JP2012232816A - Paper sheet feeding device, and image forming apparatus with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably make a paper sheet conveying belt suck various paper sheets without increasing sucking force of a fan greatly.SOLUTION: A height of a paper sheet loading mount 74 is changed in response to a size, basis weight, and air permeability of recording paper sheet, and a clearance between paper sheets of uppermost layers of paper sheet bundles on the paper sheet loading mount 74 and under surfaces of the respective paper sheet conveying belts 81 is adjusted. Thus, regardless of a kind of the recording paper sheets, the recording paper sheets are rapidly sucked onto the under surfaces of the respective paper sheet conveying belts 81 and drawn out. Additionally, even when drawing-out of the recording paper sheets by the respective paper sheet conveying belts 81 delays, the height of the paper sheet loading mount 74 is changed and the recording paper sheets are rapidly sucked onto the under surfaces of the respective paper sheet conveying belts 81 and drawn out, and thereby the delay of the drawing-out of the recording paper sheets is inhibited.

Description

  The present invention relates to a sheet feeding device that draws out and feeds a sheet from a bundle of sheets stacked on a sheet stacking table, and an image forming apparatus including the sheet feeding device.

  This type of paper feeding device includes a paper stacking table on which a stack of sheets is stacked, a paper transporting belt disposed above the paper stacking base, and a fan that sucks air through the vent holes of the paper transporting belt. In some cases, the uppermost sheet of the sheet bundle is attracted to and conveyed by the sheet conveying belt by suction of air through the ventilation holes of the conveying belt.

  In Patent Document 1, a stack of sheets is stacked on a sheet stacking table, and air is blown onto the upper side of the sheet bundle to reduce the adhesion between the sheets, and the pickup roller is pushed onto the uppermost sheet. The uppermost sheet is pulled out by the pickup roller. Further, the amount, pressure, speed, and the like of the air blown onto the upper layer of the side surface of the sheet bundle are adjusted according to the type of the sheet.

  Furthermore, in Patent Document 2, a sheet bundle is placed on a conveyance belt, and air is blown to the lower layer on the side surface of the sheet bundle to reduce the adhesion between the sheets. While adsorbing, the lowermost sheet is pulled out and conveyed by the conveyor belt. Further, the amount of air blown to the lower layer on the side surface of the sheet bundle is adjusted according to the size and weight of the sheet.

JP 2001-19187 A JP-A-3-172244

  By the way, as described above, in the configuration in which the paper transport belt is arranged above the paper stacking table and the uppermost sheet of the paper bundle is attracted to the paper transport belt and transported, the paper becomes thicker, When the size is increased, it becomes difficult to attract the paper to the paper transport belt, and a paper transport error occurs.

  For this reason, conventionally, the suction force of the fan that adsorbs the paper to the paper transport belt is adjusted according to the type of paper. However, in this case, it is necessary to sufficiently increase the maximum suction force of the fan in order to secure the adjustment range of the suction force of the fan, which requires a fan with large power consumption, which hinders power saving. became. In addition, it is difficult to control the suction force of the fan, and various sheets cannot be properly adsorbed to the sheet transport belt.

  Also, in Patent Documents 1 and 2, the amount of air blown to the side of the sheet bundle is adjusted according to the type of the sheet, thereby reducing the adhesion between the sheets and suppressing the paper fluttering. However, this is not a configuration in which the sheet is attracted to the sheet conveying belt above the sheet, and the problem of the conveyance error associated with the type of the sheet is not solved.

  Accordingly, the present invention has been made in view of the above-described problems of the related art, and can feed various types of paper to the paper transport belt reliably without increasing the suction force of the fan. An object is to provide an apparatus and an image forming apparatus including the apparatus.

  In order to solve the above problems, a sheet feeding device according to the present invention includes a sheet stacking table on which sheets are stacked, a sheet transport unit disposed above the sheet stacking table, and air vent holes in the sheet transport unit. An air suction section that sucks through the sheet transport section, and sucks air through the air hole of the sheet transport section to suck and transport the sheets on the sheet stacking table to the sheet transport section, A lifting / lowering unit that raises / lowers the loading table or the sheet conveying unit to change a separation distance of the sheet conveying unit with respect to the sheet on the sheet loading table, and controls the lifting unit, and types of sheets on the sheet loading table And a control unit that adjusts a separation distance of the paper transport unit with respect to the paper on the paper stacking board.

  In the present invention, air is sucked through the air hole of the paper transport unit, and the paper on the paper stacking table is sucked and transported to the paper transport unit. The distance of the sheet conveying unit with respect to the sheet on the sheet stacking table is adjusted by moving the unit up and down. For this reason, for example, for a type of paper that is difficult to attract, the distance of the paper transport unit to the paper on the paper stacking table can be shortened, and the paper can be reliably sucked and transported to the paper transport unit.

  For example, the paper transport unit is a paper transport belt.

  The paper feeding device of the present invention further includes an input unit for inputting the type of paper on the paper stacking table or a detection unit for detecting the type of paper on the paper stacking table.

  Furthermore, in the paper feeding device of the present invention, the type of the paper is represented by at least one of size, basis weight, and air permeability.

  For example, the weight of the paper varies depending on the size of the paper, and the suction force for properly sucking the paper to the paper transport unit changes. Further, the weight and rigidity of the paper differ depending on the basis weight of the paper, and the suction force for properly sucking the paper to the paper transport unit changes. Further, the ease of air removal varies depending on the air permeability of the paper, and the suction force for properly sucking the paper into the paper transport unit changes. For this reason, the distance between the paper transport unit and the paper on the paper stack is adjusted by raising and lowering the paper stack or the paper transport unit according to at least one of the paper size, basis weight, and air permeability. Yes.

  In the paper feeding device of the present invention, the type of paper is represented by size, basis weight, or air permeability, and the control unit increases the size, basis weight, or air permeability of the paper. The separation distance of the paper transport unit with respect to the paper on the paper stacking base is shortened.

  Here, the larger the values of paper size, basis weight, and air permeability, the more difficult it is to attract the paper to the paper transport unit, so the separation distance of the paper transport unit from the paper on the paper stacking base Is shortened so that the sheet is more securely adsorbed to the sheet conveying section.

  The paper feeding device of the present invention further includes an air blowing unit that blows air against the paper on the paper stacking table.

  This air enters between a plurality of sheets stacked on the sheet stacking table and reduces the adhesion between the sheets. Accordingly, it becomes easy to suck and convey the sheets one by one to the sheet conveyance unit.

  Furthermore, in the sheet feeding device of the present invention, the air blowing unit and the air suction unit operate by exhaust and intake of the same fan.

  Thereby, exhaust and intake of a single fan can be used without waste, and the number of fans can be minimized.

  Further, in the paper feeding device of the present invention, the paper feeding unit is provided on the downstream side in the paper conveyance direction by the paper conveyance unit, and includes a sensor that detects the leading edge of the paper, the paper conveyance unit rotates intermittently, and the control unit The longer the time from the start of rotation of the paper transport unit to the time of detection of the front end of the paper by the sensor, the shorter the separation distance of the paper transport unit from the paper on the paper stacking table.

  The more difficult the sheet is attracted to the sheet transport unit, the later the timing at which the sheet is attracted to the sheet transport unit, and the more the sheet is transported by the sheet transport unit. For this reason, the longer the time from the start of rotation of the paper transport unit to the time of detection of the leading edge of the paper by the sensor, the shorter the separation distance of the paper transport unit from the paper on the paper stacking base, and the faster the paper transports the paper transport unit. Adsorbed.

  On the other hand, an image forming apparatus of the present invention includes the paper feeding device of the present invention.

  Such an image forming apparatus of the present invention also has the same operational effects as the sheet feeding apparatus of the present invention.

