JP2012041156A - Post-processing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a post-processing device capable of avoiding erroneous detection caused by the floating of paper occurring when the paper is pressed.SOLUTION: The post-processing device 130 includes: a paper ejection port 28 for ejecting paper; an ejection tray 29 for stacking the ejected paper; a paper existence/nonexistence detection means 40 for detecting the existence or nonexistence of stacked paper that is stacked on the ejection tray 29; a detection instruction means 41 for instructing the paper existence/nonexistence detection means 40 to start detection or stop the detection; a tray height detection means 42 for detecting a height of the tray; a control means 44 for moving the ejection tray 29 to ascend and descend; a paper surface height detection means 43 for detecting a height of a paper surface; and a paper information receiving means 45 for receiving the kind of paper as paper information 45d. If the kind of the paper corresponding to the paper information 45d is specific paper, the detection instruction means 41 instructs to stop the detection before detecting the height of a paper surface, and instructs to start the detection when the paper ejection tray 29 is allowed to descend after detecting the height of the paper surface.

Description

  The present invention relates to a post-processing apparatus, and to an image forming apparatus including the post-processing apparatus.

  Conventionally, in an image forming apparatus, a post-processing device that performs post-processing such as paper sorting, stapling, and punching is disposed adjacent to a paper discharge port, and the post-processed paper is sequentially placed on a discharge tray. Loaded. In such an image forming apparatus, various types of paper having different characteristics such as size, paper quality, stiffness (rigidity), and paper thickness are subjected to image formation and post-processing without distinction.

  Therefore, when discharging the paper to the discharge tray, a technique for controlling the discharge position according to the type of the paper, suppressing the bending or variation of the paper on the discharge tray, and improving the consistency (for example, (See Patent Document 1).

JP 2007-182263 A

  Incidentally, in recent years, there are increasing opportunities for image forming apparatuses to be used in workplaces where office work is performed by a plurality of people such as offices. In such a workplace, before the user collects the paper, a new paper on which an image is formed is discharged according to an instruction from another user, and overloading on the discharge tray becomes a problem. Therefore, functions such as detection of presence / absence of paper on the discharge tray and restriction of paper stacking amount are required.

  Further, it has been studied to improve the consistency of the paper on the discharge tray by adopting a paper pressing lever that presses one end of the paper on the discharge tray. If the paper holding lever is used, when the paper holding lever presses one end of the paper on the discharge tray, the other end of the paper floats up, causing the sensor that detects the presence or absence of the paper on the discharge tray to falsely detect. There is a problem of doing.

  However, the paper post-processing apparatus described in Patent Document 1 only improves the consistency when paper is discharged to the discharge tray, and cannot manage the stacked paper.

  The present invention has been made to solve the above-described problem, and detects the presence or absence of a sheet after the discharge tray is lowered, thereby avoiding erroneous detection due to the floating of the sheet that occurs when the sheet is pressed. It is an object of the present invention to provide a post-processing apparatus that can perform such processing.

  Another object of the present invention is to provide an image forming apparatus that can prevent problems such as sheet overloading by providing a post-processing device that can avoid erroneous detection due to sheet floating.

  A post-processing apparatus according to the present invention is a post-processing apparatus including a paper discharge port that discharges a sheet conveyed from a sheet conveyance path and a discharge tray that stacks the discharged sheet, and is loaded on the discharge tray. A paper presence / absence detecting unit for detecting the presence / absence of loaded paper, and a detection start for causing the paper presence / absence detecting unit to start detecting the presence / absence of the loaded paper, or the paper presence / absence detecting unit to stop detecting the presence / absence of the stacked paper Detection instruction means for instructing to stop detection, tray height detection means for detecting the height of the discharge tray with respect to the sheet discharge port as a tray height, and controlling the tray height by moving the discharge tray up and down. Control means, a paper pressing lever for pressing one end of the stacked paper on the paper discharge port side, and when the stacked paper is pressed by the paper pressing lever, A paper surface height detecting means for detecting the height of the loaded paper as the paper surface height, and a paper information receiving means for receiving, as paper information, the type of the paper transported in the paper transport path. The discharge tray is raised before discharging, and the detection instruction means detects the paper surface height when the paper type corresponding to the paper information received by the paper information receiving means is a specific paper specified in advance. The means instructs the stop of detection before detecting the paper surface height, and after detecting the paper surface height, the detection means detects when the control means lowers the discharge tray by a first preset amount. A start is instructed.

  According to this configuration, by detecting the presence or absence of the sheet after the discharge tray is lowered, it is possible to avoid erroneous detection due to the floating of the sheet that occurs when the sheet is pressed.

  In the post-processing apparatus according to the present invention, the specific sheet is a postcard or an envelope.

  According to this configuration, a strong paper such as a postcard or an envelope can be specified as the specific paper.

  The post-processing apparatus according to the present invention includes a sheet upper limit determination unit that determines that the stacking is possible or the sheet upper limit based on a detection result of the sheet height detection unit, and the control unit includes the sheet upper limit determination unit. When it is determined that the upper limit of the sheet is reached, the discharge tray is lowered by a preset second set amount.

  According to this configuration, the paper surface height can be controlled to an appropriate position when the paper is discharged.

  The post-processing apparatus according to the present invention includes a history information storage unit that stores received sheet information as history information in a history information database, and history information update that updates history information based on a detection result of the sheet presence / absence detection unit. Means.

  According to this configuration, the type and order of the stacked sheets can be grasped.

  In the post-processing apparatus according to the present invention, the sheet information receiving unit notifies the control unit that the sheet is a plain sheet specified in advance based on the history information, and the control unit includes the plain sheet. In the case of the first stacking, the lowering of the first set amount is stopped after detecting the paper surface height before discharging the paper.

  According to this configuration, even if a specific sheet stacked on the top is lifted, the presence or absence of the sheet can be detected by the normal sheet stacked below, so that an excessive operation of the discharge tray can be avoided.

  In the post-processing apparatus according to the present invention, when the number of stacked sheets exceeds a preset number, the control unit detects the paper surface height before discharging the sheets, and then decreases the first set amount. It is characterized by canceling.

  According to this configuration, it is possible to determine that no lifting occurs if the sheets are sufficiently stacked, and therefore it is possible to shift to a normal operation.

  The post-processing apparatus according to the present invention includes a tray lower limit determination unit that determines that loading is possible or impossible based on a detection result of the tray height detection unit, and the tray lower limit determination unit is not capable of stacking. When it is determined that there is, the paper discharge is stopped.

  According to this configuration, it is possible to prevent abnormality of the apparatus due to overloading.

  The post-processing apparatus according to the present invention detects the height of the paper by raising the discharge tray when the discharge tray is lowered by the first set amount and the tray lower limit determination unit determines that stacking is impossible. Thereafter, if it is determined by the tray lower limit determining means that the stacking is possible, the sheet is discharged.

  According to this configuration, it is possible to make an accurate determination by re-determining the lower limit of the discharge tray.

