JP2010008879A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of early and surely detecting defective separation of paper (image forming medium) from a secondary transfer belt, and easily removing the paper of which defective separation is detected. <P>SOLUTION: A simple and easy, low-cost sensor 49 comprising a rotary lever 51 and a reflection type optical sensor 54 is disposed between a secondary transfer part 40 and a belt type fixing device 37. The paper detecting position of the sensor 49 is located at a distance L2 from the secondary transfer part 40. Since the distance L2 is shorter than a distance L1 between the secondary transfer part 40 and a cleaning part 45, when the leading end of the paper is not detected by the sensor 49 even after a lapse of time required for the leading end of the paper passed through the secondary transfer part 40 to reach the paper detecting position of the sensor 49, it is judged that jamming occurs in the direction toward the cleaning part 45 due to the sticking of the paper to the transfer belt 24, so that the whole device is stopped so as to urge the maintenance to recover from jamming. Since L2<L1 is established, the paper surely stops this side of the cleaning part 45 when the whole device is stopped. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that can reliably detect a peeling defect of an image forming medium from a secondary transfer belt and easily remove the image forming medium in which the peeling defect is detected.

  2. Description of the Related Art Conventionally, there is an image forming apparatus that prints a color image (hereinafter, also referred to as “printing” or “image formation”) using an electrophotographic method using toner. In color printing using toner, the total of magenta (M), cyan (C), and yellow (Y) colors and black (K) dedicated to the black portion and characters of an image for one page of paper. Four color toner images are superimposed and transferred.

  A transfer medium such as a sheet as an image forming medium onto which four color toner images are transferred is fixed with a color image on the paper surface by applying heat and pressure in a fixing device.

  When the toner image is transferred to a transfer medium, the image is transferred directly from a photosensitive drum or the like as an image carrier to a transfer medium, or the image is temporarily transferred from the image carrier to an intermediate transfer body and then the primary transfer image. There is known an intermediate transfer type image forming apparatus that performs secondary transfer from an intermediate transfer member to a transfer medium.

  In such an intermediate transfer type image forming apparatus, for example, an intermediate transfer belt is used as an intermediate transfer member, and a primary transfer image on the intermediate transfer belt is secondarily transferred to a transfer medium in a secondary transfer portion and then transferred onto the transfer medium. I'm getting an image.

  Thus, in order to secondary transfer the toner image primarily transferred onto the intermediate transfer belt to the transfer medium, a secondary transfer voltage is applied to the transfer medium by, for example, a secondary transfer roller in the secondary transfer unit.

  If the secondary transfer voltage applied to the transfer medium at this time is not a secondary transfer voltage suitable for the transfer medium, not only a good image is not formed on the transfer medium, but also after the secondary transfer of the toner image. Is electrostatically attracted to the intermediate transfer belt and does not peel off from the intermediate transfer belt, but is wound around the intermediate transfer belt as it is.

  Since the electrostatic function of the intermediate transfer belt due to the secondary transfer voltage is affected by the temperature and humidity inside the image forming apparatus, the secondary transfer voltage, which was optimal at the beginning of operation, sometimes varies depending on the temperature and humidity inside the image forming apparatus. It changes according to the change, strengthens the electrostatic function of the intermediate transfer belt, and wraps the transfer medium around the intermediate transfer belt, so-called paper jam.

  In order to prevent such abnormal operation of a transfer medium such as a sheet as an image forming medium, it is determined by detecting whether or not the transfer medium is in a normal position. In general, an optical transmission type sensor is used to detect the position of the transfer medium.

  However, the optical transmission type sensor is expensive, has a complicated configuration, requires a technique for assembly, and often causes a detection error. When a detection error occurs, the above-described transfer medium is wound around the intermediate transfer belt.

  When the transfer medium is wound around the intermediate transfer belt, the transfer medium enters the cleaner unit disposed downstream of the secondary transfer unit in the rotation direction of the intermediate transfer belt, and the transfer medium comes into contact with the cleaning blade. If the peeling failure that results in this occurs repeatedly, there will be a problem in the performance of the cleaner part.

  In addition, the toner of the toner image before fixing on the transfer medium is scraped off at the cleaner section, or the paper rolls up, and a large amount of toner may be scattered inside the apparatus. It is not easy to remove toner scattered inside the apparatus.

  Therefore, it not only detects that the transfer medium is wound around the intermediate transfer belt, but also accurately detects abnormal conveyance of the transfer medium before the tip of the transfer medium wound around the intermediate transfer belt reaches the cleaning blade of the cleaner unit. There is a need.

  SUMMARY OF THE INVENTION In view of the above-described conventional situation, an object of the present invention is to quickly and surely detect a peeling failure of a transfer medium (image forming medium) from a secondary transfer belt and easily remove the image forming medium in which the peeling failure is detected. An image forming apparatus is provided.

