JP2007183684A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which achieves excellent cleaning performance in accordance with the state of damage to a transfer belt, then, prevents the turn-up of a blade and the back surface staining of paper over a long term, and consequently achieves the prolongation of the life of the transfer belt. <P>SOLUTION: A copying machine 1 has a photoreceptor drum 2 carrying a toner image based on an image signal. An exposure device 40 forming a line image for supplying toner functioning as lubricant to the transfer belt 12 is disposed around the photoreceptor drum 2. The line image is formed on the conveying surface of the belt 12 during the initializing operation of the copying machine and in timing between paper and paper when making a predetermined number of sheets of paper pass, and scraped by a cleaning blade 19. The number of sheets of paper made to pass on the transfer belt 12 is counted to adjust toner amount supplied as the line image to be smaller gradually as the number of sheets of passing paper becomes larger. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that supplies a developer to an electrostatic latent image formed on an image carrier and develops the image, transfers the developer image onto a transfer medium, and outputs an image. The present invention relates to an image forming apparatus that holds a transfer medium on an endless transfer belt and supplies the medium to a developer image.

  Conventionally, as an image forming apparatus, a peripheral surface of a photosensitive drum charged to a predetermined potential is exposed by a laser energized according to a digitally converted image signal, and an electrostatic latent image is formed on the peripheral surface of the drum. There is known a digital copying machine that forms, supplies a developer to the electrostatic latent image, develops it, transfers the developer image onto a sheet as a transfer medium, and outputs the image. The sheet onto which the developer image is transferred is, for example, electrostatically adsorbed and held on a transfer belt that is run endlessly in a state of rolling contact with the circumferential surface of the photosensitive drum, and between the drum circumferential surface and the sheet. Supplied to the transfer area.

  In this case, on the sheet conveying surface of the transfer belt, a cleaning blade for scraping off foreign matters such as paper dust generated when the sheet is conveyed is disposed in contact therewith. The cleaning blade is formed of a rubber material such as urethane rubber in a plate shape, and one end thereof is pressed against the transfer surface of the transfer belt with a predetermined pressure. Accordingly, when the paper dust adhered on the transfer belt conveyance surface passes between the cleaning blade, the paper dust is scraped off by the cleaning blade, and the transfer belt conveyance surface is cleaned.

  As described above, when the paper dust is scraped off by the cleaning blade pressed against the transfer belt, when the paper dust attached on the transfer surface of the transfer belt passes between the end portions of the cleaning blade, As a result, paper dust is caught on the transfer belt and the conveying surface of the transfer belt is damaged. Since the paper dust contains relatively hard particles such as calcium carbonate, as the number of conveyed sheets increases, the scratches on the conveying surface become severe.

If the transfer belt is scratched on the conveyance surface, residual toner enters the portion and the cleaning performance is deteriorated, resulting in contamination of the back side of the paper or printing surface during double-sided printing. Furthermore, if the transport surface is severely damaged and the coat layer covering the transfer belt transport surface is damaged, the rubber layer under the coat layer is exposed and the coefficient of friction with the cleaning blade increases. As a result, serious problems such as turning over the blade occur.
JP-A-9-258627

    The present invention has been made in view of the above points, and the purpose thereof is to achieve a good cleaning performance according to the degree of pain of the transfer belt, and to prevent blade turnover and paper stains over a long period of time. An object of the present invention is to provide an image forming apparatus capable of extending the service life of a transfer belt.

  In order to achieve the above object, an image forming apparatus according to claim 1 of the present invention comprises an image forming means for forming an image by a developer on an image carrier, and a developer image formed by the image forming means. A medium supply means for supplying a transfer medium for transferring the image and a conveyance surface that travels along the image carrier, and the transfer medium supplied via the medium supply means is placed on the conveyance surface. Held by the image forming means and conveyed to the developer image formed on the image carrier by the image forming means, and held by the conveying means on the conveying surface. A transfer unit that transfers the developer image formed on the image carrier on the transfer medium by the image forming unit; and a cleaning member that is disposed in contact with the transfer surface. The developer adhered undesirably to the surface is scraped off by the cleaning member to A cleaning means for sweeping, a lubricant supply means for supplying a lubricant onto the transport surface before being cleaned by the cleaning means at a predetermined timing when the image forming operation is not executed, and a medium supply means. Adjusting means for adjusting the amount of lubricant supplied by the lubricant supplying means in accordance with the number and type of transfer medium supplied onto the transport surface.

  According to a second aspect of the present invention, there is provided an image forming apparatus for transferring an image forming means for forming an image by a developer on an image carrier and a developer image formed by the image forming means. A medium supply unit that supplies a transfer medium; a conveyance surface that travels along the image carrier; and the transfer medium that is supplied via the medium supply unit is held on the conveyance surface; A transfer unit configured to transfer the transfer medium to a developer image formed on the image carrier by an image forming unit; and a transfer medium held on the transfer surface and transferred by the transfer unit. The image forming means has a transfer means for transferring the developer image formed on the image carrier and a cleaning member disposed in contact with the transport surface, and undesirably adheres to the transport surface. Cleaning means for scraping off the developed developer with the cleaning member and cleaning the conveying surface; Lubricant supply means for supplying a lubricant onto the transport surface before being cleaned by the cleaning means at a predetermined timing when no image forming operation is being performed, and the medium supply means on the transport surface. Adjusting means for adjusting the number of times the lubricant is supplied by the lubricant supplying means according to the number and type of the transfer medium to be supplied.

