JP3643310B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a digital copying machine, a facsimile, a printer, and a multifunction machine having these functions.
[0002]
[Prior art]
  <Conventional Example 1> Most analog type copiers have an original reading unit on the upper surface of the image forming apparatus main body, and a paper cassette is laid out on the side surface and discharged on the opposite side surface. Therefore, it was very disturbing where the horizontal size was large and there was not much office space. FIG. 7 shows a typical example. The conventional example 1 includes a paper feed unit 51, a conveyance path 52, a registration roller pair 53, an image forming unit 54, a fixing unit 55, a discharge roller pair 56, a paper discharge tray 57, an automatic document feeder 58, an optical unit 59, and the like. Consists of. The paper fed from any of the paper feed cassettes (511 to 513) passes through the conveyance path 52 and is temporarily stopped by the pair of registration rollers 53 for synchronization with the timing of reading the original and for leading edge of the paper. The toner image is transferred by the image forming unit 54 at the timing, and then the toner image is fixed by being sandwiched between the heat roller and the pressure roller by the fixing unit 55 and heated, and then discharged onto the paper discharge tray 57. In such a configuration, a plurality of paper feed cassettes (511 to 513) are set from the right side in the figure, and a distance to the left end of the paper discharge tray 57 is considerably long. Further, since the paper feed cassettes (511 to 513) are inserted and removed from the right direction, installation conditions with a space in the direction in which the cassette is substantially required are necessary. However, since the conveyance path 52 is substantially straight in a horizontal direction from paper feeding to discharging, it can be said that the occurrence of paper jam is small and the processing is easy. Since the lower part in the figure is not used in particular, it is often used on a large desk or on a dedicated desk 60 with casters.
[0003]
  <Conventional Example 2> Therefore, a front loading type in which a drawer cassette capable of replenishing paper from the entire surface is laid out below the main body of the image forming apparatus, and paper is fed from a paper feeding cassette below the image forming unit. The mainstream has been vertical conveyance, horizontal conveyance, transfer of a toner image, fixing, and discharge. As a result, since the cassette does not protrude laterally, considerable space saving can be realized. FIG. 8 shows an example. This conventional example 2 includes a paper feeding unit 61, a conveyance path 62, a registration roller pair 63, an image forming unit 64, a fixing unit 65, a double-sided branching unit 66, a discharge roller pair 67, a paper discharge tray 68, an automatic document feeder 69, Consists of a digital optical unit 70, a switchback unit 71, a double-sided conveyance path 72, and the like. In the case of one-eye printing, a sheet fed from either the sheet feeding cassette (611-613) or the sheet feeding tray 614 is conveyed. Through the path 62, the registration roller pair 63 is temporarily stopped to synchronize with the timing of writing the latent image from the LSU to the photosensitive drum and to align the leading edge of the sheet. The toner image is transferred onto the surface, and is then sandwiched between the heat roller and the pressure roller by the fixing unit 65 and heated to fix the toner image, and is then discharged to the paper discharge tray 68. In the case of double-sided printing, the paper printed on the first side is sent to the switchback unit 71 by the double-side branching unit 66 to switch back the conveyance direction, merges again with the conveyance path 62, and is printed on the second side of the paper. Discharged. However, with such a configuration, there is a problem in that even in single-sided printing, the transport distance from feeding to ejection is long. Further, immediately after the sheet is fed, the sheet conveyance is directed upward in the vertical direction against the gravity, and the direction is changed by 90 °. For this reason, the jam occurrence rate is higher in the sheet feeding from the sheet feeding cassettes (611 to 613), particularly in the lower sheet feeding cassette 613.
[0004]
  <Conventional Example 3> In recent years, the discharge space has also become a hindrance, so that the discharge of paper has been made on the upper surface of the image forming apparatus, and the copying machine has been digitized. Since there is no longer an optical path for the exposure to light, and exposure to the photosensitive drum can be performed with a laser or LED, there are no restrictions on the layout, and copiers, printers, and the like that discharge inside the cylinder have appeared, and further space saving has become possible. FIG. 9 shows an example. This conventional example 3 includes a paper feed unit 68, a conveyance path 82, a registration roller pair 83, an image forming unit 84, a fixing unit 85, a discharge port 86, an in-body discharge tray 87, an automatic document feeder 88, and a digital optical unit 89. The sheet fed from either the sheet feed cassette (811 to 813) or the sheet feed tray 814 passes through the conveyance path 82 and the timing of writing the latent image from the LSU to the photosensitive drum. In order to synchronize the image and align the leading edge of the paper, it is temporarily stopped by the pair of registration rollers 83, the toner image is transferred to the paper by the image forming unit 84 at the timing, and then the fixing unit 85 is sandwiched between the heat roller and the pressure roller. The toner image is fixed by heating, and is then discharged to the in-body discharge tray 68. However, with such a configuration, more space saving is realized, but the paper conveyance repeats a sharp curve, and the occurrence rate of jam increases. Furthermore, jam processing has become difficult due to the complicated conveyance path.
