JP2002104674A - Sheet transport device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet transport device capable of forming a gap for transporting each sheet in good performance without causing a touch with a transport roller between the transport roller and a friction member after the completion of sheet transport and of transporting the sheets certainly one by one without generating double feed or dragged feed of another sheet and also provide an image forming device equipped with such a sheet transport device. SOLUTION: The shaft 52 of a feed roller 51 is furnished with a different diameter portion 57, on which a roller 53 is fitted loosely, and in the prescribed rotating phase, the roller 53 is abutted to a sheet feed pad 9 so that a gap is formed between the pad 9 and feed roller 51, while the rotational center 69 of the feed roller 51 is arranged eccentrically from the axis of the roller shaft 52 in the direction of going apart from the pad 9 when gap is formed between the pad 9 and feed roller 51.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a sheet conveying apparatus for conveying a sheet such as a sheet, and an image forming apparatus including the sheet conveying apparatus, such as a laser printer.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a laser printer, there is provided a sheet feeding device for separating and feeding sheets stacked one by one on a sheet feeding tray. Such a paper feeding device is described in, for example, Japanese Patent Application Laid-Open No. H11-116084 and is described in FIG.
1 and FIG. 12 are proposed.

In FIG. 11, a paper feeder 101 is
A paper feed roller 102, supporting the paper feed roller 102,
A roller shaft 104 provided with a different diameter bulging portion 103, a roller 105 loosely fitted to the different diameter bulging portion 103, and facing the paper feeding roller 102 with the paper 106 interposed therebetween, and attached toward the paper feeding roller 102. And a paper feed pad 107 to be driven.

When the paper is fed, as shown in FIG. 11, the different diameter bulging portion 103 is in a positional relationship not facing the paper feed pad 107. Therefore, the paper feed roller 102 is pressed by the paper feed pad 107, While the paper 106 is separated and fed one by one between the paper feed roller 102 and the paper feed pad 107, when the paper feeding is completed, as shown in FIG. The position is opposed to the pat 107, so that the rollers 105
3 and moves downward, and is rotatable on the paper 106 so as to form a gap between the paper feed pad 107 and the paper feed roller 102 against the urging force of the paper feed pad 107. Thus, the sheet 106 can be satisfactorily conveyed by the guide roller 108 provided on the upstream side of the sheet supply roller 102.

[0005]

However, in such a paper feeder 101, after the paper 106 has been fed, a gap is not simply formed between the paper feed pad 107 and the paper feed roller 102. In order for the paper 106 to be properly conveyed by the guide roller 108, it is necessary to secure a gap between the paper supply pad 107 and the paper supply roller 102 such that the paper 106 does not contact the paper supply roller 102.
For that purpose, for example, it is necessary to make the different-diameter bulging portion 103 bulge more, and to move the roller 105 further downward.

However, if the vertical movement of the roller 105 is increased, the step at the time of transition from the roller 105 to the paper feed roller 102 or from the paper feed roller 102 to the roller 105 on the contact surface with the paper 106 is increased. In some cases, so-called double feed or double feed, in which a plurality of sheets 106 are simultaneously conveyed, may occur.

That is, at the start of feeding the sheet 106,
As the rollers 105 move upward, the paper feed pad 107
When the movement is large, the paper feed pad 107 moves up and down, and at this moment, the fluctuation of the pressing force on the paper 106 becomes large, and a plurality of papers 106 are simultaneously moved with the paper feed pad 107. The so-called double feed, which enters between the paper feed rollers 102, is likely to occur.

Further, at the end of sheet feeding, the sheet feeding pad 107 also moves downward with the movement of the rollers 105 downward, but if this movement is large, the sheet feeding pad 107 moves up and down. At this moment, the fluctuation of the pressing force on the sheet 106 increases, and the double-feeding, that is, a plurality of sheets 106 to be fed next are conveyed together, is likely to occur.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method in which a sheet is brought into contact with a conveying roller between a conveying roller and a friction member after the sheet is conveyed. A sheet conveyance device capable of forming a gap that can be satisfactorily conveyed without causing the sheet to be conveyed one by one without causing double feeding and double feeding of the sheet, and such a sheet An object of the present invention is to provide an image forming apparatus including a transport device.

[0010]

According to one aspect of the present invention, there is provided a sheet conveying apparatus, comprising: a conveying roller having a circumferential surface for contacting a sheet and conveying the sheet; A roller shaft for supporting and rotating the transport roller, a friction member opposed to the transport roller with a sheet interposed therebetween and urged toward the transport roller, and a support hole; In the predetermined rotation phase, a gap forming member that contacts the friction member and forms a gap between the circumferential surface of the transport roller and the friction member against the urging force of the friction member; The support hole of the gap forming member is loosely supported, and at a predetermined rotation phase of the conveyance roller, the distance from the axis of the roller shaft to the contact portion between the gap formation member and the friction member is determined by the conveyance roller. Larger than the radius of It has a shape that can, and a support means for rotating integrally with the roller shaft, the conveyance roller with respect to the roller shaft, is characterized in that is provided eccentrically.

According to such a configuration, the gap forming member is loosely supported by the support means which rotates integrally with the roller shaft supporting the transport roller. However, in the predetermined rotation phase of the transport roller, the gap forming member is supported. The member forms a gap between the circumferential surface of the transport roller and the friction member against the urging force of the friction member.

In addition, the transport roller is provided with respect to the roller shaft.
Since the conveying roller is rotated eccentrically in a direction away from the friction member in the predetermined rotation phase, the circular shape of the conveying roller formed by the gap forming member is provided. The gap between the peripheral surface and the friction member can be made larger.

