JP2012218909A - Sheet feeding device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet feeding device for securing an attraction time of an attraction belt even during high-speed operation and for keeping an attraction distance stable, and also to provide an image forming apparatus.SOLUTION: The sheet feeding device has an attraction separation unit 12 which includes: the attraction belt 13 rotatably stretched between two tension rollers 13A and 13B arranged to face each other on a top face of a bundle 2 of sheets loaded; and a charging roller 14 for charging a surface of the attraction belt. The attraction separation unit 12 is mounted rotatably to approach to or separate from the top face of the bundle of sheets through a gear 21 meshing with a drive gear 22. As to the attraction separation unit 12 on the top face of the bundle 2 of the sheets, the attraction belt 13 is elastically biased by a biasing member to contact the top face of the bundle 2 of sheets. Further, a tension spring 26 is provided for biasing an elastic force to the attraction separation unit 12 in the direction to separate from the top face of the bundle 2 of sheets.

Description

  The present invention relates to a sheet feeding apparatus and an image forming apparatus that separate and feed sheets such as stacked originals and recording paper.

  Conventionally known methods for separating stacked sheets such as originals and recording paper at the time of feeding include a separation method using frictional force and a separation method using air suction. In the former method using a frictional force, a rubber material or the like is used for the feeding roller, so that the frictional force changes due to a change over time such as wear, and the separation performance deteriorates. In addition, when sheets with different (coefficient) friction coefficients or sheets with different friction coefficients are separated at the same time, separation failures such as multiple feeding simultaneously feeding multiple sheets or separation of sheets from stacked sheets occur. Sometimes. Furthermore, since the sheet is separated by applying pressure when the sheet is separated, wrinkles and streaks may occur on the sheet or may become dirty.

  On the other hand, the latter separation method using air suction is a non-friction separation method that does not depend on the friction coefficient of the roller or the sheet, but requires an air suction blower and an air duct. The suction sound is noisy and is not suitable for use in an office.

  Therefore, Patent Document 1 describes an electrostatic attraction separation method that is a kind of non-friction separation method, in which an electric field is formed on a dielectric belt, and this is brought into contact with a sheet to be adsorbed and separated. Such an electrostatic adsorption separation method is an adsorption belt in which an alternating charge is applied to an endless dielectric belt wound around a plurality of rollers, the adsorption belt is swung or translated with respect to a sheet, and is brought close to or in contact with the sheet. In this method, after the uppermost sheet is adsorbed by the adsorbing belt, the adsorbing belt is moved away from the stack of stacked sheets.

  The sheet feeding device using this electrostatic adsorption separation method is superior in that it can suppress wear, sheet damage, noise generation, etc., and can achieve downsizing of the device as compared with the above-described separation method. ing.

Next, the operation of the sheet feeding apparatus using the electrostatic adsorption separation method will be described.
A. The suction belt descends and the uppermost sheet of the laminated sheet group contacts the suction belt surface.
B. The uppermost sheet is adsorbed to the belt surface by waiting in a contact state for a predetermined time.
C. The suction belt rises in a state where the uppermost sheet is sucked and held, and the suction belt moves to a feeding position separated from the sheet bundle.
D. The stretch roller that holds the suction belt is rotated to feed the sheet.
E. After sheet feeding, return to A for continuous paper feeding.

  In the proposed separation mechanism using the suction belt, separation is ensured by separating the sheet adsorbed on the electrostatic belt by the “belt movement” of C in a series of operations, from the sheet bundle. .

  In this electrostatic adsorption separation system, as means for moving the endless dielectric belt in the direction away from the sheet bundle, a method of moving the adsorption belt using a solenoid as used in Patent Document 2, There has been proposed a system in which a gear meshed with a gear portion installed in an adsorption separation unit provided with an adsorption belt as used in Document 3 is rotated around a rotation axis by a motor.

  When separating and feeding by the electrostatic adsorption separation method using an adsorption belt, the contact state such as the contact area and contact distance of the belt surface with respect to the sheet is important, and the contact distance is set so that the contact surface is the entire belt surface. The adsorption performance is optimized by bringing the values close to zero. In addition, since the adsorption force increases as the adsorption time (adsorption time) in contact increases, securing the adsorption time in the contact state is also important when performing a stable adsorption separation operation.

