JP2008308245A - Sheet feeder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet feeder capable of suppressing the occurrence of double feed by using electrostatic attraction by a simple and low-cost constitution. <P>SOLUTION: A charging plate 50 is arranged on the bottom surface of a paper feed cassette 20 with stacked sheets loaded thereon, and a voltage is supplied to the charging plate 50 from a voltage source 55. In addition, a demagnetizing brush 40 is arranged at a position in contact with a sheet on the highest position, and the demagnetizing brush 40 is grounded. An electric field 80 is applied to each sheet to generate polarization, the sheets other than the sheet at the highest position are attracted by a Coulomb force to suppress double feed when the sheet 11 at the highest position is conveyed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sheet feeding apparatus.

  As is well known, when the uppermost sheet is conveyed by a conveyance force applied by a sheet feeding roller or the like in a sheet feeding device or a sheet feeding device installed in a printer, a copying machine, etc. It is important to prevent so-called double feeding in which the sheet at the position is simultaneously conveyed. As typical measures for this purpose, for example, a method using a friction pad, a reverse roller method, and the like are known.

  However, the friction pad deteriorates its ability to prevent double feeding by reducing the frictional force due to the adhesion of paper dust during long-term use. Further, in the reverse rotation roller system that rotates reversely in pressure contact with the paper feed roller, it is necessary to generate a large driving force in the motor that drives these, and a torque limiter that limits the load applied to the reverse rotation roller to a constant magnitude. Must be equipped.

  In order to overcome these problems, a mechanism for preventing double feed using static electricity has been proposed. For example, Patent Document 1 below discloses a technology in which a belt that feeds a sheet is charged, the uppermost sheet is adsorbed by electrostatic attraction, and further, static electricity is removed as necessary, so that the second and subsequent sheets are not adsorbed. Has been.

  Patent Document 2 discloses a technique for improving the mechanical strength of an endless belt that conveys a sheet by electrostatic attraction. Further, Patent Document 3 discloses a technique using an electrostatic film actuator that is disposed to face a roller for conveyance and conveys a sheet while repeating an electric attractive force and a repulsive force.

JP 58-100042 A Japanese Patent Laid-Open No. 3-152034 JP-A-5-338839

  However, the paper conveyance using the charging belt disclosed in Patent Documents 1 and 2 has the disadvantages that a large apparatus configuration is required and the apparatus price is expensive. Further, the technique of Patent Document 3 requires a device having a complicated structure called an electrostatic film actuator, which causes a problem of high cost. Therefore, it is difficult to say that a conventional sheet feeding apparatus that suppresses double feeding using attraction due to static electricity realizes a simple structure and low cost.

  SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a sheet feeding apparatus that suppresses double feeding by applying electrostatic attraction to a sheet with a simple structure.

Means for Solving the Problems and Effects of the Invention

  In order to achieve the above object, a sheet feeding apparatus according to the present invention includes a feeding unit configured to convey a conveying force to the uppermost sheet among the sheets stacked on the stacking unit. A sheet feeding apparatus comprising: a charging unit that charges the stacked sheets excluding the uppermost sheet by applying an electric field; and the uppermost position disposed in contact with the uppermost sheet. And a charge removal unit for removing charge from the sheet.

  As a result, the sheet feeding apparatus according to the present invention is disposed in contact with the uppermost sheet, with the charging unit that charges the stacked sheets excluding the uppermost sheet by applying an electric field to the uppermost sheet. And a neutralization unit that neutralizes the sheet, and the sheets other than the uppermost position are attracted to each other when charged. Thereby, in particular, the second sheet is attracted to the third sheet, so that the possibility of double feeding in which the second sheet is simultaneously conveyed when the uppermost sheet is conveyed is reduced. Therefore, it is possible to realize stable paper feeding in which double feeding is suppressed. At this time, since the structure including the charging unit and the charge removal unit is simple and can be configured at low cost, it is possible to realize a sheet feeding apparatus that can suppress double feeding without cost.