Therefore, it is possible to form a gap between the transport roller and the friction member, which can satisfactorily transport the sheet without contacting the transport roller, without increasing the vertical movement of the gap forming member. When the friction member shifts from a state in which the friction member is in contact with the circumferential surface of the conveyance roller to a state in which the friction member is in contact with the gap formation member, and a state in which the friction member is in contact with the gap formation member, the circle of the conveyance roller is changed. When shifting to a state in which the friction member is brought into contact with the peripheral surface, the vertical movement of the friction member can be reduced with almost no step. Therefore, it is possible to form a gap between the transport roller and the friction member that allows the sheet to be satisfactorily transported without bringing the sheet into contact with the transport roller. They can be transported one by one.

[0014] The invention described in claim 2 is the first invention.
In the invention described in (1), in the transport roller, at a predetermined rotation phase of the transport roller with respect to the roller shaft, the gap forming member is configured to rotate the transport roller in a circle against the urging force of the friction member. When a gap is formed between the peripheral surface and the friction member, the circumferential surface of the transport roller is provided so as to be eccentric in a direction away from the friction member.

According to such a configuration, when the gap forming member forms a gap between the circumferential surface of the conveyance roller and the friction member against the urging force of the friction member in the predetermined rotation phase of the conveyance roller. Since the circumferential surface of the conveying roller is eccentric in a direction away from the friction member, the eccentricity of the conveying roller further increases the gap between the circumferential surface of the conveying roller formed by the gap forming member and the friction member. Can be bigger.

Therefore, it is possible to form a gap between the transport roller and the friction member, which can satisfactorily transport the sheet without contacting the transport roller, without increasing the vertical movement of the gap forming member. When the friction member shifts from a state in which the friction member is in contact with the circumferential surface of the conveyance roller to a state in which the friction member is in contact with the gap formation member, and a state in which the friction member is in contact with the gap formation member, the circle of the conveyance roller is changed. When shifting to a state in which the friction member is brought into contact with the peripheral surface, the vertical movement of the friction member can be reduced with almost no step. Therefore, it is possible to reliably form a gap between the conveyance roller and the friction member that can convey the sheet satisfactorily without bringing the sheet into contact with the conveyance roller, and without causing double feeding or double feeding of the sheet. The sheets can be transported one by one without fail.

The invention described in claim 3 is the first invention.
In the invention described in or 2, the gap forming member is
The support hole is formed at the center thereof, and is formed of a circular body having a radius larger than the radius of the transport roller, and the support means is formed by a first radial portion and a first radial portion formed on the roller shaft. A first diameter portion having a second diameter portion also having a small diameter, and a radius of the first diameter portion is a difference between a radius of the gap forming member and a distance from the outer peripheral surface of the gap forming member to the support hole. It is characterized in that it is formed to have a length substantially equal to.

According to this configuration, when the outer peripheral surface of the gap forming member is brought into contact with the friction member via the sheet, the first diameter portion is opposed to the inner peripheral surface of the support hole of the gap forming member. When the circumferential surface of the conveying roller is brought into contact with the friction member via the sheet, if the second diameter portion is opposed to the inner circumferential surface of the support hole of the gap forming member, reliable operation of the gap forming member is ensured. The gap forming member can be moved up and down smoothly. Therefore, the vertical movement of the friction member can be reduced reliably and smoothly, and the sheets can be transported one by one without causing double feeding or double feeding.

The invention described in claim 4 is the same as the invention described in claim 3.
In the invention described in the above, the radius of the first diameter portion and the second
The difference between the radius of the radial portion and the radius of the gap forming member is greater than the difference between the radius of the transport roller and the length obtained by adding the amount of eccentricity.

According to this configuration, when the circumferential surface of the conveying roller is brought into contact with the sheet, the second diameter portion is opposed to the inner circumferential surface of the support hole of the gap forming member, so that the outer circumference of the gap forming member is formed. The surface can freely move radially inward from the circumferential surface of the transport roller. Therefore, when the sheet is conveyed on the circumferential surface of the conveying roller, even if the outer peripheral surface of the gap forming member abuts on the sheet, the sheet is not pressed, and good sheet conveyance can be ensured.

The invention described in claim 5 is the same as the invention in claim 4.
In the invention described in the above, the radius of the first diameter portion and the second
The difference between the radius of the diameter portion and the difference between the radius of the gap forming member and the length obtained by adding the amount of eccentricity to the radius of the conveyance roller, when the circumferential surface of the conveyance roller is pressed by the friction member. It is characterized by being equal to or greater than a value obtained by adding the amount of deformation when the circumferential surface is deformed in the radial direction by the pressing force.

According to such a configuration, when the circumferential surface of the conveying roller is brought into contact with the sheet, even if the circumferential surface is deformed radially inward by the pressing force from the friction member, the first position is maintained.
Since the difference between the radius of the radial portion and the radius of the second radial portion is greater than or equal to the difference between the radius of the gap forming member and the length of the transport roller plus the eccentricity plus the amount of deformation. By making the second diameter portion face the inner peripheral surface of the support hole of the gap forming member, the outer peripheral surface of the gap forming member is
It can be freely movable inward in the radial direction. Therefore, even when the circumferential surface of the conveying roller is deformed radially inward due to the pressing force from the friction member during sheet conveyance on the circumferential surface of the conveying roller, the outer peripheral surface of the gap forming member presses the sheet. And good sheet conveyance can be ensured.

Further, the invention described in claim 6 is the same as claim 3.
In the invention described in any one of the above (1) to (5), the first diameter portion is formed at a position facing the friction member in a predetermined rotation phase of the transport roller, and the second diameter portion is formed of the second diameter portion. It is characterized in that it is formed on the opposite side of the one radial portion.

According to such a configuration, when the conveying roller has a predetermined rotation phase, the first diameter portion faces the inner peripheral surface of the support hole of the gap forming member, so that the outer peripheral surface of the gap forming member holds the sheet. Through the friction member. In addition, when the circumferential surface of the conveying roller contacts and conveys the sheet, the second diameter portion faces the inner peripheral surface of the support hole of the gap forming member, so that the gap forming member can freely move, and It comes into contact with the sheet by its own weight. Therefore, the vertical movement of the friction member can be reduced, and the sheet can be conveyed by the conveying roller without receiving the resistance of the gap forming member.
Therefore, the sheets can be transported one by one without causing double feeding or double feeding of sheets.

