JP2000321914A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the load on a cleaning means, to prolong serrce life, and to prevent the occurrence of image soiling by surely removing the soil on a fixing roller and pressure roller by allowing a contact uncontact operation means to shorten the contact separation operation interval of a cleaning means for the surface of a contacted roller in comparison to an initial value when the number of inserted sheets, an operating time, and so on exceed predetermined thresholds. SOLUTION: A cleaning web is movably supported so as to be nearer to and away from a fixing roller by a contact uncontact operation means. In a relationship between the contact uncontact operation interval of a cleaning web as a cleaning means for the fixing roller of the device and the cumulative number of copies, the contact separation operation interval is made long until a first broken line, gradually shorter between the first broken line and the next broken line, and short and constant after the last broken line. Performing the contact separation operation in such a manner maintains the fixing roller for a long time without causing a problem that the releasability of the fixing roller is degraded, and realizes a decrease in load on the cleaning web, a low cost, and a long life.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to: The present invention relates to a fixing device used in an electrophotographic image forming apparatus such as a copying machine, a facsimile, and a printer.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus such as a copying machine, a photoconductor is charged by a charging device, and then an electrostatic latent image is formed on the photoconductor by exposure of a document image or optical writing according to image information. Is formed by developing the electrostatic latent image with toner of a developing device to form a visible image, the toner image is transferred to a transfer material of a recording sheet, and the unfixed toner image on the transfer material carrying the unfixed toner image is formed. Copies and prints are obtained by fixing the toner image to a transfer material by a fixing device.

As a fixing device provided in such an image forming apparatus, there is a fixing roller having a heat source (a type having a built-in heater, a self-heating type in which the roller itself generates heat, and the like).
And a pressure roller in contact with the fixing roller, and heat-presses the unfixed toner image on the transfer material by conveying the transfer material carrying the unfixed toner image between the fixing roller and the pressure roller. The ones that settle down are well known.

In this type of fixing device, if the releasability of the fixing roller is poor, an offset occurs in which some toner adheres to the fixing roller. A configuration has been put to practical use in which a release layer is provided on the peripheral surface of the fixing roller, and various types of cleaning means and oil applying means for applying silicone oil as a release material are provided on the fixing roller.

[0005]

However, in recent years, due to a change in the use environment of a copying machine such as the use of recycled paper and transfer paper on both sides, the offset of paper powder and toner to the fixing roller and the pressure roller has increased, Despite the increased load on the cleaning means of the fixing roller and the pressure roller, it is also important to reduce the life and reduce the cost.

In view of the above-mentioned conventional problems, the present invention can reduce the load on the cleaning means, prolong the service life, and reliably clean the fixing roller and the pressure roller.
An object of the present invention is to provide a fixing device that does not generate image stains.

[0007]

According to a first aspect of the present invention, there is provided a fixing device which is mounted on an electrophotographic image forming apparatus, and includes a fixing roller and a fixing roller. A pressure roller in contact with a roller, and the unfixed toner image on the transfer material is heated and pressed by the fixing roller and the pressure roller by transporting the transfer material carrying the unfixed toner image therebetween. Fixing device that fixes
One or more cleaning means for contacting at least one of the fixing roller and the pressure roller to clean dirt adhered to the surface of the contacted roller; and contacting and separating the cleaning means with the surface of the contacted roller. One or more contacting / separating means for causing the contacting / separating means to move the contacting / separating operation interval of the cleaning means to / from the surface of the abutted roller beyond a predetermined threshold value such as the number of passed sheets or the operating time. Is shorter than the initial value.

According to a second aspect of the present invention, in order to achieve the above object, there is provided a fixing device mounted on an electrophotographic image forming apparatus, comprising a fixing roller and a pressure roller contacting the fixing roller. A fixing device that fixes the unfixed toner image on the transfer material by heat and pressure by transporting the transfer material carrying the unfixed toner image between the fixing roller and the pressure roller. One or more cleaning means for contacting at least one of a roller and the pressure roller to clean dirt adhered to the surface of the contacted roller; and one or more cleaning means for bringing the cleaning means into contact with or separating from the surface of the contacted roller. Having the above-mentioned contacting / separating means, the contacting / separating means when the contacting time of the cleaning means to the surface of the contacted roller exceeds a predetermined threshold value such as the number of sheets passed or the operating time. Specially, make it longer than the initial value. To.