[0005]
[Problems to be solved by the invention]
  As described above, as the conventional front loading method or the one to be discharged into the upper surface or the cylinder of the image forming unit, the distance for transporting the paper becomes longer and the reverse of the sharp curve is forced. It has become. For this reason, the paper handling technology becomes complicated and the occurrence of jams tends to increase. In addition, since the paper conveyance path is complicated, it is difficult to handle jams, and it is necessary to provide opening / closing mechanisms everywhere, which complicates the entire image forming apparatus. In fact, looking at the places where jams occur in recent copying machines and the like, they frequently occur in the above-mentioned unreasonable curved portions of the conveyance, the junctions of paper, and the like.
[0006]
  On the other hand, in recent years, from the viewpoint of saving resources, poor quality paper such as used paper, recycled paper, reuse of paper on which only one side is printed, and rough paper have been used. It can be said that this tendency further increases the incidence of jam.
[0007]
  Therefore, looking at how the copiers are used in general offices, most of them use A4 plain paper. Other A3 paper and B size paper are rarely used. In many cases, envelopes and postcards are not copied at all. However, even a paper of a size that is not often used occupies one stage of the cassette. For this reason, the place of the frequently used paper is cut and the paper is frequently set.
[0008]
  As described above, the concept of the present invention
(1)Use paper that is frequently used as straight and as short as possible.
(2)Basically, paper is fed from the bypass except for cassettes loaded with frequently used paper.
(3)Jam caused by slip is reduced by conveying from the paper feed to the discharge in the horizontal direction or from the top to the bottom.
(4)For paper feeding units that are used frequently, a highly reliable paper feeding technology is used.
[0009]
[Means for Solving the Problems]
  In order to solve the above problem, the first invention of the present invention has been provided with a paper cassette capable of stacking a plurality of papers, a paper feeding means for feeding the paper of the paper cassettes one by one to a transport path, and the transport An electrophotographic image forming means having a pair of registration rollers for adjusting the leading edge of the paper and adjusting the timing, and a developing device having a developing roller for forming a toner image on the photosensitive drum, and the image forming means In the image forming apparatus having transfer means for transferring the toner image transferred onto paper, fixing means for fixing the paper on which the toner image has been transferred, and discharge means for discharging the paper, the paper cassette is a large capacity paper Are built in the main body of the image forming apparatus and can be pulled out to the front.bypassIt has a common feed bypass tray and one of these bypass conveyance paths,bypassPaper can be fed from the paper feed tray, and this bypass conveyance path smoothly joins in the conveyance direction from the obliquely upward direction to the downstream of the paper supply means of the large capacity paper cassette and upstream of the resist. The position of the means, the position of the resist, the position of the transfer, the position of the fixing means, and the position of the discharge means are substantially in a straight line.Further, downstream of the fixing unit, there is a branching unit for branching to a double-sided conveyance path, and the double-sided conveyance path goes around the image forming unit after the branching unit and is discharged to the bypass paper feed tray. This paper can be printed on both sides by feeding paper from the bypass paper feed tray and printing on the second side of the paper.An image forming apparatus characterized by this is used.
[0011]
  This case2The invention ofVipaAt least one of the paper feed trays is built in the image forming apparatus main body.bypassThe image forming apparatus according to the first aspect, wherein the image forming apparatus is a paper cassette and can be pulled out to the front.
[0012]
  This case3The invention ofbypassAll paper feed trays are built into the main body of the image forming apparatus.bypassIt is a single unit in the paper feed tray.bypassThe image forming apparatus according to the first aspect, wherein the paper feed tray unit can be pulled out to the front.