The invention described in claim 7 is the first invention.
In the invention according to any one of the first to sixth aspects, the gap forming member is attached to both sides of the transport roller.

According to such a configuration, when the conveyance of the sheet on the circumferential surface of the conveyance roller is completed and the conveyance roller is in a predetermined rotation phase and the gap forming member comes into contact with the sheet, the conveyance roller is positioned on both sides of the conveyance roller. The attached gap forming member reliably forms a gap between the circumferential surface of the transport roller and the friction member against the urging force of the friction member.

According to an eighth aspect of the present invention, there is provided an image forming apparatus including the sheet conveying device according to any one of the first to seventh aspects.

With such a sheet conveying device, a gap can be formed between the conveying roller and the friction member so that the sheet can be satisfactorily conveyed without being brought into contact with the conveying roller. The sheet can be transported one sheet at a time without causing double feeding. Therefore, the occurrence of a jam or the like and the image formation failure can be significantly reduced by favorable sheet conveyance.

[0029]

FIG. 1 is a side sectional view showing a main part of an embodiment of a laser printer as an image forming apparatus according to the present invention. In FIG. 1, a laser printer 1 includes a feeder unit 4 as a sheet conveying device for feeding paper 3 as a sheet in a main body casing 2 and a predetermined image on the fed paper 3. Image forming unit 5 and the like.

The feeder unit 4 includes the main casing 2.
Paper tray 6, detachably mounted on the bottom of the paper tray, a paper pressing plate 7 provided in the paper tray 6, and a paper feed roller unit provided above one end of the paper tray 6 8, a paper feed pad 9 as a friction member, paper dust rollers 10 and 11 provided downstream of the paper feed roller unit 8 in the transport direction of the paper 3, and a paper dust roller 1.
A registration roller 12 is provided on the downstream side in the transport direction of the sheet 3 with respect to 0 and 11.

The sheet pressing plate 7 is capable of stacking the sheets 3 in a stacked manner, and is swingably supported at an end farther from the sheet feeding roller unit 8 so that a nearer end is provided. It is movable in the vertical direction, and is urged upward by a spring (not shown) from the back side. Therefore, as the stacking amount of the paper 3 increases, the paper pressing plate 7 is rotated downward against the urging force of the spring with the end remote from the paper feed roller unit 8 as a fulcrum.
As will be described in detail later, the paper feed roller unit 8 and the paper feed pad 9 are disposed to face each other, and the paper feed pad 9 is moved by a spring 13 disposed on the back side of the paper feed pad 9. It is pressed toward the unit 8. The uppermost sheet 3 on the sheet pressing plate 7 is pressed from the back side of the sheet pressing plate 7 toward the feed roller unit 8 by a spring (not shown), and the rotation of the feed roller unit 8 causes the feed roller unit 8 to rotate. And the paper feed pad 9
Paper is fed one by one. After the paper dust is removed by the paper dust removal rollers 10 and 11, the fed paper 3 is
The sheet is sent to the registration roller 12. Registration roller 12
Is composed of a pair of rollers, and is configured to send the sheet 3 to the image forming unit 5 after a predetermined registration.

The feeder unit 4 further includes a multi-purpose tray 14, a multi-purpose side feed roller unit 15 for feeding the sheets 3 stacked on the multi-purpose tray 14, and a multi-purpose side feed roller unit 15. And a multi-purpose side sheet supply roller unit 15 and a multi-purpose side sheet supply pad 70 are disposed opposite to each other, and a spring 71 disposed on the back side of the multi-purpose side sheet supply pad 70. By
The multipurpose paper feed pad 70 is pressed toward the multipurpose paper feed roller unit 15. The paper 3 stacked on the multi-purpose tray 14 is sandwiched between the multi-purpose side paper feed roller unit 15 and the multi-purpose side paper feed pad 70 by the rotation of the multi-purpose side paper feed roller unit 15 and then, Paper. Note that the multi-purpose side paper feed roller unit 15
Has the same configuration as the sheet feeding roller unit 8 described in detail later.

The image forming unit 5 includes a scanner unit 16, a process unit 17, a fixing unit 18, and the like.

The scanner unit 16 is provided at an upper part in the main body casing 2 and has a laser emitting unit (not shown),
A polygon mirror 19, which is driven to rotate, lenses 20 and 21, reflection mirrors 22, 23 and 24, etc.
A laser beam based on predetermined image data emitted from the laser emitting unit is indicated by a chain line as shown by a polygon mirror 19, a lens 20, reflection mirrors 22 and 23, and a lens 2.
1. The light passes through or is reflected in the order of the reflecting mirror 24, and irradiates the surface of the photosensitive drum 27 of the process unit 17 described later by high-speed scanning.

The process unit 17 is disposed below the scanner unit 16 and includes a photosensitive drum 27, a developing cartridge 28, a scorotron charger 29, A transfer roller 30 and the like are provided. The developing cartridge 28 is detachably attached to the drum cartridge 26, and includes a developing roller 31, a layer thickness regulating blade 32, a supply roller 33, a toner box 34, and the like.

The toner box 34 is filled with a positively chargeable non-magnetic one-component toner as a developer. Examples of the toner include polymerizable monomers such as styrene-based monomers such as styrene, acrylic acid, alkyl (C1 to C4) acrylate, and alkyl (C1 to C4).
4) A polymerized toner obtained by copolymerizing an acrylic monomer such as methacrylate by a known polymerization method such as suspension polymerization is used. Such a polymerized toner is spherical and has extremely good fluidity. In addition, such a toner is blended with a coloring agent such as carbon black, a wax, and the like, and an external additive such as silica is added in order to improve fluidity. The particle size is about 6 to 10 μm.

