JP2000211755A - Sheet feeding device - Google Patents

Abstract

(57) [Problem] To provide a sheet feeding device having a configuration capable of suppressing a variation in a moving amount at the time of an intermittent feeding operation and preventing an image defect from occurring. A sheet feeding device for intermittently feeding a sheet material S such as paper along a direction perpendicular to a width direction thereof, comprising at least a driving unit 1 for moving the sheet material S and the sheet material S The suction unit 2 has a unit structure in which the paper discharge unit and the suction unit 2 are integrally arranged.
The present invention is characterized in that a frictional force is effectively applied to the sheet material S adsorbed by the above to prevent a change in the movement amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding apparatus, and more particularly, to a sheet feeding structure for intermittently controlling the feeding of sheet-like paper such as an ink jet printer.

[0002]

2. Description of the Related Art One of image forming apparatuses is an ink jet printer. 2. Description of the Related Art Ink jet printers have a print head equipped with fine nozzles on a carriage that can reciprocate in a main scanning direction parallel to the width direction of a sheet of paper (hereinafter, referred to as paper). Is provided to form an image on a sheet by ejecting the sheet.

The paper is intermittently fed by an amount corresponding to one scanning line in the sub-scanning direction, which is a direction perpendicular to the main scanning direction, and the print head moves in the main scanning direction at the fed-out position to remove fine particles. An image is formed by ejecting ink at a necessary location. Conventionally, as a configuration of a sheet feeding apparatus for performing intermittent feeding, there is one disclosed in Japanese Patent Application Laid-Open No. 9-234920. The above-mentioned publication discloses that a plurality of suction holes are formed in a platen opposed to a print head, and a conveyance roller and a driven roller capable of nipping and conveying a part of a sheet moving on the platen are provided. A configuration is disclosed in which the paper is sucked and conveyed by nipping and conveying by each roller, and the paper is prevented from being rubbed in contact with the print head by pressing the surface of the paper in the conveyance process. .

[0004]

In the configuration disclosed in the above-mentioned publication, it is possible to prevent the paper conveyed by suction from being lifted up and to suppress the deterioration of the image quality due to the rubbing with the print head. However, in this type of ink-jet printer, as described above, due to the necessity of accurate feed control in the sub-scanning direction, when a configuration that presses the surface of the paper is used, the rubbing resistance is reduced. Therefore, there is a possibility that the feeding amount may be slightly changed. That is, even if the pressing force of the paper pressing member is reduced, the frictional resistance cannot be eliminated, and there is a possibility that the feeding amount at the time of suction conveyance may change.

[0005] When the paper becomes highly hygroscopic due to the ejection of a large amount of ink, the stiffness of the paper, the so-called bending stiffness, is reduced, causing buckling or uneven movement, and the movement in the sub-scanning direction. And as a result, white streaks and shading are generated on the image. The high moisture absorption state refers to a state in which the fine particle ink itself adheres to the paper surface, and is a phenomenon that occurs as a result of attaching a large amount of ink before drying during high-speed printing operation. The above publication only discloses a technique for preventing the floating of the paper due to a difference in expansion between the front and back surfaces of the paper due to moisture absorption, and also discloses a configuration related to the above-described configuration for preventing variation in the movement amount in the sub-scanning direction. Is not mentioned.

With respect to the suction conveyance, there is also a configuration in which a flat belt having a suction hole formed on the side of the paper conveyance surface in an air chamber having a negative pressure inside is moved. However, since the flat belt can only transport the paper depending on the suction force, in a configuration that requires a plurality of suction paths such as a suction section of the air chamber and suction holes of the flat belt, the suction path is not used. The flow resistance of the air increases, and it is difficult to apply the transport driving force by the flat belt to the paper. As a result, there is a possibility that an accurate intermittent feeding operation cannot be guaranteed with a precise intermittent feeding operation, for example, with a feeding amount of 10 μm or less. As a result, at present, it is not suitable for a high-precision feeding operation in which variation in the amount of movement in the sub-scanning direction must be prevented.

In a configuration in which suction holes are provided in a flat belt, when a friction coefficient changes due to adhesion of ink droplets ejected from a print head, a state in which a moving force is applied to a sheet moved while being placed on the surface thereof Becomes inadequate, and a displacement of the moving amount occurs when precise minute feeding is performed. Therefore, when it is necessary to clean or replace the suction surface of the flat belt, it is necessary to remove each member one by one. Therefore, at the time of reassembly, if the positioning accuracy of each member is not accurate, a positional relationship such as an appropriate tension of the belt for feeding the flat belt cannot be obtained. The paper cannot be intermittently moved by the amount.