  In the post-processing apparatus according to the present invention, the discharge tray includes a tray base portion provided along the paper discharge port, and a tray extending portion that extends from the tray base toward the opposite side of the paper discharge port. The discharge tray is arranged so that the sheet discharge port side is lowered, and the sheet presence / absence detecting means is provided in the tray extending portion.

  According to this configuration, the sheets can be arranged so that the leading ends of the sheets are concentrated on the tray base.

  An image forming apparatus according to the present invention includes the post-processing apparatus according to the present invention.

  According to this configuration, it is possible to provide an image forming apparatus that can prevent problems such as sheet overloading by including a post-processing device that can avoid erroneous detection due to sheet floating.

  According to the present invention, by detecting the presence or absence of a sheet after the discharge tray is lowered, it is possible to avoid erroneous detection due to the floating of the sheet that occurs when the sheet is pressed.

  In addition, according to the present invention, it is possible to provide an image forming apparatus that can prevent problems such as overloading of paper by including a post-processing device that can avoid erroneous detection due to paper floating.

1 is a side view illustrating a schematic configuration of an image forming apparatus including a post-processing apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged side view showing a portion of a post-processing device in the image forming apparatus of FIG. 1. FIG. 4 is an enlarged view showing a discharge tray and a sheet pressing lever in FIG. 2, and is a side view showing a first modification of the discharge tray. FIG. 9 is an enlarged view showing a discharge tray and a sheet pressing lever in FIG. 2, and is a side view showing a second modification of the discharge tray. FIG. 9 is an enlarged view showing a discharge tray and a sheet pressing lever in FIG. 2, and is a side view showing a third modification of the discharge tray. FIG. 3 is an enlarged view showing a discharge tray and a paper pressing lever in FIG. 2, and is an explanatory view showing a case where no paper is lifted. FIG. 3 is an enlarged view showing a discharge tray and a paper pressing lever in FIG. 2, and is an explanatory view showing a case where the paper is lifted up. FIG. 3 is an enlarged view showing a discharge tray and a sheet pressing lever in FIG. 2, and is an explanatory view showing a case where the discharge tray is lowered. FIG. 3 is an enlarged view illustrating a discharge tray and a sheet pressing lever in FIG. 2, and is an explanatory diagram illustrating a case where a plurality of sheets are stacked. FIG. 3 is an enlarged view illustrating a discharge tray and a sheet pressing lever in FIG. 2, and is an explanatory diagram illustrating a case where plain sheets are first stacked. It is a schematic block diagram which shows schematic structure of the post-processing apparatus which concerns on embodiment of this invention. FIG. 6 is a flowchart showing a first processing flow when a sheet is discharged by the post-processing apparatus according to the embodiment of the present invention until the first sheet is discharged. FIG. 10 is a first processing flow when the paper is discharged by the post-processing apparatus according to the embodiment of the present invention, and is a flowchart showing an operation after discharging the paper. FIG. 10 is a second processing flow in the case where the post-processing apparatus according to the embodiment of the present invention discharges a sheet, and is a flowchart showing an operation until the first sheet is discharged. FIG. 10 is a second processing flow in the case where a sheet is discharged by the post-processing apparatus according to the embodiment of the present invention, and is a flowchart showing an operation after discharging the sheet. FIG. 10 is a third processing flow when a sheet is discharged by the post-processing apparatus according to the embodiment of the present invention, and is a flowchart showing an operation until the first sheet is discharged. FIG. 10 is a third processing flow when the paper is discharged by the post-processing apparatus according to the embodiment of the present invention, and is a flowchart showing an operation after discharging the paper.

  Hereinafter, an image forming apparatus including a post-processing apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a side view showing a schematic configuration of an image forming apparatus including a post-processing apparatus according to an embodiment of the present invention.

  The image forming apparatus 100 includes an apparatus main body 110 and an automatic document processing apparatus 120, and forms multicolor and single color images on a predetermined sheet (original) in accordance with image data transmitted from the outside.

  The apparatus main body 110 includes an exposure unit 1, a developing device 2, a photosensitive drum 3, a cleaner unit 4, a charger 5, an intermediate transfer belt unit 6, and a fixing unit 7.

  In addition to the above-described configuration, the image forming apparatus 100 includes a document reading device 90 that reads an image of a document and a document placement table 92 on which the document is placed.

  The document reading device 90 is provided on the upper portion of the apparatus main body 110.

  The document placing table 92 is made of transparent glass and is provided on the upper side of the document reading device 90.

  The automatic document processing device 120 is attached to the upper side of the document placement table 92 and automatically conveys the document onto the document placement table 92. Further, the document processing device 120 is configured to be rotatable in the direction of arrow M, and the document can be placed manually by opening the document table 92.

  The image data handled in this image forming apparatus corresponds to a color image using each color of black (K), cyan (C), magenta (M), and yellow (Y). Accordingly, four developing devices 2, photosensitive drums 3, charging devices 5, and cleaner units 4 are provided to form four types of latent images corresponding to the respective colors, and are respectively provided in black, cyan, magenta, and yellow. These are set to form four image stations.

  The charger 5 is a charging means for uniformly charging the surface of the photosensitive drum 3 to a predetermined potential. In addition to a charger type as shown in FIG. 1, a contact type charger (for example, a roller type or a brush) is used. Type).

  The exposure unit 1 has a function of exposing the charged surface of the photosensitive drum 3 in accordance with input image data and forming an electrostatic latent image in accordance with the image data on the surface of the photosensitive drum 3. Specifically, the exposure unit 1 includes a polygon mirror that scans a laser beam and optical elements such as a lens and a mirror for guiding the laser beam reflected by the polygon mirror to the photosensitive drum 3.

  As the exposure unit 1, a laser scanning unit (LSU) provided with a laser emitting part, a reflection mirror, and the like, and a writing device (for example, a writing head) in which light emitting elements such as EL and LED are arranged in an array can be used.

  The developing device 2 visualizes the electrostatic latent images formed on the respective photosensitive drums 3 with toner of four colors (YMCK).

  The cleaner unit 4 removes and collects toner remaining on the surface of the photosensitive drum 3 after development and image transfer.

  The intermediate transfer belt unit 6 is disposed above the photosensitive drum 3 and includes an intermediate transfer belt 61, an intermediate transfer belt driving roller 62, an intermediate transfer belt driven roller 63, an intermediate transfer roller 64, and an intermediate transfer belt cleaning unit 65. ing. Four intermediate transfer rollers 64 are provided corresponding to the image stations for each color for YMCK.

  The intermediate transfer belt driving roller 62, the intermediate transfer belt driven roller 63, and the intermediate transfer roller 64 stretch the intermediate transfer belt 61 and move the surface of the intermediate transfer belt 61 in a predetermined direction (the arrow D direction in the figure). It is configured as follows.

  The intermediate transfer belt 61 is provided so as to be in contact with the respective photosensitive drums 3, and the toner images of the respective colors formed on the photosensitive drums 3 are sequentially transferred to the intermediate transfer belt 61 so as to be transferred. It has a function of forming a color toner image (multicolor toner image) on the belt 61. The intermediate transfer belt 61 is formed in an endless shape using, for example, a film having a thickness of about 100 μm to 150 μm.

