JP2000109259A - Sheet material feeder and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet material feeder and an image forming device that both can afford jam suppression and stable carrying of sheet materials through avoidance of any insufficient negative pressure (suction gas quantity) at a plurality of places in their sheet material carrying path. SOLUTION: A separation duct 123 and a transfer duct 127 branching off from a suction fan 124 via a duct confluence portion 129 apply negative pressure to sheet materials being transferred to help to carry the sheet material. The duct confluence portion 129 is equipped with a directional control valve 130 that can change the ratio of the negative pressure supplied between the separation duct 123 and the transfer duct 127.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying apparatus which performs a sheet conveying assisting operation by utilizing a negative pressure, and is a technique applicable to an image forming apparatus such as a copying machine, a laser beam printer, a facsimile and the like. It is.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, a toner image developed on a surface of a photosensitive drum is transferred onto a sheet material (transferred sheet material) on which an image is formed by a transfer charger, and is separated and charged. There is a configuration in which the sheet material is electrostatically separated from the surface of the photosensitive drum by the static elimination action of the container.

[0003] The sheet material electrostatically separated from the surface of the photosensitive drum is then conveyed to a fixing device by a conveyance belt, and the unfixed toner image is heated and melted to be fixed on the sheet material.

In the image forming apparatus having such a configuration, a negative pressure is generated by suctioning air from below the separation charger (the side opposite to the photosensitive drum) with a suction fan to assist electrostatic separation.

[0005] Further, also in the conveying section, the sheet material is attracted to the surface of the conveying belt by suctioning air from inside the conveying belt with a suction fan, thereby increasing the conveying force of the conveying belt.

In a usual configuration, there is a single fan that sucks air from the separation section and the transport section, and a duct extending from the fan branches in the middle and is connected to each transport section and the separation section.

[0007] The air volume of the air sucked at each part is set so as to be a fixed amount that is not changed (for example, a substantially equal air suction air volume in the transport unit and the separation unit).

[0008]

However, in the above-mentioned conventional example, since the suction of the separation unit and the conveyance unit is performed simultaneously by one suction fan, the air volume of each may be insufficient. There was a problem like

If the air volume at the separation section is insufficient, the sheet material is difficult to separate from the photosensitive drum when the sheet material is thin or when the operating environment of the apparatus is low, and the leading end of the sheet material is separated from the photosensitive drum. There is a concern that it may enter the cleaner section without getting rid of the jam.

As a countermeasure, there is a method of increasing the supply voltage to the fan, increasing the size of the fan, and providing a dedicated suction fan in each of the separation section and the transport section to increase the air volume. It is expected that the power supply capacity of the device will increase, and that the device configuration will become complicated and the entire device will become larger.

In order to improve the separability of the sheet material from the photosensitive drum, a curling roller is disposed upstream of the separation unit in the sheet material conveying direction, and a curl shape is imparted to the leading end of the sheet material. There are devices that do.

However, since the sheet material has a curl shape at the leading end, the sheet material is liable to be caught by a conveyance guide or the like in the middle of conveyance, and a jam may easily occur.

On the other hand, if the air volume in the transport section is insufficient, the force of attracting the sheet material to the transport belt becomes weak, and when the sheet material is thick paper or the like, a rush shock when entering the roller nip portion of the fixing device is generated. And transfer blurring may occur.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art. It is an object of the present invention to provide a plurality of sheet material conveyance paths (specifically, a sheet material separation section and a conveyance section). Negative pressure (suction air volume) required for each
The object of the present invention is to provide a sheet conveying apparatus and an image forming apparatus which can solve the problem of shortage and can suppress the jam and can stably convey the sheet.

[0015]

In order to achieve the above object, according to the present invention, at a plurality of points on a conveying path for conveying a sheet material, a negative pressure is supplied through an air flow path branched from a negative pressure generating means. To the sheet material, in a sheet material transporting apparatus that performs a sheet material transport assisting operation, a branch means of the air flow path or a valve means disposed in any air flow path downstream of the branch part, Valve control means for controlling the opening and closing of the valve means, wherein the valve control means can change the negative pressure state at the plurality of locations where negative pressure is applied to the conveyed sheet material.

