JP5573582B2 - Paper feeding device and image forming apparatus - Google Patents

Description

  The present invention relates to a sheet feeding device that sucks a sheet placed on a sheet placing table onto a suction surface and conveys the sheet to a sheet conveyance path, and an image forming apparatus including the sheet feeding device.

  2. Description of the Related Art In recent years, an air feeding device that is a paper feeding device capable of feeding a large amount of paper is used in an image forming apparatus such as a copying machine or a printer. The air feeding device blows air to the loaded paper, floats the paper, sucks the paper with a suction surface such as a suction belt with a suction hole through which air is sucked, and rotates the belt. Thus, the sheet is conveyed to a sheet conveyance path located downstream.

  In such a paper feeding device, when the paper sucked by the suction surface continues when the paper sucked on the suction surface is sent out to the paper transport path, the transport suction belt is rotated and the next suction belt is rotated. There is a case where the paper is fed and carried.

  In order to prevent this, it is conceivable to provide a brake mechanism on the conveyance suction belt. However, this brake mechanism has a problem that the paper is scratched or wrinkled due to an increase in the conveyance load or an increase in the load on the paper. There is.

  Patent Document 1 discloses a paper feeding device that provides a shutter between a conveyance suction belt and a fan and opens and closes the shutter each time a sheet is conveyed on a sheet conveyance path. This paper feeding device is provided in a duct for sucking paper onto a conveyance suction belt having a suction surface (suction opening) for sucking paper, a fan for making negative pressure in the inside of the duct, and the duct. A shutter for communicating / blocking between the suction surface of the conveyance suction belt and the fan, and an opening / closing member capable of opening and closing an opening communicating between the inside and outside of the duct between the suction surface and the shutter. The sheet feeding device opens the opening by the opening / closing member according to the shutter shut-off operation, thereby stopping the generation of the negative pressure by the fan and opening the duct.

JP 2008-1458 A

  By the way, the paper feeding device described in Japanese Patent Laid-Open No. 2004-228561 can prevent the paper from being fed because the paper can be sucked to / released from the suction surface. However, since this paper feeding device needs to instantaneously and reliably perform opening / cutting of the air path inside the duct, the driving means for driving the shutter becomes large, and the duct In order to ensure the sealing between the inner wall of the shutter and the shutter, a seal member or the like must be provided on the shutter or the like.

  As a result, the paper feeding device described in Patent Document 1 has a problem that noise is generated during the opening and closing operation of the shutter, the device itself becomes large, and the manufacturing cost increases. Further, since the fan is turned on / off every time one sheet is conveyed, the switching response is poor, and there is a problem that it cannot be applied to a sheet feeding apparatus that feeds paper at high speed.

  Therefore, the present invention solves such a problem, and it is possible to reduce noise and reduce the size during the paper feeding and conveying operation by adopting a configuration that does not require sealing between the inner wall of the duct and the shutter. Another object of the present invention is to provide a paper feeding device and an image forming apparatus that can reduce the manufacturing cost and can feed paper at high speed.

In order to solve the above-described problem, a paper feeding device according to a first aspect of the present invention has an adsorption surface that adsorbs a sheet placed on a sheet placing table, and the sheet adsorbed on the adsorption surface is used as a sheet conveyance path. A suction conveyance mechanism for conveying, a negative pressure generating source for sucking air from the intake port for sucking paper onto the suction surface, and blowing out the air sucked from the intake port from the blowout port, and an adsorption conveyance mechanism and a negative pressure generation source A negative pressure duct that connects the intake port of the negative pressure source, and an exhaust port that exhausts air blown from the blower outlet of the negative pressure generation source to the outside, and connects the outlet of the negative pressure generation source and the negative pressure duct Switchable between a wind guide duct, a first position where air passing through the wind guide duct is exhausted to the outside from a discharge port, and a second position where air passing through the wind guide duct is returned to the negative pressure duct A switching mechanism provided between the negative pressure duct and the wind guide duct; And a control unit for controlling switching the switching mechanism so that the position, the negative pressure generating source bypass air passage is provided with an opening hole for collecting an external air, the position switching mechanism of the second The air that has flowed into the bypass air passage returns to the negative pressure duct when located at the position .

  In the paper feeding device according to the first aspect, air is sucked from the suction port of the negative pressure generation source in order to suck the paper placed on the paper placing table to the suction surface of the suction conveyance mechanism. A negative pressure duct is provided between the suction conveyance mechanism and the suction port of the negative pressure generation source, and the negative pressure duct and the negative pressure generation source are connected to the negative pressure duct and the negative pressure generation source by the air flowing from the suction conveyance mechanism to the negative pressure generation source. The placed paper is sucked by the suction surface and is transported to the paper transport path.

On the premise of this, the wind guide duct has an exhaust port for exhausting air blown from the outlet of the negative pressure generation source to the outside, and connects the outlet of the negative pressure source and the negative pressure duct. The switching mechanism is switchable between a first position where air passing through the air duct is discharged to the outside from a discharge port and a second position where air passing through the air duct is returned to the negative pressure duct, It is provided between the negative pressure duct and the wind guide duct. And a control part carries out switching control of the switching mechanism so that it may be located in the 1st or 2nd position. Further, when the switching mechanism is switched to the second position, the air that has flowed into the bypass air passage returns to the negative pressure duct, so that the air flows toward the sheet adsorbed on the suction surface.

As a result, when the switching mechanism is switched to the first position, the inside of the negative pressure duct becomes negative pressure by the negative pressure generation source, so that the paper is adsorbed on the adsorption surface. When the switching mechanism is switched to the second position, the air passing through the air guide duct returns to the negative pressure duct, so that the adsorption action of the adsorption surface is canceled and the sheet adsorbed on the adsorption surface is released from the adsorption surface. Spaced apart. Further, when the switching mechanism is switched to the second position, the air that has flowed into the bypass air passage returns to the negative pressure duct, so that the air flows toward the sheet adsorbed on the suction surface. As a result, the sheet adsorbed on the adsorption surface can be reliably separated from the adsorption surface by being pushed by the air from the bypass air passage.

  According to a second aspect of the present invention, in the paper feeding device according to the first aspect, the suction transport mechanism is provided with a transport driving roller for sending the paper to the paper transport path, and the control unit switches when the paper is sucked to the suction surface. The mechanism is positioned at the first position, and the switching mechanism is positioned from the first position to the second position when the sheet adsorbed on the suction surface is sent out to the sheet conveyance path by the conveyance drive roller. The switching mechanism is positioned from the second position to the first position when the trailing edge of the fed sheet passes through the suction surface.

