JP2004309661A - Fixing device and image forming apparatus loaded with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent offset to the following sheet of paper by thoroughly eliminating toner even when the toner stays in a web nip by continuous paper feed in a fixing device where the surface of a fixing member is cleaned by a cleaning web. <P>SOLUTION: A fixing device is provided with: a fixing roll 51 integrating a heat source; and a press roll 52 also integrating a heat source and forming a fixing nip by being brought into press contact with the fixing roll 51. The cleaning web 60 which is rolled out from a rolling out reel 61 and rolled up to a rolling up reel 62 is brought into contact with the fixing roll 51 to form a web nip 64. A web feeding device 65 rotates the rolling up reel 62 and imparts a specified amount of feeding to the cleaning web 60. When continuous paper passing of more than a specified number of sheets is carried out, the web feeding device 65 imparts additional feeding of the specified amount to the cleaning web 60 after the device 65 passed the final sheet of paper P and before the movement of the fixing roll 51 is stopped. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fixing device used in an image forming apparatus such as a PPC (Plain Paper Copier) or a printer. Further, the present invention relates to an image forming apparatus equipped with the fixing device.
[0002]
[Prior art]
In an electrophotographic image forming apparatus such as a PPC or a printer, it is necessary to fix the toner by applying heat to the sheet on which the toner is transferred. A fixing member such as a fixing roller or a fixing belt is used to apply heat to the sheet. Since the fixing member comes into direct contact with the toner, a release layer for preventing the toner from adhering is provided on the surface of the fixing member. However, no matter how high the performance of the release layer is, it is unavoidable that a certain amount of toner remains. Therefore, a method is used in which a cleaning web is brought into contact with the surface of the fixing member, and the toner is wiped from the surface of the fixing member by the cleaning web. Patent Documents 1, 2, and 3 show examples of a fixing device that cleans the surface of a fixing member with a cleaning web.
[0003]
[Patent Document 1]
JP-A-2-280181 [Patent Document 2]
JP 2000-162917 A [Patent Document 3]
JP-A-5-204274
[Problems to be solved by the invention]
In any of the fixing devices described in the above-mentioned patent documents, no special consideration is given to a problem that occurs at the time of re-driving after continuous paper passing.
[0005]
Problems that occur during re-drive after continuous paper passing are as follows. That is, in order to enable the cleaning web to be used for the entire use period of the image forming apparatus without replacement, the feed amount per operation is set to be very small. For this reason, when many sheets of paper having a high printing rate are continuously passed, the same portion of the cleaning web wipes a large amount of toner, and the web is absorbed by the web nip between the cleaning web and the fixing member. Unremoved toner accumulates. While the fixing roller is continuously driven, the staying toner prevents the toner from slipping through.However, when the fixing roller is driven again after the driving of the fixing roller is stopped, the staying toner slips through the web nip and adheres to the paper. This causes a so-called "offset".
[0006]
In the fixing device described in Patent Literature 1, the rotation amount or rotation time of a winding shaft for winding the cleaning web is controlled according to the total number of sheets passed. No measures are taken when toner concentrates on the nip portion of the cleaning web due to continuous paper passing.
[0007]
In the fixing device described in Patent Literature 2, in addition to the normal web winding performed for each sheet passing, a special web winding is performed at the time of recovery after jam processing to remove a large amount of toner attached to the fixing member. are doing. However, it does not address the problem of toner concentration on the nip portion of the cleaning web due to normal continuous paper passing.
[0008]
In the fixing device described in Patent Document 3, the degree of contamination of the cleaning web is estimated, and the web is wound up only when the degree of contamination of the web exceeds a certain value. However, whether continuous paper is passed is not listed as a factor for estimating the degree of dirt.
[0009]
In order to prevent toner offset, the feed amount of the cleaning web per operation may be increased. However, in such a case, the consumption rate of the cleaning web increases, and it is difficult to use the cleaning web without replacing the cleaning web over the entire service life of the image forming apparatus. If an attempt is made to extend the use period by increasing the length of the cleaning web, the roll diameter of the cleaning web increases, which makes it difficult to store the cleaning web in the image forming apparatus.