  In the present invention, air is sucked through the air hole of the paper transport unit, and the paper on the paper stacking table is sucked and transported to the paper transport unit. The distance of the sheet conveying unit with respect to the sheet on the sheet stacking table is adjusted by moving the unit up and down. For this reason, for example, for a type of paper that is difficult to attract, the distance of the paper transport unit to the paper on the paper stacking table can be shortened, and the paper can be reliably sucked and transported to the paper transport unit.

1 is a cross-sectional view illustrating an image forming apparatus to which an embodiment of a paper feeding device of the present invention is applied. It is a top view which shows the paper feeder of this embodiment. It is a front view which shows the paper feeder of this embodiment. FIG. 3 is a perspective view showing the sheet feeding device with the sheet drawer portion removed, as viewed obliquely from the rear. FIG. 3 is a side view illustrating a paper stacking base, a wire, a driven pulley, and a take-up pulley in the paper feeding device in a simplified manner. (A), (b) is the side view and top view which show simply the height position sensor which detects the height of the sheet | seat stack | stacked loaded on the paper stacking base, (c) is a height position sensor. It is a side view which shows one operation state. FIG. 6 is a perspective view showing a paper drawer portion when viewed obliquely from the upper front. It is a perspective view which shows a paper drawer part seeing from diagonally upper back. It is a perspective view which shows a paper drawer part seeing from diagonally lower back. FIG. 3 is an enlarged plan view showing a paper conveying belt and the like in a paper drawing unit. FIG. 3 is a side view showing a paper feeding device in a simplified manner. 3 is a block diagram illustrating a configuration of a control system of the image forming apparatus and the paper feeding apparatus. FIG. (A), (b), (c), (d) is a figure which shows notionally the structure of each data table. It is a side view which shows the modification of a height position sensor.

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

  FIG. 1 is a cross-sectional view showing an image forming apparatus to which an embodiment of a paper feeding device of the present invention is applied. The image forming apparatus 1 prints a monochrome image indicated by image data on a recording sheet. The configuration of the image forming apparatus 1 is roughly divided into a document reading device 2, a printing unit 11, a sheet feeding device 12, a sheet feeding unit 13, and the like. It consists of a large capacity paper feed cassette (LCC) 14.

  In this image forming apparatus 1, an original image is read from the original reading device 2 to generate image data, or image data is received and input from an external terminal device or the like to acquire image data, and various kinds of image data are obtained. After the image processing is performed, the printing unit 11 prints an image indicated by the image data on a recording sheet.

  A photosensitive drum 21 is disposed at the approximate center of the printing unit 11, and a charging device 22, a laser exposure device 23, a developing device 24, a transfer roller 25, and a cleaning device 26 are disposed around the photosensitive drum 21.

  The photosensitive drum 21 has a photosensitive layer on its surface, and while rotating in the direction of the arrow, the surface is cleaned by the cleaning device 26 and then the surface is uniformly charged by the charging device 22. The laser exposure device 23 is a laser scanning unit (LSU) including a laser diode and a reflection mirror, and receives image data, modulates the intensity of the laser beam according to the image data, and uses the photosensitive drum 21 with the laser beam. The surface is scanned and an electrostatic latent image is written on the surface of the photosensitive drum 21. The developing device 24 develops the electrostatic latent image on the surface of the photosensitive drum 21 with toner to form a toner image on the surface of the photosensitive drum 21.

  The transfer roller 25 is pressed against the photosensitive drum 21, forms a nip area with the photosensitive drum 21, and rotates together with the photosensitive drum 21. The photoconductive drum 21 and the transfer roller 25 transfer the toner image on the surface of the photoconductive drum 21 onto the recording paper while the recording paper conveyed through the conveying path 33 is sandwiched and conveyed in the nip region.

  A fixing device 27 is disposed above the printing unit 11. The fixing device 27 includes a heating roller 28 and a pressure roller 29 that are pressed against each other. The recording paper is sandwiched in a nip area between the heating roller 28 and the pressure roller 29 to heat and apply the recording paper. The toner image transferred onto the recording paper is fixed. The recording sheet is conveyed from the fixing device 27 to the discharge roller pair 36 and is discharged to the discharge tray 37 by the discharge roller pair 36.

  On the other hand, the sheet feeding device 12 includes a plurality of conveyance roller pairs 31, a registration roller pair 32, a conveyance path 33, a detour path 34, a branching claw 35, a discharge roller pair 36, a discharge tray 37, and the like for conveying recording sheets. It has.

  The paper supply unit 13 includes a plurality of paper supply cassettes 38. Each paper feed cassette 38 is a tray for storing recording paper, and is provided in a plurality of stages below the image forming apparatus 1. Each paper feed cassette 38 is provided with a pickup roller 39 and the like for drawing out the recording paper one by one and sending it out to the conveyance path 33, and sends out the drawn recording paper to the conveyance path 33 of the paper feeding device 12. .

  The large-capacity paper feed cassette (LCC) 14 can store a large amount of recording paper, and, like each paper feed cassette 38, pulls out the recording paper one by one and sends it out to the transport path 33.

  In the transport path 33, the recording paper drawn from any of the paper feed cassettes is transported in the paper transport direction C and delivered to the registration roller pair 32, and the leading edge of the recording paper is temporarily stopped at the registration roller pair 32. The recording sheet is bent and bent, and the leading edge of the recording sheet is aligned in parallel with the registration roller pair 32 by the elastic force of the recording sheet, and then the rotation of the registration roller pair 32 is started. The sheet is conveyed to the nip area between the photosensitive drum 21 and the transfer roller 25. This recording sheet passes through the nip area between the photosensitive drum 21 and the transfer roller 25 to transfer the toner image, passes through the nip area between the heating roller 28 and the pressure roller 29, and the toner image is fixed. Then, the paper is conveyed in the forward direction A by the paper discharge roller pair 36 and discharged to the paper discharge tray 37.

  When printing an image on the back side of the recording paper, the paper discharge roller pair 36 is stopped while the recording paper is conveyed in the forward direction A and discharged to the paper discharge tray 37, that is, the recording paper is sandwiched. In this state, the paper discharge roller pair 36 is stopped, the branch claw 35 is switched to the obliquely downward direction, the paper discharge roller pair 36 is rotated in the reverse direction, and the recording paper is conveyed in the reverse direction B to the detour path 34. Then, the recording sheet is guided again to the conveyance path 33 through the detour path 34, and the recording sheet is returned to the registration roller pair 32.

  Such switching of the conveyance direction of the recording paper is referred to as switchback conveyance. By this switchback conveyance, the front and back sides of the recording paper are reversed, and at the same time, the leading edge and the trailing edge of the recording paper are switched. Therefore, when the recording paper is reversed and returned, the trailing edge of the recording paper comes into contact with the registration roller pair 32, and the trailing edge of the recording paper is aligned parallel to the registration roller pair 32. Is conveyed from the rear end to the nip area between the photosensitive drum 21 and the transfer roller 25, printing is performed on the back surface of the recording paper, and the toner image is fixed on the back surface of the recording paper by the heating roller 28 and the pressure roller 29. Then, the recording paper is discharged to the paper discharge tray 37 via the paper discharge roller pair 36.

  Next, the document reading device 2 mounted on the upper body of the image forming apparatus 1 will be described. The document reading device 2 includes a lower first reading unit 41 and an upper document conveying unit 42. The document conveying unit 42 is pivotally supported by the back side of the first reading unit 41 by a hinge (not shown) and opened and closed by moving the front portion up and down. When the document conveying unit 42 is opened, the platen glass 44 of the first reading unit 41 is opened, and a document sheet is placed on the platen glass 44.