First, an image forming apparatus according to a first aspect of the present invention primarily transfers a toner image formed on an image carrier onto an intermediate transfer belt, and the primary transferred toner image is transferred to an image forming medium being conveyed in a secondary transfer unit. An image forming apparatus having a cleaning unit disposed on the downstream side of the rotation of the intermediate transfer belt with respect to the secondary transfer unit to clean the primary transfer surface of the intermediate transfer belt after the secondary transfer and the secondary transfer. And a sensor arranged to detect the passage of the image forming medium on the way the image forming medium secondarily transferred with the toner image is conveyed toward the fixing unit, and the image based on the output of the sensor. A discriminating means for discriminating whether or not the forming medium has passed the sensor position within a predetermined time after passing through the secondary transfer portion; and the discriminating means has a predetermined after the image forming medium passes through the secondary transfer portion. Time When it is determined that does not pass through the sensor located within configured and a control means for stopping the conveyance of the image forming medium.
In this image forming apparatus, for example, the sensor is disposed at a distance L2 from the secondary transfer unit on the conveyance path in which the image forming medium is conveyed toward the fixing unit, and the cleaning unit is the secondary transfer unit. The distance L2 and the distance L1 are configured to have a relationship of “L2 <L1”.
In this case, for example, the position of the distance L2 where the sensor is disposed is a position where the passage of the leading end of the image forming medium is to be detected, and the position of the distance L1 where the cleaning section is disposed is the position of the cleaning section. The cleaning blade is configured to be in a position in contact with the primary transfer surface of the intermediate transfer belt. Further, the sensor can be constituted by, for example, a paper passage detection sensor including a rotary lever and a reflection type optical sensor.
Next, an image forming apparatus according to a second aspect of the present invention includes at least a transfer unit that transfers a carried toner image to an image forming medium, a feeding roller that supplies the image forming medium to the transfer unit, and the transfer unit. A detection unit that detects a conveyance failure of the image forming medium after passing through the sheet, and when the detection unit detects a conveyance failure after passing the transfer unit of the image forming medium, the entire apparatus is stopped and the feeding And a control means for stopping only the roller after driving for a predetermined time.
In the image forming apparatus, for example, the transfer unit is a portion where the intermediate transfer belt and the transfer roller are opposed to and in pressure contact with each other, and the feeding roller is located upstream of the transfer unit in the conveyance direction of the image forming medium. A standby conveying roller disposed immediately before, wherein the detection unit is a sensor that detects winding of the image forming medium around the intermediate transfer belt after passing through the transfer unit, and the control unit includes the feeding roller During the predetermined time for driving only the image forming medium, the image forming medium is fed out so as to form a slack gap in which a human finger can be easily inserted between the transfer unit and the feeding roller by the rotation of the feeding roller. It is configured to be time.

  According to the present invention, there is provided an image forming apparatus capable of early and surely detecting a peeling failure of a transfer medium (image forming medium) from a secondary transfer belt and easily removing the image forming medium in which the peeling failure is detected. It becomes possible.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Embodiment 1)
FIG. 1 is a schematic cross-sectional view showing the configuration of a color image forming apparatus (hereinafter simply referred to as a printer) in Embodiment 1 of the present invention.

  The printer 10 shown in FIG. 1 is an electrophotographic secondary transfer tandem color image forming apparatus, and includes an image forming unit 12, an intermediate transfer belt unit 13, a paper feeding unit 14, and a duplex printing transport unit 15. It consists of

  The image forming unit 12 has a configuration in which four image forming units 16 (16M, 16C, 16Y, 16K) are arranged side by side in a multistage manner from right to left in FIG.

  Of the four image forming units 16, the three upstream image forming units 16M, 16C, and 16Y are magenta (M), cyan (C), and yellow, which are subtractive three primary colors, respectively. A mono-color image is formed with the (Y) color toner, and the image forming unit 16K forms a monochrome image with the black (K) toner mainly used for dark portions of characters and images.

  Each of the image forming units 16 has the same configuration except for the color of toner stored in a toner container (toner cartridge). Accordingly, the configuration of the black (K) image forming unit 16K will be described below as an example.

  The image forming unit 16 includes a photosensitive drum 17 at the bottom. The peripheral surface of the photosensitive drum 17 is made of, for example, an organic photoconductive material. A cleaner 18, a charging roller 19, an optical writing head 21, and a developing roller 23 of the developing device 22 are arranged around the periphery of the photosensitive drum 17.

  The developing unit 22 puts one of magenta (M), cyan (C), yellow (Y), and black (K) toners in the upper toner container as indicated by M, C, Y, and K in the figure. An intermediate portion is provided with a toner replenishing mechanism for the lower portion.

  The developing unit 22 is provided with the developing roller 23 in the side opening at the lower portion thereof, a toner stirring member, a toner supply roller for supplying toner to the developing roller 23, and a toner layer on the developing roller 23 as a fixed layer. It has a doctor blade that regulates the thickness.

  The intermediate transfer belt unit 13 has an endless transfer belt 24 extending in a flat loop shape from substantially the left and right sides of the figure at the center of the main body, and the transfer belt 24 is stretched over the transfer belt 24. A driving roller 25 and a driven roller 26 are provided to circulate and move the belt 24 counterclockwise in the figure.

