JPH0891635A - Paper sheet carrying device - Google Patents

Abstract

PURPOSE: To provide the paper sheet carrying device provided with a registering function, of which pressurization is stabilized along the axial direction and in which displacement of positioning is not generated by the abutment of the paper sheet having different stiffness. CONSTITUTION: A paper sheet carrying device, which has a pair of register rollers 14 for synchronizing the tip of the carried paper sheet with the tip of the image of a photoreceptor, is provided with pressurizing mechanisms 30, 31, which abut on the roller surface in the central area of at least one of the rollers so as to pressurize it to the other roller side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, in an electrophotographic image forming apparatus such as a copying machine, a facsimile, a laser printer or the like, conveys a sheet so that the leading edge positions of the sheet and the image on the photoconductor are aligned with each other. The present invention relates to a sheet conveying device having a pair of registration rollers provided for the purpose.

[0002]

2. Description of the Related Art The functions required for a pair of registration rollers are to correct the inclination of the conveyance posture of a sheet to be conveyed (hereinafter referred to as "skew correction"), to convey the sheet at a constant speed, and The leading edge of the paper may be synchronized with the image on the photoconductor. In order to satisfy these functions, the conventional pair of registration rollers is configured such that the core metal 61 of at least one roller is provided with the rubber layer 6 as shown in FIG.
2 and the spring 6 on both end bearings 63 of the roller.
4 and the like are configured to apply a high load of, for example, about 2 kg.

However, in such a configuration, FIG.
As will be understood from the above, since a reaction force acts near both ends of the registration roller that receives a pressure force, the shaft that receives the pressure force bends and a sufficient load is not applied to the center area of the roller. If so, some problems occur. For example, if a relatively high load due to the friction separating mechanism is applied to the upstream side of the registration roller pair in the sheet conveyance, the sheet conveyance is hindered, the sheet is wrinkled, and the sheet conveyance is slipped. . Also, skew correction is performed by the leading edge of the paper hitting the pressure contact portion of the registration roller pair.When the registration roller pair is stopped at the time of the correction, if the center area of the roller is lifted up, the paper will not move to the registration roller pair. There is a possibility that slip-through, skew correction, and timing adjustment may be incomplete.

Therefore, it has been proposed to make one of the pair of registration rollers into a drum shape. However, in the case of such a drum-shaped roller, a high-speed conveying force is generated in the central portion and a low-speed conveying force is generated in the vicinity of both ends, so that wrinkles are apt to occur on the paper unexpectedly. Therefore, JP-A-62-11643
As disclosed in Japanese Patent No. 8 publication, the pre-transfer roller is gradually reduced in diameter from both end portions to the central portion in order to prevent wrinkling of the paper, so that the registration roller can change the conveyance speed given to the paper. However, it is necessary to cancel it out, which is structurally complicated. Further, in such a drum-shaped roller, since the pressure contact force of the roller pair changes along the roller axis line and the conveying force is different, there is a risk that skew conveyance may occur especially in an apparatus configured to perform conveyance on one side basis. .

The diameter of the shaft may be increased in order to prevent the shaft from flexing so that the central area of the roller does not float up, but if the shaft diameter is increased, the entire roller becomes thicker due to the structure, which leads to downsizing of the apparatus. Contrary to the request, it is also disadvantageous in terms of cost.

[0006]

Therefore, as disclosed in Japanese Utility Model Laid-Open No. 62-84069, it is not related to the registration roller, but it is a supplementary device that presses one roller toward the other roller in the central region in the axial direction. We have a pressure roller,
As disclosed in JP-A-2-24687, a bearing is inserted in the longitudinal center portion of a tubular core metal of a pressure roller, and a pressure shaft having an annular convex portion penetrates the pressure roller to form the bearing. It is considered that the pressure roller is brought into line contact with the surface, and the pressure roller is pressed against another corresponding roller with one end of the pressure shaft as a fulcrum, the other end as a force point, and the convex portion as an action point. However, since these disclosed techniques relate to the fixing device, they are insufficient for satisfying the function of the registration roller pair.

In particular, when an electromagnetic clutch or the like is used to transmit the drive force of the pair of registration rollers, the load torque when the pair of registration rollers is stopped is small. However, there is a fatal problem for the registration roller in that the paper is rotated by the paper.

Therefore, the present invention provides a sheet conveying device having a registration function in which the pressure is stable along the axial direction and the positioning does not occur even when the sheets having different waist strengths abut. It is an issue.

[0009]

In order to solve the above-mentioned problems, according to the present invention, in a paper conveying apparatus having a registration roller pair for synchronizing the front end of the conveyed paper with the image front end of the photoconductor, A pressure mechanism that abuts on the surface of the roller in at least one central region and applies pressure to the other roller is provided.

