JP3667866B2 - Fixing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fixing device applied to an image forming apparatus such as a copying machine, a facsimile, and a printer.
[0002]
[Prior art]
As a fixing device for fixing a toner image on a transfer paper, there is one having a heat roller having a heater, a heat pipe for uniformly diffusing heat from the heater, and a pressure roller in pressure contact with the heat roller. Well known. Some heat pipes are arranged in the axial direction of the heat roller in order to make the temperature uniform in the axial direction of the heat roller and reduce the cost.
[0003]
The fixing device fixes the toner image on the transfer paper by passing the transfer paper on which the toner image is formed at the contact portion between the heat roller and the pressure roller. The degree of bonding of the toner to the transfer paper varies depending on the thermal conditions given by the fixing device. That is, if the applied heat is large, the toner melts well and the fixing property is good. On the other hand, if the heat is small, the toner does not melt so much and the fixing property is deteriorated. This is related to the surface temperature of the heat roller or pressure roller, and the fixing property is improved by keeping the surface temperature of the heat roller or pressure roller high, and the fixing property is deteriorated if the surface temperature is low. .
[0004]
[Problems to be solved by the invention]
When the transfer paper on which an image having poor fixability is formed is conveyed, the toner image is rubbed off by a conveyance roller, a guide member, a reversing part of double-sided image formation, and the toner is peeled off, and the rubbed member is soiled. The transfer paper itself will be soiled. Further, when this image is used as a document, the document transport section is soiled, and there is a problem that the next transfer paper is soiled or the transfer paper is damaged by the accumulated toner.
[0005]
In addition, when the fixing property is poor, toner offset that the toner remains on the heat roller is likely to occur, and a peeling claw for peeling the transfer paper from the heat roller or the pressure roller (when fixing the toner on the transfer paper, The toner is melted and pressed into the fibers of the transfer paper with pressure, but the melted toner is sticky, adheres to the heat roller and the transfer paper winds around the heat roller, and a paper jam occurs. In recent copying machines and the like, double-sided copying is generally possible, and a toner image is also present on the pressure roller side, causing the transfer paper to be wound as described above. The roller is generally an elastic body such as Si rubber, and has low electrical conductivity and is likely to be charged by rotation and friction, so that the transfer paper is wound around the pressure roller by static electricity even when double-sided copying is not performed. Addition The roller is also provided with a peeling claw.) Offset toner adheres to it, causing poor peeling, reverse transfer of the toner, and toner adhering to the peeling claw solidifies and damages the heat roller and pressure roller. There is also a problem.
[0006]
Therefore, as shown in Japanese Patent Laid-Open No. 52-58927, the above-mentioned contamination problem is caused by making the conveying member after fixing have a shape that reduces the contact area with the transfer paper or a material that does not adhere toner. However, this technique has a problem in that transferability of transfer paper is poor. In other words, during double-sided copying, feeding from the double-sided tray feeds out the stopped transfer paper, so a large conveying force is required, and the shape and material of the conveying member of the above technique cannot be expected to be sufficient. There are problems such as untransfer of transfer paper.
[0007]
Accordingly, the present invention has been made in view of the above-mentioned problems, prevents contamination of the transfer paper conveying member with toner, can perform good image formation without causing dirt and scratches on the transfer paper, and a heat roller. Another object of the present invention is to provide a fixing device capable of reliably peeling from the pressure roller and preventing the heat roller and pressure roller from being damaged.
[0008]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a fixing device used in an image forming apparatus, a heat roller heated by a heater, a heat pipe that conducts heat of the heater, and a pressure roller pressed against the heat roller. And a fixing device for fixing the toner image to the transfer paper by passing a transfer paper on which a toner image is formed at a contact portion between the heat roller and the pressure roller. It has a heat conducting portion that extends in the axial direction of the roller and that conducts heat intensively at least at one location of the heat roller.
[0009]
According to a second aspect of the present invention, in the fixing device according to the first aspect, the heat conducting portion is provided at a position corresponding to the conveying member of the image forming apparatus.
[0010]
According to a third aspect of the present invention, in the fixing device according to the first aspect, the heat conducting portion is provided at a position corresponding to a peeling claw for peeling the transfer paper from the heat roller and / or the pressure roller. It is characterized by being.
[0011]
According to a fourth aspect of the present invention, in the fixing device according to the first aspect, the heat conducting portion is provided at a position corresponding to a conveying member that feeds a document of the image forming apparatus.
[0012]
According to a fifth aspect of the present invention, in the fixing device according to the first, second, third, or fourth aspect, the heat conducting portion is formed by expanding a part of the heat pipe.