The assisting operation of conveying the sheet material assisted by the negative pressure includes the separating operation of the separating means for separating the sheet material from the contact member with which the sheet material contacts, and the operation of disposing the sheet material on the conveying path downstream of the separating means. It is also preferable that the suction operation is performed by a suction unit that causes the sheet material to be sucked by the transport unit that has been set.

It is also preferable that the apparatus further comprises sheet material position detecting means for detecting the position of the conveyed sheet material, and wherein the valve control means changes the negative pressure state at the plurality of locations according to the position of the conveyed sheet material. It is.

A sheet material position detecting means for detecting a position of the conveyed sheet material, wherein the valve control means controls a ratio of a negative pressure supplied to the separating means and the suction means in accordance with the position of the conveyed sheet material. It is also preferable to change.

Preferably, the valve control means can change the ratio of the negative pressure supplied to the separation means and the adsorption means in a plurality of stages.

It is also preferable that the valve control means includes a stepping motor so that the ratio of the negative pressure supplied to the separation means and the suction means can be changed in a plurality of stages.

The negative pressure generating means is preferably a suction fan.

It is also preferable to provide an opening width changing means for changing the opening width of the opening of the air flow passage according to the size of the sheet material to be conveyed.

The image forming apparatus includes an image forming means for forming an image on a sheet material, and the above-described sheet material conveying device for conveying the sheet material on which the image is formed. .

[0024]

(Embodiment 1) Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory cross-sectional configuration diagram of an image forming apparatus having a configuration to which the present invention can be applied.

In FIG. 1, 101 is the main body of the image forming apparatus, 102 is a storage device for the sheet material S, 103 is a sheet feeding means, 104 is a registration roller, 105 is an image forming unit,
Reference numeral 06 denotes a transport belt as transport means, 107 denotes a fixing device, 108 denotes a paper discharge roller, and 109 denotes a stacking tray.

Here, the sheet material S stored in the storage device 102 is fed by the sheet feeding means 103, and once stands by while the leading end thereof is sandwiched between the nips of the registration rollers 104. Then, at the timing when the leading edge of the image formed by the image forming unit 105 and the leading edge of the sheet material S are synchronized, the registration roller 104 rotates again, and the sheet material S
Is conveyed to the image forming unit 105.

Thereafter, the image formed by the image forming section 105 is transferred to the sheet material S, and guided to the fixing device 107 by the transport belt 106. Then, in the fixing device 107, the image on the sheet material S is fixed, and the sheet material S on which the image has been fixed is discharged to the outside of the image forming apparatus main body 101 by the discharge roller 108, and the stacking tray 1
09 is loaded. Thus, a series of image forming operations is completed.

Next, FIG. 2 is a sectional configuration explanatory view showing a detailed configuration of the image forming section 105 in the image forming apparatus 101, and the image forming process will be described in more detail.

Here, 100 is a photosensitive drum, 110 is a developing device, T is toner, 111 is a transfer guide, 112 is a transfer charger, 113 is a separation charger as separation means, 114
Is a paper transport guide attached to the separation charger.

The latent image formed on the photosensitive drum 100 is
The toner T in the developing device 110 is developed by electrically flying, and a toner image is formed on the photosensitive drum 100.

Next, the sheet material S conveyed by the registration rollers 104 is guided by a transfer guide 111 and sent between the photosensitive drum 100 and the transfer charger 112, and the surface of the photosensitive drum is transferred by the transfer charger 112. The toner image on 100 is transferred.

Thereafter, the sheet material S is separated from the photosensitive drum 100 by the separation charger 113 while carrying the toner image, and is guided by the paper transport guide 114 to be transported by the transport belt 1.
06.

Next, the separation and conveyance of the sheet material S will be described in detail with reference to FIGS. 3, 4, 5, 6, and 7. FIG.

FIG. 3 is an explanatory sectional view showing in detail a main part of the image forming apparatus main body 101. In FIG. 3, the sheet material S fed by the sheet feeding means is guided by a registration roller front guide 121. Then, the sheet material S abuts on the nip of the registration roller 104. At this time, the size of the sheet material S conveyed in the direction perpendicular to the conveying direction is detected by the sheet material size detection sensor 122 located in front of the nip.

