JPH1179441A - Sheet feeding device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet feeding device emitting less noise. SOLUTION: An endless feeding member 106 having many sucking holes is disposed over a sheet loading means 101, a duct part 11 communicated with a sucking force producing part is disposed inside the feeding member 106, and the uppermost sheet S1 on the sheet loading means 101 is sucked, for feeding, to the feeding member 106 by a sucking force imparted from the sucking force producing part through the duct part 11. Also, based on a detection signal from a sucking start detector means 54 which detects the start of sucking of a sheet S, a sucking force control means 145 is disposed in a communication part between the duct part 11 and the sucking force producing part, and closes, by a specified amount, an opening and closing member which is opened to open the communication part when the sheet is sucked and fed. Thus, the sucking force is reduced immediately before the sheet S1 is sucked to the feeding member 106.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper feeder provided in an image forming apparatus such as an electrophotographic copying machine, and more particularly, to separating sheets stacked on a sheet tray one by one using an air suction force. The present invention relates to a device for transporting.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus such as an electrophotographic copying machine is provided with a sheet feeding device. The sheet feeding device rotates a sheet stacked on a sheet tray by rotation of a sheet feeding roller. A roller feeder that conveys to the side is generally used.

However, in this roller feeder, the roller surface is made of an elastic material such as rubber, and its performance largely depends on the friction coefficient of the roller surface. The paper feed performance is not stable due to a change in the coefficient of friction of the roller surface due to the above-mentioned problems, and it is not possible to cope with various sheets having different surface properties.

In view of the above drawbacks, there has been proposed an air sheet feeding device that sucks and conveys a sheet by using an air suction force. FIG. 9 is a side sectional view of a typical air feeding device proposed in the related art. A sheet suction duct unit 11 having a suction opening 103 is provided above a vertically movable sheet tray 101 'on which sheets are stacked. Sheet conveying section 102 having a conveying belt 106 'having suction holes 105
Is arranged. In the vicinity of the leading end of the sheet, a nozzle 108 for ejecting air to float the sheet, and a nozzle 109 for blowing air to the second and subsequent sheets to separate only one sheet are arranged.

[0005] The device operates as follows. First, air is ejected from the nozzle 108 to float several sheets S on the sheet tray 101 '. Next, the uppermost sheet S1 is sucked to the transport belt 106 'by the suction action of the sheet suction duct unit 11. At this time, air is blown to the front end of the sheet by the nozzle 109, and the second floating sheet from the top is pushed back and separated.

Next, by driving the transport belt 106 ', the uppermost sheet S1 is transported to the transport roller pair 112. Then, the leading end of the sheet S1 is the conveying roller pair 1
When the number reaches 12, the driving of the transport belt 106 'is stopped, and the suction of the sheet is stopped. Thereafter, the sheet S1
Is transported by the set distance by the transport roller 112, the sheet S is sucked again and transported.

[0007]

However, in such a conventional sheet feeding device, the sheet is suddenly sucked at the time of sucking the sheet, so that a strong suction sound is generated at the moment when the sheet is sucked to the transport belt. Was.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a paper feeder with less noise.

[0009]

According to the present invention, there is provided a sheet stacking means for stacking and storing sheets, and a plurality of suction holes provided above the sheet stacking means for sucking and conveying the uppermost sheet of the sheet stacking means. A conveying unit having an endless conveying member having a suction force generating unit for generating a suction force for sucking the uppermost sheet, and a suction unit that is provided inside the conveyance member while communicating with the suction force generating unit. A duct portion for applying the suction force to the conveyance member, and a communication portion between the duct portion and the suction force generation portion, which is provided in the duct portion and is opened when the sheet is suctioned and conveyed. An opening / closing member to be opened, and suction start detection means provided in the duct portion and detecting that suction of the sheet has started,
Suction force control means for reducing the suction force immediately before the sheet is sucked by the conveyance member based on a detection signal from the suction start detection means.

Further, the present invention is characterized in that the suction force control means controls the opened and closed member to be closed by a predetermined amount so as to reduce the suction force immediately before the sheet is attracted to the conveying member. It is assumed that.