  In the sheet feeding device according to the second aspect, the switching mechanism is switched to the first position until the sheet adsorbed on the adsorption surface is sent to the conveyance drive roller, so that the sheet can be reliably adsorbed on the adsorption surface. When the paper is sent out by the transport driving roller, the switching mechanism is switched from the first position to the second position, so that the paper sucked on the suction surface is separated from the suction surface and another paper is fed along. Can be prevented. Further, since the switching mechanism is switched from the second position to the first position when the rear end of the sheet fed to the transport driving roller passes through the suction surface, the sheet is placed on the sheet placing table and is next. The sheet conveyed to the sheet can be sucked onto the suction surface.

According to a third aspect of the present invention, in the paper feeding device according to the first or second aspect , the bypass air passage adjustment mechanism is provided in the bypass air passage, and the bypass air passage adjustment mechanism controls the amount of air flowing into the bypass air passage. It is characterized by adjusting.

In the paper feeding device according to the third aspect , since the bypass air path adjustment mechanism adjusts the amount of air flowing into the bypass air path, the paper is adsorbed on the adsorption surface without depending on the type of paper such as cardboard or thin paper. / The adsorption can be released.

According to a fourth aspect of the present invention, there is provided the sheet feeding device according to the third aspect , wherein the bypass air path adjustment mechanism is configured with a rack gear provided so that an opening hole of the bypass air path can be opened and closed, and a pinion gear fitted to the rack gear. And a motor having a motor, and by rotating a rotating shaft of the motor, the rack gear is moved via the pinion gear to adjust the opening area of the opening hole of the bypass air passage.

In the sheet feeder according to claim 4 , the bypass air path adjustment mechanism adjusts the opening area of the opening of the bypass air path by moving the rack gear via the pinion gear by rotating the rotating shaft of the motor. The amount of air flowing into the opening hole of the bypass air passage can be easily adjusted, and the paper can be sucked / released on the suction surface without depending on the type of paper such as cardboard or thin paper. .

An image forming apparatus according to a fifth aspect includes an image forming unit that forms an image on a predetermined sheet, and a sheet feeding device according to any one of claims 1 to 4 that feeds the sheet to the image forming unit. It is characterized by that.

Since the image forming apparatus according to a fifth aspect includes the paper feeding device according to any one of the first to fourth aspects, when the switching mechanism is switched to the first position, the negative pressure generating source causes the negative pressure duct. Since the internal pressure is negative, the paper is sucked onto the suction surface. When the switching mechanism is switched to the second position, the air flowing from the negative pressure generation source returns to the inside of the negative pressure duct, so that the suction action of the suction surface is released and the paper sucked on the suction surface is removed. Separated from the surface.

  According to the paper feeding device of the present invention, the paper can be sucked to / released from the suction surface by switching the air path with the switching mechanism, so when separating the paper from the suction surface, There is no need to seal the switching mechanism, the negative pressure duct, and the wind guide duct as in the conventional paper feeder that seals the inside of the suction duct and the shutter in order to block the flow of wind. As a result, it is possible to reduce noise during the opening / closing operation of the shutter (at the time of paper feeding / conveying operation) as in the conventional paper feeding device, the paper feeding device can be reduced in size, and the manufacturing cost of the paper feeding device can be reduced. Can be reduced.

  Furthermore, as in the conventional paper feeding device, the responsiveness of switching between the first position and the second position is good without turning on / off the negative pressure source (fan) every time a sheet is conveyed. Since the air path is switched by a simple switching mechanism and the suction / releasing of the sheet is executed, the present invention can be applied to a sheet feeding device that feeds paper at high speed.

  According to the image forming apparatus of the present invention, since the switching mechanism capable of switching to the first position and the second position at high speed is provided, the image forming apparatus can be applied to an image forming apparatus that performs image formation at high speed.

1 is a perspective view illustrating a configuration example of a sheet feeding device 100 according to a first embodiment. 2 is a front sectional view illustrating a configuration example of a sheet feeding device 100. FIG. 3 is a front sectional view showing a configuration example of a switching mechanism 35. FIG. 3 is a block diagram illustrating a configuration example of a control system of the sheet feeding device 100. FIG. 6 is a timing chart illustrating an operation example of the sheet feeding device 100. 6 is a front sectional view showing an operation example (No. 1) of the switching mechanism 35. FIG. 6 is a front sectional view showing an operation example (No. 2) of the switching mechanism 35. FIG. FIG. 10 is a front sectional view showing an operation example (No. 3) of the switching mechanism. It is a perspective view which shows the structural example of the bypass air path adjustment mechanism 36 which concerns on 2nd Embodiment. 6 is a timing chart illustrating an operation example of the sheet feeding device 200. It is explanatory drawing which shows the structural example of the paper feed unit 300 which concerns on 3rd Embodiment. It is explanatory drawing which shows the structural example of the image forming apparatus 400 which concerns on 4th Embodiment. It is explanatory drawing which shows the structural example of the image forming system 500 which concerns on 5th Embodiment.

  Hereinafter, a sheet feeding device and an image forming apparatus will be described as an example of the present invention with reference to the drawings, and a sheet feeding unit and an image forming system to which these are applied will also be described.

<First Embodiment>
[Configuration Example of Paper Feed Device 100]
First, a configuration example of the sheet feeding device 100 according to the first embodiment will be described. As shown in FIGS. 1 and 2, the sheet feeding device 100 includes a suction conveyance mechanism 3, a negative pressure duct 32, a fan 33 that is an example of a negative pressure generation source, a wind guide duct 34, a switching mechanism 35, and a control unit 10 ( (See FIG. 4).

  The paper feeding device 100 sucks air from the fan air inlet 33a of the fan 33 in order to suck the uppermost paper P1 of the paper P placed on the paper placing table 20 to the suction surface 30a of the transport suction belt 30. . A negative pressure duct 32 is provided between the suction conveyance mechanism 3 and the fan intake port 33a, and the uppermost sheet P1 is moved by the air flowing from the suction conveyance mechanism 3 to the negative pressure duct 32 and the fan 33. It is attracted to the suction surface 30a and is transported toward the paper transport path by the transport driving roller 24.

  On the premise of this, the air guide duct 34 has an exhaust port 34a for exhausting air blown from the fan outlet 33f of the fan 33 to the outside, and connects the fan outlet 33f and the negative pressure duct 32. The switching mechanism 35 includes a first position (see FIGS. 6 and 7) where the air passing through the air guide duct 34 is discharged to the outside from the exhaust port 34a, and the air passing through the air guide duct 34 is the negative pressure duct 32. It is provided between the negative pressure duct 32 and the wind guide duct 34 so that the second position (see FIG. 8) returned to the position can be switched. And the control part 10 shown in FIG. 4 controls switching mechanism 35 so that it may become a 1st or 2nd position.