  The intermediate transfer roller 64 provides a transfer bias for transferring the toner image on the photosensitive drum 3 to the intermediate transfer belt 61. The intermediate transfer roller 64 is rotatably supported on the side opposite to the photosensitive drum 3 with the intermediate transfer belt 61 interposed therebetween. A high-voltage transfer bias (a high voltage having a polarity (+) opposite to the toner charging polarity (−)) is applied to the intermediate transfer roller 64 in order to transfer the toner image.

  The intermediate transfer roller 64 is a roller whose base is a metal (for example, stainless steel) shaft having a diameter of 8 to 10 mm and whose surface is covered with a conductive elastic material (for example, EPDM, urethane foam, or the like). With this conductive elastic material, a high voltage can be uniformly applied to the intermediate transfer belt 61. In this embodiment, a roller shape is used as the transfer electrode, but a brush shape or the like can be used.

  As described above, the toner images visualized by the toners of the respective colors on the respective photosensitive drums 3 are laminated on the intermediate transfer belt 61. The stacked toner images of the respective colors are moved by the rotation of the intermediate transfer belt 61 and transferred onto the paper by the transfer roller 10 disposed at the contact position between the paper and the intermediate transfer belt 61.

  The intermediate transfer belt 61 and the transfer roller 10 are pressed against each other to form a nip region. A voltage for transferring the toner onto the sheet is applied to the transfer roller 10 (a high voltage having a polarity (+) opposite to the charging polarity (−) of the toner). Further, in order to form the nip region constantly, either the transfer roller 10 or the intermediate transfer belt driving roller 62 is made of a hard material (metal or the like), and the other is a soft material such as an elastic roller (elastic rubber roller or foaming). Resin roller etc.).

  By the way, the toner image on the intermediate transfer belt 61 may not be completely transferred to the paper, and the toner may remain on the intermediate transfer belt 61. The remaining toner causes toner color mixture in the next step.

  For this reason, the intermediate transfer belt cleaning unit 65 is configured to remove and collect the remaining toner. For example, the intermediate transfer belt cleaning unit 65 is provided with a cleaning blade that contacts the intermediate transfer belt 61 as a cleaning member, and the back side of the intermediate transfer belt 61 (that is, the opposite side of the intermediate transfer belt 61 from the driven roller 63). ).

  The image forming apparatus 100 further includes a paper feed cassette 81, a manual paper feed cassette 82, and a post-processing device 130.

  The paper feed cassette 81 is a tray for storing paper P used for image formation, and is provided below the exposure unit 1. Further, paper used for image formation can also be placed in the manual paper feed cassette 82.

  The post-processing apparatus 130 is provided above the apparatus main body 110 and accumulates printed sheets. Since the image forming apparatus 100 includes the post-processing device 130 that can avoid erroneous detection due to the floating of the paper, it is possible to prevent problems such as paper overloading. The post-processing device 130 will be described in detail later.

  The apparatus main body 110 is provided with a substantially vertical sheet conveyance path S for sending the sheets of the sheet feeding cassette 81 and the manual sheet feeding cassette 82 to the post-processing apparatus 130 via the transfer roller 10 and the fixing unit 7. ing. In the vicinity of the sheet conveyance path S from the sheet feeding cassette 81 and the manual sheet feeding cassette 82 to the post-processing device 130, pickup rollers 11a to 11b, a plurality of conveying rollers 12a to 12d, a registration roller 13, a transfer roller 10, and a fixing unit. Unit 7 is arranged.

  The transport rollers 12 a to 12 d are small rollers for promoting and assisting the transport of paper, and a plurality of transport rollers 12 a to 12 d are provided along the paper transport path S.

  The pickup roller 11 a is a call-in roller that is provided near the ends of the paper feed cassette 81 and the manual paper feed cassette 82 and supplies the paper from the paper feed cassette 81 to the paper transport path S one by one.

  The registration roller 13 temporarily holds the sheet conveyed through the sheet conveyance path S, and conveys the sheet to the transfer roller 10 at a timing when the leading edge of the toner image on the photosensitive drum 3 and the leading edge of the sheet are aligned.

  The fixing unit 7 includes a heat roller 71 and a pressure roller 72 that rotate with a sheet interposed therebetween, and further includes an external heating belt 73 for heating the heat roller 71 from the outside.

  The heat roller 71 is set to have a predetermined fixing temperature by a control unit based on a signal from a temperature detector (not shown), and is transferred onto the sheet by thermocompression bonding of the toner to the sheet together with the pressure roller 72. The resulting multicolor toner image is melted, mixed, and pressed to thermally fix the sheet.

  In the image forming apparatus 100 described above, the sheet conveyed from the sheet feeding cassette 81 and the manual sheet feeding cassette 82 is conveyed to the registration roller 13 by the conveying roller 12a during image formation. Next, the registration roller 13 conveys the sheet to the transfer roller 10 in synchronization with the toner image on the intermediate transfer belt 61, and the toner image is transferred to the sheet by the transfer roller 10. Thereafter, when the paper passes through the fixing unit 7, the unfixed toner transferred onto the paper is melted and fixed by heat and fixed on the paper. The sheet on which the toner image is fixed is conveyed to the post-processing device 130 via the conveyance roller 12b.

  The image forming apparatus 100 includes a control unit 140 (see FIG. 8 to be described later), and the control unit 140 determines the type of paper by an input operation of a user when forming an image. Further, the paper type may be determined by the paper feed tray 81. The control unit 140 transmits the paper type as paper information to the post-processing device 130.

  The control unit 140 is realized by a computer program (computer) incorporated in advance in a CPU (central processing unit, not shown) included in the image forming apparatus 100.

  FIG. 2 is an enlarged side view showing a portion of the post-processing apparatus in the image forming apparatus of FIG.

  The post-processing device 130 includes a paper discharge port 28 for discharging the paper transported from the paper transport path S, a discharge tray 29 for stacking the discharged paper, a pull-in belt 30, a staple unit 31, a paper placement plate 32, alignment. A plate 33, a paper pressing lever 34, and a paper presence / absence detection plate 35 are provided, and along the paper transport path S, a paper inlet 21, a punch unit 22, an inlet sensor 23, an inlet roller 24, an intermediate roller 25, A discharge roller 26, a driven roller 27, and a paper discharge port 28 are provided. In the following, for the sake of explanation, the sheets stacked on the discharge tray 29 may be referred to as stacked sheets.

  In the post-processing device 130, the sheet conveyed from the conveying roller 12 b is introduced through the sheet receiving port 21, conveyed to the inlet roller 24 through the punch unit 22, and further discharged from the inlet roller 24 through the intermediate roller 25. 26. When the paper stapling process or the like is not performed, the paper is discharged from the paper discharge port 28 to the discharge tray 29 by the discharge roller 26 without stopping the conveyance of the paper. Further, when performing sheet stapling processing or the like, the conveyance of the sheet is temporarily stopped at the position of the discharge roller 26, and the sheet is reversely conveyed to the staple unit 31 by the drawing belt 30. The paper is stapled by the staple unit 31 and discharged from the paper discharge port 28 to the discharge tray 29 by the discharge roller 26.