The pair of registration rollers is made of a material having at least the same longitudinal elastic modulus, and a half force of the pressing force of the pressing mechanism that abuts against the central area of one roller to press it in opposite directions at both ends of the other roller. It is suitable if it depends on.

It is even more preferable that the diameter of the roller pressed in the central region is 0.6 times the fourth root of the diameter of the other roller.

It is preferable that the pressing mechanism formed in a size corresponding to the sheet separating member of the sheet feeding unit in the sheet conveying direction has a shape protruding from the registration roller.

It is preferable that the pressure mechanism is provided on the drive roller side of the registration roller pair.

It is advantageous if the pressure mechanism is made of a conductive material and the pair of registration rollers is electrically connected to the ground of the machine body.

It is preferable that the pressurizing member and the pressurized member of the pressurizing mechanism are attached so as to be separated from each other during the jam processing to be in the depressurized state.

The pressure mechanism may be attached to the replaceable image forming unit.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described based on the embodiments shown in the drawings.

FIG. 1 shows a printer which is an image forming apparatus equipped with a sheet conveying device according to the present invention. The basic configuration of this printer is, as is well known in the art, a charging device 2, a laser beam L by a laser optical system 3, and a developing roller 4 for supplying a toner 5 around a photosensitive drum 1 which rotates in an arrow direction. A developing unit including the transfer roller 7 is arranged. The sheet P in the sheet cassette 10 arranged on the lower side of the drawing and detachable in the direction of the arrow a is supported by the bottom plate 11 and pressed against the sheet feeding roller 12 by the force of a spring (not shown).

When a command is issued from a control unit (not shown) and the paper feed roller 12 rotates, the paper feed cassette 10
The uppermost paper in the inside is conveyed to the registration roller pair 14 on the downstream side while preventing the double feeding by the separation pad 13. At this point, the registration roller pair 14 is stopped, and the leading edge of the sheet is abutted against the pressure contact portion of the registration roller pair 14,
The skew is corrected.

Thereafter, an electromagnetic clutch (not shown) is turned on at the timing synchronized with the image on the photosensitive member 1, the registration roller pair 14 is rotated, and the paper is further sent toward the transfer roller 7. The sheet on which the image is obtained from the photoconductor 1 by the transfer roller 7 is further conveyed to the fixing device 16 and the heater 1
The toner image is fixed by being passed through a fixing roller 18 having a built-in 7 and a pressure roller 19 which is pressed against and opposed to the fixing roller 18. After that, the image-formed sheet is ejected onto the sheet ejection tray 21 via the sheet ejection roller 20.

The registration roller pair 14 of the above construction will be described in detail. In FIG. 2, the registration roller pair is
It has a driving roller 14a whose core metal 26 is covered with a rubber layer 25 over a width wider than the maximum planned sheet width, and a driven roller 14b which is in pressure contact with the driving roller 14a.
The shaft diameter of these rollers is, for example, φ for the drive roller 14a.
The driven roller 14b has a diameter of 12 mm and a diameter of 10 mm. Drive roller 14a attached to the main body via bearing 27
Driving force is transmitted from the main body drive system to the side via the electromagnetic clutch 28. On the other hand, the driven roller 1
Both ends of 4b are also supported by bearings 29, but the support is not fixed, and the roller can be slid in the direction of the driving roller to pressurize the roller. A curved sliding contact member 30 corresponding to the surface curve of the driven roller 14b comes into contact with the center of the driven roller 14b in the longitudinal direction, and a spring 31 presses the driven roller 14b against the drive roller 14a.

FIG. 3 shows a pair of registration rollers 14 having different configurations.
Indicates. This pair of registration rollers has a driving roller 14a and a driven roller 14b, but has an electromagnetic clutch 28.
The rubber layer 25 covering the cored bar 26 of the drive roller 14a to which the driving force is transmitted from the main body drive system does not cover the cored bar 26 over the whole area, but the core is formed on the entire circumference of the roller surface at the central portion in the longitudinal direction of the roller shaft. The gold 26 is exposed. The sliding contact member 30 comes into contact with the central portion without the rubber layer, and the drive roller 14a is pressed by the spring 31 against the driven roller 14b with the pressing force K. Sliding contact member 30
If is made of a conductive resin, the drive roller 14a is electrically connected to the ground of the apparatus body via the spring 31. On the other hand, the driven roller 14b is pressed toward the drive roller 14a side by the spring 33 at the bearing portions at both ends thereof.
It is pressurized with. These driven roller side springs 33
The pressing force F due to the
It is adjusted to about half of the pressing force K by 1 and the deflection curves of the two axes in the roller shaft longitudinal direction become equal, so that the contact state can be made uniform.

