JP4024176B2 - Fixing apparatus and image forming apparatus equipped with the same - Google Patents

Description

[0001]
BACKGROUND 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. The present invention also relates to an image forming apparatus equipped with this 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 paper onto which the toner has been 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 is in direct contact with the toner, a release layer for preventing adhesion of the toner is provided on the surface thereof. However, no matter how high the performance of the release layer, it is difficult to avoid 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 off from the surface of the fixing member by the cleaning web. Patent Documents 1, 2, and 3 show examples of fixing devices that clean 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 [0004]
[Problems to be solved by the invention]
In any of the fixing devices described in the above patent documents, no special consideration is given to a problem that occurs when re-driving after continuous paper feeding.
[0005]
The problems that occur when re-driving after continuous paper feeding are as follows. That is, the feeding amount per one time is set to be very small so that the cleaning web can be used over the entire use period of the image forming apparatus without being replaced. For this reason, if a number of sheets with 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. Toner that cannot be collected accumulates. While the fixing roller is continuously driven, the staying toner prevents the toner from slipping through.However, when the driving of the fixing roller is stopped and then restarted, the staying toner passes through the web nip and adheres to the paper. This causes a so-called “offset”.
[0006]
In the fixing device described in Patent Document 1, the rotation amount or the rotation time of the winding shaft for winding the cleaning web is controlled according to the total number of sheets to be passed. No countermeasure is taken when toner concentrates on the nip portion of the cleaning web by continuous paper feeding.
[0007]
In the fixing device described in Patent Document 2, in addition to the normal web winding performed for each sheet, a special web winding is performed to recover a large amount of toner adhered to the fixing member when recovering after the jam processing. is doing. However, the problem of toner concentration at the nip portion of the cleaning web due to normal continuous paper feeding cannot be dealt with.
[0008]
In the fixing device described in Patent Document 3, the degree of dirt on the cleaning web is estimated, and the web is wound only when the degree of dirt on the web exceeds a certain value. However, whether continuous paper is passed is not listed as a factor for estimating the degree of contamination.
[0009]
In order to prevent toner offset, the feed amount per cleaning web may be increased. However, if this is done, the consumption rate of the cleaning web will increase, and it will be difficult to use the cleaning web for the entire period of use without replacing the cleaning web. If it is intended to extend the period of use by increasing the length of the cleaning web, the roll diameter of the cleaning web will increase and it will be 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 prevent mischief when toner stays in the web nip by continuous paper passing in a fixing device that cleans the surface of a fixing member with a cleaning web. In addition, the remaining toner is surely removed without increasing the consumption amount of the cleaning web and is not offset on the subsequent 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, according to the present invention, a fixing device contacts a surface of a sheet on which a toner image is transferred to fix the toner on the sheet, a cleaning web that contacts the fixing member , The reel for feeding the cleaning web, the take-up reel for taking up the cleaning web , and controlling the take-up reel so as to take up the first predetermined amount of the cleaning web for each sheet passing, and continuously If the predetermined number of sheets have been continuously passed after counting the number of sheets to be passed and the last sheet has been passed , the cleaning web is removed before the fixing member stops moving. And a web feeding device that controls the take-up reel so as to take up the second predetermined amount.
[0012]
According to this configuration, even if a number of sheets having a high image ratio are continuously passed and toner is accumulated in the web nip, the cleaning web is added to the first predetermined amount and the second predetermined amount is wound up. The unused portion of the cleaning web faces the accumulated toner, and the toner is absorbed by this unused portion. Therefore, the toner staying in the web nip passes through the web nip and adheres to the succeeding paper, which does not cause an offset. In addition, since the cleaning web is added to the first predetermined amount and the second predetermined amount is wound only when necessary, the consumption amount of the cleaning web does not increase unnecessarily. It is possible to cover the entire use period of the image forming apparatus with the cleaning web.
[0013]
(2) In the fixing device as described above, the second predetermined amount is changed stepwise according to the number of continuous sheets.
[0014]
According to this configuration, if the number of continuous sheets is large, the unused portion of the cleaning web is pulled out accordingly, and the toner is reliably absorbed.
[0015]
(3) Further, in the present invention, since the fixing device is mounted on the image forming apparatus, it is possible to obtain a high-quality print or copy without toner offset.
[0016]