  According to a third aspect of the present invention, an image forming apparatus according to a third aspect of the present invention comprises an image forming means for forming an image by a developer on the surface of a photosensitive drum rotatably provided, and the image forming means on the drum surface A sheet feeding means for feeding a sheet for transferring the developer image formed thereon, and a belt that runs endlessly along the drum surface in a direction substantially perpendicular to the axial direction of the photosensitive drum, The belt holds a sheet fed via the sheet feeding unit on a conveying surface opposed to the drum surface, and the sheet is transferred to the developer image formed on the drum surface by the image forming unit. A transfer unit that transfers the developer image formed on the drum surface by the image forming unit onto a sheet that is held on the transfer surface of the belt and transferred by the transfer unit. And extending in the axial direction on the conveying surface A cleaning blade that is disposed in contact and scrapes off the developer or paper dust that is undesirably adhered onto the transport surface to clean the transport surface, and the cleaning at a predetermined timing when no image forming operation is performed. Lubricant supply means for supplying a lubricant onto the transport surface before being cleaned by a blade, and the lubrication according to the number and type of sheets fed onto the transport surface by the paper feed means. Adjusting means for adjusting the amount of lubricant supplied by the agent supply means.

  According to a fourth aspect of the present invention, there is provided an image forming apparatus for transferring an image forming means for forming an image by a developer on an image carrier and a developer image formed by the image forming means. A medium supply means for supplying a transfer medium, a medium detection means for detecting the size of the transfer medium supplied by the medium supply means, and the number of sheets for each size, and the image carrier. A transfer medium having a transfer surface and supplied via the medium supply unit is held on the transfer surface, and transferred to the developer image formed on the image carrier by the image forming unit. The developer image formed on the image carrier is transferred by the image forming unit onto the transfer unit that transfers the medium and the transfer medium that is held and transferred on the transfer surface by the transfer unit. A transfer means and a cleaning member disposed in contact with the conveying surface; The cleaning unit scrapes off the developer adhering undesirably onto the conveying surface with the cleaning member to clean the conveying surface, and the cleaning unit at a predetermined timing when the image forming operation is not performed. Lubricant supply means for supplying a lubricant onto the transport surface before cleaning, and the transport by the lubricant supply means according to the number of transfer mediums detected by the medium detection means for each size. Adjusting means for changing a supply amount of the lubricant supplied on the surface along a direction crossing the conveying direction of the conveying surface.

  According to a fifth aspect of the present invention, an image forming apparatus according to a fifth aspect of the present invention comprises an image forming means for forming an image by a developer on the surface of a photosensitive drum rotatably provided, and the image forming means on the drum surface. A sheet feeding unit that feeds a sheet for transferring a developer image formed on the sheet; a sheet detection unit that detects a size of a sheet fed through the sheet feeding unit and a number of sheets fed for each size; And a belt that runs endlessly along the surface of the drum in a direction substantially orthogonal to the axial direction of the photosensitive drum, and the belt is placed on a conveying surface that faces the drum surface. The sheet fed through the conveying means for conveying the sheet to the developer image formed on the drum surface by the image forming means, and on the conveying surface of the belt by the conveying means. The image forming means on the held and conveyed paper Transfer means for transferring the developer image formed on the drum surface, and a developer that is arranged in the axial direction and is in contact with the transport surface, and is undesirably attached to the transport surface. And a cleaning blade for scraping off the paper dust to clean the transport surface, and on the transport surface before being cleaned by the cleaning blade at a predetermined timing when the image forming operation is not performed. Lubricant supply means for supplying an extended belt-like lubricant, and supply on the transport surface by the lubricant supply means in accordance with the number of sheets fed for each size of the paper detected by the paper detection means. Adjusting means for changing the supply amount of the lubricant along the axial direction.

  As described above, since the image forming apparatus of the present invention has the above-described configuration and operation, it is possible to achieve a good cleaning performance corresponding to the degree of pain of the transfer belt and to turn the blade over a long period of time. And the backside of paper can be prevented, and the service life of the transfer belt can be extended.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a schematic configuration of a digital copying machine (hereinafter simply referred to as a copying machine) 1 as an image forming apparatus of the present invention. The copying machine 1 has a photosensitive drum 2 as an image carrier that is rotatably arranged in the direction of arrow a in the figure.

  Around the photosensitive drum 2, there is a charging charger 3 for charging the drum surface to a predetermined potential (in this case, a negative potential of -500 to -800V), and the drum surface charged to the predetermined potential is exposed to the drum surface. An exposure device 4 that forms an electrostatic latent image thereon, a developing device that develops the electrostatic latent image by supplying negatively charged toner (developer) to the electrostatic latent image on the drum surface via a developing roller 5. A transfer bias of +300 to +5 KV is applied via a high-voltage power supply 10 to transfer a toner image (developer image) formed on the drum surface onto a sheet P fed from a sheet cassette described later. A power supply roller 6, a cleaning device 7 that cleans toner remaining on the drum surface without being transferred onto the paper P, and a static elimination lamp 8 that removes charge remaining on the drum surface in the rotational direction of the photosensitive drum 2. Arranged in order along That.