Further, the present invention is characterized in that the suction force control means controls the suction force generation force of the suction force generation section so as to reduce the suction force immediately before the sheet is sucked by the conveying member. Is what you do.

According to another aspect of the present invention, there is provided an image forming apparatus having a sheet feeding device and an image forming section for forming an image on a sheet fed from the sheet feeding device.
Characterized in that it is described in any one of (1) to (3).

Further, as in the present invention, an endless conveying member having a large number of suction holes is provided above the sheet stacking means, and a duct portion communicating with the suction force generating portion is provided inside the conveying member. The uppermost sheet of the sheet stacking means is sucked and conveyed to the conveying member by the suction force from the suction force generating section provided via the duct portion. Further, the suction force control means is provided in a communication portion between the duct portion and the suction force generation portion based on a detection signal from the suction start detection means for detecting the start of the sheet suction, and sucks and conveys the sheet. By closing the opening / closing member which is opened when opening the communication portion by a predetermined amount, the suction force is reduced immediately before the sheet is sucked by the conveying member.

[0014]

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

FIG. 1 is a top view of a sheet feeding device according to an embodiment of the present invention, and FIG. 2 is a side sectional view thereof.

In FIGS. 1 and 2, reference numeral 101 denotes a sheet feeding tray which is a sheet stacking means for stacking and storing sheets, and an end portion of a sheet S placed on the tray comes into contact with the sheet feeding tray 101. And a sheet guide frame 125 used for positioning the sheet S and the sheet S placed on the tray.
A height detection sensor 115 for detecting the height of the sensor and a sensor lever 114 are provided.

The height detection sensor 115 is connected to a switch SW shown in FIG.
Is turned on / off, and the control device 145 described later controls the rotation of the tray motor M1 shown in FIG. 3 by turning on / off the switch SW, and in this embodiment, turning on the switch SW. The paper feed tray 101 is moved up and down to a predetermined position.

On the other hand, above the paper feed tray 101,
The sheet attracting / conveying unit 102, which is conveying means including a driving roller 130, a driven roller 131, and a conveying belt 106 as an endless conveying member wound around the rollers 130 and 131, slightly moves in the sheet feeding direction. It is arranged in a state of being up. The transport belt 106 is rotated in the direction of arrow B by the rotation of the driving roller 130 and the driven roller 131.

An ejection duct 10 having a blower fan 110 and the like is disposed in the sheet feeding tray 101 in the sheet feeding direction and below the driving roller 130. The ejection duct 10 has an arrow C direction, That is, a separating nozzle 108 for ejecting air horizontally and a separating nozzle 109 for ejecting air in the direction of arrow D are formed.

By the way, inside the conveyor belt 106,
A suction force generating unit 107a having a suction fan 107 for generating a suction force for sucking a sheet is communicated with a relay duct 88 as a communication unit, and a suction valve 122,
A suction duct 11, which is a duct including a suction sensor 52 and a suction start detection sensor 54, is provided. By a suction action through an opening 103 of the suction duct 11, a suction hole 105 formed in a transport belt 106 is provided in the vicinity of the suction hole 105. A negative pressure is generated.

The suction sensor 52 detects that the sheet S has been sucked by the conveyor belt 106.
A suction sensor lever 51 which is pressed by the sheet S to be sucked and pivots upward is provided.
Is rotated by a predetermined angle, an adsorption detection signal is output.

The suction start detecting sensor 54, which is a suction start detecting means, detects that the sheet S
The suction start sensor lever 53 detects the start of suction by being sucked by the suction sheet 6 and is rotated upward by being pressed by the sheet to be sucked. When rotated by an angle, a suction start detection signal is output. Note that the suction start detection sensor lever 53 is
It is arranged upstream from 1.

In FIG. 1, reference numeral 140 denotes a DC motor for rotating the driving roller 130.
The rotation of the motor 140 is controlled by the rotation shaft 14 of the DC motor 140.
0a and pulleys 111a and 111b provided on the rotation shaft 132 of the drive roller 130, respectively.
The power is transmitted to the rotation shaft 132 via the belt 115 wound around 11a and 111b, whereby the drive roller 130 rotates.