The present invention has been made in view of the above-mentioned problems in the conventional sheet feeding apparatus, and has a structure capable of suppressing a variation in a moving amount in an intermittent feeding operation and preventing an image defect from occurring. To provide a sheet feeding device.

[0009]

According to the first aspect of the present invention,
A sheet feeding device that intermittently feeds a sheet material such as paper along a direction perpendicular to the width direction, at least,
It is characterized in that it has a unit structure in which the sheet material moving drive unit, the sheet material suction unit, and the sheet discharge unit are integrally arranged.

According to a second aspect of the present invention, in the sheet feeding apparatus according to the first aspect, the driving unit for moving the sheet material includes a roller portion for feeding the sheet material and the roller fed from the roller portion. It is characterized by comprising a plurality of belt members for moving the sheet material forward in the movement direction, and a pair of rotating roller members around which the belt members are looped.

According to a third aspect of the present invention, in the sheet feeding apparatus according to the first aspect, the driving unit for moving the sheet material includes a sheet material facing the belt member at a front side in a moving direction of the sheet material. It is characterized in that a discharge rotating body is provided.

According to a fourth aspect of the present invention, in the sheet feeding apparatus of the second aspect, the belt body is set at a moving speed that is higher than the linear speed of the driving roller body around which the belt body is wound. It is characterized by:

According to a fifth aspect of the present invention, in the sheet feeding apparatus according to the second aspect, the surface of the belt body with which the sheet material can abut is located at a position slightly higher than the surface of the suction portion. The surface of the suction portion is opposed to the sheet material between the belt members.

According to a sixth aspect of the present invention, in the sheet feeding apparatus according to the second aspect, the friction coefficient between the belt member and the sheet material is such that the friction coefficient between the sheet material and the surface of the suction portion is increased. It is characterized in that it is set larger than the coefficient.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing an example for explaining an embodiment of the present invention. FIG. 1 shows an arrangement of a sheet material moving drive unit 1 and a sheet material suction unit 2 in a sheet feeding apparatus. The relationship is shown. The movement driving unit 1 for sheet-like paper (hereinafter, referred to as a sheet S and referred to as a sheet) includes a pair of rollers 3 and 4 and these rollers 3 and 4.
The suction unit 2 for the sheet material S includes an air chamber 6 and an exhaust fan 7 that is a negative pressure source that can communicate with the internal space of the air chamber 6. .

The rollers 3 and 4 provided on the movement driving unit 1 for the sheet material S are arranged in parallel in the direction in which the sheet S is fed out in FIG. Among the above rollers, the roller 3 located on the rear side in the moving direction of the sheet S is
A driving roller 3A for feeding the sheet is provided coaxially so that the driving roller 3A works together. In FIG. 1, reference symbol L indicates the width of the sheet S, which is parallel to a main scanning direction of a print head 13 described later. In FIG. 1, a roller driving gear 9 is integrated with the rotating shaft of the roller 3, and the roller driving gear 9 engages with a driving gear 11 attached to an output shaft of a driving motor 10 so that the sheet S Can be rotated in the direction in which it is fed out. Therefore, the rotation of the driving motor 10 is transmitted to the roller 3 and the driving roller 3A via the roller driving gear 9, so that the pinch roller 1 facing the driving roller 3A.
2, the leading end of the sheet S is fed toward the suction unit 2, and a belt body 5 described later is moved in the sheet S feeding direction.

A belt 5 using a plurality of flat belts is wrapped around the rollers 3 and 4 in the axial direction. A flexible rubber or plastics belt substrate having a coefficient of friction greater than the coefficient of friction between the sheet S and the surface of a belt made of plastics, and FIG.
As shown in FIG. 1, a round rubber ring or the like is used.

The belt body 5 has a gap between a print head 13 to be described later and the surface of the sheet S facing the print head 13 of 1 to 2 m.
In consideration of the small gap of about m, the gap from the surface of the air chamber 6 to the surface to which the sheet S is adsorbed is set to a thickness that can be specified to be 0.5 mm or less. .

The exhaust fan 7 and the air chamber 6 in the suction section 2 are connected by a joint member 8, and the exhaust fan 7 is detachably provided to the joint member 8 by a screw-in structure.

In the air chamber 6, as shown in FIGS. 1 and 2, a plurality of suction holes 6B are formed in an upper wall 6A constituting a sheet conveying surface. It is open to the internal space of the air chamber 6 communicating with 7. For this reason, the internal space of the air chamber 6 is made negative pressure, so that outside air is taken in from the suction holes 6 </ b> B, and the sheet S is sucked to the suction surface of the air chamber 6.