  The discharge roller 26 is supported so as to rotate around the axis of the intermediate roller 25 and to contact the driven roller 27. The discharge roller 26 and the driven roller 27 are configured to rotate with a sheet interposed therebetween.

  The punch unit 22 performs a punching process for punching holes and molds in the paper.

  The entrance sensor 23 detects a sheet conveyed from the sheet receiving port 21.

  The paper placement plate 32 is disposed between the discharge roller 26 and the staple unit 31 and stacks the paper that is conveyed back to the staple unit 31.

  The pair of alignment plates 33 are provided on the paper placement plate 32 and move along a direction orthogonal to the reverse conveyance direction of the paper to arrange the papers stacked on the paper placement plate 32.

  The staple unit 31 receives the paper reversely conveyed from the paper placement plate 32 and performs a staple process on one end of the paper.

  The discharge tray 29 includes a tray base portion 29 a provided along the paper discharge port 28 and a tray extending portion 29 b extending from the tray base portion 29 a toward the opposite side of the paper discharge port 28. It is arranged so that the side is lowered. The tray base portion 29a is formed so as to be inclined more toward the paper discharge port 28. The discharge tray 29 can be moved up and down, and is provided at a position lower than the paper discharge port 28.

  In the present embodiment, the tray base portion 29a has a curved shape so as to protrude toward the paper discharge port 28 (upward), and the tray extending portion 29b has a linearly extended shape. In addition, this invention is not limited to this, The discharge tray 29 is good also as another shape. A modification of the discharge tray 29 will be described in detail with reference to FIGS. 3 to 5 described later.

  Further, the post-processing device 130 is provided with a tray height detecting means 42 (see FIG. 8 described later) for detecting the height of the discharge tray 29 with respect to the paper discharge port 28 as the tray height. The detection output of the tray height detection means 42 changes according to the tray height. In accordance with the detection output of the tray height detection means 42, the control means 44 (see FIG. 8 described later) controls the tray height.

  The sheet pressing lever 34 is supported so as to be rotatable about a shaft 34a, and rotates by its own weight, and the leading end 34b presses the discharge tray 29 or the stacked sheets. Further, when the paper is discharged, rotation is controlled by a drive unit (not shown), and the leading end 34b is retracted from the discharge tray 29, so that the discharge of the paper is not hindered. The sheet pressing lever 34 is arranged so that the tip end 34b presses the tray base 29a.

  Further, an upper optical sensor 34c and a lower optical sensor 34d for detecting the rotational position of the paper pressing lever 34 are provided. The detection output of the upper optical sensor 34c changes according to the rotational position of the paper pressing lever 34 when the leading end 34b presses the discharge tray 29 or the stacked paper. The detection output of the lower optical sensor 34d changes according to the rotational position of the sheet pressing lever 34 when the leading end 34b is retracted from the discharge tray 29. In accordance with the detection output of the upper optical sensor 34c, the paper surface height detection means 43 (see FIG. 8 described later) detects the height of the paper loaded on the discharge tray 29 as the paper surface height.

  Note that the range in which the sheet pressing lever 34 can be rotated is limited by the side wall 36, and when the sheet pressing lever 34 is rotated by its own weight, the discharge tray 29 or the stacked sheet is positioned at a height sufficiently separated from the sheet discharge port 28. In this case, the leading end 34b does not hold the discharge tray 29 or the stacked sheets.

  Further, a sheet presence / absence detection plate 35 is provided in the tray extending portion 29 b of the discharge tray 29.

  The sheet presence / absence detection plate 35 is supported so as to be rotatable around a shaft 35a and rotates by its own weight. Usually, the protruding portion 35b protrudes from the tray extending portion 29b. When a sheet is stacked on the discharge tray 29, the protruding portion 35b is pushed by the weight of the sheet, and the sheet presence / absence detection plate 35 rotates.

  In addition, a presence / absence detection sensor 35c for detecting the rotational position of the sheet presence / absence detection plate 35 is provided. The presence / absence detection sensor 35c changes its detection output according to the rotation position of the paper presence / absence detection plate 35 when the paper presence / absence detection plate 35 is rotated by the weight of the paper. According to the detection output of the presence / absence detection sensor 35c, it can be detected that sheets are stacked on the discharge tray 29.

  Next, a modified example of the discharge tray 29 will be described. In the post-processing apparatus 130 according to the embodiment of the present invention, instead of the discharge tray 29 shown in FIG. 2, modifications of the discharge tray 29 shown in FIGS. 3 to 5 may be used.

  FIG. 3 is an enlarged view of the discharge tray and the paper pressing lever in FIG. 2, and is a side view showing Modification 1 of the discharge tray.

  Modification 1 is different from the discharge tray 29 shown in FIG. 2 in that the tray base 29a has a linearly inclined shape. That is, the tray base portion 29a and the tray extending portion 29b are formed to be flat surfaces. The tray base portion 29a is inclined downward from the tray extending portion 29b.

  FIG. 4 is an enlarged view of the discharge tray and the sheet pressing lever in FIG. 2, and is a side view showing a second modification of the discharge tray.

  The second modification differs from the discharge tray 29 shown in FIG. 2 in that the tray extending portion 29b is curved so as to protrude toward the paper discharge port 28 (upward). That is, the tray base portion 29a and the tray extending portion 29b are formed to have a continuous curved surface.

  FIG. 5 is an enlarged view of the discharge tray and the sheet pressing lever in FIG. 2, and is a side view showing a third modification of the discharge tray.

  Modification 3 is different from Modification 2 in that the tray base 29a has a linearly inclined shape. That is, the tray base portion 29a is a flat surface and the tray extending portion 29b is a curved surface. The tray base portion 29a is inclined downward from the tray extending portion 29b.

  Next, with reference to FIG. 6 to FIG. 10, a description will be given of how the paper floats when the stacked paper is pressed by the paper pressing lever. Note that components having substantially the same function and structure as those in FIG. 2 are denoted by the same reference numerals and description thereof is omitted.

  FIG. 6 is an enlarged view of the discharge tray and the paper pressing lever in FIG. 2, and is an explanatory view showing a case where no paper is lifted.

  On the discharge tray 29, one sheet P is stacked along the tray extending portion 29b and the tray base portion 29a. The paper pressing lever 34 presses the end of the paper P located on the tray base 29a. Hereinafter, for the sake of explanation, the end of the paper P positioned on the tray base 29a is referred to as a paper base Pa, and the portion other than the paper base Pa of the paper P is referred to as a paper main surface Pb.

  Since the sheet presence / absence detection plate 35 is pushed by the sheet P (sheet main surface Pb), it can be detected that sheets are stacked on the discharge tray 29.

  FIG. 7 is an enlarged view showing the discharge tray and the paper pressing lever in FIG. 2, and is an explanatory view showing a case where the paper is lifted.