[0013]
【Example】
Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 10 represents a fixing device applied to the image forming apparatus. First, the image forming apparatus will be described.
[0014]
As shown in FIG. 3, the image forming apparatus is disposed on the image forming apparatus main body 30, and is conveyed by an ADF 31 and an auto document feeder 31 (hereinafter referred to as ADF 31) that conveys a document G to a predetermined reading position. A charging unit 2 that reads an image of the original G, an image processing unit 3 that converts the read image information into an electrical image signal, a photoconductor 1, and a charging charger 4 that uniformly charges the photoconductor 1 are charged. A writing unit 5 for forming an electrostatic latent image corresponding to the original on the photosensitive member 1, a developing device 6 for visualizing the electrostatic latent image, and a visible image formed by the developing device 6 are fed. A transfer separation charger 7 that transfers the transfer paper transferred from the cassette 8 and transferred by a registration roller 27 to the transfer paper and separates the transferred transfer paper from the photosensitive member 1, and a fixing device that fixes the transferred toner image. A 0, a cleaning unit 9 that cleans the toner is removed photoreceptor 1 remaining on the photoreceptor 11 after the transfer, and a charge removing lamp 22 for erasing the electric remaining on the photosensitive member 11 after transfer.
[0015]
The ADF 31 includes a separation conveyance roller 32 that separates and conveys a plurality of documents G one by one, a reversing roller 33 that reversely conveys the document G, a conveyance belt 34 that conveys the reversed document G, and a reading unit 2. A reversing roller 35 that reverses the read original G again and a feed roller 36 that sends out the original G are included.
[0016]
As shown in FIG. 1, the fixing device 10 includes a heat roller 11 having a heater 15 that thermally melts the toner T on the transfer paper P, and a heat pipe 16 that conducts heat from the heater 15, and a heat roller. The pressure roller 12 is pressed against the heat roller 11 by the pressure means 23, the cleaning roller 13 is in contact with the heat roller 11 and removes toner and paper dust adhering to the heat roller 11, and is contacted with the cleaning roller 13 for cleaning. A blade 14 that scrapes off deposits such as toner adhering to the roller 13, a felt 17 that applies a release agent 21 to the outer peripheral surface of the heat roller 11, and an excess of the release agent 21 that is applied by the felt 17. A release agent blade 18 for scraping the release agent, a release claw 19 for separating the transfer paper P, on which the toner image is fixed by the heat roller 11 and the pressure roller 12, from the heat roller 11, and a release Discharge rollers 20a for discharging the separated transfer sheet P at 19, consists mainly of a 20b.
[0017]
The pressure unit 23 includes a pressure arm 24 that is in contact with the bearing 12 c of the pressure roller 12 and a spring 25 that biases the pressure arm 24. A thermistor 26 that detects the temperature of the heat roller 11 is disposed on the surface of the heat roller 11 in the center in the axial direction. The temperature information of the thermistor 26 is input to a control means (not shown), and the control means controls the energization to the heater 15 based on the temperature information of the thermistor 26 to keep the temperature of the heat roller 11 at a predetermined temperature.
[0018]
The pressure roller 12 is formed of a core metal 12a such as aluminum and a rubber layer 12b made of silicon rubber provided outside the core metal 12a. On the other hand, the heat roller 1 includes a metal core 11a made of aluminum, iron, copper or the like, and a resin layer 11b made of ethylene tetrafluoride or the like that is formed on the outer peripheral surface of the metal core 11a to improve the releasability of the toner T. have. A heat pipe 16 that conducts heat from the heater 15 to the surface of the heat roller 1 is inserted into the metal core 11a.
[0019]
As shown in FIG. 2, the heat pipe 16 is inserted into a hole 37 formed in the cored bar 11 a and extends in the axial direction of the heat roller 11. The heat pipe 16 is formed by enclosing a liquid such as water in a glass or copper tube, for example, and has a well-known function of conducting heat by circulation of vaporization, evaporation, and aggregation of the liquid.
[0020]
In the heat pipe 16, a heat conducting portion 16 a that intensively transfers heat from the heater 15 is formed in at least one place of the heat roller 11. The area of the contact portion 16A that contacts the cored bar 11a in the portion of the heat conducting portion 16a that faces the outer peripheral surface of the heat roller 11 is determined to be smaller than the area of the heat receiving portion 16B that receives heat from the heater 15. As a result, a large amount of heat from the heater 15 is conducted to the portion of the heat roller 11 corresponding to the heat conducting portion 16a. The heat conducting portion 16a is formed by bulging a part of the heat pipe 16, and is provided at a position corresponding to the paper discharge roller 20a and the peeling claw 19 described above.