  As a result, when the switching mechanism 35 is switched to the first position, the inside of the negative pressure duct 32 becomes negative pressure by the fan 33, so the paper P is adsorbed to the adsorption surface 30a. When the switching mechanism 35 is switched to the second position, the air passing through the air guide duct 34 returns to the negative pressure duct 32, so that the adsorption action of the adsorption surface 30a is released and the paper adsorbed on the adsorption surface 30a. P is separated from the suction surface 30a.

  Details of the sheet feeding device 100 according to the present embodiment will be described below. The sheet feeding device 100 includes a sheet placing table 20 that can store a predetermined number of sheets P stacked thereon. The sheet placing table 20 is moved up and down along the stacking direction of the sheets P by a sheet lifting mechanism 2 described later with reference to FIG.

  The paper placement table 20 is provided with a rear end guide 23 that regulates the rear end position of the paper P loaded on the paper placement table 20. The rear end guide 23 is an example of a paper guide, and guides the paper P along the elevation direction of the paper placement table 20. Further, the rear end guide 23 can be adjusted in position according to various sizes of paper P by sliding along the conveyance direction A of the paper P.

  Further, the paper mounting table 20 is provided with a side guide 22 that regulates the side surface position of the paper P loaded on the paper mounting table 20. The side guide 22 is an example of a paper guide, and guides the paper P along the elevation direction of the paper placement table 20. Further, the side guide 22 can be adjusted in position according to various sizes of paper P by sliding along the direction orthogonal to the conveyance direction A of the paper P.

  The upper end of the side guide 22 protrudes upward from the suction surface 30 a configured by the conveyance suction belt 30. As a result, the side surface of the paper P sucked and fed by the transport suction belt 30 can be guided by the side surface guide 22. Similarly, the upper end of the rear end guide 23 protrudes above the suction surface 30a. As a result, the rear end of the sheet P sucked by the transport suction belt 30 can be guided by the rear end guide 23.

  As described above, when the paper P loaded on the paper mounting table 20 is floated and sucked to the transport suction belt 30, and when the paper P sucked by the transport suction belt 30 is transported to the paper transport path, the paper Since the position of the side surface and the rear end of P is regulated, it is possible to prevent the occurrence of bending or deviation due to flapping of the paper.

  The suction conveyance mechanism 3 includes a conveyance suction belt 30 on an upper portion of the sheet placing table 20. Further, the suction conveyance mechanism 3 includes a driving roller 33g and a driven roller 33h around which the conveyance suction belt 30 is wound.

  The transport suction belt 30 is endless, and a plurality of suction holes 30b penetrating the transport suction belt 30 are provided. For example, the suction holes 30 b are juxtaposed in the width direction of the transport suction belt 30, and a plurality of suction holes 30 b juxtaposed in the width direction of the transport suction belt 30 are in a length direction perpendicular to the width direction of the transport suction belt 30. It has a porous shape formed throughout.

  The drive roller 33g has an axis in a direction orthogonal to the conveyance direction A of the paper P, and is driven to rotate by a motor (not shown). The driven roller 33h has an axis parallel to the axis of the drive roller 33g, and is configured to rotate following the rotation of the conveyance suction belt 30 when the drive roller 33g is rotationally driven.

  In the suction conveyance mechanism 3, the conveyance suction belt 30 is stretched along the conveyance direction A of the paper P between the driving roller 33g and the driven roller 33h. The rear end side wound around the driving roller 33g of the conveyance suction belt 30 is positioned above the paper P stacked on the paper mounting table 20, and the front end side wound around the driven roller 33h of the conveyance suction belt 30 is It is located in front of the tip of P. In the suction conveyance mechanism 3, the two conveyance suction belts 30 are arranged side by side with respect to the conveyance direction A of the paper P.

  Accordingly, the conveyance suction belt 30 is rotated by the drive roller 33g being rotated, and the side of the conveyance suction belt 30 facing the paper placement table 20 is moved in the conveyance direction A of the paper P.

  The suction conveyance mechanism 3 includes an adsorption chamber 31 into which air that adsorbs the paper P to the conveyance suction belt 30 is sucked. The suction chamber 31 is formed inside the transport suction belt 30, and the lower side thereof is opened.

  A negative pressure duct 32 extending from the suction chamber 31 and connected to the fan 33 is provided. The negative pressure duct 32 connects the suction chamber 31 of the suction transport mechanism 3 and the fan air inlet 33 a of the fan 33. In the negative pressure duct 32, a space through which air shielded from the outside passes is formed between the adsorption chamber 31 and the fan intake port 33a.

  The fan 33 is a multi-blade fan called a sirocco fan, and includes a fan case 33c that forms an air passage, a multi-blade impeller 33d, and a fan motor 33e that drives the impeller 33d. In the fan case 33c, a fan air inlet 33a and a bypass air passage 33b are formed along the axial direction of the impeller 33d, and a fan air outlet 33f is formed in a tangential direction of the impeller 33d.

  The fan air inlet 33a is an opening through which air from the negative pressure duct 32 is sucked, and the bypass air passage 33b is an opening through which air from outside is sucked. The bypass air passage 33b is configured by a portion exposed to the outside of the fan air inlet 33a.

  The amount of air sucked from the fan air inlet 33a and the amount of air sucked from the bypass air passage 33b are, for example, 95% and 5%, respectively. This ratio varies depending on the capacity of the fan 33, the thickness and type of the sheet to be sucked, and can be changed as appropriate.

  When the fan 33 is driven, the air in the adsorption chamber 31 passes through the negative pressure duct 32 and is sucked from the fan intake port 33a, and external air is sucked from the bypass air passage 33b. Air sucked from the fan air inlet 33a and the bypass air passage 33b is blown out from the fan air outlet 33f, passes through a wind guide duct 34 described later, and is exhausted from the air outlet 34a.

  In this way, air in the suction chamber 31 is sucked in by the fan 33 and the suction chamber 31 becomes negative pressure, so that air is sucked in from the suction hole 30b of the transport suction belt 30 located on the side facing the paper mounting table 20. As a result, a flow of air that adsorbs the paper P to the transport suction belt 30 on the side facing the paper mounting table 20 is generated.

  An air guide duct 34 connected to the negative pressure duct 32 is provided at the fan outlet 33 f of the fan 33. The air guide duct 34 has an exhaust port 34a that exhausts the air blown from the fan outlet 33f to the outside. In this example, the exhaust port 34a is directed toward the sheet placing table 20, but the present invention is not limited to this.