The toner in the toner box 34 is rotated by a rotating shaft 35 provided at the center of the toner box 34.
The toner is agitated by an agitator 36 supported by the toner box 34 and is discharged from a toner supply port 37 opened on the side of the toner box 34. A window 38 for detecting the remaining amount of toner is provided on the side wall of the toner box 34,
The cleaning is performed by the cleaner 39 supported by the cleaning member 5.

A supply roller 33 is rotatably disposed at a side position of the toner supply port 37, and a developing roller 31 is rotatably disposed opposite the supply roller 33. . The supply roller 33 and the developing roller 31 are in contact with each other so that each of them is compressed to some extent.

The supply roller 33 is connected to a metal roller shaft.
A roller made of a conductive foam material is covered. The developing roller 31 has a metal roller shaft covered with a roller made of a conductive rubber material. More specifically, the roller portion of the developing roller 31 has a coating layer of urethane rubber or silicone rubber containing fluorine on the surface of a roller body made of conductive urethane rubber or silicone rubber containing fine carbon particles or the like. Coated. The developing roller 31 includes a photosensitive drum 27.
, A predetermined developing bias is applied.

A layer thickness regulating blade 32 is provided near the developing roller 31. The layer thickness regulating blade 32 has a pressing portion 40 having a semicircular cross section made of insulating silicone rubber at the tip of a blade body made of a metal leaf spring material. 28, the pressing portion 40 is configured to be pressed against the developing roller 31 by the elastic force of the blade body.

The toner discharged from the toner supply port 37 is supplied to the developing roller 3 by the rotation of the supply roller 33.
1, the supply roller 33 and the developing roller 3
1 is positively triboelectrically charged, and the developing roller 31
The toner supplied above is pressed by the pressing portion 40 of the layer thickness regulating blade 32 and the developing roller 3 with the rotation of the developing roller 31.
1 and is further triboelectrically charged and carried on the developing roller 31 as a thin layer having a constant thickness.

The photosensitive drum 27 is rotatably disposed at a side position of the developing roller 31 so as to face the developing roller 31. This photosensitive drum 27
The drum body is grounded, and its surface is formed of a positively charged photosensitive layer made of polycarbonate or the like.

The scorotron charger 29 is arranged above the photosensitive drum 27 at a predetermined interval so as not to contact the photosensitive drum 27. The scorotron charger 29 is a positive scorotron charger for generating corona discharge from a charging wire such as tungsten, and is configured to uniformly charge the surface of the photosensitive drum 27 to a positive polarity. ing.

After the surface of the photosensitive drum 27 is uniformly charged positively by the scorotron charger 29, the surface is exposed by high-speed scanning of a laser beam from the scanner unit 16, and an electrostatic latent image based on predetermined image data is obtained. An image is formed. Next, by the rotation of the developing roller 31, the toner that is carried on the developing roller 31 and is positively charged,
When the photosensitive drum 27 is opposed to and contacts the photosensitive drum 27, the photosensitive drum 2
The electrostatic latent image formed on the surface of the photosensitive drum 27, that is, the surface of the uniformly positively charged photosensitive drum 27, which is exposed to a laser beam and has a reduced potential, is supplied to the photosensitive drum 27 and selectively carried. Is visualized by
Thereby, reversal development is achieved.

The transfer roller 30 is disposed below the photosensitive drum 27 so as to face the photosensitive drum 27 and is rotatably supported by the drum cartridge 26. The transfer roller 30 has a metal roller shaft covered with a roller made of a conductive rubber material, and a predetermined transfer bias is applied to the photosensitive drum 27. Therefore, the visible image carried on the photosensitive drum 27 is transferred to the sheet 3 while the sheet 3 passes between the photosensitive drum 27 and the transfer roller 30.

The fixing unit 18 includes the process unit 1
7, a heating roller 41, a pressing roller 42 pressing the heating roller 41, and a pair of transport rollers 43 provided downstream of the heating roller 41 and the pressing roller 42. I have. Heating roller 41
Is made of metal and has a halogen lamp for heating. The process unit 17 transfers the toner transferred onto the sheet 3 to the sheet 3 using the heating roller 41 and the pressing roller 42.
And heat-fixed while passing between
Is conveyed to a paper discharge path 44 by a conveying roller 43. The sheet 3 sent to the sheet ejection path 44 is sent to a sheet ejection roller 45, and is ejected onto a sheet ejection tray 46 by the sheet ejection roller 45.

In the laser printer 1, the photosensitive drum 2 is transferred to the sheet 3 by the transfer roller 30.
The remaining toner is collected by a developing roller 31 by a so-called cleaner-less method. If the toner remaining on the photosensitive drum 27 is collected by such a cleanerless system, there is no need to provide a cleaner device such as a blade or a storage means for waste toner, so that the device configuration can be simplified, downsized, and reduced in cost. Can be achieved.

The laser printer 1 has a paper 3
Reverse image forming unit 47 for forming images on both sides of
Is provided. The reverse transport unit 47 includes a paper discharge roller 45, a reverse transport path 48, a flapper 49,
A plurality of reverse transport rollers 50;

The paper discharge roller 45 is composed of a pair of rollers, and is configured to be able to switch between normal rotation and reverse rotation. As described above, this paper discharge roller 45
When the paper 3 is discharged onto the paper discharge tray 46, the paper rotates in the forward direction. When the paper 3 is reversed, the paper 3 rotates in the reverse direction.

The reverse transport path 48 is configured to transport the sheet 3 from the discharge roller 45 to a plurality of reverse transport rollers 50 disposed below the image forming unit 5.
It is provided along the up and down direction, and its upstream end is
It is arranged near the paper discharge roller 45, and its downstream end is arranged near the reverse conveyance roller 50.