DETAILED DESCRIPTION OF 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 a 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 cross-sectional view showing a schematic structure of an image forming unit of the printer, and FIG. 5 is a schematic cross-sectional view showing a schematic structure of a tandem color printer as an example.
[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 20 sheets / minute in A4 size for both full color and monochrome. In addition to specific image output speeds, specific numerical values such as dimensions, ratios, speeds, voltages, temperatures, and the like appear in this specification. These numerical values are examples of a preferred example.
[0018]
A paper conveying 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. A sheet feeding device 12 and a sheet conveying path 13 are disposed on the sheet receiving side of the sheet conveying belt 8. A fixing device 50, a paper transport path 15, and a discharge unit 16 are disposed on the paper discharge side of the paper transport belt 8. The discharge part 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 sheet conveying belt 8 from the upstream side to the downstream side in the sheet conveying 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]
The structure of the image forming units 30M, 30C, 30Y, and 30B is shown in FIG. Since each image forming unit has the same structure, the identification symbols “M”, “C”, “Y”, and “B” are omitted, and only the symbol “30” is placed.
[0021]
The core of the image forming unit 30 is a photosensitive drum 4 using amorphous silicon as a photosensitive member, and a main charger 5, an LED print head unit 6, a developing device 3, and a cleaning device 20 are arranged around the photosensitive drum 4. Yes. Further, as shown in FIG. 4, the transfer roller 9 faces the photosensitive drum 4 with the sheet conveying belt 8 interposed therebetween. The transfer roller 9 supports the paper conveyance belt 8 and also plays a role of contacting the photosensitive drum 4. A voltage of −1.5 kV is applied to the transfer roller 9.
[0022]
The developing device 3 accommodates toner obtained by mixing toners of magenta, cyan, yellow, and black and a ferrite carrier at a weight ratio of 5:95. The toner has a median diameter (volume basis) of 9 μm 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 incorporating a fixed magnet (not shown).
[0023]
The photosensitive drum 4 and the developing sleeve 3a face each other with a gap of 0.5 mm, and the opposing surfaces rotate in a direction in which they 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 with toner. The toner is positively charged by friction with the carrier. A cutting plate (not shown) is provided for the developing sleeve 3a. The gap between the spike plate 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 the toner is replenished by a conveyance unit (not shown). As a result, 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 off the toner that has not been transferred to the sheet from the photosensitive drum 4, and a discharge spiral 23 that discharges the toner to a collection container (not shown). Have Note that 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 + 25V, and an electrostatic latent image is formed together with the + 400V portion of the non-exposed portion. By 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 with 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 movement direction of the surface of the photosensitive drum 4 at the same peripheral speed of the photosensitive drum 4 as 100 mm / sec. The exposure timing of the photosensitive drum 4 by the LED print head 6 is set so that toner transfer starts from a predetermined position on the paper.
[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. Thereby, the toner is transferred to the paper.
[0030]
The toner that has not been transferred to the paper is scraped off by the cleaning blade 22 and discharged to a collection container (not shown) by a discharge spiral 23. The cleaning roller 21 prepares the surface of the photosensitive drum 4 after the toner transfer.
[0031]
The magenta, cyan, yellow, and black toners are sequentially transferred by the image forming units 30M, 30C, 30Y, and 30B, and the sheet on which the color image is formed with the toner that has not been fixed is discharged from the sheet conveying belt 8 and fixed. Pulled into device 50. Then, after the toner is fixed by the fixing roller inside the fixing device 50, the toner is discharged to the discharge portion 16 through 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 constitutes a fixing member, and the pressure roller 52 constitutes a pressure member. The fixing roller 51 and the pressure roller 52 are brought into pressure contact with each other with a predetermined pressure to form a fixing nip having a predetermined width. The sheet 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 so that the peripheral speeds of the fixing roller 51 and the pressure roller 52 are 100 mm / sec, which is the same as the traveling speed of the paper 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 RFA (tetrafluoroethylene-per-fluoroalkyl vinyl ether copolymer) or PTFE (polytetrafluoroethylene) on the surface. The release layer 57 is formed by covering an ethylene) tube or coating, thereby improving smoothness and toner release properties. 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 that of the fixing roller 51, and a halogen lamp 54 as a heat source is disposed inside.
[0037]
The cleaning web 60 contacts the surface of the fixing roller 51. The cleaning web 60 is a 54 μm thick nonwoven fabric in which aramid fibers and polyethylene terephthalate (PET) fibers are mixed at a weight ratio of 3: 7 and impregnated with silicone oil. The cleaning web 60 is fed out from the feed reel 61 and taken up on the take-up reel 62. When the pressure roller 63 presses the cleaning web 60 between the supply reel 61 and the take-up reel 62 against the fixing roller 51, a web nip 64 having a width of about 4 mm is formed.
[0038]