  The air guide duct 34 is connected to a bypass 34 b opened in the negative pressure duct 32. A switching mechanism 35 is provided in the bypass 34 b between the negative pressure duct 32 and the air guide duct 34. The switching mechanism 35 includes a first position (see FIGS. 6 and 7) where air passing through the air guide duct 34 is discharged to the outside from the exhaust port 34a, and air passing through the air guide duct 34 via the bypass 34b. The second position (see FIG. 8) returned to the negative pressure duct 32 can be switched freely.

  Switching between the first and second positions of the switching mechanism 35 is executed by the control unit 10 described later with reference to FIG. For example, when the control unit 10 controls the switching mechanism 35 so that the switching mechanism 35 is located at the first position, the bypass 34b between the negative pressure duct 32 and the air guide duct 34 is shielded and negative by the fan 33. The inside of the pressure duct 32 becomes negative pressure. Thereby, air is sucked from the suction hole 30b, and the paper P is sucked to the suction surface 30a.

  Further, when the control unit 10 switches the switching mechanism 35 to the second position, the bypass 34 b is opened, and the air passing through the air guide duct 34 returns to the negative pressure duct 32. As a result, air is blown out from the suction holes 30b and the suction action of the suction surface 30a is released, so that the paper P sucked on the suction surface 30a is separated from the suction surface 30a.

  The paper P sucked by the suction transport mechanism 3 is transported to a paper transport path downstream of the suction transport mechanism 3. A conveyance roller 24a and a driven roller 24b facing the conveyance roller 24a are provided between the suction conveyance mechanism 3 and the sheet conveyance path. The transport roller 24a is rotationally driven by a transport roller motor 24c, which will be described later with reference to FIG. 4, and sandwiches the paper P sent out from the suction transport mechanism 3 with the driven roller 24b and transports it to the paper transport path.

  In order to make it easy to attract the sheet P to the suction surface 30a in the sheet feeding device 100 of this example, a floating mechanism that blows air from the side surface of the sheet P stacked on the sheet placing table 20 to float the sheet P. In addition, a separation mechanism that blows air so that only one sheet P is attracted to the suction surface 30a and separates other sheets may be added as appropriate.

[Configuration Example of Switching Mechanism 35]
Next, a configuration example of the switching mechanism 35 will be described. As shown in FIG. 3, the switching mechanism 35 includes a gate member 35a, a cantilever portion 35c, a spring 35d, a solenoid 35e, and a wire 35f.

  The gate member 35 a has a rotation shaft 35 b and is provided in a bypass 34 b between the negative pressure duct 32 and the air guide duct 34. The gate member 35a rotates about the rotation shaft 35b. One end of a spring 35d is connected to the upper surface of the gate member 35a. The other end of the spring 35d is connected to the inside of the negative pressure duct 32, and is attached so that a force is applied in a direction in which the gate member 35a is closed (upper right direction in FIG. 3).

  A cantilever portion 35c is provided on the lower surface of the gate member 35a. The cantilever 35c has a shape bent toward the exhaust port 34a, and a wire 35f is connected to the tip of the cantilever 35c. A solenoid 35e is connected to the wire 35f. When the solenoid 35e is driven to the left and right in FIG. 3, the gate member 35a opens and closes around the rotating shaft 35b via the wire 35f and the cantilever 35c.

  The switching mechanism 35 does not have to have a large driving means for driving a shutter like a conventional paper feeding device. The reason for this is that the sealing between the inner wall of the negative pressure duct 32 or the wind guide duct 34 and the tip of the gate member 35a is not ensured (the inner wall of the negative pressure duct 32 or the wind guide duct 34 and the tip of the gate member 35a). (Even if there is a slight gap), when the switching mechanism 35 stands by at the first position, the sheet P can be sucked by the suction surface 30a, and the switching mechanism 35 stands by at the second position. This is because the sheet P is separated from the suction surface 30a when the sheet P is present.

[Configuration Example of Control System of Paper Feed Device 100]
Next, a configuration example of the control system of the sheet feeding device 100 will be described. As shown in FIG. 4, the control system of the paper feeding device 100 includes a paper lifting mechanism 2, a transport roller motor 24 c, a paper feed sensor 25, a belt drive motor 30 c, a belt drive clutch 30 d, a fan motor 33 e, a solenoid 35 e, and a control. The unit 10 is configured.

  The sheet elevating mechanism 2, the conveyance roller motor 24c, the paper feed sensor 25, the belt drive motor 30c, the belt drive clutch 30d, the fan motor 33e, and the solenoid 35e are connected to the control unit 10, respectively.

  The paper lifting mechanism 2 is for raising and lowering the paper mounting table 20. For example, the paper lifting mechanism 2 is mounted on the paper mounting table 20 or a solenoid that is provided below the paper mounting table 20 and has a movable iron core that moves in the vertical direction. A paper detection sensor for detecting the uppermost paper P1 of the paper P. In addition, the paper lifting mechanism 2 lifts and lowers the paper mounting table 20 by a lift signal S1 from the control unit 10.

  For example, the paper elevating mechanism 2 lowers the paper placing table 20 to the lowest position when the user loads the paper P on the paper placing table 20, and the suction conveyance mechanism 3 when the paper feeding operation is performed. Raises the sheet mounting table 20 to a height at which the uppermost sheet P1 can be adsorbed.

  The conveyance roller motor 24c is connected to the conveyance roller 24a and rotates the conveyance roller 24a. For example, when the uppermost sheet P1 is sucked and conveyed by the conveyance suction belt 30 toward the sheet conveyance path, for example, the paper feed sensor 25 provided between the conveyance suction belt 30 and the conveyance roller 24a is the uppermost sheet. The tip of P1 is detected. Then, the paper feed sensor 25 outputs a paper detection signal S3 to the control unit 10. The control unit 10 receives the paper detection signal S3 output from the paper feed sensor 25, and outputs a motor drive signal S2 to the transport roller motor 24c. The transport roller motor 24c receives the motor drive signal S2 output from the control unit 10 and rotates the transport roller 24a.

  The belt drive motor 30c is connected to a drive roller 33g provided on the transport suction belt 30, and drives the transport suction belt 30 by rotating the drive roller 33g. For example, when the uppermost sheet P1 of the sheets P stacked on the sheet placing table 20 is conveyed to the sheet conveying path, the sheet placing table 20 is raised. Then, a sheet detection sensor (not shown) that detects the uppermost sheet P1 outputs a detection signal to the control unit 10. The control unit 10 receives the detection signal output from the paper detection sensor and outputs a motor drive signal S4 to the belt drive motor 30c. The belt drive motor 30c receives the motor drive signal S4 output from the control unit 10, rotates the drive roller 33g, and drives the transport suction belt 30.