  On the other hand, in order to improve the productivity of the feeding device, when this separated feeding is operated at a high speed, the method using the solenoid of Patent Document 2 is operated at a high speed because of the restriction of the response speed of the solenoid. However, when considering high speed operation, the unit is rotated around the rotation axis by a motor with a gear meshed with the gear portion described in Patent Document 3 (hereinafter referred to as a gear). (Referred to as "gear system") is advantageous. In the gear system, the position of the adsorption / separation unit is maintained by meshing between a gear unit installed in the adsorption / separation unit and a gear connected from a driving unit such as a stepping motor or a DC motor. Thus, the unit position on the rotation axis is determined, and the position of the suction belt with respect to the sheet is also determined.

  However, in sheet materials such as sheets, the flatness varies depending on the surface irregularities and waviness, and it is difficult to ensure the contact state just by touching. It is necessary to apply a certain amount of pressure to bring the suction belt into contact with the sheet bundle. When the contact pressure is considered, in the gear system, the belt position is fixed by the meshing of the gears, so it is difficult to set the contact pressure to exert the adsorption performance. Therefore, in order to stop the suction belt in contact with the upper surface of the sheet, precise unit drive control is required. In the case of continuous feeding, the unit stop position for suction differs depending on the number of sheets passed. As a method specifically realized by drive control, a detection sensor for detecting the DC motor and the sheet upper surface position, an encoder for detecting the rotation amount of the motor, a control device for calculating detection information and performing feedback, and the like are required.

  If a stepping motor is used, these configurations can be easily realized, but the contact position cannot be made constant because the stop position is strictly discrete due to the step angle. Therefore, although not known, the applicant of the present application has proposed means using a biasing member that elastically biases the suction belt to the upper surface of the sheet bundle.

  Under these conditions, a gear-type operating mechanism has been proposed for high-speed operation. However, when high-speed operation is actually performed, the unit stops at the suction position due to the elasticity of the parts of the unit itself or the elastic biasing member. Sometimes the suction belt can vibrate. Then, the problem that the adsorbing time of the sheet cannot be ensured and the adsorbability of the sheet is deteriorated may occur.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described conventional problems and provide a sheet feeding device and an image forming apparatus in which the suction time of the suction belt is secured and the suction distance is stable even during high-speed operation.

  In order to achieve the above-described object, the present invention includes an adsorption belt that is stretched and rotated by two tension rollers disposed opposite to each other on the upper surface of a stacked sheet bundle, and a charging unit that charges the surface of the adsorption belt. A suction separation unit provided, and the suction separation unit is rotatably mounted in a direction to come into contact with and separate from the upper surface of the sheet bundle via a gear meshing with a drive gear, In the sheet feeding apparatus in which the suction belt is elastically urged against and in contact with the upper surface of the sheet bundle by the urging member, the separation unit has an elastic force in a direction away from the upper surface of the sheet bundle. Proposed is a sheet feeding apparatus provided with elastic urging means for urging the sheet.

  According to the present invention, the operation of contacting and separating the suction separation unit with respect to the upper surface of the sheet bundle is separated from the sheet bundle after the suction position and the uppermost sheet contacting the upper surface of the sheet bundle on which the suction belt is stacked. In the region including the feeding position where the feeding is started, the swinging operation is performed with the rotation axis of the gear as the center, and the elastic urging means has an elastic force between the feeding position and the suction position. It is advantageous to switch.

Furthermore, the present invention is advantageous when the elastic urging means loses the elastic urging force to the adsorption separation unit when the adsorption separation unit is at the feeding position.
Furthermore, in the present invention, it is advantageous that the elastic biasing means includes an elastic member that pulls the adsorption / separation unit upward.

Furthermore, in the present invention, it is advantageous that the elastic urging means comprises an elastic member that pulls upward and a string-like rigid body that is connected to the elastic member.
Still further, according to the present invention, it is advantageous that the elastic biasing means includes an elastic member that pushes the adsorption / separation unit upward.