  On the discharge tray 29, one specific sheet YP is stacked. Here, the specific paper YP is a strong paper such as a postcard or an envelope. That is, the paper is thicker than the thin paper called plain paper, and has a feature that it is not easily bent. As with the paper P, the specific paper YP is also referred to as a paper base YPa and a paper main surface YPb depending on the position with respect to the discharge tray 29. In addition, thin paper such as plain paper may be collectively referred to as plain paper.

  The paper pressing lever 34 presses the paper base YPa. Here, unlike the paper P shown in FIG. 3, the specific paper YP does not bend due to its own weight, so the paper main surface YPb is separated from the tray extending portion 29b and floats. Since the sheet main surface YPb is lifted, the protruding portion 35b is not pushed, so that it is not possible to detect that sheets are stacked on the discharge tray 29.

  That is, when the paper base YPa is pushed and comes into contact with the tray base 29a, the paper base YPa has the same inclination as the contact with the tray base 29a, and the paper main surface YPb has the same inclination as the paper base YPa. Since the tray extending portion 29b is formed to have a smaller inclination than the tray base portion 29a, the distance between the paper main surface YPb and the tray extending portion 29b increases as the distance from the paper discharge port 28 increases.

  FIG. 8 is an enlarged view of the discharge tray and the sheet pressing lever in FIG. 2, and is an explanatory view showing a case where the discharge tray is lowered.

  On the discharge tray 29, one specific sheet YP is stacked. Compared to FIG. 4, the discharge tray 29 is lowered to a height at which the sheet pressing lever 34 does not contact the specific sheet YP. The paper main surface YPb is in contact with the tray extending portion 29b, and the paper base YPa is lifted from the tray base 29a. Since the sheet presence / absence detection plate 35 is pushed by the sheet main surface YPb, it can be detected that sheets are stacked on the discharge tray 29.

  FIG. 9 is an enlarged view showing the discharge tray and the paper pressing lever in FIG. 2, and is an explanatory view showing a case where a plurality of sheets are stacked.

  A plurality of sheets P are stacked on the discharge tray 29 along the tray extending portion 29b and the tray base 29a, and the sheet pressing lever 34 presses the sheet base Pa. Regardless of the type of paper such as postcards and plain paper, a plurality of papers are stacked, whereby the plurality of papers P are bent by their own weight, and the paper main surface Pb is in contact with the tray extending portion 29b. Since the sheet presence / absence detection plate 35 is pushed by the sheet main surface Pb, it can be detected that a plurality of sheets P are stacked on the discharge tray 29.

  FIG. 10 is an enlarged view of the discharge tray and the paper pressing lever in FIG. 2, and is an explanatory view showing a case where plain paper is first stacked.

  In the discharge tray 29, one specific sheet YP is stacked on one plain sheet HP. The paper pressing lever 34 presses the paper base HPa and the paper base YPa. The plain paper HP is bent by its own weight and is stacked along the tray extending portion 29b and the tray base portion 29a. In the specific paper YP, the paper main surface YPb is lifted by pressing the paper base YPa. Since the sheet presence / absence detection plate 35 is pushed by the sheet main surface HPb of the ordinary sheet HP, it can be detected that sheets are stacked on the discharge tray 29.

  FIG. 11 is a schematic configuration diagram showing a schematic configuration of the post-processing apparatus according to the embodiment of the present invention. In the figure, only the part related to the post-processing apparatus is described for the image forming apparatus, and the other parts are omitted.

  The post-processing device 130 according to the embodiment of the present invention includes a paper discharge port 28 for discharging the paper conveyed from the paper conveyance path S, and a discharge tray 29 for stacking the discharged paper. The post-processing device 130 detects a sheet presence / absence detection unit 40 (sheet presence / absence detection plate 35) for detecting the presence / absence of a stacked sheet loaded on the discharge tray 29, and a detection for causing the sheet presence / absence detection unit 40 to start detecting the presence / absence of a stacked sheet. Detection instruction means 41 for instructing the start or stop of detection of the presence / absence of stacked paper to the paper presence / absence detection means 40, and a tray height for detecting the height of the discharge tray 29 relative to the paper discharge port 28 as the tray height. The sheet detecting lever 42, the control means 44 for controlling the height of the discharge tray 29 by moving the discharge tray 29 up and down, the sheet pressing lever 34 for pressing one end of the stacked sheet on the sheet discharge port 28 side, and the sheet pressing lever 34 for stacking sheets. The sheet height detecting means 43 for detecting the height of the loaded sheet relative to the tray height as the sheet surface height, and the type of the sheet conveyed by the sheet conveying path S. And a paper-information receiving unit 45 for receiving as paper information 45d. The control means 44 raises the discharge tray 29 before discharging the paper. When the paper type corresponding to the paper information received by the paper information receiving means is a specific paper specified in advance, the detection instruction means 41 stops detection before the paper height detection means 43 detects the paper height. And the control means 44 instructs the start of detection when the discharge tray 29 is lowered by a preset first set amount. The paper presence / absence detection means 40 corresponds to the paper presence / absence detection plate 35 described above.

  According to this configuration, by detecting the presence or absence of the sheet after the discharge tray 29 is lowered, it is possible to avoid erroneous detection due to the floating of the sheet that occurs when the sheet is pressed.

  The post-processing apparatus 130 includes a paper surface upper limit determination unit 53 that determines that the stacking is possible or the paper surface upper limit is based on the detection result of the paper surface height detection unit 43. When the paper surface upper limit determining unit 53 determines that the paper surface upper limit is the paper surface upper limit, the control unit 44 lowers the discharge tray 29 by a second preset amount. According to this configuration, the paper surface height can be controlled to an appropriate position when the paper is discharged.

  The post-processing device 130 updates the history information 47d based on the detection result of the history information storage unit 48 that stores the received sheet information 45d in the history information database 47 as the history information 47d and the sheet presence / absence detection unit 40. Information updating means 49. According to this configuration, the type and order of the stacked sheets can be grasped.

  The post-processing device 130 includes a tray lower limit determination unit 50 that determines that stacking is possible or impossible based on the detection result of the tray height detection unit 42. When the tray lower limit judging means 50 judges that the stacking is impossible, the paper discharge is stopped. According to this configuration, it is possible to prevent abnormality of the apparatus due to overloading.

  As described above, the discharge tray 29 includes the tray base portion 29a provided along the paper discharge port 28 and the tray extending portion 29b extending from the tray base portion 29a toward the opposite side of the paper discharge port 28. ing. The discharge tray 29 is arranged so that the sheet discharge port 28 side is lowered, and the sheet presence / absence detection means 40 is provided in the tray extending portion 29b. According to this configuration, the sheets can be arranged so that the leading ends of the sheets are concentrated on the tray base 29a.

  As described above, the specific sheet is a postcard or an envelope. According to this configuration, a strong paper such as a postcard or an envelope can be specified as the specific paper.