  The belt driving motor 30c rotates the driving roller 33g from the start of feeding the first sheet P until the feeding of a predetermined number of sheets P set by the user is completed. However, when the drive roller 33g and the conveyance suction belt 30 are driven in the same manner as the belt drive motor 30c, a sheet other than the sheet to be conveyed (for example, a sheet below the uppermost sheet P1) should be conveyed. In some cases, the paper is transported along with the paper to the paper transport path. For this reason, a belt drive clutch 30d is provided between the belt drive motor 30c and the drive roller 33g, and the drive roller 33g and the conveyance suction belt 30 are driven intermittently.

  For example, when the paper feed sensor 25 detects the leading edge of the paper P, the control unit 10 outputs a clutch drive signal S5 to the belt drive clutch 30d. Then, the belt drive clutch 30d turns off the clutch mechanism and stops the driving of the transport suction belt 30. When the paper feed sensor 25 detects the trailing edge of the paper P, the controller 10 outputs the clutch drive signal S5 to the belt drive clutch 30d again. Then, the belt drive clutch 30d connects the clutch mechanism to drive the transport suction belt 30. Thereby, it is possible to prevent a sheet other than the sheet to be conveyed from being conveyed to the sheet conveyance path together with the sheet to be conveyed.

  The fan motor 33e is connected to the rotation shaft of the impeller 33d and rotates the impeller 33d. For example, when the uppermost sheet P1 of the sheets P stacked on the sheet placing table 20 is attracted to the suction surface 30a of the transport suction belt 30, the control unit 10 outputs a motor drive signal S6 to the fan motor 33e. Then, the fan motor 33e receives the motor drive signal S6 output by the control unit 10, and rotates the impeller 33d. When the impeller 33d rotates, the air in the adsorption chamber 31 is sucked from the fan intake port 33a, and the sucked air is blown out from the fan outlet 33f. By this action, outside air is sucked from the suction hole 30b, and the uppermost sheet P1 is sucked to the suction surface 30a.

  The solenoid 35e opens and closes the gate member 35a through the wire 35f and the cantilever 35c. For example, when the leading edge of the paper P is detected by the paper feed sensor 25 and transported to the paper transport path by the transport roller 24a, the control unit 10 outputs a solenoid drive signal S7 to the solenoid 35e. Then, the solenoid 35e receives the solenoid driving signal S7 output by the control unit 10, and moves the movable iron core of the solenoid 35e on the left side in FIG. 3 to move the gate member 35a to the rotating shaft 35b. Rotate clockwise using as a fulcrum. Thereby, the bypass 34b is opened, and the air blown from the fan outlet 33f flows into the negative pressure duct 32 through the bypass 34b.

  When the trailing edge of the paper P is detected by the paper feed sensor 25 and the paper P is transported to the paper transport path by the transport roller 24a, the control unit 10 outputs the solenoid drive signal S7 to the solenoid 35e again. Then, the solenoid 35e receives the solenoid drive signal S7 output by the control unit 10, and moves the movable iron core to the right side in FIG. 3, for example, so that the gate member 35a is turned around the rotation shaft 35b as a fulcrum. Rotate clockwise. Thus, the bypass 34b is blocked by the gate member 35a, and the air blown from the fan outlet 33f is exhausted from the exhaust port 34a.

[Operation Example of Paper Feed Device 100]
Next, as shown in FIG. 5, an operation example of the sheet feeding device 100 includes a fan motor 33e, a sheet feeding sensor 25, a belt driving motor 30c, a belt driving clutch 30d, a conveyance roller motor 24c, and a solenoid 35e. Will be described.

  At time t1, the control unit 10 outputs a motor drive signal S6 to the fan motor 33e to drive the fan motor 33e in order to start a job. The fan motor 33e receives the motor drive signal S6 output from the control unit 10, and rotates the impeller 33d. It takes some time until the rotational speed of the fan motor 33e becomes constant.

  At time t2, the belt drive motor 30c is turned on to rotate, the belt drive clutch 30d is turned on to connect the clutch mechanism, and the transport roller motor 24c is turned on to rotate. That is, the conveyance suction belt 30 is driven to rotate, and air is sucked from the suction holes 30b of the conveyance suction belt 30 so that the sheet P can be sucked and conveyed.

  The state of the switching mechanism 35 at time t2 is shown in FIGS. As shown in FIG. 6, the switching mechanism 35 switches to the first position, and the impeller 33d of the fan 33 rotates, so that the air in the adsorption chamber 31 flows from the fan intake port 33a, and the bypass air path. External air flows from 33b. For example, the amount of air sucked from the fan intake port 33a is set to 95%, and the amount of air sucked from the bypass air passage 33b is set to 5%. In this example, the bypass air passage 33b has an opening of about φ8 mm.

  The air that has flowed in from the fan air inlet 33a and the bypass air passage 33b is blown out from the fan air outlet 33f. The amount of air blown from the fan outlet 33f is 95% of the amount of air sucked from the fan intake port 33a, and the amount of air sucked from the bypass air passage 33b is 5%. Is 100%.

  The air blown out from the fan outlet 33f passes through the air guide duct 34 and is discharged from the exhaust port 34a. At this time, the spring 35d of the switching mechanism 35 pulls the gate member 35a, thereby shielding the bypass 34b. For example, even if some gap air passes through the bypass 34b, the paper P is not separated from the transport suction belt 30.

  In the time between the time t2 and the time t3, as shown in FIGS. 7A and 7B, the uppermost sheet P1 is sucked to the suction surface 30a. At this time, there is no wind inside the negative pressure duct 32, but the negative pressure is maintained by the suction force of the fan 33. The air from the bypass air passage 33b passes through the air guide duct 34 and is discharged from the exhaust port 34a.

  At time t3, the paper feed sensor 25 detects the leading edge of the uppermost paper P1, the belt drive clutch 30d is turned off to disconnect the clutch mechanism, the movable iron core of the solenoid 35e moves to the left side, and the rotating shaft 35b. By rotating the gate member 35a clockwise around the fulcrum, the bypass 34b is opened. That is, the drive of the conveyance suction belt 30 is stopped, the air that has passed through the air guide duct 34 passes through the bypass 34b, and returns to the negative pressure duct 32 to apply positive pressure.

  A state of the switching mechanism 35 at time t3 is shown in FIGS. As shown in FIG. 8, the switching mechanism 35 is switched to the second position, the air passing through the air duct 34 and the bypass 34 b and returning to the negative pressure duct 32 is sucked into the fan intake port 33 a. Some are blown out from the suction holes 30 b of the transport suction belt 30 through the suction chamber 31. As described with reference to FIG. 6, the amount of air sucked from the fan intake port 33a is 95%, and the amount of air sucked from the bypass air passage 33b is 5%. The amount of air that is returned and sucked into the fan intake port 33a is 95%, and the amount of air that is returned to the negative pressure duct 32 and blown out from the suction hole 30b is 5%.