  The lower end of the photosensitive drum 2 is in contact with a transfer belt 12 that runs endlessly so as to convey the paper P as a transfer medium through a transfer region defined between the photosensitive drum 2 and the transfer roller 6. The transfer belt 12 is wound around a plurality of rollers and stretched, and a driving roller 11 positioned at the left end in the drawing is driven by a motor (not shown), whereby a predetermined speed, that is, the photosensitive drum 2 in the direction of arrow b in the drawing. It travels at the same speed as the peripheral speed. The power supply roller 6 is disposed inside the endless transfer belt 12, is brought into rolling contact with the drum surface via the transfer belt 12, and applies the transfer bias from the inside of the transfer belt 12.

The transfer belt 12 is formed of an elastic belt having a volume resistance of 10 ⁸ to 10 ¹² Ω · cm, and the power supply roller 6 is formed of a conductive elastic roller having a volume resistance of 10 ² to 10 ⁸ Ω · cm. Yes.

  A fixing device 14 is disposed via a conveyance guide 13 on the downstream side in the conveyance direction of the paper P from the driving roller 11, that is, on the left side of the driving roller 11 in the drawing. The fixing device 14 includes a heat roller 14a for heating the paper P to a predetermined temperature, and a press roller 14b that is pressed against the heat roller 14a with a predetermined pressure and sandwiches and conveys the paper P between the heat roller 14a. is doing. When the paper P is conveyed between the rollers 14a and 14b, the toner image on the paper P is heated to a predetermined temperature and melted, and the melted toner image is fixed on the paper P.

  In addition, toner or paper dust that is undesirably attached on the conveyance surface of the transfer belt 12 at a portion of the surface (conveyance surface) of the transfer belt 12 wound around the drive roller 11, that is, the lower end of the drive roller 11. A cleaning blade 19 (cleaning means) for scraping off the toner is abutted and arranged at a predetermined angle in a state of being pressed at a predetermined pressure. As the toner that undesirably adheres to the conveyance surface, toner generated when a paper jam occurs or a special paper size is used, or fog toner generated during a normal printing operation can be considered. The cleaning blade 19 is formed of an elastic rubber blade or the like.

  Below the transfer belt 12, a plurality of paper cassettes 15 and 16 that can be pulled out from the copying machine main body are arranged in a stacked state. Here, two sheet cassettes each accommodating a plurality of sheets of different sizes are illustrated. When the paper cassettes 15 and 16 are set in the main body of the copying machine 1, they are detected by a well-known cassette sensor (not shown) provided on the main body side of the copying machine, and the size of the paper P set in the copying machine 1 is determined. Acquired on the 1 side.

  Pickup rollers 17 and 18 for taking out the sheets P stored in the cassette one by one from the uppermost one are disposed at positions close to the right end of each sheet cassette 15 and 16. Further, a conveyance path 20 is formed between each cassette and the photosensitive drum 2 to guide the sheet P taken out by the pickup rollers 17 and 18 toward the photosensitive drum 2. The conveyance path 20 further extends through a transfer region defined between the photosensitive drum 2 and the power supply roller 6 and the fixing device 14. A plurality of pairs of paper feed rollers 24 for transporting the paper P taken out from the paper cassettes 15 and 16 are disposed on the transport path 20. When paper is taken out from each paper cassette, the number of sheets fed for each size is detected together with the paper size, and the size of the fed paper and the number of sheets fed for each size are acquired on the copier side. It has become.

  The copying machine 1 configured as described above is operated as follows.

  Prior to the operation, the transfer belt 12 and the photosensitive drum 2 are driven in a state where the transfer belt 12 is separated from the drum surface of the photosensitive drum 2, and when both reach the same speed, the transfer belt 12 is moved to the drum surface. Is transferred to.

  Then, the paper P taken out from the paper cassette 15 (or 16) containing the paper P of a desired size is transported through the transport path 20 and guided to the transfer area. At the same time, a transfer bias is applied via the power supply roller 6, and a toner image formed on the drum surface by a predetermined electrophotographic process (here, detailed description is omitted) is transferred onto the sheet P conveyed to the transfer region. Transcribed.

  The sheet P on which the toner image has been transferred is further conveyed by the transfer belt 12, peeled off from the transfer belt 12 by the curvature of the driving roller 11 and the sheet P, and passed between the heat roller 14a and the press roller 14b of the fixing device 14. The toner image is fixed on the paper P and the image is output.

  Toner and paper dust adhered to the transfer surface of the transfer belt 12 after the sheet P is peeled off are scraped off by the cleaning blade 19 disposed in contact with the downstream side in the transfer direction. The transfer belt 12 is formed by applying a fluorine-based resin to the transport surface thereof, and is in contact with the drum surface of the photosensitive drum 2 in a state where a predetermined tension is applied. Further, the cleaning blade 19 is always kept in sliding contact with the transfer belt 12.

  The amount of paper dust adhering to the conveyance surface of the transfer belt 12 is increased according to the conveyance amount of the paper P. For this reason, the paper dust attached on the transfer surface of the transfer belt 12 is caught between the tip of the cleaning blade 19 and the transfer belt 12, and the transfer surface of the transfer belt 12 is damaged. Therefore, when the new transfer belt 12 is used, the conveying surface can be cleaned well by the cleaning blade 19, but after passing several hundred kilograms of paper P, countless scratches are generated on the conveying surface. Since the toner enters the scratches, the cleaning surface 19 cannot be sufficiently cleaned by the cleaning blade 19.