  Further, the charging unit may be disposed at a position in contact with the lowermost sheet at the bottom of the stacking unit, and may be charged by applying an electric field to the lowermost sheet.

  As a result, the charging unit directly contacts the lowermost sheet and acts to charge the electric field, so that the electric field can be stably acted on the stacked sheets, and sheet feeding that stably suppresses multi-feeding. A feeding device can be realized.

  Further, the charging unit may be disposed at a position adjacent to the lowermost sheet of the stacking unit with the stacking unit interposed therebetween to charge the lowermost sheet by applying an electric field. .

  With such a configuration, the charging unit is disposed at a position close to the sheet at the lowest position of the stacking unit with the stacking unit interposed therebetween, so that the structure of the stacking unit is not changed, such as being disposed in contact with the bottom of the stacking unit. A charging unit can be configured. Therefore, it is possible to configure a sheet feeding apparatus having a function of suppressing the multi-feeding at a lower cost without incurring the cost of the configuration of the charging unit.

  Further, the switch unit that switches between a connection state and a cutoff state of the electric supply to the charging unit, and the switch unit are set to the connection state when the feeding unit applies the conveyance force to the uppermost sheet. The control unit may be configured to include a control unit configured to perform the blocking state when the feeding unit does not apply the conveyance force to the uppermost sheet.

  Since the switch unit and the control means for controlling connection and disconnection are provided in this way, the charging unit is only transferred when the uppermost sheet is conveyed, that is, there is a possibility of double feeding. When the uppermost sheet is not conveyed, that is, when there is no possibility of double feeding, no electricity is supplied to the charging unit. Therefore, electricity is supplied only when it is necessary to avoid double feeding, and double feeding is suppressed, and a sheet feeding apparatus that suppresses double feeding while saving unnecessary power consumption can be configured.

  A detecting unit configured to detect the number of stacked sheets; and an adjusting unit configured to adjust a voltage value supplied to the charging unit according to the number of stacked sheets detected by the detecting unit. It can also be set as the structure provided.

  With this configuration, the number of sheets is detected by the detection unit, and the voltage value supplied to the charging unit is adjusted according to the number of sheets, so that the voltage value suitable for the number of stacked sheets can be obtained. Therefore, it is possible to realize a sheet feeding apparatus that does not accidentally consume wasteful power with a voltage value that is too large, and that can suppress double feeding with an appropriate voltage value that avoids that double feeding cannot be suppressed with a voltage value that is too small. .

  Further, the detecting means includes a measuring means for measuring a leakage current value flowing through the stacked sheets, and a calculating means for calculating the number of stacked sheets from the leakage current value measured by the measuring means. It is good also as a structure provided.

  In this way, the leakage current value flowing through the stacked sheets is measured by the measuring means, and the number of sheets stacked by the calculating means is calculated from the leakage current value, so that information on the number of sheets can be obtained accurately. it can. Therefore, a more appropriate voltage value, and more stable double feed suppression can be realized. And since the simple method of measuring a leak current with an ammeter is used, there also exists an effect that a detection means is realizable with a simple structure.

  Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 is a cross-sectional view schematically showing a first embodiment of a sheet feeding apparatus according to the present invention. The sheet feeding apparatus 1 a includes a sheet feeding roller 30, a friction pad 35, a sheet feeding cassette 20, and a control unit 65, and sheets 11, 12, 13, and 19 (sheets) placed on the sheet feeding cassette 20. The paper is sequentially conveyed by the rotation of the paper feed roller 30. The rotation and stationary of the paper feed roller 30 are controlled by the control unit 65.

  The paper feed cassette 20 is not shown except for the bottom plate. The friction pad 35 is provided to suppress the double feeding of the papers 11, 12, 13, and 19. When the uppermost paper 11 is transported, the second paper is not transported at the same time. It is only necessary that the friction pad 35 can generate a frictional force having the same magnitude as that of the frictional force 11 pulls the paper 12 (in the opposite direction). For this purpose, the friction coefficient of the friction pad 35 is set.