  The uppermost sheet P1 adsorbed on the adsorption surface 30a is separated from the adsorption surface 30a by the action of the air returning to the negative pressure duct 32 and blown out from the suction hole 30b. At this time, since the leading edge of the uppermost sheet P1 is detected by the sheet feeding sensor 25 and the driving of the conveying suction belt 30 is stopped, the conveying roller 24a conveys the sheet without applying stress to the uppermost sheet P1. Can be transported to the road.

  Incidentally, when the uppermost sheet P1 is adsorbed to the adsorption surface 30a or the conveyance suction belt 30 is driven and the conveyance roller 24a conveys the uppermost sheet P1 to the sheet conveyance path, the uppermost sheet P1 is conveyed. P1 may be stressed, and scratches and wrinkles may occur.

  At time t4, the paper feed sensor 25 detects the trailing edge of the uppermost paper P1 (paper detection OFF), the movable iron core of the solenoid 35e moves to the right, and the gate member 35a is moved around the rotating shaft 35b. By rotating counterclockwise, the bypass 34b is shielded. At this time, the sheet stacked under the transported uppermost sheet P1 is adsorbed to the adsorption surface 30a.

  At time t5, the belt drive clutch 30d is turned on by the paper detection OFF of the paper feed sensor 25, and the clutch mechanism is connected. That is, the driving of the conveyance suction belt 30 is resumed, and the sheet adsorbed on the adsorption surface 30a is conveyed toward the conveyance roller 24a.

  At time t6, the last sheet is sucked and transported to the transport and suction belt 30, the fan motor 33e is turned off, and the drive of the fan 33 is stopped.

  At time t7, the last sheet is conveyed to the sheet conveyance path by the conveyance roller 24a, the paper feed sensor 25 is turned off, the conveyance roller motor 24c is turned off, and the movable iron core of the solenoid 35e returns to the right side. Then, the operation of the sheet feeding device 100 ends.

  As described above, according to the sheet feeding device 100 according to the first embodiment, the control unit 10 causes the switching mechanism 35 to discharge the air passing through the air guide duct 34 from the exhaust port 34a to the outside. Or the second position where the air passing through the air guide duct 34 is returned to the negative pressure duct 32.

  As a result, when the switching mechanism 35 is switched to the first position, the inside of the negative pressure duct 32 becomes negative pressure by the fan 33, so that the sheet is adsorbed to the adsorption surface 30a. When the switching mechanism 35 is switched to the second position, the air passing through the air guide duct 34 returns to the negative pressure duct 32, so that the adsorption action of the adsorption surface 30a is released and the paper adsorbed on the adsorption surface 30a. Is separated from the suction surface 30a.

  Further, since the bypass air passage 33b is provided, when the switching mechanism 35 is switched to the second position, external air from the bypass air passage 33b is taken into the fan 33, and the air guide duct 34 and the bypass 34b. Since the air is blown out from the suction hole 30b of the transport suction belt 30 through the negative pressure duct 32, the paper adsorbed on the suction surface 30a is pushed by the air and reliably separated from the suction surface 30a.

  As a result, by switching the air path with the switching mechanism 35, the sheet can be sucked / released from the suction surface 30a, so that when the paper is separated from the suction surface 30a, the flow of wind from the fan is blocked. Therefore, it is not necessary to seal the switching mechanism 35, the negative pressure duct 32, and the air guide duct 34 as in the conventional paper feeding device that seals the inside of the suction duct and the shutter. Therefore, it is possible to reduce noise during the opening / closing operation of the shutter (at the time of paper feeding / conveying operation) as in a conventional paper feeding device, the paper feeding device can be reduced in size, and the manufacturing cost of the paper feeding device is reduced. can do.

  Further, as in the conventional paper feeder, the fan is always operated during the carrying operation without turning on / off the fan every time a sheet is carried (see FIG. 5). Since the switching mechanism 35 with good responsiveness for switching between the position 2 and the second position switches the air path and performs suction / releasing of the sheet, the present invention is applied to a sheet feeding device that feeds paper at high speed. be able to.

  In the present embodiment, the paper feeder 100 provided with the bypass air passage 33b has been described. However, the present invention is not limited to this, and the bypass air passage 33b may not be provided. In this case, air is not actively blown out from the suction hole 30b of the transport suction belt 30, but can be separated from the suction surface 30a by the weight of the paper P sucked on the suction surface 30a.

<Second Embodiment>
In the second embodiment, a paper feeding device 200 in which a bypass air path adjustment mechanism 36 is added to the paper feeding device 100 described in the first embodiment will be described. The same names and reference numerals as those of the first embodiment have the same functions, and thus description thereof is omitted.

  As shown in FIG. 9, a bypass air path adjustment mechanism 36 is provided in the bypass air path 33 b of the fan 33 of the sheet feeding device 200. The bypass air path adjustment mechanism 36 adjusts the amount of external air that flows into the bypass air path 33b.

  The bypass air path adjustment mechanism 36 includes a bypass air path adjustment motor 36a, a pinion gear 36b, and a rack gear 36c. The rack gear 36c is provided above the bypass air passage 33b so that the opening hole of the bypass air passage 33b can be freely opened and closed.

  A pinion gear 36b is fitted to the gear portion of the rack gear 36c, and the pinion gear 36b is provided on the rotating shaft of the bypass air path adjustment motor 36a.

  In the bypass air path adjustment mechanism 36 having such a configuration, when the rotating shaft of the bypass air path adjustment motor 36a rotates, the rack gear 36c slides through the pinion gear 36b (for example, in the direction of the up and down arrows in FIG. 9). Moving.). By this movement, the opening area of the opening hole of the bypass air passage 33b can be adjusted.

  For example, the control unit 10 described above with reference to FIG. 4 is connected to the bypass air path adjustment motor 36a, and the rotation shaft of the bypass air path adjustment motor 36a rotates by a predetermined number of rotations according to a command from the control unit 10. The rack gear 36c is moved by a predetermined distance. Thereby, the opening area of the opening hole of the bypass air passage 33b can be adjusted to a desired size.

  Incidentally, the opening area is preferably 30% or less when the opening area of the fan air inlet 33a and the bypass air passage 33b is 100%. Therefore, the bypass air path adjustment mechanism 36 is preferably provided so that the opening area of the opening hole of the bypass air path 33b can be adjusted to 0% to 30%.