[0013]
  According to a fourth aspect of the present invention, there is provided a first discharge position for discharging the discharge tray, and a discharge tray for lifting to a second discharge position where the user can easily take out the discharged sheet. The image forming apparatus according to any one of the first to third inventions, characterized by having a lift means.
[0014]
[Action]
  In the first aspect of the present invention, only one large-capacity paper cassette is provided and no other paper cassette is provided. Therefore, the distance from paper feed to paper discharge of the paper cassette can be shortened. Also, instead of other paper cassettes,bypassSince a paper tray is used, it is sufficient to feed paper that is not often used.bypassSince a plurality of paper feed trays are prepared, a plurality of types other than the main paper can be set. This is because the usage rate of sheets other than the main size is less than a few percent of the total size, and it is sufficient to feed other sheets as needed from time to time. In addition, the usage rate of papers other than the main is low, but each type is large (small quantity and variety).bypassA plurality of trays are provided. More types of paper can be set in less space than providing multiple cassettes. Also thesebypassSince the paper feed tray is positioned above the main paper feed cassette, it is transported from the top to the bottom, and slippage of the transport roller can be reduced. Furthermore, by making the large-capacity paper cassette from the paper feed position to the discharge substantially straight, it becomes a straight conveyance path, and the cause of jam occurrence can be reduced.In addition, in the case where the double-sided carrying printing function is provided, space can be saved by using one of a plurality of bypass paper feed trays as the double-sided switchback means.
[0016]
  This case2In the invention ofbypassSince the paper feed tray is built in the image forming main body and can be pulled out in the forward direction, lateral protrusion can be reduced. Further, only a small sheet may be drawn out into a cassette.
[0017]
  This case3In the invention, the plurality ofbypassSince the paper feed tray is grouped as a single unit, a configuration for pulling out the entire surface is also available.bypassThere is no need to provide for each of the paper feed trays, and this is simplified. This is onebypassThis is because the number of paper feed trays set is small and the size can be reduced.
[0018]
  This case4In this invention, since the paper transport direction is from the top to the bottom, the paper is discharged downward. Therefore, this is compensated by lifting the discharge tray. This is because if a paper path is provided and discharged upward, a paper that may be curled after fixing is transported from the bottom to the top, and jamming is likely to occur. Paper ejected and loaded will not jam.
[0019]
【Example】
  A first embodiment employing the first invention will be described with reference to FIG. In the figure, the image forming apparatus includes a large-capacity cassette 01, a sheet feeding unit 02, a registration roller pair 03, a conveying path 04, an image forming unit 05, a fixing unit 07, a branching unit 08, a discharge unit. Means 09, paper discharge tray 10,bypassThe sheet feeding tray 11, the scanner 21, and the automatic document feeder 22 are configured.
[0020]
  The large capacity cassette 01 and the paper feeding means will be described with reference to FIG. In the figure, the large-capacity cassette 01 includes a cassette frame body 011, a paper stacking plate 012, a paper sensor 0121, a paper stacking plate lifting / lowering unit 013, and the like, and stacks only main sheets. In a general office, the paper size that is normally used is A4. In recent years, digital copiers are mainly used, so that A4 landscape can be output regardless of the direction in which the document is placed. Further, the horizontal direction is preferable for increasing the number of printed sheets per hour. Since there is only one sheet feeding cassette, a large capacity can be realized because there is no space for other sheet feeding cassettes and no vertical conveyance path as described in the prior arts 2 and 3. Furthermore, even if a large-capacity cassette having a large number of parts is used, since only one of these cassettes is used, the cost is not significantly increased. The paper sensor 0121 uses a photo sensor or the like to detect the presence or absence of paper stacked on the paper stacking plate 012.
[0021]
  The sheet stacking plate raising / lowering means 013 includes a motor (01321, 0131b), a drive pulley (0132a, 0132b), a wire (0133a, 0133b), and an idle pulley (0134a, 0134b). Control is performed so that the distance between the upper surface of the uppermost sheet of the sheets stacked on the sheet stacking unit 01 and the portion of the sheet feeding unit 02 that sucks the sheet is maintained at a predetermined distance. The predetermined distance is determined by various related parameters such as the air volume of the paper blowing means 023 and the suction force of the paper suction means 022, the weight of the paper per sheet, the paper size, and the coefficient of friction between the papers. When the sheet is being conveyed, the distance between the sheet and the sheet that is scheduled to be fed next is such a distance that the sheet that is scheduled to be fed next does not start moving, and the sheet spraying unit 023. This distance is such that one sheet of paper can be attracted to the lower surface side of the paper feed belt 021 by the air volume and the suction force of the paper suction means 022. Further, the predetermined distance may be set in advance, and the other related parameters may be determined. Further, the paper stacking plate raising / lowering means 013 also plays a role of lowering the paper stacking plate 012 to a predetermined position during paper replenishment and paper jam processing.