The flapper 49 is swingably provided so as to reach a branch portion between the paper discharge path 44 and the reverse transport path 48. The flapper 49 is inverted by a paper discharge roller 45 by excitation or non-excitation of a solenoid (not shown). The transport direction of the fed sheet 3 can be switched from the direction toward the discharge path 44 to the direction toward the reverse transport path 48.

A plurality of reversing conveyance rollers 50 are provided in a substantially horizontal direction above the sheet feeding tray 6, and the most upstream reversing conveyance roller 50 is arranged near the rear end of the reversing conveyance path 48. In addition, the most downstream reverse transport roller 50 is provided below the registration roller 12.

When images are formed on both sides of the sheet 3, the reverse transport unit 47 is operated as follows. That is, the sheet 3 on which an image is formed on one side
Is transported from the paper discharge path 44 to the paper discharge roller 45 by the transport roller 43, the paper discharge roller 45 rotates forward with the paper 3 sandwiched therebetween, and temporarily moves the paper 3 to the outside (the paper discharge tray 46). Side), most of the sheet 3 is sent to the outside, and the normal rotation is stopped when the rear end of the sheet 3 is sandwiched by the sheet discharging rollers 45. Next, the paper discharge roller 45 rotates in the reverse direction, and the flapper 49 switches the transport direction so that the paper 3 is transported to the reverse transport path 48.
The sheet 3 is transported to the reverse transport path 48 in a state where the paper 3 is reversed. When the conveyance of the sheet 3 is completed, the flapper 49 is switched to the original state, that is, the state in which the sheet 3 sent from the conveying roller 43 is sent to the sheet discharging roller 45. Next, the sheet 3 transported in the reverse direction to the reverse transport path 48 is transported to the reverse transport roller 50, from which the paper 3 is inverted upward and sent to the registration roller 12. The sheet 3 conveyed to the registration roller 12 is again turned upside down and sent to the image forming unit 5 after a predetermined registration, whereby a predetermined image is formed on both sides of the sheet 3.

In the laser printer 1, as described above, the feeder unit 4 is provided with the paper feed roller unit 8 and the paper feed pad 9.

That is, the paper feed roller unit 8
As shown in FIGS. 2 to 4, a feed roller 51 serving as a transport roller and a roller shaft 52 supporting the feed roller 51 are provided.
And rollers 53 as gap forming members attached to both axial sides of the paper feed roller 51.

The paper feed roller 51 includes a cylindrical portion 55 made of a resin member, and a roller portion 56 made of an elastic member that covers around the cylindrical portion 55. This roller section 56
Is formed as a predetermined pattern so that the sheet 3 can be conveyed by contacting the sheet 3.

The roller shaft 52 is made of a resin member, and is integrally formed with the cylindrical portion 55 so as to protrude from the cylindrical portion 55 of the paper feed roller 51 in both axial directions. Further, at the base end of each roller shaft 52, a different diameter shaft portion 57 is integrally formed as support means for loosely supporting a roller 53 described below. Note that the different diameter shaft portion 57 may be formed separately from or separately from the roller shaft 52.

The roller 53 is made of a resin member, has a support hole 58 formed at the center thereof, is formed as a hollow circular body having a radius larger than the radius of the paper feed roller 51, and has a different diameter shaft portion of the roller shaft 52. 57 is rotatably fitted and supported rotatably.

As shown in FIG. 4A, a first diameter portion 59 and a second diameter portion 60 are formed on the different diameter shaft portion 57, and the radius 64 of the first diameter portion 59 is , The distance from the axis of the roller shaft 52 to the contact portion between the roller 53 and the paper feed pad 9
As shown in FIG. 4B, the difference between the radius 63 of the roller 53 and the distance 63 from the outer peripheral surface 62 to the support hole 58 shown in FIG. The length, that is, the length is substantially equal to the radius 67 of the support hole 58.

The second diameter part 60 is formed to have a smaller diameter than the first diameter part 59, and the difference between the radius 64 of the first diameter part 59 and the radius 65 of the second diameter part 60 is equal to that of the rollers 53. Is formed to be larger than the difference between the radius 61 of the paper feed roller 51 and the radius 66 of the paper feed roller 51. Thus, in a state where the first radial portion 59 is in contact with the inner peripheral surface of the support hole 58 of the roller 53, a predetermined play (interval) exists between the second radial portion 60 and the inner peripheral surface of the support hole 58. Is formed.

More specifically, as described later,
The difference between the radius 64 of the first diameter portion 59 and the radius 65 of the second diameter portion 60 is the radius 61 of the roller 53 and the radius 66 of the paper feed roller 51.
When the circumferential surface 54 of the paper feed roller 51 is pressed against the paper feed pad 9, a difference between the length of the circumferential surface 54 and the length (the amount of eccentricity in the claims) obtained by adding a displacement amount α described later to the circumferential surface 54 is formed to have a value equal to or greater than a value obtained by adding a deformation amount when deformed in the radial direction.

Further, the first diameter portion 59 has a predetermined rotation phase of the paper feed roller 51, that is, a standby state (0 °) described later.
And in the transport state (360 °), the second diameter portion 60 is formed so as to face the paper feed pad 9.
It is formed on the opposite side of the first diameter part 59.

The first diameter part 59 and the second diameter part 6
0 are formed, and each of them is
If it is made to abut on the inner peripheral surface of, as described later,
When the first diameter portion 59 is located at a position facing the paper feed pad 9, the pressing force from the paper feed pad 9 causes the rollers 53 to be pressed against the paper feed pad 9, and the circumferential surface of the paper feed roller 51. A predetermined gap can be formed between the sheet feeding pad 9 and the second diameter portion 59.
When the sheet is located at a position facing the sheet feeding pad 9, the circumferential surface 54 of the sheet feeding roller 51 can be pressed against the sheet feeding pad 9 by the pressing force from the sheet feeding pad 9.