  The sheet information receiving unit 45 notifies the detection instruction unit 41 that the sheet is a specific sheet based on the sheet information 45d. Further, the paper information receiving unit 45 notifies the control unit 44 when the paper is a plain paper specified in advance. The paper type corresponding to the specific paper or the plain paper is stored in the paper information receiving unit 45 in advance.

  The sheet presence / absence detection unit 40 does not detect the presence / absence of stacked sheets until a detection start is instructed when detection stop is instructed by the detection instruction unit 41.

  The post-processing device 130 further includes a storage area 51 in which the paper information 45d is stored. The storage area 51 is, for example, a memory. In the storage area 51, a first set amount, a second set amount, a lower limit for the tray height, an upper limit for the paper surface height, and a set number of sheets for the stacked paper are stored in advance.

  The control unit 44 lowers the discharge tray 29 based on the first set amount and the second set amount stored in the storage area 51.

  The paper upper limit determining unit 53 determines that the paper upper limit is higher when the detected paper height is higher than the upper limit stored in the storage area 51, and determines that stacking is possible when it is lower than the upper limit stored in the storage area 51.

  The tray lower limit determination unit 50 determines that stacking is possible when the detected tray height is higher than the lower limit stored in the storage area 51, and determines that stacking is impossible when lower than the lower limit stored in the storage area 51.

  The history information 47d stores the order in which the paper information 45d is received and the paper type in association with each other.

  When the paper information 45d is received, the history information storage unit 48 adds and stores the received paper information 45d to the history information 47d.

  The history information update unit 49 deletes and updates the sheet information 45d stored as the history information 47d when the sheet presence / absence detection unit 40 detects that the stacked sheets are removed from the discharge tray 29. When the detection instruction unit 41 instructs the sheet presence / absence detection unit 40 to stop detection, the history information update unit 49 does not update the history information 47d.

  In the present embodiment, continuous processing for one sheet or a plurality of sheets is referred to as a job, and the image forming apparatus 100 collectively transmits a plurality of sheet information 45d as a job. In the case of processing a plurality of sheets, the sheet information receiving unit 45 collectively stores the received plurality of sheet information 45d in the storage area 51, and corresponds to the first sheet conveyed from the plurality of sheet information 45d. The paper information 45d to be specified is designated. Further, when the paper corresponding to the designated paper information 45d is ejected, the paper information receiving means 45 designates the paper information 45d corresponding to the paper to be transported next, and receives a plurality of paper information 45d collected as a job. Repeat the process until all are specified.

  The detection instruction unit 41, the history information storage unit 48, the history information update unit 49, the paper surface upper limit determination unit 53, the tray lower limit determination unit 50, and the control unit 44 are connected to the CPU 52 (central processing unit) included in the post-processing device 130. It is realized by a computer program (computer) incorporated in advance.

  FIG. 12A is a first processing flow in the case of discharging a sheet by the post-processing apparatus according to the embodiment of the present invention, and is a flowchart showing an operation until the first sheet is discharged. FIG. 12B is a first processing flow when the paper is discharged by the post-processing apparatus according to the embodiment of the present invention, and is a flowchart showing an operation after the paper is discharged.

  In step S101, the first sheet information 45d is received from the image forming apparatus 100. When a plurality of pieces of paper information 45d are received, the paper information receiving means 45 designates paper information 45d corresponding to the paper that is transported first. In the following description, for the sake of explanation, a sheet corresponding to the sheet information 45d designated by the sheet information receiving unit 45 may be referred to as a discharged sheet. Here, the sheet pressing lever 34 is controlled to rotate by its own weight.

  In step S102, the paper information receiving unit 45 notifies that the stacked paper and the discharged paper are specific paper. Note that the type of stacked paper can be specified by the paper information 45 d stored in the storage area 51. When either the stacked paper or the discharged paper is not a specific paper (step S102: No), the process proceeds to step S103 without notification. When either the loaded paper or the discharged paper is the specific paper (step S102: Yes), the detection instructing means 41 is notified and the process proceeds to step S104.

  In step S <b> 103, the control unit 44 raises the discharge tray 29 to a height at which the sheet pressing lever 34 presses the stacked sheets or the discharge tray 29. When the paper pressing lever 34 presses the stacked paper or the discharge tray 29 (see, for example, FIG. 6), the paper surface height detecting means 43 detects the paper surface height, and the process proceeds to step S120 (see FIG. 12B described later).

  In step S104, the detection instruction means 41 instructs the sheet presence / absence detection means 40 to stop detection.

  In step S <b> 105, the control unit 44 raises the discharge tray 29 to a height at which the paper pressing lever 34 presses the stacked paper (specific paper) or the discharge tray 29. When the paper pressing lever 34 presses the stacked paper (see, for example, FIG. 7), the paper height detecting unit 43 detects the paper height. When there is no stacked paper, the paper pressing lever 34 presses the discharge tray 29, and the paper surface height is detected.

  In step S106, the control means 44 lowers the discharge tray 29 by the first set amount (see, for example, FIG. 8). The first set amount is not limited as long as the sheet pressing lever 34 is at a height that does not contact the stacked sheets, and is, for example, 1 cm.

  In step S107, the detection instruction unit 41 instructs the sheet presence / absence detection unit 40 to start detection, and the process proceeds to step S120 (see FIG. 12B described later).

  In step S120, the paper transported from the paper transport path S is discharged. Here, the paper pressing lever 34 has its tip 34b retracted from the discharge tray 29 so as not to hinder paper discharge. When the discharged paper is stacked on the discharge tray 29 and the discharge of the paper is completed, the paper pressing lever 34 is controlled to rotate by its own weight, and when the leading edge 34b presses the stacked paper, the paper surface height is detected. The

  In step S121, the paper upper limit determination unit 53 determines whether stacking is possible or the paper upper limit. When the paper surface height is lower than the upper limit (step S121: No), the process proceeds to step S123. When the paper pressing lever 34 does not press the stacked paper, it is determined that the paper can be stacked. When the paper surface height is higher than the upper limit (step S121: Yes), the process proceeds to step S122.

  In step S122, the control means 44 lowers the discharge tray 29 by the second set amount. By lowering the second set amount, it is sufficient that the stacked sheets can be set to a height that does not hinder the discharge of the sheet. The second set amount is, for example, about the thickness of one specific sheet YP.

  In step S123, the tray lower limit determination unit 50 determines whether the stacking is possible or not. When the tray height is above the lower limit (step S123: No), the process proceeds to step S125. When the tray height is below the lower limit (step S123: Yes), the process proceeds to step S124.

  In step S124, the tray lower limit determination unit 50 notifies that the stacking is impossible, and the post-processing device 130 stops the discharge of the sheet and proceeds to step S127.

  In step S125, it is determined whether the job is finished. When there is paper information 45d not specified by the paper information receiving means 45 (step S125: No), that is, when there is a paper that has not been discharged, the process proceeds to step S126. When all the paper information 45d is designated (step S125: Yes), that is, when the discharge of the paper corresponding to the received paper information 45d is completed, the process proceeds to step S127.

  In step S126, the sheet information receiving unit 45 designates sheet information 45d corresponding to the sheet to be conveyed next, and the process returns to step S120 described above.

