JP2015083520A - Sheet separation paper-supply device and image formation device equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet separation paper-supply device and an image formation device, capable of uniformly pressing an endless belt against a sheet, for stable supply of paper, without affecting on productivity.SOLUTION: A sheet separation paper-supply device 104 is equipped with a separation part 107 which attracts and holds a top sheet 1a from a sheet bundle 1 by using an electrostatic force and separates it from the sheet bundle 1. The separation part 107 includes a lower stream roller 5 and an upper stream roller 6, an endless dielectric belt 2 which is bridged between the rollers for moving endlessly, and a pressing member 20 which is arranged inside the dielectric belt 2 and presses a flat portion FL of the dielectric belt 2 that faces the top sheet 1a against the top sheet 1a. The pressing member 20 can be moved in the direction parallel to the endless movement direction of the dielectric belt 2.

Description

  The present invention relates to a sheet separating and feeding apparatus and an image forming apparatus, and more particularly, to a sheet separating and feeding apparatus that separates and feeds sheets positioned on the uppermost surface one by one from a stacked sheet bundle and includes the same, for example The present invention relates to an image forming apparatus including an electrophotographic copying machine, a facsimile apparatus, a printer apparatus, and the like.

  In general, as this type of sheet separating and feeding device, a device that employs a so-called electrostatic adsorption separation method that uses static electricity to adsorb and separate sheets is proposed.

  The sheet separating and feeding apparatus adopting the electrostatic adsorption separation method alternates between an endless belt made of a derivative that moves in the feeding direction facing the upper surface of the stacked sheet bundle, and the surface of the endless belt. A charging member for applying a voltage is provided, and the charging member has a charging function for forming an alternating charge pattern on the surface of the endless belt, and a discharging function for discharging the endless belt.

  The electrostatic separation / separation type sheet separating and feeding apparatus configured as described above applies a charged charge on an endless belt, and generates an attractive force by an electric field generated by the charged charge, thereby removing the stacked sheet bundle. The top sheet is separated. In such an electrostatic adsorption separation system, it is important to uniformly contact the endless belt and the sheet in order to obtain a sufficient sheet adsorption force.

  In recent years, for the purpose of bringing the endless belt and the sheet into uniform contact with each other, the inner surface of the endless belt spanned between the driving roller and the driven roller is brought into contact with a predetermined urging force, and the tension of the endless belt is increased. There has been proposed a sheet separating and feeding apparatus including a belt holding unit that holds the sheet constant (see, for example, Patent Document 1). The belt holding means of the sheet separating / feeding device includes a first roller and a second roller that are spaced apart from each other in the sheet conveying direction, and supports and swings the first roller and the second roller. A support member capable of swinging about a shaft as a fulcrum, and the support member is constantly urged in a predetermined direction by an elastic member. In the sheet separating and feeding apparatus configured as described above, when the endless belt contacts the sheet, the surface of the endless belt stretched by the first roller and the second roller becomes a contact surface with the sheet, The contact surface is pressed against the sheet by the urging force of the elastic member. As a result, the endless belt corrects deformations such as curling and folding of the sheet and is brought into close contact with the sheet, and a desired sheet adsorbing force can be exhibited.

  In addition, the sheet separation force that varies the contact time between the endless belt and the sheet according to the detection result of the humidity detection sensor in order to change the sheet adsorption force acting on the sheet in consideration of the usage environment of the device, particularly humidity. A paper feeding device is known (see, for example, Patent Document 2). According to the sheet separating and feeding apparatus described in Patent Document 2, the contact time is shortened at high humidity when a desired sheet adsorption force can be obtained in a relatively short contact time, and the desired sheet is compared with that at high humidity. By increasing the contact time at low humidity, which takes time until the contact force is obtained, a good sheet contact force corresponding to a change in humidity can be obtained.