  The first reading unit 41 includes a platen glass 44, a first scanning unit 45, a second scanning unit 46, an imaging lens 47, a CCD (Charge Coupled Device) 48, and the like. The first scanning unit 45 includes a light source 51 and a first reflecting mirror 52, and moves on the platen glass 44 on the platen glass 44 while moving in the sub-scanning direction by a distance corresponding to the size of the document sheet at a constant speed V. Is reflected by the first reflecting mirror 52 and guided to the second scanning unit 46, whereby the image on the surface of the original paper is scanned in the sub-scanning direction. The second scanning unit 46 includes second and third reflecting mirrors 53 and 54, and follows the first scanning unit 45 while moving at a speed V / 2, while reflecting the reflected light from the document sheet to the second and third scanning units 46. The light is reflected by the third reflecting mirrors 53 and 54 and guided to the imaging lens 47. The imaging lens 47 focuses the reflected light from the original paper on the CCD 48 and forms an image on the original paper surface on the CCD 48. The CCD 48 repeatedly scans the image on the surface of the original paper in the main scanning direction, and outputs an analog image signal of one main scanning line each time.

  In addition, the first reading unit 41 can read not only a stationary document but also an image on the surface of the document sheet conveyed by the document conveying unit 42. In this case, as shown in FIG. 1, the first scanning unit 45 is moved to a reading position below the original reading glass 55, and the second scanning unit 46 is positioned in accordance with the position of the first scanning unit 45. Then, the document conveying unit 42 starts conveying the document sheet.

  In the document transport unit 42, the pickup roller 56 is pressed against the document paper on the document tray 57 and rotated to pull out the document paper, transport the document paper through the document transport path 58, and feed the document paper to the document of the first reading unit 41. The paper is passed over the reading glass 55, and further, the original paper is passed under the second reading unit 43 and conveyed from the paper discharge roller pair 61 to the paper discharge tray 62.

  When transporting the original paper, the surface of the original paper is illuminated through the original reading glass 55 by the light source 51 of the first scanning unit 45, and the reflected light from the original paper is reflected by the first and second scanning units 45 and 46. The light is guided to the imaging lens 47 by the mirror, and the reflected light from the original paper is condensed on the CCD 48 by the imaging lens 47, the image on the original paper surface is formed on the CCD 48, and the image on the original paper surface is read by the CCD 48. .

  Further, at the same time as reading the image on the surface of the original sheet being conveyed by the original conveying unit 42, the image on the back side of the original sheet can be read by the second reading unit 43 built in the original conveying unit 42. The second reading unit (hereinafter referred to as CIS) 43 is a contact image sensor (CIS), and is disposed above the platen glass 44. The document sheet that has passed over the document reading glass 55 of the first reading unit 41 passes under the CIS 43 and is discharged to the sheet discharge tray 62. When the document sheet passes, the CIS 43 illuminates the back side of the document sheet, receives reflected light from the document sheet, and reads an image on the back side of the document sheet.

  The original paper image read by the CCD 48 and the CIS 43 is output as an analog image signal from the CCD 48 and the CIS 43, and the analog image signal is A / D converted into a digital image signal. The digital image signal (image data) is subjected to various image processing and then sent to the laser exposure device 23 of the image forming apparatus 1, where the image is recorded on a recording sheet. The paper is output as a copy original.

  Next, the configuration of the paper feeding device of the present embodiment built in the large capacity paper feeding cassette 14 will be described in detail. This paper feeding device stacks and stores a large amount of recording paper, pulls out the recording paper one by one, and sends it out to a conveyance path 33 (shown in FIG. 1).

  2 and 3 are a plan view and a front view showing the sheet feeding device of the present embodiment. As shown in FIGS. 2 and 3, the sheet feeding device 71 is disposed on the outer frame 72, the bottom plate 73, the sheet stacking plate 74 disposed on the inner side of the outer frame 72, and one end upper side of the outer frame 72. A paper drawer 75 and the like are provided.

  The sheet stacking table 74 is used for stacking a large amount of recording sheets (sheet bundle) and is provided inside the outer frame 72 so as to be moved up and down. An opening 74 a that is long in the recording paper drawing direction (paper feeding and transport direction) E is formed in the paper stacking table 74. The paper trailing edge guide 76 is supported on the bottom plate 73 so as to be reciprocally movable along the recording paper drawing direction E, and protrudes upward through the opening 74 a of the paper stacking table 74. Note that the drawing direction E of the recording paper is the front, and the direction opposite to the drawing direction E is the rear.

  Recesses 74b are formed on both sides of the sheet stacking table 74, and assist ducts 77 and 78 are disposed in the respective recesses 74b. The assist ducts 77 and 78 are supported on both sides of the outer frame 72 so as to be able to reciprocate in a direction orthogonal to the drawing direction E, and are moved so as to approach each other or interlock so as to be separated from each other. Moved.

  The paper drawing unit 75 includes four paper conveyance belts 81, a pair of rollers 82 and 83 that bridge the respective paper conveyance belts 81, an intake / exhaust fan 84, an intake duct 85, an exhaust duct 86, and the like. Each paper transport belt 81 is formed with a large number of air holes 81 a, and air is sucked from the air holes 81 a of each paper transport belt 81 to the intake / exhaust fan 84 through the intake duct 85. The air exhausted from the intake / exhaust fan 84 is guided through the exhaust duct 86 and is blown out from the exhaust duct 86 to the inside of the outer frame body 72 in the direction opposite to the drawing direction E (backward).

  FIG. 4 is a perspective view showing the outer frame body 72, the bottom plate 73, the paper stacking board 74, and the like as viewed obliquely from the rear side with the paper drawing portion 75 removed. As shown in FIG. 4, assist fans 79 and 80 are provided outside the assist ducts 77 and 78, respectively. Each of the assist ducts 77 and 78 is a hollow body and has a ventilation path therein. Air sucked by each of the assist fans 79 and 80 is sent to the ventilation paths of the respective assist ducts 77 and 78. The air is blown out from the exhaust ports 77a and 78a of the assist ducts 77 and 78 to the inside of the outer frame 72.

  As shown in FIGS. 2 and 4, the paper trailing edge guide 76 can reciprocate along the drawing direction E of the recording paper, and is positioned at an arbitrary position along the drawing direction E. Further, as shown in FIGS. 2 and 4, each of the assist ducts 77 and 78 can reciprocate in a direction perpendicular to the drawing direction E, and is positioned at an arbitrary position along the direction perpendicular to the drawing direction E. .

  Here, when the sheet bundle is mounted on the sheet stacking board 74, the sheet rear end guide 76 is moved rearward to widen the gap between the sheet rear end guide 76 and the contact plate 72b of the outer frame 72, or The assist ducts 77 and 78 are moved in directions away from each other so that the space between the assist ducts 77 and 78 is wide open. In this state, the sheet bundle is placed on the sheet stacking table 74, and then the sheet trailing edge guide 76 is moved in the drawing direction E, and the trailing edge of the sheet bundle is pushed in the drawing direction E by the column portion 76a of the sheet trailing edge guide 76. Then, the sheet bundle is slid and moved on the sheet stacking table 74, the leading end of the sheet bundle is brought into contact with the contact plate 72 b of the outer frame body 72, and the leading end and the trailing end of the sheet bundle are aligned with the pillars of the sheet trailing end guide 76. Positioning is performed by being sandwiched between the portion 76a and the contact plate 72b of the outer frame 72. Further, the assist ducts 77 and 78 are moved in a direction approaching each other so that both ends of the sheet bundle are sandwiched between the assist ducts 77 and 78 and positioned.

