thus used as a means of preventing offset. However, in this method, since the length of the web is finite, it is necessary to replace the web with a new one at regular intervals.

As a result, there were problems in that the service cost increased and, in addition, it was time-consuming. In order to compensate for the problems with the structure using the above-mentioned web, a release agent application roller as shown in FIG. 5 was proposed.

The structure of the release agent application roller includes a core metal 7 made of SUS, a silicone rubber layer 8 as an intermediate layer, and a felt layer 9 made of heat-resistant felt formed on the surface layer. The felt layer 9 contains a mold release agent with a viscosity of 10,000.
It is uniformly impregnated with C3 silicone oil in the longitudinal direction. The same silicone oil 11 as described above is also contained in the oil pan 10, and the silicone oil 11 is supplied to the release agent application roller by the capillary action of the felt bat 12. The release agent application roller having such a structure is driven by contacting the fixing roller and applies silicone oil to the fixing roller to prevent offset.

[Problem to be Solved by the Invention] However, when the release agent application roller method is used, the application roller rotates as a result of the fixing roller, so both rollers rotate without a difference in circumferential speed. Along with this, there has been a problem in that the ability to scrape off offset toner from the fixing roller and the ability to apply a release agent are reduced compared to the web method.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a fixing device equipped with a release agent application roller that is not inferior to the web method in terms of offset scraping ability and release agent application ability.

[Means for Solving the Problems] According to the present invention, the above object is achieved by: a fixing roller disposed rotatably; a pressure roller disposed in pressure contact with the fixing roller and rotatable as a driven; In a fixing device having a release agent application roller disposed in pressure contact with a fixing roller or a pressure roller and for applying a release agent to the fixing roller or pressure roller, the release agent application roller is connected to the release agent application roller. This is achieved by comprising a driving means for driving the fixing roller or pressure roller, which the agent application roller is in pressure contact with, so as to have a relative peripheral speed difference therebetween.

[Function] According to the present invention, the release agent application roller driving means or the release agent application roller is driven so as to have a peripheral speed difference relative to the fixing roller or the pressure roller. As a result, the surface of the release agent application roller rubs against the surface of the rotating fixing roller or pressure roller, thereby reliably removing the offset toner and applying the release agent.

[Embodiments] A first embodiment and a second embodiment of the present invention will be described with reference to FIGS. 1 to 3 of the accompanying drawings.

<First Embodiment> First, a first embodiment of the present invention will be described with reference to FIG.

In FIG. 1, 1 is a fixing roller, 2 is a pressure roller, and a recording material on which an unfixed image has been formed enters the nip between these two rollers to fix the image. A release agent application roller (hereinafter referred to as oil application roller) 13 is in contact with the toner on the upper part of the fixing roller l, and as in the conventional example, the oil application roller 13 serves as a means for applying oil to the fixing roller 1. It has become. The silicone oil 11 contained in the oil pan 1O is supplied by the capillary action of the felt pad 12 to an oil application roller 13 whose outer periphery is made of felt and whose interior is made of silicone sponge.

Here, in the present invention, the rotation of the drive shaft 14 driven by a motor (not shown) is transmitted to the oil application roller 13 via belt pulleys 15, 16 and a timing belt 17, and is driven independently from the fixing roller l. I'm letting you do it. In this configuration, the circumferential speed of the fixing roller in the forward direction is increased by 30%. Therefore, since the oil application roller 13 and the fixing roller l rotate while rubbing against each other, the ability to scrape off offset toner from the surface of the fixing roller l is increased compared to the conventional oil application roller method, and the silicone oil fixing roller The ability to supply l to the surface was also improved.

Here, in this embodiment, the rotational speed of the oil application roller 13 was set to be 130% of the circumferential speed of the fixing roller at the nip portion with the fixing roller 1;
The fixing roller is not limited to 0%, and the rotation direction can be effective in either forward or reverse direction with respect to the fixing roller rotation direction. In other words, the feature of the present invention is that it can provide a difference in circumferential speed, and the optimum difference in circumferential speed differs depending on each device.

In addition, the driving direction is also transmitted by gears from other rotating shafts, etc.
There are various means, and the method is not limited to the method of this embodiment.