  In order to eliminate such poor cleaning due to scratches on the conveying surface, a method of changing the contact condition of the cleaning blade 19 in accordance with the degree of pain of the transfer belt 12 can be considered. Specifically, as the degree of scratches on the conveyance surface, that is, the belt pain progresses, the contact angle of the cleaning blade 19 is increased or the contact pressure of the cleaning blade 19 is increased, whereby the pain of the conveyance surface is increased. Regardless of the degree, good cleaning performance can always be achieved.

  FIG. 2 is a table in which the contact condition of the cleaning blade 19, that is, the presence or absence of cleaning failure when the contact angle and the contact pressure are variously changed is examined for each number of sheets P (belt life). Is shown. In addition, the presence or absence of the cleaning failure is a region where the paper P on the conveyance surface of the transfer belt 12 will be held, that is, a paper passing portion, and a region where the paper P on the conveyance surface is not held, that is, a non-paper passing portion. I investigated each.

Here, a urethane cleaning blade with a hardness of 68 degrees and a Young's modulus of 59 kg / cm ² is used. Before passing paper P, after passing 100 kg, after passing 200 kg, and after passing 400 kg. On the conveying surface of the transfer belt 12 in each state after the paper, while forming a solid image of a predetermined size in a low-temperature and low-humidity environment, about 100 sheets of A4 size paper P are continuously passed, A test print was made for one sheet. In each case, the contact condition of the cleaning blade 19 was changed to examine whether or not a cleaning failure occurred. The cleaning failure was judged in each case by looking at the amount of toner attached to the tape when the tape was applied to the transfer surface of the transfer belt 12 and the tape was peeled off. The solid test image was a rectangular image having a width in the longitudinal direction of the A4 size paper P and a length of ¼ in a direction perpendicular to the longitudinal direction. As a matter of course, in the new (initial) transfer belt just replaced before passing the paper P, there was no difference between the paper passing portion and the non-paper passing portion.

  According to FIG. 2, the initial transfer belt has a wide margin for the contact condition of the cleaning blade 19, and good cleaning can be achieved even with a contact angle of about 14 ° and a contact pressure of about 1.8 to 2.2 kg / mm. You can see that it has been done. However, the margin of the contact angle and the contact pressure becomes narrower as the number of sheets to be passed increases. For example, after passing 400 kilograms of paper P, the cleaning blade 19 is moved particularly at the paper passing portion of the transfer belt 12. Only when the contact angle is set to 18 ° and the contact pressure is set to 3.2 to 3.5 kg / mm, the transfer surface of the transfer belt can be cleaned.

  That is, when the transfer belt 12 becomes more painful as the number of sheets to be passed increases, a good cleaning result cannot be obtained unless the contact angle of the cleaning blade 19 is increased to increase the contact pressure. Further, since the pain of the transfer belt 12 is more severe in the paper passing portion than in the non-paper passing portion, the margin of the contact condition is narrower in the paper passing portion.

  On the other hand, it is known that when the contact angle of the cleaning blade 19 is increased as the number of sheets to be passed increases, the blade is likely to be turned over.

  FIG. 3 shows a case where the transfer belt 12 is rotated for 10 minutes in a state where the cleaning blade 19 is in contact with the conveyance surface without transferring the toner onto the conveyance surface of the transfer belt 12 in a high temperature and humidity environment. The presence or absence of occurrence of blade turning is shown in a table. Here, the number of sheets P of the paper P (belt life), the contact angle of the cleaning blade 19 and the contact pressure are used as parameters, and in each case, each of the sheet passing portion and the non-sheet passing portion of the transfer belt. The presence or absence of blade turning was judged.

  According to this, for example, in the sheet passing portion of the transfer belt through which 400 kg of paper P is passed, even if the contact angle of the cleaning blade 19 is set to 18 °, the blade is not turned over at all contact pressures. I understand that. On the other hand, in the initial transfer belt, even if the contact angle of the blade is 16 °, the blade is turned over. That is, in the initial belt, if the cleaning blade 19 is not set to a contact angle as small as about 14 °, the belt is turned up.

  As described above, since the pain of the conveying surface has progressed particularly in the paper passing portion of the damaged transfer belt after passing several hundred kilograms of paper P, it is preferable that the contact angle of the cleaning blade 19 is not increased. On the other hand, since the initial transfer belt has no belt pain, the blade is turned up unless the contact angle of the cleaning blade 19 is reduced. In other words, when the contact angle of the cleaning blade 19 is increased in the initial setting, the blade is turned up in the initial state, and when the contact angle is decreased in the initial setting, the cleaning of the transport surface is caused after passing several hundred kilograms. End up.

  Therefore, as a method of solving the above-described problems, the contact angle of the cleaning blade 19 is increased in the initial setting to prevent the cleaning failure of the conveying surface after passing several hundred kilos of sheets, and then the initial belt In order to prevent the blade from turning up, a method of supplying a lubricant onto the conveying surface of the transfer belt 12 can be considered. In this embodiment, toner is used as the lubricant to be supplied onto the conveying surface of the transfer belt 12.

  However, in this method, it is effective to supply toner for lubrication onto the belt in the initial state. However, if toner is positively supplied onto the damaged belt after passing several hundred kilograms, good cleaning can be achieved. Will not be able to. Further, in this method, since the toner for lubrication is transferred onto the transfer belt and then the toner transferred by the cleaning blade 19 is scraped off, the amount of waste toner increases and the amount of toner consumption increases.

