JP3914326B2 - Fixing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a recording apparatus using an electrophotographic system such as a printer, a copying machine, and a facsimile machine, and more particularly to a fixing apparatus that fixes a toner image formed on the surface of a recording body to the recording body.
[0002]
[Prior art]
A recording apparatus using an electrophotographic method includes a step of developing toner as an image on the surface of a recording body and a step of fixing the visualized toner image on the recording body. The toner melts upon heating and solidifies upon cooling. In the fixing step, utilizing the properties of the toner, the toner is melted by heating, and then fused to the recording material by natural cooling, that is, fixed.
[0003]
Hereinafter, a conventional fixing device will be described.
[0004]
In the fixing process, a heating method often performed is to press a pair of fixing rollers including one roller and one support roller, and heat at least one of the fixing rollers to heat the two fixing units. In this method, a melt sandwiching portion where the rollers come into contact with each other is formed, and a recording body on which a toner image is formed is inserted into the melt sandwiching portion. Then, by inserting the recording body through the fusion sandwiching portion, the toner arranged as an image on the surface of the recording body is heated and pressurized at the same time. The toner is melted and deformed by receiving two types of energy supply, that is, heat energy and work by pressure in the melt sandwiching portion. By this action, the toner is fixed on the recording medium. Note that at least one of the fixing rollers may be heated. Further, when the toner image formed on the recording paper body is inserted into the fixing roller, the toner image carrying surface and the heated fixing roller are inserted in contact with each other. The heating roller is called a heat roller. The support roller is called a backup roller. In this specification, in order to simplify the description, the heat roller may be abbreviated as HR and the backup roller may be abbreviated as BR. Both the HR and BR rollers are called a fixing roller pair. In addition, any one of HR and BR may be referred to as a fixing roller.
[0005]
The HR is made of an aluminum hollow cylinder, and a heater is provided at the center thereof. An aluminum hollow cylinder is called a metal core. Also, a halogen lamp is often used for the heater.
[0006]
On the other hand, the support roller BR is provided with an elastic layer on the outer side of the metal rotating shaft, and the elastic layer is deformed when pressed against the HR to form a fusion sandwiched portion.
[0007]
In the fixing device, when the toner image is fixed, the toner may adhere to the fixing roller. This development is called offset, and the toner adhering to the fixing roller is called offset toner. When a large amount of offset toner is generated, the offset toner is re-transferred to the recording medium, causing a problem that erroneous printing is caused because the offset toner cannot be distinguished from the recorded information. In order to prevent this, it is common to use silicon rubber, fluororubber, or fluororesin having high releasability as a release layer for the outer layer in contact with the HR toner. Since the release layer has a lower thermal conductivity than the core metal, it acts as a thermal resistance during fixing.
[0008]
Next, offset generation characteristics and conventional countermeasures will be described.
[0009]
FIG. 2 is a diagram showing the generation characteristics of offset toner.
[0010]
11 is a low temperature region, 12 is a high temperature region, and 13 is a non-offset band.
[0011]
The horizontal axis shows the temperature of the fixing roller, and the vertical axis shows the amount of offset toner.
[0012]
The amount of offset toner is large in the low temperature region 11 and the high temperature region 12, and the offset generated in the low temperature region 11 is referred to as a low temperature offset, and the offset generated in the high temperature region 12 is referred to as a high temperature offset. The region narrowed between the low temperature region 11 and the high temperature region 12 is called a non-offset band 13 and the amount of offset toner is small.
[0013]
In the fixing device, the temperature of the fixing roller is usually set in the non-offset band 13 in order to minimize the amount of offset toner.