  Further, as shown in FIG. 4, two protruding pieces 74 c are formed on both sides of the paper stacking base 74, and each protruding piece 74 c protrudes from the opening 72 a on both sides of the outer frame 72. On one side of the outer frame 72, two wires 87 are connected to the protruding pieces 74 c on one side of the paper stacking base 74, and each wire 87 is hooked around a plurality of driven pulleys 88 and drawn around a take-up pulley 89. It is connected. On the other side of the outer frame 72, the other two wires 87 are connected to the protruding pieces 74c on the other side of the sheet stacking table 74, and the other wires 87 are connected to a plurality of other driven pulleys 88. It is drawn around and connected to another take-up pulley 89. Each winding pulley 89 is fixed to both ends of a common shaft 91 that is rotatably supported. The shaft 91 is rotationally driven by a pulse motor 92 to rotate each winding pulley 89, and each wire 87 is wound to each winding 87. It is wound around the pulley 89 and is fed out from each winding pulley 89.

  FIG. 5 is a side view showing the paper stacking base 74, the wires 87, the driven pulleys 88, and the winding pulleys 89 in a simplified manner. As is apparent from FIG. 5, when the shaft 91 is rotationally driven by the pulse motor 92 and each take-up pulley 89 is rotated in the clockwise direction, each wire 87 is taken up by each take-up pulley 89, and the paper stacking table When 74 rises and each take-up pulley 89 is rotated in the counterclockwise direction, each wire 87 is fed out from each take-up pulley 89 and the paper stacking table 74 is lowered. Further, the rotation angle of the take-up pulley 89 that is rotationally driven by the pulse motor 92 and the height of the paper stacking base 74 are in a corresponding relationship. Therefore, by controlling the rotation direction and rotation angle of the pulse motor 92, the height of the sheet stacking base 74 can be adjusted and set.

  As shown in FIG. 4, a head position 76 b of the paper trailing edge guide 76 is provided with a height position sensor 93 that detects the height of the uppermost layer of the paper bundle on the paper stacking base 74. FIGS. 6A and 6B are a side view and a plan view showing the height position sensor 93 provided on the head portion 76b of the paper trailing edge guide 76 in a simplified manner. As shown in FIGS. 6A and 6B, the height position sensor 93 includes a dogleg-shaped lever 95 rotatably supported by a horizontal shaft 94, and rotation of one end portion 95a of the dogleg-shaped lever 95. A light-emitting element 96 and a light-receiving element 97 are provided so as to face each other across the moving region. The front end portion 95 c of the dogleg-shaped lever 95 faces the contact plate 72 b of the outer frame body 72, and the bent portion 95 b protrudes downward from the head portion 76 b of the paper rear end guide 76. For this reason, when the sheet bundle on the sheet stacking table 74 is sandwiched between the column portion 76a of the sheet rear end guide 76 and the contact plate 72b of the outer frame 72, the dogleg-shaped lever 95 holds the sheet bundle. Located above the rear end.

  Here, as shown in FIG. 5, each take-up pulley 89 is rotated counterclockwise by the pulse motor 92, the sheet stacking table 74 is lowered, and the sheet bundle on the sheet stacking table 74 is moved by the height position sensor 93. In a state separated from the dog-shaped lever 95, as shown in FIG. 6C, the dog-shaped lever 95 rotates counterclockwise around the shaft 94 by its own weight, and the dog-shaped lever. 95 is in contact with the stopper 98, and the one end portion 95 a of the dog-shaped lever 95 is removed from the optical path between the light emitting element 96 and the light receiving element 97, and the light from the light emitting element 96 is received by the light receiving element 97. Further, when each winding pulley 89 is rotated clockwise by the pulse motor 92, the paper stacking table 74 is raised, and when the uppermost sheet of the sheet bundle on the paper stacking table 74 reaches the detection reference height, As shown in FIG. 6A, the uppermost sheet of paper contacts the bent portion 95b of the dogleg-shaped lever 95 to push up the bent portion 95b, and the dogleg-shaped lever 95 rotates in the clockwise direction around the shaft 94. Then, the one end portion 95 a of the dog-shaped lever 95 blocks the optical path between the light emitting element 96 and the light receiving element 97, and the light from the light emitting element 96 is not received by the light receiving element 97. Further, when the paper stacking table 74 is further raised and the uppermost sheet of the sheet bundle on the paper stacking table 74 exceeds the height of the detection reference, the character-shaped lever 95 rotates in the clockwise direction, One end portion 95 a of the U-shaped lever 95 deviates from the optical path between the light emitting element 96 and the light receiving element 97, and the light from the light emitting element 96 is received by the light receiving element 97.

  Therefore, it is possible to detect whether the uppermost sheet of the sheet bundle on the sheet stacking board 74 is at the detection reference height based on the change in the light reception output of the light receiving element 97.

  Next, the configuration of the paper drawer 75 will be described in detail. FIG. 7 is a perspective view showing the paper drawer portion 75 as viewed obliquely from the upper front. FIG. 8 is a perspective view showing the paper drawer portion 75 as viewed obliquely from above and behind. FIG. 9 is a perspective view of the paper drawer portion 75 as seen from diagonally below and rear.

  As shown in FIGS. 7, 8, and 9, the paper drawing unit 75 includes four paper conveyance belts 81, a pair of rollers 82 and 83 that bridge the paper conveyance belts 81, an intake / exhaust fan 84, an intake duct 85, And an exhaust duct 86 and the like.

  The intake duct 85 is a hollow body, and has a long ventilation path in the direction orthogonal to the drawing direction E. One end 85a of the intake duct 85 is connected to the intake / exhaust fan 84 and is indicated by an arrow F. In this way, air is sucked from the ventilation path of the intake duct 85 to the intake port (not shown) of the intake / exhaust fan 84 through the one side end 85a.

  Further, the upper surface 85b of the intake duct 85 is flat, and the lower surface 85g of the intake duct 85 is flat. Furthermore, the front end portion 85c and the rear end portion 85d of the intake duct 85 are formed with respective recesses 85h, and the rollers 82 and 83 are disposed in these recesses 85h so as to be rotatably supported. ing.

  A plurality of ribs 85j that are long in the pull-out direction E are formed on the lower surface 85g of the intake duct 85. As shown in an enlarged plan view in FIG. 10, a plurality of intake holes 85 e communicating with the ventilation path of the intake duct 85 are formed between the ribs 85 j on the lower surface 85 g of the intake duct 85.

  The conveyance motor 107 rotationally drives the front roller 82 in the arrow direction D, the rear roller 83 is driven to rotate, and each paper conveyance belt 81 rotates in the arrow direction D. At this time, each sheet conveying belt 81 is in sliding contact with each rib 85j formed on the lower surface 85g of the intake duct 85.

  Here, as shown in an enlarged view in the plan view of FIG. 10, the air holes 81a of the paper transport belt 81 are formed in a plurality of rows along the pull-out direction E, and these rows are at the same intervals as the ribs 85j. The sheet conveying belt 81 is bridged so that these rows are located between the ribs 85j. Therefore, a space surrounded by the ribs 85j, the sheet conveying belt 81, and the lower surface 85g of the intake duct 85 is formed between the ribs 85j. Each air hole 81a and each air intake hole 85e on the lower surface 85g of the air intake duct 85 serve as an air inlet / outlet port. For this reason, when the air in the intake duct 85 is sucked by the intake / exhaust fan 84, the air flows into the intake holes 85e of the lower surface 85g of the intake duct 85 through the air holes 81a of the paper transport belt 81 and the spaces. The air flows through the intake duct 85 to the intake / exhaust fan 84. As a result, the recording sheet can be adsorbed to the lower surface of each sheet conveying belt 81 and conveyed.