According to a third aspect of the present invention, in order to achieve the above object, a plurality of the cleaning means are provided, and at least one of the plurality of cleaning means has an oil supply means. .

According to a fourth aspect of the present invention, in order to achieve the above object, the cleaning means having the oil supply means comprises:
It is a long sheet-shaped cleaning web.

According to a fifth aspect of the present invention, in order to achieve the above object, at least one of the plurality of cleaning means is a cleaning blade, and at least another of the plurality of cleaning means is a cleaning web. The cleaning blade is arranged on the upstream side in the rotation direction of the roller, and the cleaning web is arranged on the downstream side in the rotation direction of the contacted roller of the cleaning blade.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram of an example of a fixing device to which the present invention is applied. In FIG. 1, 1 is a fixing roller, 2 is a cleaning web, 3 is a pressing roller, 4
Is an extrusion roller, 5 is a take-up roller, and 6 is an elastic member, and the cleaning web 2 is pressed against the fixing roller 1 by the pressing roller 3 at a constant pressure.

The cleaning web 2 is unwound from the extruding roller 4 and cleans the surface of the fixing roller 1 while being wound up by the roller 5. The pressing roller 3 is movably supported by an unillustrated contact / separation driving means (for example, a solenoid) so that the cleaning web 2 is brought into contact with and separated from the fixing roller 1.

FIG. 2 is a diagram showing the relationship between the releasability of the fixing roller 1 and the number of copies in the apparatus having the configuration shown in FIG.
Note that the term "release property" in FIG. 2 and its description is based on the amount of dirt offset to the fixing roller 1 and the offset image in order to indicate the release property that is inherently difficult to numerically indicate. Is a substitute value. According to the present inventors, the releasability of the surface of the fixing roller 1 gradually decreases as the cumulative number of copies after the start of use of the apparatus increases as shown in FIG. It began to drop at a stretch and was found to reach an unusable value (C). In other words, it suffices if the releasability of the fixing roller 1 can be maintained at a value equal to or higher than the value B in the number of copies (A) in FIG.

FIG. 3 is a view conceptually showing a first embodiment of the fixing device according to the present invention. The interval between the contacting / separating operation (separation time) of the cleaning web 2 which is a cleaning means for the fixing roller 1 of the apparatus of FIG. FIG. 6 is a diagram showing the relationship between the number of copies and the cumulative number of copies. The contact / separation operation interval is a long time interval up to point D, and is gradually shortened between points D to E,
After point E, it is constant at short time intervals.

FIG. 4 shows a case where the cleaning web 2 as a cleaning means is constantly brought into contact with the fixing roller 1 and a case where the contact / separation operation of the present embodiment as shown in FIG. FIG. 4 is a diagram showing a comparison of changes in the releasability of the fixing roller 1. When the cleaning web 2 is not provided, the releasability of the fixing roller 1 naturally changes as shown in FIG. 2 (indicated by a solid line in FIG. 2), but when the cleaning web 2 is constantly brought into contact, it is indicated by a dotted line in FIG. As shown, even if the cumulative number of copies increases, the releasability of the fixing roller 1 slightly decreases, but is maintained in an ideal state in which almost the initial value is maintained. However, in this case, does the cleaning web 2 have a short life and must be replaced frequently, or does it need to extend the life of the cleaning means 2 by increasing the size of the cleaning means such as making the cleaning web 2 longer? Either way, in any case the result will be less favorable.

On the other hand, in the case of the contact / separation operation according to the embodiment of the present invention, the releasability of the fixing roller 1 gradually decreases as shown by a one-dot chain line in the figure, but gradually becomes stable as the cumulative operating time increases. However, when the cleaning web 2 is brought into contact with the fixing roller 1 at a fixed operation interval, if the operation interval is short, the short life of the cleaning web 2 becomes a problem as in the case of constant contact, and if the operation interval is too long, Although the cleaning web 2 has a long service life, the cleaning web 2 reaches a point B which is a threshold at which the cleaning web 2 becomes unusable due to a decrease in releasability of the fixing roller 1. On the other hand, when the contact / separation operation according to the embodiment of the present invention as shown in FIG. 3 is performed, a decrease in the releasability of the fixing roller 1 can be maintained for a long time as long as no problem occurs, and the load on the cleaning web 2 can be reduced. Low cost and long life can be realized.