[0014]
Even if the temperature of the fixing roller is set in the non-offset band 13, a slight offset is generated. Therefore, during the period in which the offset is generated, the nonwoven fabric or porous material is brought into contact with the fixing roller to set the offset toner. There is a fixing device having a cleaner for wiping off. In this case, when an amount of offset toner that can be collected by the nonwoven fabric or porous material is collected, the offset toner once collected by the nonwoven fabric or porous material is transferred again to the fixing roller. Furthermore, there is a problem that this is transferred to the recording medium. In order to prevent this, the cleaner composed of the nonwoven fabric or porous material must be replaced before the offset toner wiped off by the nonwoven fabric or porous material accumulates beyond the amount that can be collected. . Moreover, there is a problem that the exchange must be performed in a relatively short period.
[0015]
Further, in order to reduce the amount of offset toner in the non-offset band 13, a release agent such as silicone oil may be applied to the fixing roller. Furthermore, there are cases where a cleaner and a release agent are used in combination, but in these cases as well, the offset is not zero, so the cleaner cannot collect offset toner that exceeds its collection capacity. Replacement is required. By the way, when the release agent is not applied, the period until the cleaner is changed is longer than when the offset toner is removed only by the cleaner, but even if this method is used, The period until the cleaner is changed is not sufficient, and further extension of the period is desired.
[0016]
Furthermore, when a cleaner made of a nonwoven fabric or a porous material is used, even if the amount of accumulated offset toner is at a level that can be collected, the toner is a fluororesin or silicone rubber used for the release layer, Since it is harder than a material such as fluororubber, the HR is constantly rubbed, and there is a problem that the life of the HR is reduced.
[0017]
Incidentally, as described in JP-A-1-140181, there is known a method in which offset toner is attached to a recording sheet to be printed and removed.
[0018]
However, when offset toner that can be recognized by the fixing roller is present, the offset toner is transferred as it is to a recording sheet that is used for printing. Exists. Such a situation occurs particularly when printing is interrupted. That is, when printing is temporarily interrupted for some reason during fixing, the recording paper is stopped when printing is stopped, and then the HR and BR pressure contact of the fusing unit of the fixing device is released. When printing is resumed, the recording paper is conveyed after the HR and BR are brought into pressure contact to form the melt sandwiched portion. If a toner image exists at a position corresponding to the melted nipping portion of the stopped recording paper, a state occurs in which the recording paper is stopped and HR and BR are pressed against each other, so a larger amount of heat is input to the toner than in the normal transport state. As a result, high temperature offset occurs. The interruption of printing occurs in the case of a running failure of the recording paper, or when the running is normal but an error occurs in the printing apparatus due to other factors.
[0019]
In addition to the above-mentioned publications, for example, Japanese Patent Laid-Open No. 3-107183 can be cited as a prior art related to the present invention.
[0020]
[Problems to be solved by the invention]
In the conventional techniques described above, there is a problem that the period until the replacement of the cleaner for wiping off the offset toner is not considered, and the period until the cleaner replacement is short.
[0021]
Further, there is a problem that the wiped toner is not considered about rubbing the release layer of the heat roller, and the life of the heat roller is short.
[0022]
Furthermore, the method of removing offset toner by adhering to the recording paper used for printing without using a cleaner is not particularly concerned with high temperature offsets that occur when printing is interrupted. There was a problem of causing erroneous printing.
[0023]
SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device for an electrophotographic recording apparatus that has a long period until replacement of a cleaner, a long life of a heat roller, and no occurrence of erroneous printing.
[0024]
[Means for Solving the Problems]
A problem when offset occurs is that offset toner adhering to the fixing roller is retransferred to the recording paper and causes erroneous printing. Therefore, this problem cannot occur unless the offset toner re-transferred to the recording paper is recognized as an image. In the non-offset band, offset toner is an unrecognizable small particle. Unless wiping is performed, these particles are not recognized and re-transferred to a recording sheet to be used for fixing and discharged outside the recording apparatus. In normal printing, if the temperature of the heat roller is set in a non-offset band, erroneous printing does not occur. An offset recognized as erroneous printing occurs when printing is interrupted as described above.
[0025]
Therefore, in the present invention, the temperature of the heat roller is set in the non-offset band, and during normal printing or standby, the cleaner that wipes off the offset toner is installed in a non-contact state from the heat roller, and only when printing is interrupted. The high temperature offset toner was wiped off in contact with the heat roller.