[0010]
The present invention has been made in view of the above points, and an object of the present invention is to provide a fixing device that cleans the surface of a fixing member by using a cleaning web, in a case where toner stays in a web nip due to continuous paper feeding. Another object of the present invention is to reliably remove the staying toner without increasing the consumption of the cleaning web, so as not to offset the succeeding paper. Another object of the present invention is to provide a high-performance image forming apparatus equipped with such a fixing device.
[0011]
[Means for Solving the Problems]
(1) In order to achieve the above object, in the present invention, a fixing device includes: a fixing member that contacts a surface of a sheet onto which a toner image has been transferred to fix toner on the sheet; a cleaning web that contacts the fixing member; In addition to feeding a predetermined amount to the cleaning web in response to paper passing, and when a predetermined number or more of continuous paper passes, the fixing member stops moving after passing the last paper. And a web feeder for feeding a predetermined amount of additional feed to the cleaning web.
[0012]
According to this configuration, even if many sheets having a high image ratio are continuously passed and toner is accumulated in the web nip, the unused portion of the cleaning web faces the accumulated toner due to the additional feeding of the cleaning web. The toner is absorbed by the unused portion. Therefore, a situation in which the toner staying in the web nip slips through the web nip and adheres to the subsequent sheet to cause an offset does not occur. In addition, since the additional feeding of the cleaning web is performed only when necessary, the consumption of the cleaning web does not increase unnecessarily, and the entire usage period of the image forming apparatus can be covered with the cleaning web of a conventionally used amount. Is possible.
[0013]
(2) In the fixing device as described above, the feed amount of the additional feed changes stepwise according to the number of sheets continuously passed.
[0014]
According to this configuration, if the number of continuous paper passes is large, the unused portion of the cleaning web is drawn out in accordance with the number, and the toner is reliably absorbed.
[0015]
(3) Further, in the present invention, since the fixing device is mounted on the image forming apparatus, high quality prints and copies without toner offset can be obtained.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 is a schematic cross-sectional view showing a schematic structure of the fixing device, FIG. 2 is a cross-sectional view of a roller constituting the fixing device cut along a plane including an axis, FIG. 3 is a flowchart of a fixing operation, and FIG. FIG. 5 is a schematic sectional view showing a schematic structure of a tandem type color printer as an example, and FIG. 5 is a schematic sectional view showing a schematic structure of an image forming section of the printer.
[0017]
In the printer 1 of FIG. 4, either full-color image output or monochrome image output is selected according to the color information of the document image data from the external computer. The image output speed is set to 20 sheets / minute in A4 size in both full color and monochrome. In this specification, specific numerical values such as dimensions, ratios, speeds, voltages, and temperatures appear in addition to the image output speed, but these numerical values are examples of one preferred example.
[0018]
A paper transport belt 8 is disposed inside the housing 2 of the printer 1. The paper transport belt 8 is wound around pulleys 10 and 11, and transports the paper horizontally from right to left in FIG. On the paper receiving side of the paper transport belt 8, a paper feed device 12 and a paper transport path 13 are arranged. A fixing device 50, a sheet conveyance path 15, and a discharge unit 16 are disposed on the sheet discharge side of the sheet conveyance belt 8. The discharge section 16 is provided on the upper surface of the housing 2.
[0019]
A total of four image forming units are arranged in series on the paper transport belt 8 from the upstream side to the downstream side in the paper transport direction. The four image forming units are, in order from the upstream side, a magenta image forming unit 30M, a cyan image forming unit 30C, a yellow image forming unit 30Y, and a black image forming unit 30B.
[0020]
FIG. 5 shows the structure of the image forming units 30M, 30C, 30Y, and 30B. Since the image forming units have the same structure, the identification symbols “M”, “C”, “Y”, and “B” are omitted, and only the reference numeral “30” is provided.