  On the other hand, the exhaust duct 86 is also a hollow body and has a long ventilation path in a direction orthogonal to the drawing direction E. One end 86a of the exhaust duct 86 is connected to the intake / exhaust fan 84 and is indicated by an arrow K. As described above, air is sent from the exhaust port (not shown) of the intake / exhaust fan 84 to the ventilation path of the exhaust duct 86 through the one end 86a of the exhaust duct 86.

  Further, each exhaust port 86 b communicating with the ventilation path of the exhaust duct 86 is formed on the inner wall surface 86 d of the exhaust duct 86. An inner wall surface 86 d of the exhaust duct 86 is provided so as to overlap with an outer surface of the contact plate 72 b of the outer frame body 72, and each exhaust port 86 b of the exhaust duct 86 forms a notch 72 c of the contact plate 72 b of the outer frame body 72. Via the outer frame 72. When air is sent from the intake / exhaust fan 84 to the exhaust duct 86, the air is blown out from the exhaust ports 86 b to the inner rear side of the outer frame 72.

  Further, one end 85a of the intake duct 85 and one end 86a of the exhaust duct 86 are connected to the intake / exhaust fan 84, and the other side end 85f of the intake duct 85 and the other side of the exhaust duct 86 are connected. The end portions 86c are connected to each other, whereby the intake / exhaust fan 84, the intake duct 85, and the exhaust duct 86 are integrated.

  In such a sheet feeding device 71, as shown in the side view of FIG. 11, the sheet bundle is placed on the sheet stacking board 74, and the leading end and the rear end of the sheet bundle are the column portion 76a of the sheet rear end guide 76 and the outer frame. The sheet bundle is positioned by being sandwiched between the contact plates 72b of 72, and both ends of the sheet bundle are sandwiched between the assist ducts 77 and 78 for positioning. Then, each winding pulley 89 is rotated in the clockwise direction by the pulse motor 92 to raise the paper stacking table 74. At this time, when the uppermost sheet of the sheet stack on the sheet stacking board 74 is detected by the height position sensor 93, that is, when the uppermost sheet reaches the detection reference height, the pulse motor 92 is stopped. Then, the height of the uppermost sheet is set to the detection reference height, or the rotation direction and the rotation angle of the pulse motor 92 are further controlled to adjust and set the height of the uppermost sheet. Also, air is sent from the assist fans 79 and 80 to the assist ducts 77 and 78, and the air is exhausted from the exhaust ports 77a and 78a of the assist ducts 77 and 78 on both sides near the front end of the sheet stack loaded on the sheet stacking board 74. Air is blown onto the upper layer of the surface, allowing air to enter between the sheets and causing the sheets to scatter. Further, air is sent from the intake / exhaust fan 84 to the exhaust duct 86, and air is blown from the air holes 81a of the exhaust duct 86 to the upper layer of the front end surface of the sheet bundle so that the air enters between the sheets, To disperse. As a result, the adhesion of each sheet in the upper layer of the sheet bundle is reduced, and the sheet can be easily pulled out from the sheet bundle, and the sheets can be pulled out one by one.

  In this state, air is sucked from the intake duct 85 to the intake / exhaust fan 84, and the air is sucked through the air holes 81a of the paper conveying belt 81 and the air holes 85e of the lower surface 85g of the air intake duct 85, and the rollers 82. , 83 are rotated intermittently, and each sheet conveying belt 81 is intermittently moved around, and one recording sheet is attracted to the lower surface of each sheet conveying belt 81, and the recording sheet is recorded by each sheet conveying belt 81. Is pulled out in the drawing direction E and is conveyed to the conveyance roller pair 31 of the image forming apparatus 1, and the recording paper is conveyed through the conveyance path 33, and then the next one recording paper is placed on the lower surface of each paper conveyance belt 81. The sheet is attracted, and the recording paper is drawn in the drawing direction E by each paper transport belt 81 and transported to the transport roller pair 31. Thereafter, the recording is similarly performed on the lower surface of each paper transport belt 81. Paper is adsorbed, the recording sheet by the sheet conveying belt 81 is gradually is transported drawn in the drawing direction E.

  By the way, in the sheet feeding device 71, various recording sheets are set on the sheet stacking board 74, so that the recording sheet is attracted to the lower surface of each sheet conveying belt 81 and pulled out regardless of the type of the recording sheet. Must be able to.

  However, depending on the type of the recording paper, the recording paper is easily attracted to the lower surface of each paper transport belt 81, and a recording paper transport error occurs. For example, the types of recording paper include size, basis weight, and air permeability. Depending on the size, basis weight, and air permeability, the recording paper may be adsorbed.

  For example, the size of the recording paper is generally a standard size such as B5, A4, B4, etc. When the size of the recording paper changes, the weight of the recording paper changes. The basis weight of the recording paper is the weight per unit area of the recording paper. When the basis weight of the recording paper changes, the weight and rigidity of the recording paper change. If the recording paper becomes too heavy, even if the air is sucked from the air holes 81 a of the paper transport belt 81, the recording paper is not easily lifted and it is difficult to attract the recording paper to the lower surface of each paper transport belt 81. . Further, if the recording paper is too rigid, the recording paper is difficult to adhere to the lower surface of each paper conveying belt 81, and it is difficult to attract the recording paper to the lower surface of each paper conveying belt 81.

  The air permeability is the speed at which air escapes from one side of the recording paper to the other side, and is the ease of air escape. If the air permeability is excessively large, when air is sucked from the air holes 81a of the paper transport belt 81, the air is released from the lower surface to the upper surface of the recording paper, and the recording paper is hardly lifted. It becomes difficult to attract the recording paper to the lower surface of the belt 81.

  As described above, depending on the type of the recording paper, the recording paper may be attracted to the lower surface of each paper transport belt 81, which may cause a recording paper transport error.

  Therefore, in the present embodiment, the height of the paper stacking base 74 is changed in accordance with the size, basis weight, and air permeability of the recording paper, and the uppermost sheet of the paper stack on the paper stacking base 74 and each paper The distance from the lower surface of the conveyance belt 81 is adjusted so that the recording sheets can be quickly adsorbed and pulled out one by one on the lower surface of each sheet conveyance belt 81 regardless of the type of recording paper. .

  In addition, even when there is a delay in the withdrawal of the recording paper by each paper transport belt 81, the height of the paper stacking base 74 is changed, and the recording paper is quickly attracted to the lower surface of each paper transport belt 81 and pulled out. , The delay in drawing out the recording paper is suppressed.

  Next, a description will be given of a configuration for quickly adsorbing and pulling out a recording sheet to the lower surface of each sheet conveying belt 81 regardless of the type of recording sheet or when the recording sheet is delayed.

  FIG. 12 is a block diagram illustrating a configuration of a control system of the image forming apparatus 1 and the paper feeding device 71. In FIG. 12, a control unit 101 controls the image forming apparatus 1 and the sheet feeding device 71 in an integrated manner, and includes a CPU, a RAM, a ROM, various interfaces, and the like. The input operation unit 102 includes, for example, a plurality of operation keys, a liquid crystal display device, and a touch panel superimposed on the screen of the liquid crystal display device, and displays operation guidance and the like of the image forming apparatus 1 on the screen of the liquid crystal display device. For example, data input by an operation of each operation key or the like is output to the control unit 101. The memory 103 is, for example, a hard disk device (HDD), and stores various data and programs. The image processing unit 104 performs various image processes on the image data.