Among the rollers 3 and 4, the roller 4 located on the front side in the moving direction of the sheet S is provided with a spur 14 (see FIG. 2) capable of contacting the belt body 5 worn on the roller 4. ing. The spur 14 is provided as a paper discharge unit that nips, conveys, and discharges the sheet S that has passed the nip position between the driving roller 3A and the pinch roller 11 in cooperation with the belt body 5.

In FIG. 1, a print head 13 is provided near the sheet movement drive unit 1 and the suction unit 2. The print head 13 is provided with a roller 13A that is connected to the traction rod 15 and can roll on the guide rail 16, and performs printing while reciprocating in the main scanning direction according to the traction direction of the traction rod 15. Ink drop at position (Fig. 1
(Indicated by broken lines in the middle) can be jetted onto the sheet S.

In the present embodiment, the sheet movement drive unit 1
The paper discharge unit including the suction unit 2, the spur 14, and the contact position of the belt body 5 is put together to form a unit (in FIG.
). The configuration of the unit U is such that the dynamic drive unit 1, the suction unit 2, and the paper discharge unit are supported by a common housing, and the housing can be detachably supported on, for example, an inkjet printer. can get. It should be noted that this unit may include a drive motor 10 in some cases.

Since the present embodiment has the above configuration,
The unitized movement drive unit 1, suction unit 2, and paper discharge unit are mounted in the inkjet printer with the positional relationship within the housing being optimized. The print head 13 is incorporated in the ink jet printer separately from the above-mentioned housing, and the positioning with the print head 13 is performed by incorporating the housing. Sheet S for print head 13
The positional relationship among the moving drive unit 1, the suction unit 2, and the paper discharge unit is defined in the housing, and the housing is optimized by simply mounting the housing in the inkjet printer. Belt body 5
When the exhaust fan 7 is operated and the pressure in the air chamber 6 is reduced to a negative pressure, the sheet S sucked toward the suction surface thereof is sucked.
Is pressed into contact. At this time, since the coefficient of friction of the belt body 5 with respect to the sheet S is higher than the coefficient of friction between the sheet S and the suction surface, the frictional force with respect to the sheet S becomes stronger than that between the sheet S and the suction surface. Can be moved. As a result, the sheet S can move in the feeding direction in conjunction with the movement of the belt body 5, and is moved by the driving force at the time of the movement, that is, the friction driving force generated between the sheet S and the belt body 5. It is fed without unevenness. Even if the sheet S swells due to the adhesion of the ink and the bending stiffness decreases, so-called buckling is likely to occur, the frictional force due to the movement of the belt body 5 on the surface adsorbed by the air chamber 6 is reduced. Since the sheet S can be actuated, the fed sheet S can be moved without causing deformation. Thereby, the belt body 5
Can be accurately advanced with an amount corresponding to the amount of movement of the belt body 5, so that line feeding in the sub-scanning direction is performed accurately, and white on an image due to a variation in the amount of movement. The occurrence of streaks and uneven shading is prevented. Since the suction between the belt member 5 and the sheet S is performed only by the suction force by the air chamber 6, the suction between the moving member and the belt member is smaller than in the conventional case where the suction hole is formed in the belt member. As a result, the movement of the sheet S by the belt member 5 can be favorably controlled.

On the other hand, when the rear end in the moving direction of the sheet S which is nipped and fed by the roller 3 and the pinch roller 12 is disengaged from the above-mentioned members, the nipping and conveying by the roller 4 and the spur 14 is continued. Do not change the volume. This allows the rear end to move while being regulated by the roller 4 and the spur 14 while the rear end is being sucked by the suction unit 2. As a result, the sheet S moves from the front end to the rear end in the moving direction without changing the moving amount by the moving driving unit 1 while passing through the suction unit 2.
White streaks and shading on the image due to the change in the moving amount are reliably prevented.

According to the present embodiment, since the moving drive unit 1, the suction unit 2, and the paper discharge unit are unitized and integrated, it is extremely easy to insert and remove from the ink jet printer during maintenance such as replacement. In this case, since the exhaust fan 7 and the air chamber 6 can be disengaged via the joint member 8 at this time,
The assembly workability can be improved as compared with a case where each member is individually attached and detached.