[0021]
The core of the image forming unit 30 is a photosensitive drum 4 using amorphous silicon as a photosensitive member, around which a main charger 5, an LED print head unit 6, a developing device 3, and a cleaning device 20 are arranged. I have. Further, as shown in FIG. 4, the transfer roller 9 faces the photosensitive drum 4 with the sheet conveyance belt 8 interposed therebetween. The transfer roller 9 also has a role of supporting the sheet conveying belt 8 and bringing it into contact with the photosensitive drum 4. A voltage of -1.5 kV is applied to the transfer roller 9.
[0022]
The developing device 3 contains a toner in which toners of each color of magenta, cyan, yellow, and black and a ferrite carrier are mixed at a weight ratio of 5:95. The toner has a median diameter (by volume) of 9 μm as measured by a Coulter counter, and the ferrite carrier has an average particle diameter of 70 μm. The developing device 3 is provided with a developing sleeve 3a containing a fixed magnet (not shown).
[0023]
The photoreceptor drum 4 and the developing sleeve 3a face each other with a gap of 0.5 mm therebetween, and rotate so that the opposing surfaces move in the same direction. The peripheral speed of the photosensitive drum 4 is 100 mm / sec, and the peripheral speed of the developing sleeve 3a is 200 mm / sec. A magnetic brush is formed on the surface of the developing sleeve 3a by toner. Further, the toner is positively charged by friction with the carrier. An uncut plate (not shown) is provided for the developing sleeve 3a. The gap between the cutting board and the developing sleeve 3a is 0.5 mm. A developing bias voltage of +300 V is applied to the developing sleeve 3a.
[0024]
The toner in the developing device 3 is consumed by the development. In order to supplement the consumed toner, toner supply containers 7B, 7Y, 7C, and 7M are provided corresponding to the image forming units 30B, 30Y, 30C, and 30M, and toner is replenished by conveyance means (not shown). Thus, the developing device 3 always holds an appropriate amount of toner inside.
[0025]
The cleaning device 20 includes a rubber cleaning roller 21 that contacts the photosensitive drum 4, a cleaning blade 22 that scrapes toner not transferred onto the paper from the photosensitive drum 4, and a discharge spiral 23 that discharges the toner to a collection container (not shown). Having. The cover of the cleaning device 20 is not shown in FIG.
[0026]
The printer 1 performs an image output operation as follows.
[0027]
The surface of the photosensitive drum 4 is uniformly charged to +400 V by the main charger 5. When document image data is input from an external computer or the like, the LED print head 6 irradiates the surface of the photosensitive drum 4 with LED light corresponding to the document image data. On the surface of the photosensitive drum 4, the voltage of the exposed portion irradiated with the LED light is attenuated to +25 V, and an electrostatic latent image is formed together with the +400 V portion of the non-exposed portion. With the developing bias voltage of +300 V applied to the developing sleeve 3a, the positively charged toner in the toner adheres to the exposed portion, and the electrostatic latent image is visualized by the toner.
[0028]
The paper transport belt 8 carries the paper supplied from the paper feeding device 12 and travels in the same direction as the moving direction of the surface of the photosensitive drum 4 at the same peripheral speed of the photosensitive drum 4 at 100 mm / sec. The exposure timing of the photosensitive drum 4 by the LED print head 6 is set so that the transfer of the toner is started from a predetermined position on the sheet.
[0029]
When the paper on the paper transport belt 8 passes under the photosensitive drum 4, the toner attached to the photosensitive drum 4 is attracted to the paper by the voltage of -1.5 KV applied to the transfer roller 9. As a result, the toner is transferred to the paper.
[0030]
The toner not transferred to the paper is scraped off by the cleaning blade 22 and discharged to a collection container (not shown) by the discharge spiral 23. The cleaning roller 21 adjusts the surface of the photosensitive drum 4 after the toner transfer.
[0031]
Magenta, cyan, yellow, and black toners are sequentially transferred by the image forming units 30M, 30C, 30Y, and 30B, and the paper on which a color image has been formed by the unfixed toner exits the paper transport belt 8 and is fixed. It is drawn into the device 50. Then, after the toner is fixed by the fixing roller inside the fixing device 50, the toner is discharged to the discharge unit 16 via the paper conveyance path 15.