  As shown in FIG. 10, the operation of the paper feeder 200 is obtained by adding a bypass air path adjustment motor 36a to the operation of the paper feeder 100 described above with reference to FIG. That is, at time t1, the bypass air path adjustment motor 36a is turned on substantially simultaneously with the ON operation of the fan motor 33e, and adjusts the opening area of the bypass air path 33b. When the adjustment is completed, the sheet feeding device 200 turns off the operation of the bypass air path adjustment motor 36a, and similarly to the operation of the sheet feeding device 100, the sheet feeding sensor 25, the belt driving motor 30c, the belt driving clutch 30d, Various operations are performed on the transport roller motor 24c and the solenoid 35e to execute a paper feed process.

  As described above, according to the sheet feeding device 200 according to the second embodiment, the bypass air path adjustment mechanism 36 that adjusts the amount of air flowing into the bypass air path 33b is provided, so that it flows into the bypass air path 33b. The amount of air can be easily adjusted, and the sheet can be sucked / released on the suction surface without depending on the type of paper such as thick paper or thin paper.

<Third Embodiment>
In the third embodiment, a paper feeding unit 300 including a plurality of paper feeding devices 100 described in the first embodiment will be described. The same names and reference numerals as those of the first embodiment have the same functions, and thus description thereof is omitted.

  As shown in FIG. 11, the paper feeding unit 300 includes a plurality of paper feeding devices 100. Further, the paper supply unit 300 includes, for example, three paper trays P220, P221, and P222 in the vertical direction. In this embodiment, three paper trays are provided, but the present invention is not limited to this, and two or four or more may be used. Further, on each of the paper trays P220, P221, and P222, a suction conveyance mechanism 3 having the conveyance suction belt 30 shown in FIG.

  The paper trays P220, P221, and P222 are provided so that they can be pulled out in the front-rear direction of the drawing by opening a front door (not shown) provided on the front side of the drawing. The front surface of the paper tray can be configured as an exterior plate, and a handle or the like that can be put on the exterior plate can be provided, and the paper tray can be pulled out and pushed in using the handle or the like.

  The paper feeding direction of the paper P by the suction conveyance mechanism 3 is a direction (left direction in the drawing) orthogonal to the drawing direction of the paper trays P220, P221, and P222. The paper P fed out from the paper tray P220 by the suction transport mechanism 3 is sandwiched between the transport roller 24a and the driven roller 24b.

  The paper P sandwiched between the transport roller 24a and the driven roller 24b is transported by the transport roller 24a, and the transport direction is changed downward by the action of the guide member. Next, the paper is transported downward by the transport rollers R223 to R226 constituting the vertical paper transport path, guided in the substantially horizontal direction on the left side of the drawing by the guide member, and then contacted with the transport roller R227 in the rotation stopped state. Stop in contact. Thereafter, the sheet P is fed into the image forming apparatus with the start of rotation of the transport roller 227 and the like. The transport roller R227 functions as a registration roller for timing the image forming process in the image forming apparatus.

  Similarly, the paper P fed from the paper trays P221 and P222 by the suction conveyance mechanism 3 is sandwiched between the conveyance roller 24a and the driven roller 24b. The paper P sandwiched between the transport roller 24a and the driven roller 24b is transported to the transport rollers R225, R226 and the like, and is sent into the image forming apparatus as the transport roller R227 starts to rotate.

  Thus, according to the paper feeding unit 300 according to the third embodiment, since the paper feeding device 100 described in the first embodiment is provided, when the shutter is opened and closed like the conventional paper feeding device. Noise during the paper feeding and conveying operation can be reduced, the paper feeding device can be reduced in size, and the manufacturing cost of the paper feeding device can be reduced.

  Further, as in the conventional paper feeder, the fan is always operated during the carrying operation without turning on / off the fan every time a sheet is carried (see FIG. 5). Since the paper path is switched / released by switching the air path using a switching mechanism with good responsiveness in switching between the first position and the second position, the present invention is applied to a paper feeding unit that feeds paper at high speed. Can do.

<Fourth embodiment>
In the fourth embodiment, an image forming apparatus 400 including the sheet feeding device 100 described in the first embodiment will be described. The same names and reference numerals as those of the first embodiment have the same functions, and thus description thereof is omitted.

  As shown in FIG. 12, the image forming apparatus 400 is a digital color copying machine, for example, and includes an image forming unit 114 and an image reading device 111. The image forming apparatus 400 further includes a paper feeding unit 90, a fixing unit 87, and the control unit 10. The image forming unit 114 is called a tandem color image forming unit, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K and a transfer unit 80.

  The image reading device 111 includes an automatic document feeder 112 and a scanning exposure device 113, and is installed on the upper part of the image forming unit 114. The document G placed on the document table of the automatic document feeder 112 is transported by a transport unit (not shown), and an image on one or both sides of the document G is scanned and exposed by the optical system of the scanning exposure device 113. Or a line image sensor 8 composed of CMOS or the like. The image data photoelectrically converted by the line image sensor 8 is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like in an image processing unit (not shown), and then exposure units 3Y, 3M, 3C, 3K. Sent to.

  An image forming unit 10Y that forms a yellow (Y) image includes a charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, a primary transfer unit 5Y, and a cleaning unit 6Y around a cylindrical photosensitive drum 1Y. An image forming unit 10M that forms a magenta (M) color image includes a charging unit 2M, an exposure unit 3M, a developing unit 4M, a primary transfer unit 5M, and a cleaning unit 6M around a cylindrical photosensitive drum 1M. An image forming unit 10C for forming a cyan (C) color image includes a charging unit 2C, an exposure unit 3C, a developing unit 4C, a primary transfer unit 5C, and a cleaning unit 6C around a cylindrical photosensitive drum 1C. An image forming unit 10K that forms a black (K) image includes a charging unit 2K, an exposure unit 3K, a developing unit 4K, a primary transfer unit 5K, and a cleaning unit 6K around a cylindrical photosensitive drum 1K. When color image data is input to the image forming apparatus 110, each color toner image is formed from the image forming units 10Y, 10M, 10C, and 10K. When monochrome image data is input to the image forming apparatus 110, the image forming unit 110 A black toner image is formed from 10K.

  The transfer unit 80 includes an intermediate transfer belt 81, a secondary transfer unit 82, a driving roller 83, and a belt cleaning unit 84. The intermediate transfer belt 81 is wound around a plurality of rollers including a driving roller 83 and is rotatably supported. The photosensitive drums 1Y, 1M, 1C, 1K and the primary transfer portions 5Y, 5M, 5C, 5K press the intermediate transfer belt 81. The toner images formed on the photosensitive drums 1Y, 1M, 1C, and 1K are sequentially transferred to the intermediate transfer belt 81, and a toner image is formed on the intermediate transfer belt 81.