  However, in the conventional sheet separating and feeding apparatus described in Patent Document 1, the surface of the endless belt stretched by the first roller and the second roller is in contact with the endless belt and the sheet. The contact surface becomes a contact surface with the sheet, and this contact surface is pressed against the sheet by the elastic member. Actually, the contact surface formed between these rollers only by pressing the first roller or the second roller against the sheet is It is not sufficiently pressed against the sheet. For this reason, for example, when a strong sheet is deformed due to curling, bending, or undulation, a gap is formed between the contact surface and the sheet, and such a deformed strong sheet is sufficient. Cannot be pressed against. In this way, the pressing force of the endless belt against the sheet is different between the portion where the first roller or the second roller is positioned and the other portion, and the endless belt cannot be pressed uniformly against the sheet, and is stable. There was a problem that the paper could not be fed.

  Further, in the conventional sheet separating and feeding apparatus described in Patent Document 2 described above, the contact time between the endless belt and the sheet is long when the humidity is low and it takes time to obtain a desired sheet contact force. Therefore, there is a problem that the productivity, that is, the number of sheets fed per time is lowered.

  The present invention has been made to solve the above-described conventional problems. The endless belt can be uniformly pressed against the sheet without affecting the productivity, and stable paper feeding can be performed. An object of the present invention is to provide a sheet separating and feeding apparatus and an image forming apparatus that can be used.

  In order to achieve the above object, a sheet feeding apparatus according to the present invention is separated from a sheet stacking unit that stacks a sheet bundle and an elevating unit that raises and lowers the sheet bundle stacked on the sheet stacking unit. A plurality of rollers provided, an endless belt which is stretched across the plurality of rollers and moves endlessly; a charging member which forms a charge pattern on the belt; and an inner side of the belt, A pressing member that presses the belt facing the uppermost sheet positioned at the uppermost position against the uppermost sheet, and is a sheet feeding device that sucks and feeds the uppermost sheet by the belt. The sheet bundle is raised to a position where it comes into contact with the belt by the elevating means, and after the pressing member presses the belt, the belt rotates and the It is configured to start conveying the upper sheet.

  With this configuration, the pressing member disposed inside the dielectric belt is configured to be movable in a direction parallel to the endless movement direction of the dielectric belt. On the other hand, the dielectric belt can be pressed uniformly, and stable paper feeding can be performed. In addition, because the dielectric belt is forcibly pressed against the uppermost sheet by the pressing member, a relatively long contact time is ensured as in the conventional case, for example, in low humidity where it takes time to obtain the desired sheet contact force. Even if it does not do, desired sheet contact | adhesion power can be ensured. For this reason, stable paper feeding can be performed without affecting the productivity.

  The present invention provides a sheet separating and feeding apparatus and an image forming apparatus capable of uniformly pressing an endless belt against a sheet without affecting productivity and capable of performing stable feeding. Can do.

1 is a schematic configuration diagram of an image forming apparatus including a sheet separating and feeding device according to an embodiment of the present invention. 1 is a cross-sectional view illustrating an outline of a sheet separating and feeding apparatus according to an embodiment of the present invention. 1 is a perspective view showing an outline of a sheet separating and feeding apparatus according to an embodiment of the present invention. (A)-(c) is sectional drawing which shows operation | movement of the sheet | seat separation paper feeder which concerns on embodiment of this invention. (A), (b) is sectional drawing which shows the operation | movement following FIG.4 (a)-(c). (A)-(c) is sectional drawing which shows operation | movement of the pressing member which concerns on embodiment of this invention. FIG. 9 is a perspective view showing a modified example of the sheet separating and feeding apparatus according to the embodiment of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, the configuration will be described. As shown in FIG. 1, the image forming apparatus 101 is configured as an electrophotographic digital copier, and includes an original reading unit 102 that reads an original and an uppermost sheet (from a sheet separating and feeding apparatus 104). An image forming unit 103 as an image forming unit that forms an image read by the document reading unit 102 on a recording sheet) 1a, and a sheet separating and feeding device 104 that feeds the uppermost sheet 1a to the image forming unit 103. ing. In the image forming apparatus 101 of this embodiment, the image forming unit 103 and the sheet separating and feeding apparatus 104 can be divided.

  The uppermost sheet 1a fed by the sheet separating and feeding device 104 is transported by the pair of conveying rollers 108, and the toner image formed by the image forming unit 103 is transferred by the transfer device 109. This toner image is transferred to the fixing device 110. The heat transfer is performed by the sheet discharge roller 111 and is discharged to the sheet discharge tray 112 by the sheet discharge roller pair 111.