In the above embodiment, a flat belt is used as the belt body, but the present invention is not limited to this configuration. FIGS. 3 to 5 show a case where the belt body 5 is made of a round rubber band (indicated by a reference numeral 5A for convenience). In this case, a concave groove 6C is formed on the surface of the air chamber 6, and FIG. The belt body 5A is inserted into the concave groove 6C. FIG.
At the depth of the concave groove 6C (indicated by the symbol H in FIG. 4)
As shown in FIG. 1, in consideration of the fact that the gap between the print head 13 and the surface of the sheet S is set to a minute gap of about 1 to 2 mm, The gap between the surface to which S is adsorbed is 0.5 mm
Alternatively, it is set to a depth at which the belt body 5A can protrude so as to have a dimension smaller than that.

In such a configuration, as shown in FIG. 5, the sheet S is sucked toward the suction holes 6B of the air chamber 6 by the suction negative pressure from the air chamber 6 of the suction unit 2, but the belt body Since the portion facing 5A is pressed against belt 5A, it is pulled in the feeding direction in conjunction with movement of belt 5A. At this time, the belt body 5A
Is higher than the friction coefficient between the suction surface of the air chamber 6 and the sheet S, the frictional force at the time of moving becomes stronger than when moving along the suction surface of the air chamber 6, and the The amount of movement can be set in.

According to such a configuration, the air chamber 6
While the sheet S is attracted to the suction surface by the above, since the sheet S is slightly lifted from the suction surface by the belt body 5 or 5A, the rub resistance when the belt body 5 or 5A moves is reduced, and the change in the movement amount is reduced. Can be suppressed.

Next, another embodiment of the present invention will be described. FIGS. 6 and 7 are schematic diagrams for explaining a drive path which is a configuration for increasing the moving speed of the belt member 5 or 5A with respect to the feeding speed of the sheet nipped between the roller 3 and the nip roller 12. is there.
In the drive path shown in FIG. 5, unlike the example shown in FIG. 1, among the rollers 3 and 4 around which the belt body 5 is hung, the roller 3 located on the rear side in the movement direction of the sheet S is coaxial. Instead of directly transmitting the rotation from the driving motor 10 to the driving roller 3A, the driving motor 3A
The pinch roller 12 is opposed to the drive roller 3A. A roller driving gear 9 that meshes with a driving gear 11 located on the side of the driving motor 10 is coaxially supported on the driving roller 3A, and a transmission gear group 20 is provided for the roller driving gear 9. The roller 4 located on the front side in the moving direction of the sheet S and the driven gear 21 supported coaxially are interlocked. Number of teeth (Z1) of roller driving gear 9 and driven gear 21
The relationship with the number of teeth (Z2) is Z1> Z2,
The linear velocity of the roller 4 rotates faster than the linear velocity of the driving roller 3A. It is to be noted that not only the relationship between the number of teeth of the roller driving gear 9 and the driven gear 21 but also the speed increase ratio in the gear group 20 functioning as a transmission unit between these gears is set, so that The number of teeth of the driven gear 21 may be the same, and the space occupied by both gears 9 and 21 may be reduced.

For setting the speed relationship, the configuration shown in FIG. 7 can be used. In FIG. 7, the driving roller 3A is arranged coaxially with the roller 3 located on the rear side in the moving direction of the sheet S among the rollers 3 and 4 around which the belt member 5 is looped, as shown in FIG. , And a roller driving gear 9 is supported on the shaft. A driven gear 21 is supported on the axis of the roller 4 that is located on the front side in the movement direction of the sheet S among the rollers 3 and 4. The rotation from the driving gear 11 to the roller driving gear 9 is transmitted by an idle gear 23, and the rotation from the driving gear 11 to the driven gear 21 is a pulley supported coaxially with the idle gear 23 and coaxially with the roller 4. The transmission is performed by an idle gear 27 that is coaxially supported by the timing belt 26, which is hung around 24, 25, and the pulley 25, and meshes with the driven gear 21. In this case,
The relationship between the number of teeth (Z1) of the roller driving gear 9 and the number of teeth (Z2) of the driven gear 21 is defined as Z1> Z2, and the rotation speed of the roller 4 with respect to the rotation of the driving roller 3A is reduced. Hastened. In setting such a rotational speed relationship, the roller 3 is supported on a shaft of the driving roller 3A via a bearing 28 so that the belt body 5 can be moved independently of the rotation of the driving roller 3A. Has become. As a result, the linear velocity of the belt body 5 is reduced by the drive roller 3A.
When the linear velocity is higher than the linear velocity, mutual rotational interference is prevented from occurring.