The toner image on the photosensitive drum 100 is transferred onto the sheet material S by the transfer charger 112 by the transfer roller 112, and the sheet material S is exposed by the separation charger 113. Separated from the drum 100 surface.

Here, below the separation charger 113, an air suction separation duct 1 as an air flow path for introducing a negative pressure.
23 is provided and extends to a suction fan 124 as a negative pressure generating means.

The suction fan 124 sucks the air inside the separation charger 113 from below the separation charger 113 through the separation duct 123, and assists the electrostatic separation of the sheet material S by the air suction force.

A separation air shutter 125 is provided between the lower surface of the separation charger 113 and the separation duct 123 so as to operate according to the width of the sheet material S. And contributes to further improving the separation performance. For a description of this feature,
Details will be described later.

Then, the sheet material S separated from the photosensitive drum 100 is transported to the transport belt 106. Here, in the vicinity of the transport belt 106, a sheet material detection sensor 126 is provided as a sheet material position detecting unit that detects that the leading end of the sheet material S has reached the transport belt 106.

A conveying duct 127 is provided from the inner surface of the conveying belt 106 to the suction fan 124, which functions as an air suction means and an air flow path. The sheet material S is attracted to the surface of the transport belt 106 by the suction force, and is transported with a strong transport force. Then, the sheet material S is conveyed to the fixing device 107.

Here, similarly to the separation section, the transport belt 10
A transfer air shutter 128 as an opening width changing means is provided between the inner peripheral surface of the sheet 6 and the transfer duct 127, and is controlled to operate according to the width size of the sheet material S. The operation will be described later in detail.

The separation duct 123 and the transport duct 12
A switching valve 130 as a valve means for switching the air suction direction of the suction fan 124 is provided at a duct junction 129 as a branch that branches off from a fan duct 131 as an air flow path that is directly connected to the suction fan 124. Is provided.

By switching the switching valve 130, the suction fan 124 causes the separation charger 113
Alternatively, control is performed so that switching can be performed so that air is sucked from one of the transport belts 106 via the fan duct 131. The control method and the like will be described later in detail.

Next, referring to FIG.
, The configuration and control of the switching valve 130 will be described in detail.

The switching valve 130 includes a valve unit 130
a, a rotation center 130b, and a lever portion 130c, and are supported rotatably about the rotation center 130b.

Here, one end of a tension spring 132 is attached to the tip of the lever portion 130c, and the other end of the tension spring 132 is attached to the image forming apparatus main body 101 side. As shown in FIG. 4, the fan duct 131 is in contact with one wall surface.

Therefore, in the normal state, the suction fan 12
Numeral 4 sucks air from the separation charger 113 via the fan duct 131 and the separation duct 123 to assist the sheet material S in separating from the photosensitive drum 100 (conveyance assisting operation).

Then, the leading end of the conveyed sheet material S is
Upon reaching the sheet material detection sensor 126, a solenoid 133, which is one configuration of valve control means attached to the tip of the lever portion 130c of the switching valve 130,
By being absorbed by the command of the CPU 134,
The switching valve 130 has a rotation center 130b as a center,
4 rotates against the tension of the tension spring 132, and FIG.
Come to the position of the dashed line.

Then, the air suction direction of the suction fan 124 is switched, and the fan duct 131 and the transport duct 12 are switched.
7, the air of the conveyor belt 106 is sucked.

As a result, the suction fan 124 sucks the entire suction force from the side of the transport belt 106, so that the suction force of the sheet material S on the transport belt 106 is improved, and the transport of the sheet material S by the transport belt 106 is performed. Power improves.

For this reason, the sheet material S is transferred to the fixing device 107.
This can prevent problems such as transfer blurring caused by transmission of a shock to the transfer section when the sheet enters the transfer section, thereby enabling stable sheet material conveyance and image formation.

When the rear end of the sheet material passes through the sheet material detection sensor 126, the solenoid 133 is opened by a command from the CPU, the switching valve 130 is pulled by the tension spring 132, and turns to the position shown in FIG. Then, the air is controlled to be sucked from the separation unit side.