  Note that the image forming apparatus 101 is not limited to the electrophotographic method, and may employ another method such as an ink jet method. The image forming apparatus 101 is not limited to a copying machine, and may be configured as a facsimile machine, a printing machine, or a multifunction machine.

  As shown in FIGS. 2 and 3, the sheet separating and feeding device 104 includes a sheet feeding tray 12 that stores the sheet bundle 1, and a bottom plate 7 that is disposed at the bottom of the sheet feeding tray 12 and on which the sheet bundle 1 is stacked. The bottom plate raising arm 8 for raising and lowering the bottom plate 7 and the upper surface of the sheet bundle 1 are brought into contact with each other, and the uppermost sheet 1a located at the uppermost position is separated from the sheet bundle 1 by electrostatic force. And a separation unit 107 that conveys the separated uppermost sheet 1a. The bottom plate 7 in the present embodiment constitutes the sheet stacking means according to the present invention, and the bottom plate raising arm 8 constitutes the lifting means according to the present invention.

  The separation unit 107 includes a downstream roller 5, an upstream roller 6, and a dielectric belt 2 that is wound around the downstream roller 5 and the upstream roller 6 and made of an endless dielectric. The separation unit 107 in the present embodiment constitutes an adsorption separation unit and a sheet conveyance unit according to the present invention, and the downstream roller 5 and the upstream roller 6 constitute a plurality of rollers according to the present invention.

  The upstream roller 6 is configured as a driving roller to which driving force is coupled from a driving source (not shown), and the downstream roller 5 is configured as a driven roller that is driven to rotate via the dielectric belt 2 by the rotation of the upstream roller 6. ing. A driving force from a driving source (not shown) is transmitted to the upstream roller 6 via an electromagnetic clutch 16. The upstream roller 6 is driven intermittently when the electromagnetic clutch 16 is actuated in response to a paper feed signal.

  The surface of the upstream roller 6 is composed of a conductive rubber layer having a resistance value of about 106 Ω · cm, and the surface of the downstream roller 5 is composed of metal. The upstream roller 6 and the downstream roller 5 are electrically grounded. The downstream roller 5 has a small diameter suitable for separating the uppermost sheet 1a from the dielectric belt 2 by the curvature. That is, by setting the diameter of the downstream roller 5 to be small and increasing the curvature, the uppermost sheet 1a attracted to the dielectric belt 2 and separated and conveyed is separated from the downstream roller 5 and is located downstream in the sheet conveying direction. It can enter between the guide plate pair 10.

  The downstream roller 5 as a driven roller and the upstream roller 6 as a driving roller are arranged so that the lower tangent of the dielectric belt 2 formed by the downstream roller 5 and the upstream roller 6 is horizontal with the upper surface of the uppermost sheet 1a. ing.

  The dielectric belt 2 is made of a dielectric having a resistance of 108 Ω · cm or more. As the dielectric constituting the dielectric belt 2, for example, a film such as polyethylene terephthalate having a thickness of about 100 μm can be used.

  The dielectric belt 2 is stretched between the downstream roller 5 and the upstream roller 6 so that the upstream roller 6 is slacked so that the upstream roller 6 does not idle, and comes into contact with the uppermost sheet 1a in a slackened state. The contact area is ensured even when undulation occurs in the uppermost sheet 1a.

  In this embodiment, the dielectric belt 2 is stretched around two rollers, the downstream roller 5 and the upstream roller 6, but the dielectric belt 2 is stretched around more rollers. Alternatively, the roller on the most upstream side in the sheet conveying direction among the plurality of rollers may be configured as the driving roller.

  The dielectric belt 2 is disposed between the center position and the rear end position in the sheet conveying direction of the stacking position of the minimum-size sheet bundle 1 corresponding to the apparatus. For example, when the size of the corresponding uppermost sheet 1a is an apparatus of A5 to A3, the dielectric belt 2 moves from the center of the sheet conveying direction length (210 mm) of the uppermost sheet 1a of A5 size which is the minimum size. The dielectric belt 2 is disposed at the end position (position of 105 mm to 210 mm from the front end) such that the front end of the dielectric belt 2 (the ground contact position of the downstream roller 5 with respect to the uppermost sheet 1a).