[0032]

According to the first aspect of the present invention, the moving drive unit, the suction unit, and the paper discharge unit related to the feeding of the sheet material are separately configured as a unit separately from the print head. , Positioning accuracy can be improved. As a result, the positional accuracy between the sheet material and the suction unit and the movement driving unit is ensured, and the movement amount of the sheet material is prevented from being changed by eliminating the sheet material moving resistance and the like generated when the positional accuracy is low. be able to. As a result,
It is possible to prevent white stripes and shading that occur due to a change in the movement amount.

According to the second and fifth aspects of the present invention, the belt member is moved on the surface on which the fed sheet material is sucked, so that the fed sheet material is in contact with the suction surface. The belt body is moved while being pressed against the belt body without receiving the frictional resistance, and the feeding is performed in accordance with the movement amount of the belt body. As a result, a stable and accurate movement amount can be secured depending on the movement of the belt body, so that the movement amount does not change, and white stripes or the like on the printed image due to the variation in the movement amount can be secured. It is possible to prevent the occurrence of shading unevenness.

According to the third aspect of the present invention, since the sheet material that has left the feeding roller is continued to be fed by the rotating member for discharging the sheet material located on the front side in the moving direction, the front end of the sheet material in the moving direction. From the rear end to the rear end. As a result, it is possible to prevent white spots and uneven shading on an image due to a change in the movement amount without changing the movement amount of the sheet material.

According to the fourth aspect of the present invention, when the fed sheet material is moved by the belt body, it can move faster than the feeding speed. Can be made uniform.

According to the sixth aspect of the present invention, the coefficient of friction of the belt member with respect to the sheet material to be sucked is made higher than that of the contact surface between the suction portion and the sheet material, so that the feeding can be performed in accordance with the movement of the belt member. I can do it. As a result, the belt can be fed out while ignoring the influence of the frictional resistance at the suction portion, so that it is possible to eliminate the variation in the amount of movement that occurs when the frictional resistance is received, which causes the variation in the amount of movement. This makes it possible to prevent white spots and shading in the image beforehand.

[Brief description of the drawings]

FIG. 1 is a perspective view of an example for describing an embodiment of the present invention.

FIG. 2 is a partial sectional view showing a main part of the embodiment shown in FIG.

FIG. 3 is a perspective view for explaining a modification of the belt member used in the embodiment shown in FIG. 1;

FIG. 4 is a sectional view showing a part of the modification shown in FIG. 3;

FIG. 5 is a sectional view showing another part of the modification shown in FIG. 3;

FIG. 6 is a schematic diagram for explaining a modification of the drive path used in the embodiment shown in FIG.

FIG. 7 is a schematic diagram for explaining another modification of the drive path used in the embodiment shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Movement drive part 2 Suction part 3, 4 roller 3A Drive roller 5, 5A Belt body 6 Air chamber 6B Suction hole 6C Concave groove 7 Exhaust fan used as a suction source 8 Joint part 9 Roller drive gear 10 Drive motor 11 Drive gear 12 Pinch roller 13 Print head 14 Spur which is one component of paper discharge unit 20 Transmission gear group 21 Follower gear 23, 27 Idle gear 24, 25 Pulley 26 Timing belt U Unit area

Claims (6)

[Claims] 1. A sheet feeding device for intermittently feeding a sheet material such as paper along a direction perpendicular to a width direction thereof, comprising at least a driving unit for moving the sheet material and a suction unit for the sheet material. And a sheet discharging unit having a unit structure integrally disposed. 2. The sheet feeding device according to claim 1, wherein the driving unit for moving the sheet material includes a roller unit for feeding the sheet material and a sheet material fed from the roller unit. A sheet feeding device comprising: a plurality of belt members that move toward the side; and a pair of rotating roller members around which the belt members are wound. 3. The sheet feeding device according to claim 1, wherein the sheet material moving drive unit is provided with a sheet material discharging rotator facing the belt body in a front side in the moving direction of the sheet material. A sheet feeding device, comprising: 4. A sheet feeding apparatus according to claim 2, wherein said belt member is set at a moving speed higher than a linear speed of a driving roller member around which said belt member is wound. Feeding device. 5. The sheet feeding device according to claim 2, wherein the surface of the belt member with which the sheet material can abut is located at a position slightly higher than the surface of the suction portion. A sheet feeding device, wherein a surface of the suction section faces the sheet material. 6. The sheet feeding device according to claim 2, wherein a coefficient of friction between the belt member and the sheet material is set to be larger than a coefficient of friction between the sheet material and the surface of the suction portion. A sheet feeding device.