  The transfer belt 24 transfers the toner image directly to the belt surface (primary transfer) and conveys the toner image to the transfer position to the paper for further transfer (secondary transfer). The whole is called an intermediate transfer belt unit.

  The intermediate transfer belt unit 13 includes a belt position control mechanism 27 in the loop of the flat loop-shaped transfer belt 24. The belt position control mechanism 27 includes a primary transfer roller 28 made of a conductive foam sponge that presses against the lower peripheral surface of the photosensitive drum 17 via the transfer belt 24.

  The belt position control mechanism 27 includes three primary transfer rollers 28 corresponding to the three image forming units 16M, 16C, and 16Y of magenta (M), cyan (C), and yellow (Y) as vertical support shafts. Rotate to the center with the same period.

  Then, the belt position control mechanism 27 performs transfer by rotating one primary transfer roller 28 corresponding to the black (K) image forming unit 16K at a rotational movement period different from the period of the three primary transfer rollers 28. The belt 24 is separated from the photosensitive drum 17.

  That is, the belt position control mechanism 27 sets the position of the transfer belt 24 of the intermediate transfer belt unit 13 in the full color mode (all four primary transfer rollers 28 are in contact with the transfer belt 24) and the monochrome mode (in the image forming unit 16K). Only the corresponding primary transfer roller 28 is in contact with the transfer belt 24) and all non-transfer modes (all four primary transfer rollers 28 are separated from the transfer belt 24).

  In the intermediate transfer belt unit 13, a belt cleaner unit is disposed further upstream of the image forming unit 16M on the uppermost stream side in the belt movement direction on the upper surface, and is flat and thin so as to be almost along the entire lower surface. The waste toner collecting container 29 is detachably disposed.

  The paper feed unit 14 includes two paper feed cassettes 31 arranged in two upper and lower stages, and a paper take-out roller 32 is provided in the vicinity of the paper feed opening (right side in FIG. 1) of the two paper feed cassettes 31. A feeding roller 33, a separating roller 34, and a standby conveyance roller pair 35 are disposed.

  In the paper conveyance direction (vertical upward direction in the figure) of the standby conveyance roller pair 35, a secondary transfer roller 36 that is in pressure contact with the driven roller 26 via the transfer belt 24 is disposed. A secondary transfer portion 40 to the paper is formed at the pressure contact portion with the roller 36.

  A belt-type fixing device 37 is disposed on the downstream side (upper side in the drawing) of the secondary transfer unit 40. On the further downstream side of the belt-type fixing device 37, the fixed sheet is fed from the belt-type fixing device 37. A pair of carry-out rollers 38 to be carried out and a pair of paper discharge rollers 41 to discharge the carried-out paper to a paper discharge tray 39 formed on the upper surface of the apparatus are arranged.

  The duplex printing conveyance unit 15 includes a start return path 42a branched from the intermediate conveyance path between the carry-out roller pair 38 and the paper discharge roller pair 41 in the right lateral direction in the figure, and then an intermediate return path 42b bent downward. A terminal return path 42c that bends in the left lateral direction opposite to the above and eventually reverses the return sheet, and four return roller pairs 43a, 43b, 43c, 43d arranged in the middle of these return paths. ing.

  The exit of the end return path 42 c communicates with a conveyance path to the pair of standby conveyance rollers 35 corresponding to the sheet feeding cassette 31 below the sheet feeding section 14.

  In this example, a cleaning unit 45 is disposed on the upper surface of the intermediate transfer belt unit 13. In the cleaning unit 45, the cleaning blade 46 comes into contact with the upper surface of the transfer belt 24 and scrapes off and removes the waste toner.

  The removed waste toner is taken in by the take-in roller 47 and stored in a temporary storage section of a belt cleaner unit (not shown), and the stored waste toner is transported to the upper part by a transport screw to the upper part. To the waste toner collecting container 29.

  Further, in order to bring the cleaning blade 46 of the cleaning unit 45 into pressure contact with the transfer belt 24 with an appropriate pressure, a pressure roller that presses the transfer belt 24 toward the cleaning unit 45 from below on the intermediate transfer belt unit 13 side. 48 is provided.

  As shown in FIG. 1, the printer 10 does not directly transfer a toner image onto a conventional sheet, but passes a transfer belt 24 to a sheet that is vertically conveyed to a secondary transfer unit by a standby conveyance roller pair 35. Thus, the toner image is transferred.

  Accordingly, during a maintenance process for recovering from a problem such as a paper jam occurring in the paper conveyance path, the maintenance can be dealt with by merely rotating the double-sided printing conveyance unit 15 outward and opening the right side of FIG. ing.

  In addition, since troubles such as paper jam do not occur in the arrangement section of the kits, the operation for attaching and detaching consumables such as the kits concentrated on the left side of FIG. 1 may be a small space that can be replaced in the longitudinal direction. It is configured as follows.