  The dielectric belt 2 is disposed at the center in the direction orthogonal to the sheet conveying direction. That is, with respect to the sheet width direction (depth direction in FIG. 1) orthogonal to the sheet conveying direction, the dielectric belt is arranged so that the center position of the sheet bundle 1 installed on the center reference matches the center position of the dielectric belt 2. 2 is arranged with respect to the sheet bundle 1. The width of the dielectric belt 2 is set to be 20 mm shorter from the width of the corresponding maximum size uppermost sheet 1a.

  On the downstream side of the dielectric belt 2 in the sheet conveyance direction, a guide plate pair 10 that guides conveyance of the uppermost sheet 1a and a paper feed roller pair 9 that conveys the uppermost sheet 1a contained in the guide plate pair 10 are provided. It has been.

  Ribs 17 are provided inside both side edges of the dielectric belt 2, and the ribs 17 of the dielectric belt 2 are engaged with both side end surfaces of the downstream roller 5 and the upstream roller 6, whereby the dielectric belt 2. Are prevented from slipping off in the width direction, and falling off from the downstream roller 5 and the upstream roller 6.

  On the upstream side in the sheet conveying direction of the separation unit 107, the sheet bundle 1 is raised by the bottom plate raising arm 8 and the uppermost uppermost sheet 1 a of the sheet bundle 1 is in a sheet feeding position where it contacts the dielectric belt 2. A filler sensor 18 for detection is provided. The filler sensor 18 is disposed at the end of the sheet bundle 1 in the sheet width direction, and does not come into contact with the dielectric belt 2 even when the dielectric belt 2 is disposed on the upstream side in the sheet conveyance direction.

  At a position where the dielectric belt 2 is wound around the upstream roller 6, a charging roller electrode 3 is provided which rotates in contact with the outer peripheral surface of the dielectric belt 2. Is connected to the power source 4.

  It is to be noted that a roller for static elimination connected to a static elimination power source (alternating power source) not shown on the upstream side of the roller electrode 3 in the rotation direction of the dielectric belt 2 and downstream of the separation position of the sheet bundle 1 and the dielectric belt 2. The electrode may be provided so as to be driven and rotated in contact with the dielectric belt 2. In that case, the charging roller electrode 3 and the discharging roller electrode are controlled so that the attracting force on the dielectric belt 2 is removed at the position where the leading edge of the uppermost sheet 1a abuts on the pair of feeding rollers 9. Is done. Since the roller electrode for discharging is not always necessary and can be omitted, in the present embodiment, it is assumed that only the roller electrode 3 for charging is provided without the roller electrode for removing electricity.

  Next, a characteristic configuration of the sheet separating and feeding apparatus 104 according to the present embodiment will be described with reference to FIGS.

  As shown in FIGS. 2 and 3, a pressing member 20 is provided inside the dielectric belt 2, and the pressing member 20 abuts on the dielectric belt 2 so that the flat portion FL of the dielectric belt 2 is positioned at the uppermost position. While pressing against the sheet 1a, the dielectric belt 2 moves in the endless moving direction or in the direction parallel to the sheet conveying direction (left and right direction in FIG. 2). As a result, the surface of the dielectric belt 2, specifically, the flat portion FL of the dielectric belt 2 facing the uppermost sheet 1a is uniformly pressed against the uppermost sheet 1a. For this reason, for example, even when the uppermost sheet 1a is a strong sheet and is curled or wavy due to moisture absorption or the like, there is a gap between the flat portion FL of the dielectric belt 2 and the uppermost sheet 1a. The flat portion FL of the dielectric belt 2 can be reliably brought into close contact with the uppermost sheet 1a without causing the desired sheet attracting force.