A further consideration will be given to a structure in which the deflection curves of the two axes are made equal to equalize the pressure contact state in the roller shaft longitudinal direction. As shown in FIG. 4A, the driving roller 14a whose core metal 26 is covered with the rubber layer 25 except the central portion receives the pressing force K, while the driven roller 14b applies the pressing force F at both ends.
If both rollers having the length L and made of the same material or having the same longitudinal elastic modulus are subjected to the same flexure in the receiving state, the drive roller 14a becomes a cantilever flexure state, The driven roller 14b is in a flexed state of the simple beam. Therefore, in the state shown in FIG. 4B, the deflection amount Q of the cantilever-shaped drive roller 14a that receives the uniformly distributed load f via the rubber layer 25 is determined by the basic deflection formula (1) of material mechanics. become that way.

[0024]

[Equation 1]

On the other hand, the deflection amount Q of the simple beam driven roller 14b which receives the uniformly distributed load f through the rubber layer 25 is as shown in the deflection formula (2).

[0026]

[Equation 2]

Since these expressions (1) and (2) are the same, the relationship between the diameter φt of the driving roller 14a and the diameter φT of the driven roller 14b is as follows.

[0028]

[Equation 3]

That is, by setting the diameter of the roller whose central portion is pressed to be the fourth root times 0.6 of the diameter of the other roller, the deflection curves of the two axes can be surely made equal.

As shown in FIG. 5A, since the sliding contact member 30 is pressed by the spring 31, it is in contact with the curved portion corresponding to the surface of the core metal 26 of the drive roller 14a. The pair of registration rollers also functions as a braking member. Further, as shown in FIG. 5B, a braking member 35 made of another material having a large frictional resistance may be attached to the sliding contact member 30.
With this configuration, for example, the braking members 35 are attached to both ends of the sliding contact member 30 that abuts the core metal 26 in a relatively wide range in the roller shaft longitudinal direction, and the pressing force of the spring 31 and the sliding friction resistance of the braking member 35. It becomes easy to adjust the size of.

When rubbing separation such as the friction pad separation method when feeding from a paper cassette, double feeding is prevented by rubbing the surface of the paper, but the paper whose surface is rubbed is prevented. When the paper is fed, the paper dust scraped on the paper surface is supplied to the image forming section with the paper dust left on the surface, which causes problems during processing by the transfer roller, the photoconductor, and the fixing device. May occur. Therefore, as recognized in FIG. 6, the width b of the sliding contact member 30 is
In the roller shaft longitudinal direction of the registration roller pair 14, the width is made wider than the width c of the paper feed roller 12, and the contact member 3
The roller contact area of 0 is formed to have a V-shape, and the paper dust adhered to the driven roller 14b of the registration roller pair is scraped off. In order to enhance the effect of scraping the paper dust, it is preferable that the sliding contact member 30 is located on the side of the paper surface, such as the friction pad, on which the rubbing member abuts. Sliding contact member 3
It is preferable that the registration roller abutting 0 is made.

A part of the apparatus main body may be opened when a paper jam occurs. For example, as shown in FIG. 7, the spring 31 and the sliding contact member 30 are fixedly attached to the front cover 40. If the registration roller pair 14 is configured to be attached to the main body base 41, the pressure applied to the registration roller pair 14 is automatically released at the time of paper jam processing, and the processing becomes smooth. .

As described above, since the sliding contact member 30 is pressed by the spring 31 to bring the registration roller to a stable pressing state, exerts a braking action on the roller, and scrapes paper dust, Has a relatively short life. Therefore, as shown in FIG. 8, for example, as shown in FIG. 8, the spring 31 and the sliding contact member are provided at one end of the sheet feeding member unit 42 including the sheet feeding roller 12 so that the image forming unit can be exchanged in accordance with the exchange cycle. Incorporate 30. As a result, when the paper feed member unit 42 is replaced, the contact member 30 and the spring 31 are necessarily replaced before the end of their life.

[0034]

According to the sheet conveying apparatus of the first aspect of the present invention, the sheet conveying apparatus is provided with the pressing mechanism that abuts on the surface of at least one of the pair of registration rollers and presses the other roller. , The pressure is stable along the axial direction, the paper slips between the registration roller pair,
There is no slippage due to the high load on the upstream side of the registration roller pair. Further, since the roller surface is brought into contact with the surface to apply pressure, the pressing mechanism has a braking function, so that the positioning is prevented from being misaligned even when the sheets having different waist strength collide.

According to the sheet conveying device of the second aspect,
The pair of registration rollers is made of a material having at least the same longitudinal elastic modulus, and half the force of the pressing force of the pressing mechanism that abuts and presses against the central region of one roller is applied in opposite directions at the other ends of the other roller. Therefore, the bending curves of the two axes can be made equal, the pressure contact force at the roller pressure contact portion becomes equal in the longitudinal direction, and a reliable conveying force can be secured.

According to the sheet conveying device of the third aspect,
Since the diameter of the roller pressed in the central area is the fourth root multiple of 0.6 of the diameter of the other roller, the biaxial deflection curves can be more reliably identified.

According to the sheet conveying device of the fourth aspect,
The pressure mechanism, which is formed in the size corresponding to the paper separating member of the paper feeding unit in the paper transport direction, has a shape protruding from the registration roller, so that paper dust can be removed without adding a dedicated member. Is possible.

According to the sheet conveying apparatus of the fifth aspect,
Since the pressure mechanism is provided on the drive roller side of the registration roller pair, slippage occurs due to the presence of the sliding contact member, as in the case of being provided on the driven roller side that rotates only by the pressure contact force with the drive roller. There is no such thing.

According to the sheet conveying device of the sixth aspect,
Since the pressure mechanism is made of a conductive material and the registration roller pair is electrically connected to the ground of the machine body, it can be grounded not only from the roller end but also from the center, which is a countermeasure against the roller antenna. Easy to take.

According to the sheet conveying device of the seventh aspect,
Since the pressurizing member and the pressurized member of the pressurizing mechanism are attached so as to be separated from each other during the jam processing to be in the depressurized state, smooth jam processing is possible.

According to the paper transporting device of the eighth aspect,
Since the pressurizing mechanism is attached to the replaceable image forming unit, the pressurizing mechanism is surely replaced in the replacement cycle of the unit.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a printer provided with a sheet conveying device according to the present invention.

FIG. 2 is a schematic view of a pair of registration rollers according to the embodiment.

FIG. 3 is a schematic view of a pair of registration rollers according to another embodiment.

4A and 4B are views for explaining equalization of biaxial flexure curves, FIG. 4A shows a biaxial contact state, FIG. 4B shows flexure of a cantilever-shaped roller, and FIG. Indicates the deflection of a simple beam-shaped roller.

5A and 5B are views for explaining how braking is applied to the roller surface. FIG. 5A shows that the sliding contact member itself functions as a braking member, and FIG. 5B shows that a dedicated braking member is provided. .

6A and 6B are views for explaining how to scrape off paper dust on the surface of paper, FIG. 6A is a conceptual plan view, and FIG. 6B is a conceptual cross-sectional view.

FIG. 7 is a schematic configuration diagram illustrating that the pressurizing mechanism is depressurizable.

FIG. 8 is a schematic configuration diagram illustrating that the pressure mechanism is attached to a replaceable image forming unit.

FIG. 9 is a diagram showing a conventional problem of a pair of registration rollers.

[Explanation of symbols]

 14 Registration Roller Pair 14a Driving Roller 14b Driven Roller 25 Rubber Layer 26 Core Bar 28 Electromagnetic Clutch 30 Sliding Contact Member 31 Spring 33 Spring

Claims (8)

[Claims] 1. A paper transporting device having a pair of registration rollers for synchronizing a leading edge of a transported sheet with an image leading edge of a photoconductor, in a central region of at least one of the pair of rollers, abutting against the surface of the roller to the other roller side. A sheet conveying device comprising a pressurizing mechanism for pressurizing the sheet. 2. A pair of registration rollers is made of a material having at least the same longitudinal elastic modulus, and a half force of the pressing force of the pressing mechanism that abuts against the central area of one of the rollers and presses it.
The sheet conveying device according to claim 1, wherein the other roller is applied in opposite directions at both ends. 3. The sheet conveying apparatus according to claim 2, wherein the diameter of the roller pressed in the central area is the fourth power of 0.6 of the diameter of the other roller. 4. The pressing mechanism, which is formed in a size corresponding to the sheet separating member of the sheet feeding unit in the sheet conveying direction, has a shape protruding from the registration roller. The sheet conveying device according to the item 1. 5. The sheet conveying apparatus according to claim 1, wherein the pressing mechanism is provided on the drive roller side of the registration roller pair. 6. The pressing mechanism is made of a conductive material,
The sheet conveying device according to claim 1, wherein the pair of registration rollers is electrically connected to the ground of the machine body. 7. The pressurizing member and the pressurized member of the pressurizing mechanism are attached so as to be separated and in a depressurized state during a jam process. The sheet conveying device according to item 1. 8. The pressurizing mechanism is attached to a replaceable image forming unit.
The sheet conveyance device according to any one of 1.