  In order to achieve the above object, the present invention proposes an image forming apparatus including the sheet feeding device according to any one of claims 1 to 6.

  According to the present invention, by providing an elastic urging means that urges the adsorption / separation unit in the direction away from the upper surface of the sheet bundle, an elastic holding force is applied to the adsorption / separation unit, so that vibration is generated. It is possible to speed up the attenuation when this occurs.

1 is a schematic configuration diagram illustrating an image forming apparatus including a sheet feeding device according to the present invention. It is a side view showing a schematic configuration of the sheet feeding apparatus. FIG. 3 is an external perspective view of a sheet feeding device. (A), (B) is explanatory drawing which shows one Embodiment of this invention. (A), (B) is explanatory drawing which shows other embodiment of this invention. It is a perspective view which shows an example of a charging means. It is a perspective view which shows the other example of a charging means.

Hereinafter, an embodiment using an electrophotographic copying machine as an image forming apparatus to which the present invention is applied will be described. First, the overall configuration and operation of the copying machine will be described.
FIG. 1 is a schematic configuration diagram of a copying machine according to the present embodiment.

  As an image forming unit 30 serving as an image forming unit of the copying machine, a charging device 32, a developing device 34, a transfer device 35, a photoconductor cleaning device 36, and the like are provided around a photoconductor 31 as a latent image carrier. The image forming unit 30 also includes an optical writing unit (not shown) for irradiating the photoreceptor 31 with laser light 33, a fixing device 37 for fixing a toner image on the sheet, and the like. A scanner is provided above the image forming unit 30, and a sheet for transferring an image formed by the image forming unit is stacked and accommodated below the image forming unit 30. A sheet feeding apparatus 1 that feeds the sheet 30 to be supplied to the unit 30 is provided.

  In the image forming unit 30 configured as described above, the surface of the photoconductor 31 is first uniformly charged by the charging device 32 as the photoconductor 31 rotates. Next, a laser beam 33 from an optical writing unit (not shown) based on the image data is irradiated to form an electrostatic latent image on the photoreceptor 31. Thereafter, a toner image is formed on the photosensitive member 31 by attaching toner with the developing device 34 to visualize the electrostatic latent image. On the other hand, the sheet feeding apparatus 1 separates and feeds one sheet, puts it into the sheet feeding path 44, feeds it with the feeding roller 45 of the sheet feeding path 44, and pushes it against the registration roller 46. Stop it. Then, in synchronization with the toner image formation timing of the image forming unit 30, the sheet abutted against the registration roller 46 is sent to the transfer unit where the photoconductor 31 and the transfer device 35 face each other. In the transfer unit, the toner image on the photoreceptor 31 is transferred to the supplied sheet. The sheet on which the toner image has been transferred is discharged outside the apparatus after the toner image is fixed by the fixing device 37. On the other hand, the surface of the photoconductor 31 after the toner image transfer is cleaned by removing residual toner by the photoconductor cleaning device 36 to prepare for image formation again.

Next, the sheet feeding apparatus 1 that is a characteristic part of the copying machine of the present embodiment will be described.
FIG. 2 is a side view showing a schematic configuration of the sheet feeding apparatus 1, and FIG. 3 is an external perspective view of the sheet feeding apparatus.

As shown in FIGS. 2 and 3, the sheet feeding apparatus 1 includes a sheet storage unit 11 and an adsorption separation unit 12 above the sheet storage unit 11.
The sheet storage unit 11 includes a bottom plate 19 on which a plurality of stacked sheet bundles 2 are stacked. A support member 18 that supports the bottom plate 19 is rotatably attached to the bottom of the sheet storage unit 11. ing.

  The bottom plate 19 is moved as follows. The sheet storage unit 11 includes a sheet detection unit (not shown) that detects that the uppermost sheet 2a of the sheet bundle 2 has reached a predetermined position. When the support member 18 is rotated counterclockwise in the figure by a drive motor (not shown) and the bottom plate 19 is raised, the sheet bundle 2 stacked on the bottom plate 19 rises, and the sheet detection means (not shown) moves the uppermost sheet 2a. Is detected. When the sheet detecting means (not shown) detects that the uppermost sheet 2a of the sheet bundle has reached a predetermined position, the rotation of the support member 18 is stopped.