[0026]
Since the temperature of the heat roller is set within the non-offset band, even if the cleaner is in a non-contact state, erroneous printing will not occur.If printing is interrupted and high temperature offset occurs, the cleaner will contact the heat roller. Since the offset toner is wiped off, no erroneous printing occurs in the operation of all the recording apparatuses. The cleaner is in a non-contact state from the heat roller during normal printing and standby, which occupies most of the operating time of the recording apparatus, so that the heat roller is hardly rubbed and the invisible offset toner is not wiped off. Therefore, the life of the heat roller can be extended, and the period until the cleaner is replaced can be extended.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to FIGS.
[0028]
FIG. 1 is a longitudinal side view of a fixing device according to the present embodiment.
[0029]
1 is a heat roller (HR), 2 is a backup roller (BR), 3 is a fusing unit, 4 is a recording paper, 5 is a cleaner unit, 6 is a felt, 7 is a pressing member, 8 is an oil injection hole, and 9 is a spring. Reference numeral 10 denotes an extrusion member.
[0030]
FIG. 2 is a diagram showing the occurrence characteristics of offset as described above. 11 is a low temperature region, 12 is a high temperature region, 13 is a non-offset band, the horizontal axis indicates the temperature of the fixing roller, and the vertical axis indicates the offset toner. The amount of
[0031]
HR1 is heated, and HR1 and BR2 are pressed to form a fusion sandwiching portion 3 where two fixing rollers (HR1 and BR2) are in contact with each other, and a recording body on which a toner image is formed is inserted into the fusion sandwiching portion 3 Let By inserting the recording medium through the fusion sandwiching section 3, the toner arranged as an image on the surface of the recording medium is heated and pressurized at the same time, and receives two types of energy supply, heat energy and work by pressure. Melts and deforms. By this action, the toner is fixed on the recording medium. HR1 is made of an aluminum hollow cylinder, and a heater is provided at the center thereof. For example, a halogen lamp is used as the heater. In order to prevent the offset phenomenon, for example, PFA (perfluoroalkoxy) having high releasability is used for the outer layer in contact with the toner of HR1. On the other hand, the BR 2 is provided with an elastic layer made of silicon rubber on the outer side of the metal rotation shaft, and the elastic layer is deformed when the pressure contact with the HR 1 is formed, thereby forming the fusion sandwiching portion 3.
[0032]
Reference numeral 5 denotes a cleaner unit. In the cleaner unit, parts necessary for wiping off offset toner such as a movable felt 6, a pressing member 7, and an oil injection hole 8 are arranged.
[0033]
The pressing member 7 is pulled by the spring 9 during normal printing or standby, and as a result, the felt 6 is in a state of being separated from the HR 1. The felt 6 is mobile, but the felt 6 stops moving while the felt 6 is away from the HR 1. The temperature of HR1 is constantly monitored by a temperature sensor (not shown). The temperature of HR1 during printing is controlled to be a predetermined temperature in the range of the non-offset band 13 based on the output of the sensor. The amount of offset toner is large in the low temperature region 11 and the high temperature region 12, and the offset generated in the low temperature region 11 is referred to as a low temperature offset, and the offset generated in the high temperature region 12 is referred to as a high temperature offset. The region narrowed between the low temperature region 11 and the high temperature region 12 is called a non-offset band 13 and the amount of offset toner is small. The amount of offset toner in the non-offset band 13 range is so small that it cannot be recognized visually. Therefore, during normal printing, even if the felt 6 is separated from the HR1, there is no erroneous printing due to the offset toner.