  As described above, the height position sensor 93 is provided on the head portion 76b of the sheet trailing edge guide 76 of the sheet feeding device 71, and the uppermost sheet of the sheet bundle on the sheet stacking table 74 is the height of the detection reference. It is detected whether it exists in. The size detection unit 105 detects, for example, the position of the sheet trailing edge guide 76 in the drawing direction E and the position of the assist ducts 77 and 78 in the direction orthogonal to the drawing direction E of the sheet feeding device 71 and corresponds to these positions. A detection output indicating the size of the recording paper is output. As shown in FIG. 11, the sheet leading edge sensor 106 is an optical sensor that is positioned at a predetermined position spaced from the front end of each sheet conveying belt 81 in the sheet feeding device 71 in the drawing direction E. The leading edge of the recording paper drawn by the conveyance belt 81 is detected.

  In such a configuration, for example, the control unit 101 causes the document reading device 2 to read an image of the document, stores image data indicating the image of the document in the memory 103, and causes the image processing unit 104 to store the image in the memory 103. The data is processed, and the image of the document indicated by the image data in the memory 103 is recorded on the recording paper by the printing unit 11.

  When the paper supply unit 13 is selected and instructed by the operation of the input operation unit 102, in response to this, the control unit 101 controls the paper supply unit 13 to record from the paper supply unit 13 to the printing unit 11. A sheet is fed, and an image of a document is recorded on the recording sheet.

  Alternatively, when the large-capacity paper cassette 14 is selected and instructed by the operation of the input operation unit 102, the control unit 101 controls the paper feeding device 71 of the large-capacity paper feeding cassette 14 to control the printing unit from the paper feeding device 71. 11 is fed with a recording sheet, and an image of a document is recorded on the recording sheet.

  Next, the control of the sheet feeding device 71 will be described in detail. First, the memory 103 has four data tables D1, D2, D3, and D4 used for controlling the sheet feeding device 71 as shown in FIGS. 13 (a), (b), (c), and (d). Stored in advance. In the data table D1 of FIG. 13A, the standard sizes B5, A4,... Of the recording paper and the correction amounts m11, m12,. In addition, in the data table D2 of FIG. 13B, a plurality of basis weight ranges G1, G2,... And correction amounts m21, m22,. Further, in the data table D3 in FIG. 13C, a plurality of air permeability ranges J1, J2,... And correction amounts m31, m32,. In the data table D4 in FIG. 13D, a plurality of time ranges T1, T2,... And correction amounts m41, m42,.

  The sheet height correction amount indicates the rotation direction and rotation angle of the pulse motor 92, and is a correction amount of the height of the uppermost sheet in the sheet bundle on the sheet stacking table 74. FIG. This is used to adjust and set the separation distance h0 between the uppermost sheet of the sheet bundle on the sheet stacking table 74 and the lower surface of each sheet conveying belt 81 as shown. Further, each time range T1, T2,... Is a time point at which the leading edge of the recording paper is detected by the paper leading edge sensor 106 from a time point at which the paper conveying belt 81 that is intermittently moved is started to rotate (recording paper drawing start time). Is compared with the time interval Δt.

  Here, in the data table D1 of FIG. 13A, the correction amount of the paper height corresponding to the standard standard size B5 of the recording paper is “0”, and the paper height corresponding to the size larger than the standard is set. The correction amount is set to a positive value other than “0”. In the data table D2 of FIG. 13B, the correction amount of the paper height corresponding to the standard basis weight range G1 of the recording paper is “0”, and the paper height corresponding to the basis weight range larger than the standard. The correction amount is set to a positive value other than “0”. Further, in the data table D3 of FIG. 13C, the correction amount of the paper height corresponding to the standard air permeability range J1 of the recording paper is “0”, and the paper corresponding to the air permeability greater than the standard. The height correction amount is set to a positive value other than “0”. In the data table D4 of FIG. 13D, the paper height correction amount corresponding to the standard time range T1 is “0”, and the paper height correction amount corresponding to the time range longer than the standard is set. It is set to a positive value other than “0”.

  For example, when the size of the recording paper is the standard standard size B, the basis weight of the recording paper is in the standard basis weight range G1, and the air permeability of the recording paper is in the standard air permeability range J1, When the recording paper is standard, the paper height correction amount corresponding to the standard size B5 is “0”, the paper height correction amount corresponding to the standard basis weight range G1 is “0”, and the standard paper size correction amount is “0”. Since the paper height correction amount corresponding to the air permeability range J1 is “0”, the sum of the paper height correction amounts (“0”) is set as the control correction amount, and this control correction amount (“ 0 ”), the uppermost sheet of the sheet bundle on the sheet stacking board 74 is positioned at the height of the detection reference, and as shown in FIG. A distance h0 from the lower surface of the sheet conveying belt 81 is set to a distance h1. This distance h 1 is a distance suitable for adsorbing the standard recording paper on the paper stacking table 74 to the lower surface of each paper transport belt 81.

  Further, when at least one of the size, basis weight, and air permeability of the recording paper is not standard, the paper height correction amount corresponding to the size corresponds to a positive value and basis weight range other than “0”. The correction amount of the paper height is a positive value other than “0”, the correction amount of the paper height corresponding to the air permeability range is a positive value other than “0”, and the sum of the correction amounts of the respective paper heights ( A positive value that is not “0” is set as the control correction amount, and the height of the uppermost sheet in the sheet stack on the paper stacking base 74 is set according to this control correction amount (a positive value that is not “0”). Is adjusted to be higher than the detection reference height, and as shown in FIG. 11, the distance h0 between the uppermost sheet of the sheet bundle on the sheet stacking table 74 and the lower surface of each sheet conveying belt 81 is set to the distance h2. . This distance h <b> 2 is a distance suitable for attracting various non-standard recording sheets on the sheet stacking table 74 to the lower surface of each sheet transport belt 81.

  The control unit 101 acquires the size of the recording paper on the paper stacking plate 74 detected by the size detection unit 105 of the paper feeding device 71 prior to paper feeding from the paper feeding device 71 of the large capacity paper feeding cassette 14. Then, referring to the data table D1 in the memory 103, a correction amount of the paper height corresponding to the detected size is obtained. Alternatively, when the input of the size of the recording paper on the paper stacking board 74 is instructed by the operation of the input operation unit 102, the control unit 101 refers to the data table D1 in the memory 103 and corresponds to the input instructed size. Find the correction amount for the paper height to be used.

  Further, when the basis weight of the recording paper on the paper stacking board 74 is instructed by the operation of the input operation unit 102, the control unit 101 refers to the data table D2 in the memory 103 and the input basis weight is instructed. Is selected, and a correction amount of the paper height corresponding to the selected basis weight range is obtained.

  Further, when the air permeability of the recording paper on the paper stacking board 74 is instructed to input by the operation of the input operation unit 102, the control unit 101 refers to the data table D3 in the memory 103 and inputs the instructed transparent light. The air permeability range including the air temperature is selected, and the correction amount of the paper height corresponding to the selected air permeability range is obtained.

  Then, the control unit 101 obtains the sum of the correction amounts of the respective paper heights corresponding to the recording paper size, basis weight, and air permeability, and sets this sum as the control correction amount.

  Note that the weighting coefficient (0 <coefficient <1) is set in advance for the correction amount of each paper height corresponding to the size, basis weight, and air permeability of the recording paper, and the size, basis weight, and transparency are set. The sum of these products may be set as the control correction amount by multiplying the correction amount of the paper height corresponding to the temperament by the respective weighting coefficient.

  Here, for example, when the recording sheet has a standard size, a standard basis weight, and a standard air permeability, and the control correction amount is “0”, the control unit 101 drives and controls the pulse motor 92. Each take-up pulley 89 is rotated to raise the paper stacking table 74. When the height position sensor 93 detects that the uppermost sheet of the sheet stack on the sheet stacking board 74 has reached the detection reference height, the control unit 101, as shown in FIG. 92 is stopped, and the uppermost sheet of the sheet bundle on the sheet stacking board 74 is positioned at the detection reference height. At this time, as shown in FIG. 11, the distance h0 between the uppermost sheet of the sheet bundle on the sheet stacking board 74 and the lower surface of each sheet conveying belt 81 is the distance h1.