The cleaning web 2 of the present invention
3 is not limited to the form shown in FIG. 3 and may be shortened linearly or exponentially, and the degree of decrease in the distance may be set variously depending on the mechanical characteristics. I just need. Cleaning web 2
In order to prevent re-transfer of dirt, it is preferable to drive the fixing roller 1 at the time of paper passing and perform the operation at a normal fixing roller set temperature. Further, the present embodiment is not limited to only one using the cleaning web as the cleaning means.

FIG. 5 is a conceptual diagram showing a second embodiment of the fixing device according to the present invention. The contact time (cleaning time) of the cleaning web 2 as a cleaning means to the fixing roller 1 is shown.
And the cumulative number of copies. In the second embodiment, the maintenance of the releasability of the fixing roller 1 and the reduction of the load of the cleaning means and the prolongation of the service life are made by gradually increasing the contact time of the cleaning web 2 with the fixing roller 1 as the cumulative number of copies increases. It is something that you try to achieve. That is, when the operation characteristics of the present embodiment are adopted, it is not necessary to shorten the time interval for the contact and separation of the cleaning web 2, so that it is possible to cope with the case where the cleaning web 2 is provided in an image forming apparatus having a large number of continuous copies such as a high-speed machine. In addition, the load on the means for driving the cleaning means toward and away can be reduced. Of course, in the present embodiment, similarly to the previous embodiment, the degree of increase in the contact time of the cleaning means may be set variously according to the characteristics of the machine, and is not limited to the embodiment of FIG.

Each of the above-described embodiments is not limited to the apparatus having the configuration shown in FIG. 1, but may be applied to the apparatus having the configuration shown in FIGS. FIG. 6 shows a configuration in which the oil application roller 7 and the cleaning roller 8 are in contact with the fixing roller 1, and the cleaning roller 8 a is in contact with the oil application roller 7. Oil application roller 7 and cleaning roller 8
Is pressed against the surface of the fixing roller 1 by an elastic member 6 and is movably supported so as to be able to contact and separate from the fixing roller 1 by a not-shown driving device.

FIG. 7 shows a configuration in which the oil application roller 7 and the cleaning blade 9 are in contact with the fixing roller 1. The dirt adhering to the fixing roller 1 is mainly a mixture of paper dust and toner, and when these are cleaned by a cleaning unit having no oil supply function such as a cleaning roller or a cleaning blade, the cleaned dirt is removed. Is charged,
In some cases, the toner is scattered from the cleaning unit to the surroundings and re-adhered to the fixing roller 1 to cause image stains. The viscosity prevents the dirt collected by the cleaning means from re-adhering to the fixing roller due to charging.

It should be noted that the fixing roller 1 having a certain degree of releasability in addition to preventing the re-adhesion of dirt by the silicone oil.
In order to clean the cleaning roller, the cleaning means that is in sliding contact with the fixing roller 1 has a higher cleaning efficiency. As the cleaning means, it is preferable to use a cleaning felt or a cleaning web impregnated with oil. When the contacting / separating operation is performed, retransfer of dirt occurs with time, so that the method of sequentially sending out the cleaning surface using the cleaning web 2 as shown in FIG. 1 is most suitable when the contacting / separating operation is performed. .

FIG. 8 shows a configuration in which the cleaning web 2 and the cleaning blade 9 are brought into contact with the fixing roller 1. As described above, the dirt adhering to the fixing roller 1 is mainly paper dust and toner. However, in the case of paper used abroad, many of them contain a large amount of calcium carbonate. If it adheres, it may be buried in the fluororesin on the surface of the fixing roller 1 and cause a problem that dirt is fixed. In such a state, the releasability of the fixing roller 1 is suddenly reduced and the fixing roller 1 cannot be used. Therefore, in the illustrated apparatus, dirt is scraped by the cleaning blade 9, and dirt that has passed through the cleaning blade 9 is cleaned by the cleaning web 2. In this configuration, the releasability of the fixing roller 1 can be almost restored to the initial state. The material of the cleaning blade 9 is preferably a heat-resistant resin or a metallic material. Also, the contact and separation operations of the cleaning blade 9 and the cleaning web 2 are simultaneous,
The cleaning blade 9 is brought into and out of contact with the fixing roller 1 in the state of contact, but the latter is more preferable. That is, as described above, the dirt that has passed through the scraping by the cleaning blade 9 is removed from the cleaning web 2.
This is because it can be collected at.

[0024]

According to the first aspect of the present invention, as described above, when a predetermined threshold value such as the number of sheets passed or the operation time is exceeded, that is, in accordance with a decrease in the releasability of the fixing roller, Since the contact interval of the cleaning unit is shorter than the initial value, the releasability of the fixing roller can be maintained within a usable range,
Moreover, there is an effect that the life of the cleaning means can be prolonged.