  A bottom plate spring 21 is disposed below the bottom plate of the paper feed cassette 20, and the paper 11, 12, 13, 19 is pressed against the paper feed roller 30 by this spring force. The above structure of the sheet feeding apparatus 1a according to the first embodiment is the same as that of the conventional sheet feeding apparatus 2 shown in FIG. In some cases, such a configuration alone cannot completely prevent double feeding. For this reason, the sheet feeding apparatus 1a of the present invention shown in FIG. 1 has a configuration described below.

  First, a part of the bottom plate of the paper feed cassette 20 is replaced with the charging plate 50. Then, one pole of a DC voltage source 55 is connected to the charging plate 50. The other pole of the DC voltage source 55 is grounded. A neutralizing brush 40 is disposed at a position in contact with the uppermost sheet 11. As shown in FIG. 1, the static eliminating brush 40 is grounded.

  FIG. 5 is a top view of the sheet feeding apparatus 1a and shows an example of the arrangement of the charge eliminating brush 40. FIG. In this way, for example, a plurality of static eliminating brushes 40 may be provided at a position that does not hinder the sheet feeding roller 30 and the sheet feeding roller shaft 31 that is a rotating shaft when the sheet feeding roller rotates. On the other hand, FIG. 6 illustrates a bottom view of the sheet feeding apparatus 1a. For example, as shown in FIG. 6, a part of the bottom plate of the sheet feeding cassette 20 may be replaced with one rectangular charging plate 50.

  As described above, the static eliminating brush 40 and the charging plate 50 are disposed on the upper and lower portions of the paper 11, 12, 13, 19 in FIG. Since the DC voltage source 55 is connected to the charging plate 50, an electric field 80 is generated between the charging plate 50 and the charge eliminating brush 40. As shown in FIG. 1, when the charging plate 50 is connected to the positive electrode of the voltage source 55, the electric field 80 is directed from the bottom to the top as shown in FIG.

  Due to the presence of the electric field 80, the paper 12, 13, 19 is polarized. FIG. 1 shows a state in which negative charges are collected on the lower side of the sheets 12, 13, and 19 due to polarization, and positive charges are collected on the upper side. However, since the grounding static elimination brush 40 is in contact with the uppermost sheet 11, no polarization occurs.

  Since the papers 12, 13, and 19 other than the uppermost paper 11 are polarized, a force attracting between the adjacent papers 12, 13, and 19 is generated by the Coulomb force. Therefore, in particular, the second sheet 12 is attracted to the third and subsequent sheets 13. Therefore, when the uppermost sheet 11 is conveyed, the force acting in the direction in which the second sheet 12 is not conveyed becomes larger than when only the friction pad 35 is used. This ultimately reduces the possibility of double feeding. The above is the first embodiment.

  Next, Example 2 will be described. In the sheet feeding apparatus 1b according to the second embodiment, the charging plate 50 according to the first embodiment is replaced with the charging plate 51 illustrated in FIG. The rest is the same as in Example 1. In the first embodiment, a part of the bottom plate of the paper feed cassette 20 is removed, and the charging plate 50 is disposed there. On the other hand, in the second embodiment, as shown in FIG. 2, the sheet feeding cassette 20 is left as it is, and the charging plate 51 is mounted on the bottom side.

  In the configuration of FIG. 1, the charging plate 50 is in direct contact with the lowest sheet 19 among the stacked sheets 11, 12, 13, and 19, so that an electric field is applied to the sheets 12, 13, and 19 to generate polarization. It was effective to make it. On the other hand, in the configuration of FIG. 2, a process of removing a part of the bottom plate of the paper feed cassette 20 can be omitted. Therefore, the creation of the device can be simplified.

  Next, Example 3 will be described. The configuration of the sheet feeding apparatus 1c according to the third embodiment is illustrated in FIG. As shown in the figure, a switch 60 for switching the DC voltage source 55 on and off is disposed. On / off of the switch 60 is controlled by the control unit 65. As described above, the control unit 65 also controls the rotation and stationary of the paper feed roller 30. In the third embodiment, using this information, the control unit 65 turns on the switch 60 only while the paper feed roller 30 is rotating, and turns off the switch 60 when the paper feed roller 30 is stationary.