  Thereby, the dimension between kits is reduced as much as possible, and size reduction of the whole apparatus main body is achieved. Further, the optical writing head itself is also miniaturized and is configured closer to the photosensitive drum.

  FIG. 2 is a circuit block diagram including the control device of the printer 1 described above. As shown in FIG. 2, the circuit block has a central processing unit (CPU) 61 as a center, and an interface controller (I / F_CONT) 61 and a printer controller (PR_CONT) 62 are connected to the CPU 61 via data buses. ing. A printer printing unit 63 is connected to the PR_CONT 62.

  Further, the CPU 61 includes a ROM (read only memory) 64, an EEPROM (electrically erasable programmable ROM) 65, an operation panel 66 of the main body operation unit, a downstream side of the secondary transfer unit 40, and outputs from sensors disposed in each unit. Is connected to the sensor unit 67.

  The ROM 64 stores a system program, and the CPU 61 performs processing by controlling each unit in accordance with the system program.

  That is, in each unit, first, the I / F_CONT 61 converts print data supplied from a host device such as a personal computer into bitmap data and develops it in the frame memory 68. In the frame memory 68, a storage area is set for each of black (K), magenta (M), cyan (C), and yellow (Y), and data of each color is developed in the corresponding area.

  The data developed in the frame memory 68 is output to the PR_CONT 62 and is output from the PR_CONT 62 to the printer printing unit 63.

  The printer printing unit 63 is an engine unit, and under the control of the PR_CONT 62, the rotational drive system including the photosensitive drum 17, the primary transfer roller 28, etc. shown in FIG. 1, the charging roller 19, the optical writing head 21, etc. An image forming unit having a driven portion, a belt driving unit 25 that moves the intermediate transfer unit 13 up and down and rotationally drives the transfer belt 24, and a rotationally driven unit such as a paper take-out roller 32 to a paper discharge roller pair 41. A drive output to a process load such as a conveyance mechanism, a heat generating drive, and a belt type fixing device 37 driven to rotate is controlled.

  The black (K), magenta (M), cyan (C), and yellow (Y) data output from the PR_CONT 62 are respectively sent from the printer printing unit 63 to the corresponding optical writing head 21 shown in FIG. To be supplied.

  Next, the basic operation of the printer 10 having the above configuration will be described. In the following description of the basic operation, the operation in the color printing state will be described.

  First, printing (printing) is started when the power is turned on and the number of sheets to be used, the print mode, and other designations are input as keys or as signals from the connected host device.

  That is, the driving roller 25 rotates counterclockwise in FIG. 1, and the transfer belt 24 starts to circulate. The image forming units 16 are sequentially driven, and the photosensitive drum 17 rotates in the clockwise direction in the figure.

  The charging roller 19 initializes the peripheral surface of the photosensitive drum 17 by applying a uniform high negative charge, and the optical writing head 21 performs exposure according to the image signal on the peripheral surface of the photosensitive drum 17 by initialization. An electrostatic latent image including a high negative potential portion and a low negative potential portion by the exposure is formed.

  The developing roller 23 transfers the toner in the developing unit 22 to the low potential portion of the electrostatic latent image to form a toner image (reverse development) on the circumferential surface of the photosensitive drum 17.

  A magenta toner image formed on the peripheral surface of the photosensitive drum 17 of the image forming unit 16M in the uppermost stream in the sheet conveying direction is rotated and conveyed to the surface facing the transfer belt 24.

  The primary transfer roller 28 applies a transfer current output from a transfer bias power source (not shown) to the transfer belt 24. As a result, the magenta toner image on the photosensitive drum 17 is primarily transferred to the transfer belt 24.

  A cyan toner image formed on the peripheral surface of the photosensitive drum 17 of the image forming unit 16C is superimposed on the toner image primarily transferred to the transfer belt 24, and then is transferred by a primary transfer roller 28 directly below the image forming unit 16C. Transcribed.

  Further, the yellow toner image formed on the peripheral surface of the photoconductive drum 17 of the image forming unit 16Y is overlaid and transferred by the primary transfer roller 28 directly below the image forming unit 16Y, and finally, the photoconductive body of the image forming unit 16K. The black toner image formed on the peripheral surface of the drum 17 is transferred onto the primary transfer roller 28 directly below the image forming unit 16K.

  As described above, the toner images of four colors of magenta (M), cyan (C), yellow (Y), and black (K) are sequentially superimposed and primarily transferred to complete a full-color image on the transfer belt 24.

  The transfer belt 24 on which the four-color toner images are primarily transferred is continuously circulated as it is to transfer the four-color toner images to the secondary transfer position (secondary transfer) where the driven roller 26 and the secondary transfer roller 36 face each other. Transport to transfer section 40).

  On the other hand, the paper take-out roller 32 rotates to take out the paper stored in the paper feed cassette 31 slightly earlier than the printing timing on the paper. The roll roller 34 rotates in the reverse direction in order to inhibit the lower sheet from being fed in order to feed out only the uppermost sheet of the sheet taken out from the sheet cassette 31.