  As shown in FIG. 3, the pressing member 20 is configured by a columnar member extending in the width direction of the dielectric belt 2 perpendicular to the endless movement direction of the dielectric belt 2. Therefore, the portion of the pressing member 20 that presses the dielectric belt 2 is arcuate, and the load applied to the dielectric belt 2 when the pressing member 20 is moved in the endless moving direction or in the direction parallel to the sheet conveying direction is reduced. Can do.

  Further, one end of the pressing member 20 is supported by the support member 21, and the other end is an open end. Note that the other end of the pressing member 20 may be engaged with a guide portion such as a guide groove provided on the inner surface of the main body of the image forming apparatus 101 (see FIG. 1), for example.

  The support member 21 is configured to be movable in an endless movement direction or a direction parallel to the sheet conveying direction via a so-called rack and pinion type drive mechanism 22 constituted by a rack 22a and a pinion 22b meshing with the rack 22a. Yes. That is, the support member 21 moves through the rack 22a in accordance with the rotation of the pinion 22b connected to a driving unit (not shown). Thereby, the pressing member 20 can be moved in the endless movement direction or the direction parallel to the sheet conveying direction without requiring a complicated mechanism.

  The support member 21 includes a holding body 23 having the rack 22a formed on the upper surface, a bearing portion 24 that supports one end of the pressing member 20, and a biasing member 25 that biases the bearing portion 24 downward in the drawing. And.

  The holding body 23 is formed with a guide portion 23 a that holds the bearing portion 24 slidably in a sliding direction (vertical direction in FIG. 3) perpendicular to the flat portion FL of the dielectric belt 2. A guide groove 23b that guides the movement of the bearing portion 24 in the sliding direction is formed on at least one inner surface of the guide portion 23a. Although not shown in the present embodiment, a guide groove 23b is also formed on the other inner surface opposite to one inner surface of the illustrated guide portion 23a, as described above.

  The bearing portion 24 is configured to rotatably support the pressing member 20. Therefore, since the inside of the dielectric belt 2 can be moved while rotating the pressing member 20, the load applied to the dielectric belt 2 when the pressing member 20 is moved can be further reduced. In this embodiment, the pressing member 20 is rotatably supported. However, the present invention is not limited to this, and the pressing member 20 may be non-rotating and one end of the pressing member 20 may be fixedly supported. In this case, since the pressing member 20 does not rotate, the shape of the pressing member 20 is not limited to a cylindrical shape, and may be a semicircular arc shape, for example.

  The bearing portion 24 is configured to be movable in the sliding direction along the guide groove 23b.

  The urging member 25 is composed of an elastic member such as a compression coil spring, for example, and is provided between the inner upper surface of the guide portion 23 a and the upper surface of the bearing portion 24. The urging member 25 always urges the bearing portion 24 downward in the sliding direction so that the pressing member 20 presses the dielectric belt 2. Therefore, since the pressing member 20 elastically presses the dielectric belt 2, even if the surface of the uppermost sheet 1a has a large variation due to irregularities or undulations, the dielectric belt 2 is surely attached to the uppermost sheet 1a. Can be pressed. Here, the urging force of the urging member 25 is such that, for example, even against a sheet that is strong and wavy, the pressing member 20 ensures that the flat portion FL of the dielectric belt 2 is in surface contact with the sheet. Therefore, it is set to a value that can secure a pressing force necessary for the purpose.

  Next, the operation of the sheet separating and feeding device 104 will be described with reference to FIGS. In FIGS. 4 and 5, the pressing member 20 (see FIG. 3) described above is not shown.

  First, as shown in FIG. 4A, when a paper feed command signal from a control unit (not shown) is received, the electromagnetic clutch 16 is engaged and the upstream roller 6 is rotationally driven to move endlessly (hereinafter also referred to as a circumferential motion). An alternating voltage is applied from the power source 4 to the dielectric belt 2 that has started the operation via the roller electrode 3. Thereby, on the surface of the dielectric belt 2, an alternating charge pattern is formed at a pitch (pitch should be about 4 mm to 16 mm) according to the AC power source frequency and the circumferential speed of the dielectric belt 2. .