Reference numeral 139 denotes a clutch provided on the rotating shaft 132 of the drive roller 130. When the clutch 139 is turned on during sheet feeding, the DC motor 1
The rotation of 40 is transmitted to the rotation shaft 132 and the drive roller 130
Is designed to rotate.

On the other hand, reference numeral 145 denotes a control device which is a suction force control means provided at a predetermined position of the sheet feeding device. FIG. 3 is a diagram showing a control block of the control device 145. In the figure, M1 is a tray motor for moving the paper feed tray 101 up and down. M2 is a valve opening / closing motor which is a pulse motor for opening and closing a suction valve 122 which is an opening / closing member for opening and opening the relay duct 88 when the sheet is sucked and conveyed. The suction valve 122 is opened and closed.

Here, when the suction valve 122 is opened,
The suction operation of the suction fan 107 generates a negative pressure in the suction duct 11, so that the sheet can be sucked. When the suction of the sheet is started, the suction start detection sensor 54 detects this through the suction start detection sensor lever 53, and a suction start detection signal is input to the control device 145.

When the suction start detection signal is input from the suction start detection sensor 54, the control device 145 drives the valve opening / closing motor M2 to close the suction valve 122 to a predetermined position. . This allows
The static pressure (suction force) in the suction duct 11 is reduced immediately before the sheet S is attracted to the transport belt 106, so that the suction noise generated at the moment when the sheet S is attracted to the transport belt 106 is reduced.

Next, the operation of the control device 145 for reducing the suction noise will be described.

When a sheet feed start switch (not shown) is pressed after the sheets S are stacked on the sheet feed tray 101, the controller 145 first drives the tray motor M1 to move the sheet feed tray 101 to the sheet attracting and conveying section 102. In the direction of. Then, after this, the sheet suction conveyance unit 1
02 and the uppermost sheet S1 of the sheet S become constant, and this is detected by the height detection sensor 115 via the sensor lever 114.
Is detected, and accordingly, the switch SW is turned from OFF to ON.
Then, the driving of the tray motor M1 is stopped, and the raising of the sheet feeding tray 101 is stopped.

Next, in order to feed the sheet S, the DC motor 110 is turned on, and the suction fan 107 and the blowing fan 110 are driven to supply air to the ejection duct 10, and the sheet is separated as shown in FIG. Air is ejected from the nozzle 108 and the separation nozzle 109 in the directions of arrows C and D, respectively. At this time, the air jetted from the separating nozzle 108 enters between the sheets S, and floats while separating some upper parts of the sheets S as shown in FIG.

Next, the valve opening / closing motor M2 is driven,
The suction valve 122 is opened by rotating it from the position shown by the broken line in FIG. 1 to the position shown by the solid line. Then, when the suction valve 122 is opened in this way, a negative pressure is generated in the suction duct 11 due to the suction of air by the suction fan 107, and FIG.
As shown in (1), of the sheets S floating by the air from the separation nozzle 108, the uppermost sheet S1 starts to be attracted to the transport belt 106. At this time, the suction start detection sensor 54 detects the start of sheet suction via the suction start detection sensor lever 53, and a suction start detection signal is input.

When the suction start detection signal is input, the valve opening / closing motor M2 is driven to move the suction valve 122 from the open position shown by the broken line to the predetermined position shown by the solid line as shown in FIG. Close the cap. Then, by closing the suction valve 122 to a predetermined position in this way,
Immediately before the top sheet S1 is attracted to the transport belt 106, the static pressure in the suction duct 11 decreases. Thus, the suction noise generated at the moment when the sheet is suctioned to the conveyance belt 106 is reduced.

Then, with the static pressure in the suction duct 11 reduced, the uppermost sheet S 1 is attracted to the conveyor belt 106. At this time, the sheet S2 located below the sheet S1 may be adsorbed together. However, as shown in FIG. 7, the air ejected from the separation nozzle 109 is the highest in the sheet S2. By flowing between the sheet S1 and the lower sheet S2, the sheet S2 located below the uppermost sheet S1 is pushed back in the sheet S direction.