  The feeding roller 33 rotates in the forward direction and feeds the uppermost sheet to the standby conveyance roller pair 35.

  The standby conveyance roller pair 35 temporarily stops the rotation to stop the paper advance, corrects the conveyance posture such as the skew of the paper, waits for the conveyance timing, and sets the print start position of the paper by the transfer belt 24. In accordance with the timing coincident with the leading end of the four-color toner image conveyed to the secondary transfer position, the conveyance of the sheet is resumed and the sheet is fed to the secondary transfer position.

  At the secondary transfer position, the secondary transfer roller 36 applies a bias voltage supplied from a bias power source (not shown) to the sheet. As a result, the four color toner images on the transfer belt 24 are secondarily transferred to the paper.

  The sheet on which the four color toner images have been transferred is carried into the belt type fixing device 37 as it is. The belt-type fixing device 37 presses and holds the paper with an appropriate pressure contact force by the heat generation roller and the pressure contact roller, and applies heat and pressure to the paper and discharges it upward while fixing the four color toner images on the paper surface.

  The sheet discharged from the belt-type fixing device 37 is nipped by the pair of carry-out rollers 38 and taken over, and the pair of paper discharge rollers 41 places the image forming surface of the four color toner images on the paper discharge tray 39 downward. Discharged.

  In the above description, color printing is described. However, for monochrome printing, the transfer belt 24 contacts only the photosensitive drum 17 of the image forming unit 16K and moves away from the other photosensitive drums 17; Except for the point that only the unit 16K is operated, the other operations are almost the same as those in the color printing described above.

  Also in the printer 10 of this example having the above configuration, in order to secondarily transfer the toner image primarily transferred onto the intermediate transfer belt 24 onto the sheet, the secondary transfer unit 40 uses the secondary transfer roller or the like to transfer the toner image to the sheet. Apply the next transfer voltage.

  As described above, the electrostatic function of the intermediate transfer belt 24 by the secondary transfer voltage is affected by the temperature and humidity inside the image forming apparatus. The temperature changes in accordance with changes in temperature and humidity inside the apparatus, and the electrostatic function of the intermediate transfer belt 24 is strengthened, so that the paper is wound around the intermediate transfer belt 24, so-called paper jam occurs.

  If the winding of the paper around the intermediate transfer belt 24 cannot be detected early and reliably without a detection error, the paper carrying the toner image before fixing enters the cleaning unit 45 and damages the cleaning blade. There is a problem that toner is scattered inside the image forming apparatus.

  In this example, the paper passing detection sensor having a very inexpensive configuration is used to detect the winding of the paper around the intermediate transfer belt 24 early and reliably without any detection error, thereby reliably preventing the above-described problems. . This will be described below.

  FIG. 3 is a diagram showing a mechanism for detecting early and surely the winding of the paper around the intermediate transfer belt. 3 shows the configuration in the vicinity of the secondary transfer unit 40 and the arrangement position of the paper passage detection sensor 49 (not shown in FIG. 1).

  3 shows the configuration of each part in an easy-to-understand manner, and schematically shows the whole as a whole. However, the same components as those in FIG. 1 are given the same numbers as those in FIG.

  In FIG. 3, the sheet that has passed through the secondary transfer unit 40 is carried into the belt-type fixing device 37 along the conveyance path a if it is a book. In this example, a sensor 49 is arranged to detect the passage of the sheet while the sheet (image forming medium) on which the toner image is secondarily transferred is conveyed toward the belt-type fixing device 37 (fixing unit). ing.

  Normally, a light transmissive non-contact sensor is used as a sensor for detecting the paper position, but the light transmissive non-contact sensor is an expensive device. Further, the light transmissive non-contact type sensor is greatly influenced by the printed image on the paper. For example, when the print image is a black solid image printed from the front end of the paper, the position of the front end of the paper may not be detected.

  Further, in the case of a light transmission type non-contact type sensor, the space on the surface of the intermediate transfer belt is widely taken for the sensor, and as a result, the apparatus becomes large. Also, depending on the position, the toner is likely to adhere to the sensor light receiving surface, so there are many inconveniences such as periodic cleaning of the sensor light receiving surface.

  In this example, the sensor 49 is a sensor having a simple and inexpensive configuration including the rotary lever 51 and the reflective optical sensor 54.

  The rotation lever 51 of the sensor 49 is rotatably disposed at a solid line position 52 and a broken line position 53 in the figure, and is always at the solid line position 52 and the free end side is inserted into the sheet conveyance path a. Permanent.

  A sheet that passes through the secondary transfer unit 40 and is transported toward the belt-type fixing device 37 along the transport path a is rotated at the leading end at a solid line position 52 immediately before being fed into the belt-type fixing device 37. Abutting on the movable lever 51, the rotary lever 51 is pushed back to the broken line position 53. The reflection type optical sensor 54 detects the rotary lever 51 pushed back to the broken line position 53.

  A sensor position for detecting passage of the leading edge of the paper by the cooperation of the rotary lever 51 and the reflection type optical sensor 54 is set at a position of a distance L2 from the secondary transfer unit 40.