  The procedure of paper feed processing in the third embodiment is shown in FIG. This series of procedures is executed by the control unit 65. First, in step S10, a paper feed is instructed. This is performed, for example, by user input from an input unit (not shown). Next, when the switch 60 is connected in S20, the voltage from the voltage source 55 is applied to the charging plate 50.

  As a result, an electric field 80 is formed, and polarization occurs in the stacked sheets 12, 13, and 19. Since the neutralization brush is in contact with the uppermost sheet 11, no polarization occurs. As a result, a Coulomb force is generated and attracted between the sheets 12, 13, and 19 other than the uppermost position.

  Next, in step S <b> 30, the control unit 65 instructs to start the rotation of the paper feed roller 30. As a result, the paper feed roller 30 rotates and pulls and conveys the uppermost paper 11 by friction. However, since the second sheet 12 is pulled by the Coulomb force from the third and subsequent sheets 13, the possibility that the second sheet 12 stays in the sheet feeding cassette 20 and is not conveyed increases.

  When the predetermined number of sheets have been conveyed, the control unit 65 commands the end of the rotation of the sheet feeding roller 30 in S40. As a result, the paper feed roller 30 is in a stationary state and waits for the next paper feed command. Next, the control unit 65 issues a command to shut off the switch 60 in S50. As a result, the DC voltage source 55 is disconnected from the charging plate 50 and no voltage is applied to the charging plate 50.

  As a result, the rotation and the stationary of the paper feed roller 30 correspond to the state where the paper is being fed and the state where the paper is not being fed, respectively, so that voltage is applied by the voltage source 55 only while paper is being fed. Become. The voltage at the voltage source 55 may be a relatively high voltage. Therefore, turning off the voltage supply when it is not necessary as described above has an effect of safety and saving power consumption.

  In the third exemplary embodiment, there may be a case where the rotation and stationary of the paper feed roller do not accurately correspond to execution and non-execution of the paper feed operation. Therefore, the switch 60 may be connected when the paper feeding operation is performed, and the switch may be shut off when the paper feeding operation is not performed. Further, the charging plate 50 in the third embodiment may be replaced with the charging plate 51 of FIG.

  Next, Example 4 will be described. The configuration of the sheet feeding apparatus 1d according to the fourth embodiment is illustrated in FIG. As shown in the figure, a DC variable voltage source 56 is connected to the charging plate 50. Further, a DC ammeter 70 is connected in series to the DC variable voltage source 56. The current value measured by the DC ammeter 70 is sent to the control unit 65. The voltage value of the DC variable voltage source 56 is changed and adjusted by the control unit 65.

  In the fourth embodiment, the voltage value adjustment process in the DC variable voltage source 56 is performed by the above configuration. FIG. 9 shows the procedure of paper feed processing in the fourth embodiment. In the flowchart of FIG. 9, the S5 voltage value adjustment process is added to the flowchart of FIG. Others are the same as FIG. A more specific procedure of the S5 voltage value adjustment process is shown in FIG. The processing procedure illustrated in FIG. 10 described below is executed in the control unit 65.

  First, in step S51, the value of the leak current flowing between the stacked sheets is measured by the DC ammeter 70. Basically, no current flows between the stacked sheets, but a minute current flows when the voltage value at the DC variable voltage source 56 is relatively high. In step S51, this current value is measured. Then, the measured value is sent to the control unit 65. In step S52, the control unit 65 estimates the number of stacked sheets based on the leakage current value. For this estimation procedure, the relationship between the value of the leakage current and the number of stacked sheets can be obtained in advance, for example, in a map form. At that time, if a detailed map classified for each type of paper such as plain paper and glossy paper is created, a more accurate estimate of the number of sheets can be obtained.

  Next, in S53, the voltage value of the DC variable voltage source 56 is adjusted based on the estimated value of the number of stacked sheets obtained in S52. For example, for this procedure, an optimum voltage value may be determined in advance for each numerical value of the number of stacked sheets. Then, this optimum voltage value may be selected in S53.