[0021]
At the time of fixing the toner image, heat is uniformly removed from the surface of the heat roller 11, but due to the heat conductivity of the heat pipe 16, the portion of the heat roller 11 corresponding to the heat conduction portion 16 a is moved to another position of the heat roller 11. Faster than this, a large amount of heat is applied to increase the temperature, and the fixing property of the toner T in the region P1 corresponding to that portion of the transfer paper P is improved.
[0022]
Hereinafter, the operation of the above configuration will be briefly described.
The document G set at a predetermined position of the ADF 31 is separated one by one by the separation and conveyance roller 32, reversed and conveyed by the conveyance belt 34, and the image information of the document G is read by the reading unit 2 and image processing is performed. The unit 3 converts it into an electrical image signal. The original G read by the reading unit 2 is reversed again and sent out by the feed roller 36.
[0023]
The image of the document is projected by the writing unit 5 onto the surface of the photoreceptor 1 whose surface is uniformly charged by the charging charger 4 to form an electrostatic latent image. The developing device 6 attaches toner to the electrostatic latent image on the photoreceptor 1 to form a toner image.
[0024]
On the other hand, one transfer sheet P is fed from one of the sheet feeding cassettes 8 of the sheet feeding device and is sent to the registration roller 27. The registration roller 27 sends the transfer paper P to the transfer separation charger 7 at a timing at which the toner image on the photoconductor 1 and the transfer paper match at the transfer separation charger 7. The transfer paper P having the image transferred by the transfer separation charger 7 and separated from the photoreceptor 1 is sent to the fixing device 10.
[0025]
As shown in FIG. 1, the transfer paper P is inserted between the heat roller 11 heated to a predetermined temperature by the control means and the pressure roller 12, and the toner image is heat-fixed. At this time, the portion of the heat roller 11 corresponding to the heat conducting portion 16a is heated to a higher temperature than the other position of the heat roller 11, and the toner in the region P1 corresponding to that portion of the transfer paper P is heated. T is fixed well. Since the toner T in the area P1 of the transfer paper P corresponding to the peeling claw 19 is fixed well, the toner T does not accumulate on the peeling claw 19, and the transfer paper P is reliably attached to the surface of the heat roller 11 by the peeling claw 19. And are transported and discharged by a pair of paper discharge rollers 20a and 20b.
[0026]
On the other hand, the toner remaining on the photoreceptor 1 is removed and cleaned by the cleaning unit 9 to be ready for the next image formation. The transfer paper P is sent to the next conveyance path after fixing, and by providing a conveyance member in the conveyance path, for example, a guide member (not shown), a branching claw, a conveyance roller, and the like at a position corresponding to the heat conduction unit 16a, Contamination due to toner after fixing can be prevented.
[0027]
A case where the transfer paper P on which an image is formed is used as a document is also conceivable. Therefore, if the conveying member for feeding the original, that is, each roller 32, 33, 35, 36 of the ADF 31 is provided at a position corresponding to the heat conducting portion 16a, contamination of the ADF 31 with toner and contamination of other originals can be prevented.
In this example, the peeling claw 19 is provided only on the heat roller 11 side. However, as shown in FIG. 4, a peeling claw 19 ′ may also be provided on the pressure roller 12 side. Thereby, it can respond to double-sided copying. In the figure, the pressure means is not shown.
[0028]
FIG. 5 shows another embodiment. In the above-described embodiment, the heat conducting portion 16a of the heat pipe 16 is provided only at a position corresponding to the peeling claw 19 or the conveying member of the image forming apparatus, and heat is concentrated to improve the toner fixing property of that portion. On the other hand, the present embodiment is different in that a plurality of heat conducting portions 46a of the heat pipe 46 are provided.
[0029]
That is, the heat conducting portion 46a is provided at a position corresponding to the non-sheet passing portion X (the end portion of the heat roller 11) of the small size transfer paper P2 and the peeling claw 19 or the conveying member of the image forming apparatus. . The heat of the heat roller 11 is taken away by fixing the toner at the sheet passing portion Y, but tends to remain at the non-sheet passing portion X. Therefore, if nothing is done, it is radiated to the atmosphere or the fixing operation is completed. Later, the sheet gradually moves to the sheet passing portion Y. In this example, the heat of the non-sheet passing portion X is conducted from the heat conducting portion 46a at both ends of the heat pipe 46 to the heat conducting portion 46a at the central portion, and is effectively utilized.