  2 is based on the output of the sensor 49 notified from the sensor unit 67 (the output indicating that the reflective optical sensor 54 has detected the rotary lever 51 pushed back to the broken line position 53). It is determined whether or not the sensor position (position of distance L2) has passed within a predetermined time after passing through the secondary transfer portion 40. Here, the predetermined time is a time during which the sheet is transported the distance L2 after passing through the secondary transfer unit 40.

  The distance L2 is set to be shorter than the distance L1 from the conveyance path a to the position where the cleaning blade 46 of the cleaning unit 45 faces the pressing roller 47 via the transfer belt 24. That is, the distance L2 and the distance L1 are set to have a relationship of “L2 <L1”.

  The CPU 60 does not pass the sensor position (the position at the distance L2) within a predetermined time (the time during which the paper is transported the distance L2 after the paper passes through the secondary transfer unit 40) after the paper passes through the secondary transfer unit 40. When it is determined that there is no output indicating that the rotary lever 51 pushed back to the broken line position 53 from the reflective optical sensor 54 is detected, the printer printing unit 63 is controlled to stop the conveyance of the paper. Then, a stop instruction is issued to each unit to stop the operation of the entire image forming apparatus.

  As described above, the sheet does not pass through the sensor position within a predetermined time after passing through the secondary transfer unit 40, which means that the sheet is wound around the intermediate transfer belt 24 and is carried toward the cleaning unit 45. It is causing a jam.

  However, when the CPU 60 stops the operation of the entire image forming apparatus as described above, the paper wound around the intermediate transfer belt 24 stops in a state where it is conveyed by the distance L2 toward the cleaning unit 45. This distance L2 is shorter than the distance L1. That is, the leading edge of the paper does not enter the cleaning unit 45.

  Here, the maintenance work for eliminating the paper jam is performed by the maintenance worker. That is, the maintenance operation can be performed by stopping the operation of the entire image forming apparatus before the sheet enters the cleaning unit 45 and a problem occurs in which a large amount of toner is scattered inside the apparatus.

  As described above, according to the first embodiment, the sheet passing detection sensor having the inexpensive configuration of the rotary lever 51 and the reflection-type optical sensor 54 is used, and the separation of the sheet from the secondary transfer belt 24, that is, the middle Winding around the transfer belt 24 can be detected early (before the leading edge of the paper enters the cleaning unit 45) and reliably.

  If the sensor 49 used in the first embodiment is also arranged on the downstream side of the belt-type fixing device 37, the detection method for checking the elapsed time is the same as described above, and the belt-type fixing device 37 detects a paper winding jam. Can be applied.

(Embodiment 2)
By the way, when it is detected that the sheet has been wound around the secondary transfer belt 24 due to a peeling failure, the operation of the entire image forming apparatus is stopped, and maintenance work is performed by a maintenance worker. As described above, it is possible to perform maintenance work by rotating the outer side to open the right side.

  FIG. 4 is a diagram illustrating a state where the paper is wound around the secondary transfer belt 24 and the duplex printing conveyance unit 15 is rotated outward to perform maintenance work.

  In FIG. 4, the same components as those shown in FIG. 1 are denoted by the same reference numerals as those in FIG. As for the two paper feed cassettes 31, the upper one is indicated by 31u, the lower one is indicated by 31d, the feeding roller 33 related thereto is also indicated by 33u and 33d, and the separating roller 34 is also indicated by 34u and 34d. The standby conveyance roller pair 35 is also indicated by 35u and 35d.

  As shown in FIG. 4, the conveyance unit 15 for double-sided printing is rotated outward with the hinge 30 as a fulcrum, and a sheet conveyance path extending vertically to the belt-type fixing device 37 through the pair of standby conveyance rollers 35d to 35u. When viewed, the paper P (P-1, P-2) causing the jam is conveyed in the direction of the cleaning unit 45 while the leading end P-1 is wound around the transfer belt 24 and is stuck to the transfer belt 24. ing.

  At this time, the front end portion P-1 side of the paper P is firmly attached to the intermediate transfer belt 24 because a high voltage is applied by the secondary transfer portion 40. In addition, the paper P is taken out from the lower paper feed cassette 31d or taken out from the upper paper feed cassette 31u. The standby conveyance roller pair 35u or 35d.

  Therefore, as shown in FIG. 4, the sheet P is pulled at both front and rear ends, and a finger is put between the sheet P and the transfer unit as shown by a broken-line circle b in the figure. There is no gap, and the paper P cannot be gripped and taken out from the left and right (front and back) with fingers.

  As described above, when the paper jam occurs, it is very difficult to remove the paper P wound around the transfer belt 24 without any gap between the paper and the transfer unit.

  Further, when removing the paper wound around the transfer belt 24, if the paper is forcibly pulled, the paper is torn and further processing becomes difficult, or a part of the torn paper remains in the apparatus, resulting in a secondary failure. there is a possibility.