The suction separation unit 12 includes a suction belt 13 that is stretched between two stretching rollers, a driving roller 13A on the downstream side in the sheet conveying direction and a driven roller 13B on the upstream side. The driven roller 13B is urged leftward in the figure by a spring (not shown), and applies tension to the suction belt 13. The suction belt 13 is made of a dielectric having a resistance of 10 ⁸ Ωcm or more, and is made of a film such as polyethylene terephthalate having a thickness of about 100 μm, for example. The driving roller 13A is provided with a conductive rubber layer having a resistance value of 10 ⁶ Ωcm on the surface, and the driven roller 13B is a metal roller. Both the driving roller 13A and the driven roller 13B are grounded. The driving roller 13A has a small diameter suitable for separating the sheet from the suction belt 13 by the curvature. The driving roller 13A is configured to be intermittently driven by a driving motor (not shown) via an electromagnetic clutch according to a paper feed signal. The driving roller 13 </ b> A and the driven roller 13 </ b> B are rotatably supported on one end side of the swing bracket 15 of the adsorption separation unit 12.

  The other end side of the swing bracket 15 is fixed to the rotary shaft 20, the drive roller 13A to which the drive is transmitted is held by the swing bracket 15, and the shaft position is also fixed to the unit. The driving roller 13A has a small diameter suitable for separating the sheet from the belt by the curvature. In the suction belt 13, the driven roller 13 </ b> B is freely rotatable within the range of the abutting portion of the driven roller shaft installed in the swing bracket 15 with the driving roller 13 </ b> A as the center of rotation. When the driving roller 13A comes into contact with the sheet bundle 2 by the rotation of the unit, the lower surface of the belt 13 comes into surface contact with the upper surface of the sheet bundle regardless of the stop position of the driving roller by the free rotation operation of the driven roller 13B.

  The swing bracket 15 is configured to be rotatable about the rotation shaft 20, and a unit-side gear 21 having the same rotation center as that of the rotation shaft 20 is fixed to the swing bracket 15. . The unit-side gear 21 meshes with a drive gear 22 that is drivingly connected to a unit drive motor 23, and the adsorption / separation unit 12 is swung between an adsorption position and a feeding position, which will be described later, by driving the unit drive motor 23. Note that the unit-side gear 21 may be configured as the same component as the swing bracket 15, and the gear 21 may be in the shape of a half-moon gear as long as it engages with the drive gear 22 in the unit rotation region. In addition, the present invention employs the gear system described above, which is advantageous for high-speed operation.

  The adsorption / separation unit 12 has a charging roller 14 as a charging unit that comes into contact with a portion of the adsorption belt 13 wound around the drive roller 13A. The charging roller 14 is connected to an AC power source 16 and applies an alternating charge to the front surface of the suction belt 13 to charge the suction belt 13.

  The charging roller 14 is rotatably supported by the adsorption / separation unit 12, and the position with respect to the adsorption belt 13 is uniquely determined. Further, ribs for stopper are provided on the back surfaces of both side edges of the suction belt 13, and engage with both side end surfaces of the stretching rollers 13A and 13B to prevent the suction belt 13 from shifting. The drive roller 13A is configured to be intermittently driven by a drive motor (not shown) via an electromagnetic clutch according to a paper feed signal.

Next, the operation of the sheet feeding apparatus using the adsorption separation unit 12 will be described.
The suction separation unit 12 normally stands by at the feeding position shown in FIG. 4A. When a paper feed signal is input, an electromagnetic clutch is engaged, the drive roller 13A is rotationally driven, and the suction belt 13 is moved endlessly. . Next, an alternating voltage is applied from the AC power source 16 to the suction belt 13 that moves endlessly via the charging roller 14, and a pitch (pitch is determined according to the AC power frequency and the circumferential speed of the suction belt 13 on the surface of the suction belt 13. 5 to 15 mm is preferable), and an alternating charge pattern is formed. The power source 16 may be an alternating current or an alternating potential of high and low, and a rectangular wave, a sine wave, or the like is conceivable. In the present embodiment, a rectangular wave having an amplitude of 4 KV is applied to the surface of the suction belt 13.