Next, referring to FIG.
The configuration of the separation air shutter 125 between the separation duct 13 and the separation duct 123 will be described.

FIG. 5 is a sectional view of the separation charger 113 as viewed from the transfer charger 112 side.

Here, the separation charger 113 comprises a frame 113a and a wire 113b as a schematic configuration, and an opening 113c for sucking air of the separation portion by a suction fan 124 is provided in the frame 113a.
It is open along 3b.

Then, air is sucked from the opening 113c by the suction fan 124, and the sheet material S is suctioned by the generated negative pressure, thereby separating the sheet charger S11.
By pulling to the third side, electrostatic separation from the photosensitive drum 100 is assisted to enhance the separation performance.

More specifically, first, the width of the conveyed sheet S in the direction perpendicular to the conveying direction is detected by the sheet size detecting sensor 122.

Assuming that the width size of the sheet material S is L, the separation air shutter 125 is driven to adjust the opening 113c of the separation charger 113 to the size of the sheet material by the configuration and control described in detail later. Thus, the opening 113c outside the sheet material size L is closed.

As a result, in the related art, since the opening is entirely open, the air is sucked from the outside of the width of the sheet material S, and the inefficient and sufficient separation force cannot be exhibited. .

Further, referring to FIG.
The configuration, operation, and control of the transport air shutter 128 between the transport ducts 127 of FIG.

FIG. 6 is a sectional view of the conveyor belt 106 as viewed from the separation charger side.

More specifically, as shown in FIG.
6 has a belt portion 106a and a hole portion 106b. The suction fan 1 is inserted through the hole 106b and the transfer duct 127.
24, the sheet material S to be conveyed is suctioned to the surface of the conveyance belt 106 by sucking air on the surface of the conveyance belt 106, and the sheet material S is held by rotating the conveyance belt 106 to maintain a high conveyance force. Transport.

Here, the conveying belt 106 and the conveying duct 1
27, a conveyance air shutter 128 is provided, which detects the width of the sheet material S conveyed by the sheet material size detection sensor 122, and drives and moves the conveyance air shutter 128 according to the width to convey the sheet material S. Belt 106
By blocking the hole 106b, the suction of the air in an extra portion other than the sheet material S is prevented, the efficient air suction is achieved, and the conveying force is kept high.

Next, referring to FIG. 7, the structure, drive and operation of the separation air shutter 125 and the transport air shutter 128 will be described.
The control will be described.

Since the separation air shutter 125 and the transport air shutter 128 have the same configuration, only the separation air shutter 125 will be described here. However, the same applies to the transport air shutter 128. I do.

In FIG. 7, reference numeral 125 denotes a separation air shutter, which is provided between the opening 113 c on the lower surface of the separation charger 113 and the separation duct 123. A rack 141 is attached to an end of the separation air shutter 125, and a pinion gear 143 connected to an output shaft of the drive motor 142 meshes with the rack 141. Accordingly, when the drive motor 142 is driven by a command from the CPU 134 to rotate the pinion gear 143, the separation air shutter 125 moves in the direction of the arrow in FIG.

Here, the separation air shutter 125 has
Notch portions 144 having widths L ₁ , L ₂ , and L ₃ are formed substantially equal to the width dimension of the sheet material S.

Therefore, the sheet material size detection sensor 12
2, the width dimension of the sheet material S is detected, and the notch 144 corresponding to the width is formed in the opening 1 of the separation charger 113.
By controlling the drive motor 134 to move to the position 33c, the opening 113c other than the width substantially equal to the width of the sheet material S is shielded.

As a result, since the extra air is not sucked, all the sucked air is sucked from the sheet material S, and the suction force of the sheet material S is increased.
As a result, the separation performance is improved.

As described above, the direction of air suction from the suction fan is switched according to the position of the front end of the sheet material, and further, the opening width of the air suction portion is changed according to the width size of the sheet material. Since the suction air is sucked without escaping, the suction force for sucking the sheet material is improved, so that the separation property from the photosensitive drum in the separation unit and the conveyance property of the sheet material in the conveyance unit are improved.