[0022]
  The paper feeding unit 02 includes a paper feeding belt unit 021, a paper suction unit 022, and a paper blowing unit 023, and the paper blowing unit 022 receives the paper stacking plate via an air blowing port 0232 from a blowing fan 0231. The paper is separated by blowing air from the downstream side in the paper transport direction to the upper part of the plurality of papers stacked in 012. The sheet feeding belt unit 021 is at least two rollers (0212, 0213) and an upper surface on the downstream side in the sheet conveying direction of the sheets stacked on the sheet stacking plate 012 so as to be spanned between the at least two rollers at substantially equal intervals. The sheet suction means 022 is composed of a suction fan 0221 and a suction duct 0222, and this sheet suction means is composed of a plurality of belts (0211) facing the surface and a part 0214 of the suction duct. A plurality of sheet suction holes (not shown) 022 are provided, and the topmost sheet among the plurality of sheets stacked on the sheet stacking plate 012 is fed from the plurality of holes of the belt. When the sheet is sucked to the lower surface of the plurality of belts 021 and further conveyed by rotating the belt, the sheet is conveyed while being attracted to the lower surface. It passed to the sending passage 121.
[0023]
  Next, the basic operation of the image forming apparatus that employs the above-described air suction type paper feeding and conveying apparatus will be described. First, it is determined whether or not there is a sheet on the sheet stacking plate 012. If there is not, a paper empty is displayed to request replenishment of the sheet. If there is a sheet, the distance between the lower surface of the sheet feeding belt and the upper surface of the uppermost sheet stacked on the sheet stacking plate 011 is set to a predetermined distance, and the suction fan and the blowing fan 31 are Check if it is working. Next, the sheet is sucked by the lower surface of the sheet feeding belt 021. Subsequently, the sheet feeding belt 021 is rotated to transfer the sheet to the sheet feeding conveyance path, and the sheet feeding belt 021 is stopped. Thus, in the present invention, it is better to use one that can accurately feed one by one.
[0024]
  bypassThe paper feed tray 11 is provided with a plurality of paper feed trays similar to conventional bypass paper feed. Here for large sizebypassFeed tray 111, medium sizebypassPaper tray 112 for small sizebypassThree of the paper tray 113bypassA paper feed tray is provided, and regardless of which paper is fed, the paper is conveyed from the diagonally upward direction via the bypass conveyance path 15 to the downstream of the paper feeding means 02 and the upstream of the registration roller pair 03 of the large capacity paper cassette. It merges gently in the direction. For this reason, the fed paper does not resist gravity, and the conveyance path does not have a particularly sharp curve, so that the occurrence of jam is extremely small. Each of the paper feed rollers provided is made of ordinary urethane rubber, EPDM, or the like, and a simple one having a flat knurl around it for preventing slipping or a complicated one such as a gate system is used. thisbypassSince it is assumed that the paper feed tray is not used frequently, even if a simple paper feed roller is used, consumption is low and replacement is easy. Fulfill. Usually like thisbypassThe paper feed tray is of an openable type, and when it is not used, it often closes with a sense of unity with the cover of the image forming apparatus.bypassSince there are a plurality of paper feed trays, a paper feed position is provided inside the image forming apparatus main body, and a tray that expands and contracts as usual is easily applied.
[0025]
  The registration roller pair 03 is made of a slippery resin such as polyacetal and a rubber roller that are appropriately pressed against each other, and the conveyed paper tip is first slid against the resin roller, and the paper tip is niped by the nip. By stopping, the tip is arranged parallel to the transport direction. The registration roller pair 03 rotates in synchronization with the image formation timing. In the figure, this is also performed for the paper fed from the large-capacity cassette 01, but here, air feeding is used for paper feeding, and the distance from the paper feeding to the transfer position is very short.Bypass paper feedIf the configuration is performed only for the tray 11 and the double-sided refeeding, the distance from the feeding to the discharge can be further shortened.