  As described above, when the charge pattern is formed on the suction belt 13, the support member 18 is rotated to raise the bottom plate 19. Before and after this, the suction separation unit 12 is driven by the unit drive motor 23 to rotate the swing bracket 15 in the clockwise direction to move the suction belt 13 to the suction position shown in FIG. The belt 13 contacts the uppermost sheet 2a of the sheet bundle 2. Thus, when the suction belt 13 abuts on the uppermost sheet 2a, Maxwell's stress acts on the dielectric sheet due to the unequal electric field formed by the charge pattern on the surface of the suction belt 13, and the sheet bundle 2 The uppermost sheet 2a is sucked and held on the suction belt 13. The uppermost sheet 2 a is separated in curvature as the suction belt 13 travels and is fed out in the sheet feeding direction, and is fed to the image forming unit by the guide member 10 and the feeding roller 9. The sheet attracting force due to the charge pattern acts only on the uppermost sheet 2a, and does not act on the second and subsequent sheets. In this paper feeding method, since the frictional force between the pickup means and the sheet is not used, the contact pressure between the suction belt 13 and the sheet bundle 2 can be made sufficiently small, so that double feeding due to friction does not occur. .

  The linear speed of the feeding roller pair 9 and the suction belt 13 is set to the same speed, and when the feeding roller 9 is intermittently driven at a timing, the suction belt 13 is also controlled to be intermittently driven. Is done. The suction belt 13 is separated from the sheet bundle 1 before the rear end of the sheet 2a reaches the position facing the driven roller 13B, so that the second sheet S is not sucked by the suction belt 13. Further, the separation of the sheet from the belt 13 at the portion of the driving roller 13A is based on the curvature separation.

  In this embodiment, the charging roller 14 is used as the charging means as shown in FIGS. 2 and 6, but a blade-like charging member 40 may be used as shown in FIG. The blade-shaped charging member 40 can form a charge pattern with a small pitch width compared to the roller-shaped charging member (charging roller 14), and the adsorption power to the first stacked sheet material increases quickly. Further, since the adsorption force acting on the second and subsequent sheets decreases rapidly, it is advantageous in that the time required for the separation operation can be shortened.

  As an urging member for elastically urging the suction belt 13 to the upper surface of the sheet bundle 2, as shown in FIGS. 2 and 3, the bearings of the two stretching rollers 13A and 13B that stretch the suction belt 13 are sheets. A compression spring 24 as an urging member that exerts an elastic force in a direction in which the suction belt 13 is pressed against the sheet bundle 2 after the fixing hole 25 of the bracket of the unit is formed in a long hole shape so as to have a degree of freedom of movement in the pressing direction. Can be realized by providing between the bracket 15 of the unit and the bearing.

  In the sheet feeding apparatus 10 configured as described above, the suction position of the suction belt 13 when the suction belt 13 is sucked needs to be elastically abutted against the sheet bundle 2 by the compression spring 24. More pivoting operation is performed as much as the more elastic biasing member bends. For this reason, the suction belt 13 and the surface of the uppermost sheet 2a of the sheet bundle 2 come into contact with each other before the stop position, causing a collision and a main cause of vibration. The width of this vibration is generated by the accumulation of component elasticity from the rotary shaft 20 which is the rotation center of the adsorption separation unit 12 to the position of the adsorption belt 13 where the collision occurs, and the gap between the engagement between the unit side gear 21 and the drive gear 22. To do.

  Therefore, in the present invention, as shown in FIG. 4B, a tension spring 26 as an elastic urging means for urging an elastic force in a direction away from the upper surface of the sheet bundle 2 to the adsorption separation unit 12 at the adsorption position. Is provided. The length of the tension spring 26 is set to be a relationship between the fixed length and the length of the tension that extends beyond the free length even at the feeding position shown in FIG. Also, when moving to the adsorption position where the length is the longest and the tension is the largest, the load on the motor is the largest, so the tension of the tension spring 26 is set so that the motor does not step out even at the adsorption position. ing.