  Further, the control unit 101 drives the assist fans 79 and 80 to blow air from the exhaust ports 77a and 78a of the assist ducts 77 and 78 to the upper layers on both side surfaces near the leading edge of the sheet stack on the sheet stacking table 74. Let Further, the control unit 101 drives the intake / exhaust fan 84 to blow out air from the vent holes 81a of the exhaust duct 86 through the exhaust duct 86 to the upper layer of the front end surface of the sheet bundle on the sheet stacking board 74. Is sucked into the air intake duct 85 through the air holes 81a of the paper conveying belts 81 and the air intake holes 85e on the lower surface 85g of the air intake duct 85. As a result, the adhesion of each sheet in the upper layer of the sheet bundle is reduced, it becomes easy to pull out the sheets one by one, and the recording sheet is attracted to the lower surface of each sheet conveying belt 81.

  Then, the control unit 101 drives and controls the transport motor 107, intermittently rotates the rollers 82 and 83, and intermittently moves the paper transport belts 81. As a result, the recording paper is attracted to the lower surface of each paper transport belt 81, and the recording paper is drawn out and transported by each paper transport belt 81 being drawn out and transported to the transport path 33 of the image forming apparatus 1. It is.

  When the recording sheets are sequentially pulled out and conveyed from the sheet bundle on the sheet stacking board 74 in this way, the height of the uppermost sheet of the sheet bundle on the sheet stacking board 74 is lowered, and the height position sensor 93 causes the sheet to be removed. It is detected that the uppermost sheet in the stack of sheets on the loading platform 74 has fallen below the detection reference height (h0> h1). In response to this, the control unit 101 drives and controls the pulse motor 92 to raise the paper stacking table 74 again, and positions the uppermost sheet of the stack of sheets on the paper stacking table 74 at the detection reference height. Then, the separation distance h0 between the uppermost sheet of the sheet bundle on the sheet stacking board 74 and the lower surface of each sheet conveying belt 81 is reset to the distance h1.

  Thereafter, similarly, the recording sheets are sequentially pulled out from the sheet bundle on the sheet stacking board 74 and conveyed, and when the uppermost sheet of the sheet bundle on the sheet stacking board 74 falls below the detection reference height (h0> h1). Then, the sheet loading table 74 is raised, the uppermost sheet of the sheet bundle on the sheet loading table 74 is positioned at the detection reference height, and the separation distance h0 is set to the distance h1.

  Therefore, when the recording paper has a standard size, standard basis weight, and standard air permeability, the separation distance h0 is set to the distance h1, and the separation distance h0 is set when the separation distance h0 is longer than the distance h1. Is repeatedly set to the distance h1, and the separation distance h0 is generally set to the distance h1. Since the distance h1 is a distance suitable for adsorbing standard recording paper to the lower surface of each paper transport belt 81 as described above, standard recording on the paper stacking board 74 by each paper transport belt 81. The sheets can be quickly sucked and pulled out one by one, and the occurrence of recording sheet conveyance errors can be suppressed.

  Next, even when at least one of the size, basis weight, and air permeability of the recording paper is not standard, the control unit 101 drives and controls the pulse motor 92 to raise the paper stacking base 74 to increase the height. When the position sensor 93 detects that the uppermost sheet in the sheet stack on the sheet stacking board 74 has reached the detection reference height (h0 = h1), the rotation direction and rotation according to the control correction amount are subsequently performed. The pulse motor 92 is rotationally driven by an angle to further raise the paper stacking table 74, so that the uppermost sheet of the sheet bundle on the paper stacking table 74 is separated from the lower surface of each paper transport belt 81 as shown in FIG. The distance h0 is set to the distance h2.

  Further, the control unit 101 drives the assist fans 79 and 80 and the intake / exhaust fan 84 to blow air onto the upper layer of the sheet bundle, thereby reducing the adhesion of each sheet of the upper layer of the sheet bundle, Suction is performed through the air holes 81 a of the paper transport belt 81.

  Then, the control unit 101 drives and controls the conveyance motor 107 to intermittently move the respective sheet conveyance belts 81 so that the recording sheets are pulled out in the drawing direction E one by one by the respective sheet conveyance belts 81 and conveyed.

  Further, as the recording sheet is pulled out from the sheet bundle on the sheet stacking board 74, the height of the uppermost sheet in the sheet bundle on the sheet stacking board 74 is lowered. When it is detected that the uppermost sheet of the sheet bundle is lower than the detection reference height (h0> h1), in response to this, the control unit 101 drives and controls the pulse motor 92 to load the sheets. When the stage 74 is raised and the height position sensor 93 detects that the uppermost sheet of the sheet stack on the sheet stacking stage 74 has reached the detection reference height (h0 = h1), the control correction is subsequently performed. The pulse motor 92 is rotationally driven by a rotation direction and a rotation angle according to the amount to raise the paper stacking table 74 again, and the uppermost sheet of the sheet bundle on the paper stacking table 74 and the lower surface of each paper transport belt 81 The separation distance h0 is reset to the distance h2.

  Thereafter, similarly, when the recording sheets are sequentially pulled out from the sheet bundle on the sheet stacking board 74 and conveyed, and the uppermost sheet of the sheet bundle on the sheet stacking board 74 is lowered to the detection reference height (h0> h1), The sheet loading table 74 is raised and the separation distance h0 is set to the distance h2.

  Accordingly, when at least one of the size, basis weight, and air permeability of the recording paper is not standard, the separation distance h0 is set to the distance h2, and the separation distance is set when the separation distance h0 is longer than the distance h1. The process of resetting h0 to the distance h2 is repeated, and the separation distance h0 is set in the range of distances h1 to h2. Since the distance h2 is a distance suitable for adsorbing various non-standard recording papers to the lower surface of each paper transport belt 81 as described above, even for various non-standard recording papers, The recording sheets on the sheet stacking board 74 by each sheet conveying belt 81 can be sucked and pulled out one by one, and the occurrence of recording sheet conveying errors can be suppressed.

  Note that a rotary encoder may be applied as the height position sensor 93. For example, as shown in FIG. 14, the rotary encoder 111 is fixed to the shaft 95d of the dog-shaped lever 95, and the rotary encoder 111 detects the rotation direction and the rotation angle of the dog-shaped lever 95. Then, the paper stacking base 74 is raised, the uppermost sheet of the paper stack on the paper stacking base 74 is pushed up, and the rotary lever 111 sets the square lever 95 in the clockwise direction. When it is detected that the sheet has been rotated by the rotation angle, it is considered that the uppermost sheet of the sheet bundle on the sheet stacking board 74 has reached the detection reference height (h0 = h1). Further, the pulse motor 92 is driven to rotate by a rotation direction and a rotation angle corresponding to the correction amount of the sheet height, and the sheet stacking table 74 is further raised, and the uppermost sheet of the sheet bundle on the sheet stacking table 74 and each sheet When the distance h0 from the lower surface of the paper transport belt 81 is set to the distance h2, the rotary encoder 111 detects the rotation angle of the dog-shaped lever 95 and sets this rotation angle to the target rotation angle. Further, when the recording sheets are sequentially pulled out from the sheet bundle on the sheet stacking table 74 and the height of the uppermost sheet of the sheet bundle is lowered and the rotation angle detected by the rotary encoder 111 is changed, it is detected. The paper stacking base 74 is raised so that the rotation angle returns to the specified rotation angle or the target rotation angle. Thereby, the separation distance h0 can be maintained at the distance h1 or h2, and can always be optimized.