<Second Embodiment> Next, a second embodiment of the present invention will be described using FIGS. 2 and 3. Note that the same reference numerals are given to the same parts as in the first embodiment, and the explanation thereof will be omitted.

This embodiment differs from the first embodiment in that the rotational speed of the release agent coating roller is changed depending on the type of developer used.

FIG. 2 is a sectional view of the entire copying apparatus including the fixing device of this embodiment.

A feature of this copying apparatus is that it has two developing devices, a black developing device 18 and a red developing device 19, and the color of the image can be changed to either black or red by the user or by manually pressing keys on the operation panel (not shown). You can choose to. The developing device having the toner of the selected color is pressurized by this key manually. Therefore, the following problem arises regarding the offset.

The physical properties of black toner and red toner are significantly different, and therefore the ease of offset is also different. Therefore, a mold release agent (in this example, silicone) that satisfies the offset prevention effect.
It is also necessary to change the amount of oil applied depending on the toner.

The optimum application amount for this example device is black toner or 0.3g/
For red toner, there is a wide difference of 0.7g/sheet, and in order to reasonably obtain the effect of both toners, it is necessary to change the amount of application in these two cases. In this embodiment, it has been found through experiments that an effect can be obtained by increasing the rotational speed of the coating roller by 30% for black and 70% for red. In order to deal with this, the present invention takes the following approach.

FIG. 3 is a diagram showing a method of changing the amount of silicone oil applied according to this embodiment. When the user selects an image color using the keys on the operation unit 20 and presses the copy button, this information is transmitted to the DC controller 21. Based on this information, the DC controller 21 changes the driving speed of the pulse motor 22 depending on whether the color is black or red. The rotation of the pulse motor 22 is transmitted to the drive shaft 14 through gears 23 and 24, and is transmitted to the oil application roller 13 along the path shown in FIG.
drive. At this time, as per the above experimental data, the oil application roller 1 is
3, the rotation speed of the fixing roller is increased by 30% for black images and by 70% for red images. This configuration makes it possible to apply the optimum amount of silicone oil for each color.

In this embodiment, the peripheral speed is different depending on the difference in toner color, but this is not limited to this, and the same effect can be obtained even if it is done depending on other copy modes, environment, number of durable sheets, etc. Needless to say, there is.

[Effects of the Invention] As described above, according to the present invention, since the release agent applying roller is driven by the driving means with a peripheral speed difference relative to the fixing roller or the pressure roller, Improves offset toner removal ability and release agent application ability.

In addition, since the rotation speed of the release agent application roller can be changed depending on the type of developer used or the surrounding environment, it is possible to always maintain optimal offset toner removal ability and release agent application ability. .

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a schematic configuration of a device according to a first embodiment of the present invention, FIG. 2 is a cross-sectional view showing a schematic configuration of a device according to a second embodiment of the present invention, and FIG. A block diagram showing a schematic configuration of a control means for a mold agent application roller, FIG. 4 is a sectional view showing a schematic configuration of a conventional device using a web, and FIG. 5 is a schematic configuration of a conventional device using a mold release agent application roller. FIG.

Claims (6)

[Claims] (1) A fixing roller disposed rotatably; a pressure roller disposed in pressure contact with the fixing roller and rotatable as a driven; and a fixing roller disposed in pressure contact with the fixing roller or the pressure roller. Alternatively, in a fixing device having a release agent application roller for applying a release agent to a pressure roller, the release agent application roller is placed in pressure contact with the fixing roller or the pressure roller. A fixing device comprising: a drive means for driving the fixing device so as to have a relative circumferential speed difference. (2) The fixing device according to claim (1), wherein the driving means is set to make the circumferential speed difference variable. (3) The fixing device according to claim (1) or claim (2), wherein the outer layer of the release agent application roller is made of a material that has a high ability to retain the release agent. (4) The fixing device according to claim 3, wherein the outer layer of the release agent application roller is made of heat-resistant felt. (5) The fixing device according to claim (3), wherein the outer layer of the release agent application roller is a foam. (6) The fixing device according to any one of claims (1) to (5), further comprising a release agent supply means for supplying the release agent to the release agent coating roller.