As described above, the fixing device according to the second aspect of the present invention is configured such that, when a predetermined threshold value such as the number of sheets passed or the operation time is exceeded, that is, when the releasing property of the fixing roller decreases, Since the contact time of the cleaning unit with the contact roller surface is made longer than the initial value, the releasability of the fixing roller can be maintained within a usable range, and the cleaning unit can have a long service life and can be adapted to a high-speed machine. There is an effect that it becomes.

Since the fixing device according to the third aspect has the oil application function as described above, in addition to the same effects as those of the first and second aspects, the fixing device can also fix the cleaned dirt by charging. This has the effect of preventing re-adhesion to the roller and re-transfer.

Since the fixing device of the fourth aspect uses the cleaning web as described above, it has the same effects as those of the third aspect of the invention, and also has the advantage that the operation of the cleaning means can be performed when the cleaning means comes into contact with or separates from the cleaning means. There is an effect that the most suitable configuration can be obtained.

Since the fixing device of the fifth aspect uses the cleaning blade and the cleaning web as described above, in addition to the same effects as the device of the third aspect, the releasability of the fixing roller is substantially reduced. There is an effect that it can be restored to the initial state.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an example of a fixing device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between the releasability of a fixing roller and the number of copies in the apparatus of FIG.

FIG. 3 is a diagram conceptually showing a first embodiment of a fixing device according to the present invention.

FIG. 4 illustrates a change in the releasability of the fixing roller between a case where the cleaning unit is constantly in contact with the fixing roller and a case where the fixing unit is moved toward and away as in the first embodiment of the present invention. It is a figure which shows the comparison of.

FIG. 5 is a conceptual diagram illustrating a fixing device according to a second embodiment of the invention.

FIG. 6 is a conceptual diagram of another example of a fixing device to which the present invention is applied.

FIG. 7 is a conceptual diagram of still another example of a fixing device to which the present invention is applied.

FIG. 8 is a conceptual diagram of still another example of a fixing device to which the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing roller 2 Cleaning web 3 Push-pressure roller 4 Extrusion roller 5 Take-up roller 6 Elastic member oil 7 Application roller 8, 8a Cleaning roller 9 Cleaning blade

Claims (5)

[Claims] 1. A fixing device to be mounted on an electrophotographic image forming apparatus, comprising: a fixing roller; and a pressure roller in contact with the fixing roller. In a fixing device in which an unfixed toner image on the transfer material is heated and pressed to fix the image by transferring the transfer material holding the image therebetween, the fixing device contacts at least one of the fixing roller and the pressure roller. It has one or more cleaning means for cleaning dirt attached to the surface of the contacted roller, and one or more contacting / separating means for contacting / separating the cleaning means from / to the surface of the contacted roller. A fixing unit that sets an interval between the operation of the cleaning unit and the surface of the abutted roller to be separated from the surface of the abutted roller when the threshold exceeds a predetermined threshold value such as the number of sheets passed or the operation time. 2. A fixing device to be mounted on an electrophotographic image forming apparatus, comprising: a fixing roller; and a pressure roller in contact with the fixing roller. In a fixing device in which an unfixed toner image on the transfer material is heated and pressed to fix the image by transferring the transfer material holding the image therebetween, the fixing device contacts at least one of the fixing roller and the pressure roller. It has one or more cleaning means for cleaning dirt attached to the surface of the contacted roller, and one or more contacting / separating means for contacting / separating the cleaning means from / to the surface of the contacted roller. A fixing unit that sets a contact time of the cleaning unit to the surface of the contacted roller to be longer than an initial value when a predetermined threshold value such as the number of sheets passed or an operation time is exceeded. 3. The fixing device according to claim 1, wherein a plurality of the cleaning units are provided, and at least one of the plurality of cleaning units includes an oil supply unit. 4. The fixing device according to claim 3, wherein the cleaning unit having the oil supply unit is a long sheet-shaped cleaning web. 5. A cleaning blade, wherein at least one of the plurality of cleaning means is a cleaning blade, and at least another is a cleaning web, and the cleaning blade is disposed upstream of the contacted roller in a rotation direction. 4. The fixing device according to claim 3, wherein the cleaning web is disposed downstream of a cleaning blade in a rotation direction of the contact roller.