Therefore, the first diameter portion 59 and the second diameter portion 60 are formed, and each of them is
By contacting the inner peripheral surface of the support hole 58, the vertical movement of the roller 53 can be ensured, and the roller 53 can be smoothly moved up and down.

In the paper feed roller unit 8,
The paper feed roller 51 is provided such that its rotation center 69 is eccentric with respect to the axis of the roller shaft 52. More specifically, as shown in FIG. 4A, the circumferential surface 54 of the paper feed roller 51 is separated from the paper feed pad 9 in a standby state (0 °) and a transport state (360 °) described later. From the axis of the roller shaft 52 in order to decenter in the direction
The paper feed roller 51 is configured to move from the state shown in FIG. 4A by a displacement amount α with respect to the roller shaft 52 so that the decentered position becomes the rotation center 69 of the paper feed roller 51. I have.

As shown in FIGS. 5 to 9, the paper feed pad 9 includes a support shaft 72, a receiving member 73, and a pad member 74. The receiving member 73 has a plate shape extending in the transport direction of the sheet 3, is disposed to face the sheet feeding roller unit 8, and is swingably supported by a support shaft 72 at a downstream end thereof. The pad member 74 is made of a friction member having a friction coefficient capable of separating the sheets 3 one by one, and is fitted on the upper surface of the receiving member 73.
Since the receiving member 73 is urged toward the paper feed roller unit 8 by the urging force of the spring 13 from the back surface side, the receiving member 73 swings with the support shaft 72 as a fulcrum. Is pressed toward the paper feed roller unit 8.

Next, the operation of feeding the sheets 3 one by one by the feed roller unit 8 and the feed pad 9 will be described with reference to FIGS.
In the phase graph shown in FIG. 10, the radius of the feed roller 51 is 17 mm, the radius of the first radial portion 59 of the roller shaft 52 is 5.4 mm, and the radius of the second radial portion 60 of the roller shaft 52 is 4 m.
m, the radius of the roller 53 is 17.5 mm, the radius of the support hole 58 of the roller 53 is 5.4 mm, and the rotation center 69 of the paper feed roller 51 is in the standby state (0 °) and the transport state (360). °), the rollers 53 and the pad member 7
In the description, an example in which the displacement amount is eccentric by 0.2 mm in a direction extending from the point where the roller 4 is in contact with the axis of the roller shaft 52 is described.

First, as shown in FIG. 5, the standby state (0
In (°), since the first radial portion 59 faces the paper feed pad 9, the pressing force from the paper feed pad 9 causes the first radial portion 59 to contact the inner peripheral surface of the support hole 58 of the roller 53, and
As a result, the distance from the axis of the roller shaft 52 to the outer peripheral surface 62 of the roller 53 on the line connecting the pad member 74 and the axis of the roller shaft 52 becomes longer than the radius 66 of the paper feed roller 51. The outer peripheral surface 62 of 53 is positioned closer to the paper feed pad 9 (lower side) than the circumferential surface 54 of the paper feed roller 51. Therefore, the outer peripheral surface 62 of the roller 53 comes into contact with the paper feed pad 9, and a gap is formed between the circumferential surface 54 of the paper feed roller 51 and the paper feed pad 9.

In this standby state (0 °), FIG.
As shown in FIG. 0, the circumferential surface 54 of the paper feed roller 51 is eccentric in the direction away from the paper feed pad 9. The gap with the paper feed pad 9 is formed larger.

Next, as shown in FIGS. 6 to 8, at the time of paper feeding (60 ° to 300 °), the support holes 58 of the rollers 53 are provided.
The first diameter portion 59 that has been in contact with the inner peripheral surface of the paper is separated, and then the second diameter portion 60 faces the paper feed pad 9,
Since the second diameter portion 60 contacts the inner peripheral surface of the support hole 58 of the roller 53, the distance from the axis of the roller shaft 52 to the outer peripheral surface 62 of the roller 53 is larger than the radius 66 of the paper feed roller 51. The outer circumferential surface 54 of the paper feed roller 51 moves so that the circumferential surface 54 of the paper feed roller 51 is positioned closer to (the lower side of) the paper feed pad 9 than the outer circumferential surface 62 of the roller 53. The paper 54 comes into contact with the paper 3 and the paper 3 is fed as it is by the rotation of the paper feed roller 51.

Then, in this paper feeding state (60 ° to 300 °)
In (°), as shown in FIG. 10, the circumferential surface 54 of the paper feed roller 51 is eccentric in the direction approaching the paper feed pad 9,
By the eccentricity of the paper feed roller 51, the paper feed roller 51 can be satisfactorily brought into contact with the paper 3 and the paper 3 can be satisfactorily fed.

At the start of sheet feeding (60 °),
As shown in FIG. 6, when the paper 3 enters between the paper supply roller 51 and the paper supply pad 9, the pressing force from the paper supply pad 9, which has been received by the rollers 53, is applied via the paper 3. At this time, on the inner peripheral surface of the support hole 58, the first radial portion 59 separates and the second radial portion 60 abuts on the inner peripheral surface of the support hole 58, and the roller 53 The outer peripheral surface 62 gradually moves upward, and at the same time, the circumferential surface 54 of the paper feed roller 51 is eccentric in a direction approaching the paper feed pad 9. Without making any steps
Paper 3 can be fed smoothly. Therefore, the sheets 3 can be fed one by one without causing double feeding.