[0026]
  The image forming unit 05 will be described with reference to FIG. In the figure, the image forming unit 05 includes a photosensitive drum 051, a main charging unit 052, an exposure unit 053, a developing unit 054, a transfer roller 55, a drum cleaner 056, a toner container 057, and the like. In particular, the developing device 054 uses a vertical circulation developing device. The positional relationship between the transport path 04 and the developing device 054 is higher than the interference with the registration roller pair 03.
[0027]
  The photosensitive drum 051 has undergone charging and exposure processes before reaching the development process. The main charging device 052 charges the surface of the photosensitive drum 051 to a predetermined surface potential, and the exposure unit 053 exposes image information. As a result, the electrostatic latent image formed on the peripheral surface is rotating. The main charging device 052 uses any one of the corotron method, the scorotron method, the charging roller, etc., and generates a corona discharge by applying a high voltage or charges the surface of the photosensitive drum 051 to a predetermined surface potential. I am letting. The exposure unit 053 uses LSU or the like to reduce the cost. However, if LPH (LED PRINT HEAD) is used, space can be saved.
[0028]
  The developing device 054 includes a developing housing 0541, a developing roller 0542, a supplementary cutting plate 0543, a first stirring unit 0544, a second stirring unit 0545, a pumping roller 0546, and the like. The developing housing 0541 is a housing of the developing device main body, maintains the components of the developing device in a predetermined positional relationship, and is a developer tank. The material is generally made of a resin containing glass fiber to provide dimensional accuracy. The first agitation unit 0544 and the second agitation unit 0545 use an agitation paddle or spiral to agitate and convey the developer composed of carrier particles and toner to uniformly mix them, causing frictional charging and charging the toner. I am letting.
[0029]
  A developing roller 0542 is disposed in the developing housing 0541 in parallel with the photosensitive drum 051, and rotates in the forward direction with respect to the rotational movement direction of the peripheral surface of the photosensitive drum 1 and the sleeve member. It is comprised by the magnet arrange | positioned in the inside. The sleeve member sucks and conveys the developer onto the peripheral surface, sends it to a development area that forms a nip with the photosensitive drum 051, and applies the developer to the electrostatic latent image on the peripheral surface of the photosensitive drum 051. A toner image is formed. Here, an appropriate developing bias is applied to the first sleeve member, and an electrostatic latent image on the peripheral surface of the photosensitive drum 1 is formed by forming an electric field using the photosensitive drum 051 as a counter electrode. Toner image. The sleeve member is generally made of an aluminum alloy, and its peripheral surface is subjected to a knurling process, a sand blasting process, and a wire brushing process in order to improve the developer conveying performance. The magnet has multipolar magnetic poles in the radial direction, and a ferrite permanent magnet (sintered or binder magnet) is used as the material.
[0030]
  The panning plate 0543 has an end portion positioned with a predetermined gap from the developing roller 0542, and has a role of regulating the layer thickness of the developer conveyed on the peripheral surface of the developing roller 0542. In consideration of wear resistance and prevention of toner adhesion, a material such as stainless steel, brass or aluminum alloy is used as the material. Setting the layer thickness requires accuracy.
[0031]
  The drawing-up roller 0546 is located at a position that is out of the developing area of the developing roller in the longitudinal direction, and is in a direction from bottom to top when the developer is transferred from the first stirring unit 0544 to the second stirring unit 0545. Therefore, the developer from the first stirring unit 0544 is magnetically adsorbed on the surface of the pumping roller 0546, and the second stirring unit 0545 is removed by a simple blade.
[0032]
  The toner concentration detecting means 0547 uses a magnetic permeability sensor, and may be installed anywhere as long as the toner and carrier particles are sufficiently agitated and mixed developer flows.
[0033]
  Next, the flow of the developer will be described. First, the developer is agitated by circulating the first agitation means 0544 and the second agitation means 0545 through a pumping roller 0546. Further, the first agitating unit 0544 agitates the circulating developer while delivering it to the developing roller 0542. The developing roller 0542 magnetically attracts and holds the developer on the circumferential surface by a magnetic pumping magnetic pole disposed inside the sleeve member, and the pumped developer is held by the cutting plate 0543 as the sleeve member rotates. The amount is regulated, and is transported by the transport magnetic pole and raised by the magnetic field generated by the main pole, and sent to the developing area formed by the sleeve member and the photosensitive drum 051. The developer after the development continues to transfer the developer to the first stirring means 0544 near the peeling pole of the same polarity adjacent to the internal magnet by the rotational movement of the sleeve member. The developer that has consumed the toner collected by the first stirring unit 0544 is replenished with toner while being circulated again through the first stirring unit 0544 and the second stirring unit 0545 through the roller 0546. To maintain a predetermined concentration.