[0034]
However, when the printing is temporarily interrupted, the recording paper 4 is stopped when the printing is stopped, and then the press contact between the HR1 and the BR2 of the fusing unit 3 of the fixing device is released. Further, when printing is resumed, the recording paper 4 is conveyed after the HR1 and BR2 are brought into pressure contact to form the melt sandwiching portion 3. If the toner image is present at a position corresponding to the melted nipping portion 3 of the stopped recording paper 4, a state occurs in which the recording paper 4 is stopped and the HR 1 and BR 2 are pressed against each other. A high temperature offset occurs when it is put into the toner. In order to prevent erroneous printing caused by this, in the fixing device of this embodiment, when printing is temporarily interrupted, the pushing member 10 quickly pushes the holding member 7 in the direction of HR1, and the felt 6 Is brought into contact with HR1, and wiping of the offset toner is started. The longitudinal movement of the pushing member 10 is performed by a solenoid. The contact of the felt 6 with the HR 1 is continued for a predetermined period after the interruption of printing is released and the printing is resumed to return to the normal printing state. Further, the felt 6 is moved during the period in which the felt 6 is in contact with HR1. In this embodiment, the time from returning to the normal printing state to returning the felt 6 to the non-contact state is set to 1 minute. Further, the moving speed of the felt 6 when the felt 6 is in contact with the HR 1 is set to 0.005 mm / s. In the fixing device of this embodiment, in the case of a jam of a recording paper, a case where an error occurs in the recording device is handled as a temporary printing interruption.
[0035]
When the high temperature offset occurs in this manner, the felt 6 wipes off the HR1, and the occurrence of erroneous printing is prevented.
[0036]
To summarize the effects of the present embodiment described above, since the temperature of HR1 is set in the non-offset band 13, even if the felt 6 is in a non-contact state, erroneous printing does not occur, printing is interrupted and high temperature offset is performed. When 12 occurs, the felt 6 comes into contact with the HR 1 and wipes off the offset toner, so that no erroneous printing occurs. Since the felt 6 is in a non-contact state from the HR 1 during normal printing or standby, which occupies most of the operation time of the fixing device, the HR 1 is hardly rubbed and the invisible offset toner is not wiped off. , The life of HR1 can be extended, and the period until the felt 6 is replaced can be extended.
[0037]
【The invention's effect】
According to the present invention, the cleaning member is brought into a non-contact state during normal printing, but since the temperature of the heating roller is set within the non-offset band, no erroneous printing occurs. When printing is interrupted and high temperature offset occurs, the cleaning member contacts the heating roller and wipes off the offset toner, so that no erroneous printing occurs in the operation of all the recording apparatuses. Since the cleaning member is in a non-contact state from the heating roller during normal printing or standby, which occupies most of the operation time of the recording apparatus, the heating roller is hardly rubbed, and the invisible offset toner can be wiped off. Since there is no, the lifetime of a heating roller can be extended and the period until replacement | exchange of a cleaning member can be extended.
[Brief description of the drawings]
FIG. 1 is a longitudinal side view of a fixing device according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating an offset generation characteristic.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Heat roller, 2 ... Backup roller, 3 ... Melting pinching part, 4 ... Recording paper, 5 ... Cleaner unit, 6 ... Felt, 7 ... Holding member, 8 ... Oil injection hole, 9 ... Spring, 10 ... Extruding member, 11 ... low temperature region, 12 ... high temperature region, 13 ... non-offset band.

Claims (1)

A heating roller, a supporting roller pressed against the heating roller, and a cleaning member for wiping off offset toner generated on the surface of the heating roller are provided, and the recording medium on which the toner image is formed is heated and pressed by the heating roller and the supporting roller. In a fixing device for nipping and conveying and fixing a toner image on a recording medium,
The cleaning member is provided so as to be detachable from the heating roller, and during the normal printing after resuming printing , the heating roller and the supporting roller are released from pressure contact during the stop period of the recording medium, and the cleaning is performed. The member is brought into contact with the heating roller, the offset toner is wiped off while rotating the heating roller in the same direction as printing, and the cleaning member is brought into contact with the heating roller for a predetermined period after printing is resumed and normal printing is started. The fixing device, wherein the cleaning member is in a non-contact state with respect to the heating roller during other periods.

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