Next, as shown in FIG. 7, during the paper feeding, the difference between the radius 64 of the first radial portion 59 and the radius 65 of the second radial portion 60 is determined by the radius 61 of the roller 53 and the paper feeding roller 51. Is larger than the length obtained by adding the displacement amount α to the radius 66, and the rollers 53 can freely move in the direction of the arrow 68 because the second diameter portion 60 faces the paper feed pad 9. Although it becomes movable, the outer peripheral surface 62 always comes into contact with the sheet 3 by its own weight. (Such a state is indicated by a dotted line in FIG. 10, for example.) However, since the rollers 53 are simply brought into contact with the paper 3 by their own weight, the outer peripheral surface 62 of the rollers 53 comes into contact with the paper 3. Even if the sheet 3 comes into contact with the sheet 3, the sheet 3 is not pressed, and a favorable sheet feeding operation can be ensured.

During the paper feeding, the circumferential surface 54 of the paper feeding roller 51 formed by the elastic member is pressed radially inward (in the direction of arrow 68) by the pressing force from the paper feeding pad 9. The radius 64 of the first radius 59 and the radius 65 of the second radius 60 are
Difference between the radius 61 of the roller 53 and the length obtained by adding the displacement amount α to the radius 66 of the feed roller 51,
When the circumferential surface 54 is pressed by the paper feed pad 9, the circumferential surface 54 is formed to have a value equal to or greater than the value obtained by adding the deformation amount when the circumferential surface 54 is deformed in the radial direction by the pressing force. Even if such deformation occurs, the outer peripheral surface 62 of the roller 53 does not press the paper 3, and a favorable paper feeding operation can be ensured.

At the end of sheet feeding (300 °), as shown in FIG. 8, when the sheet 3 separates from the circumferential surface 54 of the sheet feeding roller 51, the circumferential surface 54 of the sheet feeding roller 51 The outer peripheral surface 62 of the roller 53 receives again the pressing force from the paper feed pad 9 which has been received through the third diameter portion 3 at this time. At the same time when 60 is separated, the first diameter portion 59 abuts, and the outer peripheral surface 62 of the roller 53 gradually moves downward,
At the same time, the circumferential surface 54 of the paper feed roller 51
The roller 53 is eccentric in the direction away from the paper feeding pad 9 and
The paper 3 can be fed smoothly without increasing the downward movement and with almost no level difference. Therefore, the sheets 3 can be fed one by one without causing the double feeding of the sheets 3.

Then, as shown in FIG.
60 °), the paper 3 is conveyed by the registration roller 12, while the paper feed roller unit 8
9 again faces the paper feed pad 9 and stops in that state, so that the pressing force from the paper feed pad 9 causes the first diameter portion 59 to abut on the inner peripheral surface of the support hole 58 of the roller 53, The outer peripheral surface 62 of the roller 53 is positioned closer to the paper feed pad 9 (lower side) than the circumferential surface 54 of the paper feed roller 51, and the outer peripheral surface 62 of the roller 53 comes into contact with the paper feed pad 9 to supply the paper. A gap is formed between the paper roller 51 and the paper feed pad 9.

Then, in this transport state (360 °),
As shown in FIG. 10, the circumferential surface 54 of the paper feed roller 51
The eccentricity of the paper feed roller 51 causes the gap between the paper feed roller 51 formed by the rollers 53 and the paper feed pad 9 to be eccentric in a direction away from the paper feed pad 9.
It is formed larger. Therefore, a gap can be formed between the paper feed roller 51 and the paper feed pad 9 so that the paper 3 can be satisfactorily conveyed without making contact with the paper feed roller 51. As a result, the paper feed roller 51 and the paper 3 can be satisfactorily conveyed without rubbing with the sheet 3.

Further, as described above, at the start and end of sheet feeding, the sheet feeding pad 9 is brought into contact with the circumferential surface 54 of the sheet feeding roller 51 via the sheet 3 from the state described above. When transitioning to a state in which the roller 53 comes into contact with the outer peripheral surface 62, and when transitioning from a state in which the roller 53 comes into contact with the outer peripheral surface 62 to a state in which the roller 53 comes into contact with the peripheral surface 54 of the sheet feeding roller 51, Since there is almost no level difference and the vertical movement of the paper feed pad 9 can be reduced, the paper 3 can be transported one sheet at a time without causing double feed or double feed.

Since the rollers 53 are mounted on both sides of the paper feed roller 51, the urging force of the paper feed pad 9 when the rollers 53 rotatably contact the paper 3 in the transport state (360 °). Therefore, a gap can be reliably formed between the circumferential surface 54 of the paper feed roller 51 and the paper feed pad 9 and the paper 3 can be satisfactorily conveyed.

In the laser printer 1 provided with such a feeder unit 4, the occurrence of jams and the like and image formation defects can be greatly reduced by feeding the sheet 3 well.

In the above description, the sheet conveying device of the present invention has been mainly described as the sheet feeding roller unit 8 and the sheet feeding pad 9 of the feeder unit 4. However, the sheet conveying device of the present invention has a sheet-like shape. Is not limited to this, and can be used for various purposes.

[0082]

As described above, according to the first aspect of the present invention, a gap is formed between the conveying roller and the friction member so that the sheet can be satisfactorily conveyed without contacting the conveying roller. In addition, the sheets can be transported one by one without causing double feeding or double feeding.

According to the second aspect of the present invention, it is possible to reliably form a gap between the transport roller and the friction member so that the sheet can be satisfactorily transported without bringing the sheet into contact with the transport roller. Can be transported one sheet at a time without causing double feeding or double feeding.

According to the third aspect of the present invention, the gap forming member can be reliably operated, and the gap forming member can be smoothly moved up and down. Therefore, the vertical movement of the friction member can be reduced reliably and smoothly, and the sheet can be reliably moved without causing double feeding or double feeding of the sheet.
It can be conveyed one by one.

According to the fourth aspect of the present invention, when the sheet is conveyed on the circumferential surface of the conveying roller, the sheet is not pressed even if the outer peripheral surface of the gap forming member comes into contact with the sheet. Sheet conveyance can be ensured.