  Alternatively, when the input operation unit 102 is operated to input the number of recording sheets stacked on the sheet stacking board 74 and the height position sensor 93 detects the uppermost sheet in the sheet stack on the sheet stacking board 74. If the height of the sheet bundle of the sheet stacking board 74 is obtained based on the rotation angle of the pulse motor 92, the thickness of the recording sheet can be obtained by dividing the height of the sheet bundle by the number of stacked recording sheets. The separation distance h0 is also set to the distance h1 or h2 by raising the paper stacking base 74 by a height corresponding to the product of the number of recording papers drawn from the paper stack on the stacking base 74 and the thickness of the recording paper. It is possible to keep the optimization and always optimize.

  On the other hand, the control unit 101 intermittently moves each paper transport belt 81 every time the front end of the recording paper is detected by the paper front end sensor 106 when the recording paper is drawn from the paper bundle on the paper stacking base 74. A time interval Δt from the start time (recording paper drawing start time) to the time when the leading edge sensor 106 detects the leading edge of the recording paper is obtained, and a time range including the time interval Δt is obtained by referring to the data table D4 in the memory 103. A sheet height correction amount corresponding to the selected time range is selected.

  When the control unit 101 obtains the correction amount of the paper height corresponding to the time range, the control unit 101 adds the correction amount of the paper height to the correction amount of the paper height obtained from each of the data tables D1, D2, and D3. Then, this sum is set as the control correction amount, or the correction amount of each paper height obtained from each data table D1, D2, D3, D4 is multiplied by the respective weighting coefficient (<1), and these products are obtained. Is set as the control correction amount. Then, the control unit 101 raises the sheet stacking table 74 until the height position sensor 93 detects that the uppermost sheet of the sheet bundle on the sheet stacking table 74 has reached the detection reference height (separation). Distance h0 = distance h1), and subsequently, the pulse motor 92 is rotationally driven by the rotation direction and rotation angle corresponding to the control correction amount to further raise the paper stacking table 74, and as shown in FIG. The distance h0 between the uppermost sheet of the sheet bundle and the lower surface of each sheet conveying belt 81 is set to a distance h3.

  Here, for example, in the data table D4, when the paper height correction amount corresponding to the time range including the time interval Δt is “0”, the separation distance h0 is merely maintained at the distance h1 or h2. Thus, the separation distance h0 is not reset to the distance h3. In other words, when there is no delay in the time when the leading edge sensor 106 detects the leading edge of the recording paper, it is not necessary to reset the separation distance h0 (= h1 or h2) to the distance h3.

  In the data table D4, when the paper height correction amount corresponding to the time range including the time interval Δt is set to a positive value other than “0”, the separation distance h0 is set to the distance h3. That is, when a delay occurs at the time when the leading edge sensor 106 detects the leading edge of the recording sheet, the separation distance h0 (= h1 or h2) is reset to the distance h3.

  For this reason, although the separation distance h0 between the uppermost sheet of the sheet bundle on the sheet stacking board 74 and the lower surface of each sheet conveying belt 81 is set to the distance h1 or h2, depending on the type of recording sheet, When the recording paper is pulled out by the paper transport belt 81, the recording paper is attracted by each paper transport belt 81, the recording paper is pulled out, and the delay of the recording paper is suppressed.

  Even when the separation distance h0 is not adjusted and set to the distance h1 or h2 according to the type of recording paper, when the recording paper is pulled out by each paper transport belt 81, the recording paper is not printed by each paper transport belt 81. Adsorption is advanced, recording paper is drawn out earlier, and a delay in drawing out the recording paper is suppressed.

  As described above, in the sheet feeding device according to the present embodiment, the uppermost sheet of the sheet bundle on the sheet stacking board 74 is separated from the lower surface of each sheet conveying belt 81 according to the size, basis weight, and air permeability of the recording sheet. Since the distance h0 is adjusted appropriately, regardless of the type of recording paper, the recording paper on the paper stacking board 74 can be sucked and pulled out one by one by each paper transport belt 81, and a recording paper transport error occurs. Can be suppressed. Further, it is not necessary to increase the size of the intake / exhaust fan 84, and the power consumption thereof does not increase.

  Further, when the time interval Δt from the start of the circular movement of each paper transport belt 81 to the time when the front edge of the recording paper is detected by the paper front sensor 106 becomes longer, that is, the withdrawal of the recording paper by each paper transport belt 81 is delayed. In this case, the separation distance h0 between the uppermost sheet of the sheet bundle on the sheet stacking table 74 and the lower surface of each sheet conveying belt 81 is appropriately shortened, so that the recording sheet is adsorbed by each sheet conveying belt 81. Is advanced, the recording paper is drawn out earlier, and the delay in the drawing of the recording paper is suppressed.

  In the above-described embodiment, the paper stacking table 74 is lifted and lowered. Alternatively, each paper transport belt 81 may be lifted and / or the paper stacking table 74 and each paper transport belt 81 may be lifted and lowered. .

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. It is understood.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Document reader 11 Printing part 12 Paper feeding device 13 Paper supply part 14 Large capacity paper feed cassette (LCC)
71 Paper feeder 72 Outer frame 73 Bottom plate 74 Paper stacking board 75 Paper drawer part 76 Paper rear end guides 77 and 78 Assist ducts 79 and 80 Assist fan 81 Paper conveyance belt (paper conveyance part)
82, 83 Roller 84 Intake / exhaust fan (air suction part)
85 Air intake duct (air suction part)
86 Exhaust duct (air blowing part)
92 Pulse motor (elevating part)
93 Height position sensor 101 Control unit 102 Input operation unit (input unit)
103 Memory 104 Image processing unit 105 Size detection unit (detection unit)
106 Paper edge sensor

Claims (9)

A sheet stacking unit on which sheets are stacked; a sheet conveying unit disposed above the sheet stacking unit; and an air suction unit for sucking air through a vent hole of the sheet conveying unit. A paper feeding device that sucks and transports the paper on the paper stacking base to the paper transport unit by sucking air through pores;
An elevating unit that elevates and lowers the sheet stacking unit or the sheet conveying unit to change a separation distance of the sheet conveying unit with respect to the sheet on the sheet stacking unit;
And a control unit that controls the elevating unit and adjusts a separation distance of the sheet conveying unit from the sheet on the sheet stacking table according to a type of the sheet on the sheet stacking table. apparatus. The sheet feeding device according to claim 1,
The paper feeding device, wherein the paper transport unit is a paper transport belt. The sheet feeding device according to claim 1 or 2,
A paper feeding device comprising: an input unit that inputs a type of paper on the paper stacking table; or a detection unit that detects the type of paper on the paper stacking table. The sheet feeding device according to any one of claims 1 to 3,
The paper type is represented by at least one of size, basis weight, and air permeability. The sheet feeding device according to any one of claims 1 to 3,
The paper type is represented by size, basis weight, or air permeability,
The paper feeding device, wherein the control unit shortens the separation distance of the paper transport unit from the paper on the paper stacking base as the size, basis weight, or air permeability of the paper increases. The sheet feeding device according to any one of claims 1 to 5,
A paper feeding device comprising an air blowing unit for blowing air to the paper on the paper stacking table. The sheet feeding device according to claim 6,
The paper feeding device, wherein the air blowing unit and the air suction unit are operated by exhaust and intake of the same fan. The sheet feeding device according to any one of claims 1 to 7,
A sensor provided on the downstream side in the paper conveyance direction by the paper conveyance unit, for detecting the leading edge of the paper;
The paper transport unit rotates intermittently,
The control unit shortens the separation distance of the paper transport unit from the paper on the paper stacking base as the time from the start of rotation of the paper transport unit to the time of detection of the front end of the paper by the sensor increases. A paper feeder.   An image forming apparatus comprising the paper feeding device according to claim 1.

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