[0032]
Next, the structure of the fixing device 50 will be described with reference to FIGS.
[0033]
The fixing device 50 includes a fixing member and a pressure member. In this embodiment, the fixing roller 51 forms a fixing member, and the pressing roller 52 forms a pressing member. The fixing roller 51 and the pressure roller 52 are pressed against each other with a predetermined pressure to form a fixing nip having a predetermined width. The paper P carrying the unfixed toner T passes through the fixing nip.
[0034]
The fixing roller 51 is driven to rotate by a driving device (not shown). The pressure roller 52 rotates according to the fixing roller 51. The number of rotations of the fixing roller 51 is controlled such that the peripheral speed of the fixing roller 51 and the pressing roller 52 becomes 100 mm / sec, which is the same as the traveling speed of the sheet conveying belt 8.
[0035]
As shown in FIG. 2, the fixing roller 51 is provided with a silicon rubber layer 56 on the surface of an aluminum tube 55, and further has an RFA (tetrafluoroethylene-per-fluoroalkylvinyl ether copolymer) or PTFE (polytetrafluoroethylene) on the surface. (Ethylene) A release layer 57 is formed by covering a tube or applying a coating to improve smoothness and toner releasability. Inside the fixing roller 51, a halogen lamp 53 as a heat source is arranged.
[0036]
The pressure roller 52 has the same structure as the fixing roller 51, and has a halogen lamp 54 as a heat source disposed therein.
[0037]
The cleaning web 60 contacts the surface of the fixing roller 51. The cleaning web 60 is a 54 μm-thick non-woven fabric in which aramid fiber and polyethylene terephthalate (PET) fiber are mixed at a weight ratio of 3: 7, and is impregnated with silicone oil. The cleaning web 60 is paid out from a pay-out reel 61 and wound up on a take-up reel 62. The pressure roller 63 presses the cleaning web 60 between the pay-out reel 61 and the take-up reel 62 against the fixing roller 51 to form a web nip 64 having a width of about 4 mm.
[0038]
The web feed device 65 drives the take-up reel 62. The web feeder 65 rotates the take-up reel 62 by a predetermined angle using a solenoid (not shown) as a power source. The feed amount of the cleaning web 60 varies in proportion to the amount of the cleaning web 60 wound on the take-up reel 62, and the rotation of the take-up reel 62 is adjusted so that the average feed amount is 0.03 mm. Set the angle.
[0039]
A braking device (not shown) applies a brake to the payout reel 61 so that the cleaning web 60 does not slack between the payout reel 61 and the pressure roller 63. Therefore, the payout reel 61 does not rotate unless the cleaning web 60 is pulled.
[0040]
Next, the fixing operation will be described with reference to the flowchart of FIG.
[0041]
The driving of the fixing roller 51 is started with the start of printing, and the fixing roller 51 and the pressure roller 52 rotate in the directions of arrows in FIG. Further, the energization of the halogen lamps 53 and 54 is started, and the fixing device 50 enters a warm-up phase (step # 101).
[0042]
After the completion of the warm-up, the paper P to which magenta, cyan, yellow, and black toners are sequentially transferred in the image forming units 30M, 30C, 30Y, and 30B passes through the fixing nip. After the toner T is fixed on the sheet P by heat and pressure, the surface of the fixing roller 51 is cleaned by the cleaning web 60. The web feeder 65 gives a fine feed of an average feed amount of 0.03 mm to the cleaning web 60 for each sheet passing (step # 102). When the size of the sheet P is large, which corresponds to a so-called double count size, two minute feeds are given for each sheet passing.
[0043]
In step # 103, the number of continuous sheets is counted. In step # 104, the remaining number of sheets continuously fed is checked. If paper P to be passed remains, the process returns to step # 102 and the operation is repeated. When the last sheet P has passed and the number of remaining sheets has reached zero, the process proceeds to step # 105.