[0034]
  The toner container 057 includes a toner supply roller 0571, a toner feeding unit 0572, and the like. The toner supply roller 0571 is rotated by rotating a toner supply motor, and a second opening of the developing housing 0541 is rotated from the lower opening. The toner is dropped to the upstream side of the developer agitating / conveying means 0545. This toner fall is replenished when the measured toner density is lower than the set toner density by comparing the developer toner density measured by the toner density detecting means 0547 with the set toner density. The toner supply is stopped when the measured toner density becomes higher than the set toner density. The toner feeding means 0572 rotates so as to bring the toner toward the opening, and is driven by the same driving as that of the toner replenishing roller 0571.
[0035]
  The toner image formed on the photosensitive drum 051 is conveyed at a transfer position 055 by a voltage having a polarity opposite to that of the toner applied to the transfer roller 063 and an electric field generated by using the photosensitive drum 051 as a counter electrode. Transcribed above. At the second transfer position 057 with the rotational movement of the toner image on the transfer belt, the second transfer roller 07 is fed by a voltage having a polarity opposite to that of the toner and an electric field generated by the second transfer counter roller 064. It is transferred onto the incoming paper. The photosensitive drum 051 and the transfer roller 06 are in contact with each other or have a positional relationship of about 0.1 mm. As the voltage applied to the transfer roller 06, an appropriate voltage of about 1 to 6 kV is applied from the high voltage transformer. The material of the transfer roller 06 is made of a polyurethane elastomer with lithium perchlorate added around a shaft core such as aluminum, a polyester elastomer with lithium perchlorate added, or urethane rubber with conductive carbon black added. Each of them is provided with an elastic layer having a volume resistance of 10 4 to 10 5 Ω · cm and an Asker C hardness of about 50 to 80 °.
[0036]
  The drum cleaner 056 scrapes and collects the toner remaining on the photosensitive drum 051 with a blade. The collected toner is sent to a collection container (not shown) or returned to the toner container and recycled.
[0037]
  The fixing device 07 is composed of a heat roller 071, a fixing heater 0711, a pressure roller 072, and a guide plate 073. The heat roller 071 uses a roller with a fluorine coating on the outer periphery of a roller such as aluminum having good heat conductivity. By incorporating 0711, the temperature is controlled to a predetermined temperature necessary for fixing. As the pressure roller 072, a roller having good heat conductivity such as aluminum is covered with an elastic layer made of heat-resistant urethane rubber, and the outer periphery has a release layer made of fluororesin such as PTFE. The guide plate 073 guides the leading edge of the conveyed paper in a direction in which the leading edge of the paper contacts the heat roller 071. The heat roller 071 and the pressure roller 072 are pressed against each other with an appropriate pressure, and a sheet having unfixed toner transferred to the surface is sandwiched and pressed by a nip formed by the two rollers, thereby being fixed.
[0038]
  The branching unit 08 takes a posture shown by a broken line in the drawing when discharging one-sided printing or printing on the second side of both sides, and the sheet after fixing is sequentially discharged to the discharge tray 10 by the discharging unit 09. . When the first side of double-sided printing is printed, the sheet takes the posture of a solid line in the figure and is conveyed toward the double-sided conveyance path 12.
[0039]
  Returning again to FIG. The double-sided conveyance path 12 conveys the fixed sheet in the first half in the vertically upward direction. Therefore, it can be said that the double-sided conveyance path 12 is the most likely place for jamming in the image forming apparatus of the present invention.
[0040]
  The paper discharge tray 10 is here4As described above, the discharge tray lifting means 101 is provided, and the discharge tray 10 can be raised and lowered as necessary. This is because, in the layout of this case, the paper discharge position is low, so when the user picks up the printed paper, it is difficult to pick it up at the low position. Lift up to the indicated position. Further, when the next job is entered and printing is started in a state where the printed sheet is not removed, control is performed so that the original paper discharge position is returned again. Recently, many copiers are provided with a finisher. In this case, such a lift means is not necessary.