  Similarly, if the paper wound around the transfer belt 24 is forcibly peeled off from the belt and the belt is damaged by a nail or the like, the transfer belt 24 must be replaced with a new one because it causes a printing defect. It becomes inconvenient such as disappearing.

  In the second exemplary embodiment, when the toner image is secondarily transferred to the paper P by the transfer belt 24, the conveyance of the paper P is stopped after detecting that the paper P is wound around the transfer belt 24 without being separated. A gap is created between the paper P and the transfer unit so that the paper P can be easily taken out by hand. This will be described below.

  FIG. 5 is a flowchart for explaining the operation of processing after jamming detection so that the paper P that has caused a jamming failure from the transfer belt 24 and causes jamming in the second embodiment can be easily taken out.

  6 is a diagram illustrating a state where the duplex printing transport unit 15 is rotated outward in order to perform a maintenance operation after the jam detection, and a state after the processing of FIG. 5 of the paper wound around the transfer belt and causing a jam. It is. 6 are given the same numbers as in FIG.

  The post-print jam post-processing shown in FIG. 5 is performed after the CPU 60 shown in FIG. 2 constantly monitors the notification from the sensor unit 67 in the interrupt process during the print process and confirms that a jam has occurred. It is processing. Note that the jam detection method is not limited to the method described in the first embodiment, and any jam detection method may be used.

  In FIG. 5, the CPU 60 monitors whether a jam has occurred (step S1), and if not (S1 is No), monitors whether a jam has occurred again in step S1 in the next interrupt processing cycle. Repeat that.

  If the occurrence of a jam is notified from the sensor unit 67 (S1 is Yes), the entire apparatus is stopped (step S2). In this process, a stop command is output to the high voltage generator, heater drive, motor drive, etc., and the entire apparatus stops.

  Next, it is determined whether or not the generated jam is wound around the transfer belt 24 by the paper P (step S3). There are several types of jams in at least a paper feeding unit, a sheeting unit, a standby unit, a secondary transfer unit, and a fixing unit.

  The site where these jams occur is determined by knowing the arrangement position of the sensor that outputs the jam detection signal indicated by the notification from the sensor unit 67. A jam around the transfer belt 24 is detected as a jam in the secondary transfer portion.

  If the generated jam is not a wrap around the transfer belt 24 (No in S3), the CPU 60 displays a warning of the occurrence of the jam and a display indicating the occurrence site on a display device (not shown) of the operation panel 66. To end the process.

  Further, when the generated jam is a wrap around the transfer belt 24 (Yes in S3), the CPU 60 drives the printer controller (PR_CONT) 62 to drive the standby conveyance roller pair 35 while stopping the entire operation in Step S2. (Step S4). As a result, the motor that drives the standby conveyance roller pair 35 starts to rotate.

  Then, the CPU 60 determines whether or not the specified time has elapsed (step S5). In this process, in step S4, the printer controller 62 is instructed to drive the standby conveyance roller pair 35, and at the same time, the value of the time counter activated by the CPU 60 is monitored.

  When the standby conveyance roller pair 35 (35u, 35d) is driven and the sheet P is fed in the normal conveyance direction as indicated by an arrow c in FIG. 6, the downstream end portion P-1 from the secondary transfer portion 40 is obtained. Sticks to the transfer belt 24 and does not move, but since the second half P-2 on the upstream side from the secondary transfer unit 40 is free, the secondary transfer unit 40 and the standby transport roller pair are fed by the amount sent in the transport direction. A slack is formed with 35u.

  This slack is caused between the sheet P and the intermediate transfer belt unit 13 as shown by the dotted circle d in FIG. 6 according to the amount (elapsed time) of the latter half P-2 of the sheet P sent out by the standby conveyance roller pair 35u. In between, a slack gap is formed in which a human finger can be easily inserted.

  During the specified time for driving only the standby transport roller 35 (35d, 35u), the second half P-2 of the fed paper P is placed between the standby transport roller pair 35u and the intermediate transfer belt unit 13 with a human finger. This is the time that is sent out to form a slack gap indicated by a dashed circle d that can be easily inserted.

  When reading that the specified time has elapsed from the value of the time counter, the CPU 60 outputs an instruction to stop driving the standby conveyance roller pair 35 to the printer controller 62 (step S6). As a result, the motor that rotationally drives the standby transport roller pair 35 stops, and the standby transport roller pair 35 stops rotating.

  In step S7, the CPU 60 displays a warning indicating the occurrence of a jam and a display indicating that the generated portion is wound around the transfer belt 24 on a display device (not shown) of the operation panel 66, and performs processing. Exit.

  As shown in FIG. 6, when the maintenance worker performs the maintenance work by looking at the notification display, the double-sided printing transport unit 15 is rotated outward and the right side of the apparatus is opened. A gap is formed between the intermediate transfer belt unit 13 so that a human finger can be easily inserted, and maintenance is not required without tearing the paper or raising the nail on the belt surface. The operator can easily remove the paper P.