The web feeding device 65 drives the take-up reel 62. The web feeding device 65 applies rotation of a predetermined angle unit to the take-up reel 62 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 around the take-up reel 62. The rotation of the take-up reel 62 so that the average feed amount is 0.03 mm. Set the angle.
[0039]
A brake device (not shown) brakes the supply reel 61 so that the cleaning web 60 does not sag between the supply reel 61 and the pressure roller 63. Therefore, the supply 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 direction of the arrow in FIG. 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 warm-up is completed, the paper P on which the magenta, cyan, yellow, and black toners are sequentially transferred by the image forming units 30M, 30C, 30Y, and 30B passes through the fixing nip. After fixing the toner T onto the paper P by heat and pressure, the surface of the fixing roller 51 is cleaned by the cleaning web 60. The web feed device 65 gives a fine feed with an average feed amount of 0.03 mm to the cleaning web 60 for each sheet (step # 102). When the size of the paper P is large and corresponds to a so-called double count size, a minute feed of two times is given for each sheet.
[0043]
In step # 103, the number of continuous sheets is counted. In step # 104, the remaining number of continuous sheets 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 is passed and the remaining number of sheets is zero, the process proceeds to step # 105.
[0044]
In step # 105, it is checked whether the number of continuous sheets is 11 or more. If it is not 11 sheets or more, that is, up to 10 sheets, 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 is finished. If the number of continuous sheets is 11 or more, the process proceeds to step # 106.
[0045]
In step # 106, it is checked whether the number of continuous sheets is 51 or more. If the number is not 51 or more, that is, 11 to 50, the process proceeds to step # 107. In step # 107, the web feeding device 65 gives an additional feed of 0.15 mm to the cleaning web 60. Even after the last sheet P is passed, the fixing roller 51 rotates several times until the fixing roller 51 stops moving completely. During this rotation period, the additionally fed 0.15 mm unused portion absorbs the remaining toner, so that the toner staying in the web nip 64 passes through the web nip 64 and adheres to the subsequent 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 sheets is 51 or more in step # 106, the process proceeds to step # 108. In step # 108, the web feeding device 65 gives an additional feed of 0.3 mm to the cleaning web 60. Even after the last sheet P is passed, the fixing roller 51 rotates several times until the fixing roller 51 stops moving completely. During this rotation period, the additionally fed 0.3 mm unused portion absorbs the remaining toner, so that the toner staying in the web nip 64 passes through the web nip 64 and adheres to the subsequent 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, various modifications can be made without departing from the spirit of the invention.
[0048]
【The invention's effect】
According to the present invention, when a predetermined number of sheets or more are continuously passed, the web feeding device removes the cleaning web from the second place after the last sheet passes and before the fixing member stops moving. Since a certain amount of additional winding is performed , even if a number of sheets with a high image ratio are continuously fed and toner remains in the web nip, the cleaning web that has been facing the toner due to the additional feed has not been removed. The used part absorbs the toner staying in the web nip. Therefore, it does not develop into a situation in which the staying toner passes through the web nip and adheres to the succeeding paper and causes an offset. Further, since the cleaning web is added to the first predetermined amount and the second predetermined amount is wound up only when necessary, the consumption amount of the cleaning web does not increase unnecessarily, and is an amount that has been used conventionally. It is possible to cover the entire use period of the image forming apparatus with this cleaning web. Since such a fixing device is mounted on the image forming apparatus, it is possible to obtain a high-quality print or copy without toner offset.
[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. 4 is a schematic cross-sectional view showing a schematic structure of a tandem color printer. FIG. 5 is a schematic cross-sectional view showing a schematic structure of an image forming unit of the printer shown in FIG.
DESCRIPTION OF SYMBOLS 1 Printer 2 Housing 8 Paper conveyance belt 9 Transfer roller 12 Paper feeder 13, 15 Paper conveyance path 16 Discharge part 30M, 30C, 30Y, 30B Image formation part 50 Fixing part 51 Fixing roller 52 Pressure roller 53, 54 Halogen lamp 60 Cleaning web 61 Feed reel 62 Take-up reel 63 Pressure roller 64 Web nip 65 Web feeding device P Paper T Toner

Claims (3)

Fixing device with the following configuration:
(A) a fixing member that contacts the surface of the paper on which the toner image is transferred and fixes the toner on the paper; (b) a cleaning web that contacts the fixing member ; a feed reel that feeds the cleaning web; The take-up reel (c) controls the take-up reel to take up the first predetermined amount of the cleaning web for each pass of the take-up reel (c) paper , counts the number of continuous pass-through sheets, If a predetermined number of sheets have been continuously passed after passing, the take-up reel is wound so that the cleaning web is taken up by a second predetermined amount before the fixing member stops moving. Web feeder to control . 2. The fixing device according to claim 1, wherein the second predetermined amount changes stepwise according to the number of continuous sheets.   An image forming apparatus comprising the fixing device according to claim 1.

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