  The paper feeding unit 90 includes the paper feeding device 100 described above in the first embodiment, and further includes paper trays P10, P11, P12, a paper feeding roller 91, a registration roller 92, and the like. The sheets P accommodated in the sheet trays P10, P11, and P12 are attracted and separated one by one by the sheet feeding device 100 provided in the sheet feeding unit 90, and pass through the sheet feeding roller 91, and are in a stopped state. Paper is fed to the roller 92. The sheet P is temporarily stopped by the registration roller 92, and the secondary transfer unit 82 is started by the rotation of the registration roller 92 at the timing when the position of the leading end of the sheet P and the toner image formed on the intermediate transfer belt 81 coincide. The toner image is transferred onto the paper P. After the toner image is transferred to the paper P by the secondary transfer unit 82, the residual toner adhering to the intermediate transfer belt 81 is removed by the belt cleaning unit 84.

  The fixing unit 87 includes a fixing roller 88 and a pressure roller 89. The sheet P on which the toner image has been transferred is heated and pressed on the image formed on the sheet P at the nip formed between the fixing roller 88 and the pressure roller 89, so that the toner image is formed on the sheet P. It is fixed. Thereafter, the paper P is sandwiched between paper discharge rollers 93 and placed on a paper discharge tray 94 outside the apparatus.

  The control unit 10 includes a CPU that performs arithmetic control processing, a ROM that stores various programs, a RAM that stores various data, and the like, and performs all controls such as control related to a series of image forming processes. The control unit 10 is the same as that described with reference to FIG. 4 and controls the sheet feeding device 100.

  As described above, the image forming apparatus 400 according to the fourth embodiment includes the paper feeding device 100 described in the first embodiment. Therefore, when the shutter is opened and closed like the conventional paper feeding device. Noise during the paper feeding and conveying operation can be reduced, the paper feeding device can be reduced in size, and the manufacturing cost of the paper feeding device can be reduced.

  Further, as in the conventional paper feeder, the fan is always operated during the carrying operation without turning on / off the fan every time a sheet is carried (see FIG. 5). Since the air path is switched by a switching mechanism with good responsiveness for switching between the second position and the second position, and the suction / releasing of the paper is executed, the image forming apparatus that feeds and forms the image at high speed Can be applied.

  In this embodiment, an image forming apparatus that forms a color image has been described. However, an image forming apparatus that forms a monochrome image may be used.

<Fifth embodiment>
In the fifth embodiment, an image forming system 500 including the paper feeding unit 300 described in the third embodiment and the image forming apparatus 400 described in the fourth embodiment will be described. The same names and reference numerals as those in the third and fourth embodiments have the same functions, and thus the description thereof is omitted.

  As shown in FIG. 13, the image forming system 500 includes a paper feed unit 300 and an image forming apparatus 400. The sheets separated and discharged one by one by the sheet feeding unit 300 shown in FIG. An image forming apparatus 400 is connected to the communication port 95. After the image forming apparatus 400 receives the paper conveyed to the communication port 95 and performs various image forming processes, it is placed on a discharge tray outside the apparatus. Placed.

  As described above, according to the image forming system 500 according to the fifth embodiment, the paper feed unit 300 described in the third embodiment and the image forming apparatus 400 described in the fourth embodiment. Therefore, it is possible to reduce noise at the time of shutter opening / closing operation (at the time of paper feeding / conveying operation) as in a conventional paper feeding device, to reduce the size of the paper feeding device, and to reduce the manufacturing cost of the paper feeding device. Can be reduced.

  Further, as in the conventional paper feeder, the fan is always operated during the carrying operation without turning on / off the fan every time a sheet is carried (see FIG. 5). Since the air path is switched by a switching mechanism with good responsiveness for switching between the second position and the second position, and the suction / releasing of the paper is executed, an image forming system that performs paper feeding and image formation at high speed is realized. Can be applied.

DESCRIPTION OF SYMBOLS 3 Adsorption conveyance mechanism 10 Control part 20 Paper mounting base 30 Conveyance suction belt 30a Adsorption surface 30b Suction hole 31 Adsorption chamber 32 Negative pressure duct 33 Fan (negative pressure generation source)
33a Fan inlet 33b Bypass air passage 33f Fan outlet 34 Air guide duct 34a Exhaust outlet 34b Bypass 35 Switching mechanism 36 Bypass air passage adjustment mechanism 100, 200 Paper feeder 300 Paper feeder unit 400 Image forming apparatus 500 Image forming system

Claims (5)

A suction conveyance mechanism that has a suction surface that sucks the paper placed on the paper placement table, and that transports the paper sucked by the suction surface to the paper transport path;
A negative pressure generating source that sucks in air for sucking the sheet on the suction surface from an air inlet, and blows out air sucked from the air inlet from the air outlet;
A negative pressure duct connecting the suction conveyance mechanism and the suction port of the negative pressure generation source;
An air duct that exhausts the air blown out from the outlet of the negative pressure generation source to the outside, and connects the outlet of the negative pressure source and the negative pressure duct;
A first position where air passing through the air guide duct is exhausted to the outside from the discharge port and a second position where air passing through the air guide duct is returned to the negative pressure duct are switchable. A switching mechanism provided between the negative pressure duct and the wind guide duct;
A control unit that controls the switching mechanism so as to be in the first or second position ,
The negative pressure generation source is provided with a bypass air passage having an opening for allowing external air to flow in,
When the switching mechanism is located at the second position, the air that has flowed into the bypass air path returns to the negative pressure duct . The suction conveyance mechanism is provided with a conveyance drive roller that sends out a sheet to the sheet conveyance path
The controller is
When the sheet is sucked onto the suction surface, the switching mechanism is positioned at the first position;
When the paper sucked on the suction surface is sent out to the paper transport path by the transport driving roller, the switching mechanism is positioned from the first position to the second position,
2. The sheet feeding according to claim 1, wherein the switching mechanism is switched from the second position to the first position when a rear end of the sheet fed to the transport driving roller passes through the suction surface. apparatus. The bypass air passage is provided with a bypass air passage adjustment mechanism,
The bypass air path adjustment mechanism is
Sheet feeding apparatus according to claim 1 or 2, characterized in that adjusting the amount of air flowing into the bypass air passage. The bypass air path adjustment mechanism is
A rack gear provided to freely open and close the opening of the bypass air passage;
A motor having a pinion gear fitted to the rack gear on a rotating shaft;
4. The sheet feeding device according to claim 3 , wherein the rack gear is moved via the pinion gear by rotating a rotation shaft of the motor to adjust an opening area of the opening hole of the bypass air passage. . An image forming unit for forming an image on a predetermined sheet;
An image forming apparatus comprising the sheet feeding apparatus according to any one of claims 1 to 4 feeding a sheet to the image forming unit.

Images