  After the charging of the dielectric belt 2 is completed, the bottom plate 7 that has been lowered starts to rise by the bottom plate raising arm 8, and the uppermost uppermost sheet 1 a of the sheet bundle 1 is in the raised position where it contacts the dielectric belt 2. If the filler sensor 18 (refer FIG. 2) detects this, the raise of the baseplate 7 will stop. When the bottom plate 7 is raised, the upper surface position of the uppermost sheet 1a before the bottom plate 7 is raised is sensed by the filler sensor 18 and the height difference from the lower surface of the dielectric belt 2 is calculated. Thus, the amount of the bottom plate 7 to be raised may be determined. 4 and 5, the filler sensor 18 is not shown.

  At this time, as shown in FIG. 6A, when the uppermost sheet 1 a comes into contact with the dielectric belt 2, the pressing member 20 presses the dielectric belt 2 by the biasing force of the biasing member 25, and the pressing member 20. The dielectric belt 2 pressed by the above is pressed against the uppermost sheet 1a. In this state, the pressing member 20 is still stopped at a predetermined position near the upstream roller 6, and only the contact surface on the upstream roller 6 side of the flat portion FL of the dielectric belt 2 is pressed against the uppermost sheet 1a. Yes.

  Next, from this state, as shown in FIG. 6B, the driving means connected to the pinion 22b is driven in response to a driving signal from a control unit (not shown), and the pressing member 20 is made of a dielectric as the pinion 22b rotates. The flat portion FL of the belt 2 moves to the right side, that is, the downstream roller 5 side in the figure. As a result, the entire contact surface of the flat portion FL of the dielectric belt 2 is pressed by the moving pressing member 20 and pressed against the uppermost sheet 1a without a gap. Therefore, the entire contact surface of the flat portion FL of the dielectric belt 2 can be uniformly contacted with the uppermost sheet 1a evenly, and a desired contact area can be ensured. As a result, even when the uppermost sheet 1a is a strong sheet and there is a deformation such as undulation, the adhesion between the flat portion FL of the dielectric belt 2 and the uppermost sheet 1a can be improved. It becomes possible.

  Thereafter, as shown in FIG. 6 (c), the driving means connected to the pinion 22b is reversely rotated, so that the pressing member 20 moves the flat portion FL of the dielectric belt 2 to the left side, that is, the upstream roller 6 side. To return to the predetermined position shown in FIG. Naturally, even by the movement of the pressing member 20 shown in FIG. 6C, the entire contact surface of the flat portion FL of the dielectric belt 2 is pressed against the uppermost sheet 1a. Thereby, a series of pressing operations of the dielectric belt 2 is completed.

  Next, as shown in FIG. 4B, in a state in which the dielectric belt 2 and the uppermost uppermost sheet 1a of the sheet bundle 1 are in contact, by waiting for a predetermined time set in advance for each sheet type, Maxwell stress acts on the uppermost uppermost sheet 1a, which is a dielectric, due to an uneven electric field formed by the charge pattern on the surface of the dielectric belt 2, and only the uppermost uppermost sheet 1a Adsorbed and held on the dielectric belt 2.

  Immediately after contact between the dielectric belt 2 and the uppermost uppermost sheet 1a, an electric field generated by non-uniform charging of the dielectric belt 2 is applied to a plurality of sheets of the sheet bundle 1 based on the effect of Maxwell's stress. However, after the elapse of a predetermined time, free electrons gather on the dielectric belt 2 side in the uppermost uppermost sheet 1a. The electric field of the belt 2 cancels out, and the attracting force of the dielectric belt 2 acts only on the uppermost uppermost sheet 1a.

  Next, as shown in FIG. 4C, the dielectric belt 2 rotates and starts conveying the uppermost sheet 1a while the sheet bundle 1 is raised to the raised position. As described above, after the top sheet 1a is attracted, the transport of the top sheet 1a is started without changing the positions of the dielectric belt 2 and the sheet bundle 1, thereby shortening the transport time of the top sheet 1a. be able to.