(Embodiment 2) In the first embodiment,
The configuration in which the switching valve 130 of the duct junction 129 is moved by being driven by the solenoid 133 has been described. However, the driving means of the valve control means is not limited to the solenoid, and is driven by the stepping motor 135 as shown in FIG. Is also good.

More specifically, the position of the switching valve 130 in the normal state is located at the position indicated by the solid line in FIG.
This state is detected by the photo sensor 137. Here, the switching valve 130 has a pulley on the axis of the rotation center 130b, and the timing valve 136
It is connected to a stepping motor 135.

Therefore, when the stepping motor 135 is rotated by a command from the CPU 134, the switching valve 130 is rotated to switch the suction direction of the suction fan 124.

Here, since the driving means is a stepping motor, the rotation angle can be freely changed according to the number of pulses issued from the CPU 134. for that reason,
The switching valve 130 can be stopped at an arbitrary position, and can be changed according to the state of the apparatus main body.

That is, in the separation of the sheet material S from the photosensitive drum 100, the separability of the front end portion of the sheet material S is the worst. By setting the switching valve 130 to, the suction fan 124 sucks air only from the separation section, thereby improving the separation property of the leading end of the sheet material S,
When the leading end of the sheet material S reaches the paper detection sensor 126,
Since the suction force of the sheet material S to the conveyor belt 106 is required, the switching valve 130 is moved to the opposite side so that the suction fan 124 sucks air only from the conveyor belt 106 side.

Further, the leading end of the sheet material S is
Is reached, the sheet material S is also conveyed by the fixing device, so that neither the conveying force of the conveying belt 106 nor the separating force of the separating section is required.

On the other hand, ozone is generated in the separation charger section,
If the ozone adheres to the surface of the photosensitive drum 100, a defective image called image deletion occurs. Therefore, the switching valve is stopped at a position intermediate between the above two positions, and air is sucked from both the separation unit and the conveyance unit. Then, the sheet material S is conveyed to the conveying belt 106 while being adsorbed to some extent, and the ozone generated in the separation charger 113 is suctioned, thereby preventing ozone from adhering to the surface of the photosensitive drum 100. Can be prevented from being caused by image failure.

(Embodiment 3) A third embodiment of the present invention will be described with reference to FIG.

The air shutter 125 has two shutter sections 125a and 125 in a direction perpendicular to the sheet conveying direction.
5b, and a rack 14 is provided at each end of the shutter section.
1a and 141b are attached, and a pinion gear 14 attached to an output shaft end of a drive motor 142 is mounted on the rack.
3 are engaged.

Accordingly, when the drive motor 142 is driven by the command of the CPU 134 in accordance with the size of the sheet material S detected by the sheet material size detection sensor 122 and the pinion gear 143 is rotationally driven, the drive is performed by the rack 141. Through the shutter 125, and the shutter 125 moves in the direction of the arrow.

As described above, in the first embodiment, the width of the cutout portion of the air shutter is the width corresponding to the fixed size of the sheet material S. Is controlled, the distance L between the air shutters can be changed arbitrarily, so that the present invention is also effective for a sheet material S of an irregular size.

(Embodiment 4) In the first embodiment, the separation air shutter 125 is provided between the separation charger 113 and the separation duct 123, and the conveyance air shutter 128 is provided between the conveyance belt 106 and the conveyance duct 127. Although the arrangement is described above, the same effect can be obtained by disposing the separation air shutter between the separation charger and the sheet material and disposing the conveyance air shutter between the conveyance belt and the sheet material.

[0083]

According to the present invention described above, in a configuration in which a negative pressure is applied to a sheet material at a plurality of locations on a transport path to perform a transport assist operation, the negative pressure state is reduced to a required amount at each location. Accordingly, it is possible to appropriately perform the auxiliary operation of conveying the sheet material by the negative pressure, and it is possible to suppress the jam of the sheet material and stably convey the sheet material.

By providing the opening width changing means for changing the opening width of the opening of the air flow path, it is possible to suppress the reduction of the generated negative pressure and to more effectively perform the sheet conveyance assisting operation by the negative pressure. it can.