  Therefore, in the present embodiment, the contact angle of the cleaning blade 19 with respect to the transfer belt 12 is set to be relatively large, and a predetermined timing is provided on the conveyance surface of the transfer belt 12 so that the belt is not turned over by the initial belt. The toner as a lubricant is transferred with the toner so that the amount of toner transferred onto the conveying surface gradually decreases as the number of sheets of paper P increases, that is, according to the progress of scratches on the conveying surface. The supply amount of was adjusted.

  Specifically, the contact condition of the cleaning blade 19 is such that the belt passing portion of the belt after passing 400 kilo sheets can be satisfactorily cleaned (that is, in FIG. 2, the contact angle is 18 ° and the contact pressure is 3.2 to 3.5 kg / mm) on the transfer belt 12 conveying surface and in an area between the sheets at a predetermined timing with a belt-like belt made of toner along the axial direction of the drive roller 11 that crosses the conveying direction of the transfer belt 12. A line image was formed.

  In FIG. 4, the amount of toner transferred as a line image on the conveying surface of the transfer belt 12 and the presence / absence of blade turning when the belt life is used as a parameter were examined in each of the passing part and the non-passing part. The results are tabulated.

  According to this, every 1.0 kilogram of toner on the initial transfer belt, if about 1.0 g of toner is not transferred onto the belt, the blade will turn up, but the non-passage of the transfer belt after 100 kilograms has passed. It was found that if 0.75 g of toner was transferred onto the belt and 0.5 g of toner was transferred onto the belt, the belt would not be turned up. In addition, it is only necessary to transfer 0.25 g of toner onto the belt at the non-passage portion of the belt after passing 400 kilo sheets, and even if the toner for lubrication is not transferred onto the belt at the passage portion, the blade There was no turning.

  Therefore, in the present embodiment, a line image of toner of an amount corresponding to the belt life is conveyed on the transfer belt 12 at a predetermined timing using the copying machine 1 ′ having the configuration shown in FIG. It was made to form on the surface. The copying machine 1 ′ shown in FIG. 5 has the same configuration as the copying machine 1 of FIG. 1 except that an exposure device 40 for forming a line image is provided between the exposure device 4 and the developing device 5. Therefore, detailed description of the same parts is omitted. Here, the exposure device 40 for forming a line image is provided, but the exposure device 4 used for normal image formation may also be used. Hereinafter, an image forming operation by the copying machine 1 'will be described.

  As shown in FIG. 6, when a copy start signal is given to the copying machine 1 ′ (step 1), it is determined whether or not the transfer belt 12 set in the copying machine 1 ′ is new (step 2). . That is, at the time when the new transfer belt 12 is set (step 2; YES), the copying machine 1 ′ side resets the number of sheets that have been accumulated so far (step 3), and starts counting the number of sheets to be passed. (Step 4).

  Then, a line image is formed on the transfer belt 12 at the timing of the initialization operation of the copying machine 1 ′ and the timing between sheets when a predetermined number of sheets are passed. This line image forms an electrostatic latent image on the drum surface via the exposure device 40 based on the calculated supply toner amount (steps 5 and 6), and this electrostatic latent image is used to form a normal image. The image is developed together with the electrostatic latent image through the developing device 5, and the developed visible image is transferred onto the conveying surface of the transfer belt 12 (step 7).

  At this time, the toner amount T1 (g / kilo sheets) output as a line image on the transfer belt 12 is calculated based on the following equation.

T1 = 1-number of sheets (kilo) x 2/1000
However, T1> 0.25 (g / kg)
That is, with the initial belt (the number of sheets to be passed 0), the amount of toner formed as a line image is 1 g / kilogram. For example, with the transfer belt after passing over 375 kg of paper P, the amount of toner is It becomes constant at 0.25g / kg.

  Then, when it is determined that continuous printing is not performed (step 8; NO), the image forming operation is ended (step 9).

  As described above, the contact angle and contact pressure of the cleaning blade 19 are increased, and the amount of toner supplied onto the transfer belt 12 is adjusted to gradually decrease as the number of sheets passing increases. In addition to being able to achieve good cleaning performance in the initial transfer belt 12, good cleaning performance can also be achieved without causing blade turning even in a transfer belt after passing 400 kilo sheets.

  In the above-described embodiment, the belt life is determined by counting the number of sheets P to be passed. However, the toner supply amount may be adjusted by determining the belt life from the number of rotations of the transfer belt 12. good. Further, instead of adjusting the toner supply amount, the number of times of toner supply may be adjusted.

  Next, the degree of pain on the conveyance surface of the transfer belt 12 is determined for each of the paper passing portion where the paper P is held and the non-paper passing portion, so that the amount of toner supplied to the paper passing portion where the degree of pain is large is reduced. A second embodiment to be adjusted will be described. For example, in the example shown in FIG. 4, when the paper passing portion exceeds 200 kg, the blade is not turned even if the toner is not supplied, and the belt that passes 100 kg is not used. It is sufficient to supply 0.5 g / kg of toner. As described above, the toner supply amount can be adjusted more finely as compared with the first embodiment described above by making the toner supply amount different between the sheet passing portion and the non-sheet passing portion. It is possible to reduce the consumption of useless toner supplied onto the conveying surface, and to further reduce the probability of occurrence of poor cleaning of the transfer belt 12.

  Specifically, the size of the paper P fed on the transfer belt 12 is detected, and the number of sheets that pass for each size is counted. That is, since the size of the paper P set in the copying machine 1 is acquired from the output of a cassette sensor (not shown), the number of papers for each size is counted by counting the paper P taken out from each paper cassette. The At this time, the direction (vertical direction or horizontal direction) of the fed paper P is also detected at the same time. When the paper P is fed through a manual paper feeding unit (not shown), it is counted as the minimum size of the specification of the apparatus.