  Then, the uppermost sheet 1 a is separated from the dielectric belt 2 by the curvature of the downstream roller 5 at the downstream roller 5. The conveyance of the uppermost sheet 1a by the rotation of the dielectric belt 2 does not use a frictional force between the dielectric belt 2 and the uppermost sheet 1a but uses an electrostatic adsorption force. For this reason, the contact pressure between the dielectric belt 2 and the uppermost sheet 1a can be made sufficiently small, so that the uppermost uppermost sheet 1a and the second uppermost sheet 1b are affected by the frictional force between the uppermost uppermost sheet 1a and the second sheet 1b. The upper sheet 1a and the second sheet 1b are prevented from being simultaneously conveyed while being overlapped (double feeding). The linear velocities of the paper feed roller pair 9 and the dielectric belt 2 are the same, and when the paper feed roller pair 9 is intermittently driven at a timing, the belt 2 is also controlled to be intermittently driven. Is done.

  Next, as shown in FIG. 5A, the bottom plate 7 is lowered for a predetermined time before the rear end of the uppermost sheet 1 a reaches the position facing the upstream roller 6, and the dielectric belt 2 is separated from the sheet bundle 1. This prevents the second sheet 1b of the sheet bundle 1 from being attracted to the dielectric belt 2 while the uppermost uppermost sheet 1a is being conveyed. Further, the dielectric belt 2 is charged in preparation for the adsorption of the next sheet 1b in a state where the dielectric belt 2 and the sheet bundle 1 are separated from each other.

  Next, as shown in FIG. 5B, the bottom plate 7 is raised after the rear end of the uppermost sheet 1a has passed the position facing the downstream roller 5, and the sheet bundle 1 (sheets) as in FIG. 1b is the uppermost layer) is brought into contact with the dielectric belt 2. The uppermost sheet 1 a separated and conveyed by the dielectric belt 2 passes between the guide plate pair 10 and is conveyed to the image forming unit 103 by the pair of paper feed rollers 9.

  The power source 4 is not limited to alternating current, but may be one in which direct current is changed to high and low alternating potentials, and the waveform may be a rectangular wave or a sine wave. In the present embodiment, a rectangular wave having an amplitude of 4 KV is applied to the surface of the belt 2.

  In the case where the roller electrode for charge removal is provided, the charge of the charged belt 2 can be removed by applying an alternating voltage to the belt 2 by the roller electrode for charge removal.

  More specifically, when a DC voltage is applied by a DC power supply with the neutralizing roller electrode brought into contact with the outer peripheral surface of the dielectric belt 2, the dielectric belt 2 is charged at a voltage equal to or lower than a certain voltage. This voltage is called the charging start voltage, but the value V0 of the charging start voltage varies depending on the thickness of the dielectric belt 2, the volume resistance, and the like.

  Therefore, it is confirmed that when an alternating voltage having a charging start voltage value V0 as a peak value is applied to the roller electrode for static elimination, the surface potential of the charged dielectric belt 2 is eliminated to almost 0V. ing. This is because, by setting the peak value of the applied voltage to the value V0 of the charging start voltage, this applied voltage does not have the ability to charge the charged object that is a dielectric, but the space charge charged on the charged object is reduced. Means that the moving force works and can be neutralized. In addition, since an alternately applied voltage is used, there is a charge eliminating effect regardless of whether the dielectric is charged to (+) or (-). However, if the applied voltage is lower than the charging start voltage, insufficient static elimination occurs. If the applied voltage is higher than the charging start voltage, charging occurs at the applied frequency (120 Hz, v / f = 1 mm cycle) and cannot be eliminated to 0 V. The alternating voltage applied to the roller electrode may be controlled so that the peak value becomes the charging start voltage for the dielectric belt 2.

  As described above, in this embodiment, the pressing member 20 disposed inside the dielectric belt 2 is configured to be movable in the endless movement direction of the dielectric belt 2 or in a direction parallel to the sheet conveying direction. The dielectric belt 2 can be uniformly pressed against the uppermost sheet 1a by the moving pressing member 20, and stable paper feeding can be performed. Further, since the dielectric belt 2 is forcibly pressed against the uppermost sheet 1a by the pressing member 20, for example, in the case of low humidity where it takes a long time to obtain a desired sheet adhesion force, a relatively long adhesion as in the prior art. A desired sheet adhesion can be ensured without securing time. For this reason, stable paper feeding can be performed without affecting the productivity.