Therefore, when the present invention is applied to a configuration that requires a negative pressure for the sheet separating means and the suction means of the conveying means, the negative pressure applied to the sheet material, that is, the amount of suction air is increased. The separation force of the means and the transfer force of the transfer means are improved.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional configuration diagram of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional configuration explanatory view of a main part of the image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is a schematic cross-sectional configuration explanatory diagram of an air suction configuration according to the first embodiment of the present invention.

FIG. 4 is a sectional configuration explanatory view of a switching valve unit according to the first embodiment of the present invention.

FIG. 5 is a sectional configuration explanatory view of a separation charger section according to the first embodiment of the present invention.

FIG. 6 is an explanatory cross-sectional configuration diagram of a transport belt unit according to the first embodiment of the present invention.

FIG. 7 is a perspective view of a separation air shutter unit according to the first embodiment of the present invention.

FIG. 8 is a cross-sectional configuration explanatory view of a switching valve unit according to a second embodiment of the present invention.

FIG. 9 is a perspective view of an air shutter unit according to a third embodiment of the present invention.

DESCRIPTION OF SYMBOLS 100 Photosensitive drum 101 Image forming apparatus main body 102 Storage device 103 Paper feeding means 104 Registration roller 105 Image forming unit 106 Conveying belt (conveying means) 107 Fixing device 108 Discharge roller 109 Stacking tray 110 Developing device 111 Transfer guide 112 Transfer charger 113 Separation charger (separation means) 114 Paper transport guide 121 Registration roller front guide 122 Sheet material size detection sensor 123 Separation duct (air flow path) 124 Suction fan (negative pressure generation means) 125 Separation air shutter (opening) Width change means) 126 sheet material detection sensor (sheet material position detection means) 127 transport duct (air flow path, suction means) 128 transport air shutter (opening width change means) 129 duct junction (branch) 130 switching valve (valve) Means 1 0a valve portion 130b pivot center 130c lever portion 131 fan duct (air passage) 132 tension spring 133 solenoid (valve control means) 134 CPU

Claims (9)

[Claims] 1. A sheet conveying apparatus for applying a negative pressure to a sheet through an air flow path branched from a negative pressure generating means at a plurality of positions of a conveying path for conveying the sheet, and performing a sheet conveying assisting operation. In the above, the valve control means comprises: valve means disposed in a branch portion of the air flow path or any air flow path downstream of the branch portion; and valve control means for controlling opening and closing of the valve means. A negative pressure state at which the negative pressure is applied to the conveyed sheet material can be changed. 2. A sheet material conveyance assisting operation assisted by a negative pressure includes: a separating operation of separating means for separating a sheet material from a contact member with which the sheet material contacts, and a conveying path downstream of the separating means. 2. The sheet material conveying device according to claim 1, wherein the suction operation is performed by a suction device that causes the sheet material to be sucked by the conveying device disposed in the sheet conveying device. 3. A sheet material position detecting means for detecting a position of a conveyed sheet material, wherein said valve control means changes a negative pressure state at said plurality of places according to a position of the conveyed sheet material. The sheet conveying device according to claim 1 or 2, wherein 4. A sheet material position detecting means for detecting a position of a conveyed sheet material, wherein said valve control means comprises a negative pressure supplied to a separating means and a suction means in accordance with the position of the conveyed sheet material. 3. The sheet conveying apparatus according to claim 2, wherein the ratio of the sheet material is changed. 5. The sheet conveying apparatus according to claim 4, wherein the valve control means can change the ratio of the negative pressure supplied to the separation means and the suction means in a plurality of stages. 6. The valve control device according to claim 4, further comprising a stepping motor, wherein a ratio of the negative pressure supplied to the separation device and the suction device can be changed in a plurality of stages.
The sheet material conveying device according to item 1. 7. The sheet conveying apparatus according to claim 1, wherein said negative pressure generating means is a suction fan. 8. According to the size of the sheet material to be conveyed,
The sheet conveying apparatus according to any one of claims 1 to 7, further comprising an opening width changing unit configured to change an opening width of the opening of the air flow path. 9. An image forming means for forming an image on a sheet material, and the sheet material conveying apparatus according to claim 1 for conveying the sheet material on which the image is formed. An image forming apparatus comprising: