JP2000351470A - Sheet material conveying device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hold conveying accuracy constant regardless of the thickness or the size of a sheet material. SOLUTION: In a sheet material conveying device, a sheet material having the different thickness and size is pinched by a roller pair 4, 5 in which a pinch roller 5 having the front surface of a member such as rubber having the high coefficient of friction and a conveying roller 4 of a rigid material such as iron arranged so as to face the pinch roller 5 are brought into pressure-contact with each other by taking the axial center intersecting with the conveying direction as a reference. The pinch roller 5 is axially divided, and rotatable guide rollers 16 having the hardness higher than rubber of a roller 14 and having the diameter smaller than that of the roller 14 are provided on both ends of the roller 14 in the axial central part, out of the divided rollers 13, 14 and 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying apparatus for pinching and conveying a sheet, and more particularly to a sheet conveying apparatus used for an image forming apparatus such as a copying machine or a printer.

[0002]

2. Description of the Related Art Most of conveying devices for sheet materials (especially thin sheet materials) such as plain paper use a pair of rollers. This consists of a rubber roller having a member with a high coefficient of friction such as rubber on the surface, and a pressure roller made of a hard material such as iron pressed against the rubber roller. This is a mechanism for rotating the rollers and transporting them by the frictional force.

In this mechanism, the distortion of the rubber surface of the rubber roller affects the transfer accuracy. The rubber of the rubber roller is crushed by the pressure of the pressure roller via the sheet material, and the surface is stretched due to the incompressible property. Since the rubber roller contacts and conveys the sheet material in a state where the surface is stretched, the sheet material is conveyed at a speed higher than the conveying speed calculated from the roller diameter of the design value before the stretching, by an amount corresponding to the elongation.

Further, if there is a non-uniformity in the floating force of the gear driving the roller or the load position at both ends which is unavoidable in design, the rubber surface of the rubber roller on the left and right sides (both sides in the width direction intersecting the conveying direction) of the sheet material is affected. Since the amount of distortion is different, the conveyance speed is different, and as a result, conveyance failure such as skew occurs.

Conventionally, the influence of this inaccuracy has been reduced by changing the thickness or rubber hardness of the rubber, or by adjusting the strength of the right and left loads in anticipation of uneven loads. I was

[0006]

However, even with the above-described method, it is not possible to prevent a difference in conveyance accuracy when sheet materials having different thicknesses and sizes are pinched and conveyed by the same roller pair.

For example, when A4 high quality paper (about 80 μm thick) is sandwiched between the pair of rollers 51 and 52 as a sheet material,
As shown in FIG. 5, since the sheet material 56a is thin and wide, the rubber rollers 53 and 55 and the pressure roller 52 directly contact the outside of the sheet material 56a, and the pressure applied to the sheet material 56a is Distributed. Therefore, the unevenness of the pressure on the left and right (both sides in the width direction) which causes the skew is small.

On the other hand, as a sheet material, a postcard (having a thickness of about 200
μm) between the roller pairs 51 and 52, FIG.
As shown in FIG. 5, since the sheet material 56b is thick, the rollers (rubber rollers 53, 55) are located immediately beside the sheet material 56b.
And the pressure roller 52) float without contact. In addition to the fact that the width of the sheet material itself is narrow, the unevenness of the pressure is further amplified, the transport speed becomes uneven left and right, and skew tends to occur.

The result of analyzing the above phenomenon is shown in the graph of FIG. FIG. 7 shows a contact force distribution when two types of sheet materials having the same width (100 mm) and different thicknesses (80 μm and 200 μm) are sandwiched by the same roller pair. Since the fixing positions of the roller pairs are not uniform left and right, the contact force is not symmetric. The graph is divided into three parts because the rubber roller is divided into three parts in the axial direction as shown in FIGS. The sheet material having a width of 100 mm is in contact only with the center rubber roller 54.

As can be seen from this graph, the paper thickness is 80 μm.
In this case, the contact force is applied to the left and right rubber rollers 53 and 55, and the contact force of the center roller 54 is almost non-uniform. However, when the paper thickness becomes 200 μm, the contact force between the left and right rubber rollers 53 and 55 becomes 0 (that is, floats), so that the load concentrates on the central roller 54 and the contact force between the right and left Heterogeneity is also amplified.

Accordingly, the present invention has been made in view of the above-mentioned problems, and an object of the present invention is to make it possible to keep the conveying accuracy constant irrespective of the difference in thickness and size of the sheet material. is there.

[0012]

To achieve the above object, a typical configuration of the present invention comprises a first roller having a member having a high coefficient of friction such as rubber on its surface, and a first roller facing the first roller. Sheet material transport that sandwiches and transports sheet materials of different thicknesses and sizes with reference to the center in the axial direction that intersects the transport direction, using a roller pair that is pressed against a second roller made of a hard material such as iron that is provided. In the apparatus, the first roller is divided in the axial direction, and among the divided first rollers, both ends of the roller at the center in the axial direction have higher hardness than rubber of the roller, and have a diameter larger than that of the roller. A small rotatable guide roller is provided.

The radius of the guide roller is made smaller by about 10 μm to 200 μm than the radius of the roller.

[0014] The guide roller is a roller provided with rubber, plastic or the like having a higher hardness than the rubber of the first roller.

According to the above configuration, even when a thick and small sheet material is pinched and conveyed, the pressure between the central roller of the divided first rollers and the sheet material is increased. Since the guide rollers as described above are provided at both ends of the central roller, the amount of rubber crushing of the first roller does not become smaller than the diameter of the guide roller, and pressure unevenness on the left and right is also reduced. Since the sheet does not come out, skew of the sheet material can be prevented, and the distortion amount of the rubber surface, that is, the conveyance accuracy can be kept constant regardless of the type of the sheet material.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a sheet conveying apparatus to which the present invention is applied will be specifically described with reference to the drawings. In the following embodiments, a sheet conveying device used in an image forming apparatus will be described as an example.

[First Embodiment] FIG. 1 to FIG. 4 show an image forming apparatus provided with a sheet conveying apparatus according to a first embodiment.
This will be described in detail with reference to FIG.

First, the overall schematic configuration of the image forming apparatus will be described with reference to FIG. FIG. 4 is a partial cross-sectional view of a process in which a sheet material is nipped and conveyed by a conveying unit of the image forming apparatus, as viewed from a side.

In FIG. 4, reference numeral 4 denotes a conveying roller, and 5 denotes a pinch roller. The pinch roller 5 is pressed against the conveying roller 4 by a spring (not shown). The transport roller 4 is a grindstone roller in which fine particles such as a grindstone and alumina are adhered to the roller surface, and the pinch roller 5 is a rubber roller. When the transport roller 4 is a grindstone roller, the outer diameter accuracy and the runout accuracy of the transport roller 4 can be improved as compared with the conventional rubber roller. Therefore, the conveyance accuracy of the sheet material 3 can be improved more than when the conveyance roller 4 is a rubber roller. The transport roller 4 cooperates with the pinch roller 5 to serve as a transport unit that transports the sheet material in the transport direction (the direction of the arrow A in the figure). Transport roller 4
Is performed by driving a not-shown transport motor,
As a result, the sheet material 3 is conveyed by a predetermined amount. A PE sensor lever 1 and a PE sensor 2 are provided upstream of the transport roller 4 and the pinch roller 5 in the sheet transport direction, and serve as sheet material detecting means for detecting the presence or absence and the end of the sheet material 3. I have.

The recording section 6 as an image forming means is provided with a guide shaft 9 for enabling the carriage 8 to reciprocate in a direction perpendicular to the direction of transport of the sheet material 3 (the direction of arrow A). A recording head 7 is mounted on the carriage 8, and the recording head 7 records an ink image on the sheet material 3 conveyed on the platen 10 by the conveying roller 4 and the pinch roller 5. is there. In addition, this apparatus uses an ink jet recording method in which ink is ejected from a recording head for recording. A spur 12 is pressed against the discharge roller 11 by a spring (not shown) and functions as a pinch roller of the discharge roller 11. The discharge roller 11 and the spur 12 cooperate to discharge the sheet material 3 onto a discharge tray (not shown) without soiling the recording surface of the sheet material 3 on which recording has been performed.

Next, a transport device for nipping and transporting a sheet material will be described in detail with reference to FIGS. 1 to 3
FIG. 2 is a diagram illustrating a schematic configuration and an operation state of a roller pair which is a transport device according to the embodiment.

As shown in FIG. 1, the pinch roller 5, which is the first roller, is divided into three rollers 13, 14, and 15 in the axial direction intersecting the sheet material conveying direction. Further, among the above rollers, the roller
A rotatable guide roller 16 made of a hard material such as plastic having a higher hardness than that of the rubber 14 is provided. The diameter of the guide roller 16 is several tens μm more than that of the rubber roller 14.
m smaller. Further, when a thick and narrow sheet material 3b such as a postcard is sandwiched, the dividing position of each rubber roller is determined so that the sheet material 3b does not touch the rubber rollers 13 and 15 on both sides in the axial direction. The guide rollers 16 at both ends of the roller 14 at the center are also provided at positions not protruding from the sheet material 3b.

FIGS. 2 and 3 illustrate a state in which sheet members 3 having different thicknesses and widths are sandwiched by the roller pair having the above-described configuration. FIG. 2 shows a thick and narrow sheet material 3b such as a postcard.
FIG. 3 is a diagram showing a state in which a thin and wide sheet material 3a such as plain paper is being nipped and conveyed.

First, a sheet material 3 such as a thick and narrow postcard is used.
b is transported by the rollers 4 and 5 as shown in FIG.
As shown in (1), the pressure between the central roller 14 and the sheet material 3b rises, and the central roller 14 in contact with the sheet material 3b receives this pressure at this width, and the collapse tends to increase. However, since the guide rollers 16 as described above are provided at both ends of the rollers 14, the rollers 14 are not crushed smaller than the diameter of the guide rollers 16. Also,
Even if the center rubber roller 44 is crushed, the rollers 13 and 15 on both sides are lifted from the transport roller 4 and hardly contact with each other because of the thickness of the sheet material. Therefore, it is possible to suppress unevenness in the amount of rubber distortion of the roller 5 due to the thickness of the sheet material 3b, and to prevent skew.

On the other hand, when the thin and wide sheet material 3a such as plain paper is nipped and conveyed by the pair of rollers 4 and 5, as shown in FIG. (The size that touches the rollers), so not only the center roller 14 but also all the divided rollers 13, 14,
15 (almost the entire pinch roller 5) contacts the sheet material 3a,
The sheet material 3a is sandwiched between the transport rollers 4.
In this case, since the pressure is dispersed, the amount of crushing of the rubber of the pinch roller 5 (each of the rollers 13, 14, 15), which is a rubber roller, does not become so large. Further, the guide roller 16 is moved so that the rubber of the roller 5 is crushed to the diameter of the guide roller 16.
By adjusting the diameter and the load, the amount of distortion on the rubber surface, that is, the conveyance accuracy can be kept constant regardless of the type of the sheet material 3.

As described above, according to the present embodiment, regardless of the difference in the thickness and size of the sheet material, it is possible to reduce the conveyance failure such as the skew of the sheet material, and to carry out the conveyance with high precision. Can be realized.

[Second Embodiment] In the roller pairs 4 and 5 of the first embodiment described above, in order to keep the rubber distortion of the pinch roller (rubber roller) 5 constant irrespective of the paper thickness, the diameter of the guide roller 16 is required. The question is how much to take. That is, the difference between the amount of pushing of the rubber of the pinch roller 5 between the thick sheet material 3b and the thin sheet material 3a is checked, and if possible, the guide roller is adjusted according to the pushing amount of the thin sheet material 3a. Ideally, a diameter of 16 is determined so that the thick sheet material 3b is not warped any more.

Although the diameter of the guide roller 16 depends on the thickness and hardness of the rubber of the pinch roller 5, the thickness of plain paper, which is generally the thin sheet material 3a, is about 80 μm.
Since the thickness of the postcard, which is the thick sheet material 3b, is about 200 μm, the diameter of the pinch roller 5 is smaller than about 10 μm to 200 μm.

[Third Embodiment] In the roller pairs 4 and 5 of the first embodiment described above, when the pressure is strong, the pressure may be concentrated on the guide roller 16 and a conveyance failure such as paper wrinkles may occur. is there. Therefore, the guide roller 16 is configured to be covered with a member such as rubber which is sufficiently harder than the pinch roller 14 which is a rubber roller. Thus, the influence on the sheet material can be reduced while suppressing the amount of rubber crush of the pinch roller 14.

[Other Embodiments] In the above-described embodiment,
Although a printer is illustrated as an example of the image forming apparatus, the present invention is not limited to this, and may be another image forming apparatus such as a scanner, a copier, a facsimile apparatus, and may be used in the image forming apparatus. A similar effect can be obtained by applying the present invention to the sheet material conveying device.

Further, in the above-described embodiment, the sheet conveying apparatus for conveying the sheet material such as the recording paper as the recording object is exemplified, but the present invention is not limited to this.
For example, the same effect can be obtained by applying the present invention to a sheet conveying apparatus that conveys a sheet such as a document to be read.

In the above-described embodiment, the ink jet system is exemplified as the recording system. However, the present invention is not limited to this, and another recording system such as an electrophotographic system may be used.

[0033]

As described above, according to the present invention,
Irrespective of the difference in thickness and size of the sheet material, it is possible to reduce conveyance failure such as skew of the sheet material, and to realize high-precision conveyance.

[Brief description of the drawings]

FIG. 1 is an overall view of a sheet material conveying device according to the present invention.

FIG. 2 is a modified view of the present invention when a load is applied across a thick sheet material.

FIG. 3 is a modified view of the present invention when a load is applied across a thin sheet material.

FIG. 4 is a schematic configuration diagram of an image forming apparatus including a sheet material conveying device according to the present invention.

FIG. 5 is a modified view when a load is applied to a conventional transport device with thin paper sandwiched therebetween.

FIG. 6 is a modified view when a load is applied to a conventional conveyance device with thick paper sandwiched therebetween.

FIG. 7 is a graph showing a difference in contact force distribution in a roller axis direction depending on a paper thickness.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Sensor lever 2 ... Sensor 3, 3a, 3b ... Sheet material 4 ... Conveying roller 5 ... Pinch roller 6 ... Recording part 7 ... Recording head 8 ... Carriage 9 ... Guide shaft 10 ... Platen 11 ... Discharge roller 12 ... Spur 13 , 14,15… roller 16… guide roller

Claims (4)

[Claims] 1. A roller formed by pressing a first roller having a member with a high coefficient of friction such as rubber on its surface and a second roller made of a hard material such as iron disposed opposite to the first roller. In a sheet material transporting device that sandwiches and transports sheet materials having different thicknesses and sizes, the first roller is divided in the axial direction, and the divided first roller A roller member having a hardness higher than that of the rubber of the roller and a rotatable guide roller having a smaller diameter than the roller are provided at both ends of the roller at the central portion in the axial direction. 2. The sheet conveying apparatus according to claim 1, wherein a radius of the guide roller is smaller than a radius of the roller by about 10 μm to 200 μm. 3. The sheet conveying apparatus according to claim 1, wherein the guide roller is a roller having rubber, plastic, or the like having a higher hardness than rubber of the first roller. 4. An image forming apparatus comprising: a conveying unit for nipping and conveying a sheet material; and an image forming unit for forming an image on the sheet material, wherein the conveying unit is one of the first to third embodiments.
An image forming apparatus comprising the sheet material conveying device according to any one of the preceding claims.