  Here, a case where three types of paper P of A3, A4, and A4R are randomly fed will be described. A3 size paper is fed along the longitudinal direction, A4 size paper is fed along the direction perpendicular to the longitudinal direction, and A4R size paper is fed along the longitudinal direction. The Therefore, the length of each size sheet along the sheet feeding direction is A3: A4: A4R = 2: 1: 1.4, and the width orthogonal to the sheet feeding direction is A3: A4: A4R = 1.4. : 1.4: 1.

  In this case, the degree of pain of the transfer belt 12 can be classified into the following three regions along the width direction orthogonal to the conveyance direction. That is, the A4R size paper having the smallest width among the three sizes is held on the transfer belt 12, and the A3 size paper and the A4 size paper are held outside the first region in the width direction. The second region is classified into the second region and the third region within the development width outside the second region in the width direction. Among these, in the third area where no paper of any size is passed, the toner amount is adjusted as in the first embodiment.

  On the other hand, in the first area among the above areas, sheets of all sizes including sheets manually fed are always passed. In the second area, only A3 size paper and A4 size paper are passed. That is, the first region of the transfer belt 12 is most painful, and the second region is then most painful. Therefore, the number of sheets passing through the first and second areas is counted separately to vary the amount of toner supplied to each area. At this time, since the length in the transport direction is different for each size of paper, conversion was performed assuming that two sheets of A3 size paper, one sheet of A4 size paper, and 1.4 sheets of A4R size paper were used.

  Next, with reference to the flowchart in FIG. 7, a method for counting the number of sheets to be passed for each size and a method for calculating the toner supply amount will be described. Here, except for the operations of step 4 and step 5, since it is substantially the same as the flowchart shown in FIG. 6, detailed description of the other steps will be omitted.

  The number of sheets to be passed is counted in each of the first and second areas described above. For example, when an A4 size sheet is passed, the first and second areas are passed by a length of one sheet, so the number of sheets passing through the first area is K2 + 1, and the second area is The number of passing sheets is K1 + 1. In the case of A3 size paper, K2 + 2 and K1 + 2 are obtained. In the case of A4R size, only the first area passes, so the number of sheets to be passed is K2 + 1.4. Note that the number of manually fed sheets is K2 + 1.

  Accordingly, the amount of toner Ta to Tc (g / kilo sheets) supplied to each region is calculated based on the following equation. The amount of toner supplied to the first region is Tc, the amount of toner supplied to the second region is Tb, and the amount of toner supplied to the third region is Ta.

Ta = 1−K2 × 2/1000 × (development width−A4 width) / development width Tb = 1−K1 × 5/1000 × (A4 width−A4R width) / development width Tc = 1−K2 × 5/1000 × A4R width / development width As described above, by adjusting the toner supply amount along the width direction of the belt according to the number of sheets to be passed for each size, finer adjustment than the first embodiment described above is possible. It becomes. Also in this embodiment, good cleaning performance could be achieved without causing belt turning in the belt after passing 400 kilo sheets.

  By the way, in the first and second embodiments described above, the toner line in which the supply amount is adjusted on the conveyance surface of the transfer belt 12 during the initialization operation of the copying machine and the timing between sheets when a predetermined number of sheets pass. In order to form an image, a transfer bias is applied in a state where the sheet P is not held on the transfer belt 12. When a transfer bias is applied while the sheet P is not held on the transfer belt 12, the drum surface potential is easily affected by the transfer bias, and a transfer memory is likely to be generated depending on the use environment. In order to prevent such a transfer memory, the transfer bias is made smaller than usual when a line image is formed on the transfer belt 12.

  FIG. 8 is a flowchart for explaining the operation of forming a line image while preventing the transfer memory described above.

  First, when a copy start signal is given (step 1), it is determined whether or not the transfer belt 12 is new (step 2). If a new transfer belt 12 has been set (step 2; YES), the counter for counting the belt life is reset (step 3). At this time, if the belt has not been exchanged (step 2; NO), only the copy number counter is reset (step 4).

  Then, counting of the number of sheets to be passed is started (step 5), and it is determined whether or not the number of copies has become an integral multiple of 100 (step 6). That is, for every 100 copies, the toner supply amount is calculated (step 7), and a line image based on the calculated toner amount is exposed (step 8).

  Then, after the photosensitive drum 2 is rotated by one rotation (step 9), an image to be copied is formed (step 10). When the copying operation is continued (step 11; YES), the number of copies is counted (step 12), and the process returns to step 5.

  On the other hand, when it is determined that continuous printing is not performed (step 11; NO), the image forming operation is terminated (step 13).

  As described above, a line image is formed every 100 sheets passed, and a blank for one rotation of the photosensitive drum is provided to prevent transfer memory from being generated on the drum surface.

  Next, a belt unit 50 that holds the above-described transfer belt 12 and that is replaceably mounted on the copying machine main body will be described with reference to FIG.

  The belt unit 50 that accommodates the transfer belt 12 has a socket 52 that is inserted into a socket 51 on the copier side while being mounted at a predetermined position in the copier 1. In addition, the belt unit 50 is provided with a memory (not shown) that stores the size of the paper that has been passed through, the number of sheets that pass through each size, the number of rotations of the transfer belt 12, and the like.