According to the fifth aspect of the present invention, even if the circumferential surface of the conveying roller is deformed radially inward by the pressing force from the friction member during sheet conveyance on the circumferential surface of the conveying roller,
The outer peripheral surface of the gap forming member does not press the sheet,
Good sheet conveyance can be ensured.

According to the sixth aspect of the present invention, the vertical movement of the friction member can be reduced, and the conveying roller can convey the sheet without receiving the resistance of the gap forming member. Therefore, the sheets can be transported one by one without causing double feeding or double feeding of sheets.

According to the seventh aspect of the present invention, when the transport roller is in a predetermined rotation phase, the gap forming members attached to both sides of the transport roller have the circumferential surface of the transport roller opposed to the urging force of the friction member. A gap can be reliably formed between the friction member and the friction member.

According to the eighth aspect of the present invention, the occurrence of jams and the like and the image formation failure can be greatly reduced by good sheet conveyance.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a main part of an embodiment of a laser printer as an image forming apparatus of the present invention.

FIG. 2 is a perspective view showing a paper feed roller unit of the laser printer shown in FIG.

FIG. 3 is a sectional view of the sheet feeding roller unit shown in FIG. 2;

4A and 4B are side views of the sheet feeding roller unit shown in FIG. 2, wherein FIG. 4A is a side view of a transport roller, and FIG.

FIG. 5 is a side view showing a sheet feeding operation of the sheet feeding roller unit shown in FIG. 2 and showing a standby state.

FIG. 6 is a side view showing a sheet feeding operation in the sheet feeding roller unit shown in FIG. 2 and showing a state at the time of starting sheet feeding.

FIG. 7 is a side view showing a sheet feeding operation of the sheet feeding roller unit shown in FIG.

FIG. 8 is a side view showing a sheet feeding operation in the sheet feeding roller unit shown in FIG. 2 and showing a state when the sheet feeding is completed.

FIG. 9 is a side view showing a sheet feeding operation of the sheet feeding roller unit shown in FIG. 2 and illustrating a state during sheet conveyance.

10 is a diagram illustrating a sheet feeding operation of the sheet feeding roller unit illustrated in FIG. 2, wherein a distance between a roller circumferential surface and a roller outer circumferential surface from an axis of the roller shaft when the sheet feeding roller is rotated once; 6 is a phase graph showing the displacement of.

FIG. 11 is a side view (at the time of paper feeding) of a conventional paper feeding roller.

FIG. 12 is a side view of a conventional paper feed roller (at the end of paper feed).

[Explanation of symbols]

 Reference Signs List 1 laser printer 3 paper 4 feeder unit 8 paper feed roller unit 9 paper feed pad 51 paper feed roller 52 roller shaft 53 roller 54 circumferential surface of paper feed roller 58 roller support hole 57 different diameter shaft portion 59 first diameter portion 60 Second Radial Part 61 Radius of Roller 62 Outer Peripheral Surface of Roller 63 Distance from Outer Peripheral Surface of Roller to Support Hole 64 Radius of First Radial Part 65 Radius of Second Radial Part 66 Radius of Feed Roller

Claims (8)

[Claims] A transport roller having a circumferential surface for transporting the sheet in contact with the sheet, a roller shaft for supporting and rotating the transport roller, facing the transport roller with the sheet interposed therebetween, A friction member urged toward the conveyance roller; and a support hole. The conveyance member contacts the friction member at a predetermined rotation phase of the conveyance roller, and conveys the conveyance member against the urging force of the friction member. A gap forming member that forms a gap between a circumferential surface of a roller and the friction member; a support hole of the gap forming member that is loosely supported; and a shaft of the roller shaft in a predetermined rotation phase of the transport roller. Supporting means that has a shape that allows a distance from the center to a contact portion between the gap forming member and the friction member to be larger than a radius of the transport roller, and that rotates integrally with the roller shaft; The transport Over La is, with respect to the roller axis, and being provided with an eccentric, the sheet conveying device. 2. The conveyance roller according to claim 1, wherein, at a predetermined rotation phase of the conveyance roller with respect to the roller shaft, the gap forming member is configured to rotate around the circumference of the conveyance roller against a biasing force of the friction member. The peripheral surface of the conveyance roller is provided so as to be eccentric in a direction away from the friction member when a gap is formed between the surface and the friction member. Sheet conveying device. 3. The gap forming member is formed of a circular body having the support hole formed at the center thereof and having a radius larger than the radius of the transport roller, and the support means is formed on the roller shaft. A first diameter portion and a second diameter portion having a smaller diameter than the first diameter portion, wherein the first diameter portion has a radius different from a radius of the gap forming member and a radius of the gap forming member; The sheet conveying device according to claim 1, wherein the sheet conveying device is formed to have a length substantially equal to a difference from a distance from an outer peripheral surface to a support hole. 4. A difference between a radius of the first diameter portion and a radius of the second diameter portion is larger than a difference between a radius of the gap forming member and a length obtained by adding an eccentricity to a radius of the transport roller. The sheet conveying device according to claim 3, wherein: 5. The difference between the radius of the first diameter portion and the radius of the second diameter portion is defined as the difference between the radius of the gap forming member and the length obtained by adding the eccentricity to the radius of the conveyance roller. The method according to claim 4, wherein when the circumferential surface of the conveying roller is pressed by the friction member, the pressing force is equal to or greater than a value obtained by adding an amount of deformation when the circumferential surface is deformed in a radial direction. The sheet conveying device as described in the above. 6. The first diameter portion is formed at a position facing the friction member in a predetermined rotation phase of the transport roller, and the second diameter portion is opposite to the first diameter portion. 6. The semiconductor device according to claim 3, wherein:
The sheet conveying device according to any one of the above. 7. The apparatus according to claim 1, wherein the gap forming member is attached to both sides of the transport roller.
7. The sheet conveying device according to any one of items 1 to 6, above. 8. An image forming apparatus comprising the sheet conveying device according to claim 1.