  With this configuration, by applying an elastic holding force to the adsorption / separation unit 12 by the tension spring 26 as an elastic urging means, the degree of freedom due to the above-described gap is eliminated, and attenuation when vibration occurs is generated. Can be expedited. In this embodiment, the tension spring 26 is provided as the elastic biasing means. However, the elastic biasing means biases the elastic force in the direction away from the upper surface of the sheet bundle 2 to the suction separation unit 12 at the suction position. The pressing spring 26 may be used.

5A and 5B are explanatory views showing another embodiment of the present invention. In this embodiment, the free spring is shorter than the tension spring 26 at the position of the tension spring 26 in the configuration of FIG. A combination of a tension spring 26A and a wire 27 is used. At this time, the length of the tension spring 26A and the wire 27 is “the length of the wire” + “the free length of the tension spring”> “the distance from the fixed portion to the unit fixed portion (feeding position)”.
"Wire length" + "Free length of tension spring"<"Distance from fixed part to unit fixed part (suction position)"
Is set to satisfy.

  Therefore, in the feeding position shown in FIG. 5A, the tension spring 26A is free length, the wire 27 is loosened, and no tension is applied. On the other hand, at the suction position shown in FIG. 5B lowered from this position, the wire 27 is stretched and the tension spring 26A is also stretched so that tension is applied. It is hanging.

DESCRIPTION OF SYMBOLS 1 Sheet feeding apparatus 2 Sheet bundle 12 Adsorption / separation unit 13 Adsorption belt 13A Drive roller 13B Drive roller 14 Charging roller 15 Oscillation bracket 20 Rotating shaft 21 Unit side gear 22 Drive gear 23 Unit drive motor 24 Compression spring 26, 26A Tension spring 27 wires

JP 05-139548 A Japanese Patent Laid-Open No. 2003-237862 JP 2010-126317 A

Claims (7)

A suction separation unit comprising: a suction belt that is stretched and rotated by two tension rollers disposed opposite to the upper surface of the stacked sheet bundle; and a charging unit that charges the surface of the suction belt.
The adsorption separation unit is mounted so as to be rotatable in a direction of coming into contact with and separating from the upper surface of the sheet bundle via a gear meshing with a drive gear,
In the sheet feeding apparatus in which the suction separation unit on the upper surface of the sheet bundle is in contact with the suction belt elastically biased to the upper surface of the sheet bundle by a biasing member,
A sheet feeding apparatus, comprising: an elastic biasing unit that biases an elastic force in a direction away from the upper surface of the sheet bundle with respect to the adsorption separation unit.   2. The sheet feeding device according to claim 1, wherein the adsorption / separation operation of the adsorption separation unit with respect to the upper surface of the sheet bundle is performed by using an adsorption belt to bring the adsorption position and uppermost sheet into contact with the upper surface of the sheet bundle on which the adsorption belt is stacked A swinging operation centered on the rotational axis of the gear in a region including a feeding position where the sheet is separated from the sheet bundle after the suction and starts feeding, and the elastic biasing means is between the feeding position and the suction position. The sheet feeding device is characterized in that the presence or absence of an elastic force is switched at the same time.   3. The sheet feeding apparatus according to claim 2, wherein the elastic biasing means loses an elastic biasing force to the adsorption / separation unit when the adsorption / separation unit is in the feeding position. .   4. The sheet feeding apparatus according to claim 1, wherein the elastic biasing means includes an elastic member that pulls the adsorption / separation unit upward.   5. The sheet feeding apparatus according to claim 4, wherein the elastic urging means includes an elastic member that pulls upward and a string-like rigid body that is connected to the elastic member.   4. The sheet feeding apparatus according to claim 1, wherein the elastic urging unit includes an elastic member that pushes the adsorption / separation unit upward. 5.   An image forming apparatus comprising the sheet feeding device according to claim 1.

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