  In step S127, the control means 44 lowers the discharge tray 29 to a height (standby position) at which the user can collect the stacked sheets, and the process ends. The standby position is, for example, the lowest position in the range in which the discharge tray 29 can be raised and lowered. Whether or not the user has collected the loaded paper can be detected by the paper presence / absence detecting means 40.

  FIG. 13A is a second processing flow when the paper is discharged by the post-processing apparatus according to the embodiment of the present invention, and is a flowchart showing an operation until the first paper is discharged. FIG. 13B is a second processing flow in the case where the paper is discharged by the post-processing apparatus according to the embodiment of the present invention, and is a flowchart showing the operation after discharging the paper.

  In the second processing flow, instead of the first processing flow, the type and number of stacked sheets are determined based on the history information 47d.

  In step S201, the first sheet information 45d is received from the image forming apparatus 100. When a plurality of pieces of paper information 45d are received, the paper information receiving means 45 designates paper information 45d corresponding to the paper that is transported first. Here, the sheet pressing lever 34 is controlled to rotate by its own weight. Also, the specified paper information 45d is added to the history information 47d by the history information storage means 48.

  In step S202, the paper information receiving unit 45 notifies that the first stacked paper and discharged paper are specified paper or plain paper. The type of loaded paper can be specified by the history information 47 d stored in the history information database 47. When the first stacked paper and discharged paper are not specific paper (step S202: No), the control means 44 is notified that the paper is plain paper, and the process proceeds to step S204. That is, even if the specific sheet is loaded on the discharge tray 29, when the normal sheet is loaded at the first (bottom) (for example, see FIG. 10), the sheet presence / absence detection unit 40 is not instructed to stop detection. . When the first stacked paper and the discharged paper are specific paper (step S202: Yes), the detection instruction means 41 is notified that the paper is the specific paper, and the process proceeds to step S203.

  In step S203, based on the history information 47d, it is determined whether the number of stacked sheets is larger than the set number. When the number of sheets stacked on the discharge tray 29 is less than the set number (step S203: No), the process proceeds to step S205. When the number of sheets stacked on the discharge tray 29 is greater than the set number (step S203: Yes), the process proceeds to step S204. That is, regardless of the type of paper, when a plurality of paper is stacked (for example, see FIG. 9), the paper presence / absence detection unit 40 is not instructed to stop detection.

  In step S <b> 204, the control unit 44 raises the discharge tray 29 to a height at which the paper pressing lever 34 presses the stacked paper or the discharge tray 29. When the paper pressing lever 34 presses the stacked paper or the discharge tray 29 (see, for example, FIG. 6), the paper surface height detection unit 43 detects the paper surface height, and the process proceeds to step S220 (see FIG. 13B described later).

  In step S205, the detection instruction means 41 instructs the paper presence / absence detection means 40 to stop detection.

  In step S <b> 206, the control unit 44 raises the discharge tray 29 to a height at which the paper pressing lever 34 presses the stacked paper (specific paper) or the discharge tray 29. When the paper pressing lever 34 presses the stacked paper (see, for example, FIG. 7), the paper height detecting unit 43 detects the paper height. When there is no stacked paper, the paper pressing lever 34 presses the discharge tray 29, and the paper surface height is detected.

  In step S207, the control means 44 lowers the discharge tray 29 by a first set amount (see, for example, FIG. 8).

  In step S208, the detection instruction unit 41 instructs the sheet presence / absence detection unit 40 to start detection, and the process proceeds to step S220 (see FIG. 13B described later).

  In step S220, the paper transported from the paper transport path S is discharged. Here, the paper pressing lever 34 has its tip 34b retracted from the discharge tray 29 so as not to hinder paper discharge. When the discharged paper is stacked on the discharge tray 29 and the discharge of the paper is completed, the paper pressing lever 34 is controlled to rotate by its own weight, and when the leading edge 34b presses the stacked paper, the paper surface height is detected. The

  In step S221, the paper upper limit determination unit 53 determines whether the stacking is possible or the paper upper limit. When the paper surface height is lower than the upper limit (step S221: No), the process proceeds to step S223. When the paper surface height is above the upper limit (step S221: Yes), the process proceeds to step S222.

  In step S222, the control unit 44 lowers the discharge tray 29 by the second set amount. It is only necessary that the stacked sheets can be set to a height that does not hinder the discharge of the sheets by lowering the second set amount.

  In step S223, the tray lower limit determination unit 50 determines whether the stacking is possible or not. When the tray height is above the lower limit (step S223: No), the process proceeds to step S225. When the tray height is below the lower limit (step S223: Yes), the process proceeds to step S224.

  In step S224, the tray lower limit determination unit 50 notifies that the stacking is impossible, and the post-processing device 130 stops discharging the paper and proceeds to step S227.

  In step S225, it is determined whether the job is finished. When there is paper information 45d not specified by the paper information receiving means 45 (step S225: No), that is, when there is a paper that has not been discharged, the process proceeds to step S226. When all the sheet information 45d is designated (step S225: Yes), that is, when the discharge of the sheet corresponding to the received sheet information 45d is completed, the process proceeds to step S227.

  In step S226, the paper information receiving unit 45 specifies paper information 45d corresponding to the next paper to be transported. Further, the designated sheet information 45d is added to the history information 47d by the history information storage means 48, and the process returns to the above-described step S220.

  In step S227, the control unit 44 lowers the discharge tray 29 to a height (standby position) at which the user can collect the stacked sheets, and the process ends. Whether or not the user has collected the loaded paper can be detected by the paper presence / absence detecting means 40.

  As described above, the sheet information receiving unit 45 notifies the control unit 44 that the sheet is a previously specified plain sheet based on the sheet information 45d. The control unit 44 stops the lowering of the first set amount after detecting the paper surface height before discharging the paper when the normal paper is stacked for the first time. That is, the paper surface height is detected in a state where the presence or absence of the paper is detected. According to this configuration, even if a specific sheet stacked on the upper surface is lifted, the presence or absence of the sheet can be detected by the normal sheet stacked below, so that an excessive operation of the discharge tray 29 can be avoided.

  In addition, when the number of stacked sheets exceeds the preset number, the control unit 44 detects the paper surface height before discharging the sheets and then stops the lowering of the first set amount. That is, the paper surface height is detected in a state where the presence or absence of the paper is detected. According to this configuration, it is possible to determine that no lifting occurs if the sheets are sufficiently stacked, and therefore it is possible to shift to a normal operation. The set number of sheets is a number that can be bent by its own weight, for example, 20 sheets.

  FIG. 14A is a third processing flow when a sheet is discharged by the post-processing apparatus according to the embodiment of the present invention, and is a flowchart showing an operation until the first sheet is discharged. FIG. 14B is a third processing flow in the case where the paper is discharged by the post-processing apparatus according to the embodiment of the present invention, and is a flowchart showing the operation after discharging the paper.

  In the third processing flow, instead of the first processing flow, it is determined whether or not the tray height is below the lower limit when the discharge tray 29 is lowered by the first set amount in step S106.