  In FIG. 10, a two-step procedure is performed in which the number of sheets is obtained from the leakage current value in S52 and the voltage value is obtained from the number of sheets in S53, but this may be combined into one. That is, a map for directly determining the voltage value directly from the leakage current value may be determined in advance. The above is the fourth embodiment. The charging plate 50 in FIG. 4 may be replaced with the charging plate 51 in FIG.

  In the above embodiment, the paper feed cassette 20 constitutes a stacking unit. The paper feed roller 30 constitutes a feeding unit. The charging plates 50 and 51 constitute a charging unit. The static elimination brush 40 comprises a static elimination part. The switch 60 constitutes a switch unit. The procedures of S20 and S50 function as control means. The procedures of S51 and S52 function as detection means. The procedure of S53 functions as adjusting means. The procedure of S51 functions as a measurement unit. The procedure of S52 functions as calculation means.

1 is a cross-sectional view of a sheet feeding apparatus according to a first embodiment of the present invention. Sectional drawing of the sheet feeding apparatus of Example 2 of this invention. Sectional drawing of the sheet feeding apparatus of Example 3 of this invention. Sectional drawing of the sheet feeding apparatus of Example 4 of this invention. FIG. 3 is a top view of the sheet feeding apparatus according to the first exemplary embodiment of the present invention. FIG. 3 is a bottom view of the sheet feeding device according to the first exemplary embodiment of the present invention. Sectional drawing of the conventional sheet feeding apparatus. 9 is a flowchart illustrating a sheet feeding processing procedure of the sheet feeding apparatus according to the third exemplary embodiment of the present invention. 9 is a flowchart illustrating a sheet feeding processing procedure of the sheet feeding apparatus according to the fourth embodiment of the present invention. 10 is a flowchart illustrating a voltage adjustment processing procedure of the sheet feeding device according to the fourth exemplary embodiment of the present invention.

Explanation of symbols

1a, 1b, 1c, 1d, 2 Sheet feeding device 11, 12, 13, 19 Paper (sheet)
DESCRIPTION OF SYMBOLS 20 Paper feed cassette 30 Paper feed roller 35 Friction pad 40 Static elimination brush 50, 51 Charge plate 55 DC voltage source 56 DC variable voltage source 60 Switch 65 Control part 70 DC ammeter 80 Electric field

Claims (6)

Among the sheets stacked on the stacking unit, a sheet feeding device including a feeding unit that conveys the uppermost sheet with a conveyance force for conveyance,
A charging unit that charges the stacked sheets by applying an electric field to the stacked sheets excluding the uppermost sheet;
A sheet feeding apparatus, comprising: a neutralization unit that is disposed in contact with the uppermost sheet and neutralizes the uppermost sheet.   2. The sheet feeding device according to claim 1, wherein the charging unit is disposed at a position in contact with the lowermost sheet at the bottom of the stacking unit, and charges the lowermost sheet by applying an electric field. 3.   2. The charging unit according to claim 1, wherein the charging unit is disposed at a position adjacent to a lowermost sheet of the stacking unit with the stacking unit interposed therebetween, and charges the lowermost sheet by applying an electric field. The sheet feeding apparatus according to the description. A switch unit that switches between a connected state and a cut-off state of electricity supply to the charging unit;
The switch unit is in the connected state when the feeding unit applies the conveying force to the uppermost sheet, and when the feeding unit does not apply the conveying force to the uppermost sheet. The sheet feeding apparatus according to any one of claims 1 to 3, further comprising a control unit that sets the shut-off state. Detecting means for detecting the number of stacked sheets;
5. The sheet according to claim 1, further comprising an adjusting unit that adjusts a voltage value supplied to the charging unit in accordance with the number of stacked sheets detected by the detecting unit. Feeding device. The detection means includes
Measuring means for measuring a leakage current value flowing through the stacked sheets;
The sheet feeding apparatus according to claim 5, further comprising a calculating unit that calculates the number of stacked sheets from the leakage current value measured by the measuring unit.

Images