[0044]
In step # 105, it is checked whether or not the number of continuous paper passes is 11 or more. If it is not 11 or more, that is, up to 10, the process proceeds to step # 109.
In step # 109, the driving of the fixing device roller 51 is stopped, the energization of the halogen lamps 53 and 54 is also stopped, and the fixing operation ends. If the number of continuous paper passes is 11 or more, the process proceeds to step # 106.
[0045]
In step # 106, it is checked whether or not the number of continuous paper passes is 51 or more. If it is not 51 or more, that is, if there are 11 to 50 sheets, the process proceeds to step # 107. In step # 107, the web feeder 65 gives the cleaning web 60 an additional feed of 0.15 mm. Even after the last sheet P has passed, the fixing roller 51 rotates several times until the fixing roller 51 completely stops moving. During this rotation period, the additionally fed unused portion of 0.15 mm absorbs the staying toner, so that the toner staying in the web nip 64 passes through the web nip 64 and adheres to the succeeding paper P, causing an offset. It does not develop into such a situation. After step # 107, the process proceeds to step # 109, and the fixing operation ends.
[0046]
If the number of continuous paper passes is 51 or more in step # 106, the flow proceeds to step # 108. In step # 108, the web feeder 65 gives the cleaning web 60 an additional feed of 0.3 mm. Even after the last sheet P has passed, the fixing roller 51 rotates several times until the fixing roller 51 completely stops moving. During this rotation, the 0.3 mm unused portion additionally fed absorbs the staying toner, so that the toner staying in the web nip 64 slips through the web nip 64 and adheres to the succeeding paper P, causing an offset. It does not develop into such a situation. After step # 108, the process proceeds to step # 109, and the fixing operation ends.
[0047]
Although the embodiments of the present invention have been described above, other various modifications can be made without departing from the gist of the present invention.
[0048]
【The invention's effect】
According to the present invention, when a predetermined number or more of continuous sheets are passed, the web feeder sends a predetermined amount of the cleaning web to the cleaning web after the last sheet is passed and before the fixing member stops moving. Since additional feed is provided, even if many sheets with a high image ratio are continuously passed and toner is accumulated in the web nip, the unused portion of the cleaning web that has faced the toner by additional feed is removed from the web. Absorbs toner remaining in the nip. Therefore, the situation where the staying toner slips through the web nip and adheres to the succeeding paper and causes an offset does not develop. Further, since the additional feeding of the cleaning web is performed only when necessary, the consumption of the cleaning web does not increase unnecessarily, and the entire usage period of the image forming apparatus can be covered with the cleaning web having a conventionally used amount. It is possible. Since such a fixing device is mounted on the image forming apparatus, high quality prints and copies without toner offset can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a schematic structure of a fixing device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of a roller constituting the fixing device cut along a plane including an axis. FIG. FIG. 4 is a schematic sectional view showing a schematic structure of a tandem type color printer. FIG. 5 is a schematic sectional view showing a schematic structure of an image forming unit of the printer of FIG.
Reference Signs List 1 printer 2 housing 8 paper transport belt 9 transfer roller 12 paper feeder 13, 15 paper transport path 16 discharge unit 30M, 30C, 30Y, 30B image forming unit 50 fixing unit 51 fixing roller 52 pressure roller 53, 54 halogen lamp 60 Cleaning web 61 Feeding reel 62 Take-up reel 63 Pressure roller 64 Web nip 65 Web feeder P Paper T Toner

Claims (3)

Fixing device with the following configuration:
(A) a fixing member that contacts the surface of the sheet on which the toner image has been transferred and fixes the toner on the sheet; (b) a cleaning web that contacts the fixing member; and (c) a cleaning web that contacts the fixing member. In addition to providing a fixed amount of feeding, when a predetermined number or more of continuous sheets are passed, a predetermined amount of paper is added to the cleaning web after the last sheet is passed and before the fixing member stops moving. Web feeder to give feed. The fixing device according to claim 1, wherein a feed amount of the additional feed changes in a stepwise manner according to the number of sheets continuously fed. An image forming apparatus comprising the fixing device according to claim 1.

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