  In step S301, the first sheet information 45d is received from the image forming apparatus 100. When a plurality of pieces of paper information 45d are received, the paper information receiving means 45 designates paper information 45d corresponding to the paper that is transported first. Here, the sheet pressing lever 34 is controlled to rotate by its own weight.

  In step S302, the paper information receiving unit 45 notifies that the stacked paper and the discharged paper are specific paper. When either the stacked paper or the discharged paper is not a specific paper (step S302: No), the process proceeds to step S303 without notification. When either the loaded paper or the discharged paper is a specific paper (step S302: Yes), the detection instructing means 41 is notified and the process proceeds to step S304.

  In step S <b> 303, the control unit 44 raises the discharge tray 29 to a height at which the sheet pressing lever 34 presses the stacked sheets or the discharge tray 29. When the paper pressing lever 34 presses the loaded paper or the discharge tray 29, the paper height detecting means 43 detects the paper surface height, and the process proceeds to step S320 (see FIG. 14B).

  In step S304, the detection instruction means 41 instructs the sheet presence / absence detection means 40 to stop detection.

  In step S 305, the control unit 44 raises the discharge tray 29 to a height at which the paper pressing lever 34 presses the stacked paper (specific paper) or the discharge tray 29. When the paper pressing lever 34 presses the stacked paper, the paper height detecting means 43 detects the paper height. When there is no stacked paper, the paper pressing lever 34 presses the discharge tray 29, and the paper surface height is detected.

  In step S306, the control means 44 lowers the discharge tray 29 by the first set amount.

  In step S307, the tray lower limit determination unit 50 determines whether stacking is possible or not. When the tray height is above the lower limit (step S307: No), the process proceeds to step S308. When the tray height is below the lower limit (step S307: Yes), the process proceeds to step S309.

  In step S308, the detection instruction means 41 instructs the sheet presence / absence detection means 40 to start detection, and the process proceeds to step S320 (see FIG. 14B).

  In step S309, as in step S305, the discharge tray 29 is raised by the control means 44, and the paper surface height is detected.

  In step S310, as in step S307, the tray lower limit determination unit 50 determines once again whether or not stacking is possible. When the tray height is above the lower limit (step S310: No), the process proceeds to step S308. When the tray height is below the lower limit (step S310: Yes), the process proceeds to step S311.

  In step S311, the tray lower limit determination unit 50 notifies that the stacking is impossible, and the post-processing device 130 stops the paper discharge and proceeds to step S312.

  In step S312, the control means 44 lowers the discharge tray 29 to the standby position and ends the process.

  The flow from the discharge of the sheet in step S320 shown in FIG. 14B to the end of the processing is the same as the first processing flow shown in FIG. 12B, and steps S320 to S327 are the same as steps S120 to S127. Since there is, explanation is omitted.

  As described above, in the post-processing device 130, when the discharge tray 29 is lowered by the first set amount and the tray lower limit determination means 50 determines that the stacking is impossible, the discharge tray 29 is raised to detect the paper surface height. Thereafter, if it is determined by the tray lower limit determination means 50 that the stacking is possible, the sheet is discharged. According to this configuration, the determination of the lower limit of the discharge tray 29 can be made accurately by redoing the determination.

28 Paper discharge port 29 Paper discharge tray 34 Paper press lever 40 Paper presence / absence detection means 41 Detection instruction means 42 Tray height detection means 43 Paper surface height detection means 44 Control means 45 Paper information reception means 45d Paper information 47 History information database 47d History information 48 History information storage means 49 History information update means 50 Tray lower limit judgment means 53 Paper surface upper limit judgment means 100 Image forming apparatus 130 Post-processing apparatus S Paper transport path

Claims (10)

A post-processing device comprising a paper discharge port for discharging the paper conveyed from the paper conveyance path, and a discharge tray for stacking the discharged paper,
A paper presence / absence detecting means for detecting the presence / absence of the loaded paper loaded on the discharge tray;
A detection instruction means for instructing the detection start to start the detection of the presence or absence of the stacked paper in the paper presence detection means, or the detection stop to stop the detection of the presence or absence of the stacked paper to the paper presence or absence detection means;
Tray height detection means for detecting the height of the discharge tray with respect to the paper discharge port as a tray height;
Control means for controlling the tray height by moving the discharge tray up and down;
A paper holding lever for holding one end of the loaded paper on the paper discharge port side;
A paper surface height detecting means for detecting the height of the stacked paper with respect to the tray height as the paper surface height when the paper is pressed by the paper pressing lever;
Paper information receiving means for receiving, as paper information, the type of paper conveyed on the paper conveyance path;
The control means raises the discharge tray before discharging the paper,
When the paper type corresponding to the paper information received by the paper information receiving means is a specific paper that has been specified in advance, the detection instruction means is configured to detect the paper height before the paper height detection means detects the paper height. After the detection stop is instructed and the paper surface height is detected, the control means instructs the start of detection when the control unit lowers the discharge tray by a first preset amount. . The post-processing apparatus according to claim 1,
The post-processing apparatus, wherein the specific sheet is a postcard or an envelope. The post-processing apparatus according to claim 1 or 2, wherein
Based on the detection result of the paper surface height detection means, the paper surface upper limit determination means for determining that the stacking is possible or the paper surface upper limit,
The post-processing apparatus, wherein the control means lowers the discharge tray by a second preset amount when the paper upper limit determination means determines that the paper upper limit is reached. A post-processing apparatus according to any one of claims 1 to 3, comprising:
History information storage means for storing received paper information as history information in a history information database;
A post-processing apparatus comprising: history information updating means for updating history information based on a detection result of the sheet presence / absence detection means. The post-processing apparatus according to claim 4,
The paper information receiving means notifies the control means that the paper is a plain paper specified in advance based on the history information,
The control means stops the lowering of the first set amount after detecting the paper surface height before discharging the paper when the plain paper is stacked for the first time. . The post-processing apparatus according to claim 4,
The control means stops the lowering of the first set amount after detecting the paper surface height before discharging the sheets when the number of stacked sheets is larger than a preset number of sheets. Processing equipment. A post-processing apparatus according to any one of claims 1 to 4, comprising:
Based on the detection result of the tray height detection means, comprises a tray lower limit determination means for determining that loading is possible or impossible.
The post-processing device, wherein when the tray lower limit judging means judges that the stacking is impossible, the paper discharge is stopped. The post-processing apparatus according to claim 7,
When the discharge tray is lowered by the first set amount and the tray lower limit judging means judges that the stacking is impossible, the discharge tray is raised and the paper surface height is detected. A post-processing device that discharges paper if it is determined to be possible. The post-processing apparatus according to claim 1,
The discharge tray is composed of a tray base provided along the paper discharge port, and a tray extending portion extending from the tray base toward the opposite side of the paper discharge port,
The discharge tray is arranged so that the paper discharge port side is lowered,
The post-processing apparatus, wherein the sheet presence / absence detecting means is provided in the tray extending section.   An image forming apparatus comprising the post-processing device according to any one of claims 1 to 9.

Images