1 is a schematic cross-sectional view showing a configuration of a color image forming apparatus (printer) in Embodiment 1 of the present invention. FIG. 2 is a circuit block diagram including a printer control device according to the first embodiment. FIG. 3 is a diagram illustrating a mechanism for early and surely detecting winding of a sheet around an intermediate transfer belt of the printer according to the first exemplary embodiment. FIG. 5 is a diagram illustrating a state where a sheet is wound around a secondary transfer belt and a duplex printing conveyance unit is rotated outward in order to perform maintenance work. 10 is a flowchart for explaining the operation of processing after detecting a jam so that a sheet having a separation failure from the transfer belt and causing a jam in the second embodiment can be easily taken out. FIGS. 6A and 6B are diagrams illustrating a state in which a duplex printing conveyance unit is rotated outward in order to perform a maintenance operation after a jam is detected and a state after processing of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Printer 12 Image formation part 13 Intermediate transfer belt unit 14 Paper feed part 15 Duplex printing conveyance unit 16 (16M, 16C, 16Y, 16K) Image formation unit 17 (17m, 17c, 17y, 17k) Photosensitive drum 18 Cleaner 19 Charging roller 21 Optical writing head 22 Developing device 23 Developing roller 24 Transfer belt 25 Drive roller 26 Driven roller 27 Belt position control mechanism 28 Primary transfer roller 29 Waste toner collection container 30 Hinge 31 (31u, 31d) Paper feed cassette 32 Paper take-out Roller 33 (33u, 33d) Feed roller 34 (34u, 34d) Rolling roller 35 (35u, 35d) Standby conveyance roller pair 36 Secondary transfer roller 37 Belt-type fixing device 37a Carry-in inlet 38 Carry-out roller pair 39 Paper discharge tray 40 Secondary transfer part 41 Paper discharge Roller pair 42a Start return path 42b Intermediate return path 42c End return path 43a, 43b, 43c, 43d Return roller pair 45 Cleaning unit 46 Cleaning blade 47 Capture roller 48 Press roller 49 Sensor 51 Rotary lever 52 Solid line position 53 Broken line position 54 Reflective light sensor 61 CPU (central processing unit)
61 Interface controller (I / F_CONT)
42 Printer Controller (PR_CONT)
63 Printer printing section 64 ROM (read only memory)
65 EEPROM (electrically erasable programable ROM)
66 Operation panel 67 Sensor section 68 Frame memory

Claims (6)

The toner image formed on the image carrier is primarily transferred to the intermediate transfer belt, and the primary transferred toner image is secondarily transferred to the image forming medium being transported in the secondary transfer portion. In the image forming apparatus having a cleaning unit disposed on the downstream side of the rotation of the intermediate transfer belt from the secondary transfer unit to clean the primary transfer surface of the intermediate transfer belt,
A sensor arranged to detect passage of the image forming medium while the image forming medium secondarily transferred with the toner image is conveyed toward the fixing unit;
Discrimination means for discriminating whether or not the image forming medium has passed through the sensor portion within a predetermined time after passing through the secondary transfer portion based on the output of the sensor;
Control means for stopping conveyance of the image forming medium when the determining means determines that the image forming medium does not pass through the sensor part within a predetermined time after passing through the secondary transfer part;
An image forming apparatus comprising:   The sensor is disposed at a distance L2 from the secondary transfer portion of the conveyance path through which the image forming medium is conveyed toward the fixing portion, and the cleaning portion is disposed at a distance L1 from the secondary transfer portion. 2. The image forming apparatus according to claim 1, wherein the distance L2 and the distance L1 have a relationship of “L2 <L1”.   The position of the distance L2 where the sensor is arranged is a position where the passage of the leading end of the image forming medium is to be detected, and the position of the distance L1 where the cleaning unit is arranged is that the cleaning blade of the cleaning unit is in the middle The image forming apparatus according to claim 1, wherein the image forming apparatus is a position in contact with a primary transfer surface of the transfer belt.   The image forming apparatus according to claim 1, wherein the sensor is a paper passage detection sensor including a rotary lever and a reflective optical sensor. At least a transfer unit that transfers the carried toner image to an image forming medium;
A feeding roller for feeding the image forming medium to the transfer unit;
A detection unit for detecting a conveyance failure of the image forming medium after passing through the transfer unit;
Control means for stopping the entire apparatus when the detection unit detects a conveyance failure after passing through the transfer unit of the image forming medium, driving only the feeding roller for a predetermined time, and then stopping;
An image forming apparatus comprising: The transfer portion is a portion where the intermediate transfer belt and the transfer roller are pressed against each other,
The feeding roller is a standby conveyance roller disposed immediately before the transfer unit on the upstream side in the conveyance direction of the image forming medium,
The detection unit is a sensor that detects winding of the image forming medium around the intermediate transfer belt after passing through the transfer unit;
For a predetermined time during which the control unit drives only the feeding roller, the image forming medium can easily insert a human finger between the transfer unit and the feeding roller by the rotation of the feeding roller. 6. The image forming apparatus according to claim 5, wherein the time for feeding is as long as possible to form a slack gap.