[0041]
  Bypass paper feedA first embodiment in which the uppermost tray is also used as a switchback tray will be described with reference to FIG. The paper on which the image is printed on the first surface is transferred by the switchback paper feed roller pair 133 via the conveyance path 12.bypassThe paper is ejected to the paper feed tray 114, and the rear end of the paper is directed toward the switchback discharge roller pair 134 by the hitting roller 132. Subsequently, the hitting roller 132 is reversed in the discharge direction, and the refeed conveyance path 14 The toner image is transferred to the second surface again through the conveyance path 04 and the registration unit 03, and is discharged to the paper tray 10 through the fixing unit 07, the branching unit 08 (in a broken line state), and the discharge unit 09. thisbypassThe paper feed tray 114 can normally be used as bypass paper feed. When a double-sided instruction is given, it is confirmed that no paper is set here, and if it is set, that fact is indicated. To inform the user. On the other hand, if the duplex instruction is not given,bypassIt can be used as a paper feed tray.
[0042]
  This case2Adopting the invention2The embodiment will be briefly described with reference to FIG. The main part is the same as that of the first embodiment, but a plurality ofbypassFor loading relatively small paper in the paper traybypassTwo paper cassettes are built-in. These are independent of each other. When setting a sheet, it is pulled out to the front. The sheet fed from here passes through the bypass conveyance path 15 and is laid out obliquely with the sheet feeding position lowered in order to merge with the conveyance path 04 at a gentle angle. Here everythingbypassLarge paper up to A3 size can be set without using a paper cassettebypassThe paper feed tray 11 is provided because at least one of them should be capable of setting a large paper size.bypassIf it is configured so that large paper can be set in the paper cassette (161, 162), it can be pulled out to the front by itself.bypassThis is because the merit of the paper cassette is halved.
[0043]
  A third embodiment employing the third invention of the present case will be briefly described with reference to FIG. The main part is the same as the first embodiment, but a plurality ofbypassThe paper feed trays (171 to 173) are one unit.bypassThe paper feed tray unit 17 is used. As described in the related art 2, conventionally, the concept of one cassette per sheet has been used. However, in the present invention, the number of sheets that are not often used is not required so much. As in the third example,bypassThe three sheet feeding trays (171 to 173) are built in the image forming apparatus main body as one unit, and are set so as to be pulled out and set to the front side when setting sheets.
[0044]
【The invention's effect】
  As described above, according to the first aspect of the present invention, only one large-capacity paper cassette is provided, and no other paper cassette is provided. Therefore, the distance from the paper cassette to the paper discharge Can be shortened. Also, instead of other paper cassettes,VipaSince the paper feed tray is used, it is sufficient to feed paper that is not frequently used.bypassSince a plurality of paper feed trays are prepared, a plurality of types other than the main paper can be set. This is because the usage rate of the sheets other than the main sheet is less than a few percent of the total, so that it is sufficient to feed other sheets as needed. In addition, the usage rate of papers other than the main size is low, but there are many types (small quantities, many types).Bypass paper feedA plurality of trays are provided. More types of paper can be loaded in less space than providing multiple cassettes. Also thesebypassSince the paper feed tray is positioned above the main paper feed cassette, it is transported from the top to the bottom, and slippage of the transport roller can be reduced. Furthermore, by making the large-capacity paper cassette from the paper feed position to the discharge substantially straight, it becomes a straight conveyance path, and the cause of jam occurrence can be reduced.In addition, when the double-sided carrying printing function is provided, space can be saved by using one of a plurality of bypass paper feed trays as the double-sided switchback means. If there is no double-sided job, it can be used as a normal bypass paper feed tray.
[0046]
  This case2With the invention ofbypassSince the paper feed tray is built in the image forming main body and can be pulled out in the forward direction, lateral protrusion can be reduced. Further, only a small sheet may be drawn out into a cassette.
[0047]
  This case3If the invention ofbypassSince the paper feed tray is grouped as a single unit, a configuration for pulling out the entire surface is also available.bypassThere is no need to provide for each of the paper feed trays, and this is simplified. This is onebypassThis is because the number of paper feed trays set is small and the size can be reduced.