  Thus, when the belt unit 50 holding the new transfer belt 12 is attached to the copying machine 1, the number of sheets to be passed and the number of rotations of the belt are reset, and the copying machine recognizes that a new belt has been attached. It is like that.

  Further, when the socket unit 52 is inserted into the socket 51 when the belt unit 50 is mounted on the copying machine 1, a switch (not shown) on the copying machine 1 side is turned on / off to integrate the belt history. The counter may be reset.

  Next, a third embodiment of the present invention in which the contact condition of the cleaning blade 19 with the transfer belt 12 is changed as the number of sheets passed increases will be described with reference to FIGS. 10 and 11 together with FIG. To do.

  As shown in FIG. 2, the initial transfer belt can be satisfactorily cleaned without causing blade turning at all contact angles and contact pressures of the cleaning blade 19. On the other hand, when the contact angle of the cleaning blade 19 is set to 14 °, the transfer belt after passing 100 kilo sheets is subjected to good cleaning unless the contact pressure of the blade is set to 2.4 g / mm or more. Can not. In addition, when the contact angle of the cleaning blade 19 is set to 14 °, good cleaning cannot be performed on the transfer belt after passing 200 kilo sheets unless the contact pressure of the blade is set to 3.2 g / mm or more. At this time, if the contact angle of the cleaning blade 19 is 16 °, the contact pressure margin increases, and the contact pressure may be set to 2.4 g / mm or more.

  That is, if the contact angle of the cleaning blade 19 is increased in accordance with the increase in the number of sheets to be passed, good cleaning can be achieved over a long period of time, and the service life of the transfer belt 12 can be extended.

  FIG. 10 shows a mechanism for adjusting the contact angle of the cleaning blade 19. According to this, the cleaning blade 19 is attached to one end of the alpha spring 61, and the tip of the cleaning blade 19 is pressed against the predetermined position of the transfer belt 12 by the restoring force of the alpha spring 61. The alpha spring 61 is slidably provided so as to be detachable from the transfer belt 12 via a slider 62. Accordingly, the contact angle of the cleaning blade 19 with respect to the transfer belt 12 can be adjusted by moving the fulcrum 63 of the alpha spring 61 up and down in the drawing.

  For example, in the example shown in FIG. 2, the fulcrum 63 of the cleaning blade 19 is moved downward from the position A (14 °) to the position B (16 °) when the number of sheets passed exceeds 200 kilos. The movement of the blade, that is, the contact angle may be adjusted every several tens of kilos to several hundreds of kilos, but the cam 64 or the like is used to gradually move according to the number of sheets to be passed. May be.

  Further, as shown in FIG. 3, it is known that blade turning is more likely to occur as the contact pressure of the cleaning blade 19 is higher. On the other hand, according to FIG. 2, it can be seen that the higher the contact pressure of the cleaning blade 19, the better the cleaning. Therefore, for the initial transfer belt, the contact pressure of the cleaning blade 19 is set to be low, and the contact pressure of the cleaning blade 19 is adjusted so as to increase as the number of sheets passing increases. Also, good cleaning can be performed.

  FIG. 11 shows a mechanism for adjusting the contact pressure of the cleaning blade 19. According to this, the cleaning blade 19 is attached to one end of the alpha spring 61, and the tip of the cleaning blade 19 is pressed against the predetermined position of the transfer belt 12 by the restoring force of the alpha spring 61. The alpha spring 61 is slidable along the traveling direction of the transfer belt 12 via the slider 62. Accordingly, the contact pressure of the cleaning blade 19 with respect to the transfer belt 12 can be lowered by moving the slider 62 in the left direction in the figure, and the contact pressure is increased by moving the slider 62 in the right direction in the figure. be able to.

  In addition, this invention is not limited to embodiment mentioned above, A various deformation | transformation is possible within the scope of this invention. For example, in each of the above-described embodiments, the belt life is determined based on the number of passing sheets. However, the belt life may be determined based on the number of rotations of the transfer belt.

1 is a diagram schematically showing a general copying machine. The figure which shows the cleaning state in the paper passing part and the non-sheet passing part when changing the belt life, the contact angle of the blade, and the contact pressure. The figure which shows the presence or absence of the blade turning in the paper passing part and non-paper passing part when changing the belt life, the contact angle of the blade, and the contact pressure. FIG. 6 is a diagram illustrating the presence or absence of belt turning with respect to the toner supply amount. 1 is a diagram schematically showing a copying machine according to the present invention. 6 is a flowchart for explaining an operation of adjusting a toner supply amount according to the first embodiment of the present invention. 9 is a flowchart for explaining an operation of adjusting a toner supply amount according to a second embodiment of the present invention. 6 is a flowchart for explaining an operation for preventing a transfer memory. The figure which shows the bell and unit which hold | maintained the transfer belt of a copying machine. FIG. 3 is a diagram schematically showing a mechanism for adjusting a contact angle of a cleaning blade with respect to a transfer belt. FIG. 4 is a diagram schematically showing a mechanism for adjusting a contact pressure of a cleaning blade against a transfer belt.

Explanation of symbols

1 ... Digital copier,
2 ... photosensitive drum,
12 ... transfer belt,
19 ... cleaning blade,
40. Exposure apparatus,
50 ... belt unit,
P: Paper.