[0030]
In each of the above embodiments, the heat pipes 16 and 46 are disposed inside the heat roller 11, but may be brought into contact with the outer peripheral surface of the heat roller 11 as shown in FIG. 6.
Further, a peeling claw 19 on the heat roller 11 side, a peeling claw 19 ′ on the pressure roller 12 side, a conveying member, and the like are arranged in the longitudinal direction with respect to the portion where heat is intensively transferred by the heat pipe 46. However, all the parts may be in the same position, but in that case, it tends to be disadvantageous in terms of dirt and durability. Therefore, it is effective to shift each in the longitudinal direction within the corresponding range. Although the installation of the heat pipes 16 and 46 has been described on the heat roller 11 side, the heat pipes 16 and 46 can be installed on the pressure roller 11 side in the same positional relationship. In this case, the heat pipes 16 and 46 pressurize the heat of the heater 15. This is transmitted to the heat roller 11 through the roller 12. Furthermore, heat pipes 16 and 46 may be provided on both rollers, which is effective. Further, the heater 15 may be provided on both the heat roller 11 side and the pressure roller 12 side. Each example can be used in combination, and the more the examples, the greater the heat transfer, the greater the margin for fixability, and the better the effect.
[0031]
【The invention's effect】
According to the first aspect of the present invention, since the heat conducting portion that conducts the heat of the heater in a concentrated manner is provided, the fixing property at the heat conducting portion is improved.
[0032]
According to the second aspect of the present invention, the heat conduction portion concentrates the heat of the heater to a position corresponding to the conveying member of the image forming apparatus, so that the fixing property at that position is improved and the conveying member is not soiled. In addition, scratches and stains are not generated on the transfer paper, and good image formation can be performed.
[0033]
According to the third aspect of the present invention, since the heat conduction part intensively transfers the heat of the heater to the position corresponding to the peeling claw, the fixing property at that position is improved, and the heat at the position corresponding to the peeling claw is improved. The offset of the roller is small, the toner is less likely to accumulate on the peeling claw, the transfer paper can be peeled off, and the reverse transfer of the toner and the breakage of the heat roller and pressure roller can be prevented.
[0034]
According to the fourth aspect of the present invention, since the heat conduction unit intensively transfers the heat of the heater to the position corresponding to the conveying member that sends the document of the image forming apparatus, the fixing property at that position is improved and the conveying is performed. Good image formation can be performed without soiling the member or the original.
[0035]
According to the fifth aspect of the present invention, since the heat conduction part is formed by expanding a part of the heat pipe, the heat conduction part can be easily formed.
[Brief description of the drawings]
FIG. 1 is a schematic side view of a fixing device showing an embodiment of the present invention.
FIG. 2 is a cross-sectional view of the fixing device shown in FIG.
FIG. 3 is a side view of an image forming apparatus to which the fixing device shown in FIG. 1 is applied.
4 is a schematic side view showing a modification of the fixing device shown in FIG. 1. FIG.
FIG. 5 is a perspective view of a main part of a fixing device showing another embodiment of the present invention.
6 is a perspective view of a main part of a fixing device showing a modification of FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Fixing device 11 Heat roller 12 Pressure roller 13 Cleaning roller 14 Blade 15 Heater 16, 46 Heat pipe 16a, 46a Heat conduction part 17 Felt 18 Release agent blade 19, 19 'Peeling claw 20a, 20b Paper discharge roller pair 23 Addition Pressure means 26 Thermistor

Claims (5)

A fixing device used in an image forming apparatus,
A heat roller heated by the heater, a heat pipe that conducts heat of the heater, and a pressure roller that is in pressure contact with the heat roller, and a toner image is formed at a contact portion between the heat roller and the pressure roller. In a fixing device for passing the formed transfer paper and fixing the toner image on the transfer paper,
The fixing device according to claim 1, wherein the heat pipe extends in an axial direction of the heat roller, and has a heat conducting portion that conducts heat intensively at least at one position of the heat roller. The fixing device according to claim 1.
The fixing device, wherein the heat conducting unit is provided at a position corresponding to a conveying member of the image forming apparatus. The fixing device according to claim 1.
The fixing device, wherein the heat conducting unit is provided at a position corresponding to a peeling claw for peeling the transfer paper from the heat roller and / or the pressure roller. The fixing device according to claim 1.
The fixing device according to claim 1, wherein the heat conducting unit is provided at a position corresponding to a conveying member that feeds a document of the image forming apparatus. In the fixing device according to claim 1, 2, 3, or 4,
The fixing device according to claim 1, wherein the heat conducting portion is formed by expanding a part of the heat pipe.

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