Next, when the suction of the sheet S1 is completed, the suction sensor 5 is determined based on the rotation angle of the suction sensor lever 51.
2, a suction detection signal is input. Then, based on the suction detection signal, the clutch 139 is turned on after a predetermined time, and the rotation of the DC motor 110 is transmitted to the drive roller 130 to drive the transport belt 106. Thus, the sucked sheet S1 is conveyed in the sheet feeding direction.

Thereafter, when the leading end of the sheet S1 reaches the transport roller pair 112, the clutch 139 is turned off, the rotation of the drive roller 130 is stopped, and the drive of the transport belt 106 is stopped. At the same time, the suction valve 122 is rotated to the broken line position shown in FIG. As a result, the sheet S1 is transported by the transport roller pair 112 to an image forming section (not shown).

Then, the valve opening / closing motor M2 is driven again, and the suction valve 122 is rotated from the closed position shown by the broken line to the position shown by the solid line in FIG.
The next sheet S2 is sucked and conveyed.

In the above description, the suction force is reduced immediately before the sheet is sucked. After the suction force is reduced in this manner, the sheet is conveyed with the suction force as it is. However, it is desirable to return to the normal suction force in order to surely suck and convey the sheet. To return to the normal suction force, when the suction detection signal is input from the suction sensor 52, the control device 145 drives the valve opening / closing motor M2 to move the suction valve 122 to the position shown in FIG. Back to.

In the above description, the case where one suction start detection sensor 54 is provided has been described. However, the present embodiment is not limited to this, and the suction start detection sensor 54
A plurality may be provided to increase the detection accuracy. In addition,
When a plurality of such sensors are provided, the control device 145 closes the suction valve 122 when the suction start detection signals are input from all the sensors.

Although the suction sensor lever 51 and the suction start detection sensor lever 53 are separate, they may be one sensor lever.

In the above description, the case where the suction valve 122 is closed to a predetermined position in order to reduce the static pressure (suction force) in the suction duct 11 has been described, but the present invention is not limited to this. For example, the static pressure (suction force) in the suction duct 11 is reduced by lowering the applied voltage of the suction fan 107 to a predetermined value immediately before the sheet S1 is attracted to the conveyance belt 106 to reduce the suction force generation force of the suction fan 107. May be reduced.

FIG. 8 is a view showing an example of an image forming apparatus provided with the sheet feeding device of the present invention. The image forming apparatus main body (hereinafter simply referred to as “apparatus main body”) 900 includes a document table ( Platen glass) 906, light source 907, lens system 9
08, paper feeding unit 909, image forming unit (image forming unit) 90
2 etc. are provided. Also, a document table (platen)
On 906, an automatic document feeder is installed.

A paper feed unit 909 is provided with a cassette 91 in which recording sheets S are stored and which can be detachably mounted on the apparatus main body 900.
0, 911 and a deck 913 arranged on the pedestal 912. Further, the above-described paper feeding device is employed as a feeding mechanism for feeding the sheets (sheets) S stored in the cassette 910 or the like.

The image forming section 902 includes a cylindrical photosensitive drum 914, a developing device 915, a transfer charger 916, a separation charger 917, a cleaner 918, a primary charger 919, and the like. Further, on the downstream side of the image forming unit 902, a transport device 920, a fixing device 904, a discharge roller pair 905, and the like are provided. The main controller 930 controls and controls the entire image forming apparatus.

The operation of the image forming apparatus will be described.

When an image formation start signal is output from main controller 930, the automatic document feeder conveys the document through a predetermined conveyance path, and the document placing table (platen glass) 90
This is placed at a predetermined position on the device 6.

Thereafter, the image forming section 902 and the sheet feeding section 909 are driven at a predetermined timing. Paper feed unit 909
Feeds the sheet S from one of the cassettes 910 and 911 or the deck 913 to the image forming unit 902. The details of the feeding are as described above.
The skew of the sheet S fed from the sheet feeding unit 909 is corrected by the registration rollers 901, and the sheet S is sent to the image forming unit 902 at a timing appropriate for image formation described later.