[0048]
  This case4With this invention, since the paper transport direction is from the top to the bottom, the paper discharge is at the lower position. Therefore, this is compensated by lifting the discharge tray. This is because if a paper path is provided and discharged upward, a paper that may be curled after fixing is transported from the bottom to the top, and jamming is likely to occur. Paper ejected and loaded will not jam. In recent years, since the mounting rate of post-processing devices has increased, the functions of the present invention may be provided in the post-processing devices.
[0049]
  As described above, when an image forming apparatus having a new layout created by combining existing techniques such as the present invention is used, even if a jam occurs and a jam occurs, a jam occurs due to a short conveyance path. It is possible to provide an image forming apparatus that can easily identify the location and that can easily be processed.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an image forming apparatus according to a first embodiment employing the first invention.
FIG. 2 is a schematic diagram of a large capacity paper cassette and air feeding of the present invention.
FIG. 3 is a schematic view of the periphery of the image forming unit, transfer roller, fixing unit, branching unit, and discharging unit of the present invention.
FIG. 4 is a schematic diagram of an image forming apparatus according to a first embodiment employing the first invention.
FIG. 5 is a schematic view of an image forming apparatus according to a second embodiment employing the second invention.
FIG. 6 is a schematic view of an image forming apparatus according to a third embodiment employing the third invention.
FIG. 7 is a schematic diagram of an image forming apparatus according to a conventional technique <Conventional Example 1>.
FIG. 8 is a schematic diagram of an image forming apparatus according to a conventional technique <Conventional Example 2>.
FIG. 9 is a schematic diagram of an image forming apparatus according to a conventional technique <Conventional Example 2>.
[Explanation of symbols]
  01; Large capacity paper cassette
  02: Paper feeding means
  03: Registration roller pair
  04: Transport path
  05; Image forming means
051; Photosensitive drum
052; Main charging device
053; Exposure means (LPH or LSU)
054; Development device
055: Transfer position
056; Drum cleaner
057; Toner container
  06: Transfer roller
  07: Fixing means
  08: Branch means
  09: Discharge roller
  10; discharge tray,
  11;bypassPaper feed tray
111; Large size tray
112; Medium size tray
113; Small tray
  12: Double-sided conveyance path
  13: Switchback tray
  14: Re-feed conveyance path
  15: Bypass transport path
  21: Digital optical system
  22; Automatic document feeder

Claims (4)

A paper cassette capable of stacking a plurality of papers, a paper feeding means for feeding the papers of the paper cassette one by one to the transport path, and a pair of registration rollers for adjusting the leading edge of the transported paper and adjusting the timing An electrophotographic image forming means having a developing device having a developing roller for forming a toner image on a photosensitive drum, a transfer means for transferring the toner image formed by the image forming means to a sheet, and the toner In an image forming apparatus having a fixing unit that fixes a sheet onto which an image has been transferred, and a discharge unit that discharges the sheet.
The paper cassette can load a large amount of paper, is built in the main body of the image forming apparatus, and can be pulled out to the front. A plurality of bypass paper feed trays and a common one of them are disposed above the paper cassette. Has two bypass conveyance paths, and can selectively feed paper from a plurality of bypass paper feed trays, and this bypass conveyance path is inclined downstream of the large capacity paper cassette and upstream of the resist. It smoothly merges from the upper direction to the conveying direction, and the position of the paper feeding means, the position of the resist, the position of transfer, the position of the fixing means, and the position of the discharging means are substantially in a straight line, and are downstream of the fixing means. Has a branching means for branching to a double-sided conveyance path, and the double-sided conveyance path goes around the image forming unit and the like from above and is discharged to the bypass paper feed tray. Image forming apparatus characterized by possible double-sided printing by to feed paper from the bypass tray paper feeding means for printing on the second surface of the sheet of paper. At least one of the bypass feed tray is bypass paper cassette incorporated in the image forming apparatus main body, and according to claim 1, characterized in that the bypass paper cassette can be pulled out to the front Image forming apparatus. The bypass paper feed trays are all built in the image forming apparatus main body, and a plurality of bypass paper feed trays form one unit, and the bypass paper feed tray unit can be pulled out to the front. The image forming apparatus according to claim 1 . A first discharge position for discharging the discharge tray and a second discharge position for lifting the discharged sheet to a position where the user can easily take the discharged sheet; the image forming apparatus according to any one of claims 1 to 3.

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