Claims (5)

An image forming means for forming an image with a developer on the image carrier;
Medium supply means for supplying a transfer medium for transferring the developer image formed by the image forming means;
A transfer surface that travels along the image carrier, holds a transfer medium supplied via the medium supply unit on the transfer surface, and is formed on the image carrier by the image forming unit; Conveying means for conveying the transferred medium to the formed developer image;
A transfer unit that transfers the developer image formed on the image carrier by the image forming unit onto a transfer medium held and transported by the transport unit on the transport surface;
A cleaning member disposed in contact with the transport surface, and cleaning means for cleaning the transport surface by scraping the developer undesirably deposited on the transport surface with the cleaning member;
A lubricant supply means for supplying a lubricant onto the transport surface before being cleaned by the cleaning means at a predetermined timing when the image forming operation is not performed;
Adjusting means for adjusting the amount of lubricant supplied by the lubricant supplying means in accordance with the number and type of transfer medium supplied onto the transport surface by the medium supplying means;
An image forming apparatus comprising: An image forming means for forming an image with a developer on the image carrier;
Medium supply means for supplying a transfer medium for transferring the developer image formed by the image forming means;
A transfer surface that travels along the image carrier, holds a transfer medium supplied via the medium supply unit on the transfer surface, and is formed on the image carrier by the image forming unit; Conveying means for conveying the transferred medium to the formed developer image;
A transfer unit that transfers the developer image formed on the image carrier by the image forming unit onto a transfer medium held and transported by the transport unit on the transport surface;
A cleaning member disposed in contact with the transport surface, and cleaning means for cleaning the transport surface by scraping the developer undesirably deposited on the transport surface with the cleaning member;
A lubricant supply means for supplying a lubricant onto the transport surface before being cleaned by the cleaning means at a predetermined timing when the image forming operation is not performed;
An adjusting means for adjusting the number of times the lubricant is supplied by the lubricant supplying means in accordance with the number and type of transfer medium supplied onto the transport surface by the medium supplying means;
An image forming apparatus comprising: Image forming means for forming an image by a developer on the surface of a photosensitive drum provided rotatably;
A paper feeding means for feeding paper for transferring the developer image formed on the drum surface by the image forming means;
A belt that runs endlessly along the drum surface in a direction substantially perpendicular to the axial direction of the photosensitive drum, and the belt is fed via a sheet feeding means onto a conveying surface facing the drum surface. Conveying means for holding paper to be paper and conveying the paper to a developer image formed on the drum surface by the image forming means;
Transfer means for transferring the developer image formed on the drum surface by the image forming means onto the paper held and conveyed by the conveying means on the conveying surface of the belt;
A cleaning blade that extends in the axial direction and is disposed in contact with the transport surface, and scrapes off the developer or paper powder that is undesirably adhered onto the transport surface to clean the transport surface;
Lubricant supply means for supplying a lubricant onto the transport surface before being cleaned by the cleaning blade at a predetermined timing when the image forming operation is not performed;
Adjusting means for adjusting the amount of lubricant supplied by the lubricant supplying means according to the number and type of sheets fed on the conveying surface by the paper feeding means;
An image forming apparatus comprising: An image forming means for forming an image with a developer on the image carrier;
Medium supply means for supplying a transfer medium for transferring the developer image formed by the image forming means;
Medium detection means for detecting the size of the transfer medium supplied by the medium supply means and the number of sheets for each size;
A transfer surface that travels along the image carrier, holds a transfer medium supplied via the medium supply unit on the transfer surface, and is formed on the image carrier by the image forming unit; Conveying means for conveying the transferred medium to the formed developer image;
A transfer unit that transfers the developer image formed on the image carrier by the image forming unit onto a transfer medium held and transported by the transport unit on the transport surface;
A cleaning member disposed in contact with the transport surface, and cleaning means for cleaning the transport surface by scraping the developer undesirably deposited on the transport surface with the cleaning member;
A lubricant supply means for supplying a lubricant onto the transport surface before being cleaned by the cleaning means at a predetermined timing when the image forming operation is not performed;
In accordance with the number of transfer mediums detected by the medium detection means, the amount of lubricant supplied onto the transport surface by the lubricant supply means in a direction crossing the transport direction of the transport surface. Adjusting means to change along,
An image forming apparatus comprising: Image forming means for forming an image by a developer on the surface of a photosensitive drum provided rotatably;
A paper feeding means for feeding paper for transferring the developer image formed on the drum surface by the image forming means;
Paper detection means for detecting the size of paper fed through the paper feed means and the number of papers fed for each size;
A belt that runs endlessly along the drum surface in a direction substantially perpendicular to the axial direction of the photosensitive drum, and the belt is fed via a sheet feeding means onto a conveying surface facing the drum surface. Conveying means for holding paper to be paper and conveying the paper to a developer image formed on the drum surface by the image forming means;
Transfer means for transferring the developer image formed on the drum surface by the image forming means onto the paper held and conveyed by the conveying means on the conveying surface of the belt;
A cleaning blade that extends in the axial direction and is disposed in contact with the transport surface, and scrapes off the developer or paper powder that is undesirably adhered onto the transport surface to clean the transport surface;
Lubricant supply means for supplying a strip-like lubricant extending in the axial direction onto the transport surface before being cleaned by the cleaning blade at a predetermined timing when no image forming operation is performed;
Adjustment for changing the amount of lubricant supplied onto the transport surface by the lubricant supplying means along the axial direction in accordance with the number of sheets fed for each size of the paper detected by the paper detecting means. Means,
An image forming apparatus comprising:

Images