  In the present embodiment, the support member 21 is configured to support the pressing member 20 via the bearing portion 24 urged by the urging member 25. However, the present invention is not limited to this, and for example, as shown in FIG. Alternatively, the pressing member 20 may be directly supported by the holding member 123 as the support member 121.

  As described above, the sheet separating and feeding apparatus and the image forming apparatus according to the present invention can uniformly press the endless belt against the sheet without affecting the productivity, and perform stable feeding. A sheet separating / feeding apparatus that separates and feeds the sheets positioned on the uppermost surface from the stacked sheet bundle one by one, and an electrophotographic copying machine including the sheet separating / feeding apparatus It is useful as an image forming apparatus composed of a printer, a facsimile machine, a printer apparatus, and the like.

1 Sheet bundle 1a Top sheet 2 Dielectric belt 5 Downstream roller (multiple rollers)
6 Upstream roller (multiple rollers)
7 Bottom plate (sheet stacking means)
8 Bottom plate raising arm (lifting means)
DESCRIPTION OF SYMBOLS 20 Pushing member 21, 121 Support member 22 Drive mechanism 22a Rack 22b Pinion 23, 123 Holder 24 Bearing part 25 Energizing member 101 Image forming apparatus 103 Image forming part (image forming means)
104 Sheet separating and feeding apparatus 107 Separating section (adsorption separating means, sheet conveying means)
FL flat part

JP 2003-237958 A JP-A-11-184171

Claims (8)

Sheet stacking means for stacking sheet bundles;
Elevating means for raising and lowering the sheet bundle loaded on the sheet stacking means;
A plurality of rollers provided apart from each other;
An endless belt that travels endlessly across the plurality of rollers;
A charging member that forms a charge pattern on the belt;
A pressing member disposed inside the belt and pressing the belt facing the uppermost sheet positioned at the uppermost position of the sheet bundle against the uppermost sheet;
A sheet feeding device configured to suck and feed the uppermost sheet by the belt;
After the sheet bundle is raised to a position in contact with the belt by the elevating means and the pressing member presses the belt, the belt rotates to start conveying the uppermost sheet. Feeding device. Sheet stacking means for stacking sheet bundles;
Elevating means for raising and lowering the sheet bundle loaded on the sheet stacking means;
A plurality of rollers provided apart from each other;
An endless belt that travels endlessly across the plurality of rollers;
A charging member for applying a voltage to the belt;
A pressing member disposed inside the belt and pressing the belt facing the uppermost sheet positioned at the uppermost position of the sheet bundle against the uppermost sheet;
A sheet feeding device configured to suck and feed the uppermost sheet by the belt;
After the sheet bundle is raised to a position in contact with the belt by the elevating means and the pressing member presses the belt, the belt rotates to start conveying the uppermost sheet. Feeding device.   The sheet feeding apparatus according to claim 1, wherein the pressing member is formed of a columnar member extending in a width direction of the belt. A support member for supporting one end of the pressing member;
The seat according to any one of claims 1 to 3, wherein the support member is configured to be movable in a direction parallel to a rotation direction of the belt via a rack and pinion type drive mechanism. Sheet feeding device.   The sheet feeding apparatus according to claim 4, wherein the pressing member is rotatably supported by the support member.   The support member includes a bearing portion that supports one end of the pressing member, a holding body that slidably holds the bearing portion in a sliding direction perpendicular to a flat portion of the belt, and the pressing member holds the belt. The sheet feeding device according to claim 4, further comprising a biasing member that biases the bearing member so as to press.   The elevating means raises the sheet bundle to a raised position where the uppermost sheet contacts the adsorption separation means, stops the belt for a predetermined time, and adsorbs the uppermost sheet, and after the predetermined time elapses, the sheet bundle 7. The sheet feeding apparatus according to claim 1, wherein the uppermost sheet is started to be conveyed by the sheet conveying unit while being raised to the raised position. An image forming apparatus comprising the sheet feeding device according to claim 1,
An image forming apparatus comprising image forming means for forming an image on the uppermost sheet fed by the sheet feeding apparatus.

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