On the other hand, the image forming section 902 irradiates the light emitted from the light source 907 to the original D placed on the original placing table (platen) 902, and irradiates the reflected light to the photosensitive drum 914 via the lens system 908. . Since the photosensitive drum 914 is charged in advance by the primary charger 919, an electrostatic latent image is formed on the surface of the photosensitive drum 914 when reflected light is incident thereon.
Next, the developing device 915 develops the electrostatic latent image,
Form a toner image.

The transfer charger 916 includes a photosensitive drum 914
The upper toner image is transferred to the fed sheet S.
The separation charger 917 charges the sheet S on which the toner image has been transferred to a polarity opposite to that of the transfer charger 916, thereby separating the sheet S from the photosensitive drum 914.

The conveying device 920 conveys the separated sheet S to the fixing device 904. The fixing device 904 permanently fixes the transferred image on the sheet S. Finally, the discharge roller pair 905 transfers the sheet S on which the image is fixed to
It is discharged from the apparatus main body 900. In the image forming apparatus described above, the speed of image formation can be increased without causing double feeding of sheets.

[0050]

As described above, according to the present invention, by lowering the suction force immediately before the stacked sheets are sucked, it is possible to reduce the suction sound when the sheets are sucked to the conveying member. This makes it possible to provide a paper feeder with less noise.

[Brief description of the drawings]

FIG. 1 is a top view of a sheet feeding device according to an embodiment of the present invention.

FIG. 2 is a side sectional view of the paper feeding device.

FIG. 3 is a control block diagram of a control device of the paper feeding device.

FIG. 4 is a diagram illustrating a state in which several sheets float on an upper portion of a sheet feeding tray of the sheet feeding device during sheet feeding.

FIG. 5 is a diagram illustrating a state when suction of a sheet located at the top of the paper feed tray is started.

FIG. 6 is a view showing a state in which a suction valve of the paper feeding device has rotated from an open position to a predetermined closed position.

FIG. 7 is a view showing a state in which the uppermost sheet and the lowermost sheet are separated.

FIG. 8 is a diagram illustrating an example of an image forming apparatus including the sheet feeding device according to the invention.

FIG. 9 is a side sectional view of a conventional sheet feeding device.

[Explanation of symbols]

 Reference Signs List 11 suction duct 54 suction start detection sensor 88 relay duct 101, 101 'sheet feed tray 102 sheet suction conveyance unit 106 conveyance belt 107 suction fan 107a suction power generation unit 122 suction valve 145 control device 900 device main body M1 tray motor M2 valve opening / closing Motor S sheet S1 Top sheet

Claims (4)

[Claims] An endless conveying member provided above the sheet stacking means and having a number of suction holes for sucking and conveying the uppermost sheet of the sheet stacking means. A conveying unit provided with: a suction force generating unit that generates a suction force for sucking the uppermost sheet; and a communication unit that communicates with the suction force generation unit and is provided inside the conveyance member, and the suction unit generates the suction force. A duct portion for applying the sheet, an opening / closing member which is provided in the duct portion and is opened when the sheet is sucked and conveyed, and opens a communication portion between the duct portion and the suction force generating portion; A suction start detection unit provided in the unit, for detecting that the suction of the sheet has started, and a step immediately before the sheet is suctioned to the conveyance member based on a detection signal from the suction start detection unit. A sheet feeding device, comprising: suction force control means for reducing suction force. 2. The apparatus according to claim 1, wherein the suction force control means controls the opened and closed member to be closed by a predetermined amount so as to reduce the suction force immediately before the sheet is attracted to the conveyance member. Item 2. The paper feeding device according to Item 1. 3. The suction force control unit controls a suction force generation force of the suction force generation unit so as to reduce the suction force immediately before the sheet is sucked by a conveyance member. 2. The paper feeding device according to 1. 4. An image forming apparatus having a sheet feeding device and an image forming section for forming an image on a sheet fed from the sheet feeding device, wherein the sheet feeding device is any one of claims 1 to 3. An image forming apparatus characterized in that: